View Filing Data

Document and Entity Information - shares	9 Months Ended
Sep. 30, 2018	Nov. 01, 2018
Document And Entity Information [Abstract]
Document Type	10-Q
Amendment Flag	false
Document Period End Date	Sep. 30, 2018
Document Fiscal Year Focus	2018
Document Fiscal Period Focus	Q3
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		102,092,863

Condensed Consolidated Balance Sheets - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Current assets:
Cash and cash equivalents	$ 39,298	$ 49,826
Marketable securities	419,272	193,482
Interest receivable	683	240
Accounts receivable	5,567	3,343
Prepaids and other current assets	3,382	1,506
Total current assets	468,202	248,397
Marketable securities, non-current		1,012
Property and equipment, net	50,497	31,066
Goodwill	1,585	1,585
Other non-current assets	6,379	1,181
Non-current restricted cash	79,941	3,500
Total assets	606,604	286,741
Current liabilities:
Accounts payable and accrued liabilities	16,424	11,035
Accrued compensation and employee benefits	6,605	5,479
Deferred revenues	51,094	28,345
Total current liabilities	74,123	44,859
Deferred revenues, non-current	123,917	29,244
Build-to-suit lease obligation	26,928	24,738
Non-current liabilities	1,730
Total liabilities	226,698	98,841
Commitments and contingencies
Stockholders' equity:
Common stock, $0.01 par value; 160,000,000 shares authorized, 101,839,668 and 85,598,534 shares issued and outstanding at September 30, 2018 and December 31, 2017, respectively	1,018	856
Additional paid-in capital	923,164	682,809
Accumulated deficit	(544,032)	(495,479)
Accumulated other comprehensive loss	(244)	(286)
Total stockholders' equity	379,906	187,900
Total liabilities and stockholders' equity	$ 606,604	$ 286,741

Condensed Consolidated Statements of Operations - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Revenues:
Revenues	$ 23,562	$ 11,812	$ 57,615	$ 23,490
Operating expenses:
Research and development	28,810	18,425	81,612	46,351
General and administrative	10,993	6,422	32,381	19,734
Total operating expenses	39,803	24,847	113,993	66,085
Loss from operations	(16,241)	(13,035)	(56,378)	(42,595)
Interest and other income, net	3,398	681	6,708	1,118
Net loss	$ (12,843)	$ (12,354)	$ (49,670)	$ (41,477)
Basic and diluted net loss per share	$ (0.13)	$ (0.15)	$ (0.52)	$ (0.55)
Shares used in computing basic and diluted net loss per share	101,725	83,750	95,165	75,814
Collaboration Agreements [Member]
Revenues:
Revenues	$ 23,538	$ 11,759	$ 57,378	$ 23,042
Research Grants [Member]
Revenues:
Revenues	$ 24	$ 53	$ 237	$ 448

Condensed Consolidated Statements of Cash Flows - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017
Operating Activities:
Net loss	$ (49,670)	$ (41,477)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation and amortization	1,668	1,030
Amortization of (discount) premium on marketable securities	(4,043)	(310)
Stock-based compensation	10,374	6,969
Taxes paid related to net share settlement of equity awards		(71)
Other	715
Net changes in operating assets and liabilities:
Interest receivable	(443)	(259)
Accounts receivable	(2,225)	1,539
Prepaid expenses and other assets	(1,851)	(743)
Accounts payable and accrued liabilities	789	3,676
Accrued compensation and employee benefits	1,127	1,589
Non-current liabilities	1,730
Deferred revenues	118,540	56,078
Net cash provided by operating activities	76,711	28,021
Investing Activities:
Purchases of marketable securities	(451,239)	(229,595)
Maturities of marketable securities	230,547	127,093
Purchases of property and equipment	(15,028)	(2,873)
Other investment	(5,221)
Net cash used in investing activities	(240,941)	(105,375)
Financing Activities:
Proceeds from public offering of common stock, net of issuance costs	215,757	81,573
Taxes paid related to net share settlement of equity awards	(83)
Proceeds from issuance of common stock	14,469	3,614
Net cash provided by financing activities	230,143	85,187
Net increase in cash, cash equivalents, and restricted cash	65,913	7,833
Cash, cash equivalents, and restricted cash, beginning of period	53,326	22,061
Cash, cash equivalents, and restricted cash, end of period	119,239	29,894
Property and Equipment [Member]
Supplemental disclosure of noncash investing activities:
Property and equipment included in accrued liabilities	$ 5,813	$ 50

Organization, Basis of Presentation and Summary of Significant Accounting Policies

9 Months Ended

Sep. 30, 2018

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. was incorporated in the state of Delaware in 1995 and changed its name from Sangamo Biosciences, Inc. in January 2017 (“Sangamo” or the “Company”). Sangamo is focused on the research, development and commercialization of novel genomic therapies 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”).

Sangamo is currently working on a number of long-term development projects that 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, research grants and from the issuance of equity or debt securities. Sangamo believes that its available cash, cash equivalents, marketable securities and interest receivable as of September 30, 2018, along with expected revenues from collaborations, strategic partnerships and research grants, will be adequate to fund its operations at least through the next twelve months. Sangamo will need to raise substantial additional capital to fund the development, manufacturing and potential commercialization of its product candidates. Additional capital may not be available on terms acceptable to the Company, if 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 product candidates could 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 U.S. generally accepted accounting principles 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 generally accepted accounting principles 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 and nine months ended September 30, 2018 are not necessarily indicative of the results that may be expected for the year ending December 31, 2018. The condensed consolidated balance sheet data at December 31, 2017 were derived from the audited consolidated financial statements included in Sangamo’s Annual Report on Form 10-K for the year ended December 31, 2017, (the “2017 Annual Report”), as filed with the SEC. 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, 2017, included in the 2017 Annual Report.

Use of Estimates

The preparation of financial statements in conformity with generally accepted accounting principles 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, 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.

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 which are recorded at estimated fair value based on quoted market prices or observable market inputs of almost identical assets. Unrealized holding gains and losses are included in accumulated other comprehensive income.

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, which is determined using the specific identification method.

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 and liabilities are stated at their estimated fair values. The counterparties to the agreements relating to the Company’s investment securities consist of the US Treasury, governmental agencies and various major corporations and financial institutions with investment-grade high credit ratings.

Revenue Recognition

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

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 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 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.

