Arcus Biosciences (RCUS) 10-Q 8 Nov 21 2021 Q3 Quarterly report Financial data

Document and Entity Information

Document and Entity Information - shares	9 Months Ended
	Sep. 30, 2021	Oct. 29, 2021
Cover [Abstract]
Document Type	10-Q
Amendment Flag	false
Document Period End Date	Sep. 30, 2021
Document Fiscal Year Focus	2021
Document Fiscal Period Focus	Q3
Trading Symbol	RCUS
Entity Registrant Name	Arcus Biosciences, Inc.
Entity Central Index Key	0001724521
Current Fiscal Year End Date	--12-31
Entity Filer Category	Large Accelerated Filer
Entity Small Business	false
Entity Emerging Growth Company	false
Entity Current Reporting Status	Yes
Entity Shell Company	false
Entity File Number	001-38419
Entity Tax Identification Number	47-3898435
Entity Address, Address Line One	3928 Point Eden Way
Entity Address, City or Town	Hayward
Entity Address, State or Province	CA
Entity Address, Postal Zip Code	94545
City Area Code	510
Local Phone Number	694-6200
Entity Common Stock, Shares Outstanding		70,249,475
Entity Interactive Data Current	Yes
Title of 12(b) Security	Common Stock, Par Value $0.0001 Per Share
Security Exchange Name	NYSE
Entity Incorporation, State or Country Code	DE
Document Quarterly Report	true
Document Transition Report	false

Condensed Consolidated Balance

Condensed Consolidated Balance Sheets - USD ($) $ in Thousands	Sep. 30, 2021	Dec. 31, 2020
Current assets:
Cash and cash equivalents	$ 179,432	$ 173,415
Short-term investments	345,210	555,231
Receivable from collaboration partners ($617 and $943 from a related party)	871	1,049
Accrued interest receivable	2,201	649
Prepaid expenses and other current assets	17,574	5,471
Total current assets	545,288	735,815
Long-term investments	218,730	6,440
Property and equipment, net	28,818	10,807
Right-of-use assets	35,553	12,781
Restricted cash	3,005	203
Other long-term assets	7,896	6,246
Total assets	839,290	772,292
Current liabilities:
Accounts payable	13,219	15,682
Accrued research and development	40,470	18,307
Other accrued liabilities	14,625	9,543
Deferred revenue, current ($67,571 and $67,571 to a related party)	74,343	74,571
Other current liabilities	209	3,566
Total current liabilities	142,866	121,669
Deferred revenue, noncurrent ($94,675 and $117,808 to a related party)	94,675	122,830
Operating lease liabilities, noncurrent	48,943	15,243
Other long-term liabilities ($9,703 and $9,703 to a related party)	10,199	10,246
Total liabilities	296,683	269,988
Commitments (Note 11)
Stockholders’ equity:
Preferred stock, $0.0001 par value, 10,000,000 shares authorized as of September 30, 2021 and December 31, 2020; no shares issued and outstanding as of September 30, 2021 and December 31, 2020	0	0
Common stock, $0.0001 par value, 400,000,000 shares authorized as of September 30, 2021 and December 31, 2020; 70,241,590 and 65,114,685 shares issued and outstanding as of September 30, 2021 and December 31, 2020, respectively. Shares outstanding includes 39,142 and 1,422,784 shares issued but subject to vesting as of September 30, 2021 and December 31, 2020, respectively	7	6
Additional paid-in capital	1,097,414	830,438
Accumulated deficit	(554,722)	(328,184)
Accumulated other comprehensive (loss) income	(92)	44
Total stockholders’ equity	542,607	502,304
Total liabilities and stockholders’ equity	$ 839,290	$ 772,292

Condensed Consolidated Balanc_2

Condensed Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Thousands	Sep. 30, 2021	Dec. 31, 2020
Statement Of Financial Position [Abstract]
Related party, receivable from collaboration partners	$ 617	$ 943
Related party, deferred revenue - current	67,571	67,571
Related party, deferred revenue - noncurrent	94,675	117,808
Related party, other long-term liabilities	$ 9,703	$ 9,703
Preferred stock, par value	$ 0.0001	$ 0.0001
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	$ 0.0001	$ 0.0001
Common stock, shares authorized	400,000,000	400,000,000
Common stock, shares issued	70,241,590	65,114,685
Common stock, shares outstanding	70,241,590	65,114,685
Common stock, shares outstanding includes shares issued but subject to vesting	39,142	1,422,784

Condensed Consolidated Statemen

Condensed Consolidated Statements of Operations and Comprehensive Income (Loss) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Revenues:
Total revenues	$ 9,461	$ 64,530	$ 28,383	$ 68,030
Operating expenses:
Research and development (($756), ($2,971), ($6,856) and ($2,971) from a related party)	71,254	51,801	206,412	110,636
General and administrative	16,343	11,177	48,990	29,617
Total operating expenses	87,597	62,978	255,402	140,253
Income (loss) from operations	(78,136)	1,552	(227,019)	(72,223)
Non-operating income (expense):
Interest and other income, net	161	270	481	1,218
Gain on deemed sale from equity method investee				613
Share of loss from equity method investee				(613)
Total non-operating income, net	161	270	481	1,218
Net income (loss)	(77,975)	1,822	(226,538)	(71,005)
Other comprehensive income (loss)	(46)	(63)	(136)	17
Comprehensive income (loss)	$ (78,021)	$ 1,759	$ (226,674)	$ (70,988)
Net income (loss) per share, basic	$ (1.11)	$ 0.03	$ (3.28)	$ (1.37)
Weighted-average number of shares used to compute basic net income (loss) per share	70,110,138	62,599,193	68,990,290	51,852,247
Net income (loss) per share, diluted	$ (1.11)	$ 0.03	$ (3.28)	$ (1.37)
Weighted-average number of shares used to compute diluted net income (loss) per share	70,110,138	65,145,707	68,990,290	51,852,247
License Revenue
Revenues:
Total revenues		$ 55,096		$ 55,096
Collaboration Revenue
Revenues:
Total revenues	$ 9,461	$ 9,434	$ 28,383	$ 12,934

Condensed Consolidated Statem_2

Condensed Consolidated Statements of Operations and Comprehensive Income (Loss) (Parenthetical) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
License Revenue
Revenue from related parties	$ 0	$ 55,096	$ 0	$ 55,096
Collaboration Revenue
Revenue from related parties	7,711	7,684	23,133	7,684
Research and Development
Reimbursement from related party for shared costs	$ (756)	$ (2,971)	$ (6,856)	$ (2,971)

Condensed Consolidated Statem_3

Condensed Consolidated Statements of Stockholders' Equity - USD ($) $ in Thousands	Total	Purchase AgreementGilead	Common Stock	Common StockPurchase AgreementGilead	Additional Paid-In Capital	Additional Paid-In CapitalPurchase AgreementGilead	Accumulated Deficit	Accumulated Other Comprehensive Income (Loss)
Balance at Dec. 31, 2019	$ 163,842		$ 4		$ 369,100		$ (205,326)	$ 64
Balance, shares at Dec. 31, 2019			44,212,195
Issuance of common stock upon exercise of stock options	643				643
Issuance of common stock upon exercise of stock options, shares			59,939
Vesting of early exercised stock options	220				220
Vesting of early exercised stock options, shares			77,388
Stock-based compensation	3,462				3,462
Other comprehensive income (loss)	224							224
Net Income Loss	(27,753)						(27,753)
Balance at Mar. 31, 2020	140,638		$ 4		373,425		(233,079)	288
Balance, shares at Mar. 31, 2020			44,349,522
Balance at Dec. 31, 2019	163,842		$ 4		369,100		(205,326)	64
Balance, shares at Dec. 31, 2019			44,212,195
Net Income Loss	(71,005)
Balance at Sep. 30, 2020	544,417		$ 6		820,661		(276,331)	81
Balance, shares at Sep. 30, 2020			63,425,445
Balance at Mar. 31, 2020	140,638		$ 4		373,425		(233,079)	288
Balance, shares at Mar. 31, 2020			44,349,522
Issuance of common stock	326,246		$ 2		326,244
Issuance of common stock, shares			12,650,000
Issuance of common stock upon exercise of stock options	1,751				1,751
Issuance of common stock upon exercise of stock options, shares			216,286
Vesting of early exercised stock options	216				216
Vesting of early exercised stock options, shares			64,501
Issuance of common stock under Employee Stock Purchase Plan	607				607
Issuance of common stock under Employee Stock Purchase Plan, shares			91,859
Stock-based compensation	4,470				4,470
Other comprehensive income (loss)	(144)							(144)
Net Income Loss	(45,074)						(45,074)
Balance at Jun. 30, 2020	428,710		$ 6		706,713		(278,153)	144
Balance, shares at Jun. 30, 2020			57,372,168
Issuance of common stock		$ 107,468				$ 107,468
Issuance of common stock, shares				5,963,029
Issuance of common stock upon exercise of stock options	270				270
Issuance of common stock upon exercise of stock options, shares			30,039
Vesting of early exercised stock options	208				208
Vesting of early exercised stock options, shares			60,209
Stock-based compensation	6,002				6,002
Other comprehensive income (loss)	(63)							(63)
Net Income Loss	1,822						1,822
Balance at Sep. 30, 2020	544,417		$ 6		820,661		(276,331)	81
Balance, shares at Sep. 30, 2020			63,425,445
Balance at Dec. 31, 2020	$ 502,304		$ 6		830,438		(328,184)	44
Balance, shares at Dec. 31, 2020	65,114,685		63,691,901
Issuance of common stock		$ 220,296		$ 1		$ 220,295
Issuance of common stock, shares				5,650,000
Issuance of common stock upon exercise of stock options and vesting of restricted stock	$ 1,885				1,885
Issuance of common stock upon exercise of stock options and vesting of restricted stock, shares			200,828
Vesting of early exercised stock options	183				183
Vesting of early exercised stock options, shares			54,039
Stock-based compensation	12,761				12,761
Other comprehensive income (loss)	(46)							(46)
Net Income Loss	(72,593)						(72,593)
Balance at Mar. 31, 2021	664,790		$ 7		1,065,562		(400,777)	(2)
Balance, shares at Mar. 31, 2021			69,596,768
Balance at Dec. 31, 2020	$ 502,304		$ 6		830,438		(328,184)	44
Balance, shares at Dec. 31, 2020	65,114,685		63,691,901
Net Income Loss	$ (226,538)
Balance at Sep. 30, 2021	$ 542,607		$ 7		1,097,414		(554,722)	(92)
Balance, shares at Sep. 30, 2021	70,241,590		70,202,448
Balance at Mar. 31, 2021	$ 664,790		$ 7		1,065,562		(400,777)	(2)
Balance, shares at Mar. 31, 2021			69,596,768
Issuance of common stock upon exercise of stock options and vesting of restricted stock	843				843
Issuance of common stock upon exercise of stock options and vesting of restricted stock, shares			269,369
Vesting of early exercised stock options	175				175
Vesting of early exercised stock options, shares			36,245
Issuance of common stock under Employee Stock Purchase Plan	1,394				1,394
Issuance of common stock under Employee Stock Purchase Plan, shares			140,408
Stock-based compensation	13,367				13,367
Other comprehensive income (loss)	(44)							(44)
Net Income Loss	(75,970)						(75,970)
Balance at Jun. 30, 2021	604,555		$ 7		1,081,341		(476,747)	(46)
Balance, shares at Jun. 30, 2021			70,042,790
Issuance of common stock upon exercise of stock options and vesting of restricted stock	1,318				1,318
Issuance of common stock upon exercise of stock options and vesting of restricted stock, shares			125,182
Vesting of early exercised stock options	170				170
Vesting of early exercised stock options, shares			34,476
Stock-based compensation	14,585				14,585
Other comprehensive income (loss)	(46)							(46)
Net Income Loss	(77,975)						(77,975)
Balance at Sep. 30, 2021	$ 542,607		$ 7		$ 1,097,414		$ (554,722)	$ (92)
Balance, shares at Sep. 30, 2021	70,241,590		70,202,448

Condensed Consolidated Statem_4

Condensed Consolidated Statements of Stockholders' Equity (Parenthetical) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2021	Sep. 30, 2020	Jun. 30, 2020
Offering costs			$ 21,629
Issuance of common stock			$ 326,246
Purchase Agreement | Gilead
Offering costs	$ 55	$ 1,931
Issuance of common stock	$ 220,296	$ 107,468
Public Offering | Related Party Participation
Issuance of common stock, shares			2,200,000
Issuance of common stock			$ 56,738
Offering cost from related party			$ 3,762

