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Organization and Summary of Significant Accounting Policies - Revenues from Strategic Partnering Collaboration Agreements and Research Activity Grants (Detail) - Revenue from Contract with Customer - Revenue From Collaboration Agreements, Grants And Licensing Concentration Risk	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Pfizer
Concentration Risk [Line Items]
Percentage of revenues	40.00%	40.00%	47.00%
Biogen MA Inc
Concentration Risk [Line Items]
Percentage of revenues	24.00%	0.00%	0.00%
Kite Pharma, Inc. ("Kite")
Concentration Risk [Line Items]
Percentage of revenues	24.00%	34.00%	30.00%
Novartis Institutes For Bio Medical Research Inc
Concentration Risk [Line Items]
Percentage of revenues	4.00%	0.00%	0.00%
Sanofi
Concentration Risk [Line Items]
Percentage of revenues	5.00%	22.00%	16.00%

Consolidated Balance Sheets - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Current assets:
Cash and cash equivalents	$ 131,329	$ 80,428
Marketable securities	510,094	282,046
Interest receivable	1,035	682
Accounts receivable	5,224	36,909
Prepaid expenses and other current assets	11,986	5,408
Total current assets	659,668	405,473
Marketable securities, non-current	50,530	21,832
Property and equipment, net	41,324	29,926
Intangible assets	58,128	53,156
Goodwill	42,798	39,273
Operating lease right-of-use assets	71,045	77,289
Other non-current assets	13,557	9,067
Restricted cash	1,500	1,500
Total assets	938,550	637,516
Current liabilities:
Accounts payable	12,553	6,671
Other accrued liabilities	18,612	10,885
Accrued compensation and employee benefits	20,738	13,605
Deferred revenues	91,644	38,711
Total current liabilities	143,547	69,872
Deferred revenues, non-current	245,045	81,432
Long-term portion of lease liabilities	38,396	41,192
Deferred income tax	7,185	6,570
Other non-current liabilities	7,011	5,711
Total liabilities	441,184	204,777
Commitments and contingencies
Stockholders’ equity:
Preferred stock, $0.01 par value, 5,000,000 shares authorized, and no shares issued or outstanding	0	0
Common stock, $0.01 par value; 320,000,000 shares authorized, 142,063,203 and 115,972,708 shares issued and outstanding at December 31, 2020 and 2019, respectively	1,421	1,160
Additional paid-in capital	1,269,375	1,090,828
Accumulated deficit	(777,981)	(656,985)
Accumulated other comprehensive income (loss)	5,419	(2,449)
Total Sangamo Therapeutics, Inc. stockholders’ equity	498,234	432,554
Non-controlling interest	(868)	185
Total stockholders’ equity	497,366	432,739
Total liabilities and stockholders’ equity	$ 938,550	$ 637,516

Consolidated Statements of Comprehensive Loss - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Statement of Comprehensive Income [Abstract]
Net loss	$ (121,122)	$ (95,419)	$ (68,889)
Foreign currency translation adjustment	8,345	(1,573)	(1,148)
Net pension losses	(193)	(28)	(21)
Change in unrealized (loss) gain on marketable securities, net of tax	(284)	592	(4)
Comprehensive loss	(113,254)	(96,428)	(70,062)
Comprehensive loss attributable to non-controlling interest	(126)	(233)	(574)
Comprehensive loss attributable to Sangamo Therapeutics, Inc.	$ (113,128)	$ (96,195)	$ (69,488)

- Definition

Amount after tax of increase (decrease) in equity from transactions and other events and circumstances from net income (loss) and other comprehensive income (loss), attributable to noncontrolling interests. Excludes changes in equity resulting from investments by owners and distributions to owners.

+ References + Details

- Definition

Amount after tax of increase (decrease) in equity from transactions and other events and circumstances from net income and other comprehensive income. Excludes changes in equity resulting from investments by owners and distributions to owners.

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- Definition

The consolidated profit or loss for the period, net of income taxes, including the portion attributable to the noncontrolling interest.

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+ Details

Other Balance Sheet Details - Summary of Accounts Payable and Accrued Liabilities (Detail) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Balance Sheet Related Disclosures [Abstract]
Customer advance	$ 5,000	$ 0
Accrued research and development expenses	4,257	4,102
Operating lease liabilities – current	3,690	3,214
Accrued professional fees	1,532	1,118
Other accrued liabilities	4,133	2,451
Total other accrued liabilities	$ 18,612	$ 10,885
Operating Lease, Liability, Current, Statement of Financial Position [Extensible List]	us-gaap:AccruedLiabilitiesCurrent	us-gaap:AccruedLiabilitiesCurrent

Subsequent Events (Details) - Subsequent Event - At-the-market Stock Offering $ in Millions	2 Months Ended
	Feb. 19, 2021 USD ($) shares
Subsequent Event [Line Items]
Sale of stock, number of shares issued in transaction (in shares) \| shares	1,034,762
Sale of stock, consideration received on transaction, gross	$ 16.1
Consideration received from sale of stock	$ 15.7

Organization and Summary of Significant Accounting Policies

12 Months Ended

Dec. 31, 2020

Accounting Policies [Abstract]

Organization and Summary of Significant Accounting Policies

ORGANIZATION AND SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES

Business Overview

Sangamo Therapeutics, Inc. (“Sangamo” or “the Company”) was incorporated in the State of Delaware in June 1995 and changed its name from Sangamo Biosciences, Inc. in January 2017. Sangamo is a clinical-stage genomic medicine company committed to translating ground-breaking science into medicines that transform the lives of patients with serious diseases using its platform technologies in gene therapy, cell therapy and genome engineering.

Basis of Presentation

The accompanying Consolidated Financial Statements have been prepared in conformity with generally accepted accounting principles in the United States of America (“U.S. GAAP”) and include the accounts of the Company and its subsidiaries. All intercompany balances and transactions have been eliminated in the Consolidated Financial Statements. For consolidated entities where the Company owns or is exposed to less than 100% of the economics, the Company records net loss attributable to non-controlling interests on its Consolidated Statements of Operations equal to the percentage of the economic or ownership interest retained in such entities by the respective non-controlling parties.

Liquidity and Management’s Plan

Sangamo is currently working on a number of long-term development projects that involve experimental technologies. The projects may require several years and substantial expenditures to complete and ultimately may be unsuccessful. The Company plans to finance operations with available cash resources, collaborations and strategic partnerships funds, research grants and from the issuance of equity or debt securities. Sangamo believes that its available cash, cash equivalents and marketable securities as of December 31, 2020, when combined with additional capital raises and expected revenues from collaborations, strategic partnerships and research grants, will be adequate to fund its operations at least through the next 12 months from the date these Consolidated Financial Statements are issued. Sangamo will require substantial additional financial resources to complete the development and commercialization of its product candidates. Additional capital may not be available on terms acceptable to the Company, or at all. If adequate funds are not available, or if the terms of potential funding sources are unfavorable, the Company’s business and ability to develop its technology and therapeutic products would be harmed. Furthermore, any sales of additional equity securities may result in dilution to the Company’s stockholders, and any debt financing may include covenants that restrict the Company’s business.

Summary of Significant Accounting Policies

Use of Estimates

The preparation of the accompanying Consolidated Financial Statements in conformity with U.S. GAAP requires management to make estimates and assumptions that affect the amounts reported in the Consolidated Financial Statements and the accompanying notes. On an ongoing basis, management evaluates its estimates including critical accounting policies or estimates related to revenue recognition, including the estimated fair value of common shares issued as part of the transaction price, clinical trial accruals, fair value of assets and liabilities, including from acquisitions, and stock-based compensation. Estimates are based on historical experience and on various other market specific and other relevant assumptions that the Company believes to be reasonable under the circumstances, the results of which form the basis for making judgments about the carrying values of assets and liabilities that are not readily apparent from other sources. Actual results could differ from those estimates.

During the year ended December 31, 2020, the Company recorded adjustments to revenue related to changes in estimates in connection with the collaboration agreements with Sanofi Genzyme (“Sanofi”) and Pfizer Inc. (“Pfizer”). These changes in estimates were driven by changes in project scope and related project costs which resulted in changes to the measure of proportional cumulative performance. These adjustments increased revenue by $8.9 million, decreased net loss by $8.9 million and decreased the Company’s basic net loss per share by $0.06 for the year ended December 31, 2020.

During the year ended December 31, 2019, the Company recorded adjustments to revenue related to a change in estimate in connection with the giroctocogene fitelparvovec collaboration agreement with Pfizer Inc. (“Pfizer”). This change in estimate was driven by changes in project scope and related project costs which resulted in changes to the measure of proportional cumulative performance. These adjustments increased revenue by $5.7 million, decreased net loss by $5.7 million and decreased the Company’s basic net loss per share by $0.05 for the year ended December 31, 2019.

Revenue Recognition

The Company accounts for its revenues pursuant to the provisions of Accounting Standards Codification (“ASC”) Topic 606, Revenue from Contracts with Customers (“ASC Topic 606”). The Company’s contract revenues are derived from collaboration agreements including licensing arrangements and research activity grants. Research and licensing agreements typically include upfront signing or license fees, cost reimbursements for research services, minimum sublicense fees, milestone payments and royalties on future licensee’s product sales. The Company has agreements with both fixed and variable consideration. Non-refundable upfront fees and funding of research and development activities are considered fixed, while milestone payments are generally identified as variable consideration. Sangamo’s research grants are typically multi-year agreements and provide for the reimbursement of qualified expenses for research and development as defined under the terms of the grant agreement. Revenues under research grant agreements are generally recognized when the related qualified research expenses are incurred. Deferred revenue primarily represents the portion of research or license payments received but not earned.

In determining the appropriate amount of revenue to be recognized as the Company fulfills its obligations under its agreements, the Company performs the following steps: (i) identification of the promised goods or services in the contract; (ii) determination of whether the promised goods or services are performance obligations, including whether they are distinct in the context of the contract; (iii) measurement of the transaction price, including the constraint on variable consideration; (iv) allocation of the transaction price to the performance obligations based on estimated selling prices; and (v) recognition of revenue when (or as) the Company satisfies each performance obligation.

A performance obligation is a promise in a contract to transfer a distinct good or service to the customer and is the unit of account in ASC Topic 606. The Company’s performance obligations include license rights, development services and services associated with regulatory submission and approval processes. Revenues from research services earned under collaboration agreements are generally recognized as revenue as the related services are provided. Revenues from non-refundable upfront fees are recognized over time either by measuring progress towards satisfaction of the relevant performance obligation, using the input method (i.e., cumulative actual costs incurred relative to total estimated costs) or on a straight-line basis when a performance obligation is expected to be satisfied evenly over a period of time (or when the entity has a stand-ready obligation). Significant management judgment is required to determine the level of effort required under an arrangement, and the period over which the Company expects to complete its performance obligations under the arrangement, which may include total internal personnel costs and external costs to be incurred as well as, in certain cases, the estimated stand-ready obligation period. Changes in these estimates can have a material effect on revenue recognized. If the Company cannot reasonably estimate when its performance obligations either are completed or become inconsequential, then revenue recognition is deferred until the Company can reasonably make such estimates. The Company includes the unconstrained amount of estimated variable consideration in the transaction price. The amount included in the transaction price is constrained to the amount for which it is probable that a significant reversal of cumulative revenue recognized will not occur. At the end of each subsequent reporting period, the Company re-evaluates the estimated variable consideration included in the transaction price and any related constraint and, if necessary, adjusts its estimate of the overall transaction price. Revenue is then recognized over the remaining estimated period of performance using the cumulative catch-up method. The estimated period of performance and project costs, such as personnel and manufacturing cost, are reviewed quarterly and adjusted, as needed, to reflect the Company’s current assumptions regarding the timing of its deliverables.

As part of the accounting for these arrangements, the Company must develop assumptions that require judgment to determine the stand-alone selling price of each performance obligation identified in the contract. The Company uses key assumptions to determine the stand-alone selling price, which may include forecasted revenues, development timelines, reimbursement rates for personnel costs, discount rates and probabilities of technical and regulatory success. Related costs and expenses under these arrangements have historically approximated the revenues recognized.

Revenues from major collaboration agreements and research activity grants as a percentage of total revenues were as follows:


	Year Ended December 31,
	2020		2019		2018
Pfizer Inc.	40	%	40	%	47	%
Kite Pharma, Inc.	24	%	34	%	30	%
Biogen MA, Inc.	24	%	—		—
Sanofi Genzyme	5	%	22	%	16	%
Novartis Institutes for BioMedical Research, Inc.	4	%	—		—

Receivables from collaborations are typically unsecured and are concentrated in the biopharmaceutical industry. Accordingly, the Company may be exposed to credit risk generally associated with biopharmaceutical companies or specific to its collaboration agreements. To date, the Company has not experienced any losses related to these receivables.

Funds received from the Company’s collaboration partners are generally not refundable and are recorded as revenue as it fulfills its performance obligations. The Company’s performance obligations are satisfied over time (i.e., stand ready obligations) or using the input method (i.e., cumulative actual costs incurred relative to total estimated costs). Revenue is also recognized when the Company has incurred qualified research and development costs that are reimbursable from its collaboration partners and when there is reasonable assurance that such costs will be reimbursed. Any payments received from a collaboration partner in advance of the completion of the relevant performance obligation are recorded as deferred revenue.

Business Combinations

The Company accounts for acquisitions using the acquisition method of accounting, which requires that assets acquired, including in-process research and development (“IPR&D”) projects, liabilities assumed and any non-controlling interests in the acquired target in an acquisition be recorded at their fair values as of the acquisition date on the Company’s Consolidated Balance Sheets. Any excess of purchase consideration over the fair value of net assets acquired is recorded as goodwill. The determination of estimated fair value requires the Company to make significant estimates and assumptions. As a result, the Company may record adjustments to the fair values of assets acquired and liabilities assumed within the measurement period (up to one year from the acquisition date) with the corresponding offset to goodwill. Transaction costs associated with business combinations are expensed as they are incurred.

Goodwill and Intangible Assets

Goodwill represents the excess of the purchase consideration transferred over the estimated fair values of assets acquired and liabilities assumed in a business combination. Intangible assets with indefinite useful lives are related to purchased IPR&D projects and are measured at their respective fair values as of the acquisition date. Goodwill and intangible assets with indefinite useful lives are not amortized. Intangible assets related to IPR&D projects are considered to be indefinite-lived until the completion or abandonment of the associated research and development efforts. If and when development is complete, which generally occurs if and when regulatory approval to market a product is obtained, the associated assets would be deemed finite-lived and would then be amortized based on their respective estimated useful lives at that point in time. The Company tests goodwill and indefinite-lived intangible assets for impairment on an annual basis and between annual tests if the Company becomes aware of any events occurring or changes in circumstances that would indicate the fair values of the assets are below their respective carrying amounts. As of December 31, 2020, no impairment of goodwill or indefinite-lived intangible assets was identified.

Valuation of Long-Lived Assets

Long-lived assets, including property and equipment and finite-lived intangible assets, are reviewed for impairment whenever facts or circumstances either internally or externally may suggest that the carrying value of an asset may not be recoverable. Recoverability of these assets is measured by comparison of the carrying amount of each asset to the future undiscounted cash flows expected to result from the use of the asset and its eventual disposition. If the asset is considered to be impaired, the amount of any impairment is measured as the difference between the carrying value and the fair value of the impaired asset. As of December 31, 2020, no impairment of any long-lived assets was identified.

Fair Value Measurements

The carrying amounts for financial instruments consisting of cash and cash equivalents, accounts receivable, accounts payable and accrued liabilities approximate fair value due to their short maturities. Marketable securities are stated at their estimated fair values. The free shares asset or liability is measured using a binomial-lattice pricing model and is reviewed each reporting period and adjusted, as needed, and is expected to approximate fair value.

Cash, Cash Equivalents and Restricted Cash

Sangamo considers all highly-liquid investments purchased with original maturities of three months or less at the purchase date to be cash equivalents. Cash and cash equivalents consist of cash, deposits in demand money market accounts, and commercial paper. Restricted cash consists of a letter of credit for $1.5 million as a deposit for the Brisbane lease.

A reconciliation of cash, cash equivalents and restricted cash reported within the accompanying Consolidated Balance Sheets to the amounts reported within the accompanying Consolidated Statements of Cash Flows is as follows (in thousands):


	As of December 31,
	2020		2019		2018
Cash and cash equivalents	$	131,329	$	80,428	$	140,418

Non-current restricted cash	1,500		1,500		3,500
Cash, cash equivalents and restricted cash as reported within the Consolidated Statements of Cash Flows	$	132,829	$	81,928	$	143,918

Marketable Securities

Sangamo classifies its marketable securities as available-for-sale and records its investments at estimated fair value based on quoted market prices or observable market inputs of almost identical assets, with the unrealized holding gains and losses included in accumulated other comprehensive loss (“AOCI”). The Company classifies those investments that are not required for use in current operations and that mature in more than 12 months as non-current marketable securities in the accompanying Consolidated Balance Sheets.

The Company’s investments are subject to a periodic impairment review. The Company recognizes an impairment charge, if material, when a decline in the fair value of its investments below the cost basis is judged to be other-than-temporary. The Company considers various factors in determining whether to recognize an impairment charge, including the length of time and extent to which the fair value has been less than the Company’s cost basis, the financial condition and near-term prospects of the investee and the Company’s intent and ability to hold the investment for a period of time sufficient to allow for any anticipated recovery in the market value. Realized gains and losses on marketable securities are included in interest and other income, net, which are determined using the specific identification method.

Concentrations of Credit Risk and Other Risks

Cash, cash equivalents, and marketable securities consist of financial instruments that potentially subject the Company to a concentration of credit risk to the extent of the fair value recorded in the Consolidated Balance Sheets. The Company invests cash that is not required for immediate operating needs primarily in highly liquid instruments with high credit ratings which are expected to bear minimal risk. The Company has established policies relating to the quality, diversification, and maturities of securities to enable the Company to manage its credit risk. The Company is exposed to credit risk in the event of a default by the financial institutions holding its cash, cash equivalents, and marketable securities and issuers of investments to the extent recorded on the Consolidated Balance Sheets.

Certain materials and key components that the Company utilizes in its operations are obtained through single suppliers. Since the suppliers of key components and materials must be named in an investigational new drug (“IND”) application filed with the U.S. Food and Drug Administration for a product, significant delays can occur if the qualification of a new supplier is required. If delivery of material from the Company’s suppliers was interrupted for any reason, the Company may be unable to supply any of its product candidates for clinical trials.

Property and Equipment

Property and equipment are stated at cost, less accumulated depreciation and amortization. Depreciation is calculated using the straight-line method based on the estimated useful lives of the related assets which is generally three to five years. For leasehold improvements, amortization is calculated using the straight-line method based on the shorter of the useful life or the lease term. The Company reviews its property and equipment for impairment whenever events or changes in circumstances indicate that the carrying amount of an asset may not be recoverable.

Research and Development Expenses

Research and development expenses consist primarily of personnel costs, including salaries, benefits and stock-based compensation, clinical studies performed by contract research organizations, materials and supplies and overhead allocations consisting of various support and facility-related costs. Research and development costs are expensed as incurred.

General and Administrative Expenses

General and administrative expenses consist of finance, human resources, legal and other administrative activities. These expenses consist primarily of personnel costs, including salaries, benefits and stock-based compensation, facilities and overhead costs, legal expenses, and other general and administrative costs.

Stock-based Compensation

The Company measures and recognizes compensation expense for all stock-based payment awards made to Sangamo employees and directors, including employee share options, restricted stock units (“RSUs”) and employee stock purchases related to the Employee Stock Purchase Plan (“ESPP”) based on estimated fair values at the award grant date. The fair value of stock-based awards is amortized over the vesting period of the award using a straight-line method.

To estimate the fair value of an award, the Company uses the Black-Scholes option pricing model. This model requires inputs such as expected life, expected volatility and risk-free interest rate. These inputs are subjective and generally require significant analysis and judgment to develop. While estimates of expected life and volatility are derived primarily from the Company’s historical data, the risk-free rate is based on the U.S. Treasury yield curve in effect at the time of grant commensurate with the expected life assumption. The Company accounts for forfeitures in the period they occur.

Income Taxes

Income tax expense has been provided using the liability method. Deferred tax assets and liabilities are determined based on the difference between the financial statement and tax bases of assets and liabilities as measured by the enacted tax rates that will be in effect when these differences reverse. The Company provides a valuation allowance against net deferred tax assets if, based upon the available evidence, it is not more likely than not that the deferred tax assets will be realized.

The Company recognizes a tax benefit from an uncertain tax position only if it is more likely than not that the tax position will be sustained on examination by the taxing authorities, based on the technical merits of the position. The tax benefits recognized in the Company’s Consolidated Financial Statements from such positions are measured based on the largest benefit that has a greater than 50% likelihood of being realized. The Company recognizes interest and penalties associated with tax matters as part of the income tax provision and includes accrued interest and penalties with the related income tax liability within other accrued liabilities on its Consolidated Balance Sheets.

Leases

The Company adopted the Accounting Standard Update (“ASU”) No. 2016-02, Leases (Topic 842) on January 1, 2019, using the modified retrospective approach with a cumulative-effect adjustment. The Company determines if an arrangement is or contains a lease at inception by assessing whether the arrangement contains an identified asset and whether it has the right to control the identified asset. Right-of-use (“ROU”) assets represent the Company’s right to use an underlying asset for the lease term and lease liabilities represent the Company’s obligation to make lease payments arising from the lease. Lease liabilities are recognized at the lease commencement date based on the present value of future lease payments over the lease term. ROU assets are based on the measurement of the lease liability and also include any lease payments made prior to or on lease commencement and exclude lease incentives and initial direct costs incurred, as applicable.

As the implicit rate in the Company’s leases is generally unknown, the Company uses its incremental borrowing rate based on the information available at the lease commencement date in determining the present value of remaining lease payments. The incremental borrowing rate represents an estimate of the interest rate the Company would incur at lease commencement to borrow an amount equal to the lease payments on a collateralized basis over the term of a lease in a similar economic environment. The Company considers its credit risk, term of the lease, and total lease payments and adjusts for the impacts of collateral, as necessary, when calculating its incremental borrowing rates. The lease terms may include options to extend or terminate the lease when it is reasonably certain the Company will exercise any such options. Rent expense for the Company’s operating leases is recognized on a straight-line basis over the lease term.

The Company has elected to not separate lease and non-lease components for its real estate and copier leases and, as a result, accounts for any lease and non-lease components as a single lease component. The Company has also elected to not apply the recognition requirement to any leases with a term of 12 months or less and does not include an option to purchase the underlying asset that the Company is reasonably certain to exercise.

Foreign Currency Translation

The functional currency of the Company’s foreign subsidiaries is primarily the Euro. Assets and liabilities denominated in foreign currencies are translated to U.S. dollars using the exchange rates at the balance sheet date. Foreign currency translation adjustments are recorded as a component of AOCI within stockholders’ equity. Revenues and expenses from the Company’s foreign subsidiaries are translated using the monthly average exchange rates in effect during the period in which the transactions occur. Foreign currency transaction gains and losses are recorded in interest and other income, net, on the Company’s Consolidated Statements of Operations.

Net Loss Per Share

Basic net loss per share attributable to Sangamo Therapeutics, Inc. stockholders has been computed by dividing net loss attributable to Sangamo Therapeutics, Inc. stockholders by the weighted-average number of shares of common stock outstanding during the period. Diluted net loss per share attributable to Sangamo Therapeutics, Inc. stockholders is calculated by dividing net loss attributable to Sangamo Therapeutics, Inc. stockholders by the weighted-average number of shares of common stock plus potentially dilutive securities outstanding during the period.

The total number of shares subject to stock options and RSUs outstanding and the ESPP shares reserved for issuance, which are all anti-dilutive, were excluded from consideration in the calculation of diluted net loss per share attributable to Sangamo Therapeutics, Inc. stockholders. Stock options and RSUs outstanding and ESPP shares reserved for issuance as of December 31, 2020, 2019 and 2018 were 14,237,871, 10,750,550, and 9,048,793, respectively.

Segments

The Company operates in one segment. Management uses one measure of profitability and does not segregate its business for internal reporting. As of December 31, 2020 and 2019, substantially all of the Company’s assets were maintained in the United States. For the years ended December 31, 2020, 2019 and 2018, substantially all of the Company’s revenues and operating expenses were generated and incurred in the United States.

Recent Accounting Pronouncements

Recently Adopted

Collaborative Arrangements

In November 2018, the FASB issued ASU No. 2018-18, Collaborative Arrangements (ASC Topic 808): Clarifying the Interaction between Topic 808 and Topic 606 (“ASU 2018-18”), which clarifies that certain transactions between participants in a collaborative arrangement should be accounted for under ASC Topic 606 when the counterparty is a customer. In addition, ASU 2018-18 precludes an entity from presenting consideration from a transaction in a collaborative arrangement as revenue from contracts with customers if the counterparty is not a customer for that transaction. ASU 2018-18 is effective for all interim and annual reporting periods beginning after December 15, 2019. On January 1, 2020, the Company adopted ASU 2018-18. The adoption of ASU 2018-18 did not have a material impact on the Company’s Consolidated Financial Statements.

Goodwill Impairment Testing

In January 2017, the FASB issued ASU No. 2017-04, Intangibles – Goodwill and Other (Topic 350): Simplifying the Test of Goodwill Impairment (“ASU 2017-04”). The new guidance simplifies the subsequent measurement of goodwill by eliminating Step 2 from the goodwill impairment test. ASU 2017-04 requires goodwill impairment to be measured as the amount by which a reporting unit’s carrying amount exceeds its fair value, not to exceed the carrying amount of its goodwill. ASU 2017-04 requires prospective application and is effective for annual periods beginning after December 15, 2019. ASU 2017-04 required the Company to amend its methodology for determining any goodwill impairment beginning in 2020. On January 1, 2020, the Company adopted ASU 2017-04. The adoption of ASU 2017-04 did not have a material impact on the Company’s Consolidated Financial Statements.

Credit Losses

In June 2016, the FASB issued ASU No. 2016-13, Financial Instruments – Credit Losses (Topic 326) (“ASU 2016-13”). ASU 2016-13 implements an impairment model, known as the current expected credit loss model, that is based on expected losses rather than incurred losses. Under the new guidance, an entity will recognize as an allowance its estimate of expected credit losses. ASU 2016-13 is effective for all interim and annual reporting periods beginning after December 15, 2019 and must be adopted using a modified retrospective approach, with certain exceptions. Early adoption is permitted. On January 1, 2020, the Company adopted ASU 2016-13 by using a modified retrospective approach. The adoption of ASU 2016-13 did not have a material impact on the Company’s Consolidated Financial Statements.

Income Taxes

In December 2019, the FASB issued ASU No. 2019-12, Income Taxes – Simplifying the Accounting for Income Taxes (“ASU 2019-12”). The guidance removes exceptions to the general principles in Income Taxes (Topic 740) for allocating tax expense between financial statement components, accounting basis differences stemming from an ownership change in foreign investments and interim period income tax accounting for year-to-date losses that exceed projected losses. The guidance becomes effective for annual reporting periods beginning after December 15, 2020 and interim periods within those fiscal years with early adoption permitted. On January 1, 2020, the Company early adopted ASU 2019-12. The adoption of ASU 2019-12 did not have a material impact on the Company's Consolidated Financial Statements.