During the nine months ended September 30, 2018, revenues related to the hemophilia A collaboration agreement with Pfizer Inc. (“Pfizer”) and Kite Pharma, Inc. (“Kite”), a wholly-owned subsidiary of Gilead Sciences, Inc., represented 46% and 29%, respectively, of the Company’s total revenue. During the nine months ended September 30, 2017, revenues related to the Company’s hemophilia A collaboration agreement with Pfizer and the hemoglobinopathies agreement with Bioverativ, a Sanofi company (“Bioverativ”) represented 44% and 39%, respectively, of 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

In May 2014, the Financial Accounting Standards Board (“FASB”) issued Accounting Standards Updated (“ASU”) 2014-09, Revenue from Contracts with Customers (“Topic 606”). This standard outlines a single comprehensive model for entities to use in accounting for revenue arising from contracts with customers and supersedes most current revenue recognition guidance, including industry-specific guidance. The main principle of 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. Topic 606 provides companies with two implementation methods: (i) apply the standard retrospectively to each prior reporting period presented (full retrospective application); or (ii) apply the standard retrospectively with the cumulative effect of initially applying the standard as an adjustment to the opening balance of retained earnings of the annual reporting period that includes the date of initial application (modified retrospective application). The Company implemented this standard under the modified retrospective method. This guidance is effective for annual reporting periods beginning after December 15, 2017, including interim periods within that reporting period. Under Topic 606, an entity recognizes revenue when its customer obtains control of promised goods or services, in an amount that reflects the consideration which the entity expects to receive in exchange for those goods or services. To determine revenue recognition for arrangements that an entity determines are within the scope of Topic 606, the entity performs the following five steps: (i) identify the contract(s) with a customer; (ii) identify the performance obligations in the contract; (iii) determine the transaction price; (iv) allocate the transaction price to the performance obligations in the contract; and (v) recognize revenue when (or as) the entity satisfies a performance obligation. Topic 606 also impacts certain other areas, such as the accounting for costs to obtain or fulfill a contract. The Company adopted Topic 606 effective January 1, 2018, using the modified retrospective method with a cumulative effect adjustment of $1.1 million reflected as a decrease to the opening balance of accumulated deficit and a decrease to deferred revenues, respectively.

Refer below for a summary of the amount by which each financial statement line item was affected by the impact of the cumulative adjustment and as compared with the guidance that was in effect prior to the adoption:

	Impact of Topic 606 Adoption on Condensed Consolidated Balance Sheet as of January 1, 2018
(in thousands)	As reported under Topic 606			Adjustments			Balances without adoption of Topic 606
Deferred revenue, current portion	$	29,626		$	1,281		$	28,345
Deferred revenue, noncurrent portion	$	26,846		$	(2,398	)	$	29,244
Accumulated deficit	$	(494,362	)	$	1,117		$	(495,479	)

	Impact of Topic 606 Adoption on Condensed Consolidated Balance Sheet as of September 30, 2018
(in thousands)	As reported under Topic 606			Adjustments			Balances without adoption of Topic 606
Deferred revenue, current portion	$	51,094		$	12,741		$	63,835
Deferred revenue, noncurrent portion	$	123,917		$	(3,130	)	$	120,787
Accumulated deficit	$	(544,032	)	$	(9,611	)	$	(553,643	)

	Impact of Topic 606 Adoption on Condensed Consolidated Statement of Operations and Comprehensive Loss for the Three Months Ended September 30, 2018									Impact of Topic 606 Adoption on Condensed Consolidated Statement of Operations and Comprehensive Loss for the Nine Months Ended September 30, 2018
(in thousands)	As reported under Topic 606			Adjustments			Balances without adoption of Topic 606			As reported under Topic 606			Adjustments			Balances without adoption of Topic 606
Collaboration revenue	$	23,538		$	(4,461	)	$	19,077		$	57,378		$	(8,495	)	$	48,883
Net loss	$	(12,843	)	$	(4,461	)	$	(17,304	)	$	(49,670	)	$	(8,495	)	$	(58,165	)
Net loss per share - basic and diluted:	$	(0.13	)	$	(0.04	)	$	(0.17	)	$	(0.52	)	$	(0.09	)	$	(0.61	)

	Impact of Topic 606 Adoption on Condensed Consolidated Statement of Cash Flows for the Nine Months Ended September 30, 2018
(in thousands)	As reported under Topic 606			Adjustments			Balances without adoption of Topic 606
Net loss	$	(49,670	)	$	(8,495	)	$	(58,165	)
Changes in deferred revenue	$	118,540		$	8,495		$	127,035

In November 2016, the FASB issued ASU 2016-18, Statement of Cash Flows (“Topic 230”). The Company adopted Topic 230 in the beginning of fiscal 2018, which requires the statement of cash flows to explain the change during the period relating to total cash, cash equivalents, and restricted cash. The Company adopted this standard using the retrospective transition method by restating its condensed consolidated statements of cash flows to include restricted cash of $3.5 million as of January 1, 2018 and $79.9 million in the ending cash, cash equivalents, and restricted cash balances for the nine months ended September 30, 2018. The restricted cash balance as of September 30, 2018 includes the letter of credit for $3.5 million established as a deposit for the Brisbane build-to-suit lease and $76.4 million to acquire the equity of TxCell S.A., a French société anonyme (“TxCell”). Net cash flows for the nine months ended September 30, 2017, changed as a result of including restricted cash with cash and cash equivalents when reconciling the beginning-of-period and end-of-period amounts presented on the statements of cash flows. Restricted cash was included in other current and other non-current assets on the Company's condensed consolidated balance sheets.

The following table provides a reconciliation of cash, cash equivalents, and restricted cash within the statement of financial position that sum to the total of the same amounts in the statement of cash flows:

	As of September 30,
(in thousands)	2018		2017
Cash and cash equivalents	$	39,298	$	29,894
Restricted cash included in other non-current assets		79,941		—
Total cash, cash equivalents, and restricted cash shown in the statements of cash flows	$	119,239	$	29,894

In August 2018, the SEC adopted amendments to certain disclosure requirements in Securities Act Release No. 33-10532, Disclosure Update and Simplification. 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. In light of the anticipated timing of effectiveness of the amendments and expected proximity of effectiveness to the filing date for most filers’ quarterly reports, the SEC’s Division of Corporate Finance issued a Compliance and Disclosure Interpretation related to Exchange Act Forms, or CDI – Question 105.09, that provides transition guidance related to this disclosure requirement. CDI – Question 105.09 states that the SEC would not object if the filer’s first presentation of the changes in shareholders’ equity is included in its Form 10-Q for the quarter that begins after the effective date of the amendments. As such, the Company adopted these SEC amendments on November 5, 2018 and will present the analysis of changes in stockholders’ equity in its interim financial statements in its March 31, 2019 Form 10-Q. The Company does not anticipate that the adoption of these SEC amendments will have a material effect on the Company’s financial position, results of operations, cash flows or shareholders’ equity.

