Ngm Biopharmaceuticals (NGM) 10-K 17 Mar 20 2019 FY Annual report Financial data

Document and Entity Information

Document and Entity Information - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Mar. 12, 2020	Jun. 28, 2019
Cover [Abstract]
Document Type	10-K
Amendment Flag	false
Document Period End Date	Dec. 31, 2019
Document Fiscal Year Focus	2019
Document Fiscal Period Focus	FY
Trading Symbol	NGM
Entity Registrant Name	NGM BIOPHARMACEUTICALS INC
Entity Central Index Key	0001426332
Current Fiscal Year End Date	--12-31
Entity Filer Category	Non-accelerated Filer
Entity Small Business	false
Entity Emerging Growth Company	true
Entity Ex Transition Period	false
Entity Common Stock, Shares Outstanding		67,752,589
Entity File Number	001-38853
Entity Tax Identification Number	26-1679911
Entity Current Reporting Status	Yes
Entity Shell Company	false
Entity Address, Address Line One	333 Oyster Point Boulevard
Entity Address, City or Town	South San Francisco
Entity Address, State or Province	CA
Entity Address, Postal Zip Code	94080
City Area Code	650
Local Phone Number	243-5555
Entity Interactive Data Current	Yes
Entity Well-known Seasoned Issuer	No
Entity Voluntary Filers	No
Title of 12(b) Security	Common Stock, par value $0.001 per share
Security Exchange Name	NASDAQ
Entity Incorporation, State or Country Code	DE
Document Annual Report	true
Document Transition Report	false
Entity Public Float			$ 359
Documents Incorporated by Reference	Portions of the registrant’s definitive Proxy Statement for the 2020 Annual Meeting of Stockholders to be filed with the U.S. Securities and Exchange Commission pursuant to Regulation 14A not later than 120 days after the end of the fiscal year covered by this Annual Report on Form 10-K are incorporated by reference in Part III, Items 10-14 of this Annual Report on Form 10-K.

CONSOLIDATED BALANCE SHEETS

CONSOLIDATED BALANCE SHEETS - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Current assets:
Cash and cash equivalents	$ 245,598	$ 56,923
Short-term marketable securities	98,913	149,710
Related party receivable from collaboration	5,206	3,669
Prepaid expenses and other current assets	5,531	4,255
Total current assets	355,248	214,557
Non-current assets:
Property and equipment, net	19,475	23,893
Restricted cash	1,874	2,249
Deferred IPO costs	0	2,292
Other non-current assets	3,806	3,094
Total assets	380,403	246,085
Current liabilities:
Accounts payable	9,026	5,775
Accrued liabilities	22,991	14,003
Deferred rent, current	2,829	2,683
Deferred revenue, current	4,872	19,025
Total current liabilities	39,718	41,486
Deferred rent, non-current	9,392	12,221
Deferred revenue, non-current		3,942
Early exercise stock option liability	574	1,559
Convertible preferred stock warrant liability		198
Total liabilities	49,684	59,406
Commitments and contingencies (Note 7)
Convertible preferred stock, $0.001 par value; 96,268,206 shares authorized; zero and 47,267,466 shares issued and outstanding as of December 31, 2019 and 2018, respectively		294,874
Stockholders' equity (deficit):
Preferred stock, $0.001 par value; 10,000,000 shares authorized; no shares issued or outstanding as of December 31, 2019 and 2018, respectively
Common stock, $0.001 par value; 400,000,000 shares authorized; 66,960,279 and 6,937,890 shares issued and outstanding as of December 31, 2019 and 2018, respectively	67	7
Additional paid-in capital	526,771	39,258
Accumulated other comprehensive gain (loss)	25	(267)
Accumulated deficit	(196,144)	(147,193)
Total stockholders' equity (deficit)	330,719	(108,195)
Total liabilities, convertible preferred stock and stockholders' equity (deficit)	$ 380,403	$ 246,085

CONSOLIDATED BALANCE SHEETS (Pa

CONSOLIDATED BALANCE SHEETS (Parenthetical) - $ / shares	Dec. 31, 2019	Dec. 31, 2018
Statement Of Financial Position [Abstract]
Convertible preferred stock, par value	$ 0.001	$ 0.001
Convertible preferred stock, shares authorized	96,268,206	96,268,206
Convertible preferred stock, shares issued	0	47,267,466
Convertible preferred stock, shares outstanding	0	47,267,466
Preferred stock, par value	$ 0.001	$ 0.001
Preferred stock, shares authorized	10,000,000	10,000,000
Preferred stock, shares issued	0	0
Preferred stock, shares outstanding	0	0
Common stock, par value	$ 0.001	$ 0.001
Common stock, shares authorized	400,000,000	400,000,000
Common stock, shares issued	66,960,279	6,937,890
Common stock, shares outstanding	66,960,279	6,937,890

CONSOLIDATED STATEMENTS OF OPER

CONSOLIDATED STATEMENTS OF OPERATIONS - USD ($)	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Income Statement [Abstract]
Related party revenue	$ 103,544,000	$ 108,665,000	$ 77,141,000
Operating expenses:
Research and development	129,253,000	95,714,000	79,736,000
General and administrative	23,631,000	17,265,000	14,830,000
Total operating expenses	152,884,000	112,979,000	94,566,000
Loss from operations	(49,340,000)	(4,314,000)	(17,425,000)
Interest income	6,692,000	3,622,000	2,358,000
Other income (expense), net	(147,000)	199,000	(152,000)
Net loss before taxes	(42,795,000)	(493,000)	(15,219,000)
Benefit from income taxes	0	0	(1,060,000)
Net loss	$ (42,795,000)	$ (493,000)	$ (14,159,000)
Net loss per share, basic and diluted	$ (0.85)	$ (0.08)	$ (2.37)
Weighted average shares used to compute net loss per share, basic and diluted	50,297,524	6,383,751	5,961,767

CONSOLIDATED STATEMENTS OF COMP

CONSOLIDATED STATEMENTS OF COMPREHENSIVE LOSS - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Statement Of Income And Comprehensive Income [Abstract]
Net Loss	$ (42,795)	$ (493)	$ (14,159)
Other comprehensive gain (loss), net of tax:
Net unrealized gain (loss) on available-for-sale marketable securities	292	164	(329)
Total comprehensive loss	$ (42,503)	$ (329)	$ (14,488)

CONDENSED CONSOLIDATED CONVERTI

CONDENSED CONSOLIDATED CONVERTIBLE PREFERRED STOCK AND STOCKHOLDERS' EQUITY (DEFICIT) - USD ($) $ in Thousands	Total	Convertible Preferred Stock	Common Stock	Additional Paid-In Capital	Other Comprehensive Gain (Loss)	Accumulated Deficit
Balance at Dec. 31, 2016	$ (115,062)	$ 294,874	$ 6	$ 17,575	$ (102)	$ (132,541)
Balance, shares at Dec. 31, 2016		47,267,000	5,802,000
Issuance of common stock to participants in 401(k) Plan	82			82
Issuance of common stock to participants in 401(k) Plan, shares			10,000
Issuance of common stock upon exercise of stock options	339			339
Issuance of common stock upon exercise of stock options, shares			109,000
Vesting of common stock from early exercises	527			527
Vesting of common stock from early exercises, shares			184,000
Stock-based compensation expense	7,624			7,624
Changes in unrealized (loss) gain on available-for-sale securities	(329)				(329)
Net loss	(14,159)					(14,159)
Balance at Dec. 31, 2017	(120,978)	$ 294,874	$ 6	26,147	(431)	(146,700)
Balance, shares at Dec. 31, 2017		47,267,000	6,105,000
Issuance of common stock to participants in 401(k) Plan	91			91
Issuance of common stock to participants in 401(k) Plan, shares			11,000
Issuance of common stock upon exercise of stock options	2,583		$ 1	2,582
Issuance of common stock upon exercise of stock options, shares			479,000
Vesting of common stock from early exercises	764			764
Vesting of common stock from early exercises, shares			161,000
Repurchase of common stock	(185)			(185)
Repurchase of common stock, shares			(23,000)
Stock-based compensation expense	9,859			9,859
Changes in unrealized (loss) gain on available-for-sale securities	164				164
Net loss	(493)					(493)
Balance at Dec. 31, 2018	(108,195)	$ 294,874	$ 7	39,258	(267)	(147,193)
Balance, shares at Dec. 31, 2018		47,267,000	6,733,000
Cumulative effect adjustment upon adoption of ASU 2014-09	(6,156)					(6,156)
Net exercise of preferred stock warrant to Series A preferred stock		$ 198
Net exercise of preferred stock warrant to Series A preferred stock, shares		16,000
Conversion of Series A, B, C, D, E convertible preferred stock to common stock	295,072	$ (295,072)	$ 47	295,025
Conversion of Series A, B, C, D, E convertible preferred stock to common stock, shares		(47,283,000)
Conversion of Series A, B, C, D, E convertible preferred stock to common stock, shares			47,283,000
Issuance of common stock upon initial public offering, net of issuance cost	107,756		$ 8	107,748
Issuance of common stock upon initial public offering, net of issuance cost, shares			7,521,000
Issuance of common stock upon private placement	65,947		$ 4	65,943
Issuance of common stock upon private placement, shares			4,122,000
Issuance of common stock to participants in 401(k) Plan	98			98
Issuance of common stock to participants in 401(k) Plan, shares			8,000
Issuance of common stock upon exercise of stock options	$ 3,575		$ 1	3,574
Issuance of common stock upon exercise of stock options, shares	987,479		984,000
Issuance of common stock in connection with employee stock purchase plan	$ 1,270			1,270
Issuance of common stock in connection with employee stock purchase plan, shares			103,000
Vesting of common stock from early exercises	993			993
Vesting of common stock from early exercises, shares			132,000
Stock-based compensation expense	12,862			12,862
Changes in unrealized (loss) gain on available-for-sale securities	292				292
Net loss	(42,795)					(42,795)
Balance at Dec. 31, 2019	$ 330,719		$ 67	$ 526,771	$ 25	$ (196,144)
Balance, shares at Dec. 31, 2019			66,886,000

CONSOLIDATED STATEMENTS OF CASH

CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Cash flows from operating activities
Net loss	$ (42,795)	$ (493)	$ (14,159)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation	7,605	7,223	6,441
Amortization of discount on marketable securities	(1,123)	(876)	241
Stock-based compensation expense	12,981	9,962	7,717
Change in fair value of convertible preferred stock warrant liability		77	3
Other non-cash expenses	98	91	82
Changes in operating assets and liabilities:
Related party receivable from collaboration	(1,537)	(3,669)	2,769
Prepaid expenses and other assets	(1,988)	(4,365)	(1,103)
Accounts payable	3,642	3,484	(4,230)
Accrued expenses and other liabilities	8,877	4,059	2,603
Deferred rent	(2,683)	(1,957)	(1,256)
Deferred revenue	(24,251)	(21,133)	(16,521)
Net cash used in operating activities	(41,174)	(7,597)	(17,413)
Cash flows from investing activities
Purchase of marketable securities	(134,306)	(133,609)	(217,291)
Proceeds from sales and maturities of marketable securities	186,518	178,182	220,917
Purchase of property and equipment	(3,489)	(5,844)	(6,422)
Net cash provided by (used in) investing activities	48,723	38,729	(2,796)
Cash flows from financing activities
Proceeds from issuance of common stock upon initial public offering, net of issuance costs	109,959
Proceeds from issuance of common stock upon completion of private placement	65,947
Proceeds from issuance of common stock upon exercise of stock options	3,575	2,583	339
Proceeds from issuance of common stock in connection with employee stock purchase plan	1,270
Repurchase of common stock		(185)
Deferred IPO costs		(2,200)
Net cash provided by financing activities	180,751	198	339
Net increase (decrease) in cash and cash equivalents	188,300	31,330	(19,870)
Cash, cash equivalents and restricted cash at beginning of period	59,172	27,842	47,712
Cash, cash equivalents and restricted cash at end of period	247,472	59,172	27,842
Reconciliation of cash, cash equivalents and restricted cash to the consolidated balance sheets:
Cash and cash equivalents	245,598	56,923	25,593
Restricted cash	1,874	2,249	2,249
Cash, cash equivalents and restricted cash at end of period	247,472	59,172	27,842
Supplemental disclosures of cash flow information:
Income taxes paid		1	536
Non-cash investing and financing activities:
Net exercise of convertible preferred stock warrant to Series A preferred stock	198
Vesting of common stock from early exercises	993	764	527
Cost of property and equipment in accounts payable and accrued liabilities	$ 305	607	$ 208
Deferred IPO costs in accounts payable and accrued liabilities		$ 92

Organization and Description of

Organization and Description of Business	12 Months Ended
	Dec. 31, 2019
Organization Consolidation And Presentation Of Financial Statements [Abstract]
Organization and Description of Business	1. Organization and Description of Business NGM Biopharmaceuticals, Inc. and its wholly-owned subsidiary (collectively, referred to as the “Company”) is a research-driven, clinical-stage biopharmaceutical company committed to discovering and developing first-in-class therapeutics for major diseases with an initial focus on cardio-metabolic, liver, oncologic and ophthalmic diseases. The Company’s current portfolio is composed of six product candidates (aldafermin (NGM282), NGM313, NGM120, NGM217, NGM621 and NGM395) focused on NASH, diabetes, oncology, AMD and metabolic disease. The Company was incorporated in Delaware in December 2007 and its headquarters are located at 333 Oyster Point Blvd., South San Francisco, California 94080. The Company operates in one business segment. Stock Split On March 22, 2019, the Company filed an amendment to the Company’s amended and restated certificate of incorporation to effect a reverse split of shares of the Company’s common stock on a two-for-one basis (the “Reverse Stock Split”). In connection with the Reverse Stock Split, the conversion ratio for the Company’s outstanding convertible preferred stock was proportionately adjusted such that the common stock issuable upon conversion of such preferred stock was decreased in proportion to the Reverse Stock Split. The par value of the common stock was not adjusted as a result of the Reverse Stock Split. All references to common stock, options to purchase common stock, early exercised options, share data, per share data, convertible preferred stock (to the extent presented on an as-converted to common stock basis) and related information contained in these consolidated financial statements have been retrospectively adjusted to reflect the effect of the Reverse Stock Split for all periods presented. Initial Public Offering On April 3, 2019, the Company’s registration statement on the Form S-1 was declared effective by the SEC for its IPO of its common stock. The Company’s shares of common stock started trading on the Nasdaq Global Select Market on April 4, 2019 and the transaction closed on April 8, 2019. In connection with the IPO, the Company sold an aggregate of 7,521,394 shares of common stock, which included 6,666,667 shares of common stock and 854,727 shares of common stock sold pursuant to the underwriters’ exercise of their option to purchase additional shares, at a public offering price of $16.00 per share. The aggregate net proceeds received by the Company from the offering were $107.8 million, net of underwriting discounts and commissions as well as offering expenses of $4.1 million, of which $2.2 million were paid in 2018. Upon the closing of the IPO, all shares of the Company’s outstanding convertible preferred stock were automatically converted to 47,283,839 shares of common stock and the related carrying amount of $295.1 million was reclassified to common stock and additional paid-in capital within stockholders’ equity (deficit). Concurrent with the closing of the IPO, the Company also issued 4,121,683 shares of its common stock to Merck in a private placement at a price of $16.00 per share for proceeds of $65.9 million, which resulted in Merck owning approximately 19.9% of the Company’s outstanding shares of common stock (Note 6)

