Jounce Therapeutics (JNCE) 10-K 25 Feb 21 2020 FY Annual report Financial data

Cover

Cover - USD ($)	12 Months Ended
	Dec. 31, 2020	Feb. 19, 2021	Jun. 30, 2020
Cover [Abstract]
Document Type	10-K
Document Annual Report	true
Document Period End Date	Dec. 31, 2020
Current Fiscal Year End Date	--12-31
Document Transition Report	false
Entity File Number	001-37998
Entity Registrant Name	JOUNCE THERAPEUTICS, INC.
Entity Incorporation, State or Country Code	DE
Entity Tax Identification Number	45-4870634
Entity Address, Address Line One	780 Memorial Drive
Entity Address, State or Province	MA
Entity Address, City or Town	Cambridge,
Entity Address, Postal Zip Code	02139
City Area Code	857
Local Phone Number	259‑3840
Title of 12(b) Security	Common Stock, $0.001 par value per share
Trading Symbol	JNCE
Security Exchange Name	NASDAQ
Entity Well-known Seasoned Issuer	No
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Accelerated Filer
Entity Small Business	true
Entity Emerging Growth Company	true
Entity Ex Transition Period	true
ICFR Auditor Attestation Flag	false
Entity Shell Company	false
Entity Public Float			$ 117,863,213
Entity Common Stock, Shares Outstanding		45,393,561
Documents Incorporated by Reference	Documents Incorporated by Reference Portions of the registrant’s Definitive Proxy Statement on Schedule 14A relating to its 2021 Annual Meeting of Stockholders to be filed within 120 days of the end of the registrant’s fiscal year ended December 31, 2020 are incorporated by reference into Part III of this Annual Report on Form 10-K to the extent stated herein.
Entity Central Index Key	0001640455
Document Fiscal Year Focus	2020
Document Fiscal Period Focus	FY
Amendment Flag	false

Consolidated Balance Sheets

Consolidated Balance Sheets - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Current assets:
Cash and cash equivalents	$ 147,493	$ 53,241
Short-term investments	58,985	115,602
Prepaid expenses and other current assets	4,913	4,854
Total current assets	211,391	173,697
Property and equipment, net	7,336	10,672
Long-term investments	6,710	1,601
Operating lease right-of-use asset	14,856	17,615
Other non-current assets	3,943	2,297
Total assets	244,236	205,882
Current liabilities:
Accounts payable	2,036	2,460
Accrued expenses	12,044	8,907
Deferred revenue, current—related party	1,931	0
Operating lease liability, current	3,271	2,901
Other current liabilities	42	132
Total current liabilities	19,324	14,400
Operating lease liability, net of current portion	13,618	16,889
Total liabilities	32,942	31,289
Commitments and contingencies (Note 13)
Stockholders’ equity:
Preferred stock, $0.001 par value: 5,000 shares authorized at December 31, 2020 and 2019; no shares issued or outstanding at December 31, 2020 and 2019	0	0
Common stock, $0.001 par value: 160,000 shares authorized at December 31, 2020 and 2019; 41,729 and 33,738 shares issued at December 31, 2020 and 2019, respectively; 41,729 and 33,738 shares outstanding at December 31, 2020 and 2019, respectively	42	34
Additional paid-in capital	362,270	281,664
Accumulated other comprehensive (loss) income	(17)	54
Accumulated deficit	(151,001)	(107,159)
Total stockholders’ equity	211,294	174,593
Total liabilities and stockholders’ equity	$ 244,236	$ 205,882

Consolidated Balance Sheets (Pa

Consolidated Balance Sheets (Parenthetical) - $ / shares	Dec. 31, 2020	Dec. 31, 2019
Statement of Financial Position [Abstract]
Preferred stock, par value (in dollars per share)	$ 0.001	$ 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, par value (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)	41,729,000	33,738,000
Common stock, shares outstanding (in shares)	41,729,000	33,738,000

Consolidated Statements of Oper

Consolidated Statements of Operations - USD ($) shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Revenue:
License and collaboration revenue—related party	$ 62,339	$ 147,872
Operating expenses:
Research and development	78,690	67,135
General and administrative	28,766	27,920
Total operating expenses	107,456	95,055
Operating (loss) income	(45,117)	52,817
Other income, net	1,289	4,052
(Loss) income before provision for income taxes	(43,828)	56,869
Provision for income taxes	14	46
Net (loss) income	$ (43,842)	$ 56,823
Net income (loss) per share, basic (in dollars per share)	$ (1.24)	$ 1.72
Net income (loss) per share, diluted (in dollars per share)	$ (1.24)	$ 1.66
Weighted-average common shares outstanding, basic (in shares)	35,426	33,080
Weighted-average common shares outstanding, diluted (in shares)	35,426	34,294
Comprehensive (loss) income:
Net (loss) income	$ (43,842)	$ 56,823
Other comprehensive income:
Unrealized gain on available-for-sale securities	(71)	132
Comprehensive (loss) income	$ (43,913)	$ 56,955

Consolidated Statements of Stoc

Consolidated Statements of Stockholders’ Equity - USD ($) $ in Thousands	Total	Gilead Stock Purchase Agreement	Cumulative Effect, Period of Adoption, Adjustment	Common Stock	Common StockGilead Stock Purchase Agreement	Additional Paid-In Capital	Additional Paid-In CapitalGilead Stock Purchase Agreement	Accumulated Other Comprehensive (Loss) Income	Accumulated Deficit	Accumulated DeficitCumulative Effect, Period of Adoption, Adjustment
Beginning balance, common stock (in shares) at Dec. 31, 2018				32,941,000
Beginning balance at Dec. 31, 2018	$ 104,129		$ (75)	$ 33		$ 268,081		$ (78)	$ (163,907)	$ (75)
Issuance of common stock (in shares)				448,000
Issuance of common stock	$ 3,511			$ 1		3,510
Exercise of stock options (in shares)	185,000
Exercise of stock options	$ 437			$ 0		437
Vesting of restricted stock awards and restricted stock units (in shares)				164,000
Vesting of restricted stock awards and restricted stock units	27					27
Stock-based compensation expense	9,609					9,609
Other comprehensive income (loss)	$ 132							132
Accounting Standards Update [Extensible List]	us-gaap:AccountingStandardsUpdate201602Member
Net (loss) income	$ 56,823								56,823
Ending balance, common stock (in shares) at Dec. 31, 2019	33,738,000			33,738,000
Ending balance at Dec. 31, 2019	$ 174,593			$ 34		281,664		54	(107,159)
Issuance of common stock (in shares)				2,074,000	5,540,000
Issuance of common stock	$ 14,513	$ 55,730		$ 2	$ 6	14,511	$ 55,724
Exercise of stock options (in shares)	128,000			128,000
Exercise of stock options	$ 600					600
Vesting of restricted stock awards and restricted stock units (in shares)				249,000
Vesting of restricted stock awards and restricted stock units	0					0
Stock-based compensation expense	9,771					9,771
Other comprehensive income (loss)	(71)							(71)
Net (loss) income	$ (43,842)								(43,842)
Ending balance, common stock (in shares) at Dec. 31, 2020	41,729,000			41,729,000
Ending balance at Dec. 31, 2020	$ 211,294			$ 42		$ 362,270		$ (17)	$ (151,001)

Consolidated Statements of Cash

Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Operating activities:
Net (loss) income	$ (43,842)	$ 56,823
Adjustments to reconcile net (loss) income to net cash used in operating activities:
Stock-based compensation expense	9,771	9,609
Depreciation expense	3,401	3,851
Net amortization of premiums and discounts on investments	47	(1,480)
Changes in operating assets and liabilities:
Prepaid expenses and other current assets	(236)	(1,375)
Other non-current assets	(1,469)	(728)
Accounts payable	(296)	(944)
Accrued expenses and other current liabilities	3,047	1,983
Deferred revenue—related party	1,931	(97,872)
Other liabilities	(142)	4
Net cash used in operating activities	(27,788)	(30,129)
Investing activities:
Purchases of investments	(85,895)	(188,999)
Proceeds from maturities of investments	137,287	221,366
Purchases of property and equipment	(94)	(985)
Net cash provided by investing activities	51,298	31,382
Financing activities:
Proceeds from issuance of common stock	14,412	3,645
Proceeds from exercise of stock options	600	437
Net cash provided by financing activities	70,742	4,082
Net increase in cash, cash equivalents and restricted cash	94,252	5,335
Cash, cash equivalents and restricted cash, beginning of period	54,511	49,176
Cash, cash equivalents and restricted cash, end of period	148,763	54,511
Non-cash investing and financing activities:
Purchases of property and equipment in accounts payable and accrued expenses	0	29
Issuance costs in accounts payable and accrued expenses	33	134
Discount on common stock issued under a stock purchase agreement	(20,730)	0
Supplemental cash flow information:
Cash paid for lease liabilities	4,024	4,270
Cash paid for income taxes	45	101
Gilead Stock Purchase Agreement
Financing activities:
Proceeds from issuance of common stock	$ 55,730	$ 0