Not yet adopted

In February 2016 the FASB issued ASU 2016-02, Leases (“ASU 2016-02”). ASU 2016-02 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 right-of-use asset and corresponding liability, measured at the present value of the lease payments. The guidance will become effective for the Company beginning in the first quarter of 2019 with early adoption permitted and will be adopted using a modified retrospective approach. The Company expects to adopt the new standard on January 1, 2019 and use the effective date as the date of initial application. Consequently, financial information will not be updated and the disclosures required under the new standard will not be provided for dates and periods before January 1, 2019.

The Company expects that this standard will have a material effect on the financial statements. While the Company continues to assess the various impacts of adoption, the most significant effects will primarily relate to (1) the recognition of a right-of-use assets and lease liabilities on the balance sheet for the Company’s existing operating leases; (2) the derecognition of existing assets and liabilities for sale-leaseback transactions arising from build-to-suit lease arrangements for which construction is complete and we are leasing the constructed asset that currently do not qualify for sale accounting; (3) the derecognition of existing assets and liabilities for certain assets under construction in build-to-suit lease arrangements that the Company will lease when construction is complete; and (4) providing significant new disclosures about leasing activities.

Fair Value Measurement

9 Months Ended

Sep. 30, 2018

Fair Value Disclosures [Abstract]

Fair Value Measurement

NOTE 2—FAIR VALUE MEASUREMENT

The Company measures certain financial assets and liabilities at fair value on a recurring basis, including cash equivalents, and available-for-sale marketable securities. The fair values of these assets were 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; and

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 and available-for-sale marketable securities are identified at the following levels within the fair value hierarchy (in thousands):

	September 30, 2018
	Fair Value Measurements
	Total		Level 1		Level 2		Level 3
Assets:
Cash equivalents:
Money market funds	$	18	$	18	$	—	$	—
Total		18		18		—		—
Marketable securities:
Commercial paper securities		317,119		—		317,119		—
Corporate debt securities		83,579		—		83,579		—
U.S. government-sponsored entity debt securities		18,574		—		18,574		—
Total		419,272		—		419,272		—
Total cash equivalents and marketable securities	$	419,290	$	18	$	419,272		—

	December 31, 2017
	Fair Value Measurements
	Total		Level 1		Level 2		Level 3
Assets:
Cash equivalents:
Money market funds	$	24,290	$	24,290	$	—	$	—
Commercial paper securities		4,595		—		4,595		—
Total		28,885		24,290		4,595		—
Marketable securities:
Commercial paper securities		110,247		—		110,247		—
Corporate debt securities		75,755		—		75,755		—
U.S. government-sponsored entity debt securities		8,492		—		8,492		—
Total		194,494		—		194,494		—
Total cash equivalents and marketable securities	$	223,379	$	24,290	$	199,089		—

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.

- 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

9 Months Ended

Sep. 30, 2018

Investments Debt And Equity Securities [Abstract]

Marketable Securities

NOTE 3—MARKETABLE SECURITIES

The Company 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 substantially identical assets. Unrealized holding gains and losses are included in accumulated other comprehensive income (loss). Investments that have maturities beyond one year as of the end of the reporting period are classified as non-current.

The table below summarizes the Company’s investments (in thousands):

			Gross		Gross
	Amortized		Unrealized		Unrealized			Estimated
	Cost		Gains		(Losses)			Fair Value
September 30, 2018
Cash equivalents:
Money market funds	$	18	$	—	$	—		$	18
Total		18		—		—			18
Available-for-sale securities:
Commercial paper securities		317,203		11		(95	)		317,119
Corporate debt securities		83,684		—		(105	)		83,579
U.S. government-sponsored entity debt securities		18,598		—		(24	)		18,574
Total		419,485		11		(224	)		419,272
Total cash equivalents and available-for-sale securities	$	419,503	$	11	$	(224	)	$	419,290
December 31, 2017
Cash equivalents:
Money market funds	$	24,290	$	—	$	—		$	24,290
Commercial paper securities		4,595		—		—			4,595
Total		28,885		—		—			28,885
Available-for-sale securities:
Commercial paper securities		110,365		—		(118	)		110,247
Corporate debt securities		75,886		—		(131	)		75,755
U.S. government-sponsored entity debt securities		8,498		—		(6	)		8,492
Total		194,749		—		(255	)		194,494
Total cash equivalents and available-for-sale securities	$	223,634		—	$	(255	)	$	223,379

The Company had no material realized losses or other-than-temporary impairments of its investments for the nine months ended September 30, 2018 and 2017. As of September 30, 2018, all of the Company’s investments had maturity dates within one year. The Company has the intent and ability to hold its investments for a period of time sufficient to allow for any anticipated recovery in market value.

Major Customers, Partnerships and Strategic Alliances

9 Months Ended

Sep. 30, 2018

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 transaction price of $185.9 million 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. 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 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 September 30, 2018, the Company had deferred revenue of $137.8 million related to this agreement.

Revenues recognized under the agreement for the three and nine months ended September 30, 2018 were as follows (in thousands):

	September 30, 2018
	Three Months Ended		Nine Months Ended
Revenue related to Kite Collaboration:
Recognition of upfront fee	$	6,296	$	12,249
Research services		2,732		4,295
Total	$	9,028	$	16,544

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 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 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 September 30, 2018, the Company had deferred revenue of $21.5 million related to this agreement.

Revenues recognized under the agreement for the three and nine months ended September 30, 2018 and 2017 were as follows (in thousands):

	Three Months Ended				Nine Months Ended
	September 30,				September 30,
	2018		2017		2018		2017
Revenue related to Pfizer Collaboration for SB-525:
Recognition of upfront fee	$	10,421	$	6,624	$	26,262	$	10,384

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 is 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 through March 31, 2019 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 September 30, 2018, the Company had deferred revenue of $10.5 million related to this agreement. During the three and nine months ended September 30, 2018 the Company recognized revenue of $0.4 million and $1.5 million, respectively, related to the upfront fee that was received upon entering into the agreement.

Bioverativ, a Sanofi company.

In January 2014, the Company entered into an exclusive worldwide collaboration and license agreement with Bioverativ 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, Bioverativ 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, Bioverativ has the right to step in and take over any of our remaining activities. Furthermore, the Company has an option to co-promote in the United States any licensed products to treat beta-thalassemia and SCD developed under the agreement, and Bioverativ will compensate the Company for such co-promotion activities. Subject to the terms of the agreement, the Company has granted Bioverativ 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 Bioverativ 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. Bioverativ 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 Bioverativ agreement.

The agreement may be terminated by (i) the Company or Bioverativ for the uncured material breach of the other party, (ii) the Company or Bioverativ for the bankruptcy or other insolvency proceeding of the other party; (iii) Bioverativ, upon 180 days’ advance written notice to the Company and (iv) Bioverativ, 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 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 Bioverativ 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 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 September 30, 2018, the Company had deferred revenue of $5.1 million related to this agreement.

