Sutro Biopharma (STRO) 10-Q 10 Nov 21 2021 Q3 Quarterly report Financial data

Document and Entity Information

Document and Entity Information - shares	9 Months Ended
	Sep. 30, 2021	Nov. 04, 2021
Cover [Abstract]
Document Type	10-Q
Amendment Flag	false
Document Period End Date	Sep. 30, 2021
Document Fiscal Year Focus	2021
Document Fiscal Period Focus	Q3
Trading Symbol	STRO
Entity Registrant Name	SUTRO BIOPHARMA, INC.
Entity Central Index Key	0001382101
Current Fiscal Year End Date	--12-31
Entity Filer Category	Non-accelerated Filer
Entity Small Business	true
Entity Emerging Growth Company	true
Entity Ex Transition Period	false
Entity Current Reporting Status	Yes
Entity Shell Company	false
Entity File Number	001-38662
Entity Tax Identification Number	47-0926186
Entity Address, Address Line One	111 Oyster Point Blvd
Entity Address, City or Town	South San Francisco
Entity Address, State or Province	CA
Entity Address, Postal Zip Code	94080
City Area Code	650
Local Phone Number	392-8412
Entity Common Stock, Shares Outstanding		46,270,347
Security Exchange Name	NASDAQ
Title of 12(b) Security	Common stock, $0.001 par value
Document Quarterly Report	true
Document Transition Report	false
Entity Incorporation, State or Country Code	DE
Entity Interactive Data Current	Yes

Condensed Balance Sheets (Unaud

Condensed Balance Sheets (Unaudited) - USD ($) $ in Thousands	Sep. 30, 2021	Dec. 31, 2020
Current assets:
Cash and cash equivalents	$ 30,707	$ 206,152
Marketable securities	159,231	120,341
Investment in equity securities	39,763	41,644
Accounts receivable	12,330	5,559
Prepaid expenses and other current assets	8,698	4,486
Total current assets	250,729	378,182
Property and equipment, net	23,319	12,935
Operating lease right-of-use assets	30,129
Marketable securities, non-current	64,279	0
Other non-current assets	2,144	2,122
Restricted cash	872	872
Total assets	371,472	394,111
Current liabilities:
Accounts payable	11,173	5,544
Accrued compensation	8,487	8,823
Deferred revenue—current	7,804	14,603
Operating lease liability - current	1,445
Debt—current	6,250
Other current liabilities	296	627
Total current liabilities	35,455	29,597
Deferred revenue, non-current	145	6,100
Operating lease liability - non-current	32,073
Deferred rent		1,340
Debt—non-current	18,714	24,545
Other noncurrent liabilities	1,505	481
Total liabilities	87,892	62,063
Stockholders’ equity:
Preferred stock, $0.001 par value — 10,000,000 shares authorized as of September 30, 2021 and December 31, 2020; 0 shares issued and outstanding as of September 30, 2021 and December 31, 2020
Common stock, $0.001 par value — 300,000,000 shares authorized as of September 30, 2021 and December 31, 2020; 46,261,060 and 45,752,116 shares issued and outstanding as of September 30, 2021 and December 31, 2020, respectively	46	46
Additional paid-in-capital	578,850	559,746
Accumulated other comprehensive (loss) income	(30)	129
Accumulated deficit	(295,286)	(227,873)
Total stockholders’ equity	283,580	332,048
Total Liabilities and Stockholders’ Equity	$ 371,472	$ 394,111

Condensed Balance Sheets (Una_2

Condensed Balance Sheets (Unaudited) (Parenthetical) - $ / shares	Sep. 30, 2021	Dec. 31, 2020
Statement Of Financial Position [Abstract]
Preferred stock, par value	$ 0.001	$ 0.001
Preferred stock shares authorized	10,000,000	10,000,000
Preferred stock, shares issued	0	0
Preferred stock shares outstanding	0	0
Common stock, par value	$ 0.001	$ 0.001
Common stock, shares authorized	300,000,000	300,000,000
Common stock, shares issued	46,261,060	45,752,116
Common stock, shares outstanding	46,261,060	45,752,116