Nature of Business

Nature of Business	12 Months Ended
	Dec. 31, 2020
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 through a biomarker-driven approach. 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 December 31, 2020, the Company had cash, cash equivalents, and investments of $213.2 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 February 25, 2021, the filing date of this Annual Report on Form 10-K. 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	12 Months Ended
	Dec. 31, 2020
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 consolidated financial statements 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”). These 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. Segment Information Operating segments are defined as components of an enterprise about which separate discrete information is available for evaluation by the chief operating decision-maker in deciding how to allocate resources and assess performance. The Company and the Company’s chief operating decision maker, the Company’s chief executive officer, views the Company’s operations and manages its business as a single operating segment. The Company operates only in the United States. 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 Gilead License Agreement and Celgene Collaboration Agreement (including estimates of standalone selling prices of each performance obligation and internal and external costs expected to be incurred to satisfy performance obligations), accrued expenses, stock-based compensation expense and income taxes. In addition, in 2019, the Company made estimates to determine the discount rate utilized in the initial application of ASC Topic 842, Leases (“ASC 842”). 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. Fair Value of Financial Instruments ASC Topic 820, Fair Value Measurement (“ASC 820”) establishes a fair value hierarchy for instruments measured at fair value that distinguishes between assumptions based on market data (observable inputs) and the Company’s own assumptions (unobservable inputs). Observable inputs are inputs that market participants would use in pricing the asset or liability based on market data obtained from sources independent of the Company. Unobservable inputs are inputs that reflect the Company’s assumptions about the inputs that market participants would use in pricing the asset or liability and are developed based on the best information available in the circumstances. ASC 820 identifies fair value as the exchange price, or exit price, representing the amount that would be received to sell an asset or paid to transfer a liability in an orderly transaction between market participants. As a basis for considering market participant assumptions in fair value measurements, ASC 820 establishes a three-tier fair value hierarchy that distinguishes between the following: • Level 1 inputs are quoted prices (unadjusted) in active markets for identical assets or liabilities. • Level 2 inputs are inputs other than quoted prices included within Level 1 that are observable for the asset or liability, either directly or indirectly. • Level 3 inputs are unobservable inputs that reflect the Company’s own assumptions about the assumptions market participants would use in pricing the asset or liability. Financial assets and liabilities are classified in their entirety based on the lowest level of input that is significant to the fair value measurement. To the extent that the valuation is based on models or inputs that are less observable or unobservable in the market, the determination of fair value requires more judgment. Accordingly, the degree of judgment exercised by the Company in determining fair value is greatest for instruments categorized in Level 3. A financial instrument’s level within the fair value hierarchy is based on the lowest level of any input that is significant to the fair value measurement. Cash Equivalents Cash equivalents are highly-liquid investments that are readily convertible into cash with original maturities of three months or less when purchased. These assets include investment in money market funds that invests in U.S. Treasury obligations. 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. Property and Equipment Property and equipment is recorded at cost and consists of laboratory equipment, furniture and office equipment, computer equipment, leasehold improvements. The Company capitalizes property and equipment that is acquired for research and development activities and that has alternate future use. Expenditures for maintenance and repairs are recorded to expense as incurred, whereas major betterments are capitalized as additions to property and equipment. Leasehold improvements are depreciated over the lesser of their useful life or the term of the lease. Depreciation is calculated over the estimated useful lives of the assets using the straight-line method. Impairment of Long-lived Assets The Company reviews its property and equipment whenever events or changes in circumstances indicate that the carrying value of certain assets might not be recoverable and recognizes an impairment loss when it is probable that an asset’s realizable value is less than the carrying value. Leases Effective January 1, 2019, the Company adopted ASC 842. 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, although separation of lease and non-lease components is required under ASC 842, the Company elected a practical expedient to not separate lease and non-lease components and rather accounts for lease and non-lease components together as a single lease component. At the inception of an arrangement, the Company determines whether the arrangement is or contains a lease based on the unique facts and circumstances present in the arrangement. Leases with a term greater than one year are recognized on the balance sheet as right-of-use assets and short-term and long-term lease liabilities, as applicable. The Company does not recognize leases with terms of one year or less on the balance sheet. Options to renew a lease are not included in the Company’s initial lease term assessment unless there is reasonable certainty that the Company will renew. The Company monitors its plans to renew its material leases on a quarterly basis. Operating lease liabilities and their corresponding right-of-use assets are recorded based on the present value of lease payments over the expected remaining lease term. Certain adjustments to the right-of-use asset may be required for items such as incentives received. The interest rate implicit in lease contracts is typically not readily determinable. As a result, the Company utilizes its incremental borrowing rate (“IBR”), which reflects the fixed rate at which the Company could borrow on a collateralized basis the amount of the lease payments in the same currency, for a similar term, and in a similar economic environment. The Company subsequently measures its lease liability at the present value of remaining lease payments, discounted using the IBR 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. Revenue Recognition The Company recognizes revenue in accordance with ASC Topic 606, Revenue from Contracts with Customers (“ASC 606”). Under ASC 606, an entity recognizes revenue when its customer obtains control of promised goods or services, in an amount that reflects the consideration that the entity expects to receive in exchange for those goods or services. In applying ASC 606, the Company performs the following five steps: (i) identify the contract(s) with a customer; (ii) identify the promises and performance obligations in the contract; (iii) determine the transaction price; (iv) allocate the transaction price to the performance obligations in the contract; and (v) recognize revenue when (or as) the Company satisfies the performance obligations. The Company only applies the five-step model to contracts when it is probable that it will collect the consideration to which it is entitled in exchange for the goods or services it transfers to the customer. At contract inception, once the contract is determined to be within the scope of ASC 606, the Company assesses the goods or services promised within each contract, determines those that are performance obligations and assesses whether each promised good or service is distinct. The Company then recognizes as revenue the amount of the transaction price that is allocated to the respective performance obligation when (or as) the performance obligation is satisfied. As part of the assessment, the Company must develop assumptions that require judgment to determine the standalone selling price for each performance obligation identified in the contract. The Company uses key assumptions to determine the standalone selling price, which may include reimbursement rates for personnel costs, development timelines and probabilities of regulatory success. The Company does not assess whether a contract has a significant financing component if the expectation at contract inception is that the period between payment by the customer and the transfer of promised goods or services to the customer will be one year or less. Arrangements that include upfront payments may require deferral of revenue recognition to a future period until obligations under these arrangements are fulfilled. The event-based milestone payments represent variable consideration, and the Company uses the “most likely amount” method to estimate this variable consideration. Given the high degree of uncertainty around the occurrence of these events, the Company determined the milestone and other contingent amounts to be fully constrained until the uncertainty associated with these payments is resolved. Revenue will be recognized from sales-based royalty payments when or as the sales occur. The Company will re-evaluate the transaction price in each reporting period as uncertain events are resolved and other changes in circumstances occur. See Note 3, “License and Collaboration Revenue”, for further information on the Company’s application of ASC 606. Research and Development Expenses Expenditures relating to research and development are expensed as incurred. Research and development expenses include external expenses incurred under arrangements with third parties, academic and non-profit institutions and consultants; salaries and personnel-related costs, including non-cash stock-based compensation expense; license fees to acquire in-process technology and other expenses, which include direct and allocated expenses for laboratory, facilities and other costs. Non‑refundable advance payments for goods and services that will be used in future research and development activities are expensed when the activity has been performed or when the goods have been received rather than when the payment is made. As part of the process of preparing the consolidated financial statements, the Company is required to estimate its accrued research and development expenses as of each balance sheet date. In accruing service fees, the Company estimates the time period over which services will be performed and the level of effort to be expended in each period. This process involves reviewing open contracts and purchase orders, communicating with internal personnel to identify services that have been performed on the Company’s behalf and estimating the level of service performed and the associated cost incurred for the service when the Company has not yet been invoiced or otherwise notified of the actual cost. The Company periodically confirms the accuracy of its estimates with its service providers and makes adjustments if necessary. The majority of the Company’s service providers invoice monthly in arrears for services performed or when contractual milestones are met. The financial terms of agreements with these service providers are subject to negotiation, vary from contract-to-contract and may result in uneven payment flows. In circumstances where amounts have been paid in excess of costs incurred, the Company records a prepaid expense. Intellectual Property Expenses The Company expenses costs associated with intellectual property-related matters as incurred and classifies such costs as general and administrative expenses within the consolidated statements of operations and comprehensive (loss) income. Stock-based Compensation The Company accounts for stock-based payments in accordance with ASC Topic 718, Compensation—Stock Compensation . This guidance requires all stock-based payments to employees, including grants of employee stock options, restricted stock awards (“RSAs”) and restricted stock units (“RSUs”), to be recognized as expense in the consolidated statements of operations and comprehensive (loss) income based on their grant date fair values. For stock options granted to employees and to members of the Company’s board of directors for their services on the board of directors, the Company estimates the grant date fair value of each stock option using the Black-Scholes option-pricing model. For RSUs and RSAs granted to employees, the Company estimates the grant date fair value of each award using intrinsic value, which is based on the value of the underlying common stock less any purchase price. For stock-based payments subject to service-based vesting conditions, the Company recognizes stock-based compensation expense equal to the grant date fair value of stock-based payment on a straight-line basis over the requisite service period. The Black‑Scholes option pricing model requires the input of certain subjective assumptions, including (i) the calculation of expected term of the stock-based payment, (ii) the risk‑free interest rate, (iii) the expected stock price volatility and (iv) the expected dividend yield. The Company uses the simplified method as proscribed by SEC Staff Accounting Bulletin No. 107 to calculate the expected term for stock options granted to employees as the Company does not have sufficient historical exercise data to provide a reasonable basis upon which to estimate the expected term. The Company determines the risk‑free interest rate based on a treasury instrument whose term is consistent with the expected term of the stock options. Because there had been no public market for the Company’s common stock prior to the Company’s initial public offering (“IPO”), there is a lack of Company‑specific historical and implied volatility data. Accordingly, the Company bases its estimates of expected volatility on the historical volatility of a group of publicly-traded companies with similar characteristics to itself, including stage of product development and therapeutic focus within the life sciences industry. Historical volatility is calculated over a period of time commensurate with the expected term of the stock-based payment. The Company uses an assumed dividend yield of zero as the Company has never paid dividends on its common stock, nor does it expect to pay dividends on its common stock in the foreseeable future. The Company accounts for forfeitures of all stock-based payments when such forfeitures occur. Income Taxes Income taxes are recorded in accordance with ASC Topic 740, Income Taxes , which provides for deferred taxes using an asset and liability approach. The Company recognizes deferred tax assets and liabilities for the expected future tax consequences of events that have been included in the consolidated financial statements or tax returns. Deferred tax assets and liabilities are determined based on the difference between the financial statement and tax bases of assets and liabilities using enacted tax rates in effect for the year in which the differences are expected to reverse. A valuation allowance against deferred tax assets is recorded if, based on the weight of the available evidence, it is more likely than not that some or all of the deferred tax assets will not be realized. The Company accounts for uncertain tax positions using a more-likely-than-not threshold for recognizing and resolving uncertain tax positions. The evaluation of uncertain tax positions is based on factors, including, but not limited to, changes in the law, the measurement of tax positions taken or expected to be taken in tax returns, the effective settlement of matters subject to audit, new audit activity and changes in facts or circumstances related to a tax position. Comprehensive (Loss) Income Comprehensive (loss) income is comprised of net (loss) income and other comprehensive income. Other comprehensive income for all periods presented consists solely of unrealized gains on available-for-sale securities. Net (Loss) Income per Share Basic net (loss) income per share is calculated based upon the weighted-average number of common shares outstanding during the period, excluding outstanding stock options and RSAs and RSUs that have been issued but are not yet vested. Diluted net (loss) income per share is calculated based upon the weighted-average number of common shares outstanding during the period plus the dilutive impact of weighted-average common equivalent shares outstanding during the period. The potentially dilutive shares of common stock resulting from the assumed exercise of outstanding stock options and the assumed vesting of RSAs and RSUs are determined under the treasury stock method. Concentrations of Credit Risk and Off-Balance Sheet Risk Financial instruments that potentially expose the Company to concentrations of credit risk primarily consist of cash, cash equivalents and investments. The Company maintains its cash and cash equivalent balances with high-quality financial institutions and, consequently, the Company believes that such funds are subject to minimal credit risk. The Company’s cash equivalents and investments are comprised of money market funds that are invested in U.S. Treasury obligations, corporate debt securities, U.S. Treasury obligations and government agency securities. Credit risk in these securities is reduced as a result of the Company’s investment policy to limit the amount invested in any single issuer and to only invest in securities of a high credit quality. The Company has no significant off-balance sheet risk such as foreign exchange contracts, option contracts or other foreign hedging arrangements. Recently Adopted Accounting Pronouncements In August 2018, the FASB issued Accounting Standards Updates (“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 became effective for fiscal years beginning after December 15, 2019, including interim periods within those fiscal years. Accordingly, the Company adopted ASU 2018-13 effective January 1, 2020, and there was no impact to the condensed consolidated financial statements due to the adoption of this guidance. In August 2018, the FASB issued ASU 2018-15, Intangibles—Goodwill and Other—Internal-Use Software (Subtopic 350-40): Customer’s Accounting for Implementation Costs Incurred in a Cloud Computing Arrangement That Is a Service Contract . This guidance aligns the requirements for capitalizing implementation costs incurred in a hosting arrangement that is a service contract with the requirements for capitalizing implementation costs incurred to develop or obtain internal-use software (and hosting arrangements that include an internal-use software license). The accounting for the service element of a hosting arrangement that is a service contract is not affected. This guidance became effective for fiscal years beginning after December 15, 2019, including interim periods within those fiscal years. The amendments in this update are able to be applied either retrospectively or prospectively to all implementation costs incurred after the date of adoption. Accordingly, the Company adopted ASU 2018-15 effective January 1, 2020, and it elected to apply this guidance on a prospective basis. There was no impact to the condensed consolidated financial statements due to 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 60 6, 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 became effective for fiscal years beginning after December 15, 2019, including interim periods within those fiscal years. Accordingly, the Company adopted ASU 2018-18 effective January 1, 2020, and there was no impact to the condensed consolidated financial statements due to the adoption of this guidance. In December 2019, the FASB issued ASU 2019-12, Income Taxes (Topic 740): Simplifying the Accounting for Income Taxes , which eliminates certain exceptions to the guidance in ASC 740 related to the approach for intraperiod tax allocation, the methodology for calculating income taxes in an interim period and the recognition of deferred tax liabilities when investment ownership changes. In addition, ASU 2019-12 simplifies the accounting for the interim period effects of changes in tax laws or rates and transactions that result in a step-up in the tax basis of goodwill. While this guidance is effective for fiscal years beginning after December 15, 2020, including interim periods within those fiscal years, early adoption is permitted. Consequently, the Company elected to early adopt ASU 2019-12 effective January 1, 2020. Due to the adoption of this guidance, the Company did not record an intraperiod tax allocation to other comprehensive income for the three months ended March 31, 2020. In accordance with ASU 2019-12, the Company has applied the new provisions related to the intraperiod tax allocation on a prospective basis. Recent Accounting Pronouncements, Not Yet Adopted In June 2016, the FASB issued ASU 2016-13, Financial 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 expected credit losses, this standard now requires allowances to be recorded instead of reducing the amortized cost of the investment. This guidance was originally effective for annual reporting periods beginning after December 15, 2019, including interim periods within those annual reporting periods, and early adoption was permitted. In November 2019, the FASB subsequently issued ASU 2019-10, Financial Instruments—Credit Losses (Topic 326), Derivatives and Hedging (Topic 815), and Leases (Topic 842): Effective Dates , whereby the effective date of this standard for smaller reporting companies was deferred to annual reporting periods beginning after December 15, 2022, including interim periods within those annual reporting periods, and early adoption is still permitted. Accordingly, the Company will now adopt this standard effective January 1, 2023, and it is currently evaluating the potential impact that ASU 2016-13 may have on the consolidated financial statements.

