Jounce Therapeutics (JNCE) 10-Q 7 Aug 19 2019 Q2 Quarterly report Financial data

Document and Entity Information

Document and Entity Information - shares	6 Months Ended
	Jun. 30, 2019	Aug. 02, 2019
Document and Entity Information [Abstract]
Entity Registrant Name	JOUNCE THERAPEUTICS, INC.
Entity Central Index Key	0001640455
Current Fiscal Year End Date	--12-31
Entity Filer Category	Accelerated Filer
Entity Emerging Growth Company	true
Entity Ex Transition Period	true
Entity Small Business	true
Document Type	10-Q
Document Period End Date	Jun. 30, 2019
Document Fiscal Year Focus	2019
Document Fiscal Period Focus	Q2
Amendment Flag	false
Entity Common Stock, Shares Outstanding		32,981,637
Entity Shell Company	false
Entity Current Reporting Status	Yes

Condensed Consolidated Balance

Condensed Consolidated Balance Sheets (Unaudited) - USD ($)	Jun. 30, 2019	Dec. 31, 2018
Current assets:
Cash and cash equivalents	$ 37,994,000	$ 47,906,000
Short-term investments	114,026,000	141,968,000
Prepaid expenses and other current assets	5,328,000	2,335,000
Total current assets	157,348,000	192,209,000
Property and equipment, net	12,148,000	13,540,000
Long-term investments	0	5,990,000
Operating lease right-of-use asset	18,911,000
Other non-current assets	2,197,000	2,713,000
Total assets	190,604,000	214,452,000
Current liabilities:
Accounts payable	2,596,000	3,272,000
Accrued expenses	7,344,000	6,952,000
Deferred revenue, current—related party	64,879,000	55,157,000
Operating lease liability, current	2,729,000
Other current liabilities	47,000	165,000
Total current liabilities	77,595,000	65,546,000
Deferred revenue, net of current portion—related party	4,566,000	42,715,000
Operating lease liability, net of current portion	18,379,000
Other non-current liabilities	0	2,062,000
Total liabilities	100,540,000	110,323,000
Commitments and contingencies
Stockholders’ equity:
Preferred stock, $0.001 par value: 5,000 shares authorized at June 30, 2019 and December 31, 2018; no shares issued or outstanding at June 30, 2019 or December 31, 2018	0	0
Common stock, $0.001 par value: 160,000 shares authorized at June 30, 2019 and December 31, 2018; 32,981 and 32,948 shares issued at June 30, 2019 and December 31, 2018, respectively; 32,978 and 32,941 shares outstanding at June 30, 2019 and December 31, 2018, respectively	33,000	33,000
Additional paid-in capital	273,248,000	268,081,000
Accumulated other comprehensive income (loss)	135,000	(78,000)
Accumulated deficit	(183,352,000)	(163,907,000)
Total stockholders’ equity	90,064,000	104,129,000
Total liabilities and stockholders’ equity	$ 190,604,000	$ 214,452,000

Condensed Consolidated Balanc_2

Condensed Consolidated Balance Sheets (Unaudited) (Parenthetical) - $ / shares	Jun. 30, 2019	Dec. 31, 2018
Statement of Financial Position [Abstract]
Preferred stock (in dollars per share)	$ 0.001	$ 0.001
Preferred stock shares authorized (in shares)	5,000,000	5,000,000
Preferred stock shares issued (in shares)	0	0
Preferred stock shares outstanding (in shares)	0	0
Common stock (in dollars per share)	$ 0.001	$ 0.001
Common stock shares authorized (in shares)	160,000,000	160,000,000
Common stock shares issued (in shares)	32,981,000	32,948,000
Common stock shares outstanding	32,978,000	32,941,000

Condensed Consolidated Statemen

Condensed Consolidated Statements of Operations and Comprehensive Loss (Unaudited) - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Revenue:
Collaboration revenue—related party	$ 17,446	$ 19,378	$ 28,427	$ 30,573
Operating expenses:
Research and development	18,130	18,495	35,410	36,657
General and administrative	7,323	6,523	14,515	13,325
Total operating expenses	25,453	25,018	49,925	49,982
Operating loss	(8,007)	(5,640)	(21,498)	(19,409)
Other income, net	1,026	966	2,152	1,707
Loss before provision for income taxes	(6,981)	(4,674)	(19,346)	(17,702)
Provision for income taxes	12	0	24	0
Net loss	$ (6,993)	$ (4,674)	$ (19,370)	$ (17,702)
Net loss per share, basic and diluted (in dollars per share)	$ (0.21)	$ (0.14)	$ (0.59)	$ (0.55)
Weighted-average common shares outstanding, basic and diluted (in shares)	32,973	32,497	32,966	32,435
Comprehensive loss:
Net loss	$ (6,993)	$ (4,674)	$ (19,370)	$ (17,702)
Other comprehensive income:
Unrealized gain on available-for-sale securities	84	135	213	193
Comprehensive loss	$ (6,909)	$ (4,539)	$ (19,157)	$ (17,509)

Condensed Consolidated Statem_2

Condensed Consolidated Statements of Stockholders' Equity (Unaudited) - USD ($) shares in Thousands, $ in Thousands	Total	Common Stock	Additional Paid-In Capital	Accumulated Other Comprehensive (Loss) Income	Accumulated Deficit
Beginning balance, common stock (in shares) at Dec. 31, 2017		32,249
Beginning balance at Dec. 31, 2017	$ 167,109	$ 32	$ 257,101	$ (409)	$ (89,615)
Exercises of common stock options (in shares)	198
Exercises of common stock options	$ 784		784
Vesting of restricted common stock (in shares)		4
Vesting of restricted common stock	8		8
Stock-based compensation expense	2,268		2,268
Other comprehensive income	58			58
Net loss	(13,028)				(13,028)
Ending balance (in shares) at Mar. 31, 2018		32,451
Ending balance at Mar. 31, 2018	110,286	$ 32	260,161	(351)	(149,556)
Beginning balance, common stock (in shares) at Dec. 31, 2017		32,249
Beginning balance at Dec. 31, 2017	167,109	$ 32	257,101	(409)	(89,615)
Other comprehensive income	193
Net loss	(17,702)
Ending balance (in shares) at Jun. 30, 2018		32,596
Ending balance at Jun. 30, 2018	108,495	$ 33	262,908	(216)	(154,230)
Beginning balance, common stock (in shares) at Mar. 31, 2018		32,451
Beginning balance at Mar. 31, 2018	$ 110,286	$ 32	260,161	(351)	(149,556)
Exercises of common stock options (in shares)	143
Exercises of common stock options	$ 381	$ 1	380
Vesting of restricted common stock (in shares)		2
Vesting of restricted common stock	7		7
Stock-based compensation expense	2,360		2,360
Other comprehensive income	135			135
Net loss	(4,674)				(4,674)
Ending balance (in shares) at Jun. 30, 2018		32,596
Ending balance at Jun. 30, 2018	$ 108,495	$ 33	262,908	(216)	(154,230)
Beginning balance, common stock (in shares) at Dec. 31, 2018	32,941	32,941
Beginning balance at Dec. 31, 2018	$ 104,129	$ 33	268,081	(78)	(163,907)
Exercises of common stock options (in shares)	24
Exercises of common stock options	$ 69		69
Vesting of restricted common stock (in shares)		2
Vesting of restricted common stock	7		7
Stock-based compensation expense	2,542		2,542
Other comprehensive income	129			129
Net loss	(12,377)				(12,377)
Ending balance (in shares) at Mar. 31, 2019		32,967
Ending balance at Mar. 31, 2019	$ 94,424	$ 33	270,699	51	(176,359)
Beginning balance, common stock (in shares) at Dec. 31, 2018	32,941	32,941
Beginning balance at Dec. 31, 2018	$ 104,129	$ 33	268,081	(78)	(163,907)
Exercises of common stock options (in shares)	33
Other comprehensive income	$ 213
Net loss	$ (19,370)
Ending balance (in shares) at Jun. 30, 2019	32,978	32,978
Ending balance at Jun. 30, 2019	$ 90,064	$ 33	273,248	135	(183,352)
Beginning balance, common stock (in shares) at Mar. 31, 2019		32,967
Beginning balance at Mar. 31, 2019	$ 94,424	$ 33	270,699	51	(176,359)
Exercises of common stock options (in shares)	9
Exercises of common stock options	$ 29		29
Vesting of restricted common stock (in shares)		2
Vesting of restricted common stock	7		7
Stock-based compensation expense	2,513		2,513
Other comprehensive income	84			84
Net loss	$ (6,993)				(6,993)
Ending balance (in shares) at Jun. 30, 2019	32,978	32,978
Ending balance at Jun. 30, 2019	$ 90,064	$ 33	$ 273,248	$ 135	$ (183,352)

Condensed Consolidated Statem_3

Condensed Consolidated Statements of Cash Flows (Unaudited) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018
Operating activities:
Net loss	$ (19,370)	$ (17,702)
Adjustments to reconcile net loss to net cash used in operating activities:
Stock-based compensation expense	5,055	4,628
Depreciation expense	1,923	1,908
Net amortization of premiums and discounts on investments	(883)	(138)
Changes in operating assets and liabilities:
Taxes receivable	0	16,737
Prepaid expenses and other current assets	(1,849)	589
Other non-current assets	(628)	31
Accounts payable	(645)	201
Accrued expenses and other current liabilities	335	(1,421)
Deferred revenue—related party	(28,427)	(30,573)
Other liabilities	13	63
Net cash used in operating activities	(44,476)	(25,677)
Investing activities:
Purchases of investments	(89,480)	(127,889)
Proceeds from maturities of investments	124,508	175,913
Proceeds from sales of investments	0	3,997
Purchases of property and equipment	(562)	(959)
Net cash provided by investing activities	34,466	51,062
Financing activities:
Proceeds from exercise of stock options	98	1,165
Net cash provided by financing activities	98	1,165
Net (decrease) increase in cash, cash equivalents and restricted cash	(9,912)	26,550
Cash, cash equivalents and restricted cash, beginning of period	49,176	24,829
Cash, cash equivalents and restricted cash, end of period	39,264	51,379
Non-cash investing and financing activities:
Purchases of property and equipment in accounts payable and accrued expenses	0	110
Supplemental cash flow information:
Cash paid for lease liabilities	2,130	0
Cash paid for income taxes	$ 101	$ 0

Nature of Business

Nature of Business	6 Months Ended
	Jun. 30, 2019
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Nature of Business	Nature of Business Jounce Therapeutics, Inc. (the “Company”) is a clinical-stage immunotherapy company dedicated to transforming the treatment of cancer by developing therapies that enable the immune system to attack tumors and provide long-lasting benefits to patients. The Company is subject to a number of risks similar to those of other clinical-stage immunotherapy companies, including dependence on key individuals; the need to develop commercially viable products; competition from other companies, many of which are larger and better capitalized; and the need to obtain adequate additional financing to fund the development of its products. As of June 30, 2019 , the Company had cash, cash equivalents and investments of $152.0 million . The Company expects that its existing cash, cash equivalents and investments will enable it to fund its expected operating expenses and capital expenditure requirements for at least 12 months from August 7, 2019 , the filing date of this Quarterly Report on Form 10-Q. The Company expects to finance its future cash needs through a combination of equity or debt financings, collaborations, licensing arrangements and strategic alliances.