Summary of Significant Accounti

Summary of Significant Accounting Policies	12 Months Ended
	Dec. 31, 2019
Accounting Policies [Abstract]
Summary of Significant Accounting Policies	2. Summary of Significant Accounting Policies Basis of Presentation and Principles of Consolidation The accompanying consolidated financial statements have been prepared in accordance with U.S. GAAP and include the consolidated accounts of the Company and its subsidiary. These consolidated financial statements include the consolidated accounts of the Company and its wholly-owned foreign subsidiary in Australia. All intercompany balances and transactions have been eliminated upon consolidation. Use of Estimates The preparation of consolidated financial statements in conformity with U.S. GAAP requires management to make judgments, assumptions and estimates that affect the reported amounts of assets, liabilities, revenues and expenses. Specific accounts that require management estimates include, but are not limited to, stock-based compensation, the valuation of convertible preferred stock warrants, the fair value of convertible preferred and common stock, contract manufacturing and clinical trial accruals, collaboration revenue and associated transaction price determined in accordance with Accounting Standards Codification Topic 606, Revenue from Contracts with Customers (“ASC 606”). Management bases its estimates on historical experience and on various other assumptions that are believed to be reasonable under the circumstances, the results of which form the basis for making judgments about the carrying value of assets and liabilities that are not readily apparent from other sources. Actual results could differ materially from those estimates. Need for Additional Capital Since inception, the Company has incurred net losses and negative cash flow from operations. During the years ended December 31, 2019, 2018 and 2017, the Company incurred net losses of $42.8 million, $0.5 million and $14.2 million, respectively. As of December 31, 2019, the Company had an accumulated deficit of $196.1 million and does not expect to experience positive cash flows from operations in the near future. The Company had $344.5 million of cash, cash equivalents and marketable securities as of December 31, 2019, and therefore the Company expects that its cash and cash equivalents and marketable securities will be sufficient to fund its operations for a period of at least one year from the date these consolidated financial statements are available for issuance. To fully implement the Company’s business plan and fund its operations, the Company will need to raise additional capital through the issuance of equity securities or debt financings, collaborations, strategic alliances and licensing arrangements, government or other third-party funding or a combination of these. Deferred Initial Public Offering Costs Costs incurred in connection with the IPO primarily consisted of direct incremental legal, printing and accounting fees. IPO costs were capitalized as incurred and upon completion of the IPO, these costs were offset against the proceeds and recorded in additional paid-in capital. As of December 31, 2019 and 2018, deferred IPO costs included on the accompanying consolidated balance sheets were zero and $2.3 million, respectively. Fair Value of Financial Instruments The carrying amounts of cash and cash equivalents, the related party receivables from collaboration and other current assets and liabilities approximate their respective fair values because of the short-term nature of those instruments. Fair value accounting is applied to the convertible preferred stock warrant liabilities that were recorded at their estimated fair value in the consolidated financial statements. Cash and Cash Equivalents Cash and cash equivalents are stated at fair value. Cash equivalents are securities with an original maturity of three months or less at the time of purchase. The Company limits its credit risk associated with cash and cash equivalents by placing its investments with a bank it believes is highly creditworthy and with highly rated money market funds. As of December 31, 2019 and 2018, cash and cash equivalents consisted of bank deposits and investments in money market funds. Marketable Securities The appropriate classification of the Company’s marketable securities is determined at the time of purchase and such designations are re-evaluated at each balance sheet date. All of the Company’s securities are considered as available-for-sale and carried at estimated fair values and reported in cash equivalents, short-term marketable securities or long-term marketable securities. Unrealized gains and losses on available-for-sale securities are excluded from net loss and reported in accumulated other comprehensive loss as a separate component of stockholders’ equity (deficit). Other income (expense), net, includes interest, amortization of purchase premiums and accretion of purchase discounts, realized gains and losses on sales of securities and other-than-temporary declines in the fair value of securities, if any. The cost of securities sold is based on the specific identification method. The Company’s investments are regularly reviewed for other-than-temporary declines in fair value. This review includes the consideration of the cause of the impairment, including the creditworthiness of the security issuers, the number of securities in an unrealized loss position, the severity and duration of the unrealized losses, whether the Company has the intent to sell the securities and whether it is more likely than not that the Company will be required to sell the securities before the recovery of their amortized cost basis. When the Company determines that the decline in fair value of an investment is below its carrying value and this decline is other-than-temporary, the Company reduces the carrying value of the security it holds and records a loss for the amount of such decline. Restricted Cash The Company’s restricted cash represents collateral in connection with the lease on the Company’s headquarters entered into in 2015 and is classified as a non-current asset on the consolidated balance sheets as the collateral will not be returned to the Company in less than 12 months (Note 7) Concentration of Credit and Other Risks Cash and cash equivalents and marketable securities from the Company’s available-for-sale and marketable security portfolio potentially subject the Company to concentrations of credit risk. The Company is invested in money market funds and marketable securities through custodial relationships with major U.S. and Australian banks. Under its investment policy, the Company limits amounts invested in such securities by credit rating, maturity, industry group, investment type and issuer, except for securities issued by the U.S. government. Related party receivables from collaborations (Notes 5 and 6) Merck accounted for 100% of the Company’s revenue for the years ended December 31, 2019, 2018 and 2017. Property and Equipment, Net Property and equipment is recorded at cost and consists of computer equipment, laboratory equipment and office furniture and leasehold improvements. Maintenance and repairs, and training on the use of equipment, are expensed as incurred. Costs that improve assets or extend their economic lives are capitalized. Depreciation is recognized using the straight-line method based on an estimated useful life of the asset, which is as follows: Computer equipment 3 years Laboratory equipment and office furniture 3 years Leasehold improvement Shorter of life of asset or lease term Leases The Company’s lease agreements for its laboratory and office facilities are classified as operating leases. Rent expense is recognized on a straight-line basis over the term of the lease. Incentives granted under the Company’s facilities leases, including allowances to fund leasehold improvements and rent holidays, are capitalized and are recognized as reductions to rental expense on a straight-line basis over the term of the lease. Impairment of Long-Lived Assets Long-lived assets, such as property and equipment, are reviewed for impairment whenever events or changes in circumstances indicate that the carrying amount of an asset may not be recoverable. Recoverability of assets to be held and used is measured by a comparison of the carrying amount of an asset to the estimated undiscounted future cash flows expected to be generated by the asset. If the carrying amount of an asset exceeds its estimated undiscounted future cash flows, an impairment charge is recognized as the amount by which the carrying amount of the asset exceeds the estimated fair value of the asset. As of December 31, 2019 and 2018, no revision to the remaining useful lives or write-down of long-lived assets was required. Income Taxes Income taxes are accounted for under the liability method. Deferred tax assets and liabilities are recognized for the future tax consequences attributable to the differences between the financial statement carrying amounts of existing assets and liabilities and their respective tax bases and the operating loss and tax credit carryforwards. Valuation allowances are established when necessary to reduce deferred tax assets to the amount expected to be realized. Deferred tax assets and liabilities are measured at the balance sheet date using the enacted tax rates expected to apply to taxable income in the years in which those temporary differences are expected to be recovered or settled. The effect on deferred tax assets and liabilities of a change in tax rates is recognized in the period such tax rate changes are enacted. Convertible Preferred Stock Warrant Freestanding warrants to purchase the Company’s convertible preferred stock were classified as a liability on the consolidated balance sheet at December 31, 2018 as the underlying shares of convertible preferred stock were contingently redeemable, which could have obligated the Company to transfer assets at some point in the future to settle the warrants. The convertible preferred stock warrants are subject to remeasurement at each balance sheet date, with changes in estimated fair value recorded in the Company’s consolidated statements of operations as a component of total other income (expense), net. On February 3, 2019, all convertible preferred stock warrants were automatically exercised on a net basis into 16,380 shares of Series A convertible preferred stock at a fair value of $0.2 million. As of December 31, 2019, there were no convertible preferred stock warrants outstanding. Revenue Recognition On January 1, 2019, the Company adopted ASU 2014-09, Revenue from Contracts with Customers (Topic 606), and subsequent amendments, using the modified retrospective transition method applied to those contracts that were not completed as of January 1, 2019. ASC 606 supersedes all prior revenue recognition guidance. Results for operating periods beginning after January 1, 2019 are presented under ASC 606, while prior period amounts have not been adjusted and continue to be reported in accordance with previous accounting rules under Accounting Standards Codification Topic 605, Revenue Recognition (“ASC 605”). Prior to the adoption of ASC 606, the Company’s revenue from collaboration agreements was recognized when the Company determined that persuasive evidence of an arrangement exists, services had been rendered, the price was fixed or determinable and collectability was reasonably assured. The Company would record amounts received prior to satisfying the above revenue recognition criteria as deferred revenue until all applicable revenue recognition criteria were met. Revenue allocated to research activities was generally recognized in the period the services were performed, and revenue allocated to licenses was generally recognized on a straight-line basis over the contractual term. Allocations to non-contingent elements were based on the relative selling price of each element using vendor-specific objective evidence or third-party evidence, where available. In the absence of either of these measures, the Company used the best estimate of selling price for that deliverable. The most significant change to the Company’s policies upon the adoption of ASC 606 is the estimation of an arrangement’s total transaction price, which includes unconstrained Note 2 – Recently Adopted Accounting Pronouncements The core principle in ASC 606 requires an entity to recognize revenue upon the transfer of goods or services to customers in an amount that reflects the consideration to which the entity expects to be entitled in exchange for those goods or services. The Company applies the following five-step revenue recognition model outlined in ASC 606 to adhere to this core principle: (1) identify the contract(s) with a customer; (2) identify the performance obligations in the contract; (3) determine the transaction price; (4) allocate the transaction price to the performance obligations in the contract; and (5) recognize revenue when (or as) the Company satisfies a performance obligation. All of the Company’s revenue to date has been generated from its collaboration agreements. The terms of these agreements generally require the Company to provide (i) license options for its compounds, (ii) research and development services and (iii) non-mandatory services in connection with participation in research or steering committees. Payments received under these arrangements may include non-refundable upfront license fees, partial or complete reimbursement of research and development costs, contingent consideration payments based on the achievement of defined collaboration objectives and royalties on sales of commercialized products. In some agreements, the collaboration partner is solely responsible for meeting defined objectives that trigger contingent or royalty payments. Often the partner only pursues such objectives subsequent to exercising an optional license on compounds identified as a result of the research and development services performed under the collaboration agreement. The Company assesses whether the promises in its arrangements, including any options provided to the customer, are considered distinct performance obligations that should be accounted for separately. Judgment is required to determine whether the license to a compound is distinct from research and development services or participation in steering committees, as well as whether options create material rights in the contract. The transaction price in each arrangement is generally comprised of a non-refundable upfront fee and unconstrained The Company’s collaboration agreements may include contingent payments related to specified development and regulatory milestones or contingent payments for royalties based on sales of a commercialized product. Milestones can be achieved for such activities in connection with progress in clinical trials, regulatory filings in various geographical markets and marketing approvals from regulatory authorities. Sales-based royalties are generally related to the volume of annual sales of a commercialized product. At the inception of each agreement that includes such payments, the Company evaluates whether the milestones are considered probable of being achieved and estimates the amount to be included in the transaction price by using the most likely amount method. If it is probable that a significant revenue reversal would not occur, the associated milestone value is included in the transaction price. Milestone payments that are not within the Company’s or its customer’s control, such as those related to regulatory approvals, are not considered probable of being achieved until those approvals are received. The transaction price is then allocated to each performance obligation based on a relative SSP basis. At the end of each subsequent reporting period, the Company re-evaluates the probability of achievement of each such milestone and any related constraint and, if necessary, adjusts its estimate of the overall transaction price. Pursuant to the guidance in ASC 606, sales-based royalties are not included in the transaction price. Instead, royalties are recognized at the later of when the performance obligation is satisfied or partially satisfied, or when the sale that gives rise to the royalty occurs. Research and Development Research and development costs are expensed as incurred. Research and development expenses primarily include salaries and benefits for medical, clinical, quality, preclinical, manufacturing and research personnel, costs related to research activities, preclinical studies, clinical trials, drug manufacturing expenses and allocated overhead and facility occupancy costs. The Company accounts for non-refundable advance payments for goods or services that will be used in future research and development activities as expenses when the goods have been received or when the service has been performed rather than when the payment is made. Clinical trial costs are a component of research and development expenses. The Company expenses costs for its clinical trial activities performed by third parties, including CROs and other service providers, as they are incurred, based upon estimates of the work completed over the life of the individual study in accordance with associated agreements. The Company uses information it receives from internal personnel and outside service providers to estimate the clinical trial costs incurred. Stock-Based Compensation The Company’s stock-based compensation programs include stock options and shares that will be issued under the Company’s 2019 ESPP. Stock-based compensation to employees is valued on the grant date of each award using the Black-Scholes option-pricing model, and its estimated fair value is recognized over the period during which the employee is required to provide service in exchange for the award, which is generally the vesting period of each award. Subsequent to the adoption of ASU 2018-07, Stock Compensation (Topic 718): Improvements to Nonemployee Share-Based Payment Accounting on January 1, 2019, stock-based compensation expense for non-employee stock-based awards is also measured based on the fair value on grant date with its estimated fair value recorded over the period for which the non-employee is required to provide service in exchange for the award. As non-cash stock-based compensation expense is based on awards ultimately expected to vest, it is reduced by an estimate for future forfeitures. Forfeitures are estimated at the time of grant and revised, if necessary, in subsequent periods if actual forfeitures materially differ from estimates. Foreign Currency Transactions The functional currency of NGM Biopharmaceuticals Australia Pty Ltd., a wholly-owned subsidiary, is the U.S. Dollar. Accordingly, all monetary assets and liabilities of the subsidiary are remeasured into U.S. Dollars at the current period-end exchange rates and non-monetary assets are remeasured using historical exchange rates. Income and expense elements are remeasured to U.S. Dollars using the average exchange rates in effect during the period. Remeasurement gains and losses are recorded as other income (expense), net on the consolidated statements of operations. The Company is subject to foreign currency risk with respect to its clinical and manufacturing contracts denominated in currencies other than the U.S. Dollar, primarily British Pounds, Swiss Francs, Australian Dollars and the Euro. Payments on contracts denominated in foreign currencies are made at the spot rate on the day of payment. Changes in the exchange rate between billing dates and payment dates are recorded within other income (expense), net on the consolidated statements of operations. Comprehensive Loss Comprehensive loss is comprised of net loss and certain changes in equity that are excluded from net loss. For the years ended December 31, 2019, 2018 and 2017, the difference between comprehensive loss and net loss consisted of changes in net unrealized gain on marketable securities of $0.3 million, net unrealized gain on marketable securities of $0.2 million and net unrealized loss on marketable securities of $0.3 million, respectively. Net Loss per Share Basic net loss per share is calculated by dividing net loss by the weighted average number of shares outstanding during the period, less shares subject to repurchase and excludes any dilutive effects of stock-based awards and warrants. Diluted net loss per share is computed giving effect to all potentially dilutive shares, including common stock issuable upon exercise of stock options, and unvested restricted common stock and stock units. As the Company had net losses for the years ended December 31, 2019, 2018 and 2017, all potential shares were determined to be anti-dilutive. The following table sets forth the computation of net loss per share (in thousands, except share and per share amounts): Year Ended December 31, 2019 2018 2017 Numerator: Net loss $ (42,795 ) $ (493 ) $ (14,159 ) Denominator: Weighted average number of shares used in calculating net loss per share—basic and diluted 50,297,524 6,383,751 5,961,767 Net loss per share—basic and diluted $ (0.85 ) $ (0.08 ) $ (2.37 ) Potential gross dilutive securities that were not included in the diluted per share calculations because they would be anti-dilutive were as follows: Year Ended December 31, 2019 2018 2017 Convertible preferred stock — 47,267,466 47,267,466 Options to purchase common stock 10,824,780 9,806,689 8,468,702 Warrants to purchase convertible preferred stock — 19,637 19,637 Shares committed under ESPP 396,682 — — Total 11,221,462 57,093,792 55,755,805 Segment and Geographical Information The Company operates in one segment. Substantially all of the Company’s long-lived assets, primarily comprised of property and equipment, are based in the United States. For the years ended December 31, 2019, 2018 and 2017, the Company’s revenues were entirely within the United States. Recent Accounting Pronouncements New accounting pronouncements are issued by the Financial Accounting Standards Board (“FASB”) or other standard setting bodies and adopted by the Company as of the specified effective date. Unless otherwise discussed, the impact of recently issued standards that are not yet effective will not have a material impact on our consolidated financial statements upon adoption. Under the JOBS Act, the Company meets the definition of an emerging growth company, and has elected the extended transition period for complying with new or revised accounting standards pursuant to Section 107(b) of the JOBS Act. Recently Adopted Accounting Pronouncements In June 2018, the FASB issued ASU 2018-07, Compensation – Stock Compensation (Topic 718): Improvements to Non-Employee Share-Based Payment Accounting as part of the FASB simplification initiative. The new standard expands the scope of Topic 718, allowing the Company to apply the requirements of Topic 718 to certain non-employee awards issued in exchange for the acquisition of goods and services from non-employees. ASU 2018-07 is intended to supersede Subtopic 505-50, Equity-Based Payments to Non-Employees and is effective for the Company for fiscal years beginning after December 15, 2019. Effective January 1, 2019, the Company early adopted this ASU using the modified retrospective transition method in which all previously issued equity-classified share-based payment awards to non-employees were remeasured at fair value as of the adoption date. Newly issued equity-classified share-based payments awards to non-employees are measured at fair value as of grant date. The adoption of this ASU did not have a material impact on the Company’s consolidated financial statements. In May 2014, the FASB issued ASU 2014-09, Revenue from Contracts with Customers (Topic 606), which requires an entity to recognize the amount of revenue to which it expects to be entitled for the transfer of promised goods or services to customers. ASU 2014-09 replaced existing revenue recognition guidance and permits the use of either the full retrospective or modified retrospective transition method. Additionally, in March 2016, the FASB issued ASU 2016-08, Revenue from Contracts with Customers (Topic 606): Principal versus Agent Considerations (Reporting Revenue Gross versus Net), which clarifies the implementation guidance on principal versus agent considerations in ASU 2014-09. In April 2016, the FASB issued ASU 2016-10, Revenue from Contracts with Customers (Topic 606): Identifying Performance Obligations and Licensing, which clarifies certain aspects of identifying performance obligations and licensing implementation guidance. In May 2016, the FASB issued ASU 2016-12, Revenue from Contracts with Customers (Topic 606): Narrow-Scope Improvements and Practical Expedients, which relates to disclosures of remaining performance obligations, as well as other amendments to guidance on collectability, non-cash consideration and the presentation of sales and other similar taxes collected from customers. For the Company, these standards (collectively, ASC 606) have the same effective date and transition date of January 1, 2019. The Company adopted ASC 606 on January 1, 2019, using the modified retrospective transition method and, therefore, evaluated its contract with Merck under ASC 606. The Company recorded adjustments upon the adoption of ASC 606 as a result of the Company concluding that licenses and research and development services promised in the agreement are a single combined performance obligation. This determination impacts the timing of recognition of both the non-refundable upfront fee and the payments related to the services. Under previous guidance, the upfront fee was recognized ratably over the contract term, and fees related to the services were recognized in the period the services were performed. Under ASC 606, revenue for the single performance obligation is recognized over time using a cost-based input method to measure progress toward completion of the single combined performance obligation. The adoption of ASC 606 impacted the Company’s contract liabilities and accumulated deficit balance as of January 1, 2019 as follows (in thousands): December 31, 2018 Adjustments due to the Adoption of ASC 606 January 1, 2019 Deferred revenue, current $ 19,025 $ 5,171 $ 24,196 Deferred revenue, noncurrent 3,942 985 4,927 Accumulated deficit (147,193 ) (6,156 ) (153,349 ) The impact of the adoption of ASC 606 on the consolidated statement of operations and cash flows for the year ended December 31, 2019 was as follows (in thousands): As of December 31, 2019 Amount Under ASC 605 Effect of Adoption Higher (Lower) As Reported Deferred revenue, current $ 3,887 $ 985 $ 4,872 Accumulated deficit (195,159 ) (985 ) (196,144 ) Year Ended December 31, 2019 Amount Under ASC 605 Effect of Adoption Higher (Lower) As Reported Related party revenue $ 98,373 $ 5,171 $ 103,544 Loss from operations (54,511 ) 5,171 (49,340 ) Net loss (47,966 ) 5,171 (42,795 ) Net loss per common share, basic and diluted (0.95 ) (0.85 ) Year Ended December 31, 2019 Amount Under ASC 605 Effect of Adoption Higher (Lower) As Reported Cash flows from operating activities: Net loss $ (47,966 ) $ 5,171 $ (42,795 ) Changes in operating assets and liabilities: Deferred revenue (19,080 ) (5,171 ) (24,251 ) Recent Accounting Pronouncements Not Yet Adopted In February 2016, the FASB issued ASU 2016-02, Leases (Topic 842), which increases lease transparency and comparability among organizations. Under the new standard, lessees will be required to recognize right-of-use (“ROU”) assets and lease liabilities arising from lease arrangements on the consolidated balance sheets, with the exception of leases with a term of 12 months or less, which permits a lessee to make an accounting policy election by class of underlying asset not to recognize the ROU assets and lease liabilities. In March 2018, the FASB approved an alternative transition method to the modified retrospective approach, which eliminates the requirement to restate prior period consolidated financial statements and allows the cumulative effect of the retrospective allocation to be recorded as an adjustment to the opening balance of retained earnings at the date of adoption. In November 2019, the FASB issued ASU 2019-10, which defers the effective date for certain ASUs including ASU 2016-02. The new guidance is now effective for the Company’s fiscal year beginning after December 15, 2020, and interim periods within fiscal years beginning after December 15, 2021. The Company plans to adopt the new lease standard using the optional transition method, which allows the Company to recognize a cumulative-effect adjustment to the opening balance of accumulated deficit at the date of adoption and apply the new disclosure requirements beginning in the period of adoption. The Company also plans to elect the package of practical expedients permitted under the transition guidance within the new standard, which, among other things, allows the Company to carryforward the historical lease classification and make an accounting policy election whereby ROU assets and lease liabilities associated with lease arrangements with terms less than one year will not be recognized. We will continue to evaluate the effect that this guidance will have on our consolidated financial statements. In June 2016, the FASB issued ASU 2016-13, Financial Instruments – Credit Losses (Topic 326): Measurement of Credit Losses on Financial Instruments. The new guidance amended guidance on reporting credit losses for assets held at amortized cost basis and available-for-sale debt securities. For available-for-sale debt securities, credit losses will be presented as an allowance rather than as a write-down. This standard is effective for the Company’s fiscal year beginning after December 15, 2020. Early adoption is permitted for all entities. The Company is currently assessing the timing of adoption and the impact that the adoption of ASU 2016-13 will have on its consolidated financial statements. In August 2018, the FASB issued ASU 2018-13, Fair Value Measurements (Topic 820): Disclosure Framework – Changes to the Disclosure Requirements for Fair Value Measurement as part of the FASB’s disclosure framework project. This ASU modifies the disclosure requirements on fair value measurements in Topic 820, Fair Value Measurement by removing the requirement to disclose amounts of and reasons for transfers between Level 1 and Level 2 of the fair value hierarchy, the policy for timing of transfers between levels and the valuation process for Level 3 fair value measurements. This ASU also modifies existing disclosure requirements by clarifying that the measurement uncertainty disclosure is to communicate information about the uncertainty in measurement as of the reporting date, and it adds required disclosures for the changes in unrealized gains and losses for the period included in other comprehensive income for recurring Level 3 fair value measurements held at the end of the reporting period, and the range and weighted average of significant unobservable inputs used to develop Level 3 fair value measurements. This ASU will be effective for the Company for fiscal years and interim periods within those fiscal years, beginning after December 15, 2019. The Company is currently assessing the impact of this ASU on its consolidated financial statements. In November 2018, the FASB issued ASU 2018-18, Collaborative Arrangements (ASC 808): Clarifying the Interaction between ASC 808 and ASC 606, which clarifies that certain transactions between collaborative arrangement participants should be accounted for as revenue under ASC 606 when the collaborative arrangement participant is a customer in the context of a unit of account. In those situations, all the guidance in ASC 606 should be applied, including recognition, measurement, presentation and disclosure requirements. This ASU adds unit-of-account guidance in ASC 808 to align with the guidance in ASC 606 (that is, a distinct good or service) when an entity is assessing whether the collaborative arrangement or a part of the arrangement is within the scope of ASC 606, and requires that in a transaction with a collaborative arrangement participant that is not directly related to sales to third parties, presenting the transaction together with revenue recognized under ASC 606 is precluded if the collaborative arrangement participant is not a customer. This ASU will be effective for the Company for fiscal years beginning after December 15, 2020, and interim periods within fiscal years beginning after December 15, 2021. Th