Cloud Computing Arrangements

In August 2018, the FASB issued ASU 2018-15, Intangibles-Goodwill and Other-Internal Use Software: Customer’s Accounting for Implementation Costs Incurred in a Cloud Computing Arrangement That Is a Service Contract (“ASU 2018-15”). ASU 2018-15 aligns the requirements for capitalizing implementation costs incurred in a cloud computing arrangement that is a service contract with the requirements for capitalizing implementation costs incurred to develop or obtain internal-use software. The guidance becomes effective for annual reporting periods beginning after December 15, 2019 and interim periods within those fiscal years with early adoption permitted. The Company adopted this standard on January 1, 2020 using the prospective method. The adoption of ASU 2018-15 did not have a material impact on the Company’s Consolidated Financial Statements.

Income Taxes - Schedule of Company's Deferred Tax Assets (Detail) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Deferred tax assets:
Net operating loss carryforwards	$ 164,276	$ 133,765
Research and development tax credit carryforwards	27,679	21,459
Stock-based compensation	5,321	4,194
Deferred revenue	20,681	32,171
Fixed assets	10,525	11,282
Lease liability	10,251	11,722
Accruals and reserves	430	675
Other	308	151
Total deferred tax asset	239,471	215,419
Valuation allowance	214,351	187,724
Deferred tax assets	25,120	27,695
Liabilities:
Intangible assets	(14,321)	(13,609)
Operating lease right-of-use assets	(17,510)	(20,656)
Deferred tax liabilities	(31,831)	(34,265)
Total net deferred tax liabilities	$ (6,711)	$ (6,570)

Acquisition of Sangamo France - Summary of Non-controlling Interest (Detail) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2020	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Stockholders' Equity Attributable to Noncontrolling Interest
Stockholders' equity attributable to noncontrolling interest, beginning balance				$ 185					$ 185
Fair value of additional shares acquired									(927)
Net loss attributable to non-controlling interest	$ (71)	$ 42	$ (36)	(61)	$ (54)	$ (54)	$ (72)	$ (53)	(126)	$ (233)	$ (555)
Stockholders' equity attributable to noncontrolling interest, ending balance	(868)				185				(868)	185
Non- Controlling Interest
Stockholders' Equity Attributable to Noncontrolling Interest
Stockholders' equity attributable to noncontrolling interest, beginning balance				$ 185					185
Stockholders' equity attributable to noncontrolling interest, ending balance	$ (868)				$ 185				$ (868)	$ 185

- Definition

Total of all stockholders' equity (deficit) items, net of receivables from officers, directors, owners, and affiliates of the entity which is directly or indirectly attributable to that ownership interest in subsidiary equity which is not attributable to the parent (that is, noncontrolling interest, previously referred to as minority interest).

+ References + Details

Stockholders' Equity

12 Months Ended

Dec. 31, 2020

Equity [Abstract]

Stockholders' Equity

STOCKHOLDERS’ EQUITY

Preferred Stock

The Company’s Certificate of Incorporation authorizes the Company to issue up to 5,000,000 shares of preferred stock, which may be issued at the discretion of the Company’s Board of Directors. As of December 31, 2020, no shares of the Company’s preferred stock have been issued or are outstanding.

Common Stock

In June 2020, the Company’s stockholders approved an amendment to the Company’s Certificate of Incorporation to increase the total number of shares of the Company’s common stock authorized for issuance from 160,000,000 shares to 320,000,000 shares. As of December 31, 2020, 142,063,203 shares of the Company’s common stock are outstanding.

In connection with the collaboration agreement with BIMA described in Note 4 of these Consolidated Financial Statements, the Company entered into a stock purchase agreement with BIMA, pursuant to which BIMA agreed to purchase the Biogen Shares at a price per share of $9.2137, for an aggregate purchase price of $225.0 million. The Company closed the sale of the Biogen Shares in April 2020.

In April 2019, the Company completed an underwritten public offering of its common stock, in which the Company sold an aggregate of 12.7 million shares of its common stock at a public offering price of $11.50 per share. The net proceeds to the Company from the sale of shares in this offering, after deducting underwriting discounts and commissions and other offering expenses, were approximately $136.3 million.

In April 2018, the Company completed an underwritten public offering of its common stock, in which the Company sold an aggregate of 14.2 million shares of its common stock at a public offering price of $16.25 per share. The net proceeds to the Company from the sale of shares in this offering, after deducting underwriting discounts and commissions and other offering expenses, were approximately $215.8 million.

At-the-Market Offering Agreement

In August 2020, the Company entered into an Open Market Sale Agreement℠ with Jefferies LLC (“Jefferies”) with respect to an at-the-market offering program under which the Company may offer and sell, from time to time at its sole discretion, shares of the Company’s common stock having an aggregate offering price of up to $150.0 million through Jefferies as the Company’s sales agent or principal. The Company is not obligated to sell any shares under the sales agreement. As of December 31, 2020, no shares had been sold under the sales agreement.

2018 Equity Incentive Plan

In June 2018, the Company’s stockholders approved the Sangamo Therapeutics, Inc. 2018 Equity Incentive Plan (the “2018 Plan”). In connection with the approval of the 2018 Plan, no additional equity awards will be granted under the previous 2013 Plan, however all outstanding equity awards under the 2013 Plan will continue to be subject to the terms and conditions as set forth in the agreements evidencing such awards and the terms of the 2013 Plan.

In May 2020, the Company’s stockholders approved an amendment and restatement of the 2018 Plan, to, among other things, increase the aggregate number of shares of the Company’s common stock reserved for issuance under the 2018 Plan by 9,900,000 shares.

The exercise price of a stock option granted under the 2018 Plan may not be less than 100% of the fair market value of the Company's common stock subject to the stock option on the date of grant, and the option term will not exceed 10 years. If the person to whom the stock option is granted is a 10% stockholder of the Company, and the stock option granted qualifies as an incentive stock option, then the exercise price per share will not be less than 110% of the fair market value of the Company’s common stock on the date of grant, and the option term will not exceed five years. Generally, stock options granted under the 2018 Plan vest over four years at a rate of 25% on the one-year anniversary of the date of grant and 1/48 per month thereafter and expire 10 years after the date of grant, or earlier upon termination of employment or services to the Company.

The number of shares of common stock reserved for issuance under the 2018 Plan will be reduced: (i) on a 1-for-1 basis for each share of common stock subject to a stock option or stock appreciation right granted under the plan, (ii) by a fixed

ratio of 1.33 shares of common stock for each share of common stock issued pursuant to a full-value award granted under the plan.

Shares subject to any outstanding stock options or other awards under the 2018 Plan that expire or otherwise terminate prior to the issuance of the shares subject to those stock options or awards will be available for subsequent issuance under the 2018 Plan. Any unvested shares issued under the 2018 Plan that the Company subsequently purchases, pursuant to repurchase rights under the 2018 Plan, will be added back to the number of shares reserved for issuance under the 2018 Plan on a 1-for-1 basis or a 1.33-for-1 basis (depending on the ratio at which the share reserve was debited for the original award) and will accordingly be available for subsequent issuance in accordance with the terms of the 2018 Plan.

As of December 31, 2020, there were 10,942,576 shares of the Company’s common stock reserved for future awards under the Company’s 2018 Plan.

2010 Employee Stock Purchase Plan

On June 2018, the Company’s stockholders approved an amendment and restatement of the Company’s 2010 Employee Stock Purchase Plan (“the ESPP”). As amended, the ESPP provides for a total of 4.6 million shares of common stock reserved for issuance thereunder. Eligible employees may purchase common stock at 85% of the lesser of the fair market value of the Company’s common stock on the first day of the applicable two-year offering period or the last day of the applicable six-month purchase period. As of December 31, 2020, there were 2,483,218 shares of the Company’s common stock reserved for future issuance under the ESPP. The ESPP expired on April 30, 2020. The ongoing offering will continue through the end of its 24 months offering period ending on October 29, 2021 at which point the ESPP will be fully terminated.

Stock Option Activity

A summary of the Company’s stock option activity is as follows:


	Number of Shares	Weighted- Average Exercise per Share Price		Weighted-Average Remaining Contractual Term	Aggregate Intrinsic Value
				(In years)	(In thousands)
Options outstanding at December 31, 2019	9,829,287	$	10.71
Options granted	4,563,425	$	8.09
Options exercised	(1,162,268)	$	8.02
Options canceled	(1,751,746)	$	10.19
Options outstanding at December 31, 2020	11,478,698	$	10.02	7.80	$	69,616
Options vested and expected to vest at December 31, 2020	11,478,698	$	10.02	7.80	$	69,616
Options exercisable at December 31, 2020	5,127,517	$	10.71	6.48	$	29,025

The intrinsic value of options exercised was $5.4 million, $4.7 million and $27.0 million during 2020, 2019 and 2018, respectively.

At December 31, 2020, the aggregate intrinsic values of outstanding and exercisable options were $69.6 million and $29.0 million, respectively. The aggregate intrinsic value of options vested and expected to vest as of December 31, 2020, 2019 and 2018 was $69.6 million, $7.5 million and $24.5 million, respectively.

Restricted Stock Units

During 2020, 2019 and 2018, the Company awarded 2,517,101, 834,745, and 346,055 RSUs, respectively. The RSUs awarded in 2020, 2019 and 2018 had an average grant date fair value per award of $8.06, $9.49 and $17.87, respectively. These awards generally vest in a series of three successive equal annual installments. The aggregate fair value of RSUs vested during 2020, 2019 and 2018 was $3.7 million, $2.0 million and $0.6 million, respectively.

A summary of the Company’s RSU activity is as follows:


	Number of Shares	Weighted-Average Remaining Contractual Term	Aggregate Intrinsic Value
		(In years)	(In thousands)
RSUs outstanding at December 31, 2019	862,850
RSUs awarded	2,517,101
RSUs released	(324,305)
RSUs forfeited	(384,118)
RSUs outstanding at December 31, 2020	2,671,528	1.19	$	41,689
RSUs vested and expected to vest at December 31, 2020	2,671,528	1.19	$	41,689

RSUs that vested in 2020, 2019 and 2018 were net-share settled such that the Company withheld shares with value equivalent to the employees’ minimum statutory obligation for the applicable income and other employment taxes and remitted the cash to the appropriate taxing authorities. The total shares withheld were approximately 90,617, 39,160, and 20,193 for 2020, 2019 and 2018, respectively, and were based on the value of the RSUs on their respective issuance dates as determined by the Company’s closing stock price. Total payments for the employees’ tax obligations to taxing authorities were $0.8 million, $0.4 million and $0.3 million in 2020, 2019 and 2018, respectively and are reflected as a financing activity within the accompanying Consolidated Statements of Cash Flows. These net-share settlements had the effect of share repurchases by the Company as they reduced and retired the number of shares that would have otherwise been issued as a result of the vesting and did not represent an expense to the Company.

Income Taxes - Summary of Benefit for Income Taxes (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Current:
Federal	$ 0	$ 0	$ 0
State	133	0	0
Foreign	686	0	0
Subtotal	819	0	0
Deferred:
Federal	0	0	0
State	0	0	0
Foreign	(474)	0	0
Subtotal	(474)	0	0
Income tax expense	$ 345	$ 0	$ 0

Commitments and Contingencies - Additional Information (Detail) $ in Millions	12 Months Ended
	Dec. 31, 2020 USD ($) ft²	Dec. 31, 2019 USD ($)	Dec. 31, 2018 USD ($)	Oct. 01, 2020 USD ($)	May 31, 2020 USD ($) ft²
Commitments And Contingencies [Line Items]
Operating lease, cost	$ 10.4
Variable lease, cost	2.3
Operating lease, payments	6.4
Operating lease, expense	$ 10.4	$ 7.9
Rent expenses			$ 2.3
Operating lease, weighted average remaining lease term	7 years 7 months 6 days
Operating lease, weighted average discount rate, percent	6.10%
License obligations	$ 1.0
Minimum
Commitments And Contingencies [Line Items]
Lease agreement, extendable lease term	5 years
Maximum
Commitments And Contingencies [Line Items]
Lease agreement, extendable lease term	10 years
Richmond, California
Commitments And Contingencies [Line Items]
Lease not yet commenced, area of real estate \| ft²					8,500
Lessee Operating Lease Lease Not Yet Commenced Amount				$ 1.3	$ 1.6
Office And Laboratory \| Brisbane, California
Commitments And Contingencies [Line Items]
Area of space leased (in sqft) \| ft²	87,700
Office And Laboratory \| Richmond, California
Commitments And Contingencies [Line Items]
Area of space leased (in sqft) \| ft²	54,200
Research and Office Space \| Valbonne, France
Commitments And Contingencies [Line Items]
Area of space leased (in sqft) \| ft²	20,800

Income Taxes - Additional Information (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Income Taxes [Line Items]
Increase (decrease) in deferred tax assets valuation allowance	$ (26,600,000)	$ (29,600,000)	$ (45,300,000)
Deferred tax assets, net operating loss carryforwards for federal	622,600,000
Deferred tax assets, net operating loss carryforwards for state	261,700,000
Federal research tax credit carryforwards	21,900,000
State research tax credit carryforwards	18,300,000
Accrued interest and/or penalties	0
French
Income Taxes [Line Items]
Deferred tax assets, net operating loss carryforwards for foreign	$ 145,900,000

Fair Value Measurement (Tables)

12 Months Ended

Dec. 31, 2020

Fair Value Disclosures [Abstract]

Summary of Fair Value Measurements of Cash Equivalents, Available-for-Sale Securities and Free Share Liability

The fair value measurements of the Company’s cash equivalents, marketable securities and the free shares asset are identified at the following levels within the fair value hierarchy (in thousands):


	December 31, 2020
	Fair Value Measurement
	Total		Level 1		Level 2		Level 3
Assets:
Cash equivalents:
Money market funds	$	53,165	$	53,165	$	—	$	—

Total	53,165		53,165		—		—
Marketable securities:
Commercial paper	213,533		—		213,533		—
Corporate debt securities	59,574		—		59,574		—
Certificates of deposit	12,311		—		12,311		—
Asset-backed securities	17,908		—		17,908		—
U.S. government-sponsored entity debt securities	257,298		—		257,298		—
Total	560,624		—		560,624		—
Total cash equivalents and marketable securities	$	613,789	$	53,165	$	560,624	$	—

Free shares asset	$	70	$	—	$	—	$	70


	December 31, 2019
	Fair Value Measurement
	Total		Level 1		Level 2		Level 3
Assets:
Cash equivalents:
Money market funds	$	30,496	$	30,496	$	—	$	—
Commercial paper	2,999		—		2,999		—
Total	33,495		30,496		2,999		—
Marketable securities:
Commercial paper	155,368		—		155,368		—
Corporate debt securities	95,017		—		95,017		—
U.S. government-sponsored entity debt securities	53,493		—		53,493		—
Total	303,878		—		303,878		—
Total cash equivalents and marketable securities	$	337,373	$	30,496	$	306,877	$	—

Free shares asset	$	236	$	—	$	—	$	236

Summary of Estimated Fair Value of Free Share Liability Assumptions


	December 31,
Free Shares valuation assumptions:	2020			2019
Sangamo stock price (USD)	$	15.61		$	8.68
Sangamo France stock price (EUR)	€	3.85		€	2.14
EUR/ USD exchange rate	0.82			0.91
Estimated correlation Sangamo and Sangamo France stock prices	100.0		%	100.0		%
Sangamo stock price (USD) volatility estimate	88.9		%	72.5		%
Sangamo France stock price (EUR) volatility estimate	88.9		%	72.5		%
EUR/ USD exchange rate volatility estimate	6.3		%	6.6		%
Risk free rate and cost of debt by expected exercise date	Varies			Varies

- Definition

Tabular disclosure of financial instruments measured at fair value, including those classified in shareholders' equity measured on a recurring or nonrecurring basis. Disclosures include, but are not limited to, fair value measurements recorded and the reasons for the measurements, level within the fair value hierarchy in which the fair value measurements are categorized and transfers between levels 1 and 2. Nonrecurring fair value measurements are those that are required or permitted in the statement of financial position in particular circumstances.

+ References + Details

Major Customers, Partnerships and Strategic Alliances - Revenues Recognized under Agreement (Detail) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2020	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Revenue related to Sanofi agreement:
Total	$ 25,800	$ 57,763	$ 21,553	$ 13,076	$ 54,851	$ 21,958	$ 17,548	$ 8,071	$ 118,192	$ 102,428	$ 84,452
Novartis Institutes For Bio Medical Research Inc \| Research services
Revenue related to Sanofi agreement:
Total									1,100
Novartis Institutes For Bio Medical Research Inc \| Recognition of upfront fee
Revenue related to Sanofi agreement:
Total									4,100
Biogen MA Inc \| Research services
Revenue related to Sanofi agreement:
Total									6,500
Biogen MA Inc \| Recognition of upfront fee
Revenue related to Sanofi agreement:
Total									21,400
Kite Pharma, Inc. ("Kite")
Revenue related to Sanofi agreement:
Total									28,608	34,350	25,517
Kite Pharma, Inc. ("Kite") \| Research services
Revenue related to Sanofi agreement:
Total									3,562	9,373	6,972
Kite Pharma, Inc. ("Kite") \| Recognition of upfront fee
Revenue related to Sanofi agreement:
Total									25,046	24,977	18,545
Pfizer, Giroctocogene Fitelparvovec
Revenue related to Sanofi agreement:
Total									34,449	39,359	37,810
Pfizer, Giroctocogene Fitelparvovec \| Recognition of upfront fee
Revenue related to Sanofi agreement:
Total	$ 8,700								3,111	15,697	37,810
Pfizer, Giroctocogene Fitelparvovec \| Milestone achievement
Revenue related to Sanofi agreement:
Total									31,338	23,662	0
Pfizer C9ORF72
Revenue related to Sanofi agreement:
Total									12,985	1,827	2,188
Pfizer C9ORF72 \| Recognition of upfront fee
Revenue related to Sanofi agreement:
Total									7,985	1,827	2,188
Pfizer C9ORF72 \| Milestone achievement
Revenue related to Sanofi agreement:
Total									5,000	0	0
Sanofi
Revenue related to Sanofi agreement:
Total									5,322	22,680	13,516
Sanofi \| Research services
Revenue related to Sanofi agreement:
Total									4,823	6,367	9,503
Sanofi \| Recognition of upfront fee
Revenue related to Sanofi agreement:
Total									298	3,494	4,013
Sanofi \| Milestone achievement
Revenue related to Sanofi agreement:
Total									$ 201	$ 12,819	$ 0

Income Taxes - Schedule of Difference Between Benefit for Income Taxes and Federal Statutory Income Tax Rate (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Income Tax Disclosure [Abstract]
Tax at federal statutory rate	$ (25,363)	$ (20,038)	$ (14,467)
State taxes, net	(3,168)	(9,597)	(2,849)
Foreign rate differential	376	(665)	(177)
Global Intangible Low-Taxed Income	1,335	0	0
Non-deductible stock-based compensation	4,232	2,817	(2,729)
Research credits	(3,657)	(3,429)	(1,005)
Change in valuation allowance	26,537	29,655	20,271
Other	53	1,257	956
Income tax expense	$ 345	$ 0	$ 0

Organization and Summary of Significant Accounting Policies (Tables)

12 Months Ended

Dec. 31, 2020

Accounting Policies [Abstract]

Schedule of Revenue from Strategic Partnering Collaboration Agreements and Research Activity Grants as a Percentage of Total Revenues

Revenues from major collaboration agreements and research activity grants as a percentage of total revenues were as follows:


	Year Ended December 31,
	2020		2019		2018
Pfizer Inc.	40	%	40	%	47	%
Kite Pharma, Inc.	24	%	34	%	30	%
Biogen MA, Inc.	24	%	—		—
Sanofi Genzyme	5	%	22	%	16	%
Novartis Institutes for BioMedical Research, Inc.	4	%	—		—

Schedule of Cash and Cash Equivalents


	As of December 31,
	2020		2019		2018
Cash and cash equivalents	$	131,329	$	80,428	$	140,418

Non-current restricted cash	1,500		1,500		3,500
Cash, cash equivalents and restricted cash as reported within the Consolidated Statements of Cash Flows	$	132,829	$	81,928	$	143,918

Restrictions on Cash and Cash Equivalents


	As of December 31,
	2020		2019		2018
Cash and cash equivalents	$	131,329	$	80,428	$	140,418

Non-current restricted cash	1,500		1,500		3,500
Cash, cash equivalents and restricted cash as reported within the Consolidated Statements of Cash Flows	$	132,829	$	81,928	$	143,918

Other Balance Sheet Details (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Property, Plant and Equipment [Line Items]
Property and equipment, gross	$ 58,740	$ 41,607
Less: accumulated depreciation and amortization	(17,416)	(11,681)
Property and equipment, net	41,324	29,926
Depreciation and amortization	5,682	3,930	$ 2,359
Laboratory equipment
Property, Plant and Equipment [Line Items]
Property and equipment, gross	24,737	17,179
Furniture and fixtures
Property, Plant and Equipment [Line Items]
Property and equipment, gross	4,870	4,639
Leasehold improvements
Property, Plant and Equipment [Line Items]
Property and equipment, gross	15,953	13,888
Manufacturing equipment
Property, Plant and Equipment [Line Items]
Property and equipment, gross	1,089	0
Construction in progress
Property, Plant and Equipment [Line Items]
Property and equipment, gross	$ 12,091	$ 5,901

Commitments and Contingencies - Non-cancelable Material Contractual Commitments (Detail) $ in Thousands	Dec. 31, 2020 USD ($)
Other Commitments [Line Items]
Contractual obligation	$ 21,507
Brammer Bio MA
Other Commitments [Line Items]
Contractual obligation	7,736
Lonza Netherlands, B.V.
Other Commitments [Line Items]
Contractual obligation	$ 13,771

Stockholders' Equity - Additional Information (Detail) $ / shares in Units, $ in Thousands		1 Months Ended					12 Months Ended
	Aug. 05, 2020 USD ($)	Apr. 30, 2020 USD ($) $ / shares	Apr. 30, 2020 USD ($) $ / shares	Apr. 30, 2019 USD ($) $ / shares shares	Jun. 30, 2018 shares	Apr. 30, 2018 USD ($) $ / shares shares	Dec. 31, 2020 USD ($) installment $ / shares shares	Dec. 31, 2019 USD ($) $ / shares shares	Dec. 31, 2018 USD ($) $ / shares shares	Jun. 30, 2020 shares	Jun. 29, 2020 shares	May 31, 2020 shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Preferred shares authorized (in shares)							5,000,000	5,000,000
Preferred stock issued (in shares)							0	0
Preferred stock outstanding (in shares)							0	0
Common stock, shares authorized (in shares)							320,000,000	320,000,000		320,000,000	160,000,000
Common stock, shares outstanding (in shares)							142,063,203	115,972,708
Net proceeds from issuance of common stock, after deducting offering expenses \| $							$ 0	$ 136,308	$ 215,758
Additional equity award (in shares)							4,563,425
Stock option maximum term							6 years 5 months 23 days
Specified stockholder ownership percentage							10.00%
Purchase price of common stock percent under stock incentive plans for specified stockholder							110.00%
Stock option maximum term for specified stockholder							5 years
Share of common stock subject to a stock option or stock appreciation right (in shares)							100.00%
Intrinsic value of options exercised \| $							$ 5,400	4,700	27,000
Options vested and expected to vest, aggregate intrinsic value \| $							69,600	7,500	24,500
Options exercisable, aggregate intrinsic value \| $							$ 29,025
Restricted stock units awarded (in shares)							2,517,101
Total payments for the employees' tax obligations to taxing authorities \| $							$ 765	$ 422	$ 254
Shares reserved for issuance of future awards (in shares)							2,483,218
Share-Based Compensation Awards, Tranche 2
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock options granted vesting percentage							33.33%
Share-Based Compensation Awards, Tranche 3
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock options granted vesting percentage							33.33%
2018 Stock Incentive Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Additional equity award (in shares)						0
Percent of fair value per share of common stock on option grant date							100.00%
Stock options vesting period							4 years
Stock options expiration term							10 years
Fixed ratio shares of common stock							1.33
Shares reserved for issuance of future awards (in shares)							10,942,576
2010 Employee Stock Purchase Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Percent of fair value per share of common stock on option grant date					85.00%
Stock reserved for issuance under plan (in shares)					4,600,000
Purchase plan offering period					2 years
Purchase plan purchase period					6 months
Restated 2018 Stock Incentive Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Increase in capital shares reserved for future issuance (in shares)												9,900,000
Maximum \| 2018 Stock Incentive Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock option maximum term							10 years
Employee Stock Options \| 2018 Stock Incentive Plan \| Share-Based Compensation Awards, Tranche 1
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock options granted vesting percentage							25.00%
Employee Stock Options \| 2018 Stock Incentive Plan \| Share-Based Compensation Awards, Tranche 2
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock options granted vesting percentage							2.08%
Restricted Stock Units (RSUs)
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Restricted stock units awarded (in shares)							2,517,101	834,745	346,055
Grant date fair value per award of restricted stock units (in dollars per share) \| $ / shares							$ 8.06	$ 9.49	$ 17.87
Share-based compensation arrangement by share-based payment award, number of vesting installment \| installment							3
Aggregate fair value of RSUs vested in period \| $							$ 3,700	$ 2,000	$ 600
Shares withheld from issuance in order to pay employee taxes (in shares)							90,617	39,160	20,193
Restricted Stock Units (RSUs) \| Share-Based Compensation Awards, Tranche 1
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock options granted vesting percentage							33.33%
Jefferies LLC \| ATM Agreement
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Issuance of common stock, net of issuance costs (in shares)							0
Stock offering program, maximum value \| $	$ 150,000
Stock Purchase Agreement \| Biogen MA Inc
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Sale of stock, price per share (in dollars per share) \| $ / shares		$ 9.2137	$ 9.2137
Consideration received from sale of stock \| $		$ 225,000	$ 225,000
Common Stock
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Issuance of common stock, net of issuance costs (in shares)				12,700,000		14,200,000	24,420,157	12,650,000	14,156,500
Public offering price of common stock issued (in dollars per share) \| $ / shares				$ 11.50		$ 16.25
Net proceeds from issuance of common stock, after deducting offering expenses \| $				$ 136,300		$ 215,800

Major Customers, Partnerships and Strategic Alliances - Agreement with DAS (Detail) - USD ($)	3 Months Ended								12 Months Ended
	Dec. 31, 2020	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2005
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Revenues	$ 25,800,000	$ 57,763,000	$ 21,553,000	$ 13,076,000	$ 54,851,000	$ 21,958,000	$ 17,548,000	$ 8,071,000	$ 118,192,000	$ 102,428,000	$ 84,452,000
Dow Agro Sciences \| License agreement terms
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Research program to develop laboratory research reagents												3 years
One-time license fee earned on exercise of option												$ 6,000,000.0
Previously agreed research, development and commercialization milestone payments, and royalties on sales of products												$ 4,000,000.0
Percentage of royalties to be received from sublicensing												25.00%
Fee due												$ 25,300,000
Minimum license annual fees specific reckoning period												11 years
Dow Agro Sciences \| License agreement terms \| Minimum
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Annual fees												$ 300,000
Dow Agro Sciences \| License agreement terms \| Maximum
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Annual fees												3,000,000.0
Dow Agro Sciences \| License agreement terms \| Royalty revenues
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Revenues												$ 2,300,000
Dow Agro Sciences \| License agreement terms \| License fee revenues
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Revenues									$ 3,000,000.0	$ 3,000,000.0	$ 3,000,000.0

Stock-Based Compensation - Weighted-Average Assumptions Used for Estimating Fair Value of ESPP Purchased Rights (Detail) - 2010 Employee Stock Purchase Plan	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected dividend yield of stock	0.00%	0.00%	0.00%
Minimum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Risk-free interest rate	1.53%	1.53%	2.16%
Expected term (in years)	6 months	6 months	6 months
Expected volatility	51.02%	51.02%	73.21%
Maximum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Risk-free interest rate	2.80%	2.42%	2.80%
Expected term (in years)	2 years	2 years	2 years
Expected volatility	91.96%	91.96%	83.25%

Quarterly Financial Data (Unaudited) - Summary of Quarterly Financial Data (Detail) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2020	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Quarterly Financial Information Disclosure [Abstract]
Revenues	$ 25,800	$ 57,763	$ 21,553	$ 13,076	$ 54,851	$ 21,958	$ 17,548	$ 8,071	$ 118,192	$ 102,428	$ 84,452
Operating expenses	69,232	61,464	59,450	57,598	53,382	51,206	51,052	51,968	247,744	207,608	161,602
Net loss	(40,675)	(1,508)	(35,965)	(42,974)	4,501	(27,361)	(30,356)	(42,203)	(121,122)	(95,419)	(68,889)
Net loss attributable to non-controlling interest	(71)	42	(36)	(61)	(54)	(54)	(72)	(53)	(126)	(233)	(555)
Net (loss) income attributable to Sangamo Therapeutics, Inc.	$ (40,604)	$ (1,550)	$ (35,929)	$ (42,913)	$ 4,555	$ (27,307)	$ (30,284)	$ (42,150)	$ (120,996)	$ (95,186)	$ (68,334)
Net loss per share - basic and diluted (in dollars per share)	$ (0.29)	$ (0.01)	$ (0.26)	$ (0.37)	$ 0.04	$ (0.24)	$ (0.26)	$ (0.41)	$ (0.90)	$ (0.85)	$ (0.70)

- Definition

The portion of profit or loss for the period, net of income taxes, which is attributable to the parent.