Basis of Presentation and Summa

Basis of Presentation and Summary of Significant Accounting Policies	6 Months Ended
	Jun. 30, 2019
Accounting Policies [Abstract]
Basis of Presentation and Summary of Significant Accounting Policies	Basis of Presentation and Summary of Significant Accounting Policies Basis of Presentation and Consolidation The accompanying condensed consolidated financial statements as of June 30, 2019 and December 31, 2018 , and for the three and six months ended June 30, 2019 and 2018 , have been prepared in accordance with the rules and regulations of the Securities and Exchange Commission (the “SEC”) and generally accepted accounting principles in the United States of America (“GAAP”) as found in the Accounting Standards Codification (“ASC”) of the Financial Accounting Standards Board (“FASB”) for condensed consolidated financial information. Accordingly, they do not include all of the information and footnotes required by GAAP for complete financial statements. In the opinion of management, these condensed consolidated financial statements reflect all normal recurring adjustments which are necessary for a fair presentation of the Company’s financial position and results of its operations, as of and for the periods presented. These condensed consolidated financial statements should be read in conjunction with the consolidated financial statements and notes thereto contained in the Company’s Annual Report on Form 10-K for the year ended December 31, 2018 filed with the SEC on March 6, 2019 (the “Annual Report on Form 10-K”). The information presented in the condensed consolidated financial statements and related notes as of June 30, 2019 , and for the three and six months ended June 30, 2019 and 2018 , is unaudited. The December 31, 2018 condensed consolidated balance sheet included herein was derived from the audited financial statements as of that date, but does not include all disclosures, including notes, required by GAAP for complete financial statements. Interim results for the six months ended June 30, 2019 are not necessarily indicative of the results that may be expected for the fiscal year ending December 31, 2019 , or any future period. The accompanying condensed consolidated financial statements include the accounts of Jounce Therapeutics, Inc. and its wholly-owned subsidiary, Jounce Mass Securities, Inc. All intercompany transactions and balances have been eliminated in consolidation. Summary of Significant Accounting Policies The significant accounting policies and estimates used in the preparation of the condensed consolidated financial statements are described in the Company’s audited financial statements as of and for the year ended December 31, 2018 , and the notes thereto, which are included in the Annual Report on Form 10-K. There have been no material changes in the Company’s significant accounting policies during the six months ended June 30, 2019 , except as discussed below with respect to the adoption of ASC Topic 842, Leases (“ASC 842”). Use of Estimates The preparation of financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the amounts reported in the financial statements and accompanying notes. On an ongoing basis, the Company’s management evaluates its estimates which include, but are not limited to, estimates related to revenue recognized under the Master Research and Collaboration Agreement (the “Celgene Collaboration Agreement”) with Celgene Corporation (“Celgene”) (including estimates of internal and external costs expected to be incurred to satisfy performance obligations), the determination of the discount rate utilized in the initial application of ASC 842, accrued expenses, stock-based compensation expense and income taxes. The Company bases its estimates on historical experience and other market specific or other relevant assumptions it believes to be reasonable under the circumstances. Actual results could differ from those estimates. Recent Accounting Pronouncements In February 2016, the FASB issued Accounting Standards Update (“ASU”) 2016-02, Leases (Topic 842) , which requires a lessee to recognize assets and liabilities on the balance sheet for operating leases and changes many key definitions, including the definition of a lease. The new standard includes a short-term lease exception for leases with a term of 12 months or less, as part of which a lessee can make an accounting policy election not to recognize lease assets and lease liabilities. Lessees will continue to differentiate between finance leases (previously referred to as capital leases) and operating leases using classification criteria that are substantially similar to the previous guidance. In July 2018, the FASB also issued ASU 2018-11, Leases (Topic 842): Targeted Improvements , which permits entities to continue applying legacy guidance in ASC Topic 840, Leases (“ASC 840”), including its disclosure requirements, in the comparative periods presented in the year that the entity adopts the new leasing standard. Under this transition method, the cumulative effect of initially applying ASC 842 is recognized as an adjustment to the opening balance of retained earnings or accumulated deficit at the beginning of the annual reporting period that includes the date of initial application. The new standard became effective for annual reporting periods beginning after December 15, 2018, including interim periods within those annual reporting periods. Accordingly, the Company adopted ASC 842 on January 1, 2019 using the transition method permitted by ASU 2018-11. In adopting ASC 842, the Company elected to utilize a package of practical expedients under which an entity need not reassess whether any expired or existing contracts are or contain leases, the lease classification for any expired or existing leases or initial direct costs for any existing leases. The Company also elected a practical expedient whereby an entity can utilize hindsight in determining the lease term, including options to extend or terminate the lease. Finally, the Company elected a practical expedient related to not separating lease and nonlease components. In addition, as discussed above, an entity may elect an accounting policy whereby it does not apply the recognition requirements of ASC 842 to short-term leases with a term of 12 months or less. Under this accounting policy, an entity does not recognize a right-of-use asset or lease liability on its balance sheet and instead recognizes lease payments as an expense on a straight-line basis over the lease term. The Company has elected this short-term lease accounting policy. Upon the adoption of ASC 842, the Company removed its legacy deferred rent balances that were previously recorded under ASC 840 and established an operating lease right-of-use asset of $20.2 million , an operating lease liability, current of $2.6 million and an operating lease liability, net of current portion of $19.8 million , all relating to the Company’s existing operating lease for its current corporate headquarters. The Company also recorded an increase to the opening balance of accumulated deficit of less than $0.1 million as a result of the adoption of ASC 842. The following table presents a summary of the amount by which each financial statement line item was affected by the adoption of ASC 842 (in thousands): January 1, 2019 Prior to the Adoption of ASC 842 Effect of Adoption Subsequent to the Adoption of ASC 842 Operating lease right of use asset $ — $ 20,156 $ 20,156 Operating lease liability, current $ — $ 2,563 $ 2,563 Other current liabilities $ 165 $ (61 ) $ 104 Operating lease liability, net of current portion $ — $ 19,790 $ 19,790 Other non-current liabilities $ 2,062 $ (2,062 ) $ — Accumulated deficit $ (163,907 ) $ (75 ) $ (163,982 ) The adoption of ASC 842 did not have a material impact on the condensed consolidated statement of operations and comprehensive loss or the condensed consolidated statement of cash flows for the three and six months ended June 30, 2019 . The Company subsequently measures its lease liability at the present value of remaining lease payments, discounted using the discount rate for the lease. The right-of-use asset is subsequently measured at the amount of the lease liability, adjusted for prepaid or accrued lease payments and the remaining balance of lease incentives received. The Company recognizes operating lease expense on a straight-line basis over the lease term. See Note 11, “Corporate Headquarters Lease”, for further information on the application of ASC 842 to the Company’s operating lease for its current corporate headquarters. In June 2016, the FASB issued ASU 2016-13, F inancial Instruments—Credit Losses (Topic 326): Measurement of Credit Losses on Financial Instruments . This standard requires that credit losses be reported using an expected losses model rather than the incurred losses model that is currently used, and it establishes additional disclosure requirements related to credit risks. For available-for-sale debt securities with unrealized losses, this standard now requires allowances to be recorded instead of reducing the amortized cost of the investment. This guidance will be effective for annual reporting periods beginning after December 15, 2019, including interim periods within those annual reporting periods, and early adoption is permitted. The Company is currently evaluating the potential impact that ASU 2016-13 may have on the condensed consolidated financial statements. In June 2018, the FASB issued ASU 2018-07, Compensation—Stock Compensation (Topic 718): Improvements to Nonemployee Share-Based Payment Accounting . This guidance is intended to simplify the accounting for share-based payments to nonemployees by aligning it with the accounting for share-based payments to employees, with certain exceptions. This guidance became effective for annual reporting periods beginning after December 15, 2018, including interim periods within those annual reporting periods. Accordingly, the Company adopted ASU 2018-07 effective January 1, 2019, and there was no impact to the condensed consolidated financial statements as a result of the adoption of this guidance. In August 2018, the FASB issued ASU 2018-13, Fair Value Measurement (Topic 820): Disclosure Framework—Changes to the Disclosure Requirements for Fair Value Measurement, which eliminates, adds and modifies certain disclosure requirements for fair value measurements. This guidance will be effective for annual reporting periods beginning after December 15, 2019, including interim periods within those annual reporting periods, and early adoption is permitted. More specifically, an entity is permitted to early adopt any removed or modified disclosure requirements immediately and delay adoption of additional disclosure requirements until the effective date of this guidance. The Company does not anticipate a material impact to the condensed consolidated financial statements as a result of the adoption of this guidance. In November 2018, the FASB issued ASU 2018-18, Collaborative Arrangements (Topic 808): Clarifying the Interaction between Topic 808 and Topic 606 , which clarifies that certain transactions between participants in a collaborative arrangement should be accounted for under ASC Topic 606, Revenue from Contracts with Customers (“ASC 606”) when the counterparty is a customer. In addition, ASU 2018-18 adds unit-of-account guidance to ASC Topic 808, Collaborative Arrangements , in order to align this guidance with ASC 606 and also precludes an entity from presenting consideration from a transaction in a collaborative arrangement as revenue from contracts with customers if the counterparty is not a customer for that transaction. This guidance will be effective for annual reporting periods beginning after December 15, 2019, including interim periods within those annual reporting periods, and early adoption is permitted. The Company is currently evaluating the potential impact that ASU 2018-18 may have on the condensed consolidated financial statements.

