Ngm Biopharmaceuticals (NGM) 10-Q 12 Aug 20 2020 Q2 Quarterly report Financial data

Document and Entity Information

Document and Entity Information - shares	6 Months Ended
	Jun. 30, 2020	Aug. 07, 2020
Cover [Abstract]
Document Type	10-Q
Amendment Flag	false
Document Period End Date	Jun. 30, 2020
Document Fiscal Year Focus	2020
Document Fiscal Period Focus	Q2
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 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
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 Quarterly Report	true
Document Transition Report	false
Entity Common Stock, Shares Outstanding		68,827,752

CONDENSED CONSOLIDATED BALANCE

CONDENSED CONSOLIDATED BALANCE SHEETS (Unaudited) - USD ($) $ in Thousands	Jun. 30, 2020	Dec. 31, 2019
Current assets:
Cash and cash equivalents	$ 249,317	$ 245,598
Short-term marketable securities	62,778	98,913
Related party receivable from collaboration	3,079	5,206
Prepaid expenses and other current assets	7,448	5,531
Total current assets	322,622	355,248
Property and equipment, net	17,321	19,475
Restricted cash	1,874	1,874
Other non-current assets	5,467	3,806
Total assets	347,284	380,403
Current liabilities:
Accounts payable	1,934	9,026
Accrued liabilities	26,792	22,991
Deferred rent, current	2,902	2,829
Deferred revenue, current	2,074	4,872
Total current liabilities	33,702	39,718
Deferred rent, non-current	7,941	9,392
Other non-current liabilities	4,188
Early exercise stock option liability	289	574
Total liabilities	46,120	49,684
Commitments and contingencies (Note 6)
Stockholders' equity:
Preferred stock, $0.001 par value; 10,000,000 shares authorized; no shares issued or outstanding as of June 30, 2020 and December 31, 2019, respectively
Common stock, $0.001 par value; 400,000,000 shares authorized; 68,739,866 and 66,960,279 shares issued and outstanding as of June 30, 2020 and December 31, 2019, respectively	69	67
Additional paid-in capital	541,833	526,771
Accumulated other comprehensive gain	137	25
Accumulated deficit	(240,875)	(196,144)
Total stockholders' equity	301,164	330,719
Total liabilities and stockholders' equity	$ 347,284	$ 380,403

CONDENSED CONSOLIDATED BALANC_2

CONDENSED CONSOLIDATED BALANCE SHEETS (Unaudited) (Parenthetical) - $ / shares	Jun. 30, 2020	Dec. 31, 2019
Statement Of Financial Position [Abstract]
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	68,739,866	66,960,279
Common stock, shares outstanding	68,739,866	66,960,279

CONDENSED CONSOLIDATED STATEMEN

CONDENSED CONSOLIDATED STATEMENTS OF OPERATIONS (Unaudited) - USD ($) $ in Thousands	3 Months Ended			6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019		Jun. 30, 2020	Jun. 30, 2019
Income Statement [Abstract]
Related party revenue	$ 19,755	$ 25,341		$ 44,119	$ 50,893
Operating expenses:
Research and development	38,494	28,819		76,933	58,346
General and administrative	6,794	6,229		13,389	11,596
Total operating expenses	45,288	35,048		90,322	69,942
Loss from operations	(25,533)	(9,707)		(46,203)	(19,049)
Interest income	388	2,044		1,563	3,154
Other expense, net	(471)	(6)		(91)	(42)
Net loss	$ (25,616)	$ (7,669)		$ (44,731)	$ (15,937)
Net loss per share, basic and diluted	$ (0.38)	$ (0.13)		$ (0.66)	$ (0.47)
Weighted average shares used to compute net loss per share, basic and diluted	68,305,056	61,044,450	[1]	67,850,640	34,078,099
[1]	In April 2019, the Company completed its IPO and concurrent private placement with Merck, in which the Company issued an aggregate of 7,521,394 and 4,121,683 shares of common stock, respectively, and all of the then outstanding shares of convertible preferred stock were automatically converted into shares of common stock upon the closing of the IPO.

CONDENSED CONSOLIDATED STATEM_2

CONDENSED CONSOLIDATED STATEMENTS OF COMPREHENSIVE LOSS (Unaudited) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Statement Of Income And Comprehensive Income [Abstract]
Net loss	$ (25,616)	$ (7,669)	$ (44,731)	$ (15,937)
Other comprehensive gain (loss), net of tax:
Net unrealized gain on available-for-sale marketable securities	192	147	112	369
Total comprehensive loss	$ (25,424)	$ (7,522)	$ (44,619)	$ (15,568)

CONDENSED CONSOLIDATED STATEM_3

CONDENSED CONSOLIDATED STATEMENTS OF CONVERTIBLE PREFERRED STOCK AND STOCKHOLDERS' EQUITY (DEFICIT) (Unaudited) - USD ($) shares in Thousands, $ in Thousands		Total	Cumulative Effect Period of Adoption Adjustment	Convertible Preferred Stock	Common Stock		Additional Paid-In Capital	Other Comprehensive Gain (Loss)	Accumulated Deficit	Accumulated DeficitCumulative Effect Period of Adoption Adjustment
Balance at Dec. 31, 2018		$ (108,195)		$ 294,874	$ 7	[1]	$ 39,258	$ (267)	$ (147,193)
Balance, shares at Dec. 31, 2018				47,267	6,733	[1]
Issuance of common stock upon exercise of stock options		279					279
Issuance of common stock upon exercise of stock options, shares	[1]				80
Issuance of common stock under 401(k) Plan		98					98
Issuance of common stock under 401(k) Plan, shares	[1]				8
Vesting of common stock from early exercises		237					237
Vesting of common stock from early exercises, shares	[1]				34
Stock-based compensation expense		2,605					2,605
Changes in unrealized (loss) gain on available-for-sale securities		222						222
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
Balance at Mar. 31, 2019		$ (119,178)	$ (6,156)	$ 295,072	$ 7	[1]	42,477	(45)	(161,617)	$ (6,156)
Accounting Standards Update [Extensible List]		us-gaap:AccountingStandardsUpdate201409Member
Net loss		$ (8,268)							(8,268)
Balance, shares at Mar. 31, 2019				47,283	6,855	[1]
Balance at Dec. 31, 2018		(108,195)		$ 294,874	$ 7	[1]	39,258	(267)	(147,193)
Balance, shares at Dec. 31, 2018				47,267	6,733	[1]
Balance at Jun. 30, 2019		346,130			$ 66	[1]	515,248	102	(169,286)
Net loss		(15,937)
Balance, shares at Jun. 30, 2019	[1]				65,899
Balance at Mar. 31, 2019		(119,178)	$ (6,156)	$ 295,072	$ 7	[1]	42,477	(45)	(161,617)	$ (6,156)
Balance, shares at Mar. 31, 2019				47,283	6,855	[1]
Conversion of Series A, B, C, D, E convertible preferred stock to common stock		295,072		$ (295,072)	$ 47	[1]	295,025
Conversion of Series A, B, C, D, E convertible preferred stock to common stock, shares				(47,283)
Conversion of Series A, B, C, D, E convertible preferred stock to common stock, shares	[1]				47,283
Issuance of common stock upon initial public offering, net of issuance cost		107,756			$ 8	[1]	107,748
Issuance of common stock upon initial public offering, net of issuance cost, shares	[1]				7,521
Issuance of common stock upon private placement		65,947			$ 4	[1]	65,943
Issuance of common stock upon private placement, shares	[1]				4,122
Issuance of common stock upon exercise of stock options		258					258
Issuance of common stock upon exercise of stock options, shares	[1]				86
Vesting of common stock from early exercises		245					245
Vesting of common stock from early exercises, shares	[1]				32
Stock-based compensation expense		3,552					3,552
Changes in unrealized (loss) gain on available-for-sale securities		147						147
Balance at Jun. 30, 2019		346,130			$ 66	[1]	515,248	102	(169,286)
Net loss		(7,669)							(7,669)
Balance, shares at Jun. 30, 2019	[1]				65,899
Balance at Dec. 31, 2019		330,719			$ 67		526,771	25	(196,144)
Balance, shares at Dec. 31, 2019					66,886
Issuance of common stock upon exercise of stock options		3,591			$ 1		3,590
Issuance of common stock upon exercise of stock options, shares					984
Vesting of common stock from early exercises		162					162
Vesting of common stock from early exercises, shares					21
Stock-based compensation expense		3,695					3,695
Changes in unrealized (loss) gain on available-for-sale securities		(80)						(80)
Balance at Mar. 31, 2020		$ 318,972			$ 68		534,218	(55)	(215,259)
Accounting Standards Update [Extensible List]		us-gaap:AccountingStandardsUpdate201409Member
Net loss		$ (19,115)							(19,115)
Balance, shares at Mar. 31, 2020					67,891
Balance at Dec. 31, 2019		330,719			$ 67		526,771	25	(196,144)
Balance, shares at Dec. 31, 2019					66,886
Balance at Jun. 30, 2020		301,164			$ 69		541,833	137	(240,875)
Net loss		(44,731)
Balance, shares at Jun. 30, 2020					68,702
Balance at Mar. 31, 2020		318,972			$ 68		534,218	(55)	(215,259)
Balance, shares at Mar. 31, 2020					67,891
Issuance of common stock upon exercise of stock options		2,366			$ 1		2,365
Issuance of common stock upon exercise of stock options, shares					680
Issuance of common stock in connection with employee stock purchase plan		1,285					1,285
Issuance of common stock in connection with employee stock purchase plan, shares					109
Issuance of common stock under 401(k) Plan		119					119
Issuance of common stock under 401(k) Plan, shares					6
Vesting of common stock from early exercises		123					123
Vesting of common stock from early exercises, shares					16
Stock-based compensation expense		3,723					3,723
Changes in unrealized (loss) gain on available-for-sale securities		192						192
Balance at Jun. 30, 2020		301,164			$ 69		$ 541,833	$ 137	(240,875)
Net loss		$ (25,616)							$ (25,616)
Balance, shares at Jun. 30, 2020					68,702
[1]	In April 2019, the Company completed its initial public offering (“IPO”) and concurrent private placement with Merck Sharp & Dohme Corp. (“Merck”), in which the Company issued an aggregate of 7,521,394 and 4,121,683 shares of common stock, respectively, for net proceeds of $107.8 million and $65.9 million, respectively. Upon the closing of the IPO, all of the then outstanding shares of convertible preferred stock were automatically converted into shares of common stock and its related carrying amount of $295.1 million was reclassified to common stock and additional paid-in-capital.

