Erasca (ERAS) 10-Q 9 Nov 22 2022 Q3 Quarterly report Financial data

Document and Entity Information

Document and Entity Information - shares	9 Months Ended
	Sep. 30, 2022	Nov. 02, 2022
Cover [Abstract]
Document Type	10-Q
Amendment Flag	false
Document Period End Date	Sep. 30, 2022
Document Fiscal Year Focus	2022
Document Fiscal Period Focus	Q3
Entity Registrant Name	ERASCA, INC.
Entity Central Index Key	0001761918
Current Fiscal Year End Date	--12-31
Entity Filer Category	Non-accelerated Filer
Entity File Number	001-40602
Entity Incorporation, State or Country Code	DE
Entity Tax Identification Number	83-1217027
Entity Address, Address Line One	3115 Merryfield Row
Entity Address, Address Line Two	Suite 300
Entity Address, City or Town	San Diego
Entity Address, State or Province	CA
Entity Address, Postal Zip Code	92121
City Area Code	858
Local Phone Number	465-6511
Entity Current Reporting Status	Yes
Entity Small Business	true
Entity Emerging Growth Company	true
Entity Ex Transition Period	false
Entity Shell Company	false
Entity Interactive Data Current	Yes
Entity Common Stock, Shares Outstanding		122,361,616
Document Quarterly Report	true
Document Transition Report	false
Title of 12(b) Security	Common Stock, $0.0001 par value per share
Trading Symbol	ERAS
Security Exchange Name	NASDAQ

Condensed Consolidated Balance

Condensed Consolidated Balance Sheets (Unaudited) - USD ($)	Sep. 30, 2022	Dec. 31, 2021
Current assets:
Cash and cash equivalents	$ 219,260,000	$ 360,487,000
Short-term marketable securities	136,668,000	53,988,000
Prepaid expenses and other current assets	9,823,000	5,542,000
Total current assets	365,751,000	420,017,000
Long-term marketable securities	9,569,000	44,770,000
Property and equipment, net	24,875,000	15,954,000
Operating lease assets	41,051,000	17,356,000
Restricted cash	408,000	408,000
Other assets	4,775,000	2,910,000
Total assets	446,429,000	501,415,000
Current liabilities:
Accounts payable	4,319,000	4,677,000
Accrued expenses and other current liabilities	22,332,000	21,419,000
Operating lease liabilities	1,028,000	285,000
Total current liabilities	27,679,000	26,381,000
Operating lease liabilities, net of current portion	53,431,000	18,506,000
Total liabilities	81,110,000	44,887,000
Commitments and contingencies (Note 12)
Stockholders' equity:
Preferred stock, $0.0001 par value; 80,000,000 shares authorized as of September 30, 2022 and December 31, 2021; no shares issued and outstanding as of September 30, 2022 and December 31, 2021
Common stock, $0.0001 par value; 800,000,000 shares authorized as of September 30, 2022 and December 31, 2021; 122,306,969 and 121,382,547 shares issued at September 30, 2022 and December 31, 2021, respectively; 121,024,938 and 119,102,505 shares outstanding at September 30, 2022 and December 31, 2021, respectively	12,000	12,000
Additional paid-in capital	712,407,000	694,844,000
Accumulated other comprehensive loss	(1,379,000)	(162,000)
Accumulated deficit	(345,721,000)	(238,166,000)
Total stockholders' equity	365,319,000	456,528,000
Total liabilities and stockholders' equity	$ 446,429,000	$ 501,415,000

Condensed Consolidated Balanc_2

Condensed Consolidated Balance Sheets (Unaudited) (Parenthetical) - $ / shares	Sep. 30, 2022	Dec. 31, 2021
Preferred stock, par value	$ 0.0001	$ 0.0001
Preferred stock, shares authorized	80,000,000	80,000,000
Preferred stock, shares issued	0	0
Preferred stock, shares outstanding	0	0
Common stock, par value	$ 0.0001	$ 0.0001
Common stock, shares authorized	800,000,000	800,000,000
Common stock, shares issued	122,306,969	121,382,547
Common stock, shares outstanding	121,024,938	119,102,505

Condensed Consolidated Statemen

Condensed Consolidated Statements of Operations and Comprehensive Loss (Unaudited) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2022	Sep. 30, 2021	Sep. 30, 2022	Sep. 30, 2021
Operating expenses:
Research and development	$ 28,184	$ 19,951	$ 83,101	$ 49,794
In-process research and development		1,680	2,000	10,848
General and administrative	8,778	6,916	24,271	15,696
Contribution of common stock to Erasca Foundation		17,497		17,497
Total operating expenses	36,962	46,044	109,372	93,835
Loss from operations	(36,962)	(46,044)	(109,372)	(93,835)
Other income (expense)
Interest income	1,522	49	2,024	110
Other expense	(49)	(74)	(207)	(190)
Change in fair value of preferred stock purchase right liability				1,615
Total other income (expense), net	1,473	(25)	1,817	1,535
Net loss	$ (35,489)	$ (46,069)	$ (107,555)	$ (92,300)
Net loss per share, basic	$ (0.29)	$ (0.46)	$ (0.90)	$ (1.90)
Net loss per share, diluted	$ (0.29)	$ (0.46)	$ (0.90)	$ (1.90)
Weighted-average shares of common stock used in computing net loss per share, basic	120,798,322	99,127,286	120,166,023	48,584,029
Weighted-average shares of common stock used in computing net loss per share, diluted	120,798,322	99,127,286	120,166,023	48,584,029
Other comprehensive income (loss):
Unrealized (loss) gain on marketable securities, net	$ (156)	$ 1	$ (1,217)	$ (2)
Comprehensive loss	$ (35,645)	$ (46,068)	$ (108,772)	$ (92,302)

Condensed Consolidated Statem_2

Condensed Consolidated Statements of Convertible Preferred Stock and Stockholders' Equity (Deficit) (Unaudited) - USD ($) $ in Thousands	Total	Erasca Foundation	IPO	Convertible Preferred Stock	Common Stock	Common Stock Erasca Foundation	Common Stock IPO	Additional Paid-in Capital	Additional Paid-in Capital Erasca Foundation	Additional Paid-in Capital IPO	Accumulated Other Comprehensive Income (Loss)	Accumulated Deficit
Convertible preferred stock, beginning balance, shares at Dec. 31, 2020				69,584,682
Convertible preferred stock, beginning balance, value at Dec. 31, 2020				$ 221,405
Beginning balance, shares at Dec. 31, 2020					25,189,673
Beginning balance at Dec. 31, 2020	$ (113,984)				$ 3			$ 1,413			$ 2	$ (115,402)
Issuance of Series B-1 and B-2 convertible preferred stock for cash, shares				15,931,772
Issuance of Series B-1 and B-2 convertible preferred stock for cash				$ 119,393
Issuance of common stock in connection with asset acquisition, shares					500,000
Issuance of common stock in connection with asset acquisition	1,680							1,680
Exercise of stock options, shares					439,610
Exercise of stock options	94							94
Vesting of early exercised stock options	174							174
Stock-based compensation expense	795							795
Net loss	(18,017)											(18,017)
Unrealized loss on marketable securities, net	(1)										(1)
Convertible preferred stock, ending balance, shares at Mar. 31, 2021				85,516,454
Convertible preferred stock,ending balance, value at Mar. 31, 2021				$ 340,798
Ending balance, shares at Mar. 31, 2021					26,129,283
Ending balance at Mar. 31, 2021	(129,259)				$ 3			4,156			1	(133,419)
Convertible preferred stock, beginning balance, shares at Dec. 31, 2020				69,584,682
Convertible preferred stock, beginning balance, value at Dec. 31, 2020				$ 221,405
Beginning balance, shares at Dec. 31, 2020					25,189,673
Beginning balance at Dec. 31, 2020	(113,984)				$ 3			1,413			2	(115,402)
Net loss	(92,300)
Ending balance, shares at Sep. 30, 2021					121,250,375
Ending balance at Sep. 30, 2021	482,991				$ 12			690,681				(207,702)
Convertible preferred stock, beginning balance, shares at Mar. 31, 2021				85,516,454
Convertible preferred stock, beginning balance, value at Mar. 31, 2021				$ 340,798
Beginning balance, shares at Mar. 31, 2021					26,129,283
Beginning balance at Mar. 31, 2021	(129,259)				$ 3			4,156			1	(133,419)
Issuance of common stock in connection with license agreement, shares					944,945
Issuance of common stock in connection with license agreement	5,488							5,488
Exercise of stock options, shares					225,895
Exercise of stock options	180							180
Vesting of early exercised stock options	174							174
Stock-based compensation expense	1,636							1,636
Net loss	(28,214)											(28,214)
Unrealized loss on marketable securities, net	(2)										(2)
Convertible preferred stock, ending balance, shares at Jun. 30, 2021				85,516,454
Convertible preferred stock,ending balance, value at Jun. 30, 2021				$ 340,798
Ending balance, shares at Jun. 30, 2021					27,300,123
Ending balance at Jun. 30, 2021	(149,997)				$ 3			11,634			(1)	(161,633)
Temporary equity stock issued during period shares conversion of convertible securities, shares				(85,516,454)
Temporary equity stock issued during period value conversion of convertible securities				$ (340,798)
Conversion of convertible preferred stock into common stock upon initial public offering, shares					71,263,685
Conversion of convertible preferred stock into common stock upon initial public offering	340,798				$ 7			340,791
Issuance of common stock, net of discounts and issuance costs, Shares						1,093,557	21,562,500
Issuance of common stock, net of discounts and issuance costs		$ 17,497	$ 316,999				$ 2		$ 17,497	$ 316,997
Disgorgement of stockholder's short-swing profits	553							553
Exercise of stock options, shares					30,510
Exercise of stock options	21							21
Vesting of early exercised stock options	171							171
Stock-based compensation expense	3,017							3,017
Net loss	(46,069)											(46,069)
Unrealized loss on marketable securities, net	1										1
Ending balance, shares at Sep. 30, 2021					121,250,375
Ending balance at Sep. 30, 2021	$ 482,991				$ 12			690,681				(207,702)
Convertible preferred stock, beginning balance, shares at Dec. 31, 2021				0
Beginning balance, shares at Dec. 31, 2021	121,382,547				121,382,547
Beginning balance at Dec. 31, 2021	$ 456,528				$ 12			694,844			(162)	(238,166)
Exercise of stock options, shares					357,244
Exercise of stock options	460							460
Vesting of early exercised stock options	479							479
Repurchases of early exercised stock options and restricted stock, Shares					(6,945)
Stock-based compensation expense	4,442							4,442
Net loss	(36,458)											(36,458)
Unrealized loss on marketable securities, net	(789)										(789)
Ending balance, shares at Mar. 31, 2022					121,732,846
Ending balance at Mar. 31, 2022	$ 424,662				$ 12			700,225			(951)	(274,624)
Convertible preferred stock, beginning balance, shares at Dec. 31, 2021				0
Beginning balance, shares at Dec. 31, 2021	121,382,547				121,382,547
Beginning balance at Dec. 31, 2021	$ 456,528				$ 12			694,844			(162)	(238,166)
Net loss	$ (107,555)
Convertible preferred stock, ending balance, shares at Sep. 30, 2022				0
Ending balance, shares at Sep. 30, 2022	122,306,969				122,306,969
Ending balance at Sep. 30, 2022	$ 365,319				$ 12			712,407			(1,379)	(345,721)
Beginning balance, shares at Mar. 31, 2022					121,732,846
Beginning balance at Mar. 31, 2022	424,662				$ 12			700,225			(951)	(274,624)
Exercise of stock options, shares					179,985
Exercise of stock options	375							375
Issuance of common stock under the Employee Stock Purchase Plan, Shares					150,642
Issuance of common stock under the Employee Stock Purchase Plan	617							617
Vesting of early exercised stock options	238							238
Stock-based compensation expense	5,055							5,055
Net loss	(35,608)											(35,608)
Unrealized loss on marketable securities, net	(272)										(272)
Ending balance, shares at Jun. 30, 2022					122,063,473
Ending balance at Jun. 30, 2022	395,067				$ 12			706,510			(1,223)	(310,232)
Exercise of stock options, shares					243,496
Exercise of stock options	427							427
Vesting of early exercised stock options	238							238
Stock-based compensation expense	5,232							5,232
Net loss	(35,489)											(35,489)
Unrealized loss on marketable securities, net	$ (156)										(156)
Convertible preferred stock, ending balance, shares at Sep. 30, 2022				0
Ending balance, shares at Sep. 30, 2022	122,306,969				122,306,969
Ending balance at Sep. 30, 2022	$ 365,319				$ 12			$ 712,407			$ (1,379)	$ (345,721)

Condensed Consolidated Statem_3

Condensed Consolidated Statements of Convertible Preferred Stock and Stockholders' Deficit (Deficit) (Unaudited) (Parenthetical) - USD ($) $ in Thousands	3 Months Ended
	Sep. 30, 2021	Mar. 31, 2021
Common Stock
Discounts and offering costs	$ 28,001
Convertible Preferred Stock
Stock issuance costs		$ 95

Condensed Consolidated Statem_4

Condensed Consolidated Statements of Cash Flows (Unaudited) - USD ($)	9 Months Ended
	Sep. 30, 2022	Sep. 30, 2021
Cash flows from operating activities:
Net loss	$ (107,555,000)	$ (92,300,000)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation and amortization	1,708,000	509,000
Stock-based compensation expense	14,729,000	5,448,000
In-process research and development expenses	2,000,000	10,848,000
Issuance of common stock to Erasca Foundation		17,497,000
(Accretion) amortization on marketable securities, net	(169,000)	75,000
Change in fair value of preferred stock purchase right liability		(1,615,000)
Changes in operating assets and liabilities:
Prepaid expenses and other current and long-term assets	(4,512,000)	(5,592,000)
Accounts payable	1,540,000	409,000
Accrued expenses and other current liabilities	2,936,000	7,173,000
Operating lease assets and liabilities, net	12,431,000	430,000
Net cash used in operating activities	(76,892,000)	(57,118,000)
Cash flows from investing activities:
Purchases of marketable securities	(94,427,000)	(41,696,000)
Maturities of marketable securities	45,900,000	54,110,000
In-process research and development	(2,000,000)	(7,680,000)
Payment made for investment in equity securities	(2,000,000)
Purchases of property and equipment	(13,687,000)	(5,375,000)
Net cash used in investing activities	(66,214,000)	(641,000)
Cash flows from financing activities:
Proceeds from the issuance of common stock in initial public offering, net of discounts and issuance costs		316,999,000
Proceeds from the issuance of convertible preferred stock, net of issuance costs		119,393,000
Proceeds from the exercise of stock options, net of repurchases	1,262,000	1,345,000
Proceeds from issuance of common stock under the Employee Stock Purchase Plan	617,000
Proceeds from the disgorgement of stockholder's short-swing profits		553,000
Net cash provided by financing activities	1,879,000	438,290,000
Net (decrease) increase in cash, cash equivalents and restricted cash	(141,227,000)	380,531,000
Cash, cash equivalents and restricted cash at beginning of the period	360,895,000	65,688,000
Cash, cash equivalents and restricted cash at end of the period	219,668,000	446,219,000
Supplemental disclosure of noncash investing and financing activities:
Issuance of common stock to Erasca Foundation		17,497,000
Issuance of common stock in connection with asset acquisition		1,680,000
Issuance of common stock in connection with license agreement		5,488,000
Amounts accrued for purchases of property and equipment	841,000	1,882,000
Conversion of preferred stock to common stock upon initial public offering		340,798,000
Vesting of early exercised options	955,000	519,000
Operating lease assets obtained in exchange for lease obligation	22,704,000	17,498,000
Reduction in operating lease assets due to lease amendment	$ 3,361,000
Tenant improvement allowance included in operating lease liabilities		$ 16,774,000