Celgene Collaboration Agreement

Celgene Collaboration Agreement	6 Months Ended
	Jun. 30, 2019
Research and Development [Abstract]
Celgene Collaboration Agreement	Celgene Collaboration Agreement In July 2016, the Company entered into the Celgene Collaboration Agreement. The primary goal of the collaboration is to co-develop and co-commercialize innovative biologic immunotherapies that either activate or suppress the immune system by binding to targets identified by leveraging the Company’s Translational Science Platform. Under the Celgene Collaboration Agreement, the Company granted Celgene exclusive options to develop and commercialize the Company’s lead product candidate, vopratelimab, and up to four early-stage programs, consisting of targets to be selected from a pool of certain B cell, T regulatory cell and tumor-associated macrophage targets. Additionally, the Company granted Celgene an exclusive option to develop and commercialize the Company’s product candidate JTX-4014, an anti-PD-1 antibody, which, upon exercise of such option, will be a shared program that may be used by both parties in and outside of the collaboration. The Celgene Collaboration Agreement was subsequently terminated effective July 22, 2019, as outlined further in Note 13, “Subsequent Events”. The Company received a non-refundable upfront cash payment of $225.0 million in July 2016 upon the execution of the Celgene Collaboration Agreement. The Company also received $36.1 million from the sale of 10,448,100 shares of Series B-1 convertible preferred stock upon the execution of a Series B-1 Preferred Stock Purchase Agreement with Celgene, which shares converted into 2,831,463 shares of common stock upon the completion of the Company’s initial public offering (“IPO”). If Celgene elects to exercise any of the program options, Celgene will pay the Company an option-exercise fee of $10.0 million to $60.0 million that varies by program, with an aggregate of $182.5 million if Celgene exercises all six program options. The initial research term of the collaboration is four years, which can be extended, at Celgene’s option, annually for up to three additional years for additional consideration that ranges from $30.0 million to $45.0 million per year, for an aggregate of $120.0 million if the term is extended for an additional three years. Worldwide Development Cost and U.S. Operating Profit and Loss Sharing Prior to Celgene exercising any of its options, the Company is responsible for all research and development activities under the Celgene Collaboration Agreement. Upon the exercise of each program option, the parties will enter into a co-development and co-commercialization agreement (“Co-Co Agreements”) or, in the case of JTX-4014, a license agreement (“JTX-4014 License Agreement”) that governs the development and commercialization of the applicable program. Although the agreements will not be executed unless and until Celgene exercises an option, the parties have agreed to the terms of the Co-Co Agreements and the JTX-4014 License Agreement as part of the Celgene Collaboration Agreement. Under the Co-Co Agreements and the JTX-4014 License Agreement, the Company will share with Celgene the U.S. profits or losses and development costs on such collaboration program as follows: • The Company will retain 60 percent of the U.S. operating profits or losses arising from commercialization of vopratelimab, with 40 percent allocated to Celgene. • The Company will retain 25 percent of the U.S. operating profits or losses arising from commercialization of the first program (the “Lead Program”), other than vopratelimab or JTX-4014, for which an investigational new drug application (“IND”) is filed under the collaboration, with 75 percent allocated to Celgene. Celgene has a one-time right to substitute and swap the economics and governance of this program with that of another program for which it exercises an option (other than vopratelimab and JTX-4014). • The Company and Celgene will equally share U.S. operating profits or losses arising from commercialization of up to three additional programs (other than vopratelimab, JTX-4014 or the Lead Program) (the “Other Programs”). • The Company and Celgene will share all development costs, other than for JTX-4014, in accordance with the applicable Co-Co Agreements, of which Celgene’s portion of the costs range from 67 percent to 85 percent. If Celgene exercises its option for a program other than JTX-4014, the Company will enter into a Co-Co Agreement, pursuant to which Celgene will have the exclusive right to develop and commercialize the products arising out of such collaboration program outside of the United States, and the Company will be eligible to receive tiered royalties ranging from a high single digit to mid-teen percentage rate on net product sales outside of the United States. Under each Co-Co Agreement, the Company will also have the right to opt out of profit sharing and instead receive milestones and royalties. Furthermore, if Celgene exercises its option for JTX-4014, the Company will enter into the JTX-4014 License Agreement, pursuant to which Celgene and the Company will each have equal rights to develop and commercialize JTX-4014 in combination with other proprietary molecules in their or the Company’s respective pipelines or in combination with products arising out of collaboration programs. Subject to terms specified in the license agreement for JTX-4014, the party owning the proprietary molecule that is combined with JTX-4014, if such molecule does not arise from a collaboration program with Celgene, will be solely responsible for all development and commercialization costs related to such combination. If JTX-4014 is combined with a product arising from a collaboration program, then the parties will share costs and, if co-packaged or co-formulated, profits or losses in accordance with the Co-Co Agreements for such other product. Milestones and Royalties Under the Co-Co Agreements and the JTX-4014 License Agreement, Celgene is required to pay the Company for specified development, regulatory and commercial milestones, if achieved, up to approximately $2.3 billion , across all collaboration programs. The development milestones are payable on initiation of certain clinical trials and range from $32.5 million to $105.0 million , per program, with an aggregate total of $290.0 million . The regulatory approval milestones are payable upon regulatory approval in the United States and outside the United States and range from $7.5 million to $50.0 million per milestone, with an aggregate total of $700.0 million . The commercial milestones are payable upon achievement of specified aggregate product sales outside the United States for each program and range from $40.0 million to $200.0 million per milestone, with an aggregate total of $1.270 billion . The Company is also eligible to receive royalties on product sales outside the United States ranging from high single digit to mid-teen royalties. Exercise of Options Celgene may exercise its option for a program at any time until the expiration of an option term for that program. For each program, the option term ends 45 to 60 days following Celgene’s receipt of a data package that includes certain information relating to the program’s research and development activities. The data package for a program may be delivered to Celgene after the applicable development milestone for such program has been achieved. Depending on the program, the applicable development milestone is (i) IND acceptance, (ii) availability of certain Phase 1a data or (iii) availability of certain Phase 1/2 data. If Celgene fails to exercise its option during the option term for a program, the Company will continue to retain all rights to such program. If Celgene exercises its option for a program other than JTX-4014, then the Company will enter into a Co-Co Agreement with Celgene for such program in substantially the form attached to the agreement as an exhibit. Under the Co-Co Agreement for vopratelimab and one additional program for which Celgene opts in, other than JTX-4014, the Company will be responsible for leading development and commercialization activities in the United States and Celgene will be responsible for development and commercialization activities outside the United States. For all other additional programs for which Celgene opts in, other than JTX-4014, Celgene will lead development and commercialization activities worldwide. If Celgene exercises its option for JTX-4014, the Company and Celgene will enter into a license agreement, in substantially the form attached to the agreement as an exhibit, pursuant to which the Company and Celgene will both be able to equally access JTX-4014 for combinations within each other’s portfolios and with other molecules that are subject to the agreement, subject to joint governance. Once Celgene opts in with respect to a given program, Celgene and the Company must each use commercially reasonable efforts to develop and commercialize the corresponding product in the United States. Termination At any point during the Celgene Collaboration Agreement, including during the research, development and clinical trial process, or during the term of the applicable co-development and co-commercialization or license agreement, respectively, Celgene can terminate the applicable agreement with the Company in its entirety, or with respect to any program under the Celgene Collaboration Agreement, upon 120 days’ notice and can terminate the entire agreement with the Company in connection with a material breach of the agreement by the Company that remains uncured for 90 days. Exclusivity During the Celgene Collaboration Agreement’s research term (i.e., for four years plus up to three one -year extensions that Celgene may elect), the Company may not alone, or with a third party, research, develop, manufacture or commercialize a biologic that binds to ICOS or a defined pool of B cell, T regulatory cell or tumor-associated macrophage targets that meet certain criteria, each termed a “Collaboration Exclusive Target”, and inhibit, activate or otherwise modulate the activity of such Collaboration Exclusive Target. In addition, if Celgene exercises its option for a program within the Celgene Collaboration Agreement, other than JTX-4014, then until termination or expiration of the applicable Co-Co Agreement for such program, the Company may not directly or indirectly research, develop, manufacture or commercialize, outside of the Celgene Collaboration Agreement, any biologic with specified activity against that program’s Collaboration Exclusive Target. Accounting Analysis under ASC 606 Identification of the Contract(s) The Company assessed the Celgene Collaboration Agreement and concluded that it represents a contract with a customer within the scope of ASC 606. The Company also concluded that each of the Co-Co Agreements and the JTX-4014 License Agreement, if executed in the future, would represent separate contracts apart from the Celgene Collaboration Agreement. Identification of Promises and Performance Obligations The Company determined that the Celgene Collaboration Agreement contains the following promises: (i) research and development services for the product candidate, vopratelimab (“Vopratelimab Research Services”) (ii) research and development services for the product candidate, JTX-4014 (“JTX-4014 Research Services”) (iii) research and development services associated with the Lead Program and Other Programs (“Lead and Other Programs Research Services”), (iv) research services associated with target screening (“Target Screening Services”), (v) non-transferable, limited sub-licensable and non-exclusive licenses to use the Company’s intellectual property and the Company’s rights in the collaboration intellectual property to conduct certain activities, on a program-by-program basis (the “Research Licenses”), (vi) various record-keeping and reporting requirements on a program-by-program basis, (vii) exclusivity provisions with respect to each Collaboration Exclusive Target and biologics binding to such Collaboration Exclusive Targets and (viii) establishment of and participation in a joint steering committee (the “JSC”) and a joint patent committee (the “JPC”). The Company also evaluated the six program options as well as the research term extension options and concluded that none convey a material right to Celgene. Accordingly, neither the program options nor the research term extension options are considered to be promises within the Celgene Collaboration Agreement. The Company assessed the above promises and concluded that each of the Vopratelimab Research Services, JTX-4014 Research Services, Lead and Other Programs Research Services and Target Screening Services are both capable of being distinct and distinct within the context of the Celgene Collaboration Agreement. Therefore, the Company has concluded that each of the Vopratelimab Research Services, JTX-4014 Research Services, Lead and Other Programs Research Services and Target Screening Services represent separate performance obligations. The Company determined that the Research Licenses are not distinct within the context of the Celgene Collaboration Agreement as the Research Licenses allow Celgene to evaluate the results of the research and development services performed by the Company and the right to perform its duties under the Celgene Collaboration Agreement, but do not provide Celgene with any commercialization rights. Celgene can only benefit from the Research Licenses in conjunction with the related research and development services. Accordingly, the Research Licenses related to vopratelimab, JTX-4014 and the Lead and Other Programs have been combined with their respective research and development services performance obligations. Similarly, the Company also determined that the various record-keeping and reporting requirements related to each program and the exclusivity provisions with respect to each Collaboration Exclusive Target and biologics binding to such Collaboration Exclusive Targets are not distinct within the context of the Celgene Collaboration Agreement. Accordingly, the various record-keeping and reporting requirements on a program-by-program basis and the exclusivity provisions with respect to each Collaboration Exclusive Target and biologics binding to such Collaboration Exclusive Targets have been combined with their respective research and development services performance obligations. Finally, the Company assessed its participation in the JSC and the JPC and concluded that, while it does meet the definition of a performance obligation, it is both quantitatively and qualitatively immaterial in the context of the Celgene Collaboration Agreement. Accordingly, the Company has disregarded its participation in the JSC and the JPC as a performance obligation. Determination of Transaction Price As noted above, the Company received a non-refundable upfront cash payment of $225.0 million upon the execution of the Celgene Collaboration Agreement. This upfront payment represents an element of fixed consideration under the Celgene Collaboration Agreement. Celgene also purchased 10,448,100 shares of Series B-1 convertible preferred stock (“Series B-1 Preferred Stock”) for gross proceeds of $36.1 million , which shares converted into 2,831,463 shares of common stock upon the completion of the IPO. The Company determined the shares of Series B-1 Preferred Stock were sold at fair value. Therefore, the proceeds from the issuance of Series B-1 Preferred Stock did not impact the transaction price to be allocated to the performance obligations. The Company evaluated as possible variable consideration the milestones, royalties, development cost sharing and profit sharing provisions discussed above. The Company concluded that none of these items represent variable consideration under the Celgene Collaboration Agreement as all such amounts are dependent upon the execution of a related Co-Co Agreement or the JTX-4014 License Agreement. The Co-Co Agreements and the JTX-4014 License Agreement, if executed in the future, would represent separate contracts apart from the Celgene Collaboration Agreement. The Company also considered the existence of any significant financing component within the Celgene Collaboration Agreement given its upfront payment structure. Based upon this assessment, the Company concluded that any difference between the promised consideration and the cash selling price of the services under the Celgene Collaboration Agreement arises for reasons other than the provision of financing, and the difference between those amounts is proportional to the reason for the difference. Accordingly, the Company has concluded that the upfront payment structure of the Celgene Collaboration Agreement does not result in the existence of a significant financing component. Based upon the above considerations, the Company has concluded that the transaction price associated with the Celgene Collaboration Agreement consists solely of the upfront payment of $225.0 million . Allocation of Transaction Price to Performance Obligations The Company has allocated the transaction price to each performance obligation on a relative standalone selling price basis. For all performance obligations, the Company determined the standalone selling price using estimates of the costs to perform the research and development services, including expected internal and external costs for services and supplies, adjusted to reflect a reasonable profit margin. The total estimated cost of the research and development services reflects the nature of the services to be performed and the Company’s best estimate of the length of time required to perform the services. Recognition of Revenue The Company recognizes revenue related to the Celgene Collaboration Agreement over time as the services related to each performance obligation are rendered. The Company has concluded that an input method under ASC 606 is a representative depiction of the transfer of services under the Celgene Collaboration Agreement. The method of measuring progress towards delivery of the services incorporates actual internal and external costs incurred, relative to total internal and external costs expected to be incurred to satisfy the performance obligations. The period over which total costs are estimated reflects the Company’s estimate of the period over which it will perform the research and development services to deliver a pre-defined data package to Celgene for each program subject to an option. The Company recognizes revenue for each performance obligation over periods ranging from twelve months to four years. Changes in estimates of total internal and external costs expected to be incurred are recognized in the period of change as a cumulative catch-up adjustment. For the three months ended June 30, 2019 and 2018 , the Company recognized collaboration revenue of $17.4 million and $19.4 million , respectively, under the Celgene Collaboration Agreement related to the $225.0 million upfront payment received in 2016. For the six months ended June 30, 2019 and 2018 , the Company recognized collaboration revenue of $28.4 million and $30.6 million , respectively. As of June 30, 2019 , the Company had $69.4 million of deferred revenue, which is classified as either current or net of current portion in the accompanying condensed consolidated balance sheets based on the period over which the revenue is expected to be recognized. As of June 30, 2019 , prior to the termination of the Celgene Collaboration Agreement on July 22, 2019, the Company expected to recognize this revenue over the initial research term of the Celgene Collaboration Agreement. This deferred revenue balance represents the aggregate amount of the transaction price allocated to the performance obligations that are partially unsatisfied as of June 30, 2019 . The following table presents changes in the Company’s contract liabilities during the six months ended June 30, 2019 (in thousands): Balance as of Balance as of January 1, 2019 Additions Reductions June 30, 2019 Contract liabilities: Deferred revenue $ 97,872 $ — $ (28,427 ) $ 69,445 Totals $ 97,872 $ — $ (28,427 ) $ 69,445 The reductions to the deferred revenue contract liability during the six months ended June 30, 2019 were comprised of revenue recognized for research and development services performed during the period, offset by a cumulative decrease of revenue previously recognized of $1.3 million arising from changes in costs estimated to be incurred under the Celgene Collaboration Agreement. All revenue recognized during the six months ended June 30, 2019 was included within the beginning balance of the deferred revenue contract liability. As of June 30, 2019 , the Company had not received any option exercise, research term extension, milestone or royalty payments under the Celgene Collaboration Agreement.

Fair Value Measurements

Fair Value Measurements	6 Months Ended
	Jun. 30, 2019
Fair Value Disclosures [Abstract]
Fair Value Measurements	Fair Value Measurements Fair value is an exit price, representing the amount that would be received from the sale of an asset or paid to transfer a liability in an orderly transaction between market participants. Fair value is determined based on observable and unobservable inputs. Observable inputs reflect readily obtainable data from independent sources, while unobservable inputs reflect certain market assumptions. As a basis for considering such assumptions, GAAP establishes a three-tier value hierarchy, which prioritizes the inputs used to develop the assumptions and for measuring fair value as follows: (Level 1) observable inputs such as quoted prices in active markets for identical assets; (Level 2) inputs other than the quoted prices in active markets that are observable either directly or indirectly; and (Level 3) unobservable inputs in which there is little or no market data, which requires the Company to develop its own assumptions. This hierarchy requires the Company to use observable market data, when available, and to minimize the use of unobservable inputs when determining fair value. The Company measures the fair value of money market funds, U.S. Treasuries and government agency securities based on quoted prices in active markets for identical securities. Investments also include corporate debt securities which 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 carrying amounts reflected in the condensed consolidated balance sheets for cash, prepaid expenses and other current assets, accounts payable and accrued expenses approximate their fair values, due to their short-term nature. Assets measured at fair value on a recurring basis as of June 30, 2019 were as follows (in thousands): Total Quoted Prices in Active Markets for Identical Assets (Level 1) Significant Other Observable Inputs (Level 2) Significant Unobservable Inputs Money market funds, included in cash equivalents $ 37,994 $ 37,994 $ — $ — Investments: Corporate debt securities 32,952 — 32,952 — U.S. Treasuries 60,300 60,300 — — Government agency securities 20,774 20,774 — — Totals $ 152,020 $ 119,068 $ 32,952 $ — Assets measured at fair value on a recurring basis as of December 31, 2018 were as follows (in thousands): Total Quoted Prices in Active Markets for Identical Assets (Level 1) Significant Other Observable Inputs (Level 2) Significant Unobservable Inputs Money market funds, included in cash equivalents $ 41,434 $ 41,434 $ — $ — Investments: Corporate debt securities 67,843 — 67,843 — U.S. Treasuries 53,758 53,758 — — Government agency securities 32,829 32,829 — — Totals $ 195,864 $ 128,021 $ 67,843 $ — There were no changes in valuation techniques or transfers between the fair value measurement levels during the three and six months ended June 30, 2019 or during the year ended December 31, 2018 . There were no liabilities measured at fair value on a recurring basis as of June 30, 2019 or December 31, 2018 .