CONDENSED CONSOLIDATED STATEM_4

CONDENSED CONSOLIDATED STATEMENTS OF CONVERTIBLE PREFERRED STOCK AND STOCKHOLDERS' EQUITY (DEFICIT) (Unaudited) (Parenthetical) $ in Thousands	1 Months Ended
	Apr. 30, 2019USD ($)shares
Common Stock
Proceeds from issuance of common stock upon initial public offering, net	$ 107,800
Reclassification to common stock and additional paid-in capital	295,100
Proceeds from issuance of common stock upon completion of private placement	$ 65,900
Common Stock | IPO
Number of shares issued in transaction | shares	7,521,394
Common Stock | Private Placement
Number of shares issued in transaction | shares	4,121,683

CONDENSED CONSOLIDATED STATEM_5

CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS (Unaudited) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019
Cash flows from operating activities
Net loss	$ (44,731)	$ (15,937)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation	3,381	3,896
Amortization of discount on marketable securities	(190)	(803)
Stock-based compensation expense	7,418	6,157
Other non-cash expenses	239	217
Changes in operating assets and liabilities:
Related party receivable from collaboration	2,127	2,788
Prepaid expenses and other assets	(3,119)	(1,864)
Accounts payable	(6,874)	(2,511)
Accrued expenses and other liabilities	7,634	1,167
Deferred rent	(1,378)	(1,305)
Deferred revenue	(2,798)	(11,682)
Net cash used in operating activities	(38,291)	(19,877)
Cash flows from investing activities
Purchase of marketable securities	(29,399)	(75,224)
Proceeds from sales and maturities of marketable securities	65,836	128,990
Purchase of property and equipment	(1,445)	(2,275)
Net cash provided by investing activities	34,992	51,491
Cash flows from financing activities
Proceeds from issuance of common stock upon initial public offering, net		110,078
Proceeds from issuance of common stock upon completion of private placement		65,947
Proceeds from issuance of common stock upon exercise of stock options	5,957	510
Proceeds from issuance of common stock in connection with employee stock purchase plan	1,285
Payments of deferred financing costs	(224)
Net cash provided by financing activities	7,018	176,535
Net increase in cash and cash equivalents	3,719	208,149
Cash, cash equivalents and restricted cash at beginning of period	247,472	59,172
Cash, cash equivalents and restricted cash at end of period	251,191	267,321
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	285	482
Cost of property and equipment purchases accrued but not yet paid	87	128
Deferred offering costs accrued but not yet paid	$ 235	$ 30

Organization and Description of

Organization and Description of Business	6 Months Ended
	Jun. 30, 2020
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 biopharmaceutical company focused on discovering and developing novel therapeutics based on scientific understanding of key biological pathways underlying liver, retinal and metabolic diseases and cancer. The five most advanced proprietary product candidates in the Company’s portfolio are aldafermin (NGM282), NGM313, NGM621, NGM120 and NGM395. The Company was incorporated in Delaware in December 2007 and commenced operations in 2008. Its headquarters are located at 333 Oyster Point Blvd., South San Francisco, California 94080.

Summary of Significant Accounti

Summary of Significant Accounting Policies	6 Months Ended
	Jun. 30, 2020
Accounting Policies [Abstract]
Summary of Significant Accounting Policies	2. Summary of Significant Accounting Policies Basis of Presentation and Principles of Consolidation The accompanying unaudited condensed consolidated financial statements have been prepared in accordance with generally accepted accounting principles in the United States of America (“U.S. GAAP”) and Regulation S-X for interim consolidated financial information. These unaudited condensed consolidated financial statements should be read in conjunction with the audited consolidated financial statements and notes for the year ended December 31, 2019 included in the Company’s Annual Report on Form 10-K for the year ended December 31, 2019 filed with the United States Securities and Exchange Commission (“SEC”) on March 17, 2020 (the “Annual Report”). These unaudited condensed consolidated financial statements reflect all adjustments that management believes are necessary for a fair presentation of the periods presented. All such adjustments are of a normal recurring nature and are not necessarily indicative of results expected for the full fiscal year or for any subsequent interim period. These unaudited condensed 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 condensed 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, the valuation of common stock and the associated stock-based compensation expense, contract manufacturing accruals, clinical trial accruals and revenue recognition in accordance with Accounting Standards Codification 606 ( “ 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 three and six months ended June 30, 2020, the Company incurred net losses of $25.6 million and $44.7 million, respectively, compared to $7.7 million and $15.9 million, respectively, for the three and six months ended June 30, 2019. As of June 30, 2020, the Company had an accumulated deficit of $240.9 million and does not expect to experience positive cash flows from operations in the near future. The Company had $312.1 million of cash, cash equivalents and marketable securities as of June 30, 2020, unaudited condensed The Company plans to continue to fund its operations and pursue its strategy through public or private equity or debt financings, government or other third-party funding, collaborations, strategic alliances and licensing arrangements or a combination of these. Deferred Offering Costs In June 2020, the Company filed a registration statement on Form S-3 and entered into an Open Market Sale Agreement SM Fair Value of Financial Instruments The carrying amounts of cash and cash equivalents, receivables from collaborations, 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. 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 June 30, 2020 and December 31, 2019, 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 available-for-sale, 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. 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 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. As of June 30, 2020, the Company did not record any impairment related to other-than-temporary declines in the fair value of securities. 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 condensed consolidated balance sheets as the collateral will not be returned to the Company in less than 12 months (Note 6) 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 (Note 5) are typically unsecured. Accordingly, the Company may be exposed to credit risk generally associated with its Research Collaboration, Product Development and License Agreement with Merck (“Collaboration Agreement”). To date, the Company has not experienced any losses related to these receivables. Merck accounted for 100% of the Company’s revenue for the three and six months ended June 30, 2020 and 2019. 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 applicable 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 applicable 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 June 30, 2020 and December 31, 2019, 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. Revenue Recognition The Company adopted Accounting Standards Update (“ASU”) 2014-09, Revenue from Contracts with Customers (Topic 606), and subsequent amendments, on January 1, 2019. 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, primarily with Merck. 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 partner, 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 research or 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 partner’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 clinical research organizations (“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 issued under the Company’s 2019 Employee Stock Purchase Plan (“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 services in exchange for the award, which is generally the vesting period of each award. 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 services 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., the Company’s 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 condensed 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 three and six months ended June 30, 2020, the difference between comprehensive loss and net loss consisted . 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, shares committed under the ESPP and unvested restricted common stock and stock units. As the Company incurred net losses for the three and six months ended June 30, 2020 and 2019, all potential common shares were determined to be anti-dilutive and have been excluded in the diluted net loss per share calculations. The following table sets forth the computation of net loss per common share (in thousands, except share and per share amounts): Three Months Ended Six Months Ended June 30, June 30, 2020 2019 2020 2019 Numerator: Net loss $ (25,616 ) $ (7,669 ) $ (44,731 ) $ (15,937 ) Denominator: Weighted average number of shares used in calculating net loss per share—basic and diluted 68,305,056 61,044,450 (1) 67,850,640 34,078,099 Net loss per share—basic and diluted $ (0.38 ) $ (0.13 ) $ (0.66 ) $ (0.47 ) (1) In April 2019, the Company completed its IPO and concurrent private placement with Merck, in which the Company issued an aggregate of 7,521,394 and 4,121,683 shares of common stock, respectively, and all of the then outstanding shares of convertible preferred stock were automatically converted into shares of common stock upon the closing of the IPO. Potentially dilutive securities that were not included in the diluted net loss per share calculations because they would be anti-dilutive were as follows: Six Months Ended June 30, 2020 2019 Options to purchase common stock 10,478,682 11,417,124 Shares committed under ESPP 467,614 406,200 Total 10,946,296 11,823,324 Segment and Geographical Information The Company operates in one business segment. Substantially all of the Company’s long-lived assets, comprised of property and equipment, are based in the United States. For the three and six months ended June 30, 2020 and 2019, the Company’s revenues were entirely within the United States based upon the location of its partner 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 condensed consolidated financial statements upon adoption. Under the Jumpstart Our Business Startups Act of 2012, as amended (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 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. ASU 2018-13 modifies the disclosure requirements on fair value measurements in Topic 820, Fair Value Measurements 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. ASU 2018-13 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 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. The Company adopted ASU 2018-13 effective January 1, 2020, noting no material impact on the Company’s condensed consolidated financial statements. 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 condensed 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 deferred the effective date for certain ASUs including ASU 2016-02. In June 2020, due to the evolving impacts of the COVID-19 pandemic, the FASB issued ASU 2020-05, which further defers the effective date of ASU 2016-02. The new guidance is now effective for the Company’s fiscal year beginning after December 15, 2021, and interim periods within fiscal years beginning after December 15, 2022. Early adoption continues to be permitted for all entities. The Company plans to adopt the new lease standard in accordance with the new guidance, in the fiscal year beginning after December 15, 2021, 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 condensed 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 standard amends guidance on reporting credit losses for financial assets held at amortized cost basis, including accounts receivable, investments classified as available for sale, such as our debt securities, and unbilled related party revenue. Estimated credit losses will be recorded as an allowance rather than a write-down. In November 2019, the FASB issued ASU 2019-10, which deferred the effective date for certain ASUs including ASU 2016-13. This standard is now effective for the Company’s fiscal year beginning after December 15, 2022. 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 condensed 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 and presentation and disclosure requirements. ASU 2018-18 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. ASU 2018-18 will be 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 is currently assessing the timing of adoption and the impact that the adoption of ASU 2018-18 will have on its condensed 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. ASU 2019-12 will be effective for the Company for fiscal year beginning after December 15, 2021, and interim periods within fiscal year 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 timing of adoption and the impact that the adoption of ASU 2019‑12 will have on its condensed consolidated financial statements.