Organization and Basis of Prese

Organization and Basis of Presentation	9 Months Ended
	Sep. 30, 2022
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Organization and Basis of Presentation	Note 1. Organization and basis of presentation Organization and nature of operations Erasca, Inc. (Erasca or the Company) is a clinical-stage precision oncology company singularly focused on discovering, developing, and commercializing therapies for RAS/MAPK pathway-driven cancers. The Company has assembled a wholly-owned or controlled RAS/MAPK pathway-focused pipeline including 11 disclosed modality-agnostic programs aligned with its three therapeutic strategies of: (i) targeting key upstream and downstream signaling nodes in the RAS/MAPK pathway; (ii) targeting RAS directly; and (iii) targeting escape routes that emerge in response to treatment. The Company was incorporated under the laws of the State of Delaware on July 2, 2018, as Erasca, Inc., and is headquartered in San Diego, California. In September 2020, the Company established a wholly-owned Australian subsidiary, Erasca Australia Pty Ltd (Erasca Australia), in order to conduct clinical activities in Australia for its development candidates. In November 2020, the Company entered into an agreement and plan of merger with Asana BioSciences, LLC (Asana) and ASN Product Development, Inc. (ASN) (the Asana Merger Agreement), pursuant to which ASN became the Company's wholly-owned subsidiary. In March 2021, the Company established a wholly-owned subsidiary, Erasca Ventures, LLC (Erasca Ventures), to make equity investments in early-stage biotechnology companies that are aligned with the Company’s mission and strategy. Since inception, the Company has devoted substantially all of its efforts and resources to organizing and staffing the Company, business planning, raising capital, identifying, acquiring and in-licensing the Company’s product candidates, establishing its intellectual property portfolio, conducting research, preclinical studies, and clinical trials, establishing arrangements with third parties for the manufacture of its product candidates and related raw materials, and providing general and administrative support for these operations. As of September 30, 2022, the Company had $ 355.9 million in cash, cash equivalents, and short-term marketable securities, and $ 9.6 million in long-term marketable securities. As of September 30, 2022, the Company had an accumulated deficit of $ 345.7 million. The Company has incurred significant operating losses and negative cash flows from operations. From its inception through September 30, 2022, the Company’s financial support has primarily been provided from the sale of its convertible preferred stock and the sale of its common stock in its initial public offering (IPO). As the Company continues its expansion, it expects to use its cash, cash equivalents, and short-term marketable securities to fund research and development, working capital, and other general corporate purposes. The Company does not expect to generate any revenues from product sales unless and until the Company successfully completes development and obtains regulatory approval for any of its product candidates, which will not be for at least the next several years, if ever. Accordingly, until such time as the Company can generate significant revenue from sales of its product candidates, if ever, the Company expects to finance its cash needs through equity offerings, debt financings, or other capital sources, including potential collaborations, licenses or other similar arrangements. However, the Company may not be able to secure additional financing or enter into such other arrangements in a timely manner or on favorable terms, if at all. The Company’s failure to raise capital or enter into such other arrangements when needed would have a negative impact on the Company’s financial condition and could force the Company to delay, limit, reduce or terminate its research and development programs or other operations, or grant rights to develop and market product candidates that the Company would otherwise prefer to develop and market itself. The Company believes its cash, cash equivalents, and short-term marketable securities as of September 30, 2022 will be sufficient for the Company to fund operations for at least one year from the issuance date of these condensed consolidated financial statements. Initial public offering On July 20, 2021, the Company completed its IPO in which the Company issued and sold 21,562,500 shares of its common stock, including the exercise in full by the underwriters of their option to purchase 2,812,500 shares of common stock, at a price to the public of $ 16.00 per share. Proceeds from the IPO, net of underwriting discounts and commissions of $ 24.2 million and offering costs of $ 3.8 million, were $ 317.0 million. In connection with the completion of the IPO, all outstanding shares of convertible preferred stock were converted into 71,263,685 shares of common stock. Reverse stock split On July 9, 2021, the Company effected a one-for- 1.2 reverse stock split of its issued and outstanding shares of common stock (the Reverse Stock Split). The par value and the number of authorized shares of the convertible preferred stock and common stock were not adjusted as a result of the Reverse Stock Split. All issued and outstanding common stock and the conversion prices and ratio of the convertible preferred stock have been retroactively adjusted to reflect this Reverse Stock Split for all periods presented. Basis of presentation The accompanying unaudited condensed consolidated financial statements have been prepared in accordance with US generally accepted accounting principles (US 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 notes required by US GAAP for complete financial statements. Any reference in these notes to applicable guidance is meant to refer to US GAAP as found in the Accounting Standards Codification (ASC) and Accounting Standards Updates (ASU) promulgated by the Financial Accounting Standards Board (FASB). The Company’s condensed consolidated financial statements include the accounts of the Company and its wholly-owned subsidiaries, Erasca Australia, ASN, and Erasca Ventures. All intercompany balances and transactions have been eliminated.

Summary of Significant Accounti

Summary of Significant Accounting Policies	9 Months Ended
	Sep. 30, 2022
Accounting Policies [Abstract]
Summary of Significant Accounting Policies	Note 2. Summary of significant accounting policies Use of estimates The preparation of the Company’s condensed consolidated financial statements in conformity with US GAAP requires the Company to make estimates and assumptions that impact the reported amounts of assets, liabilities, expenses, and the disclosure of contingent assets and liabilities in the condensed consolidated financial statements and accompanying notes. Accounting estimates and management judgments reflected in the condensed consolidated financial statements include, but are not limited to, the accrual of research and development expenses, fair value of common stock, preferred stock and freestanding instruments, stock-based compensation expense, and the incremental borrowing rate for determining the operating lease asset and liability. Management evaluates its estimates on an ongoing basis. Although estimates are based on the Company’s historical experience, knowledge of current events, and actions it may undertake in the future, actual results may ultimately materially differ from these estimates and assumptions. Unaudited interim financial information The accompanying condensed consolidated balance sheet as of September 30, 2022, the condensed consolidated statements of operations and comprehensive loss for the three and nine months ended September 30, 2022 and 2021, the condensed consolidated statements of convertible preferred stock and stockholders’ equity (deficit) for the three and nine months ended September 30, 2022 and 2021 and the condensed consolidated statements of cash flows for the nine months ended September 30, 2022 and 2021 are unaudited. The unaudited condensed consolidated interim financial statements have been prepared on the same basis as the audited annual consolidated financial statements and, in the opinion of management, reflect all adjustments, which include only normal recurring adjustments, necessary for the fair statement of the Company’s condensed consolidated financial position as of September 30, 2022 and the condensed consolidated results of its operations and cash flows for the three and nine months ended September 30, 2022 and 2021. The condensed consolidated financial data and other information disclosed in these notes related to the three and nine months ended September 30, 2022 and 2021 are unaudited. The condensed consolidated results for the three and nine months ended September 30, 2022 are not necessarily indicative of results to be expected for the year ending December 31, 2022 , any other interim periods, or any future year or period. These unaudited condensed consolidated financial statements should be read in conjunction with the Company's audited consolidated financial statements included in its Annual Report on Form 10-K for the year ended December 31, 2021 filed with the SEC on March 24, 2022. Concentration of credit risk and off-balance sheet risk Financial instruments which potentially subject the Company to significant concentration of credit risk consist of cash and cash equivalents and marketable securities. The Company maintains deposits in federally insured financial institutions in excess of federally insured limits. The Company has not experienced any losses in such accounts, and management believes that the Company is not exposed to significant credit risk due to the financial position of the depository institutions in which those deposits are held. The Company’s investment policy includes guidelines for the quality of the related institutions and financial instruments and defines allowable investments that the Company may invest in, which the Company believes minimizes the exposure to concentration of credit risk. Cash, cash equivalents and restricted cash Cash and cash equivalents include cash in readily available checking and savings accounts, money market funds, and US treasury securities. The Company considers all highly liquid investments with an original maturity of three months or less from the date of purchase to be cash equivalents. The Company had deposited cash of $ 408,000 as of September 30, 2022 and December 31, 2021 to secure a letter of credit in connection with the lease of the Company’s facilities (see Note 11). The Company has classified the restricted cash as a noncurrent asset on its condensed consolidated balance sheets. The following table provides a reconciliation of cash, cash equivalents and restricted cash reported within the condensed consolidated balance sheets that sum to the total of the same amounts shown in the condensed consolidated statements of cash flows (in thousands): September 30, 2022 2021 Cash and cash equivalents $ 219,260 $ 445,811 Restricted cash 408 408 Total cash, cash equivalents and restricted cash $ 219,668 $ 446,219 Marketable securities and investments The Company classifies all marketable securities as available-for-sale, as the sale of such securities may be required prior to maturity. Management determines the appropriate classification of its marketable securities at the time of purchase. Marketable securities with original maturities beyond three months at the date of purchase and which mature at, or less than 12 months from, the balance sheet date are classified as short-term marketable securities. Available-for-sale securities are carried at fair value, with the unrealized gains and losses reported as accumulated other comprehensive income (loss) until realized. The amortized cost of available-for-sale debt securities is adjusted for amortization of premiums and accretion of discounts to maturity. Such amortization and accretion are included in interest income. The Company regularly reviews all of its marketable securities for declines in fair value. The review includes the consideration of the cause of the impairment, including the creditworthiness of the security issuers, the number of securities in an unrealized loss position, the severity of the unrealized loss(es), whether the Company has the intent to sell the securities and whether it is more likely than not that the Company will be required to sell the securities before the recovery of their amortized cost basis. If the decline in fair value is due to credit-related factors, a loss is recognized in net income; whereas, if the decline in fair value is not due to credit-related factors, the loss is recorded in other comprehensive income (loss). Realized gains and losses on available-for-sale securities are included in other income or expense. The cost of securities sold is based on the specific identification method. Interest and dividends on securities classified as available-for-sale are included in interest income. Through its wholly-owned subsidiary, Erasca Ventures, the Company has also invested in equity securities of a company whose securities are not publicly traded and whose fair value is not readily available. This investment is recorded using cost minus impairment, plus or minus changes in its estimated fair value resulting from observable price changes in orderly transactions for the identical or a similar investment of the same issuer. Investments in equity securities without readily determinable fair values are assessed for potential impairment on a quarterly basis based on qualitative factors. This investment is included in other assets in the Company's condensed consolidated balance sheets. Fair value measurements Certain assets and liabilities are carried at fair value under US GAAP. Fair value is defined as an exit price, representing the amount that would be received to sell an asset or paid to transfer a liability in an orderly transaction between market participants. As such, fair value is a market-based measurement that should be determined based on assumptions that market participants would use in pricing an asset or liability. Financial assets and liabilities carried at fair value are classified and disclosed in one of the following three levels of the fair value hierarchy, of which the first two are considered observable and the last is considered unobservable: Level 1—Unadjusted quoted prices in active markets that are accessible at the measurement date for identical, unrestricted assets or liabilities. Level 2—Quoted prices for similar assets and liabilities in active markets, quoted prices in markets that are not active, or inputs which are observable, either directly or indirectly, for substantially the full term of the asset or liability. Level 3—Prices or valuation techniques that require inputs that are both significant to the fair value measurement and unobservable (i.e., supported by little or no market activity). Recently adopted accounting pronouncements In June 2016, the FASB issued ASU 2016-13, Financial Instruments—Credit Losses (Topic 326): Measurement of Credit Losses on Financial Instruments (ASU 2016-13) and also issued subsequent amendments to the initial guidance: ASU 2018-19, ASU 2019-04, ASU 2019-05, and ASU 2019-11. The standard requires that credit losses be reported using an expected losses model rather than the incurred losses model that is currently used, and it establishes additional disclosure requirements related to credit risks. For available-for-sale debt securities with expected credit losses, this standard now requires allowances to be recorded instead of reducing the amortized cost of the investment. This guidance was originally effective for fiscal years beginning after December 15, 2019, including interim periods within those fiscal years, and early adoption was permitted. In November 2019, the FASB subsequently issued ASU 2019-10, Financial Instruments—Credit Losses (Topic 326), Derivatives and Hedging (Topic 815), and Leases (Topic 842): Effective Dates, whereby the effective date of this standard for smaller reporting companies was deferred to fiscal years beginning after December 15, 2022, including interim periods within those fiscal years, and early adoption is still permitted. The Company adopted ASU 2016-13, and related updates, on a modified retrospective basis on January 1, 2022 , and the adoption had an immaterial impact on its condensed consolidated financial statements and related disclosures. In August 2020, the FASB issued ASU 2020-06, Debt: Debt with Conversion and Other Options (Subtopic 470-20) and Derivatives and Hedging—Contracts in Entity’s Own Equity (Subtopic 815-40) (ASU 2020-06), which simplifies the accounting for convertible instruments and contracts in an entity’s own equity. This guidance is effective for the Company in its annual reporting period beginning after December 15, 2023, including interim periods within that reporting period, with early adoption permitted only as of annual reporting periods beginning after December 15, 2020. The Company adopted ASU 2020-06 on a modified retrospective basis on January 1, 2022 , and the adoption had no impact on its condensed consolidated financial statements and related disclosures. In January 2020, the FASB issued ASU 2020-01, Clarifying the Interactions Between Topic 321, Topic 323, and Topic 815 (ASU 2020-01), which clarifies that an entity should consider observable transactions that require it to either apply or discontinue the equity method of accounting for the purposes of applying the measurement alternative in accordance with Topic 321 immediately before applying or upon discontinuing the equity method. In addition, ASU 2020-01 states that for the purpose of applying paragraph 815-10-15-141(a), an entity should not consider whether, upon the settlement of the forward contract or exercise of the purchased option, individually or with existing investments, the underlying securities would be accounted for under the equity method in Topic 323 or the fair value option in accordance with the financial instruments guidance in Topic 825. The Company adopted the provisions of ASU 2020-01 prospectively as of January 1, 2022 , and the adoption had no impact on its condensed consolidated financial statements and related disclosures. Recently issued accounting pronouncements not yet adopted From time to time, new accounting pronouncements are issued by the FASB or other standard setting bodies that the Company adopts as of the specified effective date. The Company qualifies as an “emerging growth company” as defined in the Jumpstart Our Business Startups Act of 2012 (JOBS Act) and has elected not to “opt out” of the extended transition related to complying with new or revised accounting standards, which means that when a standard is issued or revised and it has different application dates for public and nonpublic companies, the Company can adopt the new or revised standard at the time nonpublic companies adopt the new or revised standard and can do so until such time that the Company either (i) irrevocably elects to “opt out” of such extended transition period or (ii) no longer qualifies as an emerging growth company.

Fair Value Measurements

Fair Value Measurements	9 Months Ended
	Sep. 30, 2022
Fair Value Disclosures [Abstract]
Fair value measurements	Note 3. Fair value measurements The following tables summarize the Company’s financial assets measured at fair value on a recurring basis and their respective input levels based on the fair value hierarchy (in thousands): Fair value measurements as of September 30, 2022 using Quoted prices in Significant Significant active markets other unobservable September 30, for identical observable inputs 2022 assets (level 1) inputs (level 2) (level 3) Assets: Money market funds (1) $ 187,565 $ 187,565 $ — $ — US treasury securities (1) 9,953 9,953 — — US treasury securities (2) 106,078 106,078 — — Commercial paper (2) 28,619 — 28,619 — Corporate debt securities (2) 1,336 — 1,336 — Supranational debt security (2) 635 — 635 — US treasury securities (3) 9,569 9,569 — — Total fair value of assets $ 343,755 $ 313,165 $ 30,590 $ — (1) Included as cash and cash equivalents on the condensed consolidated balance sheets. (2) Included as short-term marketable securities on the condensed consolidated balance sheets. (3) Included as long-term marketable securities on the condensed consolidated balance sheets. Fair value measurements as of December 31, 2021 using Quoted prices in Significant Significant active markets other unobservable December 31, for identical observable inputs 2021 assets (level 1) inputs (level 2) (level 3) Assets: Money market funds (1) $ 351,625 $ 351,625 $ — $ — US treasury securities (2) 18,097 18,097 — — Corporate debt securities (2) 2,822 — 2,822 — Commercial paper (2) 31,566 — 31,566 — Supranational debt securities (2) 1,503 — 1,503 — US treasury securities (3) 44,770 44,770 — — Total fair value of assets $ 450,383 $ 414,492 $ 35,891 $ — (1) Included as cash and cash equivalents on the condensed consolidated balance sheets. (2) Included as short-term marketable securities on the condensed consolidated balance sheets. (3) Included as long-term marketable securities on the condensed consolidated balance sheets. The carrying amounts of the Company’s financial instruments, including cash, prepaid expenses and other current assets, accounts payable, and accrued expenses and other current liabilities, approximate fair value due to their short maturities. As of September 30, 2022 , the Company has recorded a $ 2.0 million equity investment in Affini-T Therapeutics, Inc. (Affini-T) at cost, subject to impairment in accordance with ASC 321, Investments—Equity Securities. None of the Company’s non-financial assets or liabilities are recorded at fair value on a non-recurring basis. No transfers between levels have occurred during the periods presented. Cash equivalents consist of money market funds and US treasury securities; short-term marketable securities consist of US treasury securities, commercial paper, corporate debt securities, and supranational debt securities; and long-term marketable securities consist of US treasury securities. The Company obtains pricing information from its investment manager and generally determines the fair value of marketable securities usi ng standard observable inputs, including reported trades, broker/dealer quotes, and bid and/or offers.

