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Document and Entity Information - shares	3 Months Ended
Mar. 31, 2019	May 03, 2019
Document And Entity Information [Abstract]
Document Type	10-Q
Amendment Flag	false
Document Period End Date	Mar. 31, 2019
Document Fiscal Year Focus	2019
Document Fiscal Period Focus	Q1
Trading Symbol	SGMO
Entity Registrant Name	SANGAMO THERAPEUTICS, INC
Entity Central Index Key	0001001233
Current Fiscal Year End Date	--12-31
Entity Filer Category	Large Accelerated Filer
Entity Small Business	false
Entity Emerging Growth Company	false
Entity Common Stock, Shares Outstanding		115,361,866

Condensed Consolidated Balance Sheets - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018
Current assets:
Cash and cash equivalents	$ 80,968	$ 140,418
Marketable securities	270,028	259,715
Interest receivable	594	375
Accounts receivable	7,311	4,673
Prepaid expenses and other current assets	3,727	5,340
Total current assets	362,628	410,521
Property and equipment, net	18,281	78,723
Intangible assets	53,170	54,243
Goodwill	39,283	40,044
Operating lease right-of-use assets	28,190
Prepaid rent	33,559
Other non-current assets	4,118	3,364
Non-current restricted cash	3,500	3,500
Total assets	542,729	590,395
Current liabilities:
Accounts payable and accrued liabilities	30,135	21,457
Accrued compensation and employee benefits	6,168	9,490
Deferred revenues	54,824	47,564
Total current liabilities	91,127	78,511
Deferred revenues, non-current	100,639	108,273
Long-term portion of lease liabilities	13,299	27,689
Deferred income tax	6,572	6,705
Other non-current liabilities	1,911	1,960
Total liabilities	213,548	223,138
Commitments and contingencies
Stockholders' equity:
Preferred stock
Common stock	1,023	1,022
Additional paid-in capital	934,112	929,632
Accumulated deficit	(603,949)	(562,696)
Accumulated other comprehensive loss	(2,691)	(1,440)
Total Sangamo Therapeutics Inc. stockholders' equity	328,495	366,518
Non-controlling interest	686	739
Total stockholders' equity	329,181	367,257
Total liabilities and stockholders' equity	$ 542,729	$ 590,395

Condensed Consolidated Statements of Operations - USD ($) shares in Thousands, $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Income Statement [Abstract]
Revenues	$ 8,071	$ 12,637
Operating expenses:
Research and development	34,850	23,547
General and administrative	17,118	10,087
Total operating expenses	51,968	33,634
Loss from operations	(43,897)	(20,997)
Interest and other income, net	1,694	810
Net loss	(42,203)	(20,187)
Net loss attributable to non-controlling interest	(53)
Net loss to Sangamo Therapeutics, Inc. stockholders	$ (42,150)	$ (20,187)
Basic and diluted net loss per share attributable to Sangamo Therapeutics, Inc. stockholders	$ (0.41)	$ (0.23)
Shares used in computing basic and diluted net loss per share attributable to Sangamo Therapeutics, Inc. stockholders	102,270	86,334

Condensed Consolidated Statements of Comprehensive Loss - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Statement Of Income And Comprehensive Income [Abstract]
Net loss	$ (42,203)	$ (20,187)
Foreign currency translation adjustment	(1,504)
Change in unrealized gain (loss) on available-for-sale securities	253	(99)
Comprehensive loss	(43,454)	(20,286)
Comprehensive loss attributable to non-controlling interest	(53)
Comprehensive loss attributable to Sangamo Therapeutics, Inc.	$ (43,401)	$ (20,286)

- 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

Condensed Consolidated Statements of Stockholders' Equity - USD ($) $ in Thousands	Total	Common Stock [Member]	Additional Paid-in Capital [Member]	Accumulated Deficit [Member]	Accumulated Other Comprehensive Income (Loss) [Member]	Non-Controlling Interest [Member]
Beginning Balances at Dec. 31, 2017	$ 187,900	$ 856	$ 682,809	$ (495,479)	$ (286)
Beginning Balances, shares at Dec. 31, 2017		85,598,534
Cumulative-effect adjustment \| Topic 606 [Member]	1,117			1,117
Issuance of common stock upon exercise of stock options and in connection with restricted stock units, net of tax	10,584	$ 14	10,570
Issuance of common stock upon exercise of stock options and in connection with restricted stock units, net of tax, shares		1,442,674
Stock-based compensation	3,050		3,050
Net unrealized gain (loss) on marketable securities	(99)				(99)
Net loss	(20,187)			(20,187)
Ending Balances at Mar. 31, 2018	182,365	$ 870	696,429	(514,549)	(385)
Ending Balances, shares at Mar. 31, 2018		87,041,208
Beginning Balances at Dec. 31, 2018	367,257	$ 1,022	929,632	(562,696)	(1,440)	$ 739
Beginning Balances, shares at Dec. 31, 2018		102,187,471
Cumulative-effect adjustment \| Topic 842 [Member]	897			897
Issuance of common stock upon exercise of stock options and in connection with restricted stock units, net of tax	216	$ 1	215
Issuance of common stock upon exercise of stock options and in connection with restricted stock units, net of tax, shares		141,281
Issuance costs related to public offering	(258)		(258)
Stock-based compensation	4,523		4,523
Foreign currency translation adjustment	(1,504)				(1,504)
Net unrealized gain (loss) on marketable securities	253				253
Net loss	(42,203)			(42,150)		(53)
Ending Balances at Mar. 31, 2019	$ 329,181	$ 1,023	$ 934,112	$ (603,949)	$ (2,691)	$ 686
Ending Balances, shares at Mar. 31, 2019		102,328,752

Condensed Consolidated Statements of Cash Flows - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Operating Activities:
Net loss	$ (42,203)	$ (20,187)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation and amortization	715	588
Amortization of discount on marketable securities	(1,238)	(459)
Gain on free shares	(545)
Stock-based compensation	4,523	3,050
Build-to-suit leases		217
Net loss on lease termination	218
Other	44
Net changes in operating assets and liabilities:
Interest receivable	(219)	(133)
Accounts receivable	(2,638)	(232)
Prepaid expenses and other assets	1,152	(1,334)
Operating lease right-of-use assets	782
Prepaid rent	(12,101)
Accounts payable and accrued liabilities	10,183	(77)
Accrued compensation and employee benefits	(3,306)	(2,268)
Deferred revenues	(370)	2,701
Long-term portion of lease liabilities	(66)
Other non-current liabilities	(50)
Net cash used in operating activities	(45,119)	(18,134)
Investing Activities:
Purchases of marketable securities	(87,075)	(63,401)
Maturities of marketable securities	78,253	54,450
Purchases of property and equipment	(5,977)	(2,616)
Net cash used in investing activities	(14,799)	(11,567)
Financing Activities:
Taxes paid related to net share settlement of equity awards	(265)	(14)
Proceeds from issuance of common stock	481	10,597
Net cash provided by financing activities	216	10,583
Effects of changes in foreign exchange rates	252
Net increase in cash, cash equivalents, and restricted cash	(59,450)	(19,118)
Cash, cash equivalents, and restricted cash, beginning of period	143,918	53,326
Cash, cash equivalents, and restricted cash, end of period	84,468	34,208
Supplemental disclosure of non-cash activities:
Right-of-use assets obtained in exchange for lease obligations	6,676
Property and Equipment [Member]
Supplemental disclosure of non-cash activities:
Property and equipment included in accrued liabilities	$ 1,834	$ 1,227

Organization, Basis of Presentation and Summary of Significant Accounting Policies

3 Months Ended

Mar. 31, 2019

Accounting Policies [Abstract]

Organization, Basis of Presentation and Summary of Significant Accounting Policies

NOTE 1—ORGANIZATION, BASIS OF PRESENTATION AND SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES

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 focused on the research, development and commercialization of novel therapeutic strategies for unmet medical needs. Sangamo’s genome editing and gene regulation technology platform is enabled by the engineering of a class of transcription factors known as zinc finger DNA-binding proteins (“ZFPs”). Potential applications of Sangamo’s technology include development of human therapeutics, plant agriculture and enhancement of pharmaceutical protein production.

Sangamo is currently working on a number of long-term development projects that will involve experimental technology. 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 investments as of March 31, 2019, along with proceeds from the underwritten public offering in April 2019 (see Note 11 — Subsequent Events) and expected revenues from collaborations, strategic partnerships and research grants, will be adequate to fund its operations at least through the next twelve months from the date the financial statements are issued. Sangamo will require additional financial resources to complete the development and commercialization of its products including ZFP Therapeutic products. 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 ZFP 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.

Basis of Presentation

The accompanying unaudited condensed consolidated financial statements have been prepared in accordance with generally accepted accounting principles in the United States of America (“U.S. GAAP”) for interim financial information and pursuant to the rules and regulations of the Securities and Exchange Commission (“SEC”). Accordingly, they do not include all of the information and footnotes required by U.S. GAAP for complete financial statements. In the opinion of management, all adjustments (consisting of normal recurring adjustments) considered necessary for a fair presentation have been included. Operating results for the three months ended March 31, 2019 are not necessarily indicative of the results that may be expected for the year ending December 31, 2019. The condensed consolidated balance sheet data at December 31, 2018 was derived from the audited consolidated financial statements included in Sangamo’s Annual Report on Form 10-K for the year ended December 31, 2018 (the “2018 Annual Report”) as filed with the SEC on March 1, 2019. The accompanying condensed consolidated financial statements and related financial information should be read in conjunction with the audited financial statements and footnotes thereto for the year ended December 31, 2018, included in the 2018 Annual Report.