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- Definition

Amount, excluding tax collected from customer, of revenue from satisfaction of performance obligation by transferring promised good or service to customer. Tax collected from customer is tax assessed by governmental authority that is both imposed on and concurrent with specific revenue-producing transaction, including, but not limited to, sales, use, value added and excise.

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+ Details

Income Taxes

12 Months Ended

Dec. 31, 2020

Income Tax Disclosure [Abstract]

Income Taxes

INCOME TAXES

The domestic and foreign components of loss before income taxes were as follows (in thousands):


	Year Ended December 31,
	2020		2019		2018
Domestic	$	(126,624)	$	(77,354)	$	(65,695)
Foreign	5,847		(18,065)		(3,194)
Loss before income taxes	$	(120,777)	$	(95,419)	$	(68,889)

The income tax expense consisted of the following (in thousands):


	Year Ended December 31,
	2020		2019		2018
Income tax expense:
Current:
Federal	$	—	$	—	$	—
State	133		—		—
Foreign	686		—		—
Subtotal	819		—		—
Deferred:
Federal	—		—		—
State	—		—		—
Foreign	(474)		—		—
Subtotal	(474)		—		—
Income tax expense	$	345	$	—	$	—

The difference between the income tax expense and the amount computed by applying the federal statutory income tax rate to loss before income taxes is explained as follows (in thousands):


	Year Ended December 31,
	2020		2019		2018
Tax at federal statutory rate	$	(25,363)	$	(20,038)	$	(14,467)
State taxes, net	(3,168)		(9,597)		(2,849)
Foreign rate differential	376		(665)		(177)
Global Intangible Low-Taxed Income	1,335		—		—
Non-deductible stock-based compensation	4,232		2,817		(2,729)
Research credits	(3,657)		(3,429)		(1,005)
Change in valuation allowance	26,537		29,655		20,271
Other	53		1,257		956
Income tax expense	$	345	$	—	$	—

In March and December 2020, in response to the COVID-19 pandemic, the CARES Act and the Consolidated Appropriations Act, 2021 were passed into law and provide additional economic stimulus to address the impact of the COVID-19 pandemic. The Company does not expect any significant benefit to its income tax provision as a result of this legislation.

Deferred income taxes reflect the net tax effects of temporary differences between the carrying amounts of assets and liabilities for financial reporting purposes and the amounts used for income tax purposes. Significant components of the Company’s deferred tax assets and liabilities are as follows (in thousands):


	December 31,
	2020		2019
Assets:
Deferred tax assets:
Net operating loss carryforwards	$	164,276	$	133,765
Research and development tax credit carryforwards	27,679		21,459
Stock-based compensation	5,321		4,194
Deferred revenue	20,681		32,171
Fixed assets	10,525		11,282
Lease liability	10,251		11,722
Accruals and reserves	430		675
Other	308		151
Total deferred tax asset	239,471		215,419
Valuation allowance	214,351		187,724
Deferred tax assets	25,120		27,695
Liabilities:
Intangible assets	(14,321)		(13,609)
Operating lease right-of-use assets	(17,510)		(20,656)
Deferred tax liabilities	(31,831)		(34,265)
Total net deferred tax liabilities	$	(6,711)	$	(6,570)

The deferred tax assets and liabilities based on tax jurisdictions are presented on the Consolidated Balance Sheet as follows (in thousands):


	December 31,
	2020		2019
Deferred tax assets (included in Other non-current assets on the Consolidated Balance Sheet)	$	474	$	—
Deferred tax liabilities	(7,185)		(6,570)
Net deferred tax liabilities	$	(6,711)	$	(6,570)

In October 2018, the Company acquired Sangamo France. The Company recorded goodwill and intangible assets as part of accounting for the acquisition of Sangamo France. There is no corresponding tax basis for the goodwill or intangible assets. A portion of the intangible assets acquired were for the use in a particular research and development project and are considered indefinite-lived assets with no tax basis.

The changes in the fair value of the unrealized gain (loss) on marketable securities are recorded as a component of accumulated other comprehensive income (loss), net of a provision for income taxes.

A valuation allowance is recorded when it is more likely than not that all or some portion of the deferred income tax assets will not be realized. The Company regularly assesses the need for a valuation allowance against its deferred income tax assets by considering both positive and negative evidence related to whether it is more likely than not that the Company’s deferred income tax assets will be realized. In evaluating the Company’s ability to recover its deferred income tax assets within the jurisdiction from which they arise, the Company considers all available positive and negative evidence, including scheduled reversals of deferred income tax liabilities, projected future taxable income, tax-planning strategies, and results of recent operations. Accordingly, based upon the Company’s analysis of these factors the net deferred tax assets have been substantially offset by a valuation allowance. The valuation allowance increased by $26.6 million, $29.6 million and $45.3 million for the years ended December 31, 2020, 2019 and 2018, respectively.

As of December 31, 2020, Sangamo had net operating loss carryforwards for federal and state income tax purposes of approximately $622.6 million and $261.7 million, respectively. The federal net operating loss generated before 2018 will begin to expire in 2024 and will keep expiring through 2037, if not utilized. Federal net operating loss generated in 2018 will carry forward indefinitely. If not utilized, the state net operating loss carryforwards will begin to expire in 2029, respectively. The Company’s French net operating loss carryforward balance is $145.9 million, which carries over indefinitely. The Company

also has federal and state research tax credit carryforwards of $21.9 million and $18.3 million, respectively. The federal research credits will begin to expire in 2021, while the state research credits have no expiration date. Utilization of the Company’s net operating loss carryforwards and research tax credit carryforwards may be subject to substantial annual limitations due to the ownership change limitations provided by the Internal Revenue Code and similar state provisions. The annual limitation could result in the expiration of the net operating loss carryforwards and research tax credit carryforwards before utilization.

The Company’s policy is to reinvest the earnings of its non-U.S. subsidiaries in those operations. The Company does not provide for U.S. taxes on the earnings of foreign subsidiaries because the Company intends to reinvest such earnings offshore indefinitely. However, if these funds were repatriated, the Company would be required to accrue and pay applicable U.S. taxes and withholding taxes. Due to the cumulative losses generated in foreign countries there are no earnings to repatriate.

The Company files federal and state income tax returns with varying statutes of limitations. The tax years from 2002 forward remain open to examination due to the carryover of net operating losses or tax credits. The Company also files United Kingdom and French income tax returns, and the tax years from 2008 and thereafter remain open in the United Kingdom and 2016 and thereafter in France are still subject to examination.

The Company’s practice is to recognize interest and/or penalties related to income tax matters in income tax expense. As of December 31, 2020, the Company had no accrued interest and/or penalties. The unrecognized tax benefits may change during the next year for items that arise in the ordinary course of business. In the event that any unrecognized tax benefits are recognized, the effective tax rate will not be affected.

The following table summarizes the activity related to the Company’s unrecognized tax benefits (in thousands):


	December 31,
	2020		2019		2018
Beginning balance	$	11,630	$	6,288	$	5,659
Additions based on tax positions related to the current year	2,834		5,393		636
Additions for tax positions of prior years	1,982		—		—
Reductions for tax positions of prior years	(3,554)		(51)		(7)
Ending balance	$	12,892	$	11,630	$	6,288

- Definition

The entire disclosure for income taxes. Disclosures may include net deferred tax liability or asset recognized in an enterprise's statement of financial position, net change during the year in the total valuation allowance, approximate tax effect of each type of temporary difference and carryforward that gives rise to a significant portion of deferred tax liabilities and deferred tax assets, utilization of a tax carryback, and tax uncertainties information.

+ References + Details

Acquisition of Sangamo France - Additional Information (Detail) - USD ($)		2 Months Ended	12 Months Ended
	Oct. 01, 2018	Nov. 23, 2018	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018	Jul. 20, 2018
Business Acquisition [Line Items]
Goodwill impairments			$ 0	$ 0	$ 0
TxCell S.A.
Business Acquisition [Line Items]
Number of ordinary shares acquired (in shares)	13,519,036	11,528,635
Percentage of share capital and voting rights acquired					98.20%
Business Combination, Consideration Transferred	$ 45,900,000
Purchase price per share (in dollars per share)	$ 2.99
TxCell S.A. \| SPA and TOA
Business Acquisition [Line Items]
Percentage of equity interests agreed to acquire						100.00%
Number of ordinary shares acquired (in shares)			322,000	111,000	25,047,671
Number of free shares held by the holders (in shares)						477,000
Business acquisition estimated fair value liabilities of free shares						$ 200,000
Business acquisition estimated fair value assets of free shares			$ 100,000
TxCell S.A. \| SPA and TOA \| Option Pricing Method
Business Acquisition [Line Items]
Business acquisition estimated fair value liabilities of free shares	$ 200,000
TxCell S.A. \| SPA and TOA
Business Acquisition [Line Items]
Noncontrolling interest, ownership percentage by parent			99.80%	98.70%
Cash paid for shares acquired			$ 700,000

Other Balance Sheet Details

12 Months Ended

Dec. 31, 2020

Balance Sheet Related Disclosures [Abstract]

Other Balance Sheet Details

OTHER BALANCE SHEET DETAILS

Property and Equipment, Net

Property and equipment, net consist of the following (in thousands):


	December 31,
	2020		2019
Laboratory equipment	$	24,737	$	17,179
Furniture and fixtures	4,870		4,639
Leasehold improvements	15,953		13,888
Manufacturing equipment	1,089		—
Construction in progress	12,091		5,901
	58,740		41,607
Less: accumulated depreciation and amortization	(17,416)		(11,681)
Property and equipment, net	$	41,324	$	29,926

Depreciation and amortization expense was $5.7 million in 2020, $3.9 million in 2019 and $2.4 million in 2018.

Intangible Assets

The changes in intangible assets were as follows (in thousands):


	December 31,
	2020		2019
Balance at beginning of year	$	53,156	$	54,243

Foreign currency translation adjustment	4,972		(1,087)
Balance at end of year	$	58,128	$	53,156

Goodwill

The changes in goodwill were as follows (in thousands):


	December 31,
	2020		2019
Balance at beginning of year	$	39,273	$	40,044

Foreign currency translation adjustment	3,525		(771)
Balance at end of year	$	42,798	$	39,273

Other Accrued Liabilities

Other accrued liabilities consist of the following (in thousands):


	December 31,
	2020		2019
Customer advance	$	5,000	$	—
Accrued research and development expenses	4,257		4,102
Operating lease liabilities – current	3,690		3,214
Accrued professional fees	1,532		1,118
Other	4,133		2,451
Total other accrued liabilities	$	18,612	$	10,885

Subsequent Events	12 Months Ended
Subsequent Events	Dec. 31, 2020
Subsequent Events [Abstract]
SUBSEQUENT EVENTS	SUBSEQUENT EVENTSIn the first quarter of 2021 through February 19, 2021, the Company sold 1,034,762 shares of its common stock for gross proceeds of approximately $16.1 million from an at-the-market offering program under an Open Market Sale Agreement℠ with Jefferies dated August 5, 2020. After deducting sales commissions and expenses, net cash proceeds through February 19, 2021 under the at-the-market offering are approximately $15.7 million.

Commitments and Contingencies

12 Months Ended

Dec. 31, 2020

Commitments and Contingencies Disclosure [Abstract]

Commitments and Contingencies

COMMITMENTS AND CONTINGENCIES

Leases

Sangamo occupies approximately 87,700 square feet of office and research and development laboratory facilities in Brisbane, California pursuant to a lease that expires in May 2029. Sangamo also occupies approximately 54,200 square feet of research and office space in Richmond, California, pursuant to leases that expire in August 2026. In addition, the Company

leases approximately 20,800 square feet of office, and research and development space in Valbonne, France, subject to leases that expire beginning in June 2025 through March 2028.

In May 2020, the Company entered into an amendment to an existing lease to acquire approximately 8,500 square feet of research and office space in Richmond, California that expires in August 2026. Total lease payments over the life of this amended lease are approximately $1.6 million. Variable lease payments include the Company’s allocated share of costs incurred and expenditures made by the landlord in the operation and management of the building. The amended lease was effective October 1, 2020, and the Company recorded a lease liability and corresponding ROU asset of $1.3 million upon inception of this amended lease.

Certain of these leases also include renewal options at the election of the Company to renew or extend the lease for an additional five to 10 years. These optional periods have not been considered in the determination of the ROU assets or lease liabilities associated with these leases as the Company did not consider it reasonably certain it would exercise the options.

The Company performed evaluations of its contracts and determined each of its identified leases are operating leases. For the year ended December 31, 2020, the Company incurred $10.4 million of lease costs included in operating expenses in the Consolidated Statement of Operations in relation to these operating leases. Variable lease expense was $2.3 million for the year ended December 31, 2020 and was not included in the measurement of the Company’s operating ROU assets and lease liabilities. The variable expense consists primarily of the Company’s proportionate share of operating expenses, property taxes and insurance and is classified as lease expense due to the Company’s election to not separate lease and non-lease components.

Cash paid for amounts included in the measurement of operating lease liabilities for the year ended December 31, 2020 was $6.4 million and was included in net cash provided by operating activities in the Company’s Consolidated Statement of Cash Flows.

Rent expense related to lease agreements was $10.4 million, $7.9 million, and $2.3 million for 2020, 2019 and 2018, respectively. Future minimum payments under lease obligations at December 31, 2020 consist of the following (in thousands):


	Total
2021	$	6,191
2022	6,756
2023	6,851
2024	6,995
2025	7,058
Thereafter	19,571
Total lease payments	53,422
Less:
Imputed interest	(11,336)
Total	$	42,086

Reported as of December 31, 2020:
Operating lease liabilities - current (included in Other accrued liabilities on the Consolidated Balance Sheet)	$	3,690
Operating lease liabilities - long-term	38,396
Total	$	42,086

As of December 31, 2020, the weighted-average remaining lease term is 7.6 years and the weighted-average incremental borrowing rate used to determine the operating lease liability was 6.1% for the Company’s operating leases.

The Company does not have any financing leases.

Contractual Commitments

The following table sets forth the non-cancelable material contractual commitments under manufacturing-related supplier arrangements as of December 31, 2020 (in thousands):

Party

Total commitments

Expiry date

Brammer Bio MA - a Thermo Fisher Scientific Inc. subsidiary

7,736

December 2022

Lonza Netherlands, B.V.

13,771

December 2022

Total contractual commitments

21,507

The Company also had $1.0 million of license obligations related to its intellectual property as of December 31, 2020.

Contingencies

Sangamo is not party to any material pending legal proceeding. From time to time, Sangamo may be involved in legal proceedings arising in the ordinary course of business.

Commitments and Contingencies - Summary of Future Minimum Payments under Contractual Obligations (Detail) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Commitments and Contingencies Disclosure [Abstract]
2021	$ 6,191
2022	6,756
2023	6,851
2024	6,995
2025	7,058
Thereafter	19,571
Total lease payments	53,422
Imputed interest	(11,336)
Total	42,086
Operating lease liabilities - current (included in Other accrued liabilities on the Consolidated Balance Sheet)	3,690	$ 3,214
Operating lease liabilities - long-term	$ 38,396	$ 41,192
Operating Lease, Liability, Current, Statement of Financial Position [Extensible List]	us-gaap:AccruedLiabilitiesCurrent	us-gaap:AccruedLiabilitiesCurrent

Fair Value Measurement - Summary of Estimated Fair Value of Free Share Liability Assumptions (Detail)	Dec. 31, 2020 $ / shares	Dec. 31, 2020 € / shares	Dec. 31, 2019 $ / shares	Dec. 31, 2019 € / shares	Oct. 01, 2018 $ / shares
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
EUR/ USD exchange rate	0.82	0.82	0.91	0.91
Measurement Input, Share Price
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Sangamo Stock Price (USD) (in dollars per share)	$ 15.61		$ 8.68
Stock Price Volatility Estimate
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Volatility Estimate	0.889	0.889	0.725	0.725
Exchange Rate Volatility Estimate
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Volatility Estimate	0.063	0.063	0.066	0.066
TxCell S.A.
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Sangamo France Stock Price (EUR) (in Euro per share)					$ 2.99
TxCell S.A. \| Measurement Input, Share Price
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Sangamo France Stock Price (EUR) (in Euro per share) \| € / shares		€ 3.85		€ 2.14
TxCell S.A. \| Measurement Input Stock Price Correlation
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Estimated correlation Sangamo and Sangamo France stock prices	1.000	1.000	1.000	1.000
TxCell S.A. \| Stock Price Volatility Estimate
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Volatility Estimate	0.889	0.889	0.725	0.725

Organization and Summary of Significant Accounting Policies - Additional Information (Detail)	3 Months Ended								12 Months Ended
	Dec. 31, 2020 USD ($) shares	Sep. 30, 2020 USD ($)	Jun. 30, 2020 USD ($)	Mar. 31, 2020 USD ($)	Dec. 31, 2019 USD ($) shares	Sep. 30, 2019 USD ($)	Jun. 30, 2019 USD ($)	Mar. 31, 2019 USD ($)	Dec. 31, 2020 USD ($) segment $ / shares shares	Dec. 31, 2019 USD ($) $ / shares shares	Dec. 31, 2018 USD ($) shares
Organization and Summary of Significant Accounting Policies [Line Items]
Revenues	$ 25,800,000	$ 57,763,000	$ 21,553,000	$ 13,076,000	$ 54,851,000	$ 21,958,000	$ 17,548,000	$ 8,071,000	$ 118,192,000	$ 102,428,000	$ 84,452,000
Net loss	(40,675,000)	$ (1,508,000)	$ (35,965,000)	$ (42,974,000)	$ 4,501,000	$ (27,361,000)	$ (30,356,000)	$ (42,203,000)	(121,122,000)	$ (95,419,000)	$ (68,889,000)
Goodwill and intangible asset impairment									0
Impairment of long-lived assets held-for-use									0
Letter of credit	$ 1,500,000								$ 1,500,000
Stock options and RSUs outstanding (in shares) \| shares	14,237,871				10,750,550				14,237,871	10,750,550	9,048,793
Number of operating segments \| segment									1
Pfizer SB-525 \| Change in collaboration agreement scope \| Collaborative arrangement
Organization and Summary of Significant Accounting Policies [Line Items]
Revenues									$ 8,900,000	$ 5,700,000
Net loss									$ 8,900,000	$ 5,700,000
Earnings per share, basic (in dollars per share) \| $ / shares									$ 0.06	$ 0.05
Minimum
Organization and Summary of Significant Accounting Policies [Line Items]
Estimated useful lives of related assets									3 years
Maximum
Organization and Summary of Significant Accounting Policies [Line Items]
Estimated useful lives of related assets									5 years

Cash Equivalents and Marketable Securities - Summary of Available-for-Sale Securities by Contractual Maturity (Detail) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Investments, Debt and Equity Securities [Abstract]
Maturing in one year or less	$ 510,094	$ 282,046
Maturing after one year through five years	50,530	21,832
Total	$ 560,624	$ 303,878

Cover - USD ($)	12 Months Ended
Cover - USD ($)	Dec. 31, 2020	Feb. 19, 2021	Jun. 30, 2020
Cover [Abstract]
Document Type	10-K
Document Annual Report	true
Document Period End Date	Dec. 31, 2020
Current Fiscal Year End Date	--12-31
Document Transition Report	false
Entity File Number	000-30171
Entity Registrant Name	SANGAMO THERAPEUTICS, INC.
Entity Incorporation, State or Country Code	DE
Entity Tax Identification Number	68-0359556
Entity Address, Address Line One	7000 Marina Blvd.
Entity Address, City or Town	Brisbane
Entity Address, State or Province	CA
Entity Address, Postal Zip Code	94005
City Area Code	510
Local Phone Number	970-6000
Title of 12(b) Security	Common Stock, par value $0.01 per share
Trading Symbol	SGMO
Security Exchange Name	NASDAQ
Entity Well-known Seasoned Issuer	Yes
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Large Accelerated Filer
Entity Small Business	false
Entity Emerging Growth Company	false
ICFR Auditor Attestation Flag	true
Entity Shell Company	false
Entity Public Float			$ 1,262,431,735
Entity Common Stock, Shares Outstanding		143,251,243
Documents Incorporated by Reference	Certain information required by Part III, Items 10-14 of this Form 10-K is incorporated by reference to the registrant’s definitive Proxy Statement for the 2021 Annual Meeting of Stockholders to be filed with the Securities and Exchange Commission pursuant to Regulation 14A not later than 120 days after the end of the fiscal year covered by this Form 10-K, provided that if such Proxy Statement is not filed within such period, such information will be included in an amendment to this Form 10-K to be filed within such 120-day period.
Amendment Flag	false
Document Fiscal Year Focus	2020
Document Fiscal Period Focus	FY
Entity Central Index Key	0001001233

Stock-Based Compensation (Tables)

12 Months Ended

Dec. 31, 2020

Share-based Payment Arrangement [Abstract]

Stock-Based Compensation Expense

The following table shows total stock-based compensation expense recognized in the accompanying Consolidated Statements of Operations (in thousands):


	Year Ended December 31,
	2020		2019		2018
Research and development	$	13,523	$	10,135	$	8,249
General and administrative	12,185		9,195		6,428
Total stock-based compensation expense	$	25,708	$	19,330	$	14,677

Assumptions Used for Estimating Fair Value of Employee Stock Options

The assumptions used for estimating the fair value of the employee stock options were as follows:


	Year Ended December 31,
	2020	2019	2018
Risk-free interest rate	0.34-0.61%	1.68-2.25%	2.53-2.96%
Expected term (in years)	5.51-5.57	5.50-5.62	5.59-5.61
Expected dividend yield of stock	—	—	—
Expected volatility	77.61-80.32%	76.46-78.39%	72.33-75.49%

Weighted-Average Assumptions Used for Estimating Fair Value of ESPP Purchase Rights

The assumptions used for estimating the fair value of the ESPP purchase rights are as follows:


	Year Ended December 31,
	2020	2019	2018
Risk-free interest rate	1.53-2.80%	1.53-2.42%	2.16-2.80%
Expected term (in years)	0.5-2.0	0.5-2.0	0.5-2.0
Expected dividend yield of stock	—	—	—
Expected volatility	51.02-91.96%	51.02-91.96%	73.21-83.25%

Quarterly Financial Data (Unaudited)

12 Months Ended

Dec. 31, 2020

Quarterly Financial Information Disclosure [Abstract]

Quarterly Financial Data (Unaudited)

QUARTERLY FINANCIAL DATA (UNAUDITED)

The following table sets forth certain unaudited quarterly financial data for the eight quarters ended December 31, 2020. The unaudited information set forth below has been prepared on the same basis as the audited information contained herein and includes all adjustments necessary to present fairly the information set forth. The operating results for any quarter are not indicative of results for any future period. All amounts are in thousands except per share amounts.