Fair Value Measurements

Fair Value Measurements	12 Months Ended
	Dec. 31, 2019
Fair Value Disclosures [Abstract]
Fair Value Measurements	3. Fair Value Measurements Financial assets and liabilities are recorded at fair value. The carrying amount of certain financial instruments, including cash and cash equivalents, receivable from collaboration, related party receivable from collaboration and other current assets and liabilities approximate fair value due to their relatively short maturities. Assets and liabilities recorded at fair value on a recurring basis in the balance sheets are categorized based upon the level of judgment associated with the inputs used to measure their fair values. Fair value accounting is applied to the convertible preferred stock warrant liabilities that are recorded at their estimated fair value in the consolidated financial statements. The FASB has defined fair value as the exchange price that would be received for an asset or paid to transfer a liability, or an exit price, in the principal or most advantageous market for that asset or liability in an orderly transaction between market participants on the measurement date, and established a fair value hierarchy that requires an entity to maximize the use of observable inputs, where available, and minimize the use of unobservable inputs when measuring fair value. The FASB set forth three levels of inputs that may be used to measure fair value: Level 1: Quoted prices in active markets for identical assets or liabilities. Level 2: Observable inputs other than Level 1 prices, such as quoted prices for similar assets or liabilities, quoted prices in markets that are not active, or other inputs that are observable or can be corroborated by observable market data for substantially the full term of the assets or liabilities. Level 3: Unobservable inputs that are supported by little or no market activity and that are significant to the fair value of the assets or liabilities. Assets and liabilities measured at fair value are classified in their entirety based on the lowest level of input that is significant to the fair value measurement. The Company’s assessment of the significance of a particular input to the fair value measurement in its entirety requires management to make judgments and consider factors specific to the asset or liability. To date, the Company has not recorded any impairment charges on marketable securities other than temporary declines in market value. In determining whether a decline is other than temporary, the Company considers various factors including the length of time and extent to which the market value has been less than cost, the financial condition and near-term prospects of the issuer and the Company’s intent and ability to retain its investment in the issuer for a period of time sufficient to allow for any anticipated recovery in market value. The Company estimates the fair values of investments in corporate agency bond securities, commercial paper and government agencies securities using level 2 inputs, by taking into consideration valuations obtained from third-party pricing services. The pricing services utilize industry standard valuation models, including both income and market-based approaches, for which all significant inputs are observable, either directly or indirectly, to estimate fair value. These inputs include reported trades of and broker/dealer quotes on the same or similar securities, issuer credit spreads, benchmark securities, prepayment/default projections based on historical data and other observable inputs. Cash and cash equivalents and marketable securities, all of which are classified as available-for-sale securities consisted of the following (in thousands): Amortized Cost Gross Unrealized Gain Gross Unrealized Loss Fair Value As of December 31, 2019 Money market funds $ 244,973 $ — $ — $ 244,973 Corporate and agency bonds 66,063 14 — 66,077 Commercial paper 24,840 — — 24,840 U.S. government agencies securities 7,985 11 — 7,996 Total $ 343,861 $ 25 $ — $ 343,886 Classified as: Cash and cash equivalents $ 244,973 Short-term marketable securities (amortized cost of $98,888) 98,913 Total cash equivalents and marketable securities $ 343,886 Amortized Cost Gross Unrealized Gain Gross Unrealized Loss Fair Value As of December 31, 2018 Money market funds $ 34,983 $ — $ — $ 34,983 Corporate and agency bonds 68,322 — (241 ) 68,081 Commercial paper 17,904 — — 17,904 U.S. government agencies securities 63,751 — (26 ) 63,725 Total $ 184,960 $ — $ (267 ) $ 184,693 Classified as: Cash and cash equivalents $ 34,983 Short-term marketable securities (amortized cost of $149,977) 149,710 Total cash equivalents and marketable securities $ 184,693 Cash and cash equivalents in the table above excludes cash on deposit with banks of $0.6 million and $21.9 million as of December 31, 2019 and 2018, respectively. As of December 31, 2019 and 2018, the Company’s marketable securities all had remaining contractual maturities less than one year. Assets and Liabilities Measured at Fair Value on a Recurring Basis The following table sets forth the estimated fair value of the Company’s financial assets and liabilities that were measured at fair value on a recurring basis as of December 31, 2019 and 2018 (in thousands): Fair Value Measurements As of December 31, 2019 Level 1 Level 2 Level 3 Total Assets: Money market funds $ 244,973 $ — $ — $ 244,973 Corporate and agency bonds — 66,077 — 66,077 Commercial paper — 24,840 — 24,840 U.S. government agencies securities — 7,996 — 7,996 $ 244,973 $ 98,913 $ — $ 343,886 Fair Value Measurements As of December 31, 2018 Level 1 Level 2 Level 3 Total Assets: Money market funds $ 34,983 $ — $ — $ 34,983 Corporate and agency bonds — 68,081 — 68,081 Commercial paper — 17,904 — 17,904 U.S. government agencies securities — 63,725 — 63,725 $ 34,983 $ 149,710 $ — $ 184,693 Liabilities: Convertible preferred stock warrant liability $ — $ — $ 198 $ 198 $ — $ — $ 198 $ 198 There were no transfers of assets or liabilities between the fair value measurement levels during the years ended December 31, 2019 and 2018. The following table provides a summary of changes in the fair value of the Company’s convertible preferred stock warrant liability (in thousands): Fair Value Using Level 3 Inputs Amounts Balance at December 31, 2017 $ 121 Change in fair value of warrant liability included in other income (expense), net 77 Balance at December 31, 2018 $ 198 Balance at December 31, 2018 $ 198 Net exercise of preferred stock warrant to Series A preferred stock (198 ) Balance at December 31, 2019 $ — On February 3, 2019, all of the warrants were automatically exercised on a net basis into shares of Series A preferred stock. There were no convertible preferred stock warrants outstanding as of December 31, 2019.

Balance Sheet Components

Balance Sheet Components	12 Months Ended
	Dec. 31, 2019
Statement Of Financial Position [Abstract]
Balance Sheet Components	4. Balance Sheet Components Property and Equipment Property and equipment consist of the following (in thousands): December 31, 2019 2018 Computer equipment $ 1,201 $ 1,123 Laboratory equipment and office furniture 21,652 18,977 Leasehold improvements 25,880 25,314 Construction in process 498 679 Total property and equipment, gross 49,231 46,093 Less: accumulated depreciation and amortization (29,756 ) (22,200 ) Total property and equipment, net $ 19,475 $ 23,893 Depreciation expense for the years ended December 31, 2019, 2018 and 2017 was approximately $7.6 million, $7.2 million and $6.4 million, respectively. Accrued Liabilities Accrued liabilities consist of the following (in thousands): December 31, 2019 2018 Accrued expenses $ 2,901 $ 2,595 Clinical trials and research and development costs 11,051 4,844 Personnel-related costs 6,446 4,148 Manufacturing costs 2,593 2,416 Total accrued liabilities $ 22,991 $ 14,003

Research Collaboration and Lice

Research Collaboration and License Agreements	12 Months Ended
	Dec. 31, 2019
Collaboration And License Agreement Disclosure [Abstract]
Research Collaboration and License Agreements	5. Research Collaboration and License Agreements Merck In February 2015, the Company entered into the Collaboration Agreement with Merck, covering the discovery, development and commercialization of novel therapies across a range of therapeutic areas. Pursuant to this agreement, the Company received an upfront payment of $94.0 million in April 2015. Concurrent with entry into the Collaboration Agreement, the parties entered into a Stock Purchase Agreement in which Merck agreed to purchase 8,833,333 shares of Series E convertible preferred stock at a price of $12.00 per share, resulting in net proceeds of approximately $106.0 million. The Company considered the ASC 606 criteria for combining contracts and determined that the Collaboration Agreement and Stock Purchase Agreement should be combined into a single contract. The Company accounted for the overall agreement based on the fair values of the assets and services exchanged, resulting in $106.0 million allocated to the equity component and $94.0 million allocated to the revenue components. The Collaboration Agreement became effective in March 2015 and has a non-cancellable five-year term running through March 16, 2020. The agreement included an exclusive worldwide license to our GDF15 receptor agonist program. In March 2019, Merck exercised its option to extend the research phase of the collaboration through March 16, 2022. Merck terminated its license to the GDF15 receptor agonist program effective May 31, 2019. The collaboration also includes a broad, multiyear drug discovery and early development program financially supported by Merck but scientifically directed by the Company with input from Merck. The Company determines the scientific direction and areas of therapeutic interest, with input from Merck, and is primarily responsible for the conduct of all research, preclinical and early clinical development activities, through human proof of concept. The Company makes the final determinations as to which compounds to advance into and through initial clinical trials, which to progress into human proof-of-concept studies and the design of any such studies, with input from Merck through various governance committees. The Company may terminate its participation in any of the governance committees by providing written notice to Merck of its intention to disband and no longer participate. Merck will fund both the internal and external costs of the Company’s research and early development activities up to $75.0 million each year of the initial five-year term and during the extended two-year research period. Upon completion of a human proof-of-concept study for a particular compound, regardless of the results of such study, Merck has the one-time option, at a cost of $20.0 million, to obtain an exclusive, worldwide license, on specified terms, to that compound, as well as to other molecules that are directed against the same target in the same manner. If Merck exercises its option, Merck will be responsible, at its own cost, for any further development and commercialization activities for compounds within that Optioned Program. Upon such exercise by Merck, the Company in turn has the right, at the start of the first Phase 3 clinical study for that compound, to elect to participate in a worldwide cost and profit share with Merck, as well as the option to co-detail the compound in the United States, or the Company can elect instead to receive milestones and royalties from Merck based on Merck’s further development and commercialization of the compound. If the Company elects to participate in the cost and profit share, subject to certain limitations, Merck will provide the Company with financial assistance in the form of interest bearing advances of the Company’s share of the overall development costs, which Merck will recoup from the Company’s share of any profit ultimately resulting from sales of the compound and other compounds that reach commercialization. If the Company does not opt in to the cost and profit sharing option, then the Company is eligible to receive development and regulatory milestone payments upon the achievement of specific clinical development or regulatory events with respect to the licensed compound indications in the United States, EU and Japan of up to an aggregate of $449.0 million. The Company may also receive commercial milestone payments up to $125.0 million and royalty payments of varying percentages based on the achievement of certain levels of net sales. Under the Collaboration Agreement, the Company also granted Merck a worldwide, exclusive right to conduct research and development on small molecule compounds generated by Merck that have specified activity against any target that the Company is researching or developing under the research phase and about which the Company has generated unique biological insights. If Merck ultimately does not exercise its license option to the compound the Company has taken through a human proof-of-concept study that is directed to any such target, Merck’s research license for its own small molecule program will become non-exclusive, but it will retain an exclusive license to any small molecule compounds that it has, as of that time, identified and developed. Merck has sole responsibility for the research and development of any of these small molecule compounds, at its own cost. The Company is eligible to receive milestone and royalty payments on small molecule compounds that are developed by Merck under the Company’s license, in some cases at the same rates as those the Company is eligible to receive from Merck for a licensed program originating from the Company’s own research and development efforts, provided that, but for use of the Company’s proprietary information, Merck would not have discovered such small molecule compounds. However, the Company will not have the option to cost and profit share or the option to co-detail those small molecule products. The research and early development program had an initial term of five years, until March 16, 2020. In March 2019, Merck exercised its option to extend the research phase of the collaboration through March 16, 2022. In connection with this extension, Merck agreed to continue to fund the Company’s research and development efforts during the two-year extension period at the same levels as during the initial term and, in lieu of a $20.0 million extension fee that would have otherwise been payable to the Company, Merck will make additional payments totaling up to $20.0 million in support of the Company’s research and development program activities across 2021 and the first quarter of 2022. Under the terms of the agreement, Merck is required to pay a $20.0 million extension fee if it elects to exercise its second option to extend the research phase of the collaboration through March 16, 2024. At the end of the research phase, Merck has the right to either require the Company to continue to conduct research and development activities with respect to certain of the then-existing programs for up to three years, which we call the tail period, by agreeing to pay all its internal and external costs for related work, or to take over such selected programs and conduct such research and development activities itself, at its own cost. The Company evaluated the Collaboration Agreement with Merck under ASC 606. The Company identified the following promised goods or services at the inception of the Collaboration Arrangement: (i) license to GDF15 receptor agonist program; (ii) license to pursue research and development and commercialization of small molecule compounds; (iii) performance of research and development services for five years; (iv) two options to extend performance of the research and development services, each for two additional years; and (v) options to obtain licenses to additional compounds after proof of concept trials. The Company determined the GDF15 receptor agonist program license and small molecule program license are not distinct from the research and development services, resulting in these items being combined into a single performance obligation. The Company considered whether the options created material rights in the contract and concluded that the fee attached to the exercise of such options approximated the SSP of the promised goods or services included in the options. Therefore, the options do not give rise to material rights, are not performance obligations in the Collaboration Agreement and, if and when exercised, will be accounted for as separate arrangements under ASC 606. The transaction price consists of the $94.0 million upfront fee and the potential funding amounts of up to $75.0 million per year for each of the first five years of the Collaboration Agreement. No milestones or other forms of consideration are included in the transaction price as those amounts are contingent upon Merck exercising an option for licenses on additional compounds and would, therefore, be pursuant to separate arrangements and are not part of the Collaboration Agreement estimated transaction price. Additionally, if a separate arrangement is created by the exercise of an option, such amounts would then be contingent on events outside of either party’s control, such as products proving to be commercially viable and governmental agencies granting regulatory approval. Such contingencies and uncertainties result in the amounts being constrained and withheld from inclusion in the estimated transaction price of a separate arrangement. Consequently, the estimated transaction price related to the Collaboration Agreement is comprised of the up-front payment and the ongoing research and development reimbursements. Any fees associated with options, including upfront fees, funding fees, milestones, etc., are not included in the transaction price as they are associated with options that are not material rights and, thus, are not performance obligations within the Collaboration Agreement. This includes the $20.0 million license fee associated with Merck’s exercise of its option on NGM313. That amount was recognized in the period of exercise (i.e., fourth quarter of 2018) as the Company has no further obligations related to that license. Merck exercised its option on the NGM313 compound and paid the Company the $20.0 million option exercise fee in November 2018. The Phase 3 clinical study for NGM313 has not begun, and the Company has not made an election as to whether it will participate in the cost and profit share or receive milestone and royalty payments. The amounts do not impact the estimated transaction price associated with the single performance obligation identified in the Collaboration Agreement. As there is only one performance obligation in the Collaboration Agreement, the transaction price was allocated entirely to that performance obligation. The Company uses a cost-based input method to measure proportional performance and calculate the corresponding amount of revenue to recognize. The Company believes this is the best measure of progress given that other measures do not reflect how the Company transfers its performance obligation to Merck. In applying the cost-based input measure of revenue recognition, the Company measures actual costs incurred relative to budgeted costs to fulfill the combined performance obligation. These costs consist of full-time equivalent hours plus allowable external (third-party) costs incurred. Revenue is recognized based on actual costs incurred as a percentage of total budgeted costs as the Company completes its performance obligation. The Company re-evaluates the estimate of expected costs to satisfy the performance obligation each reporting period and makes adjustments for any significant changes. On May 31, 2019, Merck terminated its license to the GDF15 receptor agonist program. The research and development services within the Collaboration Agreement are not affected by the GDF15 receptor agonist program license termination and are expected to continue through the remainder of the research program term. As of December 31, 2019 and 2018, deferred revenue related to the single performance obligation in the Collaboration Agreement was $4.9 million and $23.0 million, respectively. Of the amount recognized for the adoption of ASC 606 in the reporting period ended December 31, 2019, $6.2 million was in deferred revenue at the end of the prior reporting period. As of December 31, 2018, $3.7 million was due from Merck under the Collaboration Agreement. To date, the Company has recognized revenue of approximately $367.8 million related to the single performance obligation in the Collaboration Agreement. In connection with the Series E convertible preferred stock purchase agreement, the Company and Merck entered into an agreement whereby Merck agreed to purchase 4,121,683 shares of our common stock in a separate private placement concurrent with the completion of the Company’s IPO at a price per share equal to the public offering price of $16.00, resulting in Merck owning approximately 19.9% of the Company’s outstanding shares of common stock following the completion of the IPO. The Company is also eligible to receive additional payments specific to Merck opting into an Optioned Program. Each Optioned Program is eligible to receive a one-time payment of $20.0 million upon Merck’s exercise of its one-time option to obtain an exclusive, worldwide license to a compound following its completion of a human proof-of-concept study. In addition, if the Company does not opt into the cost and profit sharing option, then the Company is eligible to receive an aggregate of $449.0 million in milestone payments, of which $77.7 million relates to the potential achievement of specific clinical development events and $371.3 million relates to the potential achievement of certain regulatory events with respect to the licensed compounds for the first three indications in the United States, EU and Japan. A breakout of the milestone payments in connection with the potential achievement of certain clinical development events is as follows (in thousands): First Indication Second Indication Third Indication Upon administration of an applicable product to the first patient in the first Phase 3 clinical trial for such product for the given indication $ 35,000 $ 25,250 $ 17,500 A breakout of the milestone payments in connection with the potential achievement of various regulatory events for each of the three indications, for each of the three geographic areas, is as follows (in thousands): First Indication Second Indication Third Indication Total United States $ 75,000 $ 56,250 $ 37,500 $ 168,750 European Union 60,000 45,000 30,000 135,000 Japan 30,000 22,500 15,000 67,500 $ 165,000 $ 123,750 $ 82,500 $ 371,250 Summary of Collaboration Revenue The Company recognized revenue from its collaboration and license agreements as follows (in thousands): Year Ended December 31, 2019 2018 2017 Related party revenue $ 103,544 $ 108,665 $ 77,141 For the year ended December 31, 2019, the Company recognized collaboration and license revenue under the Collaboration Agreement of $103.5 million, of which $24.0 million The Company is also eligible to receive commercial milestone payments of up to $125.0 million payable for each licensed product. In addition, the Company is eligible to receive royalties at ascending low-double digit to mid-teen percentage rates, depending on the level of net sales Merck achieves worldwide for each licensed compound. Contract Assets and Liabilities Changes in contract liabilities under ASC 606 were as follows (in thousands): Amounts Balance at December 31, 2018 $ 22,967 Adoption of ASC 606 6,156 Balance at January 1, 2019 29,123 Revenue recognized included in the contract liability balance at the beginning of the period (24,251 ) Balance at December 31, 2019 $ 4,872 There were no contract assets for all the periods presented.

Related Party Transactions

Related Party Transactions	12 Months Ended
	Dec. 31, 2019
Related Party Transactions [Abstract]
Related Party Transactions	6. Related Party Transactions Revenues from related parties refer to the Collaboration Agreement with Merck. For the years ended December 31, 2019, 2018 and 2017, the Company recognized related party revenues of $103.5 million, $108.7 million and $77.1 million, respectively. As of December 31, 2019 and 2018, the Company had deferred revenue from the Collaboration Agreement of $4.9 million and $23.0 million, respectively. Other related party transactions include the Company’s assignment of its operating lease of 630 Gateway to Merck (Note 7) (Note 1)

Commitments and Contingencies

Commitments and Contingencies	12 Months Ended
	Dec. 31, 2019
Commitments And Contingencies Disclosure [Abstract]
Commitments and Contingencies	7. Commitments and Contingencies Operating Lease and Lease Guarantee In September 2009, the Company entered into an operating lease for a corporate office space and laboratory facility at 630 Gateway Blvd, in South San Francisco, California (“630 Gateway”) for approximately 50,000 square feet, as amended in June 2014 (“2014 Lease Amendment”), which expires in November 2020. The 2014 Lease Amendment provided for tenant improvement allowances of $0.8 million. The 2014 Lease Amendment contains scheduled rent increases over the lease term and has an option for the Company to extend the lease for an additional three-year term. In December 2015, the Company entered into a new operating lease for its corporate office space and laboratory facility at 333 Oyster Point Blvd, South San Francisco, California (“333 Oyster Point”) for approximately 122,000 square feet that expires in December 2023. The lease provided a tenant improvement allowance of $15.2 million that the Company used in 2016 towards $22.3 million in total leasehold improvements that are amortized over the lease term of seven years. The 333 Oyster Point lease agreement required a letter of credit in the amount of $2.3 million as a security deposit to the lease, which the Company has recorded as non-current restricted cash on the consolidated balance sheets. The Company has the right to reduce the letter of credit amount by $0.4 million on each of the third anniversary and fourth anniversary of the rent commencement date. For the year ended December 31, 2019, the Company reduced its letter of credit by $0.4 million and reclassified that amount from restricted cash to cash and cash equivalents on the consolidated balance sheets. In July 2016, the Company assigned its operating lease of 630 Gateway to Merck, as part of the Company’s relocation to 333 Oyster Point. As part of the assignment of the lease, the Company is liable to the lessor if Merck defaults on its lease obligations. Therefore, in substance, the Company has guaranteed the lease payments for 630 Gateway, including lease-related expenses such as utilities, property tax and common area maintenance without any limitations. The Company assessed the need for a potential guarantee liability on the assigned lease, and concluded that the value of the guarantee was insignificant as of December 31, 2019 due to the short duration of the remaining lease term through November 2020, and Merck’s credit rating of AA/A1 and subsequent investment in tenant improvements to the facility. As of December 31, 2019 and 2018, the remaining lease payment obligations that are due for 630 Gateway were approximately $2.0 million and $3.9 million, respectively, which are to be paid directly from Merck to the lessor. The Company recognizes rent expense on a straight-line basis over the lease period with the difference recorded as deferred rent. In addition, tenant improvement allowances recorded are amortized as a reduction to rent expense on a straight-line basis over the lease term. Rent expense under these facility operating leases was approximately $2.2 million for the years ended December 31, 2019, 2018 and 2017, respectively. Future minimum payments under the unassigned lease obligations described above are as follows as of December 31, 2019 (in thousands): Year Ended December 31, 2020 $ 4,995 2021 5,141 2022 5,294 2023 5,455 Total $ 20,885 Indemnification In the normal course of business, the Company enters into contracts and agreements that contain a variety of representations and warranties and may provide for indemnification of the counterparty. The Company’s exposure under these agreements is unknown because it involves claims that may be made against it in the future, but have not yet been made. In accordance with the Company’s amended and restated certificate of incorporation and its amended and restated bylaws, the Company has indemnification obligations to its officers and directors, subject to some limits, with respect to their service in such capacities. The Company has also entered into indemnification agreements with its directors and certain of its officers. To date, the Company has not been subject to any claims, and it maintains director and officer insurance that may enable it to recover a portion of any amounts paid for future potential claims. The Company’s exposure under these agreements is unknown because it involves claims that may be made against it in the future, but have not yet been made. The Company believes that the fair value of these indemnification obligations is minimal and, accordingly, it has not recognized any liabilities relating to these obligations for any period presented.