Investments

Investments	6 Months Ended
	Jun. 30, 2019
Investments, Debt and Equity Securities [Abstract]
Investments	Investments Short-term investments consist of investments with maturities greater than ninety days and less than one year from the balance sheet date. Long-term investments consist of investments with maturities of greater than one year that are not expected to be used to fund current operations. The Company classifies all of its investments as available-for-sale securities. Accordingly, these investments are recorded at fair value. Realized gains and losses, amortization and accretion of discounts and premiums are included in other income, net. Unrealized gains and losses on available-for-sale securities are included in other comprehensive income as a component of stockholders’ equity until realized. Cash equivalents and short-term investments as of June 30, 2019 were comprised as follows (in thousands): June 30, 2019 Amortized Cost Unrealized Gains Unrealized Losses Fair Value Cash equivalents and short-term investments: Money market funds, included in cash equivalents $ 37,994 $ — $ — $ 37,994 Corporate debt securities 32,937 15 — 32,952 U.S. Treasuries 60,229 72 (1 ) 60,300 Government agency securities 20,725 49 — 20,774 Total cash equivalents and short-term investments $ 151,885 $ 136 $ (1 ) $ 152,020 The Company maintained no long-term investments as of June 30, 2019 . Cash equivalents, short-term investments and long-term investments as of December 31, 2018 were comprised as follows (in thousands): December 31, 2018 Amortized Cost Unrealized Gains Unrealized Losses Fair Value Cash equivalents and short-term investments: Money market funds, included in cash equivalents $ 41,434 $ — $ — $ 41,434 Corporate debt securities 65,887 2 (39 ) 65,850 U.S. Treasuries 53,765 1 (8 ) 53,758 Government agency securities 28,866 — (34 ) 28,832 Total cash equivalents and short-term investments 189,952 3 (81 ) 189,874 Long-term investments: Corporate debt securities 2,001 — (8 ) 1,993 Government agency securities 3,989 8 — 3,997 Total long-term investments 5,990 8 (8 ) 5,990 Total cash equivalents and investments $ 195,942 $ 11 $ (89 ) $ 195,864 As of June 30, 2019 and December 31, 2018 , the aggregate fair value of securities that were in an unrealized loss position for less than twelve months was $6.5 million and $81.4 million , respectively. As of June 30, 2019 , no securities were in an unrealized loss position for more than twelve months. As of December 31, 2018 , the aggregate fair value of securities that were in an unrealized loss position for more than twelve months was $22.3 million . As of June 30, 2019 , the Company did not intend to sell, and would not be more likely than not required to sell, the securities in an unrealized loss position before recovery of their amortized cost bases. Furthermore, the Company determined that there was no material change in the credit risk of these securities. As a result, the Company determined it did not hold any securities with any other-than-temporary impairment as of June 30, 2019 . There were no realized gains and losses on available-for-sale securities during the three and six months ended June 30, 2019 . There were immaterial realized gains and losses on available-for-sale securities during the three and six months ended June 30, 2018 .

Restricted Cash

Restricted Cash	6 Months Ended
	Jun. 30, 2019
Cash and Cash Equivalents [Abstract]
Restricted Cash	Restricted Cash As of both June 30, 2019 and December 31, 2018 , the Company maintained non-current restricted cash of $1.3 million . This amount is included within “Other non-current assets” in the accompanying condensed consolidated balance sheets and is comprised solely of a letter of credit required pursuant to the lease for the Company’s corporate headquarters. The following table provides a reconciliation of cash, cash equivalents and restricted cash that sums to the total of the same such amounts shown in the condensed consolidated statements of cash flows (in thousands): Six Months Ended Six Months Ended Beginning of Period End of Period Beginning of Period End of Period Cash and cash equivalents $ 47,906 $ 37,994 $ 23,559 $ 50,109 Restricted cash 1,270 1,270 1,270 1,270 Cash, cash equivalents and restricted cash $ 49,176 $ 39,264 $ 24,829 $ 51,379

Accrued Expenses

Accrued Expenses	6 Months Ended
	Jun. 30, 2019
Payables and Accruals [Abstract]
Accrued Expenses	Accrued Expenses Accrued expenses as of June 30, 2019 and December 31, 2018 were comprised as follows (in thousands): June 30, December 31, 2019 2018 Employee compensation and benefits $ 3,350 $ 4,063 External research and professional services 3,757 2,796 Lab consumables and other 237 93 Total accrued expenses $ 7,344 $ 6,952

Common Stock and Preferred Stoc

Common Stock and Preferred Stock	6 Months Ended
	Jun. 30, 2019
Equity [Abstract]
Common Stock and Preferred Stock	Common Stock and Preferred Stock Common Stock The Company is authorized to issue 160,000,000 shares of common stock. Holders of common stock are entitled to one vote per share. Holders of common stock are entitled to receive dividends, if and when declared by the board of directors. Preferred Stock The Company is authorized to issue 5,000,000 shares of undesignated preferred stock in one or more series. As of June 30, 2019 , no shares of preferred stock were issued or outstanding. Shares Reserved for Future Issuance As of June 30, 2019 and December 31, 2018 , the Company had reserved for future issuance the following number of shares of common stock (in thousands): June 30, December 31, 2019 2018 Shares reserved for vesting of restricted stock awards 4 7 Shares reserved for vesting of restricted stock units 649 371 Shares reserved for exercises of outstanding stock options 5,792 5,023 Shares reserved for future issuance under the 2017 Stock Option and Incentive Plan 1,352 1,114 Total shares reserved for future issuance 7,797 6,515

Stock-based Compensation

Stock-based Compensation	6 Months Ended
	Jun. 30, 2019
Share-based Payment Arrangement [Abstract]
Stock-based Compensation	Stock-based Compensation 2013 Stock Option and Grant Plan In February 2013, the board of directors adopted and the Company’s stockholders approved the 2013 Stock Option and Grant Plan (the “2013 Plan”), as amended and restated, under which it could grant incentive stock options (“ISOs”), non-qualified stock options, restricted stock awards (“RSAs”) and restricted stock units (“RSUs”) to eligible employees, officers, directors, and consultants. The 2013 Plan was subsequently amended in January 2015, April 2015, July 2015, March 2016 and October 2016 to allow for the issuance of additional shares of common stock. 2017 Stock Option and Incentive Plan In January 2017, the board of directors adopted and the Company’s stockholders approved the 2017 Stock Option and Incentive Plan (the “2017 Plan”), which became effective immediately prior to the effectiveness of the IPO. Upon the adoption of the 2017 Plan, no further awards will be granted under the 2013 Plan. The 2017 Plan provides for the grant of ISOs, non-qualified stock options, RSAs, RSUs, stock appreciation rights and other stock-based awards. The Company’s employees, officers, directors and consultants and advisors are eligible to receive awards under the 2017 Plan. The terms of awards, including vesting requirements, are determined by the board of directors, subject to the provisions of the 2017 Plan. The Company initially registered on Form S-8 1,753,758 shares of common stock under the 2017 Plan, which was comprised of (i) 1,510,000 shares of common stock reserved for issuance under the 2017 Plan, plus (ii) 243,758 shares of common stock originally reserved for issuance under the 2013 Plan that became available for issuance under the 2017 Plan upon the completion of the Company’s IPO. The 2017 Plan also provides that an additional number of shares will automatically be added to the shares authorized for issuance under the 2017 Plan on January 1, 2018 and each January 1 st thereafter. The number of shares added each year will be equal to the lesser of (i) 4% of the outstanding shares on the immediately preceding December 31 st or (ii) such amount as determined by the compensation committee of the board of directors. Effective January 1, 2018 and 2019, 1,290,609 and 1,317,935 additional shares, respectively, were automatically added to the shares authorized for issuance under the 2017 Plan. As of June 30, 2019 , there were 1,351,940 shares available for future issuance under the 2017 Plan. 2017 Employee Stock Purchase Plan In January 2017, the board of directors adopted and the Company’s stockholders approved the 2017 Employee Stock Purchase Plan (the “2017 ESPP”), which became effective upon the closing of the IPO. The Company initially reserved 302,000 shares of common stock for future issuance under the 2017 ESPP. The 2017 ESPP also provides that an additional number of shares will automatically be added to the shares authorized for issuance under the 2017 ESPP on January 1, 2018 and each January 1 st thereafter through January 1, 2027. The number of shares added each year will be equal to the lesser of (i) 1% of the outstanding shares on the immediately preceding December 31 st , (ii) 603,000 shares or (iii) such amount as determined by the compensation committee of the board of directors. Effective January 1, 2018 and 2019, 322,652 and 329,483 additional shares, respectively, were automatically added to the shares authorized for issuance under the 2017 ESPP. No offering periods under the 2017 ESPP had been initiated as of June 30, 2019 . Stock-based Compensation Expense Total stock-based compensation expense recognized in the condensed consolidated statements of operations and comprehensive loss for the three and six months ended June 30, 2019 and 2018 was as follows (in thousands): Three Months Ended Six Months Ended 2019 2018 2019 2018 Research and development $ 1,097 $ 1,212 $ 2,194 $ 2,362 General and administrative 1,416 1,148 2,861 2,266 Total stock-based compensation expense $ 2,513 $ 2,360 $ 5,055 $ 4,628 RSA Activity Pursuant to RSA agreements issued under the terms of the 2013 Plan, the Company, at its discretion, has the option to repurchase unvested shares underlying RSAs at the initial purchase price if the employees or non-employees terminate their service relationships with the Company. The shares underlying RSAs are recorded in stockholders’ equity as they vest. The following table summarizes RSA activity for the six months ended June 30, 2019 (in thousands, except per share amounts): RSAs Weighted-Average Grant Date Fair Value per Share Unvested as of December 31, 2018 7 $ — Issued — $ — Vested (3 ) $ — Repurchased — $ — Unvested as of June 30, 2019 4 $ — The aggregate fair value of RSAs that vested during each of the three months ended June 30, 2019 and 2018 , based upon the fair values of the stock underlying the RSAs on the day of vesting, was less than $0.1 million . The aggregate fair value of RSAs that vested during each of the six months ended June 30, 2019 and 2018 , based upon the fair values of the stock underlying the RSAs on the day of vesting, was less than $0.1 million . RSU Activity The Company has also granted RSUs to its employees under the 2017 Plan. The following table summarizes RSU activity for the six months ended June 30, 2019 (in thousands, except per share amounts): RSUs Weighted-Average Grant Date Fair Value per Share Unvested as of December 31, 2018 371 $ 8.02 Issued 351 $ 4.40 Vested — $ — Cancelled (73 ) $ 6.08 Unvested as of June 30, 2019 649 $ 6.28 No RSUs vested during the three or six months ended June 30, 2019 or 2018 . As of June 30, 2019 , there was unrecognized stock-based compensation expense related to unvested RSUs of $2.7 million , which the Company expects to recognize over a weighted-average period of approximately 1.8 years . Stock Option Activity The fair value of stock options granted during the three and six months ended June 30, 2019 and 2018 was calculated on the date of grant using the following weighted-average assumptions: Three Months Ended Six Months Ended 2019 2018 2019 2018 Risk-free interest rate 2.1 % 2.8 % 2.5 % 2.7 % Expected dividend yield — % — % — % — % Expected term (in years) 5.7 5.8 6.0 6.0 Expected volatility 70.0 % 66.6 % 69.2 % 65.1 % Using the Black-Scholes option pricing model, the weighted-average grant date fair value of stock options granted during the three months ended June 30, 2019 and 2018 was $3.30 per share and $8.89 per share, respectively. The weighted-average grant date fair value of stock options granted during the six months ended June 30, 2019 and 2018 was $2.88 per share and $13.74 per share, respectively. The following table summarizes stock option activity during the six months ended June 30, 2019 (in thousands, except per share amounts): Options Weighted-Average Exercise Price Weighted Average Remaining Contractual Term (in years) Aggregate Intrinsic Value Outstanding at December 31, 2018 5,023 $ 10.23 7.6 $ 3,133 Granted 1,020 $ 4.56 Exercised (33 ) $ 3.01 Cancelled (218 ) $ 15.11 Outstanding at June 30, 2019 5,792 $ 9.09 7.4 $ 6,508 Exercisable at June 30, 2019 3,278 $ 6.92 6.4 $ 5,822 The aggregate intrinsic value of stock options exercised during the three months ended June 30, 2019 and 2018 was less than $0.1 million and $1.0 million , respectively. The aggregate intrinsic value of stock options exercised during the six months ended June 30, 2019 and 2018 was $0.1 million and $4.4 million , respectively. As of June 30, 2019 , there was unrecognized stock-based compensation expense related to unvested stock options of $16.8 million , which the Company expects to recognize over a weighted-average period of approximately 2.4 years .

Related-party Transactions

Related-party Transactions	6 Months Ended
	Jun. 30, 2019
Related Party Transactions [Abstract]
Related-party Transactions	Related-party Transactions In July 2016, the Company entered into the Celgene Collaboration Agreement and a Series B-1 Preferred Stock Purchase Agreement with Celgene. Under the Celgene Collaboration Agreement, the Company received a non-refundable upfront payment of $225.0 million . Under the Series B-1 Preferred Stock Purchase Agreement, Celgene purchased 10,448,100 shares of Series B-1 convertible preferred stock for $36.1 million . These shares of Series B-1 convertible preferred stock converted into 2,831,463 shares of common stock upon the completion of the IPO. In addition, an affiliate of Celgene purchased 625,000 shares of the Company’s common stock in the IPO at the public offering price of $16.00 per share for a total of $10.0 million . Further information on subsequent transactions between the Company and Celgene are outlined in Note 13, “Subsequent Events”.