	2020								2019
	Q1		Q2		Q3		Q4		Q1		Q2		Q3		Q4
Revenues	$	13,076	$	21,553	$	57,763	$	25,800	$	8,071	$	17,548	$	21,958	$	54,851
Operating expenses	$	57,598	$	59,450	$	61,464	$	69,232	$	51,968	$	51,052	$	51,206	$	53,382
Net (loss) income	$	(42,974)	$	(35,965)	$	(1,508)	$	(40,675)	$	(42,203)	$	(30,356)	$	(27,361)	$	4,501
Net (loss) income attributable to non-controlling interest	$	(61)	$	(36)	$	42	$	(71)	$	(53)	$	(72)	$	(54)	$	(54)
Net (loss) income attributable to Sangamo Therapeutics, Inc.	$	(42,913)	$	(35,929)	$	(1,550)	$	(40,604)	$	(42,150)	$	(30,284)	$	(27,307)	$	4,555
Basic and diluted net (loss) income per share attributable to Sangamo Therapeutics, Inc.	$	(0.37)	$	(0.26)	$	(0.01)	$	(0.29)	$	(0.41)	$	(0.26)	$	(0.24)	$	0.04

Consolidated Balance Sheets (Parenthetical) - $ / shares	Dec. 31, 2020	Dec. 31, 2019
Statement of Financial Position [Abstract]
Preferred stock par value (in dollars per share)	$ 0.01	$ 0.01
Preferred shares authorized (in shares)	5,000,000	5,000,000
Preferred stock issued (in shares)	0	0
Preferred stock outstanding (in shares)	0	0
Common stock, par value (in dollars per share)	$ 0.01	$ 0.01
Common stock, shares authorized (in shares)	320,000,000	320,000,000
Common stock, shares issued (in shares)	142,063,203	115,972,708
Common stock, shares outstanding (in shares)	142,063,203	115,972,708

Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Operating Activities:
Net loss	$ (121,122)	$ (95,419)	$ (68,889)
Adjustments to reconcile net loss to net cash provided by (used in) operating activities:
Depreciation and amortization	5,682	3,930	2,359
Amortization of discount on marketable securities	(825)	(4,708)	(5,829)
Amortization and other changes in right-of-use assets	(7,687)	(5,677)	0
Gain on free shares	(63)	(488)	0
Net loss on disposal of property and equipment	222	68	0
Stock-based compensation	25,708	19,330	14,677
Net loss on lease termination	0	218	0
Build-to-suit leases		0	966
Net changes in operating assets and liabilities:
Interest receivable	(353)	(307)	(135)
Accounts receivable	31,685	(32,236)	(1,330)
Prepaid expenses and other assets	(10,411)	(6,660)	(2,828)
Accounts payable and other accrued liabilities	10,703	(4,192)	(6,372)
Accrued compensation and employee benefits	6,877	4,129	2,604
Deferred revenues	216,546	(35,693)	99,364
Long-term portion of lease liabilities	(3,761)	(1,800)	0
Other non-current liabilities	1,300	3,749	1,963
Net cash provided by (used in) operating activities	169,875	(144,402)	36,550
Investing Activities:
Acquisition, net of cash acquired	0	0	(75,647)
Purchases of marketable securities	(570,779)	(443,711)	(451,239)
Maturities of marketable securities	314,570	404,847	391,845
Purchases of property and equipment	(14,714)	(20,675)	(43,065)
Purchase of additional Sangamo France shares	(704)	(262)	0
Net cash used in investing activities	(271,627)	(59,801)	(178,106)
Financing Activities:
Proceeds from public offering of common stock, net of issuance costs	0	136,308	215,758
Proceeds from issuance of common stock in connection with the Biogen collaboration agreement, net of issuance costs	142,526	0	0
Taxes paid related to net share settlement of equity awards	(765)	(422)	(254)
Proceeds from issuance of common stock under employee stock purchase plan	2,015	2,044	1,484
Proceeds from exercise of stock options and restricted stock units	9,324	4,099	14,721
Net cash provided by financing activities	153,100	142,029	231,709
Effect of exchange rate changes on cash and cash equivalents	(447)	184	439
Net increase (decrease) in cash, cash equivalents, and restricted cash	50,901	(61,990)	90,592
Cash, cash equivalents, and restricted cash, beginning of period	81,928	143,918	53,326
Cash, cash equivalents, and restricted cash, end of period	132,829	81,928	143,918
Supplemental cash flow disclosures:
Non-controlling interest for acquisition	0	0	1,313
Right-of-use assets obtained in exchange for lease obligations	1,333	31,291	0
Property and Equipment
Supplemental cash flow disclosures:
Capital expenditures included in unpaid liabilities	4,569	2,114	4,953
Build-to-Suit Leases
Supplemental cash flow disclosures:
Capital expenditures included in unpaid liabilities	$ 0	$ 0	$ 2,950

Fair Value Measurement - Additional Information (Detail) - USD ($) $ in Thousands		2 Months Ended	12 Months Ended
	Oct. 01, 2018	Nov. 23, 2018	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018	Jul. 20, 2018
Debt Securities, Available-for-sale [Line Items]
Payments to acquire additional interest in subsidiaries			$ 704	$ 262	$ 0
Business acquisition, number of free shares outstanding subject to purchase (in shares)			44,000
TxCell S.A.
Debt Securities, Available-for-sale [Line Items]
Number of ordinary shares acquired (in shares)	13,519,036	11,528,635
TxCell S.A. \| Share Purchase Agreement and Tender Offer Agreement
Debt Securities, Available-for-sale [Line Items]
Number of free shares held by the holders (in shares)						477,000
Business acquisition estimated fair value liabilities of free shares						$ 200
Number of ordinary shares acquired (in shares)			322,000	111,000	25,047,671
Payments to acquire additional interest in subsidiaries			$ 700	$ 300
Increase in fair value of free shares asset and liability			100
Business acquisition estimated fair value assets of free shares			$ 100
TxCell S.A. \| Share Purchase Agreement and Tender Offer Agreement \| Option Pricing Method
Debt Securities, Available-for-sale [Line Items]
Business acquisition estimated fair value liabilities of free shares	$ 200

Cash Equivalents and Marketable Securities (Tables)

12 Months Ended

Dec. 31, 2020

Investments, Debt and Equity Securities [Abstract]

Marketable Securities

The table below summarizes the Company’s cash equivalents and marketable securities (in thousands):


	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses		Estimated Fair Value
December 31, 2020
Cash equivalents:
Money market funds	$	53,165	$	—	$	—	$	53,165

Total	53,165		—		—		53,165
Marketable securities:
Commercial paper	213,500		41		(8)		213,533
Corporate debt securities	59,575		16		(17)		59,574
Certificates of deposit	12,311		—		—		12,311
Asset-backed securities	17,905		10		(7)		17,908
U.S. government-sponsored entity debt securities	257,284		19		(5)		257,298
Total	560,575		86		(37)		560,624
Total cash equivalents and marketable securities	$	613,740	$	86	$	(37)	$	613,789

December 31, 2019
Cash equivalents:
Money market funds	$	30,496	$	—	$	—	$	30,496
Commercial paper	2,998		1		—		2,999
Total	33,494		1		—		33,495
Marketable securities:
Commercial paper	155,230		145		(7)		155,368
Corporate debt securities	94,905		115		(3)		95,017
U.S. government-sponsored entity debt securities	53,411		91		(9)		53,493
Total	303,546		351		(19)		303,878
Total cash equivalents and marketable securities	$	337,040	$	352	$	(19)	$	337,373

Investments Classified by Contractual Maturity Date

The fair value of marketable securities by contractual maturity were as follows (in thousands):


	December 31,
	2020		2019
Maturing in one year or less	$	510,094	$	282,046
Maturing after one year through five years	50,530		21,832
Total	$	560,624	$	303,878

Quarterly Financial Data (Unaudited) (Tables)

12 Months Ended

Dec. 31, 2020

Quarterly Financial Information Disclosure [Abstract]

Summary of Quarterly Financial Data


	2020								2019
	Q1		Q2		Q3		Q4		Q1		Q2		Q3		Q4
Revenues	$	13,076	$	21,553	$	57,763	$	25,800	$	8,071	$	17,548	$	21,958	$	54,851
Operating expenses	$	57,598	$	59,450	$	61,464	$	69,232	$	51,968	$	51,052	$	51,206	$	53,382
Net (loss) income	$	(42,974)	$	(35,965)	$	(1,508)	$	(40,675)	$	(42,203)	$	(30,356)	$	(27,361)	$	4,501
Net (loss) income attributable to non-controlling interest	$	(61)	$	(36)	$	42	$	(71)	$	(53)	$	(72)	$	(54)	$	(54)
Net (loss) income attributable to Sangamo Therapeutics, Inc.	$	(42,913)	$	(35,929)	$	(1,550)	$	(40,604)	$	(42,150)	$	(30,284)	$	(27,307)	$	4,555
Basic and diluted net (loss) income per share attributable to Sangamo Therapeutics, Inc.	$	(0.37)	$	(0.26)	$	(0.01)	$	(0.29)	$	(0.41)	$	(0.26)	$	(0.24)	$	0.04

Employee Benefit Plan	12 Months Ended
Employee Benefit Plan	Dec. 31, 2020
Retirement Benefits [Abstract]
Employee Benefit Plan	EMPLOYEE BENEFIT PLAN The Company sponsors a defined-contribution savings plan under Section 401(k) of the Internal Revenue Code covering all full-time employees (“Sangamo 401(k) Plan”). The Sangamo 401(k) Plan is intended to qualify under Section 401 of the Internal Revenue Code. The Company matched employee contributions equal to 50% for the first 8% in 2020, 2019 and 2018, up to a limit of $4,000 in 2020, 2019 and 2018. Matching funds are fully vested when contributed. Contributions to the Sangamo 401(k) Plan by the Company were $1.2 million, $0.9 million, and $0.8 million for the years ended December 31, 2020, 2019 and 2018, respectively.

- Definition

The entire disclosure for retirement benefits.

+ References

Reference 1: http://www.xbrl.org/2003/role/exampleRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 715
-SubTopic 20
-Section 55
-Paragraph 17
-URI http://asc.fasb.org/extlink&oid=118257860&loc=d3e4179-114921

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 715
-SubTopic 20
-Section S99
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=21916913&loc=d3e273930-122802

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
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-Name Accounting Standards Codification
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-Paragraph 1
-Subparagraph (d)(i)
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Reference 4: http://www.xbrl.org/2003/role/disclosureRef
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Reference 5: http://www.xbrl.org/2003/role/disclosureRef
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-Name Accounting Standards Codification
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-SubTopic 20
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-Paragraph 1
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-URI http://asc.fasb.org/extlink&oid=118255775&loc=d3e1928-114920

Reference 6: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 715
-SubTopic 70
-Section 50
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=49170846&loc=d3e28014-114942

Reference 7: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 715
-URI http://asc.fasb.org/topic&trid=2235017

Reference 8: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
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-SubTopic 60
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-Paragraph 3
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=6414203&loc=d3e39689-114964

Reference 9: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 715
-SubTopic 20
-Section 50
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-Subparagraph (d)(iv)(03)
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Reference 10: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
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-SubTopic 20
-Section 50
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-URI http://asc.fasb.org/extlink&oid=118255775&loc=d3e1928-114920

Reference 11: http://www.xbrl.org/2003/role/disclosureRef
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Reference 12: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
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-Subparagraph (d)(iii)
-URI http://asc.fasb.org/extlink&oid=118255775&loc=d3e1928-114920

Reference 13: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 715
-SubTopic 20
-Section 50
-Paragraph 1
-Subparagraph (l)
-URI http://asc.fasb.org/extlink&oid=118255775&loc=d3e1928-114920

Reference 14: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
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-URI http://asc.fasb.org/extlink&oid=118255775&loc=d3e1928-114920

+ Details

Major Customers, Partnerships and Strategic Alliances (Tables)

12 Months Ended

Dec. 31, 2020

Kite Pharma, Inc. ("Kite")

Research and Development Arrangement, Contract to Perform for Others [Line Items]

Revenues recognized under agreement

Revenues recognized under the agreement were as follows (in thousands):


	Year Ended December 31,
	2020		2019		2018
Revenue related to Kite agreement:
Recognition of license and stand-ready fee	$	25,046	$	24,977	$	18,545
Research services	3,562		9,373		6,972
Total	$	28,608	$	34,350	$	25,517

Pfizer, Giroctocogene Fitelparvovec

Research and Development Arrangement, Contract to Perform for Others [Line Items]

Revenues recognized under agreement

Revenues recognized under the agreement were as follows (in thousands):


	Year Ended December 31,
	2020		2019		2018
Revenue related to Pfizer giroctocogene fitelparvovec agreement:
Recognition of upfront fee and research services	$	3,111	$	15,697	$	37,810
Milestone achievement	31,338		23,662		—
Total	$	34,449	$	39,359	$	37,810

Pfizer C9ORF72

Research and Development Arrangement, Contract to Perform for Others [Line Items]

Revenues recognized under agreement

Revenues recognized under the agreement were as follows (in thousands):


	Year Ended December 31,
	2020		2019		2018
Revenue related to Pfizer C9ORF72 agreement:
Recognition of upfront fee	$	7,985	$	1,827	$	2,188
Milestone achievement	5,000		—		—
Total	$	12,985	$	1,827	$	2,188

During the year ended December 31, 2020, the Company recorded adjustments to revenue related to changes in estimate in connection with the C9ORF72 collaboration agreement with Pfizer. These adjustments were a direct result of the decision to decrease the project scope and the corresponding costs due to advancement of the program, which resulted in an increase in the measure of proportional cumulative performance. These adjustments increased revenue by $8.8 million, decreased net loss by $8.8 million and decreased the Company’s basic net loss per share by $0.06 for the year ended December 31, 2020.

Sanofi

Research and Development Arrangement, Contract to Perform for Others [Line Items]

Revenues recognized under agreement

Revenues recognized under the agreement were as follows (in thousands):


	Year Ended December 31,
	2020		2019		2018
Revenue related to Sanofi agreement:
Recognition of upfront fee	$	298	$	3,494	$	4,013
Research services	4,823		6,367		9,503
Milestone achievement	201		12,819		—
Total	$	5,322	$	22,680	$	13,516

Stock-Based Compensation

12 Months Ended

Dec. 31, 2020

Share-based Payment Arrangement [Abstract]

Stock-Based Compensation

STOCK-BASED COMPENSATION

The following table shows total stock-based compensation expense recognized in the accompanying Consolidated Statements of Operations (in thousands):


	Year Ended December 31,
	2020		2019		2018
Research and development	$	13,523	$	10,135	$	8,249
General and administrative	12,185		9,195		6,428
Total stock-based compensation expense	$	25,708	$	19,330	$	14,677

As of December 31, 2020, total stock-based compensation expense to be recognized in future periods related to unvested stock options was $35.5 million, which is expected to be expensed over a weighted-average period of 2.72 years. As of December 31, 2020, total stock-based compensation expense to be recognized in future periods related to unvested RSUs was $17.1 million, which is expected to be expensed over a weighted-average period of 2.07 years. There was no capitalized stock-based employee compensation expense as of December 31, 2020, 2019 or 2018.

Valuation Assumptions

Employee stock-based compensation expense was determined using the Black-Scholes option valuation model for stock options and employee share purchases under the ESPP. Option valuation models require the input of subjective assumptions and these assumptions can vary over time. The fair value of RSUs was based on the closing price of the underlying common stock on the date of grant.

The Company bases its determination of expected volatility through its assessment of the historical volatility of its common stock. The Company relied on its historical exercise and post-vested termination activity for estimating its expected term for use in determining the fair value of these options.

The weighted-average estimated fair value per share of options granted during 2020, 2019 and 2018 was $5.25, $6.37, and $11.39, respectively, based upon the assumptions used in the Black-Scholes valuation model. The assumptions used for estimating the fair value of the employee stock options were as follows:


	Year Ended December 31,
	2020	2019	2018
Risk-free interest rate	0.34-0.61%	1.68-2.25%	2.53-2.96%
Expected term (in years)	5.51-5.57	5.50-5.62	5.59-5.61
Expected dividend yield of stock	—	—	—
Expected volatility	77.61-80.32%	76.46-78.39%	72.33-75.49%

Employees purchased 274,382, 249,364 and 328,710 shares of common stock through the ESPP at an average exercise price of $7.34, $8.53, and $4.51 per share during 2020, 2019 and 2018, respectively. The weighted-average estimated fair values of shares purchased under the Company’s ESPP during 2020, 2019 and 2018 were $8.02, $4.70 and $7.07, respectively, based upon the assumptions used in the Black-Scholes valuation model.

The assumptions used for estimating the fair value of the ESPP purchase rights are as follows:


	Year Ended December 31,
	2020	2019	2018
Risk-free interest rate	1.53-2.80%	1.53-2.42%	2.16-2.80%
Expected term (in years)	0.5-2.0	0.5-2.0	0.5-2.0
Expected dividend yield of stock	—	—	—
Expected volatility	51.02-91.96%	51.02-91.96%	73.21-83.25%

Organization and Summary of Significant Accounting Policies (Policies)	12 Months Ended
	Dec. 31, 2020
Accounting Policies [Abstract]
Basis of Presentation	Basis of Presentation The accompanying Consolidated Financial Statements have been prepared in conformity with generally accepted accounting principles in the United States of America (“U.S. GAAP”) and include the accounts of the Company and its subsidiaries. All intercompany balances and transactions have been eliminated in the Consolidated Financial Statements. For consolidated entities where the Company owns or is exposed to less than 100% of the economics, the Company records net loss attributable to non-controlling interests on its Consolidated Statements of Operations equal to the percentage of the economic or ownership interest retained in such entities by the respective non-controlling parties.
Use of Estimates	Use of Estimates The preparation of the accompanying Consolidated Financial Statements in conformity with U.S. GAAP requires management to make estimates and assumptions that affect the amounts reported in the Consolidated Financial Statements and the accompanying notes. On an ongoing basis, management evaluates its estimates including critical accounting policies or estimates related to revenue recognition, including the estimated fair value of common shares issued as part of the transaction price, clinical trial accruals, fair value of assets and liabilities, including from acquisitions, and stock-based compensation. Estimates are based on historical experience and on various other market specific and other relevant assumptions that the Company believes to be reasonable under the circumstances, the results of which form the basis for making judgments about the carrying values of assets and liabilities that are not readily apparent from other sources. Actual results could differ from those estimates. During the year ended December 31, 2020, the Company recorded adjustments to revenue related to changes in estimates in connection with the collaboration agreements with Sanofi Genzyme (“Sanofi”) and Pfizer Inc. (“Pfizer”). These changes in estimates were driven by changes in project scope and related project costs which resulted in changes to the measure of proportional cumulative performance. These adjustments increased revenue by $8.9 million, decreased net loss by $8.9 million and decreased the Company’s basic net loss per share by $0.06 for the year ended December 31, 2020. During the year ended December 31, 2019, the Company recorded adjustments to revenue related to a change in estimate in connection with the giroctocogene fitelparvovec collaboration agreement with Pfizer Inc. (“Pfizer”). This change in estimate was driven by changes in project scope and related project costs which resulted in changes to the measure of proportional cumulative performance.
Revenue Recognition	Revenue Recognition The Company accounts for its revenues pursuant to the provisions of Accounting Standards Codification (“ASC”) Topic 606, Revenue from Contracts with Customers (“ASC Topic 606”). The Company’s contract revenues are derived from collaboration agreements including licensing arrangements and research activity grants. Research and licensing agreements typically include upfront signing or license fees, cost reimbursements for research services, minimum sublicense fees, milestone payments and royalties on future licensee’s product sales. The Company has agreements with both fixed and variable consideration. Non-refundable upfront fees and funding of research and development activities are considered fixed, while milestone payments are generally identified as variable consideration. Sangamo’s research grants are typically multi-year agreements and provide for the reimbursement of qualified expenses for research and development as defined under the terms of the grant agreement. Revenues under research grant agreements are generally recognized when the related qualified research expenses are incurred. Deferred revenue primarily represents the portion of research or license payments received but not earned. In determining the appropriate amount of revenue to be recognized as the Company fulfills its obligations under its agreements, the Company performs the following steps: (i) identification of the promised goods or services in the contract; (ii) determination of whether the promised goods or services are performance obligations, including whether they are distinct in the context of the contract; (iii) measurement of the transaction price, including the constraint on variable consideration; (iv) allocation of the transaction price to the performance obligations based on estimated selling prices; and (v) recognition of revenue when (or as) the Company satisfies each performance obligation. A performance obligation is a promise in a contract to transfer a distinct good or service to the customer and is the unit of account in ASC Topic 606. The Company’s performance obligations include license rights, development services and services associated with regulatory submission and approval processes. Revenues from research services earned under collaboration agreements are generally recognized as revenue as the related services are provided. Revenues from non-refundable upfront fees are recognized over time either by measuring progress towards satisfaction of the relevant performance obligation, using the input method (i.e., cumulative actual costs incurred relative to total estimated costs) or on a straight-line basis when a performance obligation is expected to be satisfied evenly over a period of time (or when the entity has a stand-ready obligation). Significant management judgment is required to determine the level of effort required under an arrangement, and the period over which the Company expects to complete its performance obligations under the arrangement, which may include total internal personnel costs and external costs to be incurred as well as, in certain cases, the estimated stand-ready obligation period. Changes in these estimates can have a material effect on revenue recognized. If the Company cannot reasonably estimate when its performance obligations either are completed or become inconsequential, then revenue recognition is deferred until the Company can reasonably make such estimates. The Company includes the unconstrained amount of estimated variable consideration in the transaction price. The amount included in the transaction price is constrained to the amount for which it is probable that a significant reversal of cumulative revenue recognized will not occur. At the end of each subsequent reporting period, the Company re-evaluates the estimated variable consideration included in the transaction price and any related constraint and, if necessary, adjusts its estimate of the overall transaction price. Revenue is then recognized over the remaining estimated period of performance using the cumulative catch-up method. The estimated period of performance and project costs, such as personnel and manufacturing cost, are reviewed quarterly and adjusted, as needed, to reflect the Company’s current assumptions regarding the timing of its deliverables. As part of the accounting for these arrangements, the Company must develop assumptions that require judgment to determine the stand-alone selling price of each performance obligation identified in the contract. The Company uses key assumptions to determine the stand-alone selling price, which may include forecasted revenues, development timelines, reimbursement rates for personnel costs, discount rates and probabilities of technical and regulatory success. Related costs and expenses under these arrangements have historically approximated the revenues recognized. Receivables from collaborations are typically unsecured and are concentrated in the biopharmaceutical industry. Accordingly, the Company may be exposed to credit risk generally associated with biopharmaceutical companies or specific to its collaboration agreements. To date, the Company has not experienced any losses related to these receivables. Funds received from the Company’s collaboration partners are generally not refundable and are recorded as revenue as it fulfills its performance obligations. The Company’s performance obligations are satisfied over time (i.e., stand ready obligations) or using the input method (i.e., cumulative actual costs incurred relative to total estimated costs). Revenue is also recognized when the Company has incurred qualified research and development costs that are reimbursable from its collaboration partners and when there is reasonable assurance that such costs will be reimbursed. Any payments received from a collaboration partner in advance of the completion of the relevant performance obligation are recorded as deferred revenue.
Business Combinations	Business Combinations The Company accounts for acquisitions using the acquisition method of accounting, which requires that assets acquired, including in-process research and development (“IPR&D”) projects, liabilities assumed and any non-controlling interests in the acquired target in an acquisition be recorded at their fair values as of the acquisition date on the Company’s Consolidated Balance Sheets. Any excess of purchase consideration over the fair value of net assets acquired is recorded as goodwill. The determination of estimated fair value requires the Company to make significant estimates and assumptions. As a result, the Company may record adjustments to the fair values of assets acquired and liabilities assumed within the measurement period (up to one year from the acquisition date) with the corresponding offset to goodwill. Transaction costs associated with business combinations are expensed as they are incurred.
Goodwill and Intangible Assets	Goodwill and Intangible AssetsGoodwill represents the excess of the purchase consideration transferred over the estimated fair values of assets acquired and liabilities assumed in a business combination. Intangible assets with indefinite useful lives are related to purchased IPR&D projects and are measured at their respective fair values as of the acquisition date. Goodwill and intangible assets with indefinite useful lives are not amortized. Intangible assets related to IPR&D projects are considered to be indefinite-lived until the completion or abandonment of the associated research and development efforts. If and when development is complete, which generally occurs if and when regulatory approval to market a product is obtained, the associated assets would be deemed finite-lived and would then be amortized based on their respective estimated useful lives at that point in time. The Company tests goodwill and indefinite-lived intangible assets for impairment on an annual basis and between annual tests if the Company becomes aware of any events occurring or changes in circumstances that would indicate the fair values of the assets are below their respective carrying amounts.
Valuation of Long-Lived Assets	Valuation of Long-Lived AssetsLong-lived assets, including property and equipment and finite-lived intangible assets, are reviewed for impairment whenever facts or circumstances either internally or externally may suggest that the carrying value of an asset may not be recoverable. Recoverability of these assets is measured by comparison of the carrying amount of each asset to the future undiscounted cash flows expected to result from the use of the asset and its eventual disposition. If the asset is considered to be impaired, the amount of any impairment is measured as the difference between the carrying value and the fair value of the impaired asset.
Fair Value Measurements	Fair Value Measurements The carrying amounts for financial instruments consisting of cash and cash equivalents, accounts receivable, accounts payable and accrued liabilities approximate fair value due to their short maturities. Marketable securities are stated at their estimated fair values. The free shares asset or liability is measured using a binomial-lattice pricing model and is reviewed each reporting period and adjusted, as needed, and is expected to approximate fair value.
Cash, Cash Equivalents and Restricted Cash	Cash, Cash Equivalents and Restricted CashSangamo considers all highly-liquid investments purchased with original maturities of three months or less at the purchase date to be cash equivalents. Cash and cash equivalents consist of cash, deposits in demand money market accounts, and commercial paper.
Marketable Securities	Marketable Securities Sangamo classifies its marketable securities as available-for-sale and records its investments at estimated fair value based on quoted market prices or observable market inputs of almost identical assets, with the unrealized holding gains and losses included in accumulated other comprehensive loss (“AOCI”). The Company classifies those investments that are not required for use in current operations and that mature in more than 12 months as non-current marketable securities in the accompanying Consolidated Balance Sheets. The Company’s investments are subject to a periodic impairment review. The Company recognizes an impairment charge, if material, when a decline in the fair value of its investments below the cost basis is judged to be other-than-temporary. The Company considers various factors in determining whether to recognize an impairment charge, including the length of time and extent to which the fair value has been less than the Company’s cost basis, the financial condition and near-term prospects of the investee and the Company’s intent and ability to hold the investment for a period of time sufficient to allow for any anticipated recovery in the market value. Realized gains and losses on marketable securities are included in interest and other income, net, which are determined using the specific identification method.
Concentrations of Risk	Concentrations of Credit Risk and Other Risks Cash, cash equivalents, and marketable securities consist of financial instruments that potentially subject the Company to a concentration of credit risk to the extent of the fair value recorded in the Consolidated Balance Sheets. The Company invests cash that is not required for immediate operating needs primarily in highly liquid instruments with high credit ratings which are expected to bear minimal risk. The Company has established policies relating to the quality, diversification, and maturities of securities to enable the Company to manage its credit risk. The Company is exposed to credit risk in the event of a default by the financial institutions holding its cash, cash equivalents, and marketable securities and issuers of investments to the extent recorded on the Consolidated Balance Sheets. Certain materials and key components that the Company utilizes in its operations are obtained through single suppliers. Since the suppliers of key components and materials must be named in an investigational new drug (“IND”) application filed with the U.S. Food and Drug Administration for a product, significant delays can occur if the qualification of a new supplier is required. If delivery of material from the Company’s suppliers was interrupted for any reason, the Company may be unable to supply any of its product candidates for clinical trials.
Property and Equipment	Property and Equipment Property and equipment are stated at cost, less accumulated depreciation and amortization. Depreciation is calculated using the straight-line method based on the estimated useful lives of the related assets which is generally three to five years. For leasehold improvements, amortization is calculated using the straight-line method based on the shorter of the useful life or the lease term. The Company reviews its property and equipment for impairment whenever events or changes in circumstances indicate that the carrying amount of an asset may not be recoverable.
Research and Development Expenses	Research and Development Expenses Research and development expenses consist primarily of personnel costs, including salaries, benefits and stock-based compensation, clinical studies performed by contract research organizations, materials and supplies and overhead allocations consisting of various support and facility-related costs. Research and development costs are expensed as incurred.
General and Administrative Expenses	General and Administrative Expenses General and administrative expenses consist of finance, human resources, legal and other administrative activities. These expenses consist primarily of personnel costs, including salaries, benefits and stock-based compensation, facilities and overhead costs, legal expenses, and other general and administrative costs.
Stock-based Compensation	Stock-based Compensation The Company measures and recognizes compensation expense for all stock-based payment awards made to Sangamo employees and directors, including employee share options, restricted stock units (“RSUs”) and employee stock purchases related to the Employee Stock Purchase Plan (“ESPP”) based on estimated fair values at the award grant date. The fair value of stock-based awards is amortized over the vesting period of the award using a straight-line method. To estimate the fair value of an award, the Company uses the Black-Scholes option pricing model. This model requires inputs such as expected life, expected volatility and risk-free interest rate. These inputs are subjective and generally require significant analysis and judgment to develop. While estimates of expected life and volatility are derived primarily from the Company’s historical data, the risk-free rate is based on the U.S. Treasury yield curve in effect at the time of grant commensurate with the expected life assumption. The Company accounts for forfeitures in the period they occur.
Income Taxes	Income Taxes Income tax expense has been provided using the liability method. Deferred tax assets and liabilities are determined based on the difference between the financial statement and tax bases of assets and liabilities as measured by the enacted tax rates that will be in effect when these differences reverse. The Company provides a valuation allowance against net deferred tax assets if, based upon the available evidence, it is not more likely than not that the deferred tax assets will be realized. The Company recognizes a tax benefit from an uncertain tax position only if it is more likely than not that the tax position will be sustained on examination by the taxing authorities, based on the technical merits of the position. The tax benefits recognized in the Company’s Consolidated Financial Statements from such positions are measured based on the largest benefit that has a greater than 50% likelihood of being realized. The Company recognizes interest and penalties associated with tax matters as part of the income tax provision and includes accrued interest and penalties with the related income tax liability within other accrued liabilities on its Consolidated Balance Sheets.
Leases	Leases The Company adopted the Accounting Standard Update (“ASU”) No. 2016-02, Leases (Topic 842) on January 1, 2019, using the modified retrospective approach with a cumulative-effect adjustment. The Company determines if an arrangement is or contains a lease at inception by assessing whether the arrangement contains an identified asset and whether it has the right to control the identified asset. Right-of-use (“ROU”) assets represent the Company’s right to use an underlying asset for the lease term and lease liabilities represent the Company’s obligation to make lease payments arising from the lease. Lease liabilities are recognized at the lease commencement date based on the present value of future lease payments over the lease term. ROU assets are based on the measurement of the lease liability and also include any lease payments made prior to or on lease commencement and exclude lease incentives and initial direct costs incurred, as applicable. As the implicit rate in the Company’s leases is generally unknown, the Company uses its incremental borrowing rate based on the information available at the lease commencement date in determining the present value of remaining lease payments. The incremental borrowing rate represents an estimate of the interest rate the Company would incur at lease commencement to borrow an amount equal to the lease payments on a collateralized basis over the term of a lease in a similar economic environment. The Company considers its credit risk, term of the lease, and total lease payments and adjusts for the impacts of collateral, as necessary, when calculating its incremental borrowing rates. The lease terms may include options to extend or terminate the lease when it is reasonably certain the Company will exercise any such options. Rent expense for the Company’s operating leases is recognized on a straight-line basis over the lease term. The Company has elected to not separate lease and non-lease components for its real estate and copier leases and, as a result, accounts for any lease and non-lease components as a single lease component. The Company has also elected to not apply the recognition requirement to any leases with a term of 12 months or less and does not include an option to purchase the underlying asset that the Company is reasonably certain to exercise.
Foreign Currency Translation	Foreign Currency Translation The functional currency of the Company’s foreign subsidiaries is primarily the Euro. Assets and liabilities denominated in foreign currencies are translated to U.S. dollars using the exchange rates at the balance sheet date. Foreign currency translation adjustments are recorded as a component of AOCI within stockholders’ equity. Revenues and expenses from the Company’s foreign subsidiaries are translated using the monthly average exchange rates in effect during the period in which the transactions occur. Foreign currency transaction gains and losses are recorded in interest and other income, net, on the Company’s Consolidated Statements of Operations.
Net Loss Per Share	Net Loss Per Share Basic net loss per share attributable to Sangamo Therapeutics, Inc. stockholders has been computed by dividing net loss attributable to Sangamo Therapeutics, Inc. stockholders by the weighted-average number of shares of common stock outstanding during the period. Diluted net loss per share attributable to Sangamo Therapeutics, Inc. stockholders is calculated by dividing net loss attributable to Sangamo Therapeutics, Inc. stockholders by the weighted-average number of shares of common stock plus potentially dilutive securities outstanding during the period. The total number of shares subject to stock options and RSUs outstanding and the ESPP shares reserved for issuance, which are all anti-dilutive, were excluded from consideration in the calculation of diluted net loss per share attributable to Sangamo Therapeutics, Inc. stockholders.
Segments	SegmentsThe Company operates in one segment. Management uses one measure of profitability and does not segregate its business for internal reporting.
Recent Accounting Pronouncements	Recent Accounting Pronouncements Recently Adopted Collaborative Arrangements In November 2018, the FASB issued ASU No. 2018-18, Collaborative Arrangements (ASC Topic 808): Clarifying the Interaction between Topic 808 and Topic 606 (“ASU 2018-18”), which clarifies that certain transactions between participants in a collaborative arrangement should be accounted for under ASC Topic 606 when the counterparty is a customer. In addition, ASU 2018-18 precludes an entity from presenting consideration from a transaction in a collaborative arrangement as revenue from contracts with customers if the counterparty is not a customer for that transaction. ASU 2018-18 is effective for all interim and annual reporting periods beginning after December 15, 2019. On January 1, 2020, the Company adopted ASU 2018-18. The adoption of ASU 2018-18 did not have a material impact on the Company’s Consolidated Financial Statements. Goodwill Impairment Testing In January 2017, the FASB issued ASU No. 2017-04, Intangibles – Goodwill and Other (Topic 350): Simplifying the Test of Goodwill Impairment (“ASU 2017-04”). The new guidance simplifies the subsequent measurement of goodwill by eliminating Step 2 from the goodwill impairment test. ASU 2017-04 requires goodwill impairment to be measured as the amount by which a reporting unit’s carrying amount exceeds its fair value, not to exceed the carrying amount of its goodwill. ASU 2017-04 requires prospective application and is effective for annual periods beginning after December 15, 2019. ASU 2017-04 required the Company to amend its methodology for determining any goodwill impairment beginning in 2020. On January 1, 2020, the Company adopted ASU 2017-04. The adoption of ASU 2017-04 did not have a material impact on the Company’s Consolidated Financial Statements. Credit Losses In June 2016, the FASB issued ASU No. 2016-13, Financial Instruments – Credit Losses (Topic 326) (“ASU 2016-13”). ASU 2016-13 implements an impairment model, known as the current expected credit loss model, that is based on expected losses rather than incurred losses. Under the new guidance, an entity will recognize as an allowance its estimate of expected credit losses. ASU 2016-13 is effective for all interim and annual reporting periods beginning after December 15, 2019 and must be adopted using a modified retrospective approach, with certain exceptions. Early adoption is permitted. On January 1, 2020, the Company adopted ASU 2016-13 by using a modified retrospective approach. The adoption of ASU 2016-13 did not have a material impact on the Company’s Consolidated Financial Statements. Income Taxes In December 2019, the FASB issued ASU No. 2019-12, Income Taxes – Simplifying the Accounting for Income Taxes (“ASU 2019-12”). The guidance removes exceptions to the general principles in Income Taxes (Topic 740) for allocating tax expense between financial statement components, accounting basis differences stemming from an ownership change in foreign investments and interim period income tax accounting for year-to-date losses that exceed projected losses. The guidance becomes effective for annual reporting periods beginning after December 15, 2020 and interim periods within those fiscal years with early adoption permitted. On January 1, 2020, the Company early adopted ASU 2019-12. The adoption of ASU 2019-12 did not have a material impact on the Company's Consolidated Financial Statements. Cloud Computing Arrangements In August 2018, the FASB issued ASU 2018-15, Intangibles-Goodwill and Other-Internal Use Software: Customer’s Accounting for Implementation Costs Incurred in a Cloud Computing Arrangement That Is a Service Contract (“ASU 2018-15”). ASU 2018-15 aligns the requirements for capitalizing implementation costs incurred in a cloud computing arrangement that is a service contract with the requirements for capitalizing implementation costs incurred to develop or obtain internal-use software. The guidance becomes effective for annual reporting periods beginning after December 15, 2019 and interim periods within those fiscal years with early adoption permitted. The Company adopted this standard on January 1, 2020 using the prospective method. The adoption of ASU 2018-15 did not have a material impact on the Company’s Consolidated Financial Statements.

