Juno Therapeutics 10-Q 9 Nov 16 2016 Q3 Quarterly report Financial data

Document and Entity Information

Document and Entity Information - shares	9 Months Ended
	Sep. 30, 2016	Nov. 02, 2016
Document And Entity Information [Abstract]
Document Type	10-Q
Amendment Flag	false
Document Period End Date	Sep. 30, 2016
Document Fiscal Year Focus	2,016
Document Fiscal Period Focus	Q3
Trading Symbol	JUNO
Entity Registrant Name	Juno Therapeutics, Inc.
Entity Central Index Key	1,594,864
Current Fiscal Year End Date	--12-31
Entity Filer Category	Large Accelerated Filer
Entity Common Stock, Shares Outstanding		105,871,441

Condensed Consolidated Balance

Condensed Consolidated Balance Sheets - USD ($) $ in Thousands	Sep. 30, 2016	Dec. 31, 2015
Current assets:
Cash and cash equivalents	$ 223,420	$ 252,398
Marketable securities	597,236	691,013
Accounts receivable	10,603	315
Prepaid expenses and other current assets	13,514	8,113
Total current assets	844,773	951,839
Property and equipment, net	57,708	42,086
Long-term marketable securities	214,880	272,888
Goodwill	221,306	122,092
Intangible assets	80,135	50,177
Other assets	7,495	6,046
Total assets	1,426,297	1,445,128
Current liabilities:
Accounts payable	3,740	4,248
Accrued liabilities and other current liabilities	44,115	33,376
Success payment liabilities	34,502	64,829
Contingent consideration	9,271	1,905
Deferred revenue	41,403	15,370
Total current liabilities	133,031	119,728
Build-to-suit lease obligation, less current portion	8,758	9,294
Contingent consideration, less current portion	22,820	35,361
Deferred revenue, less current portion	129,969	129,831
Deferred tax liabilities	7,351	8,946
Other long-term liabilities	7,431	435
Commitments and contingencies (Note 10)
Stockholders’ equity:
Preferred stock, $0.0001 par value; 5,000,000 shares authorized; 0 shares issued and outstanding	0	0
Common stock, $0.0001 par value, 495,000,000 shares authorized at September 30, 2016 and December 31, 2015; 102,617,147 and 97,247,058 shares issued and outstanding at September 30, 2016 and December 31, 2015, respectively	10	10
Additional paid-in-capital	1,895,825	1,733,263
Accumulated other comprehensive loss	(439)	(6,083)
Accumulated deficit	(778,459)	(585,657)
Total stockholders’ equity	1,116,937	1,141,533
Total liabilities and stockholders’ equity	$ 1,426,297	$ 1,445,128

Condensed Consolidated Balance3

Condensed Consolidated Balance Sheets (Parenthetical) - $ / shares	Sep. 30, 2016	Dec. 31, 2015
Statement of Financial Position [Abstract]
Preferred stock, par value (usd per share)	$ 0.0001	$ 0.0001
Preferred stock, shares authorized (shares)	5,000,000	5,000,000
Preferred stock, shares issued (shares)	0	0
Preferred stock, shares outstanding (shares)	0	0
Common stock, par value (shares)	$ 0.0001	$ 0.0001
Common stock, shares authorized (shares)	495,000,000	495,000,000
Common stock, shares issued (shares)	102,617,147	97,247,058
Common stock, shares outstanding (shares)	102,617,147	97,247,058

Condensed Consolidated Statemen

Condensed Consolidated Statements of Operations (Unaudited) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Income Statement [Abstract]
Revenue	$ 20,826	$ 1,602	$ 58,203	$ 14,063
Operating expenses:
Research and development	60,854	11,503	206,887	129,537
General and administrative	18,441	13,632	51,210	41,184
Total operating expenses	79,295	25,135	258,097	170,721
Loss from operations	(58,469)	(23,533)	(199,894)	(156,658)
Other-than-temporary impairment loss	0	0	(5,490)	0
Interest income, net	1,485	356	4,322	709
Other income (expenses), net	(507)	0	(871)	233
Loss before income taxes	(57,491)	(23,177)	(201,933)	(155,716)
Benefit from (provision for) income taxes	594	(63)	9,131	1,553
Net loss	$ (56,897)	$ (23,240)	$ (192,802)	$ (154,163)
Net loss per share, basic and diluted (in usd per share)	$ (0.56)	$ (0.26)	$ (1.91)	$ (1.80)
Weighted average common shares outstanding, basic and diluted (in shares)	102,177,808	90,827,026	100,961,382	85,702,518

Condensed Consolidated Stateme5

Condensed Consolidated Statements of Comprehensive Loss - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Statement of Comprehensive Income [Abstract]
Net loss	$ (56,897)	$ (23,240)	$ (192,802)	$ (154,163)
Other comprehensive income (loss), net of tax:
Foreign currency translation adjustments	263	357	673	232
Net unrealized gain (loss) on marketable securities	(239)	(906)	(519)	(1,540)
Reclassification adjustment for loss included in net loss	0	0	5,490	0
Total other comprehensive income (loss)	24	(549)	5,644	(1,308)
Comprehensive loss	$ (56,873)	$ (23,789)	$ (187,158)	$ (155,471)

Condensed Consolidated Stateme6

Condensed Consolidated Statements of Cash Flows (Unaudited) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015
OPERATING ACTIVITIES
Net loss	$ (192,802)	$ (154,163)
Adjustments to reconcile net loss to net cash (used in) provided by operating activities:
Depreciation and amortization	10,433	3,564
Non-cash stock-based compensation	42,760	21,539
Non-cash expense in connection with equity issuance	23,226	0
Deferred income taxes	(2,459)	(458)
Deferred tax benefit recorded in connection with acquisition	(6,655)	(1,100)
Change in fair value of success payment liabilities	(20,758)	17,284
Change in fair value of contingent consideration	(5,175)	1,203
Other-than-temporary impairment on marketable securities	5,490	0
Other	948	(227)
Changes in operating assets and liabilities:
Accounts receivable	(10,285)	89
Prepaid expenses and other assets	179	(3,203)
Accounts payable, accrued liabilities and other liabilities	8,562	16,746
Deferred revenue	26,169	148,587
Net cash (used in) provided by operating activities	(120,367)	49,861
INVESTING ACTIVITIES
Purchases of marketable securities and other investments	(623,243)	(724,714)
Sales and maturities of marketable securities	767,147	140,158
Acquisitions, net of cash acquired	(74,575)	(77,666)
Purchase of property and equipment	(17,795)	(23,336)
Net cash provided by (used in) investing activities	51,534	(685,558)
FINANCING ACTIVITIES
Payments of issuance costs related to issuance of common stock	0	(1,683)
Proceeds from issuance of common stock to strategic partner	47,000	849,804
Proceeds from exercise of stock options	3,946	899
Repurchases of common stock	(10,073)	0
Minimum tax withholdings on stock-based awards	(692)	0
Payments of build-to-suit lease obligation	(274)	(165)
Net cash provided by financing activities	39,907	848,855
Effect of exchange rate changes on cash and cash equivalents	(52)	11
Net (decrease) increase in cash and cash equivalents	(28,978)	213,169
Cash and cash equivalents at beginning of period	252,398	355,968
Cash and cash equivalents at end of period	223,420	569,137
SUPPLEMENTAL CASH FLOW INFORMATION
Purchases of property and equipment included in accounts payable and accrued liabilities	2,948	1,639
Amounts capitalized under build-to-suit leases	0	9,910
Issuance of common stock for acquisitions	46,914	41,611
Issuance of common stock for success payments	9,481	0
Tenant allowance receivable	$ 5,243	$ 0

Significant Accounting Policies

Significant Accounting Policies	9 Months Ended
	Sep. 30, 2016
Accounting Policies [Abstract]
Significant Accounting Policies	Significant Accounting Policies Organization and Basis of Presentation Juno Therapeutics, Inc. (the “Company”) was incorporated in Delaware on August 5, 2013 as FC Therapeutics, Inc., and changed its name to Juno Therapeutics, Inc. on October 23, 2013. The Company is building a fully-integrated biopharmaceutical company focused on re-engaging the body’s immune system to revolutionize the treatment of cancer. Founded on the vision that the use of human cells as therapeutic entities will drive one of the next important phases in medicine, the Company is developing cell-based cancer immunotherapies based on its chimeric antigen receptor (“CAR”) and high-affinity T cell receptor (“TCR”) technologies to genetically engineer T cells to recognize and kill cancer cells. In July 2016, the Company acquired RedoxTherapies, Inc. (“RedoxTherapies”), a privately-held company. See Note 2, Acquisitions. The acquisition provides the Company with an exclusive license to vipadenant, a small molecule A2a receptor antagonist that has the potential to disrupt important immunosuppressive pathways in the tumor microenvironment in certain cancers. In January 2016, the Company acquired AbVitro, Inc., (“AbVitro”) a company with a leading next-generation single cell sequencing platform. See Note 2, Acquisition. The AbVitro acquisition is intended to augment the Company’s capabilities to create engineered T cells against a broad array of cancer targets. The Company will initially use this technology in its translation research assays, to find and generate fully-human TCRs and antibodies, and to find novel targets. The Company is subject to a number of risks similar to other biopharmaceutical companies in the early stage, including, but not limited to, possible failure of preclinical testing or clinical trials, the need to obtain marketing approval for its product candidates, competitors developing new technological innovations, the need to successfully commercialize and gain market acceptance of the Company’s products, protection of proprietary technology, and the need to obtain adequate additional funding. If the Company, or any commercialization partner for the Company’s product candidates, does not successfully commercialize any of the Company’s product candidates, the Company will not be able to generate product revenue or achieve profitability. As of September 30, 2016 , the Company had an accumulated deficit of $778.5 million . The financial data as of December 31, 2015 is derived from the Company’s audited financial statements, which are included in the Company’s Annual Report on Form 10-K, which was filed with the Securities and Exchange Commission (the “SEC”) on February 29, 2016 (the “ 2015 Annual Report”), and should be read in conjunction with the audited financial statements and notes thereto. The Company’s significant accounting policies are described in Note 2 to the financial statements included in the 2015 Annual Report. Certain prior period amounts have been reclassified to conform to the current period presentation. For the nine months ended September 30, 2015 , $6.0 million was reclassified from litigation to general and administrative on the condensed consolidated statements of operations. This reclassification does not have a material impact on the Company’s condensed consolidated financial statements. These unaudited interim condensed consolidated financial statements have been prepared in accordance with U.S. generally accepted accounting principles (“GAAP”). In management’s opinion, the unaudited interim condensed consolidated financial statements have been prepared on the same basis as the audited financial statements and include all adjustments, consisting of normal recurring adjustments, necessary for the fair presentation of the Company’s financial position, results of operations and comprehensive loss and cash flows for the interim periods. The results for the three and nine months ended September 30, 2016 are not necessarily indicative of the results expected for the full fiscal year or any other interim period. Use of Estimates The preparation of the Company’s condensed consolidated financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the amounts reported in the condensed consolidated financial statements and accompanying notes. Actual results could differ from such estimates. See Note 2 to the audited financial statements included in the 2015 Annual Report for additional discussion of these estimates and assumptions. The Company utilizes significant estimates and assumptions in determining the estimated success payment and contingent consideration liabilities and associated expense or gain at each balance sheet date. A small change in the Company’s stock price may have a relatively large change in the estimated fair value of the success payment liability and associated expense or gain. Changes in the probabilities and estimated timing of milestones used in the calculation of the contingent consideration liability may have a relatively large impact on the resulting liability and associated expense or gain. Recent Accounting Pronouncements In March 2016, the Financial Accounting Standards Board (“FASB”) issued Accounting Standards Update (“ASU”) No. 2016-09, Compensation—Stock Compensation (Topic 718) , intended to simplify the accounting for share-based payment transactions, including the income tax consequences, classification of awards as either equity or liabilities, and classification on the statement of cash flows. The guidance is effective for reporting periods beginning after December 15, 2016, with early adoption permitted. The Company plans to adopt this standard on January 1, 2017 and expects the adoption of this new accounting guidance will not have a material impact on its consolidated financial statements. In February 2016, the FASB issued ASU No. 2016-02, Leases (Topic 842) . The new guidance requires lessees to recognize the assets and liabilities arising from leases on the balance sheet and additional qualitative and quantitative disclosures will be required. The amendment is effective for reporting periods beginning after December 15, 2018, with early adoption permitted. The Company plans to adopt this standard on January 1, 2019 and is evaluating the impact of adopting the new accounting guidance on its consolidated financial statements. In 2014, the FASB issued ASU No. 2014-09, Revenue From Contracts With Customers (Topic 606) , amended by ASU No. 2015-14. This new standard will replace all current GAAP guidance on this topic and establishes principles for recognizing revenue upon the transfer of promised goods or services to customers, in an amount that reflects the expected consideration received in exchange for those goods or services. This guidance can be applied either retrospectively to each period presented or as a cumulative-effect adjustment as of the date of adoption. In 2015, the FASB voted to defer the effective date to reporting periods beginning after December 15, 2017, with early adoption permitted. The Company plans to adopt this standard on January 1, 2018 and is evaluating the impact of adopting the new accounting guidance on its consolidated financial statements.