Marketable Securities

Marketable Securities	9 Months Ended
	Sep. 30, 2022
Investments, Debt and Equity Securities [Abstract]
Marketable Securities	Note 4. Marketable securities The following tables summarize the Company’s marketable securities accounted for as available-for-sale securities (in thousands, except years): September 30, 2022 Maturity Amortized Unrealized Unrealized Estimated (in years) cost gains losses fair value US treasury securities 1 or less $ 107,042 $ 7 $ ( 971 ) 106,078 Commercial paper 1 or less 28,619 — — 28,619 Corporate debt securities 1 or less 1,348 — ( 12 ) 1,336 Supranational debt security 1 or less 642 — ( 7 ) 635 US treasury securities 1 - 2 9,965 — ( 396 ) 9,569 Total $ 147,616 $ 7 $ ( 1,386 ) $ 146,237 December 31, 2021 Maturity Amortized Unrealized Unrealized Estimated (in years) cost gains losses fair value US treasury securities 1 or less $ 18,116 $ — $ ( 19 ) $ 18,097 Corporate debt securities 1 or less 2,824 — ( 2 ) 2,822 Commercial paper 1 or less 31,566 — — 31,566 Supranational debt securities 1 or less 1,503 — — 1,503 US treasury securities 1 - 2 44,911 — ( 141 ) 44,770 Total $ 98,920 $ — $ ( 162 ) $ 98,758 As of September 30, 2022, there were 30 available-for-sale securities with an estimated fair value of $ 88.0 million that were in gross unrealized loss positions. None had been in such position for greater than 12 months. As of December 31, 2021 , there were 19 available-for-sale securities with an estimated fair value of $ 68.0 million in gross unrealized loss positions. As of September 30, 2022 and December 31, 2021 , unrealized losses on available-for-sale securities are not attributed to credit risk. The Company believes that an allowance for credit losses is unnecessary because the unrealized losses on certain of the Company’s available-for-sale securities are due to market factors and interest rate increases. Additionally, the Company does not intend to sell the securities nor is it more likely than not that the Company will be required to sell the securities before recovery of their amortized cost basis.

Property and Equipment, Net

Property and Equipment, Net	9 Months Ended
	Sep. 30, 2022
Property, Plant and Equipment [Abstract]
Property and Equipment, Net	Note 5. Property and equipment, net Property and equipment, net consisted of the following (in thousands): September 30, December 31, 2022 2021 Construction in process $ — $ 11,228 Laboratory equipment 4,098 2,488 Furniture and fixtures 4,127 2,455 Leasehold improvements 18,315 795 Computer equipment and software 902 715 Property and equipment 27,442 17,681 Less accumulated depreciation and amortization ( 2,567 ) ( 1,727 ) Property and equipment, net $ 24,875 $ 15,954 Depreciation and amortization expense related to property and equipment was $ 771,000 and $ 1.7 million for the three and nine months ended September 30, 2022 , respectively, and $ 191,000 and $ 509,000 for the three and nine months ended September 30, 2021 , respectively.

Accrued Expenses and Other Curr

Accrued Expenses and Other Current Liabilities	9 Months Ended
	Sep. 30, 2022
Payables and Accruals [Abstract]
Accrued Expenses and Other Current Liabilities	Note 6. Accrued expenses and other current liabilities Accrued expenses and other current liabilities consisted of the following (in thousands): September 30, December 31, 2022 2021 Accrued research and development expenses $ 11,623 $ 9,122 Accrued compensation 7,104 7,275 Unvested early exercised stock option liability 1,929 2,884 Accrued property and equipment 273 1,272 Accrued professional services 1,048 383 Other accruals 355 483 Total $ 22,332 $ 21,419

Asset Acquisitions

Asset Acquisitions	9 Months Ended
	Sep. 30, 2022
Asset Acquisitions [Abstract]
Asset Acquisitions	Note 7. Asset acquisitions The following purchased assets were accounted for as asset acquisitions as substantially all of the fair value of the assets acquired were concentrated in a group of similar assets, and the acquired assets did not have outputs or employees. Because the assets had not yet received regulatory approval, the fair value attributable to these assets was recorded as in-process research and development expenses in the Company’s condensed consolidated statements of operations and comprehensive loss. Asana BioSciences, LLC In November 2020, the Company entered into the Asana Merger Agreement, pursuant to which ASN became its wholly-owned subsidiary. Asana and ASN had previously entered into a license agreement, which was amended and restated prior to the closing of the merger transaction (the Asana License Agreement, and collectively with the Asana Merger Agreement, the Asana Agreements), pursuant to which ASN acquired an exclusive, worldwide license to certain intellectual property rights relating to inhibitors of ERK1 and ERK2 owned or controlled by Asana to develop and commercialize ERAS-007 and certain other related compounds for all applications. Under the Asana Merger Agreement, the Company made an upfront payment of $ 20.0 million and issued 4,000,000 shares of its Series B-2 convertible preferred stock to Asana at a value of $ 7.50 per share or a total fair value of $ 30.0 million. In connection with the Company’s IPO, these shares of Series B-2 convertible preferred stock were converted into 3,333,333 shares of the Company’s common stock. The Company is obligated to make future development and regulatory milestone cash payments for a licensed product in an amount of up to $ 90.0 million. Additionally, upon achieving a development milestone related to demonstration of successful proof-of-concept in a specified clinical trial, the Company will also be required to issue 3,888,889 shares of its common stock to Asana. The Company is not obligated to pay royalties on the net sales of licensed products. The Company recorded IPR&D expense of $ 50.0 million during the year ended December 31, 2020 in connection with the asset acquisition. No IPR&D expense was recorded during the three and nine months ended September 30, 2022 and 2021. As of September 30, 2022 and December 31, 2021 , no milestones had been accrued as the underlying contingencies were not probable or estimable. Emerge Life Sciences, Pte. Ltd. In March 2021, the Company entered into an asset purchase agreement (ELS Purchase Agreement) with Emerge Life Sciences, Pte. Ltd. (ELS) wherein it purchased all rights, title, and interest (including all patent and other intellectual property rights) to EGFR antibodies directed against the EGFR domain II (EGFR-D2) and domain III (EGFR-D3) as well as a bispecific antibody where one arm is directed against EGFR-D2 and the other is directed against EGFR-D3 (the Antibodies). Under the terms of the ELS Purchase Agreement, the Company made an upfront payment of $ 2.0 million and issued to ELS 500,000 shares of the Company’s common stock at a value of $ 3.36 per share or a total fair value of $ 1.7 million. Under the ELS Purchase Agreement, ELS was committed to performing certain studies on the applicable antibodies to assist in development activities, the costs of which were mutually agreed upon and for which the Company was responsible. No IPR&D expense was recorded during the three and nine months ended September 30, 2022 . The Company recorded IPR&D expense of $ 0 and $ 3.7 million during the three and nine months ended September 30, 2021, respectively, in connection with the asset acquisition. Pursuant to the ELS Purchase Agreement, at any time between 12 months and 36 months after the effective date of the ELS Purchase Agreement, if the Company reasonably determines that none of the Antibodies should be taken into human clinical trials due to safety, efficacy or chemistry, manufacturing and controls (CMC) issues, then the Company has the option to select another antibody developed and solely owned by ELS that is not the subject of a license, collaboration, or option to a third party (the Option). If the Company elects to exercise the Option, then ELS will provide to the Company a list of all available antibodies that meet the aforementioned requirements, and the Company has the right to select one antibody from the list. Upon the Company’s selection of an antibody, ELS will assign to the Company all rights, title and interest to such antibody (including patent and other intellectual property rights) subject to any pre-existing obligations or restrictions. In the event that the Company wishes to have ELS conduct any studies on such optioned antibody, then after mutual agreement as to the scope of the studies, the Company will be responsible for the cost for such studies.

License Agreements

License Agreements	9 Months Ended
	Sep. 30, 2022
License Agreements [Abstract]
License Agreements	Note 8. License agreements NiKang Therapeutics, Inc. In February 2020, the Company entered into a license agreement (the NiKang Agreement) with NiKang Therapeutics, Inc. (NiKang) under which the Company was granted an exclusive, worldwide license to certain intellectual property rights owned or controlled by NiKang related to certain SHP2 inhibitors to develop and commercialize ERAS-601 and certain other related compounds for all applications. Under the NiKang Agreement, the Company made an upfront payment of $ 5.0 million to NiKang and reimbursed NiKang $ 0.4 million for certain initial manufacturing costs. In addition, the Company paid $ 7.0 million in April 2020 related to the publication of a US patent application that covered the composition of matter of ERAS-601. The Company is also obligated to pay (i) development and regulatory milestone payments in an aggregate amount of up to $ 16.0 million for the first licensed product, of which $ 4.0 million was paid in January 2021, and $ 12.0 million for a second licensed product, and (ii) commercial milestone payments in an aggregate amount of up to $ 157.0 million for the first licensed product and $ 151.0 million for a second licensed product. The Company is also obligated to: (i) pay tiered royalties on net sales of all licensed products in the mid-single digit percentages, subject to certain reductions; and (ii) equally split all net sublicensing revenues earned under sublicense agreements that the Company enters into with any third party before commencement of the first Phase I clinical trial for a licensed product. No IPR&D expense was recorded during the three and nine months ended September 30, 2022 and 2021. Katmai Pharmaceuticals, Inc. In March 2020, the Company entered into a license agreement (the Katmai Agreement) with Katmai Pharmaceuticals, Inc. (Katmai) under which the Company was granted an exclusive, worldwide, royalty-bearing license to certain patent rights and know-how controlled by Katmai related to the development of small molecule therapeutic and diagnostic products that modulate EGFR and enable the identification, diagnosis, selection, treatment, and/or monitoring of patients for neuro-oncological applications to develop, manufacture, use, and commercialize ERAS-801 and certain other related compounds in all fields of use. Under the Katmai Agreement, the Company made an upfront payment of $ 5.7 million and Katmai agreed to purchase shares of the Company’s Series B-1 convertible preferred stock and Series B-2 convertible preferred stock having an aggregate value of $ 2.7 million. In April 2020, Katmai purchased 356,000 shares of the Company’s Series B-1 convertible preferred stock for $ 1.8 million, and in January 2021, Katmai purchased 118,666 shares of the Company’s Series B-2 convertible preferred stock for $ 0.9 million. In connection with the Company's IPO, these shares of Series B-1 convertible preferred stock and Series B-2 convertible preferred stock were converted into 395,555 shares of the Company's common stock, in the aggregate. The Company is obligated to make future development and regulatory milestone payments of up to $ 24.0 million and commercial milestone payments of up to $ 101.0 million. The Company is also obligated to pay tiered royalties on net sales of each licensed product, at rates ranging from the mid- to high-single digit percentages, subject to a minimum annual royalty payment in the low six figures and certain permitted deductions. The Company recorded IPR&D expense of $ 0 and $ 2.0 million in connection with a development milestone payment made during the three and nine months ended September 30, 2022 , respectively. No IPR&D expense was recorded during the three and nine months ended September 30, 2021. LifeArc In April 2020, the Company entered into a license agreement with LifeArc (the LifeArc Agreement) under which the Company was granted an exclusive, worldwide license to certain materials, know-how, and intellectual property rights owned or controlled by LifeArc to develop, manufacture, use, and commercialize certain ULK inhibitors for all applications. Under the LifeArc Agreement, the Company was granted the license at no upfront cost and a period of three months after the effective date to conduct experiments on LifeArc’s compounds. Upon completion of this initial testing period, the Company had the option to continue the license and make a one-time license payment of $ 75,000 to LifeArc, which payment was subsequently made. The Company is obligated to make future development milestone payments for a licensed product of up to $ 11.0 million and sales milestone payments of up to $ 50.0 million. The Company is also obligated to pay royalties on net sales of all licensed products, in the low-single digit percentages, subject to certain reductions. No IPR&D expense was recorded during the three and nine months ended September 30, 2022 and 2021. University of California, San Francisco In December 2018, the Company entered into a license agreement, as amended (the UCSF Agreement), with The Regents of the University of California, San Francisco (the Regents), under which the Company was granted an exclusive, worldwide, royalty-bearing license under certain patent rights claiming novel covalent inhibitors of GTP- and GDP-bound RAS for the development and commercialization of products covered by such patent rights for the prevention, treatment and amelioration of human cancers and other diseases and conditions. The UCSF Agreement was amended in May 2021. Under the UCSF Agreement, the Company made upfront payments of $ 50,000 to the Regents and pays the Regents an annual license maintenance fee during the term of the license, but such fee will not be due on any anniversary if, on that date, the Company is making royalty payments to the Regents. The Company is obligated to make future development and regulatory milestone payments of up to $ 6.4 million and a sales milestone payment of $ 2.0 million for either of the first two licensed products. The Company is also obligated to pay royalties on net sales of all licensed products in the low-single digit percentages, subject to a minimum annual royalty payment in the low six figures, commencing on the year of the first sale of a licensed product and continuing, on a licensed product-by-licensed product and country-by-country basis, until there are no valid claims of the licensed patent rights covering the licensed product in such country. Additionally, the Company is obligated to pay tiered sublicensing fees, with the first two tiers in the low-to-mid teen percentages and the third tier at 30 %, on certain fees the Company receives from any sublicense that the Company grants, depending on the stage of development of a licensed product when such sublicense is granted. Prior to the execution of the amendment, the Company was obligated to make a cash payment to the Regents in the event of the Company’s initial public offering, a change of control transaction or a reverse merger (the Corporate Milestone). In the amendment, the amount of the cash payment payable upon the Company’s achievement of a Corporate Milestone was reduced and the Company agreed to issue the Regents 944,945 shares of the Company’s common stock, which issuance was not contingent upon the achievement of a Corporate Milestone and occurred in May 2021. In August 2021, following the achievement of the Corporate Milestone, the Company made a cash payment to the Regents in the amount of $ 1.7 million. No IPR&D expense was recorded during the three and nine months ended September 30, 2022 . The Company recorded IPR&D expense of $ 1.7 million and $ 7.2 million during the three and nine months ended September 30, 2021 related to the Corporate Milestone cash payment and issuance of 944,945 shares of the Company's common stock to the Regents, respectively.