Consolidated Statements of Operations - USD ($) shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Revenues:
Revenues	$ 118,192	$ 102,428	$ 84,452
Operating expenses:
Research and development	180,647	145,922	114,866
General and administrative	67,097	61,686	46,736
Total operating expenses	247,744	207,608	161,602
Loss from operations	(129,552)	(105,180)	(77,150)
Interest and other income, net	8,775	9,761	8,261
Loss before income taxes	(120,777)	(95,419)	(68,889)
Income tax expense	(345)	0	0
Net loss	(121,122)	(95,419)	(68,889)
Net loss attributable to non-controlling interest	(126)	(233)	(555)
Net loss attributable to Sangamo Therapeutics, Inc. stockholders	$ (120,996)	$ (95,186)	$ (68,334)
Basic and diluted net loss per share attributable to Sangamo Therapeutics, Inc. stockholders (in dollars per share)	$ (0.90)	$ (0.85)	$ (0.70)
Shares used in computing basic and diluted net loss per share attributable to Sangamo Therapeutics, Inc. stockholders (in shares)	134,449	112,114	96,941

Stockholders' Equity - Summary of Restricted Stock Unit Activity (Detail) $ in Thousands	12 Months Ended
	Dec. 31, 2020 USD ($) shares
Number of Shares
RSUs outstanding at beginning of period (in shares)	862,850
RSUs awarded (in shares)	2,517,101
RSUs released (in shares)	(324,305)
RSUs forfeited (in shares)	(384,118)
RSUs outstanding at end of period (in shares)	2,671,528
RSUs vested and expected to vest at end of period (in shares)	2,671,528
Weighted-Average Remaining Contractual Term
RSUs outstanding at end of period (in years)	1 year 2 months 8 days
RSUs vested and expected to vest at end of period (in years)	1 year 2 months 8 days
Aggregate Intrinsic Value
RSUs outstanding at end of period \| $	$ 41,689
RSUs vested and expected to vest at end of period \| $	$ 41,689

Income Taxes - Summary of Activity Related to Company's Unrecognized Tax Benefits (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Reconciliation of Unrecognized Tax Benefits, Excluding Amounts Pertaining to Examined Tax Returns [Roll Forward]
Beginning balance	$ 11,630	$ 6,288	$ 5,659
Additions based on tax positions related to the current year	2,834	5,393	636
Additions for tax positions of prior years	1,982	0	0
Reductions for tax positions of prior years	(3,554)	(51)	(7)
Ending balance	$ 12,892	$ 11,630	$ 6,288

Related Party Disclosures	12 Months Ended
Related Party Disclosures	Dec. 31, 2020
Related Party Transactions [Abstract]
Related Party Transaction	RELATED PARTY TRANSACTIONThe Company acquired 185,400 and 52,700 vested free shares from a former executive of Sangamo, pursuant to the exercise of the Free Shares Options for approximately $0.4 million and $0.1 million of cash, during the years ended December 31, 2020 and 2019, respectively.

Stock-Based Compensation - Additional Information (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total compensation cost related to unvested stock options and RSU	$ 35,500,000
Weighted-average period of unvested stock options and RSU	2 years 8 months 19 days
Capitalized stock-based employee compensation expense	$ 0	$ 0	$ 0
Weighted-average estimated fair value per share of options granted (in dollars per share)	$ 5.25	$ 6.37	$ 11.39
Issuance of common stock under employee stock purchase plan (in shares)	274,382	249,364	328,710
Stock issued under employee stock purchase plans, average exercise price (in dollars per share)	$ 7.34	$ 8.53	$ 4.51
Weighted-average estimated fair value of shares purchased under ESPP plan (in dollars per share)	$ 8.02	$ 4.70	$ 7.07
Restricted Stock Units (RSUs)
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total compensation cost related to unvested stock options and RSU	$ 17,100,000
Weighted-average period of unvested stock options and RSU	2 years 25 days

Other Balance Sheet Details (Tables)

12 Months Ended

Dec. 31, 2020

Balance Sheet Related Disclosures [Abstract]

Summary of Property and Equipment, Net

Property and equipment, net consist of the following (in thousands):


	December 31,
	2020		2019
Laboratory equipment	$	24,737	$	17,179
Furniture and fixtures	4,870		4,639
Leasehold improvements	15,953		13,888
Manufacturing equipment	1,089		—
Construction in progress	12,091		5,901
	58,740		41,607
Less: accumulated depreciation and amortization	(17,416)		(11,681)
Property and equipment, net	$	41,324	$	29,926

Schedule of Intangible Assets and Goodwill

The changes in intangible assets were as follows (in thousands):


	December 31,
	2020		2019
Balance at beginning of year	$	53,156	$	54,243

Foreign currency translation adjustment	4,972		(1,087)
Balance at end of year	$	58,128	$	53,156

The changes in goodwill were as follows (in thousands):


	December 31,
	2020		2019
Balance at beginning of year	$	39,273	$	40,044

Foreign currency translation adjustment	3,525		(771)
Balance at end of year	$	42,798	$	39,273

Summary of Accounts Payable and Accrued Liabilities

Other accrued liabilities consist of the following (in thousands):


	December 31,
	2020		2019
Customer advance	$	5,000	$	—
Accrued research and development expenses	4,257		4,102
Operating lease liabilities – current	3,690		3,214
Accrued professional fees	1,532		1,118
Other	4,133		2,451
Total other accrued liabilities	$	18,612	$	10,885

Fair Value Measurement

12 Months Ended

Dec. 31, 2020

Fair Value Disclosures [Abstract]

Fair Value Measurement

FAIR VALUE MEASUREMENT

The Company measures certain assets and liabilities at fair value on a recurring basis, including cash equivalents, marketable securities and the free shares asset. The accounting guidance establishes a three-tier hierarchy, which prioritizes the inputs used in the valuation methodologies in measuring fair value as follows:

Level 1: Unadjusted quoted prices in active markets that are accessible at the measurement date for identical, unrestricted assets or liabilities;

Level 2: Quoted prices in markets that are not active, or inputs which are observable, either directly or indirectly, for substantially the full term of the asset or liability; and

Level 3: Prices or valuation techniques that require inputs that are both significant to the fair value measurement and unobservable (i.e., supported by little or no market activity).

The fair value measurements of the Company’s cash equivalents, marketable securities and the free shares asset are identified at the following levels within the fair value hierarchy (in thousands):


	December 31, 2020
	Fair Value Measurement
	Total		Level 1		Level 2		Level 3
Assets:
Cash equivalents:
Money market funds	$	53,165	$	53,165	$	—	$	—

Total	53,165		53,165		—		—
Marketable securities:
Commercial paper	213,533		—		213,533		—
Corporate debt securities	59,574		—		59,574		—
Certificates of deposit	12,311		—		12,311		—
Asset-backed securities	17,908		—		17,908		—
U.S. government-sponsored entity debt securities	257,298		—		257,298		—
Total	560,624		—		560,624		—
Total cash equivalents and marketable securities	$	613,789	$	53,165	$	560,624	$	—

Free shares asset	$	70	$	—	$	—	$	70


	December 31, 2019
	Fair Value Measurement
	Total		Level 1		Level 2		Level 3
Assets:
Cash equivalents:
Money market funds	$	30,496	$	30,496	$	—	$	—
Commercial paper	2,999		—		2,999		—
Total	33,495		30,496		2,999		—
Marketable securities:
Commercial paper	155,368		—		155,368		—
Corporate debt securities	95,017		—		95,017		—
U.S. government-sponsored entity debt securities	53,493		—		53,493		—
Total	303,878		—		303,878		—
Total cash equivalents and marketable securities	$	337,373	$	30,496	$	306,877	$	—

Free shares asset	$	236	$	—	$	—	$	236

Cash Equivalents and Marketable Securities

The Company generally classifies its marketable securities and some cash equivalents as Level 2. Instruments are classified as Level 2 when observable market prices for identical securities that are traded in less active markets are used. When observable market prices for identical securities are not available, such instruments are priced using benchmark curves, benchmarking of like securities, sector groupings, matrix pricing and valuation models. These valuation models are proprietary to the pricing providers or brokers and incorporate a number of inputs, including in approximate order of priority: benchmark yields, reported trades, broker/dealer quotes, issuer spreads, two-sided markets, benchmark securities, bids, offers and reference data including market research publications. For certain security types, additional inputs may be used, or some of the standard inputs may not be applicable. Evaluators may prioritize inputs differently on any given day for any security based on market conditions, and not all inputs listed are available for use in the evaluation process for each security evaluation on any given day.

Free Shares Asset

As a result of the July 20, 2018 Share Purchase Agreement (“Sangamo France SPA”) to acquire Sangamo France (see Note 5 – Acquisition of Sangamo France), the Company entered into arrangements with the holders of approximately 477,000 “free shares” of Sangamo France pursuant to which the Company has the right to purchase such shares from the holders (a call option) and such holders have the right to sell to the Company such shares from time to time through mid-2021 (a put option). The Company initially recorded a liability of $0.2 million on the acquisition date. The put options were classified within Level 3 of the fair value hierarchy as the Company utilized a binomial-lattice pricing model (the “Monte Carlo simulation model”) that involved certain market conditions to estimate the fair value of the options. The assumptions used in this simulation model are reviewed on a quarterly basis and adjusted, as needed. Subsequent changes in the fair value of the free shares are recorded in general and administrative expenses in the Consolidated Statements of Operations. The Company purchased approximately 111,000 and 322,000 shares during 2019 and 2020 respectively, of the 477,000 total free shares for a cash payment of approximately $0.3 million and $0.7 million respectively, upon exercise of the put options. As of December 31, 2020, approximately 44,000 free shares remain outstanding and subject to purchase by the Company.

The fair value of the free shares’ asset was approximately $0.2 million at December 31, 2019. The Company recognized a gain due to an increase in the fair value of the free shares of approximately $0.1 million for the year ended December 31, 2020, offset by approximately $0.2 million for the shares purchased during the year, resulting in an asset balance of approximately $0.1 million at December 31, 2020.


	December 31,
Free Shares valuation assumptions:	2020			2019
Sangamo stock price (USD)	$	15.61		$	8.68
Sangamo France stock price (EUR)	€	3.85		€	2.14
EUR/ USD exchange rate	0.82			0.91
Estimated correlation Sangamo and Sangamo France stock prices	100.0		%	100.0		%
Sangamo stock price (USD) volatility estimate	88.9		%	72.5		%
Sangamo France stock price (EUR) volatility estimate	88.9		%	72.5		%
EUR/ USD exchange rate volatility estimate	6.3		%	6.6		%
Risk free rate and cost of debt by expected exercise date	Varies			Varies

- Definition

The entire disclosure for the fair value of financial instruments (as defined), including financial assets and financial liabilities (collectively, as defined), and the measurements of those instruments as well as disclosures related to the fair value of non-financial assets and liabilities. Such disclosures about the financial instruments, assets, and liabilities would include: (1) the fair value of the required items together with their carrying amounts (as appropriate); (2) for items for which it is not practicable to estimate fair value, disclosure would include: (a) information pertinent to estimating fair value (including, carrying amount, effective interest rate, and maturity, and (b) the reasons why it is not practicable to estimate fair value; (3) significant concentrations of credit risk including: (a) information about the activity, region, or economic characteristics identifying a concentration, (b) the maximum amount of loss the entity is exposed to based on the gross fair value of the related item, (c) policy for requiring collateral or other security and information as to accessing such collateral or security, and (d) the nature and brief description of such collateral or security; (4) quantitative information about market risks and how such risks are managed; (5) for items measured on both a recurring and nonrecurring basis information regarding the inputs used to develop the fair value measurement; and (6) for items presented in the financial statement for which fair value measurement is elected: (a) information necessary to understand the reasons for the election, (b) discussion of the effect of fair value changes on earnings, (c) a description of [similar groups] items for which the election is made and the relation thereof to the balance sheet, the aggregate carrying value of items included in the balance sheet that are not eligible for the election; (7) all other required (as defined) and desired information.

+ References + Details

Major Customers, Partnerships and Strategic Alliances

12 Months Ended

Dec. 31, 2020

Organization, Consolidation and Presentation of Financial Statements [Abstract]

Major Customers, Partnerships and Strategic Alliances

MAJOR CUSTOMERS, PARTNERSHIPS AND STRATEGIC ALLIANCES

Collaboration Agreements

Novartis Institutes for BioMedical Research, Inc.

On July 27, 2020, the Company entered into a collaboration and license agreement with Novartis Institutes for BioMedical Research, Inc. (“Novartis”) for the research, development and commercialization of gene regulation therapies to treat three neurodevelopmental disorders. Under the agreement, which was effective upon execution, the Company granted Novartis an exclusive, royalty bearing and worldwide license, under its relevant patents and know-how, to develop, manufacture and commercialize certain of its zinc finger protein (“ZFP”) transcription factors (“ZFP-TFs”) targeted to three undisclosed genes that are associated with certain neurodevelopmental disorders, including autism spectrum disorder and intellectual disability. The Company performs early research activities over the collaboration period for each gene target and manufacture the ZPF-TFs required for such research, costs of which will be funded by Novartis. Novartis is responsible for additional research activities, investigational new drug-enabling studies, clinical development, regulatory approvals, manufacturing of preclinical, clinical and approved products, and global commercialization. Subject to certain exceptions set forth in the agreement, the Company is prohibited from developing, manufacturing or commercializing any therapeutic product targeting any of the three genes that are the subject of the collaboration. Novartis also has the option to license certain of the Company’s proprietary adeno-associated viruses (“AAVs”) for the sole purpose of developing, manufacturing and commercializing licensed products arising from the collaboration.

Under the agreement, Novartis paid the Company a $75.0 million upfront license fee in August 2020. In addition to this fee and the cost reimbursements for early research activities, the Company is eligible to earn from Novartis up to $420.0 million in development milestones and up to $300.0 million in commercial milestones. The Company is also eligible to earn from Novartis tiered high single-digit to sub-teen double-digit royalties on potential net commercial sales of licensed products arising from the collaboration. These royalty payments will be subject to reduction due to patent expiration, loss of market exclusivity and payments made under certain licenses for third-party intellectual property. The agreement will continue, on a product-by-product and country-by-country basis, until the expiration of the applicable royalty term. Novartis has the right to terminate the agreement, in its entirety or on a target-by-target basis, for any reason after a specified notice period. Each party also has the right to terminate the agreement on account of the other party’s bankruptcy or material, uncured breach.

All payments received under the agreement, when earned, are non-refundable and non-creditable. The transaction price of $95.1 million includes the upfront license fee of $75.0 million and estimated research costs of $20.1 million for identified research projects over the estimated research period. None of the development and commercial milestones have been included in the transaction price, as all such amounts are fully constrained. As part of its evaluation of the constraint, the Company considered numerous factors, including the fact that achievement of the milestones at this time is uncertain and contingent upon future periods when the uncertainty related to the variable consideration is resolved. The Company will re-evaluate the transaction price, including the estimated variable consideration included in the transaction price and all constrained amounts, in each reporting period and as uncertain events are resolved or other changes in circumstances occur.

The Company assessed the agreement with Novartis in accordance with ASC Topic 606 and concluded that Novartis is a customer. The Company has identified a single performance obligation within this arrangement as a license to the technology and ongoing research services. The Company concluded that the license is not discrete as it does not have stand-alone value to Novartis apart from the research services to be performed pursuant to the agreement. As a result, the Company recognizes revenue from the upfront payment based on proportional performance of the ongoing research services through the estimated research period. The estimation of progress towards the satisfaction of performance obligation and project cost is reviewed quarterly and adjusted, as needed, to reflect the Company’s current assumptions regarding the timing of its performance obligation. As of December 31, 2020, the Company had deferred revenue of $70.9 million related to the upfront license fee received.

The Company recognized $4.1 million of upfront license fee and $1.1 million research reimbursement costs as revenue related to the Novartis agreement during the year ended December 31, 2020.

The Company paid $1.5 million for financial advisory fees related to the Novartis collaboration and license agreement during the year ended December 31, 2020, equal to 2% of $75.0 million received for the upfront license fee related to the collaboration and license agreement with Novartis. The Company recognized this $1.5 million as a contract asset as such amount represents a cost of obtaining the agreement. This balance will be amortized and included in general and administrative costs on a systematic basis consistent with the transfer of the services to Novartis in accordance with ASC Topic 340, Other Assets and Deferred Costs. The Company amortized $0.1 million during the year ended December 31, 2020.

Biogen MA, Inc.

In February 2020, the Company entered into a collaboration and license agreement with Biogen MA, Inc. (“BIMA”) and Biogen International GmbH (together with BIMA, “Biogen”) for the research, development and commercialization of gene

regulation therapies for the treatment of neurological diseases. The Company and Biogen plan to leverage the Company’s proprietary ZFP technology delivered via AAV to modulate expression of key genes involved in neurological diseases. Concurrently with the execution of the collaboration agreement, the Company entered into a stock purchase agreement with BIMA, pursuant to which BIMA agreed to purchase 24,420,157 shares of the Company’s common stock (the “Biogen Shares”), at a price per share of $9.2137, for an aggregate purchase price of approximately $225.0 million.

The collaboration agreement became effective in April 2020 following the termination of the waiting period under the Hart-Scott-Rodino Antitrust Improvements Act of 1976, as amended, and satisfaction of other customary closing conditions, including the payment of $225.0 million for the purchase of the Biogen Shares.

Under the collaboration agreement, Biogen paid the Company an upfront license fee of $125.0 million in May 2020. The Company is also eligible to receive research, development, regulatory and commercial milestone payments that could total up to approximately $2.37 billion if Biogen selects all of the targets allowed under the agreement and all the specified milestones set forth in the agreement are achieved, which includes up to $925.0 million in pre-approval milestone payments and up to $1.45 billion in first commercial sale and other sales-based milestone payments. In addition, the Company is also eligible to receive tiered high single-digit to sub-teen royalties on potential net commercial sales of licensed products arising from the collaboration. These royalty payments are subject to reduction due to patent expiration, entry of biosimilar products to the market and payments made under certain licenses for third-party intellectual property.

Under the collaboration agreement, the Company granted to Biogen an exclusive, royalty bearing and worldwide license, under its relevant patents and know-how, to develop, manufacture and commercialize certain ZFP and/or AAV-based products directed to up to 12 neurological disease gene targets selected by Biogen. Biogen has already selected three of these: ST-501 for tauopathies including Alzheimer’s disease, ST-502 for synucleinopathies including Parkinson’s disease, and a third undisclosed neuromuscular disease target. Biogen has exclusive rights to nominate up to nine additional targets over a target selection period of five years. For each gene target selected by Biogen, the Company performs early research activities, costs for which are shared by the companies, aimed at the development of the combination of proprietary central nervous system delivery vectors and ZFP-TFs (or potential other ZFP products) targeting therapeutically relevant genes. Biogen has assumed responsibility and costs for the IND enabling studies, clinical development, related regulatory interactions, and global commercialization. The Company is responsible for manufacturing activities for the initial clinical trials for the first three products of the collaboration and plans to leverage its in-house manufacturing capacity, where appropriate, which is currently in development. Biogen is responsible for manufacturing activities beyond the first clinical trial for each of the first three products. The Company’s research activities for any targets will be performed over the period not to exceed seven years from the effective date of the agreement (i.e., through April 2027). Subject to certain exceptions set forth in the collaboration agreement, the Company is prohibited from developing, manufacturing or commercializing any therapeutic product directed to the targets selected by Biogen.