Corporate Headquarters Lease

Corporate Headquarters Lease	6 Months Ended
	Jun. 30, 2019
Leases [Abstract]
Corporate Headquarters Lease	Corporate Headquarters Lease In November 2016, the Company entered into an operating lease agreement (the “Corporate Headquarters Lease”) to occupy 51,000 square feet of laboratory and office space in Cambridge, Massachusetts. This facility serves as the Company’s corporate headquarters. The lease term began on November 1, 2016 and extends to March 31, 2025. The Company has the option to extend the lease term for one consecutive five -year period, at the market rate, by giving the landlord written notice of its election to exercise the extension at least twelve months prior to the original expiration of the lease term. The Company provided the landlord with a security deposit in the form of a letter of credit in the amount of $1.3 million , which is recorded as restricted cash in other non-current assets in the condensed consolidated balance sheets. The Corporate Headquarters Lease also provided the Company with a tenant improvement allowance of $0.5 million . Leasehold improvements related to this facility are being amortized over the shorter of their useful life or the lease term. Accounting under ASC 842 As a result of the adoption of ASC 842 on January 1, 2019, the Company has recorded a right-of-use asset and a corresponding lease liability on the condensed consolidated balance sheets as of June 30, 2019 . As there is no rate implicit in the Corporate Headquarters Lease, the Company estimated its incremental borrowing rate based upon a synthetic credit rating and yield curve analysis. Based upon this analysis, the Company calculated a discount rate of 8.0% for the Corporate Headquarters Lease. As of June 30, 2019 , the remaining minimum rental payments due under the Corporate Headquarters Lease were as follows (in thousands): Amount Remainder of 2019 $ 2,140 2020 4,380 2021 4,505 2022 4,633 2023 4,764 2024 and thereafter 6,143 Total remaining minimum rental payments 26,565 Less: effect of discounting (5,457 ) Total lease liability $ 21,108 The Company recorded operating lease expense for the Corporate Headquarters Lease of $1.0 million and $2.1 million for the three and six months ended June 30, 2019 , respectively, pursuant to ASC 842. As of June 30, 2019 , the remaining lease term of the Corporate Headquarters Lease was 5.8 years . Accounting under ASC 840 Prior to the adoption of ASC 842, and pursuant to the legacy guidance within ASC 840, the Company recorded rent expense on a straight-line basis through the end of the lease term and also recorded deferred rent on the condensed consolidated balance sheets. The Company recorded the tenant improvement allowance as a deferred lease incentive and was amortizing the deferred lease incentive through a reduction of rent expense ratably over the lease term. As of December 31, 2018 , the future minimum lease payments due under the Corporate Headquarters Lease were as follows (in thousands): Minimum Lease Payments 2019 $ 4,260 2020 4,380 2021 4,505 2022 4,633 2023 4,764 2024 and thereafter 6,142 Total future minimum lease payments $ 28,684 The Company recorded total rent expense for the Corporate Headquarters Lease of $1.0 million and $2.0 million for the three and six months ended June 30, 2018 , respectively, pursuant to ASC 840.

Net Loss per Share

Net Loss per Share	6 Months Ended
	Jun. 30, 2019
Earnings Per Share [Abstract]
Net Loss per Share	Net Loss per Share For purposes of the diluted loss per share calculation, outstanding stock options, unvested RSAs and unvested RSUs are considered to be potentially dilutive securities, however the following amounts were excluded from the calculation of diluted net loss per share because their effect would be anti-dilutive (in thousands): Three and Six Months Ended 2019 2018 Outstanding stock options 5,792 5,769 Unvested RSAs 4 10 Unvested RSUs 649 — Total 6,445 5,779

Subsequent Events

Subsequent Events	6 Months Ended
	Jun. 30, 2019
Subsequent Events [Abstract]
Subsequent Events	Subsequent Events Celgene License Agreement On July 22, 2019 (the “Effective Date”), the Company entered into a License Agreement (the “Celgene License Agreement”) with Celgene. Pursuant to the Celgene License Agreement, the Company granted to Celgene a worldwide and exclusive license to develop, manufacture and commercialize JTX-8064 and certain derivatives thereof (an “Initial Licensed Compound”), as well as any antibody (other than the Initial Licensed Compound) or other biologic controlled by the Company as of the Effective Date that is specifically directed to the LILRB2 receptor (“LILRB2”) (the “Licensed Compounds”). The Celgene License Agreement provides Celgene with the sole right, at its sole cost and expense, to develop, seek regulatory approval for, manufacture and commercialize the Licensed Compounds and any product that comprises a Licensed Compound (each a “Licensed Product”) for all uses and purposes. Celgene is obligated to use commercially reasonable efforts to develop, seek regulatory approval for and commercialize at least one Licensed Product comprising or incorporating the Initial Licensed Compound (any such Licensed Product, an “Initial Licensed Product”). During the term of the license, the Company is prohibited from developing, manufacturing or commercializing any product, other than Licensed Products, that contains an antibody or other biologic that is specifically directed to LILRB2 or any related antibody or related biologic. Under the terms of the Celgene License Agreement, Celgene paid the Company a one-time, non-refundable upfront payment of $50.0 million in July 2019. The Company is also entitled to receive payments from Celgene upon the achievement of specified clinical, regulatory and sales milestones for the first Initial Licensed Product to achieve such milestones, including potential clinical and regulatory milestone payments up to an aggregate total of $180.0 million and potential sales milestone payments up to an aggregate total of $300.0 million . The Company is also eligible to receive royalties at percentage rates ranging from mid-single-digits to low-double-digits, based on future annual net sales of the Initial Licensed Products, on an Initial Licensed Product-by-Initial Licensed Product and country-by-country basis until the later of (i) the date on which there are no longer any valid composition of matter or method of use claims within the Company’s patents or patents jointly owned by the Company and Celgene related to the Initial Licensed Product in such country and (ii) the twelve-year anniversary of the date of the first commercial sale of the first Initial Licensed Product in such country (the “Royalty Term”). Royalty payments may be reduced in specified circumstances, including payments required to be made by Celgene to third parties to acquire patent rights, up to an aggregate minimum floor, or may be reduced upon the occurrence of certain specified events, including certain compulsory licenses, or if associated with a Licensed Product that is not an Initial Licensed Product. Unless terminated earlier in accordance with its terms, the Celgene License Agreement provides that it will expire (i) on an Initial Licensed Product-by-Initial Licensed Product and country-by-country basis on the date of the expiration of the Royalty Term with respect to such Initial Licensed Product in such country and (ii) in its entirety upon the expiration of all applicable Royalty Terms with respect to the Initial Licensed Products in all countries, following which the applicable licenses under the License Agreement will become fully paid-up, perpetual, irrevocable and royalty-free. Termination of Celgene Collaboration Agreement In connection with the entry into the License Agreement, the Company and Celgene also entered into a termination agreement, terminating the Celgene Collaboration Agreement effective as of July 22, 2019. Upon the effectiveness of the Termination Agreement, the Company will have no further performance obligations under the Celgene Collaboration Agreement. As a result, the Company now expects to recognize the balance of deferred revenue related to the Celgene Collaboration Agreement in the third quarter of 2019.

Basis of Presentation and Sum_2

Basis of Presentation and Summary of Significant Accounting Policies (Policies)	6 Months Ended
	Jun. 30, 2019
Accounting Policies [Abstract]
Basis of Presentation	The accompanying condensed consolidated financial statements as of June 30, 2019 and December 31, 2018 , and for the three and six months ended June 30, 2019 and 2018 , have been prepared in accordance with the rules and regulations of the Securities and Exchange Commission (the “SEC”) and generally accepted accounting principles in the United States of America (“GAAP”) as found in the Accounting Standards Codification (“ASC”) of the Financial Accounting Standards Board (“FASB”) for condensed consolidated financial information. Accordingly, they do not include all of the information and footnotes required by GAAP for complete financial statements. In the opinion of management, these condensed consolidated financial statements reflect all normal recurring adjustments which are necessary for a fair presentation of the Company’s financial position and results of its operations, as of and for the periods presented. These condensed consolidated financial statements should be read in conjunction with the consolidated financial statements and notes thereto contained in the Company’s Annual Report on Form 10-K for the year ended December 31, 2018 filed with the SEC on March 6, 2019 (the “Annual Report on Form 10-K”). The information presented in the condensed consolidated financial statements and related notes as of June 30, 2019 , and for the three and six months ended June 30, 2019 and 2018 , is unaudited. The December 31, 2018 condensed consolidated balance sheet included herein was derived from the audited financial statements as of that date, but does not include all disclosures, including notes, required by GAAP for complete financial statements. Interim results for the six months ended June 30, 2019 are not necessarily indicative of the results that may be expected for the fiscal year ending December 31, 2019 , or any future period.
Principles of Consolidation	The accompanying condensed consolidated financial statements include the accounts of Jounce Therapeutics, Inc. and its wholly-owned subsidiary, Jounce Mass Securities, Inc. All intercompany transactions and balances have been eliminated in consolidation.
Use of Estimates	Use of Estimates The preparation of financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the amounts reported in the financial statements and accompanying notes. On an ongoing basis, the Company’s management evaluates its estimates which include, but are not limited to, estimates related to revenue recognized under the Master Research and Collaboration Agreement (the “Celgene Collaboration Agreement”) with Celgene Corporation (“Celgene”) (including estimates of internal and external costs expected to be incurred to satisfy performance obligations), the determination of the discount rate utilized in the initial application of ASC 842, accrued expenses, stock-based compensation expense and income taxes. The Company bases its estimates on historical experience and other market specific or other relevant assumptions it believes to be reasonable under the circumstances. Actual results could differ from those estimates.
Recent Accounting Pronouncements	Recent Accounting Pronouncements In February 2016, the FASB issued Accounting Standards Update (“ASU”) 2016-02, Leases (Topic 842) , which requires a lessee to recognize assets and liabilities on the balance sheet for operating leases and changes many key definitions, including the definition of a lease. The new standard includes a short-term lease exception for leases with a term of 12 months or less, as part of which a lessee can make an accounting policy election not to recognize lease assets and lease liabilities. Lessees will continue to differentiate between finance leases (previously referred to as capital leases) and operating leases using classification criteria that are substantially similar to the previous guidance. In July 2018, the FASB also issued ASU 2018-11, Leases (Topic 842): Targeted Improvements , which permits entities to continue applying legacy guidance in ASC Topic 840, Leases (“ASC 840”), including its disclosure requirements, in the comparative periods presented in the year that the entity adopts the new leasing standard. Under this transition method, the cumulative effect of initially applying ASC 842 is recognized as an adjustment to the opening balance of retained earnings or accumulated deficit at the beginning of the annual reporting period that includes the date of initial application. The new standard became effective for annual reporting periods beginning after December 15, 2018, including interim periods within those annual reporting periods. Accordingly, the Company adopted ASC 842 on January 1, 2019 using the transition method permitted by ASU 2018-11. In adopting ASC 842, the Company elected to utilize a package of practical expedients under which an entity need not reassess whether any expired or existing contracts are or contain leases, the lease classification for any expired or existing leases or initial direct costs for any existing leases. The Company also elected a practical expedient whereby an entity can utilize hindsight in determining the lease term, including options to extend or terminate the lease. Finally, the Company elected a practical expedient related to not separating lease and nonlease components. In addition, as discussed above, an entity may elect an accounting policy whereby it does not apply the recognition requirements of ASC 842 to short-term leases with a term of 12 months or less. Under this accounting policy, an entity does not recognize a right-of-use asset or lease liability on its balance sheet and instead recognizes lease payments as an expense on a straight-line basis over the lease term. The Company has elected this short-term lease accounting policy. Upon the adoption of ASC 842, the Company removed its legacy deferred rent balances that were previously recorded under ASC 840 and established an operating lease right-of-use asset of $20.2 million , an operating lease liability, current of $2.6 million and an operating lease liability, net of current portion of $19.8 million , all relating to the Company’s existing operating lease for its current corporate headquarters. The Company also recorded an increase to the opening balance of accumulated deficit of less than $0.1 million as a result of the adoption of ASC 842. The following table presents a summary of the amount by which each financial statement line item was affected by the adoption of ASC 842 (in thousands): January 1, 2019 Prior to the Adoption of ASC 842 Effect of Adoption Subsequent to the Adoption of ASC 842 Operating lease right of use asset $ — $ 20,156 $ 20,156 Operating lease liability, current $ — $ 2,563 $ 2,563 Other current liabilities $ 165 $ (61 ) $ 104 Operating lease liability, net of current portion $ — $ 19,790 $ 19,790 Other non-current liabilities $ 2,062 $ (2,062 ) $ — Accumulated deficit $ (163,907 ) $ (75 ) $ (163,982 ) The adoption of ASC 842 did not have a material impact on the condensed consolidated statement of operations and comprehensive loss or the condensed consolidated statement of cash flows for the three and six months ended June 30, 2019 . The Company subsequently measures its lease liability at the present value of remaining lease payments, discounted using the discount rate for the lease. The right-of-use asset is subsequently measured at the amount of the lease liability, adjusted for prepaid or accrued lease payments and the remaining balance of lease incentives received. The Company recognizes operating lease expense on a straight-line basis over the lease term. See Note 11, “Corporate Headquarters Lease”, for further information on the application of ASC 842 to the Company’s operating lease for its current corporate headquarters. In June 2016, the FASB issued ASU 2016-13, F inancial Instruments—Credit Losses (Topic 326): Measurement of Credit Losses on Financial Instruments . This standard requires that credit losses be reported using an expected losses model rather than the incurred losses model that is currently used, and it establishes additional disclosure requirements related to credit risks. For available-for-sale debt securities with unrealized losses, this standard now requires allowances to be recorded instead of reducing the amortized cost of the investment. This guidance will be effective for annual reporting periods beginning after December 15, 2019, including interim periods within those annual reporting periods, and early adoption is permitted. The Company is currently evaluating the potential impact that ASU 2016-13 may have on the condensed consolidated financial statements. In June 2018, the FASB issued ASU 2018-07, Compensation—Stock Compensation (Topic 718): Improvements to Nonemployee Share-Based Payment Accounting . This guidance is intended to simplify the accounting for share-based payments to nonemployees by aligning it with the accounting for share-based payments to employees, with certain exceptions. This guidance became effective for annual reporting periods beginning after December 15, 2018, including interim periods within those annual reporting periods. Accordingly, the Company adopted ASU 2018-07 effective January 1, 2019, and there was no impact to the condensed consolidated financial statements as a result of the adoption of this guidance. In August 2018, the FASB issued ASU 2018-13, Fair Value Measurement (Topic 820): Disclosure Framework—Changes to the Disclosure Requirements for Fair Value Measurement, which eliminates, adds and modifies certain disclosure requirements for fair value measurements. This guidance will be effective for annual reporting periods beginning after December 15, 2019, including interim periods within those annual reporting periods, and early adoption is permitted. More specifically, an entity is permitted to early adopt any removed or modified disclosure requirements immediately and delay adoption of additional disclosure requirements until the effective date of this guidance. The Company does not anticipate a material impact to the condensed consolidated financial statements as a result of the adoption of this guidance. In November 2018, the FASB issued ASU 2018-18, Collaborative Arrangements (Topic 808): Clarifying the Interaction between Topic 808 and Topic 606 , which clarifies that certain transactions between participants in a collaborative arrangement should be accounted for under ASC Topic 606, Revenue from Contracts with Customers (“ASC 606”) when the counterparty is a customer. In addition, ASU 2018-18 adds unit-of-account guidance to ASC Topic 808, Collaborative Arrangements , in order to align this guidance with ASC 606 and also precludes an entity from presenting consideration from a transaction in a collaborative arrangement as revenue from contracts with customers if the counterparty is not a customer for that transaction. This guidance will be effective for annual reporting periods beginning after December 15, 2019, including interim periods within those annual reporting periods, and early adoption is permitted. The Company is currently evaluating the potential impact that ASU 2018-18 may have on the condensed consolidated financial statements.
Fair Value Measurement Policy	Fair value is an exit price, representing the amount that would be received from the sale of an asset or paid to transfer a liability in an orderly transaction between market participants. Fair value is determined based on observable and unobservable inputs. Observable inputs reflect readily obtainable data from independent sources, while unobservable inputs reflect certain market assumptions. As a basis for considering such assumptions, GAAP establishes a three-tier value hierarchy, which prioritizes the inputs used to develop the assumptions and for measuring fair value as follows: (Level 1) observable inputs such as quoted prices in active markets for identical assets; (Level 2) inputs other than the quoted prices in active markets that are observable either directly or indirectly; and (Level 3) unobservable inputs in which there is little or no market data, which requires the Company to develop its own assumptions. This hierarchy requires the Company to use observable market data, when available, and to minimize the use of unobservable inputs when determining fair value. The Company measures the fair value of money market funds, U.S. Treasuries and government agency securities based on quoted prices in active markets for identical securities. Investments also include corporate debt securities which 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 carrying amounts reflected in the condensed consolidated balance sheets for cash, prepaid expenses and other current assets, accounts payable and accrued expenses approximate their fair values, due to their short-term nature.