Convertible Preferred Stock

Convertible Preferred Stock	12 Months Ended
	Dec. 31, 2019
Temporary Equity Disclosure [Abstract]
Convertible Preferred Stock	8. Convertible Preferred Stock Upon the closing of the Company’s IPO, each then outstanding share of convertible preferred stock was converted into shares of common stock. With respect to the Company’s convertible preferred stock outstanding prior to the IPO, the Company elected to follow the SEC staff’s guidance (included in ASC 480-10-S99, SEC Materials) when evaluating the classification of its shares within the consolidated balance sheets. A liquidation, winding up, change in control, or sale of substantially all assets of the Company could constitute a redemption event. Although the majority of the Company’s preferred stock was not mandatorily or currently redeemable, a liquidation or winding up of the Company could have constituted an event outside its control. Therefore, all shares of convertible preferred stock have been presented outside the permanent equity for all periods presented due to its contingently redeemable nature. Convertible preferred stock as of December 31, 2018, on an as-converted basis, consisted of the following (in thousands): Issuance Aggregate Aggregate Shares Price per Liquidation Carrying Authorized Outstanding Share Value Value Series A 13,295 13,275 $ 2.00 $ 26,550 $ 26,462 Series B 11,078 11,078 5.00 55,389 55,148 Series C 8,328 8,328 6.00 49,970 49,887 Series D 6,600 5,753 10.00 57,530 57,461 Series E 8,833 8,833 12.00 88,335 105,916 48,134 47,267 $ 277,774 $ 294,874 In March 2015, the Company amended and restated its certificate of incorporation in conjunction with the Series E convertible preferred stock offering. Prior to the conversion of the convertible preferred stock upon closing of the IPO, the significant rights and obligations of the Company’s convertible preferred stock were as follows: Voting Rights: Each holder of convertible preferred stock was entitled to the number of votes equal to the number of shares of common stock into which such shares of convertible preferred stock were convertible. In the event the preferred stockholders controlled a majority of the board of directors through direct representation on the board of directors or through other rights, the stockholders could approve redemption of the preferred stock. Dividends: Each holder of convertible preferred stock was entitled to receive non-cumulative dividends at the rate of 8% per annum for each share of convertible preferred stock outstanding, when, as and if declared by the board of directors. These dividends were payable in preference to common stock dividends. The Company did not declare or pay any dividends. Liquidation: In the event of any liquidation, dissolution or winding-up of the Company, each holder of convertible preferred stock was entitled to receive payment out of the assets of the Company legally available for distribution for each share of convertible preferred stock held by the holder of an amount per share of preferred stock equal to the original issue price plus all declared and unpaid dividends on the convertible preferred stock, with the exception that the holder of the Series E convertible preferred stock was only eligible to receive an amount equal to $10.00 per share plus all declared and unpaid dividends on the convertible preferred stock. In the event that the available funds and assets were insufficient for full payment to the holders of convertible preferred stock on a per-share basis as outlined above, the entire assets and funds of the Company legally available for distribution would have been distributed ratably among the holders of convertible preferred stock in proportion to the full amount to which they would otherwise have been respectively entitled. Upon completion of the distribution of assets as set forth above, all of the remaining assets, if any, would have been distributed ratably among the holders of common stock. As of December 31, 2019, the Company does not have any convertible preferred stock issued or outstanding.

Stockholders' Equity (Deficit)

Stockholders' Equity (Deficit)	12 Months Ended
	Dec. 31, 2019
Equity [Abstract]
Stockholders' Equity (Deficit)	9. Stockholders’ Equity (Deficit) Preferred Stock The Company has 10,000,000 shares of preferred stock authorized, which may be issued at the discretion of the Company’s board of directors. The board of directors may issue shares of preferred stock in one or more series and to fix the number, rights, preferences, privileges and restrictions. These rights, preferences and privileges could include dividend rights, conversion rights, voting rights, terms of redemption, liquidation preferences and sinking fund terms. As of December 31, 2019, the Company does not have any shares of preferred stock issued or outstanding. Common Stock As of December 31, 2019 and 2018, the Company had 66,960,279 and 6,937,890 shares of common stock outstanding, respectively, which included shares subject to repurchase of 74,454 and 205,108, respectively, as a result of early exercise of stock options not yet vested. As of December 31, 2019 and 2018, the Company reserved shares of common stock for issuance as follows: December 31, 2019 2018 Conversion of convertible preferred stock — 47,267,466 Common stock options outstanding 10,824,780 9,806,689 Common stock options available for grant 5,316,066 2,125,875 Warrant to purchase convertible preferred stock — 19,637 401(k) Matching Plan 28,274 36,751 ESPP shares available for purchase 897,255 — Total 17,066,375 59,256,418 Stock Option Plan In 2018, the Company adopted the 2018 Plan for eligible employees, officers, directors, advisors and consultants, which provides for the grant of incentive and non-statutory stock options, restricted stock awards and stock appreciation rights. The terms of the stock option agreements, including vesting requirements, are determined by the board of directors, subject to the provisions of the 2018 Plan. Options granted by the Company generally vest within four years and are exercisable from the grant date until ten years after the date of grant. Vesting of certain employee options may be accelerated in the event of a change in control of the Company. As of December 31, 2019, 17,874,624 shares of common stock had been authorized for issuance under the 2018 Plan. Pursuant to the terms of the 2018 Plan, the number of shares reserved and available to issue will automatically increase on January 1st of each year in an amount equal to 4% of the total number of common shares outstanding on the December 31st immediately preceding calendar year, unless the board of directors elects to forego or reduce such increase. The Company’s 2008 Plan expired at the beginning of 2018. Stock options are governed by stock option agreements between the Company and recipients of stock options. Prior to the closing of the Company’s IPO, the board of directors exercised reasonable judgment and considered a number of objective and subjective factors to determine the best estimate of the fair value of our common stock, including the Company’s stage of development; progress of its research and development efforts; the rights, preferences and privileges of its convertible preferred stock relative to those of its common stock; equity market conditions affecting comparable companies; and the lack of marketability of our common stock. Subsequent to the IPO, the exercise price of each option shall not be less than 100% of the fair market value of the common stock subject to the option on the date the option is granted. A 10% or greater stockholder shall not be granted an incentive stock option unless the exercise price of such option is at least 110% of the fair value of the common stock on the date of grant and the option is not exercisable after the expiration of five years from the grant date. Options become exercisable and expire as determined by the Compensation Committee, provided that the term of incentive stock options may not exceed ten years from the date of grant for options granted to those other than 10% stockholders. Stock Option Activity A summary of the outstanding stock options is as follows: Outstanding Options Options Available for Grant Number of Options Weighted Average Exercise Price Weighted Average Remaining Contractual Life (in Years) Aggregate Intrinsic Value (in Thousands) Balances at December 31, 2018 2,125,875 9,806,689 $ 5.86 6.62 $ 105,226 Additional shares reserved 5,193,322 Options granted (2,424,198 ) 2,424,198 12.84 Options exercised — (987,479 ) 3.65 Options cancelled 418,628 (418,628 ) 8.60 Options repurchased 2,439 — 7.69 Balances at December 31, 2019 5,316,066 10,824,780 $ 7.52 6.29 $ 118,770 Vested and expected to vest at December 31, 2019 10,727,013 $ 7.48 6.26 $ 118,143 Outstanding and exercisable at December 31, 2019 10,824,780 $ 7.52 6.29 $ 118,770 The aggregate intrinsic values of options outstanding, exercisable, vested and expected to vest were calculated as the difference between the exercise price of the options and the estimated fair value of the Company’s common stock, as determined by the board of directors. The weighted average grant-date fair value of stock options granted during the years ended December 31, 2019, 2018 and 2017 was $8.00, $5.71 and $4.60 per share, respectively. The intrinsic value of stock options exercised was $10.2 million, $1.9 million and $0.5 million for the years ended December 31, 2019, 2018 and 2017, respectively. The total grant-date fair value of stock options that vested during the years ended December 31, 2019, 2018 and 2017 was $10.0 million, $7.5 million and $5.2 million, respectively. Due to the Company’s net operating losses, the Company did not realize any tax benefits from stock-based payment arrangements for the year ended December 31, 2019, 2018 and 2017. Early Exercise of Stock Options The 2018 Plan allows for the granting of options that may be exercised before the options have vested. Shares issued as a result of early exercise that have not vested are subject to repurchase by the Company upon termination of the purchaser’s employment or services, at the price paid by the purchaser, and are not deemed to be issued for accounting purposes until those related shares vest. The amounts received in exchange for these shares have been recorded as a liability on the consolidated balance sheets and will be reclassified into common stock and additional paid-in-capital as the shares vest. The Company’s right to repurchase these shares generally lapses in equal installments over four years beginning from the original vesting commencement date. As of December 31, 2019, there were 74,454 shares of common stock outstanding subject to the Company’s right of repurchase at prices ranging from $7.64 to $8.14 per share. At December 31, 2018, there were 205,108 shares of common stock outstanding subject to the Company’s right of repurchase at prices ranging from $4.00 to $8.14 per share. As of December 31, 2019 and 2018, the Company recorded $0.6 million and $1.6 million, respectively, as early exercise stock option liabilities associated with shares issued with repurchase rights. Employee Stock-Based Compensation Expense Employee and director stock-based compensation expense was calculated based on awards ultimately expected to vest and has been reduced for estimated forfeitures. The following table summarizes stock-based compensation expense related to Year Ended December 31, 2019 2018 2017 Research and development $ 7,145 $ 5,232 $ 4,473 General and administrative 5,584 4,524 2,994 Total stock-based compensation expense $ 12,729 $ 9,756 $ 7,467 Valuation Assumptions The Company uses the Black-Scholes option-pricing model to estimate the fair value of stock options at the grant date. The Black-Scholes option-pricing model requires the Company to make certain estimates and assumptions, including assumptions related to the expected price volatility of the Company’s stock, the period during which the options will be outstanding, the rate of return on risk-free investments and the expected dividend yield for the Company’s stock. The fair value of stock option awards granted to employees and directors were estimated at the date of grant using a Black-Scholes option-pricing model with the following weighted average valuation assumptions: Year Ended December 31, 2019 2018 2017 Risk-free interest rate 2.25 % 2.59 % 1.73 % Expected term of options (in years) 6.18 5.98 6.25 Expected stock price volatility 64.85 % 64.60 % 75.48 % Forfeiture rate 2.20 % 4.42 % 3.04 % Expected dividends — — — The weighted average valuation assumptions were determined as follows: Expected Stock Price Volatility: The expected volatility is based on the historical volatility of the stock of similar entities within the Company’s industry over periods commensurate with the Company’s expected term assumption. Expected Term of Options: The expected term of options represents the period of time options are expected to be outstanding. The expected term of the options granted is derived using the “simplified” method (that is, estimating the expected term as the midpoint between the vesting date and the end of the contractual term for each option). Risk-Free Interest Rate: The Company bases the risk-free interest rate on the interest rate payable on U.S. Treasury securities in effect at the time of grant for a period that is commensurate with the assumed expected option term. Expected Annual Dividends: The Company has not historically paid, and does not expect for the foreseeable future to pay, a dividend. Forfeiture Rate: The forfeiture rate represents the percentage of unvested stock options the Company expects will not vest, and, therefore, should not be expensed. The Company estimates forfeiture rates based on historical stock option grants and cancellations. As of December 31, 2019, there was approximately $24.1 million in total unrecognized compensation expense, net of estimated forfeitures, related to unvested options granted to employees and directors under the 2008 and 2018 Plans. The expense is expected to be recognized over a weighted average period of 2.67 years. Stock Options Granted to Non-employees The Company grants stock options to non-employees in exchange for services performed for the Company. The Company granted 22,500 options to non-employees for the year ended December 31, 2019. For the years ended December 31, 2018 and 2017, the Company did not grant any options to non-employees. Stock-based compensation expense related to stock-based payment awards to non-employees for the years ended December 31, 2019, 2018 and 2017 was $133,000, $103,000 and $250,000, respectively. The fair value of stock option awards granted to non-employees was estimated at the date of grant using a Black-Scholes option-pricing model with the following weighted average valuation assumptions: Year Ended December 31, 2019 2018 2017 Risk-free interest rate 2.26 % — 2.48 % Expected term of options (in years) 6.00 — 6.95 Expected stock price volatility 65.77 % — 64.93 % Expected dividends — — — 2019 Employee Stock Purchase Plan Under the 2019 ESPP, eligible employees are granted options to purchase shares of our common stock through payroll deductions that cannot exceed 15% of each employee’s salary. The 2019 ESPP provides for a 24-month offering period, which includes four six-month purchase periods. At the end of each purchase period, eligible employees are permitted to purchase shares of common stock at the lower of 85% of fair market value at the beginning of the offering period or fair market value at the end of the purchase period. The 2019 ESPP is considered a compensatory plan and the Company has recorded stock-based compensation expense of $1.0 million for the year ended December 31, 2019. As of December 31, 2019, 102,745 shares of common stock were purchased under the 2019 ESPP. The fair value of the rights granted to employees under the 2019 ESPP was estimated at the date of offer using a Black-Scholes option-pricing model with the following weighted average valuation assumptions: Year Ended December 31, 2019 2018 2017 Risk-free interest rate 1.97 % — — Expected term of options (in years) 1.23 — — Expected stock price volatility 59.46 % — — Expected dividends — — —

Income Taxes

Income Taxes	12 Months Ended
	Dec. 31, 2019
Income Tax Disclosure [Abstract]
Income Taxes	10. Income Taxes Income Taxes For the years ended December 31, 2019 and 2018, there were no provision or benefit from income tax. The benefit from income taxes recognized for the year ended December 31, 2017 was $1.0 million, which was related to the Company’s Minimum Tax Credit payments prior to enactment of the 2017 Tax Act. Of the benefit from income taxes recognized for the year ended December 31, 2017, the Company received $0.5 million in 2019. The components of the Company’s losses before income taxes were as follows (in thousands): Year Ended December 31, 2019 2018 2017 Domestic $ (34,634 ) $ 5,502 $ (8,974 ) Foreign (8,161 ) (5,995 ) (6,245 ) Total $ (42,795 ) $ (493 ) $ (15,219 ) A reconciliation of the statutory U.S. federal rate to the Company’s effective tax rate is as follows: Year Ended December 31, 2019 2018 2017 U.S. federal tax at statutory rate 21.0 % 21.0 % 34.0 % Foreign Australian subsidiary 1.7 109.5 (1.6 ) State, Net of Federal Benefit 0.0 (4.5 ) 1.3 Stock-based compensation 0.2 (93.1 ) (14.5 ) Change in valuation allowance (23.2 ) 401.6 68.7 Tax reform tax rate change — — (85.0 ) Other 0.2 (434.7 ) 4.0 Total 0.0 % (0.2 ) % 6.9 % The components of the net deferred tax assets are as follows (in thousands): December 31, 2019 2018 Deferred tax assets: Net operating loss carryforwards $ 37,679 $ 26,545 Stock-based compensation 3,478 1,961 Research and development credit 2,918 2,918 Deferred revenue 1,026 4,838 Other temporary differences 1,217 1,389 Total gross deferred tax assets 46,318 37,651 Deferred tax liabilities: Depreciation and amortization (570 ) (1,368 ) Non-qualified stock options with 83(b) election (15 ) (54 ) Total gross deferred tax liabilities (585 ) (1,422 ) Net deferred tax assets before valuation allowance 45,733 36,229 Deferred tax asset valuation allowance (45,733 ) (36,229 ) Net deferred tax assets $ — $ — ASC 740 requires that the tax benefit of net operating losses, temporary differences and credit carryforwards be recorded as an asset to the extent that management assesses that realization is “more likely than not.” Realization of the future tax benefits is dependent on the Company’s ability to generate sufficient taxable income within the carryforward period. Because of the Company’s recent history of operating losses, management believes that recognition of the deferred tax assets arising from the above-mentioned future tax benefits is currently more-likely-than-not to be realized and, accordingly, has provided a valuation allowance. Realization of deferred tax assets is dependent upon future earnings, if any, the timing and amount of which are uncertain. Accordingly, the net deferred tax assets have been fully offset by a valuation allowance. The valuation allowance increased by approximately $9.5 million and decreased by approximately $2.2 million during the years ended December 31, 2019 and 2018, respectively. As of December 31, 2019, the Company had approximately $113.1 million in federal net operating loss carryforwards to reduce future taxable income. Of this amount, $47.7 million was generated after December 31, 2017 and do not expire as per the 2017 Tax Act and can be carried forward indefinitely. The federal net operating loss carryforwards generated prior to January 1, 2018 are subject to a 20-year carryforward period and will begin to expire after 2032. Subsequent to the enactment of the 2017 Tax Act, the utilization of the federal net operating loss carryforwards generated in fiscal year 2018 and onwards are limited to 80% of the federal taxable income. The Company also had approximately $71.9 million in state net operating loss carryforwards to reduce future taxable income which will begin to expire after 2028, if not utilized. The Company had approximately $3.1 million and $3.1 million in federal research and development tax credits for the years ended December 31, 2019 and 2018, respectively. In addition, the Company had approximately $4.0 million and $4.0 million in state research and development tax credits for the years ended December 31, 2019 and 2018. The federal research credits will begin to expire in the years 2028 through 2035, if not utilized. The state research and development credits have no expiration date and can be carried forward indefinitely. As of December 31, 2019 and 2018, the Company had foreign net operating loss carryforwards of approximately $29.7 million and $22.9 million, respectively, which have no expiration date. Utilization of the Company’s net operating losses and credits may be subject to a substantial annual limitation due to the “change in ownership” provisions of the Internal Revenue Code of 1986, as amended, and similar state provisions. The annual limitation may result in the expiration of net operating losses and credits before utilization. A reconciliation of the Company’s unrecognized tax benefits for the years ended December 31, 2019, 2018 and 2017 is as follows (in thousands): December 31, 2019 2018 2017 Balance at beginning of year $ 3,819 $ 1,528 $ 1,528 Additions (deletions) based on tax positions related to prior year — 2,291 — Balance at end of year $ 3,819 $ 3,819 $ 1,528 There are approximately $3.8 million of unrecognized tax benefits included in the consolidated balance sheets that would, if recognized, affect the effective tax rate before consideration of valuation allowance. The Company does not believe that its unrecognized tax benefits will significantly change within the next 12 months. It is the Company’s practice to recognize interest and penalties related to income tax matters in income tax expense. As of December 31, 2019, the Company had no accrued interest and penalties related to uncertain tax positions. The Company files federal, state, and foreign income tax returns with varying statutes of limitations. The tax years from inception in 2008 forward remain open to examination due to the carryover of unused net operating losses and tax credits.

Employee Benefit Plan

Employee Benefit Plan	12 Months Ended
	Dec. 31, 2019
Compensation And Retirement Disclosure [Abstract]
Employee Benefit Plan	11. Employee Benefit Plan The Company sponsors a 401(k) defined contribution plan for its employees. Employee contributions are voluntary. In December 2011, the Company adopted the 401(k) Matching Plan, whereby the Company will make matching contributions in the form of common stock at a rate of $1.00 for each $2.00 of employee contributions up to a maximum $750 of common stock per year. As of December 31, 2019 and 2018, the Company had reserved 28,274 and 36,751 shares of common stock for issuance pursuant to the 401(k) Matching Plan, respectively. Matching contributions of 8,477 and 11,223 shares, or $106,000 and $103,000 were issued for the years ended December 31, 2019 and 2018, respectively.

Selected Quarterly Financial Da

Selected Quarterly Financial Data - (Unaudited)	12 Months Ended
	Dec. 31, 2019
Quarterly Financial Information Disclosure [Abstract]
Selected Quarterly Financial Data (Unaudited)	12. Selected Quarterly Financial Data (Unaudited) The following tables provide the selected quarterly financial data for the years ended December 31, 2019 and 2018 (in thousands, except share and per share amounts): 2019 Q4 Q3 Q2 Q1 Related party revenue $ 31,083 $ 21,568 $ 25,341 $ 25,552 Loss from operations (17,294 ) (12,997 ) (9,707 ) (9,342 ) Net loss (15,941 ) (10,917 ) (7,669 ) (8,268 ) Net loss per share, basic and diluted (2),(3) $ (0.24 ) $ (0.17 ) $ (0.13 ) $ (1.21 ) 2018 Q4 Q3 Q2 Q1 Related party revenue $ 47,119 $ 20,815 $ 22,118 $ 18,613 Income (loss) from operations 13,056 (8,469 ) (4,186 ) (4,715 ) Net income (loss) 14,165 (7,517 ) (3,200 ) (3,941 ) Net loss per share, basic and diluted (1),(3) $ — $ (1.15 ) $ (0.52 ) $ (0.64 ) (1) Through the application of the two-class method, all undistributed earnings were allocated to then outstanding convertible preferred stock for the three months ended December 31, 2018. (2) On March 22, 2019, the Company filed an amendment to the Company’s amended and restated certificate of incorporation to effect a reverse split of shares of the Company’s common stock on a two-for-one basis. (3) Net loss per common share is computed independently for each of the quarters presented. Therefore, the sum of quarterly Net loss per common share information may not equal annual Net loss per common share.