Stockholders' Equity

Stockholders' Equity	9 Months Ended
	Sep. 30, 2022
Equity [Abstract]
Stockholders' Equity	Note 9. Stockholders’ equity In connection with the IPO, on July 20, 2021, the Company amended and restated its certificate of incorporation to, among other things, (i) increase the number of authorized shares of common stock from 156,000,000 to 800,000,000 and (ii) authorize 80,000,000 shares of undesignated preferred stock with a par value of $ 0.0001 per share. Convertible preferred stock Upon the closing of the IPO in July 2021, all shares of convertible preferred stock then outstanding converted into 71,263,685 shares of common stock. Prior to conversion, t he Company’s convertible preferred stock was classified outside of stockholders’ equity (deficit) on the consolidated balance sheets because the holders of such shares had liquidation rights in the event of a deemed liquidation that, in certain situations, were not solely within the control of the Company and would require the redemption of the then-outstanding convertible preferred stock. There were no shares of convertible preferred stock outstanding as of September 30, 2022 and December 31, 2021. Common stock The Company had 800,000,000 shares of its common stock authorized as of September 30, 2022 and December 31, 2021. The Company had 122,306,969 and 121,382,547 shares of its common stock issued and 121,024,938 and 119,102,505 s hares of common stock outstanding as of September 30, 2022 and December 31, 2021, respectively. In August 2022, the Company entered into an Open Market Sale Agreement (the Sale Agreement) with Jefferies LLC (the Agent), pursuant to which the Company may offer and sell shares of the Company’s common stock having an aggregate offering price of up to $ 200 million from time to time, in “at the market” offerings through the Agent. Sales of the shares of common stock, if any, will be made at prevailing market prices at the time of sale, or as otherwise agreed with the Agent. The Agent will receive a commission from the Company of up to 3.0 % of the gross proceeds of any shares of common stock sold under the Sale Agreement. There have been no shares of the Company's common stock sold under the Sale Agreement as of September 30, 2022. Shares of common stock subject to repurchase During 2018, the Company issued 1,458,332 shares of restricted stock for cash at a price of $ 0.0001 per share. The restricted stock vests 25 % one year from the vesting commencement date and monthly thereafter over a three-year period and is subject to repurchase by the Company in the event of any voluntary or involuntary termination of services to the Company prior to vesting. Any shares subject to repurchase by the Company are not deemed, for accounting purposes, to be outstanding until those shares vest. As of September 30, 2022 and December 31, 2021 , zero and 212,674 shares of common stock, respectively, were subject to repurchase by the Company. The unvested stock liability related to these awards is immaterial for all periods presented. For the three and nine months ended September 30, 2022 , 30,384 and 212,674 shares vested, respectively. For the three and nine months ended September 30, 2021 , 91,146 and 273,439 shares vested, respectively.

Stock-based Compensation

Stock-based Compensation	9 Months Ended
	Sep. 30, 2022
Share-Based Payment Arrangement [Abstract]
Stock-based Compensation	Note 10. Stock-based compensation In July 2021, the Company’s board of directors adopted and the Company’s stockholders approved the Company’s 2021 Incentive Award Plan (the 2021 Plan), which became effective in connection with the IPO. Upon the adoption of the 2021 Plan, the Company ceased making equity grants under its 2018 Equity Incentive Plan (the 2018 Plan). Under the 2021 Plan, the Company may grant stock options, restricted stock, restricted stock units, stock appreciation rights, and other stock or cash-based awards to individuals who are then employees, officers, directors or non-entity consultants of the Company. A total of 15,150,000 shares of common stock were initially reserved for issuance under the 2021 Plan. In addition, the number of shares of common stock available for issuance under the 2021 Plan may be increased annually on the first day of each calendar year during the term of the 2021 Plan, beginning in 2022, by an amount equal to the lesser of (i) 5 % of the shares of common stock outstanding on the final day of the immediately preceding calendar year or (ii) such smaller number of shares as determined by the Company’s board of directors or an authorized committee of the board of directors. As of September 30, 2022, there were 16,170,804 stock-based awards available for future grant under the 2021 Plan. Subsequent to July 2021, no further awards will be granted under the 2018 Plan and all future stock-based awards will be granted under the 2021 Plan. To the extent outstanding options or restricted stock granted under the 2018 Plan are cancelled, forfeited, repurchased, or otherwise terminated without being exercised or becoming vested, and would otherwise have been returned to the share reserve under the 2018 Plan, the number of shares underlying such awards will be available for future grant under the 2021 Plan. Options granted are exercisable at various dates as determined upon grant and will expire no more than ten years from their date of grant. Stock options generally vest over a four-year term. The exercise price of each option shall be determined by the Company’s board of directors based on the estimated fair value of the Company’s stock on the date of the option grant. The exercise price shall not be less than 100 % of the fair market value of the Company’s common stock at the time the option is granted. For holders of more than 10% of the Company’s total combined voting power of all classes of stock, incentive stock options may not be granted at less than 110 % of the fair market value of the Company’s common stock on the date of grant and for a term that exceeds five years . Early exercise is permitted for certain grants under the 2018 Plan. Stock options A summary of the Company’s stock option activity under the 2021 Plan and 2018 Plan is as follows (in thousands, except share and per share data and years): Weighted- Weighted- average remaining Aggregate average contractual intrinsic Shares exercise price term (years) value Outstanding at December 31, 2021 13,818,212 $ 3.87 8.82 $ 163,264 Granted 5,732,046 10.37 Exercised ( 780,725 ) 1.62 Canceled ( 1,127,348 ) 5.57 Outstanding at September 30, 2022 17,642,185 $ 5.74 8.42 $ 54,708 Options exercisable at September 30, 2022 6,537,157 $ 3.80 7.83 $ 29,165 The weighted-average grant date fair value of options granted for the three and nine months ended September 30, 2022 was $ 4.91 and $ 7.50 , respectively, and for the three and nine months ended September 30, 2021 was $ 12.29 and $ 3.96 , respectively. As of September 30, 2022, the unrecognized compensation cost related to unvested stock option grants was $ 57.0 million and is expected to be recognized as expense over approximately 2.59 years. The intrinsic value of the options exercised for the three and nine months ended September 30, 2022 was $ 1.5 million and $ 5.9 million, respectively. The intrinsic value of the options exercised for the three and nine months ended September 30, 2021 was $ 663,000 and $ 2.5 million, respectively. Prior to the Company's IPO, certain individuals were granted the ability to early exercise their stock options. The shares of common stock issued from the early exercise of unvested stock options are restricted and continue to vest in accordance with the original vesting schedule. The Company has the option to repurchase any unvested shares at the original purchase price upon any voluntary or involuntary termination. The shares purchased by the employees and non-employees pursuant to the early exercise of stock options are not deemed, for accounting purposes, to be outstanding until those shares vest. The cash received in exchange for exercised and unvested shares related to stock options granted is recorded as a liability for the early exercise of stock options on the accompanying condensed consolidated balance sheets and will be transferred into common stock and additional paid-in capital as the shares vest. As of September 30, 2022 and December 31, 2021, there were 1,282,031 shares and 1,854,427 shares subject to repurchase by the Company, respectively. As of September 30, 2022 and December 31, 2021, the Company recorded $ 1.9 million and $ 2.9 million of liabilities associated with shares issued with repurchase rights, respectively, which is recorded in accrued expenses and other current liabilities. The assumptions used in the Black-Scholes option pricing model to determine the fair value of the employee and nonemployee stock option grants were as follows: Three Months Ended September 30, Nine Months Ended September 30, 2022 2021 2022 2021 Risk-free interest rate 2.65 %- 3.38 % 0.91 %- 0.97 % 1.46 %- 3.38 % 0.59 %- 1.09 % Expected volatility 85.76 %- 86.34 % 81.93 %- 84.98 % 85.51 %- 87.11 % 81.93 %- 84.98 % Expected term (in years) 6.03 - 6.08 6.08 5.50 - 6.08 6.08 Expected dividend yield - -% - -% - -% - -% Employee stock purchase plan In July 2021, the Company’s board of directors adopted and the Company’s stockholders approved the ESPP, which became effective in connection with the IPO. The ESPP permits participants to contribute up to a specified percentage of their eligible compensation during a series of offering periods of 24 months , each comprised of four six-month purchase periods, to purchase the Company’s common stock. The purchase price of the shares will be 85 % of the fair market value of the Company’s common stock on the first day of trading of the applicable offering period or on the applicable purchase date, whichever is lower. A total of 1,260,000 shares of common stock was initially reserved for issuance under the ESPP. In addition, the number of shares of common stock available for issuance under the ESPP may be increased annually on the first day of each calendar year during the term of the ESPP, beginning in 2022, by an amount equal to the lesser of (i) 1% of the shares of common stock outstanding on the final day of the immediately preceding calendar year or (ii) such smaller number of shares as determined by the Company’s board of directors or an authorized committee of the board of directors. The Company recognized stock-based compensation expense related to the ESPP of $ 166,000 and $ 834,000 during the three and nine months ended September 30, 2022, respectively, and $ 278,000 during the three and nine months ended September 30, 2021. As of September 30, 2022, the unrecognized compensation cost related to the ESPP was $ 3.4 million and is expected to be recognized as expense over approximately 1.70 years. As of September 30, 2022 and December 31, 2021, $ 261,000 and $ 102,000 h as been withheld on behalf of employees for future purchase under the ESPP, respectively, and is included in accrued expenses and other current liabilities on the condensed consolidated balance sheets. The Company issued and sold zero and 150,642 shares under the ESPP during the three and nine months ended September 30, 2022 . No shares were issued and sold under the ESPP during the three and nine months ended September 30, 2021. The assumptions used in the Black-Scholes option pricing model to determine the fair value of the stock to be purchased under the ESPP were as follows: Three Months Ended September 30, Nine Months Ended September 30, 2022 (1) 2021 2022 2021 Risk-free interest rate --% 0.05 %- 0.19 % 2.24 %- 3.14 % 0.05 %- 0.19 % Expected volatility --% 70.99 %- 88.50 % 84.74 %- 87.89 % 70.99 %- 88.50 % Expected term (in years) -- 0.39 - 1.89 0.50 - 1.99 0.39 - 1.89 Expected dividend yield --% - -% - -% - -% (1) No grant was made under the ESPP during the three months ended September 30, 2022. Restricted stock The Company granted 1,795,827 shares of its restricted stock in 2018, which vest 25 % one year from the vesting commencement date and monthly thereafter over a three-year period. The weighted-average grant date fair value of restricted stock granted in 2018 was $ 0 . No shares of restricted stock were granted during the three and nine months ended September 30, 2022 and 2021. The restricted stock shares are subject to forfeiture upon the stockholders’ termination of employment or service to the Company. Any shares subject to forfeiture are not deemed, for accounting purposes, to be outstanding until those shares vest. As such, the Company recognizes the measurement date fair value of the restricted stock over the vesting period as compensation expense. As of September 30, 2022 and December 31, 2021 , zero and 212,941 shares of common stock, respectively, were subject to forfeiture. The summary of the Company’s restricted stock activity during the nine months ended September 30, 2022 is as follows: Number of Weighted- restricted average stock shares grant date outstanding fair value Nonvested at December 31, 2021 212,941 $ 0.001 Vested ( 205,996 ) 0.001 Forfeited ( 6,945 ) 0.001 Nonvested at September 30, 2022 - $ 0.001 At September 30, 2022 , the total unrecognized compensation related to unvested restricted stock awards granted was $ 0 . Stock-based compensation expense The allocation of stock-based compensation for all stock awards was as follows (in thousands): Three Months Ended September 30, Nine Months Ended September 30, 2022 2021 2022 2021 Research and development $ 2,872 $ 1,665 $ 8,607 $ 3,080 General and administrative 2,360 1,352 6,122 2,368 Total $ 5,232 $ 3,017 $ 14,729 $ 5,448 Common stock reserved for future issuance Common stock reserved for future issuance consisted of the following as of September 30, 2022 and December 31, 2021: September 30, December 31, 2022 2021 Stock options issued and outstanding 17,642,185 13,818,212 Awards available for future grant 16,170,804 14,699,430 Shares available for purchase under the ESPP 1,017,371 1,168,013 Total 34,830,360 29,685,655

Leases

Leases	9 Months Ended
	Sep. 30, 2022
Leases [Abstract]
Leases	Note 11. Leases Operating leases The Company has facility leases for office space under non-cancellable and cancelable operating leases with various expiration dates through 2032 and equipment under a non-cancellable operating lease with a term expiring in 2026 . Operating lease cost was approximatel y $ 2.6 million and $ 5.1 million, including variable lease costs of $ 701,000 and $ 1.1 million, and short-term lease costs of $ 24,000 and $ 86,000 , durin g the three and nine months ended September 30, 2022 , respectively. Operating lease cost was approximately $ 905,000 and $ 1.6 million, including variable lease costs of $ 96,000 and $ 324,000 , and short-term lease costs of $ 30,000 and $ 89,000 , during the three and nine months ended September 30, 2021, respectively. The Company paid $ 585,000 and $ 803,000 in ca sh for operating leases that were included in the operating activities section of the condensed consolidated statements of cash flows for the nine months ended September 30, 2022 and 2021, respectively. The weighted-average remaining lease term and the weighted-average discount rate of the Company’s operating leases were 9.50 years and 8.97 % at September 30, 2022 , respectively. The weighted-average remaining lease term and the weighted-average discount rate of the Company’s operating leases was 9.86 years and 6.9 % at December 31, 2021, respectively. The weighted-average remaining lease term does not include any renewal options at the election of the Company. The Company’s lease agreements do not contain any material residual value guarantees or material restrictive covenants. Facility leases In 2018, the Company entered into a lease agreement for approximately 11,000 square feet of office space in San Diego, California which was subsequently amended resulting in a total of 16,153 square feet of office space leased (the 2018 Lease). The amended space was accounted for as a separate lease. The 2018 Lease was again modified in November 2021 to amend the termination date from May 2024 to April 2022 . The Company remeasured the associated lease liability using the incremental borrowing rate at the date of the second amendment selected on the basis of the remaining lease term and remaining lease payments and adjusted the operating lease asset accordingly, resulting in a $ 539,000 gain on remeasurement, which was recorded as other income (expense), net in the consolidated statements of operations and comprehensive loss. The 2018 Lease was again modified in April 2022 to amend the termination date from April 2022 to May 2022 . The Company’s lea se payments consisted primarily of fixed rental payments for the right to use the underlying leased assets over the lease term. The Company was responsible for operating expenses over base operating expenses as defined in the original lease agreement. In September 2020, the Company entered into a lease agreement for 59,407 square feet of laboratory and office space in San Diego, California, which represented a portion of a new facility that was under construction and which was subsequently amended in March 2021 to expand the rented premises by 18,421 square feet (the 2020 Lease). The construction and design of the asset was the primary responsibility of the lessor. The Company was involved in certain aspects of construction and design for certain interior features and leasehold improvements that is beneficial to the Company to better suit its business needs and intended purpose of the space. The lease is accounted for as an operating lease and commenced in August 2021 . In April 2022, the 2020 Lease was modified to amend the rent commencement date from February 2022 to May 2022 . The 2020 Lease, as amended, has an initial term of 10.75 years and includes aggregate monthly payments to the lessor of approximately $ 51.6 million beginning in May 2023 with a rent escalation clause, and a tenant improvement allowance of approximately $ 16.8 million. The 2020 Lease is cancellable at the Company’s request after the 84 th month with 12 months written notice and a lump-sum cancellation payment of $ 2.5 million. As discussed in Note 2, the Company provided a letter of credit to the lessor for $ 408,000 , which expires October 31, 2031 . In December 2021, the Company entered into a lease agreement for 29,542 square feet of office and laboratory space in South San Francisco, California. The lease is accounted for as an operating lease with the associated operating lease assets and liabilities recorded upon commencement, which occurred in July 2022 . T he non-cancellable operating lease has an initial term of 124 months with an option to extend the lease term by 5 years at the then current market rates and includes aggregate monthly payments to the lessor of approximately $ 34.4 million beginning in November 2022 with a rent escalation clause and a tenant improvement allowance of approximately $ 8.2 million. The construction and design of the tenant improvements is the primary responsibility of the lessor. While the Company was involved in certain aspects of construction and design for certain interior features and leasehold improvements that is beneficial to the Company to better suit its business needs and intended purpose of the space, all construction was handled directly by the landlord. The Company was not deemed to be the accounting owner of the tenant improvements prior to or after the construction period. All payments made by the Company for landlord-owned tenant improvements were recorded as prepaid rent on the condensed consolidated balance sheets prior to lease commencement. In February 2022, the expected project costs exceeded the tenant improvement allowances by $ 5.1 million, which was paid directly to the landlord by the Company and was recorded as prepaid rent in the condensed consolidated balance sheets and as a cash outflow from operating activities in the condensed consolidated statements of cash flows. The Company paid a security deposit of $ 874,000 in December 2021 that was recorded as other assets in the condensed consolidated balance sheets. Future minimum lease payments under the operating leases with initial lease terms in excess of one year as of September 30, 2022 are as follows (in thousands): Year ending December 31, 2022 (remaining three months) $ 640 2023 6,858 2024 8,752 2025 9,024 2026 9,170 Thereafter 53,574 Total lease payments $ 88,018 Less: Amount representing interest ( 31,026 ) Less: Tenant improvement allowance receivable ( 2,533 ) Operating lease liabilities $ 54,459

Commitments and Contingencies

Commitments and Contingencies	9 Months Ended
	Sep. 30, 2022
Commitments and Contingencies Disclosure [Abstract]
Commitments and Contingencies	Note 12. Commitments and contingencies Liabilities for loss contingencies arising from claims, assessments, litigation, fines, penalties and other sources are recorded when it is probable that a liability has been incurred and the amount can be reasonably estimated. There are no matters currently outstanding for which any such liabilities have been accrued.