Basis of Presentation and Sum_3

Basis of Presentation and Summary of Significant Accounting Policies (Tables)	6 Months Ended
	Jun. 30, 2019
Accounting Policies [Abstract]
ASC 842 adoption	The following table presents a summary of the amount by which each financial statement line item was affected by the adoption of ASC 842 (in thousands): January 1, 2019 Prior to the Adoption of ASC 842 Effect of Adoption Subsequent to the Adoption of ASC 842 Operating lease right of use asset $ — $ 20,156 $ 20,156 Operating lease liability, current $ — $ 2,563 $ 2,563 Other current liabilities $ 165 $ (61 ) $ 104 Operating lease liability, net of current portion $ — $ 19,790 $ 19,790 Other non-current liabilities $ 2,062 $ (2,062 ) $ — Accumulated deficit $ (163,907 ) $ (75 ) $ (163,982 )

Celgene Collaboration Agreeme_2

Celgene Collaboration Agreement (Tables)	6 Months Ended
	Jun. 30, 2019
Research and Development [Abstract]
Contract with Customer, Asset and Liability	The following table presents changes in the Company’s contract liabilities during the six months ended June 30, 2019 (in thousands): Balance as of Balance as of January 1, 2019 Additions Reductions June 30, 2019 Contract liabilities: Deferred revenue $ 97,872 $ — $ (28,427 ) $ 69,445 Totals $ 97,872 $ — $ (28,427 ) $ 69,445

Fair Value Measurements (Tables

Fair Value Measurements (Tables)	6 Months Ended
	Jun. 30, 2019
Fair Value Disclosures [Abstract]
Assets Measured at Fair Value	Assets measured at fair value on a recurring basis as of June 30, 2019 were as follows (in thousands): Total Quoted Prices in Active Markets for Identical Assets (Level 1) Significant Other Observable Inputs (Level 2) Significant Unobservable Inputs Money market funds, included in cash equivalents $ 37,994 $ 37,994 $ — $ — Investments: Corporate debt securities 32,952 — 32,952 — U.S. Treasuries 60,300 60,300 — — Government agency securities 20,774 20,774 — — Totals $ 152,020 $ 119,068 $ 32,952 $ — Assets measured at fair value on a recurring basis as of December 31, 2018 were as follows (in thousands): Total Quoted Prices in Active Markets for Identical Assets (Level 1) Significant Other Observable Inputs (Level 2) Significant Unobservable Inputs Money market funds, included in cash equivalents $ 41,434 $ 41,434 $ — $ — Investments: Corporate debt securities 67,843 — 67,843 — U.S. Treasuries 53,758 53,758 — — Government agency securities 32,829 32,829 — — Totals $ 195,864 $ 128,021 $ 67,843 $ —

Investments (Tables)

Investments (Tables)	6 Months Ended
	Jun. 30, 2019
Investments, Debt and Equity Securities [Abstract]
Schedule of Available-for-sale Securities by Security Type	Cash equivalents and short-term investments as of June 30, 2019 were comprised as follows (in thousands): June 30, 2019 Amortized Cost Unrealized Gains Unrealized Losses Fair Value Cash equivalents and short-term investments: Money market funds, included in cash equivalents $ 37,994 $ — $ — $ 37,994 Corporate debt securities 32,937 15 — 32,952 U.S. Treasuries 60,229 72 (1 ) 60,300 Government agency securities 20,725 49 — 20,774 Total cash equivalents and short-term investments $ 151,885 $ 136 $ (1 ) $ 152,020 Cash equivalents, short-term investments and long-term investments as of December 31, 2018 were comprised as follows (in thousands): December 31, 2018 Amortized Cost Unrealized Gains Unrealized Losses Fair Value Cash equivalents and short-term investments: Money market funds, included in cash equivalents $ 41,434 $ — $ — $ 41,434 Corporate debt securities 65,887 2 (39 ) 65,850 U.S. Treasuries 53,765 1 (8 ) 53,758 Government agency securities 28,866 — (34 ) 28,832 Total cash equivalents and short-term investments 189,952 3 (81 ) 189,874 Long-term investments: Corporate debt securities 2,001 — (8 ) 1,993 Government agency securities 3,989 8 — 3,997 Total long-term investments 5,990 8 (8 ) 5,990 Total cash equivalents and investments $ 195,942 $ 11 $ (89 ) $ 195,864

Restricted Cash (Tables)

Restricted Cash (Tables)	6 Months Ended
	Jun. 30, 2019
Cash and Cash Equivalents [Abstract]
Schedule of Restricted Cash	The following table provides a reconciliation of cash, cash equivalents and restricted cash that sums to the total of the same such amounts shown in the condensed consolidated statements of cash flows (in thousands): Six Months Ended Six Months Ended Beginning of Period End of Period Beginning of Period End of Period Cash and cash equivalents $ 47,906 $ 37,994 $ 23,559 $ 50,109 Restricted cash 1,270 1,270 1,270 1,270 Cash, cash equivalents and restricted cash $ 49,176 $ 39,264 $ 24,829 $ 51,379
Schedule of Cash and Cash Equivalents	The following table provides a reconciliation of cash, cash equivalents and restricted cash that sums to the total of the same such amounts shown in the condensed consolidated statements of cash flows (in thousands): Six Months Ended Six Months Ended Beginning of Period End of Period Beginning of Period End of Period Cash and cash equivalents $ 47,906 $ 37,994 $ 23,559 $ 50,109 Restricted cash 1,270 1,270 1,270 1,270 Cash, cash equivalents and restricted cash $ 49,176 $ 39,264 $ 24,829 $ 51,379

Accrued Expenses (Tables)

Accrued Expenses (Tables)	6 Months Ended
	Jun. 30, 2019
Payables and Accruals [Abstract]
Schedule of Accrued Expenses	Accrued expenses as of June 30, 2019 and December 31, 2018 were comprised as follows (in thousands): June 30, December 31, 2019 2018 Employee compensation and benefits $ 3,350 $ 4,063 External research and professional services 3,757 2,796 Lab consumables and other 237 93 Total accrued expenses $ 7,344 $ 6,952

Common Stock and Preferred St_2

Common Stock and Preferred Stock (Tables)	6 Months Ended
	Jun. 30, 2019
Equity [Abstract]
Schedule of Stock by Class	As of June 30, 2019 and December 31, 2018 , the Company had reserved for future issuance the following number of shares of common stock (in thousands): June 30, December 31, 2019 2018 Shares reserved for vesting of restricted stock awards 4 7 Shares reserved for vesting of restricted stock units 649 371 Shares reserved for exercises of outstanding stock options 5,792 5,023 Shares reserved for future issuance under the 2017 Stock Option and Incentive Plan 1,352 1,114 Total shares reserved for future issuance 7,797 6,515

Stock-based Compensation (Table

Stock-based Compensation (Tables)	6 Months Ended
	Jun. 30, 2019
Share-based Payment Arrangement [Abstract]
Schedule of Stock-Based Compensation Expense	Total stock-based compensation expense recognized in the condensed consolidated statements of operations and comprehensive loss for the three and six months ended June 30, 2019 and 2018 was as follows (in thousands): Three Months Ended Six Months Ended 2019 2018 2019 2018 Research and development $ 1,097 $ 1,212 $ 2,194 $ 2,362 General and administrative 1,416 1,148 2,861 2,266 Total stock-based compensation expense $ 2,513 $ 2,360 $ 5,055 $ 4,628
Schedule of Restricted Stock Activity	The following table summarizes RSA activity for the six months ended June 30, 2019 (in thousands, except per share amounts): RSAs Weighted-Average Grant Date Fair Value per Share Unvested as of December 31, 2018 7 $ — Issued — $ — Vested (3 ) $ — Repurchased — $ — Unvested as of June 30, 2019 4 $ — The Company has also granted RSUs to its employees under the 2017 Plan. The following table summarizes RSU activity for the six months ended June 30, 2019 (in thousands, except per share amounts): RSUs Weighted-Average Grant Date Fair Value per Share Unvested as of December 31, 2018 371 $ 8.02 Issued 351 $ 4.40 Vested — $ — Cancelled (73 ) $ 6.08 Unvested as of June 30, 2019 649 $ 6.28
Schedule of Share-based Payment Award, Stock Options, Valuation Assumptions	The fair value of stock options granted during the three and six months ended June 30, 2019 and 2018 was calculated on the date of grant using the following weighted-average assumptions: Three Months Ended Six Months Ended 2019 2018 2019 2018 Risk-free interest rate 2.1 % 2.8 % 2.5 % 2.7 % Expected dividend yield — % — % — % — % Expected term (in years) 5.7 5.8 6.0 6.0 Expected volatility 70.0 % 66.6 % 69.2 % 65.1 %
Schedule of Stock Options, Activity	The following table summarizes stock option activity during the six months ended June 30, 2019 (in thousands, except per share amounts): Options Weighted-Average Exercise Price Weighted Average Remaining Contractual Term (in years) Aggregate Intrinsic Value Outstanding at December 31, 2018 5,023 $ 10.23 7.6 $ 3,133 Granted 1,020 $ 4.56 Exercised (33 ) $ 3.01 Cancelled (218 ) $ 15.11 Outstanding at June 30, 2019 5,792 $ 9.09 7.4 $ 6,508 Exercisable at June 30, 2019 3,278 $ 6.92 6.4 $ 5,822

Corporate Headquarters Lease (T

Corporate Headquarters Lease (Tables)	6 Months Ended
	Jun. 30, 2019
Leases [Abstract]
Remaining minimum rental payments due under the Corporate Headquarters Lease	As of June 30, 2019 , the remaining minimum rental payments due under the Corporate Headquarters Lease were as follows (in thousands): Amount Remainder of 2019 $ 2,140 2020 4,380 2021 4,505 2022 4,633 2023 4,764 2024 and thereafter 6,143 Total remaining minimum rental payments 26,565 Less: effect of discounting (5,457 ) Total lease liability $ 21,108
Future minimum lease payments due under the Corporate Headquarters Lease	As of December 31, 2018 , the future minimum lease payments due under the Corporate Headquarters Lease were as follows (in thousands): Minimum Lease Payments 2019 $ 4,260 2020 4,380 2021 4,505 2022 4,633 2023 4,764 2024 and thereafter 6,142 Total future minimum lease payments $ 28,684

Net Loss per Share (Tables)