Summary of Significant Accoun_2

Summary of Significant Accounting Policies (Policies)	12 Months Ended
	Dec. 31, 2019
Accounting Policies [Abstract]
Basis of Presentation and Principles of Consolidation	Basis of Presentation and Principles of Consolidation The accompanying consolidated financial statements have been prepared in accordance with U.S. GAAP and include the consolidated accounts of the Company and its subsidiary. These consolidated financial statements include the consolidated accounts of the Company and its wholly-owned foreign subsidiary in Australia. All intercompany balances and transactions have been eliminated upon consolidation.
Use of Estimates	Use of Estimates The preparation of consolidated financial statements in conformity with U.S. GAAP requires management to make judgments, assumptions and estimates that affect the reported amounts of assets, liabilities, revenues and expenses. Specific accounts that require management estimates include, but are not limited to, stock-based compensation, the valuation of convertible preferred stock warrants, the fair value of convertible preferred and common stock, contract manufacturing and clinical trial accruals, collaboration revenue and associated transaction price determined in accordance with Accounting Standards Codification Topic 606, Revenue from Contracts with Customers (“ASC 606”). Management bases its estimates on historical experience and on various other assumptions that are believed to be reasonable under the circumstances, the results of which form the basis for making judgments about the carrying value of assets and liabilities that are not readily apparent from other sources. Actual results could differ materially from those estimates.
Need for Additional Capital	Need for Additional Capital Since inception, the Company has incurred net losses and negative cash flow from operations. During the years ended December 31, 2019, 2018 and 2017, the Company incurred net losses of $42.8 million, $0.5 million and $14.2 million, respectively. As of December 31, 2019, the Company had an accumulated deficit of $196.1 million and does not expect to experience positive cash flows from operations in the near future. The Company had $344.5 million of cash, cash equivalents and marketable securities as of December 31, 2019, and therefore the Company expects that its cash and cash equivalents and marketable securities will be sufficient to fund its operations for a period of at least one year from the date these consolidated financial statements are available for issuance. To fully implement the Company’s business plan and fund its operations, the Company will need to raise additional capital through the issuance of equity securities or debt financings, collaborations, strategic alliances and licensing arrangements, government or other third-party funding or a combination of these.
Deferred Initial Public Offering Costs	Deferred Initial Public Offering Costs Costs incurred in connection with the IPO primarily consisted of direct incremental legal, printing and accounting fees. IPO costs were capitalized as incurred and upon completion of the IPO, these costs were offset against the proceeds and recorded in additional paid-in capital. As of December 31, 2019 and 2018, deferred IPO costs included on the accompanying consolidated balance sheets were zero and $2.3 million, respectively.
Fair Value of Financial Instruments	Fair Value of Financial Instruments The carrying amounts of cash and cash equivalents, the related party receivables from collaboration and other current assets and liabilities approximate their respective fair values because of the short-term nature of those instruments. Fair value accounting is applied to the convertible preferred stock warrant liabilities that were recorded at their estimated fair value in the consolidated financial statements.
Cash and Cash Equivalents	Cash and Cash Equivalents Cash and cash equivalents are stated at fair value. Cash equivalents are securities with an original maturity of three months or less at the time of purchase. The Company limits its credit risk associated with cash and cash equivalents by placing its investments with a bank it believes is highly creditworthy and with highly rated money market funds. As of December 31, 2019 and 2018, cash and cash equivalents consisted of bank deposits and investments in money market funds.
Marketable Securities	Marketable Securities The appropriate classification of the Company’s marketable securities is determined at the time of purchase and such designations are re-evaluated at each balance sheet date. All of the Company’s securities are considered as available-for-sale and carried at estimated fair values and reported in cash equivalents, short-term marketable securities or long-term marketable securities. Unrealized gains and losses on available-for-sale securities are excluded from net loss and reported in accumulated other comprehensive loss as a separate component of stockholders’ equity (deficit). Other income (expense), net, includes interest, amortization of purchase premiums and accretion of purchase discounts, realized gains and losses on sales of securities and other-than-temporary declines in the fair value of securities, if any. The cost of securities sold is based on the specific identification method. The Company’s investments are regularly reviewed for other-than-temporary declines in fair value. This review includes the consideration of the cause of the impairment, including the creditworthiness of the security issuers, the number of securities in an unrealized loss position, the severity and duration of the unrealized losses, whether the Company has the intent to sell the securities and whether it is more likely than not that the Company will be required to sell the securities before the recovery of their amortized cost basis. When the Company determines that the decline in fair value of an investment is below its carrying value and this decline is other-than-temporary, the Company reduces the carrying value of the security it holds and records a loss for the amount of such decline.
Restricted Cash	Restricted Cash The Company’s restricted cash represents collateral in connection with the lease on the Company’s headquarters entered into in 2015 and is classified as a non-current asset on the consolidated balance sheets as the collateral will not be returned to the Company in less than 12 months (Note 7)
Concentration of Credit and Other Risks	Concentration of Credit and Other Risks Cash and cash equivalents and marketable securities from the Company’s available-for-sale and marketable security portfolio potentially subject the Company to concentrations of credit risk. The Company is invested in money market funds and marketable securities through custodial relationships with major U.S. and Australian banks. Under its investment policy, the Company limits amounts invested in such securities by credit rating, maturity, industry group, investment type and issuer, except for securities issued by the U.S. government. Related party receivables from collaborations (Notes 5 and 6) Merck accounted for 100% of the Company’s revenue for the years ended December 31, 2019, 2018 and 2017.
Property and Equipment, Net	Property and Equipment, Net Property and equipment is recorded at cost and consists of computer equipment, laboratory equipment and office furniture and leasehold improvements. Maintenance and repairs, and training on the use of equipment, are expensed as incurred. Costs that improve assets or extend their economic lives are capitalized. Depreciation is recognized using the straight-line method based on an estimated useful life of the asset, which is as follows: Computer equipment 3 years Laboratory equipment and office furniture 3 years Leasehold improvement Shorter of life of asset or lease term
Leases	Leases The Company’s lease agreements for its laboratory and office facilities are classified as operating leases. Rent expense is recognized on a straight-line basis over the term of the lease. Incentives granted under the Company’s facilities leases, including allowances to fund leasehold improvements and rent holidays, are capitalized and are recognized as reductions to rental expense on a straight-line basis over the term of the lease.
Impairment of Long-Lived Assets	Impairment of Long-Lived Assets Long-lived assets, such as property and equipment, are reviewed for impairment whenever events or changes in circumstances indicate that the carrying amount of an asset may not be recoverable. Recoverability of assets to be held and used is measured by a comparison of the carrying amount of an asset to the estimated undiscounted future cash flows expected to be generated by the asset. If the carrying amount of an asset exceeds its estimated undiscounted future cash flows, an impairment charge is recognized as the amount by which the carrying amount of the asset exceeds the estimated fair value of the asset. As of December 31, 2019 and 2018, no revision to the remaining useful lives or write-down of long-lived assets was required.
Income Taxes	Income Taxes Income taxes are accounted for under the liability method. Deferred tax assets and liabilities are recognized for the future tax consequences attributable to the differences between the financial statement carrying amounts of existing assets and liabilities and their respective tax bases and the operating loss and tax credit carryforwards. Valuation allowances are established when necessary to reduce deferred tax assets to the amount expected to be realized. Deferred tax assets and liabilities are measured at the balance sheet date using the enacted tax rates expected to apply to taxable income in the years in which those temporary differences are expected to be recovered or settled. The effect on deferred tax assets and liabilities of a change in tax rates is recognized in the period such tax rate changes are enacted.
Convertible Preferred Stock Warrant	Convertible Preferred Stock Warrant Freestanding warrants to purchase the Company’s convertible preferred stock were classified as a liability on the consolidated balance sheet at December 31, 2018 as the underlying shares of convertible preferred stock were contingently redeemable, which could have obligated the Company to transfer assets at some point in the future to settle the warrants. The convertible preferred stock warrants are subject to remeasurement at each balance sheet date, with changes in estimated fair value recorded in the Company’s consolidated statements of operations as a component of total other income (expense), net. On February 3, 2019, all convertible preferred stock warrants were automatically exercised on a net basis into 16,380 shares of Series A convertible preferred stock at a fair value of $0.2 million. As of December 31, 2019, there were no convertible preferred stock warrants outstanding.
Revenue Recognition	Revenue Recognition On January 1, 2019, the Company adopted ASU 2014-09, Revenue from Contracts with Customers (Topic 606), and subsequent amendments, using the modified retrospective transition method applied to those contracts that were not completed as of January 1, 2019. ASC 606 supersedes all prior revenue recognition guidance. Results for operating periods beginning after January 1, 2019 are presented under ASC 606, while prior period amounts have not been adjusted and continue to be reported in accordance with previous accounting rules under Accounting Standards Codification Topic 605, Revenue Recognition (“ASC 605”). Prior to the adoption of ASC 606, the Company’s revenue from collaboration agreements was recognized when the Company determined that persuasive evidence of an arrangement exists, services had been rendered, the price was fixed or determinable and collectability was reasonably assured. The Company would record amounts received prior to satisfying the above revenue recognition criteria as deferred revenue until all applicable revenue recognition criteria were met. Revenue allocated to research activities was generally recognized in the period the services were performed, and revenue allocated to licenses was generally recognized on a straight-line basis over the contractual term. Allocations to non-contingent elements were based on the relative selling price of each element using vendor-specific objective evidence or third-party evidence, where available. In the absence of either of these measures, the Company used the best estimate of selling price for that deliverable. The most significant change to the Company’s policies upon the adoption of ASC 606 is the estimation of an arrangement’s total transaction price, which includes unconstrained Note 2 – Recently Adopted Accounting Pronouncements The core principle in ASC 606 requires an entity to recognize revenue upon the transfer of goods or services to customers in an amount that reflects the consideration to which the entity expects to be entitled in exchange for those goods or services. The Company applies the following five-step revenue recognition model outlined in ASC 606 to adhere to this core principle: (1) identify the contract(s) with a customer; (2) identify the performance obligations in the contract; (3) determine the transaction price; (4) allocate the transaction price to the performance obligations in the contract; and (5) recognize revenue when (or as) the Company satisfies a performance obligation. All of the Company’s revenue to date has been generated from its collaboration agreements. The terms of these agreements generally require the Company to provide (i) license options for its compounds, (ii) research and development services and (iii) non-mandatory services in connection with participation in research or steering committees. Payments received under these arrangements may include non-refundable upfront license fees, partial or complete reimbursement of research and development costs, contingent consideration payments based on the achievement of defined collaboration objectives and royalties on sales of commercialized products. In some agreements, the collaboration partner is solely responsible for meeting defined objectives that trigger contingent or royalty payments. Often the partner only pursues such objectives subsequent to exercising an optional license on compounds identified as a result of the research and development services performed under the collaboration agreement. The Company assesses whether the promises in its arrangements, including any options provided to the customer, are considered distinct performance obligations that should be accounted for separately. Judgment is required to determine whether the license to a compound is distinct from research and development services or participation in steering committees, as well as whether options create material rights in the contract. The transaction price in each arrangement is generally comprised of a non-refundable upfront fee and unconstrained The Company’s collaboration agreements may include contingent payments related to specified development and regulatory milestones or contingent payments for royalties based on sales of a commercialized product. Milestones can be achieved for such activities in connection with progress in clinical trials, regulatory filings in various geographical markets and marketing approvals from regulatory authorities. Sales-based royalties are generally related to the volume of annual sales of a commercialized product. At the inception of each agreement that includes such payments, the Company evaluates whether the milestones are considered probable of being achieved and estimates the amount to be included in the transaction price by using the most likely amount method. If it is probable that a significant revenue reversal would not occur, the associated milestone value is included in the transaction price. Milestone payments that are not within the Company’s or its customer’s control, such as those related to regulatory approvals, are not considered probable of being achieved until those approvals are received. The transaction price is then allocated to each performance obligation based on a relative SSP basis. At the end of each subsequent reporting period, the Company re-evaluates the probability of achievement of each such milestone and any related constraint and, if necessary, adjusts its estimate of the overall transaction price. Pursuant to the guidance in ASC 606, sales-based royalties are not included in the transaction price. Instead, royalties are recognized at the later of when the performance obligation is satisfied or partially satisfied, or when the sale that gives rise to the royalty occurs.
Research and Development	Research and Development Research and development costs are expensed as incurred. Research and development expenses primarily include salaries and benefits for medical, clinical, quality, preclinical, manufacturing and research personnel, costs related to research activities, preclinical studies, clinical trials, drug manufacturing expenses and allocated overhead and facility occupancy costs. The Company accounts for non-refundable advance payments for goods or services that will be used in future research and development activities as expenses when the goods have been received or when the service has been performed rather than when the payment is made. Clinical trial costs are a component of research and development expenses. The Company expenses costs for its clinical trial activities performed by third parties, including CROs and other service providers, as they are incurred, based upon estimates of the work completed over the life of the individual study in accordance with associated agreements. The Company uses information it receives from internal personnel and outside service providers to estimate the clinical trial costs incurred.
Stock-Based Compensation	Stock-Based Compensation The Company’s stock-based compensation programs include stock options and shares that will be issued under the Company’s 2019 ESPP. Stock-based compensation to employees is valued on the grant date of each award using the Black-Scholes option-pricing model, and its estimated fair value is recognized over the period during which the employee is required to provide service in exchange for the award, which is generally the vesting period of each award. Subsequent to the adoption of ASU 2018-07, Stock Compensation (Topic 718): Improvements to Nonemployee Share-Based Payment Accounting on January 1, 2019, stock-based compensation expense for non-employee stock-based awards is also measured based on the fair value on grant date with its estimated fair value recorded over the period for which the non-employee is required to provide service in exchange for the award. As non-cash stock-based compensation expense is based on awards ultimately expected to vest, it is reduced by an estimate for future forfeitures. Forfeitures are estimated at the time of grant and revised, if necessary, in subsequent periods if actual forfeitures materially differ from estimates.
Foreign Currency Transactions	Foreign Currency Transactions The functional currency of NGM Biopharmaceuticals Australia Pty Ltd., a wholly-owned subsidiary, is the U.S. Dollar. Accordingly, all monetary assets and liabilities of the subsidiary are remeasured into U.S. Dollars at the current period-end exchange rates and non-monetary assets are remeasured using historical exchange rates. Income and expense elements are remeasured to U.S. Dollars using the average exchange rates in effect during the period. Remeasurement gains and losses are recorded as other income (expense), net on the consolidated statements of operations. The Company is subject to foreign currency risk with respect to its clinical and manufacturing contracts denominated in currencies other than the U.S. Dollar, primarily British Pounds, Swiss Francs, Australian Dollars and the Euro. Payments on contracts denominated in foreign currencies are made at the spot rate on the day of payment. Changes in the exchange rate between billing dates and payment dates are recorded within other income (expense), net on the consolidated statements of operations.
Comprehensive Loss	Comprehensive Loss Comprehensive loss is comprised of net loss and certain changes in equity that are excluded from net loss. For the years ended December 31, 2019, 2018 and 2017, the difference between comprehensive loss and net loss consisted of changes in net unrealized gain on marketable securities of $0.3 million, net unrealized gain on marketable securities of $0.2 million and net unrealized loss on marketable securities of $0.3 million, respectively.
Net Loss per Share	Net Loss per Share Basic net loss per share is calculated by dividing net loss by the weighted average number of shares outstanding during the period, less shares subject to repurchase and excludes any dilutive effects of stock-based awards and warrants. Diluted net loss per share is computed giving effect to all potentially dilutive shares, including common stock issuable upon exercise of stock options, and unvested restricted common stock and stock units. As the Company had net losses for the years ended December 31, 2019, 2018 and 2017, all potential shares were determined to be anti-dilutive. The following table sets forth the computation of net loss per share (in thousands, except share and per share amounts): Year Ended December 31, 2019 2018 2017 Numerator: Net loss $ (42,795 ) $ (493 ) $ (14,159 ) Denominator: Weighted average number of shares used in calculating net loss per share—basic and diluted 50,297,524 6,383,751 5,961,767 Net loss per share—basic and diluted $ (0.85 ) $ (0.08 ) $ (2.37 ) Potential gross dilutive securities that were not included in the diluted per share calculations because they would be anti-dilutive were as follows: Year Ended December 31, 2019 2018 2017 Convertible preferred stock — 47,267,466 47,267,466 Options to purchase common stock 10,824,780 9,806,689 8,468,702 Warrants to purchase convertible preferred stock — 19,637 19,637 Shares committed under ESPP 396,682 — — Total 11,221,462 57,093,792 55,755,805
Segment and Geographical Information	Segment and Geographical Information The Company operates in one segment. Substantially all of the Company’s long-lived assets, primarily comprised of property and equipment, are based in the United States. For the years ended December 31, 2019, 2018 and 2017, the Company’s revenues were entirely within the United States.
Recent Accounting Pronouncements	Recent Accounting Pronouncements New accounting pronouncements are issued by the Financial Accounting Standards Board (“FASB”) or other standard setting bodies and adopted by the Company as of the specified effective date. Unless otherwise discussed, the impact of recently issued standards that are not yet effective will not have a material impact on our consolidated financial statements upon adoption. Under the JOBS Act, the Company meets the definition of an emerging growth company, and has elected the extended transition period for complying with new or revised accounting standards pursuant to Section 107(b) of the JOBS Act. Recently Adopted Accounting Pronouncements In June 2018, the FASB issued ASU 2018-07, Compensation – Stock Compensation (Topic 718): Improvements to Non-Employee Share-Based Payment Accounting as part of the FASB simplification initiative. The new standard expands the scope of Topic 718, allowing the Company to apply the requirements of Topic 718 to certain non-employee awards issued in exchange for the acquisition of goods and services from non-employees. ASU 2018-07 is intended to supersede Subtopic 505-50, Equity-Based Payments to Non-Employees and is effective for the Company for fiscal years beginning after December 15, 2019. Effective January 1, 2019, the Company early adopted this ASU using the modified retrospective transition method in which all previously issued equity-classified share-based payment awards to non-employees were remeasured at fair value as of the adoption date. Newly issued equity-classified share-based payments awards to non-employees are measured at fair value as of grant date. The adoption of this ASU did not have a material impact on the Company’s consolidated financial statements. In May 2014, the FASB issued ASU 2014-09, Revenue from Contracts with Customers (Topic 606), which requires an entity to recognize the amount of revenue to which it expects to be entitled for the transfer of promised goods or services to customers. ASU 2014-09 replaced existing revenue recognition guidance and permits the use of either the full retrospective or modified retrospective transition method. Additionally, in March 2016, the FASB issued ASU 2016-08, Revenue from Contracts with Customers (Topic 606): Principal versus Agent Considerations (Reporting Revenue Gross versus Net), which clarifies the implementation guidance on principal versus agent considerations in ASU 2014-09. In April 2016, the FASB issued ASU 2016-10, Revenue from Contracts with Customers (Topic 606): Identifying Performance Obligations and Licensing, which clarifies certain aspects of identifying performance obligations and licensing implementation guidance. In May 2016, the FASB issued ASU 2016-12, Revenue from Contracts with Customers (Topic 606): Narrow-Scope Improvements and Practical Expedients, which relates to disclosures of remaining performance obligations, as well as other amendments to guidance on collectability, non-cash consideration and the presentation of sales and other similar taxes collected from customers. For the Company, these standards (collectively, ASC 606) have the same effective date and transition date of January 1, 2019. The Company adopted ASC 606 on January 1, 2019, using the modified retrospective transition method and, therefore, evaluated its contract with Merck under ASC 606. The Company recorded adjustments upon the adoption of ASC 606 as a result of the Company concluding that licenses and research and development services promised in the agreement are a single combined performance obligation. This determination impacts the timing of recognition of both the non-refundable upfront fee and the payments related to the services. Under previous guidance, the upfront fee was recognized ratably over the contract term, and fees related to the services were recognized in the period the services were performed. Under ASC 606, revenue for the single performance obligation is recognized over time using a cost-based input method to measure progress toward completion of the single combined performance obligation. The adoption of ASC 606 impacted the Company’s contract liabilities and accumulated deficit balance as of January 1, 2019 as follows (in thousands): December 31, 2018 Adjustments due to the Adoption of ASC 606 January 1, 2019 Deferred revenue, current $ 19,025 $ 5,171 $ 24,196 Deferred revenue, noncurrent 3,942 985 4,927 Accumulated deficit (147,193 ) (6,156 ) (153,349 ) The impact of the adoption of ASC 606 on the consolidated statement of operations and cash flows for the year ended December 31, 2019 was as follows (in thousands): As of December 31, 2019 Amount Under ASC 605 Effect of Adoption Higher (Lower) As Reported Deferred revenue, current $ 3,887 $ 985 $ 4,872 Accumulated deficit (195,159 ) (985 ) (196,144 ) Year Ended December 31, 2019 Amount Under ASC 605 Effect of Adoption Higher (Lower) As Reported Related party revenue $ 98,373 $ 5,171 $ 103,544 Loss from operations (54,511 ) 5,171 (49,340 ) Net loss (47,966 ) 5,171 (42,795 ) Net loss per common share, basic and diluted (0.95 ) (0.85 ) Year Ended December 31, 2019 Amount Under ASC 605 Effect of Adoption Higher (Lower) As Reported Cash flows from operating activities: Net loss $ (47,966 ) $ 5,171 $ (42,795 ) Changes in operating assets and liabilities: Deferred revenue (19,080 ) (5,171 ) (24,251 ) Recent Accounting Pronouncements Not Yet Adopted In February 2016, the FASB issued ASU 2016-02, Leases (Topic 842), which increases lease transparency and comparability among organizations. Under the new standard, lessees will be required to recognize right-of-use (“ROU”) assets and lease liabilities arising from lease arrangements on the consolidated balance sheets, with the exception of leases with a term of 12 months or less, which permits a lessee to make an accounting policy election by class of underlying asset not to recognize the ROU assets and lease liabilities. In March 2018, the FASB approved an alternative transition method to the modified retrospective approach, which eliminates the requirement to restate prior period consolidated financial statements and allows the cumulative effect of the retrospective allocation to be recorded as an adjustment to the opening balance of retained earnings at the date of adoption. In November 2019, the FASB issued ASU 2019-10, which defers the effective date for certain ASUs including ASU 2016-02. The new guidance is now effective for the Company’s fiscal year beginning after December 15, 2020, and interim periods within fiscal years beginning after December 15, 2021. The Company plans to adopt the new lease standard using the optional transition method, which allows the Company to recognize a cumulative-effect adjustment to the opening balance of accumulated deficit at the date of adoption and apply the new disclosure requirements beginning in the period of adoption. The Company also plans to elect the package of practical expedients permitted under the transition guidance within the new standard, which, among other things, allows the Company to carryforward the historical lease classification and make an accounting policy election whereby ROU assets and lease liabilities associated with lease arrangements with terms less than one year will not be recognized. We will continue to evaluate the effect that this guidance will have on our consolidated financial statements. In June 2016, the FASB issued ASU 2016-13, Financial Instruments – Credit Losses (Topic 326): Measurement of Credit Losses on Financial Instruments. The new guidance amended guidance on reporting credit losses for assets held at amortized cost basis and available-for-sale debt securities. For available-for-sale debt securities, credit losses will be presented as an allowance rather than as a write-down. This standard is effective for the Company’s fiscal year beginning after December 15, 2020. Early adoption is permitted for all entities. The Company is currently assessing the timing of adoption and the impact that the adoption of ASU 2016-13 will have on its consolidated financial statements. In August 2018, the FASB issued ASU 2018-13, Fair Value Measurements (Topic 820): Disclosure Framework – Changes to the Disclosure Requirements for Fair Value Measurement as part of the FASB’s disclosure framework project. This ASU modifies the disclosure requirements on fair value measurements in Topic 820, Fair Value Measurement by removing the requirement to disclose amounts of and reasons for transfers between Level 1 and Level 2 of the fair value hierarchy, the policy for timing of transfers between levels and the valuation process for Level 3 fair value measurements. This ASU also modifies existing disclosure requirements by clarifying that the measurement uncertainty disclosure is to communicate information about the uncertainty in measurement as of the reporting date, and it adds required disclosures for the changes in unrealized gains and losses for the period included in other comprehensive income for recurring Level 3 fair value measurements held at the end of the reporting period, and the range and weighted average of significant unobservable inputs used to develop Level 3 fair value measurements. This ASU will be effective for the Company for fiscal years and interim periods within those fiscal years, beginning after December 15, 2019. The Company is currently assessing the impact of this ASU on its consolidated financial statements. In November 2018, the FASB issued ASU 2018-18, Collaborative Arrangements (ASC 808): Clarifying the Interaction between ASC 808 and ASC 606, which clarifies that certain transactions between collaborative arrangement participants should be accounted for as revenue under ASC 606 when the collaborative arrangement participant is a customer in the context of a unit of account. In those situations, all the guidance in ASC 606 should be applied, including recognition, measurement, presentation and disclosure requirements. This ASU adds unit-of-account guidance in ASC 808 to align with the guidance in ASC 606 (that is, a distinct good or service) when an entity is assessing whether the collaborative arrangement or a part of the arrangement is within the scope of ASC 606, and requires that in a transaction with a collaborative arrangement participant that is not directly related to sales to third parties, presenting the transaction together with revenue recognized under ASC 606 is precluded if the collaborative arrangement participant is not a customer. This ASU will be effective for the Company for fiscal years beginning after December 15, 2020, and interim periods within fiscal years beginning after December 15, 2021. The Company is currently assessing the impact of this ASU on its consolidated financial statements. In December 2019, the FASB issued ASU 2019-12, Income Taxes (Topic 740): Simplifying the Accounting for Income Taxes. The new guidance modifies ASC 740 to simplify several aspects of accounting for income taxes, including eliminating certain exceptions to the guidance in ASC 740 related to the approach for intraperiod tax allocation. This ASU will be effective for fiscal years after December 15, 2021, and interim periods within fiscal years beginning after December 15, 2022, and is required to be adopted prospectively, with the exception of certain specific amendments. The Company is currently assessing the impact of this ASU on its consolidated financial statements.