Income Taxes

Income Taxes	9 Months Ended
	Sep. 30, 2022
Income Tax Disclosure [Abstract]
Income Taxes	Note 13. Income taxes No provision for federal, state or foreign income taxes has been recorded for the three and nine months ended September 30, 2 0 22 and 2 0 21 . The Company has incurred net operating losses for all the periods presented and has not reflected any benefit of such net operating loss carryforwards in the accompanying condensed consolidated financial statements due to uncertainty around utilizing these tax attributes within their respective carryforward periods. The Company has recorded a full valuation allowance against all of its deferred tax assets as it is not more likely than not that such assets will be realized in the near future. The Company’s policy is to recognize interest expense and penalties related to income tax matters as tax expense. For the three and nine months ended September 30, 2022 and 2021 , the Company has no t recognized any interest or penalties related to income taxes. In March and December 2020, in response to the COVID-19 pandemic, the Coronavirus Aid, Relief and Economic Security Act (the CARES Act) was passed and provided for a refundable employee retention credit, which can be used to offset payroll tax liabilities. On March 11, 2021, President Biden signed the American Rescue Plan Act, which includes several provisions previously enacted under the CARES Act, such as measures that extended and expanded the employee retention credit through December 31, 2021. However, on November 15, 2021, President Biden signed into law the Infrastructure Investment and Jobs Act, which terminated the employee retention credit for wages paid in the fourth calendar quarter of 2021 for employers that are not recovery startup businesses. Pursuant to the employee retention credit, eligible employers could receive a 50 % or 70 % credit on qualified wages against their employment taxes each quarter during the eligible periods in 2020 and 2021, respectively, with any excess credits eligible for refunds. During the three months ended September 30, 2022, the Company recorded an employee retention credit of $ 2.2 million upon completion of an analysis providing reasonable assurance that the Company met the conditions set forth in the CARES Act and it was reasonably assured that the Company will receive the employee retention credit. The employee retention credit is recorded in research and development expenses and general and administrative expenses in the manner in which the qualified wages and related costs were classified.

Net Loss Per Share

Net Loss Per Share	9 Months Ended
	Sep. 30, 2022
Earnings Per Share [Abstract]
Net Loss Per Share	Note 14. Net loss per share The following table summarizes the computation of basic and diluted net loss per share of the Company (in thousands, except share and per share data): Three Months Ended September 30, Nine Months Ended September 30, 2022 2021 2022 2021 Net loss $ ( 35,489 ) $ ( 46,069 ) $ ( 107,555 ) $ ( 92,300 ) Weighted-average shares of common stock used in computing net loss per share, basic and diluted 120,798,322 99,127,286 120,166,023 48,584,029 Net loss per share, basic and diluted $ ( 0.29 ) $ ( 0.46 ) $ ( 0.90 ) $ ( 1.90 ) The Company’s potentially dilutive securities, which include options to purchase common stock, shares purchasable under the ESPP and common stock subject to repurchase related to unvested restricted stock and options early exercised, have been excluded from the computation of diluted net loss per share as the effect would be to reduce the net loss per share. Therefore, the weighted-average number of common shares outstanding used to calculate both basic and diluted net loss per share is the same. The Company excluded the following potential common shares, presented as amounts outstanding at each period end, from the computation of diluted net loss per share for the periods indicated because including them would have had an anti-dilutive effect: September 30, September 30, 2022 2021 Options to purchase common stock 17,642,185 13,782,167 Restricted stock subject to future vesting — 602,959 Options early exercised subject to future vesting 1,282,031 2,001,823 Estimated shares purchasable under the ESPP 876,347 299,092 Total potentially dilutive shares 19,800,563 16,686,041

COVID-19 pandemic

COVID-19 pandemic	9 Months Ended
	Sep. 30, 2022
Risks and Uncertainties [Abstract]
COVID-19 Pandemic	Note 15. COVID-19 pandemic The current COVID-19 pandemic, which is impacting worldwide economic activity, poses the risk that the Company or its employees, contractors, suppliers, and other partners may be prevented from conducting business activities for an indefinite period of time, including due to shutdowns that may be requested or mandated by governmental authorities. During the three and nine months ended September 30, 2022 and 2021, the Company has not experienced significant impact from the pandemic. The extent to which the COVID-19 pandemic will impact the Company’s business will depend on future developments that are highly uncertain and cannot be predicted at this time.

Related Party Transactions

Related Party Transactions	9 Months Ended
	Sep. 30, 2022
Related Party Transactions [Abstract]
Related Party Transactions	Note 16. Related party transactions Erasca Foundation In May 2021, the Company established the Erasca Foundation to provide support such as direct research grants, hardship grants, patient advocacy, patient education in underserved populations, and funding for other initiatives to positively impact society that align with the Company’s mission. The Company's chief executive officer and certain board members serve as directors of the Erasca Foundation and the Company's chief executive officer, chief financial officer, and general counsel are also officers of the Erasca Foundation. In July 2021, the Company issued 1,093,557 shares of its common stock to the Erasca Foundation as a contribution and recorded $ 17.5 million to such contribution of common stock to the Erasca Foundation in the Company's condensed consolidated statements of operations and comprehensive loss. In December 2021, the Company loaned the Erasca Foundation $ 100,000 in exchange for a non-interest bearing promissory note that matures one year following the date of the note. As of September 30, 2022 , $ 100,000 is recorded as a receivable in prepaid expenses and other current assets in the condensed consolidated balance sheet. Affini-T Therapeutics, Inc. The Company holds a $ 2.0 million equity investment in Affini-T. One of the Company’s board members is also a member of the board of Affini-T.

Summary of Significant Accoun_2

Summary of Significant Accounting Policies (Policies)	9 Months Ended
	Sep. 30, 2022
Accounting Policies [Abstract]
Use of Estimates	Use of estimates The preparation of the Company’s condensed consolidated financial statements in conformity with US GAAP requires the Company to make estimates and assumptions that impact the reported amounts of assets, liabilities, expenses, and the disclosure of contingent assets and liabilities in the condensed consolidated financial statements and accompanying notes. Accounting estimates and management judgments reflected in the condensed consolidated financial statements include, but are not limited to, the accrual of research and development expenses, fair value of common stock, preferred stock and freestanding instruments, stock-based compensation expense, and the incremental borrowing rate for determining the operating lease asset and liability. Management evaluates its estimates on an ongoing basis. Although estimates are based on the Company’s historical experience, knowledge of current events, and actions it may undertake in the future, actual results may ultimately materially differ from these estimates and assumptions.
Unaudited Interim Financial Information	Unaudited interim financial information The accompanying condensed consolidated balance sheet as of September 30, 2022, the condensed consolidated statements of operations and comprehensive loss for the three and nine months ended September 30, 2022 and 2021, the condensed consolidated statements of convertible preferred stock and stockholders’ equity (deficit) for the three and nine months ended September 30, 2022 and 2021 and the condensed consolidated statements of cash flows for the nine months ended September 30, 2022 and 2021 are unaudited. The unaudited condensed consolidated interim financial statements have been prepared on the same basis as the audited annual consolidated financial statements and, in the opinion of management, reflect all adjustments, which include only normal recurring adjustments, necessary for the fair statement of the Company’s condensed consolidated financial position as of September 30, 2022 and the condensed consolidated results of its operations and cash flows for the three and nine months ended September 30, 2022 and 2021. The condensed consolidated financial data and other information disclosed in these notes related to the three and nine months ended September 30, 2022 and 2021 are unaudited. The condensed consolidated results for the three and nine months ended September 30, 2022 are not necessarily indicative of results to be expected for the year ending December 31, 2022 , any other interim periods, or any future year or period. These unaudited condensed consolidated financial statements should be read in conjunction with the Company's audited consolidated financial statements included in its Annual Report on Form 10-K for the year ended December 31, 2021 filed with the SEC on March 24, 2022.
Concentration of Credit Risk and Off-Balance Sheet Risk	Concentration of credit risk and off-balance sheet risk Financial instruments which potentially subject the Company to significant concentration of credit risk consist of cash and cash equivalents and marketable securities. The Company maintains deposits in federally insured financial institutions in excess of federally insured limits. The Company has not experienced any losses in such accounts, and management believes that the Company is not exposed to significant credit risk due to the financial position of the depository institutions in which those deposits are held. The Company’s investment policy includes guidelines for the quality of the related institutions and financial instruments and defines allowable investments that the Company may invest in, which the Company believes minimizes the exposure to concentration of credit risk.
Cash, Cash Equivalents and Restricted Cash	Cash, cash equivalents and restricted cash Cash and cash equivalents include cash in readily available checking and savings accounts, money market funds, and US treasury securities. The Company considers all highly liquid investments with an original maturity of three months or less from the date of purchase to be cash equivalents. The Company had deposited cash of $ 408,000 as of September 30, 2022 and December 31, 2021 to secure a letter of credit in connection with the lease of the Company’s facilities (see Note 11). The Company has classified the restricted cash as a noncurrent asset on its condensed consolidated balance sheets. The following table provides a reconciliation of cash, cash equivalents and restricted cash reported within the condensed consolidated balance sheets that sum to the total of the same amounts shown in the condensed consolidated statements of cash flows (in thousands): September 30, 2022 2021 Cash and cash equivalents $ 219,260 $ 445,811 Restricted cash 408 408 Total cash, cash equivalents and restricted cash $ 219,668 $ 446,219
Marketable Securities and Investments	Marketable securities and investments The Company classifies all marketable securities as available-for-sale, as the sale of such securities may be required prior to maturity. Management determines the appropriate classification of its marketable securities at the time of purchase. Marketable securities with original maturities beyond three months at the date of purchase and which mature at, or less than 12 months from, the balance sheet date are classified as short-term marketable securities. Available-for-sale securities are carried at fair value, with the unrealized gains and losses reported as accumulated other comprehensive income (loss) until realized. The amortized cost of available-for-sale debt securities is adjusted for amortization of premiums and accretion of discounts to maturity. Such amortization and accretion are included in interest income. The Company regularly reviews all of its marketable securities for declines in fair value. The review includes the consideration of the cause of the impairment, including the creditworthiness of the security issuers, the number of securities in an unrealized loss position, the severity of the unrealized loss(es), whether the Company has the intent to sell the securities and whether it is more likely than not that the Company will be required to sell the securities before the recovery of their amortized cost basis. If the decline in fair value is due to credit-related factors, a loss is recognized in net income; whereas, if the decline in fair value is not due to credit-related factors, the loss is recorded in other comprehensive income (loss). Realized gains and losses on available-for-sale securities are included in other income or expense. The cost of securities sold is based on the specific identification method. Interest and dividends on securities classified as available-for-sale are included in interest income. Through its wholly-owned subsidiary, Erasca Ventures, the Company has also invested in equity securities of a company whose securities are not publicly traded and whose fair value is not readily available. This investment is recorded using cost minus impairment, plus or minus changes in its estimated fair value resulting from observable price changes in orderly transactions for the identical or a similar investment of the same issuer. Investments in equity securities without readily determinable fair values are assessed for potential impairment on a quarterly basis based on qualitative factors. This investment is included in other assets in the Company's condensed consolidated balance sheets.
Fair Value Measurements	Fair value measurements Certain assets and liabilities are carried at fair value under US GAAP. Fair value is defined as an exit price, representing the amount that would be received to sell an asset or paid to transfer a liability in an orderly transaction between market participants. As such, fair value is a market-based measurement that should be determined based on assumptions that market participants would use in pricing an asset or liability. Financial assets and liabilities carried at fair value are classified and disclosed in one of the following three levels of the fair value hierarchy, of which the first two are considered observable and the last is considered unobservable: Level 1—Unadjusted quoted prices in active markets that are accessible at the measurement date for identical, unrestricted assets or liabilities. Level 2—Quoted prices for similar assets and liabilities in active markets, quoted prices in markets that are not active, or inputs which are observable, either directly or indirectly, for substantially the full term of the asset or liability. Level 3—Prices or valuation techniques that require inputs that are both significant to the fair value measurement and unobservable (i.e., supported by little or no market activity).
Recently Adopted Accounting Pronouncements and Recently Issued Accounting Pronouncements Not Yet Adopted	Recently adopted accounting pronouncements In June 2016, the FASB issued ASU 2016-13, Financial Instruments—Credit Losses (Topic 326): Measurement of Credit Losses on Financial Instruments (ASU 2016-13) and also issued subsequent amendments to the initial guidance: ASU 2018-19, ASU 2019-04, ASU 2019-05, and ASU 2019-11. The standard requires that credit losses be reported using an expected losses model rather than the incurred losses model that is currently used, and it establishes additional disclosure requirements related to credit risks. For available-for-sale debt securities with expected credit losses, this standard now requires allowances to be recorded instead of reducing the amortized cost of the investment. This guidance was originally effective for fiscal years beginning after December 15, 2019, including interim periods within those fiscal years, and early adoption was permitted. In November 2019, the FASB subsequently issued ASU 2019-10, Financial Instruments—Credit Losses (Topic 326), Derivatives and Hedging (Topic 815), and Leases (Topic 842): Effective Dates, whereby the effective date of this standard for smaller reporting companies was deferred to fiscal years beginning after December 15, 2022, including interim periods within those fiscal years, and early adoption is still permitted. The Company adopted ASU 2016-13, and related updates, on a modified retrospective basis on January 1, 2022 , and the adoption had an immaterial impact on its condensed consolidated financial statements and related disclosures. In August 2020, the FASB issued ASU 2020-06, Debt: Debt with Conversion and Other Options (Subtopic 470-20) and Derivatives and Hedging—Contracts in Entity’s Own Equity (Subtopic 815-40) (ASU 2020-06), which simplifies the accounting for convertible instruments and contracts in an entity’s own equity. This guidance is effective for the Company in its annual reporting period beginning after December 15, 2023, including interim periods within that reporting period, with early adoption permitted only as of annual reporting periods beginning after December 15, 2020. The Company adopted ASU 2020-06 on a modified retrospective basis on January 1, 2022 , and the adoption had no impact on its condensed consolidated financial statements and related disclosures. In January 2020, the FASB issued ASU 2020-01, Clarifying the Interactions Between Topic 321, Topic 323, and Topic 815 (ASU 2020-01), which clarifies that an entity should consider observable transactions that require it to either apply or discontinue the equity method of accounting for the purposes of applying the measurement alternative in accordance with Topic 321 immediately before applying or upon discontinuing the equity method. In addition, ASU 2020-01 states that for the purpose of applying paragraph 815-10-15-141(a), an entity should not consider whether, upon the settlement of the forward contract or exercise of the purchased option, individually or with existing investments, the underlying securities would be accounted for under the equity method in Topic 323 or the fair value option in accordance with the financial instruments guidance in Topic 825. The Company adopted the provisions of ASU 2020-01 prospectively as of January 1, 2022 , and the adoption had no impact on its condensed consolidated financial statements and related disclosures. Recently issued accounting pronouncements not yet adopted From time to time, new accounting pronouncements are issued by the FASB or other standard setting bodies that the Company adopts as of the specified effective date. The Company qualifies as an “emerging growth company” as defined in the Jumpstart Our Business Startups Act of 2012 (JOBS Act) and has elected not to “opt out” of the extended transition related to complying with new or revised accounting standards, which means that when a standard is issued or revised and it has different application dates for public and nonpublic companies, the Company can adopt the new or revised standard at the time nonpublic companies adopt the new or revised standard and can do so until such time that the Company either (i) irrevocably elects to “opt out” of such extended transition period or (ii) no longer qualifies as an emerging growth company.