Condensed Statements of Operati

Condensed Statements of Operations (Unaudited) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Income Statement [Abstract]
Revenues (including amounts from related parties of $0 during both the three and nine months ended September 30, 2021, and $0 and $2,813 during the three and nine months ended September 30, 2020, respectively)	$ 8,517	$ 17,823	$ 51,226	$ 34,444
Operating expenses
Research and development	26,602	19,361	74,473	54,223
General and administrative	16,589	9,079	40,241	26,435
Total operating expenses	43,191	28,440	114,714	80,658
Loss from operations	(34,674)	(10,617)	(63,488)	(46,214)
Interest income	109	295	481	1,320
Unrealized gain (loss) on equity securities	4,483	29,778	(1,881)	78,638
Interest and other expense, net	(820)	(2,317)	(2,525)	(6,328)
Net (loss) income	$ (30,902)	$ 17,139	$ (67,413)	$ 27,416
Net (loss) income per share, basic	$ (0.67)	$ 0.46	$ (1.46)	$ 0.91
Net (loss) income per share, diluted	$ (0.67)	$ 0.45	$ (1.46)	$ 0.90
Weighted-average shares used in computing basic net (loss) income per share	46,162,544	36,887,266	46,060,010	29,994,917
Weighted-average shares used in computing diluted net (loss) income per share	46,162,544	37,877,552	46,060,010	30,349,856

Condensed Statements of Opera_2

Condensed Statements of Operations (Parenthetical) (Unaudited) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Income Statement [Abstract]
Revenue from related parties	$ 0	$ 0	$ 0	$ 2,813

Condensed Statements of Compreh

Condensed Statements of Comprehensive (Loss) Income (Unaudited) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Statement Of Income And Comprehensive Income [Abstract]
Net (loss) income	$ (30,902)	$ 17,139	$ (67,413)	$ 27,416
Other comprehensive (loss) income:
Unrealized (loss) gain on available-for-sale securities	15	(161)	(159)	72
Comprehensive (loss) income	$ (30,887)	$ 16,978	$ (67,572)	$ 27,488