Condensed Consolidated Statem_5

Condensed Consolidated Statements of Cash Flows - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020
Cash flow from operating activities
Net loss	$ (226,538)	$ (71,005)
Adjustments to reconcile net loss to net cash used in operating activities:
Stock-based compensation expense	40,713	13,934
Depreciation and amortization	2,583	2,371
Amortization of right-of-use assets	1,701	552
Amortization of premiums on investments	2,804	(333)
Changes in operating assets and liabilities:
Receivable from collaboration partners ($326 and ($2,504) from a related party)	178	(2,447)
Prepaid expenses and other current assets	(5,290)	(6,906)
Other long-term assets	750	(1,373)
Accounts payable	(5,424)	3,165
Accrued research and development	19,163	23,665
Other accrued liabilities	5,082	2,485
Other current liabilities ($0 and $1,869 to a related party)		1,869
Deferred revenue (($23,133) and $193,140 to a related party)	(28,383)	187,890
Operating lease liabilities	(1,405)	(790)
Other long-term liabilities ($0 and $7,344 to a related party)	(2)	7,973
Net cash used in operating activities	(194,068)	161,050
Cash flow from investing activities
Purchases of short-term and long-term investments	(584,850)	(568,903)
Proceeds from maturities of short-term and long-term investments	572,140	135,300
Sales of short-term and long-term investments	7,500	1,003
Purchases of property and equipment	(17,572)	(1,536)
Net cash used in investing activities	(22,782)	(434,136)
Cash flow from financing activities
Proceeds from issuance of common stock ($220,235 and $164,207 from a related party)	220,235	433,776
Proceeds from issuance of common stock pursuant to equity award plans	5,440	3,271
Repurchase of unvested shares of stock	(6)	(49)
Net cash provided by financing activities	225,669	436,998
Net increase in cash and cash equivalents	8,819	163,912
Cash, cash equivalents and restricted cash at beginning of period	173,618	58,140
Cash, cash equivalents and restricted cash at end of period	182,437	222,052
Supplemental disclosures:
Cash paid for amounts included in measurement of lease liabilities	3,074	1,572
Cash received from tenant improvement allowances	792
Non-cash investing and financing activities:
Right-of-use assets obtained in exchange for new operating lease liabilities	24,473	13,004
Recognition of tenant improvement allowance receivable included in other current assets	10,598	979
Unpaid portion of property and equipment purchases included in accounts payable and accrued liabilities	4,605	245
Unpaid portion of other assets included in accrued research and development	3,000	0
Vesting of early exercised stock options and restricted stock	$ 529	643
Unpaid portion of financing costs included in accrued liabilities		$ 61

Condensed Consolidated Statem_6

Condensed Consolidated Statements of Cash Flows (Parenthetical) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020
Statement Of Cash Flows [Abstract]
Receivable from related party	$ 326	$ (2,504)
Other current liabilities to related party	0	1,869
Deferred revenue from related party	(23,133)	193,140
Other long-term liabilities to related party	0	7,344
Proceeds from issuance of common stock from a related party	$ 220,235	$ 164,207

Organization

Organization	9 Months Ended
	Sep. 30, 2021
Organization Consolidation And Presentation Of Financial Statements [Abstract]
Organization	Note 1. Organization Description of Business Arcus Biosciences, Inc. (the Company) is a clinical-stage biopharmaceutical company focused on creating best-in-class cancer therapies. The Company’s initial focus has been on well-characterized biological pathways with significant scientific data supporting their importance. Since its inception in 2015, the Company has built a robust and highly efficient drug discovery capability to create highly differentiated small molecules, which the Company is developing in combination with its in-licensed monoclonal antibodies through rationally designed, indication-specific clinical trial designs. The Company currently has six investigational products in clinical development: domvanalimab (formerly referred to as AB154), etrumadenant (formerly referred to as AB928), quemliclustat (formerly referred to as AB680), zimberelimab (formerly referred to as AB122), AB308 and AB521. Liquidity and Capital Resources As of September 30, 2021, the Company had cash and investments of $ 743.4 m illion, which are cash, cash equivalents, and investments in marketable securities, which the Company believes will be sufficient to fund its planned operations for a period of at least twelve months following the date of filing of this report.

Significant Accounting Policies

Significant Accounting Policies	9 Months Ended
	Sep. 30, 2021
Accounting Policies [Abstract]
Significant Accounting Policies	Note 2. Significant Accounting Policies Basis of Presentation The accompanying unaudited condensed consolidated financial statements have been prepared in accordance with U.S. generally accepted accounting principles (U.S. GAAP) for interim financial information and pursuant to Form 10-Q and Article 10 of Regulation S-X of the Securities and Exchange Commission (SEC). Accordingly, they do not include all of the information and footnotes required by U.S. GAAP for complete financial statements. In the Company’s opinion, all adjustments (consisting only of normal recurring adjustments) considered necessary for a fair presentation of the results of operations and cash flows for the periods presented have been included. Operating results for the nine months ended September 30, 2021 are not necessarily indicative of the results that may be expected for the year ending December 31, 2021 or for any future period. The balance sheet as of December 31, 2020 has been derived from audited consolidated financial statements at that date but does not include all of the information required by U.S. GAAP for complete financial statements. The accompanying unaudited condensed consolidated financial statements and related financial information should be read in conjunction with the audited consolidated financial statements and the related notes thereto for the year ended December 31, 2020 included in the Company’s Annual Report on Form 10-K filed with the SEC on February 25, 2021. There have been no significant changes to the Company’s significant accounting policies described in Note 2, Summary of Significant Accounting Policies, in Notes to Consolidated Financial Statements in Item 8 of Part II of the Form 10-K. Principles of Consolidation The accompanying consolidated financial statements include the accounts of Arcus Biosciences, Inc. and its wholly-owned subsidiaries. All intercompany balances and transactions have been eliminated in consolidation. Use of Estimates The preparation of the Company’s condensed consolidated financial statements in conformity with U.S. GAAP requires management to make estimates and assumptions that affect the reported amounts of assets, liabilities, revenues and expenses, as well as related disclosures of contingent assets and liabilities. Estimates were used to determine the standalone selling price of performance obligations and the timing of revenue recognition, the value of stock-based awards and other issuances, accruals for research and development costs, useful lives of long-lived assets, and uncertain tax positions. Actual results could differ materially from the Company’s estimates. Cash Equivalents and Investments Cash equivalents include marketable securities having an original maturity of three months or less at the time of purchase. Short-term investments have maturities of greater than three months and up to twelve months at the time of purchase. Long-term investments have maturities greater than 12 months at the time of purchase. Collectively, cash equivalents, short-term and long-term investments are considered available-for-sale and are recorded at fair value. Unrealized gains and losses are recorded in accumulated other comprehensive income (loss). Realized gains and losses are included in interest and other income, net in the condensed consolidated statements of operations and comprehensive income or loss. The basis on which the cost of a security that is sold or an amount that is reclassified out of accumulated other comprehensive income or loss into earnings is determined using the specific identification method. Reconciliation of Cash, Cash Equivalents, and Restricted Cash as Reported in Condensed Consolidated Statements of Cash Flows Restricted cash at September 30, 2021 and 2020 represents cash balances held as security in connection with the Company’s facility lease agreements. The following table provides a reconciliation of cash, cash equivalents, and restricted cash within the condensed consolidated balance sheets to the total shown in the condensed consolidated statements of cash flows (in thousands): September 30, 2021 2020 Cash and cash equivalents $ 179,432 $ 221,849 Restricted cash 3,005 203 Cash, cash equivalents and restricted cash $ 182,437 $ 222,052 Concentration of Credit Risk Cash equivalents, short-term and long-term investments are financial instruments that potentially subject the Company to concentrations of credit risk. The Company invests in money market funds, treasury bills and notes, government bonds, commercial paper and corporate notes. The Company limits its credit risk associated with cash equivalents, short-term and long-term investments by placing them with banks and institutions it believes are credit worthy and in highly rated investments. Leases and Rent Expense The Company recognizes a lease asset for its right to use the underlying asset and a lease liability for the corresponding lease obligation. The Company determines whether an arrangement is or contains a lease at contract inception. Operating leases and related tenant improvement allowances receivable are included in operating lease right-of-use assets, prepaid expenses and other current assets, and operating lease liabilities, noncurrent in our condensed consolidated balance sheets at September 30, 2021 and December 31, 2020. Operating lease right-of-use assets and liabilities are recognized at the lease commencement date based on the present value of lease payments over the lease term. In determining the net present value of lease payments, the Company uses its incremental borrowing rate based on information available at the lease commencement date. The incremental borrowing rate represents the interest rate the Company would incur at lease commencement to borrow an amount equal to the lease payments on a collateralized basis over the term of a lease. The Company considers a lease term to be the noncancelable period that it has the right to use the underlying asset, including any periods where it is reasonably assured the Company will exercise the option to extend the contract. Periods covered by an option to extend are included in the lease term if the lessor controls the exercise of that option. The Company elected to not apply the recognition requirements of the new leasing standard to short-term leases with terms of 12 months or less which do not include an option to purchase the underlying asset that the Company is reasonably certain to exercise. For short-term leases, lease payments are recognized as operating expenses on a straight-line basis over the lease term.

Fair Value Measurements

Fair Value Measurements	9 Months Ended
	Sep. 30, 2021
Fair Value Disclosures [Abstract]
Fair Value Measurements	Note 3. Fair Value Measurements Financial assets and liabilities are recorded at fair value. The accounting guidance for fair value provides a framework for measuring fair value, clarifies the definition of fair value and expands disclosures regarding fair value measurements. Fair value is defined as the price that would be received to sell an asset or paid to transfer a liability (an exit price) in an orderly transaction between market participants at the reporting date. The accounting guidance establishes a three-tiered hierarchy, which prioritizes the inputs used in the valuation methodologies in measuring fair value. 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. During the periods presented, the Company has not changed the manner in which it values assets and liabilities that are measured at fair value. The Company recognizes transfers between levels of the fair value hierarchy as of the end of the reporting period. There were no transfers within the hierarchy as of September 30, 2021 and December 31, 2020. The following tables set forth the Company’s financial instruments that were measured at fair value on a recurring basis by level within the fair value hierarchy (in thousands): September 30, 2021 Total Level 1 Level 2 Level 3 Money market funds $ 172,431 $ 172,431 $ - $ - U.S. treasury securities 109,946 - 109,946 - Corporate securities and commercial paper 460,995 - 460,995 - Total assets measured at fair value $ 743,372 $ 172,431 $ 570,941 $ - December 31, 2020 Total Level 1 Level 2 Level 3 Money market funds $ 146,468 $ 146,468 $ - $ - U.S. treasury securities 301,112 - 301,112 - U.S. government agency obligations 25,001 - 25,001 - Corporate securities and commercial paper 262,505 - 262,505 - Total assets measured at fair value $ 735,086 $ 146,468 $ 588,618 $ - Classified as (with contractual maturities): September 30, 2021 December 31, 2020 Cash and cash equivalents $ 179,432 $ 173,415 Short-term investments (due within one year) 345,210 555,231 Long-term investments (due between one and three years) 218,730 6,440 Total cash, cash equivalents and investments in marketable securities $ 743,372 $ 735,086 Investments in marketable securities are classified as available-for-sale. At September 30, 2021 and December 31, 2020, the balance in the Company’s accumulated other comprehensive income related to the Company’s available-for-sale marketable securities. There were no realized gains or losses recognized on the sale or maturity of available-for-sale marketable securities as of September 30, 2021 and December 31, 2020, and as a result, the Company did no t reclassify any amounts out of accumulated other comprehensive income for the periods then ended. The Company has not recognized any allowances for credit losses given the nature of its receivables and investment portfolio and the immaterial amount of unrealized losses on available for sale securities. No credit related losses have been recognized for any of the periods presented. The fair value and amortized cost of investments in marketable securities by major security type as of September 30, 2021 and December 31, 2020 are presented in the tables that follow (in thousands): Amortized Unrealized Unrealized Fair As of September 30, 2021: Money market funds $ 172,431 $ - $ - $ 172,431 U.S. treasury securities 109,972 9 ( 35 ) 109,946 Corporate securities and commercial paper 461,061 53 ( 119 ) 460,995 Total $ 743,464 $ 62 $ ( 154 ) $ 743,372 Amortized Unrealized Unrealized Fair As of December 31, 2020: Money market funds $ 146,468 $ - $ - $ 146,468 U.S. treasury securities 301,075 38 ( 1 ) 301,112 U.S. government agency obligations 24,997 4 - 25,001 Corporate securities and commercial paper 262,502 15 ( 12 ) 262,505 Total $ 735,042 $ 57 $ ( 13 ) $ 735,086

Other Accrued Liabilities

Other Accrued Liabilities	9 Months Ended
	Sep. 30, 2021
Payables And Accruals [Abstract]
Other Accrued Liabilities	Note 4. Other Accrued Liabilities Other a ccrued liabilities consisted of the following (in thousands): As of September 30, 2021 As of December 31, 2020 Accrued personnel expenses $ 13,499 $ 8,632 Professional fees 523 295 Other 603 616 Total $ 14,625 $ 9,543

Equity Investment in PACT Pharm

Equity Investment in PACT Pharma	9 Months Ended
	Sep. 30, 2021
Equity Method Investment [Abstract]
Equity Investment in PACT Pharma	Note 5. Equity Investment in PACT Pharma The Company owns approximately 3.6 million shares of common stock, 1.0 million shares of Series A preferred stock, and warrants to purchase additional stock of PACT Pharma, Inc. (PACT Pharma), a privately-held clinical-stage biopharmaceutical company focused on pioneering individualized, non-viral precision genome engineered, tumor-specific T cell therapies for the treatment of patients with solid tumors. This interest in PACT Pharma is accounted for as an equity method investment, and as a result the Company records its share of PACT Pharma’s operating results in interest and other income, net, in its condensed consolidated statements of operations and comprehensive loss. The investment balance was zero at September 30, 2021 and December 31, 2020 and the Company is not required to record losses beyond the carrying amount of the investment as it has no obligation to provide further cash financing to PACT Pharma. The investment had an immaterial impact on the condensed consolidated statements of operations and comprehensive loss, as well as the statement of cash flows, for each of the three and nine months ended September 30, 2021 and 2020. At September 30, 2021 and December 31, 2020, the Company determined the fair value of the warrants to be insignificant to the condensed consolidated financial statements.