Summary of Significant Accoun_3

Summary of Significant Accounting Policies (Tables)	9 Months Ended
	Sep. 30, 2022
Accounting Policies [Abstract]
Reconciliation of Cash, Cash Equivalents and Restricted Cash	The following table provides a reconciliation of cash, cash equivalents and restricted cash reported within the condensed consolidated balance sheets that sum to the total of the same amounts shown in the condensed consolidated statements of cash flows (in thousands): September 30, 2022 2021 Cash and cash equivalents $ 219,260 $ 445,811 Restricted cash 408 408 Total cash, cash equivalents and restricted cash $ 219,668 $ 446,219

Fair Value Measurements (Tables

Fair Value Measurements (Tables)	9 Months Ended
	Sep. 30, 2022
Fair Value Disclosures [Abstract]
Summary of Financial Assets Measured at Fair Value on Recurring Basis	The following tables summarize the Company’s financial assets measured at fair value on a recurring basis and their respective input levels based on the fair value hierarchy (in thousands): Fair value measurements as of September 30, 2022 using Quoted prices in Significant Significant active markets other unobservable September 30, for identical observable inputs 2022 assets (level 1) inputs (level 2) (level 3) Assets: Money market funds (1) $ 187,565 $ 187,565 $ — $ — US treasury securities (1) 9,953 9,953 — — US treasury securities (2) 106,078 106,078 — — Commercial paper (2) 28,619 — 28,619 — Corporate debt securities (2) 1,336 — 1,336 — Supranational debt security (2) 635 — 635 — US treasury securities (3) 9,569 9,569 — — Total fair value of assets $ 343,755 $ 313,165 $ 30,590 $ — (1) Included as cash and cash equivalents on the condensed consolidated balance sheets. (2) Included as short-term marketable securities on the condensed consolidated balance sheets. (3) Included as long-term marketable securities on the condensed consolidated balance sheets. Fair value measurements as of December 31, 2021 using Quoted prices in Significant Significant active markets other unobservable December 31, for identical observable inputs 2021 assets (level 1) inputs (level 2) (level 3) Assets: Money market funds (1) $ 351,625 $ 351,625 $ — $ — US treasury securities (2) 18,097 18,097 — — Corporate debt securities (2) 2,822 — 2,822 — Commercial paper (2) 31,566 — 31,566 — Supranational debt securities (2) 1,503 — 1,503 — US treasury securities (3) 44,770 44,770 — — Total fair value of assets $ 450,383 $ 414,492 $ 35,891 $ — (1) Included as cash and cash equivalents on the condensed consolidated balance sheets. (2) Included as short-term marketable securities on the condensed consolidated balance sheets. (3) Included as long-term marketable securities on the condensed consolidated balance sheets.

Marketable Securities (Tables)

Marketable Securities (Tables)	9 Months Ended
	Sep. 30, 2022
Table Text Block [Abstract]
Summary of Marketable Securities Accounted for Available-for-Sale Securities	The following tables summarize the Company’s marketable securities accounted for as available-for-sale securities (in thousands, except years): September 30, 2022 Maturity Amortized Unrealized Unrealized Estimated (in years) cost gains losses fair value US treasury securities 1 or less $ 107,042 $ 7 $ ( 971 ) 106,078 Commercial paper 1 or less 28,619 — — 28,619 Corporate debt securities 1 or less 1,348 — ( 12 ) 1,336 Supranational debt security 1 or less 642 — ( 7 ) 635 US treasury securities 1 - 2 9,965 — ( 396 ) 9,569 Total $ 147,616 $ 7 $ ( 1,386 ) $ 146,237 December 31, 2021 Maturity Amortized Unrealized Unrealized Estimated (in years) cost gains losses fair value US treasury securities 1 or less $ 18,116 $ — $ ( 19 ) $ 18,097 Corporate debt securities 1 or less 2,824 — ( 2 ) 2,822 Commercial paper 1 or less 31,566 — — 31,566 Supranational debt securities 1 or less 1,503 — — 1,503 US treasury securities 1 - 2 44,911 — ( 141 ) 44,770 Total $ 98,920 $ — $ ( 162 ) $ 98,758

Property and Equipment, Net (Ta

Property and Equipment, Net (Tables)	9 Months Ended
	Sep. 30, 2022
Property, Plant and Equipment [Abstract]
Schedule of Property and Equipment, Net	Property and equipment, net consisted of the following (in thousands): September 30, December 31, 2022 2021 Construction in process $ — $ 11,228 Laboratory equipment 4,098 2,488 Furniture and fixtures 4,127 2,455 Leasehold improvements 18,315 795 Computer equipment and software 902 715 Property and equipment 27,442 17,681 Less accumulated depreciation and amortization ( 2,567 ) ( 1,727 ) Property and equipment, net $ 24,875 $ 15,954

Accrued Expenses and Other Cu_2

Accrued Expenses and Other Current Liabilities (Tables)	9 Months Ended
	Sep. 30, 2022
Payables and Accruals [Abstract]
Schedule of Accrued Expenses and Other Current Liabilities	Accrued expenses and other current liabilities consisted of the following (in thousands): September 30, December 31, 2022 2021 Accrued research and development expenses $ 11,623 $ 9,122 Accrued compensation 7,104 7,275 Unvested early exercised stock option liability 1,929 2,884 Accrued property and equipment 273 1,272 Accrued professional services 1,048 383 Other accruals 355 483 Total $ 22,332 $ 21,419

Stock-based Compensation (Table

Stock-based Compensation (Tables)	9 Months Ended
	Sep. 30, 2022
Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]
Summary of Stock Option Activity	A summary of the Company’s stock option activity under the 2021 Plan and 2018 Plan is as follows (in thousands, except share and per share data and years): Weighted- Weighted- average remaining Aggregate average contractual intrinsic Shares exercise price term (years) value Outstanding at December 31, 2021 13,818,212 $ 3.87 8.82 $ 163,264 Granted 5,732,046 10.37 Exercised ( 780,725 ) 1.62 Canceled ( 1,127,348 ) 5.57 Outstanding at September 30, 2022 17,642,185 $ 5.74 8.42 $ 54,708 Options exercisable at September 30, 2022 6,537,157 $ 3.80 7.83 $ 29,165
Summary of Restricted Stock Activity	The summary of the Company’s restricted stock activity during the nine months ended September 30, 2022 is as follows: Number of Weighted- restricted average stock shares grant date outstanding fair value Nonvested at December 31, 2021 212,941 $ 0.001 Vested ( 205,996 ) 0.001 Forfeited ( 6,945 ) 0.001 Nonvested at September 30, 2022 - $ 0.001
Schedule of Stock-based Compensation Expense	The allocation of stock-based compensation for all stock awards was as follows (in thousands): Three Months Ended September 30, Nine Months Ended September 30, 2022 2021 2022 2021 Research and development $ 2,872 $ 1,665 $ 8,607 $ 3,080 General and administrative 2,360 1,352 6,122 2,368 Total $ 5,232 $ 3,017 $ 14,729 $ 5,448
Summary of Common Stock Reserved for Future Issuance	Common stock reserved for future issuance consisted of the following as of September 30, 2022 and December 31, 2021: September 30, December 31, 2022 2021 Stock options issued and outstanding 17,642,185 13,818,212 Awards available for future grant 16,170,804 14,699,430 Shares available for purchase under the ESPP 1,017,371 1,168,013 Total 34,830,360 29,685,655
Stock Options
Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]
Assumptions used to Determine Fair Value of Stock Option Grants and Stock to be Purchased under ESPP	The assumptions used in the Black-Scholes option pricing model to determine the fair value of the employee and nonemployee stock option grants were as follows: Three Months Ended September 30, Nine Months Ended September 30, 2022 2021 2022 2021 Risk-free interest rate 2.65 %- 3.38 % 0.91 %- 0.97 % 1.46 %- 3.38 % 0.59 %- 1.09 % Expected volatility 85.76 %- 86.34 % 81.93 %- 84.98 % 85.51 %- 87.11 % 81.93 %- 84.98 % Expected term (in years) 6.03 - 6.08 6.08 5.50 - 6.08 6.08 Expected dividend yield - -% - -% - -% - -%
ESPP
Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]
Assumptions used to Determine Fair Value of Stock Option Grants and Stock to be Purchased under ESPP	The assumptions used in the Black-Scholes option pricing model to determine the fair value of the stock to be purchased under the ESPP were as follows: Three Months Ended September 30, Nine Months Ended September 30, 2022 (1) 2021 2022 2021 Risk-free interest rate --% 0.05 %- 0.19 % 2.24 %- 3.14 % 0.05 %- 0.19 % Expected volatility --% 70.99 %- 88.50 % 84.74 %- 87.89 % 70.99 %- 88.50 % Expected term (in years) -- 0.39 - 1.89 0.50 - 1.99 0.39 - 1.89 Expected dividend yield --% - -% - -% - -% (1) No grant was made under the ESPP during the three months ended September 30, 2022.

Leases (Tables)

Leases (Tables)	9 Months Ended
	Sep. 30, 2022
Leases [Abstract]
Schedule of Future Minimum Lease Payments under Operating Leases	Future minimum lease payments under the operating leases with initial lease terms in excess of one year as of September 30, 2022 are as follows (in thousands): Year ending December 31, 2022 (remaining three months) $ 640 2023 6,858 2024 8,752 2025 9,024 2026 9,170 Thereafter 53,574 Total lease payments $ 88,018 Less: Amount representing interest ( 31,026 ) Less: Tenant improvement allowance receivable ( 2,533 ) Operating lease liabilities $ 54,459

Net Loss Per Share (Tables)

Net Loss Per Share (Tables)	9 Months Ended
	Sep. 30, 2022
Earnings Per Share [Abstract]
Summary of Computation of Basic and Diluted Net Loss Per Share	The following table summarizes the computation of basic and diluted net loss per share of the Company (in thousands, except share and per share data): Three Months Ended September 30, Nine Months Ended September 30, 2022 2021 2022 2021 Net loss $ ( 35,489 ) $ ( 46,069 ) $ ( 107,555 ) $ ( 92,300 ) Weighted-average shares of common stock used in computing net loss per share, basic and diluted 120,798,322 99,127,286 120,166,023 48,584,029 Net loss per share, basic and diluted $ ( 0.29 ) $ ( 0.46 ) $ ( 0.90 ) $ ( 1.90 )
Anti-dilutive Securities Excluded from Calculation of Diluted Net Loss Per Share	The Company’s potentially dilutive securities, which include options to purchase common stock, shares purchasable under the ESPP and common stock subject to repurchase related to unvested restricted stock and options early exercised, have been excluded from the computation of diluted net loss per share as the effect would be to reduce the net loss per share. Therefore, the weighted-average number of common shares outstanding used to calculate both basic and diluted net loss per share is the same. The Company excluded the following potential common shares, presented as amounts outstanding at each period end, from the computation of diluted net loss per share for the periods indicated because including them would have had an anti-dilutive effect: September 30, September 30, 2022 2021 Options to purchase common stock 17,642,185 13,782,167 Restricted stock subject to future vesting — 602,959 Options early exercised subject to future vesting 1,282,031 2,001,823 Estimated shares purchasable under the ESPP 876,347 299,092 Total potentially dilutive shares 19,800,563 16,686,041

Organization and Basis of Pre_2

Organization and Basis of Presentation - Additional Information (Details) $ / shares in Units, $ in Thousands			1 Months Ended	3 Months Ended	9 Months Ended
	Jul. 20, 2021 USD ($) $ / shares shares	Jul. 09, 2021	Jul. 31, 2021 shares	Sep. 30, 2021 shares	Sep. 30, 2022 USD ($)	Sep. 30, 2021 USD ($)	Dec. 31, 2021 USD ($)
Organization And Basis Of Presentation [Line Items]
Cash, cash equivalents, and short-term marketable securities					$ 355,900
Long-term marketable securities					9,569		$ 44,770
Accumulated deficit					$ (345,721)		$ (238,166)
Net proceeds received from initial public offering (IPO)						$ 316,999
Reverse stock split ratio		1.2
Reverse stock split, description					On July 9, 2021, the Company effected a one-for-1.2 reverse stock split of its issued and outstanding shares of common stock (the Reverse Stock Split).
Common Stock
Organization And Basis Of Presentation [Line Items]
Convertible preferred stock converted into shares of common stock | shares				71,263,685
IPO | Common Stock
Organization And Basis Of Presentation [Line Items]
Net proceeds received from initial public offering (IPO)	$ 317,000
Stock issued and sold | shares	21,562,500			21,562,500
Price per share | $ / shares	$ 16
Convertible preferred stock converted into shares of common stock | shares	71,263,685		71,263,685
Underwriting discounts and commissions	$ 24,200
Offering costs	$ 3,800
Underwriters Option to Purchase Shares | Common Stock
Organization And Basis Of Presentation [Line Items]
Stock issued and sold | shares	2,812,500

Summary of Significant Accoun_4

Summary of Significant Accounting Policies - Additional Information (Details) - USD ($)	Sep. 30, 2022	Dec. 31, 2021
Summary Of Significant Accounting Policies [Line Items]
Restricted cash	$ 408,000	$ 408,000
ASU 2016-13
Summary Of Significant Accounting Policies [Line Items]
Change in Accounting Principle, Accounting Standards Update, Adopted [true false]	true
Change in Accounting Principle, Accounting Standards Update, Adoption Date	Jan. 01, 2022
Change in Accounting Principle, Accounting Standards Update, Immaterial Effect [true false]	true
ASU 2020-06
Summary Of Significant Accounting Policies [Line Items]
Change in Accounting Principle, Accounting Standards Update, Adopted [true false]	true
Change in Accounting Principle, Accounting Standards Update, Adoption Date	Jan. 01, 2022
Change in Accounting Principle, Accounting Standards Update, Immaterial Effect [true false]	true
ASU 2020-01
Summary Of Significant Accounting Policies [Line Items]
Change in Accounting Principle, Accounting Standards Update, Adopted [true false]	true
Change in Accounting Principle, Accounting Standards Update, Adoption Date	Jan. 01, 2022
Change in Accounting Principle, Accounting Standards Update, Immaterial Effect [true false]	true

Summary of Significant Accoun_5

Summary of Significant Accounting Policies - Reconciliation of Cash, Cash Equivalents and Restricted Cash (Details) - USD ($) $ in Thousands	Sep. 30, 2022	Dec. 31, 2021	Sep. 30, 2021
Cash, Cash Equivalents, Restricted Cash, and Restricted Cash Equivalents [Abstract]
Cash and cash equivalents	$ 219,260	$ 360,487	$ 445,811
Restricted cash	408		408
Total cash, cash equivalents and restricted cash	$ 219,668		$ 446,219

Fair Value Measurements - Summa

Fair Value Measurements - Summary of Financial Assets Measured at Fair Value on Recurring Basis (Details) - Fair Value, Recurring - USD ($) $ in Thousands		Sep. 30, 2022		Dec. 31, 2021
Assets:
Total fair value of assets		$ 343,755		$ 450,383
Money Market Funds | Cash and Cash Equivalents
Assets:
Total fair value of assets		187,565	[1]	351,625	[2]
US Treasury Securities | Cash and Cash Equivalents
Assets:
Total fair value of assets	[1]	9,953
US Treasury Securities | Short-Term Investments
Assets:
Total fair value of assets		106,078	[3]	18,097	[4]
US Treasury Securities | Long-Term Investments
Assets:
Total fair value of assets		9,569	[5]	44,770	[6]
Corporate Debt Securities | Short-Term Investments
Assets:
Total fair value of assets		1,336	[3]	2,822	[4]
Commercial Paper | Short-Term Investments
Assets:
Total fair value of assets		28,619	[3]	31,566	[4]
Supranational Debt Securities | Short-Term Investments
Assets:
Total fair value of assets		635	[3]	1,503	[4]
Quoted Prices in Active Markets for Identical Assets (Level 1)
Assets:
Total fair value of assets		313,165		414,492
Quoted Prices in Active Markets for Identical Assets (Level 1) | Money Market Funds | Cash and Cash Equivalents
Assets:
Total fair value of assets		187,565	[1]	351,625	[2]
Quoted Prices in Active Markets for Identical Assets (Level 1) | US Treasury Securities | Cash and Cash Equivalents
Assets:
Total fair value of assets	[1]	9,953
Quoted Prices in Active Markets for Identical Assets (Level 1) | US Treasury Securities | Short-Term Investments
Assets:
Total fair value of assets		106,078	[3]	18,097	[4]
Quoted Prices in Active Markets for Identical Assets (Level 1) | US Treasury Securities | Long-Term Investments
Assets:
Total fair value of assets		9,569	[5]	44,770	[6]
Significant Other Observable Inputs (Level 2)
Assets:
Total fair value of assets		30,590		35,891
Significant Other Observable Inputs (Level 2) | Corporate Debt Securities | Short-Term Investments
Assets:
Total fair value of assets		1,336	[3]	2,822	[4]
Significant Other Observable Inputs (Level 2) | Commercial Paper | Short-Term Investments
Assets:
Total fair value of assets		28,619	[3]	31,566	[4]
Significant Other Observable Inputs (Level 2) | Supranational Debt Securities | Short-Term Investments
Assets:
Total fair value of assets		$ 635	[3]	$ 1,503	[4]
[1] Included as cash and cash equivalents on the condensed consolidated balance sheets. Included as cash and cash equivalents on the condensed consolidated balance sheets. Included as short-term marketable securities on the condensed consolidated balance sheets. Included as short-term marketable securities on the condensed consolidated balance sheets. Included as long-term marketable securities on the condensed consolidated balance sheets. Included as long-term marketable securities on the condensed consolidated balance sheets.