Condensed Statements of Stockho

Condensed Statements of Stockholders' Equity (Unaudited) - USD ($) $ in Thousands	Total	Common Stock	Additional Paid-in Capital	Accumulated Other Comprehensive Income (Loss)	Accumulated Deficit
Balances at Dec. 31, 2019	$ 97,789	$ 23	$ 293,346	$ 165	$ (195,745)
Common Stock Balance, Shares at Dec. 31, 2019		23,098,969
Exercise of common stock options	56		56
Exercise of common stock options, Shares		12,937
Issuance of common stock under Employee Stock Purchase Plan	646		646
Issuance of common stock under Employee Stock Purchase Plan, Shares		74,465
Vesting of restricted stock units		41,050
Stock-based compensation expense	2,707		2,707
Issuance of common stock warrants in connection with debt refinancing	619		619
Net unrealized (loss) gain on available-for- sale securities	(137)			(137)
Net (loss) income	(19,595)				(19,595)
Balances at Mar. 31, 2020	82,085	$ 23	297,374	28	(215,340)
Common Stock Balance, Shares at Mar. 31, 2020		23,227,421
Balances at Dec. 31, 2019	97,789	$ 23	293,346	165	(195,745)
Common Stock Balance, Shares at Dec. 31, 2019		23,098,969
Net unrealized (loss) gain on available-for- sale securities	72
Net (loss) income	27,416
Balances at Sep. 30, 2020	244,119	$ 38	412,173	237	(168,329)
Common Stock Balance, Shares at Sep. 30, 2020		37,983,978
Balances at Dec. 31, 2019	$ 97,789	$ 23	293,346	165	(195,745)
Common Stock Balance, Shares at Dec. 31, 2019		23,098,969
Exercise of common stock options, Shares	257,834
Balances at Dec. 31, 2020	$ 332,048	$ 46	559,746	129	(227,873)
Common Stock Balance, Shares at Dec. 31, 2020		45,752,116
Balances at Mar. 31, 2020	82,085	$ 23	297,374	28	(215,340)
Common Stock Balance, Shares at Mar. 31, 2020		23,227,421
Exercise of common stock options	8		8
Exercise of common stock options, Shares		1,257
Vesting of restricted stock units		250
Stock-based compensation expense	3,011		3,011
Issuance of common stock in connection with public offering, net of issuance costs	91,411	$ 13	91,398
Issuance of common stock in connection with public offering, net of issuance costs, Shares		12,650,000
Net unrealized (loss) gain on available-for- sale securities	370			370
Net (loss) income	29,872				29,872
Balances at Jun. 30, 2020	206,757	$ 36	391,791	398	(185,468)
Common Stock Balance, Shares at Jun. 30, 2020		35,878,928
Exercise of common stock options	108		108
Exercise of common stock options, Shares		12,308
Issuance of common stock under Employee Stock Purchase Plan	639		639
Issuance of common stock under Employee Stock Purchase Plan, Shares		12,527
Vesting of restricted stock units		110,676
Stock transaction associated with taxes withheld on restricted stock units	(314)		(314)
Stock transaction associated with taxes withheld on restricted stock units,Shares		(30,461)
Stock-based compensation expense	3,112		3,112
Issuance of common stock in connection with At-The-Market sale, net of issuance costs	16,839	$ 2	16,837
Issuance of common stock in connection with At-The-Market sale, net of issuance costs, Shares		2,000,000
Net unrealized (loss) gain on available-for- sale securities	(161)			(161)
Net (loss) income	17,139				17,139
Balances at Sep. 30, 2020	244,119	$ 38	412,173	237	(168,329)
Common Stock Balance, Shares at Sep. 30, 2020		37,983,978
Balances at Dec. 31, 2020	332,048	$ 46	559,746	129	(227,873)
Common Stock Balance, Shares at Dec. 31, 2020		45,752,116
Exercise of common stock options	1,360		1,360
Exercise of common stock options, Shares		129,161
Issuance of common stock under Employee Stock Purchase Plan	873		873
Issuance of common stock under Employee Stock Purchase Plan, Shares		93,346
Vesting of restricted stock units		147,349
Stock transaction associated with taxes withheld on restricted stock units	(407)		(407)
Stock transaction associated with taxes withheld on restricted stock units,Shares		(18,366)
Stock-based compensation expense	3,952		3,952
Net unrealized (loss) gain on available-for- sale securities	(129)			(129)
Net (loss) income	(30,359)				(30,359)
Balances at Mar. 31, 2021	307,338	$ 46	565,524		(258,232)
Common Stock Balance, Shares at Mar. 31, 2021		46,103,606
Balances at Dec. 31, 2020	$ 332,048	$ 46	559,746	129	(227,873)
Common Stock Balance, Shares at Dec. 31, 2020		45,752,116
Exercise of common stock options, Shares	257,834
Net unrealized (loss) gain on available-for- sale securities	$ (159)
Net (loss) income	(67,413)
Balances at Sep. 30, 2021	283,580	$ 46	578,850	(30)	(295,286)
Common Stock Balance, Shares at Sep. 30, 2021		46,261,060
Balances at Mar. 31, 2021	307,338	$ 46	565,524		(258,232)
Common Stock Balance, Shares at Mar. 31, 2021		46,103,606
Exercise of common stock options	452		452
Exercise of common stock options, Shares		40,902
Return and retirement of common stocks		(6,804)
Vesting of restricted stock units		3,750
Stock-based compensation expense	5,907		5,907
Net unrealized (loss) gain on available-for- sale securities	(45)			(45)
Net (loss) income	(6,152)				(6,152)
Balances at Jun. 30, 2021	307,500	$ 46	571,883	(45)	(264,384)
Common Stock Balance, Shares at Jun. 30, 2021		46,141,454
Exercise of common stock options	160		160
Exercise of common stock options, Shares		15,911
Issuance of common stock under Employee Stock Purchase Plan	892		892
Issuance of common stock under Employee Stock Purchase Plan, Shares		52,463
Vesting of restricted stock units		81,375
Stock transaction associated with taxes withheld on restricted stock units	(580)		(580)
Stock transaction associated with taxes withheld on restricted stock units,Shares		(30,143)
Stock-based compensation expense	6,495		6,495
Net unrealized (loss) gain on available-for- sale securities	15			15
Net (loss) income	(30,902)				(30,902)
Balances at Sep. 30, 2021	$ 283,580	$ 46	$ 578,850	$ (30)	$ (295,286)
Common Stock Balance, Shares at Sep. 30, 2021		46,261,060