License and Collaboration Reven

License and Collaboration Revenue	12 Months Ended
	Dec. 31, 2020
Revenue from Contract with Customer [Abstract]
Celgene Collaboration Agreement	License and Collaboration Revenue Gilead License Agreement On August 31, 2020, the Company and Gilead entered into an exclusive license agreement (the “Gilead License Agreement”) to license the Company’s JTX-1811 program to Gilead. Concurrently with the license agreement, the Company and Gilead entered into a stock purchase agreement (the “Stock Purchase Agreement”) and a registration rights agreement (the “Registration Rights Agreement”, and together with the License Agreement and the Stock Purchase Agreement, the “Transaction Agreements”). The transactions with Gilead were subject to review under the Hart-Scott Rodino Antitrust Improvements Act of 1976 and other customary closing conditions, and became effective on October 16, 2020, the closing date of the agreement. Pursuant to the Gilead License Agreement, the Company granted to Gilead a worldwide and exclusive license to develop, manufacture and commercialize JTX-1811 and certain derivatives thereof (the “Licensed Products”). Gilead paid the Company a one-time, non-refundable upfront payment of $85.0 million in October 2020. The Company will continue to develop JTX-1811 during the initial development term, which includes conducting activities defined within the agreement to advance JTX-1811 through the clearance of an IND application or an earlier date specified by Gilead, at which time the program will be transitioned to Gilead. Milestone and Royalties The Company is entitled to receive payments from Gilead upon the achievement of specified clinical, regulatory and sales milestones, including potential clinical development and regulatory milestone payments up to an aggregate total of $510.0 million and potential sales milestone payments up to an aggregate total of $175.0 million. The Company is also eligible to receive tiered royalty payments based on a percentage of annual worldwide net sales ranging from the high-single digits to mid-teens, based on future annual net sales of the Licensed Products, on a Licensed Product-by-Licensed Product and country-by-country basis. Termination Gilead may terminate the License Agreement for convenience, in its sole discretion, in its entirety or on a Licensed Product-by-Licensed Product or region-by-region basis, at any time with prior written notice to the Company. Unless terminated earlier in accordance with its terms, the Gilead License Agreement provides that it will expire (i) on an Licensed Product-by-Licensed Product and country-by-country basis on the date of the expiration of the royalty term with respect to such Licensed Product in such country and (ii) in its entirety upon the expiration of all applicable royalty terms with respect to the Licensed Products in all countries, following which the applicable licenses under the License Agreement will become fully paid-up, perpetual, irrevocable and royalty-free. Accounting Analysis Identification of the Contract(s) The Company assessed the Gilead License Agreement and concluded that it represents a contract with a customer within the scope of ASC 606, Revenue from Contracts with Customers . In addition, the Company determined that the Gilead License Agreement and Stock Purchase Agreement should be evaluated as a combined contract in accordance with ASC 606 given that the agreements were executed contemporaneously, negotiated as a package and have the same commercial objective to provide funding to further the Company’s research and development activities. Identification of Promises and Performance Obligations The Company determined that the Gilead License Agreement contains the following promises: (i) delivery of a worldwide and exclusive license to develop, manufacture and commercialize JTX-1811 (the “JTX-1811 License”), (ii) provision of certain research transition activities, specifically outlined within the Gilead License Agreement, related to the advancement of JTX-1811 through the clearance of an IND application and transition of the JTX-1811 program to Gilead (the “Research and Transition Services”), (iii) appointment of an individual to act as an alliance manager and primary point of contact for Gilead, (iv) appointment of individuals to participate on the Joint Steering Committee (“JSC”), and (v) optional assistance by Jounce after completion of Research and Transition Services upon the request of Gilead. The Company assessed the above promises and concluded that each of the JTX-1811 License and Research and Transition Services is capable of being distinct and distinct within the context of the Gilead License Agreement. Based upon this evaluation, the Company concluded that its promise to deliver the JTX-1811 License and promise to perform Research and Transition Services represent separate performance obligations in the Gilead License Agreement. The Company determined that the appointment of an individual to act as an alliance manager and primary point of contact for Gilead, participation in alliance management meetings and the appointment of individuals to participate on the JSC do not constitute the transfer of a good or service to Gilead and as such, do not represent performance obligations under the contract. Finally, the Company assessed Gilead’s ability to request optional assistance by Jounce after completion of Research and Transition Services and determined that it was both quantitatively and qualitatively immaterial in the context of the Gilead License Agreement. Accordingly, the Company did not assess the optional assistance as a performance obligation. Determination of Transaction Price As noted above, the Company received a non-refundable upfront payment of $85.0 million upon the execution of the Gilead License Agreement. This upfront payment represents an element of fixed consideration under the Gilead License Agreement. The Company also evaluated as possible variable consideration the milestones and royalties discussed above. With respect to clinical development and regulatory milestones, based upon the high degree of uncertainty and risk associated with these potential payments, the Company concluded that all such amounts should be fully constrained and are not included in the initial transaction price. As part of the evaluation of the constraint the Company considered certain factors, including that receipt of such milestones is outside the control of the Company and the probability of success criteria is estimated. Each of these variable consideration items was evaluated under the most-likely amount method. As for royalties and sales milestones, the Company determined that the royalties and milestones relate solely to the JTX-1811 License, which is a license of intellectual property (“IP”). Accordingly, the Company did not include any potential royalty or sales milestone amounts in the initial transaction price, and the Company will not recognize revenue related to these royalties and sales milestones until the associated sales occur and relevant thresholds are met. The Company assessed proceeds of $35.0 million received under the Stock Purchase Agreement and determined that the fair value of the equity component was $55.7 million based on the closing price of $10.06 per share on October 16, 2020. Pursuant to the agreement, the Company sold 5,539,727 shares of common stock for aggregate cash consideration of $35.0 million, or $6.32 per share, which is equal to the daily volume weighted average per share intraday price of the Common Stock on Nasdaq over the 30-trading day period ending on and including August 28, 2020 plus a 30% premium. As a result, the Company determined that the gross proceeds of $35.0 million received under the Stock Purchase Agreement included a discount to the fair value of the Company’s stock as of October 16, 2020 equal to $20.7 million. In accordance with ASC 606, the discount amount will be included in the transaction price for revenue recognition, resulting in an initial transaction price of $64.3 million. Allocation of Transaction Price to Performance Obligations The Company allocated the transaction price to each performance obligation on a relative estimated standalone selling price basis. The Company developed the estimated standalone selling price for the JTX-1811 License based on the present value of expected future cash flows associated with the license and related clinical development and regulatory milestones. In developing such estimate, the Company applied judgement in determining the timing needed to develop the Licensed Product, the probability of success, and the discount rate. The Company developed the estimated standalone selling price for the Research and Transition Services obligation based on the nature of the services to be performed and the Company’s best estimate of the length of time required to perform the services necessary to achieve clearance of an IND application for the JTX-1811 program. Recognition of Revenue The Company determined that the JTX-1811 License is a functional license as the underlying IP has significant standalone functionality. In addition, the Company determined that the JTX-1811 License represents a right to use certain of the Company’s IP as it exists at a point in time. Finally, the Company determined that October 16, 2020 represents (i) the date at which the Company made available the IP to Gilead and (ii) the beginning of the period during which Gilead is able to use and benefit from its right to use the IP. Based upon these considerations, the Company recognized $60.8 million in revenue related to the JTX-1811 License performance obligation during the year ended December 31, 2020. Further, the Company determined the input method under ASC 606 is the most appropriate method of revenue recognition for the Research and Transition Services performance obligation. The method of measuring progress towards delivery of the services incorporated actual internal and external costs incurred, relative to total internal and external costs expected to be incurred to satisfy the performance obligation. The period over which total costs were estimated reflected the Company’s best estimate of the period over which it would perform the research and transition services to achieve clearance of an IND application of the JTX-1811 program and transition the program to Gilead. Based upon these considerations, the Company recognized $1.6 million in revenue related to the Research and Transition Services performance obligation during the year ended December 31, 2020. The following table provides a summary of the transaction price allocated to each performance obligation, in addition to revenue activity during the period (in thousands): Revenue Recognized - related party Deferred Revenue - related party Transaction Price Allocated Year Ended December 31, 2020 As of December 31, 2020 JTX-1811 License $ 60,776 $ 60,776 $ — Research and Transition Services 3,494 1,563 1,931 Totals $ 64,270 $ 62,339 $ 1,931 As of December 31, 2020, the remaining amount of the transaction price allocated to the Research and Transition Services that was unsatisfied is expected to be recognized in 2021 as services are performed. Celgene License Agreement On July 22, 2019, the Company entered into a License Agreement (the “Celgene License Agreement”) with Celgene Corporation (“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 July 22, 2019 that is specifically directed to the LILRB2 receptor (the “Licensed Compounds”), and Celgene paid the Company a one-time, non-refundable upfront payment of $50.0 million. As of November 2019, Celgene became a Bristol Myers Squibb company. As part of its Celgene integration process, Bristol Myers Squibb streamlined its pipeline to address areas of overlap. As a result, Celgene provided the Company with a notice of termination and the Celgene License Agreement was terminated effective June 3, 2020 (the “Celgene License Agreement Termination Date”). As of the Celgene License Agreement Termination Date, the Company has sole worldwide rights to JTX-8064, and all of the Company’s intellectual property rights pertaining to JTX-8064 and licensed to Celgene were reacquired by the Company. No party had any further financial or service obligations to one another beyond transition costs and efforts, which were completed during the year ended December 31, 2020. Accounting Analysis Identification of the Contract(s) The Company assessed the Celgene License Agreement and concluded that it represents a contract with a customer within the scope of ASC 606. Identification of Promises and Performance Obligations The Company determined that the Celgene License Agreement contained the following promises: (i) delivery of a worldwide and exclusive license to develop, manufacture and commercialize an Initial Licensed Compound and the Licensed Compounds (the “JTX-8064 License”) and (ii) provision of certain transition activities, specifically outlined within the Celgene License Agreement, related to the delivery of the JTX-8064 License (the “Transition Activities”). The Company also evaluated certain other optional activities outlined within the Celgene License Agreement and concluded that none conveyed a material right to Celgene. Accordingly, these options were not considered to be promises within the Celgene License Agreement. The Company assessed the above promises and concluded that the JTX-8064 License was both capable of being distinct and distinct within the context of the Celgene License Agreement. The Company also assessed its promise to perform the Transition Activities and concluded that it was both quantitatively and qualitatively immaterial in the context of the Celgene License Agreement. Accordingly, the Company did not assess the Transition Activities as a performance obligation. Based upon this evaluation, the Company concluded that its promise to deliver the JTX-8064 License represented the sole performance obligation in the Celgene License Agreement. Determination of Transaction Price As noted above, the Company received a non-refundable upfront payment of $50.0 million upon the execution of the Celgene License Agreement. This upfront payment represented an element of fixed consideration under the Celgene License Agreement. The Company also evaluated as possible variable consideration clinical, regulatory and sales milestone payments and royalties that the Company was eligible to receive under the Celgene License Agreement. With respect to clinical and regulatory milestones, based upon the high degree of uncertainty and risk associated with these potential payments, the Company concluded that all such amounts should be fully constrained and are not included in the initial transaction price. As for royalties and sales milestones, the Company determined that the royalties and milestones related solely to the JTX-8064 License, which is a license of intellectual property (“IP”). Accordingly, the Company did not include any potential royalty or sales milestone amounts in the initial transaction price, and the Company determined it would not recognize revenue related to these royalties and sales milestones until the associated sales occurred and relevant thresholds were met. Based upon the above considerations, the Company concluded that the initial transaction price associated with the Celgene License Agreement consisted solely of the upfront payment of $50.0 million. Allocation of Transaction Price to Performance Obligations As the Company’s promise to deliver the JTX-8064 License represented the sole performance obligation in the Celgene License Agreement, the entirety of the $50.0 million transaction price was allocated to this performance obligation. Recognition of Revenue The Company determined that the JTX-8064 License was a functional license as the underlying IP had significant standalone functionality. In addition, the Company determined that the JTX-8064 License represented a right to use certain of the Company’s IP as it existed at a point in time. Finally, the Company determined that July 22, 2019 represented (i) the date at which the Company made available the IP to Celgene and (ii) the beginning of the period during which Celgene was able to use and benefit from its right to use the IP. Based upon these considerations, the Company recognized $50.0 million of license revenue during the year ended December 31, 2019. As the upfront payment was non-refundable, the subsequent termination of the Celgene License Agreement had no impact on this revenue recognition. Up through the Celgene License Agreement Termination Date, the Company did not receive any milestone or royalty payments. Celgene Collaboration Agreement In July 2016, the Company entered into a Master Research and Collaboration Agreement (the “Celgene Collaboration Agreement”) with Celgene. The primary goal of the collaboration was 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, would have been a shared program to be used by both parties in and outside of the collaboration. The Company and Celgene terminated the Celgene Collaboration Agreement effective July 22, 2019. 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 IPO. If Celgene had elected to exercise any of the program options, Celgene would have been required to pay the Company an option-exercise fee that varied by program. The initial research term of the collaboration was four years, which could have been extended, at Celgene’s option, annually for up to three Worldwide Development Cost and U.S. Operating Profit and Loss Sharing Prior to Celgene exercising any of its options, the Company was responsible for all research and development activities under the Celgene Collaboration Agreement. Upon the exercise of each program option, the parties would have entered into a co-development and co-commercialization agreement (the “Co-Co Agreements”) or, in the case of JTX-4014, a license agreement (the “JTX-4014 License Agreement”) to govern the development and commercialization of the applicable program. As part of the Celgene Collaboration Agreement, the parties agreed to the terms of the Co-Co Agreements and the JTX-4014 License Agreement that would have been executed upon Celgene’s exercise of any option. Milestones and Royalties Under the Co-Co Agreements and the JTX-4014 License Agreement, Celgene would have been required to pay the Company for specified development, regulatory and commercial milestones, if achieved, across all collaboration programs. Development milestones were payable on the initiation of certain clinical trials, regulatory approval milestones were payable upon regulatory approval in the United States and outside the United States and commercial milestones were payable upon achievement of specified aggregate product sales outside the United States for each program. The Company was also eligible to receive royalties on product sales outside the United States. Accounting Analysis Identification of the Contract(s) The Company assessed the Celgene Collaboration Agreement and concluded that it represented 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 any had been executed, would have represented separate contracts apart from the Celgene Collaboration Agreement. Identification of Promises and Performance Obligations The Company determined that the Celgene Collaboration Agreement contained the following promises: (i) research and development services for vopratelimab (“Vopratelimab Research Services”), (ii) research and development services for 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 conveyed a material right to Celgene. Accordingly, neither the program options nor the research term extension options were 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 were both capable of being distinct and distinct within the context of the Celgene Collaboration Agreement. Therefore, the Company concluded that each of the Vopratelimab Research Services, JTX-4014 Research Services, Lead and Other Programs Research Services and Target Screening Services represented separate performance obligations. The Company determined that the Research Licenses were not distinct within the context of the Celgene Collaboration Agreement as the Research Licenses allowed 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 did not provide Celgene with any commercialization rights. Celgene could 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 were 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 were 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 were 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 it was both quantitatively and qualitatively immaterial in the context of the Celgene Collaboration Agreement. Accordingly, the Company did not assess 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 payment of $225.0 million upon the execution of the Celgene Collaboration Agreement. This upfront payment represented 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 represented variable consideration under the Celgene Collaboration Agreement as all such amounts were 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 any had been executed, would have represented 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 arose for reasons other than the provision of financing, and the difference between those amounts was proportional to the reason for the difference. Accordingly, the Company concluded that the upfront payment structure of the Celgene Collaboration Agreement did not result in the existence of a significant financing component. Based upon the above considerations, the Company concluded that the transaction price associated with the Celgene Collaboration Agreement consisted solely of the upfront payment of $225.0 million. Allocation of Transaction Price to Performance Obligations The Company 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 reflected 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 Prior to the termination of the Celgene Collaboration Agreement, the Company was recognizing revenue over time as the services related to each performance obligation were rendered. The Company concluded that an input method under ASC 606 was a representative depiction of the transfer of services under the Celgene Collaboration Agreement. The method of measuring progress towards delivery of the services incorporated 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 were estimated reflected the Company’s estimate of the period over which it would perform the research and development services to deliver a pre-defined data package to Celgene for each program subject to an option. The Company was recognizing 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 were recognized in the period of change as a cumulative catch-up adjustment.

Fair Value Measurements

Fair Value Measurements	12 Months Ended
	Dec. 31, 2020
Fair Value Disclosures [Abstract]
Fair Value Measurements	Fair Value Measurements 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 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 December 31, 2020 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 $ 147,492 $ 147,492 $ — $ — Investments: Corporate debt securities 63,691 — 63,691 — Government agency securities 2,005 — 2,005 — Totals $ 213,188 $ 147,492 $ 65,696 $ — Assets measured at fair value on a recurring basis as of December 31, 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 $ 50,242 $ 50,242 $ — $ — Investments: Corporate debt securities 48,300 — 48,300 — U.S. Treasuries 59,082 59,082 — — Government agency securities 12,820 — 12,820 — Totals $ 170,444 $ 109,324 $ 61,120 $ — There were no changes in valuation techniques during the years ended December 31, 2020 or 2019. There were no liabilities measured at fair value on a recurring basis as of December 31, 2020 or 2019.