Fair Value Measurements - Addit

Fair Value Measurements - Additional Information (Details)	9 Months Ended
	Sep. 30, 2022 USD ($)
Fair Value Assets Measured On Recurring Basis Unobservable Input Reconciliation [Line Items]
Measurement at fair value, transfers among Level 1, Level 2 or Level 3	$ 0
Subsidiaries | Affini T therapeutics inc
Fair Value Assets Measured On Recurring Basis Unobservable Input Reconciliation [Line Items]
Investment in equity securities	$ 2,000,000

Marketable Securities - Summary

Marketable Securities - Summary of Marketable Securities Accounted for Available-for-Sale-Securities (Details) - USD ($) $ in Thousands	Sep. 30, 2022	Dec. 31, 2021
Schedule Of Available For Sale Securities [Line Items]
Available for sale securities, Amortized cost	$ 147,616	$ 98,920
Available for sale securities, Unrealized gains	7
Available for sale securities, Unrealized losses	(1,386)	(162)
Available for sale securities, Estimated fair value	146,237	98,758
US Treasury Securities
Schedule Of Available For Sale Securities [Line Items]
Available for sale securities, Amortized cost	107,042	18,116
Available for sale securities, Unrealized gains	7
Available for sale securities, Unrealized losses	(971)	(19)
Available for sale securities, Estimated fair value	$ 106,078	$ 18,097
US Treasury Securities | Minimum
Schedule Of Available For Sale Securities [Line Items]
Maturity	1 year	1 year
US Treasury Securities
Schedule Of Available For Sale Securities [Line Items]
Available for sale securities, Amortized cost	$ 9,965	$ 44,911
Available for sale securities, Unrealized losses	(396)	(141)
Available for sale securities, Estimated fair value	$ 9,569	$ 44,770
US Treasury Securities | Minimum
Schedule Of Available For Sale Securities [Line Items]
Maturity	1 year	1 year
US Treasury Securities | Maximum
Schedule Of Available For Sale Securities [Line Items]
Maturity	2 years	2 years
Commercial paper
Schedule Of Available For Sale Securities [Line Items]
Available for sale securities, Amortized cost	$ 28,619	$ 31,566
Available for sale securities, Estimated fair value	$ 28,619	$ 31,566
Commercial paper | Minimum
Schedule Of Available For Sale Securities [Line Items]
Maturity	1 year	1 year
Corporate debt securities
Schedule Of Available For Sale Securities [Line Items]
Available for sale securities, Amortized cost	$ 1,348	$ 2,824
Available for sale securities, Unrealized losses	(12)	(2)
Available for sale securities, Estimated fair value	$ 1,336	$ 2,822
Corporate debt securities | Minimum
Schedule Of Available For Sale Securities [Line Items]
Maturity	1 year	1 year
Supranational debt security
Schedule Of Available For Sale Securities [Line Items]
Available for sale securities, Amortized cost	$ 642	$ 1,503
Available for sale securities, Unrealized losses	(7)
Available for sale securities, Estimated fair value	$ 635	$ 1,503
Supranational debt security | Minimum
Schedule Of Available For Sale Securities [Line Items]
Maturity	1 year	1 year

Marketable Securities - Additio

Marketable Securities - Additional Information (Details) $ in Millions	Sep. 30, 2022 USD ($) Position	Dec. 31, 2021 USD ($) Position
Investments, Debt and Equity Securities [Abstract]
Available of sale securities, unrealized loss position, Number of positions	30	19
Available for sale securities, gross unrealized loss position | $	$ 88	$ 68
Available of sale securities, unrealized loss position, greater than 12 months, Number of positions	0

Property and Equipment, Net - S

Property and Equipment, Net - Schedule of Property and Equipment, Net (Details) - USD ($) $ in Thousands	Sep. 30, 2022	Dec. 31, 2021
Property Plant And Equipment [Line Items]
Property and equipment	$ 27,442	$ 17,681
Less accumulated depreciation and amortization	(2,567)	(1,727)
Property and equipment, net	24,875	15,954
Construction in Progress
Property Plant And Equipment [Line Items]
Property and equipment		11,228
Laboratory Equipment
Property Plant And Equipment [Line Items]
Property and equipment	4,098	2,488
Furniture and Fixtures
Property Plant And Equipment [Line Items]
Property and equipment	4,127	2,455
Leasehold Improvements
Property Plant And Equipment [Line Items]
Property and equipment	18,315	795
Computer Equipment And Software [ Member ]
Property Plant And Equipment [Line Items]
Property and equipment	$ 902	$ 715

Property and Equipment, Net - A

Property and Equipment, Net - Additional Information (Details) - USD ($)	3 Months Ended		9 Months Ended
	Sep. 30, 2022	Sep. 30, 2021	Sep. 30, 2022	Sep. 30, 2021
Property, Plant and Equipment [Abstract]
Depreciation and amortization expense	$ 771,000	$ 191,000	$ 1,708,000	$ 509,000

Accrued Expenses and Other Cu_3

Accrued Expenses and Other Current Liabilities - Schedule of Accrued Expenses and Other Current Liabilities (Details) - USD ($) $ in Thousands	Sep. 30, 2022	Dec. 31, 2021
Payables and Accruals [Abstract]
Accrued research and development expenses	$ 11,623	$ 9,122
Accrued compensation	7,104	7,275
Unvested early exercised stock option liability	1,929	2,884
Accrued property and equipment	273	1,272
Accrued professional services	1,048	383
Other accruals	355	483
Total	$ 22,332	$ 21,419

Asset Acquisitions - Additional

Asset Acquisitions - Additional Information (Details) - USD ($)		1 Months Ended			3 Months Ended		9 Months Ended		12 Months Ended
	Jul. 20, 2021	Jul. 31, 2021	Mar. 31, 2021	Nov. 30, 2020	Sep. 30, 2022	Sep. 30, 2021	Sep. 30, 2022	Sep. 30, 2021	Dec. 31, 2020	Dec. 31, 2021
Asset Acquisitions [Line Items]
In-process research and development						$ 1,680,000	$ 2,000,000	$ 10,848,000
Common Stock
Asset Acquisitions [Line Items]
Convertible preferred stock converted into shares of common stock						71,263,685
Common Stock | IPO
Asset Acquisitions [Line Items]
Convertible preferred stock converted into shares of common stock	71,263,685	71,263,685
Asana Merger Agreement
Asset Acquisitions [Line Items]
Upfront payment made				$ 20,000,000
Future development and regulatory milestone cash payments maximum				$ 90,000,000
Additional shares required to issue upon achieving development milestone				3,888,889
In-process research and development					$ 0	$ 0	0	0	$ 50,000,000
Milestones accrued					0		0			$ 0
Asana Merger Agreement | Series B-2 Convertible Preferred Stock
Asset Acquisitions [Line Items]
Shares issued				4,000,000
Value per share				$ 7.50
Total fair value				$ 30,000,000
Asana Merger Agreement | Series B-2 Convertible Preferred Stock | Common Stock | IPO
Asset Acquisitions [Line Items]
Convertible preferred stock converted into shares of common stock				3,333,333
ELS Purchase Agreement
Asset Acquisitions [Line Items]
Upfront payment made			$ 2,000,000
In-process research and development					$ 0	$ 0	$ 0	$ 3,700,000
ELS Purchase Agreement | Common Stock
Asset Acquisitions [Line Items]
Shares issued			500,000
Value per share			$ 3.36
Total fair value			$ 1,700,000

License Agreements - Additional

License Agreements - Additional Information (Details) - USD ($)		1 Months Ended						3 Months Ended		9 Months Ended
	Jul. 20, 2021	Aug. 31, 2021	May 31, 2021	Jan. 31, 2021	Apr. 30, 2020	Mar. 31, 2020	Feb. 29, 2020	Sep. 30, 2022	Sep. 30, 2021	Sep. 30, 2022	Sep. 30, 2021
License Agreements [Line Items]
In-process research and development									$ 1,680,000	$ 2,000,000	$ 10,848,000
IPO
License Agreements [Line Items]
Stock issued, value									316,999,000
Common Stock | IPO
License Agreements [Line Items]
Stock issued, value									$ 2,000
Stock issued and sold	21,562,500								21,562,500
License Agreement | NiKang Therapeutics, Inc.
License Agreements [Line Items]
Upfront payment							$ 5,000,000
Reimbursement of certain initial manufacturing costs							400,000
Payment for US patent application					$ 7,000,000
In-process research and development								$ 0	$ 0	0	0
License Agreement | NiKang Therapeutics, Inc. | First Licensed Product
License Agreements [Line Items]
Payment of development and regulatory milestone obligation				$ 4,000,000
License Agreement | NiKang Therapeutics, Inc. | First Licensed Product | Maximum
License Agreements [Line Items]
Development and regulatory milestone payments obligation							16,000,000
Commercial milestone payments obligation							157,000,000
License Agreement | NiKang Therapeutics, Inc. | Second Licensed Product
License Agreements [Line Items]
Development and regulatory milestone payments obligation							12,000,000
Commercial milestone payments obligation							$ 151,000,000
License Agreement | Katmai Pharmaceuticals, Inc.
License Agreements [Line Items]
Upfront payment						$ 5,700,000
In-process research and development								0	0	2,000,000	0
License Agreement | Katmai Pharmaceuticals, Inc. | Series B-1 Convertible Preferred Stock and Series B-2 Convertible Preferred Stock
License Agreements [Line Items]
Stock issued, value						$ 2,700,000
License Agreement | Katmai Pharmaceuticals, Inc. | Series B-1 Convertible Preferred Stock and Series B-2 Convertible Preferred Stock | IPO
License Agreements [Line Items]
Conversion of convertible preferred stock into common stock						395,555
License Agreement | Katmai Pharmaceuticals, Inc. | Series B-1 Convertible Preferred Stock
License Agreements [Line Items]
Stock issued, value					$ 1,800,000
Stock issued and sold					356,000
License Agreement | Katmai Pharmaceuticals, Inc. | Series B-2 Convertible Preferred Stock
License Agreements [Line Items]
Stock issued, value				$ 900,000
Stock issued and sold				118,666
License Agreement | Katmai Pharmaceuticals, Inc. | Maximum
License Agreements [Line Items]
Development and regulatory milestone payments obligation						$ 24,000,000
Commercial milestone payments obligation						$ 101,000,000
License Agreement | LifeArc
License Agreements [Line Items]
Upfront payment					$ 0
In-process research and development								0	0	0	0
One-time license payment					75,000
License Agreement | LifeArc | Maximum
License Agreements [Line Items]
Development and regulatory milestone payments obligation					11,000,000
Sales milestone payments obligation					$ 50,000,000
License Agreement | The Regents
License Agreements [Line Items]
Upfront payment			$ 50,000
In-process research and development								$ 0	$ 1,700,000	$ 0	$ 7,200,000
Sales milestone payments obligation			$ 2,000,000
Percentage of third tier sublicensing fees			30%
Cash payments in license agreement upon achievement of corporate milestone		$ 1,700,000
License Agreement | The Regents | Common Stock
License Agreements [Line Items]
Stock issued and sold			944,945
License Agreement | The Regents | Maximum
License Agreements [Line Items]
Development and regulatory milestone payments obligation			$ 6,400,000

Stockholders' Equity - Addition

Stockholders' Equity - Additional Information (Details) - USD ($) $ / shares in Units, $ in Millions		1 Months Ended		3 Months Ended		9 Months Ended		12 Months Ended
	Jul. 20, 2021	Aug. 31, 2022	Jul. 31, 2021	Sep. 30, 2022	Sep. 30, 2021	Sep. 30, 2022	Sep. 30, 2021	Dec. 31, 2018	Jun. 30, 2022	Mar. 31, 2022	Dec. 31, 2021	Jun. 30, 2021	Mar. 31, 2021	Feb. 28, 2021	Dec. 31, 2020
Class of Stock [Line Items]
Common stock, shares authorized				800,000,000		800,000,000					800,000,000
Undesignated preferred stock authorized				80,000,000		80,000,000					80,000,000
Undesignated preferred stock par value				$ 0.0001		$ 0.0001					$ 0.0001
Common stock, shares issued				122,306,969		122,306,969					121,382,547
Common stock, shares outstanding				121,024,938		121,024,938					119,102,505
Share-based compensation, vesting rights description						The restricted stock vests 25% one year from the vesting commencement date and monthly thereafter over a three-year period and is subject to repurchase by the Company in the event of any voluntary or involuntary termination of services to the Company prior to vesting.
Shares of common stock subject to repurchase				0		0					212,674
Common Stock
Class of Stock [Line Items]
Convertible preferred stock converted into shares of common stock					71,263,685
Common stock, shares issued				122,306,969	121,250,375	122,306,969	121,250,375		122,063,473	121,732,846	121,382,547	27,300,123	26,129,283		25,189,673
IPO
Class of Stock [Line Items]
Common stock, shares authorized	800,000,000													156,000,000
Undesignated preferred stock authorized	80,000,000
Undesignated preferred stock par value	$ 0.0001
IPO | Common Stock
Class of Stock [Line Items]
Convertible preferred stock converted into shares of common stock	71,263,685		71,263,685
Restricted Stock
Class of Stock [Line Items]
Shares issued								1,458,332
Share price per share								$ 0.0001
Stock vesting period								3 years
Number of shares of common stock subject to repurchase vested in period				30,384	91,146	212,674	273,439
Restricted Stock | One Year from the Vesting Commencement Date and Monthly Thereafter Over Three-year Vesting Period
Class of Stock [Line Items]
Stock vesting percentage								25%
Share-based compensation, vesting rights description						The Company granted 1,795,827 shares of its restricted stock in 2018, which vest 25% one year from the vesting commencement date and monthly thereafter over a three-year period.
Jefferies LLC | Common Stock
Class of Stock [Line Items]
Number of stock sold						0
Jefferies LLC | Maximum | Common Stock
Class of Stock [Line Items]
Aggregate offering price		$ 200
Percentage of commission on gross sales proceeds		3%
Convertible Preferred Stock
Class of Stock [Line Items]
Preferred shares outstanding				0		0					0	85,516,454	85,516,454		69,584,682