The collaboration agreement continues on a product-by-product and country-by-country basis until the expiration of all applicable royalty terms. Biogen has the right to terminate the collaboration agreement, in its entirety or on target-by-target basis, for any reason after a specified notice period, and also has the right to replace up to 10 targets. Each party has the right to terminate this agreement on account of the other party’s bankruptcy or material, uncured breach. In addition, the Company may terminate the collaboration agreement if Biogen challenges any patents licensed by the Company to Biogen.

Pursuant to the terms of the stock purchase agreement, Biogen has agreed not to, without the Company’s prior written consent and subject to specified conditions and exceptions, directly or indirectly acquire shares of the Company’s outstanding common stock, seek or propose a tender or exchange offer or merger between the parties, solicit proxies or consents with respect to any matter, or undertake other specified actions related to the potential acquisition of additional equity interests in the Company. Such standstill restrictions expire on the earlier of the three-year anniversary of the effectiveness of the collaboration agreement and the date that Biogen beneficially owns less than 5% of the Company’s common stock.

The stock purchase agreement also provides that until the first anniversary of the effectiveness of the collaboration agreement, Biogen will hold and not sell any of the Biogen Shares and from the first anniversary through the second anniversary, Biogen will hold and not sell at least 50% of the Biogen Shares, in addition to being subject to certain volume limitations. The stock purchase agreement further provides that, subject to certain limitations, until such time as all remaining Biogen Shares may be sold pursuant to Rule 144 promulgated under the Securities Exchange Act of 1933, as amended, within a 90-day period, Biogen may request the Company to register for resale any of the Biogen Shares on a registration statement to be filed with the Securities and Exchange Commission.

In addition, Biogen has agreed that, excluding specified extraordinary matters, it will vote the Biogen Shares in accordance with the Company’s recommendation and has granted the Company an irrevocable proxy with respect to the foregoing. Such voting provisions expire on the earlier of (i) the two-year anniversary of the effectiveness of the collaboration agreement, (ii) the date that Biogen beneficially owns less than 5% of the Company’s common stock and (iii) the date the

collaboration agreement is terminated; provided, however, that in no event shall such expiration date be prior to the one-year anniversary of the effectiveness of the collaboration agreement.

The Company assessed the collaboration agreement with Biogen in accordance with ASC Topic 606 and concluded that Biogen is a customer. As of December 31, 2020, the transaction price includes the upfront license fee of $125.0 million and the excess consideration from the stock purchase of $79.6 million, which represents the difference between the $225.0 million received for the purchase of the Biogen Shares and the $145.4 million estimated fair value of the equity issued. The equity issued to Biogen was valued using an option pricing model to reflect certain holding period restrictions. None of the target selection fees and clinical or regulatory milestones have been included in the transaction price, as all such amounts are fully constrained. As part of its evaluation of the constraint, the Company considered numerous factors, including the fact that nomination of additional targets and achievement of the milestones at this time is uncertain and contingent upon future periods when the uncertainty related to the variable consideration is resolved. The Company will re-evaluate the transaction price as uncertain events are resolved or other changes in circumstances occur.

The Company has identified a single performance obligation within the Biogen collaboration agreement, which is a stand-ready obligation consisting of a series of distinct days of research services, during which Biogen obtains access to the Company’s license and research resources. Revenue from the upfront license fee relates to access to the license and Company’s obligation to stand-ready to perform such research services corresponding to the targets selected by Biogen. As a result of this obligation to perform research services when and if requested throughout the duration of the contract, the upfront license fee and the excess consideration from the stock purchase will be recognized over time on a straight-line basis consistent with the resources expected to be dedicated to providing the research services through April 2027, the estimated period of the obligation. The estimated period of performance is reviewed quarterly and adjusted, as needed, to reflect the Company’s current assumptions regarding the timing of its deliverable. Revenue from the reimbursement by Biogen of shared costs of early research activities performed by Sangamo is recognized as the research services are performed. As of December 31, 2020, the Company had deferred revenue of $183.2 million related to this agreement.

The Company recognized $21.4 million of upfront license fee and the excess consideration from the stock purchase, and $6.5 million research reimbursement costs as revenue related to the Biogen agreement during the year ended December 31, 2020.

The Company paid $7.0 million for financial advisory fees during the year ended December 31, 2020, equal to 2% of $225.0 million received for the sale of shares and 2% of $125.0 million received for the upfront fee. The fees incurred related to both the collaboration agreement with Biogen and to the stock purchase agreement for the sale of shares. The Company believes that the allocation of fees on a relative fair value basis between the two agreements is reasonable. The Company recognized $4.1 million, which represents 2% of the upfront license fee of $125.0 million and 2% of the excess consideration from the stock purchase of $79.6 million, as a contract asset. This balance will be amortized and included in general and administrative costs on a systematic basis consistent with the transfer of the services to Biogen in accordance with ASC Topic 340, Other Assets and Deferred Costs. The Company amortized $0.4 million during the year ended December 31, 2020. The Company recognized $2.9 million, which represents 2% of the $145.4 million estimated fair value of the equity issued, as a share issuance cost and recorded this amount in equity as reduction in proceeds during the year ended December 31, 2020.

Kite Pharma, Inc.

In February 2018, the Company entered into a global collaboration and license agreement with Kite Pharma, Inc. (“Kite”), which became effective on April 5, 2018, and was amended and restated in September 2019, for the research, development and commercialization of potential engineered cell therapies for cancer. In this collaboration, Sangamo is working together with Kite on a research program under which the companies are designing zinc finger nucleases (“ZFNs”) and viral vectors to disrupt and insert certain genes in T cells and natural killer cells (“NK-cells”) including the insertion of genes that encode chimeric antigen receptors (“CARs”), T cell receptors (“TCRs”), and NK-cell receptors (“NKRs”) directed to mutually agreed targets. Kite is responsible for all clinical development and commercialization of any resulting products.

Subject to the terms of this agreement, the Company granted Kite an exclusive, royalty-bearing, worldwide sublicensable license under the Company’s relevant patents and know-how to develop, manufacture and commercialize, for the purpose of treating cancer, specific cell therapy products that may result from the research program and that are engineered ex vivo using selected ZFNs and viral vectors developed under the research program to express CARs, TCRs or NKRs directed to candidate targets.

During the research program term and subject to certain exceptions, except pursuant to this agreement, the Company is prohibited from researching, developing, manufacturing and commercializing, for the purpose of treating cancer, any cell therapy product that, as a result of ex vivo genome editing, expresses a CAR, TCR or NKR that is directed to a target expressed on or in a human cancer cell. After the research program term concludes and subject to certain exceptions, except pursuant to this agreement, the Company will be prohibited from developing, manufacturing and commercializing, for the purpose of

treating cancer, any cell therapy product that, as a result of ex vivo genome editing, expresses a CAR, TCR or NKR that is directed to a candidate target.

Following the effective date, in April 2018, the Company received a $150.0 million upfront payment from Kite. In addition, Kite will reimburse the Company’s direct costs to conduct service under the joint research program provisions of the agreement, and Kite will be responsible for all subsequent development, manufacturing and commercialization of any licensed products. Sangamo is also eligible to receive contingent development- and sales-based milestone payments that could total up to $3.01 billion if all of the specified milestones in this agreement are achieved. Of this amount, approximately $1.26 billion relates to the achievement of specified research, clinical development, regulatory and first commercial sale milestones, and approximately $1.75 billion relates to the achievement of specified sales-based milestones if annual worldwide net sales of licensed products reach specified levels. Each development- and sales-based milestone payment is payable (i) only once for each licensed product, regardless of the number of times that the associated milestone event is achieved by such licensed product, and (ii) only for the first 10 times that the associated milestone event is achieved, regardless of the number of licensed products that may achieve such milestone event. In addition, the Company will be entitled to receive escalating, tiered royalty payments with a percentage in the single digits based on potential future annual worldwide net sales of licensed products. These royalty payments will be subject to reduction due to patent expiration, entry of biosimilar products to the market and payments made under certain licenses for third-party intellectual property.

The initial research term of the agreement is six years. Kite has an option to extend the research term for up to two additional one-year periods for a separate fee of $10.0 million per year. All contingent payments under the agreement, when earned, will be non-refundable and non-creditable. In connection with the amendment and restatement of the agreement in September 2019, the Company entered into a new research plan with Kite, with estimated reimbursable service costs of approximately $3.4 million. The Company concluded the transaction price under this agreement is $189.3 million and includes the upfront license fee of $150.0 million and $39.3 million estimated reimbursable service costs for identified research projects over the estimated performance period. The Company concluded that the estimated fees for the presumed exercise of the research term extension options and all milestone amounts are fully constrained. As part of its evaluation of the constraint, the Company considered numerous factors, including the fact that achievement of the milestones at this time is uncertain and contingent upon future periods when the uncertainty related to the variable consideration is resolved. The Company will re-evaluate the transaction price, including the estimated variable consideration included in the transaction price and all constrained amounts, in each reporting period and as uncertain events are resolved or other changes in circumstances occur. None of the development and sales-based milestone payments have been included in the transaction price.

The Company assessed the agreement with Kite in accordance with ASC Topic 606 and concluded that Kite is a customer. Kite has the right to terminate this agreement, in its entirety or on a per licensed product or per candidate target basis, for any reason after a specified notice period. Each party has the right to terminate this agreement on account of the other party’s bankruptcy or material, uncured breach.

The Company has identified the primary performance obligations within the Kite agreement as: (1) a license to the technology along with the stand-ready obligation to perform research services, and (2) the ongoing research services. Revenue from the upfront license fee relates to access to the license and Company’s obligation to stand-ready to perform such research services as additional targets are selected by Kite. As a result of this obligation to perform research services when and if requested throughout the duration of the contract, the fee for the license and the stand-ready obligation will be recognized over time on a straight-line basis through June 2024, the estimated period of the stand-ready obligation. Revenue from the reimbursable costs related to the integrated service deliverable is recognized as the research services are performed. Related costs and expenses under these arrangements have historically approximated the revenues recognized. The estimated period of performance is reviewed quarterly and adjusted, as needed, to reflect the Company’s current assumptions regarding the timing of its deliverables. As of December 31, 2020, and 2019 the Company had deferred revenue of $81.4 million and $106.5 million, respectively, related to this agreement.

Revenues recognized under the agreement were as follows (in thousands):


	Year Ended December 31,
	2020		2019		2018
Revenue related to Kite agreement:
Recognition of license and stand-ready fee	$	25,046	$	24,977	$	18,545
Research services	3,562		9,373		6,972
Total	$	28,608	$	34,350	$	25,517

Pfizer Inc.

Giroctocogene Fitelparvovec Global Collaboration and License Agreement

In May 2017, the Company entered into an exclusive, global collaboration and license agreement with Pfizer, pursuant to which it established a collaboration for the research, development and commercialization of giroctocogene fitelparvovec, its gene therapy product candidate for hemophilia A, and closely related products.

Under this agreement, the Company is responsible for conducting the Phase 1/2 clinical trial and certain manufacturing activities for giroctocogene fitelparvovec, while Pfizer is responsible for subsequent worldwide development, manufacturing, marketing and commercialization of giroctocogene fitelparvovec. Sangamo may also collaborate in the research and development of additional AAV based gene therapy products for hemophilia A.

The Company originally received an upfront fee of $70.0 million and is eligible to receive up to $208.5 million in payments upon the achievement of specified clinical development, intellectual property and regulatory milestones and up to $266.5 million in payments upon first commercial sale milestones for giroctocogene fitelparvovec and potentially other products. The total amount of potential clinical development, intellectual property, regulatory, and first commercial sale milestone payments, assuming the achievement of all specified milestones in the giroctocogene fitelparvovec Pfizer agreement, is up to $475.0 million, which includes up to $300.0 million for giroctocogene fitelparvovec and up to $175.0 million for other products that may be developed under the agreement, subject to reduction on account of payments made under certain licenses for third party intellectual property. In addition, Pfizer agreed to pay the Company royalties for each potential licensed product developed under the agreement based on an escalating tiered, double-digit percentage of the annual net sales of such product. These royalties are subject to reduction due to patent expiration, entry of biosimilar products to the market and payment made under certain licenses for third-party intellectual property. To date, two milestones of $55.0 million in aggregate have been achieved and paid, however no products have been approved and therefore no royalty fees have been earned under the giroctocogene fitelparvovec Pfizer agreement.

The Company assessed the agreement with Pfizer in accordance with ASC Topic 606 and concluded that Pfizer is a customer. As of December 31, 2020, the total transaction price under this agreement is $134.0 million, which represents the upfront and research services fees of $79.0 million and two unconstrained milestones achieved of an aggregate amount of $55.0 million. Sangamo is responsible for internal and external research costs as part of the upfront fee and has the ability to request additional reimbursement from Pfizer if certain conditions are met. None of the constrained clinical or regulatory milestones have been included in the transaction price, as all such milestone amounts are fully constrained. As part of its evaluation of the constraint, the Company considered numerous factors, including the fact that achievement of the milestones at this time is uncertain and contingent upon future periods when the uncertainty related to the variable consideration is resolved. The Company will re-evaluate the transaction price, including its estimated variable consideration included in the transaction price and all constrained amounts in each reporting period and as uncertain events are resolved or other changes in circumstances occur.

Subject to the terms of the agreement, the Company granted Pfizer an exclusive worldwide royalty-bearing license, with the right to grant sublicenses, to use certain technology controlled by the Company for the purpose of developing, manufacturing and commercializing giroctocogene fitelparvovec and related products. Pfizer granted the Company a non-exclusive, worldwide, royalty free, fully paid license, with the right to grant sublicenses, to use certain manufacturing technology developed under the agreement and controlled by Pfizer to manufacture the Company’s products that utilize the AAV delivery system. During a specified period, neither the Company nor Pfizer will be permitted to clinically develop or commercialize, outside of the collaboration, certain AAV-based gene therapy products for hemophilia A.

Unless earlier terminated, the agreement has a term that continues on a per product and per country basis until the later of (i) the expiration of patent claims that cover the product in a country, (ii) the expiration of regulatory exclusivity for a product in a country, and (iii) 15 years after the first commercial sale of a product in a country. Pfizer has the right to terminate the agreement without cause in its entirety or on a per product or per country basis. The agreement may also be terminated by either party based on an uncured material breach by the other party or the bankruptcy of the other party. Upon termination for any reason, the license granted by the Company to Pfizer to develop, manufacture and commercialize giroctocogene fitelparvovec and related products will automatically terminate. Upon termination by the Company for cause or by Pfizer in any country or countries, Pfizer will automatically grant the Company an exclusive, royalty-bearing license under certain technology controlled by Pfizer to develop, manufacture and commercialize giroctocogene fitelparvovec in the terminated country or countries.

The Company has identified one performance obligation within the giroctocogene fitelparvovec Pfizer agreement as a license to the technology and ongoing research services. The Company concluded that the license is not discrete, as it does not have stand-alone value to Pfizer apart from the research services to be performed by the Company pursuant to the agreement. As a result, the Company recognizes revenue from the upfront payment based on proportional performance of the ongoing

services through 2020, the estimated period the Company will perform research services. The estimate of progress towards the satisfaction of its performance obligation and project cost is reviewed quarterly and adjusted, as needed, to reflect the Company’s current assumptions regarding the timing of its deliverables. The Company satisfied the deliverables and research services responsibilities within the arrangement which were completed in December 2020. As a result, the Company recognized the remaining deferred revenue from the upfront payment in December 2020. As of December 31, 2019, the Company had deferred revenue of $4.0 million related to this agreement.

In December 2019, the Company entered into an amendment to the collaboration agreement, pursuant to which the Company transferred the IND for giroctocogene fitelparvovec to Pfizer. Upon this transfer the Company achieved a $25.0 million milestone as the conditions for achieving the milestone were met. The cumulative revenue recognized in connection with this milestone was $25.0 million as of December 31, 2020 and included $1.3 million recognized during the year ended December 31, 2020.

In September 2020, the Company determined that there was a high probability of achievement of a $30.0 million milestone with Pfizer for giroctocogene fitelparvovec. The milestone was subsequently achieved upon dosing of the first subject in a Phase 3 clinical trial in early October 2020. The cumulative revenue recognized in connection with this milestone was $30.0 million during the year ended December 31, 2020.

Revenues recognized under the agreement were as follows (in thousands):


	Year Ended December 31,
	2020		2019		2018
Revenue related to Pfizer giroctocogene fitelparvovec agreement:
Recognition of upfront fee and research services	$	3,111	$	15,697	$	37,810
Milestone achievement	31,338		23,662		—
Total	$	34,449	$	39,359	$	37,810

In March 2019, the Company updated its estimated project cost and related revenues under this program. This adjustment was a direct result of the increase in project scope during the first quarter of 2019 and the corresponding costs, which resulted in a decrease in the measure of proportional performance. In December 2019, the Company updated its estimated project cost and related revenues upon transfer of the IND for giroctocogene fitelparvovec to Pfizer. This adjustment was a direct result of the decrease in project scope during the fourth quarter of 2019 and the corresponding costs, which resulted in an increase in the measure of proportional performance. During the year ended December 31, 2019, the Company recognized $15.7 million in revenues related to the Pfizer giroctocogene fitelparvovec agreement, which included approximately $8.7 million acceleration in revenues recorded in the three months ended December 31, 2019 related to the updated estimated project cost, offset by approximately $3.0 million reduction in revenues recorded in the three months ended March 31, 2019 related to the updated estimated project cost.

In March 2020, the Company recorded an adjustment to revenue related to a change in estimate in connection with the giroctocogene fitelparvovec collaboration agreement with Pfizer. This adjustment was a direct result of the decision to decrease the project scope and the corresponding costs, after the successful IND transfer of the giroctocogene fitelparvovec product candidate to Pfizer, both of which resulted in an increase in the measure of proportional cumulative performance. This adjustment increased revenue by $2.4 million, decreased net loss by $2.4 million and decreased the Company’s basic net loss per share by $0.02 for year ended December 31, 2020.

C9ORF72 Research Collaboration and License Agreement

In December 2017, the Company entered into a separate exclusive, global collaboration and license agreement with Pfizer for the development and commercialization of potential gene therapy products that use ZFP-TFs to treat amyotrophic lateral sclerosis (“ALS”) and frontotemporal lobar degeneration (“FTLD”) linked to mutations of the C9ORF72 gene. Pursuant to this agreement, the Company agreed to work with Pfizer on a research program to identify, characterize and preclinically develop ZFP-TFs that bind to and specifically reduce expression of the mutant form of the C9ORF72 gene.

Subject to the terms of this agreement, the Company granted Pfizer an exclusive, royalty-bearing, worldwide license under the Company’s relevant patents and know-how to develop, manufacture and commercialize gene therapy products that use resulting ZFP-TFs that satisfy pre-agreed criteria. During a specified period, neither the Company nor Pfizer will be permitted to research, develop, manufacture or commercialize outside of the collaboration any ZFPs that specifically bind to the C9ORF72 gene.

Unless earlier terminated, the agreement has a term that continues on a per licensed product and per country basis until the later of (i) the expiration of patent claims that cover the licensed product in a country, (ii) the expiration of regulatory exclusivity for a licensed product in a country, and (iii) 15 years after the first commercial sale of a licensed product in a major

market country. Pfizer also has the right to terminate the agreement without cause in its entirety or on a per product or per country basis. The agreement may also be terminated by either party based on an uncured material breach by the other party or the bankruptcy of the other party. The agreement will also terminate if the Company is unable to identify any lead candidates for development within a specified period of time or if Pfizer elects not to advance a lead candidate beyond a certain development milestone within a specified period of time. Upon termination for any reason, the license granted by the Company to Pfizer to develop, manufacture and commercialize licensed products under the agreement will automatically terminate. Upon termination by the Company for cause or by Pfizer without cause for any licensed product or licensed products in any country or countries, the Company will have the right to negotiate with Pfizer to obtain a non-exclusive, royalty-bearing license under certain technology controlled by Pfizer to develop, manufacture and commercialize the licensed product or licensed products in the terminated country or countries.

Following termination by the Company for Pfizer’s material breach, Pfizer will not be permitted to research, develop, manufacture or commercialize ZFPs that specifically bind to the C9ORF72 gene for a period of time. Following termination by Pfizer for the Company’s material breach, the Company will not be permitted to research, develop, manufacture or commercialize ZFPs that specifically bind to the C9ORF72 gene for a period of time.

The Company received a $12.0 million upfront payment from Pfizer and is eligible to receive up to $60.0 million in development milestone payments from Pfizer contingent on the achievement of specified preclinical development, clinical development and first commercial sale milestones, and up to $90.0 million commercial milestone payments if annual worldwide net sales of the licensed products reach specified levels. In addition, Pfizer will pay the Company royalties based on an escalating tiered, mid- to high-single digit percentage of the annual worldwide net sales of the licensed products. These royalty payments are subject to reduction due to patent expiration, entry of biosimilar products to the market and payments made under certain licenses for third party intellectual property. Each party will be responsible for the cost of its performance of the research program. Pfizer will be operationally and financially responsible for subsequent development, manufacturing and commercialization of the licensed products. To date, a milestone of $5.0 million has been achieved and paid, however no products have been approved and therefore no royalty fees have been earned under the C9ORF72 Pfizer agreement.

The Company assessed the agreement with Pfizer in accordance with ASC Topic 606 and concluded that Pfizer is a customer. The Company concluded the total transaction price under this agreement is $17.0 million, which represents the upfront fee of $12.0 million and one unconstrained milestone in the amount of $5.0 million. None of the constrained clinical or regulatory milestones have been included in the transaction price. As part of its evaluation of the constraint, the Company considered numerous factors, including the fact that achievement of the milestones at this time is uncertain and contingent upon future periods when the uncertainty related to the variable consideration is resolved. The Company will re-evaluate the transaction price, including its estimated variable consideration included in the transaction price and all constrained amounts, in each reporting period and as uncertain events are resolved or other changes in circumstances occur.

The Company has identified the performance obligation within this agreement as a license to the technology and ongoing research services. The Company concluded that the license is not discrete as it does not have stand-alone value to Pfizer apart from the services to be performed by the Company pursuant to the agreement. As a result, the Company recognizes revenue from the upfront payment based on proportional performance of the ongoing services over the estimated period the Company will perform research services. The estimation of progress towards the satisfaction of its performance obligation and project cost is reviewed quarterly and adjusted, as needed, to reflect the Company’s current assumptions regarding the timing of its deliverables. The Company satisfied the deliverables and research services responsibilities within the arrangement which were completed in September 2020. As a result, the Company recognized the remaining deferred revenue from the upfront payment in September 2020. As of December 31, 2019, the Company had deferred revenue of $8.0 million related to this agreement.

In September 2020, the Company earned a $5.0 million milestone associated with the completion of the Company’s research activities in its collaboration with Pfizer to develop genome regulation therapies using ZFP-TFs for the treatment of C9ORF72-related ALS and frontotemporal lobar degeneration. This milestone was achieved upon Pfizer’s notification to the Company of its election to pay the first development milestone payment under the collaboration agreement. This milestone payment is non-refundable, and the Company recognized on a cumulative basis $5.0 million for the year ended December 31, 2020.

Revenues recognized under the agreement were as follows (in thousands):


	Year Ended December 31,
	2020		2019		2018
Revenue related to Pfizer C9ORF72 agreement:
Recognition of upfront fee	$	7,985	$	1,827	$	2,188
Milestone achievement	5,000		—		—
Total	$	12,985	$	1,827	$	2,188

Sanofi Genzyme

In January 2014, the Company entered into an exclusive worldwide collaboration and license agreement with Bioverativ Inc., (now Sanofi Genzyme, a global business unit of Sanofi S.A. (“Sanofi”)), to develop therapeutics for hemoglobinopathies, focused on beta thalassemia and sickle cell disease (“SCD”). The agreement was originally signed with BIMA, who subsequently assigned it to Bioverativ Inc., which was later acquired by Sanofi. Under the agreement, the Company is jointly conducting two research programs: the beta thalassemia program and the SCD program. In the beta thalassemia program, the Company is responsible for all discovery, research and development activities through the first human clinical trial. In the SCD program, both parties are responsible for research and development activities through the submission of an IND application for ZFP therapeutics intended to treat SCD.

Under both programs, Sanofi is responsible for subsequent worldwide clinical development, manufacturing and commercialization of licensed products developed under the agreement. At the end of the specified research terms for each program or under certain specified circumstances, Sanofi has the right to step in and take over any of the Company’s remaining activities. Furthermore, the Company has an option to co-promote in the U.S. any licensed products to treat beta thalassemia and SCD developed under the agreement, and Sanofi will compensate the Company for such co-promotion activities. Subject to the terms of the agreement, the Company has granted Sanofi an exclusive, royalty-bearing license, with the right to grant sublicenses, to use certain ZFP and other technology controlled by the Company for the purpose of researching, developing, manufacturing and commercializing licensed products developed under the agreement. The Company also granted Sanofi a non-exclusive worldwide, royalty-free fully paid license with the right to grant sublicenses, under the Company’s interest in certain other intellectual property developed pursuant to the agreement. During the term of the agreement, the Company is not permitted to research, develop, manufacture or commercialize, outside of the agreement, certain gene therapy products that target genes relevant to the licensed products.

Under the agreement, the Company received an upfront license fee of $20.0 million and is eligible to receive up to $115.8 million in payments upon the achievement of specified clinical development and regulatory milestones, as well as up to $160.5 million in payments upon the achievement of specified sales milestones. The total amount of potential regulatory, clinical development, and sales milestone payments, assuming the achievement of all specified milestones in the agreement, is up to $276.3 million. In addition, the Company will receive royalty payments for each licensed product that are a tiered double-digit percentage of annual net sales of each product. Sanofi reimburses Sangamo for agreed upon costs incurred in connection with research and development activities conducted by Sangamo. To date, a $6.0 million milestone has been achieved related to ST-400 for beta thalassemia and another $7.5 million milestone has been achieved related to SCD, however no products have been approved and therefore no royalty fees have been earned under the Sanofi agreement.

The agreement may be terminated by (i) the Company or Sanofi for the uncured material breach of the other party, (ii) the Company or Sanofi for the bankruptcy or other insolvency proceeding of the other party; (iii) Sanofi, upon 180 days’ advance written notice to the Company and (iv) Sanofi, for certain safety reasons upon written notice to, and after consultation with, the Company. As a result, actual future milestone payments could be lower than the amounts stated above.

All contingent payments under the agreement, when earned, will be non-refundable and non-creditable. The transaction price as of December 31, 2020 of $93.3 million includes the upfront license fee of $20.0 million, two unconstrained milestones of $13.5 million and estimated research costs of $59.8 million for identified research projects over the estimated performance period, as all unachieved milestone amounts are fully constrained. As part of its evaluation of the constraint, the Company considered numerous factors, including the fact that achievement of the milestones at this time is uncertain and contingent upon future periods when the uncertainty related to the variable consideration is resolved. The Company will re-

evaluate the transaction price, including the estimated variable consideration included in the transaction price and all constrained amounts, in each reporting period and as uncertain events are resolved or other changes in circumstances occur. None of the constrained clinical or regulatory milestones have been included in the transaction price.