Acquisitions

Acquisitions	9 Months Ended
	Sep. 30, 2016
Business Combinations [Abstract]
Acquisitions	Acquisitions Acquisition of Technology from RedoxTherapies, Inc. In July 2016, the Company acquired RedoxTherapies, for a $10.0 million upfront cash payment. The Company also agreed to deliver additional consideration upon achievement of specified clinical, regulatory, and commercial milestones. The acquisition provides the Company with an exclusive license to vipadenant, a small molecule A2a receptor antagonist that has the potential to disrupt important immunosuppressive pathways in the tumor microenvironment in certain cancers. The Company concluded that the assets acquired did not meet the accounting definition of a business as inputs were acquired, but no processes or outputs, and the licensed technology had not achieved technological feasibility. As such, the Company treated the acquisition as an asset purchase, recording the purchase price as $10.0 million in research and development expense in the accompanying condensed consolidated statements of operations. In addition to cash paid, the acquisition agreement stipulates that the Company is required to make milestone payments to the founder of RedoxTherapies upon the achievement of specified clinical, regulatory, and commercial milestones. Triggering of these milestone payments was not considered probable as of the date of the acquisition, and no expense has been recorded for these milestones as of September 30, 2016 . As a result of the acquisition, the Company obtained access to two license agreements to which RedoxTherapies is party, which require the payment of royalties to the licensors based on annual net sales of licensed products or processes by RedoxTherapies and its sublicensees (which may include the Company), as well as certain payments upon the achievement of specified clinical and regulatory milestones. Triggering of these milestone payments was not considered probable as of the date of the acquisition, and no expense has been recorded for these milestones as of September 30, 2016 . Acquisition of AbVitro On January 8, 2016, the Company completed the acquisition of 100% of the outstanding equity in AbVitro. The Company paid approximately $74.7 million in cash and issued an aggregate of 1,289,188 shares of the Company’s common stock valued at $46.9 million based on the closing stock price on January 8, 2016 of $36.39 per share. An additional $2.2 million was recorded as post-combination research and development expense in the first quarter of 2016 in connection with the accelerated vesting of employee stock options. Additionally, 24,446 restricted stock units (“RSUs”) were granted to former AbVitro employees, which shares are subject to monthly vesting over three years following the closing of the transaction, contingent on such employees continuing to provide services to the Company through such vesting dates. These are accounted for as post-acquisition compensation expenses. There are no milestone payment obligations under the terms of the AbVitro acquisition. The elements of the purchase consideration are as follows (in thousands): Cash paid $ 74,729 Common stock issued (1) 46,914 Total consideration $ 121,643 (1) Based on the share purchase agreement, the purchase consideration included 1,289,188 shares of the Company’s common stock. The closing stock price on the transaction date was $36.39 per share. The allocation of the purchase price is based on estimates of the fair value of assets acquired and liabilities assumed as of the acquisition date. The components of the purchase price allocation are as follows (in thousands): Net working capital $ 66 Deferred tax liabilities, net of tax attributes (6,655 ) Acquired in-process research and development 29,017 Goodwill 99,215 Total consideration $ 121,643 The fair value of the acquired in-process research and development (“IPR&D”) has been estimated using the replacement cost method. Under this method, the Company estimated the cost to recreate the technology and derived an estimated value to develop the technology. IPR&D assets are required to be classified as indefinite-lived assets until they become definite lived assets upon the successful completion or the abandonment of the associated research and development effort. Accordingly, during the development period after the date of acquisition, we do not expect these assets to begin to be amortized until the first instance they are used for translational assays. At that time, the Company will determine the useful life of the asset and begin amortization. If the associated research and development effort is abandoned, the related IPR&D assets will be written-off and an impairment charge recorded. The excess of the purchase price over the estimated fair value of the tangible net assets and identifiable intangible assets acquired was recorded as goodwill. The factors contributing to the recognition of the amount of goodwill in the AbVitro acquisition include the ability to accelerate the generation of binders that recognize known targets and discover novel cancer antigen targets. The acquisition also provides the Company with the ability to utilize translational assays to provide a better understanding of the natural immune response to cancer as well as to interrogate and monitor the immune system of patients during treatment. None of the goodwill is expected to be deductible for income tax purposes. Post-Acquisition and Pro Forma Consolidated Financial Information The AbVitro acquisition did not have a material impact on the Company’s condensed consolidated statements of operations, and therefore actual and pro forma disclosures have not been presented. The intangible assets acquired in the AbVitro acquisition are IPR&D, and as such, there would be no pro forma adjustment needed for the amortization of intangible assets. Transaction Costs The Company incurred approximately $0.4 million of direct transaction costs related to the AbVitro acquisition for the nine months ended September 30, 2016 . These costs are included in general and administrative expenses in the condensed consolidated statements of operations.

Collaboration and License Agree

Collaboration and License Agreements	9 Months Ended
	Sep. 30, 2016
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Collaboration and License Agreements	Collaboration and License Agreements Eureka Therapeutics, Inc. and Memorial Sloan Kettering Cancer Center In August 2016, the Company entered into a license agreement with Memorial Sloan Kettering Cancer Center ("MSK") and Eureka Therapeutics, Inc. pursuant to which the Company obtained an exclusive license pertaining to a fully-human binding domain targeting B-cell maturation antigen ("BCMA"), as well as binding domains against two additional undisclosed multiple myeloma targets to be used for the potential development and commercialization of CAR cell therapies for patients with multiple myeloma. The Company made an upfront cash payment and agreed to pay additional amounts upon achievement of specified clinical, regulatory, and commercial milestones, as well as royalties on net sales of licensed products and services by us or our affiliates and sublicensees. Celgene The Company is party to a Master Research and Collaboration Agreement (“Celgene Collaboration Agreement”) with Celgene Corporation and one of its wholly owned subsidiaries (together, “Celgene”) pursuant to which the Company and Celgene agreed to collaborate on researching, developing, and commercializing novel cellular therapy product candidates and other immuno-oncology and immunology therapeutics, including, in particular, CAR and TCR product candidates. The Company is also party to a Share Purchase Agreement (the “Celgene Share Purchase Agreement”) with Celgene. The Celgene Collaboration Agreement and Celgene Share Purchase Agreement, and the Company’s accounting analysis pertaining to these agreements, are described in Note 4 of the financial statements included in the 2015 Annual Report. In March 2016, Celgene exercised its annual right to purchase additional shares of the Company’s common stock to “top-up” its ownership interest in the Company. Celgene purchased 1,137,593 shares at a price of $41.32 per share, for an aggregate cash purchase price of $47.0 million . As Celgene did not exercise the top-up right in full to reach 10% ownership that would have been permitted by the top-up right, the top-up right that will be triggered by the filing of the Company’s Annual Report on Form 10-K for the fiscal year ending December 31, 2016 will only permit Celgene to top-up its ownership stake of the Company’s common stock to 9.76% . In April 2016, Celgene exercised its opt-in right to develop and commercialize product candidates from the Company’s CD19 program outside North America and China. As a result, the Company and Celgene entered into a license agreement (the “Celgene CD19 License”) pursuant to which Celgene received an exclusive, royalty-bearing license to develop and commercialize therapeutic CAR product candidates from the Company’s CD19 program in all territories outside of North America and China (the “Celgene Territory”). The Company retains all rights to develop further and commercialize such product candidates in North America and China (the “Juno Territory”). The Company and Celgene will generally share worldwide research and development costs, while the Company will be responsible for commercialization costs in the Juno Territory and Celgene will be responsible for commercialization costs in the Celgene Territory. The Company has the right to participate in specified commercialization activities for licensed products arising from the CD19 program in certain major European markets. Celgene has the right to participate in specified commercialization activities in North America for licensed products for certain indications under the CD19 program. The Company received a $50.0 million option exercise fee from Celgene upon the exercise of Celgene’s option to license CAR product candidates from the CD19 program. The Company will also receive royalties from Celgene for CAR product candidates arising from the CD19 program at a percentage in the mid-teens of net sales of such product candidates in the Celgene Territory. The Celgene CD19 License agreement contains the following deliverables: (1) an exclusive license with respect to intellectual property, (2) transfer of certain clinical and manufacturing knowledge and related support, and (3) participation on various collaboration committees during the technology transfer period. The Company has accounted for these deliverables as a single unit of accounting because they do not have standalone value and the obligations will be delivered throughout the estimated period of performance. The $50.0 million option exercise fee was recorded in deferred revenue and is being recognized ratably over the period in which the Company expects to fulfill these performance obligations, which was initially determined to be approximately two years . To the extent the Company’s research and development costs for the CD19 program exceed Celgene’s research and development costs for the CD19 program for a given quarter, Celgene is required to provide partial reimbursement to the Company for such costs. The Company recognizes the reimbursement by Celgene as revenue in the period the services are performed. To the extent Celgene’s research and development costs for the CD19 program exceed the Company’s research and development costs for the CD19 program for a given quarter, the Company is required to provide Celgene partial reimbursement for such costs. The Company recognizes the reimbursement to Celgene as additional research and development expense in the period the services are provided. The Company recognized revenue of $20.7 million and $43.4 million in the three and nine months ended September 30, 2016 , respectively, in connection with the Celgene Collaboration Agreement and the Celgene CD19 License. The Company recognized $1.3 million in revenue for the three and nine months ended September 30, 2015 in connection with the Celgene Collaboration Agreement. Fred Hutchinson Cancer Research Center In October 2013, the Company entered into a collaboration agreement with the Fred Hutchinson Cancer Research Center (“FHCRC”) focused on research and development of cancer immunotherapy products and a license agreement pertaining to certain patent rights. The Company also granted FHCRC rights to certain share-based success payments. The collaboration agreement, license agreement, the share-based success payments, and the Company’s accounting analysis pertaining to these agreements and share-based success payments, are described in Note 4 of the financial statements included in the 2015 Annual Report. In December 2015, the Company entered into an agreement with FHCRC to support the establishment of a clinical immunotherapy trial unit. Excluding the expense or gain related to success payment obligations, the Company recognized $3.2 million and $3.1 million of research and development expenses in connection with its collaboration and funding agreements with FHCRC for the three months ended September 30, 2016 and 2015 , respectively, and $11.9 million and $7.5 million for the nine months ended September 30, 2016 and 2015 , respectively. The estimated fair value of the total success payment obligation to FHCRC, after giving effect to the success payments achieved and paid in December 2015, was approximately $37.2 million and $67.3 million as of September 30, 2016 and December 31, 2015 , respectively. With respect to the FHCRC success payment obligations, the Company recognized a gain of $10.5 million and $15.3 million in the three months ended September 30, 2016 and 2015 , respectively. The Company recognized a gain of $13.3 million in the nine months ended September 30, 2016 compared to an expense of $14.6 million in the nine months ended September 30, 2015 . The expense and gain are recorded in research and development expense in the condensed consolidated statements of operations, and represent the change in the FHCRC success payment liability during such periods and the respective months of accrued expenses. The FHCRC success payment liabilities on the condensed consolidated balance sheets as of September 30, 2016 and December 31, 2015 were $20.5 million and $33.8 million , respectively. The Company’s liability for share-based success payments under the FHCRC collaboration is carried at fair value and recognized as expense over the term of the six -year collaboration agreement. To determine the estimated fair value of the success payment liability, the Company uses a Monte Carlo simulation methodology which models the future movement of stock prices based on several key variables. The following variables were incorporated in the calculation of the estimated fair value of the success payment liability as of the following balance sheet dates: Assumptions September 30, 2016 December 31, 2015 Fair value of common stock $ 30.01 $ 43.97 Risk free interest rate 1.15% - 1.48% 1.89% - 2.20% Expected volatility 70% 70% Expected term (years) 5.04 - 8.04 5.79 - 8.79 The computation of expected volatility was estimated using a combination of available information about the historical volatility of stocks of similar publicly-traded companies for a period matching the expected term assumption and the Company’s historical and implied volatility. The risk free interest rate and expected term assumptions depend on the estimated timing of U.S. Food & Drug Administration (“FDA”) approval. In addition, the Company incorporated the estimated number and timing of valuation measurement dates in the calculation of the success payment liability. Memorial Sloan Kettering Cancer Center In November 2013, the Company entered into a sponsored research agreement with MSK focused on research and development relating to CAR T cell technology and a license agreement pertaining to certain patent rights and intellectual property rights related to certain know-how. The Company also granted MSK rights to certain share-based success payments. The sponsored research agreement, license agreement, the share-based success payments, and the Company’s accounting analysis pertaining to these agreements and share-based success payments, are described in Note 4 of the financial statements included in the 2015 Annual Report. The Company is also party to clinical study agreements with MSK. Excluding the expense or gain related to success payment obligations, the Company recognized $0.9 million and $1.0 million of research and development expenses in connection with its research and clinical agreements with MSK for the three months ended September 30, 2016 and 2015 , respectively, and $1.7 million and $3.8 million for the nine months ended September 30, 2016 and 2015 , respectively. The estimated fair value of the total success payment obligation to MSK, after giving effect to the success payment achieved in December 2015 and paid in March 2016, was approximately $22.7 million and $48.9 million as of September 30, 2016 and December 31, 2015 , respectively. With respect to the MSK success payment obligations, the Company recognized a gain of $7.2 million and $10.3 million in the three months ended September 30, 2016 and 2015 . The Company recognized a gain of $7.5 million in the nine months ended September 30, 2016 compared to an expense of $2.7 million in the nine months ended September 30, 2015 . The expense and gain are recorded in research and development expense in the condensed consolidated statements of operations, and represent the change in the MSK success payment liability during such periods and the respective months of accrued expense. The MSK success payment liabilities on the condensed consolidated balance sheets as of September 30, 2016 and December 31, 2015 were $14.0 million and $31.0 million , respectively. The Company’s liability for share-based success payments under the MSK collaboration is carried at fair value and recognized as expense over the term of the five-year collaboration agreement. To determine the estimated fair value of the success payment liability, the Company uses a Monte Carlo simulation methodology which models the future movement of stock prices based on several key variables. The following variables were incorporated in the calculation of the estimated fair value of the success payment liability as of the following balance sheet dates: Assumptions September 30, 2016 December 31, 2015 Fair value of common stock $ 30.01 $ 43.97 Risk free interest rate 1.16% - 1.49% 1.91% - 2.20% Expected volatility 70% 70% Expected term (years) 5.14 - 8.14 5.89 - 8.89 The computation of expected volatility was estimated using a combination of available information about the historical volatility of stocks of similar publicly-traded companies for a period matching the expected term assumption and the Company’s historical and implied volatility. The risk free interest rate and expected term assumptions depend on the estimated timing of FDA approval. In addition, the Company incorporated the estimated number and timing of valuation measurement dates in the calculation of the success payment liability. St. Jude Children’s Research Hospital/Novartis The Company is party to a license agreement with St. Jude (“St. Jude License Agreement”) pertaining to certain patent rights owned by St. Jude. In connection with the April 2015 settlement of Trustees of the University of Pennsylvania v. St. Jude Children’s Research Hospital, Civil Action No. 2:13-cv-01502-SD (E.D. Penn.), in which the Company was a party (the “Penn Litigation”), the Company entered into a sublicense agreement (the “Penn/Novartis Sublicense Agreement”) with the Trustees of the University of Pennsylvania and an affiliate of Novartis pursuant to which the Company granted to Novartis a sublicense pertaining to patent rights licensed to the Company under the St. Jude License Agreement. The St. Jude License Agreement and the Penn/Novartis Sublicense Agreement are described in Note 4 of the financial statements included in the 2015 Annual Report. In January 2016, a clinical milestone was met under both the Penn/Novartis Sublicense Agreement and the St. Jude License Agreement, pursuant to which the Company received a payment of $5.8 million from Novartis, and the Company made a corresponding payment to St. Jude of $5.0 million . A second clinical milestone was met in June 2016, in connection with which the Company received a payment of $8.5 million from Novartis, and the Company made a corresponding payment to St. Jude of $7.5 million . Seattle Children’s Research Institute In February 2014, the Company entered into a sponsored research agreement with Seattle Children’s Research Institute (“SCRI”) and a license agreement with SCRI pertaining to certain patent rights. The Company is also party to clinical support and manufacturing services agreements with SCRI related to the Company’s JCAR017 trials. The sponsored research agreement, license agreement, and clinical support agreement with SCRI are described in Note 4 of the financial statements included in the 2015 Annual Report. The Company recognized $1.1 million of research and development expense in connection with its sponsored research, clinical support and manufacturing services agreements with SCRI for the three months ended September 30, 2016 and 2015 . The Company recognized $3.5 million and $1.4 million of research and development expense in connection with its sponsored research, clinical support and manufacturing services agreements with SCRI for the nine months ended September 30, 2016 and 2015 , respectively. Opus Bio The Company is party to a license agreement with Opus Bio, Inc. (“Opus Bio”) pertaining to certain patent rights and data. The license agreement is described in Note 4 of the financial statements included in the 2015 Annual Report. Two milestones under the license agreement were achieved in the first quarter of 2016 , for which the Company issued a total of 603,364 shares of its common stock as payment and recorded research and development expense of $23.2 million based on the fair value of the common stock on the date the milestones were achieved. After giving effect to the achievement of these milestones, as of September 30, 2016 , one milestone required to be paid in equity in the amount of $25.0 million remains to be achieved, along with up to $215.0 million in milestones payable in cash. Fate Therapeutics In May 2015, the Company entered into a collaboration and license agreement with Fate Therapeutics, Inc. (“Fate Therapeutics”), to identify and utilize small molecules to modulate the Company’s genetically-engineered T cell product candidates to improve their therapeutic potential for cancer patients. The collaboration and license agreement is described in Note 4 of the financial statements included in the 2015 Annual Report. The Company recognized $0.5 million of research and development expense in connection with its collaboration agreement with Fate Therapeutics for the three months ended September 30, 2016 and 2015 . The Company recognized $1.5 million and $0.8 million of research and development expense in the nine months ended September 30, 2016 and 2015 , respectively. Editas Medicine In May 2015, the Company entered into a collaboration and license agreement with Editas Medicine, Inc. (“Editas”), to pursue research programs utilizing Editas’ genome editing technologies with Juno’s CAR and TCR technologies. The collaboration and license agreement is described in Note 4 of the financial statements included in the 2015 Annual Report. The Company recognized $0.9 million and $0.8 million of research and development expense in connection with its collaboration agreement with Editas for the three months ended September 30, 2016 and 2015 , respectively. The Company recognized $2.9 million and $1.0 million of research and development expense in the nine months ended September 30, 2016 and 2015 , respectively.