Use of Estimates

The preparation of financial statements in conformity with U.S. GAAP requires management to make estimates and assumptions that affect the amounts reported in the financial statements and the accompanying notes. On an ongoing basis, management evaluates its estimates including critical accounting policies or estimates related to revenue recognition, 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. In March 2019, the Company recorded an adjustment to revenue related to a change in estimate in connection with the hemophilia A collaboration agreement with Pfizer Inc. (“Pfizer”) as result of a decision made in a joint steering committee of Pfizer and Sangamo in March 2019 to increase the project scope and related project cost, which resulted in a decrease in the measure of the proportional performance. This adjustment decreased revenue by $3.0 million, increased net loss by $3.0 million and increased the Company’s basic net loss per share by $0.03 for the three months ended March 31, 2019.

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 Accumulated Other Comprehensive Income (Loss) (“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 Condensed Consolidated Statements of Operations.

Reclassifications

Certain prior period amounts in the accompanying condensed consolidated financial statements have been reclassified to conform to the current period presentation. These reclassifications had no effect on the reported results of operations. The Company reclassified $0.6 million from Intangible assets to Other non-current assets on the Condensed Consolidated Balance Sheet as of December 31, 2018.

Cash and Cash Equivalents

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 and deposits in money market investment accounts.

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 AOCI.

The Company’s investments are subject to a periodic impairment review. The Company recognizes an impairment charge 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 available-for-sale securities are included in other income, net, which are determined using the specific identification method.

Non-current Restricted Cash

Non-current restricted cash consists of a letter of credit for $3.5 million established as a deposit for the Brisbane lease. Non-current restricted cash is included in cash, cash equivalents and restricted cash on the condensed consolidated statements of cash flows.

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 counterparties to the agreements relating to the Company’s investment securities consist of the U.S. government-sponsored entities and various major corporations and financial institutions with high credit ratings. The free share asset/liability is measured using a binomial-lattice pricing model and is reviewed each reporting period and adjusted, as needed.

Leases

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 Company gives consideration to its credit risk, term of the lease, 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.

Revenue Recognition

Effective January 1, 2018, the Company adopted the provisions of Accounting Standards Codification (“ASC”) Topic 606 - Revenue from Contracts with Customers (“ASC Topic 606”) using the modified retrospective method, resulting in a change to its accounting policy for revenue recognition. Topic 606 establishes a unified model to determine how revenue is recognized.

Revenues from research activities made under strategic partnering agreements and collaborations are recognized as the services are provided when there is persuasive evidence that an arrangement exists, delivery has occurred, the price is fixed or determinable, and collectability is reasonably assured. Revenue generated from research and licensing agreements typically includes upfront signing or license fees, cost reimbursements, research services, minimum sublicense fees, milestone payments and royalties on future licensee’s product sales.

The Company’s contract revenues consist of strategic partnering collaboration agreements and research activity grants and licensing. Research and licensing agreements typically include upfront signing or license fees, cost reimbursements, research services, minimum sublicense fees, milestone payments and royalties on future licensee’s product sales. The Company has both fixed and variable consideration. Non-refundable upfront fees and funding of research and development activities are considered fixed, while milestone payments are 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 recognized when the related qualified research expenses are incurred. Deferred revenue represents the portion of research or license payments received but not earned.

In determining the appropriate amount of revenue to be recognized as it 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. 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. 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 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.

During the three months ended March 31, 2019, total revenue was $8.1 million which included a $3.0 million reduction to revenue related to a change in estimate for the hemophilia A collaboration agreement with Pfizer. This change in estimate was the result of a joint steering committee of Pfizer and Sangamo in March 2019 to increase the project scope and related project cost, which thereby resulted in a decrease in the measure of the proportional performance. For the three months ended March 31, 2019, revenues related to Kite Pharma, Inc. (“Kite”), a wholly-owned subsidiary of Gilead Sciences, Inc., and the hemoglobinopathies agreement with Bioverativ Inc., a Sanofi Genzyme company (“Sanofi”), represented 75%, and 18%, respectively, of the Company’s total revenue, excluding the above revenue reversal. During the three months ended March 31, 2018, revenues related to the Company’s hemophilia A collaboration agreement with Pfizer and the hemoglobinopathies agreement with Sanofi represented 61% and 35%, respectively, of the Company’s total revenue. 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 third parties under contract or grant arrangements are recorded as revenue if the Company is deemed to be the principal participant in the arrangements because the activities under the contracts or grants are part of the Company’s development programs. Contract funds received are not refundable and are recognized when the related qualified research and development costs are incurred and there is reasonable assurance that the funds will be received. Funds received in advance are recorded as deferred revenue.

Recent Accounting Pronouncements

Recently Adopted

Revenue Recognition

ASC Topic 606 outlines a single comprehensive model for entities to use in accounting for revenue arising from contracts with customers and supersedes most previous revenue recognition guidance, including industry-specific guidance. The main principle of ASC Topic 606 is to recognize revenues when promised goods or services are transferred to customers in an amount that reflects the consideration that is expected to be received for those goods or services. The Company adopted ASC Topic 606 effective January 1, 2018, using the modified retrospective method with a cumulative-effect adjustment of $1.1 million reflected as an increase to the opening balance of accumulated deficit and a decrease to deferred revenues.

Simplified Disclosure

In August 2018, the SEC adopted amendments to certain disclosure requirements in Securities Act Release No. 33-10532, Disclosure Update and Simplification, as updated. These amendments eliminate, modify, or integrate into other SEC requirements certain disclosure rules. Among the amendments is the requirement to present an analysis of changes in stockholders’ equity in the interim financial statements included in quarterly reports on Form 10-Q. The analysis, which can be presented as a footnote or separate statement, is required for the current and comparative quarter and year-to-date interim periods. The amendments are effective for all filings made on or after November 5, 2018. As such, the Company adopted these SEC amendments on November 5, 2018 and has presented the analysis of changes in stockholders’ equity in these interim financial statements for March 31, 2019 and 2018 presented in this Quarterly Report on Form 10-Q. The Company’s adoption of these SEC amendments has no material effect on the Company’s reporting of financial position, results of operations, cash flows or stockholders’ equity.

Accounting for Leases

In February 2016, the Financial Accounting Standards Board (“FASB”) issued ASU 2016-02, Leases (“ASC Topic 842”). ASC Topic 842 amends a number of aspects of lease accounting, including requiring lessees to recognize almost all leases with a term greater than one year as a ROU asset and corresponding liability, measured at the present value of the lease payments. On January 1, 2019, the Company adopted ASC Topic 842 using the modified retrospective approach with a cumulative-effect adjustment of $0.9 million reflected as a decrease to the opening balance of accumulated deficit as of the adoption date. Results for the three months ended March 31, 2019 are presented under ASC Topic 842. No prior period amounts were adjusted and continue to be reported in accordance with previous lease guidance, ASC Topic 840 — Leases (“ASC Topic 840”).

ASC Topic 842 provides a number of optional practical expedients in transition. The Company elected the practical expedients to not reassess its prior conclusions about lease identification under the new standard, to not reassess lease classification, and to not reassess initial direct costs. The Company did not elect the practical expedient allowing the use-of-hindsight which would require the Company to reassess the lease term of its leases based on all facts and circumstances through the effective date and did not elect the practical expedient pertaining to land easements as this is not applicable to the current contract portfolio.

The impact of the adoption of ASC Topic 842 on the accompanying condensed consolidated balance sheet as of January 1, 2019 was as follows (in thousands):

	December 31, 2018			Adjustments Due to the Adoption of ASC Topic 842			January 1, 2019
Assets:
Property and equipment, net	$	78,723		$	(62,500	)	$	16,223
Operating lease right-of-use assets		—			8,753			8,753
Prepaid rent		—			36,025			36,025

Liabilities:
Operating lease liabilities - current⁽¹⁾		—			1,408			1,408
Deferred rent⁽¹⁾		271			(271	)		—
Build-to-suit lease obligation⁽²⁾		27,689			(27,689	)		—
Operating lease liabilities - long-term⁽²⁾		—			7,933			7,933

Accumulated deficit		(562,696	)		897			(561,799	)

(1)

Operating lease liabilities – current and deferred rent are included in accounts payable and accrued liabilities on the condensed consolidated balance sheets.

(2)

Build-to-suit lease obligation and operating lease liabilities – long-term are included in long-term portion of lease liabilities on the condensed consolidated balance sheets.

The adjustments due to the adoption of ASC Topic 842 primarily related to the recognition of operating lease ROU assets and operating lease liabilities for the Company’s leases. In addition, the adoption of ASC Topic 842 resulted in a change in accounting of the build-to-suit component of two leases under ASC Topic 840 to operating leases under ASC Topic 842 and as a result the Company derecognized the estimated fair value of the building shells that were included in Property and equipment, net as of December 31, 2018, as the Company had been deemed to own these buildings under ASC Topic 840. For additional discussion of the build-to-suit properties, see “Note 7 – Property and equipment, net” to the Company’s consolidated financial statements included in its Annual Report on Form 10-K for the year ended December 31, 2018 filed with the SEC on March 1, 2019. For a description of the leases, see “Note 8 – Commitments and Contingencies – Leases” in these condensed consolidated financial statements.