Summary of Significant Accoun_3

Summary of Significant Accounting Policies (Tables)	12 Months Ended
	Dec. 31, 2019
Estimated Useful Life of Asset	Depreciation is recognized using the straight-line method based on an estimated useful life of the asset, which is as follows: Computer equipment 3 years Laboratory equipment and office furniture 3 years Leasehold improvement Shorter of life of asset or lease term
Computation of Net Loss Per Share	The following table sets forth the computation of net loss per share (in thousands, except share and per share amounts): Year Ended December 31, 2019 2018 2017 Numerator: Net loss $ (42,795 ) $ (493 ) $ (14,159 ) Denominator: Weighted average number of shares used in calculating net loss per share—basic and diluted 50,297,524 6,383,751 5,961,767 Net loss per share—basic and diluted $ (0.85 ) $ (0.08 ) $ (2.37 )
Potential Gross Dilutive Securities Not Included in Diluted Per Share Calculations	Potential gross dilutive securities that were not included in the diluted per share calculations because they would be anti-dilutive were as follows: Year Ended December 31, 2019 2018 2017 Convertible preferred stock — 47,267,466 47,267,466 Options to purchase common stock 10,824,780 9,806,689 8,468,702 Warrants to purchase convertible preferred stock — 19,637 19,637 Shares committed under ESPP 396,682 — — Total 11,221,462 57,093,792 55,755,805
ASC 606
Summary of Impact of Adopting ASC 606 on Select Financial Statement Line Items	The adoption of ASC 606 impacted the Company’s contract liabilities and accumulated deficit balance as of January 1, 2019 as follows (in thousands): December 31, 2018 Adjustments due to the Adoption of ASC 606 January 1, 2019 Deferred revenue, current $ 19,025 $ 5,171 $ 24,196 Deferred revenue, noncurrent 3,942 985 4,927 Accumulated deficit (147,193 ) (6,156 ) (153,349 ) The impact of the adoption of ASC 606 on the consolidated statement of operations and cash flows for the year ended December 31, 2019 was as follows (in thousands): As of December 31, 2019 Amount Under ASC 605 Effect of Adoption Higher (Lower) As Reported Deferred revenue, current $ 3,887 $ 985 $ 4,872 Accumulated deficit (195,159 ) (985 ) (196,144 ) Year Ended December 31, 2019 Amount Under ASC 605 Effect of Adoption Higher (Lower) As Reported Related party revenue $ 98,373 $ 5,171 $ 103,544 Loss from operations (54,511 ) 5,171 (49,340 ) Net loss (47,966 ) 5,171 (42,795 ) Net loss per common share, basic and diluted (0.95 ) (0.85 ) Year Ended December 31, 2019 Amount Under ASC 605 Effect of Adoption Higher (Lower) As Reported Cash flows from operating activities: Net loss $ (47,966 ) $ 5,171 $ (42,795 ) Changes in operating assets and liabilities: Deferred revenue (19,080 ) (5,171 ) (24,251 )

Fair Value Measurements (Tables

Fair Value Measurements (Tables)	12 Months Ended
	Dec. 31, 2019
Fair Value Disclosures [Abstract]
Summary of Cash and Cash Equivalents and Marketable Securities Classified as Available-for-sale Securities	Cash and cash equivalents and marketable securities, all of which are classified as available-for-sale securities consisted of the following (in thousands): Amortized Cost Gross Unrealized Gain Gross Unrealized Loss Fair Value As of December 31, 2019 Money market funds $ 244,973 $ — $ — $ 244,973 Corporate and agency bonds 66,063 14 — 66,077 Commercial paper 24,840 — — 24,840 U.S. government agencies securities 7,985 11 — 7,996 Total $ 343,861 $ 25 $ — $ 343,886 Classified as: Cash and cash equivalents $ 244,973 Short-term marketable securities (amortized cost of $98,888) 98,913 Total cash equivalents and marketable securities $ 343,886 Amortized Cost Gross Unrealized Gain Gross Unrealized Loss Fair Value As of December 31, 2018 Money market funds $ 34,983 $ — $ — $ 34,983 Corporate and agency bonds 68,322 — (241 ) 68,081 Commercial paper 17,904 — — 17,904 U.S. government agencies securities 63,751 — (26 ) 63,725 Total $ 184,960 $ — $ (267 ) $ 184,693 Classified as: Cash and cash equivalents $ 34,983 Short-term marketable securities (amortized cost of $149,977) 149,710 Total cash equivalents and marketable securities $ 184,693
Summary of Assets and Liabilities Measured at Fair Value on Recurring Basis	The following table sets forth the estimated fair value of the Company’s financial assets and liabilities that were measured at fair value on a recurring basis as of December 31, 2019 and 2018 (in thousands): Fair Value Measurements As of December 31, 2019 Level 1 Level 2 Level 3 Total Assets: Money market funds $ 244,973 $ — $ — $ 244,973 Corporate and agency bonds — 66,077 — 66,077 Commercial paper — 24,840 — 24,840 U.S. government agencies securities — 7,996 — 7,996 $ 244,973 $ 98,913 $ — $ 343,886 Fair Value Measurements As of December 31, 2018 Level 1 Level 2 Level 3 Total Assets: Money market funds $ 34,983 $ — $ — $ 34,983 Corporate and agency bonds — 68,081 — 68,081 Commercial paper — 17,904 — 17,904 U.S. government agencies securities — 63,725 — 63,725 $ 34,983 $ 149,710 $ — $ 184,693 Liabilities: Convertible preferred stock warrant liability $ — $ — $ 198 $ 198 $ — $ — $ 198 $ 198
Summary of Changes in Fair Value of Convertible Preferred Stock Warrant Liability	The following table provides a summary of changes in the fair value of the Company’s convertible preferred stock warrant liability (in thousands): Fair Value Using Level 3 Inputs Amounts Balance at December 31, 2017 $ 121 Change in fair value of warrant liability included in other income (expense), net 77 Balance at December 31, 2018 $ 198 Balance at December 31, 2018 $ 198 Net exercise of preferred stock warrant to Series A preferred stock (198 ) Balance at December 31, 2019 $ —

Balance Sheet Components (Table

Balance Sheet Components (Tables)	12 Months Ended
	Dec. 31, 2019
Statement Of Financial Position [Abstract]
Property and Equipment	Property and equipment consist of the following (in thousands): December 31, 2019 2018 Computer equipment $ 1,201 $ 1,123 Laboratory equipment and office furniture 21,652 18,977 Leasehold improvements 25,880 25,314 Construction in process 498 679 Total property and equipment, gross 49,231 46,093 Less: accumulated depreciation and amortization (29,756 ) (22,200 ) Total property and equipment, net $ 19,475 $ 23,893
Accrued Liabilities	Accrued liabilities consist of the following (in thousands): December 31, 2019 2018 Accrued expenses $ 2,901 $ 2,595 Clinical trials and research and development costs 11,051 4,844 Personnel-related costs 6,446 4,148 Manufacturing costs 2,593 2,416 Total accrued liabilities $ 22,991 $ 14,003

Research Collaboration and Li_2

Research Collaboration and License Agreements (Tables)	12 Months Ended
	Dec. 31, 2019
Collaboration And License Agreement Disclosure [Abstract]
Schedule of Milestone Payments by Indications	A breakout of the milestone payments in connection with the potential achievement of certain clinical development events is as follows (in thousands): First Indication Second Indication Third Indication Upon administration of an applicable product to the first patient in the first Phase 3 clinical trial for such product for the given indication $ 35,000 $ 25,250 $ 17,500 A breakout of the milestone payments in connection with the potential achievement of various regulatory events for each of the three indications, for each of the three geographic areas, is as follows (in thousands): First Indication Second Indication Third Indication Total United States $ 75,000 $ 56,250 $ 37,500 $ 168,750 European Union 60,000 45,000 30,000 135,000 Japan 30,000 22,500 15,000 67,500 $ 165,000 $ 123,750 $ 82,500 $ 371,250
Schedule of Recognized Revenue from Collaboration and License Agreements	The Company recognized revenue from its collaboration and license agreements as follows (in thousands): Year Ended December 31, 2019 2018 2017 Related party revenue $ 103,544 $ 108,665 $ 77,141
Schedule of Changes in Contract Liabilities Under ASC 606	Contract Assets and Liabilities Changes in contract liabilities under ASC 606 were as follows (in thousands): Amounts Balance at December 31, 2018 $ 22,967 Adoption of ASC 606 6,156 Balance at January 1, 2019 29,123 Revenue recognized included in the contract liability balance at the beginning of the period (24,251 ) Balance at December 31, 2019 $ 4,872

Commitments and Contingencies (

Commitments and Contingencies (Tables)	12 Months Ended
	Dec. 31, 2019
Commitments And Contingencies Disclosure [Abstract]
Future Minimum Commitments under Unassigned Lease Obligations	Future minimum payments under the unassigned lease obligations described above are as follows as of December 31, 2019 (in thousands): Year Ended December 31, 2020 $ 4,995 2021 5,141 2022 5,294 2023 5,455 Total $ 20,885

Convertible Preferred Stock (Ta

Convertible Preferred Stock (Tables)	12 Months Ended
	Dec. 31, 2019
Temporary Equity Disclosure [Abstract]
Schedule of Convertible Preferred Stock	Convertible preferred stock as of December 31, 2018, on an as-converted basis, consisted of the following (in thousands): Issuance Aggregate Aggregate Shares Price per Liquidation Carrying Authorized Outstanding Share Value Value Series A 13,295 13,275 $ 2.00 $ 26,550 $ 26,462 Series B 11,078 11,078 5.00 55,389 55,148 Series C 8,328 8,328 6.00 49,970 49,887 Series D 6,600 5,753 10.00 57,530 57,461 Series E 8,833 8,833 12.00 88,335 105,916 48,134 47,267 $ 277,774 $ 294,874

Stockholders' Equity (Deficit)

Stockholders' Equity (Deficit) (Tables)	12 Months Ended
	Dec. 31, 2019
Schedule of Shares of Common Stock Reserved for Issuance	As of December 31, 2019 and 2018, the Company reserved shares of common stock for issuance as follows: December 31, 2019 2018 Conversion of convertible preferred stock — 47,267,466 Common stock options outstanding 10,824,780 9,806,689 Common stock options available for grant 5,316,066 2,125,875 Warrant to purchase convertible preferred stock — 19,637 401(k) Matching Plan 28,274 36,751 ESPP shares available for purchase 897,255 — Total 17,066,375 59,256,418
Summary of Outstanding Stock Options	A summary of the outstanding stock options is as follows: Outstanding Options Options Available for Grant Number of Options Weighted Average Exercise Price Weighted Average Remaining Contractual Life (in Years) Aggregate Intrinsic Value (in Thousands) Balances at December 31, 2018 2,125,875 9,806,689 $ 5.86 6.62 $ 105,226 Additional shares reserved 5,193,322 Options granted (2,424,198 ) 2,424,198 12.84 Options exercised — (987,479 ) 3.65 Options cancelled 418,628 (418,628 ) 8.60 Options repurchased 2,439 — 7.69 Balances at December 31, 2019 5,316,066 10,824,780 $ 7.52 6.29 $ 118,770 Vested and expected to vest at December 31, 2019 10,727,013 $ 7.48 6.26 $ 118,143 Outstanding and exercisable at December 31, 2019 10,824,780 $ 7.52 6.29 $ 118,770
Summary of Stock Based Compensation Expense	The following table summarizes stock-based compensation expense related to Year Ended December 31, 2019 2018 2017 Research and development $ 7,145 $ 5,232 $ 4,473 General and administrative 5,584 4,524 2,994 Total stock-based compensation expense $ 12,729 $ 9,756 $ 7,467
Summary of Fair Value of Stock Option to Employees and Directors were Estimated at Date of Grant Using Black-Scholes Option-pricing Model	The fair value of stock option awards granted to employees and directors were estimated at the date of grant using a Black-Scholes option-pricing model with the following weighted average valuation assumptions: Year Ended December 31, 2019 2018 2017 Risk-free interest rate 2.25 % 2.59 % 1.73 % Expected term of options (in years) 6.18 5.98 6.25 Expected stock price volatility 64.85 % 64.60 % 75.48 % Forfeiture rate 2.20 % 4.42 % 3.04 % Expected dividends — — —
2019 Employee Stock Purchase Plan
Summary of Fair Value of Stock Option to Employees and Directors were Estimated at Date of Grant Using Black-Scholes Option-pricing Model	The fair value of the rights granted to employees under the 2019 ESPP was estimated at the date of offer using a Black-Scholes option-pricing model with the following weighted average valuation assumptions: Year Ended December 31, 2019 2018 2017 Risk-free interest rate 1.97 % — — Expected term of options (in years) 1.23 — — Expected stock price volatility 59.46 % — — Expected dividends — — —
Non-employees
Summary of Fair Value of Stock Option Granted to Non-Employees was Estimated at Date of Grant Using Black-Scholes Option-pricing Model	The fair value of stock option awards granted to non-employees was estimated at the date of grant using a Black-Scholes option-pricing model with the following weighted average valuation assumptions: Year Ended December 31, 2019 2018 2017 Risk-free interest rate 2.26 % — 2.48 % Expected term of options (in years) 6.00 — 6.95 Expected stock price volatility 65.77 % — 64.93 % Expected dividends — — —

Income Taxes (Tables)

Income Taxes (Tables)	12 Months Ended
	Dec. 31, 2019
Income Tax Disclosure [Abstract]
Schedule of Components of Losses Before Income Taxes	The components of the Company’s losses before income taxes were as follows (in thousands): Year Ended December 31, 2019 2018 2017 Domestic $ (34,634 ) $ 5,502 $ (8,974 ) Foreign (8,161 ) (5,995 ) (6,245 ) Total $ (42,795 ) $ (493 ) $ (15,219 )
Schedule of Reconciliation of Statutory U.S. Federal Rate to Effective Tax Rate	A reconciliation of the statutory U.S. federal rate to the Company’s effective tax rate is as follows: Year Ended December 31, 2019 2018 2017 U.S. federal tax at statutory rate 21.0 % 21.0 % 34.0 % Foreign Australian subsidiary 1.7 109.5 (1.6 ) State, Net of Federal Benefit 0.0 (4.5 ) 1.3 Stock-based compensation 0.2 (93.1 ) (14.5 ) Change in valuation allowance (23.2 ) 401.6 68.7 Tax reform tax rate change — — (85.0 ) Other 0.2 (434.7 ) 4.0 Total 0.0 % (0.2 ) % 6.9 %
Schedule of Components of Net Deferred Tax Assets	The components of the net deferred tax assets are as follows (in thousands): December 31, 2019 2018 Deferred tax assets: Net operating loss carryforwards $ 37,679 $ 26,545 Stock-based compensation 3,478 1,961 Research and development credit 2,918 2,918 Deferred revenue 1,026 4,838 Other temporary differences 1,217 1,389 Total gross deferred tax assets 46,318 37,651 Deferred tax liabilities: Depreciation and amortization (570 ) (1,368 ) Non-qualified stock options with 83(b) election (15 ) (54 ) Total gross deferred tax liabilities (585 ) (1,422 ) Net deferred tax assets before valuation allowance 45,733 36,229 Deferred tax asset valuation allowance (45,733 ) (36,229 ) Net deferred tax assets $ — $ —
Schedule of Reconciliation of Unrecognized Tax Benefits	A reconciliation of the Company’s unrecognized tax benefits for the years ended December 31, 2019, 2018 and 2017 is as follows (in thousands): December 31, 2019 2018 2017 Balance at beginning of year $ 3,819 $ 1,528 $ 1,528 Additions (deletions) based on tax positions related to prior year — 2,291 — Balance at end of year $ 3,819 $ 3,819 $ 1,528

Selected Quarterly Financial _2

Selected Quarterly Financial Data - (Unaudited) (Tables)	12 Months Ended
	Dec. 31, 2019
Quarterly Financial Information Disclosure [Abstract]
Schedule of Selected Quarterly Financial Data	The following tables provide the selected quarterly financial data for the years ended December 31, 2019 and 2018 (in thousands, except share and per share amounts): 2019 Q4 Q3 Q2 Q1 Related party revenue $ 31,083 $ 21,568 $ 25,341 $ 25,552 Loss from operations (17,294 ) (12,997 ) (9,707 ) (9,342 ) Net loss (15,941 ) (10,917 ) (7,669 ) (8,268 ) Net loss per share, basic and diluted (2),(3) $ (0.24 ) $ (0.17 ) $ (0.13 ) $ (1.21 ) 2018 Q4 Q3 Q2 Q1 Related party revenue $ 47,119 $ 20,815 $ 22,118 $ 18,613 Income (loss) from operations 13,056 (8,469 ) (4,186 ) (4,715 ) Net income (loss) 14,165 (7,517 ) (3,200 ) (3,941 ) Net loss per share, basic and diluted (1),(3) $ — $ (1.15 ) $ (0.52 ) $ (0.64 ) (1) Through the application of the two-class method, all undistributed earnings were allocated to then outstanding convertible preferred stock for the three months ended December 31, 2018. (2) On March 22, 2019, the Company filed an amendment to the Company’s amended and restated certificate of incorporation to effect a reverse split of shares of the Company’s common stock on a two-for-one basis. (3) Net loss per common share is computed independently for each of the quarters presented. Therefore, the sum of quarterly Net loss per common share information may not equal annual Net loss per common share.