Investments

Investments	12 Months Ended
	Dec. 31, 2020
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, short-term investments and long-term investments as of December 31, 2020 were comprised as follows (in thousands): December 31, 2020 Amortized Cost Unrealized Gains Unrealized Losses Fair Value Cash equivalents and short-term investments: Money market funds, included in cash equivalents $ 147,492 $ — $ — $ 147,492 Corporate debt securities 56,985 9 (13) 56,981 Government agency securities 2,001 4 — 2,005 Total cash equivalents and short-term investments 206,478 13 (13) 206,478 Long-term investments: Corporate debt securities 6,727 — (17) 6,710 Total long-term investments 6,727 — (17) 6,710 Total cash equivalents and investments $ 213,205 $ 13 $ (30) $ 213,188 Cash equivalents, short-term investments and long-term investments as of December 31, 2019 were comprised as follows (in thousands): December 31, 2019 Amortized Cost Unrealized Gains Unrealized Losses Fair Value Cash equivalents and short-term investments: Money market funds, included in cash equivalents $ 50,242 $ — $ — $ 50,242 Corporate debt securities 46,695 8 (4) 46,699 U.S. Treasuries 59,058 26 (2) 59,082 Government agency securities 12,796 24 — 12,820 Total cash equivalents and short-term investments 168,791 58 (6) 168,843 Long-term investments: Corporate debt securities 1,599 2 — 1,601 Total long-term investments 1,599 2 — 1,601 Total cash equivalents and investments $ 170,390 $ 60 $ (6) $ 170,444 As of December 31, 2020 and 2019, the aggregate fair value of securities that were in an unrealized loss position for less than twelve months was $28.3 million and $28.3 million, respectively. As of December 31, 2020 there were no securities that were in an unrealized loss position for more than twelve months. As of December 31, 2019, the aggregate fair value of securities that were in an unrealized loss position for more than twelve months was $2.0 million. As of December 31, 2020, 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 December 31, 2020. There were no realized gains and losses on available-for-sale securities during the year ended December 31, 2020 and 2019,

Restricted Cash

Restricted Cash	12 Months Ended
	Dec. 31, 2020
Cash and Cash Equivalents [Abstract]
Restricted Cash	Restricted Cash As of both December 31, 2020 and 2019, the Company maintained non-current restricted cash of $1.3 million. This amount is included within “Other non-current assets” in the accompanying 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 consolidated statements of cash flows (in thousands): Year Ended Year Ended Beginning of Period End of Period Beginning of Period End of Period Cash and cash equivalents $ 53,241 $ 147,493 $ 47,906 $ 53,241 Restricted cash 1,270 1,270 1,270 1,270 Cash, cash equivalents and restricted cash $ 54,511 $ 148,763 $ 49,176 $ 54,511

Property and Equipment, Net

Property and Equipment, Net	12 Months Ended
	Dec. 31, 2020
Property, Plant and Equipment [Abstract]
Property and Equipment, Net	Property and Equipment, Net Property and equipment, net as of December 31, 2020 and 2019 was comprised as follows (in thousands): Estimated Useful Life (in Years) December 31, 2020 2019 Laboratory equipment 5 $ 11,408 $ 11,374 Furniture and office equipment 4 1,071 1,071 Computer equipment 3 1,528 1,505 Leasehold improvements Shorter of useful life or remaining lease term 8,572 8,572 Total property and equipment, gross 22,579 22,522 Less: accumulated depreciation (15,243) (11,850) Total property and equipment, net $ 7,336 $ 10,672 Depreciation expense for the years ended December 31, 2020 and 2019 was $3.4 million and $3.9 million, respectively.

Accrued Expenses

Accrued Expenses	12 Months Ended
	Dec. 31, 2020
Payables and Accruals [Abstract]
Accrued Expenses	Accrued Expenses Accrued expenses as of December 31, 2020 and 2019 were comprised as follows (in thousands): December 31, 2020 2019 Employee compensation and benefits $ 6,825 $ 5,147 External research and professional services 4,855 3,639 Lab consumables and other 364 121 Total accrued expenses $ 12,044 $ 8,907

Common Stock and Preferred Stoc

Common Stock and Preferred Stock	12 Months Ended
	Dec. 31, 2020
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. On December 17, 2019, the Company entered into a Sales Agreement with Cowen and Company, LLC (“Cowen”) pursuant to which the Company may offer and sell shares of its common stock with an aggregate offering price of up to $50.0 million under an “at the market” offering program (the “ATM Offering”). The Sales Agreement provides that Cowen will be entitled to a sales commission equal to 3.0% of the gross sales price per share of all shares sold under the ATM Offering. The following table summarizes sales under the ATM Offering (net proceeds shown in thousands): For the year ended December 31, Shares Sold Net Proceeds Average Selling Price 2019 447,847 $ 3,510 $ 8.57 2020 2,074,274 14,513 $ 7.23 Total sales under the ATM Offering 2,522,121 $ 18,023 In January 2021, 3,156,200 shares were sold for net proceeds of $30.2 million. Consequently, the Company completed the sale of all available amounts under the ATM Offering (Note 16). Preferred Stock The Company is authorized to issue 5,000,000 shares of undesignated preferred stock in one or more series. As of December 31, 2020, no shares of preferred stock were issued or outstanding. Shares Reserved for Future Issuance As of December 31, 2020 and 2019, the Company had reserved for future issuance the following number of shares of common stock (in thousands): December 31, 2020 2019 Shares reserved for vesting of restricted stock awards — — Shares reserved for vesting of restricted stock units 588 460 Shares reserved for exercises of outstanding stock options 6,586 5,735 Shares reserved for future issuances under the 2017 Stock Option and Incentive Plan 1,284 1,288 Total shares reserved for future issuance 8,458 7,483

Stock-based Compensation

Stock-based Compensation	12 Months Ended
	Dec. 31, 2020
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, RSAs and 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 Company’s 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 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, 2019 and 2020, 1,317,935 and 1,349,526 additional shares, respectively, were automatically added to the shares authorized for issuance under the 2017 Plan. As of December 31, 2020, there were 1,283,871 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 Company’s 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, 2019 and 2020, 329,483 and 337,381 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 December 31, 2020. Stock-based Compensation Expense Total stock-based compensation expense recognized in the consolidated statements of operations and comprehensive (loss) income for the years ended December 31, 2020 and 2019 was as follows (in thousands): Year Ended December 31, 2020 2019 Research and development $ 4,242 $ 4,353 General and administrative 5,529 5,256 Total stock-based compensation expense $ 9,771 $ 9,609 RSU Activity The Company has also granted RSUs to its employees under the 2017 Plan. The following table summarizes RSU activity for the year ended December 31, 2020 (in thousands, except per share amounts): RSUs Weighted-Average Grant Date Fair Value per Share Unvested as of December 31, 2019 460 $ 5.61 Issued 420 $ 6.50 Vested (248) $ 6.54 Cancelled (44) $ 6.14 Unvested as of December 31, 2020 588 $ 5.82 The aggregate fair value of RSUs vested during the year ended December 31, 2020, based upon the fair values of the stock underlying the RSUs on the day of vesting, was $1.5 million. The aggregate fair value of RSUs vested during the year ended December 31, 2019, based upon the fair values of the stock underlying the RSUs on the day of vesting, was $0.7 million. As of December 31, 2020, there was unrecognized stock-based compensation expense related to unvested RSUs of $2.2 million, which the Company expects to recognize over a weighted-average period of approximately 1.7 years. Stock Option Activity The fair value of stock options granted to employees and directors during the years ended December 31, 2020 and 2019 was calculated on the date of grant using the following weighted-average assumptions: Year Ended December 31, 2020 2019 Risk-free interest rate 1.2 % 2.2 % Expected dividend yield — % — % Expected term (in years) 6.0 6.0 Expected volatility 72.3 % 69.4 % Using the Black-Scholes option pricing model, the weighted-average grant date fair value of stock options granted to employees and directors during the years ended December 31, 2020 and 2019 was $4.25 and $2.76 per share, respectively. The following table summarizes changes in stock option activity during the year ended December 31, 2020 (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, 2019 5,735 $ 8.76 7.2 $ 18,959 Granted 1,230 $ 6.68 Exercised (128) $ 4.67 Cancelled (251) $ 12.69 Outstanding at December 31, 2020 6,586 $ 8.30 6.5 $ 13,110 Exercisable at December 31, 2020 4,586 $ 8.15 5.8 $ 10,832 The aggregate intrinsic value of stock options exercised during the years ended December 31, 2020 and 2019 was $0.5 million and $0.6 million, respectively. As of December 31, 2020, there was unrecognized stock-based compensation expense related to unvested stock options of $9.4 million, which the Company expects to recognize over a weighted-average period of approximately 2.2 years.

Income Taxes

Income Taxes	12 Months Ended
	Dec. 31, 2020
Income Tax Disclosure [Abstract]
Income Taxes	Income Taxes The provision for income taxes for the years ended December 31, 2020 and 2019 was comprised as follows (in thousands): Year Ended December 31, 2020 2019 Current taxes: Federal $ — $ — State 14 46 Total current taxes 14 46 Deferred taxes: Federal — — State — — Total deferred taxes — — Total provision for income taxes $ 14 $ 46 As part of Congress’s response to the COVID-19 pandemic, the Coronavirus Aid, Relief, and Economic Security Act (“CARES Act”), was signed into United States law on March 27, 2020 and modifies certain provisions of the Tax Cuts and Jobs Act, enacted in 2017, with respect to net operating losses. Under the CARES Act, the limitation on the deduction of net operating losses to 80% of annual taxable income is suspended for taxable years beginning before January 1, 2021. The CARES Act did not have a material impact on the condensed consolidated financial statements. A reconciliation of the federal statutory income tax rate to the Company’s effective tax rate is as follows: Year Ended December 31, 2020 2019 Income tax computed at federal statutory tax rate 21.0 % 21.0 % State taxes, net of federal benefit 4.2 % 4.8 % Tax credit carryforwards 7.8 % (5.4) % Permanent items (12.4) % 1.1 % Change in valuation allowance (20.4) % (21.4) % Other (0.2) % — % Effective tax rate — % 0.1 % The principal components of the Company’s deferred tax assets and liabilities as of December 31, 2020 and 2019 were comprised as follows (in thousands): December 31, 2020 2019 Deferred tax assets: Net operating loss carryforwards $ 22,717 $ 33,008 Tax credit carryforwards 21,387 17,185 Deferred revenue 528 — Operating lease liability 4,614 5,407 Intangibles 785 519 Accrued expenses and other 1,838 1,358 Unrealized loss on available-for-sale securities 17 17 Depreciation 314 — Stock-based compensation 4,031 3,376 Total deferred tax assets 56,231 60,870 Less: valuation allowance (52,172) (43,219) Net deferred tax assets 4,059 17,651 Deferred tax liabilities: Section 481(a) method change — (12,827) Operating lease right-of-use asset (4,059) (4,812) Depreciation — (12) Total deferred tax liabilities (4,059) (17,651) Net deferred taxes $ — $ — As of December 31, 2020, the Company had federal and state net operating loss (“NOL”) carryforwards of $82.2 million and $86.3 million, respectively. Federal NOLs generated through the year ended December 31, 2017 expire at various dates from 2032 through 2037, and federal NOLs generated in years beginning after December 31, 2017 may be carried forward indefinitely. State NOLs expire at various dates from 2035 through 2038. As of December 31, 2020, the Company had federal research and development tax credit carryforwards of $16.1 million which expire at various dates from 2032 through 2040. In addition, as of December 31, 2020, the Company had state research and development and investment tax credit carryforwards of $6.6 million and $0.1 million, respectively. The state research and development tax credit carryforwards expire at various dates from 2029 through 2035 and the state investment tax credit carryforwards expire at various dates from 2021 through 2023. Management has evaluated the positive and negative evidence bearing upon the realizability of its deferred tax assets, which primarily pertain to NOL carryforwards, tax credit carryforwards, the Company’s operating lease liability and stock-based compensation. Management has determined that it is more likely than not that the Company will not realize the benefits of its deferred tax assets, and as a result, a valuation allowance of $52.2 million has been established at December 31, 2020. The increase in the valuation allowance of $9.0 million during the year ended December 31, 2020 was primarily due to the reduction in the deferred tax liability that was recorded as of December 31, 2019 related to the Company’s Internal Revenue Code Section 481(a) method change for revenue recognition under the Celgene Collaboration Agreement. The deferred tax liability reversed during the year ended December 31, 2020 and is no longer available as a source of future income. NOL and tax credit carryforwards are subject to review and possible adjustment by the Internal Revenue Service (“IRS”) and may become subject to an annual limitation in the event of certain cumulative changes in the ownership interest of significant shareholders over a three-year period in excess of 50% as defined under Sections 382 and 383 in the IRC. This could limit the amount of tax attributes that can be utilized annually to offset future taxable income or tax liabilities. The amount of the annual limitation is determined based on the Company’s value immediately prior to the ownership change. An IRC Section 382 study, completed in August 2016, identified three previous ownership changes for purposes of IRC Section 382. As a result of these ownership changes, the Company’s NOL and tax credit carryforwards allocable to the periods preceding each such ownership change are subject to limitations under IRC Section 382. No additional ownership changes were identified in a study completed in May 2020. Subsequent ownership changes may further affect the limitation in future years. The Company had no unrecognized tax benefits as of either December 31, 2020 or 2019. During the year ended December 31, 2017, the Company completed a study of its research and development credit carryforwards generated during the years ended December 31, 2016 and 2015. The Company has not conducted a study of its research and development credit carryforwards generated during any subsequent years. This study may result in an adjustment to the Company’s research and development credit carryforwards; however, until a study is completed and any adjustment is known, no amounts are being presented as an uncertain tax position. A full valuation allowance has been provided against the Company’s research and development credit carryforwards, and if an adjustment is required, this adjustment would be offset by an adjustment to the valuation allowance. Thus, there would be no impact to the consolidated statements of operations and comprehensive (loss) income if an adjustment were required. Interest and penalty charges, if any, related to income taxes would be classified as a component of the provision for income taxes in the consolidated statements of operations and comprehensive (loss) income. As of December 31, 2020, the Company has not incurred any material interest or penalty charges. The Company files income tax returns in the United States federal tax jurisdiction and the Massachusetts state tax jurisdiction. Since the Company is in a loss carryforward position, it is generally subject to examination by federal and state tax authorities for all tax years in which a loss carryforward is available.

Related-party Transactions

Related-party Transactions	12 Months Ended
	Dec. 31, 2020
Related Party Transactions [Abstract]
Related-party Transactions	Related-party Transactions In July 2019, the Company entered into the Celgene License Agreement under which it received a non-refundable upfront payment of $50.0 million from Celgene. Previously, 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 Preferred Stock for $36.1 million. These shares of Series B-1 Preferred Stock converted into 2,831,463 shares of common stock upon the completion of the Company’s 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. As of December 31, 2020, the Company had recorded no reimbursable expenses due to or from Celgene. As of December 31, 2019, the Company had recorded $0.7 million of reimbursement expenses due from Celgene within prepaid expenses and other current assets in the accompanying consolidated balance sheets. As discussed within Note 3, “License and Collaboration Revenue”, BMS completed its acquisition of Celgene in November 2019, and Celgene is now a wholly-owned subsidiary of BMS.