Fair Value Measurements

Fair Value Measurements	6 Months Ended
	Jun. 30, 2020
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 condensed 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 against the market value of its marketable securities. 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 June 30, 2020 Money market funds $ 247,026 $ — $ — $ 247,026 Corporate and agency bonds 34,089 137 — 34,226 Commercial paper 28,552 — — 28,552 Total $ 309,667 $ 137 $ — $ 309,804 Classified as: Cash and cash equivalents $ 247,026 Short-term marketable securities (amortized cost of $62,641) 62,778 Total cash and cash equivalents and marketable securities $ 309,804 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 28 (14 ) 66,077 Commercial paper 24,840 — — 24,840 U.S. government agencies securities 7,985 11 — 7,996 Total $ 343,861 $ 39 $ (14 ) $ 343,886 Classified as: Cash and cash equivalents $ 244,973 Short-term marketable securities (amortized cost of $98,888) 98,913 Total cash and cash equivalents and marketable securities $ 343,886 Cash and cash equivalents in the table above excludes cash on deposit with banks of $2.3 million and $0.6 million as of June 30, 2020 and December 31, 2019, respectively. As of June 30, 2020 and December 31, 2019, the Company’s marketable securities had remaining contractual maturities less than one year. As of June 30, 2020, there were no marketable securities in an unrealized loss position compared to four marketable securities in an unrealized loss position as of December 31, 2019. Marketable securities that had been in an unrealized loss position at December 31, 2019 had been in an unrealized loss position for less than 12 months. The Company does not intend to sell marketable securities that are in an unrealized loss position and it is highly unlikely that the Company will be required to sell the investments before recovery of their amortized cost basis, which may be maturity. 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 June 30, 2020 and December 31, 2019 (in thousands): Fair Value Measurements As of June 30, 2020 Level 1 Level 2 Level 3 Total Assets: Money market funds $ 247,026 $ — $ — $ 247,026 Corporate and agency bonds — 34,226 — 34,226 Commercial paper — 28,552 — 28,552 $ 247,026 $ 62,778 $ — $ 309,804 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 There were no transfers of assets or liabilities between the fair value measurement levels during the six months ended June 30, 2020 and year ended December 31, 2019.

Balance Sheet Components

Balance Sheet Components	6 Months Ended
	Jun. 30, 2020
Statement Of Financial Position [Abstract]
Balance Sheet Components	4. Balance Sheet Components Cash, Cash Equivalent and Restricted Cash A reconciliation of cash, cash equivalents and restricted cash reported within the condensed consolidated balance sheets to the amount reported within the condensed consolidated statements of cash flows is as follows (in thousands): June 30, December 31, 2020 2019 Cash and cash equivalents $ 249,317 $ 245,598 Restricted cash 1,874 1,874 Total cash, cash equivalents and restricted cash $ 251,191 $ 247,472 Property and Equipment Property and equipment consist of the following (in thousands): June 30, December 31, 2020 2019 Computer equipment $ 1,201 $ 1,201 Laboratory equipment and office furniture 22,889 21,652 Leasehold improvements 25,880 25,880 Construction in process 488 498 Total property and equipment, gross 50,458 49,231 Less: accumulated depreciation and amortization (33,137 ) (29,756 ) Total property and equipment, net $ 17,321 $ 19,475 Depreciation expense was approximately $1.7 million and $3.4 million for the three and six months ended June 30, 2020, respectively, compared to $1.9 million and $3.9 million for the three and six months ended June 30, 2019, respectively. Accrued Liabilities Accrued liabilities consist of the following (in thousands): June 30, December 31, 2020 2019 Accrued expenses $ 2,813 $ 2,901 Clinical trials and research and development costs 12,305 11,051 Personnel-related costs 4,986 6,446 Manufacturing costs 6,688 2,593 Total accrued liabilities $ 26,792 $ 22,991