Stock-based Compensation - Addi

Stock-based Compensation - Additional Information (Details) - USD ($)	1 Months Ended	2 Months Ended	3 Months Ended		9 Months Ended		12 Months Ended
	Jul. 31, 2021	Sep. 30, 2021	Sep. 30, 2022	Sep. 30, 2021	Sep. 30, 2022	Sep. 30, 2021	Dec. 31, 2018	Dec. 31, 2021
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Common stock reserved for future issuance			34,830,360		34,830,360			29,685,655
Share-based compensation, shares subject to repurchase			1,282,031		1,282,031			1,854,427
Stock-based compensation			$ 5,232,000	$ 3,017,000	$ 14,729,000	$ 5,448,000
Share-based compensation, vesting rights description					The restricted stock vests 25% one year from the vesting commencement date and monthly thereafter over a three-year period and is subject to repurchase by the Company in the event of any voluntary or involuntary termination of services to the Company prior to vesting.
Accrued Expenses and Other Current Liabilities
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Share-based compensation, liabilities associated with shares issued with repurchase rights			$ 1,900,000		$ 1,900,000			$ 2,900,000
Minimum
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Share-based compensation, common stock grant in period, term					5 years
Stock Options
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Common stock reserved for future issuance			17,642,185		17,642,185			13,818,212
Stock vesting period					4 years
Weighted-average grant date fair value of options granted			$ 4.91	$ 12.29	$ 7.50	$ 3.96
Unrecognized compensation cost related to unvested stock option grants			$ 57,000,000		$ 57,000,000
Unrecognized compensation cost expected to be recognized as expense, period					2 years 7 months 2 days
Intrinsic value of options exercised			$ 1,500,000	$ 663,000	$ 5,900,000	$ 2,500,000
Share-based compensation, options granted that vest based on performance milestone					5,732,046
Stock Options | Minimum | At the Time Option is Granted
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Percentage of fair market value of common stock					100%
Stock Options | Minimum | For Holders of More Than 10% of Company's Total Combined Voting Power of All Classes of Stock
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Percentage of fair market value of common stock					110%
Stock Options | Maximum
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Share-based compensation, plan expiration period					10 years
Restricted Stock
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Stock vesting period							3 years
Restricted stock granted			0	0	0	0	1,795,827
Weighted-average grant date fair value of restricted stock granted							$ 0
Share-based Compensation, common stock shares subject to forfeiture			212,941		212,941			212,941
Total unrecognized compensation related to unvested restricted stock awards granted			$ 0		$ 0
Restricted Stock | One Year from the Vesting Commencement Date and Monthly Thereafter Over Three-year Vesting Period
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Stock vesting percentage							25%
Share-based compensation, vesting rights description					The Company granted 1,795,827 shares of its restricted stock in 2018, which vest 25% one year from the vesting commencement date and monthly thereafter over a three-year period.
Restricted Stock | 25% One Year from Vesting Commencement Date
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Stock vesting period							1 year
Restricted Stock | Monthly Thereafter Over Three-year Vesting Period
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Stock vesting period							3 years
2018 Equity Incentive Plan
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Share-based compensation, options granted that vest based on performance milestone		0
2021 Incentive Award Plan
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Common stock reserved for future issuance			16,170,804		16,170,804
Shares of common stock, authorized for issuance	15,150,000
Percentage of outstanding common stock maximum	5%
ESPP
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Common stock reserved for future issuance	1,260,000
Unrecognized compensation cost related to unvested stock option grants			$ 3,400,000		$ 3,400,000
Unrecognized compensation cost expected to be recognized as expense, period					1 year 8 months 12 days
Stock-based compensation			166,000	$ 278,000	$ 834,000	$ 278,000
Share-based payment arrangement, withheld on behalf of employees for future purchase			$ 261,000		$ 261,000			$ 102,000
Offering period	24 months
Purchase period	6 months
Shares issued under ESPP			0	0	150,642	0
ESPP | Minimum
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Percentage of fair market value of common stock	85%

Stock-based Compensation - Summ

Stock-based Compensation - Summary of Stock Option Activity (Details) - Stock Options $ / shares in Units, $ in Thousands	9 Months Ended	12 Months Ended
	Sep. 30, 2022 USD ($) $ / shares shares	Dec. 31, 2021 USD ($) $ / shares shares
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Shares Outstanding at December 31, 2021 | shares	13,818,212
Shares Granted | shares	5,732,046
Shares Exercised | shares	(780,725)
Shares Canceled | shares	(1,127,348)
Shares Outstanding at September 30, 2022 | shares	17,642,185	13,818,212
Shares Options exercisable at September 30, 2022 | shares	6,537,157
Weighted-average exercise price, Outstanding at December 31, 2021 | $ / shares	$ 3.87
Weighted-average exercise price, Granted | $ / shares	10.37
Weighted-average exercise price, Exercised | $ / shares	1.62
Weighted-average exercise price, Canceled | $ / shares	5.57
Weighted-average exercise price, Outstanding at September 30, 2022 | $ / shares	5.74	$ 3.87
Weighted-average exercise price, Options exercisable at September 30, 2022 | $ / shares	$ 3.80
Weighted-average remaining contractual term (years), Outstanding	8 years 5 months 1 day	8 years 9 months 25 days
Weighted-average remaining contractual term (years), Options exercisable at September 30, 2022	7 years 9 months 29 days
Aggregate intrinsic value, Outstanding | $	$ 54,708	$ 163,264
Aggregate intrinsic value, Options exercisable at September 30, 2022 | $	$ 29,165

Stock-based Compensation - Assu

Stock-based Compensation - Assumptions used to Determine Fair Value of Stock Option Grants and Stock to be Purchased under ESPP (Details)	3 Months Ended		9 Months Ended
	Sep. 30, 2022	Sep. 30, 2021	Sep. 30, 2022	Sep. 30, 2021
Stock Options
Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]
Risk-free interest rate, minimum	2.65%	0.91%	1.46%	0.59%
Risk-free interest rate, maximum	3.38%	0.97%	3.38%	1.09%
Expected volatility, minimum	85.76%	81.93%	85.51%	81.93%
Expected volatility, maximum	86.34%	84.98%	87.11%	84.98%
Expected term (in years)		6 years 29 days		6 years 29 days
Expected dividend yield	0%	0%	0%	0%
ESPP
Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]
Risk-free interest rate, minimum		0.05%	2.24%	0.05%
Risk-free interest rate, maximum		0.19%	3.14%	0.19%
Expected volatility, minimum		70.99%	84.74%	70.99%
Expected volatility, maximum		88.50%	87.89%	88.50%
Expected dividend yield		0%	0%	0%
Minimum | Stock Options
Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]
Expected term (in years)	6 years 10 days		5 years 6 months
Minimum | ESPP
Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]
Expected term (in years)		4 months 20 days	6 months	4 months 20 days
Maximum | Stock Options
Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]
Expected term (in years)	6 years 29 days		6 years 29 days
Maximum | ESPP
Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]
Expected term (in years)		1 year 10 months 20 days	1 year 11 months 26 days	1 year 10 months 20 days

Stock-based Compensation - Su_2

Stock-based Compensation - Summary of Restricted Stock Activity (Details) - Restricted Stock	9 Months Ended
	Sep. 30, 2022 $ / shares shares
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Number of restricted stock shares outstanding, Nonvested at December 31, 2021 | shares	212,941
Number of restricted stock shares outstanding, Vested | shares	(205,996)
Number of restricted stock shares outstanding, Forfeited | shares	(6,945)
Number of restricted stock shares outstanding, Nonvested at September 30, 2022 | shares	0
Weighted average grant date fair value, Nonvested at December 31, 2021 | $ / shares	$ 0.001
Weighted-average grant date fair value, Vested | $ / shares	0.001
Weighted-average grant date fair value, Forfeited | $ / shares	0.001
Weighted-average grant date fair value, Nonvested at September 30, 2022 | $ / shares	$ 0.001

Stock-based Compensation - Sche

Stock-based Compensation - Schedule of Stock-based Compensation Expense (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2022	Sep. 30, 2021	Sep. 30, 2022	Sep. 30, 2021
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Stock-based compensation	$ 5,232	$ 3,017	$ 14,729	$ 5,448
Research and Development
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Stock-based compensation	2,872	1,665	8,607	3,080
General and Administrative
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Stock-based compensation	$ 2,360	$ 1,352	$ 6,122	$ 2,368

Stock-based Compensation - Su_3

Stock-based Compensation - Summary of Common Stock Reserved for Future Issuance (Details) - shares	Sep. 30, 2022	Dec. 31, 2021
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Common stock reserved for future issuance	34,830,360	29,685,655
Stock Options Issued and Outstanding
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Common stock reserved for future issuance	17,642,185	13,818,212
Awards Available for Future Grant
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Common stock reserved for future issuance	16,170,804	14,699,430
Shares Available for Purchase Under ESPP
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Common stock reserved for future issuance	1,017,371	1,168,013

Leases - Additional Information

Leases - Additional Information (Details)

1 Months Ended

3 Months Ended

9 Months Ended

12 Months Ended

Oct. 31, 2021

Apr. 30, 2022

Dec. 31, 2021 USD ($) ft²

Nov. 30, 2021

Mar. 31, 2021 ft²

Sep. 30, 2020 USD ($) ft²

Sep. 30, 2022 USD ($)

Sep. 30, 2021 USD ($)

Sep. 30, 2022 USD ($)

Sep. 30, 2021 USD ($)

Dec. 31, 2021 USD ($) ft²

Dec. 31, 2018 ft²

Lessee Lease Description [Line Items]

Operating leases cancelable and non-cancellable expiration dates

2032

Operating leases Noncancelable expiration dates

2026

Operating lease cost

$ 2,600,000

$ 905,000

$ 5,100,000

$ 1,600,000

Variable lease costs

701,000

96,000

1,100,000

324,000

Short-term lease costs

$ 24,000

$ 30,000

86,000

89,000

Cash paid for operating leases

$ 585,000

$ 803,000

Operating lease, weighted-average remaining lease term

9 years 10 months 9 days

9 years 6 months

9 years 6 months

9 years 10 months 9 days

Operating lease, weighted-average discount rate

6.90%

8.97%

8.97%

6.90%

Operating lease, aggregate monthly payments to lessor

$ 88,018,000

$ 88,018,000

Letter of credit provided to lessor

$ 408,000

408,000

408,000

$ 408,000

Other Income (Expense), Net

Lessee Lease Description [Line Items]

Gain on lease remeasurement

$ 539,000

2020 Lease

Lessee Lease Description [Line Items]

Office space leases | ft²

59,407

Lease commencement month and year

2021-08

Operating lease initial term

10 years 9 months

Operating lease, aggregate monthly payments to lessor

$ 51,600,000

Tenant improvement allowance

$ 16,800,000

Term for cancellation of lease

84 months

Notice period for cancellation of lease

12 months

Operating lease cancellation payment

$ 2,500,000

2020 Lease | Letter of Credit

Lessee Lease Description [Line Items]

Letter of credit provided to lessor

$ 408,000

Line of credit facility, expiration date

Oct. 31, 2031

2018 Lease

Lessee Lease Description [Line Items]

Lease expiration date

May 31, 2024

May 31, 2022

Apr. 30, 2022

Office space leases | ft²

16,153

First Amendment to 2020 Lease

Lessee Lease Description [Line Items]

Office space leases | ft²

18,421

Lease commencement month and year

2022-05

2022-02

2021 Lease

Lessee Lease Description [Line Items]

Office space leases | ft²

29,542

29,542

Lease commencement month and year

2022-07

Operating lease initial term

124 months

124 months

Operating lease option to extend

5 years

Operating lease existence of option to extend [true false]

true

Operating lease, aggregate monthly payments to lessor

$ 34,400,000

$ 34,400,000

Tenant improvement allowance

8,200,000

Prepaid rent

$ 5,100,000

$ 5,100,000

2021 Lease | Other Assets

Lessee Lease Description [Line Items]

Security deposit paid

$ 874,000

$ 874,000

California | 2018 Lease

Lessee Lease Description [Line Items]

Office space leases | ft²

11,000

Leases - Schedule of Future Min

Leases - Schedule of Future Minimum Lease Payments under Operating Leases (Details) $ in Thousands	Sep. 30, 2022 USD ($)
Leases [Abstract]
2022 (remaining three months)	$ 640
2023	6,858
2024	8,752
2025	9,024
2026	9,170
Thereafter	53,574
Total lease payments	88,018
Less: Amount representing interest	(31,026)
Less: Tenant improvement allowance receivable	(2,533)
Operating lease liabilities	$ 54,459

Income Taxes - Additional Infor

Income Taxes - Additional Information (Details) - USD ($)	3 Months Ended		9 Months Ended
	Sep. 30, 2022	Sep. 30, 2021	Sep. 30, 2022	Sep. 30, 2021
Income Taxes [Line Items]
Provision for federal income taxes	$ 0	$ 0	$ 0	$ 0
Provision for state income taxes	0	0	0	0
Provision for foreign income taxes	0	0	0	0
Interest or penalties related to income taxes	0	$ 0	$ 0	$ 0
employee retention credit	$ 2,200,000
Maximum [Member]
Income Taxes [Line Items]
Credit percentage on qualified wages on employment taxes			70%
Minimum [Member]
Income Taxes [Line Items]
Credit percentage on qualified wages on employment taxes			50%

Net Loss Per Share - Summary of

Net Loss Per Share - Summary of Computation of Basic and Diluted Net Loss Per Share (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended						9 Months Ended
	Sep. 30, 2022	Jun. 30, 2022	Mar. 31, 2022	Sep. 30, 2021	Jun. 30, 2021	Mar. 31, 2021	Sep. 30, 2022	Sep. 30, 2021
Earnings Per Share [Abstract]
Net loss	$ (35,489)	$ (35,608)	$ (36,458)	$ (46,069)	$ (28,214)	$ (18,017)	$ (107,555)	$ (92,300)
Weighted-average shares of common stock used in computing net loss per share, basic	120,798,322			99,127,286			120,166,023	48,584,029
Weighted-average shares of common stock used in computing net loss per share, diluted	120,798,322			99,127,286			120,166,023	48,584,029
Net loss per share, basic	$ (0.29)			$ (0.46)			$ (0.90)	$ (1.90)
Net loss per share, diluted	$ (0.29)			$ (0.46)			$ (0.90)	$ (1.90)

Net Loss Per Share - Anti-dilut

Net Loss Per Share - Anti-dilutive Securities Excluded from Calculation of Diluted Net Loss Per Share (Details) - shares	9 Months Ended
	Sep. 30, 2022	Sep. 30, 2021
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Anti-dilutive securities excluded from calculation of diluted net loss per share	19,800,563	16,686,041
Options to Purchase Common Stock
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Anti-dilutive securities excluded from calculation of diluted net loss per share	17,642,185	13,782,167
Restricted Stock Subject to Future Vesting
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Anti-dilutive securities excluded from calculation of diluted net loss per share		602,959
Options Early Exercised Subject to Future Vesting
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Anti-dilutive securities excluded from calculation of diluted net loss per share	1,282,031	2,001,823
Estimated Shares Purchasable Under the ESPP
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Anti-dilutive securities excluded from calculation of diluted net loss per share	876,347	299,092

Related Party Transactions - Ad

Related Party Transactions - Additional Information (Details) - USD ($)	1 Months Ended		3 Months Ended
	Dec. 31, 2021	Jul. 31, 2021	Sep. 30, 2021	Sep. 30, 2022
Subsidiaries | Affini T therapeutics inc
Related Party Transaction [Line Items]
Investment in equity securities				$ 2,000,000
Erasca Foundation
Related Party Transaction [Line Items]
Contribution of common stock			$ 17,497,000
Amount loaned in exchange of non-interest bearing promissory note	$ 100,000
Prepaid Expenses And Other Current Assets | Erasca Foundation
Related Party Transaction [Line Items]
Amount receivable				$ 100,000
Common Stock [Member] | Erasca Foundation
Related Party Transaction [Line Items]
Stock issued		1,093,557	1,093,557
Contribution of common stock		$ 17,500,000