Not yet adopted

Collaborative Arrangements

In November 2018, the FASB issued ASU 2018-18, Collaborative Arrangements (ASC Topic 808): Clarifying the Interaction between Topic 808 and Topic 606 (“ASC Topic 808”), 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, ASC Topic 808 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. This guidance will be effective for the Company beginning January 1, 2020. The Company is currently evaluating the impact of the adoption of this standard on its 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 will require the Company to amend its methodology for determining any goodwill impairment beginning in 2020.

Fair Value Measurements

3 Months Ended

Mar. 31, 2019

Fair Value Disclosures [Abstract]

Fair Value Measurements

NOTE 2—FAIR VALUE MEASUREMENTS

The Company measures certain financial assets and liabilities at fair value on a recurring basis, including cash equivalents, available-for-sale marketable securities and the free share asset/liability. Fair value is determined based on a three-tier hierarchy under the authoritative guidance for fair value measurements and disclosures that prioritizes the inputs used 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, available-for-sale marketable securities and the free share asset/liability are identified at the following levels within the fair value hierarchy (in thousands):

	March 31, 2019
	Fair Value Measurements
	Total		Level 1		Level 2		Level 3
Assets:
Cash equivalents:
Money market funds	$	15,233	$	15,233	$	—	$	—
Commercial paper securities		4,990		—		4,990		—
Total		20,223		15,233		4,990		—
Marketable securities:
Commercial paper securities		180,399		—		180,399		—
Corporate debt securities		70,948		—		70,948		—
U.S. government-sponsored entity debt securities		18,681		—		18,681		—
Total		270,028		—		270,028		—
Total cash equivalents and marketable securities	$	290,251	$	15,233	$	275,018	$	—

Free shares asset	$	355	$	—	$	—	$	355

	December 31, 2018
	Fair Value Measurements
	Total		Level 1		Level 2		Level 3
Assets:
Cash equivalents:
Money market funds	$	103,291	$	103,291	$	—	$	—
Total		103,291		103,291		—		—
Marketable securities:
Commercial paper securities		177,224		—		177,224		—
Corporate debt securities		63,870		—		63,870		—
U.S. government-sponsored entity debt securities		18,621		—		18,621		—
Total		259,715		—		259,715		—
Total cash equivalents and marketable securities	$	363,006	$	103,291	$	259,715	$	—
Liabilities
Free shares liability	$	154	$	—	$	—	$	154
Total	$	154	$	—	$	—	$	154

Cash Equivalents and Marketable Securities

The Company generally classifies its marketable securities 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, listed 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 Share Asset/Liability

As a result of the July 20, 2018 Share Purchase Agreement (“SPA”) with TxCell S.A., a French société anonyme (“TxCell”) (see Note 10 — Acquisition of TxCell S.A.), the Company entered into arrangements with the holders of approximately 477,000 “free shares” of TxCell pursuant to which the Company has the right to purchase such shares from the holders thereof (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 operating expenses in the condensed consolidated statement of operations. For the three months ended March 31, 2019, the Company recognized an increase in the fair value of the free shares of approximately $0.5 million.

Free Shares valuation assumptions:	March 31, 2019			December 31, 2018
Sangamo Stock Price (USD)	$	9.54		$	11.48
TxCell Stock Price (EUR)	$	2.36		$	2.58
EUR/ USD Exchange Rate		0.89			0.87
Estimated Correlation Sangamo and TxCell Stock Prices		50.0	%		—
Sangamo Stock Price (USD) Volatility Estimate		87.7	%		79.9	%
TxCell Stock Price (EUR) Volatility Estimate		82.8	%		8.6	%
EUR/ USD Exchange Rate Volatility Estimate		7.2	%		7.7	%
Risk Free Rate	Varies by expected exercise date			Varies by expected exercise date

- 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

Marketable Securities

3 Months Ended

Mar. 31, 2019

Investments Debt And Equity Securities [Abstract]

Marketable Securities

NOTE 3—MARKETABLE SECURITIES

The table below summarizes the Company’s cash equivalents and available-for-sale securities (in thousands):

			Gross		Gross
	Amortized		Unrealized		Unrealized			Estimated
	Cost		Gains		(Losses)			Fair Value
March 31, 2019
Assets
Cash equivalents:
Money market funds	$	15,233	$	—	$	—		$	15,233
Commercial paper securities		4,990		—		—			4,990
Total		20,223		—		—			20,223
Available-for-sale securities:
Commercial paper securities		180,380		19		—			180,399
Corporate debt securities		70,973		—		(25	)		70,948
U.S. government-sponsored entity debt securities		18,681		—		—			18,681
Total		270,034		19		(25	)		270,028
Total cash equivalents and available-for-sale securities	$	290,257	$	19	$	(25	)	$	290,251
December 31, 2018
Cash equivalents:
Money market funds	$	103,291	$	—	$	—		$	103,291
Total		103,291		—		—			103,291
Available-for-sale securities:
Commercial paper securities		177,353		—		(129	)		177,224
Corporate debt securities		63,981		—		(111	)		63,870
U.S. government-sponsored entity debt securities		18,640		—		(19	)		18,621
Total		259,974		—		(259	)		259,715
Total cash equivalents and available-for-sale securities	$	363,265		—	$	(259	)	$	363,006

As of March 31, 2019 and December 31, 2018, all of the Company’s investments had maturity dates within one year as of the balance sheet date. The Company had no material realized losses of its available-for-sale securities for the three months ended March 31, 2019 or 2018. Sangamo has the intent and ability to hold its investments for a period of time sufficient to allow for any anticipated recovery in market value. No investments were other-than-temporarily impaired at either March 31, 2019 or December 31, 2018.

Major Customers, Partnerships and Strategic Alliances

3 Months Ended

Mar. 31, 2019

Organization Consolidation And Presentation Of Financial Statements [Abstract]

Major Customers, Partnerships and Strategic Alliances

NOTE 5—MAJOR CUSTOMERS, PARTNERSHIPS AND STRATEGIC ALLIANCES

Collaboration Agreements

Kite Pharma, Inc.

In February 2018, the Company entered into a collaboration and license agreement with Kite for the research, development and commercialization of potential engineered cell therapies for cancer. Kite will be responsible for all clinical development and commercialization of any resulting products. The Kite agreement became effective on April 5, 2018 when the waiting periods under the Hart-Scott-Rodino Antitrust Improvements Act of 1976, as amended, and other customary closing conditions were completed.

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 zinc finger nucleases (“ZFNs”) and adeno-associated viral vectors (“AAVs”) developed under the research program to express chimeric antigen receptors (“CARs”), T-cell receptors (“TCRs”) or NK-cell receptors (“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 the joint research program, 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 set forth 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 ten 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 in the agreement is six years. Kite has an option to extend the research term of the agreement for up to two additional one-year periods for a separate upfront fee of $10.0 million per year. All contingent payments under the agreement, when earned, will be non-refundable and non-creditable. The Company concluded the transaction price under this agreement is $185.9 million and includes the upfront license fee of $150.0 million and $35.9 million estimated reimbursable service costs for identified research projects over the estimated performance period. Further, the Company concluded 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.

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 a license to the technology and on-going services. The Company concluded that the license is not discrete as it does not have stand-alone value to Kite 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 on a straight-line basis through June 2024, the estimated period the Company will perform research services. The estimated period of performance and project cost is reviewed quarterly and adjusted, as needed, to reflect the Company’s current assumptions regarding the timing of its deliverables. As of March 31, 2019 and December 31, 2018, the Company had deferred revenue of $125.3 million and $131.5 million, respectively, related to this agreement. For the three months ended March 31, 2019 and 2018, the Company recognized revenue of approximately $6.2 million and none, respectively, related to the upfront license fee that was received upon effectiveness of the agreement and approximately $2.1 million and none, respectively, from reimbursable service costs.

Pfizer Inc.

SB-525 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 SB-525, 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 for certain manufacturing activities for SB-525, while Pfizer is responsible for subsequent worldwide development, manufacturing, marketing and commercialization of SB-525. Sangamo may also collaborate in the research and development of additional AAV-based gene therapy products for hemophilia A.

The Company received an upfront fee of $70.0 million and is eligible to receive development milestone payments contingent on the achievement of specified clinical development, intellectual property, regulatory and first commercial sale milestones for SB-525 and potentially other products. In addition, Sangamo 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 SB-525 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 hemophilia A Pfizer agreement, is up to $475.0 million, which includes up to $300.0 million for SB-525 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 that are an escalating tiered, double-digit percentage of the annual net sales of such product and 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, no milestone payments have been received and no products have been approved and therefore no royalty fees have been earned under the hemophilia A Pfizer agreement. 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 clinical or regulatory milestones have been included in the $70.0 million transaction price, as 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 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 SB-525 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) fifteen 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 SB-525 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 SB-525 in the terminated country or countries.

The Company has identified the performance obligations within the hemophilia A Pfizer agreement as a license to the technology and on-going 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 on-going services through 2020, the estimated period the Company will perform research services. The estimated period of performance and project cost is reviewed quarterly and adjusted, as needed, to reflect the Company’s current assumptions regarding the timing of its deliverables. As of March 31, 2019 and December 31, 2018, the Company had deferred revenue of $16.9 million and $10.0 million, respectively, related to this agreement.