Research Collaboration and Lice

Research Collaboration and License Agreements	6 Months Ended
	Jun. 30, 2020
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 with an original non-cancellable five-year term running through March 16, 2020. The collaboration includes a broad, multiyear drug discovery and early development program financially supported by Merck. The Company determines the scientific direction and areas of therapeutic interest, with input from Merck through various governance committees, and the Company 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 funded 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. The Collaboration Agreement included an option to extend the research phase of the collaboration for two additional years through March 16, 2022 after the initial five-year term and a second option to further extend the research phase for two additional years through March 16, 2024. In March 2019, Merck exercised its option to extend the research phase of the collaboration for an additional two years through March 16, 2022. In connection with this extension, Merck agreed to continue to fund the Company’s research and development efforts during the extension 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 agreed to make additional payments totaling up to $20.0 million in support of the Company’s research and development program activities under the collaboration across 2021 and the first quarter of 2022. Under the terms of the Collaboration 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. During any extension, including the current extension and, if exercised, the potential second extension, the Company will provide distinct research and development services. Each extension is considered to be and accounted for as a separate arrangement, if and when the option is exercised by Merck. Merck funded 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 will continue to do so during the current two-year extension. When signed, the Collaboration Agreement included an exclusive worldwide license to our growth differentiation factor 15 (“GDF15”) receptor agonist program. In May 2019, Merck terminated its license to the GDF15 receptor agonist program. 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 related compounds that are directed against the same target in the same manner. In 2018, Merck exercised its option on the NGM313 compound. If Merck exercises an option, Merck is responsible, at its own cost, for any further development and commercialization activities for compounds within that licensed 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 milestone and royalty payments 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, 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 compound on an indication-by-indication basis for up to three indications in the United States, European Union (“EU”) and Japan. 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. 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. 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 certain 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 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 during the research phase of the collaboration 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 such license from the Company, 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 such small molecule compounds. 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 a “tail period” of up to three years by agreeing to pay all of the Company’s internal and external costs for the 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 certain 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 fees attached to the exercise of such options approximated the SSP of the promised distinct services included in the options. Therefore, the options do not give rise to material rights, are not performance obligations in the Collaboration Agreement and will be accounted for as separate arrangements under ASC 606, if and when exercised by Merck. This also includes license options, such as the $20.0 million license fee that was triggered by the exercise of Merck’s license option on NGM313 in November 2018. The Company recognized the license fee as revenue in the period of exercise (i.e., the fourth quarter of 2018) as the Company has no further obligations related to such license. 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 transaction price associated with the initial five-year term of the Collaboration Agreement consisted 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 were 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 were 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 initial five-year term of the Collaboration Agreement is comprised of the up-front payment and the ongoing research and development reimbursements. 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 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. For example, in May 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. Therefore, there were no changes to the transaction price as a result of this termination. At the end of the initial five-year term of the Collaboration Agreement, the remaining deferred revenue amount of $4.9 million as of December 31, 2019 was fully earned and recognized during the three months ended March 31, 2020. The Company has fully recognized revenue of approximately $388.1 million related to the single performance obligation associated with the initial five‑year term of the Collaboration Agreement. Upon Merck exercising its option to extend the collaboration through March 16, 2022, the Company deemed that a separate arrangement containing a distinct two-year performance obligation to provide distinct research and development services was created on March 17, 2020 in accordance with ASC 606. The transaction price of $170.0 million for this two-year performance obligation consists of the potential funding amounts of up to $75.0 million initial funding caps per year and the additional funding amount of $20.0 million to be made across 2021 and the first quarter of 2022 if the Company exceeds those initial funding caps. The Company also uses a cost‑based input method to calculate the corresponding amount of revenue to recognize. In applying the cost-based input measure of revenue recognition, the Company measures actual costs incurred relative to budgeted costs to fulfill this distinct two-year 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 applied to the transaction price. The Company re-evaluates the estimate of expected costs to satisfy the performance obligation each reporting period and makes adjustments for any significant changes. In addition, the Company also considers any necessary adjustments in an effort to ensure that the transaction price is within the range of potential funding amounts as described above. As such, management applies considerable 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. Summary of Related Party Revenue The Company recognized revenue from the Collaboration Agreement as follows (in thousands): Three Months Ended June 30, Six Months Ended June 30, 2020 2019 2020 2019 Related party revenue $ 19,755 $ 25,341 $ 44,119 $ 50,893 For the three and six months ended June 30, 2020, the Company recognized related party revenue under the Collaboration Agreement of $19.8 million and $44.1 million, respectively, of which zero and $4.9 million, respectively, were recognized from the upfront license fee that was previously included in the transaction price associated with the initial five-year term of the Collaboration Agreement which concluded in March 2020, with the remaining balances related to the reimbursable research and development activities, all of which were recognized using the cost-based input model. For the three and six months ended June 30, 2019, the Company recognized related party revenue under the Collaboration Agreement of $25.3 million and $50.9 million, respectively, of which $5.7 million and $11.4 million, respectively, Contract Assets and Liabilities Changes in related party contract liabilities were as follows (in thousands): Amounts Balance at December 31, 2019 $ 4,872 Revenue recognized through March 16, 2020 (4,872 ) Increases as a result of research and development expenses to be earned under the Collaboration Agreement 2,074 Balance at June 30, 2020 $ 2,074 There were no contract assets for all the periods presented

Commitments and Contingencies

Commitments and Contingencies	6 Months Ended
	Jun. 30, 2020
Commitments And Contingencies Disclosure [Abstract]
Commitments and Contingencies	6. Commitments and Contingencies Operating Lease and Lease Guarantee In September 2009, the Company entered into an operating lease (as amended in June 2014, the “2014 Lease Amendment”) 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, 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 an operating lease for its current corporate office space and laboratory facility at 333 Oyster Point Blvd, South San Francisco, California (“333 Oyster Point”) for approximately 122,000 square feet, which 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 requires 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 condensed consolidated balance sheets. The Company has the right to reduce the letter of credit amount by $0.4 million on each of the 3rd anniversary and 4th anniversary of the rent commencement date. In September 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 condensed consolidated balance sheets. In July 2016, the Company assigned its operating lease of 630 Gateway to Merck, a related party, due to 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 June 30, 2020 because of 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 June 30, 2020 and 2019, the remaining lease payment obligations that are due for 630 Gateway were approximately $0.9 million and $2.9 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 $0.5 million for each of the three months ended June 30, 2020 and 2019 and $1.1 million for each of the six months ended June 30, 2020 and 2019. Future minimum payments under the unassigned lease obligations described above are as follows as of June 30, 2020 (in thousands): Year Ending December 31, 2020 $ 2,534 2021 5,141 2022 5,294 2023 5,455 Total $ 18,424 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 is subject to 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.

Stockholders' Equity

Stockholders' Equity	6 Months Ended
	Jun. 30, 2020
Equity [Abstract]
Stockholders' Equity	7. Stockholders’ Equity 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 fix the number, rights, preferences, privileges and restrictions for such series. These rights, preferences and privileges could include dividend rights, conversion rights, voting rights, terms of redemption, liquidation preferences and sinking fund terms. As of June 30, 2020, the Company did not have any shares of preferred stock issued or outstanding. Common Stock As of June 30, 2020 and December 31, 2019, the Company had 68,739,866 and 66,960,279 shares of common stock outstanding, respectively, which includes shares subject to repurchase of 37,467 and 74,454, respectively, as a result of early exercise of stock options not yet vested. June 30, December 31, 2020 2019 Common stock options outstanding 10,478,682 10,824,780 Common stock options available for grant 6,677,267 5,316,066 401(k) Matching Plan 21,930 28,274 ESPP shares available for purchase 788,120 897,255 Total 17,965,999 17,066,375 Stock Option Plan In 2018, the Company adopted the 2018 Equity Incentive Plan (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 over 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. The Company’s 2008 Equity Incentive Plan (the “2008 Plan”) expired at the beginning of 2018. Stock Option Activity A summary of the activity under the 2008 Plan and the 2018 Plan 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, 2019 5,316,066 10,824,780 $ 7.52 6.29 $ 118,770 Additional shares reserved 2,678,411 Options granted (1,869,701 ) 1,869,701 17.08 Options exercised — (1,663,308 ) 3.58 Options cancelled 552,491 (552,491 ) 12.19 Balances at June 30, 2020 6,677,267 10,478,682 $ 9.60 6.59 $ 106,375 Vested and expected to vest at June 30, 2020 10,360,681 $ 9.55 6.56 $ 105,769 Outstanding and exercisable at June 30, 2020 10,478,682 $ 9.60 6.59 $ 106,375 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. The weighted-average grant date fair value of stock options granted during the six months ended June 30, 2020 and 2019 was $10.05 and $7.82 per share, respectively. The intrinsic value of stock options exercised was $24.6 million and $1.7 million for the six months ended June 30, 2020 and 2019, respectively. Due to the Company’s net operating losses, the Company did not realize any tax benefits from stock-based payment arrangements for the three and six months ended June 30, 2020 and 2019. Employee Stock-Based Compensation Expense Employee and director stock-based compensation expense for the three and six months ended June 30, 2020 and 2019 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 stock-based payment awards previously granted to employees and directors and the Company’s ESPP for the three and six months ended June 30, 2020 and 2019, which was allocated as follows (in thousands): Three Months Ended Six Months Ended June 30, June 30, 2020 2019 2020 2019 Research and development $ 2,049 $ 2,053 $ 3,922 $ 3,463 General and administrative 1,639 1,460 3,433 2,624 Total stock-based compensation expense $ 3,688 $ 3,513 $ 7,355 $ 6,087 Non-employee Stock-Based Compensation Expense and Grants The Company grants stock options to non-employees in exchange for services performed for the Company. The Company granted 67,500 stock options to non-employees during the six months ended June 30, 2020 and granted 22,500 stock options to non-employees during the six months ended June 30, 2019. Stock‑based compensation expense related to stock-based payment awards to non-employees for the three and six months ended June 30, 2020 was $35,000 and $63,000, respectively, compared to $39,000 and $70,000 for the three and six months ended June 30, 2019, respectively. Employee Stock Purchase Plan Under the ESPP, eligible employees are granted the right to purchase shares of our common stock through payroll deductions that cannot exceed 15% of each employee’s salary. The 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. As of June 30, 2020, 211,880 shares of common stock had been purchased under the ESPP.