Cash Equivalents and Marketable

Cash Equivalents and Marketable Securities	9 Months Ended
	Sep. 30, 2016
Cash and Cash Equivalents [Abstract]
Cash Equivalents and Marketable Securities	Cash Equivalents and Marketable Securities The following tables summarize the estimated fair value of cash equivalents and marketable securities and gross unrealized holding gains and losses (in thousands): September 30, 2016 Amortized Cost Gross Unrealized Holding Gains Gross Unrealized Holding Losses Estimated Fair Value Cash equivalents: Money market funds $ 188,740 $ — $ — $ 188,740 Commercial paper 21,750 — — 21,750 Corporate debt securities 5,000 — — 5,000 Total cash equivalents 215,490 — — 215,490 Marketable securities: Commercial paper 98,050 — — 98,050 U.S. government and agency securities 374,614 240 (12 ) 374,842 Corporate debt securities 124,384 7 (47 ) 124,344 Total marketable securities 597,048 247 (59 ) 597,236 Long-term marketable securities: U.S. government and agency securities 126,837 20 (36 ) 126,821 Corporate debt securities 86,415 16 (72 ) 86,359 Equity securities 1,700 — — 1,700 Total long-term marketable securities $ 214,952 $ 36 $ (108 ) $ 214,880 December 31, 2015 Amortized Cost Gross Unrealized Holding Gains Gross Unrealized Holding Losses Estimated Fair Value Cash equivalents: Money market funds $ 177,164 $ — $ — $ 177,164 Commercial paper 45,352 — — 45,352 U.S. government and agency securities 2,000 — — 2,000 Corporate debt securities 5,040 — — 5,040 Total cash equivalents 229,556 — — 229,556 Marketable securities: Commercial paper 73,078 — — 73,078 U.S. government and agency securities 470,519 2 (485 ) 470,036 Corporate debt securities 148,143 1 (245 ) 147,899 Total marketable securities 691,740 3 (730 ) 691,013 Long-term marketable securities: U.S. government and agency securities 204,551 1 (770 ) 203,782 Corporate debt securities 65,898 33 (195 ) 65,736 Equity securities 7,190 — (3,820 ) 3,370 Total long-term marketable securities $ 277,639 $ 34 $ (4,785 ) $ 272,888 The following tables summarize the gross unrealized holding losses and fair value for investments in an unrealized loss position, and the length of time that individual securities have been in a continuous loss position (in thousands): September 30, 2016 Less than 12 Months 12 Months or Greater Total Fair Value Unrealized Losses Fair Value Unrealized Losses Fair Value Unrealized Losses Marketable securities: U.S. government and agency securities $ 75,295 $ (12 ) $ — $ — $ 75,295 $ (12 ) Corporate debt securities 82,122 (47 ) — — 82,122 (47 ) Total marketable securities 157,417 (59 ) — — 157,417 (59 ) Long-term marketable securities: U.S. government and agency securities 68,938 (36 ) — — 68,938 (36 ) Corporate debt securities 52,656 (72 ) — — 52,656 (72 ) Total long-term marketable securities $ 121,594 $ (108 ) $ — $ — $ 121,594 $ (108 ) December 31, 2015 Less than 12 Months 12 Months or Greater Total Fair Value Unrealized Losses Fair Value Unrealized Losses Fair Value Unrealized Losses Marketable securities: U.S. government and agency securities $ 457,641 $ (485 ) $ — $ — $ 457,641 $ (485 ) Corporate debt securities 144,499 (245 ) — — 144,499 (245 ) Total marketable securities 602,140 (730 ) — — 602,140 (730 ) Long-term marketable securities: U.S. government and agency securities 190,767 (770 ) — — 190,767 (770 ) Corporate debt securities 50,591 (195 ) — — 50,591 (195 ) Equity securities 3,370 (3,820 ) — — 3,370 (3,820 ) Total long-term marketable securities $ 244,728 $ (4,785 ) $ — $ — $ 244,728 $ (4,785 ) The Company evaluated its securities for other-than-temporary impairment and considers the decline in market value for the securities to be primarily attributable to current economic and market conditions. For the debt securities, it is not more likely than not that the Company will be required to sell the securities, and the Company does not intend to do so prior to the recovery of the amortized cost basis. The Company evaluated the near-term prospects of the Fate Therapeutics investment in relation to the severity and duration of the impairment. Based on that evaluation, in the second quarter of 2016, the Company determined that the equity security was other-than-temporarily impaired (“OTTI”), and a loss of $5.5 million was recognized at that time. The OTTI loss is included in net loss on the condensed consolidated statements of operations for the nine months ended September 30, 2016 . No additional OTTI losses were recognized for the three months ended September 30, 2016 . All marketable securities have an effective maturity date of three years or less and are available for use and therefore classified as available-for-sale.

Fair Value Measurements

Fair Value Measurements	9 Months Ended
	Sep. 30, 2016
Fair Value Disclosures [Abstract]
Fair Value Measurements	Fair Value Measurements The following tables set forth the fair value of the Company’s financial assets and liabilities measured at fair value on a recurring basis based on the three-tier fair value hierarchy (in thousands): September 30, 2016 Level 1 Level 2 Level 3 Total Financial Assets: Money market funds $ 188,740 $ — $ — $ 188,740 Commercial paper — 119,800 — 119,800 U.S. government and agency securities — 501,663 — 501,663 Corporate debt securities — 215,703 — 215,703 Equity securities 1,700 — — 1,700 Total financial assets $ 190,440 $ 837,166 $ — $ 1,027,606 Financial Liabilities: Success payment liabilities $ — $ — $ 34,502 $ 34,502 Contingent consideration — — 32,091 32,091 Total financial liabilities $ — $ — $ 66,593 $ 66,593 December 31, 2015 Level 1 Level 2 Level 3 Total Financial Assets: Money market funds $ 177,164 $ — $ — $ 177,164 Commercial paper — 118,430 — 118,430 U.S. government and agency securities — 675,818 — 675,818 Corporate debt securities — 218,675 — 218,675 Equity Securities 3,370 — — 3,370 Total financial assets $ 180,534 $ 1,012,923 $ — $ 1,193,457 Financial Liabilities: Success payment liabilities $ — $ — $ 64,829 $ 64,829 Contingent consideration — — 37,266 37,266 Total financial liabilities $ — $ — $ 102,095 $ 102,095 The Company measures the fair value of money market funds based on quoted prices in active markets for identical assets or liabilities. The Level 2 marketable securities include U.S. government and agency securities, corporate debt securities, and commercial paper and are valued either based on recent trades of securities in inactive markets or based on quoted market prices of similar instruments and other significant inputs derived from or corroborated by observable market data. The following table sets forth a summary of the changes in the fair value of the Company’s Level 3 financial liabilities (in thousands): Success Payment Liabilities Contingent Consideration Total Balance at December 31, 2015 $ 64,829 $ 37,266 $ 102,095 Payments (9,569 ) — (9,569 ) Changes in fair value (1) (20,758 ) (5,175 ) (25,933 ) Balance at September 30, 2016 $ 34,502 $ 32,091 $ 66,593 (1) The amount of success payments achieved and changes in fair value for success payment liabilities and contingent consideration are recorded in research and development expense in the condensed consolidated statements of operations. As of September 30, 2016 and December 31, 2015 , the estimated fair value of the success payment obligations, after giving effect to the success payments achieved by FHCRC and MSK, was approximately $59.9 million and $116.2 million , respectively. Included in research and development expense for the nine months ended September 30, 2016 and 2015 was a gain of $20.8 million and an expense of $17.3 million , respectively, related to success payments. See Note 3, Collaboration and License Agreements, to these condensed consolidated financial statements, as well as Note 4 to the financial statements included in the 2015 Annual Report, for additional discussion of estimated fair value of the success payment obligations. The Company utilizes significant estimates and assumptions in determining the estimated success payment liability and associated expense at each balance sheet date. A small change in the Company’s stock price may have a relatively large change in the estimated fair value of the success payment liability and associated expense. In connection with the acquisitions of Stage Cell Therapeutics GmbH (“Stage”) and X-Body, Inc. (“X-Body”) in the second quarter of 2015, the Company agreed to pay additional amounts based on the achievement of certain technical, clinical, regulatory, and commercialization milestones. This contingent consideration is measured at fair value and is based on significant inputs not observable in the market, which represents a Level 3 measurement within the fair value hierarchy. The valuation of contingent consideration uses assumptions the Company believes would be made by a market participant. The Company assesses these estimates on an on-going basis as additional data impacting the assumptions is obtained. Contingent consideration may change significantly as development progresses and additional data are obtained, impacting the Company’s assumptions regarding probabilities of successful achievement of related milestones used to estimate the fair value of the liability and the timing in which they are expected to be achieved. In evaluating the fair value information, judgment is required to interpret the data used to develop the estimates. The estimates of fair value may not be indicative of the amounts that could be realized in a current market exchange. Accordingly, the use of different market assumptions and/or different valuation techniques could result in materially different fair value estimates. The significant unobservable inputs used in the measurement of fair value of the Company’s contingent consideration are probabilities of successful achievement of the milestones, the period in which these milestones are expected to be achieved ranging from 2016 to 2043 , and a discount rate of 16% . Significant increases or decreases in any of the probabilities of success and other inputs would result in a significantly higher or lower fair value measurement, respectively. As of September 30, 2016 , the estimated fair values of the contingent consideration associated with the Stage and X-Body acquisitions were $26.2 million and $5.9 million , respectively. The Company recognized a gain of $5.2 million and expense of $1.3 million, which was recorded in research and development expense, in the nine months ended September 30, 2016 and 2015 , respectively, related to the change in fair value of the contingent consideration. A milestone requiring payment by the Company of €6.0 million to the former stockholders of Stage was achieved in the third quarter of 2016. This milestone will be paid by the Company in the fourth quarter of 2016. The liability associated with this milestone is included in contingent consideration on the condensed consolidated balance sheet as of September 30, 2016 .