Organization and Description _2

Organization and Description of Business - Additional Information (Details) $ / shares in Units, $ in Thousands	Apr. 03, 2019USD ($)$ / sharesshares	Mar. 22, 2019	Dec. 31, 2019USD ($)Segmentshares	Dec. 31, 2018USD ($)
Subsidiary Sale Of Stock [Line Items]
Place of incorporation			DE
Date of incorporation			Dec. 31, 2007
Number of operating business segment | Segment			1
Common stock reverse stock split ratio		2
Underwriting discounts and commissions as well as offering expenses				$ 2,200
Reclassification to common stock and additional paid-in capital			$ 295,072
Proceeds from issuance of stock			$ 65,947
Merck Sharp & Dohme Corp
Subsidiary Sale Of Stock [Line Items]
Percentage of outstanding shares of common stock owned by related party	19.90%
IPO
Subsidiary Sale Of Stock [Line Items]
Common stock issued upon conversion of convertible preferred stock | shares	47,283,839
Common Stock
Subsidiary Sale Of Stock [Line Items]
Number of shares issued in transaction | shares	7,521,394		7,521,000
Common stock issued upon conversion of convertible preferred stock | shares			47,283,000
Reclassification to common stock and additional paid-in capital	$ 295,100		$ 47
Proceeds from issuance of stock	$ 65,900
Common Stock | IPO
Subsidiary Sale Of Stock [Line Items]
Number of shares issued in transaction | shares	6,666,667
Share price | $ / shares	$ 16
Proceeds from issuance of common stock, net of underwriters discount and commissions	$ 107,800
Underwriting discounts and commissions as well as offering expenses	$ 4,100			$ 2,200
Common Stock | Over-Allotment Option
Subsidiary Sale Of Stock [Line Items]
Number of shares issued in transaction | shares	854,727
Share price | $ / shares	$ 16
Common Stock | Private Placement
Subsidiary Sale Of Stock [Line Items]
Number of shares issued in transaction | shares	4,121,683
Share price | $ / shares	$ 16

Summary of Significant Accoun_4

Summary of Significant Accounting Policies - Additional Information (Details) $ in Thousands	Feb. 03, 2019USD ($)shares	Dec. 31, 2019USD ($)Segmentshares	Dec. 31, 2018USD ($)	Dec. 31, 2017USD ($)
Summary Of Significant Accounting Policies [Line Items]
Net losses		$ 42,795	$ 493	$ 14,159
Accumulated deficit		196,144	147,193
Cash, cash equivalents and marketable securities		344,500
Deferred IPO costs		0	2,292
Net unrealized gain (loss) on marketable securities		$ 300	$ 200	$ (300)
Number of operating business segment | Segment		1
Convertible Preferred Stock Warrant Liability
Summary Of Significant Accounting Policies [Line Items]
Warrants outstanding | shares		0
Convertible Preferred Stock
Summary Of Significant Accounting Policies [Line Items]
Convertible preferred stock warrants exercised on net basis into shares of series A convertible preferred stock | shares	16,380
Convertible preferred stock fair value	$ 200	$ 198
Revenue | Customer Concentration Risk | Merck
Summary Of Significant Accounting Policies [Line Items]
Percentage of revenue		100.00%	100.00%	100.00%

Summary of Significant Accoun_5

Summary of Significant Accounting Policies - Estimated Useful Life of Asset (Details)	12 Months Ended
	Dec. 31, 2019
Computer Equipment
Property Plant And Equipment [Line Items]
Estimated useful life of asset	3 years
Laboratory Equipment and Office Furniture
Property Plant And Equipment [Line Items]
Estimated useful life of asset	3 years
Leasehold Improvement
Property Plant And Equipment [Line Items]
Leasehold improvement	Shorter of life of asset or lease term

Summary of Significant Accoun_6

Summary of Significant Accounting Policies - Computation of Net Loss Per Share (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Numerator:
Net Loss	$ (15,941)	$ (10,917)	$ (7,669)	$ (8,268)	$ 14,165	$ (7,517)	$ (3,200)	$ (3,941)	$ (42,795)	$ (493)	$ (14,159)
Denominator:
Weighted average shares used to compute net loss per share, basic and diluted									50,297,524	6,383,751	5,961,767
Net loss per share, basic and diluted	$ (0.24)	$ (0.17)	$ (0.13)	$ (1.21)		$ (1.15)	$ (0.52)	$ (0.64)	$ (0.85)	$ (0.08)	$ (2.37)

Summary of Significant Accoun_7

Summary of Significant Accounting Policies - Potential Gross Dilutive Securities Not Included in Diluted Per Share Calculations (Details) - shares	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Potentially dilutive securities not included in calculations of diluted per share	11,221,462	57,093,792	55,755,805
Convertible Preferred Stock
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Potentially dilutive securities not included in calculations of diluted per share		47,267,466	47,267,466
Options to Purchase Common Stock
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Potentially dilutive securities not included in calculations of diluted per share	10,824,780	9,806,689	8,468,702
Warrants to Purchase Convertible Preferred Stock
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Potentially dilutive securities not included in calculations of diluted per share		19,637	19,637
Shares Committed Under ESPP
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Potentially dilutive securities not included in calculations of diluted per share	396,682

Summary of Significant Accoun_8

Summary of Significant Accounting Policies - Summary of Impact of Adopting ASC 606 on Select Financial Statement Line Items (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Jan. 01, 2019
Summary Of Significant Accounting Policies [Line Items]
Deferred revenue, current	$ 4,872				$ 19,025				$ 4,872	$ 19,025
Deferred revenue, non-current					3,942					3,942
Accumulated deficit	(196,144)				(147,193)				(196,144)	(147,193)
Loss from operations	(17,294)	$ (12,997)	$ (9,707)	$ (9,342)	13,056	$ (8,469)	$ (4,186)	$ (4,715)	(49,340)	(4,314)	$ (17,425)
Net Loss	$ (15,941)	$ (10,917)	$ (7,669)	$ (8,268)	$ 14,165	$ (7,517)	$ (3,200)	$ (3,941)	$ (42,795)	$ (493)	$ (14,159)
Net loss per common share, basic and diluted	$ (0.24)	$ (0.17)	$ (0.13)	$ (1.21)		$ (1.15)	$ (0.52)	$ (0.64)	$ (0.85)	$ (0.08)	$ (2.37)
Cash flows from operating activities
Net loss									$ (42,795)	$ (493)	$ (14,159)
Changes in operating assets and liabilities:
Deferred revenue									(24,251)	$ (21,133)	$ (16,521)
ASC 606
Summary Of Significant Accounting Policies [Line Items]
Deferred revenue, current	$ 4,872								4,872			$ 24,196
Deferred revenue, non-current												4,927
Accumulated deficit	(196,144)								(196,144)			(153,349)
Related party revenue									103,544
Loss from operations									(49,340)
Net Loss									$ (42,795)
Net loss per common share, basic and diluted									$ (0.85)
Adjustments
Cash flows from operating activities
Net loss									$ 5,171
Changes in operating assets and liabilities:
Deferred revenue									(5,171)
Adjustments | ASC 606
Summary Of Significant Accounting Policies [Line Items]
Deferred revenue, current	985								985			5,171
Deferred revenue, non-current												985
Accumulated deficit	(985)								(985)			$ (6,156)
Related party revenue									5,171
Loss from operations									5,171
Net Loss									5,171
Amount Under ASC 605
Cash flows from operating activities
Net loss									(47,966)
Changes in operating assets and liabilities:
Deferred revenue									(19,080)
Amount Under ASC 605 | ASC 606
Summary Of Significant Accounting Policies [Line Items]
Deferred revenue, current	3,887								3,887
Accumulated deficit	$ (195,159)								(195,159)
Related party revenue									98,373
Loss from operations									(54,511)
Net Loss									$ (47,966)
Net loss per common share, basic and diluted									$ (0.95)

Fair Value Measurements - Summa

Fair Value Measurements - Summary of Cash and Cash Equivalents and Marketable Securities Classified as Available-for-sale Securities (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Schedule Of Available For Sale Securities [Line Items]
Amortized Cost	$ 343,861	$ 184,960
Gross Unrealized Gain	25
Gross Unrealized Loss		(267)
Fair Value	343,886	184,693
Money Market Funds
Schedule Of Available For Sale Securities [Line Items]
Amortized Cost	244,973	34,983
Fair Value	244,973	34,983
Corporate and Agency Bonds
Schedule Of Available For Sale Securities [Line Items]
Amortized Cost	66,063	68,322
Gross Unrealized Gain	14
Gross Unrealized Loss		(241)
Fair Value	66,077	68,081
Commercial Paper
Schedule Of Available For Sale Securities [Line Items]
Amortized Cost	24,840	17,904
Fair Value	24,840	17,904
U.S. Government Agencies Securities
Schedule Of Available For Sale Securities [Line Items]
Amortized Cost	7,985	63,751
Gross Unrealized Gain	11
Gross Unrealized Loss		(26)
Fair Value	7,996	63,725
Cash and Cash Equivalents
Schedule Of Available For Sale Securities [Line Items]
Fair Value	244,973	34,983
Short-term Marketable Securities
Schedule Of Available For Sale Securities [Line Items]
Amortized Cost	98,888	149,977
Fair Value	$ 98,913	$ 149,710

Fair Value Measurements - Sum_2

Fair Value Measurements - Summary of Cash and Cash Equivalents and Marketable Securities Classified as Available-for-sale Securities (Parenthetical) (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Schedule Of Available For Sale Securities [Line Items]
Amortized Cost	$ 343,861	$ 184,960
Short-term Marketable Securities
Schedule Of Available For Sale Securities [Line Items]
Amortized Cost	$ 98,888	$ 149,977

Fair Value Measurements - Addit

Fair Value Measurements - Additional Information (Details) - USD ($)	Dec. 31, 2019	Dec. 31, 2018
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Cash on deposit with banks	$ 600,000	$ 21,900,000
Fair value, assets, level 1 to level 2 transfers, amount	0	0
Fair value, assets, level 2 to level 1 transfers, amount	0	0
Fair value, liabilities, level 1 to level 2 transfers, amount	0	0
Fair value, liabilities, level 2 to level 1 transfers, amount	$ 0	$ 0
Convertible Preferred Stock Warrant Liability
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Warrants outstanding	0
Loan and Security Agreement | Convertible Preferred Stock Warrant Liability
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Warrants outstanding	0

Fair Value Measurements - Sum_3

Fair Value Measurements - Summary of Assets and Liabilities Measured at Fair Value on Recurring Basis (Details) - Fair Value Measurements, Recurring - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Assets:
Assets fair value	$ 343,886	$ 184,693
Liabilities:
Liabilities fair value		198
Convertible Preferred Stock Warrant Liability
Liabilities:
Liabilities fair value		198
Money Market Funds
Assets:
Assets fair value	244,973	34,983
Corporate and Agency Bonds
Assets:
Assets fair value	66,077	68,081
Commercial Paper
Assets:
Assets fair value	24,840	17,904
U.S. Government Agencies Securities
Assets:
Assets fair value	7,996	63,725
Level 1
Assets:
Assets fair value	244,973	34,983
Level 1 | Money Market Funds
Assets:
Assets fair value	244,973	34,983
Fair Value, Inputs, Level 2
Assets:
Assets fair value	98,913	149,710
Fair Value, Inputs, Level 2 | Corporate and Agency Bonds
Assets:
Assets fair value	66,077	68,081
Fair Value, Inputs, Level 2 | Commercial Paper
Assets:
Assets fair value	24,840	17,904
Fair Value, Inputs, Level 2 | U.S. Government Agencies Securities
Assets:
Assets fair value	$ 7,996	63,725
Level 3
Liabilities:
Liabilities fair value		198
Level 3 | Convertible Preferred Stock Warrant Liability
Liabilities:
Liabilities fair value		$ 198

Fair Value Measurements - Sum_4

Fair Value Measurements - Summary of Changes in Fair Value of Convertible Preferred Stock Warrant Liability (Details) - Fair Value Measurements, Recurring - Level 3 - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Fair Value Assets Measured On Recurring Basis Unobservable Input Reconciliation [Line Items]
Beginning balance	$ 198	$ 121
Change in fair value of warrant liability included in other income (expense), net		77
Net exercise of preferred stock warrant to Series A preferred stock	$ (198)
Ending balance		$ 198

Balance Sheet Components - Sche

Balance Sheet Components - Schedule of Property and Equipment (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Property Plant And Equipment [Line Items]
Property and equipment, gross	$ 49,231	$ 46,093
Less: accumulated depreciation and amortization	(29,756)	(22,200)
Total property and equipment, net	19,475	23,893
Computer Equipment
Property Plant And Equipment [Line Items]
Property and equipment, gross	1,201	1,123
Laboratory Equipment and Office Furniture
Property Plant And Equipment [Line Items]
Property and equipment, gross	21,652	18,977
Leasehold Improvement
Property Plant And Equipment [Line Items]
Property and equipment, gross	25,880	25,314
Construction In Process
Property Plant And Equipment [Line Items]
Property and equipment, gross	$ 498	$ 679

Balance Sheet Components - Addi

Balance Sheet Components - Additional Information (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Statement Of Financial Position [Abstract]
Depreciation expense	$ 7,605	$ 7,223	$ 6,441

Balance Sheet Components - Sc_2

Balance Sheet Components - Schedule of Accrued Liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Statement Of Financial Position [Abstract]
Accrued expenses	$ 2,901	$ 2,595
Clinical trials and research and development costs	11,051	4,844
Personnel-related costs	6,446	4,148
Manufacturing costs	2,593	2,416
Total accrued liabilities	$ 22,991	$ 14,003

Research Collaboration and Li_3

Research Collaboration and License Agreements - Additional Information (Details)	Apr. 03, 2019	Nov. 30, 2018USD ($)	Feb. 28, 2015USD ($)$ / sharesshares	Dec. 31, 2019USD ($)Option$ / sharesshares	Sep. 30, 2019USD ($)	Jun. 30, 2019USD ($)	Mar. 31, 2019USD ($)	Dec. 31, 2018USD ($)$ / sharesshares	Sep. 30, 2018USD ($)	Jun. 30, 2018USD ($)	Mar. 31, 2018USD ($)	Dec. 31, 2019USD ($)Option$ / sharesshares	Dec. 31, 2018USD ($)$ / sharesshares	Dec. 31, 2017USD ($)	Dec. 31, 2019USD ($)Option$ / sharesshares	Nov. 29, 2018USD ($)	Apr. 30, 2015USD ($)
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Preferred stock, shares issued | shares				0				47,267,466				0	47,267,466		0
Preferred stock, price per share | $ / shares				$ 0.001				$ 0.001				$ 0.001	$ 0.001		$ 0.001
Deferred revenue				$ 4,872,000				$ 29,123,000				$ 4,872,000	$ 29,123,000		$ 4,872,000
Deferred revenue recognized												24,251,000
Collaboration and license revenue				31,083,000	$ 21,568,000	$ 25,341,000	$ 25,552,000	47,119,000	$ 20,815,000	$ 22,118,000	$ 18,613,000	103,544,000	108,665,000	$ 77,141,000
Contract assets				$ 0				$ 0				$ 0	$ 0		$ 0
Series E Convertible Preferred Stock
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Preferred stock, price per share | $ / shares								$ 12					$ 12
Merck Sharp & Dohme Corp
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Percentage of outstanding shares of common stock owned by related party	19.90%
Collaboration Agreement | Merck Sharp & Dohme Corp
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Upfront payment received																	$ 94,000,000
Fair values of assets and services exchanged allocated to equity component			$ 106,000,000
Fair values of assets and services exchanged allocated to revenue component			$ 94,000,000
Term of agreement												5 years
Research and development services additional option extend term												2 years
License fee																$ 20,000,000
Development and regulatory milestone payments received												$ 449,000,000
Research and Development Collaboration Agreement Additional Term Description												In connection with this extension, Merck agreed to continue to fund the Company’s research and development efforts during the two-year extension period at the same levels as during the initial term and, in lieu of a $20.0 million extension fee that would have otherwise been payable to the Company, Merck will make additional payments totaling up to $20.0 million in support of the Company’s research and development program activities across 2021 and the first quarter of 2022
Amount of fund received for research activities												$ 20,000,000
Amount of additional fund received for research activities												$ 20,000,000
Performance of R&D services period												5 years
Number of options to extend performance of research program | Option				2								2			2
Upfront Fee												$ 94,000,000
Collaborative agreement milestone or other forms of consideration												0
Received amount from options		$ 20,000,000
Deferred revenue				$ 4,900,000				$ 23,000,000				4,900,000	$ 23,000,000		$ 4,900,000
Deferred revenue recognized												6,200,000
Due from related party								$ 3,700,000					3,700,000
Collaboration and license revenue												103,500,000	108,700,000	77,100,000	$ 367,800,000
One-time payment												20,000,000
Milestone payments												449,000,000
Milestone payments relates to potential achievement of specific clinical development events												77,700,000
Milestone payments relates to potential achievement of certain regulatory events												371,300,000
Upfront license fee												24,000,000
Amortized of upfront payments													18,800,000	$ 18,800,000
Collaboration Agreement | Merck Sharp & Dohme Corp | NGM313
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Collaboration and license revenue													$ 20,000,000
Collaboration Agreement | Merck Sharp & Dohme Corp | Maximum
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Collaborative arrangement funding, amount												75,000,000
Commercial milestone payments received												125,000,000
Eligible to receive commercial milestone payments												125,000,000
Collaboration Agreement | Merck Sharp & Dohme Corp | Series E Convertible Preferred Stock
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Preferred stock, shares issued | shares			8,833,333
Preferred stock, price per share | $ / shares			$ 12
Proceeds from issuance of preferred stock			$ 106,000,000
Small Molecule Compounds | Merck Sharp & Dohme Corp
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Research collaboration and license agreements extension fee												$ 20,000,000
Initial research term												5 years
Additional term												3 years
Side Letter Agreement | Merck Sharp & Dohme Corp
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Public offering price of common stock | $ / shares				$ 16								$ 16			$ 16
Percentage of outstanding shares of common stock owned by related party												19.90%
Side Letter Agreement | Merck Sharp & Dohme Corp | Private Placement
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Common stock purchased by related party | shares												4,121,683

Research Collaboration and Li_4

Research Collaboration and License Agreements - Schedule of Milestone Payments by Indications (Details) - Collaboration Agreement $ in Thousands	12 Months Ended
	Dec. 31, 2019USD ($)
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Milestone payments in connection with potential achievement of certain regulatory events	$ 371,250
First Indication
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Milestone payments in connection with potential achievement of certain regulatory events	165,000
Second Indication
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Milestone payments in connection with potential achievement of certain regulatory events	123,750
Third Indication
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Milestone payments in connection with potential achievement of certain regulatory events	82,500
United States
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Milestone payments in connection with potential achievement of certain regulatory events	168,750
United States | First Indication
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Milestone payments in connection with potential achievement of certain regulatory events	75,000
United States | Second Indication
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Milestone payments in connection with potential achievement of certain regulatory events	56,250
United States | Third Indication
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Milestone payments in connection with potential achievement of certain regulatory events	37,500
European Union
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Milestone payments in connection with potential achievement of certain regulatory events	135,000
European Union | First Indication
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Milestone payments in connection with potential achievement of certain regulatory events	60,000
European Union | Second Indication
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Milestone payments in connection with potential achievement of certain regulatory events	45,000
European Union | Third Indication
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Milestone payments in connection with potential achievement of certain regulatory events	30,000
Japan
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Milestone payments in connection with potential achievement of certain regulatory events	67,500
Japan | First Indication
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Milestone payments in connection with potential achievement of certain regulatory events	30,000
Japan | Second Indication
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Milestone payments in connection with potential achievement of certain regulatory events	22,500
Japan | Third Indication
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Milestone payments in connection with potential achievement of certain regulatory events	15,000
First Indication | Clinical Trial to First Patient in First Phase 3
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Upon administration of an applicable product to the first patient in the first Phase 3 clinical trial for such product for the given indication	35,000
Second Indication | Clinical Trial to First Patient in First Phase 3
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Upon administration of an applicable product to the first patient in the first Phase 3 clinical trial for such product for the given indication	25,250
Third Indication | Clinical Trial to First Patient in First Phase 3
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Upon administration of an applicable product to the first patient in the first Phase 3 clinical trial for such product for the given indication	$ 17,500