Income Taxes

Income Taxes	6 Months Ended
	Jun. 30, 2020
Income Tax Disclosure [Abstract]
Income Taxes	8. Income Taxes Since inception, the Company has incurred net losses and expects to record a net loss for the year ending December 31, 2020. Additionally, the Company’s net deferred tax assets have been fully offset by a valuation allowance. Therefore, the Company has not recorded a tax provision for income taxes for the three and six months ended June 30, 2020. On March 27, 2020, the Coronavirus Aid, Relief and Economic Security Act (the “CARES Act”) was enacted. Under U.S. GAAP, the Company is required to recognize the tax effects of new legislation in the reporting period in which the legislation was enacted. The CARES Act included changes to current U.S. tax provisions that benefit business entities and modified certain tax provisions of the 2017 Tax Cuts and Jobs Act (the “2017 Tax Act”). The tax relief measures included a five-year net operating loss carryback, suspension of the annual deduction limitation of 80% of taxable income from net operating losses generated in a tax year beginning after December 31, 2017, changes in the deductibility of interest, acceleration of alternative minimum tax credit refunds, payroll tax relief and a technical correction to allow accelerated deductions for qualified improvement properties. The CARES Act also provided other non-tax benefits to assist business entities impacted by the ongoing COVID-19 pandemic. The Company has evaluated the CARES Act and concluded that it did not result in any material adjustments to the Company’s income tax provision or net deferred tax assets for the three and six months ended June 30, 2020.

Summary of Significant Accoun_2

Summary of Significant Accounting Policies (Policies)	6 Months Ended
	Jun. 30, 2020
Accounting Policies [Abstract]
Basis of Presentation and Principles of Consolidation	Basis of Presentation and Principles of Consolidation The accompanying unaudited condensed consolidated financial statements have been prepared in accordance with generally accepted accounting principles in the United States of America (“U.S. GAAP”) and Regulation S-X for interim consolidated financial information. These unaudited condensed consolidated financial statements should be read in conjunction with the audited consolidated financial statements and notes for the year ended December 31, 2019 included in the Company’s Annual Report on Form 10-K for the year ended December 31, 2019 filed with the United States Securities and Exchange Commission (“SEC”) on March 17, 2020 (the “Annual Report”). These unaudited condensed consolidated financial statements reflect all adjustments that management believes are necessary for a fair presentation of the periods presented. All such adjustments are of a normal recurring nature and are not necessarily indicative of results expected for the full fiscal year or for any subsequent interim period. These unaudited condensed 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 condensed 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, the valuation of common stock and the associated stock-based compensation expense, contract manufacturing accruals, clinical trial accruals and revenue recognition in accordance with Accounting Standards Codification 606 ( “ 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 three and six months ended June 30, 2020, the Company incurred net losses of $25.6 million and $44.7 million, respectively, compared to $7.7 million and $15.9 million, respectively, for the three and six months ended June 30, 2019. As of June 30, 2020, the Company had an accumulated deficit of $240.9 million and does not expect to experience positive cash flows from operations in the near future. The Company had $312.1 million of cash, cash equivalents and marketable securities as of June 30, 2020, unaudited condensed The Company plans to continue to fund its operations and pursue its strategy through public or private equity or debt financings, government or other third-party funding, collaborations, strategic alliances and licensing arrangements or a combination of these.
Deferred Offering Costs	Deferred Offering Costs In June 2020, the Company filed a registration statement on Form S-3 and entered into an Open Market Sale Agreement SM
Fair Value of Financial Instruments	Fair Value of Financial Instruments The carrying amounts of cash and cash equivalents, receivables from collaborations, 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.
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 June 30, 2020 and December 31, 2019, 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 available-for-sale, 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. 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 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. As of June 30, 2020, the Company did not record any impairment related to other-than-temporary declines in the fair value of securities.
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 condensed consolidated balance sheets as the collateral will not be returned to the Company in less than 12 months (Note 6)
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 (Note 5) are typically unsecured. Accordingly, the Company may be exposed to credit risk generally associated with its Research Collaboration, Product Development and License Agreement with Merck (“Collaboration Agreement”). To date, the Company has not experienced any losses related to these receivables. Merck accounted for 100% of the Company’s revenue for the three and six months ended June 30, 2020 and 2019.
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 applicable 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 applicable 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 June 30, 2020 and December 31, 2019, 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.
Revenue Recognition	Revenue Recognition The Company adopted Accounting Standards Update (“ASU”) 2014-09, Revenue from Contracts with Customers (Topic 606), and subsequent amendments, on January 1, 2019. 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, primarily with Merck. 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 partner, 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 research or 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 partner’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 clinical research organizations (“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 issued under the Company’s 2019 Employee Stock Purchase Plan (“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 services in exchange for the award, which is generally the vesting period of each award. 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 services 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., the Company’s 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 condensed 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 three and six months ended June 30, 2020, the difference between comprehensive loss and net loss consisted .
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, shares committed under the ESPP and unvested restricted common stock and stock units. As the Company incurred net losses for the three and six months ended June 30, 2020 and 2019, all potential common shares were determined to be anti-dilutive and have been excluded in the diluted net loss per share calculations. The following table sets forth the computation of net loss per common share (in thousands, except share and per share amounts): Three Months Ended Six Months Ended June 30, June 30, 2020 2019 2020 2019 Numerator: Net loss $ (25,616 ) $ (7,669 ) $ (44,731 ) $ (15,937 ) Denominator: Weighted average number of shares used in calculating net loss per share—basic and diluted 68,305,056 61,044,450 (1) 67,850,640 34,078,099 Net loss per share—basic and diluted $ (0.38 ) $ (0.13 ) $ (0.66 ) $ (0.47 ) (1) In April 2019, the Company completed its IPO and concurrent private placement with Merck, in which the Company issued an aggregate of 7,521,394 and 4,121,683 shares of common stock, respectively, and all of the then outstanding shares of convertible preferred stock were automatically converted into shares of common stock upon the closing of the IPO. Potentially dilutive securities that were not included in the diluted net loss per share calculations because they would be anti-dilutive were as follows: Six Months Ended June 30, 2020 2019 Options to purchase common stock 10,478,682 11,417,124 Shares committed under ESPP 467,614 406,200 Total 10,946,296 11,823,324
Segment and Geographical Information	Segment and Geographical Information The Company operates in one business segment. Substantially all of the Company’s long-lived assets, comprised of property and equipment, are based in the United States. For the three and six months ended June 30, 2020 and 2019, the Company’s revenues were entirely within the United States based upon the location of its partner
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 condensed consolidated financial statements upon adoption. Under the Jumpstart Our Business Startups Act of 2012, as amended (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 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. ASU 2018-13 modifies the disclosure requirements on fair value measurements in Topic 820, Fair Value Measurements 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. ASU 2018-13 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 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. The Company adopted ASU 2018-13 effective January 1, 2020, noting no material impact on the Company’s condensed consolidated financial statements. 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 condensed 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 deferred the effective date for certain ASUs including ASU 2016-02. In June 2020, due to the evolving impacts of the COVID-19 pandemic, the FASB issued ASU 2020-05, which further defers the effective date of ASU 2016-02. The new guidance is now effective for the Company’s fiscal year beginning after December 15, 2021, and interim periods within fiscal years beginning after December 15, 2022. Early adoption continues to be permitted for all entities. The Company plans to adopt the new lease standard in accordance with the new guidance, in the fiscal year beginning after December 15, 2021, 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 condensed 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 standard amends guidance on reporting credit losses for financial assets held at amortized cost basis, including accounts receivable, investments classified as available for sale, such as our debt securities, and unbilled related party revenue. Estimated credit losses will be recorded as an allowance rather than a write-down. In November 2019, the FASB issued ASU 2019-10, which deferred the effective date for certain ASUs including ASU 2016-13. This standard is now effective for the Company’s fiscal year beginning after December 15, 2022. 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 condensed 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 and presentation and disclosure requirements. ASU 2018-18 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. ASU 2018-18 will be 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 is currently assessing the timing of adoption and the impact that the adoption of ASU 2018-18 will have on its condensed 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. ASU 2019-12 will be effective for the Company for fiscal year beginning after December 15, 2021, and interim periods within fiscal year 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 timing of adoption and the impact that the adoption of ASU 2019‑12 will have on its condensed consolidated financial statements.