Leases

Leases	9 Months Ended
	Sep. 30, 2021
Leases [Abstract]
Leases	Note 6. Leases In April 2021, the Company amended the non-cancelable operating lease for its corporate headquarters, which includes approximately 136,293 square feet of executive offices and research and development and business operations, in an office park in Hayward, California. The amended lease added 14,460 square feet of additional space in a new lease expected to commence in 2022 , and extended the term of the existing leases through at least December 31, 2031 . Once the lease of additional space commences, the Company’s leased space in Hayward will total 150,753 square feet. Any extension periods defined under previous amendments were cancelled under the lease amendment and replaced by two options to extend the lease term for the entire 150,753 square feet then under lease in the Hayward premises for a period of eight years each. The Company also leases space in Brisbane, California under a non-cancelable operating lease that is expected to commence in the fourth quarter of 2021 and extend through December 31, 2031 . At September 30, 2021 the Company’s lease portfolio had a weighted average remaining term of 10.3 years. T he leases require monthly lease payments that are subject to annual increases throughout the lease term. The optional extension periods have not been considered in the determination of the right-of-use assets or lease liabilities associated with this lease as the Company did not consider it reasonably certain it would exercise the option. The weighted average discount rate for the Company’s lease portfolio at September 30, 2021 was 5.2 % . Lease expense is included in operating expenses in the condensed consolidated statements o f operations and comprehensive loss. For the three and nine months ended September 30, 2021, the Company incurred lease expense of $ 1.5 million and $ 4.1 million, respectively, in relation to its operating leases. For the same periods in the prior year, the Company incurred lease expense of $ 0.7 million and $ 1.8 million, respectively. Lease costs include variable rent expense, which consists primarily of the Company’s proportionate share of operating expenses, property taxes, and insurance and is classified as lease expense due to the Company’s election to not separate lease and non-lease components. Short-term lease costs were zero and $ 0.3 mil lion for the three and nine months ended September 30, 2021, respectively. The Company incurred zero and $ 0.1 million in short-term lease costs for the same periods in the prior year. At September 30, 2021, the Company’s operating lease right-of-use asset totaled $ 35.6 million, and the operating lease liability totaled $ 51.7 million. The difference between the amount of the right-of-use asset and the lease liabilities relates to the incentives the Company received upon signing the original leases and its most recent amendment, of which approximately $ 10.8 million is expected to be received within one year of September 30, 2021 and is recorded in prepaid expenses and other current assets, net of the $ 2.8 million short-term portion of the operating lease liability. The long term portion of the lease liability was $ 48.9 million at September 30, 2021 and is reported on the balance sheet as operating lease liability, noncurrent. As of September 30, 2021, the Company’s future minimum lease payments were as follows (in thousands): Operating Year Ending December 31, Leases 2021 (from October to December) $ 1,159 2022 5,722 2023 5,908 2024 6,101 2025 6,302 Thereafter 42,489 Total undiscounted future minimum lease payments 67,681 Less: Imputed interest ( 15,905 ) Less: Tenant improvement allowance receivable ( 10,785 ) Total operating lease liabilities 40,991 Tenant improvement allowance expected to be received in 7,952 Operating lease liabilities, noncurrent $ 48,943 Total undiscounted future minimum lease payments do not include approxi mately $ 90.3 million and $ 5.3 million, respectively, related to the Company’s Brisbane lease and its additional space in Hayward, neither of which have yet commenced. The Brisbane lease is expected to commence during the fourth quarter of 2021 and the additional Hayward lease is expected to commence in 2022 , both with terms through at least December 31, 2031 . The Company has provided deposits for letters of credit totaling $ 3.0 million to secure its obligations under its leases, which have been classified as restricted cash on the Company’s condensed consolidated balance sheet as of September 30, 2021.