Revenues recognized under the agreement for the three and nine months ended September 30, 2018 and 2017 were as follows (in thousands):

	Three Months Ended				Nine Months Ended
	September 30,				September 30,
	2018		2017		2018		2017
Revenue related to Bioverativ agreement:
Recognition of upfront fee	$	1,094	$	442	$	3,432	$	1,326
Research services		1,146		2,959		7,707		7,736
Total	$	2,240	$	3,401	$	11,139	$	9,062

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 September 30, 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 September 30, 2018, the $1.7 million related to this award is recorded as a loan in other long-term liabilities on the accompanying consolidated balance sheet.

Shire International GmbH

In January 2012, the Company entered into a collaboration and license agreement with Shire to research, develop and commercialize a ZFP therapeutic for treating Huntington’s disease. The Company received an upfront license fee of $13.0 million. In 2014, Sangamo recognized a $1.0 million milestone payment related to the hemophilia program. Shire does not have any milestone payment obligations, but is required to pay single digit percentage royalties to the Company, up to a specified maximum cap, on the commercial sales of therapeutic products for Huntington’s disease. The Company is required to pay single digit percentage royalties to Shire, up to a specified maximum cap, on commercial sales of therapeutic products from programs returned under the original agreement (which include blood clotting Factors VIII and IX) that use two zinc fingers.

Pursuant to the agreement, the Company granted Shire an exclusive, world-wide, royalty-bearing license, with the right to grant sublicenses, to use the Company’s ZFP technology for the purpose of developing and commercializing human therapeutic and diagnostic products for the HTT gene. During the term of the agreement, the Company is not permitted to research, develop or commercialize, outside of the agreement, certain products that target the HTT gene. The Company satisfied the deliverables and research services responsibilities within the amended arrangement which were completed in 2017. The agreement may be terminated by (i) the Company or Shire, in whole or in part, for the uncured material breach of the other party, (ii) the Company or Shire for the bankruptcy or other insolvency proceeding of the other party and (iii) Shire, in its entirety, effective upon at least 90 days’ advance written notice.

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

Revenues recognized under the agreement for the three and nine months ended September 30, 2018 and 2017 were as follows (in thousands):

	Three Months Ended				Nine Months Ended
	September 30,				September 30,
	2018		2017		2018		2017
Revenue related to Shire agreement:
Recognition of upfront fee	$	—	$	1,166	$	—	$	2,333
Research services		—		6		—		116
Total	$	—	$	1,172	$	—	$	2,449

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

9 Months Ended

Sep. 30, 2018

Accounting Policies [Abstract]

Basis of Presentation

Use of Estimates

Cash and Cash Equivalents

Marketable Securities

Fair Value Measurements

Revenue Recognition

Recent Accounting Pronouncements

Recently Adopted

	Impact of Topic 606 Adoption on Condensed Consolidated Balance Sheet as of January 1, 2018
(in thousands)	As reported under Topic 606			Adjustments			Balances without adoption of Topic 606
Deferred revenue, current portion	$	29,626		$	1,281		$	28,345
Deferred revenue, noncurrent portion	$	26,846		$	(2,398	)	$	29,244
Accumulated deficit	$	(494,362	)	$	1,117		$	(495,479	)

	Impact of Topic 606 Adoption on Condensed Consolidated Balance Sheet as of September 30, 2018
(in thousands)	As reported under Topic 606			Adjustments			Balances without adoption of Topic 606
Deferred revenue, current portion	$	51,094		$	12,741		$	63,835
Deferred revenue, noncurrent portion	$	123,917		$	(3,130	)	$	120,787
Accumulated deficit	$	(544,032	)	$	(9,611	)	$	(553,643	)

	Impact of Topic 606 Adoption on Condensed Consolidated Statement of Operations and Comprehensive Loss for the Three Months Ended September 30, 2018									Impact of Topic 606 Adoption on Condensed Consolidated Statement of Operations and Comprehensive Loss for the Nine Months Ended September 30, 2018
(in thousands)	As reported under Topic 606			Adjustments			Balances without adoption of Topic 606			As reported under Topic 606			Adjustments			Balances without adoption of Topic 606
Collaboration revenue	$	23,538		$	(4,461	)	$	19,077		$	57,378		$	(8,495	)	$	48,883
Net loss	$	(12,843	)	$	(4,461	)	$	(17,304	)	$	(49,670	)	$	(8,495	)	$	(58,165	)
Net loss per share - basic and diluted:	$	(0.13	)	$	(0.04	)	$	(0.17	)	$	(0.52	)	$	(0.09	)	$	(0.61	)

	Impact of Topic 606 Adoption on Condensed Consolidated Statement of Cash Flows for the Nine Months Ended September 30, 2018
(in thousands)	As reported under Topic 606			Adjustments			Balances without adoption of Topic 606
Net loss	$	(49,670	)	$	(8,495	)	$	(58,165	)
Changes in deferred revenue	$	118,540		$	8,495		$	127,035

	As of September 30,
(in thousands)	2018		2017
Cash and cash equivalents	$	39,298	$	29,894
Restricted cash included in other non-current assets		79,941		—
Total cash, cash equivalents, and restricted cash shown in the statements of cash flows	$	119,239	$	29,894

Not yet adopted

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

9 Months Ended

Sep. 30, 2018

Summary of Reconciliation of Cash, Cash Equivalents and Restricted Cash

	As of September 30,
(in thousands)	2018		2017
Cash and cash equivalents	$	39,298	$	29,894
Restricted cash included in other non-current assets		79,941		—
Total cash, cash equivalents, and restricted cash shown in the statements of cash flows	$	119,239	$	29,894

Topic 606 [Member]

Summary of Financial Statement Line Item Affected Cumulative Adjustment and Compared with Guidance in Effect Prior to Adoption

	Impact of Topic 606 Adoption on Condensed Consolidated Balance Sheet as of January 1, 2018
(in thousands)	As reported under Topic 606			Adjustments			Balances without adoption of Topic 606
Deferred revenue, current portion	$	29,626		$	1,281		$	28,345
Deferred revenue, noncurrent portion	$	26,846		$	(2,398	)	$	29,244
Accumulated deficit	$	(494,362	)	$	1,117		$	(495,479	)

	Impact of Topic 606 Adoption on Condensed Consolidated Balance Sheet as of September 30, 2018
(in thousands)	As reported under Topic 606			Adjustments			Balances without adoption of Topic 606
Deferred revenue, current portion	$	51,094		$	12,741		$	63,835
Deferred revenue, noncurrent portion	$	123,917		$	(3,130	)	$	120,787
Accumulated deficit	$	(544,032	)	$	(9,611	)	$	(553,643	)