Summary of Significant Accoun_3

Summary of Significant Accounting Policies (Tables)	6 Months Ended
	Jun. 30, 2020
Accounting Policies [Abstract]
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 Common Share	The following table sets forth the computation of net loss per common share (in thousands, except share and per share amounts): Three Months Ended Six Months Ended June 30, June 30, 2020 2019 2020 2019 Numerator: Net loss $ (25,616 ) $ (7,669 ) $ (44,731 ) $ (15,937 ) Denominator: Weighted average number of shares used in calculating net loss per share—basic and diluted 68,305,056 61,044,450 (1) 67,850,640 34,078,099 Net loss per share—basic and diluted $ (0.38 ) $ (0.13 ) $ (0.66 ) $ (0.47 ) (1) In April 2019, the Company completed its IPO and concurrent private placement with Merck, in which the Company issued an aggregate of 7,521,394 and 4,121,683 shares of common stock, respectively, and all of the then outstanding shares of convertible preferred stock were automatically converted into shares of common stock upon the closing of the IPO.
Potentially Dilutive Securities Not Included in the Diluted Net Loss Per Share Calculations	Potentially dilutive securities that were not included in the diluted net loss per share calculations because they would be anti-dilutive were as follows: Six Months Ended June 30, 2020 2019 Options to purchase common stock 10,478,682 11,417,124 Shares committed under ESPP 467,614 406,200 Total 10,946,296 11,823,324

Fair Value Measurements (Tables

Fair Value Measurements (Tables)	6 Months Ended
	Jun. 30, 2020
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 June 30, 2020 Money market funds $ 247,026 $ — $ — $ 247,026 Corporate and agency bonds 34,089 137 — 34,226 Commercial paper 28,552 — — 28,552 Total $ 309,667 $ 137 $ — $ 309,804 Classified as: Cash and cash equivalents $ 247,026 Short-term marketable securities (amortized cost of $62,641) 62,778 Total cash and cash equivalents and marketable securities $ 309,804 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 28 (14 ) 66,077 Commercial paper 24,840 — — 24,840 U.S. government agencies securities 7,985 11 — 7,996 Total $ 343,861 $ 39 $ (14 ) $ 343,886 Classified as: Cash and cash equivalents $ 244,973 Short-term marketable securities (amortized cost of $98,888) 98,913 Total cash and cash equivalents and marketable securities $ 343,886
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 June 30, 2020 and December 31, 2019 (in thousands): Fair Value Measurements As of June 30, 2020 Level 1 Level 2 Level 3 Total Assets: Money market funds $ 247,026 $ — $ — $ 247,026 Corporate and agency bonds — 34,226 — 34,226 Commercial paper — 28,552 — 28,552 $ 247,026 $ 62,778 $ — $ 309,804 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

Balance Sheet Components (Table

Balance Sheet Components (Tables)	6 Months Ended
	Jun. 30, 2020
Statement Of Financial Position [Abstract]
Schedule of Reconciliation of Cash, Cash Equivalent and Restricted Cash	A reconciliation of cash, cash equivalents and restricted cash reported within the condensed consolidated balance sheets to the amount reported within the condensed consolidated statements of cash flows is as follows (in thousands): June 30, December 31, 2020 2019 Cash and cash equivalents $ 249,317 $ 245,598 Restricted cash 1,874 1,874 Total cash, cash equivalents and restricted cash $ 251,191 $ 247,472
Property and Equipment	Property and equipment consist of the following (in thousands): June 30, December 31, 2020 2019 Computer equipment $ 1,201 $ 1,201 Laboratory equipment and office furniture 22,889 21,652 Leasehold improvements 25,880 25,880 Construction in process 488 498 Total property and equipment, gross 50,458 49,231 Less: accumulated depreciation and amortization (33,137 ) (29,756 ) Total property and equipment, net $ 17,321 $ 19,475
Accrued Liabilities	Accrued liabilities consist of the following (in thousands): June 30, December 31, 2020 2019 Accrued expenses $ 2,813 $ 2,901 Clinical trials and research and development costs 12,305 11,051 Personnel-related costs 4,986 6,446 Manufacturing costs 6,688 2,593 Total accrued liabilities $ 26,792 $ 22,991

Research Collaboration and Li_2

Research Collaboration and License Agreements (Tables)	6 Months Ended
	Jun. 30, 2020
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 certain 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 the Collaboration Agreement as follows (in thousands): Three Months Ended June 30, Six Months Ended June 30, 2020 2019 2020 2019 Related party revenue $ 19,755 $ 25,341 $ 44,119 $ 50,893
Schedule of Changes in Related Party Contract Liabilities	Contract Assets and Liabilities Changes in related party contract liabilities were as follows (in thousands): Amounts Balance at December 31, 2019 $ 4,872 Revenue recognized through March 16, 2020 (4,872 ) Increases as a result of research and development expenses to be earned under the Collaboration Agreement 2,074 Balance at June 30, 2020 $ 2,074

Commitments and Contingencies (

Commitments and Contingencies (Tables)	6 Months Ended
	Jun. 30, 2020
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 June 30, 2020 (in thousands): Year Ending December 31, 2020 $ 2,534 2021 5,141 2022 5,294 2023 5,455 Total $ 18,424

Stockholders' Equity (Tables)

Stockholders' Equity (Tables)	6 Months Ended
	Jun. 30, 2020
Equity [Abstract]
Schedule of Shares of Common Stock Reserved for Issuance	As of June 30, 2020 and December 31, 2019, the Company reserved shares of common stock for issuance as follows: June 30, December 31, 2020 2019 Common stock options outstanding 10,478,682 10,824,780 Common stock options available for grant 6,677,267 5,316,066 401(k) Matching Plan 21,930 28,274 ESPP shares available for purchase 788,120 897,255 Total 17,965,999 17,066,375
Summary of Activity under 2008 Plan and 2018 Plan	A summary of the activity under the 2008 Plan and the 2018 Plan 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, 2019 5,316,066 10,824,780 $ 7.52 6.29 $ 118,770 Additional shares reserved 2,678,411 Options granted (1,869,701 ) 1,869,701 17.08 Options exercised — (1,663,308 ) 3.58 Options cancelled 552,491 (552,491 ) 12.19 Balances at June 30, 2020 6,677,267 10,478,682 $ 9.60 6.59 $ 106,375 Vested and expected to vest at June 30, 2020 10,360,681 $ 9.55 6.56 $ 105,769 Outstanding and exercisable at June 30, 2020 10,478,682 $ 9.60 6.59 $ 106,375
Summary of Stock Based Compensation Expense	The following table summarizes stock-based compensation expense related to stock-based payment awards previously granted to employees and directors and the Company’s ESPP for the three and six months ended June 30, 2020 and 2019, which was allocated as follows (in thousands): Three Months Ended Six Months Ended June 30, June 30, 2020 2019 2020 2019 Research and development $ 2,049 $ 2,053 $ 3,922 $ 3,463 General and administrative 1,639 1,460 3,433 2,624 Total stock-based compensation expense $ 3,688 $ 3,513 $ 7,355 $ 6,087

Organization and Description _2

Organization and Description of Business - Additional Information (Details)	6 Months Ended
	Jun. 30, 2020
Organization Consolidation And Presentation Of Financial Statements [Abstract]
Place of incorporation	DE
Date of incorporation	Dec. 31, 2007

Summary of Significant Accoun_4

Summary of Significant Accounting Policies - Additional Information (Details)	3 Months Ended				6 Months Ended
	Jun. 30, 2020USD ($)shares	Mar. 31, 2020USD ($)	Jun. 30, 2019USD ($)	Mar. 31, 2019USD ($)	Jun. 30, 2020USD ($)Segmentshares	Jun. 30, 2019USD ($)	Dec. 31, 2019USD ($)shares
Summary Of Significant Accounting Policies [Line Items]
Net losses	$ 25,616,000	$ 19,115,000	$ 7,669,000	$ 8,268,000	$ 44,731,000	$ 15,937,000
Accumulated deficit	240,875,000				240,875,000		$ 196,144,000
Cash, cash equivalents and marketable securities	312,100,000				312,100,000
Aggregate offering price					150,000,000
Deferred Offering Costs	$ 500,000				$ 500,000		$ 0
Common stock, shares issued | shares	68,739,866				68,739,866		66,960,279
Impairment related to other-than-temporary					$ 0
Net unrealized gain (loss) on available-for-sale marketable securities	$ 200,000		$ 200,000		$ 100,000	$ 400,000
Number of operating business segment | Segment					1
ASU 2018-13
Summary Of Significant Accounting Policies [Line Items]
Change in accounting principle, accounting standards update, adopted [true false]	true				true
Change in accounting principle, accounting standards update, adoption date	Jan. 1, 2020				Jan. 1, 2020
Change in accounting principle, accounting standards update, immaterial effect [true false]	true				true
Revenue | Customer Concentration Risk | Merck
Summary Of Significant Accounting Policies [Line Items]
Percentage of revenue	100.00%		100.00%		100.00%	100.00%
Sales Agreement
Summary Of Significant Accounting Policies [Line Items]
Common stock, shares issued | shares	0				0

Summary of Significant Accoun_5

Summary of Significant Accounting Policies - Estimated Useful Life of Asset (Details)	6 Months Ended
	Jun. 30, 2020
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 Common Share (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended					6 Months Ended
	Jun. 30, 2020	Mar. 31, 2020	Jun. 30, 2019		Mar. 31, 2019	Jun. 30, 2020	Jun. 30, 2019
Numerator:
Net loss	$ (25,616)	$ (19,115)	$ (7,669)		$ (8,268)	$ (44,731)	$ (15,937)
Denominator:
Weighted average shares used to compute net loss per share, basic and diluted	68,305,056		61,044,450	[1]		67,850,640	34,078,099
Net loss per share—basic and diluted	$ (0.38)		$ (0.13)			$ (0.66)	$ (0.47)
[1]	In April 2019, the Company completed its IPO and concurrent private placement with Merck, in which the Company issued an aggregate of 7,521,394 and 4,121,683 shares of common stock, respectively, and all of the then outstanding shares of convertible preferred stock were automatically converted into shares of common stock upon the closing of the IPO.