In March 2019 the Company received new data results in the hemophilia A collaboration agreement with Pfizer, and expansion of patients for the ongoing trial. As a result, the estimated project cost increased and the proportional performance was updated based on the actual services delivered to Pfizer as a percentage of the updated project cost as of March 31, 2019. The increase in project cost resulted in a decrease in the measure of the proportional cumulative performance. During the three months ended March 31, 2019, the Company recorded a revenue reduction of approximately $3.0 million or 38% of total revenues due to a decrease in the measure of the proportional cumulative performance. During the three months ended March 31, 2018 the Company recognized revenue of $7.7 million, related to the upfront fee that was received.

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 transcription factors (“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.

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.

None of the clinical or regulatory milestones have been included in the $12.0 million transaction price, as 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 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 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) fifteen 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 has identified the performance obligations within this agreement as a license to the technology and on-going 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 on-going services through March 31, 2019, over the estimated period the Company will perform research services. The estimated period of performance and project cost is reviewed quarterly and adjusted, as needed, to reflect the Company’s current assumptions regarding the timing of its deliverables. As of March 31, 2019 and December 31, 2018, the Company had deferred revenue of $9.2 million and $9.8 million, respectively, related to this agreement. During the three months ended March 31, 2019 and 2018 the Company recognized revenue of $0.6 million and $0.5 million, respectively, related to the upfront fee that was received upon entering into the agreement.

Bioverativ Inc., a Sanofi Genzyme company

In January 2014, the Company entered into an exclusive worldwide collaboration and license agreement with Sanofi to develop therapeutics for hemoglobinopathies, focused on beta-thalassemia and sickle cell disease (“SCD”). 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 investigational new drug (“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 development and sales milestone payments upon the achievement of specified regulatory, clinical development and sales milestones. In addition, the Company will also be 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, no milestone payments have been received and 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 of $75.7 million includes the upfront license fee of $20.0 million and $55.7 million estimated reimbursable service costs for identified research projects over the estimated performance period, as 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 clinical or regulatory milestones have been included in the transaction price.

The Company has identified the performance obligations within this arrangement as a license to the technology and on-going 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 estimated period of performance and project cost is reviewed quarterly and adjusted, as needed, to reflect the Company’s current assumptions regarding the timing of its deliverables. As of March 31, 2019 and December 31, 2018, the Company had deferred revenue of $3.8 million and $4.6 million, respectively, related to this agreement.

Revenues recognized under the agreement for the three months ended March 31, 2019 and 2018 were as follows (in thousands):

	Three Months Ended
	March 31,
	2019		2018
Revenue related to Sanofi agreement:
Recognition of upfront fee	$	752	$	1,154
Research services		1,197		3,228
Total	$	1,949	$	4,382

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 March 31, 2019 and December 31, 2018, the Company had received $1.7 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 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, therefore as of March 31, 2019 and December 31, 2018, the $1.9 million and $1.8 million, respectively, including interest, related to this award are recorded as a loan in other long-term liabilities on the accompanying Condensed Consolidated Balance Sheets.

Commitments and Contingencies

3 Months Ended

Mar. 31, 2019

Commitments And Contingencies Disclosure [Abstract]

Commitments and Contingencies

NOTE 8—COMMITMENTS AND CONTINGENCIES

Leases

Sangamo occupies approximately 37,900 square feet of office and laboratory space in Richmond, CA through August 2026. The Company leases two additional properties located in Richmond, CA: one occupies approximately 7,700 square feet of research and office space that expires in August 2019, and another one which occupies approximately 41,400 square feet with an original expiration date in December 2021, which has been terminated as of March 31, 2019. Accordingly, all assets and liabilities associated with that lease have been written off as of March 31, 2019. In addition, the Company leases two properties in Valbonne, France. The first lease is for approximately 14,036 square feet of research and office space that expires in June 2022. The second lease, which was executed in March 2019 with a commencement date of April 1, 2019, is for approximately 6,800 square feet of office space and expires in March 2022.

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 ten 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.

In November 2017, the Company executed a lease agreement for approximately 87,700 square feet of office and research and development laboratory facilities in Brisbane, California which expires in May 2029. As of March 31, 2019, certain lease components were still under construction. The commencement date for approximately 35,080 square feet of the office space occurred in January 2019 while the commencement date for the remaining approximately 52,620 square feet is currently expected to be in June 2019. Since the lease has not commenced as of March 31, 2019 for certain lease components, the related ROU asset and lease liability associated with such certain lease components have not yet been measured or recognized on the condensed consolidated balance sheets. The Company has the right to make tenant improvements, including the addition of laboratory space, with a lease incentive allowance of $6.8 million on the currently occupied space and $10.2 million on the lease component that has not yet commenced. The total undiscounted lease payments due over the lease term related to certain lease components with the expected commencement date in June 2019 are $29.3 million. This lease includes two renewal options at the election of the Company to extend the lease for an additional five years each. 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 three months ended March 31, 2019, the Company incurred $1.2 million of lease costs included in operating expenses in the condensed consolidated statement of operations in relation to these operating leases. Variable lease expense was $0.2 million and was not included in the measurement of the Company’s operating ROU assets and lease liabilities.

Cash paid for amounts included in the measurement of operating lease liabilities for the three months ended March 31, 2019 was $0.5 million and was included in net cash used in operating activities in the Company’s condensed consolidated statements of cash flows.

As of March 31, 2019, the maturities of the Company’s operating lease liabilities were as follows (in thousands):

	Total
Nine months ending December 31, 2019	$	1,845
2020		3,177
2021		3,163
2022		3,173
2023		3,240
Thereafter		14,687
Total lease payments		29,285
Less:
Imputed interest		(7,850	)
Tenant improvement allowance		(6,816	)
Total	$	14,619

Reported as of March 31, 2019:
Operating lease liabilities - current	$	1,320
Operating lease liabilities - long-term		13,299
Total	$	14,619

As of March 31, 2019, the weighted-average remaining lease term is 9.0 years and the weighted-average discount rate used to determine the operating lease liability was 6.9% for the Company’s operating leases.

The Company does not have any financing leases.

Contingencies

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

Acquisition of Txcell S.A.

3 Months Ended

Mar. 31, 2019

Business Combinations [Abstract]

Acquisition of Txcell S.A.

NOTE 10—ACQUISITION OF TXCELL S.A.

On July 20, 2018, Sangamo entered into a SPA with certain shareholders of TxCell. Additionally, the Company and TxCell entered into a Tender Offer Agreement (“TOA”), pursuant to which the Company agreed to acquire 100% of the equity interests of TxCell. On October 1, 2018 (the “Acquisition Date”), the Company completed the acquisition of 13,519,036 ordinary shares of TxCell (“TxCell Ordinary Shares”), representing approximately 53% of the outstanding share capital and voting rights of TxCell, pursuant to the SPA (the “Block Transaction”). TxCell specializes in developing cellular immunotherapy platforms that use regulator T-cells (“Tregs”) to treat severe autoimmune and inflammatory diseases and the Company expects that the acquisition of TxCell will accelerate its entry into the clinic with a CAR-Treg therapy.

The Company also entered into arrangements with the holders of approximately 477,000 “free shares” of TxCell pursuant to which the Company has the right to purchase such shares from the holders thereof (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”). Of the 477,000 shares, approximately 453,000 are related to vested free shares with the remaining related to unvested free shares. The purchase price for each such free share acquired by the Company upon exercise of a Free Shares Option will be based on the performance of the Company’s stock price from the announcement of the transactions contemplated by the SPA and TOA through the Acquisition Date. At the Acquisition Date, the Free Shares Options purchase price was valued at €2.58 per share or approximately $2.99 per share using an exchange rate of $1.16. If the Company’s stock price increases during that time period, the Free Shares Options purchase price per share will proportionately increase. If the Company’s stock price decreases, the Free Shares Options purchase price will proportionately decrease, the minimum purchase price of €2.58 per share only applies to vested Free Shares Options that are not yet transferable shares, subject to certain exceptions.

At the Acquisition Date, the fair value of the Free Shares Options was estimated to be a liability of $0.2 million based on an option pricing method. The value was included in the purchase consideration and is recorded as a non-controlling interest on the condensed consolidated balance sheets. 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 Company assesses this fair value on a quarterly basis with changes in fair value being recognized in operations. The fair value of the Free Shares Options was estimated to be an asset of $0.4 million as of March 31, 2019.

In September 2018, the Company provided TxCell with a $5.2 million loan (the “TxCell Loan”) that was deemed to be part of the purchase consideration for accounting purposes. The TxCell Loan, together with $40.5 million cash paid to acquire the TxCell Ordinary Shares and the $0.2 million estimated fair value of the Free Shares Options, comprise the aggregate purchase consideration of $45.9 million as of the Acquisition Date.

Management estimated the fair value of tangible and intangible assets and liabilities in accordance with the applicable accounting guidance for business combinations and utilized the services of third-party valuation consultants. Balances subject to adjustment primarily include the valuations of acquired assets (tangible and intangible), liabilities assumed, as well as tax-related matters. During the measurement period, the Company may record adjustments to the provisional amounts recognized. The Company expects the allocation of the consideration transferred to be final within the measurement period (up to one year from the Acquisition Date).

The TxCell Acquisition was accounted for as a business combination in accordance with ASC Topic 805, Business Combinations. The operating results of TxCell after the Acquisition Date have been included in the Company’s Condensed Consolidated Statements of Operations.