Net Loss per Share (Tables)	6 Months Ended
	Jun. 30, 2019
Earnings Per Share [Abstract]
Schedule of Antidilutive Securities Excluded from Computation of Net Loss per Share	For purposes of the diluted loss per share calculation, outstanding stock options, unvested RSAs and unvested RSUs are considered to be potentially dilutive securities, however the following amounts were excluded from the calculation of diluted net loss per share because their effect would be anti-dilutive (in thousands): Three and Six Months Ended 2019 2018 Outstanding stock options 5,792 5,769 Unvested RSAs 4 10 Unvested RSUs 649 — Total 6,445 5,779

Nature of Business (Details)

Nature of Business (Details) - USD ($) $ in Millions	Aug. 07, 2019	Jun. 30, 2019
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Cash, cash equivalents, and marketable securities		$ 152
Scenario, Forecast
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Duration of funding requirement	12 months

Basis of Presentation and Sum_4

Basis of Presentation and Summary of Significant Accounting Policies - Narrative (Details) - USD ($) $ in Thousands	Jun. 30, 2019	Jan. 01, 2019	Dec. 31, 2018
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Operating lease right-of-use asset	$ 18,911	$ 20,156
Operating lease liability, current	2,729	2,563
Operating lease liability, net of current portion	18,379	19,790
Accumulated deficit	$ 183,352	163,982	$ 163,907
Accounting Standards Update 2016-02
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Operating lease right-of-use asset		20,156
Operating lease liability, current		2,563
Operating lease liability, net of current portion		19,790
Accumulated deficit		$ 75

Basis of Presentation and Sum_5

Basis of Presentation and Summary of Significant Accounting Policies - Summary of Adoption ASC 842 (Details) - USD ($) $ in Thousands	Jun. 30, 2019	Jan. 01, 2019	Dec. 31, 2018
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Operating lease right-of-use asset	$ 18,911	$ 20,156
Operating lease liability, current	2,729	2,563
Other current liabilities	47	104	$ 165
Operating lease liability, net of current portion	18,379	19,790
Other non-current liabilities	0	0	2,062
Accumulated deficit	$ (183,352)	(163,982)	$ (163,907)
Accounting Standards Update 2016-02
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Operating lease right-of-use asset		20,156
Operating lease liability, current		2,563
Other current liabilities		(61)
Operating lease liability, net of current portion		19,790
Other non-current liabilities		(2,062)
Accumulated deficit		$ (75)

Celgene Collaboration Agreeme_3

Celgene Collaboration Agreement - Narrative (Details) $ in Thousands	Feb. 01, 2017shares	Jul. 31, 2016USD ($)extensiondeliverablecustomer_programshares	Jun. 30, 2019USD ($)	Jun. 30, 2018USD ($)	Jun. 30, 2019USD ($)	Jun. 30, 2018USD ($)	Dec. 31, 2018USD ($)
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Collaboration revenue—related party			$ 17,446	$ 19,378	$ 28,427	$ 30,573
Deferred revenue			$ 69,445		69,445		$ 97,872
Cumulative catch-up adjustment from changes in costs estimated to be incurred					$ 1,300
Common Stock | Celgene Corporation | Celgene Collaboration Agreement | IPO
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Stock converted upon completion of IPO (in shares) | shares	2,831,463
Celegene Collaborative Arrangement
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Number of early-stage programs | customer_program		4
Non-refundable upfront payment received for research agreement		$ 225,000
Aggregate option-exercise fees from program options		$ 182,500
Number of program options | deliverable		6
Initial research term		4 years
Potential addition to research term		3 years
Aggregate consideration for additional years of research		$ 120,000
Potential milestone revenue		2,300,000
Aggregate development milestone revenue		290,000
Aggregate regulatory approval milestone revenue		700,000
Aggregate commercial milestone revenue		$ 1,270,000
Number of program extensions | extension		3
Program extension research term		1 year
Celegene Collaborative Arrangement | JTX-2011
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Percent of operating profit or loss retained		60.00%
Celegene Collaborative Arrangement | Lead Program
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Percent of operating profit or loss retained		25.00%
Celegene Collaborative Arrangement | Other Programs
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Percent of operating profit or loss retained		50.00%
Celegene Collaborative Arrangement | Minimum
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Option-exercise fee for program option		$ 10,000
Consideration for additional year of research		30,000
Development milestone revenue, per program		32,500
Regulatory approval milestone revenue, per program		7,500
Commercial milestone revenue, per program		$ 40,000
Program option term		45 days
Celegene Collaborative Arrangement | Maximum
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Option-exercise fee for program option		$ 60,000
Consideration for additional year of research		45,000
Development milestone revenue, per program		105,000
Regulatory approval milestone revenue, per program		50,000
Commercial milestone revenue, per program		$ 200,000
Program option term		60 days
Celegene Collaborative Arrangement | Celgene Corporation | JTX-2011
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Percent of operating profit or loss retained		40.00%
Celegene Collaborative Arrangement | Celgene Corporation | Lead Program
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Percent of operating profit or loss retained		75.00%
Celegene Collaborative Arrangement | Celgene Corporation | Other Programs
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Percent of operating profit or loss retained		50.00%
Celegene Collaborative Arrangement | Celgene Corporation | Minimum | All Programs, Excluding JTX-4014
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Percent of development costs		67.00%
Celegene Collaborative Arrangement | Celgene Corporation | Maximum | All Programs, Excluding JTX-4014
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Percent of development costs		85.00%
Celegene Collaborative Arrangement | Celgene Corporation | Celgene Collaboration Agreement
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Non-refundable upfront payment received for research agreement		$ 225,000
Celegene Collaborative Arrangement | Convertible preferred stock (Series B-1)
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Issuances of convertible preferred stock		$ 36,100
Issuances of convertible preferred stock (in shares) | shares		10,448,100
Celegene Collaborative Arrangement | Convertible preferred stock (Series B-1) | Celgene Corporation | Celgene Collaboration Agreement
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Issuances of convertible preferred stock		$ 36,100
Issuances of convertible preferred stock (in shares) | shares		10,448,100

Celgene Collaboration Agreeme_4

Celgene Collaboration Agreement - Performance Obligations (Details) - Celegene Collaborative Arrangement - Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2018-04-01	Jun. 30, 2019
Minimum
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Performance period for unit of accounting	12 months
Maximum
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Performance period for unit of accounting	4 years

Celgene Collaboration Agreeme_5

Celgene Collaboration Agreement - Schedule of Contract Liabilities (Details) $ in Thousands	3 Months Ended
	Jun. 30, 2019USD ($)
Revenue, Performance Obligation, Contract Liability [Roll Forward]
Additions	$ 0
Reductions	(28,427)
Ending balance	$ 69,445

Fair Value Measurements - Asset

Fair Value Measurements - Assets Measured at Fair Value (Details) - USD ($)	Jun. 30, 2019	Dec. 31, 2018
Fair Value, Measurements, Recurring
Investments:
Totals	$ 152,020,000	$ 195,864,000
Liabilities measured at fair value	0	0
Fair Value, Measurements, Recurring | Quoted Prices in Active Markets for Identical Assets (Level 1)
Investments:
Totals	119,068,000	128,021,000
Fair Value, Measurements, Recurring | Significant Other Observable Inputs (Level 2)
Investments:
Totals	32,952,000	67,843,000
Fair Value, Measurements, Recurring | Significant Unobservable Inputs (Level 3)
Investments:
Totals	0	0
Corporate debt securities | Fair Value, Measurements, Recurring
Investments:
Available-for-sale debt securities, fair value	32,952,000	67,843,000
Corporate debt securities | Fair Value, Measurements, Recurring | Quoted Prices in Active Markets for Identical Assets (Level 1)
Investments:
Available-for-sale debt securities, fair value	0	0
Corporate debt securities | Fair Value, Measurements, Recurring | Significant Other Observable Inputs (Level 2)
Investments:
Available-for-sale debt securities, fair value	32,952,000	67,843,000
Corporate debt securities | Fair Value, Measurements, Recurring | Significant Unobservable Inputs (Level 3)
Investments:
Available-for-sale debt securities, fair value	0	0
U.S. Treasuries | Fair Value, Measurements, Recurring
Investments:
Available-for-sale debt securities, fair value	60,300,000	53,758,000
U.S. Treasuries | Fair Value, Measurements, Recurring | Quoted Prices in Active Markets for Identical Assets (Level 1)
Investments:
Available-for-sale debt securities, fair value	60,300,000	53,758,000
U.S. Treasuries | Fair Value, Measurements, Recurring | Significant Other Observable Inputs (Level 2)
Investments:
Available-for-sale debt securities, fair value	0	0
U.S. Treasuries | Fair Value, Measurements, Recurring | Significant Unobservable Inputs (Level 3)
Investments:
Available-for-sale debt securities, fair value	0	0
Government agency securities | Fair Value, Measurements, Recurring
Investments:
Available-for-sale debt securities, fair value	20,774,000	32,829,000
Government agency securities | Fair Value, Measurements, Recurring | Quoted Prices in Active Markets for Identical Assets (Level 1)
Investments:
Available-for-sale debt securities, fair value	20,774,000	32,829,000
Government agency securities | Fair Value, Measurements, Recurring | Significant Other Observable Inputs (Level 2)
Investments:
Available-for-sale debt securities, fair value	0	0
Government agency securities | Fair Value, Measurements, Recurring | Significant Unobservable Inputs (Level 3)
Investments:
Available-for-sale debt securities, fair value	0	0
Money market funds, included in cash equivalents
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Money market funds, included in cash equivalents	37,994,000	41,434,000
Money market funds, included in cash equivalents | Fair Value, Measurements, Recurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Money market funds, included in cash equivalents	37,994,000	41,434,000
Money market funds, included in cash equivalents | Fair Value, Measurements, Recurring | Quoted Prices in Active Markets for Identical Assets (Level 1)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Money market funds, included in cash equivalents	37,994,000	41,434,000
Money market funds, included in cash equivalents | Fair Value, Measurements, Recurring | Significant Other Observable Inputs (Level 2)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Money market funds, included in cash equivalents	0	0
Money market funds, included in cash equivalents | Fair Value, Measurements, Recurring | Significant Unobservable Inputs (Level 3)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Money market funds, included in cash equivalents	$ 0	$ 0

Investments - Available-for-sal

Investments - Available-for-sale Securities by Security Type (Details) - USD ($) $ in Thousands	Jun. 30, 2019	Dec. 31, 2018
Debt Securities, Available-for-sale, Fair Value to Amortized Cost [Abstract]
Unrealized Gains		$ 11
Unrealized Losses		(89)
Cash equivalents, short-term and long-term investments, carrying value		195,942
Cash equivalents, short-term and long-term investments, fair vale disclosure		195,864
Short-term Investments
Debt Securities, Available-for-sale, Fair Value to Amortized Cost [Abstract]
Unrealized Gains	$ 136	3
Unrealized Losses	(1)	(81)
Total cash equivalents and short-term investments, carrying value	151,885	189,952
Total cash equivalents and short-term investments, fair value	152,020	189,874
Short-term Investments | Corporate debt securities
Debt Securities, Available-for-sale, Fair Value to Amortized Cost [Abstract]
Available-for-sale debt securities, amortized cost basis	32,937	65,887
Unrealized Gains	15	2
Unrealized Losses	0	(39)
Available-for-sale debt securities, fair value	32,952	65,850
Short-term Investments | US Treasury Securities
Debt Securities, Available-for-sale, Fair Value to Amortized Cost [Abstract]
Available-for-sale debt securities, amortized cost basis	60,229	53,765
Unrealized Gains	72	1
Unrealized Losses	(1)	(8)
Available-for-sale debt securities, fair value	60,300	53,758
Short-term Investments | Government agency securities
Debt Securities, Available-for-sale, Fair Value to Amortized Cost [Abstract]
Available-for-sale debt securities, amortized cost basis	20,725	28,866
Unrealized Gains	49	0
Unrealized Losses	0	(34)
Available-for-sale debt securities, fair value	20,774	28,832
Long-term Investments
Debt Securities, Available-for-sale, Fair Value to Amortized Cost [Abstract]
Available-for-sale debt securities, amortized cost basis		5,990
Unrealized Gains		8
Unrealized Losses		(8)
Available-for-sale debt securities, fair value		5,990
Long-term Investments | Corporate debt securities
Debt Securities, Available-for-sale, Fair Value to Amortized Cost [Abstract]
Available-for-sale debt securities, amortized cost basis		2,001
Unrealized Gains		0
Unrealized Losses		(8)
Available-for-sale debt securities, fair value		1,993
Long-term Investments | Government agency securities
Debt Securities, Available-for-sale, Fair Value to Amortized Cost [Abstract]
Available-for-sale debt securities, amortized cost basis		3,989
Unrealized Gains		8
Unrealized Losses		0
Available-for-sale debt securities, fair value		3,997
Money market funds, included in cash equivalents
Debt Securities, Available-for-sale [Line Items]
Cash equivalents at carrying value	37,994	41,434
Cash equivalents at fair value	$ 37,994	$ 41,434

Investments - Narrative (Detail

Investments - Narrative (Details) - USD ($)	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018	Dec. 31, 2018
Investments, Debt and Equity Securities [Abstract]
Long-term investments	$ 0		$ 0		$ 5,990,000
Available-for-sale securities in an unrealized loss position for less than twelve months	6,500,000		6,500,000		81,400,000
Number of securities in unrealized loss position, greater than 12 months	0		0		$ 22,300,000
Realized gains or losses on available-for-sale securities	$ 0	$ 0	$ 0	$ 0