Commitments and Contingencies

Commitments and Contingencies	12 Months Ended
	Dec. 31, 2020
Commitments and Contingencies Disclosure [Abstract]
Commitments and Contingencies	Commitments and Contingencies 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 and included within “Other non-current assets” in the 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 recorded a right-of-use asset and a corresponding lease liability on the consolidated balance sheets as of December 31, 2020 and 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 December 31, 2020, the future minimum lease payments due under the operating lease for the Company’s corporate headquarters are as follows (in thousands): Amount 2021 $ 4,505 2022 4,633 2023 4,764 2024 4,900 2025 and thereafter 1,242 Total remaining minimum rental payments 20,044 Less: effect of discounting (3,155) Total lease liability $ 16,889 The Company recorded operating lease expense for the Corporate Headquarters Lease of $4.2 million for the years ended December 31, 2020 and 2019. As of December 31, 2020, the remaining lease term of the Corporate Headquarters Lease was 4.3 years. The Company presents changes in its right-of-use asset and lease liability on a combined net basis within “Other liabilities” in the consolidated statements of cash flows. License and Collaboration Agreements The Company has entered into various license agreements for certain technology. The Company could be required to make aggregate technical, clinical development and regulatory milestone payments of up to $9.0 million and low single-digit royalty payments based on a percentage of net sales of licensed products. As of December 31, 2020, the Company had made $0.7 million in aggregate milestone payments under these license agreements. The Company may cancel these agreements at any time by providing 30 to 90 days’ notice to the licensors, and all payments not previously due would no longer be owed. The Company has also entered into collaboration agreements with various third parties for research services and access to proprietary technology platforms. Under these collaboration agreements, the Company could be required to make aggregate technical, clinical development and regulatory milestones payments ranging from $12.5 million to $12.9 million per product candidate and low single-digit royalty payments based on a percentage of net sales on a product-by-product basis. As of December 31, 2020, the Company had made $1.8 million in aggregate milestone payments under these collaboration agreements.

401(k) Savings Plan

401(k) Savings Plan	12 Months Ended
	Dec. 31, 2020
Retirement Benefits [Abstract]
401(k) Savings Plan	401(k) Savings PlanThe Company has a defined-contribution savings plan under Section 401(k) of the IRC (the “401(k) Plan”). The 401(k) Plan covers all employees who meet defined minimum age and service requirements and allows participants to defer a portion of their annual compensation on a pretax basis. Beginning on January 1, 2018, the Company matches 50% of an employee’s 401(k) contributions up to a maximum of 6% of the participant’s salary, subject to employer match limitations under the IRC. As such, the Company made $0.6 million and $0.6 million in contributions to the 401(k) Plan for the years ended December 31, 2020 and 2019, respectively.

Net (Loss) Income per Share

Net (Loss) Income per Share	12 Months Ended
	Dec. 31, 2020
Earnings Per Share [Abstract]
Net (Loss) Income per Share	Net (Loss) Income per Share The following table summarizes the calculation of basic and diluted net (loss) income per share (in thousands, except per share amounts): Years Ended December 31, 2020 2019 Net (loss) income $ (43,842) $ 56,823 Weighted-average common shares outstanding, basic 35,426 33,080 Dilutive effect of outstanding stock options — 1,121 Dilutive effect of unvested RSAs — 1 Dilutive effect of unvested RSUs — 92 Weighted-average common shares outstanding, diluted 35,426 34,294 Net (loss) income per share, basic $ (1.24) $ 1.72 Net (loss) income per share, diluted $ (1.24) $ 1.66 The following weighted-average amounts were excluded from the calculation of diluted net (loss) income per share because their effect would be anti-dilutive (in thousands): Year Ended December 31, 2020 2019 Outstanding stock options 6,594 3,727 Unvested RSUs 660 24 Total 7,254 3,751

Subsequent Events

Subsequent Events	12 Months Ended
	Dec. 31, 2020
Subsequent Events [Abstract]
Subsequent Events	Subsequent EventsSubsequent to December 31, 2020 and through the filing date of this Annual Report on Form 10-K, the Company sold an aggregate of 3,156,200 shares at an average price of $9.87 per share for net proceeds of $30.2 million.

Basis of Presentation and Sum_2

Basis of Presentation and Summary of Significant Accounting Policies (Policies)	12 Months Ended
	Dec. 31, 2020
Accounting Policies [Abstract]
Basis of Presentation	Basis of Presentation and ConsolidationThe accompanying consolidated financial statements 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”).
Principles of Consolidation	These 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.
Segment Information	Segment Information Operating segments are defined as components of an enterprise about which separate discrete information is available for evaluation by the chief operating decision-maker in deciding how to allocate resources and assess performance. The Company and the Company’s chief operating decision maker, the Company’s chief executive officer, views the Company’s operations and manages its business as a single operating segment. The Company operates only in the United States.
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 Gilead License Agreement and Celgene Collaboration Agreement (including estimates of standalone selling prices of each performance obligation and internal and external costs expected to be incurred to satisfy performance obligations), accrued expenses, stock-based compensation expense and income taxes. In addition, in 2019, the Company made estimates to determine the discount rate utilized in the initial application of ASC Topic 842, Leases (“ASC 842”). 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.
Fair Value of Financial Instruments	Fair Value of Financial Instruments ASC Topic 820, Fair Value Measurement (“ASC 820”) establishes a fair value hierarchy for instruments measured at fair value that distinguishes between assumptions based on market data (observable inputs) and the Company’s own assumptions (unobservable inputs). Observable inputs are inputs that market participants would use in pricing the asset or liability based on market data obtained from sources independent of the Company. Unobservable inputs are inputs that reflect the Company’s assumptions about the inputs that market participants would use in pricing the asset or liability and are developed based on the best information available in the circumstances. ASC 820 identifies fair value as the exchange price, or exit price, representing the amount that would be received to sell an asset or paid to transfer a liability in an orderly transaction between market participants. As a basis for considering market participant assumptions in fair value measurements, ASC 820 establishes a three-tier fair value hierarchy that distinguishes between the following: • Level 1 inputs are quoted prices (unadjusted) in active markets for identical assets or liabilities. • Level 2 inputs are inputs other than quoted prices included within Level 1 that are observable for the asset or liability, either directly or indirectly. • Level 3 inputs are unobservable inputs that reflect the Company’s own assumptions about the assumptions market participants would use in pricing the asset or liability. Financial assets and liabilities are classified in their entirety based on the lowest level of input that is significant to the fair value measurement. To the extent that the valuation is based on models or inputs that are less observable or unobservable in the market, the determination of fair value requires more judgment. Accordingly, the degree of judgment exercised by the Company in determining fair value is greatest for instruments categorized in Level 3. A financial instrument’s level within the fair value hierarchy is based on the lowest level of any input that is significant to the fair value measurement. 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 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.
Cash Equivalents	Cash Equivalents Cash equivalents are highly-liquid investments that are readily convertible into cash with original maturities of three months or less when purchased. These assets include investment in money market funds that invests in U.S. Treasury obligations.
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.
Property and Equipment	Property and Equipment Property and equipment is recorded at cost and consists of laboratory equipment, furniture and office equipment, computer equipment, leasehold improvements. The Company capitalizes property and equipment that is acquired for research and development activities and that has alternate future use. Expenditures for maintenance and repairs are recorded to expense as incurred, whereas major betterments are capitalized as additions to property and equipment. Leasehold improvements are depreciated over the lesser of their useful life or the term of the lease. Depreciation is calculated over the estimated useful lives of the assets using the straight-line method.
Impairment of Long-lived Assets	Impairment of Long-lived AssetsThe Company reviews its property and equipment whenever events or changes in circumstances indicate that the carrying value of certain assets might not be recoverable and recognizes an impairment loss when it is probable that an asset’s realizable value is less than the carrying value.
Leases	Leases Effective January 1, 2019, the Company adopted ASC 842. 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, although separation of lease and non-lease components is required under ASC 842, the Company elected a practical expedient to not separate lease and non-lease components and rather accounts for lease and non-lease components together as a single lease component. At the inception of an arrangement, the Company determines whether the arrangement is or contains a lease based on the unique facts and circumstances present in the arrangement. Leases with a term greater than one year are recognized on the balance sheet as right-of-use assets and short-term and long-term lease liabilities, as applicable. The Company does not recognize leases with terms of one year or less on the balance sheet. Options to renew a lease are not included in the Company’s initial lease term assessment unless there is reasonable certainty that the Company will renew. The Company monitors its plans to renew its material leases on a quarterly basis. Operating lease liabilities and their corresponding right-of-use assets are recorded based on the present value of lease payments over the expected remaining lease term. Certain adjustments to the right-of-use asset may be required for items such as incentives received. The interest rate implicit in lease contracts is typically not readily determinable. As a result, the Company utilizes its incremental borrowing rate (“IBR”), which reflects the fixed rate at which the Company could borrow on a collateralized basis the amount of the lease payments in the same currency, for a similar term, and in a similar economic environment. The Company subsequently measures its lease liability at the present value of remaining lease payments, discounted using the IBR 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.
Revenue Recognition	Revenue Recognition The Company recognizes revenue in accordance with ASC Topic 606, Revenue from Contracts with Customers (“ASC 606”). Under ASC 606, an entity recognizes revenue when its customer obtains control of promised goods or services, in an amount that reflects the consideration that the entity expects to receive in exchange for those goods or services. In applying ASC 606, the Company performs the following five steps: (i) identify the contract(s) with a customer; (ii) identify the promises and performance obligations in the contract; (iii) determine the transaction price; (iv) allocate the transaction price to the performance obligations in the contract; and (v) recognize revenue when (or as) the Company satisfies the performance obligations. The Company only applies the five-step model to contracts when it is probable that it will collect the consideration to which it is entitled in exchange for the goods or services it transfers to the customer. At contract inception, once the contract is determined to be within the scope of ASC 606, the Company assesses the goods or services promised within each contract, determines those that are performance obligations and assesses whether each promised good or service is distinct. The Company then recognizes as revenue the amount of the transaction price that is allocated to the respective performance obligation when (or as) the performance obligation is satisfied. As part of the assessment, the Company must develop assumptions that require judgment to determine the standalone selling price for each performance obligation identified in the contract. The Company uses key assumptions to determine the standalone selling price, which may include reimbursement rates for personnel costs, development timelines and probabilities of regulatory success. The Company does not assess whether a contract has a significant financing component if the expectation at contract inception is that the period between payment by the customer and the transfer of promised goods or services to the customer will be one year or less. Arrangements that include upfront payments may require deferral of revenue recognition to a future period until obligations under these arrangements are fulfilled. The event-based milestone payments represent variable consideration, and the Company uses the “most likely amount” method to estimate this variable consideration. Given the high degree of uncertainty around the occurrence of these events, the Company determined the milestone and other contingent amounts to be fully constrained until the uncertainty associated with these payments is resolved. Revenue will be recognized from sales-based royalty payments when or as the sales occur. The Company will re-evaluate the transaction price in each reporting period as uncertain events are resolved and other changes in circumstances occur. See Note 3, “License and Collaboration Revenue”, for further information on the Company’s application of ASC 606.
Research and Development Expenses	Research and Development Expenses Expenditures relating to research and development are expensed as incurred. Research and development expenses include external expenses incurred under arrangements with third parties, academic and non-profit institutions and consultants; salaries and personnel-related costs, including non-cash stock-based compensation expense; license fees to acquire in-process technology and other expenses, which include direct and allocated expenses for laboratory, facilities and other costs. Non‑refundable advance payments for goods and services that will be used in future research and development activities are expensed when the activity has been performed or when the goods have been received rather than when the payment is made.
Intellectual Property Expenses	Intellectual Property Expenses The Company expenses costs associated with intellectual property-related matters as incurred and classifies such costs as general and administrative expenses within the consolidated statements of operations and comprehensive (loss) income.
Stock-based Compensation	Stock-based Compensation The Company accounts for stock-based payments in accordance with ASC Topic 718, Compensation—Stock Compensation . This guidance requires all stock-based payments to employees, including grants of employee stock options, restricted stock awards (“RSAs”) and restricted stock units (“RSUs”), to be recognized as expense in the consolidated statements of operations and comprehensive (loss) income based on their grant date fair values. For stock options granted to employees and to members of the Company’s board of directors for their services on the board of directors, the Company estimates the grant date fair value of each stock option using the Black-Scholes option-pricing model. For RSUs and RSAs granted to employees, the Company estimates the grant date fair value of each award using intrinsic value, which is based on the value of the underlying common stock less any purchase price. For stock-based payments subject to service-based vesting conditions, the Company recognizes stock-based compensation expense equal to the grant date fair value of stock-based payment on a straight-line basis over the requisite service period. The Black‑Scholes option pricing model requires the input of certain subjective assumptions, including (i) the calculation of expected term of the stock-based payment, (ii) the risk‑free interest rate, (iii) the expected stock price volatility and (iv) the expected dividend yield. The Company uses the simplified method as proscribed by SEC Staff Accounting Bulletin No. 107 to calculate the expected term for stock options granted to employees as the Company does not have sufficient historical exercise data to provide a reasonable basis upon which to estimate the expected term. The Company determines the risk‑free interest rate based on a treasury instrument whose term is consistent with the expected term of the stock options. Because there had been no public market for the Company’s common stock prior to the Company’s initial public offering (“IPO”), there is a lack of Company‑specific historical and implied volatility data. Accordingly, the Company bases its estimates of expected volatility on the historical volatility of a group of publicly-traded companies with similar characteristics to itself, including stage of product development and therapeutic focus within the life sciences industry. Historical volatility is calculated over a period of time commensurate with the expected term of the stock-based payment. The Company uses an assumed dividend yield of zero as the Company has never paid dividends on its common stock, nor does it expect to pay dividends on its common stock in the foreseeable future. The Company accounts for forfeitures of all stock-based payments when such forfeitures occur.
Income Taxes	Income Taxes Income taxes are recorded in accordance with ASC Topic 740, Income Taxes , which provides for deferred taxes using an asset and liability approach. The Company recognizes deferred tax assets and liabilities for the expected future tax consequences of events that have been included in the consolidated financial statements or tax returns. Deferred tax assets and liabilities are determined based on the difference between the financial statement and tax bases of assets and liabilities using enacted tax rates in effect for the year in which the differences are expected to reverse. A valuation allowance against deferred tax assets is recorded if, based on the weight of the available evidence, it is more likely than not that some or all of the deferred tax assets will not be realized.
Comprehensive (Loss) Income	Comprehensive (Loss) Income Comprehensive (loss) income is comprised of net (loss) income and other comprehensive income. Other comprehensive income for all periods presented consists solely of unrealized gains on available-for-sale securities.
Net (Loss) Income per Share	Net (Loss) Income per ShareBasic net (loss) income per share is calculated based upon the weighted-average number of common shares outstanding during the period, excluding outstanding stock options and RSAs and RSUs that have been issued but are not yet vested. Diluted net (loss) income per share is calculated based upon the weighted-average number of common shares outstanding during the period plus the dilutive impact of weighted-average common equivalent shares outstanding during the period. The potentially dilutive shares of common stock resulting from the assumed exercise of outstanding stock options and the assumed vesting of RSAs and RSUs are determined under the treasury stock method.
Concentrations of Credit Risk	Concentrations of Credit Risk and Off-Balance Sheet RiskFinancial instruments that potentially expose the Company to concentrations of credit risk primarily consist of cash, cash equivalents and investments. The Company maintains its cash and cash equivalent balances with high-quality financial institutions and, consequently, the Company believes that such funds are subject to minimal credit risk. The Company’s cash equivalents and investments are comprised of money market funds that are invested in U.S. Treasury obligations, corporate debt securities, U.S. Treasury obligations and government agency securities. Credit risk in these securities is reduced as a result of the Company’s investment policy to limit the amount invested in any single issuer and to only invest in securities of a high credit quality.
Off-Balance Sheet Risk	The Company has no significant off-balance sheet risk such as foreign exchange contracts, option contracts or other foreign hedging arrangements.
Recent Accounting Pronouncements	Recently Adopted Accounting Pronouncements In August 2018, the FASB issued Accounting Standards Updates (“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 became effective for fiscal years beginning after December 15, 2019, including interim periods within those fiscal years. Accordingly, the Company adopted ASU 2018-13 effective January 1, 2020, and there was no impact to the condensed consolidated financial statements due to the adoption of this guidance. In August 2018, the FASB issued ASU 2018-15, Intangibles—Goodwill and Other—Internal-Use Software (Subtopic 350-40): Customer’s Accounting for Implementation Costs Incurred in a Cloud Computing Arrangement That Is a Service Contract . This guidance aligns the requirements for capitalizing implementation costs incurred in a hosting arrangement that is a service contract with the requirements for capitalizing implementation costs incurred to develop or obtain internal-use software (and hosting arrangements that include an internal-use software license). The accounting for the service element of a hosting arrangement that is a service contract is not affected. This guidance became effective for fiscal years beginning after December 15, 2019, including interim periods within those fiscal years. The amendments in this update are able to be applied either retrospectively or prospectively to all implementation costs incurred after the date of adoption. Accordingly, the Company adopted ASU 2018-15 effective January 1, 2020, and it elected to apply this guidance on a prospective basis. There was no impact to the condensed consolidated financial statements due to 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 60 6, 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 became effective for fiscal years beginning after December 15, 2019, including interim periods within those fiscal years. Accordingly, the Company adopted ASU 2018-18 effective January 1, 2020, and there was no impact to the condensed consolidated financial statements due to the adoption of this guidance. In December 2019, the FASB issued ASU 2019-12, Income Taxes (Topic 740): Simplifying the Accounting for Income Taxes , which eliminates certain exceptions to the guidance in ASC 740 related to the approach for intraperiod tax allocation, the methodology for calculating income taxes in an interim period and the recognition of deferred tax liabilities when investment ownership changes. In addition, ASU 2019-12 simplifies the accounting for the interim period effects of changes in tax laws or rates and transactions that result in a step-up in the tax basis of goodwill. While this guidance is effective for fiscal years beginning after December 15, 2020, including interim periods within those fiscal years, early adoption is permitted. Consequently, the Company elected to early adopt ASU 2019-12 effective January 1, 2020. Due to the adoption of this guidance, the Company did not record an intraperiod tax allocation to other comprehensive income for the three months ended March 31, 2020. In accordance with ASU 2019-12, the Company has applied the new provisions related to the intraperiod tax allocation on a prospective basis. Recent Accounting Pronouncements, Not Yet Adopted In June 2016, the FASB issued ASU 2016-13, Financial 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 expected credit losses, this standard now requires allowances to be recorded instead of reducing the amortized cost of the investment. This guidance was originally effective for annual reporting periods beginning after December 15, 2019, including interim periods within those annual reporting periods, and early adoption was permitted. In November 2019, the FASB subsequently issued ASU 2019-10, Financial Instruments—Credit Losses (Topic 326), Derivatives and Hedging (Topic 815), and Leases (Topic 842): Effective Dates , whereby the effective date of this standard for smaller reporting companies was deferred to annual reporting periods beginning after December 15, 2022, including interim periods within those annual reporting periods, and early adoption is still permitted. Accordingly, the Company will now adopt this standard effective January 1, 2023, and it is currently evaluating the potential impact that ASU 2016-13 may have on the consolidated financial statements.