Fair Value Estimate of Assets Acquired and Liabilities Assumed

Under ASC Topic 805, an acquirer recognizes and consolidates assets acquired, liabilities assumed, and any non-controlling interest at 100% of their fair values as of the acquisition date (regardless of the acquirer’s percentage ownership in the acquiree). As goodwill is calculated as a residual, all goodwill of the acquired business, not just the acquirer’s share, is recognized under this “full-goodwill” approach. Recognized goodwill is allocated between the controlling and non-controlling interests. Although this allocation is not presented separately on the acquirer’s balance sheet, it is necessary so that a goodwill impairment charge recognized in a period following the business combination by an acquirer is appropriately allocated between controlling and non-controlling interests. There were no goodwill impairments during the three months ended March 31, 2019 or during 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 March 31, 2019 and December 31, 2018.

The following table summarizes the estimated fair value of the net assets acquired as of the Acquisition Date (in thousands):

	October 1, 2018
Consideration transferred	$	45,911
Fair value of non-controlling interest		35,829
Fair value of TxCell	$	81,740

Cash		4,779
Current assets		2,427
Property and equipment		1,857
IPR&D		55,019
Other assets		155
Current liabilities		(9,761	)
Assumed debt liabilities		(4,933	)
Deferred tax liability, net		(6,798	)
Fair value of net identifiable assets acquired		42,745
Goodwill		38,995
Total fair value of net assets acquired	$	81,740

Consideration Transferred

Consideration transferred as of October 1, 2018 consists of the 13,519,036 TxCell Ordinary Shares acquired by the Company on the Acquisition Date of approximately $2.99 per share, the $5.2 million TxCell Loan and approximately $0.2 million for the fair value of the Free Shares Options.

Non-controlling Interest

The fair value of the non-controlling interest at the Acquisition Date was based on the $2.99 acquisition price per share for the 11,981,867 Ordinary Shares that were not purchased by the Company on the Acquisition Date.

On November 1, 2018, pursuant to the TOA, the Company commenced a cash tender offer (the “Offer”) to acquire all of the TxCell Ordinary Shares not held by the Company for the same per share price paid in the Block Transaction. Following the completion of the Offer on November 23, 2018, the Company initiated compulsory squeeze-out procedures applicable to French public companies to acquire the remaining TxCell Ordinary Shares, other than the free shares that were subject to the Free Shares Options. Subsequent to the Acquisition Date and through December 31, 2018, the Company acquired 11,528,635 TxCell Ordinary Shares which, when aggregated with the 13,519,036 Ordinary Shares acquired at the Acquisition Date, resulted in the Company owning 98.2% of all TxCell Ordinary Shares as of December 31, 2018. The 11,528,635 shares acquired subsequent to the Acquisition Date were acquired for total consideration of approximately $33.9 million, or $2.94 per share. As of December 31, 2018, the aggregate purchase consideration was approximately $80.4 million through the completion of this purchase, with approximately 453,000 Ordinary Shares (vested free shares), which remain outstanding and are subject to purchase by the Company as noted above, with an estimated fair value of approximately $0.7 million as of March 31, 2019.

Non-controlling interest as of March 31, 2019 was as follows (in thousands):

Non-controlling interest at January 1, 2018	$	—
Non-controlling interest at Acquisition Date		35,829
Shares acquired post acquisition		(34,516	)
Non-controlling interest of acquired entity		1,313
Foreign currency effect		(19	)
Loss attributable to non-controlling interest		(555	)
Non-controlling interest at December 31, 2018		739
Loss attributable to non-controlling interest		(53	)
Non-controlling interest at March 31, 2019	$	686

Organization, Basis of Presentation and Summary of Significant Accounting Policies (Policies)

3 Months Ended

Mar. 31, 2019

Accounting Policies [Abstract]

Basis of Presentation

Use of Estimates

Foreign Currency Translation

Reclassifications

Cash and Cash Equivalents

Marketable Securities

Non-Current Restricted Cash

Non-current Restricted Cash

Fair Value Measurements

Leases

Revenue Recognition

Recent Accounting Pronouncements

Recently Adopted

Revenue Recognition

Simplified Disclosure

Accounting for Leases

The impact of the adoption of ASC Topic 842 on the accompanying condensed consolidated balance sheet as of January 1, 2019 was as follows (in thousands):

	December 31, 2018			Adjustments Due to the Adoption of ASC Topic 842			January 1, 2019
Assets:
Property and equipment, net	$	78,723		$	(62,500	)	$	16,223
Operating lease right-of-use assets		—			8,753			8,753
Prepaid rent		—			36,025			36,025

Liabilities:
Operating lease liabilities - current⁽¹⁾		—			1,408			1,408
Deferred rent⁽¹⁾		271			(271	)		—
Build-to-suit lease obligation⁽²⁾		27,689			(27,689	)		—
Operating lease liabilities - long-term⁽²⁾		—			7,933			7,933

Accumulated deficit		(562,696	)		897			(561,799	)

(1)

Operating lease liabilities – current and deferred rent are included in accounts payable and accrued liabilities on the condensed consolidated balance sheets.

(2)

Build-to-suit lease obligation and operating lease liabilities – long-term are included in long-term portion of lease liabilities on the condensed consolidated balance sheets.

Not yet adopted

Collaborative Arrangements

Goodwill Impairment Testing

Organization, Basis of Presentation and Summary of Significant Accounting Policies (Tables)

3 Months Ended

Mar. 31, 2019

Topic 842 [Member]

Impact of Adoption of ASC on Condensed Consolidated Balance Sheet

The impact of the adoption of ASC Topic 842 on the accompanying condensed consolidated balance sheet as of January 1, 2019 was as follows (in thousands):

	December 31, 2018			Adjustments Due to the Adoption of ASC Topic 842			January 1, 2019
Assets:
Property and equipment, net	$	78,723		$	(62,500	)	$	16,223
Operating lease right-of-use assets		—			8,753			8,753
Prepaid rent		—			36,025			36,025

Liabilities:
Operating lease liabilities - current⁽¹⁾		—			1,408			1,408
Deferred rent⁽¹⁾		271			(271	)		—
Build-to-suit lease obligation⁽²⁾		27,689			(27,689	)		—
Operating lease liabilities - long-term⁽²⁾		—			7,933			7,933

Accumulated deficit		(562,696	)		897			(561,799	)

(1)

Operating lease liabilities – current and deferred rent are included in accounts payable and accrued liabilities on the condensed consolidated balance sheets.

(2)

Build-to-suit lease obligation and operating lease liabilities – long-term are included in long-term portion of lease liabilities on the condensed consolidated balance sheets.

Fair Value Measurements (Tables)

3 Months Ended

Mar. 31, 2019

Fair Value Disclosures [Abstract]

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

	March 31, 2019
	Fair Value Measurements
	Total		Level 1		Level 2		Level 3
Assets:
Cash equivalents:
Money market funds	$	15,233	$	15,233	$	—	$	—
Commercial paper securities		4,990		—		4,990		—
Total		20,223		15,233		4,990		—
Marketable securities:
Commercial paper securities		180,399		—		180,399		—
Corporate debt securities		70,948		—		70,948		—
U.S. government-sponsored entity debt securities		18,681		—		18,681		—
Total		270,028		—		270,028		—
Total cash equivalents and marketable securities	$	290,251	$	15,233	$	275,018	$	—

Free shares asset	$	355	$	—	$	—	$	355

	December 31, 2018
	Fair Value Measurements
	Total		Level 1		Level 2		Level 3
Assets:
Cash equivalents:
Money market funds	$	103,291	$	103,291	$	—	$	—
Total		103,291		103,291		—		—
Marketable securities:
Commercial paper securities		177,224		—		177,224		—
Corporate debt securities		63,870		—		63,870		—
U.S. government-sponsored entity debt securities		18,621		—		18,621		—
Total		259,715		—		259,715		—
Total cash equivalents and marketable securities	$	363,006	$	103,291	$	259,715	$	—
Liabilities
Free shares liability	$	154	$	—	$	—	$	154
Total	$	154	$	—	$	—	$	154

Summary of Estimated Fair Value of Free Shares Valuation Assumptions

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 operating expenses in the condensed consolidated statement of operations.

Free Shares valuation assumptions:	March 31, 2019			December 31, 2018
Sangamo Stock Price (USD)	$	9.54		$	11.48
TxCell Stock Price (EUR)	$	2.36		$	2.58
EUR/ USD Exchange Rate		0.89			0.87
Estimated Correlation Sangamo and TxCell Stock Prices		50.0	%		—
Sangamo Stock Price (USD) Volatility Estimate		87.7	%		79.9	%
TxCell Stock Price (EUR) Volatility Estimate		82.8	%		8.6	%
EUR/ USD Exchange Rate Volatility Estimate		7.2	%		7.7	%
Risk Free Rate	Varies by expected exercise date			Varies by expected exercise date

- 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

Marketable Securities (Tables)

3 Months Ended

Mar. 31, 2019

Investments Debt And Equity Securities [Abstract]

Summary of Cash Equivalents and Available-for-Sale Securities

The table below summarizes the Company’s cash equivalents and available-for-sale securities (in thousands):

			Gross		Gross
	Amortized		Unrealized		Unrealized			Estimated
	Cost		Gains		(Losses)			Fair Value
March 31, 2019
Assets
Cash equivalents:
Money market funds	$	15,233	$	—	$	—		$	15,233
Commercial paper securities		4,990		—		—			4,990
Total		20,223		—		—			20,223
Available-for-sale securities:
Commercial paper securities		180,380		19		—			180,399
Corporate debt securities		70,973		—		(25	)		70,948
U.S. government-sponsored entity debt securities		18,681		—		—			18,681
Total		270,034		19		(25	)		270,028
Total cash equivalents and available-for-sale securities	$	290,257	$	19	$	(25	)	$	290,251
December 31, 2018
Cash equivalents:
Money market funds	$	103,291	$	—	$	—		$	103,291
Total		103,291		—		—			103,291
Available-for-sale securities:
Commercial paper securities		177,353		—		(129	)		177,224
Corporate debt securities		63,981		—		(111	)		63,870
U.S. government-sponsored entity debt securities		18,640		—		(19	)		18,621
Total		259,974		—		(259	)		259,715
Total cash equivalents and available-for-sale securities	$	363,265		—	$	(259	)	$	363,006