	Impact of Topic 606 Adoption on Condensed Consolidated Statement of Operations and Comprehensive Loss for the Three Months Ended September 30, 2018									Impact of Topic 606 Adoption on Condensed Consolidated Statement of Operations and Comprehensive Loss for the Nine Months Ended September 30, 2018
(in thousands)	As reported under Topic 606			Adjustments			Balances without adoption of Topic 606			As reported under Topic 606			Adjustments			Balances without adoption of Topic 606
Collaboration revenue	$	23,538		$	(4,461	)	$	19,077		$	57,378		$	(8,495	)	$	48,883
Net loss	$	(12,843	)	$	(4,461	)	$	(17,304	)	$	(49,670	)	$	(8,495	)	$	(58,165	)
Net loss per share - basic and diluted:	$	(0.13	)	$	(0.04	)	$	(0.17	)	$	(0.52	)	$	(0.09	)	$	(0.61	)

	Impact of Topic 606 Adoption on Condensed Consolidated Statement of Cash Flows for the Nine Months Ended September 30, 2018
(in thousands)	As reported under Topic 606			Adjustments			Balances without adoption of Topic 606
Net loss	$	(49,670	)	$	(8,495	)	$	(58,165	)
Changes in deferred revenue	$	118,540		$	8,495		$	127,035

Fair Value Measurement (Tables)

9 Months Ended

Sep. 30, 2018

Fair Value Disclosures [Abstract]

Summary of Fair Value Measurements of Cash Equivalents, and Available-for-Sale Marketable Securities

The fair value measurements of the Company’s cash equivalents and available-for-sale marketable securities are identified at the following levels within the fair value hierarchy (in thousands):

	September 30, 2018
	Fair Value Measurements
	Total		Level 1		Level 2		Level 3
Assets:
Cash equivalents:
Money market funds	$	18	$	18	$	—	$	—
Total		18		18		—		—
Marketable securities:
Commercial paper securities		317,119		—		317,119		—
Corporate debt securities		83,579		—		83,579		—
U.S. government-sponsored entity debt securities		18,574		—		18,574		—
Total		419,272		—		419,272		—
Total cash equivalents and marketable securities	$	419,290	$	18	$	419,272		—

	December 31, 2017
	Fair Value Measurements
	Total		Level 1		Level 2		Level 3
Assets:
Cash equivalents:
Money market funds	$	24,290	$	24,290	$	—	$	—
Commercial paper securities		4,595		—		4,595		—
Total		28,885		24,290		4,595		—
Marketable securities:
Commercial paper securities		110,247		—		110,247		—
Corporate debt securities		75,755		—		75,755		—
U.S. government-sponsored entity debt securities		8,492		—		8,492		—
Total		194,494		—		194,494		—
Total cash equivalents and marketable securities	$	223,379	$	24,290	$	199,089		—

- 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)

9 Months Ended

Sep. 30, 2018

Investments Debt And Equity Securities [Abstract]

Schedule of Investments

The table below summarizes the Company’s investments (in thousands):

			Gross		Gross
	Amortized		Unrealized		Unrealized			Estimated
	Cost		Gains		(Losses)			Fair Value
September 30, 2018
Cash equivalents:
Money market funds	$	18	$	—	$	—		$	18
Total		18		—		—			18
Available-for-sale securities:
Commercial paper securities		317,203		11		(95	)		317,119
Corporate debt securities		83,684		—		(105	)		83,579
U.S. government-sponsored entity debt securities		18,598		—		(24	)		18,574
Total		419,485		11		(224	)		419,272
Total cash equivalents and available-for-sale securities	$	419,503	$	11	$	(224	)	$	419,290
December 31, 2017
Cash equivalents:
Money market funds	$	24,290	$	—	$	—		$	24,290
Commercial paper securities		4,595		—		—			4,595
Total		28,885		—		—			28,885
Available-for-sale securities:
Commercial paper securities		110,365		—		(118	)		110,247
Corporate debt securities		75,886		—		(131	)		75,755
U.S. government-sponsored entity debt securities		8,498		—		(6	)		8,492
Total		194,749		—		(255	)		194,494
Total cash equivalents and available-for-sale securities	$	223,634		—	$	(255	)	$	223,379

Major Customers, Partnerships and Strategic Alliances (Tables)

9 Months Ended

Sep. 30, 2018

Kite Pharma, Inc. ("Kite") [Member]

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

Revenues Recognized under Agreement

Revenues recognized under the agreement for the three and nine months ended September 30, 2018 were as follows (in thousands):

	September 30, 2018
	Three Months Ended		Nine Months Ended
Revenue related to Kite Collaboration:
Recognition of upfront fee	$	6,296	$	12,249
Research services		2,732		4,295
Total	$	9,028	$	16,544

Pfizer [Member]

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

Revenues Recognized under Agreement

Revenues recognized under the agreement for the three and nine months ended September 30, 2018 and 2017 were as follows (in thousands):

	Three Months Ended				Nine Months Ended
	September 30,				September 30,
	2018		2017		2018		2017
Revenue related to Pfizer Collaboration for SB-525:
Recognition of upfront fee	$	10,421	$	6,624	$	26,262	$	10,384

Bioverativ Inc [Member]

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

Revenues Recognized under Agreement

Revenues recognized under the agreement for the three and nine months ended September 30, 2018 and 2017 were as follows (in thousands):

	Three Months Ended				Nine Months Ended
	September 30,				September 30,
	2018		2017		2018		2017
Revenue related to Bioverativ agreement:
Recognition of upfront fee	$	1,094	$	442	$	3,432	$	1,326
Research services		1,146		2,959		7,707		7,736
Total	$	2,240	$	3,401	$	11,139	$	9,062

Shire AG [Member]

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

Revenues Recognized under Agreement

Revenues recognized under the agreement for the three and nine months ended September 30, 2018 and 2017 were as follows (in thousands):

	Three Months Ended				Nine Months Ended
	September 30,				September 30,
	2018		2017		2018		2017
Revenue related to Shire agreement:
Recognition of upfront fee	$	—	$	1,166	$	—	$	2,333
Research services		—		6		—		116
Total	$	—	$	1,172	$	—	$	2,449