The Company assessed the agreement with Sanofi in accordance with ASC Topic 606 and concluded that Sanofi is a customer. The Company has identified the performance obligations within this arrangement as a license to the technology and ongoing research services activities. The Company concluded that the license is not discrete as it does not have stand-alone value to Sanofi apart from the research services to be performed pursuant to the agreement. As a result, the Company recognizes revenue from the upfront payment based on proportional performance of the ongoing services through 2022, the estimated period the Company will perform research services. The estimate of progress towards the satisfaction of performance obligation and project cost is reviewed quarterly and adjusted, as needed, to reflect the Company’s current assumptions regarding the timing of its deliverables. Revenue from the reimbursable costs related to the integrated service deliverable is recognized as the research services are performed. Related costs and expenses under these arrangements have historically approximated the revenues recognized. As of December 31, 2020 and 2019, the Company had deferred revenue of $1.2 million and $1.7 million, respectively, related to this agreement.

In August 2019, the Company achieved a $6.0 million milestone with Sanofi upon dosing of the third subject in the ST-400 beta thalassemia Phase 1 clinical trial. The cumulative revenue recognized in connection with this milestone was approximately $5.8 million as of December 31, 2020 and included $0.1 million recognized during the year ended December 31, 2020.

In December 2019, the Company achieved a $7.5 million milestone with Sanofi upon dosing of the first subject in the SCD Phase 1 clinical trial. The cumulative revenue recognized in connection with this milestone was approximately $7.2 million as of December 31, 2020 and included $0.1 million recognized during the year ended December 31, 2020.

Revenues recognized under the agreement were as follows (in thousands):


	Year Ended December 31,
	2020		2019		2018
Revenue related to Sanofi agreement:
Recognition of upfront fee	$	298	$	3,494	$	4,013
Research services	4,823		6,367		9,503
Milestone achievement	201		12,819		—
Total	$	5,322	$	22,680	$	13,516

In March 2020, the Company recorded an adjustment to revenue related to a change in estimate in connection with the collaboration agreement with Sanofi. This adjustment was a direct result of the decision in March 2020 to increase the project scope and the corresponding costs, both of which resulted in a decrease in the measure of proportional cumulative performance. This adjustment decreased revenue by $2.2 million, increased net loss by $2.2 million and increased the Company’s basic net loss per share by $0.02 for the year ended December 31, 2020.

California Institute for Regenerative Medicine

In May 2018, the California Institute for Regenerative Medicine (“CIRM”) granted a Strategic Partnership Award for $8.0 million to fund the clinical studies of a potentially curative ZFP therapeutic for the treatment of beta thalassemia based on the application of Sangamo’s ZFN genome editing technology. The grant exists through December 31, 2022 and provides matching funds to support the evaluate ST-400, a gene-edited cell therapy candidate for people with transfusion-dependent beta thalassemia. As of December 31, 2020, the Company had received $5.2 million under the award.

Under the terms of the CIRM grants, the Company is obligated to pay royalties and licensing fees based on a low single digit royalty percentage on net sales of CIRM-funded product candidates or CIRM-funded technology. The Company has the option to decline any and all amounts awarded by CIRM and as an alternative to revenue sharing, the Company has the option to convert the award to a loan. No such election has been made as of the date of the issuance of these Consolidated Financial Statements. In the event that the Company terminates a CIRM-funded clinical trial, it will be obligated to repay the remaining CIRM funds on hand. As of December 31, 2020 and 2019, $6.4 million and $5.7 million, respectively, including accrued interest, related to this award is recorded as a loan in other non-current liabilities on the Consolidated Balance Sheets.

Amended Collaboration and License Agreement with Takeda

In January 2012, the Company entered into a collaboration and license agreement with Shire International GmbH, a wholly-owned subsidiary of Takeda Pharmaceutical Company Limited (“Takeda”), to research, develop and commercialize a ZFP therapeutic for treating Huntington’s disease. The Company received an upfront license fee of $13.0 million in 2012 and

recognized a $1.0 million milestone payment in 2014. Takeda does not have any milestone payment obligations, but is required to pay single digit percentage royalties to the Company, up to a specified maximum cap, on the commercial sales of therapeutic products for Huntington’s disease. The Company is required to pay single digit percentage royalties to Takeda, up to a specified maximum cap, on commercial sales of therapeutic products from programs returned under the original agreement (which include blood clotting Factors VIII and IX) that use two zinc fingers.

Pursuant to the agreement, the Company granted Takeda an exclusive, world-wide, royalty-bearing license, with the right to grant sublicenses, to use the Company’s ZFP technology for the purpose of developing and commercializing human therapeutic and diagnostic products for the huntingtin gene (“HTT gene”). During the term of the agreement, the Company is not permitted to research, develop or commercialize, outside of the agreement, certain products that target the HTT gene. The agreement may be terminated by (i) the Company or Takeda, in whole or in part, for the uncured material breach of the other party, (ii) the Company or Takeda for the bankruptcy or other insolvency proceeding of the other party and (iii) Takeda, in its entirety, effective upon at least 90 days’ advance written notice.

The Company assessed the agreement with Takeda in accordance with ASC Topic 606 and concluded that Takeda is a customer. The Company has concluded that the license is not a separate unit of accounting as it does not have stand-alone value to Takeda apart from the research services to be performed pursuant to the Takeda agreement. The Company satisfied the deliverables and research services responsibilities within the amended arrangement which were completed in 2017. As a result, the Company recognized the remaining $2.3 million of deferred revenue from the upfront payment during the year ended December 31, 2017.

The Company did not recognize any revenues under the Takeda agreement for the years ended December 31, 2020, 2019 and 2018.

Agreement with Sigma-Aldrich Corporation

In 2007, Sangamo entered into a license agreement with Sigma-Aldrich Corporation (“Sigma”) to provide Sigma with access to Sangamo’s proprietary ZFP technology and the exclusive right to use the technology to develop and commercialize research reagent products and services in the research field, excluding certain agricultural research uses that Sangamo previously licensed to Dow AgroSciences LLC (“DAS”), a wholly-owned subsidiary of Dow Chemical Company. Sangamo developed laboratory research reagents using its ZFP technology over a three-year research services period. Sangamo has since transferred the ZFP manufacturing technology to Sigma.

In October 2009, Sangamo expanded its license agreement with Sigma. In addition to the original terms of the license agreement, Sigma received exclusive rights to develop and distribute ZFP-modified cell lines for commercial production of protein pharmaceuticals and certain ZFP-engineered transgenic animals for commercial applications. Under the terms of the agreement, Sigma made an upfront cash payment of $20.0 million consisting of a $4.9 million purchase of 636,133 shares of Sangamo common stock, valued at $4.9 million, and a $15.1 million upfront license fee. Sangamo is also eligible to receive commercial license fees of $5.0 million based upon a percentage of net sales and sublicensing revenue and thereafter a reduced royalty rate of 10.5% of net sales and sublicensing revenue. In addition, upon the achievement of certain cumulative commercial milestones, Sigma will make milestone payments to Sangamo up to an aggregate of $25.0 million. Sangamo does not have additional ongoing performance obligations under the agreement.

Revenues recognized under the agreement with Sigma for the years ended December 31, 2020, 2019 and 2018, were $0.5 million, $0.6 million and $0.5 million, respectively.

Agreement with DAS

In 2005, Sangamo entered into an exclusive commercial license with DAS, with an initial three-year research term. Under this agreement, Sangamo is providing DAS with access to its proprietary ZFP technology and the exclusive right to use the technology to modify the genomes or alter the nucleic acid or protein expression of plant cells, plants, or plant cell cultures. Sangamo has retained rights to use plants or plant-derived products to deliver ZFP-TFs or ZFNs into humans or animals for diagnostic, therapeutic or prophylactic purposes. In 2008, DAS exercised its option and obtained a commercial license to sell products incorporating or derived from plant cells generated using the Company’s ZFP technology. The exercise of the option triggered a one-time commercial license fee of $6.0 million, payment of the remaining $2.3 million of the previously agreed upon $4.0 million in research milestones, development and commercialization milestone payments for each product, and royalties on sales of products. Furthermore, DAS has the right to sublicense Sangamo’s ZFP technology to third parties for use in plant cells, plants, or plant cell cultures, and Sangamo will be entitled to 25% of any cash consideration received by DAS under such sublicenses. In December 2010, the Company amended its agreement with DAS to extend the period of reagent manufacturing services and research services through December 31, 2012.

The agreement with DAS also provides for minimum sublicense fees each year due to Sangamo every October, provided the agreement is not terminated by DAS. Annual fees range from $0.3 million to $3.0 million and total $25.3 million

over 11 years. The Company has identified the performance obligation within this arrangement as a license to the technology. In the event of any termination of the agreement, all rights to use the Company’s ZFP technology will revert to Sangamo, and DAS will no longer be permitted to practice Sangamo’s ZFP technology or to develop or, except in limited circumstances, commercialize any products derived from the Company’s ZFP technology.

Revenues under the agreement with DAS were $3.0 million, $3.0 million, and $3.0 million during 2020, 2019 and 2018, respectively.

Stock-Based Compensation - Stock-Based Compensation Expense (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Total stock-based compensation expense	$ 25,708	$ 19,330	$ 14,677
Research and development
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Total stock-based compensation expense	13,523	10,135	8,249
General and administrative
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Total stock-based compensation expense	$ 12,185	$ 9,195	$ 6,428

Major Customers, Partnerships and Strategic Alliances - Agreement with Sigma-Aldrich Corporation (Detail) - USD ($) $ in Thousands	1 Months Ended	3 Months Ended								12 Months Ended
	Oct. 31, 2009	Dec. 31, 2020	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2007
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Common stock issued										$ 142,526	$ 136,308	$ 215,758
Revenues		$ 25,800	$ 57,763	$ 21,553	$ 13,076	$ 54,851	$ 21,958	$ 17,548	$ 8,071	118,192	102,428	84,452
Sigma-Aldrich Corporation
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Developed laboratory research reagents, research services period													3 years
Deferred revenue	$ 20,000
Common stock issued	$ 4,900
Public offering, common stock shares issued	636,133
Reduced royalty rate	10.50%
Development and sales-based milestone payments to be received	$ 25,000
Revenues										$ 500	$ 600	$ 500
Sigma-Aldrich Corporation \| License agreement terms
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Revenues under agreement	5,000
Sigma-Aldrich Corporation \| License fee revenues
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Deferred revenue	$ 15,100

Commitments and Contingencies (Tables)

12 Months Ended

Dec. 31, 2020

Commitments and Contingencies Disclosure [Abstract]

Lessee, Operating Lease, Liability, Maturity

Future minimum payments under lease obligations at December 31, 2020 consist of the following (in thousands):


	Total
2021	$	6,191
2022	6,756
2023	6,851
2024	6,995
2025	7,058
Thereafter	19,571
Total lease payments	53,422
Less:
Imputed interest	(11,336)
Total	$	42,086

Reported as of December 31, 2020:
Operating lease liabilities - current (included in Other accrued liabilities on the Consolidated Balance Sheet)	$	3,690
Operating lease liabilities - long-term	38,396
Total	$	42,086

Other Commitments

The following table sets forth the non-cancelable material contractual commitments under manufacturing-related supplier arrangements as of December 31, 2020 (in thousands):

Party

Total commitments

Expiry date

Brammer Bio MA - a Thermo Fisher Scientific Inc. subsidiary

7,736

December 2022

Lonza Netherlands, B.V.

13,771

December 2022

Total contractual commitments

21,507

Stockholders' Equity - Summary of Stock Option Activity (Detail) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2020 USD ($) $ / shares shares
Number of Shares
Options outstanding at beginning of period (in shares) \| shares	9,829,287
Options granted (in shares) \| shares	4,563,425
Options exercised (in shares) \| shares	(1,162,268)
Options canceled (in shares) \| shares	(1,751,746)
Options outstanding at end of period (in shares) \| shares	11,478,698
Options vested and expected to vest at end of period (in shares) \| shares	11,478,698
Options exercisable at end of period (in shares) \| shares	5,127,517
Weighted- Average Exercise per Share Price
Options outstanding at beginning of period (in dollars per share) \| $ / shares	$ 10.71
Options granted (in dollars per share) \| $ / shares	8.09
Options exercised (in dollars per share) \| $ / shares	8.02
Options canceled (in dollars per share) \| $ / shares	10.19
Options outstanding at end of period (in dollars per share) \| $ / shares	10.02
Options vested and expected to vest at end of period (in dollars per share) \| $ / shares	10.02
Options exercisable at end of period (in dollars per share) \| $ / shares	$ 10.71
Weighted-Average Remaining Contractual Term
Options outstanding at end of period (in years)	7 years 9 months 18 days
Options vested and expected to vest at end of period (in years)	7 years 9 months 18 days
Options exercisable at end of period (in years)	6 years 5 months 23 days
Aggregate Intrinsic Value
Options outstanding at end of period \| $	$ 69,616
Options vested and expected to vest at end of period \| $	69,616
Options exercisable at end of period \| $	$ 29,025

Acquisition of Acquisition of Sangamo France (Tables)

12 Months Ended

Dec. 31, 2020

Business Combinations [Abstract]

Summary of Non-controlling Interest

Non-controlling interest as of December 31, 2020 was as follows (in thousands):


	Total






Balance at beginning of year	$	185
Fair value of additional shares acquired	(927)
Loss attributable to non-controlling interest	(126)
Balance at end of year	$	(868)

Consolidated Statements of Stockholders' Equity - USD ($) $ in Thousands	Total	Cumulative Effect, Period of Adoption, Adjustment	Common Stock	Additional Paid-in Capital	Accumulated Deficit	Accumulated Deficit Cumulative Effect, Period of Adoption, Adjustment	Accumulated Other Comprehensive Income (Loss)	Non- Controlling Interest
Beginning Balances (in shares) at Dec. 31, 2017			85,598,534
Beginning Balances at Dec. 31, 2017	$ 187,900	$ 1,117	$ 856	$ 682,809	$ (495,479)	$ 1,117	$ (286)	$ 0
Issuance of common stock upon exercise of stock options and in connection with restricted stock units, net of tax (in shares)			2,103,727
Issuance of common stock upon exercise of stock options and in connection with restricted stock units, net of tax	$ 14,467		$ 20	14,447
Issuance of common stock under employee stock purchase plan (in shares)	328,710		328,710
Issuance of common stock under employee stock purchase plan	$ 1,484		$ 4	1,480
Issuance of common stock, net of issuance costs (in shares)			14,156,500
Issuance of common stock under public offering, net of issuance costs	215,758		$ 142	215,616
Stock-based compensation	14,677			14,677
Acquisition of additional shares of Sangamo France	603			603
Non-controlling interest upon acquisition of Sangamo France	1,313							1,313
Foreign currency translation adjustment	(1,148)						(1,129)	(19)
Net pension losses	(21)						(21)
Net unrealized loss on marketable securities, net of tax	(4)						(4)
Net loss	(68,889)				(68,334)			(555)
Ending Balances (in shares) at Dec. 31, 2018			102,187,471
Ending Balances at Dec. 31, 2018	$ 367,257	$ 897	$ 1,022	929,632	(562,696)	$ 897	(1,440)	739
Accounting Standards Update [Extensible List]	us-gaap:AccountingStandardsUpdate201409Member
Issuance of common stock upon exercise of stock options and in connection with restricted stock units, net of tax (in shares)			885,873
Issuance of common stock upon exercise of stock options and in connection with restricted stock units, net of tax	$ 3,677		$ 9	3,668
Issuance of common stock under employee stock purchase plan (in shares)	249,364		249,364
Issuance of common stock under employee stock purchase plan	$ 2,044		$ 2	2,042
Issuance of common stock, net of issuance costs (in shares)			12,650,000
Issuance of common stock under public offering, net of issuance costs	136,308		$ 127	136,181
Stock-based compensation	19,330			19,330
Acquisition of additional shares of Sangamo France	(321)							(321)
Issuance costs related to Sangamo France acquisition	(25)			(25)
Foreign currency translation adjustment	(1,573)						(1,573)
Net pension losses	(28)						(28)
Net unrealized loss on marketable securities, net of tax	592						592
Net loss	$ (95,419)				(95,186)			(233)
Ending Balances (in shares) at Dec. 31, 2019	115,972,708		115,972,708
Ending Balances at Dec. 31, 2019	$ 432,739		$ 1,160	1,090,828	(656,985)		(2,449)	185
Accounting Standards Update [Extensible List]	us-gaap:AccountingStandardsUpdate201801Member
Issuance of common stock upon exercise of stock options and in connection with restricted stock units, net of tax (in shares)			1,395,956
Issuance of common stock upon exercise of stock options and in connection with restricted stock units, net of tax	$ 8,559		$ 14	8,545
Issuance of common stock under employee stock purchase plan (in shares)	274,382		274,382
Issuance of common stock under employee stock purchase plan	$ 2,015		$ 3	2,012
Issuance of common stock, net of issuance costs (in shares)			24,420,157
Issuance of common stock under public offering, net of issuance costs	142,526		$ 244	142,282
Stock-based compensation	25,708			25,708
Acquisition of additional shares of Sangamo France	(927)							(927)
Foreign currency translation adjustment	8,345						(8,345)
Net pension losses	(193)						(193)
Net unrealized loss on marketable securities, net of tax	(284)						(284)
Net loss	$ (121,122)				(120,996)			(126)
Ending Balances (in shares) at Dec. 31, 2020	142,063,203		142,063,203
Ending Balances at Dec. 31, 2020	$ 497,366		$ 1,421	$ 1,269,375	$ (777,981)		$ 5,419	$ (868)

Cash Equivalents and Marketable Securities - Summary of Cash Equivalents and Available-for-Sale Securities (Detail) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Debt Securities, Available-for-sale [Line Items]
Cash and cash equivalents, at carrying value, total	$ 131,329	$ 80,428
Available-for-sale securities, amortized cost	560,575	303,546
Available-for-sale securities, gross unrealized gains	86	351
Available-for-sale securities, gross unrealized (Losses)	(37)	(19)
Available-for-sale securities, estimated fair value	560,624	303,878
Total cash equivalents and available-for-sale securities, amortized cost	613,740	337,040
Total cash equivalents and available-for-sale securities, gross unrealized gains	86	352
Total cash equivalents and available-for-sale securities, gross unrealized (losses)	(37)	(19)
Total cash equivalents and available-for-sale securities, estimated fair value	613,789	337,373
Money market funds
Debt Securities, Available-for-sale [Line Items]
Cash and cash equivalents, at carrying value, total	53,165	30,496
Cash equivalents, gross unrealized gains	0	0
Cash and cash equivalents accumulated gross unrealized loss before tax	0	0
Cash equivalents, estimated fair value	53,165	30,496
Commercial paper
Debt Securities, Available-for-sale [Line Items]
Cash and cash equivalents, at carrying value, total		2,998
Cash equivalents, gross unrealized gains		1
Cash and cash equivalents accumulated gross unrealized loss before tax		0
Cash equivalents, estimated fair value		2,999
Available-for-sale securities, amortized cost	213,500	155,230
Available-for-sale securities, gross unrealized gains	41	145
Available-for-sale securities, gross unrealized (Losses)	(8)	(7)
Available-for-sale securities, estimated fair value	213,533	155,368
Cash equivalents:
Debt Securities, Available-for-sale [Line Items]
Cash and cash equivalents, at carrying value, total	53,165	33,494
Cash equivalents, gross unrealized gains	0	1
Cash and cash equivalents accumulated gross unrealized loss before tax	0	0
Cash equivalents, estimated fair value	53,165	33,495
Corporate debt securities
Debt Securities, Available-for-sale [Line Items]
Available-for-sale securities, amortized cost	59,575	94,905
Available-for-sale securities, gross unrealized gains	16	115
Available-for-sale securities, gross unrealized (Losses)	(17)	(3)
Available-for-sale securities, estimated fair value	59,574	95,017
Certificates of deposit
Debt Securities, Available-for-sale [Line Items]
Available-for-sale securities, amortized cost	12,311
Available-for-sale securities, gross unrealized gains	0
Available-for-sale securities, gross unrealized (Losses)	0
Available-for-sale securities, estimated fair value	12,311
U.S. government-sponsored entity debt securities
Debt Securities, Available-for-sale [Line Items]
Available-for-sale securities, amortized cost	257,284	53,411
Available-for-sale securities, gross unrealized gains	19	91
Available-for-sale securities, gross unrealized (Losses)	(5)	(9)
Available-for-sale securities, estimated fair value	257,298	$ 53,493
Asset-backed securities
Debt Securities, Available-for-sale [Line Items]
Available-for-sale securities, amortized cost	17,905
Available-for-sale securities, gross unrealized gains	10
Available-for-sale securities, gross unrealized (Losses)	(7)
Available-for-sale securities, estimated fair value	$ 17,908

Income Taxes (Tables)

12 Months Ended

Dec. 31, 2020

Income Tax Disclosure [Abstract]

Summary of Domestic and Foreign Components of Loss Before Income Taxes

The domestic and foreign components of loss before income taxes were as follows (in thousands):


	Year Ended December 31,
	2020		2019		2018
Domestic	$	(126,624)	$	(77,354)	$	(65,695)
Foreign	5,847		(18,065)		(3,194)
Loss before income taxes	$	(120,777)	$	(95,419)	$	(68,889)

Summary of Benefit for Income Taxes

The income tax expense consisted of the following (in thousands):


	Year Ended December 31,
	2020		2019		2018
Income tax expense:
Current:
Federal	$	—	$	—	$	—
State	133		—		—
Foreign	686		—		—
Subtotal	819		—		—
Deferred:
Federal	—		—		—
State	—		—		—
Foreign	(474)		—		—
Subtotal	(474)		—		—
Income tax expense	$	345	$	—	$	—

Schedule of Difference Between Benefit for Income Taxes and Federal Statutory Income Tax Rate

The difference between the income tax expense and the amount computed by applying the federal statutory income tax rate to loss before income taxes is explained as follows (in thousands):


	Year Ended December 31,
	2020		2019		2018
Tax at federal statutory rate	$	(25,363)	$	(20,038)	$	(14,467)
State taxes, net	(3,168)		(9,597)		(2,849)
Foreign rate differential	376		(665)		(177)
Global Intangible Low-Taxed Income	1,335		—		—
Non-deductible stock-based compensation	4,232		2,817		(2,729)
Research credits	(3,657)		(3,429)		(1,005)
Change in valuation allowance	26,537		29,655		20,271
Other	53		1,257		956
Income tax expense	$	345	$	—	$	—

Schedule of Company's Deferred Tax Assets

Significant components of the Company’s deferred tax assets and liabilities are as follows (in thousands):


	December 31,
	2020		2019
Assets:
Deferred tax assets:
Net operating loss carryforwards	$	164,276	$	133,765
Research and development tax credit carryforwards	27,679		21,459
Stock-based compensation	5,321		4,194
Deferred revenue	20,681		32,171
Fixed assets	10,525		11,282
Lease liability	10,251		11,722
Accruals and reserves	430		675
Other	308		151
Total deferred tax asset	239,471		215,419
Valuation allowance	214,351		187,724
Deferred tax assets	25,120		27,695
Liabilities:
Intangible assets	(14,321)		(13,609)
Operating lease right-of-use assets	(17,510)		(20,656)
Deferred tax liabilities	(31,831)		(34,265)
Total net deferred tax liabilities	$	(6,711)	$	(6,570)

The deferred tax assets and liabilities based on tax jurisdictions are presented on the Consolidated Balance Sheet as follows (in thousands):


	December 31,
	2020		2019
Deferred tax assets (included in Other non-current assets on the Consolidated Balance Sheet)	$	474	$	—
Deferred tax liabilities	(7,185)		(6,570)
Net deferred tax liabilities	$	(6,711)	$	(6,570)

Summary of Activity Related to Company's Unrecognized Tax Benefits

The following table summarizes the activity related to the Company’s unrecognized tax benefits (in thousands):


	December 31,
	2020		2019		2018
Beginning balance	$	11,630	$	6,288	$	5,659
Additions based on tax positions related to the current year	2,834		5,393		636
Additions for tax positions of prior years	1,982		—		—
Reductions for tax positions of prior years	(3,554)		(51)		(7)
Ending balance	$	12,892	$	11,630	$	6,288

Cash Equivalents and Marketable Securities - Additional Information (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Investments, Debt and Equity Securities [Abstract]
Realized losses of available-for-sale securities	$ 0	$ 0	$ 0
Investments other-than-temporarily impaired	$ 0	$ 0

Income Taxes - Summary of Domestic and Foreign Components of Loss Before Income Taxes (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Income Tax Disclosure [Abstract]
Domestic	$ (126,624)	$ (77,354)	$ (65,695)
Foreign	5,847	(18,065)	(3,194)
Loss before income taxes	$ (120,777)	$ (95,419)	$ (68,889)

- Definition

Amount of income (loss) from continuing operations, including income (loss) from equity method investments, before deduction of income tax expense (benefit), and income (loss) attributable to noncontrolling interest.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
-SubTopic 10
-Section 50
-Paragraph 32
-Subparagraph (c)
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Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
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-Section 50
-Paragraph 30
-Subparagraph (b)
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Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
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-Section 50
-Paragraph 32
-Subparagraph (f)
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Reference 4: http://fasb.org/us-gaap/role/ref/legacyRef
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-Section 25
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-URI http://asc.fasb.org/extlink&oid=68072869&loc=d3e41242-110953

Reference 5: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
-SubTopic 10
-Section 50
-Paragraph 22
-URI http://asc.fasb.org/extlink&oid=120311839&loc=d3e8736-108599

Reference 6: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 220
-SubTopic 10
-Section S99
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Reference 7: http://fasb.org/us-gaap/role/ref/legacyRef
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-Topic 944
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-Section S99
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-Subparagraph (SX 210.7-04(8))
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Reference 8: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 235
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-05(b)(2))
-URI http://asc.fasb.org/extlink&oid=120399901&loc=d3e537907-122884

Reference 9: http://www.xbrl.org/2003/role/exampleRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
-SubTopic 10
-Section 50
-Paragraph 31
-URI http://asc.fasb.org/extlink&oid=120311839&loc=d3e8924-108599

Reference 10: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 220
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-04(15))
-URI http://asc.fasb.org/extlink&oid=120399700&loc=SL114874048-224260

+ Details

Organization and Summary of Significant Accounting Policies - Reconciliation of Cash and Cash Equivalents (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Cash and cash equivalents	$ 131,329	$ 80,428	$ 140,418
Non-current restricted cash	1,500	1,500	3,500
Cash, cash equivalents and restricted cash as reported within the Consolidated Statements of Cash Flows	$ 132,829	$ 81,928	$ 143,918	$ 53,326

Other Balance Sheet Details - Schedule of Intangible Assets and Goodwill (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Intangible Assets (Excluding Goodwill)
Balance at beginning of year	$ 53,156	$ 54,243
Foreign currency translation adjustment	4,972	(1,087)
Balance at end of year	58,128	53,156
Goodwill
Goodwill, beginning balance	39,273	40,044
Foreign currency translation adjustment	3,525	(771)
Goodwill, ending balance	$ 42,798	$ 39,273

Stock-Based Compensation - Assumptions Used for Estimating Fair Value of Employee Stock Options (Detail) - Employee Stock Options	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected dividend yield of stock	0.00%	0.00%	0.00%
Minimum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Risk-free interest rate	0.34%	1.68%	2.53%
Expected term (in years)	5 years 6 months 3 days	5 years 6 months	5 years 7 months 2 days
Expected volatility	77.61%	76.46%	72.33%
Maximum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Risk-free interest rate	0.61%	2.25%	2.96%
Expected term (in years)	5 years 6 months 25 days	5 years 7 months 13 days	5 years 7 months 9 days
Expected volatility	80.32%	78.39%	75.49%

Cash Equivalents and Marketable Securities

12 Months Ended

Dec. 31, 2020

Investments, Debt and Equity Securities [Abstract]

Cash Equivalents and Marketable Securities

CASH EQUIVALENTS AND MARKETABLE SECURITIES

The table below summarizes the Company’s cash equivalents and marketable securities (in thousands):


	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses		Estimated Fair Value
December 31, 2020
Cash equivalents:
Money market funds	$	53,165	$	—	$	—	$	53,165

Total	53,165		—		—		53,165
Marketable securities:
Commercial paper	213,500		41		(8)		213,533
Corporate debt securities	59,575		16		(17)		59,574
Certificates of deposit	12,311		—		—		12,311
Asset-backed securities	17,905		10		(7)		17,908
U.S. government-sponsored entity debt securities	257,284		19		(5)		257,298
Total	560,575		86		(37)		560,624
Total cash equivalents and marketable securities	$	613,740	$	86	$	(37)	$	613,789

December 31, 2019
Cash equivalents:
Money market funds	$	30,496	$	—	$	—	$	30,496
Commercial paper	2,998		1		—		2,999
Total	33,494		1		—		33,495
Marketable securities:
Commercial paper	155,230		145		(7)		155,368
Corporate debt securities	94,905		115		(3)		95,017
U.S. government-sponsored entity debt securities	53,411		91		(9)		53,493
Total	303,546		351		(19)		303,878
Total cash equivalents and marketable securities	$	337,040	$	352	$	(19)	$	337,373

The fair value of marketable securities by contractual maturity were as follows (in thousands):


	December 31,
	2020		2019
Maturing in one year or less	$	510,094	$	282,046
Maturing after one year through five years	50,530		21,832
Total	$	560,624	$	303,878

The Company had no realized losses from the sale of marketable securities for the years ended December 31, 2020, 2019 or 2018. No investments were other-than-temporarily impaired at either December 31, 2020 or 2019. The Company considers factors such as the duration, the magnitude and the reason for the decline in value, the potential recovery period, creditworthiness of the issuers of the securities and its intent to sell. For marketable securities, it also considers whether (i) it is more likely than not that the Company will be required to sell the debt securities before recovery of their amortized cost basis, and (ii) the amortized cost basis cannot be recovered as a result of credit losses. No significant facts or circumstances have arisen to indicate that there has been any significant deterioration in the creditworthiness of the issuers of the securities held by the Company. Based on the Company’s review of these securities, including the assessment of the duration and severity of the unrealized losses and the Company’s ability and intent to hold the investments until maturity, there were no other-than-temporary impairments for these marketable securities at December 31, 2020.