Acquisition of Txcell S.A. (Tables)

3 Months Ended

Mar. 31, 2019

Business Combinations [Abstract]

Summary of Estimated Fair Value of Net Assets Acquired

The following table summarizes the estimated fair value of the net assets acquired as of the Acquisition Date (in thousands):

	October 1, 2018
Consideration transferred	$	45,911
Fair value of non-controlling interest		35,829
Fair value of TxCell	$	81,740

Cash		4,779
Current assets		2,427
Property and equipment		1,857
IPR&D		55,019
Other assets		155
Current liabilities		(9,761	)
Assumed debt liabilities		(4,933	)
Deferred tax liability, net		(6,798	)
Fair value of net identifiable assets acquired		42,745
Goodwill		38,995
Total fair value of net assets acquired	$	81,740

Summary of Non-controlling Interest

Non-controlling interest as of March 31, 2019 was as follows (in thousands):

Non-controlling interest at January 1, 2018	$	—
Non-controlling interest at Acquisition Date		35,829
Shares acquired post acquisition		(34,516	)
Non-controlling interest of acquired entity		1,313
Foreign currency effect		(19	)
Loss attributable to non-controlling interest		(555	)
Non-controlling interest at December 31, 2018		739
Loss attributable to non-controlling interest		(53	)
Non-controlling interest at March 31, 2019	$	686

Organization, Basis of Presentation and Summary of Significant Accounting Policies - Additional Information (Detail) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		12 Months Ended
	Mar. 31, 2019	Mar. 31, 2018	Dec. 31, 2018	Jan. 01, 2019	Jan. 01, 2018
Organization And Summary Of Significant Accounting Policies [Line Items]
Revenues	$ 8,071	$ 12,637
Increase in net loss	$ 42,203	$ 20,187
Liquid investments purchased with original maturities	three months or less
Non-current restricted cash	$ 3,500		$ 3,500
Accumulated deficit	(603,949)		(562,696)
Topic 606 [Member] \| Difference between Revenue Guidance in Effect before and after Topic 606 [Member]
Organization And Summary Of Significant Accounting Policies [Line Items]
Accumulated deficit					$ 1,100
Topic 842 [Member]
Organization And Summary Of Significant Accounting Policies [Line Items]
Accumulated deficit				$ (561,799)
Topic 842 [Member] \| Adjustments Due to the Adoption of ASC Topic 842 [Member]
Organization And Summary Of Significant Accounting Policies [Line Items]
Accumulated deficit				$ 897
Intangible Assets [Member]
Organization And Summary Of Significant Accounting Policies [Line Items]
Reclassification adjustment			(600)
Other Noncurrent Assets [Member]
Organization And Summary Of Significant Accounting Policies [Line Items]
Reclassification adjustment			$ 600
Pfizer [Member]
Organization And Summary Of Significant Accounting Policies [Line Items]
Revenues	$ 8,100
Pfizer [Member] \| Customer Concentration Risk [Member] \| Total revenues [Member]
Organization And Summary Of Significant Accounting Policies [Line Items]
Percentage of revenues		61.00%
Kite Pharma, Inc. ("Kite") [Member] \| Customer Concentration Risk [Member] \| Total revenues [Member]
Organization And Summary Of Significant Accounting Policies [Line Items]
Percentage of revenues	75.00%
Bioverativ Inc [Member]
Organization And Summary Of Significant Accounting Policies [Line Items]
Revenues	$ 1,949	$ 4,382
Bioverativ Inc [Member] \| Customer Concentration Risk [Member] \| Total revenues [Member]
Organization And Summary Of Significant Accounting Policies [Line Items]
Percentage of revenues	18.00%	35.00%
Collaboration Agreement [Member] \| Pfizer [Member]
Organization And Summary Of Significant Accounting Policies [Line Items]
Revenues	$ (3,000)
Increase in net loss	$ 3,000
Increase in basic net loss per share	$ 0.03

Fair Value Measurements - Summary of Fair Value Measurements of Cash Equivalents, Available-for-Sale Marketable Securities and Free Share Asset/Liability (Detail) - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Total marketable securities	$ 270,028	$ 259,715
Money market funds [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Total cash equivalents	15,233	103,291
Commercial paper securities [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Total cash equivalents	4,990
Total marketable securities	180,399	177,224
Corporate debt securities [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Total marketable securities	70,948	63,870
U.S. government sponsored entity debt securities [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Total marketable securities	18,681	18,621
Fair value on recurring basis [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Total cash equivalents	20,223	103,291
Total marketable securities	270,028	259,715
Total cash equivalents and marketable securities and free shares asset	290,251	363,006
Total liabilities		154
Fair value on recurring basis [Member] \| Money market funds [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Total cash equivalents	15,233	103,291
Fair value on recurring basis [Member] \| Commercial paper securities [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Total cash equivalents	4,990
Total marketable securities	180,399	177,224
Fair value on recurring basis [Member] \| Free Shares Asset [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Total cash equivalents and marketable securities and free shares asset	355
Fair value on recurring basis [Member] \| Free Share Liability [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Total liabilities		154
Fair value on recurring basis [Member] \| Level 1 [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Total cash equivalents	15,233	103,291
Total cash equivalents and marketable securities and free shares asset	15,233	103,291
Fair value on recurring basis [Member] \| Level 1 [Member] \| Money market funds [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Total cash equivalents	15,233	103,291
Fair value on recurring basis [Member] \| Level 2 [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Total cash equivalents	4,990
Total marketable securities	270,028	259,715
Total cash equivalents and marketable securities and free shares asset	275,018	259,715
Fair value on recurring basis [Member] \| Level 2 [Member] \| Commercial paper securities [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Total cash equivalents	4,990
Total marketable securities	180,399	177,224
Fair value on recurring basis [Member] \| Level 3 [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Total liabilities		154
Fair value on recurring basis [Member] \| Level 3 [Member] \| Free Shares Asset [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Total cash equivalents and marketable securities and free shares asset	355
Fair value on recurring basis [Member] \| Level 3 [Member] \| Free Share Liability [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Total liabilities		154
Fair value on recurring basis [Member] \| Corporate debt securities [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Total marketable securities	70,948	63,870
Fair value on recurring basis [Member] \| Corporate debt securities [Member] \| Level 2 [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Total marketable securities	70,948	63,870
Fair value on recurring basis [Member] \| U.S. government sponsored entity debt securities [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Total marketable securities	18,681	18,621
Fair value on recurring basis [Member] \| U.S. government sponsored entity debt securities [Member] \| Level 2 [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Total marketable securities	$ 18,681	$ 18,621

Marketable Securities - Summary of Cash Equivalents and Available-for-Sale Securities (Detail) - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018
Schedule Of Available For Sale Securities [Line Items]
Cash equivalents, Amortized Cost	$ 80,968	$ 140,418
Available-for-sale securities, Amortized Cost	270,034	259,974
Available-for-sale securities, Gross Unrealized Gains	19
Available-for-sale securities, Gross Unrealized (Losses)	(25)	(259)
Available-for-sale securities, Estimated Fair Value	270,028	259,715
Total cash equivalents and available-for-sale securities, Amortized Cost	290,257	363,265
Total cash equivalents and available-for-sale securities, Gross Unrealized Gains	19
Total cash equivalents and available-for-sale securities, Gross Unrealized (Losses)	(25)	(259)
Total cash equivalents and available-for-sale securities, Estimated Fair Value	290,251	363,006
Money market funds [Member]
Schedule Of Available For Sale Securities [Line Items]
Cash equivalents, Amortized Cost	15,233	103,291
Cash equivalents, Estimated Fair Value	15,233	103,291
Commercial paper securities [Member]
Schedule Of Available For Sale Securities [Line Items]
Cash equivalents, Amortized Cost	4,990
Cash equivalents, Estimated Fair Value	4,990
Available-for-sale securities, Amortized Cost	180,380	177,353
Available-for-sale securities, Gross Unrealized Gains	19
Available-for-sale securities, Gross Unrealized (Losses)		(129)
Available-for-sale securities, Estimated Fair Value	180,399	177,224
Cash equivalents [Member]
Schedule Of Available For Sale Securities [Line Items]
Cash equivalents, Amortized Cost	20,223	103,291
Cash equivalents, Estimated Fair Value	20,223	103,291
Corporate debt securities [Member]
Schedule Of Available For Sale Securities [Line Items]
Available-for-sale securities, Amortized Cost	70,973	63,981
Available-for-sale securities, Gross Unrealized (Losses)	(25)	(111)
Available-for-sale securities, Estimated Fair Value	70,948	63,870
U.S. government sponsored entity debt securities [Member]
Schedule Of Available For Sale Securities [Line Items]
Available-for-sale securities, Amortized Cost	18,681	18,640
Available-for-sale securities, Gross Unrealized (Losses)		(19)
Available-for-sale securities, Estimated Fair Value	$ 18,681	$ 18,621