License and Collaboration Agree

License and Collaboration Agreements	9 Months Ended
	Sep. 30, 2021
License And Collaboration Agreements [Abstract]
License and Collaboration Agreements	Note 7. License and Collaboration Agreements The following table summarizes the revenues for the three and nine months ended September 30, 2021 and 2020 received as a result of the Company’s collaboration agreements with Gilead Sciences, Inc. (Gilead) and Taiho Pharmaceutical Co., Ltd. (Taiho): Three Months Ended September 30, Nine Months Ended September 30, 2021 2020 2021 2020 License revenue $ - $ 55,096 $ - $ 55,096 Collaboration revenue 9,461 9,434 28,383 12,934 Total revenues $ 9,461 $ 64,530 $ 28,383 $ 68,030 The following table summarizes details of revenues for the three and nine months ended September 30, 2021 and 2020 by collaboration and by category of revenue: Three Months Ended September 30, Nine Months Ended September 30, Revenues recognized: Over time Point in time 2021 2020 2021 2020 Gilead license to zimberelimab * $ - $ 55,096 $ - $ 55,096 Gilead access rights related to the * 7,711 7,684 23,133 7,684 Taiho collaboration agreement * 1,750 1,750 5,250 5,250 Total revenues $ 9,461 $ 64,530 $ 28,383 $ 68,030 The Company recognized the following revenue as a result of changes in the deferred revenue balance during the period below (in thousands): Three Months Ended September 30, Nine Months Ended September 30, Revenue recognized in the period from: 2021 2020 2021 2020 Amounts included in deferred revenue at the beginning of the period $ 9,461 $ 1,750 $ 28,383 $ 5,250 Performance obligations satisfied in previous period - - - - Gilead Sciences, Inc. On May 27, 2020, the Company entered into an Option, License and Collaboration Agreement (Gilead Collaboration Agreement), Common Stock Purchase Agreement (the Stock Purchase Agreement), and Investor Rights Agreement, (collectively, the Gilead Agreements), each with Gilead Sciences, Inc. (Gilead). The transaction closed on July 13, 2020 following expiration of the antitrust waiting period. Upon closing, Gilead made an upfront payment of $ 175 million pursuant to the Gilead Collaboration Agreement, and made an equity investment of approximately $ 200 million in the Company by purchasing 5,963,029 shares of Arcus common stock at a per share price of $ 33.54 pursuant to the Stock Purchase Agreement. Pursuant to the Investor Rights Agreement, the Company appointed two Gilead designees to the Company’s Board of Directors. See Note 12 for further discussion of the agreements with Gilead. Pursuant to the terms of the Gilead Collaboration Agreement, Gilead has an exclusive license to develop and commercialize zimberelimab in certain markets and obtained exclusive options to acquire an exclusive license to develop and commercialize all of the Company’s current and future clinical programs during the 10-year collaboration term, contingent upon Gilead’s access rights payments of up to $ 400 million and, for those programs that enter clinical development prior to the end of the collaboration term, for up to an additional three years thereafter. Gilead's option, on a program-by-program basis, will expire after a proscribed period, following the achievement of a development milestone in such program and the Company's delivery to Gilead of the requisite data package. If Gilead exercises its option in a timely manner, after obtaining any applicable anti-trust approvals, Gilead shall pay the Company an option fee that ranges from $ 200 million to $ 275 million per program for the Company’s clinical programs in existence at the date of the agreement, and $ 150 million per program for all other programs that enter clinical development thereafter should Gilead elect to exercise its options. Gilead may exercise its option to any program at any time prior to expiration of the option. The Company may incur consulting fees to a third party if Gilead exercises its option to certain programs on or before December 31, 2022, ranging from $ 2.0 million to $ 4.5 million for those programs. Upon closing of Gilead’s exercise of its option to a program, the two companies will co-develop and equally share global development costs for the joint development program, subject to certain opt-out rights of the Company, and expense caps on the Company’s spending and related subsequent adjustments. For each optioned program, provided the Company has not exercised its opt-out rights, the Company has an option to co-promote in the United States with equal sharing of related profits and losses. Gilead has the right to exclusively commercialize any optioned programs outside of the U.S., subject to the rights of the Company’s existing partners to any territories, and Gilead will pay to the Company tiered royalties as a percentage of revenues ranging from the high teens to the low twenties. Pursuant to the Stock Purchase Agreement and the Investor Rights Agreement, Gilead has the right, at its option, to purchase additional shares from the Company, up to a maximum of 35 % of the Company’s then-outstanding voting common stock, from time to time over a five-year period from closing of the initial transaction, at a purchase price equal to the greater of a 20 % premium to market (based on a trailing five-day average closing price) at the time Gilead exercises such option, and the $ 33.54 initial purchase price. Based on the value of the Company’s common stock at the contract closing, the right to purchase additional shares had no value. In January 2021, the Company and Gilead entered into an Amended and Restated Common Stock Purchase Agreement, which amended and restated in its entirety the Common Stock Purchase Agreement, pursuant to which Gilead purchased 5,650,000 shares of the Company’s common stock at a purchase price of $ 39.00 per share for total gross proceeds of $ 220.4 million. All other terms of the original Stock Purchase Agreement remain unchanged. The Investor Rights Agreement also includes a three-year standstill and a two-year lockup and provides Gilead with registration rights commencing at the end of the lockup period, pro rata participation rights in certain future financings and the right to designate two individuals to be appointed to the Company’s Board of Directors. The Company’s assessment of the transaction price included an analysis of amounts it expected to receive, which at contract inception consisted of the upfront cash payment of $ 175.0 million due upon contract closing in July 2020, the $ 100.0 million payment related to the research and development access rights due in 2022, and the $ 90.6 million premium resulting from Gilead’s purchase of common stock. All payments to date have been made by Gilead as they became due and payable. Given this successful collection history, the Company considers the entire $ 365.6 million outlined above to be the initial transaction price. The Company evaluated the Gilead Agreements under ASC 606 and determined that the performance obligations at the contract inception consisted of the following: Zimberelimab license Effective on closing, Gilead obtained an exclusive license to zimberelimab. The standalone selling price of this license was determined using a discounted cash flow method. The Company recognized the full revenues associated with this performance obligation on the date the transaction closed. Etrumadenant option Gilead has the right to exercise an option for exclusive rights to etrumadenant, the Company’s adenosine receptor program, in exchange for an option payment of $ 250.0 million, that expires after a proscribed period following the Company’s achievement of certain development milestones. The Company calculated the standalone selling price of this program using a discounted cash flow method and concluded that it exceeded the price of the option, creating a material right and a distinct performance obligation. If the option is exercised, the performance obligations associated with the option will be identified and the Company will determine the accounting for the option’s transaction price. If the exercise occurs on or before December 31, 2022, the Company will also incur $ 4.5 million in consulting fees to a third party. If the option is allowed to lapse, the Company will recognize any deferred revenue allocated to the option at the time of the lapse. At September 30, 2021, the Company had $ 127.0 million of deferred revenue on its condensed consolidated balance sheets related to this performance obligation. The Company has evaluated the program’s status as of the balance sheet date and believes that some or all of the revenue associated with the opt-in will be recognized within the minimum four-year term of the Gilead Collaboration Agreement. Domvanalimab option Gilead has the right to exercise an option for exclusive rights to domvanalimab, the Company’s anti-TIGIT monoclonal antibody, in exchange for an option payment of $ 275.0 million, that expires after a proscribed period following the Company’s achievement of certain development milestones. In addition to the option payment, the Company has the right to receive clinical and regulatory milestones totaling up to $ 500 million. The Company calculated the standalone selling price of this program using a discounted cash flow method and concluded that it exceeded the price of the option, creating a material right and a distinct performance obligation. If the option is exercised, the performance obligations associated with the option will be identified and the Company will determine the accounting for the option’s transaction price. If the exercise occurs on or before December 31, 2022, the Company will also incur $ 4.5 million in consulting fees to a third party. If the option is allowed to lapse, the Company will recognize any deferred revenue allocated to the option at the time of the lapse. At September 30, 2021, the Company had $ 36.7 million of deferred revenue on its condensed consolidated balance sheets related to this performance obligation. The Company has evaluated the program’s status and believes that revenue associated with the opt-in will be recognized within one year . As of September 30, 2021, Gilead's option rights remained outstanding and no clinical or regulatory milestones had been achieved under this agreement. Access rights related to the Company’s research and development pipeline Gilead receives exclusive access to the Company’s current programs as well as the future programs for a period of ten years , contingent upon Gilead’s payment of $ 400 million, with the first payment of $ 100 million in 2022 , and an additional $ 100 million payment due at Gilead’s option on each of the fourth, sixth, and eighth anniversaries of the agreement. The standalone selling price of this ongoing research and development pipeline access was determined using an expected cost-plus margin approach. The Company evaluated its rights and obligations in the Gilead Collaboration Agreement and determined that Gilead is contractually obligated to make the $ 100 million payment due in 2022 resulting in a minimum term of four years for this performance obligation. As a result, the amount was included in the transaction price. The Company uses a time-elapsed input method to measure progress toward satisfying this obligation, which is the method the Company believes most faithfully depicts the Company’s performance in transferring the promised services during the time period in which Gilead has access to the Company’s research and development pipeline. Accordingly, the revenue allocated to the performance obligation is being recognized using this input method over the minimum four-year period. The Company further determined that Gilead is not obligated to pay the remaining $ 300 million due over the remainder of the term. Failure to pay the non-obligatory payments will result in Gilead’s loss of certain rights to access and obtain licenses to the programs arising from the Company’s research and development pipeline. At September 30, 2021, the Company had $ 98.6 million of deferred revenue on its consolidated balance sheets related to this performance obligation, classified between current and noncurrent based on the amortization of the revenue. Development and commercialization services for zimberelimab monotherapy In conjunction with the license, the Company determined there existed a separate obligation to perform further development and commercialization services for Gilead related to zimberelimab monotherapy. The standalone selling price of this obligation was determined using an expected cost-plus margin approach. This obligation includes a 50/50 share of the costs associated with all future development and commercialization of zimberelimab as a monotherapy. The portion of the transaction price allocated to this performance obligation has been allocated in accordance with the total costs forecast for the development and commercialization of zimberelimab as a monotherapy. The Company will recognize the amounts allocated to these services as the performance obligation is satisfied. Any additional payments received from or payments made to Gilead for the 50/50 cost share will be recognized as a reduction or an increase to R&D expense, respectively. At September 30, 2021, the Company had $ 9.7 million of contract liabilities on its consolidated balance sheets related to this performance obligation. The Company has evaluated the program’s status and believes that revenue associated with these services will be recognized over the full term of the contract. As of September 30, 2021, no revenue had been recognized from this performance obligation. Gilead was also granted option rights to programs not yet in development. These programs were not determined to be performance obligations at contract inception, as there are no identified programs, revenues, or costs to compare against the option price. Prepaid expenses The Company incurred $ 7.3 million in expenses to obtain the contract, which consisted of consultant and legal fees that were directly connected to the successful completion of the Gilead Agreements. The Company determined that $ 1.9 million of these expenses were related to the Stock Purchase Agreement and recorded them as offering costs. The Company allocated the remaining expenses between the various performance obligations, to be recognized when the underlying revenue is recognized. The portion allocated to the delivery of zimberelimab was recognized immediately, and the portion allocated to the remaining performance obligations will be recognized with timing consistent with the associated performance obligation. During the three and nine months ended September 30, 2021, the Company recognize d $ 0.1 million and $ 0.3 million, respectively, in expense from the amortization of these assets. At September 30, 2021, the Company had $ 3.9 million in prepaid expenses from costs to obtain the Gilead Agreements, of which $ 1.0 million was recorded in prepaid expenses and other current assets and $ 2.9 million was recorded in other long-term assets. Taiho Pharmaceutical Co., Ltd In September 2017, the Company and Taiho entered into an option and license agreement (the Taiho Agreement) to collaborate on the potential development and commercialization of certain investigational products from the Company’s portfolio in Japan and certain other territories in Asia (excluding China) (the Taiho Territory). The Taiho Agreement provides Taiho with exclusive options, over a five-year period ending September 2022 (the Option Period), to obtain an exclusive development and commercialization license to clinical stage investigational products from the Company’s programs (each, an Arcus Program). In consideration for the exclusive options and other rights contained in the Taiho Agreement, Taiho agreed to make non-refundable, non-creditable cash payments to the Company totaling $ 35.0 million, of which the Company received $ 25.0 million during 2017. An additional $ 5.0 million was received in 2018 and the remaining $ 5.0 million was received in 2019. For each option that Taiho elects to exercise, it will be obligated to make an option exercise payment of between $ 3.0 million to $ 15.0 million, depending on the development stage of the applicable Arcus Program for which the option is exercised. In addition, the Taiho Agreement provides that the Company is eligible to receive additional clinical and regulatory milestones totaling up to $ 130.0 million per Arcus Program, and it will be eligible to receive contingent payments of up to $ 145.0 million per Arcus Program associated with the achievement of specified levels of Taiho net sales in the Taiho Territory. In addition, the Company will receive royalties ranging from high single-digits to mid-teens on net sales of licensed products in the Taiho Territory. Royalties will be payable on a licensed product-by-licensed product and country-by-country basis during the period of time commencing on the first commercial sale of a licensed product in a country and ending upon the later of: (a) ten (10) years from the date of first commercial sale of such licensed product in such country; and (b) expiration of the last-to-expire valid claim of the Company’s patents covering the manufacture, use or sale or exploitation of such licensed product in such country (the Royalty Term). The Company determined that the identified performance obligations, which include the combined performance obligation of the research and development services and the obligation to participate on the joint steering committee, are satisfied over time. The Company uses a time-elapsed input method to measure progress toward satisfying its performance obligation, which is the method the Company believes most faithfully depicts the Company’s performance in transferring the promised services during the time period in which Taiho has access to the Company’s research and development activities. Accordingly, the transaction price of $ 35.0 million is being recognized using this input method over the estimated performance period of five years . Based on the nature of the clinical and regulatory milestones, such as the regulatory approvals which are not within the Company’s control, the Company will not consider achievement of such milestones to be probable until the uncertainty associated with the milestones has been resolved. When it is probable that a significant reversal of revenue will not occur, the milestone payment will be added to the transaction price, which will then be allocated to each performance obligation, on a relative standalone selling price basis, for which the Company recognizes revenue. As of September 30, 202 1, no clinical or regulatory milestones had been achieved under the Taiho Agreement. The Company also considers the contingent payments due from Taiho upon the achievement of specified sales volumes to be similar to royalty payments. The Company considers the license to be the predominant item to which the royalties relate. The Company will recognize revenue at the later of (i) when the related sales occur, or (ii) when the performance obligation to which some or all of the royalty has been allocated has been satisfied (or partially satisfied). As of September 30, 2021, no sales milestone or royalty revenue has been recognized. The Taiho Agreement shall remain in effect until expiry of all Royalty Terms for the licensed products, in each case subject to certain exceptions. WuXi Biologics License Agreements The Company entered into a license agreement (the WuXi PD-1 Agreement) with WuXi Biologics in August 2017, as subsequently amended, in which it obtained an exclusive license to develop, use, manufacture, and commercialize products including an anti-PD-1 antibody worldwide except for Greater China. From the inception of the WuXi PD-1 Agreement through September 30, 2021, the Company has made upfront and milestone payments of $ 41.0 million and incurred sub-license fees of $ 11.3 million. These payments were recorded as research and development expense, as the products had not reached technological feasibility and did not have an alternative future use. The WuXi PD-1 Agreement also provides for clinical and regulatory milestone payments, commercialization milestone payments of up to $ 375.0 million, and tiered royalty payments to be made to WuXi Biologics that range from the high single-digits to low teens of net sales by the Company of licensed products. The Company incurred zero and $ 10.0 m illion, respectively, in development milestone expense under the WuXi PD-1 Agreement during the three and nine months ended September 30, 2021. In December 2020, the Company entered into a separate license agreement (the WuXi CD-39 Agreement) with WuXi Biologics to develop anti-CD39 antibodies. Under the agreement, the Company was granted exclusive worldwide rights to anti-CD39 antibodies discovered under the collaboration and will be responsible for the further development and commercialization of those antibodies. From the inception of the WuXi CD-39 Agreement through September 30, 2021, the Company has paid $ 0.5 million in upfront payments which was recorded in research and development expense, as the products are still in research stage. The WuXi CD-39 Agreement provides for clinical and regulatory milestone payments totaling $ 16.5 million, and royalty payments in the low single digits of net sales by the Company of licensed products. The Company incurred no development milestone expense under the WuXi CD-39 Agreement during the three and nine months ended September 30, 2021. Abmuno License Agreement In December 2016, the Company entered into a license agreement (the Abmuno Agreement) with Abmuno Therapeutics LLC (Abmuno) in which it obtained a worldwide exclusive license to develop, use, manufacture, and commercialize products that include an anti-TIGIT antibody, including domvanalimab (formerly referred to as AB154). Under the Abmuno Agreement, the Company has made upfront and milestone payments totaling $ 14.6 m illion as of September 30, 2021. The Abmuno Agreement also provides for additional clinical, regulatory and commercialization milestone remaining payments of up to $ 93.0 million as of September 30, 2021. The Company incurred zero and $ 5.0 million in development milestone expense under the Abmuno Agreement during the three and nine months ended September 30, 2021. The Company incurr ed $ 3.0 million in development milestone expense under the Abmuno Agreement during the three and nine months ended September 30, 2020. Strata Collaboration Agreement On April 30, 2019, the Company and Strata Oncology, Inc. (Strata) entered into a Co-Development and Collaboration Agreement (the Strata Agreement) to pursue a clinical development collaboration utilizing Strata’s precision drug development platform and proprietary biomarkers to evaluate zimberelimab, the Company’s clinical-stage anti-PD-1 antibody, in patients in a tumor-agnostic fashion. Under the terms of the Strata Agreement, the parties share a portion of development costs for the clinical collaboration. From the inception of the Agreement through September 30, 2021, the Company has made a milestone payment of $ 2.5 million and has incurred expenses of $ 4.5 million, of which $ 0.9 million had b een reimbursed by Strata as development cost sharing. Net expenses related to this co-development agreement were recorded within research and development expenses. As further consideration in connection with the Strata Agreement, the Company issued to Strata 1,257,651 restricted shares of its common stock in April 2019 with an initial measured fair value of $ 15.0 million, which were subject to vesting based upon the achievement of specified regulatory milestones within certain timelines. In September 2021, the Company and Strata agreed to cancel the full amount of the restricted shares upon final determination that the biomarker indications were unlikely to be successful given the evolution of the competitive landscape. For the three and nine months ended September 30, 2021, the Company incurred expenses p ursuant to the Strata Agreement of $ 0.7 million and $ 1.8 million, respectively. Of these expenses, $ 0.1 million and $ 0.3 mi llion, respectively, were reimbursed by Strata. For the three and nine months ended September 30, 2020, the Company incurred expenses pursuant to the Strata Agreement of $ 0.3 million and $ 1.2 million, respectively. Of these expenses, $ 0.1 and $ 0.2 million, respectively, were reimbursed by Strata. AstraZeneca Agreement On October 29, 2020 the Company announced a collaboration with AstraZeneca to evaluate domvanalimab, the Company’s investigational anti-TIGIT antibody, in combination with AstraZeneca’s Imfinzi (durvalumab) in a registrational Phase 3 clinical trial in patients with unresectable Stage III non-small cell lung cancer (NSCLC). Under the terms of the agreement, each company will retain existing rights to their respective molecules and any future commercial economics. AstraZeneca will conduct the trial, and each company will supply its respective anti-cancer agent to support the trial. Under the terms of the agreement and subject to the parties’ approval of a final budget for the clinical trial, the Company may be obligated to reimburse AstraZeneca for a portion of the costs incurred. Consistent with the terms of the Gilead Collaboration Agreement, Gilead maintains an option to co-develop and co-commercialize domvanalimab. If Gilead exercises its option to domvanalimab, the trial from this AstraZeneca collaboration is expected to form part of the Arcus and Gilead joint development program and Arcus’s portion of the trial costs would be shared with Gilead. For the three and nine months ended September 30, 2021, the Company incurred $ 0.3 million and $ 0.6 million, respectively, of expenses pursuant to the AstraZeneca Agreement. Expenses from this co-development agreement are recorded within research and development expenses. Genentech Collaboration Agreement In December 2019, the Company and Genentech, through F. Hoffmann-La Roche Ltd (collectively, Genentech) entered into a Master Clinical Collaboration Agreement (the Genentech Agreement) pursuant to which the parties may conduct combination clinical studies involving Genentech’s monoclonal antibody, atezolizumab, and the Company’s investigational products. Pursuant to the Genentech Agreement, the parties entered into Trial Supplements for the evaluation of etrumadenant and atezolizumab utilizing the MORPHEUS platform in two separate study indications: second and third line metastatic colorectal cancer and first line metastatic pancreatic cancer. The Company and Genentech each supply their respective investigational products for use in the collaboration studies and share a portion of the development costs under specific terms as set forth in the agreement. For each of the three and nine months ended September 30, 2021 and 2020, the Company recorded immaterial n et expenses related to this co-development agreement within research and development expenses.