Research Collaboration and Li_5

Research Collaboration and License Agreements - Schedule of Recognized Revenue from Collaboration and License Agreements (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Collaboration Agreement | Merck Sharp & Dohme Corp
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Related party revenue	$ 103,544	$ 108,665	$ 77,141

Research Collaboration and Li_6

Research Collaboration and License Agreements - Schedule of Changes in Contract Liabilities Under ASC 606 (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Jan. 01, 2019
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Beginning Balance	$ 29,123
Revenue recognized included in the contract liability balance at the beginning of the period	(24,251)
Ending Balance	4,872
Amount Under ASC 605
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Beginning Balance	$ 22,967
ASC 606
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Adoption of ASC 606		$ 6,156

Related Party Transactions - Ad

Related Party Transactions - Additional Information (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Related Party Transaction [Line Items]
Deferred revenue	$ 4,872	$ 29,123
Merck Sharp & Dohme Corp | Collaboration Agreement
Related Party Transaction [Line Items]
Revenue from related parties	103,544	108,665	$ 77,141
Deferred revenue	$ 4,900	$ 23,000

Commitments and Contingencies -

Commitments and Contingencies - Additional Information (Details) $ in Thousands	1 Months Ended		12 Months Ended
	Dec. 31, 2015USD ($)ft²	Sep. 30, 2009USD ($)ft²	Dec. 31, 2019USD ($)	Dec. 31, 2018USD ($)	Dec. 31, 2017USD ($)
Commitments And Contingencies Disclosure [Line Items]
Total Leasehold improvements			$ 19,475	$ 23,893
Corporate Office Space and Laboratory Facility
Commitments And Contingencies Disclosure [Line Items]
Area of leased property | ft²	122,000	50,000
Operating lease agreement, amended period		2014-06
Operating lease agreement, expiration period	2023-12	2020-11
Tenant improvement allowances	$ 15,200	$ 800
Operating lease option additional extend term		3 years
Rent expense			2,200	2,200	$ 2,200
Corporate Office Space and Laboratory Facility | Merck Sharp & Dohme Corp
Commitments And Contingencies Disclosure [Line Items]
Remaining lease payment obligation			2,000	$ 3,900
Corporate Office Space and Laboratory Facility | Letter of Credit
Commitments And Contingencies Disclosure [Line Items]
Letter of credit as a security deposit	2,300
Reduction in letter of credit on each of third anniversary and fourth anniversary	400
Corporate Office Space and Laboratory Facility | Letter of Credit | Cash and Cash Equivalents
Commitments And Contingencies Disclosure [Line Items]
Reduction in letter of credit			$ 400
Corporate Office Space and Laboratory Facility | Leasehold Improvement
Commitments And Contingencies Disclosure [Line Items]
Total Leasehold improvements	$ 22,300
Operating lease term	7 years

Commitments and Contingencies_2

Commitments and Contingencies - Future Minimum Commitments under Unassigned Lease Obligations (Details) $ in Thousands	Dec. 31, 2019USD ($)
Commitments And Contingencies Disclosure [Abstract]
2020	$ 4,995
2021	5,141
2022	5,294
2023	5,455
Total	$ 20,885

Convertible Preferred Stock - S

Convertible Preferred Stock - Schedule of Convertible Preferred Stock (Details) - USD ($) $ / shares in Units, $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Temporary Equity [Line Items]
Convertible preferred stock, shares authorized	96,268,206	96,268,206
Convertible preferred stock, shares outstanding	0	47,267,466
Convertible preferred stock, par value	$ 0.001	$ 0.001
Aggregate Carrying Value		$ 294,874
Series A Convertible Preferred Stock
Temporary Equity [Line Items]
Convertible preferred stock, shares authorized		13,295,000
Convertible preferred stock, shares outstanding		13,275,000
Convertible preferred stock, par value		$ 2
Aggregate Liquidation Value		$ 26,550
Aggregate Carrying Value		$ 26,462
Series B Convertible Preferred Stock
Temporary Equity [Line Items]
Convertible preferred stock, shares authorized		11,078,000
Convertible preferred stock, shares outstanding		11,078,000
Convertible preferred stock, par value		$ 5
Aggregate Liquidation Value		$ 55,389
Aggregate Carrying Value		$ 55,148
Series C Convertible Preferred Stock
Temporary Equity [Line Items]
Convertible preferred stock, shares authorized		8,328,000
Convertible preferred stock, shares outstanding		8,328,000
Convertible preferred stock, par value		$ 6
Aggregate Liquidation Value		$ 49,970
Aggregate Carrying Value		$ 49,887
Series D Convertible Preferred Stock
Temporary Equity [Line Items]
Convertible preferred stock, shares authorized		6,600,000
Convertible preferred stock, shares outstanding		5,753,000
Convertible preferred stock, par value		$ 10
Aggregate Liquidation Value		$ 57,530
Aggregate Carrying Value		$ 57,461
Series E Convertible Preferred Stock
Temporary Equity [Line Items]
Convertible preferred stock, shares authorized		8,833,000
Convertible preferred stock, shares outstanding		8,833,000
Convertible preferred stock, par value		$ 12
Aggregate Liquidation Value		$ 88,335
Aggregate Carrying Value		$ 105,916
Series A,B,C,D and E Convertible Preferred Stock
Temporary Equity [Line Items]
Convertible preferred stock, shares authorized		48,134,000
Convertible preferred stock, shares outstanding		47,267,000
Aggregate Liquidation Value		$ 277,774
Aggregate Carrying Value		$ 294,874

Convertible Preferred Stock - A

Convertible Preferred Stock - Additional Information (Details) - $ / shares	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Temporary Equity [Line Items]
Convertible preferred stock, voting rights	Each holder of convertible preferred stock was entitled to the number of votes equal to the number of shares of common stock into which such shares of convertible preferred stock were convertible.
Convertible preferred stock, non-cumulative dividend rate per annum	8.00%
Convertible preferred stock, shares issued	0	47,267,466
Convertible preferred stock, shares outstanding	0	47,267,466
Series E Convertible Preferred Stock
Temporary Equity [Line Items]
Convertible preferred stock, liquidation preference per share	$ 10
Convertible preferred stock, liquidation terms	An amount equal to $10.00 per share plus all declared and unpaid dividends on the convertible preferred stock.
Convertible preferred stock, shares outstanding		8,833,000

Stockholders' Equity (Deficit_2

Stockholders' Equity (Deficit) - Additional Information (Details)	1 Months Ended	12 Months Ended
	Mar. 31, 2019Periodshares	Dec. 31, 2019USD ($)$ / sharesshares	Dec. 31, 2018USD ($)$ / sharesshares	Dec. 31, 2017USD ($)$ / sharesshares
Class Of Stock [Line Items]
Preferred stock, shares authorized		10,000,000	10,000,000
Preferred stock, shares issued		0	0
Preferred stock, shares outstanding		0	0
Common stock, shares outstanding		66,960,279	6,937,890
Stock repurchase plan, authorized shares		74,454	205,108
Weighted-average grant date fair value of stock options ,Granted | $ / shares		$ 8	$ 5.71	$ 4.60
Intrinsic value of stock options exercised | $		$ 10,200,000	$ 1,900,000	$ 500,000
Total grant-date fair value of stock options vested | $		10,000	7,500	5,200
Tax benefits realized | $		$ 0	$ 0	0
Options granted		2,424,198
Number of shares of common stock reserved for issuance		17,066,375	59,256,418
Common stock issued		66,960,279	6,937,890
Employees and Directors
Class Of Stock [Line Items]
Unrecognized compensation expense, net of estimated forfeitures | $		$ 24,100,000
Unrecognized compensation expense expected to be recognized over a weighted-average period		2 years 8 months 1 day
Stock-based compensation expense | $		$ 12,729,000	$ 9,756,000	7,467,000
Non-employees
Class Of Stock [Line Items]
Stock-based compensation expense | $		$ 133,000	$ 103,000	$ 250,000
Options granted		22,500	0	0
Stock options to purchase shares, remain unvested		21,564	16,042
2018 Plan
Class Of Stock [Line Items]
Common stock, shares outstanding		74,454	205,108
Common stock authorized for issuance		17,874,624
Percentage of number of shares reserved and available to issue automatically increase outstanding on preceding calendar year		4.00%
Right to repurchase shares lapses over period		4 years
Early exercise stock option liabilities | $		$ 600,000	$ 1,600,000
2018 Plan | Minimum
Class Of Stock [Line Items]
Stock options, vesting period		4 years
Share repurchase price per Share | $ / shares		$ 7.64	$ 4
2018 Plan | Minimum | IPO
Class Of Stock [Line Items]
Percentage of exercise price to fair market value common stock on grant date		100.00%
2018 Plan | Minimum | IPO | 10% or Greater Stockholder
Class Of Stock [Line Items]
Percentage of exercise price to fair market value common stock on grant date		110.00%
Stock option expiration period		5 years
2018 Plan | Maximum
Class Of Stock [Line Items]
Stock options, vesting period		10 years
Share repurchase price per Share | $ / shares		$ 8.14	$ 8.14
2018 Plan | Maximum | IPO | 10% or Greater Stockholder
Class Of Stock [Line Items]
Stock option expiration period		10 years
2019 Employee Stock Purchase Plan
Class Of Stock [Line Items]
Stock-based compensation expense | $		$ 1,000,000
Number of shares of common stock reserved for issuance	1,000,000
Number of shares reserved and available for issuance, description		the number of shares reserved and available for issuance will automatically increase on January 1 of each calendar year, beginning January 1, 2020, by the lesser of (1) 1.0% of the total number of shares of common stock outstanding on December 31 of the preceding calendar year, (2) 1,000,000 shares or (3) a number determined by our board of directors that is less than (1) and (2). The board of directors determined not to increase the number of shares reserved under the 2019 ESPP on January 1, 2020.
Maximum percentage of payroll deductions of employee's compensation	15.00%
Maximum duration for purchase under employee stock purchase plan	24 months
Number of purchase periods | Period	4
Duration of each purchase period	6 months
Percentage of purchase of common stock fair market value	85.00%
Common stock issued		102,745

Stockholders' Equity (Deficit_3

Stockholders' Equity (Deficit) - Schedule of Shares of Common Stock Reserved for Issuance (Details) - shares	Dec. 31, 2019	Dec. 31, 2018
Class Of Stock [Line Items]
Total	17,066,375	59,256,418
Convertible Preferred Stock
Class Of Stock [Line Items]
Total		47,267,466
Common Stock Options Outstanding
Class Of Stock [Line Items]
Total	10,824,780	9,806,689
Common Stock Options Available for Grant
Class Of Stock [Line Items]
Total	5,316,066	2,125,875
401(k) Matching Plan
Class Of Stock [Line Items]
Total	28,274	36,751
Warrants to Purchase Convertible Preferred Stock
Class Of Stock [Line Items]
Total		19,637
Shares Committed Under ESPP
Class Of Stock [Line Items]
Total	897,255

Stockholders' Equity (Deficit_4

Stockholders' Equity (Deficit) - Summary of Outstanding Stock Options (Details) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Equity [Abstract]
Outstanding Options, Options Available for Grant, Beginning balance	2,125,875
Outstanding Options, Options Available for Grant, Additional Shares	5,193,322
Outstanding Options, Options Available for Grant, Granted	(2,424,198)
Outstanding Options, Options Available for Grant, Cancelled	418,628
Outstanding Options, Options Available for Grant, Repurchased	2,439
Outstanding Options, Options Available for Grant, Ending balance	5,316,066	2,125,875
Outstanding Options, Number of Options, Beginning balance	9,806,689
Outstanding Options, Number of Options, Granted	2,424,198
Outstanding Options, Number of Options, Exercised	(987,479)
Outstanding Options, Number of Options, Cancelled	(418,628)
Outstanding Options, Number of Options, Ending balance	10,824,780	9,806,689
Outstanding Options, Number of Options, Options vested and expected to vest	10,727,013
Outstanding Options, Number of Options, Options exercisable	10,824,780
Outstanding Options, Weighted-Average Exercise Price, Beginning balance	$ 5.86
Outstanding Options, Weighted-Average Exercise Price, Granted	12.84
Outstanding Options, Weighted-Average Exercise Price, Exercised	3.65
Outstanding Options, Weighted-Average Exercise Price, Cancelled	8.60
Outstanding Options, Weighted-Average Exercise Price, Repurchased	7.69
Outstanding Options, Weighted-Average Exercise Price, Ending balance	7.52	$ 5.86
Outstanding Options, Weighted-Average Exercise Price, Options vested and expected to vest	7.48
Outstanding Options, Weighted-Average Exercise Price, Options exercisable	$ 7.52
Weighted Average Remaining Contractual Life (in Years)	6 years 3 months 14 days	6 years 7 months 13 days
Weighted Average Remaining Contractual Life (in Years), Vested and expected to vest	6 years 3 months 3 days
Weighted Average Remaining Contractual Life (in Years),Outstanding and Exercisable	6 years 3 months 14 days
Outstanding Options, Aggregate Intrinsic Value, Balance	$ 118,770	$ 105,226
Outstanding Options, Aggregate Intrinsic Value, Options vested and expected to vest-December 31, 2019	118,143
Options Outstanding, Aggregate Intrinsic Value, Options exercisable-December 31, 2019	$ 118,770

Stockholders' Equity (Deficit_5

Stockholders' Equity (Deficit) - Summary of Stock Based Compensation Expense (Details) - Employees and Directors - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Stock-based compensation expense	$ 12,729	$ 9,756	$ 7,467
Research and Development
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Stock-based compensation expense	7,145	5,232	4,473
General and Administrative
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Stock-based compensation expense	$ 5,584	$ 4,524	$ 2,994

Stockholders' Equity (Deficit_6

Stockholders' Equity (Deficit) - Summary of Fair Value of Stock Option Granted to Employees and Directors were Estimated at Date of Grant Using Black-Scholes Option-pricing Model (Details) - Employees and Directors	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Risk-free interest rate	2.25%	2.59%	1.73%
Expected term of options (in years)	6 years 2 months 4 days	5 years 11 months 23 days	6 years 3 months
Expected stock price volatility	64.85%	64.60%	75.48%
Forfeiture rate	2.20%	4.42%	3.04%

Stockholders' Equity (Deficit_7

Stockholders' Equity (Deficit) - Summary of Fair Value of Stock Option Granted to Non-Employees was Estimated at Date of Grant Using Black-Scholes Option-pricing Model (Details) - Non-employees	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2017
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Risk-free interest rate	2.26%	2.48%
Expected term of options (in years)	6 years	6 years 11 months 12 days
Expected stock price volatility	65.77%	64.93%

Stockholders' Equity (Deficit_8

Stockholders' Equity (Deficit) - Summary of Fair Value of the Rights Granted to Employees Under the 2019 ESPP was Estimated at the Date of Offer Using Black-Scholes Option-pricing Model (Details) - 2019 Employee Stock Purchase Plan	12 Months Ended
	Dec. 31, 2019
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Risk-free interest rate	1.97%
Expected term of options (in years)	1 year 2 months 23 days
Expected stock price volatility	59.46%

Income Taxes - Additional Infor

Income Taxes - Additional Information (Details) - USD ($)	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Income Tax Disclosure [Line Items]
Income tax provision (benefit)	$ 0	$ 0	$ (1,060,000)
Income tax benefit received	500,000
Valuation allowance, increase (decrease), amount	9,500,000	(2,200,000)
Research and development tax credits	2,918,000	2,918,000
Unrecognized tax benefits	3,819,000	3,819,000	$ 1,528,000	$ 1,528,000
Unrecognized tax benefits, accrued interest and penalties	0
Federal [Member]
Income Tax Disclosure [Line Items]
Net operating loss carryforwards	$ 113,100,000	47,700,000
Net operating loss carryforwards expiration period			20 years
Net operating loss carryforwards expiration year			2032
Operating loss carryforwards, limitations on use	Subsequent to the enactment of the 2017 Tax Act, the utilization of the federal net operating loss carryforwards generated in fiscal year 2018 and onwards are limited to 80% of the federal taxable income.
Percentage of net operating loss carryforwards utilization limit of taxable income subsequent to enactment of 2017 tax act	80.00%
Research and development tax credits	$ 3,100,000	3,100,000
Federal [Member] | Earliest Tax Year [Member]
Income Tax Disclosure [Line Items]
Research and development credits expiration year	2028
Federal [Member] | Latest Tax Year [Member]
Income Tax Disclosure [Line Items]
Research and development credits expiration year	2035
State [Member]
Income Tax Disclosure [Line Items]
Net operating loss carryforwards	$ 71,900,000
Net operating loss carryforwards expiration year	2028
Research and development tax credits	$ 4,000,000	4,000,000
Foreign [Member]
Income Tax Disclosure [Line Items]
Net operating loss carryforwards	$ 29,700,000	$ 22,900,000

Income Taxes - Schedule of Comp

Income Taxes - Schedule of Components of Losses Before Income Taxes (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Income Tax Disclosure [Abstract]
Domestic	$ (34,634)	$ 5,502	$ (8,974)
Foreign	(8,161)	(5,995)	(6,245)
Net loss before taxes	$ (42,795)	$ (493)	$ (15,219)

Income Taxes - Schedule of Reco

Income Taxes - Schedule of Reconciliation of Statutory U.S. Federal Rate to Effective Tax Rate (Details)	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Income Tax Disclosure [Abstract]
U.S. federal tax at statutory rate	21.00%	21.00%	34.00%
Foreign Australian subsidiary	1.70%	109.50%	(1.60%)
State, Net of Federal Benefit	0.00%	(4.50%)	1.30%
Stock-based compensation	0.20%	(93.10%)	(14.50%)
Change in valuation allowance	(23.20%)	401.60%	68.70%
Tax reform tax rate change			(85.00%)
Other	0.20%	(434.70%)	4.00%
Total	0.00%	(0.20%)	6.90%

Income Taxes - Schedule of Co_2

Income Taxes - Schedule of Components of Net Deferred Tax Assets (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Deferred tax assets:
Net operating loss carryforwards	$ 37,679	$ 26,545
Stock-based compensation	3,478	1,961
Research and development credit	2,918	2,918
Deferred revenue	1,026	4,838
Other temporary differences	1,217	1,389
Total gross deferred tax assets	46,318	37,651
Deferred tax liabilities:
Depreciation and amortization	(570)	(1,368)
Non-qualified stock options with 83(b) election	(15)	(54)
Total gross deferred tax liabilities	(585)	(1,422)
Net deferred tax assets before valuation allowance	45,733	36,229
Deferred tax asset valuation allowance	$ (45,733)	$ (36,229)

Income Taxes - Schedule of Re_2

Income Taxes - Schedule of Reconciliation of Unrecognized Tax Benefits (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2018USD ($)
Income Tax Disclosure [Abstract]
Balance at beginning of year	$ 1,528
Additions (deletions) based on tax positions related to prior year	2,291
Balance at end of year	$ 3,819

Employee Benefit Plan - Additio

Employee Benefit Plan - Additional Information (Details) - USD ($)	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Defined Benefit Plan Disclosure [Line Items]
Issuance of common stock to participants in 401(k) Plan	$ 98,000	$ 91,000	$ 82,000
401(k)
Defined Benefit Plan Disclosure [Line Items]
Percentage of contribution matched by employer in common stock	50.00%
Maximum annual contributions of common stock per year	$ 750
Common stock reserved for future issuance	28,274	36,751
Issuance of common stock to participants in 401(k) Plan, shares	8,477	11,223
Issuance of common stock to participants in 401(k) Plan	$ 106,000	$ 103,000

Selected Quarterly Financial _3

Selected Quarterly Financial Data - Schedule of Selected Quarterly Financial Data (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Quarterly Financial Information Disclosure [Abstract]
Related party revenue	$ 31,083	$ 21,568	$ 25,341	$ 25,552	$ 47,119	$ 20,815	$ 22,118	$ 18,613	$ 103,544	$ 108,665	$ 77,141
Loss from operations	(17,294)	(12,997)	(9,707)	(9,342)	13,056	(8,469)	(4,186)	(4,715)	(49,340)	(4,314)	(17,425)
Net Loss	$ (15,941)	$ (10,917)	$ (7,669)	$ (8,268)	$ 14,165	$ (7,517)	$ (3,200)	$ (3,941)	$ (42,795)	$ (493)	$ (14,159)
Net loss per share, basic and diluted	$ (0.24)	$ (0.17)	$ (0.13)	$ (1.21)		$ (1.15)	$ (0.52)	$ (0.64)	$ (0.85)	$ (0.08)	$ (2.37)