License and Collaboration Rev_2

License and Collaboration Revenue (Tables)	12 Months Ended
	Dec. 31, 2020
Revenue from Contract with Customer [Abstract]
Research and Development Arrangement, Contract to Perform for Others	The following table provides a summary of the transaction price allocated to each performance obligation, in addition to revenue activity during the period (in thousands): Revenue Recognized - related party Deferred Revenue - related party Transaction Price Allocated Year Ended December 31, 2020 As of December 31, 2020 JTX-1811 License $ 60,776 $ 60,776 $ — Research and Transition Services 3,494 1,563 1,931 Totals $ 64,270 $ 62,339 $ 1,931

Fair Value Measurements (Tables

Fair Value Measurements (Tables)	12 Months Ended
	Dec. 31, 2020
Fair Value Disclosures [Abstract]
Assets Measured at Fair Value	Assets measured at fair value on a recurring basis as of December 31, 2020 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 $ 147,492 $ 147,492 $ — $ — Investments: Corporate debt securities 63,691 — 63,691 — Government agency securities 2,005 — 2,005 — Totals $ 213,188 $ 147,492 $ 65,696 $ — Assets measured at fair value on a recurring basis as of December 31, 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 $ 50,242 $ 50,242 $ — $ — Investments: Corporate debt securities 48,300 — 48,300 — U.S. Treasuries 59,082 59,082 — — Government agency securities 12,820 — 12,820 — Totals $ 170,444 $ 109,324 $ 61,120 $ —

Investments (Tables)

Investments (Tables)	12 Months Ended
	Dec. 31, 2020
Investments, Debt and Equity Securities [Abstract]
Schedule of Available-for-sale Securities by Security Type	Cash equivalents, short-term investments and long-term investments as of December 31, 2020 were comprised as follows (in thousands): December 31, 2020 Amortized Cost Unrealized Gains Unrealized Losses Fair Value Cash equivalents and short-term investments: Money market funds, included in cash equivalents $ 147,492 $ — $ — $ 147,492 Corporate debt securities 56,985 9 (13) 56,981 Government agency securities 2,001 4 — 2,005 Total cash equivalents and short-term investments 206,478 13 (13) 206,478 Long-term investments: Corporate debt securities 6,727 — (17) 6,710 Total long-term investments 6,727 — (17) 6,710 Total cash equivalents and investments $ 213,205 $ 13 $ (30) $ 213,188 Cash equivalents, short-term investments and long-term investments as of December 31, 2019 were comprised as follows (in thousands): December 31, 2019 Amortized Cost Unrealized Gains Unrealized Losses Fair Value Cash equivalents and short-term investments: Money market funds, included in cash equivalents $ 50,242 $ — $ — $ 50,242 Corporate debt securities 46,695 8 (4) 46,699 U.S. Treasuries 59,058 26 (2) 59,082 Government agency securities 12,796 24 — 12,820 Total cash equivalents and short-term investments 168,791 58 (6) 168,843 Long-term investments: Corporate debt securities 1,599 2 — 1,601 Total long-term investments 1,599 2 — 1,601 Total cash equivalents and investments $ 170,390 $ 60 $ (6) $ 170,444

Restricted Cash (Tables)

Restricted Cash (Tables)	12 Months Ended
	Dec. 31, 2020
Cash and Cash Equivalents [Abstract]
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 consolidated statements of cash flows (in thousands): Year Ended Year Ended Beginning of Period End of Period Beginning of Period End of Period Cash and cash equivalents $ 53,241 $ 147,493 $ 47,906 $ 53,241 Restricted cash 1,270 1,270 1,270 1,270 Cash, cash equivalents and restricted cash $ 54,511 $ 148,763 $ 49,176 $ 54,511
Restrictions on 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 consolidated statements of cash flows (in thousands): Year Ended Year Ended Beginning of Period End of Period Beginning of Period End of Period Cash and cash equivalents $ 53,241 $ 147,493 $ 47,906 $ 53,241 Restricted cash 1,270 1,270 1,270 1,270 Cash, cash equivalents and restricted cash $ 54,511 $ 148,763 $ 49,176 $ 54,511

Property and Equipment, Net (Ta

Property and Equipment, Net (Tables)	12 Months Ended
	Dec. 31, 2020
Property, Plant and Equipment [Abstract]
Property, Plant and Equipment	Property and equipment, net as of December 31, 2020 and 2019 was comprised as follows (in thousands): Estimated Useful Life (in Years) December 31, 2020 2019 Laboratory equipment 5 $ 11,408 $ 11,374 Furniture and office equipment 4 1,071 1,071 Computer equipment 3 1,528 1,505 Leasehold improvements Shorter of useful life or remaining lease term 8,572 8,572 Total property and equipment, gross 22,579 22,522 Less: accumulated depreciation (15,243) (11,850) Total property and equipment, net $ 7,336 $ 10,672

Accrued Expenses (Tables)

Accrued Expenses (Tables)	12 Months Ended
	Dec. 31, 2020
Payables and Accruals [Abstract]
Schedule of Accrued Expenses	Accrued expenses as of December 31, 2020 and 2019 were comprised as follows (in thousands): December 31, 2020 2019 Employee compensation and benefits $ 6,825 $ 5,147 External research and professional services 4,855 3,639 Lab consumables and other 364 121 Total accrued expenses $ 12,044 $ 8,907

Common Stock and Preferred St_2

Common Stock and Preferred Stock (Tables)	12 Months Ended
	Dec. 31, 2020
Equity [Abstract]
Schedule of Stock by Class	As of December 31, 2020 and 2019, the Company had reserved for future issuance the following number of shares of common stock (in thousands): December 31, 2020 2019 Shares reserved for vesting of restricted stock awards — — Shares reserved for vesting of restricted stock units 588 460 Shares reserved for exercises of outstanding stock options 6,586 5,735 Shares reserved for future issuances under the 2017 Stock Option and Incentive Plan 1,284 1,288 Total shares reserved for future issuance 8,458 7,483
Summary of Sale of Stock under ATM Offering	The following table summarizes sales under the ATM Offering (net proceeds shown in thousands): For the year ended December 31, Shares Sold Net Proceeds Average Selling Price 2019 447,847 $ 3,510 $ 8.57 2020 2,074,274 14,513 $ 7.23 Total sales under the ATM Offering 2,522,121 $ 18,023

Stock-based Compensation (Table

Stock-based Compensation (Tables)	12 Months Ended
	Dec. 31, 2020
Share-based Payment Arrangement [Abstract]
Schedule of Stock-Based Compensation Expense	Total stock-based compensation expense recognized in the consolidated statements of operations and comprehensive (loss) income for the years ended December 31, 2020 and 2019 was as follows (in thousands): Year Ended December 31, 2020 2019 Research and development $ 4,242 $ 4,353 General and administrative 5,529 5,256 Total stock-based compensation expense $ 9,771 $ 9,609
Schedule of Restricted Stock and Restricted Stock Units Activity	The Company has also granted RSUs to its employees under the 2017 Plan. The following table summarizes RSU activity for the year ended December 31, 2020 (in thousands, except per share amounts): RSUs Weighted-Average Grant Date Fair Value per Share Unvested as of December 31, 2019 460 $ 5.61 Issued 420 $ 6.50 Vested (248) $ 6.54 Cancelled (44) $ 6.14 Unvested as of December 31, 2020 588 $ 5.82
Schedule of Share-based Payment Award, Stock Options, Valuation Assumptions	The fair value of stock options granted to employees and directors during the years ended December 31, 2020 and 2019 was calculated on the date of grant using the following weighted-average assumptions: Year Ended December 31, 2020 2019 Risk-free interest rate 1.2 % 2.2 % Expected dividend yield — % — % Expected term (in years) 6.0 6.0 Expected volatility 72.3 % 69.4 %
Schedule of Stock Options, Activity	The following table summarizes changes in stock option activity during the year ended December 31, 2020 (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, 2019 5,735 $ 8.76 7.2 $ 18,959 Granted 1,230 $ 6.68 Exercised (128) $ 4.67 Cancelled (251) $ 12.69 Outstanding at December 31, 2020 6,586 $ 8.30 6.5 $ 13,110 Exercisable at December 31, 2020 4,586 $ 8.15 5.8 $ 10,832

Income Taxes (Tables)

Income Taxes (Tables)	12 Months Ended
	Dec. 31, 2020
Income Tax Disclosure [Abstract]
Summary of Components of the Provision for Income Taxes	The provision for income taxes for the years ended December 31, 2020 and 2019 was comprised as follows (in thousands): Year Ended December 31, 2020 2019 Current taxes: Federal $ — $ — State 14 46 Total current taxes 14 46 Deferred taxes: Federal — — State — — Total deferred taxes — — Total provision for income taxes $ 14 $ 46
Reconciliation of the Federal Statutory Income Tax Rate to the Effective Tax Rate	A reconciliation of the federal statutory income tax rate to the Company’s effective tax rate is as follows: Year Ended December 31, 2020 2019 Income tax computed at federal statutory tax rate 21.0 % 21.0 % State taxes, net of federal benefit 4.2 % 4.8 % Tax credit carryforwards 7.8 % (5.4) % Permanent items (12.4) % 1.1 % Change in valuation allowance (20.4) % (21.4) % Other (0.2) % — % Effective tax rate — % 0.1 %
Schedule of Components of Deferred Tax Assets and Liabilities	The principal components of the Company’s deferred tax assets and liabilities as of December 31, 2020 and 2019 were comprised as follows (in thousands): December 31, 2020 2019 Deferred tax assets: Net operating loss carryforwards $ 22,717 $ 33,008 Tax credit carryforwards 21,387 17,185 Deferred revenue 528 — Operating lease liability 4,614 5,407 Intangibles 785 519 Accrued expenses and other 1,838 1,358 Unrealized loss on available-for-sale securities 17 17 Depreciation 314 — Stock-based compensation 4,031 3,376 Total deferred tax assets 56,231 60,870 Less: valuation allowance (52,172) (43,219) Net deferred tax assets 4,059 17,651 Deferred tax liabilities: Section 481(a) method change — (12,827) Operating lease right-of-use asset (4,059) (4,812) Depreciation — (12) Total deferred tax liabilities (4,059) (17,651) Net deferred taxes $ — $ —