Stockholders' Equity

Stockholders' Equity	9 Months Ended
	Sep. 30, 2021
Stockholders Equity Note [Abstract]
Stockholders' Equity	Note 8. Stockholders’ Equity In June 2020, pursuant to a shelf registration statement on Form S-3 that was filed in May 2020, the Company issued 12,650,000 shares of its common stock at $ 27.50 per share in an underwritten public offering (the May 2020 Public Offering). The total number of shares sold consisted of 11,000,000 base shares and an additional 1,650,000 shares sold pursuant to the underwriters’ option exercise. Net proceeds from the May 2020 Public Offering were approximately $ 326.2 million after deducting underwriting discounts, commissions and other offering expenses. In July 2020, the Company closed the Gilead Collaboration Agreement, Common Stock Purchase Agreement, and the Investor Rights Agreement, each signed with Gilead in May 2020. The transaction closed on July 13, 2020 following expiration of the antitrust waiting period. Upon closing, Gilead made an equity investment of approximately $ 200 million in the Company by purchasing 5,963,029 shares of Arcus common stock at a per share price of $ 33.54 pursuant to the Stock Purchase Agreement. Of the $ 200 million equity investment, approximately $ 90.6 million was determined to be a premium on the purchase of common stock and allocated to the performance obligations created by the Gilead Collaboration Agreement. See Note 7 in this Form 10-Q for further discussion of the agreements with Gilead. Net proceeds from Gilead’s equity investment were approximately $ 107.5 million after allocating the premium and deducting direct offering expenses of $ 1.9 million. In February 2021, the Company closed the Amended and Restated Common Stock Purchase Agreement with Gilead, pursuant to which Gilead made an equity investment of approximately $ 220.4 million in the Company by purchasing 5,650,000 shares of the Company’s common stock at a per share price of $ 39.00 .

Stock-Based Compensation

Stock-Based Compensation	9 Months Ended
	Sep. 30, 2021
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Stock-Based Compensation	Note 9. Stock-Based Compensation The Company grants awards under its 2018 Equity Incentive Plan and the 2020 Inducement Plan. Total stock-based compensation expense was recognized in the condensed consolidated statements of operations and comprehensive loss as follows (in thousands): Three Months Ended September 30, Nine Months Ended September 30, 2021 2020 2021 2020 Research and development $ 7,949 $ 3,075 $ 21,087 $ 7,179 General and administrative 6,636 2,927 19,626 6,755 Total stock-based compensation $ 14,585 $ 6,002 $ 40,713 $ 13,934

Net Income (Loss) per Share

Net Income (Loss) per Share	9 Months Ended
	Sep. 30, 2021
Earnings Per Share [Abstract]
Net Income (Loss) per Share	Note 10. Net Income (Loss) per Share Basic net income (loss) per share is calculated based on the weighted-average number of shares of the Company’s common stock during the period. Diluted net income (loss) per share is calculated based on the weighted-average number of shares of the Company’s common stock and other dilutive securities outstanding during the period. Potentially dilutive securities are excluded from the calculation if their inclusion would have been antidilutive. The potentially dilutive shares of the Company's common stock resulting from the assumed exercise of outstanding stock options and equivalents were determined under the treasury stock method. The following table sets forth the computation of basic and diluted net loss per share (in thousands, except share and per share data): Three Months Ended September 30, Nine Months Ended September 30, 2021 2020 2021 2020 Numerator: Net loss $ ( 77,975 ) $ 1,822 $ ( 226,538 ) $ ( 71,005 ) Denominator: Weighted-average common shares outstanding 71,286,685 64,132,283 70,296,187 53,452,007 Less: weighted-average common shares subject to vesting ( 1,176,547 ) ( 1,533,090 ) ( 1,305,897 ) ( 1,599,760 ) Weighted-average common shares used to compute basic net income (loss) per share 70,110,138 62,599,193 68,990,290 51,852,247 Dilutive effect of stock options - 2,538,926 - - Dilutive effect of ESPP - 7,588 - - Weighted-average common shares used to compute diluted net income (loss) per share 70,110,138 65,145,707 68,990,290 51,852,247 Net income (loss) per share: basic $ ( 1.11 ) $ 0.03 $ ( 3.28 ) $ ( 1.37 ) Net income (loss) per share: diluted $ ( 1.11 ) $ 0.03 $ ( 3.28 ) $ ( 1.37 ) The following outstanding potentially dilutive securities were excluded from the computation of diluted net loss per share because including them would have been antidilutive: Three Months Ended September 30, Nine Months Ended September 30, 2021 2020 2021 2020 Common stock options issued and outstanding 12,625,226 1,518,386 12,625,226 7,841,220 Unvested restricted stock units 1,361,008 653,950 1,361,008 653,950 Employee Stock Purchase Plan shares 166,461 12,966 166,461 79,848 Unvested early exercised common stock options 39,142 - 39,142 240,977 Unvested restricted common stock issued as - 1,257,651 - 1,257,651 Total 14,191,837 3,442,953 14,191,837 10,073,646 The Company also excluded the effect of Gilead’s right to purchase additional shares of the Company’s common stock from its calculation as these rights had no intrinsic value at September 30, 2021.

Commitments

Commitments	9 Months Ended
	Sep. 30, 2021
Commitments And Contingencies Disclosure [Abstract]
Commitments	Note 11. Commitments Standby Letters of Credit The Company has standby letters of credit up to an aggregate of $ 3.0 million provided as collateral for its leases. The letters of credit are secured by $ 3.0 million in deposits classified as restricted cash on the Company’s condensed consolidated balance sheets. At September 30, 2021 the standby letters of credit were not drawn down.

Related Parties

Related Parties	9 Months Ended
	Sep. 30, 2021
Related Party Transactions [Abstract]
Related Parties	Note 12. Related parties Relationship and transactions with Gilead Sciences, Inc. (Gilead) As of September 30, 2021, Gilead held approximate ly 19.7 % o f the Company’s outstanding common stock. These holdings resulted from Gilead’s participation in the May 2020 Public Offering as well as purchases of stock under the stock purchase agreements. In the May 2020 public offering, Gilead purchased 2,200,000 shares of common stock for an amount of $ 56.7 million, net of offering costs. Under the stock purchase agreements, Gilead purchased 5,963,029 and 5,650,000 shares in July 2020 and February 2021, respectively, for a total investment of $ 327.8 million, net of offering costs and amounts allocated to the performance obligations created by the Gilead Collaboration Agreement. Gilead has the right, at its option, to purchase up to a maximum of 35 % of the Company’s then-outstanding voting common stock, from time to time over a five-year period from the closing of the initial transaction in July 2020. Gilead also has the right under the Investor Rights Agreement to designate two individuals to be appointed to the Company’s Board of Directors. Pursuant to the Investor Rights Agreement, the Company appointed the Gilead designees, Merdad Parsey, M.D., Ph.D. and Michael Quigley, Ph.D., to its Board of Directors, in July 2020 and January 2021, respectively. In August 2021, in connection with his departure from Gilead, Dr. Quigley resigned from the Company’s Board of Directors. In his place and pursuant to the Investor Rights Agreement, the Company appointed Linda Higgins, Ph.D., Senior Vice President of Research, External Innovation at Gilead, to its board. See Note 7 for further discussion of the agreements with Gilead. At September 30, 2021, the Company had a $ 0.6 million cost sharing receivable recorded on the condensed consolidated balance sheets under receivable from collaboration partners, to be invoiced the following quarter. The Company also had $ 162.2 million in deferred revenue at September 30, 2021, of which $ 94.7 million represented the long-term portion of revenue allocated to performance obligations not expected to be completed within one year of the balance sheet date, which was recorded in deferred revenue, noncurrent on the condensed consolidated balance sheets. The Company also had $ 9.7 mil lion in contract liabilities for future development and commercialization services for zimberelimab as a monotherapy which Gilead prepaid, all of which was recorded in other long-term liabilities on the consolidated balance sheets. For the three and nine months ended September 30, 2021, the C ompany recognized $ 7.7 million and $ 23.1 million, respectively, in revenue under the Gilead Collaboration Agreement. For each of these periods, the Company also recognized reductions of $ 0.8 million and $ 6.9 million, respectively, in research and development expense, including $ 4.0 million of cost sharing reimbursement related to milestone expense, under the cost-sharing provision s of the agreement. The Company received a $ 175 million upfront payment from Gilead in connection with the Gilead Collaboration Agreement in July 2020 and identified $ 100 million in unconstrained consideration to be received in 2022. In addition, in July 2020 the Company received $ 200 million from Gilead in connection with the Stock Purchase Agreement, of which approximately $ 109.4 million represented the fair value of stock purchased at the transaction closing date with the remaining premium of $ 90.6 million allocated to the transaction price. In February 2021, the Company received $ 220.4 million from Gilead in connection with the purchase by Gilead of 5,650,000 shares of the Company’s common stock at a per share price of $ 39.00 pursuant to the amended and restated Stock Purchase Agreement.

Subsequent Event

Subsequent Event	9 Months Ended
	Sep. 30, 2021
Subsequent Events [Abstract]
Subsequent event	Note 13. Subsequent event BVF Agreement In the fourth quarter of 2021, the Company and BVF Partners L.P. (BVF) entered into an agreement (the BVF Agreement) under which BVF will pay up to $ 15 million to the Company for the discovery and development of compounds for the treatment of inflammatory diseases (the Program). The Company received $ 5 million from BVF in the fourth quarter of 2021. In return, the Company is obligated to make milestone payments upon the achievement of certain clinical and regulatory milestones and will pay royalties based on net sales of products generated by the Program. The agreement also provides BVF with the option to provide an additional $ 10 million in funding for the Program in exchange for an increase in the royalty rate. Consistent with the terms of the Gilead Collaboration Agreement, Gilead has an option to the Program.