Stock-Based Compensation

Stock-Based Compensation	9 Months Ended
	Sep. 30, 2016
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Stock-Based Compensation	Stock-Based Compensation Stock-Based Compensation Stock-based compensation expense is recognized in the condensed consolidated statements of operations as follows (in thousands): Three Months Ended September 30, Nine Months Ended September 30, 2016 2015 2016 2015 Research and development (1) $ 8,751 $ 4,406 $ 29,109 $ 12,089 General and administrative 5,436 4,658 15,863 9,450 Total stock-based compensation expense (2) $ 14,187 $ 9,064 $ 44,972 $ 21,539 (1) Included in research and development stock-based compensation expense for the nine months ended September 30, 2016 was $2.2 million related to the payout of employee stock options in connection with the AbVitro acquisition. (2) Included in stock-based compensation expense recognized for the three months ended September 30, 2016 and 2015 , is $1.4 million and $1.8 million , respectively, related to service providers other than employees, scientific founders, and directors, including $0.9 million and $1.2 million , respectively, for a former cofounding director who became a consultant upon his departure from the board of directors. Included in stock-based compensation expense recognized for the nine months ended September 30, 2016 and 2015 , is $5.7 million and $6.7 million , respectively, related to service providers other than employees, scientific founders, and directors, including $3.3 million and $4.8 million , respectively, for a former cofounding director who became a consultant upon his departure from the board of directors. Total stock-based compensation cost related to unvested awards not yet recognized and the weighted average periods over which the awards are expected to be recognized as of September 30, 2016 for all employees are as follows: Stock Options Restricted Stock Unrecognized stock-based compensation cost (in thousands) $ 115,415 $ 17,467 Expected weighted average period compensation costs to be recognized (years) 2.83 1.91 Restricted Stock and RSUs A summary of the Company’s restricted stock and RSU activity is as follows: Restricted Stock Weighted Average Fair Value at Date of Grant per Share Unvested shares as of December 31, 2015 5,476,600 $ 3.72 Granted 183,410 35.26 Vested (2,032,958 ) 2.73 Forfeited (46,567 ) 6.31 Unvested shares as of September 30, 2016 3,580,485 $ 5.86 Management estimates expected forfeitures and recognizes compensation costs only for those equity awards expected to vest. Stock Options A summary of the Company’s stock option activity is as follows: Stock Options Weighted Average Exercise Price per Share Weighted Average Remaining Contractual Life Aggregate Intrinsic Value Outstanding as of December 31, 2015 5,218,939 $ 30.25 9.13 $ 86,609 Granted 3,388,256 29.70 Exercised (396,869 ) 7.09 Forfeited/Cancelled (203,320 ) 39.01 Outstanding as of September 30, 2016 8,007,006 $ 30.78 8.82 $ 54,711 Exercisable as of September 30, 2016 1,737,758 $ 28.58 8.28 $ 17,633 The fair value of each stock option granted has been determined using the Black-Scholes option pricing model. The material factors incorporated in the Black-Scholes model in estimating the fair value of the options granted to employees, directors, and consultants included the following: Assumptions Nine Months Ended Risk free interest rate 1.13% - 1.78% Expected volatility 70% Expected life (years) 5.27 - 9.97 Expected dividend yield 0% For employees, scientific founders, and directors, the expected life was calculated based on the simplified method as permitted by the SEC Staff Accounting Bulletin No. 110, Share-Based Payment . For other service providers, the expected life was calculated using the contractual term of the award. Management’s estimate of expected volatility was based on available information about the historical volatility of stocks of similar publicly-traded companies for a period matching the expected term assumption and its own historical and implied future volatility. The risk-free interest rate is based on a U.S. Treasury instrument whose term is consistent with the expected life of the stock options. In addition to the assumptions above, management made an estimate of expected forfeitures and is recognizing compensation costs only for those equity awards expected to vest. In April 2016, the Company agreed to repurchase 240,381 shares of common stock issued to MSK at a repurchase price of $41.90 per share.

Comprehensive Income (Loss)

Comprehensive Income (Loss)	9 Months Ended
	Sep. 30, 2016
Equity [Abstract]
Comprehensive Income (Loss)	Comprehensive Income (Loss) The components of accumulated other comprehensive income (loss) and the adjustments to other comprehensive income (loss) are as follows (in thousands): Foreign Currency Translation Adjustments Net Unrealized Gain (Loss) on Marketable Securities Accumulated Other Comprehensive Income (Loss) Balance at December 31, 2015 $ (605 ) $ (5,478 ) $ (6,083 ) Other comprehensive income 673 4,971 5,644 Balance at September 30, 2016 $ 68 $ (507 ) $ (439 ) The details of the components of other comprehensive income (loss) are as follows (in thousands): Three Months Ended September 30, Nine Months Ended September 30, 2016 2015 2016 2015 Other comprehensive income (loss): Foreign currency translation adjustments (1) $ 263 $ 357 $ 673 $ 232 Net change in unrealized gain (loss) on marketable securities: Unrealized gain (loss) on marketable securities (2) (239 ) (906 ) (519 ) (1,540 ) Reclassification adjustment for loss included in net loss (3) — — 5,490 — Total other comprehensive income (loss) $ 24 $ (549 ) $ 5,644 $ (1,308 ) (1) Foreign currency translation adjustments are not adjusted for income taxes as they relate to permanent investments in our international subsidiary. (2) Unrealized gain (loss) on marketable securities is net of income taxes (benefit) provision of $(0.1) million and $0.6 million for the three and nine months ended September 30, 2016 , respectively. There was no income tax effect recorded on unrealized gain (loss) for the three and nine months ended September 30, 2015 . (3) Amounts reclassified from accumulated other comprehensive income are included in other-than-temporary impairment loss on the condensed consolidated statements of operations. There was no income tax effect on this reclassification adjustment for the three and nine months ended September 30, 2016 as it does not create taxable income in future years.

Income Taxes

Income Taxes	9 Months Ended
	Sep. 30, 2016
Income Tax Disclosure [Abstract]
Income Taxes	Income Taxes The Company recorded an income tax benefit of $9.1 million on a pre-tax loss of $201.9 million for the nine months ended September 30, 2016 . Of the total income tax benefit, $6.7 million relates to the release of valuation allowance on the U.S. deferred tax assets as a result of the deferred tax liabilities established for intangible assets from the acquisition of AbVitro, net of tax attributes, and $2.0 million relates to the benefit associated with the net loss incurred by the Company’s German subsidiary in the nine months ended September 30, 2016 . The remaining tax benefit of $0.4 million relates to intraperiod allocation of taxes between continuing operations and other comprehensive income. For the prior year, the Company recorded an income tax benefit of $1.6 million on a pre-tax loss of $155.7 million for the nine months ended September 30, 2015 . Of the $1.6 million total tax benefit, $0.5 million relates to the net loss incurred by the Company’s German subsidiary in the period from May 11, 2015 to September 30, 2015 , as the Company has determined that it is more-likely-than-not that it will realize the benefit of these losses. The remaining $1.1 million of income tax benefit relates to the release of valuation allowance on the U.S. deferred tax assets as a result of the deferred tax liabilities established for intangible assets from the acquisition of X-Body. The Company maintains a full valuation allowance on its net U.S. deferred tax assets. The assessment regarding whether a valuation allowance is required considers both positive and negative evidence when determining whether it is more-likely-than-not that deferred tax assets are recoverable. In making this assessment, significant weight is given to evidence that can be objectively verified. In its evaluation, the Company considered its cumulative loss in recent years and its forecasted losses in the near-term as significant negative evidence. Based upon a review of the four sources of income identified within ASC 740, the Company determined that the negative evidence outweighed the positive evidence and a full valuation allowance on its U.S. net deferred tax assets will be maintained. The Company will continue to assess the realizability of its deferred tax assets going forward and will adjust the valuation allowance as needed. The Company has determined that it is more-likely-than-not that it will realize the benefit of the losses for its German subsidiary and has not recorded a valuation allowance against the German deferred tax assets. The Company follows the provisions of ASC 740, Accounting for Income Taxes , and the accounting guidance related to accounting for uncertainty in income taxes. The Company determines its uncertain tax positions based on a determination of whether and how much of a tax benefit taken by the Company in its tax filings or positions is more-likely-than-not to be sustained upon examination by the relevant income tax authorities. During the third quarter of 2016, the Company completed a study of Research & Development and Orphan Drug tax credit carryforwards, which resulted in no material adjustments. The Company will recognize both accrued interest and penalties related to unrecognized benefits in income tax expense. The Company is generally subject to examination by the U.S. federal and local income tax authorities for all tax years in which a loss carryforward is available and is subject to examination in Germany for four years. The Company applies judgment in the determination of the consolidated financial statement recognition and measurement of tax positions taken or expected to be taken in a tax return. As of September 30, 2016 and December 31, 2015 , the Company had no material unrecognized or uncertain tax benefits.

Net Loss per Share

Net Loss per Share	9 Months Ended
	Sep. 30, 2016
Earnings Per Share [Abstract]
Net Loss per Share	Net Loss per Share Basic and diluted net loss per share is calculated by dividing net loss by the weighted average number of common shares outstanding during the period, without consideration for common stock equivalents. The Company’s potentially dilutive shares, which include unvested restricted stock, unvested RSUs, options to purchase common stock, and potential shares issued for success payments, are considered to be common stock equivalents and are only included in the calculation of diluted net loss per share when their effect is dilutive. The amounts in the table below were excluded from the calculation of diluted net loss per share for the periods indicated due to their anti-dilutive effect: As of September 30, 2016 2015 Unvested restricted stock and RSUs 3,580,485 5,988,252 Options to purchase common stock 8,007,006 4,582,566 Estimated number of shares issued for success payments (1) — 2,088,965 Total 11,587,491 12,659,783 (1) Represents the number of shares that would be issued if the success payment valuation date had been September 30, 2015 . The Company’s common stock price per share was $40.69 at September 30, 2015 which would have resulted in a success payment of $85 million ( $75 million for FHCRC and $10 million for MSK). The number of shares issued, for the purpose of this presentation, is calculated by dividing the success payment by the stock price per share on the valuation date. At September 30, 2016 the Company’s stock price was below the threshold that would require additional payments to FHCRC or MSK, therefore no shares are included.

Commitments and Contingencies

Commitments and Contingencies	9 Months Ended
	Sep. 30, 2016
Commitments and Contingencies Disclosure [Abstract]
Commitments and Contingencies	Commitments and Contingencies Leases The Company has entered into various lease agreements for its office, laboratory, and manufacturing spaces with original lease periods expiring between 2016 and 2026 . In addition to minimum rent, certain leases require payment of real estate taxes, insurance, common area maintenance charges and other executory costs. These executory costs are not included in the table below. Certain of these arrangements have free or escalating rent payment provisions. The Company recognizes rent expense under such arrangements on a straight-line basis over the effective term of each lease. The following table summarizes the Company’s future minimum lease commitments as of September 30, 2016 (in thousands): Year ending December 31: 2016 1,641 2017 4,973 2018 9,789 2019 12,167 2020 12,225 Thereafter 47,382 Total minimum lease payments $ 88,177 Rent expense for the three months ended September 30, 2016 and 2015 was $0.9 million and $0.6 million , respectively. Rent expense for the nine months ended September 30, 2016 and 2015 was $3.3 million and $1.5 million , respectively. Litigation From time to time the Company is involved in claims, proceedings, and litigation arising in the ordinary course of business. The amount of any liability is not probable or the amount cannot be reasonably estimated and therefore accruals have not been made. At this time, the Company does not expect litigation matters to have a material adverse impact on its business, financial position, or results of operations.