Organization, Basis of Presentation and Summary of Significant Accounting Policies - Additional Information (Detail) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Jan. 01, 2018	Dec. 31, 2017	Nov. 30, 2017	Dec. 31, 2016
Organization And Summary Of Significant Accounting Policies [Line Items]
Liquid investments purchased with original maturities	three months or less
Accumulated deficit	$ (544,032)			$ (495,479)
Cash, cash equivalents, and restricted cash	119,239	$ 29,894		53,326		$ 22,061
Restricted cash	79,941			$ 3,500
TxCell S.A. [Member]
Organization And Summary Of Significant Accounting Policies [Line Items]
Restricted cash	76,400
Brisbane Build-to-Suit Lease [Member]
Organization And Summary Of Significant Accounting Policies [Line Items]
Restricted cash	3,500				$ 3,500
Topic 606 [Member]
Organization And Summary Of Significant Accounting Policies [Line Items]
Accumulated deficit			$ (494,362)
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	(9,611)		1,117
ASU 2016-18 [Member]
Organization And Summary Of Significant Accounting Policies [Line Items]
Restricted cash balance			$ 3,500
Cash, cash equivalents, and restricted cash	$ 79,900
Pfizer [Member] \| Customer Concentration Risk [Member] \| Total revenues [Member]
Organization And Summary Of Significant Accounting Policies [Line Items]
Percentage of revenues	46.00%	44.00%
Kite Pharma, Inc. ("Kite") [Member] \| Customer Concentration Risk [Member] \| Total revenues [Member]
Organization And Summary Of Significant Accounting Policies [Line Items]
Percentage of revenues	29.00%
Bioverativ Inc [Member] \| Customer Concentration Risk [Member] \| Total revenues [Member]
Organization And Summary Of Significant Accounting Policies [Line Items]
Percentage of revenues		39.00%

Marketable Securities - Schedule of Investments (Detail) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017	Sep. 30, 2017
Schedule Of Available For Sale Securities [Line Items]
Cash equivalents, Amortized Cost	$ 39,298	$ 49,826	$ 29,894
Available-for-sale securities, Amortized Cost	419,485	194,749
Available-for-sale securities, Gross Unrealized Gains	11
Available-for-sale securities, Gross Unrealized (Losses)	(224)	(255)
Available-for-sale securities, Estimated Fair Value	419,272	194,494
Total cash equivalents and available-for-sale securities, Amortized Cost	419,503	223,634
Total cash equivalents and available-for-sale securities, Gross Unrealized Gains	11
Total cash equivalents and available-for-sale securities, Gross Unrealized (Losses)	(224)	(255)
Total cash equivalents and available-for-sale securities, Estimated Fair Value	419,290	223,379
Money market funds [Member]
Schedule Of Available For Sale Securities [Line Items]
Cash equivalents, Amortized Cost	18	24,290
Cash equivalents, Estimated Fair Value	18	24,290
Commercial paper securities [Member]
Schedule Of Available For Sale Securities [Line Items]
Cash equivalents, Amortized Cost		4,595
Cash equivalents, Estimated Fair Value		4,595
Available-for-sale securities, Amortized Cost	317,203	110,365
Available-for-sale securities, Gross Unrealized Gains	11
Available-for-sale securities, Gross Unrealized (Losses)	(95)	(118)
Available-for-sale securities, Estimated Fair Value	317,119	110,247
Cash equivalents [Member]
Schedule Of Available For Sale Securities [Line Items]
Cash equivalents, Amortized Cost	18	28,885
Cash equivalents, Estimated Fair Value	18	28,885
Corporate debt securities [Member]
Schedule Of Available For Sale Securities [Line Items]
Available-for-sale securities, Amortized Cost	83,684	75,886
Available-for-sale securities, Gross Unrealized (Losses)	(105)	(131)
Available-for-sale securities, Estimated Fair Value	83,579	75,755
U.S. government sponsored entity debt securities [Member]
Schedule Of Available For Sale Securities [Line Items]
Available-for-sale securities, Amortized Cost	18,598	8,498
Available-for-sale securities, Gross Unrealized (Losses)	(24)	(6)
Available-for-sale securities, Estimated Fair Value	$ 18,574	$ 8,492

Major Customers, Partnerships and Strategic Alliances - Additional Information (Detail)		1 Months Ended							3 Months Ended		9 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	Jan. 31, 2012 USD ($)	Sep. 30, 2018 USD ($)	Sep. 30, 2017 USD ($)	Sep. 30, 2018 USD ($) Product Milestone	Sep. 30, 2017 USD ($)	Dec. 31, 2014 USD ($)
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Revenues									$ 23,562,000	$ 11,812,000	$ 57,615,000	$ 23,490,000
Number of research programs \| Program							2
Other long-term liabilities									1,730,000		1,730,000
Research Grants [Member]
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Revenues									24,000	53,000	237,000	448,000
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									1,700,000		1,700,000
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
Kite Pharma, Inc. ("Kite") [Member]
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Revenues									$ 9,028,000		$ 16,544,000
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		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									$ 137,800,000		137,800,000
Kite Pharma, Inc. ("Kite") [Member] \| Collaboration and License Agreement [Member] \| Maximum [Member]
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Contingent 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									21,500,000		$ 21,500,000
Number of products approved \| Product											0
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									10,500,000		10,500,000
Revenues									400,000		$ 1,500,000
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 \| Maximum [Member]
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Contingent development - and sales-based milestone payments to be received						208,500,000
Pfizer [Member] \| Achievement of First Commercial Sale Milestones \| Maximum [Member]
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Contingent 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]
Contingent 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]
Contingent development - and sales-based milestone payments to be received					90,000,000
Bioverativ Inc [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
Revenues									2,240,000	3,401,000	$ 11,139,000	9,062,000
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
Deferred revenue									$ 5,100,000		$ 5,100,000
Number of milestones included in transaction price \| Milestone											0
Bioverativ Inc [Member] \| Collaboration and License Agreement [Member] \| Royalty Revenues [Member]
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Revenues											$ 0
Bioverativ Inc [Member] \| Collaboration and License Agreement [Member] \| Maximum [Member]
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Contingent development - and sales-based milestone payments to be received							276,300,000
Bioverativ Inc [Member] \| Collaboration and License Agreement [Member] \| Achievement Of Specified Clinical Development And Regulatory Milestones \| Maximum [Member]
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Contingent development - and sales-based milestone payments to be received							115,800,000
Bioverativ Inc [Member] \| Collaboration and License Agreement [Member] \| Achievement Of Specified Sales Milestones \| Maximum [Member]
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Contingent development - and sales-based milestone payments to be received							$ 160,500,000
Shire AG [Member]
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Revenues										$ 1,172,000		$ 2,449,000
Shire AG [Member] \| Collaboration and License Agreement [Member]
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Revenues under agreement								$ 13,000,000
Deferred revenue					$ 2,300,000
Recognition of milestone													$ 1,000,000

Basic and Diluted Net Loss Per Share	9 Months Ended
Basic and Diluted Net Loss Per Share	Sep. 30, 2018
Earnings Per Share [Abstract]
Basic and Diluted Net Loss Per Share	NOTE 4—BASIC AND DILUTED NET LOSS PER SHARE Basic net loss per share has been computed by dividing net loss by the weighted-average number of shares of common stock outstanding during the period. Diluted net loss per share is calculated by dividing net loss by the weighted-average number of shares of common stock and potential dilutive securities outstanding during the period. The total number of shares subject to stock options and restricted stock units outstanding, which are all anti-dilutive, were excluded from consideration in the calculation of diluted net loss per share. Stock options and restricted stock units outstanding as of September 30, 2018 and 2017 were 8,770,775 and 9,581,024, respectively.