Major Customers, Partnerships and Strategic Alliances - Additional Information (Detail)		1 Months Ended						3 Months Ended		12 Months Ended
	Apr. 05, 2018 USD ($)	May 31, 2018 USD ($)	Apr. 30, 2018 USD ($)	Feb. 28, 2018	Dec. 31, 2017 USD ($)	May 31, 2017 USD ($)	Jan. 31, 2014 USD ($) Program	Mar. 31, 2019 USD ($) Product Milestone	Mar. 31, 2018 USD ($)	Dec. 31, 2018 USD ($)
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Revenues								$ 8,071,000	$ 12,637,000
Number of research programs \| Program							2
Other long-term liabilities								1,911,000		$ 1,960,000
California Institute for Regenerative Medicine ("CIRM") [Member]
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Funds due under the agreement		$ 8,000,000
Other long-term liabilities								1,900,000		1,800,000
California Institute for Regenerative Medicine ("CIRM") [Member] \| Research Grants [Member]
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Revenues								$ 1,700,000		1,700,000
Kite Pharma, Inc. ("Kite") [Member] \| Collaboration and License Agreement [Member]
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Collaboration waiting period under HSR expiration date at which time agreement became effective				Apr. 05, 2018
Milestone payments received			$ 150,000,000
Initial research term of agreement								6 years
Research agreement term								an option to extend the research term of the agreement for up to two additional one-year periods for a separate upfront fee of $10.0 million per year.
Lease agreement, extendable lease term								2 years
Separate upfront fee								$ 10,000,000
Collaborative arrangement transaction price								185,900,000
Revenues under agreement								150,000,000
Collaborative arrangement estimated reimbursable service costs								35,900,000
Deferred revenue								125,300,000		131,500,000
Kite Pharma, Inc. ("Kite") [Member] \| Collaboration and License Agreement [Member] \| Collaboration Agreements [Member]
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Revenues								6,200,000	0
Kite Pharma, Inc. ("Kite") [Member] \| Collaboration and License Agreement [Member] \| Reimbursable Service Costs [Member]
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Revenues								2,100,000	0
Kite Pharma, Inc. ("Kite") [Member] \| Collaboration and License Agreement [Member] \| Maximum [Member]
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Development and sales-based milestone payments to be received	$ 3,010,000,000
Kite Pharma, Inc. ("Kite") [Member] \| Collaboration and License Agreement [Member] \| Achievement of Specified Research, Clinical Development, Regulatory and First Commercial Sale Milestones [Member]
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") [Member] \| Collaboration and License Agreement [Member] \| Achievement of Specified Sales-based Milestones if Annual Worldwide Net Sales of Licensed Products Reach Specified Levels [Member]
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
Pfizer [Member]
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Milestone payments received								0
Revenues under agreement						$ 70,000,000
Deferred revenue								16,900,000		10,000,000
Revenues								$ 8,100,000
Number of products approved \| Product								0
Pfizer [Member] \| Collaboration Agreements [Member]
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Revenues									7,700,000
Revenue reduction due to decrease in measure of proportional cumulative performance								$ 3,000,000
Percentage of total revenue due to decrease in measure of proportional cumulative performance								38.00%
Pfizer [Member] \| SB-525 [Member]
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Number of milestones included in transaction price \| Milestone								0
Pfizer [Member] \| Royalty Revenues [Member]
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Revenues								$ 0
Pfizer [Member] \| C9ORF72 [Member]
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Revenues under agreement					$ 12,000,000
Deferred revenue								9,200,000		9,800,000
Revenues								$ 600,000	500,000
Number of milestones included in transaction price \| Milestone								0
Pfizer [Member] \| Maximum [Member] \| SB-525 [Member]
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
Pfizer [Member] \| Maximum [Member] \| Other Products [Member]
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Milestone revenue receivable						175,000,000
Pfizer [Member] \| Achievement of Specified Clinical Development Intellectual Property and Regulatory Milestones [Member] \| Maximum [Member]
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Development and sales-based milestone payments to be received						208,500,000
Pfizer [Member] \| Achievement of First Commercial Sale Milestones [Member] \| Maximum [Member]
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Development and sales-based milestone payments to be received						$ 475,000,000
Pfizer [Member] \| Achievement of Specified Preclinical Development Clinical Development and First Commercial Sale Milestones \| Maximum [Member] \| C9ORF72 [Member]
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Development and sales-based milestone payments to be received					60,000,000
Pfizer [Member] \| Achievement of Commercial Milestones \| Maximum [Member] \| C9ORF72 [Member]
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Development and sales-based milestone payments to be received					$ 90,000,000
Sanofi [Member]
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Milestone payments received								$ 0
Revenues under agreement							$ 20,000,000
Number of products approved \| Product								0
Sanofi [Member] \| Collaboration and License Agreement [Member]
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Deferred revenue								$ 3,800,000		$ 4,600,000
Sanofi [Member] \| Collaboration and License Agreement [Member] \| Royalty Revenues [Member]
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Revenues								0
Sanofi [Member] \| Collaboration and License Agreement [Member] \| Achievement Of Specified Clinical Development And Regulatory Milestones [Member] \| Maximum [Member]
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Development and sales-based milestone payments to be received							115,800,000
Sanofi [Member] \| Collaboration and License Agreement [Member] \| Achievement of Specified Sales Milestones [Member] \| Maximum [Member]
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Development and sales-based milestone payments to be received							160,500,000
Bioverativ Inc [Member]
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Revenues								1,949,000	4,382,000
Bioverativ Inc [Member] \| Collaboration Agreements [Member]
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Revenues								752,000	$ 1,154,000
Bioverativ Inc [Member] \| Collaboration and License Agreement [Member]
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Collaborative arrangement transaction price								75,700,000
Revenues under agreement								20,000,000
Collaborative arrangement estimated reimbursable service costs								$ 55,700,000
Number of milestones included in transaction price \| Milestone								0
Bioverativ Inc [Member] \| Collaboration and License Agreement [Member] \| Maximum [Member]
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Development and sales-based milestone payments to be received							$ 276,300,000

Commitments and Contingencies - Additional Information (Detail) $ in Thousands	1 Months Ended	3 Months Ended
	Nov. 30, 2017 ft²	Mar. 31, 2019 USD ($) ft² Property Option
Commitments And Contingencies [Line Items]
Tenant improvement allowance \| $		$ 6,816
Lessee, Operating Lease, Existence of Option to Extend [true false]		true
Operating lease costs \| $		$ 1,200
Variable lease expense \| $		200
Cash paid for operating lease liabilities included net cash used in operating activities \| $		$ 500
Operating lease, weighted-average remaining lease term		9 years
Operating lease, weighted-average discount rate		6.90%
Richmond Lease [Member]
Commitments And Contingencies [Line Items]
Additional property available under lease \| Property		2
Richmond Lease [Member] \| Office and Laboratory [Member]
Commitments And Contingencies [Line Items]
Area of space leased		37,900
Richmond Lease [Member] \| Operating Lease One [Member] \| Research and Office Space [Member]
Commitments And Contingencies [Line Items]
Area of space leased		7,700
Lease expiration date		Aug. 31, 2019
Richmond Lease [Member] \| Operating Lease Two [Member]
Commitments And Contingencies [Line Items]
Area of space leased		41,400
Lease expiration date		Dec. 31, 2021
Lease termination date		Mar. 31, 2019
Valbonne Lease [Member]
Commitments And Contingencies [Line Items]
Additional property available under lease \| Property		2
Valbonne Lease [Member] \| Operating Lease One [Member] \| Research and Office Space [Member]
Commitments And Contingencies [Line Items]
Area of space leased		14,036
Lease expiration date		Jun. 30, 2022
Valbonne Lease [Member] \| Operating Lease Two [Member] \| Office Space
Commitments And Contingencies [Line Items]
Area of space leased		6,800
Lease expiration date		Mar. 31, 2022
Lease commencement date		Apr. 01, 2019
Richmond and Valbonne Leases [Member]
Commitments And Contingencies [Line Items]
Lease, option to extend, description		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 ten years.
Richmond and Valbonne Leases [Member] \| Maximum [Member]
Commitments And Contingencies [Line Items]
Lease agreement, extendable lease term		10 years
Richmond and Valbonne Leases [Member] \| Minimum [Member]
Commitments And Contingencies [Line Items]
Lease agreement, extendable lease term		5 years
Brisbane Lease [Member]
Commitments And Contingencies [Line Items]
Area of space leased	87,700
Lease expiration date	May 31, 2029
Remaining commencement, area of space leased		52,620
Expected lease commencement period		2019-06
Tenant improvement allowance \| $		$ 6,800
Lease not yet commenced, tenant improvement allowance \| $		10,200
Lease not yet commenced, undiscounted lease payments \| $		$ 29,300
Number of lease term extension options \| Option		2
Brisbane Lease [Member] \| Maximum [Member]
Commitments And Contingencies [Line Items]
Lease agreement, extendable lease term		5 years
Brisbane Lease [Member] \| Office Space
Commitments And Contingencies [Line Items]
Commencement, area of space leased		35,080
Lease commencement period		2019-01