Related-Party Transactions

Related-Party Transactions	9 Months Ended
	Sep. 30, 2016
Related Party Transactions [Abstract]
Related-Party Transactions	Related-Party Transactions The Company is party to the Celgene Collaboration Agreement, the Celgene Share Purchase Agreement, a voting agreement, and a registration rights agreement with Celgene, who is a holder of more than 5% of the Company’s common stock. See Note 3, Collaboration and License Agreements, to these condensed consolidated financial statements, as well as Note 4 to the financial statements included in the 2015 Annual Report.

Significant Accounting Polici18

Significant Accounting Policies (Policies)	9 Months Ended
	Sep. 30, 2016
Accounting Policies [Abstract]
Organization and Basis of Presentation	Organization and Basis of Presentation Juno Therapeutics, Inc. (the “Company”) was incorporated in Delaware on August 5, 2013 as FC Therapeutics, Inc., and changed its name to Juno Therapeutics, Inc. on October 23, 2013. The Company is building a fully-integrated biopharmaceutical company focused on re-engaging the body’s immune system to revolutionize the treatment of cancer. Founded on the vision that the use of human cells as therapeutic entities will drive one of the next important phases in medicine, the Company is developing cell-based cancer immunotherapies based on its chimeric antigen receptor (“CAR”) and high-affinity T cell receptor (“TCR”) technologies to genetically engineer T cells to recognize and kill cancer cells. In July 2016, the Company acquired RedoxTherapies, Inc. (“RedoxTherapies”), a privately-held company. See Note 2, Acquisitions. The acquisition provides the Company with an exclusive license to vipadenant, a small molecule A2a receptor antagonist that has the potential to disrupt important immunosuppressive pathways in the tumor microenvironment in certain cancers. In January 2016, the Company acquired AbVitro, Inc., (“AbVitro”) a company with a leading next-generation single cell sequencing platform. See Note 2, Acquisition. The AbVitro acquisition is intended to augment the Company’s capabilities to create engineered T cells against a broad array of cancer targets. The Company will initially use this technology in its translation research assays, to find and generate fully-human TCRs and antibodies, and to find novel targets. The Company is subject to a number of risks similar to other biopharmaceutical companies in the early stage, including, but not limited to, possible failure of preclinical testing or clinical trials, the need to obtain marketing approval for its product candidates, competitors developing new technological innovations, the need to successfully commercialize and gain market acceptance of the Company’s products, protection of proprietary technology, and the need to obtain adequate additional funding. If the Company, or any commercialization partner for the Company’s product candidates, does not successfully commercialize any of the Company’s product candidates, the Company will not be able to generate product revenue or achieve profitability. As of September 30, 2016 , the Company had an accumulated deficit of $778.5 million . The financial data as of December 31, 2015 is derived from the Company’s audited financial statements, which are included in the Company’s Annual Report on Form 10-K, which was filed with the Securities and Exchange Commission (the “SEC”) on February 29, 2016 (the “ 2015 Annual Report”), and should be read in conjunction with the audited financial statements and notes thereto. The Company’s significant accounting policies are described in Note 2 to the financial statements included in the 2015 Annual Report. Certain prior period amounts have been reclassified to conform to the current period presentation. For the nine months ended September 30, 2015 , $6.0 million was reclassified from litigation to general and administrative on the condensed consolidated statements of operations. This reclassification does not have a material impact on the Company’s condensed consolidated financial statements. These unaudited interim condensed consolidated financial statements have been prepared in accordance with U.S. generally accepted accounting principles (“GAAP”). In management’s opinion, the unaudited interim condensed consolidated financial statements have been prepared on the same basis as the audited financial statements and include all adjustments, consisting of normal recurring adjustments, necessary for the fair presentation of the Company’s financial position, results of operations and comprehensive loss and cash flows for the interim periods. The results for the three and nine months ended September 30, 2016 are not necessarily indicative of the results expected for the full fiscal year or any other interim period.
Use of Estimates	Use of Estimates The preparation of the Company’s condensed consolidated financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the amounts reported in the condensed consolidated financial statements and accompanying notes. Actual results could differ from such estimates. See Note 2 to the audited financial statements included in the 2015 Annual Report for additional discussion of these estimates and assumptions. The Company utilizes significant estimates and assumptions in determining the estimated success payment and contingent consideration liabilities and associated expense or gain at each balance sheet date. A small change in the Company’s stock price may have a relatively large change in the estimated fair value of the success payment liability and associated expense or gain. Changes in the probabilities and estimated timing of milestones used in the calculation of the contingent consideration liability may have a relatively large impact on the resulting liability and associated expense or gain.
Recent Accounting Pronouncements	Recent Accounting Pronouncements In March 2016, the Financial Accounting Standards Board (“FASB”) issued Accounting Standards Update (“ASU”) No. 2016-09, Compensation—Stock Compensation (Topic 718) , intended to simplify the accounting for share-based payment transactions, including the income tax consequences, classification of awards as either equity or liabilities, and classification on the statement of cash flows. The guidance is effective for reporting periods beginning after December 15, 2016, with early adoption permitted. The Company plans to adopt this standard on January 1, 2017 and expects the adoption of this new accounting guidance will not have a material impact on its consolidated financial statements. In February 2016, the FASB issued ASU No. 2016-02, Leases (Topic 842) . The new guidance requires lessees to recognize the assets and liabilities arising from leases on the balance sheet and additional qualitative and quantitative disclosures will be required. The amendment is effective for reporting periods beginning after December 15, 2018, with early adoption permitted. The Company plans to adopt this standard on January 1, 2019 and is evaluating the impact of adopting the new accounting guidance on its consolidated financial statements. In 2014, the FASB issued ASU No. 2014-09, Revenue From Contracts With Customers (Topic 606) , amended by ASU No. 2015-14. This new standard will replace all current GAAP guidance on this topic and establishes principles for recognizing revenue upon the transfer of promised goods or services to customers, in an amount that reflects the expected consideration received in exchange for those goods or services. This guidance can be applied either retrospectively to each period presented or as a cumulative-effect adjustment as of the date of adoption. In 2015, the FASB voted to defer the effective date to reporting periods beginning after December 15, 2017, with early adoption permitted. The Company plans to adopt this standard on January 1, 2018 and is evaluating the impact of adopting the new accounting guidance on its consolidated financial statements.

Acquisitions (Tables)

Acquisitions (Tables)	9 Months Ended
	Sep. 30, 2016
Business Combinations [Abstract]
Schedule of Purchase Consideration	The elements of the purchase consideration are as follows (in thousands): Cash paid $ 74,729 Common stock issued (1) 46,914 Total consideration $ 121,643 (1) Based on the share purchase agreement, the purchase consideration included 1,289,188 shares of the Company’s common stock. The closing stock price on the transaction date was $36.39 per share.
Components of Purchase Price Allocation	The components of the purchase price allocation are as follows (in thousands): Net working capital $ 66 Deferred tax liabilities, net of tax attributes (6,655 ) Acquired in-process research and development 29,017 Goodwill 99,215 Total consideration $ 121,643

Collaboration and License Agr20

Collaboration and License Agreements (Tables)	9 Months Ended
	Sep. 30, 2016
Fred Hutchinson Cancer Research Center [Member]
Related Party Transaction [Line Items]
Assumptions Used to Calculate Estimated Fair Value of Success Payment Liability	The following variables were incorporated in the calculation of the estimated fair value of the success payment liability as of the following balance sheet dates: Assumptions September 30, 2016 December 31, 2015 Fair value of common stock $ 30.01 $ 43.97 Risk free interest rate 1.15% - 1.48% 1.89% - 2.20% Expected volatility 70% 70% Expected term (years) 5.04 - 8.04 5.79 - 8.79
Memorial Sloan Kettering Cancer Center [Member]
Related Party Transaction [Line Items]
Assumptions Used to Calculate Estimated Fair Value of Success Payment Liability	The following variables were incorporated in the calculation of the estimated fair value of the success payment liability as of the following balance sheet dates: Assumptions September 30, 2016 December 31, 2015 Fair value of common stock $ 30.01 $ 43.97 Risk free interest rate 1.16% - 1.49% 1.91% - 2.20% Expected volatility 70% 70% Expected term (years) 5.14 - 8.14 5.89 - 8.89

Cash Equivalents and Marketab21

Cash Equivalents and Marketable Securities (Tables)	9 Months Ended
	Sep. 30, 2016
Cash and Cash Equivalents [Abstract]
Summary of Estimated Fair Value of Cash Equivalents and Marketable Securities	The following tables summarize the estimated fair value of cash equivalents and marketable securities and gross unrealized holding gains and losses (in thousands): September 30, 2016 Amortized Cost Gross Unrealized Holding Gains Gross Unrealized Holding Losses Estimated Fair Value Cash equivalents: Money market funds $ 188,740 $ — $ — $ 188,740 Commercial paper 21,750 — — 21,750 Corporate debt securities 5,000 — — 5,000 Total cash equivalents 215,490 — — 215,490 Marketable securities: Commercial paper 98,050 — — 98,050 U.S. government and agency securities 374,614 240 (12 ) 374,842 Corporate debt securities 124,384 7 (47 ) 124,344 Total marketable securities 597,048 247 (59 ) 597,236 Long-term marketable securities: U.S. government and agency securities 126,837 20 (36 ) 126,821 Corporate debt securities 86,415 16 (72 ) 86,359 Equity securities 1,700 — — 1,700 Total long-term marketable securities $ 214,952 $ 36 $ (108 ) $ 214,880 December 31, 2015 Amortized Cost Gross Unrealized Holding Gains Gross Unrealized Holding Losses Estimated Fair Value Cash equivalents: Money market funds $ 177,164 $ — $ — $ 177,164 Commercial paper 45,352 — — 45,352 U.S. government and agency securities 2,000 — — 2,000 Corporate debt securities 5,040 — — 5,040 Total cash equivalents 229,556 — — 229,556 Marketable securities: Commercial paper 73,078 — — 73,078 U.S. government and agency securities 470,519 2 (485 ) 470,036 Corporate debt securities 148,143 1 (245 ) 147,899 Total marketable securities 691,740 3 (730 ) 691,013 Long-term marketable securities: U.S. government and agency securities 204,551 1 (770 ) 203,782 Corporate debt securities 65,898 33 (195 ) 65,736 Equity securities 7,190 — (3,820 ) 3,370 Total long-term marketable securities $ 277,639 $ 34 $ (4,785 ) $ 272,888
Summary of Gross Unrealized Holding Losses and Fair Value for Investments in Unrealized Loss Position	The following tables summarize the gross unrealized holding losses and fair value for investments in an unrealized loss position, and the length of time that individual securities have been in a continuous loss position (in thousands): September 30, 2016 Less than 12 Months 12 Months or Greater Total Fair Value Unrealized Losses Fair Value Unrealized Losses Fair Value Unrealized Losses Marketable securities: U.S. government and agency securities $ 75,295 $ (12 ) $ — $ — $ 75,295 $ (12 ) Corporate debt securities 82,122 (47 ) — — 82,122 (47 ) Total marketable securities 157,417 (59 ) — — 157,417 (59 ) Long-term marketable securities: U.S. government and agency securities 68,938 (36 ) — — 68,938 (36 ) Corporate debt securities 52,656 (72 ) — — 52,656 (72 ) Total long-term marketable securities $ 121,594 $ (108 ) $ — $ — $ 121,594 $ (108 ) December 31, 2015 Less than 12 Months 12 Months or Greater Total Fair Value Unrealized Losses Fair Value Unrealized Losses Fair Value Unrealized Losses Marketable securities: U.S. government and agency securities $ 457,641 $ (485 ) $ — $ — $ 457,641 $ (485 ) Corporate debt securities 144,499 (245 ) — — 144,499 (245 ) Total marketable securities 602,140 (730 ) — — 602,140 (730 ) Long-term marketable securities: U.S. government and agency securities 190,767 (770 ) — — 190,767 (770 ) Corporate debt securities 50,591 (195 ) — — 50,591 (195 ) Equity securities 3,370 (3,820 ) — — 3,370 (3,820 ) Total long-term marketable securities $ 244,728 $ (4,785 ) $ — $ — $ 244,728 $ (4,785 )

Fair Value Measurements (Tables

Fair Value Measurements (Tables)	9 Months Ended
	Sep. 30, 2016
Fair Value Disclosures [Abstract]
Schedule of Fair Value of Financial Assets and Liabilities Measured on Recurring Basis	The following tables set forth the fair value of the Company’s financial assets and liabilities measured at fair value on a recurring basis based on the three-tier fair value hierarchy (in thousands): September 30, 2016 Level 1 Level 2 Level 3 Total Financial Assets: Money market funds $ 188,740 $ — $ — $ 188,740 Commercial paper — 119,800 — 119,800 U.S. government and agency securities — 501,663 — 501,663 Corporate debt securities — 215,703 — 215,703 Equity securities 1,700 — — 1,700 Total financial assets $ 190,440 $ 837,166 $ — $ 1,027,606 Financial Liabilities: Success payment liabilities $ — $ — $ 34,502 $ 34,502 Contingent consideration — — 32,091 32,091 Total financial liabilities $ — $ — $ 66,593 $ 66,593 December 31, 2015 Level 1 Level 2 Level 3 Total Financial Assets: Money market funds $ 177,164 $ — $ — $ 177,164 Commercial paper — 118,430 — 118,430 U.S. government and agency securities — 675,818 — 675,818 Corporate debt securities — 218,675 — 218,675 Equity Securities 3,370 — — 3,370 Total financial assets $ 180,534 $ 1,012,923 $ — $ 1,193,457 Financial Liabilities: Success payment liabilities $ — $ — $ 64,829 $ 64,829 Contingent consideration — — 37,266 37,266 Total financial liabilities $ — $ — $ 102,095 $ 102,095
Summary of Changes in Fair Value of Level 3 Financial Liabilities	The following table sets forth a summary of the changes in the fair value of the Company’s Level 3 financial liabilities (in thousands): Success Payment Liabilities Contingent Consideration Total Balance at December 31, 2015 $ 64,829 $ 37,266 $ 102,095 Payments (9,569 ) — (9,569 ) Changes in fair value (1) (20,758 ) (5,175 ) (25,933 ) Balance at September 30, 2016 $ 34,502 $ 32,091 $ 66,593 (1) The amount of success payments achieved and changes in fair value for success payment liabilities and contingent consideration are recorded in research and development expense in the condensed consolidated statements of operations.