Significant Accounting Polici_2

Significant Accounting Policies (Policies)	9 Months Ended
	Sep. 30, 2021
Accounting Policies [Abstract]
Basis of Presentation	Basis of Presentation The accompanying unaudited condensed consolidated financial statements have been prepared in accordance with U.S. generally accepted accounting principles (U.S. GAAP) for interim financial information and pursuant to Form 10-Q and Article 10 of Regulation S-X of the Securities and Exchange Commission (SEC). Accordingly, they do not include all of the information and footnotes required by U.S. GAAP for complete financial statements. In the Company’s opinion, all adjustments (consisting only of normal recurring adjustments) considered necessary for a fair presentation of the results of operations and cash flows for the periods presented have been included. Operating results for the nine months ended September 30, 2021 are not necessarily indicative of the results that may be expected for the year ending December 31, 2021 or for any future period. The balance sheet as of December 31, 2020 has been derived from audited consolidated financial statements at that date but does not include all of the information required by U.S. GAAP for complete financial statements. The accompanying unaudited condensed consolidated financial statements and related financial information should be read in conjunction with the audited consolidated financial statements and the related notes thereto for the year ended December 31, 2020 included in the Company’s Annual Report on Form 10-K filed with the SEC on February 25, 2021. There have been no significant changes to the Company’s significant accounting policies described in Note 2, Summary of Significant Accounting Policies, in Notes to Consolidated Financial Statements in Item 8 of Part II of the Form 10-K.
Principles of Consolidation	Principles of Consolidation The accompanying consolidated financial statements include the accounts of Arcus Biosciences, Inc. and its wholly-owned subsidiaries. All intercompany balances and transactions have been eliminated in consolidation.
Use of Estimates	Use of Estimates The preparation of the Company’s condensed consolidated financial statements in conformity with U.S. GAAP requires management to make estimates and assumptions that affect the reported amounts of assets, liabilities, revenues and expenses, as well as related disclosures of contingent assets and liabilities. Estimates were used to determine the standalone selling price of performance obligations and the timing of revenue recognition, the value of stock-based awards and other issuances, accruals for research and development costs, useful lives of long-lived assets, and uncertain tax positions. Actual results could differ materially from the Company’s estimates.
Cash Equivalents and Investments	Cash Equivalents and Investments Cash equivalents include marketable securities having an original maturity of three months or less at the time of purchase. Short-term investments have maturities of greater than three months and up to twelve months at the time of purchase. Long-term investments have maturities greater than 12 months at the time of purchase. Collectively, cash equivalents, short-term and long-term investments are considered available-for-sale and are recorded at fair value. Unrealized gains and losses are recorded in accumulated other comprehensive income (loss). Realized gains and losses are included in interest and other income, net in the condensed consolidated statements of operations and comprehensive income or loss. The basis on which the cost of a security that is sold or an amount that is reclassified out of accumulated other comprehensive income or loss into earnings is determined using the specific identification method.
Reconciliation of Cash, Cash Equivalents, and Restricted Cash as Reported in Condensed Consolidated Statements of Cash Flows	Reconciliation of Cash, Cash Equivalents, and Restricted Cash as Reported in Condensed Consolidated Statements of Cash Flows Restricted cash at September 30, 2021 and 2020 represents cash balances held as security in connection with the Company’s facility lease agreements. The following table provides a reconciliation of cash, cash equivalents, and restricted cash within the condensed consolidated balance sheets to the total shown in the condensed consolidated statements of cash flows (in thousands): September 30, 2021 2020 Cash and cash equivalents $ 179,432 $ 221,849 Restricted cash 3,005 203 Cash, cash equivalents and restricted cash $ 182,437 $ 222,052
Concentration of Credit Risk	Concentration of Credit Risk Cash equivalents, short-term and long-term investments are financial instruments that potentially subject the Company to concentrations of credit risk. The Company invests in money market funds, treasury bills and notes, government bonds, commercial paper and corporate notes. The Company limits its credit risk associated with cash equivalents, short-term and long-term investments by placing them with banks and institutions it believes are credit worthy and in highly rated investments.
Leases and Rent Expense	Leases and Rent Expense The Company recognizes a lease asset for its right to use the underlying asset and a lease liability for the corresponding lease obligation. The Company determines whether an arrangement is or contains a lease at contract inception. Operating leases and related tenant improvement allowances receivable are included in operating lease right-of-use assets, prepaid expenses and other current assets, and operating lease liabilities, noncurrent in our condensed consolidated balance sheets at September 30, 2021 and December 31, 2020. Operating lease right-of-use assets and liabilities are recognized at the lease commencement date based on the present value of lease payments over the lease term. In determining the net present value of lease payments, the Company uses its incremental borrowing rate based on information available at the lease commencement date. The incremental borrowing rate represents the interest rate the Company would incur at lease commencement to borrow an amount equal to the lease payments on a collateralized basis over the term of a lease. The Company considers a lease term to be the noncancelable period that it has the right to use the underlying asset, including any periods where it is reasonably assured the Company will exercise the option to extend the contract. Periods covered by an option to extend are included in the lease term if the lessor controls the exercise of that option. The Company elected to not apply the recognition requirements of the new leasing standard to short-term leases with terms of 12 months or less which do not include an option to purchase the underlying asset that the Company is reasonably certain to exercise. For short-term leases, lease payments are recognized as operating expenses on a straight-line basis over the lease term.

Significant Accounting Polici_3

Significant Accounting Policies (Tables)	9 Months Ended
	Sep. 30, 2021
Accounting Policies [Abstract]
Reconciliation of Cash, Cash Equivalents and Restricted Cash	Restricted cash at September 30, 2021 and 2020 represents cash balances held as security in connection with the Company’s facility lease agreements. The following table provides a reconciliation of cash, cash equivalents, and restricted cash within the condensed consolidated balance sheets to the total shown in the condensed consolidated statements of cash flows (in thousands): September 30, 2021 2020 Cash and cash equivalents $ 179,432 $ 221,849 Restricted cash 3,005 203 Cash, cash equivalents and restricted cash $ 182,437 $ 222,052

Fair Value Measurements (Tables

Fair Value Measurements (Tables)	9 Months Ended
	Sep. 30, 2021
Fair Value Disclosures [Abstract]
Schedule of Financial Instruments Measured at Fair Value on Recurring Basis	The following tables set forth the Company’s financial instruments that were measured at fair value on a recurring basis by level within the fair value hierarchy (in thousands): September 30, 2021 Total Level 1 Level 2 Level 3 Money market funds $ 172,431 $ 172,431 $ - $ - U.S. treasury securities 109,946 - 109,946 - Corporate securities and commercial paper 460,995 - 460,995 - Total assets measured at fair value $ 743,372 $ 172,431 $ 570,941 $ - December 31, 2020 Total Level 1 Level 2 Level 3 Money market funds $ 146,468 $ 146,468 $ - $ - U.S. treasury securities 301,112 - 301,112 - U.S. government agency obligations 25,001 - 25,001 - Corporate securities and commercial paper 262,505 - 262,505 - Total assets measured at fair value $ 735,086 $ 146,468 $ 588,618 $ -
Schedule of Investments Classified as Available for Sale Securities with Contractual Maturities	Classified as (with contractual maturities): September 30, 2021 December 31, 2020 Cash and cash equivalents $ 179,432 $ 173,415 Short-term investments (due within one year) 345,210 555,231 Long-term investments (due between one and three years) 218,730 6,440 Total cash, cash equivalents and investments in marketable securities $ 743,372 $ 735,086
Schedule of Fair Value and Amortized Cost of Investments in Marketable Securities by Major Security Type	The fair value and amortized cost of investments in marketable securities by major security type as of September 30, 2021 and December 31, 2020 are presented in the tables that follow (in thousands): Amortized Unrealized Unrealized Fair As of September 30, 2021: Money market funds $ 172,431 $ - $ - $ 172,431 U.S. treasury securities 109,972 9 ( 35 ) 109,946 Corporate securities and commercial paper 461,061 53 ( 119 ) 460,995 Total $ 743,464 $ 62 $ ( 154 ) $ 743,372 Amortized Unrealized Unrealized Fair As of December 31, 2020: Money market funds $ 146,468 $ - $ - $ 146,468 U.S. treasury securities 301,075 38 ( 1 ) 301,112 U.S. government agency obligations 24,997 4 - 25,001 Corporate securities and commercial paper 262,502 15 ( 12 ) 262,505 Total $ 735,042 $ 57 $ ( 13 ) $ 735,086

Other Accrued Liabilities (Tabl

Other Accrued Liabilities (Tables)	9 Months Ended
	Sep. 30, 2021
Payables And Accruals [Abstract]
Summary of Other Accrued Liabilities	ccrued liabilities consisted of the following (in thousands): As of September 30, 2021 As of December 31, 2020 Accrued personnel expenses $ 13,499 $ 8,632 Professional fees 523 295 Other 603 616 Total $ 14,625 $ 9,543

Leases (Tables)

Leases (Tables)	9 Months Ended
	Sep. 30, 2021
Leases [Abstract]
Schedule of Future Minimum Lease Payments	As of September 30, 2021, the Company’s future minimum lease payments were as follows (in thousands): Operating Year Ending December 31, Leases 2021 (from October to December) $ 1,159 2022 5,722 2023 5,908 2024 6,101 2025 6,302 Thereafter 42,489 Total undiscounted future minimum lease payments 67,681 Less: Imputed interest ( 15,905 ) Less: Tenant improvement allowance receivable ( 10,785 ) Total operating lease liabilities 40,991 Tenant improvement allowance expected to be received in 7,952 Operating lease liabilities, noncurrent $ 48,943

License and Collaboration Agr_2

License and Collaboration Agreements (Tables)	9 Months Ended
	Sep. 30, 2021
Summary of Revenues by Collaboration and by Category of Revenue	The following table summarizes details of revenues for the three and nine months ended September 30, 2021 and 2020 by collaboration and by category of revenue: Three Months Ended September 30, Nine Months Ended September 30, Revenues recognized: Over time Point in time 2021 2020 2021 2020 Gilead license to zimberelimab * $ - $ 55,096 $ - $ 55,096 Gilead access rights related to the * 7,711 7,684 23,133 7,684 Taiho collaboration agreement * 1,750 1,750 5,250 5,250 Total revenues $ 9,461 $ 64,530 $ 28,383 $ 68,030
Summary of Revenue Recognized as a Result of Changes in Deferred Revenue	The Company recognized the following revenue as a result of changes in the deferred revenue balance during the period below (in thousands): Three Months Ended September 30, Nine Months Ended September 30, Revenue recognized in the period from: 2021 2020 2021 2020 Amounts included in deferred revenue at the beginning of the period $ 9,461 $ 1,750 $ 28,383 $ 5,250 Performance obligations satisfied in previous period - - - -
Gilead and Taiho
Summary of Revenues	The following table summarizes the revenues for the three and nine months ended September 30, 2021 and 2020 received as a result of the Company’s collaboration agreements with Gilead Sciences, Inc. (Gilead) and Taiho Pharmaceutical Co., Ltd. (Taiho): Three Months Ended September 30, Nine Months Ended September 30, 2021 2020 2021 2020 License revenue $ - $ 55,096 $ - $ 55,096 Collaboration revenue 9,461 9,434 28,383 12,934 Total revenues $ 9,461 $ 64,530 $ 28,383 $ 68,030

Stock-Based Compensation (Table

Stock-Based Compensation (Tables)	9 Months Ended
	Sep. 30, 2021
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Summary of Stock-Based Compensation Expense	Total stock-based compensation expense was recognized in the condensed consolidated statements of operations and comprehensive loss as follows (in thousands): Three Months Ended September 30, Nine Months Ended September 30, 2021 2020 2021 2020 Research and development $ 7,949 $ 3,075 $ 21,087 $ 7,179 General and administrative 6,636 2,927 19,626 6,755 Total stock-based compensation $ 14,585 $ 6,002 $ 40,713 $ 13,934

Net Income (Loss) per Share (Ta

Net Income (Loss) per Share (Tables)	9 Months Ended
	Sep. 30, 2021
Earnings Per Share [Abstract]
Computation of Basic and Diluted Net Loss Per Share	The following table sets forth the computation of basic and diluted net loss per share (in thousands, except share and per share data): Three Months Ended September 30, Nine Months Ended September 30, 2021 2020 2021 2020 Numerator: Net loss $ ( 77,975 ) $ 1,822 $ ( 226,538 ) $ ( 71,005 ) Denominator: Weighted-average common shares outstanding 71,286,685 64,132,283 70,296,187 53,452,007 Less: weighted-average common shares subject to vesting ( 1,176,547 ) ( 1,533,090 ) ( 1,305,897 ) ( 1,599,760 ) Weighted-average common shares used to compute basic net income (loss) per share 70,110,138 62,599,193 68,990,290 51,852,247 Dilutive effect of stock options - 2,538,926 - - Dilutive effect of ESPP - 7,588 - - Weighted-average common shares used to compute diluted net income (loss) per share 70,110,138 65,145,707 68,990,290 51,852,247 Net income (loss) per share: basic $ ( 1.11 ) $ 0.03 $ ( 3.28 ) $ ( 1.37 ) Net income (loss) per share: diluted $ ( 1.11 ) $ 0.03 $ ( 3.28 ) $ ( 1.37 )
Summary of Outstanding Potentially Dilutive Securities Excluded from Computation of Diluted Net Loss per Share	The following outstanding potentially dilutive securities were excluded from the computation of diluted net loss per share because including them would have been antidilutive: Three Months Ended September 30, Nine Months Ended September 30, 2021 2020 2021 2020 Common stock options issued and outstanding 12,625,226 1,518,386 12,625,226 7,841,220 Unvested restricted stock units 1,361,008 653,950 1,361,008 653,950 Employee Stock Purchase Plan shares 166,461 12,966 166,461 79,848 Unvested early exercised common stock options 39,142 - 39,142 240,977 Unvested restricted common stock issued as - 1,257,651 - 1,257,651 Total 14,191,837 3,442,953 14,191,837 10,073,646