Acquisition of Txcell S.A. - Additional Information (Detail)		3 Months Ended		12 Months Ended
	Oct. 01, 2018 USD ($) $ / shares shares	Mar. 31, 2019 USD ($) shares	Dec. 31, 2018 USD ($) $ / shares shares	Dec. 31, 2018 USD ($) $ / shares shares	Mar. 31, 2019 € / shares	Dec. 31, 2018 € / shares shares	Oct. 01, 2018 € / shares	Jul. 20, 2018
Business Acquisition [Line Items]
Purchase price per share \| $ / shares	$ 2.99
Goodwill impairments		$ 0		$ 0
Number of shares not purchased by the acquirer \| shares	11,981,867
TxCell S.A. [Member]
Business Acquisition [Line Items]
Acquisition date		Oct. 01, 2018
Number of ordinary shares acquired \| shares	13,519,036		11,528,635
Percentage of share capital and voting rights acquired			98.20%	98.20%		98.20%
Number of remaining outstanding share owned by sellers \| shares		453,000	453,000	453,000		453,000
Purchase price per share \| (per share)	$ 2.99		$ 2.94	$ 2.94	€ 2.36	€ 2.58
Loan deemed to be part of purchase consideration	$ 5,200,000
Cash paid to ordinary shares acquired	40,500,000
Fair value of consideration payable	200,000	$ 700,000
Purchase consideration	$ 45,911,000		$ 33,900,000	$ 80,400,000
Fair value percentage at acquirer recognizes and consolidates assets acquired, liabilities assumed, and any non-controlling interest	100.00%
Consideration payable	$ 45,911,000		$ 33,900,000	$ 80,400,000
TxCell S.A. [Member] \| SPA and TOA [Member]
Business Acquisition [Line Items]
Percentage of equity interests agreed to acquire								100.00%
Number of free shares held by the holders \| shares	477,000
Purchase price per share \| (per share)	$ 2.99						€ 2.58
Exchange rate on purchase price	0.0116
Estimated fair value asset of free shares		$ 400,000
TxCell S.A. [Member] \| SPA and TOA [Member] \| Option Pricing Method [Member]
Business Acquisition [Line Items]
Estimated fair value liability of free shares	$ 200,000
TxCell S.A. [Member] \| SPA and TOA [Member] \| Minimum [Member]
Business Acquisition [Line Items]
Purchase price per share \| € / shares							€ 2.58
TxCell S.A. [Member] \| SPA [Member]
Business Acquisition [Line Items]
Number of ordinary shares acquired \| shares	13,519,036
Percentage of share capital and voting rights acquired	53.00%

Acquisition of Txcell S.A. - Summary of Estimated Fair Value of Net Assets Acquired (Detail) - USD ($) $ in Thousands		3 Months Ended	12 Months Ended
	Oct. 01, 2018	Dec. 31, 2018	Dec. 31, 2018	Mar. 31, 2019
Business Acquisition [Line Items]
Fair value of non-controlling interest		$ 35,829	$ 35,829
Goodwill		40,044	40,044	$ 39,283
TxCell S.A. [Member]
Business Acquisition [Line Items]
Consideration transferred	$ 45,911	$ 33,900	$ 80,400
Fair value of non-controlling interest	35,829
Fair value of TxCell	81,740
Cash	4,779
Current assets	2,427
Property and equipment	1,857
IPR&D	55,019
Other assets	155
Current liabilities	(9,761)
Assumed debt liabilities	(4,933)
Deferred tax liability, net	(6,798)
Fair value of net identifiable assets acquired	42,745
Goodwill	38,995
Total fair value of net assets acquired	$ 81,740

Basic and Diluted Net Loss Per Share - Additional Information (Detail) - shares	Mar. 31, 2019	Mar. 31, 2018
Earnings Per Share [Abstract]
Stock options and RSUs outstanding	11,604,633	8,858,623

Stock-Based Compensation - Stock-Based Compensation Expense (Detail) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Total stock-based compensation expense	$ 4,523	$ 3,050
Research and development [Member]
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Total stock-based compensation expense	2,298	1,759
General and administrative [Member]
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Total stock-based compensation expense	$ 2,225	$ 1,291

Stockholders' Equity - Additional Information (Detail) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	1 Months Ended
	Apr. 30, 2018	Mar. 31, 2019	May 31, 2017	Dec. 07, 2016
ATM Agreement [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Common stock issuable and sellable under offering agreement		$ 75.0	$ 75.0	$ 75.0
Common Stock [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Total shares issued	14.2
Public offering price of common stock issued	$ 16.25
Net proceeds from issuance of common stock, after deducting offering expenses	$ 215.8

Subsequent Events - Additional Information (Detail) - Common Stock [Member] - USD ($) $ / shares in Units, $ in Millions	1 Months Ended
	Apr. 30, 2019	Apr. 30, 2018
Subsequent Event [Line Items]
Total shares issued		14,200,000
Public offering price of common stock issued		$ 16.25
Net proceeds from issuance of common stock, after deducting offering expenses		$ 215.8
Subsequent Event [Member]
Subsequent Event [Line Items]
Total shares issued	12,650,000
Public offering price of common stock issued	$ 11.50
Net proceeds from issuance of common stock, after deducting offering expenses	$ 136.2
Subsequent Event [Member] \| Underwriters [Member]
Subsequent Event [Line Items]
Total shares issued	1,650,000

Organization, Basis of Presentation and Summary of Significant Accounting Policies - Impact of Adoption of ASC on Condensed Consolidated Balance Sheet (Details) - USD ($) $ in Thousands	Mar. 31, 2019	Jan. 01, 2019	Dec. 31, 2018
ASSETS
Property and equipment, net	$ 18,281		$ 78,723
Operating lease right-of-use assets	28,190
Prepaid rent	33,559
Liabilities:
Operating lease liabilities - current	1,320
Deferred rent			271
Build-to-suit lease obligation	13,299		27,689
Accumulated deficit	$ (603,949)		(562,696)
Build-to-Suit Lease [Member]
Liabilities:
Build-to-suit lease obligation			$ 27,689
Topic 842 [Member]
ASSETS
Property and equipment, net		$ 16,223
Operating lease right-of-use assets		8,753
Prepaid rent		36,025
Liabilities:
Operating lease liabilities - current		1,408
Build-to-suit lease obligation		7,933
Accumulated deficit		(561,799)
Topic 842 [Member] \| Adjustments Due to the Adoption of ASC Topic 842 [Member]
ASSETS
Property and equipment, net		(62,500)
Operating lease right-of-use assets		8,753
Prepaid rent		36,025
Liabilities:
Operating lease liabilities - current		1,408
Deferred rent		(271)
Build-to-suit lease obligation		7,933
Accumulated deficit		897
Topic 842 [Member] \| Build-to-Suit Lease [Member] \| Adjustments Due to the Adoption of ASC Topic 842 [Member]
Liabilities:
Build-to-suit lease obligation		$ (27,689)

Fair Value Measurements - Summary of Estimated Fair Value of Free Shares Valuation Assumptions (Detail)	3 Months Ended	12 Months Ended
	Mar. 31, 2019 $ / shares	Dec. 31, 2018 $ / shares	Mar. 31, 2019 € / shares	Dec. 31, 2018 € / shares	Oct. 01, 2018 $ / shares
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Valuation Techniques [Line Items]
Stock Price (USD)	$ 9.54	$ 11.48
Stock Price (EUR)					$ 2.99
EUR/ USD Exchange Rate	0.89	0.87	0.89	0.87
Stock Price Volatility Estimate [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Valuation Techniques [Line Items]
Volatility Estimate	87.7	79.9	87.7	79.9
Exchange Rate Volatility Estimate [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Valuation Techniques [Line Items]
Volatility Estimate	7.2	7.7	7.2	7.7
Risk Free Rate [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Valuation Techniques [Line Items]
Risk Free Rate	Varies by expected exercise date	Varies by expected exercise date
TxCell S.A. [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Valuation Techniques [Line Items]
Stock Price (EUR) \| (per share)		$ 2.94	€ 2.36	€ 2.58	$ 2.99
TxCell S.A. [Member] \| Estimated Correlation Sangamo [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Valuation Techniques [Line Items]
Volatility Estimate	50.0		50.0
TxCell S.A. [Member] \| Stock Price Volatility Estimate [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Valuation Techniques [Line Items]
Volatility Estimate	82.8	8.6	82.8	8.6

Major Customers, Partnerships and Strategic Alliances - Revenues Recognized under Agreement (Detail) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Revenues:
Total	$ 8,071	$ 12,637
Bioverativ Inc [Member]
Revenues:
Total	1,949	4,382
Bioverativ Inc [Member] \| Collaboration Agreements [Member]
Revenues:
Total	752	1,154
Bioverativ Inc [Member] \| Research Services [Member]
Revenues:
Total	$ 1,197	$ 3,228

Commitments and Contingencies - Summary of Maturities of Operating Lease Liabilities (Detail) - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018
Commitments And Contingencies Disclosure [Abstract]
Nine months ending December 31, 2019	$ 1,845
2020	3,177
2021	3,163
2022	3,173
2023	3,240
Thereafter	14,687
Total lease payments	29,285
Imputed interest	(7,850)
Tenant improvement allowance	(6,816)
Total	14,619
Operating lease liabilities - current	1,320
Build-to-suit lease obligation	13,299	$ 27,689
Total	$ 14,619

Acquisition of Txcell S.A. - Summary of Non-controlling Interest (Detail) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
	Mar. 31, 2019	Dec. 31, 2018
Noncontrolling Interest [Abstract]
Non-controlling interest at January 1, 2018	$ 739
Non-controlling interest at Acquisition Date		$ 35,829
Shares acquired post acquisition		(34,516)
Non-controlling interest of acquired entity		1,313
Foreign currency effect		(19)
Loss attributable to non-controlling interest	(53)	(555)
Non-controlling interest at December 31, 2018	$ 686	$ 739