Summary of Significant Accoun_7

Summary of Significant Accounting Policies - Computation of Net Loss Per Common Share (Parenthetical) (Details) - Common Stock - shares		1 Months Ended	3 Months Ended
		Apr. 30, 2019	Jun. 30, 2019
Subsidiary Sale Of Stock [Line Items]
Number of shares issued in transaction	[1]		7,521,000
IPO
Subsidiary Sale Of Stock [Line Items]
Number of shares issued in transaction		7,521,394
Private Placement
Subsidiary Sale Of Stock [Line Items]
Number of shares issued in transaction		4,121,683
[1]	In April 2019, the Company completed its initial public offering (“IPO”) and concurrent private placement with Merck Sharp & Dohme Corp. (“Merck”), in which the Company issued an aggregate of 7,521,394 and 4,121,683 shares of common stock, respectively, for net proceeds of $107.8 million and $65.9 million, respectively. Upon the closing of the IPO, all of the then outstanding shares of convertible preferred stock were automatically converted into shares of common stock and its related carrying amount of $295.1 million was reclassified to common stock and additional paid-in-capital.

Summary of Significant Accoun_8

Summary of Significant Accounting Policies - Potentially Dilutive Securities Not Included in the Diluted Net Loss Per Share Calculations (Details) - shares	6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Potentially dilutive securities not included in calculations of diluted per share	10,946,296	11,823,324
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	10,478,682	11,417,124
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	467,614	406,200

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	Jun. 30, 2020	Dec. 31, 2019
Schedule Of Available For Sale Securities [Line Items]
Amortized Cost	$ 309,667	$ 343,861
Gross Unrealized Gain	137	39
Gross Unrealized Loss		(14)
Fair Value	309,804	343,886
Money Market Funds
Schedule Of Available For Sale Securities [Line Items]
Amortized Cost	247,026	244,973
Fair Value	247,026	244,973
Corporate and Agency Bonds
Schedule Of Available For Sale Securities [Line Items]
Amortized Cost	34,089	66,063
Gross Unrealized Gain	137	28
Gross Unrealized Loss		(14)
Fair Value	34,226	66,077
Commercial Paper
Schedule Of Available For Sale Securities [Line Items]
Amortized Cost	28,552	24,840
Fair Value	28,552	24,840
U.S. Government Agencies Securities
Schedule Of Available For Sale Securities [Line Items]
Amortized Cost		7,985
Gross Unrealized Gain		11
Fair Value		7,996
Cash and Cash Equivalents
Schedule Of Available For Sale Securities [Line Items]
Fair Value	247,026	244,973
Short-term Marketable Securities
Schedule Of Available For Sale Securities [Line Items]
Amortized Cost	62,641	98,888
Fair Value	$ 62,778	$ 98,913

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	Jun. 30, 2020	Dec. 31, 2019
Schedule Of Available For Sale Securities [Line Items]
Amortized Cost	$ 309,667	$ 343,861
Short-term Marketable Securities
Schedule Of Available For Sale Securities [Line Items]
Amortized Cost	$ 62,641	$ 98,888

Fair Value Measurements - Addit

Fair Value Measurements - Additional Information (Details)	Jun. 30, 2020USD ($)Security	Dec. 31, 2019USD ($)Security
Fair Value Disclosures [Abstract]
Cash on deposit with banks	$ 2,300,000	$ 600,000
Number of marketable securities in unrealized loss positions less than 12 months | Security	0	4
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

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	Jun. 30, 2020	Dec. 31, 2019
Assets:
Assets fair value	$ 309,804	$ 343,886
Level 1
Assets:
Assets fair value	247,026	244,973
Level 2
Assets:
Assets fair value	62,778	98,913
Money Market Funds
Assets:
Assets fair value	247,026	244,973
Money Market Funds | Level 1
Assets:
Assets fair value	247,026	244,973
Corporate and Agency Bonds
Assets:
Assets fair value	34,226	66,077
Corporate and Agency Bonds | Level 2
Assets:
Assets fair value	34,226	66,077
Commercial Paper
Assets:
Assets fair value	28,552	24,840
Commercial Paper | Level 2
Assets:
Assets fair value	$ 28,552	24,840
U.S. Government Agencies Securities
Assets:
Assets fair value		7,996
U.S. Government Agencies Securities | Level 2
Assets:
Assets fair value		$ 7,996

Balance Sheet Components - Sche

Balance Sheet Components - Schedule of Reconciliation of Cash, Cash Equivalent and Restricted Cash (Details) - USD ($) $ in Thousands	Jun. 30, 2020	Dec. 31, 2019	Jun. 30, 2019	Dec. 31, 2018
Statement Of Financial Position [Abstract]
Cash and cash equivalents	$ 249,317	$ 245,598
Restricted cash	1,874	1,874
Total cash, cash equivalents and restricted cash	$ 251,191	$ 247,472	$ 267,321	$ 59,172

Balance Sheet Components - Sc_2

Balance Sheet Components - Schedule of Property and Equipment (Details) - USD ($) $ in Thousands	Jun. 30, 2020	Dec. 31, 2019
Property Plant And Equipment [Line Items]
Property and equipment, gross	$ 50,458	$ 49,231
Less: accumulated depreciation and amortization	(33,137)	(29,756)
Total property and equipment, net	17,321	19,475
Computer Equipment
Property Plant And Equipment [Line Items]
Property and equipment, gross	1,201	1,201
Laboratory Equipment and Office Furniture
Property Plant And Equipment [Line Items]
Property and equipment, gross	22,889	21,652
Leasehold Improvement
Property Plant And Equipment [Line Items]
Property and equipment, gross	25,880	25,880
Construction In Process
Property Plant And Equipment [Line Items]
Property and equipment, gross	$ 488	$ 498

Balance Sheet Components - Addi

Balance Sheet Components - Additional Information (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Statement Of Financial Position [Abstract]
Depreciation expense	$ 1,700	$ 1,900	$ 3,381	$ 3,896

Balance Sheet Components - Sc_3

Balance Sheet Components - Schedule of Accrued Liabilities (Details) - USD ($) $ in Thousands	Jun. 30, 2020	Dec. 31, 2019
Statement Of Financial Position [Abstract]
Accrued expenses	$ 2,813	$ 2,901
Clinical trials and research and development costs	12,305	11,051
Personnel-related costs	4,986	6,446
Manufacturing costs	6,688	2,593
Total accrued liabilities	$ 26,792	$ 22,991

Research Collaboration and Li_3

Research Collaboration and License Agreements - Additional Information (Details)	1 Months Ended	3 Months Ended			6 Months Ended		65 Months Ended
	Feb. 28, 2015USD ($)$ / sharesshares	Jun. 30, 2020USD ($)Option$ / shares	Mar. 31, 2020USD ($)	Jun. 30, 2019USD ($)	Jun. 30, 2020USD ($)Option$ / sharesshares	Jun. 30, 2019USD ($)	Jun. 30, 2020USD ($)Option$ / shares	Dec. 31, 2019USD ($)	Nov. 29, 2018USD ($)	Apr. 30, 2015USD ($)
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Deferred revenue recognized					$ 4,872,000
Collaboration and license revenue		$ 19,755,000		$ 25,341,000	44,119,000	$ 50,893,000
Contract assets		$ 0			$ 0		$ 0	$ 0
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 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 extension 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 agreed to make additional payments totaling up to $20.0 million in support of the Company’s research and development program activities under the collaboration 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
Research collaboration and license agreements extension fee					$ 20,000,000
Research and development services additional option extend term					2 years
License fee									$ 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
Performance of R&D services period					5 years
Number of options to extend performance of research program | Option		2			2		2
Initial term					5 years
Upfront Fee					$ 94,000,000
Collaborative agreement milestone or other forms of consideration					0
Deferred revenue recognized			$ 4,900,000
Collaboration and license revenue							$ 388,100,000
Related party revenue		$ 19,755,000		25,341,000	44,119,000	50,893,000
Upfront license fee		0		$ 5,700,000	$ 4,900,000	$ 11,400,000
Collaboration Agreement | Merck Sharp & Dohme Corp | ASC 606
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Performance of R&D services period					2 years
Collaboration and license revenue					$ 19,300,000
Transaction price for the two-year performance obligation		170,000,000			170,000,000		170,000,000
Collaborative arrangement additional funding to be made, amount		$ 20,000,000			20,000,000		$ 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
Collaboration Agreement | Merck Sharp & Dohme Corp | Maximum | ASC 606
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Collaborative arrangement funding, amount					$ 75,000,000
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]
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	6 Months Ended
	Jun. 30, 2020USD ($)
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Milestone payments in connection with potential achievement of certain regulatory events	$ 371,250
United States
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Milestone payments in connection with potential achievement of certain regulatory events	168,750
European Union
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Milestone payments in connection with potential achievement of certain regulatory events	135,000
Japan
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Milestone payments in connection with potential achievement of certain regulatory events	67,500
First Indication
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Milestone payments in connection with potential achievement of certain regulatory events	165,000
First Indication | United States
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Milestone payments in connection with potential achievement of certain regulatory events	75,000
First Indication | European Union
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Milestone payments in connection with potential achievement of certain regulatory events	60,000
First Indication | Japan
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Milestone payments in connection with potential achievement of certain regulatory events	30,000
Second Indication
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Milestone payments in connection with potential achievement of certain regulatory events	123,750
Second Indication | United States
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Milestone payments in connection with potential achievement of certain regulatory events	56,250
Second Indication | European Union
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Milestone payments in connection with potential achievement of certain regulatory events	45,000
Second Indication | Japan
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Milestone payments in connection with potential achievement of certain regulatory events	22,500
Third Indication
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Milestone payments in connection with potential achievement of certain regulatory events	82,500
Third Indication | United States
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Milestone payments in connection with potential achievement of certain regulatory events	37,500
Third Indication | European Union
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Milestone payments in connection with potential achievement of certain regulatory events	30,000
Third Indication | Japan
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	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Collaboration Agreement | Merck Sharp & Dohme Corp
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Related party revenue	$ 19,755	$ 25,341	$ 44,119	$ 50,893