Organization - Additional Infor

Organization - Additional Information (Details) $ in Millions	9 Months Ended
	Sep. 30, 2021USD ($)Product
Organization [Line Items]
Number of investigational product | Product	6
Cash, Cash Equivalents and Investments in Marketable Securities
Organization [Line Items]
Cash and investments | $	$ 743.4

Significant Accounting Polici_4

Significant Accounting Policies - Reconciliation of Cash, Cash Equivalents and Restricted Cash (Details) - USD ($) $ in Thousands	Sep. 30, 2021	Dec. 31, 2020	Sep. 30, 2020	Dec. 31, 2019
Accounting Policies [Abstract]
Cash and cash equivalents	$ 179,432	$ 173,415	$ 221,849
Restricted cash	3,005	203	203
Cash, cash equivalents and restricted cash	$ 182,437	$ 173,618	$ 222,052	$ 58,140

Fair Value Measurements - Addit

Fair Value Measurements - Additional Information (Details) - USD ($)	9 Months Ended	12 Months Ended
	Sep. 30, 2021	Dec. 31, 2020
Fair Value Disclosures [Abstract]
Realized gains (loss) on sale or maturity of available-for-sale marketable securities	$ 0	$ 0
Reclassification out of accumulated other comprehensive income	0	0
Credit related losses	$ 0	$ 0

Fair Value Measurements - Sched

Fair Value Measurements - Schedule of Financial Instruments Measured at Fair Value on Recurring Basis (Details) - Fair Value On Recurring Basis - USD ($) $ in Thousands	Sep. 30, 2021	Dec. 31, 2020
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Total assets measured at fair value	$ 743,372	$ 735,086
Level 1
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Total assets measured at fair value	172,431	146,468
Level 2
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Total assets measured at fair value	570,941	588,618
Money Market Funds
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Total assets measured at fair value	172,431	146,468
Money Market Funds | Level 1
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Total assets measured at fair value	172,431	146,468
U.S. Treasury Securities
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Total assets measured at fair value	109,946	301,112
U.S. Treasury Securities | Level 2
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Total assets measured at fair value	109,946	301,112
U.S. Government Agency Securities
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Total assets measured at fair value		25,001
U.S. Government Agency Securities | Level 2
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Total assets measured at fair value		25,001
Corporate Securities and Commercial Paper
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Total assets measured at fair value	460,995	262,505
Corporate Securities and Commercial Paper | Level 2
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Total assets measured at fair value	$ 460,995	$ 262,505

Fair Value Measurements - Sch_2

Fair Value Measurements - Schedule of Investments Classified as Available for Sale Securities with Contractual Maturities (Details) - USD ($) $ in Thousands	Sep. 30, 2021	Dec. 31, 2020
Fair Value Disclosures [Abstract]
Cash and cash equivalents	$ 179,432	$ 173,415
Short-term investments (due within one year)	345,210	555,231
Long-term investments (due between one and three years)	218,730	6,440
Total cash, cash equivalents and investments in marketable securities	$ 743,372	$ 735,086

Fair Value Measurements - Sch_3

Fair Value Measurements - Schedule of Fair Value and Amortized Cost of Investments in Marketable Securities by Major Security Type (Details) - USD ($) $ in Thousands	Sep. 30, 2021	Dec. 31, 2020
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Amortized Cost	$ 743,464	$ 735,042
Unrealized Gain	62	57
Unrealized Loss	(154)	(13)
Fair Value	743,372	735,086
Money Market Funds
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Amortized Cost	172,431	146,468
Fair Value	172,431	146,468
U.S. Treasury Securities
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Amortized Cost	109,972	301,075
Unrealized Gain	9	38
Unrealized Loss	(35)	(1)
Fair Value	109,946	301,112
U.S. Government Agency Securities
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Amortized Cost		24,997
Unrealized Gain		4
Fair Value		25,001
Corporate Securities and Commercial Paper
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Amortized Cost	461,061	262,502
Unrealized Gain	53	15
Unrealized Loss	(119)	(12)
Fair Value	$ 460,995	$ 262,505

Other Accrued Liabilities - Sum

Other Accrued Liabilities - Summary of Other Accrued Liabilities (Details) - USD ($) $ in Thousands	Sep. 30, 2021	Dec. 31, 2020
Accrued Liabilities Current [Abstract]
Accrued personnel expenses	$ 13,499	$ 8,632
Professional fees	523	295
Other	603	616
Total	$ 14,625	$ 9,543

Equity Investment in PACT Pha_2

Equity Investment in PACT Pharma - Additional Information (Details) - PACT Pharma - USD ($) shares in Millions, $ in Millions	12 Months Ended
	Dec. 31, 2016	Sep. 30, 2021	Dec. 31, 2020
Schedule of Equity Method Investments [Line Items]
Investment balance		$ 0	$ 0
Series A Preferred Stock
Schedule of Equity Method Investments [Line Items]
Purchase of common stock, shares	1
Common Stock
Schedule of Equity Method Investments [Line Items]
Purchase of common stock, shares	3.6

Leases - Additional Information

Leases - Additional Information (Details)	1 Months Ended	3 Months Ended		9 Months Ended
	Apr. 30, 2021ft²	Sep. 30, 2021USD ($)	Sep. 30, 2020USD ($)	Sep. 30, 2021USD ($)	Sep. 30, 2020USD ($)	Dec. 31, 2020USD ($)ft²
Lessee Lease Description [Line Items]
Operating lease, option to extend				the lease amendment and replaced by two options to extend the lease term for the entire 150,753 square feet then under lease in the Hayward premises for a period of eight years each.
Operating lease, existence of option to extend	true
Operating lease, option to extend lease term	8 years
Weighted average remaining term		10 years 3 months 18 days		10 years 3 months 18 days
Weighted average discount rate		5.20%		5.20%
Lease expense		$ 1,500,000	$ 700,000	$ 4,100,000	$ 1,800,000
Short-term lease costs		0	$ 0	300,000	$ 100,000
Right-of-use assets		35,553,000		35,553,000		$ 12,781,000
Operating lease, liabilities		51,700,000		51,700,000
Incentives receivable		10,785,000		10,785,000
Short-term portion of operating lease liability		$ 2,800,000		$ 2,800,000
Operating lease, liability, current, statement of financial position [extensible list]		us-gaap:OtherCurrentLiabilitiesMember		us-gaap:OtherCurrentLiabilitiesMember
Operating lease liabilities, noncurrent		$ 48,943,000		$ 48,943,000		$ 15,243,000
Incentives receivable, expected period				1 year
Operating lease Undiscounted amount		67,681,000		$ 67,681,000
Operating lease, lease not yet commenced, description				Total undiscounted future minimum lease payments do not include approximately $90.3 million and $5.3 million, respectively, related to the Company’s Brisbane lease and its additional space in Hayward, neither of which have yet commenced.
Deposits for letters of credit		3,000,000		$ 3,000,000
Hayward, California
Lessee Lease Description [Line Items]
Square feet of space leased | ft²	150,753
Operating lease commencement year				2022
Operating lease expiration date				Dec. 31, 2031
Operating lease Undiscounted amount		5,300,000		$ 5,300,000
Hayward, California | Executive Offices Research and Development and Business Operations
Lessee Lease Description [Line Items]
Square feet of space leased | ft²	14,460					136,293
Operating lease commencement year	2022
Operating lease expiration date	Dec. 31, 2031
Brisbane, California
Lessee Lease Description [Line Items]
Operating lease commencement period, description				fourth quarter of 2021
Operating lease expiration date				Dec. 31, 2031
Operating lease Undiscounted amount		$ 90,300,000		$ 90,300,000

Leases - Schedule of Future Min

Leases - Schedule of Future Minimum Lease Payments (Details) - USD ($) $ in Thousands	Sep. 30, 2021	Dec. 31, 2020
Leases [Abstract]
2021 (from October to December)	$ 1,159
2022	5,722
2023	5,908
2024	6,101
2025	6,302
Thereafter	42,489
Total undiscounted future minimum lease payments	67,681
Less: Imputed interest	(15,905)
Less: Tenant improvement allowance receivable	(10,785)
Total operating lease liabilities	40,991
Tenant improvement allowance expected to be received in less than one year, net of current portion of lease liability (included in prepaid expenses and other current assets)	7,952
Operating lease liabilities, noncurrent	$ 48,943	$ 15,243

License and Collaboration Agr_3

License and Collaboration Agreements - Summary of Revenues (Details) - Gilead and Taiho - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
License
License And Collaboration Agreements [Line Items]
Total revenues		$ 55,096		$ 55,096
Collaboration
License And Collaboration Agreements [Line Items]
Total revenues	$ 9,461	9,434	$ 28,383	12,934
Collaboration and License
License And Collaboration Agreements [Line Items]
Total revenues	$ 9,461	$ 64,530	$ 28,383	$ 68,030

License and Collaboration Agr_4

License and Collaboration Agreements - Summary of Revenues by Collaboration and by Category of Revenue (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
License And Collaboration Agreements [Line Items]
Total revenues	$ 9,461	$ 64,530	$ 28,383	$ 68,030
Gilead License To Zimberelimab
License And Collaboration Agreements [Line Items]
Total revenues		55,096		55,096
Gilead Access Rights
License And Collaboration Agreements [Line Items]
Total revenues	7,711	7,684	23,133	7,684
Taiho Collaboration Agreement
License And Collaboration Agreements [Line Items]
Total revenues	$ 1,750	$ 1,750	$ 5,250	$ 5,250

License and Collaboration Agr_5

License and Collaboration Agreements - Summary of Revenue Recognized as a Result of Changes in Deferred Revenue (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
License And Collaboration Agreements [Abstract]
Amounts included in deferred revenue at the beginning of the period	$ 9,461	$ 1,750	$ 28,383	$ 5,250