Commitments and Contingencies (

Commitments and Contingencies (Tables)	12 Months Ended
	Dec. 31, 2020
Commitments and Contingencies Disclosure [Abstract]
Schedule of future minimum lease payments due under the Corporate Headquarters Lease - ASC 842	As of December 31, 2020, the future minimum lease payments due under the operating lease for the Company’s corporate headquarters are as follows (in thousands): Amount 2021 $ 4,505 2022 4,633 2023 4,764 2024 4,900 2025 and thereafter 1,242 Total remaining minimum rental payments 20,044 Less: effect of discounting (3,155) Total lease liability $ 16,889

Net (Loss) Income per Share (Ta

Net (Loss) Income per Share (Tables)	12 Months Ended
	Dec. 31, 2020
Earnings Per Share [Abstract]
Schedule of Dilutive Securities Included In Computation of Net Income (Loss) per Share	The following table summarizes the calculation of basic and diluted net (loss) income per share (in thousands, except per share amounts): Years Ended December 31, 2020 2019 Net (loss) income $ (43,842) $ 56,823 Weighted-average common shares outstanding, basic 35,426 33,080 Dilutive effect of outstanding stock options — 1,121 Dilutive effect of unvested RSAs — 1 Dilutive effect of unvested RSUs — 92 Weighted-average common shares outstanding, diluted 35,426 34,294 Net (loss) income per share, basic $ (1.24) $ 1.72 Net (loss) income per share, diluted $ (1.24) $ 1.66
Schedule of Antidilutive Securities Excluded from Computation of Net Income (Loss) per Share	The following weighted-average amounts were excluded from the calculation of diluted net (loss) income per share because their effect would be anti-dilutive (in thousands): Year Ended December 31, 2020 2019 Outstanding stock options 6,594 3,727 Unvested RSUs 660 24 Total 7,254 3,751

Nature of Business (Details)

Nature of Business (Details) - USD ($) $ in Millions	Feb. 25, 2021	Dec. 31, 2020
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Cash, cash equivalents, and marketable securities		$ 213.2
Scenario, Forecast
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Duration of funding requirement	12 months

License and Collaboration Rev_3

License and Collaboration Revenue - Narrative (Details) $ / shares in Units, $ in Thousands	Oct. 16, 2020USD ($)$ / sharesshares	Aug. 31, 2020USD ($)	Jul. 22, 2019USD ($)	Feb. 01, 2017shares	Oct. 31, 2020USD ($)	Jul. 31, 2016USD ($)deliverablecustomer_programshares	Dec. 31, 2020USD ($)$ / sharesshares	Dec. 31, 2019USD ($)$ / sharesshares	Dec. 31, 2020USD ($)$ / sharesshares
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Proceeds from stock offering, net							$ 14,513	$ 3,510	$ 18,023
Sale of stock, price per share (USD per share) | $ / shares							$ 7.23	$ 8.57	$ 7.23
License and collaboration revenue—related party							$ 62,339	$ 147,872
Sale of stock, number of shares issued (in shares) | shares							2,074,274	447,847	2,522,121
Celgene Corporation | Common Stock | 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
Gilead Transaction Agreements
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Non-refundable upfront payment received for research agreement					$ 85,000
Aggregate revenue for clinical and regulatory milestones		$ 510,000
Aggregate revenue for sales milestones		$ 175,000
Transaction price	$ 64,270
License and collaboration revenue—related party							$ 62,339
Gilead Transaction Agreements | JTX-1811 License
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Transaction price	60,776
License and collaboration revenue—related party							60,776
Gilead Transaction Agreements | Research and Transition Services
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Transaction price	3,494
License and collaboration revenue—related party							$ 1,563
Gilead Stock Purchase Agreement
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Aggregate fair value of shares issued on transaction	$ 55,700
Closing price per share (in USD per share) | $ / shares	$ 10.06
Proceeds from stock offering, net					$ 35,000
Sale of stock, price per share (USD per share) | $ / shares	$ 6.32
Consecutive trading days to determine weighted average share price	30 days
Sale amount over weighted average share price, percent	30.00%
Discount on shares issued on transaction	$ 20,700
Sale of stock, number of shares issued (in shares) | shares	5,539,727
Celgene License Agreement
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Non-refundable upfront payment received for research agreement			$ 50,000
License and collaboration revenue—related party								$ 50,000
Celegene Collaborative Arrangement
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Non-refundable upfront payment received for research agreement						$ 225,000
License and collaboration revenue—related party								$ 97,900
Number of early-stage programs | customer_program						4
Initial research term						4 years
Potential addition to research term						3 years
Number of program options | deliverable						6
Celegene Collaborative Arrangement | Series B-1 Convertible Preferred Stock
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 | 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 | Celgene Corporation | Series B-1 Convertible Preferred Stock | 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

License and Collaboration Rev_4

License and Collaboration Revenue - Summary of Transaction Price Allocated to Performance Obligations (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Oct. 16, 2020
Revenue from External Customer [Line Items]
License and collaboration revenue—related party	$ 62,339	$ 147,872
Deferred revenue, current—related party	1,931	$ 0
Gilead Transaction Agreements
Revenue from External Customer [Line Items]
Transaction Price Allocated			$ 64,270
License and collaboration revenue—related party	62,339
Deferred revenue, current—related party	1,931
JTX-1811 License | Gilead Transaction Agreements
Revenue from External Customer [Line Items]
Transaction Price Allocated			60,776
License and collaboration revenue—related party	60,776
Deferred revenue, current—related party	0
Research and Transition Services | Gilead Transaction Agreements
Revenue from External Customer [Line Items]
Transaction Price Allocated			$ 3,494
License and collaboration revenue—related party	1,563
Deferred revenue, current—related party	$ 1,931

License and Collaboration Rev_5

License and Collaboration Revenue - Performance Obligations (Details) - Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2021-01-01 - Celegene Collaborative Arrangement	Dec. 31, 2020
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

Fair Value Measurements - Asset

Fair Value Measurements - Assets Measured at Fair Value (Details) - USD ($)	Dec. 31, 2020	Dec. 31, 2019
Fair Value, Measurements, Recurring
Investments:
Totals	$ 213,188,000	$ 170,444,000
Liabilities measured at fair value	0	0
Fair Value, Measurements, Recurring | Quoted Prices in Active Markets for Identical Assets (Level 1)
Investments:
Totals	147,492,000	109,324,000
Fair Value, Measurements, Recurring | Significant Other Observable Inputs (Level 2)
Investments:
Totals	65,696,000	61,120,000
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	63,691,000	48,300,000
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	63,691,000	48,300,000
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		59,082,000
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		59,082,000
U.S. Treasuries | Fair Value, Measurements, Recurring | Significant Other Observable Inputs (Level 2)
Investments:
Available-for-sale debt securities, fair value		0
U.S. Treasuries | Fair Value, Measurements, Recurring | Significant Unobservable Inputs (Level 3)
Investments:
Available-for-sale debt securities, fair value		0
Government agency securities | Fair Value, Measurements, Recurring
Investments:
Available-for-sale debt securities, fair value	2,005,000	12,820,000
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	0	0
Government agency securities | Fair Value, Measurements, Recurring | Significant Other Observable Inputs (Level 2)
Investments:
Available-for-sale debt securities, fair value	2,005,000	12,820,000
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	147,492,000	50,242,000
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	147,492,000	50,242,000
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	147,492,000	50,242,000
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 - Schedule of Inves

Investments - Schedule of Investments (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Debt Securities, Available-for-sale, Fair Value to Amortized Cost [Abstract]
Unrealized Gains	$ 13	$ 60
Unrealized Losses	(30)	(6)
Cash equivalents, short-term and long-term investments, carrying value	213,205	170,390
Cash equivalents, short-term and long-term investments, fair vale disclosure	213,188	170,444
Short-term Investments
Debt Securities, Available-for-sale, Fair Value to Amortized Cost [Abstract]
Unrealized Gains	13	58
Unrealized Losses	(13)	(6)
Total cash equivalents and short-term investments, carrying value	206,478	168,791
Total cash equivalents and short-term investments, fair value	206,478	168,843
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	56,985	46,695
Unrealized Gains	9	8
Unrealized Losses	(13)	(4)
Available-for-sale debt securities, fair value	56,981	46,699
Short-term Investments | U.S. Treasuries
Debt Securities, Available-for-sale, Fair Value to Amortized Cost [Abstract]
Available-for-sale debt securities, amortized cost basis		59,058
Unrealized Gains		26
Unrealized Losses		(2)
Available-for-sale debt securities, fair value		59,082
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	2,001	12,796
Unrealized Gains	4	24
Unrealized Losses	0	0
Available-for-sale debt securities, fair value	2,005	12,820
Long-term Investments
Debt Securities, Available-for-sale, Fair Value to Amortized Cost [Abstract]
Available-for-sale debt securities, amortized cost basis	6,727	1,599
Unrealized Gains	0	2
Unrealized Losses	(17)	0
Available-for-sale debt securities, fair value	6,710	1,601
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	6,727	1,599
Unrealized Gains	0	2
Unrealized Losses	(17)	0
Available-for-sale debt securities, fair value	6,710	1,601
Money market funds, included in cash equivalents
Debt Securities, Available-for-sale [Line Items]
Cash equivalents at carrying value	147,492	50,242
Cash equivalents at fair value	147,492	50,242
Debt Securities, Available-for-sale, Fair Value to Amortized Cost [Abstract]
Unrealized Gains	0	0
Unrealized Losses	$ 0	$ 0

Investments - Narrative (Detail

Investments - Narrative (Details) - USD ($)	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Investments, Debt and Equity Securities [Abstract]
Aggregate fair value of securities in an unrealized loss position for less than twelve months	$ 28,300,000	$ 28,300,000
Aggregate fair value of securities in an unrealized loss position for more than twelve months	2,000,000
Realized gains or losses on available-for-sale securities	$ 0	$ 0

Restricted Cash - Narrative (De

Restricted Cash - Narrative (Details) - USD ($) $ in Millions	Dec. 31, 2020	Dec. 31, 2019
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	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Cash and Cash Equivalents [Abstract]
Cash and cash equivalents	$ 147,493	$ 53,241	$ 47,906
Restricted cash	1,270	1,270	1,270
Cash, cash equivalents and restricted cash	$ 148,763	$ 54,511	$ 49,176

Property and Equipment, Net - S

Property and Equipment, Net - Schedule of Property and Equipment (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Property, Plant and Equipment [Line Items]
Total property and equipment, gross	$ 22,579	$ 22,522
Less: accumulated depreciation	(15,243)	(11,850)
Total property and equipment, net	$ 7,336	10,672
Laboratory equipment
Property, Plant and Equipment [Line Items]
Estimated Useful Life (in Years)	5 years
Total property and equipment, gross	$ 11,408	11,374
Furniture and office equipment
Property, Plant and Equipment [Line Items]
Estimated Useful Life (in Years)	4 years
Total property and equipment, gross	$ 1,071	1,071
Computer equipment
Property, Plant and Equipment [Line Items]
Estimated Useful Life (in Years)	3 years
Total property and equipment, gross	$ 1,528	1,505
Leasehold improvements
Property, Plant and Equipment [Line Items]
Total property and equipment, gross	$ 8,572	$ 8,572

Property and Equipment, Net - N

Property and Equipment, Net - Narrative (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Property, Plant and Equipment [Abstract]
Depreciation expense	$ 3,401	$ 3,851

Accrued Expenses (Details)

Accrued Expenses (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Payables and Accruals [Abstract]
Employee compensation and benefits	$ 6,825	$ 5,147
External research and professional services	4,855	3,639
Lab consumables and other	364	121
Total accrued expenses	$ 12,044	$ 8,907

Common Stock and Preferred St_3

Common Stock and Preferred Stock - Narrative (Details) $ in Thousands	Dec. 17, 2019USD ($)	Jan. 31, 2021USD ($)shares	Feb. 25, 2021USD ($)shares	Dec. 31, 2020USD ($)voteshares	Dec. 31, 2019USD ($)shares	Dec. 31, 2020USD ($)voteshares
Subsidiary, Sale of Stock [Line Items]
Common stock, shares authorized (in shares)				160,000,000	160,000,000	160,000,000
Common stock, votes per share | vote				1		1
Sale of stock, number of shares issued (in shares)				2,074,274	447,847	2,522,121
Proceeds from stock offering, net | $				$ 14,513	$ 3,510	$ 18,023
Preferred stock, shares authorized (in shares)				5,000,000	5,000,000	5,000,000
Preferred stock, shares issued (in shares)				0	0	0
Preferred stock, shares outstanding (in shares)				0	0	0
ATM Offering
Subsidiary, Sale of Stock [Line Items]
Aggregate offering price shares | $	$ 50,000
Sales commission percentage	3.00%
ATM Offering | Subsequent Event
Subsidiary, Sale of Stock [Line Items]
Sale of stock, number of shares issued (in shares)		3,156,200	3,156,200
Proceeds from stock offering, net | $		$ 30,200	$ 30,200

Common Stock and Preferred St_4

Common Stock and Preferred Stock - Sale of Stock under ATM Offering (Details) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended		24 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2020
Equity [Abstract]
Shares sold (in shares)	2,074,274	447,847	2,522,121
Proceeds from stock offering, net	$ 14,513	$ 3,510	$ 18,023
Average selling price (USD per share)	$ 7.23	$ 8.57	$ 7.23