Stock-Based Compensation (Table

Stock-Based Compensation (Tables)	9 Months Ended
	Sep. 30, 2016
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Summary of Stock-Based Compensation Expense	Stock-based compensation expense is recognized in the condensed consolidated statements of operations as follows (in thousands): Three Months Ended September 30, Nine Months Ended September 30, 2016 2015 2016 2015 Research and development (1) $ 8,751 $ 4,406 $ 29,109 $ 12,089 General and administrative 5,436 4,658 15,863 9,450 Total stock-based compensation expense (2) $ 14,187 $ 9,064 $ 44,972 $ 21,539 (1) Included in research and development stock-based compensation expense for the nine months ended September 30, 2016 was $2.2 million related to the payout of employee stock options in connection with the AbVitro acquisition. (2) Included in stock-based compensation expense recognized for the three months ended September 30, 2016 and 2015 , is $1.4 million and $1.8 million , respectively, related to service providers other than employees, scientific founders, and directors, including $0.9 million and $1.2 million , respectively, for a former cofounding director who became a consultant upon his departure from the board of directors. Included in stock-based compensation expense recognized for the nine months ended September 30, 2016 and 2015 , is $5.7 million and $6.7 million , respectively, related to service providers other than employees, scientific founders, and directors, including $3.3 million and $4.8 million , respectively, for a former cofounding director who became a consultant upon his departure from the board of directors.
Total Stock-Based Compensation Cost Related to Unvested Awards Not Yet Recognized and Weighted Average Periods	Total stock-based compensation cost related to unvested awards not yet recognized and the weighted average periods over which the awards are expected to be recognized as of September 30, 2016 for all employees are as follows: Stock Options Restricted Stock Unrecognized stock-based compensation cost (in thousands) $ 115,415 $ 17,467 Expected weighted average period compensation costs to be recognized (years) 2.83 1.91
Summary of Restricted Stock and RSU Activity	A summary of the Company’s restricted stock and RSU activity is as follows: Restricted Stock Weighted Average Fair Value at Date of Grant per Share Unvested shares as of December 31, 2015 5,476,600 $ 3.72 Granted 183,410 35.26 Vested (2,032,958 ) 2.73 Forfeited (46,567 ) 6.31 Unvested shares as of September 30, 2016 3,580,485 $ 5.86
Summary of Stock Option Activity	A summary of the Company’s stock option activity is as follows: Stock Options Weighted Average Exercise Price per Share Weighted Average Remaining Contractual Life Aggregate Intrinsic Value Outstanding as of December 31, 2015 5,218,939 $ 30.25 9.13 $ 86,609 Granted 3,388,256 29.70 Exercised (396,869 ) 7.09 Forfeited/Cancelled (203,320 ) 39.01 Outstanding as of September 30, 2016 8,007,006 $ 30.78 8.82 $ 54,711 Exercisable as of September 30, 2016 1,737,758 $ 28.58 8.28 $ 17,633
Summary of Material Factors Incorporated in Black-Scholes Model in Estimating Fair Value of Options Granted to Employees and Consultants	The fair value of each stock option granted has been determined using the Black-Scholes option pricing model. The material factors incorporated in the Black-Scholes model in estimating the fair value of the options granted to employees, directors, and consultants included the following: Assumptions Nine Months Ended Risk free interest rate 1.13% - 1.78% Expected volatility 70% Expected life (years) 5.27 - 9.97 Expected dividend yield 0%

Comprehensive Income (Loss) (Ta

Comprehensive Income (Loss) (Tables)	9 Months Ended
	Sep. 30, 2016
Equity [Abstract]
Components of Accumulated Other Comprehensive Income (Loss) and Adjustments to Other Comprehensive Income (Loss)	The components of accumulated other comprehensive income (loss) and the adjustments to other comprehensive income (loss) are as follows (in thousands): Foreign Currency Translation Adjustments Net Unrealized Gain (Loss) on Marketable Securities Accumulated Other Comprehensive Income (Loss) Balance at December 31, 2015 $ (605 ) $ (5,478 ) $ (6,083 ) Other comprehensive income 673 4,971 5,644 Balance at September 30, 2016 $ 68 $ (507 ) $ (439 )
Summary of Components of Other Comprehensive Income (Loss)	The details of the components of other comprehensive income (loss) are as follows (in thousands): Three Months Ended September 30, Nine Months Ended September 30, 2016 2015 2016 2015 Other comprehensive income (loss): Foreign currency translation adjustments (1) $ 263 $ 357 $ 673 $ 232 Net change in unrealized gain (loss) on marketable securities: Unrealized gain (loss) on marketable securities (2) (239 ) (906 ) (519 ) (1,540 ) Reclassification adjustment for loss included in net loss (3) — — 5,490 — Total other comprehensive income (loss) $ 24 $ (549 ) $ 5,644 $ (1,308 ) (1) Foreign currency translation adjustments are not adjusted for income taxes as they relate to permanent investments in our international subsidiary. (2) Unrealized gain (loss) on marketable securities is net of income taxes (benefit) provision of $(0.1) million and $0.6 million for the three and nine months ended September 30, 2016 , respectively. There was no income tax effect recorded on unrealized gain (loss) for the three and nine months ended September 30, 2015 . (3) Amounts reclassified from accumulated other comprehensive income are included in other-than-temporary impairment loss on the condensed consolidated statements of operations. There was no income tax effect on this reclassification adjustment for the three and nine months ended September 30, 2016 as it does not create taxable income in future years.

Net Loss per Share (Tables)

Net Loss per Share (Tables)	9 Months Ended
	Sep. 30, 2016
Earnings Per Share [Abstract]
Schedule of Diluted Net Loss Per Share Due to Anti-Dilutive Effect	The amounts in the table below were excluded from the calculation of diluted net loss per share for the periods indicated due to their anti-dilutive effect: As of September 30, 2016 2015 Unvested restricted stock and RSUs 3,580,485 5,988,252 Options to purchase common stock 8,007,006 4,582,566 Estimated number of shares issued for success payments (1) — 2,088,965 Total 11,587,491 12,659,783 (1) Represents the number of shares that would be issued if the success payment valuation date had been September 30, 2015 . The Company’s common stock price per share was $40.69 at September 30, 2015 which would have resulted in a success payment of $85 million ( $75 million for FHCRC and $10 million for MSK). The number of shares issued, for the purpose of this presentation, is calculated by dividing the success payment by the stock price per share on the valuation date. At September 30, 2016 the Company’s stock price was below the threshold that would require additional payments to FHCRC or MSK, therefore no shares are included.

Commitments and Contingencies (

Commitments and Contingencies (Tables)	9 Months Ended
	Sep. 30, 2016
Commitments and Contingencies Disclosure [Abstract]
Summary of Company's Future Minimum Lease Commitments	The following table summarizes the Company’s future minimum lease commitments as of September 30, 2016 (in thousands): Year ending December 31: 2016 1,641 2017 4,973 2018 9,789 2019 12,167 2020 12,225 Thereafter 47,382 Total minimum lease payments $ 88,177

Significant Accounting Polici27

Significant Accounting Policies - Additional Information (Detail) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2015	Sep. 30, 2016	Dec. 31, 2015
Organization And Basis Of Presentation [Line Items]
Accumulated deficit		$ (778,459)	$ (585,657)
General and Administrative [Member]
Organization And Basis Of Presentation [Line Items]
Amount reclassified from litigation	$ 6,000

Acquisitions - Acquisition of

Acquisitions - Acquisition of AbVitro - Additional Information (Detail) - USD ($)	Jan. 08, 2016	Jul. 31, 2016	Sep. 30, 2016
Business Acquisition [Line Items]
Cash paid for acquisition		$ 10,000,000
AbVitro Inc [Member]
Business Acquisition [Line Items]
Percentage of equity interest acquired (in percentage)	100.00%
Cash paid for acquisition	$ 74,729,000
Aggregate shares issued in acquisition (in shares)	1,289,188
Common stock value	$ 46,914,000
Closing stock price (in usd per share)	$ 36.39
Business combination, milestone payment obligations			$ 0
Business acquisition, goodwill, expected tax deductible amount			0
Direct transaction cost			$ 400,000
AbVitro Inc [Member] | Restricted Stock Units (RSUs) [Member]
Business Acquisition [Line Items]
Restricted stock units, Granted (in shares)			24,446
Vesting period (in years)			3 years

Acquisitions - Schedule of Purc

Acquisitions - Schedule of Purchase Consideration (Detail) - USD ($) $ in Thousands	Jan. 08, 2016	Jul. 31, 2016
Business Acquisition [Line Items]
Cash paid		$ 10,000
AbVitro Inc [Member]
Business Acquisition [Line Items]
Cash paid	$ 74,729
Common stock issued	46,914
Total consideration	$ 121,643

Acquisitions - Schedule of Pu30

Acquisitions - Schedule of Purchase Consideration (Non-printing section) (Detail) - AbVitro Inc [Member]	Jan. 08, 2016$ / sharesshares
Business Acquisition [Line Items]
Aggregate shares issued in acquisition (in shares) | shares	1,289,188
Closing stock price (in usd per share) | $ / shares	$ 36.39

Acquisitions - Components of Pu

Acquisitions - Components of Purchase Price Allocation (Detail) - USD ($) $ in Thousands	Sep. 30, 2016	Jan. 08, 2016	Dec. 31, 2015
Business Acquisition [Line Items]
Goodwill	$ 221,306		$ 122,092
AbVitro Inc [Member]
Business Acquisition [Line Items]
Net working capital		$ 66
Deferred tax liabilities, net of tax attributes		(6,655)
Acquired in-process research and development		29,017
Goodwill		99,215
Total consideration		$ 121,643

Collaboration and License Agr32

Collaboration and License Agreements - Celgene - Additional Information (Detail) $ / shares in Units, $ in Thousands	1 Months Ended	3 Months Ended		9 Months Ended
	Mar. 31, 2016USD ($)$ / sharesshares	Sep. 30, 2016USD ($)	Sep. 30, 2015USD ($)	Sep. 30, 2016USD ($)	Sep. 30, 2015USD ($)	Aug. 31, 2016milestone
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Number of additional undisclosed multiple myeloma targets | milestone						2
Revenue recognized during period		$ 20,826	$ 1,602	$ 58,203	$ 14,063
Celgene [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Percentage of outstanding common stock (in percentage)	9.76%
Collaborative Arrangement [Member] | Celgene [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Revenue recognized during period		$ 20,700	$ 1,300	43,400	$ 1,300
Share Purchase Agreement [Member] | Celgene [Member] | Top-Up Rights [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Common stock shares sold (in shares) | shares	1,137,593
Common stock, price per share (in usd per share) | $ / shares	$ 41.32
Aggregate cash price of common stock sold	$ 47,000
Share Purchase Agreement [Member] | Celgene [Member] | First Period Top-Up Rights [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Percentage of outstanding common stock to be acquired (in percentage)	10.00%
CD 19 Program [Member] | Celgene [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Revenue recognized in deferred revenue				$ 50,000
Performance obligations fulfill period (in years)				2 years

Collaboration and License Agr33

Collaboration and License Agreements - Fred Hutchinson Cancer Research Center - Additional Information (Detail) - USD ($) $ in Thousands	1 Months Ended	3 Months Ended		9 Months Ended
	Oct. 31, 2013	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015	Dec. 31, 2015
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Research and development expenses		$ 60,854	$ 11,503	$ 206,887	$ 129,537
Estimated fair value of total success payment obligation		59,900		59,900		$ 116,200
Success payment liabilities		34,502		34,502		64,829
Success payment (expense) gain				(20,800)	17,300
Collaborative Arrangement [Member] | Fred Hutchinson Cancer Research Center [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Research and development expenses		3,200	3,100	11,900	7,500
Estimated fair value of total success payment obligation		37,200		37,200		67,300
Success payment liabilities		20,500		20,500		$ 33,800
Success payment (expense) gain		$ (10,500)	$ (15,300)	$ (13,300)	$ 14,600
Collaboration agreement, term	6 years