Research Collaboration and Li_6

Research Collaboration and License Agreements - Schedule of Changes in Related Party Contract Liabilities (Details) $ in Thousands	6 Months Ended
	Jun. 30, 2020USD ($)
Research Collaboration And License Agreements [Abstract]
Beginning Balance	$ 4,872
Revenue recognized through March 16, 2020	(4,872)
Increases as a result of research and development expenses to be earned under the Collaboration Agreement	2,074
Ending Balance	$ 2,074

Commitments and Contingencies -

Commitments and Contingencies - Additional Information (Details) $ in Thousands	1 Months Ended		3 Months Ended		6 Months Ended
	Dec. 31, 2015USD ($)ft²	Sep. 30, 2009USD ($)ft²	Jun. 30, 2020USD ($)	Jun. 30, 2019USD ($)	Jun. 30, 2020USD ($)	Jun. 30, 2019USD ($)	Dec. 31, 2019USD ($)	Sep. 30, 2019USD ($)
Commitments And Contingencies Disclosure [Line Items]
Total Leasehold improvements			$ 17,321		$ 17,321		$ 19,475
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			$ 500	$ 500	1,100	$ 1,100
Corporate Office Space and Laboratory Facility | Merck Sharp & Dohme Corp
Commitments And Contingencies Disclosure [Line Items]
Remaining lease payment obligation					$ 900	$ 2,900
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 3rd anniversary and 4th 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	Jun. 30, 2020USD ($)
Commitments And Contingencies Disclosure [Abstract]
2020	$ 2,534
2021	5,141
2022	5,294
2023	5,455
Total	$ 18,424

Stockholders' Equity - Addition

Stockholders' Equity - Additional Information (Details)	3 Months Ended		6 Months Ended
	Jun. 30, 2020USD ($)shares	Jun. 30, 2019USD ($)	Jun. 30, 2020USD ($)Period$ / sharesshares	Jun. 30, 2019USD ($)$ / sharesshares	Dec. 31, 2019shares
Class Of Stock [Line Items]
Preferred stock, shares authorized	10,000,000		10,000,000		10,000,000
Preferred stock, shares issued	0		0		0
Preferred stock, shares outstanding	0		0		0
Common stock, shares outstanding	68,739,866		68,739,866		66,960,279
Stock repurchase plan, authorized shares	37,467		37,467		74,454
Weighted-average grant date fair value of stock options ,Granted | $ / shares			$ 10.05	$ 7.82
Intrinsic value of stock options exercised | $			$ 24,600,000	$ 1,700,000
Tax benefits realized | $	$ 0	$ 0	$ 0	0
Common stock, shares issued	68,739,866		68,739,866		66,960,279
ESPP
Class Of Stock [Line Items]
Maximum percentage of payroll deductions of employee's compensation	15.00%		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, shares issued	211,880		211,880
Non-employees
Class Of Stock [Line Items]
Stock-based compensation expense | $	$ 35,000	$ 39,000	$ 63,000	$ 70,000
Options granted			67,500	22,500
2018 Plan | Minimum
Class Of Stock [Line Items]
Stock options, vesting period			4 years
2018 Plan | Maximum
Class Of Stock [Line Items]
Stock options, vesting period			10 years

Stockholders' Equity - Schedule

Stockholders' Equity - Schedule of Shares of Common Stock Reserved for Issuance (Details) - shares	Jun. 30, 2020	Dec. 31, 2019
Class Of Stock [Line Items]
Total	17,965,999	17,066,375
Common Stock Options Outstanding
Class Of Stock [Line Items]
Total	10,478,682	10,824,780
Common Stock Options Available for Grant
Class Of Stock [Line Items]
Total	6,677,267	5,316,066
401(k) Matching Plan
Class Of Stock [Line Items]
Total	21,930	28,274
Shares Committed Under ESPP
Class Of Stock [Line Items]
Total	788,120	897,255

Stockholders' Equity - Summary

Stockholders' Equity - Summary of Activity under 2008 Plan and 2018 Plan (Details) - 2008 Plan and 2018 Plan $ / shares in Units, $ in Thousands	6 Months Ended	12 Months Ended
	Jun. 30, 2020USD ($)$ / sharesshares	Dec. 31, 2019USD ($)$ / sharesshares
Class Of Stock [Line Items]
Outstanding Options, Options Available for Grant, Beginning balance	5,316,066
Outstanding Options, Options Available for Grant, Additional Shares	2,678,411
Outstanding Options, Options Available for Grant, Granted	(1,869,701)
Outstanding Options, Options Available for Grant, Cancelled	552,491
Outstanding Options, Options Available for Grant, Ending balance	6,677,267	5,316,066
Outstanding Options, Number of Options, Beginning balance	10,824,780
Outstanding Options, Number of Options, Granted	1,869,701
Outstanding Options, Number of Options, Exercised	(1,663,308)
Outstanding Options, Number of Options, Cancelled	(552,491)
Outstanding Options, Number of Options, Ending balance	10,478,682	10,824,780
Outstanding Options, Number of Options, Options vested and expected to vest	10,360,681
Outstanding Options, Number of Options, Options exercisable	10,478,682
Outstanding Options, Weighted-Average Exercise Price, Beginning balance | $ / shares	$ 7.52
Outstanding Options, Weighted-Average Exercise Price, Granted | $ / shares	17.08
Outstanding Options, Weighted-Average Exercise Price, Exercised | $ / shares	3.58
Outstanding Options, Weighted-Average Exercise Price, Cancelled | $ / shares	12.19
Outstanding Options, Weighted-Average Exercise Price, Ending balance | $ / shares	9.60	$ 7.52
Outstanding Options, Weighted-Average Exercise Price, Options vested and expected to vest | $ / shares	9.55
Outstanding Options, Weighted-Average Exercise Price, Options exercisable | $ / shares	$ 9.60
Weighted Average Remaining Contractual Life (in Years)	6 years 7 months 2 days	6 years 3 months 14 days
Weighted Average Remaining Contractual Life (in Years), Vested and expected to vest	6 years 6 months 21 days
Weighted Average Remaining Contractual Life (in Years),Outstanding and Exercisable	6 years 7 months 2 days
Outstanding Options, Aggregate Intrinsic Value, Balance | $	$ 106,375	$ 118,770
Outstanding Options, Aggregate Intrinsic Value, Options vested and expected to vest-March 31, 2019 | $	105,769
Options Outstanding, Aggregate Intrinsic Value, Options exercisable-March 31, 2019 | $	$ 106,375

Stockholders' Equity - Summar_2

Stockholders' Equity - Summary of Stock Based Compensation Expense (Details) - Employees and Directors - ESPP - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Stock-based compensation expense	$ 3,688	$ 3,513	$ 7,355	$ 6,087
Research and Development
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Stock-based compensation expense	2,049	2,053	3,922	3,463
General and Administrative
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Stock-based compensation expense	$ 1,639	$ 1,460	$ 3,433	$ 2,624

Income Taxes - Additional Infor

Income Taxes - Additional Information (Details)	Mar. 27, 2020
Income Tax Disclosure [Abstract]
CARES Act of 2020 aid net operating loss carry forward period	5 years
CARES Act of 2020 aid net operating losses carryforward maximum percentage of taxable income	80.00%