Income Taxes	9 Months Ended
Income Taxes	Sep. 30, 2018
Income Tax Disclosure [Abstract]
Income Taxes	NOTE 6—INCOME TAXES On December 22, 2017, the U.S. government enacted comprehensive tax legislation commonly referred to as the Tax Cuts and Jobs Act (the "Tax Act"). The Tax Act makes broad and complex changes to the U.S. tax code that affected 2017, the current year and onwards, including, but not limited to, a reduction of the U.S. federal corporate tax rate from as high as 35% to 21%, a general elimination of U.S. federal income taxes on dividends from foreign subsidiaries, net operating loss deduction limitations, and 100% disallowance of entertainment expense. In addition, on December 22, 2017, the SEC staff issued Staff Accounting Bulletin No. 118 ("SAB 118") which provides guidance on accounting for the tax effects of the Tax Act. SAB 118 provides a measurement period that should not extend beyond one year from the Tax Act enactment date for companies to complete the accounting under Accounting Standards Codification 740, Income taxes for the year ended December 31, 2017. In accordance with SAB 118, a company must reflect the income tax effects of those aspects of the Tax Act for which the accounting under ASC 740 is complete. The Company is still within the measurement period as of September 30, 2018 and no further conclusions have been made, as the Company reviews the law change and the impact to the Company. Due to the Company’s valuation allowance against its deferred tax assets, it does not expect that the provisions of the Tax Act will have a material impact on the Company’s financial position, results of operations, or income tax expense or benefit.

Commitments and Contingencies	9 Months Ended
Commitments and Contingencies	Sep. 30, 2018
Commitments And Contingencies Disclosure [Abstract]
Commitments and Contingencies	NOTE 8—COMMITMENTS AND CONTINGENCIES Brisbane Build-to-Suit Lease In November 2017, the Company entered into a long-term property lease which includes construction by the lessor of a building with approximately 87,700 square feet of space, in Brisbane, California. Substantial completion of the building is estimated to occur in the last quarter of 2018. The lease agreement expires in May 2029, approximately ten years after substantial completion of the building. A letter of credit for $3.5 million was established as the deposit and is classified as restricted cash within restricted cash and other noncurrent assets in the accompanying financial statements. The Company has two options to extend the lease term for up to a combined additional ten years. The Company is deemed, for accounting purposes only, to be the owner of the entire project including the building shell, even though it is not the legal owner as a result of the cold shell condition of the building and involvement in the construction process. In connection with the Company’s accounting for this transaction, the Company capitalized the costs of construction as a build-to-suit property within property and equipment, net, and recognize a corresponding build-to-suit lease obligation, including interest. Fair value of the building was estimated at $20.9 million using comparable market prices per square foot for similar space for public real estate transactions in the surrounding area and is considered a Level 2 fair value measurement. As of September 30, 2018, $39.5 million was capitalized with a corresponding build-to-suit lease obligation recognized related to this lease for the building and construction costs. 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.

Stockholders' Equity	9 Months Ended
Stockholders' Equity	Sep. 30, 2018
Equity [Abstract]
Stockholders' Equity	NOTE 9— STOCKHOLDERS’ EQUITY In April 2018, Sangamo completed an underwritten public offering of its common stock, in which the Company sold an aggregate of 14.2 million shares of its common stock at a public offering price of $16.25 per share. The net proceeds to Sangamo from the sale of shares in this offering, after deducting underwriting discounts and commissions and other estimated offering expenses, were approximately $215.8 million. In May 2017, the Company entered into an amended and restated sales agreement with Cowen and Company, LLC (“Cowen”) (the “ATM Facility”) pursuant to which the Company may offer and sell, in its sole discretion, shares of common stock having an aggregate offering price of up to $75.0 million through Cowen acting as the Company’s sales agent. Sales of the Company’s common stock, if any, will be made at market prices by any method that is deemed to be an “at the market offering” as defined in Rule 415 under the Securities Act of 1933, as amended. The Company has not sold any common stock under the ATM Facility. As of September 30, 2018, the full $75.0 million provided for under the ATM Facility remained available for sale, subject to certain conditions as specified in the agreement.

Subsequent Events	9 Months Ended
Subsequent Events	Sep. 30, 2018
Subsequent Events [Abstract]
Subsequent Events	NOTE 10— SUBSEQUENT EVENTS On July 20, 2018, the Company entered into a Share Purchase Agreement (the “SPA”) with certain shareholders (the “Sellers”) of TxCell, and the Company and TxCell entered into a Tender Offer Agreement (the “TOA”). Pursuant to the SPA and the TOA, the Company expects to acquire 100% of the equity interests of TxCell for approximately €72 million, on a debt-free and cash-free basis. On October 1, 2018, pursuant to the SPA, the Company purchased all of the ordinary shares of TxCell the “Ordinary Shares”) held by the Sellers for €2.58 per share in cash (such per share price being the “Offer Price” and such purchase being the “Block Transaction”). The Sellers owned 13,519,036 Ordinary Shares, which represented approximately 53% of the share capital and voting rights of TxCell. Subsequent to the completion of the Block Transaction, as of November 7, 2018, we owned approximately 80% of the share capital and voting rights of TxCell. Promptly following the completion of the Block Transaction, the Company designated a number of directors on the board of directors of TxCell representing a majority of the TxCell board. Pursuant to the TOA, on November 1, 2018, the Company, commenced a cash tender offer (the “Offer”) to acquire all of the Ordinary Shares of TxCell not held by the Company for the Offer Price. In addition, the Company has agreed to: (a) grant to certain employees (including certain members of management) of TxCell stock options to purchase approximately 150,000 shares of Company common stock, which will be granted under the Company’s existing 2018 Equity Incentive Plan, with standard vesting conditions; and (b) enter into arrangements with holders of 495,396 “free shares” of TxCell, pursuant to which the Company would purchase such shares from the holders thereof from time to time through mid-2021. The purchase price for each such free share will be based on the performance of the Company’s stock price from the announcement of the transactions contemplated by the SPA and TOA (at which time each free share was valued at €2.58 per share through the time of purchase (such that, for example, if the Company’s stock price doubles during that time period, the value of each free share would similarly double). The Sellers and TxCell have made limited representations and warranties in the TOA as are customary for such an agreement governed under French law. The TOA also contains customary termination rights. If, following completion of the Offer, as it may be extended, the Company owns at least 95% of the share capital and voting rights of TxCell, it plans to acquire the remaining Ordinary Shares for the Offer Price through a compulsory squeeze-out procedure under French law. At this time, the Company is assessing the accounting impact of the agreement.