Common Stock and Preferred St_5

Common Stock and Preferred Stock - Shares Reserved for Future Issuance (Details) - shares	Dec. 31, 2020	Dec. 31, 2019	Jan. 31, 2017
Conversion of Stock [Line Items]
Common stock reserved for potential conversion (in shares)	8,458,000	7,483,000	1,753,758
Shares reserved for vesting of restricted stock awards (in shares)
Conversion of Stock [Line Items]
Common stock reserved for potential conversion (in shares)	0	0
Shares reserved for vesting for restricted stock units (in shares)
Conversion of Stock [Line Items]
Common stock reserved for potential conversion (in shares)	588,000	460,000
Shares reserved for exercise of outstanding stock options (in shares)
Conversion of Stock [Line Items]
Common stock reserved for potential conversion (in shares)	6,586,000	5,735,000
Shares reserved for future issuances under the 2017 Stock Option and Incentive Plan (in shares)
Conversion of Stock [Line Items]
Common stock reserved for potential conversion (in shares)	1,284,000	1,288,000

Stock-based Compensation - Narr

Stock-based Compensation - Narrative (Details) - USD ($) $ / shares in Units, $ in Millions	Jan. 01, 2020	Jan. 01, 2019	Dec. 31, 2020	Dec. 31, 2019	Jan. 31, 2017
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares of common stock eligible to be purchased (in shares)			8,458,000	7,483,000	1,753,758
Weighted average fair value of options granted (in dollars per share)			$ 4.25	$ 2.76
Intrinsic value of stock options exercised			$ 0.5	$ 0.6
Unrecognized stock-based compensation expense, options			$ 9.4
Shares reserved for vesting for restricted stock units (in shares)
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares of common stock eligible to be purchased (in shares)			588,000	460,000
Aggregate fair value of awards vested in period			$ 1.5
Shares vested (in shares)			248,000	700,000
Unrecognized stock-based compensation expense			$ 2.2
Remaining weighted average vesting period			1 year 8 months 12 days
Employee Stock Option
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Remaining weighted average vesting period			2 years 2 months 12 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 reserved for issuance (in shares)			1,283,871
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)	1,349,526	1,317,935
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
Number of additional shares authorized (in shares)	337,381	329,483
Percent of outstanding shares					1.00%
Maximum annual amount, shares authorized (in shares)					603,000

Stock-based Compensation - Stoc

Stock-based Compensation - Stock-Based Compensation Expense (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense	$ 9,771	$ 9,609
Research and development
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense	4,242	4,353
General and administrative
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense	$ 5,529	$ 5,256

Stock-based Compensation - RSU

Stock-based Compensation - RSU Activity (Details) - Shares reserved for vesting for restricted stock units (in shares) - $ / shares	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
RSUs
Beginning unvested balance (in shares)	460,000
Issued (in shares)	420,000
Vested (in shares)	(248,000)	(700,000)
Cancelled (in shares)	(44,000)
Ending unvested balance (in shares)	588,000	460,000
Weighted-Average Grant Date Fair Value per Share
Beginning unvested balance (in dollars per share)	$ 5.61
Issued (in dollars per share)	6.50
Vested (in dollars per share)	6.54
Cancelled (in dollars per share)	6.14
Ending unvested balance (in dollars per share)	$ 5.82	$ 5.61

Stock-based Compensation - Weig

Stock-based Compensation - Weighted Average Assumptions (Details) - Employee Stock Option	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Risk-free interest rate	1.20%	2.20%
Expected dividend yield	0.00%	0.00%
Expected term (in years)	6 years	6 years
Expected volatility	72.30%	69.40%

Stock-based Compensation - St_2

Stock-based Compensation - Stock Option Activity (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Options
Beginning outstanding balance (in shares)	5,735
Granted (in shares)	1,230
Exercised (in shares)	(128)	(185)
Cancelled (in shares)	(251)
Ending outstanding balance (in shares)	6,586	5,735
Exercisable (in shares)	4,586
Weighted-Average Exercise Price
Beginning outstanding balance (in dollars per share)	$ 8.76
Granted (in dollars per share)	6.68
Exercised (in dollars per share)	4.67
Cancelled (in dollars per share)	12.69
Ending outstanding balance (in dollars per share)	8.30	$ 8.76
Exercisable (in dollars per share)	$ 8.15
Remaining contractual life, outstanding	6 years 6 months	7 years 2 months 12 days
Remaining contractual life, exercisable	5 years 9 months 18 days
Aggregate intrinsic value, outstanding	$ 13,110	$ 18,959
Aggregate intrinsic value, exercisable	$ 10,832

Income Taxes - Schedule of Comp

Income Taxes - Schedule of Components of Income Tax Provision (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Current taxes:
Federal	$ 0	$ 0
State	14	46
Total current taxes	14	46
Deferred taxes:
Federal	0	0
State	0	0
Total deferred taxes	0	0
Total provision for income taxes	$ 14	$ 46

Income Taxes - Schedule of Effe

Income Taxes - Schedule of Effective Income Tax Rate Reconciliation (Details)	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Income Tax Disclosure [Abstract]
Income tax computed at federal statutory tax rate	21.00%	21.00%
State taxes, net of federal benefit	4.20%	4.80%
Tax credit carryforwards	7.80%	(5.40%)
Permanent items	(12.40%)	1.10%
Change in valuation allowance	(20.40%)	(21.40%)
Other	(0.20%)	0.00%
Effective tax rate	0.00%	0.10%

Income Taxes - Schedule of Defe

Income Taxes - Schedule of Deferred Tax Assets and Liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Deferred tax assets:
Net operating loss carryforwards	$ 22,717	$ 33,008
Tax credit carryforwards	21,387	17,185
Deferred revenue	528	0
Operating lease liability	4,614	5,407
Intangibles	785	519
Accrued expenses and other	1,838	1,358
Unrealized loss on available-for-sale securities	17	17
Depreciation	314	0
Stock-based compensation	4,031	3,376
Total deferred tax assets	56,231	60,870
Less: valuation allowance	(52,172)	(43,219)
Net deferred tax assets	4,059	17,651
Deferred tax liabilities:
Section 481(a) method change	0	(12,827)
Operating lease right-of-use asset	(4,059)	(4,812)
Depreciation	0	(12)
Total deferred tax liabilities	(4,059)	(17,651)
Net deferred taxes	$ 0	$ 0

Income Taxes - Narrative (Detai

Income Taxes - Narrative (Details)	12 Months Ended
	Dec. 31, 2020USD ($)	Dec. 31, 2019USD ($)	Aug. 31, 2016change
Operating Loss Carryforwards [Line Items]
Valuation allowance	$ 52,172,000	$ 43,219,000
Decrease in deferred tax asset valuation allowance	(9,000,000)
Number of previous ownership changes | change			3
Unrecognized tax benefits	0	$ 0
Interest and penalty charges incurred	0
Federal Tax Authority
Operating Loss Carryforwards [Line Items]
Net operating loss carryforwards	82,200,000
State and Local Jurisdiction
Operating Loss Carryforwards [Line Items]
Net operating loss carryforwards	86,300,000
Research and Development Tax Credit Carryforwards | Federal Tax Authority
Operating Loss Carryforwards [Line Items]
Tax credit carryforwards	16,100,000
Research and Development Tax Credit Carryforwards | State and Local Jurisdiction
Operating Loss Carryforwards [Line Items]
Tax credit carryforwards	6,600,000
Investment Tax Credit Carryforwards | State and Local Jurisdiction
Operating Loss Carryforwards [Line Items]
Tax credit carryforwards	$ 100,000

Related-party Transactions - Na

Related-party Transactions - Narrative (Details) - USD ($) $ / shares in Units, $ in Thousands	Jul. 22, 2019	Feb. 01, 2017	Oct. 31, 2020	Aug. 31, 2020	Jul. 31, 2019	Jul. 31, 2016	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2020
Related Party Transaction [Line Items]
Sale of stock, number of shares issued (in shares)							2,074,274	447,847	2,522,121
Sale of stock, price per share (USD per share)							$ 7.23	$ 8.57	$ 7.23
Proceeds from IPO, net of discounts, commissions, and other offering expenses							$ 14,513	$ 3,510	$ 18,023
License and collaboration revenue—related party							62,339	147,872
Celgene License Agreement
Related Party Transaction [Line Items]
Non-refundable upfront payment received for research agreement	$ 50,000
License and collaboration revenue—related party								50,000
Celegene Collaborative Arrangement
Related Party Transaction [Line Items]
Non-refundable upfront payment received for research agreement						$ 225,000
License and collaboration revenue—related party								97,900
Gilead Transaction Agreements
Related Party Transaction [Line Items]
Non-refundable upfront payment received for research agreement			$ 85,000
License and collaboration revenue—related party							62,339
Series B-1 Convertible Preferred Stock | Celegene Collaborative Arrangement
Related Party Transaction [Line Items]
Issuances of convertible preferred stock (in shares)						10,448,100
Issuances of convertible preferred stock						$ 36,100
Celgene Corporation | Celgene License Agreement | Celgene License Agreement
Related Party Transaction [Line Items]
Non-refundable upfront payment received for research agreement					$ 50,000
Reimbursable expenses due from related party							0	$ 700	0
Celgene Corporation | Celgene Collaboration Agreement | Celegene Collaborative Arrangement
Related Party Transaction [Line Items]
Non-refundable upfront payment received for research agreement						$ 225,000
Celgene Corporation | Celgene Collaboration Agreement | Series B-1 Convertible Preferred Stock | Celegene Collaborative Arrangement
Related Party Transaction [Line Items]
Issuances of convertible preferred stock (in shares)						10,448,100
Issuances of convertible preferred stock						$ 36,100
Celgene Corporation | IPO | Celgene Collaboration Agreement | Common Stock
Related Party Transaction [Line Items]
Stock converted upon completion of IPO (in shares)		2,831,463
Affiliated Entity | Celgene Corporation | IPO | Celgene Collaboration Agreement | Common Stock
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		$ 10,000
Gilead Sciences, Inc. | Gilead Transaction Agreements | Gilead Transaction Agreements
Related Party Transaction [Line Items]
Non-refundable upfront payment received for research agreement				$ 85,000
Reimbursable expenses due from related party							100		100
License and collaboration revenue—related party							62,300
Deferred revenue							$ 1,900		$ 1,900

Commitments and Contingencies -

Commitments and Contingencies - Narrative (Details) ft² in Thousands, $ in Millions	1 Months Ended	12 Months Ended
	Nov. 30, 2016USD ($)ft²consecutive_extension_period	Dec. 31, 2020USD ($)	Dec. 31, 2019USD ($)
Loss Contingencies [Line Items]
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%
Operating lease expense		$ 4.2	$ 4.2
Remaining lease term		4 years 3 months 18 days
Costs incurred, third party agreements		$ 1.8
Minimum
Loss Contingencies [Line Items]
Cancellation notice period, technology agreements		30 days
Potential costs, third party agreements		$ 12.5
Maximum
Loss Contingencies [Line Items]
Cancellation notice period, technology agreements		90 days
Potential costs, third party agreements		$ 12.9
License And Collaboration Agreements | Maximum
Loss Contingencies [Line Items]
Potential costs, technology agreements		9
Costs incurred, technology agreements		$ 0.7

Commitments and Contingencies_2

Commitments and Contingencies - Future Minimum Lease Payments (Details) $ in Thousands	Dec. 31, 2020USD ($)
Commitments and Contingencies Disclosure [Abstract]
2021	$ 4,505
2022	4,633
2023	4,764
2024	4,900
2025	1,242
Total remaining minimum rental payments	20,044
Less: effect of discounting	(3,155)
Total lease liability	$ 16,889

401(k) Savings Plan - Narrative

401(k) Savings Plan - Narrative (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Defined Contribution Plan Disclosure [Line Items]
Percent match	50.00%
Contributions to plan	$ 0.6	$ 0.6
Maximum
Defined Contribution Plan Disclosure [Line Items]
Maximum percent for match	6.00%

Net (Loss) Income per Share - S

Net (Loss) Income per Share - Schedule of Dilutive Securities Included In Computation of Net Income (Loss) per Share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Earnings Per Share, Diluted, by Common Class, Including Two Class Method [Line Items]
Net (loss) income	$ (43,842)	$ 56,823
Weighted-average common shares outstanding, basic (in shares)	35,426	33,080
Weighted-average common shares outstanding, diluted (in shares)	35,426	34,294
Net income (loss) per share, basic (in dollars per share)	$ (1.24)	$ 1.72
Net income (loss) per share, diluted (in dollars per share)	$ (1.24)	$ 1.66
Outstanding stock options
Earnings Per Share, Diluted, by Common Class, Including Two Class Method [Line Items]
Dilutive securities included in computation of net income (loss) per share (in shares)	0	1,121
Unvested RSUs
Earnings Per Share, Diluted, by Common Class, Including Two Class Method [Line Items]
Dilutive securities included in computation of net income (loss) per share (in shares)	0	1
Unvested RSUs
Earnings Per Share, Diluted, by Common Class, Including Two Class Method [Line Items]
Dilutive securities included in computation of net income (loss) per share (in shares)	0	92

Net (Loss) Income per Share -_2

Net (Loss) Income per Share - Share Schedule of Antidilutive Securities Excluded from Computation of Net Income (Loss) per Share (Details) - shares shares in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of net loss per share (in shares)	7,254	3,751
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)	6,594	3,727
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)	660	24

Subsequent Events (Details)

Subsequent Events (Details) - USD ($) $ / shares in Units, $ in Thousands	1 Months Ended	2 Months Ended	12 Months Ended		24 Months Ended
	Jan. 31, 2021	Feb. 25, 2021	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2020
Subsequent Event [Line Items]
Sale of stock, number of shares issued (in shares)			2,074,274	447,847	2,522,121
Sale of stock, price per share (USD per share)			$ 7.23	$ 8.57	$ 7.23
Proceeds from stock offering, net			$ 14,513	$ 3,510	$ 18,023
ATM Offering | Subsequent Event
Subsequent Event [Line Items]
Sale of stock, number of shares issued (in shares)	3,156,200	3,156,200
Sale of stock, price per share (USD per share)		$ 9.87
Proceeds from stock offering, net	$ 30,200	$ 30,200

Uncategorized Items - jnce-2020

Label	Element	Value
Gilead Stock Purchase Agreement [Member] | Gilead Transaction Agreements [Member] | Gilead Sciences, Inc. [Member]
Sale of Stock, Consideration Received on Transaction	us-gaap_SaleOfStockConsiderationReceivedOnTransaction	$ 35,000,000
Common Stock [Member] | Gilead Stock Purchase Agreement [Member] | Gilead Transaction Agreements [Member] | Gilead Sciences, Inc. [Member]
Sale of Stock, Number of Shares Issued in Transaction	us-gaap_SaleOfStockNumberOfSharesIssuedInTransaction	5,539,727