Collaboration and License Agr34

Collaboration and License Agreements - Assumptions Used to Calculate Estimated Fair Value of Success Payment Liability (Detail) - $ / shares	9 Months Ended	12 Months Ended
	Sep. 30, 2016	Dec. 31, 2015
Memorial Sloan Kettering Cancer Center [Member]
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Fair value of common stock (in usd per share)	$ 30.01	$ 43.97
Expected volatility (in percentage)	70.00%	70.00%
Memorial Sloan Kettering Cancer Center [Member] | Minimum [Member]
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Risk free interest rate (in percentage)	1.16%	1.91%
Expected term (in years)	5 years 1 month 21 days	5 years 10 months 21 days
Memorial Sloan Kettering Cancer Center [Member] | Maximum [Member]
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Risk free interest rate (in percentage)	1.49%	2.20%
Expected term (in years)	8 years 1 month 21 days	8 years 10 months 21 days
Fred Hutchinson Cancer Research Center [Member]
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Fair value of common stock (in usd per share)	$ 30.01	$ 43.97
Expected volatility (in percentage)	70.00%	70.00%
Fred Hutchinson Cancer Research Center [Member] | Minimum [Member]
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Risk free interest rate (in percentage)	1.15%	1.89%
Expected term (in years)	5 years 15 days	5 years 9 months 15 days
Fred Hutchinson Cancer Research Center [Member] | Maximum [Member]
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Risk free interest rate (in percentage)	1.48%	2.20%
Expected term (in years)	8 years 15 days	8 years 9 months 15 days

Collaboration and License Agr35

Collaboration and License Agreements - Memorial Sloan Kettering Cancer Center - Additional Information (Detail) - USD ($) $ in Thousands	1 Months Ended	3 Months Ended		9 Months Ended
	Nov. 30, 2013	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015	Dec. 31, 2015
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Research and development expenses		$ 60,854	$ 11,503	$ 206,887	$ 129,537
Estimated fair value of total success payment obligation		59,900		59,900		$ 116,200
Success payment liabilities		34,502		34,502		64,829
Success payment (expense) gain				(20,800)	17,300
Collaborative Arrangement [Member] | Memorial Sloan Kettering Cancer Center [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Research and development expenses		900	1,000	1,700	3,800
Estimated fair value of total success payment obligation		22,700		22,700		48,900
Success payment liabilities		14,000		14,000		$ 31,000
Success payment (expense) gain		$ (7,200)	$ (10,300)	$ (7,500)	$ 2,700
Collaboration agreement, term	5 years

Collaboration and License Agr36

Collaboration and License Agreements - St. Jude Children's Research Hospital/ Novartis - Additional Information (Detail) - USD ($) $ in Millions	1 Months Ended
	Jun. 30, 2016	Jan. 31, 2016	Sep. 30, 2016
St. Jude Children's Research Hospital [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Milestone payment paid		$ 5	$ 7.5
License Agreement [Member] | Novartis [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Milestone payment received	$ 8.5	$ 5.8

Collaboration and License Agr37

Collaboration and License Agreements - Seattle Children's Research Institute - Additional Information (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Research and development expenses	$ 60,854	$ 11,503	$ 206,887	$ 129,537
Collaborative Arrangement [Member] | Seattle Children's Research Institute [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Research and development expenses	$ 1,100	$ 1,100	$ 3,500	$ 1,400

Collaboration and License Agr38

Collaboration and License Agreements - Opus Bio - Additional Information (Detail)	3 Months Ended			9 Months Ended
	Sep. 30, 2016USD ($)	Mar. 31, 2016USD ($)milestoneshares	Sep. 30, 2015USD ($)	Sep. 30, 2016USD ($)	Sep. 30, 2015USD ($)
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Number of milestones achieved | milestone		2
Milestone payments paid, shares | shares		603,364
Research and development expense related to milestone payment	$ 60,854,000		$ 11,503,000	$ 206,887,000	$ 129,537,000
Milestone payments, payable in cash				215,000,000
Opus Bio [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Research and development expense related to milestone payment		$ 23,200,000
Opus Bio [Member] | License Agreement [Member] | Minimum [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Milestone payments, payable in equity				$ 25,000,000

Collaboration and License Agr39

Collaboration and License Agreements - Fate Therapeutics - Additional Information (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Research and development expense	$ 60,854	$ 11,503	$ 206,887	$ 129,537
Collaboration and License Agreement [Member] | Fate Therapeutics [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Research and development expense	$ 500		$ 1,500	$ 800

Collaboration and License Agr40

Collaboration and License Agreements - Editas Medicine - Additional Information (Detail) - USD ($)	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Research and development expense	$ 60,854,000	$ 11,503,000	$ 206,887,000	$ 129,537,000
Collaboration and License Agreement [Member] | Editas Medicine ("Editas") [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Research and development expense	$ 900,000	$ 800,000	$ 2,900,000	$ 1,000,000

Cash Equivalents and Marketab41

Cash Equivalents and Marketable Securities - Summary of Estimated Fair Value of Cash Equivalents and Marketable Securities (Detail) - USD ($) $ in Thousands	Sep. 30, 2016	Dec. 31, 2015
Cash Equivalents [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	$ 215,490	$ 229,556
Estimated Fair Value	215,490	229,556
Cash Equivalents [Member] | Corporate Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	5,000	5,040
Estimated Fair Value	5,000	5,040
Marketable Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	597,048	691,740
Gross Unrealized Holding Gains	247	3
Gross Unrealized Holding Losses	(59)	(730)
Estimated Fair Value	597,236	691,013
Marketable Securities [Member] | Corporate Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	124,384	148,143
Gross Unrealized Holding Gains	7	1
Gross Unrealized Holding Losses	(47)	(245)
Estimated Fair Value	124,344	147,899
Long Term Marketable Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	214,952	277,639
Gross Unrealized Holding Gains	36	34
Gross Unrealized Holding Losses	(108)	(4,785)
Estimated Fair Value	214,880	272,888
Long Term Marketable Securities [Member] | Corporate Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	86,415	65,898
Gross Unrealized Holding Gains	16	33
Gross Unrealized Holding Losses	(72)	(195)
Estimated Fair Value	86,359	65,736
Long Term Marketable Securities [Member] | Equity Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	1,700	7,190
Gross Unrealized Holding Losses		(3,820)
Estimated Fair Value	1,700	3,370
Money Market Funds [Member] | Cash Equivalents [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	188,740	177,164
Estimated Fair Value	188,740	177,164
Commercial Paper [Member] | Cash Equivalents [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	21,750	45,352
Estimated Fair Value	21,750	45,352
Commercial Paper [Member] | Marketable Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	98,050	73,078
Estimated Fair Value	98,050	73,078
U.S. Government and Agency Securities [Member] | Cash Equivalents [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost		2,000
Estimated Fair Value		2,000
U.S. Government and Agency Securities [Member] | Marketable Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	374,614	470,519
Gross Unrealized Holding Gains	240	2
Gross Unrealized Holding Losses	(12)	(485)
Estimated Fair Value	374,842	470,036
U.S. Government and Agency Securities [Member] | Long Term Marketable Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	126,837	204,551
Gross Unrealized Holding Gains	20	1
Gross Unrealized Holding Losses	(36)	(770)
Estimated Fair Value	$ 126,821	$ 203,782

Cash Equivalents and Marketab42

Cash Equivalents and Marketable Securities - Summary of Gross Unrealized Holding Losses and Fair Value for Investments in Unrealized Loss Position (Detail) - USD ($) $ in Thousands	Sep. 30, 2016	Dec. 31, 2015
Marketable Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Marketable securities, Fair Value, Less than 12 Months	$ 157,417	$ 602,140
Marketable securities, Unrealized Losses, Less than 12 Months	(59)	(730)
Marketable securities, Fair Value, 12 Months or Greater	0	0
Marketable securities, Unrealized Losses, 12 Months or Greater	0	0
Marketable securities, Fair Value, Total	157,417	602,140
Marketable securities, Unrealized Losses, Total	(59)	(730)
Marketable Securities [Member] | Corporate Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Marketable securities, Fair Value, Less than 12 Months	82,122	144,499
Marketable securities, Unrealized Losses, Less than 12 Months	(47)	(245)
Marketable securities, Fair Value, 12 Months or Greater	0	0
Marketable securities, Unrealized Losses, 12 Months or Greater	0	0
Marketable securities, Fair Value, Total	82,122	144,499
Marketable securities, Unrealized Losses, Total	(47)	(245)
Marketable Securities [Member] | U.S. Government and Agency Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Marketable securities, Fair Value, Less than 12 Months	75,295	457,641
Marketable securities, Unrealized Losses, Less than 12 Months	(12)	(485)
Marketable securities, Fair Value, 12 Months or Greater	0	0
Marketable securities, Unrealized Losses, 12 Months or Greater	0	0
Marketable securities, Fair Value, Total	75,295	457,641
Marketable securities, Unrealized Losses, Total	(12)	(485)
Long Term Marketable Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Marketable securities, Fair Value, Less than 12 Months	121,594	244,728
Marketable securities, Unrealized Losses, Less than 12 Months	(108)	(4,785)
Marketable securities, Fair Value, 12 Months or Greater	0	0
Marketable securities, Unrealized Losses, 12 Months or Greater	0	0
Marketable securities, Fair Value, Total	121,594	244,728
Marketable securities, Unrealized Losses, Total	(108)	(4,785)
Long Term Marketable Securities [Member] | Corporate Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Marketable securities, Fair Value, Less than 12 Months	52,656	50,591
Marketable securities, Unrealized Losses, Less than 12 Months	(72)	(195)
Marketable securities, Fair Value, 12 Months or Greater	0	0
Marketable securities, Unrealized Losses, 12 Months or Greater	0	0
Marketable securities, Fair Value, Total	52,656	50,591
Marketable securities, Unrealized Losses, Total	(72)	(195)
Long Term Marketable Securities [Member] | Equity Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Marketable securities, Fair Value, Less than 12 Months		3,370
Marketable securities, Unrealized Losses, Less than 12 Months		(3,820)
Marketable securities, Fair Value, 12 Months or Greater		0
Marketable securities, Unrealized Losses, 12 Months or Greater		0
Marketable securities, Fair Value, Total		3,370
Marketable securities, Unrealized Losses, Total		(3,820)
Long Term Marketable Securities [Member] | U.S. Government and Agency Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Marketable securities, Fair Value, Less than 12 Months	68,938	190,767
Marketable securities, Unrealized Losses, Less than 12 Months	(36)	(770)
Marketable securities, Fair Value, 12 Months or Greater	0	0
Marketable securities, Unrealized Losses, 12 Months or Greater	0	0
Marketable securities, Fair Value, Total	68,938	190,767
Marketable securities, Unrealized Losses, Total	$ (36)	$ (770)

Cash Equivalents and Marketab43

Cash Equivalents and Marketable Securities - Additional Information (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Schedule of Available-for-sale Securities [Line Items]
Other-than-temporary impairment loss	$ 0	$ 0	$ 5,490	$ 0
Fate Therapeutics [Member]
Schedule of Available-for-sale Securities [Line Items]
Other-than-temporary impairment loss	$ 0		$ 5,500

Fair Value Measurements - Sched

Fair Value Measurements - Schedule of Fair Value of Financial Assets and Liabilities Measured on Recurring Basis (Detail) - USD ($) $ in Thousands	Sep. 30, 2016	Dec. 31, 2015
Financial Assets:
Total financial assets	$ 1,027,606	$ 1,193,457
Success payment liabilities	34,502	64,829
Financial Liabilities:
Total financial liabilities	66,593	102,095
Money Market Funds [Member]
Financial Assets:
Total financial assets	188,740	177,164
Commercial Paper [Member]
Financial Assets:
Total financial assets	119,800	118,430
U.S. Government and Agency Securities [Member]
Financial Assets:
Total financial assets	501,663	675,818
Corporate Debt Securities [Member]
Financial Assets:
Total financial assets	215,703	218,675
Equity Securities [Member]
Financial Assets:
Total financial assets	1,700	3,370
Success Payment Liabilities [Member]
Financial Liabilities:
Total financial liabilities	34,502	64,829
Contingent Consideration [Member]
Financial Liabilities:
Total financial liabilities	32,091	37,266
Level 1 [Member]
Financial Assets:
Total financial assets	190,440	180,534
Financial Liabilities:
Total financial liabilities	0	0
Level 1 [Member] | Money Market Funds [Member]
Financial Assets:
Total financial assets	188,740	177,164
Level 1 [Member] | Commercial Paper [Member]
Financial Assets:
Total financial assets	0	0
Level 1 [Member] | U.S. Government and Agency Securities [Member]
Financial Assets:
Total financial assets	0	0
Level 1 [Member] | Corporate Debt Securities [Member]
Financial Assets:
Total financial assets	0	0
Level 1 [Member] | Equity Securities [Member]
Financial Assets:
Total financial assets	1,700	3,370
Level 1 [Member] | Success Payment Liabilities [Member]
Financial Liabilities:
Total financial liabilities	0	0
Level 1 [Member] | Contingent Consideration [Member]
Financial Liabilities:
Total financial liabilities	0	0
Level 2 [Member]
Financial Assets:
Total financial assets	837,166	1,012,923
Financial Liabilities:
Total financial liabilities	0	0
Level 2 [Member] | Money Market Funds [Member]
Financial Assets:
Total financial assets	0	0
Level 2 [Member] | Commercial Paper [Member]
Financial Assets:
Total financial assets	119,800	118,430
Level 2 [Member] | U.S. Government and Agency Securities [Member]
Financial Assets:
Total financial assets	501,663	675,818
Level 2 [Member] | Corporate Debt Securities [Member]
Financial Assets:
Total financial assets	215,703	218,675
Level 2 [Member] | Equity Securities [Member]
Financial Assets:
Total financial assets	0	0
Level 2 [Member] | Success Payment Liabilities [Member]
Financial Liabilities:
Total financial liabilities	0	0
Level 2 [Member] | Contingent Consideration [Member]
Financial Liabilities:
Total financial liabilities	0	0
Level 3 [Member]
Financial Assets:
Total financial assets	0	0
Financial Liabilities:
Total financial liabilities	66,593	102,095
Level 3 [Member] | Money Market Funds [Member]
Financial Assets:
Total financial assets	0	0
Level 3 [Member] | Commercial Paper [Member]
Financial Assets:
Total financial assets	0	0
Level 3 [Member] | U.S. Government and Agency Securities [Member]
Financial Assets:
Total financial assets	0	0
Level 3 [Member] | Corporate Debt Securities [Member]
Financial Assets:
Total financial assets	0	0
Level 3 [Member] | Equity Securities [Member]
Financial Assets:
Total financial assets	0	0
Level 3 [Member] | Success Payment Liabilities [Member]
Financial Assets:
Success payment liabilities	34,502
Financial Liabilities:
Total financial liabilities		64,829
Level 3 [Member] | Contingent Consideration [Member]
Financial Liabilities:
Total financial liabilities	$ 32,091	$ 37,266