Restricted Cash - Narrative (De

Restricted Cash - Narrative (Details) - USD ($) $ in Millions	Jun. 30, 2019	Dec. 31, 2018
Cash and Cash Equivalents [Abstract]
Non-current restricted cash	$ 1.3	$ 1.3

Restricted Cash - Schedule of C

Restricted Cash - Schedule of Cash, Cash Equivalents and Restricted Cash (Details) - USD ($) $ in Thousands	Jun. 30, 2019	Dec. 31, 2018	Jun. 30, 2018	Dec. 31, 2017
Cash and Cash Equivalents [Abstract]
Cash and cash equivalents	$ 37,994	$ 47,906	$ 50,109	$ 23,559
Restricted cash	1,270	1,270	1,270	1,270
Cash, cash equivalents and restricted cash	$ 39,264	$ 49,176	$ 51,379	$ 24,829

Accrued Expenses (Details)

Accrued Expenses (Details) - USD ($) $ in Thousands	Jun. 30, 2019	Dec. 31, 2018
Payables and Accruals [Abstract]
Employee compensation and benefits	$ 3,350	$ 4,063
External research and professional services	3,757	2,796
Lab consumables and other	237	93
Total accrued expenses	$ 7,344	$ 6,952

Common Stock and Preferred St_3

Common Stock and Preferred Stock - Narrative (Details)	Jun. 30, 2019voteshares	Dec. 31, 2018shares
Equity [Abstract]
Common stock shares authorized (in shares)	160,000,000	160,000,000
Common stock, votes per share | vote	1
Preferred stock shares authorized (in shares)	5,000,000	5,000,000
Preferred stock shares issued (in shares)	0	0
Preferred stock shares outstanding (in shares)	0	0

Common Stock and Preferred St_4

Common Stock and Preferred Stock - Shares Reserved for Future Issuance (Details) - shares	Jun. 30, 2019	Dec. 31, 2018	Jan. 31, 2017
Conversion of Stock [Line Items]
Common stock reserved for potential conversion (in shares)	7,797,000	6,515,000	1,753,758
Restricted Stock
Conversion of Stock [Line Items]
Common stock reserved for potential conversion (in shares)	4,000	7,000
Restricted Stock Units (RSUs)
Conversion of Stock [Line Items]
Common stock reserved for potential conversion (in shares)	649,000	371,000
Outstanding Employee Stock Options
Conversion of Stock [Line Items]
Common stock reserved for potential conversion (in shares)	5,792,000	5,023,000
Future Issuances from Employee Stock Options
Conversion of Stock [Line Items]
Common stock reserved for potential conversion (in shares)	1,352,000	1,114,000

Stock-based Compensation - Narr

Stock-based Compensation - Narrative (Details) - USD ($) $ / shares in Units, $ in Millions	Jan. 01, 2019	Jan. 01, 2018	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018	Dec. 31, 2018	Jan. 31, 2017
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares of common stock eligible to be purchased (in shares)			7,797,000		7,797,000		6,515,000	1,753,758
Weighted average fair value of options granted (in dollars per share)			$ 3.30	$ 8.89	$ 2.88	$ 13.74
Intrinsic value of stock options exercised			$ 0.1	$ 1	$ 0.1	$ 4.4
Unrecognized stock-based compensation expense, options			$ 16.8		$ 16.8
Future Issuances from Employee Stock Options
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares of common stock reserved for issuance (in shares)			1,351,940		1,351,940
Shares of common stock eligible to be purchased (in shares)			1,352,000		1,352,000		1,114,000
Restricted Stock
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares of common stock eligible to be purchased (in shares)			4,000		4,000		7,000
Aggregate fair value of awards vested in period			$ 0.1	$ 0.1	$ 0.1	$ 0.1
Vested (in shares)					3,000
Restricted Stock Units (RSUs)
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares of common stock eligible to be purchased (in shares)			649,000		649,000		371,000
Vested (in shares)			0	0	0	0
Unrecognized stock-based compensation expense, RSUs			$ 2.7		$ 2.7
Remaining weighted average vesting period					1 year 9 months 15 days
Employee Stock Option
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Remaining weighted average vesting period					2 years 4 months 13 days
2013 Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares of common stock reserved for issuance (in shares)								0
Shares of common stock eligible to be purchased (in shares)								243,758
2017 Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares of common stock eligible to be purchased (in shares)								1,510,000
Percent of outstanding shares able to be added each year								4.00%
Number of additional shares authorized (in shares)	1,317,935	1,290,609
2017 Employee Stock Purchase Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares of common stock eligible to be purchased (in shares)								302,000
Percent of outstanding shares able to be added each year								1.00%
Number of additional shares authorized (in shares)	329,483	322,652
Shares of common stock to determine number of additional shares (in shares)								603,000

Stock-based Compensation - Stoc

Stock-based Compensation - Stock-based Compensation Expense (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense	$ 2,513	$ 2,360	$ 5,055	$ 4,628
Research and development
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense	1,097	1,212	2,194	2,362
General and administrative
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense	$ 1,416	$ 1,148	$ 2,861	$ 2,266

Stock-based Compensation - RSA

Stock-based Compensation - RSA and RSU Activity (Details) - $ / shares	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Restricted Stock
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number of Shares [Roll Forward]
Beginning unvested balance (in shares)			7,000
Issued (in shares)			0
Vested (in shares)			(3,000)
Repurchased (in shares)			0
Ending unvested balance (in shares)	4,000		4,000
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Weighted Average Grant Date Fair Value [Abstract]
Beginning unvested balance (in dollars per share)			$ 0
Issued (in dollars per share)			0
Vested (in dollars per share)			0
Repurchased (in dollars per share)			0
Ending unvested balance (in dollars per share)	$ 0		$ 0
Restricted Stock Units (RSUs)
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number of Shares [Roll Forward]
Beginning unvested balance (in shares)			371,000
Issued (in shares)			351,000
Vested (in shares)	0	0	0	0
Cancelled (in shares)			(73,000)
Ending unvested balance (in shares)	649,000		649,000
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Weighted Average Grant Date Fair Value [Abstract]
Beginning unvested balance (in dollars per share)			$ 8.02
Issued (in dollars per share)			4.40
Vested (in dollars per share)			0
Cancelled (in dollars per share)			6.08
Ending unvested balance (in dollars per share)	$ 6.28		$ 6.28

Stock-based Compensation - Weig

Stock-based Compensation - Weighted Average Assumptions (Details) - Employee Stock Option	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Risk-free interest rate	2.10%	2.80%	2.50%	2.70%
Expected dividend yield	0.00%	0.00%	0.00%	0.00%
Expected term (in years)	5 years 8 months 12 days	5 years 9 months 18 days	5 years 11 months 27 days	6 years
Expected volatility	70.00%	66.60%	69.20%	65.10%

Stock-based Compensation - St_2

Stock-based Compensation - Stock Option Activity (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended				6 Months Ended	12 Months Ended
	Jun. 30, 2019	Mar. 31, 2019	Jun. 30, 2018	Mar. 31, 2018	Jun. 30, 2019	Dec. 31, 2018
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding [Roll Forward]
Beginning outstanding balance (in shares)		5,023			5,023
Granted (in shares)					1,020
Exercises of common stock options (in shares)	(9)	(24)	(143)	(198)	(33)
Cancelled or forfeited (in shares)					(218)
Ending outstanding balance (in shares)	5,792				5,792	5,023
Exercisable (in shares)	3,278				3,278
Share-based Compensation Arrangement by Share-based Payment Award, Options, Nonvested, Weighted Average Grant Date Fair Value [Abstract]
Beginning outstanding balance (in dollars per share)		$ 10.23			$ 10.23
Granted (in dollars per share)					4.56
Exercised (in dollars per share)					3.01
Cancelled or forfeited (in dollars per share)					15.11
Ending outstanding balance (in dollars per share)	$ 9.09				9.09	$ 10.23
Exercisable (in dollars per share)	$ 6.92				$ 6.92
Remaining contractual life, outstanding					7 years 4 months 13 days	7 years 7 months 6 days
Remaining contractual life, exercisable					6 years 5 months 12 days
Aggregate intrinsic value, outstanding	$ 6,508				$ 6,508	$ 3,133
Aggregate intrinsic value, exercisable	$ 5,822				$ 5,822

Related-party Transactions (Det

Related-party Transactions (Details) - USD ($) $ / shares in Units, $ in Millions	Feb. 01, 2017	Jul. 31, 2016
Celegene Collaborative Arrangement
Related Party Transaction [Line Items]
Non-refundable upfront payment received for research agreement		$ 225
Celegene Collaborative Arrangement | Convertible preferred stock (Series B-1)
Related Party Transaction [Line Items]
Issuances of convertible preferred stock (in shares)		10,448,100
Issuances of convertible preferred stock		$ 36.1
Celgene Collaboration Agreement | Celgene Corporation | Common Stock | IPO
Related Party Transaction [Line Items]
Stock converted upon completion of IPO (in shares)	2,831,463
Celgene Collaboration Agreement | Celgene Corporation | Common Stock | IPO | Affiliated Entity
Related Party Transaction [Line Items]
Sale of stock, number of shares issued (in shares)	625,000
Sale of stock, price per share (USD per share)	$ 16
Proceeds from IPO, net of discounts, commissions, and other offering expenses	$ 10
Celgene Collaboration Agreement | Celegene Collaborative Arrangement | Celgene Corporation
Related Party Transaction [Line Items]
Non-refundable upfront payment received for research agreement		$ 225
Celgene Collaboration Agreement | Celegene Collaborative Arrangement | Celgene Corporation | Convertible preferred stock (Series B-1)
Related Party Transaction [Line Items]
Issuances of convertible preferred stock (in shares)		10,448,100
Issuances of convertible preferred stock		$ 36.1

Corporate Headquarters Lease -

Corporate Headquarters Lease - Narrative (Details) ft² in Thousands, $ in Millions	1 Months Ended	3 Months Ended		6 Months Ended
	Nov. 30, 2016USD ($)ft²consecutive_extension_period	Jun. 30, 2019USD ($)	Jun. 30, 2018USD ($)	Jun. 30, 2019USD ($)
Leases [Abstract]
Lease space occupied (in square feet) | ft²	51
Number of consecutive extension periods | consecutive_extension_period	1
Renewal term	5 years
Renewal notice period	12 months
Security deposit in form of letter of credit	$ 1.3
Tenant improvement allowance	$ 0.5
Discount rate		8.00%		8.00%
Operating lease expense		$ 1		$ 2.1
Remaining lease term				5 years 9 months
Rent expense			$ 1	$ 2

Corporate Headquarters Lease _2

Corporate Headquarters Lease - Future Minimum Lease Payments - ASC 842 (Details) $ in Thousands	Jun. 30, 2019USD ($)
Leases [Abstract]
Remainder of 2019	$ 2,140
2020	4,380
2021	4,505
2022	4,633
2023	4,764
2024 and thereafter	6,143
Total remaining minimum rental payments	26,565
Less: effect of discounting	(5,457)
Total lease liability	$ 21,108

Corporate Headquarters Lease _3

Corporate Headquarters Lease - Future Minimum Lease Payments - ASC 840 (Details) $ in Thousands	Dec. 31, 2018USD ($)
Leases [Abstract]
2019	$ 4,260
2020	4,380
2021	4,505
2022	4,633
2023	4,764
2024 and thereafter	6,142
Total future minimum lease payments	$ 28,684

Net Loss per Share (Details)

Net Loss per Share (Details) - shares shares in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of net loss per share (in shares)	6,445	5,779	6,095	5,836
Outstanding stock options
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of net loss per share (in shares)	5,792	5,769	5,387	5,824
Unvested RSAs
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of net loss per share (in shares)	4	10	5	12
Unvested RSUs
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of net loss per share (in shares)	649	0	703	0

Subsequent Events (Details)

Subsequent Events (Details) - Celegene Collaborative Arrangement - USD ($) $ in Millions	Jul. 22, 2019	Jul. 31, 2019	Jul. 31, 2016
Subsequent Event [Line Items]
Non-refundable upfront payment received for research agreement			$ 225
Subsequent Event
Subsequent Event [Line Items]
Non-refundable upfront payment received for research agreement		$ 50
Aggregate revenue for clinical and regulatory milestones	$ 180
Aggregate revenue for sales milestones	$ 300

Uncategorized Items - jnce-2019

Label	Element	Value
Accounting Standards Update 2014-09 [Member]
Cumulative Effect of New Accounting Principle in Period of Adoption	us-gaap_CumulativeEffectOfNewAccountingPrincipleInPeriodOfAdoption	$ (46,913,000)
Accounting Standards Update 2014-09 [Member] | Retained Earnings [Member]
Cumulative Effect of New Accounting Principle in Period of Adoption	us-gaap_CumulativeEffectOfNewAccountingPrincipleInPeriodOfAdoption	(46,913,000)
Accounting Standards Update 2016-02 [Member]
Cumulative Effect of New Accounting Principle in Period of Adoption	us-gaap_CumulativeEffectOfNewAccountingPrincipleInPeriodOfAdoption	(75,000)
Accounting Standards Update 2016-02 [Member] | Retained Earnings [Member]
Cumulative Effect of New Accounting Principle in Period of Adoption	us-gaap_CumulativeEffectOfNewAccountingPrincipleInPeriodOfAdoption	$ (75,000)