Condensed Consolidated Balance Sheets (Parenthetical) - $ / shares	Sep. 30, 2018	Dec. 31, 2017
Statement Of Financial Position [Abstract]
Common stock, par value	$ 0.01	$ 0.01
Common stock, shares authorized	160,000,000	160,000,000
Common stock, shares issued	101,839,668	85,598,534
Common stock, shares outstanding	101,839,668	85,598,534

Organization, Basis of Presentation and Summary of Significant Accounting Policies - Condensed Consolidated Balance Sheet (Detail) - USD ($) $ in Thousands	Sep. 30, 2018	Jan. 01, 2018	Dec. 31, 2017
Revenue Initial Application Period Cumulative Effect Transition [Line Items]
Deferred revenue, current portion	$ 51,094		$ 28,345
Deferred revenue, noncurrent portion	123,917		29,244
Accumulated deficit	(544,032)		$ (495,479)
Topic 606 [Member]
Revenue Initial Application Period Cumulative Effect Transition [Line Items]
Deferred revenue, current portion		$ 29,626
Deferred revenue, noncurrent portion		26,846
Accumulated deficit		(494,362)
Adjustments [Member] \| Topic 606 [Member]
Revenue Initial Application Period Cumulative Effect Transition [Line Items]
Deferred revenue, current portion	12,741	1,281
Deferred revenue, noncurrent portion	(3,130)	(2,398)
Accumulated deficit	(9,611)	1,117
Balances without adoption of Topic 606 [Member] \| Topic 606 [Member]
Revenue Initial Application Period Cumulative Effect Transition [Line Items]
Deferred revenue, current portion	63,835	28,345
Deferred revenue, noncurrent portion	120,787	29,244
Accumulated deficit	$ (553,643)	$ (495,479)

Fair Value Measurement - Summary of Fair Value Measurements of Cash Equivalents, and Available-for-Sale Marketable Securities (Detail) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Total marketable securities	$ 419,272	$ 194,494
Money market funds [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Total cash equivalents	18	24,290
Commercial paper securities [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Total cash equivalents		4,595
Total marketable securities	317,119	110,247
Corporate debt securities [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Total marketable securities	83,579	75,755
U.S. government sponsored entity debt securities [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Total marketable securities	18,574	8,492
Fair value on recurring basis [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Total cash equivalents	18	28,885
Total marketable securities	419,272	194,494
Total cash equivalents and marketable securities	419,290	223,379
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	18	24,290
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		4,595
Total marketable securities	317,119	110,247
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	18	24,290
Total cash equivalents and marketable securities	18	24,290
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	18	24,290
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		4,595
Total marketable securities	419,272	194,494
Total cash equivalents and marketable securities	419,272	199,089
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		4,595
Total marketable securities	317,119	110,247
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	83,579	75,755
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	83,579	75,755
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	18,574	8,492
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	$ 18,574	$ 8,492

Basic and Diluted Net Loss Per Share - Additional Information (Detail) - shares	9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017
Stock options and restricted stock units [Member]
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Number of anti-dilutive shares excluded from calculation of diluted net loss per share	8,770,775	9,581,024

Income Taxes - Additional Information (Detail)	9 Months Ended	12 Months Ended
Income Taxes - Additional Information (Detail)	Sep. 30, 2018	Dec. 31, 2017
Income Tax Disclosure [Abstract]
Federal statutory income tax rate	21.00%	35.00%
Percentage of disallowance of entertainment expense	100.00%

Commitments and Contingencies - Additional Information (Detail) $ in Thousands	1 Months Ended	9 Months Ended
	Nov. 30, 2017 USD ($) ft² Option	Sep. 30, 2018 USD ($)	Dec. 31, 2017 USD ($)
Commitments And Contingencies [Line Items]
Restricted cash		$ 79,941	$ 3,500
Brisbane Build-to-Suit Lease [Member]
Commitments And Contingencies [Line Items]
Property leased \| ft²	87,700
Lease expiration date		May 31, 2029
Operating lease expiration period	10 years
Number of lease term extension options \| Option	2
Restricted cash	$ 3,500	$ 3,500
Costs capitalized		$ 39,500
Brisbane Build-to-Suit Lease [Member] \| Building [Member]
Commitments And Contingencies [Line Items]
Costs capitalized	$ 20,900
Brisbane Build-to-Suit Lease [Member] \| Maximum [Member]
Commitments And Contingencies [Line Items]
Lease agreement, extendable lease term	10 years

Stockholders' Equity - Additional Information (Detail) - USD ($) $ / shares in Units, shares in Millions	1 Months Ended	9 Months Ended
	Apr. 30, 2018	Sep. 30, 2018	Sep. 30, 2017	May 31, 2017
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Net proceeds from sale of shares, after deducting underwriting discounts and commissions and other estimated offering expenses		$ 215,757,000	$ 81,573,000
ATM Agreement [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Common stock issuable and sellable under offering agreement		$ 75,000,000
ATM Agreement [Member] \| Maximum [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Common stock issuable and sellable under offering agreement				$ 75,000,000
Common Stock [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Sale of common stock in underwritten public offering	14.2
Sale of common stock, public offering price	$ 16.25
Net proceeds from sale of shares, after deducting underwriting discounts and commissions and other estimated offering expenses	$ 215,800,000

Subsequent Events - Additional Information (Detail) - TxCell S.A. [Member] - EUR (€) € / shares in Units, € in Millions	Jul. 20, 2018	Nov. 01, 2018	Oct. 01, 2018
Subsequent Event [Line Items]
Percentage of share capital and voting rights owned after completion of offer	95.00%
Share Purchase Agreement and Tender Offer Agreement [Member]
Subsequent Event [Line Items]
Percentage of equity interests expected to acquire	100.00%
Consideration payable	€ 72
Share Purchase Agreement [Member] \| Subsequent Event [Member]
Subsequent Event [Line Items]
Purchase price per share		€ 2.58	€ 2.58
Number of shares owned by sellers			13,519,036
Percentage of share capital and voting rights held by sellers			53.00%
Percentage of share capital and voting rights owned after completion of offer			80.00%
Tender Offer Agreement [Member] \| Subsequent Event [Member]
Subsequent Event [Line Items]
Number of free shares held by the holders		495,396
Tender Offer Agreement [Member] \| Subsequent Event [Member] \| 2018 Equity Incentive Plan [Member]
Subsequent Event [Line Items]
Number of common stock available for grant		150,000