Fair Value Measurements - Summa

Fair Value Measurements - Summary of Changes in Fair Value of Level 3 Financial Liabilities (Detail) - Level 3 [Member] $ in Thousands	9 Months Ended
	Sep. 30, 2016USD ($)
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Beginning balance	$ 102,095
Payments	(9,569)
Changes in fair value	(25,933)
Ending balance	66,593
Success Payment Liabilities [Member]
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Beginning balance	64,829
Payments	(9,569)
Changes in fair value	(20,758)
Ending balance	34,502
Contingent Consideration [Member]
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Beginning balance	37,266
Changes in fair value	(5,175)
Ending balance	$ 32,091

Fair Value Measurements - Addit

Fair Value Measurements - Additional Information (Detail) € in Thousands, $ in Thousands	9 Months Ended
	Sep. 30, 2016USD ($)	Sep. 30, 2015USD ($)	Sep. 30, 2016EUR (€)	Sep. 30, 2016USD ($)	Dec. 31, 2015USD ($)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of success payment obligations				$ 59,900	$ 116,200
Success payment (expense) gain	$ (20,800)	$ 17,300
Estimated discount percentage rate of contingent consideration	16.00%
(Gain) expense recognized in change in fair value of the contingent consideration	$ (5,175)	1,203
Stage Cell Therapeutics GmbH [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Contingent consideration, less current portion				26,200
Contingent consideration | €			€ 6,000
X-Body [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Contingent consideration, less current portion				$ 5,900
X-Body [Member] | Research and Development Expense [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
(Gain) expense recognized in change in fair value of the contingent consideration	$ (5,200)	$ 1,300
Minimum [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Measurement of contingent consideration fair value, period in which milestones are expected to achieve	2,016
Maximum [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Measurement of contingent consideration fair value, period in which milestones are expected to achieve	2,043

Stock-Based Compensation - Summ

Stock-Based Compensation - Summary of Stock-Based Compensation Expense (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Total stock-based compensation expense	$ 14,187	$ 9,064	$ 44,972	$ 21,539
Research and Development [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Total stock-based compensation expense	8,751	4,406	29,109	12,089
General and Administrative [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Total stock-based compensation expense	$ 5,436	$ 4,658	$ 15,863	$ 9,450

Stock-Based Compensation - Su48

Stock-Based Compensation - Summary of Stock-Based Compensation Expense (non-printing) (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Stock-based compensation expense recognized	$ 14,187	$ 9,064	$ 44,972	$ 21,539
Service Providers [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Stock-based compensation expense recognized	1,400	1,800	5,700	6,700
Former Co Founding Director [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Stock-based compensation expense recognized	900	1,200	3,300	4,800
Research and Development Expense [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Stock-based compensation expense recognized	$ 8,751	$ 4,406	29,109	$ 12,089
AbVitro Inc [Member] | Research and Development Expense [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Stock-based compensation expense recognized			$ 2,200

Stock-Based Compensation - Tota

Stock-Based Compensation - Total Stock-Based Compensation Cost Related to Unvested Awards Not Yet Recognized and Weighted Average Periods (Detail) $ in Thousands	9 Months Ended
	Sep. 30, 2016USD ($)
Options to Purchase Common Stock [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unrecognized stock-based compensation cost	$ 115,415
Expected weighted average period compensation costs to be recognized (usd per share)	2 years 9 months 29 days
Restricted Stock and RSUs [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unrecognized stock-based compensation cost	$ 17,467
Expected weighted average period compensation costs to be recognized (usd per share)	1 year 10 months 28 days

Stock-Based Compensation - Su50

Stock-Based Compensation - Summary of Restricted Stock and RSU Activity (Detail) - Restricted Stock and RSUs [Member]	9 Months Ended
	Sep. 30, 2016$ / sharesshares
Restricted Stock and RSUs
Unvested shares, Beginning balance | shares	5,476,600
Granted, Shares | shares	183,410
Vested, Shares | shares	(2,032,958)
Forfeited, Shares | shares	(46,567)
Unvested shares, Ending balance | shares	3,580,485
Weighted Average Fair Value at Date of Grant per Share
Unvested shares as of December 31, 2015 (usd per share) | $ / shares	$ 3.72
Granted (usd per share) | $ / shares	35.26
Vested (usd per share) | $ / shares	2.73
Forfeited (usd per share) | $ / shares	6.31
Unvested shares as of September 30, 2016 (usd per share) | $ / shares	$ 5.86

Stock-Based Compensation - Su51

Stock-Based Compensation - Summary of Stock Option Activity (Detail) - USD ($) $ / shares in Units, $ in Thousands	9 Months Ended	12 Months Ended
	Sep. 30, 2016	Dec. 31, 2015
Stock Options
Outstanding as of December 31, 2015 (shares)	5,218,939
Granted (shares)	3,388,256
Exercised (shares)	(396,869)
Forfeited/Cancelled (shares)	(203,320)
Outstanding as of September 30, 2016 (shares)	8,007,006	5,218,939
Number of Stock Options, Exercisable	1,737,758
Weighted Average Exercise Price per Share
Outstanding as of December 31, 2015 (usd per share)	$ 30.25
Granted (usd per share)	29.70
Exercised (usd per share)	7.09
Forfeited/Cancelled (usd per share)	39.01
Outstanding as of September 30, 2016 (usd per share)	30.78	$ 30.25
Weighted Average Exercise Price per Share, Exercisable (usd per share)	$ 28.58
Weighted Average Remaining Contractual Life (in years), Outstanding	8 years 9 months 26 days	9 years 1 month 17 days
Weighted Average Remaining Contractual Life (in years), Exercisable	8 years 3 months 11 days
Aggregate Intrinsic Value, Outstanding	$ 54,711	$ 86,609
Aggregate Intrinsic Value, Exercisable	$ 17,633

Stock-Based Compensation - Su52

Stock-Based Compensation - Summary of Material Factors Incorporated in Black-Scholes Model in Estimating Fair Value of Options Granted to Employees and Consultants (Detail)	9 Months Ended
	Sep. 30, 2016
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Risk free interest rate, minimum	1.13%
Risk free interest rate, maximum	1.78%
Expected volatility	70.00%
Expected dividend yield	0.00%
Minimum [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected life	5 years 3 months 7 days
Maximum [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected life	9 years 11 months 19 days

Stock-Based Compensation - Addi

Stock-Based Compensation - Additional Information (Detail) - Memorial Sloan Kettering Cancer Center [Member]	1 Months Ended
	Apr. 30, 2016$ / sharesshares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Repurchase of common stock (shares) | shares	240,381
Share repurchase price per share (usd per share) | $ / shares	$ 41.9

Comprehensive Income (Loss) - C

Comprehensive Income (Loss) - Components of Accumulated Other Comprehensive Income (Loss) and Adjustments to Other Comprehensive Income (Loss) (Detail) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Opening balance	$ 1,141,533
Other comprehensive income	5,644
Ending balance	1,116,937
Accumulated Other Comprehensive Income (Loss) [Member]
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Opening balance	(6,083)
Ending balance	(439)
Foreign Currency Translation Adjustments [Member]
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Opening balance	(605)
Other comprehensive income		$ 673
Ending balance	68
Net Unrealized Gains (Losses) on Available-For-Sale Investments [Member]
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Opening balance	(5,478)
Other comprehensive income	4,971
Ending balance	$ (507)

Comprehensive Income (Loss) - S

Comprehensive Income (Loss) - Summary of Components of Other Comprehensive Income (Loss) (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Parent [Abstract]
Foreign currency translation adjustments	$ 263	$ 357	$ 673	$ 232
Unrealized gain (loss) on marketable securities	(239)	(906)	(519)	(1,540)
Reclassification adjustment for loss included in net loss	0	0	5,490	0
Total other comprehensive income (loss)	$ 24	$ (549)	$ 5,644	$ (1,308)

Comprehensive Income (Loss) -56

Comprehensive Income (Loss) - Summary of Components of Other Comprehensive Income (Loss) (Non-printing) (Detail) - USD ($)	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Parent [Abstract]
Unrealized gain (loss) on marketable securities, tax	$ (100,000)	$ 0	$ 600,000	$ 0
Income tax effect on this reclassification adjustment	$ 0		$ 0

Income Taxes - Additional Infor

Income Taxes - Additional Information (Detail) - USD ($)	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015	Dec. 31, 2015
Income Tax Disclosure [Line Items]
Income tax benefit	$ (594,000)	$ 63,000	$ (9,131,000)	$ (1,553,000)
Pre-tax loss	57,491,000	$ 23,177,000	201,933,000	155,716,000
Deferred tax benefit recorded in connection with acquisition			(6,655,000)	(1,100,000)
Income tax benefit intraperiod allocation of taxes			(400,000)
Unrecognized tax benefits	$ 0		0		$ 0
AbVitro Inc [Member]
Income Tax Disclosure [Line Items]
Deferred tax benefit recorded in connection with acquisition			(6,655,000)
Juno GmbH [Member]
Income Tax Disclosure [Line Items]
Income tax benefit			$ (2,000,000)	(458,000)
X-Body [Member]
Income Tax Disclosure [Line Items]
Deferred tax benefit recorded in connection with acquisition				$ (1,100,000)

Net Loss Per Share - Schedule o

Net Loss Per Share - Schedule of Diluted Net Loss Per Share Due to Anti-Dilutive Effect (Detail) - shares	9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Anti-dilutive securities excluded from the calculation of diluted net loss per share (in shares)	11,587,491	12,659,783
Unvested restricted stock and RSUs [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Anti-dilutive securities excluded from the calculation of diluted net loss per share (in shares)	3,580,485	5,988,252
Options to Purchase Common Stock [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Anti-dilutive securities excluded from the calculation of diluted net loss per share (in shares)	8,007,006	4,582,566
Estimated Number of Shares Issued for Success Payments [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Anti-dilutive securities excluded from the calculation of diluted net loss per share (in shares)	0	2,088,965

Net Loss Per Share - Schedule59

Net Loss Per Share - Schedule of Diluted Net Loss Per Share Due to Anti-Dilutive Effect (Narrative) (Detail) - USD ($) $ / shares in Units, $ in Millions	Sep. 30, 2016	Dec. 31, 2015	Sep. 30, 2015
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Success payment	$ 59.9	$ 116.2
Fred Hutchinson Cancer Research Center [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Common stock closing price per share (in usd per share)	$ 30.01	$ 43.97
Memorial Sloan Kettering Cancer Center [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Common stock closing price per share (in usd per share)	$ 30.01	$ 43.97
Estimated Number of Shares Issued for Success Payments [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Common stock closing price per share (in usd per share)			$ 40.69
Success payment			$ 85
Estimated Number of Shares Issued for Success Payments [Member] | Fred Hutchinson Cancer Research Center [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Success payment			75
Estimated Number of Shares Issued for Success Payments [Member] | Memorial Sloan Kettering Cancer Center [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Success payment			$ 10

Commitments and Contingencies -

Commitments and Contingencies - Summary of Company's Future Minimum Lease Commitments (Detail) $ in Thousands	Sep. 30, 2016USD ($)
Commitments and Contingencies Disclosure [Abstract]
2,016	$ 1,641
2,017	4,973
2,018	9,789
2,019	12,167
2,020	12,225
Thereafter	47,382
Total minimum lease payments	$ 88,177

Commitments and Contingencies61

Commitments and Contingencies - Additional Information (Detail) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Commitments and Contingencies Disclosure [Abstract]
Rent expense	$ 0.9	$ 0.6	$ 3.3	$ 1.5

Related-Party Transactions - Ad

Related-Party Transactions - Additional Information (Detail)	Sep. 30, 2016
Celgene [Member]
Related Party Transaction [Line Items]
Common stock holding percentage, more than (in percentage)	5.00%