Income Taxes - Deferred Tax Assets & Liabilities, Balance Sheet Location (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Income Taxes [Line Items]
Deferred tax assets	$ 25,120	$ 27,695
Deferred tax liabilities	(7,185)	(6,570)
Net deferred tax liabilities	(6,711)	(6,570)
Other noncurrent assets
Income Taxes [Line Items]
Deferred tax assets	$ 474	$ 0

Employee Benefit Plan - Additional Information (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Retirement Benefits [Abstract]
Defined contribution plan, employer's matching contribution percent	50.00%	50.00%	50.00%
Maximum percentage limit of employee contributions	8.00%	8.00%	8.00%
Defined contribution plan, maximum employer's contribution per employee	$ 4,000	$ 4,000	$ 4,000
Aggregate employer's contributions to defined contribution plan	$ 1,200,000	$ 900,000	$ 800,000

Stockholders' Equity (Tables)

12 Months Ended

Dec. 31, 2020

Equity [Abstract]

Summary of Stock Option Activity

A summary of the Company’s stock option activity is as follows:


	Number of Shares	Weighted- Average Exercise per Share Price		Weighted-Average Remaining Contractual Term	Aggregate Intrinsic Value
				(In years)	(In thousands)
Options outstanding at December 31, 2019	9,829,287	$	10.71
Options granted	4,563,425	$	8.09
Options exercised	(1,162,268)	$	8.02
Options canceled	(1,751,746)	$	10.19
Options outstanding at December 31, 2020	11,478,698	$	10.02	7.80	$	69,616
Options vested and expected to vest at December 31, 2020	11,478,698	$	10.02	7.80	$	69,616
Options exercisable at December 31, 2020	5,127,517	$	10.71	6.48	$	29,025

Summary of Restricted Stock Unit Activity

A summary of the Company’s RSU activity is as follows:


	Number of Shares	Weighted-Average Remaining Contractual Term	Aggregate Intrinsic Value
		(In years)	(In thousands)
RSUs outstanding at December 31, 2019	862,850
RSUs awarded	2,517,101
RSUs released	(324,305)
RSUs forfeited	(384,118)
RSUs outstanding at December 31, 2020	2,671,528	1.19	$	41,689
RSUs vested and expected to vest at December 31, 2020	2,671,528	1.19	$	41,689

Acquisition of Sangamo France

12 Months Ended

Dec. 31, 2020

Business Combinations [Abstract]

Acquisition of Sangamo France

ACQUISITION OF SANGAMO FRANCE

On July 20, 2018, Sangamo entered into various agreements with the goal of eventually acquiring 100% of Sangamo France’s share capital. The Company entered into the Sangamo France SPA with certain shareholders of Sangamo France, pursuant to which it acquired 13,519,036 ordinary shares of Sangamo France (“Ordinary Shares”) as part of a block transaction that closed on October 1, 2018 (the “Acquisition Date”). Additionally, the Company and Sangamo France entered into a Tender Offer Agreement pursuant to which Sangamo agreed to acquire 11,528,635 Ordinary Shares for the same price per share as the Sangamo France SPA via a cash tender offer that closed on November 23, 2018. Following the block transaction, cash tender offer, and other open market purchases of shares, the Company owned 98.2% of the Ordinary Shares as of December 31, 2018 (or 25,047,671 Ordinary Shares). In addition to the Sangamo France SPA and the tender offer agreement, the Company also entered into arrangements with the holders of approximately 477,000 “free shares” of Sangamo France pursuant to which the Company has the right to purchase such shares from the holders (a call option) and such holders have the right to sell to the Company such shares from time to time through mid-2021 (a put option) (collectively the “Free Shares Options”). During 2019, the Company acquired approximately 111,000 vested free shares, increasing its ownership of the Ordinary Shares from 98.2% to 98.7%. During 2020, the Company acquired approximately 322,000 vested free shares, pursuant to the exercise of the put options for approximately $0.7 million of cash, increasing its ownership of the Ordinary Shares to 99.8% as of December 31, 2020.

At the Acquisition Date, the fair value of the Free Shares Options was estimated to be a liability of $0.2 million. See Note 2 – Fair Value Measurement – Free Shares Asset for information regarding the valuation method. The fair value of the Free Shares Options will vary based on future changes in the Company’s stock price during the option period. The fair value of the Free Shares Options was estimated to be an asset of $0.1 million as of December 31, 2020.

The acquisition of Sangamo France was accounted for as a business combination in accordance with ASC Topic 805, Business Combinations, in exchange for total consideration of approximately $45.9 million at the Acquisition Date. The operating results of Sangamo France after the Acquisition Date have been included in the Company’s Consolidated Statements of Operations.

There was no goodwill impairment during the years ended December 31, 2020, 2019 or 2018 and, as noted below, substantially all of the non-controlling interest on the Acquisition Date was subsequently acquired by the Company and, accordingly, substantially all of the goodwill is allocated to the Company as of December 31, 2020 and 2019.

Non-controlling Interest

The fair value of the remaining non-controlling interest was determined based on the number of outstanding shares comprising the non-controlling interest and the $2.99 acquisition price per share as of the Acquisition Date. The non-controlling interest is presented as a component of stockholders’ equity on the Company’s Consolidated Balance Sheets.

Non-controlling interest as of December 31, 2020 was as follows (in thousands):


	Total






Balance at beginning of year	$	185
Fair value of additional shares acquired	(927)
Loss attributable to non-controlling interest	(126)
Balance at end of year	$	(868)

Major Customers, Partnerships and Strategic Alliances - Additional Information (Detail)			1 Months Ended																3 Months Ended								12 Months Ended				13 Months Ended	17 Months Ended	37 Months Ended	41 Months Ended	84 Months Ended
	Jul. 27, 2020 USD ($)	Apr. 05, 2018 USD ($)	Oct. 30, 2020 USD ($)	Sep. 30, 2020 USD ($)	Aug. 31, 2020 USD ($)	May 31, 2020 USD ($)	Apr. 30, 2020 USD ($) $ / shares shares	Apr. 30, 2020 USD ($) $ / shares	Mar. 31, 2020 USD ($) $ / shares	Feb. 29, 2020 USD ($) product_target	Dec. 31, 2019 USD ($)	Sep. 30, 2019 USD ($)	May 31, 2018 USD ($)	Apr. 30, 2018 USD ($)	Dec. 31, 2017 USD ($)	May 31, 2017 USD ($)	Jan. 31, 2014 USD ($) program	Jan. 31, 2012 USD ($)	Dec. 31, 2020 USD ($)	Sep. 30, 2020 USD ($)	Jun. 30, 2020 USD ($)	Mar. 31, 2020 USD ($)	Dec. 31, 2019 USD ($)	Sep. 30, 2019 USD ($)	Jun. 30, 2019 USD ($)	Mar. 31, 2019 USD ($)	Dec. 31, 2020 USD ($) product_target option product milestone $ / shares	Dec. 31, 2019 USD ($)	Dec. 31, 2018 USD ($)	Dec. 31, 2014 USD ($)	Dec. 31, 2020 USD ($)	Dec. 31, 2020 USD ($)	Dec. 31, 2020 USD ($) milestone	Sep. 30, 2020 USD ($)	Dec. 31, 2020 USD ($)	Feb. 28, 2020	Aug. 31, 2019 USD ($)
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Collaborative arrangement, maximum number of product targets to replace \| product_target																											10
Issuance costs related to sangamo france acquisition																												$ 25,000
Agreement termination, term																											180 days
Revenues																			$ 25,800,000	$ 57,763,000	$ 21,553,000	$ 13,076,000	$ 54,851,000	$ 21,958,000	$ 17,548,000	$ 8,071,000	$ 118,192,000	102,428,000	$ 84,452,000
Other long-term liabilities											$ 5,711,000								7,011,000				5,711,000				7,011,000	5,711,000			$ 7,011,000	$ 7,011,000	$ 7,011,000		$ 7,011,000
California Institute for Regenerative Medicine ("CIRM")
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Funds due under the agreement													$ 8,000,000.0
Other long-term liabilities											5,700,000								6,400,000				5,700,000				6,400,000	5,700,000			6,400,000	6,400,000	6,400,000		6,400,000
Research grants \| California Institute for Regenerative Medicine ("CIRM")
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Revenues																											5,200,000
Novartis Institutes For Bio Medical Research Inc \| Collaboration agreements
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Revenues																											4,100,000
Novartis Institutes For Bio Medical Research Inc \| Collaboration and license agreement
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Proceeds from collaborators					$ 75,000,000.0
Collaborative arrangement transaction price	$ 95,100,000
Collaborative arrangement, license fee	75,000,000.0
Collaborative arrangement estimated reimbursable service costs	20,100,000
Deferred revenue																			70,900,000								70,900,000				70,900,000	70,900,000	70,900,000		70,900,000
Collaboration arrangement, commission fee, portion of gross proceeds, value																			$ 1,500,000								1,500,000				1,500,000	1,500,000	1,500,000		1,500,000
Collaborative agreement, percent of initial recognition																			2.00%
Amortization cost																											100,000
Novartis Institutes For Bio Medical Research Inc \| Collaboration and license agreement \| Maximum \| Achievement of specified preclinical development clinical development and first commercial sale milestones
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Development and sales-based milestone payments to be received	420,000,000.0
Novartis Institutes For Bio Medical Research Inc \| Collaboration and license agreement \| Maximum \| Achievement of commercial milestones
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Development and sales-based milestone payments to be received	$ 300,000,000.0
Biogen MA Inc \| Collaboration agreements
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Revenues																											21,400,000
Biogen MA Inc \| Collaboration and license agreement
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Proceeds from collaborators						$ 125,000,000.0				$ 125,000,000.0
Collaboration arrangement, commission fee, portion of gross proceeds, value																			$ 7,000,000.0								$ 7,000,000.0				7,000,000.0	7,000,000.0	7,000,000.0		7,000,000.0
Collaborative agreement, percent of initial recognition																			2.00%								2.00%
Amortization cost																											$ 400,000
Maximum milestone payment receivable										$ 2,370,000,000
Number of neurological disease gene targets \| product_target										12
Number of product targets selected \| product_target										3
Number of additional neurological disease gene targets \| product_target										9
Target selection period										5 years
Contract with customer, asset, after allowance for credit Loss																			$ 4,100,000								4,100,000				4,100,000	4,100,000	4,100,000		4,100,000
Biogen MA Inc \| Collaboration and license agreement \| Maximum
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Collaboration arrangement, research period										7 years
Biogen MA Inc \| Collaboration and license agreement \| Pre-approval Milestone
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Maximum milestone payment receivable										$ 925,000,000.0
Biogen MA Inc \| Collaboration and license agreement \| Sales-based Milestone
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Maximum milestone payment receivable										$ 1,450,000,000
Biogen MA Inc \| Stock Purchase Agreement
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Deferred revenue																			183,200,000								183,200,000				183,200,000	183,200,000	183,200,000		183,200,000
Sale of stock, number of shares issued in transaction (in shares) \| shares							24,420,157
Sale of stock, price per share (in dollars per share) \| $ / shares							$ 9.2137	$ 9.2137
Consideration received from sale of stock							$ 225,000,000.0	$ 225,000,000.0
Agreement restriction expiration period										3 years
Agreement restriction, ownership percentage (less than)																																				5.00%
Agreement restriction, percentage of shares held																																				50.00%
Agreement provision, expiration period										2 years
Agreement provision, ownership percentage (less than)																																				5.00%
Sale of stock, excess consideration received on transaction																											79,600,000
Collaboration agreement, equity issued																			145,400,000								145,400,000				145,400,000	145,400,000	145,400,000		145,400,000
Issuance costs related to sangamo france acquisition																			2,900,000
Kite Pharma, Inc. ("Kite")
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Revenues																											28,608,000	34,350,000	25,517,000
Kite Pharma, Inc. ("Kite") \| Collaboration agreements
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Revenues																											25,046,000	24,977,000	18,545,000
Kite Pharma, Inc. ("Kite") \| Collaboration and license agreement
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Collaborative arrangement transaction price												$ 189,300,000
Collaborative arrangement estimated reimbursable service costs												39,300,000
Deferred revenue											106,500,000								81,400,000				106,500,000				$ 81,400,000	106,500,000			81,400,000	81,400,000	81,400,000		81,400,000
Milestone payments received														$ 150,000,000.0
Initial research term of agreement																											6 years
Number of options to extend initial research term \| option																											2
Extended research term of agreement																											1 year
Separate fee for additional term																											$ 10,000,000.0
Collaborative arrangement estimated reimbursable service costs for new research plan												3,400,000
Revenues under agreement												$ 150,000,000.0
Kite Pharma, Inc. ("Kite") \| Collaboration and license agreement \| Achievement of specified research, clinical development, regulatory and first commercial sale milestones
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Contingent development and sales-based milestone payments to be received		$ 1,260,000,000
Kite Pharma, Inc. ("Kite") \| Collaboration and license agreement \| Achievement of specified sales-based milestones if annual worldwide net sales of licensed products reach specified levels
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Contingent development and sales-based milestone payments to be received		1,750,000,000
Kite Pharma, Inc. ("Kite") \| Collaboration and license agreement \| Maximum
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Development and sales-based milestone payments to be received		$ 3,010,000,000.00
Pfizer, Giroctocogene Fitelparvovec
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Deferred revenue											4,000,000.0												4,000,000.0					4,000,000.0
Revenues under agreement											25,000,000.0
Revenues																											34,449,000	39,359,000	37,810,000
Collaborative arrangement, increase (decrease) in revenue									$ 2,400,000
Collaborative arrangement, increase (decrease) in net income (loss)									$ 2,400,000
Pfizer, Giroctocogene Fitelparvovec \| Phase Three Clinical Trial
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Development and sales-based milestone payments to be received			$ 30,000,000.0
Cumulative compensation earned																			30,000,000.0								30,000,000.0				30,000,000.0	30,000,000.0	30,000,000.0		30,000,000.0
Pfizer, Giroctocogene Fitelparvovec \| Collaboration agreements
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Revenues																			8,700,000								3,111,000	15,697,000	37,810,000
Contract with customer, liability, cumulative catch-up adjustment to revenue, change in measure of progress																						$ 3,000,000.0
Pfizer, Giroctocogene Fitelparvovec \| Amended collaboration and license agreement
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Recognition of milestone																											$ 1,300,000				25,000,000.0
Pfizer C9ORF72
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Milestone payments received															$ 12,000,000.0																		$ 5,000,000.0
Number of products approved \| milestone																																	0
Number of milestones included in transaction price \| milestone																																	0
Agreement termination, term																											15 years
Revenues																											$ 12,985,000	1,827,000	2,188,000
Pfizer C9ORF72 \| Collaboration agreements
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Revenues																											$ 7,985,000	1,827,000	2,188,000
Pfizer C9ORF72 \| C9ORF72
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Deferred revenue											8,000,000.0												8,000,000.0					8,000,000.0
Revenues under agreement															12,000,000.0
Pfizer C9ORF72 \| C9ORF72 \| Maximum \| Achievement of specified preclinical development clinical development and first commercial sale milestones
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Development and sales-based milestone payments to be received															60,000,000.0
Pfizer C9ORF72 \| C9ORF72 \| Maximum \| Achievement of commercial milestones
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Development and sales-based milestone payments to be received															90,000,000.0
Sanofi
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Revenues under agreement																	$ 20,000,000.0
Number of products approved \| product																											0
Revenues																											$ 5,322,000	22,680,000	13,516,000
Collaborative arrangement, increase (decrease) in revenue																											(2,200,000)
Collaborative arrangement, increase (decrease) in net income (loss)																											$ 2,200,000
Collaborative arrangement, net Income (loss) per share \| $ / shares																											$ (0.02)
Number of research programs \| program																	2
Sanofi \| Collaboration agreements
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Revenues																											$ 298,000	3,494,000	4,013,000
Sanofi \| Collaboration and license agreement
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Collaborative arrangement transaction price																											93,300,000
Collaborative arrangement estimated reimbursable service costs																	$ 59,800,000
Deferred revenue											1,700,000								1,200,000				1,700,000				1,200,000	1,700,000			1,200,000	1,200,000	$ 1,200,000		1,200,000
Revenues under agreement																											$ 20,000,000.0
Number of milestones included in transaction price \| milestone																											0
Recognition of milestone																											$ 100,000					5,800,000			7,200,000
Sanofi \| Collaboration and license agreement \| Maximum
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Development and sales-based milestone payments to be received																	276,300,000
Sanofi \| Collaboration and license agreement \| Maximum \| Achievement of specified clinical development and regulatory milestones
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Development and sales-based milestone payments to be received																	115,800,000
Sanofi \| Collaboration and license agreement \| Maximum \| Achievement of specified sales milestones
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Development and sales-based milestone payments to be received																	$ 160,500,000
Sanofi \| Collaboration and license agreement \| Milestone One
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Milestone payments received																											6,000,000.0
Milestone revenue receivable																																					$ 6,000,000.0
Sanofi \| Collaboration and license agreement \| Milestone Two
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Milestone revenue receivable											$ 7,500,000								7,500,000				$ 7,500,000				7,500,000	7,500,000			7,500,000	7,500,000	7,500,000		7,500,000
Sanofi \| Collaboration and license agreement \| Milestone Three
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Milestone revenue receivable																			13,500,000								13,500,000				13,500,000	13,500,000	13,500,000		13,500,000
Shire AG
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Revenues																											$ 0	$ 0	$ 0
Shire AG \| Collaboration and license agreement
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Deferred revenue															2,300,000
Revenues under agreement																		$ 13,000,000.0
Agreement termination, term																											90 days
Recognition of milestone																														$ 1,000,000.0
Pfizer
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Collaborative arrangement transaction price																											$ 134,000,000.0
Revenues under agreement																$ 70,000,000.0
Number of products approved \| product																											0
Research service fees																											$ 79,000,000.0
Collaborative arrangement reimbursable service costs																			55,000,000.0								$ 55,000,000.0				$ 55,000,000.0	$ 55,000,000.0	$ 55,000,000.0		$ 55,000,000.0
Agreement termination, term																											15 years
Collaborative arrangement, increase (decrease) in revenue																											$ 8,800,000
Collaborative arrangement, increase (decrease) in net income (loss)																											$ 8,800,000
Collaborative arrangement, net Income (loss) per share \| $ / shares									$ (0.02)																		$ 0.06
Pfizer \| Maximum \| Achievement of specified clinical development intellectual property and regulatory milestones
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Development and sales-based milestone payments to be received																208,500,000
Pfizer \| Maximum \| Achievement of first commercial sale milestones
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Development and sales-based milestone payments to be received																475,000,000.0
Pfizer \| Other products \| Maximum
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Milestone revenue receivable																175,000,000.0
Pfizer \| C9ORF72
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Development and sales-based milestone payments to be received				$ 5,000,000.0
Collaborative arrangement transaction price															17,000,000.0
Revenues under agreement															$ 5,000,000.0				$ 5,000,000.0
Pfizer \| Giroctocogene Fitelparvovec
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Milestone payments received																																		$ 55,000,000.0
Number of milestones included in transaction price \| milestone																											0
Pfizer \| Giroctocogene Fitelparvovec \| Maximum
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Potential amount to be funded for achievement of specified commercialized and sales milestones																266,500,000
Milestone revenue receivable																$ 300,000,000.0

Related Party Disclosures (Detail) - USD ($) $ in Thousands		2 Months Ended	12 Months Ended
Related Party Disclosures (Detail) - USD ($) $ in Thousands	Oct. 01, 2018	Nov. 23, 2018	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Related Party Transaction [Line Items]
Payments to acquire additional interest in subsidiaries			$ 704	$ 262	$ 0
TxCell S.A.
Related Party Transaction [Line Items]
Number of ordinary shares acquired (in shares)	13,519,036	11,528,635
TxCell S.A. \| Share Purchase Agreement and Tender Offer Agreement
Related Party Transaction [Line Items]
Number of ordinary shares acquired (in shares)			322,000	111,000	25,047,671
Payments to acquire additional interest in subsidiaries			$ 700	$ 300
Former Executive of TxCell \| TxCell S.A. \| Share Purchase Agreement and Tender Offer Agreement
Related Party Transaction [Line Items]
Number of ordinary shares acquired (in shares)			185,400	52,700
Payments to acquire additional interest in subsidiaries			$ 400	$ 100

Fair Value Measurement - Summary of Fair Value Measurements of Cash Equivalents, Available-for-Sale Securities and Free Share Liability (Detail) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total marketable securities	$ 560,624	$ 303,878
Money market funds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total cash equivalents	53,165	30,496
Commercial paper
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total cash equivalents		2,999
Total marketable securities	213,533	155,368
Corporate debt securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total marketable securities	59,574	95,017
Certificates of deposit
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total marketable securities	12,311
Asset-backed securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total marketable securities	17,908
U.S. government-sponsored entity debt securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total marketable securities	257,298	53,493
Fair value on recurring basis
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total cash equivalents	53,165	33,495
Total marketable securities	560,624	303,878
Total cash equivalents and marketable securities	613,789	337,373
Fair value on recurring basis \| Money market funds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total cash equivalents	53,165	30,496
Fair value on recurring basis \| Commercial paper
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total cash equivalents		2,999
Total marketable securities	213,533	155,368
Fair value on recurring basis \| Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total cash equivalents	53,165	30,496
Total marketable securities	0	0
Total cash equivalents and marketable securities	53,165	30,496
Fair value on recurring basis \| Level 1 \| Money market funds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total cash equivalents	53,165	30,496
Fair value on recurring basis \| Level 1 \| Commercial paper
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total cash equivalents		0
Total marketable securities	0	0
Fair value on recurring basis \| Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total cash equivalents	0	2,999
Total marketable securities	560,624	303,878
Total cash equivalents and marketable securities	560,624	306,877
Fair value on recurring basis \| Level 2 \| Money market funds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total cash equivalents	0	0
Fair value on recurring basis \| Level 2 \| Commercial paper
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total cash equivalents		2,999
Total marketable securities	213,533	155,368
Fair value on recurring basis \| Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total cash equivalents	0	0
Total marketable securities	0	0
Total cash equivalents and marketable securities	0	0
Fair value on recurring basis \| Level 3 \| Money market funds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total cash equivalents	0	0
Fair value on recurring basis \| Level 3 \| Commercial paper
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total cash equivalents		0
Total marketable securities	0	0
Fair value on recurring basis \| Corporate debt securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total marketable securities	59,574	95,017
Fair value on recurring basis \| Corporate debt securities \| Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total marketable securities	0	0
Fair value on recurring basis \| Corporate debt securities \| Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total marketable securities	59,574	95,017
Fair value on recurring basis \| Corporate debt securities \| Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total marketable securities	0	0
Fair value on recurring basis \| Certificates of deposit
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total marketable securities	12,311
Fair value on recurring basis \| Certificates of deposit \| Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total marketable securities	0
Fair value on recurring basis \| Certificates of deposit \| Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total marketable securities	12,311
Fair value on recurring basis \| Certificates of deposit \| Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total marketable securities	0
Fair value on recurring basis \| Asset-backed securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total marketable securities	17,908
Fair value on recurring basis \| Asset-backed securities \| Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total marketable securities	0
Fair value on recurring basis \| Asset-backed securities \| Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total marketable securities	17,908
Fair value on recurring basis \| Asset-backed securities \| Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total marketable securities	0
Fair value on recurring basis \| U.S. government-sponsored entity debt securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total marketable securities	257,298	53,493
Fair value on recurring basis \| U.S. government-sponsored entity debt securities \| Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total marketable securities	0	0
Fair value on recurring basis \| U.S. government-sponsored entity debt securities \| Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total marketable securities	257,298	53,493
Fair value on recurring basis \| U.S. government-sponsored entity debt securities \| Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total marketable securities	0	0
Fair value on recurring basis \| Free shares asset
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total cash equivalents and marketable securities	70
Fair value on recurring basis \| Free shares asset \| Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total cash equivalents and marketable securities	0
Fair value on recurring basis \| Free shares asset \| Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total cash equivalents and marketable securities	0
Fair value on recurring basis \| Free shares asset \| Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total cash equivalents and marketable securities	$ 70
Fair value on recurring basis \| Free shares asset
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total cash equivalents and marketable securities		236
Fair value on recurring basis \| Free shares asset \| Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total cash equivalents and marketable securities		0
Fair value on recurring basis \| Free shares asset \| Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total cash equivalents and marketable securities		0
Fair value on recurring basis \| Free shares asset \| Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total cash equivalents and marketable securities		$ 236