License and Collaboration Agr_6

License and Collaboration Agreements - Additional Information (Details) - USD ($)	Dec. 31, 2022	Jul. 13, 2020	Apr. 30, 2019	Feb. 28, 2021	Jan. 31, 2021	Sep. 30, 2017	Aug. 31, 2017	Sep. 30, 2021	Mar. 31, 2021	Sep. 30, 2020	Jun. 30, 2020	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Sep. 30, 2021	Sep. 30, 2021	Dec. 31, 2020
License And Collaboration Agreements [Line Items]
Issuance of common stock											$ 326,246,000
Gross proceeds												$ 220,235,000	$ 433,776,000
Cost sharing receivable, current								$ 871,000				871,000		$ 871,000				$ 871,000	$ 871,000	$ 1,049,000
Development expense								71,254,000		$ 51,801,000		206,412,000	110,636,000
Compensation expense recognized								14,585,000		6,002,000		40,713,000	13,934,000
Research and Development
License And Collaboration Agreements [Line Items]
Compensation expense recognized								7,949,000		3,075,000		$ 21,087,000	7,179,000
WuXi Biologics License Agreement
License And Collaboration Agreements [Line Items]
Clinical and regulatory milestones achieved														16,500,000
Range of tiered royalty payments on net sales												high single-digits to low teens
Development milestone expense								0				$ 10,000,000
WuXi Biologics License Agreement | Research and Development
License And Collaboration Agreements [Line Items]
Upfront cash payment														500,000
Sub-license fees incurred																			11,300,000
Upfront and milestone payments																			41,000,000
WuXi Biologics License Agreement | Maximum
License And Collaboration Agreements [Line Items]
Clinical, regulatory and commercialization milestone payments							$ 375,000,000
Abmuno License Agreement
License And Collaboration Agreements [Line Items]
Upfront and milestone payments												14,600,000
Development milestone expense								0		3,000,000		5,000,000	3,000,000
Clinical, regulatory and commercialization remaining milestone payments												93,000,000
Gilead Collaboration Agreement | Gilead
License And Collaboration Agreements [Line Items]
Upfront cash payment		$ 175,000,000										175,000,000
Collaboration term for current and future clinical programs		10 years
Contingent milestone payments receivable		$ 400,000,000
Additional collaboration term for programs entering clinical development prior to end of collaboration term		3 years
Option fee per program for all other programs entering clinical development to exercise option		$ 150,000,000
Present value of research and development information access rights payment related to year 2022		100,000,000
Premium on stock purchased		90,600,000
Initial transaction price		365,600,000
Option payment upon achievement of certain development milestones		250,000,000
Deferred revenue related to etrumadenant option								127,000,000				$ 127,000,000		127,000,000				127,000,000	127,000,000
Etrumadenant option initial term of agreement												4 years
Option payment upon achievement of certain development milestones		$ 275,000,000
Deferred revenue related to domvanalimab option								36,700,000				$ 36,700,000		36,700,000				36,700,000	36,700,000
Domvanalimab option recognized term												1 year
Current and future programs exclusive access period		10 years
Additional payment due at each of the fourth, sixth, and eighth anniversaries of the agreement		$ 100,000,000
Contingent milestone payment start period		2022
Contractual obligation for first payment		$ 100,000,000
Performance obligation period		4 years
Contractual obligation remaining amount not obligated to pay		$ 300,000,000
Deferred revenue related to research and development pipeline								98,600,000				$ 98,600,000		98,600,000				98,600,000	98,600,000
Future development and promotion costs contract liability								9,700,000				9,700,000		9,700,000				9,700,000	9,700,000
Revenue recognized from this performance obligation												0
Consultant and legal fees		7,300,000
Amortization expense								100,000				300,000
Cost sharing receivable								3,900,000				3,900,000		3,900,000				3,900,000	3,900,000
Clinical and regulatory milestones achieved												0
Gilead Collaboration Agreement | Gilead | Scenario Forecast
License And Collaboration Agreements [Line Items]
Consulting fees to third party exercises option	$ 4,500,000
Gilead Collaboration Agreement | Gilead | Prepaid Expenses and Other Current Assets
License And Collaboration Agreements [Line Items]
Cost sharing receivable, current								1,000,000				1,000,000		1,000,000				1,000,000	1,000,000
Gilead Collaboration Agreement | Gilead | Other Noncurrent Assets
License And Collaboration Agreements [Line Items]
Cost sharing receivable, noncurrent								2,900,000				2,900,000		$ 2,900,000				2,900,000	$ 2,900,000
Gilead Collaboration Agreement | Gilead | Minimum
License And Collaboration Agreements [Line Items]
Option fee per program for current clinical programs to exercise option		200,000,000
Gilead Collaboration Agreement | Gilead | Minimum | Scenario Forecast
License And Collaboration Agreements [Line Items]
Consulting fees to third party exercises option	2,000,000
Gilead Collaboration Agreement | Gilead | Maximum
License And Collaboration Agreements [Line Items]
Contingent milestone payments receivable		400,000,000
Option fee per program for current clinical programs to exercise option		275,000,000
Clinical and regulatory milestones achieved		500,000,000
Gilead Collaboration Agreement | Gilead | Maximum | Scenario Forecast
License And Collaboration Agreements [Line Items]
Consulting fees to third party exercises option	$ 4,500,000
Purchase Agreement
License And Collaboration Agreements [Line Items]
Direct offering cost		1,900,000
Purchase Agreement | Gilead
License And Collaboration Agreements [Line Items]
Issuance of common stock		$ 200,000,000		$ 220,400,000					$ 220,296,000	107,468,000
Issuance of common stock, shares		5,963,029		5,650,000	5,650,000
Shares issued, price per share		$ 33.54		$ 39	$ 39
Percentage of option to purchase maximum shares of common stock		35.00%
Period over common stock to be purchased		5 years
Percentage of premium purchase price of common stock		20.00%
Trailing days average closing price		5 days
Share Price		$ 33.54
Gross proceeds		$ 107,500,000			$ 220,400,000
Premium on stock purchased												$ 90,600,000
Taiho Agreement | Taiho Pharmaceutical Co., Ltd
License And Collaboration Agreements [Line Items]
Option period						5 years
Option ending period						2022-09
Non refundable and non creditable cash payments																	$ 35,000,000
Payment received for license agreement															$ 5,000,000	$ 5,000,000	$ 25,000,000
Range of royalties receivable on net sales												high single-digits to mid-teens
Royalties payable description												Royalties will be payable on a licensed product-by-licensed product and country-by-country basis during the period of time commencing on the first commercial sale of a licensed product in a country and ending upon the later of: (a) ten (10) years from the date of first commercial sale of such licensed product in such country; and (b) expiration of the last-to-expire valid claim of the Company’s patents covering the manufacture, use or sale or exploitation of such licensed product in such country (the Royalty Term).
Non-refundable, non-creditable upfront cash payments												$ 35,000,000
Estimated performance period												5 years
Clinical and regulatory milestones achieved												$ 0
Sales milestone or royalty revenue recognized												0
Taiho Agreement | Taiho Pharmaceutical Co., Ltd | Minimum
License And Collaboration Agreements [Line Items]
Payment for option exercise						$ 3,000,000
Taiho Agreement | Taiho Pharmaceutical Co., Ltd | Maximum
License And Collaboration Agreements [Line Items]
Contingent milestone payments receivable						145,000,000
Payment for option exercise						15,000,000
Additional clinical and regulatory milestone payments receivable						$ 130,000,000
Strata Agreement | Strata Oncology Inc
License And Collaboration Agreements [Line Items]
Development cost recorded within research and development expenses								700,000		300,000		1,800,000	1,200,000					4,500,000
Development cost reimbursed								100,000		$ 100,000		300,000	$ 200,000					900,000
Number of restricted shares of common stock issued			1,257,651
Fair value of restricted shares of common stock issued			$ 15,000,000
Strata Agreement | Strata Oncology Inc | Research and Development
License And Collaboration Agreements [Line Items]
Milestone payments																		$ 2,500,000
AstraZeneca Agreement
License And Collaboration Agreements [Line Items]
Development cost recorded within research and development expenses								300,000				600,000
WuXi CD-39 Agreement | WuXi Biologics License Agreement
License And Collaboration Agreements [Line Items]
Development milestone expense								$ 0				$ 0

Stockholders' Equity - Addition

Stockholders' Equity - Additional Information (Details) - USD ($) $ / shares in Units, $ in Thousands	Jul. 13, 2020	Feb. 28, 2021	Jan. 31, 2021	Jun. 30, 2020	Mar. 31, 2021	Sep. 30, 2020	Jun. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Class Of Stock [Line Items]
Net proceeds from public offering after deducting underwriting discounts, commissions and other offering expenses								$ 220,235	$ 433,776
Common stock share value							$ 326,246
Stock Purchase Agreement | Gilead
Class Of Stock [Line Items]
Common stock shares issued	5,963,029	5,650,000	5,650,000
Shares issued, price per share	$ 33.54	$ 39	$ 39
Net proceeds from public offering after deducting underwriting discounts, commissions and other offering expenses	$ 107,500		$ 220,400
Common stock share value	200,000	$ 220,400			$ 220,296	$ 107,468
Purchase price of common stock allocation to performance obligation	90,600
Deferred offering expenses	$ 1,900
May 2020 Public Offering
Class Of Stock [Line Items]
Common stock shares issued				12,650,000
Shares issued, price per share				$ 27.50			$ 27.50
Net proceeds from public offering after deducting underwriting discounts, commissions and other offering expenses				$ 326,200
Base Shares
Class Of Stock [Line Items]
Common stock shares issued				11,000,000
Underwriters Option Exercise
Class Of Stock [Line Items]
Common stock shares issued				1,650,000

Stock-Based Compensation - Summ

Stock-Based Compensation - Summary of Stock-Based Compensation Expense (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Total stock-based compensation	$ 14,585	$ 6,002	$ 40,713	$ 13,934
Research and Development
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Total stock-based compensation	7,949	3,075	21,087	7,179
General and Administrative
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Total stock-based compensation	$ 6,636	$ 2,927	$ 19,626	$ 6,755

Net Income (Loss) per Share - C

Net Income (Loss) per Share - Computation of Basic and Diluted Net Loss Per Share (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended						9 Months Ended
	Sep. 30, 2021	Jun. 30, 2021	Mar. 31, 2021	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Sep. 30, 2021	Sep. 30, 2020
Numerator:
Net loss	$ (77,975)	$ (75,970)	$ (72,593)	$ 1,822	$ (45,074)	$ (27,753)	$ (226,538)	$ (71,005)
Denominator:
Weighted-average common shares outstanding	71,286,685			64,132,283			70,296,187	53,452,007
Less: weighted-average common shares subject to vesting	(1,176,547)			(1,533,090)			(1,305,897)	(1,599,760)
Weighted-average common shares used to compute basic net income (loss) per share	70,110,138			62,599,193			68,990,290	51,852,247
Dilutive effect of stock options				2,538,926
Dilutive effect of ESPP				7,588
Weighted-average common shares used to compute diluted net income (loss) per share	70,110,138			65,145,707			68,990,290	51,852,247
Net income (loss) per share: basic	$ (1.11)			$ 0.03			$ (3.28)	$ (1.37)
Net income (loss) per share: diluted	$ (1.11)			$ 0.03			$ (3.28)	$ (1.37)

Net Income (Loss) per Share - S

Net Income (Loss) per Share - Summary of Outstanding Potentially Dilutive Securities Excluded from Computation of Diluted Net Loss per Share (Details) - shares	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of diluted net loss per share	14,191,837	3,442,953	14,191,837	10,073,646
Common Stock Options Issued and Outstanding
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of diluted net loss per share	12,625,226	1,518,386	12,625,226	7,841,220
Unvested Restricted Stock Units
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of diluted net loss per share	1,361,008	653,950	1,361,008	653,950
Employee Stock Purchase Plan Shares
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of diluted net loss per share	166,461	12,966	166,461	79,848
Unvested Early Exercised Common Stock Options
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of diluted net loss per share	39,142		39,142	240,977
Unvested Restricted Common Stock Issued as Part of Collaboration Agreement
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of diluted net loss per share		1,257,651		1,257,651

Commitments - Additional Inform

Commitments - Additional Information (Details) - USD ($) $ in Thousands	Sep. 30, 2021	Dec. 31, 2020	Sep. 30, 2020
Commitments [Line Items]
Restricted cash	$ 3,005	$ 203	$ 203
Standby Letters of Credit
Commitments [Line Items]
Long-term line of credit	3,000
Restricted cash	$ 3,000

Related Parties - Additional In

Related Parties - Additional Information (Details) - USD ($)	Jul. 13, 2020	Feb. 28, 2021	Jan. 31, 2021	May 31, 2020	Sep. 30, 2021	Mar. 31, 2021	Sep. 30, 2020	Jun. 30, 2020	Sep. 30, 2021	Sep. 30, 2020	Dec. 31, 2020
Related Party Transaction [Line Items]
Issuance of common stock								$ 326,246,000
Cost sharing receivable					$ 871,000				$ 871,000		$ 1,049,000
Long-term portion of revenue allocated					94,675,000				94,675,000		$ 122,830,000
Research and Development
Related Party Transaction [Line Items]
Reimbursed under cost-sharing provisions of arrangement					$ (756,000)		$ (2,971,000)		(6,856,000)	$ (2,971,000)
Gilead Collaboration Agreement | Gilead
Related Party Transaction [Line Items]
Revenue recognized									0
Upfront cash payment	$ 175,000,000								175,000,000
Premium on stock purchased	$ 90,600,000
Stock Purchase Agreement | Gilead
Related Party Transaction [Line Items]
Issuance of common stock, shares	5,963,029	5,650,000	5,650,000
Issuance of common stock	$ 200,000,000	$ 220,400,000				$ 220,296,000	$ 107,468,000
Premium on stock purchased									$ 90,600,000
Shares issued, price per share	$ 33.54	$ 39	$ 39
Gilead
Related Party Transaction [Line Items]
Percentage of outstanding common stock held					19.70%				19.70%
Number of shares issued				2,200,000
Value of common stock issued				$ 56,700,000
Cost sharing receivable					$ 600,000				$ 600,000
Deferred revenue					162,200,000				162,200,000
Long-term portion of revenue allocated					94,700,000				94,700,000
Future development and commercialization services contract liability					9,700,000				9,700,000
Gilead | Research and Development
Related Party Transaction [Line Items]
Reimbursed under cost-sharing provisions of arrangement					$ 800,000				$ 6,900,000
Gilead | Maximum
Related Party Transaction [Line Items]
Right to purchase additional outstanding voting common stock percentage					35.00%				35.00%
Gilead | Gilead Collaboration Agreement
Related Party Transaction [Line Items]
Revenue recognized					$ 7,700,000				$ 23,100,000
Reimbursement of milestone expense of cost sharing provisions									4,000,000
Unconstrained consideration to be received					$ 100,000,000				100,000,000
Gilead | Stock Purchase Agreement
Related Party Transaction [Line Items]
Issuance of common stock, shares	5,963,029	5,650,000
Issuance of common stock		$ 220,400,000							327,800,000
Funds received for purchase of common stock									200,000,000
Fair value of stock purchased									$ 109,400,000
Shares issued, price per share		$ 39

Subsequent Event (Additional In

Subsequent Event (Additional Information) (Details) - BVF Partners L.P. - BVF Agreement - Subsequent Event $ in Millions	3 Months Ended
	Dec. 31, 2021USD ($)
Subsequent Event [Line Items]
Cash received from counterparty	$ 5
Option to provide additional funding	10
Maximum
Subsequent Event [Line Items]
Payment to be made for discovery and development of compounds	$ 15