Condensed Statements of Stock_2

Condensed Statements of Stockholders' Equity (Parenthetical) (Unaudited) - USD ($) $ in Thousands	3 Months Ended
	Sep. 30, 2020	Jun. 30, 2020
Common stock, issuance costs		$ 6,626
ATM
Common stock, issuance costs	$ 561

Condensed Statements of Cash Fl

Condensed Statements of Cash Flows (Unaudited) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020
Operating activities
Net (loss) income	$ (67,413)	$ 27,416
Adjustments to reconcile net (loss) income to net cash used in operating activities:
Depreciation and amortization	3,529	3,125
Amortization of premium on marketable securities	1,982	293
Stock-based compensation	16,354	8,830
Noncash lease expenses	3,841
Unrealized loss (gain) on equity securities	1,881	(78,638)
Remeasurement of liability awards	73	3,165
Other	406	558
Changes in operating assets and liabilities:
Accounts receivable	(6,771)	(1,185)
Prepaid expenses and other assets	(4,534)	823
Accounts payable	4,484	(716)
Accrued compensation	(336)	(127)
Other liabilities	629	(747)
Deferred rent		(129)
Deferred revenue	(12,754)	(11,591)
Change in operating lease liability	(1,470)
Net cash used in operating activities	(60,099)	(48,923)
Investing activities
Purchases of marketable securities	(226,109)	(113,999)
Maturities of marketable securities	106,750	82,300
Sales of marketable securities	14,049	22,000
Purchases of equipment and leasehold improvements	(12,786)	(5,504)
Net cash used in investing activities	(118,096)	(15,203)
Financing activities
Proceeds from public offering		115,438
Payment of issuance costs		(7,188)
Proceeds from debt refinancing		25,000
Payment of debt		(10,000)
Proceeds from exercise of common stock options	1,972	172
Taxes paid related to net shares settlement of restricted stock units	(987)	(314)
Proceeds from employee stock purchase plan	1,765	1,285
Net cash provided by financing activities	2,750	124,393
Net (decrease) increase in cash, cash equivalents and restricted cash	(175,445)	60,267
Cash, cash equivalents and restricted cash at beginning of period	207,024	4,975
Cash, cash equivalents and restricted cash at end of period	31,579	65,242
Supplemental disclosure of cash flow information:
Cash paid for interest	1,536	1,165
Supplemental disclosure of non-cash investing and financing information:
Purchases of equipment included in accounts payable	2,165	11
Embedded interest associated with program fees	561	1,544
Warrants issued to lenders		$ 619
Remeasurement of operating lease right-of-use assets for lease modification	$ 4,227

Organization and Principal Acti

Organization and Principal Activities	9 Months Ended
	Sep. 30, 2021
Disclosure Text Block [Abstract]
Organization and Principal Activities	1. Organization and Principal Activities Description of Business Sutro Biopharma, Inc. (the “Company”), is a clinical stage drug discovery, development and manufacturing company focused on leveraging its integrated cell-free protein synthesis and site-specific conjugation platform, XpressCF ® The Company operates in one business segment, the development of biopharmaceutical products. Liquidity The Company has incurred significant losses and has negative cash flows from operations. As of September 30, 2021, the Company had an accumulated deficit of $295.3 million. Management expects to continue to incur additional substantial losses in the foreseeable future as a result of the Company’s research and development and other operational activities. As of September 30, 2021, the Company had unrestricted cash, cash equivalents and marketable securities of $254.2 million, which is available to fund future operations. The Company will need to raise additional capital to support the completion of its research and development activities and to support its operations. The Company believes that its unrestricted cash, cash equivalents and marketable securities as of September 30, 2021 will enable the Company to maintain its operations for a period of at least 12 months following the filing date of its financial statements.

Summary of Significant Accounti

Summary of Significant Accounting Policies	9 Months Ended
	Sep. 30, 2021
Accounting Policies [Abstract]
Summary of Significant Accounting Policies	2. Summary of Significant Accounting Policies Basis of Presentation and Use of Estimates The accompanying interim condensed financial statements of the Company are unaudited. These interim condensed financial statements have been prepared in accordance with generally accepted accounting principles in the United States of America (“U.S. GAAP”) and the applicable rules and regulations of the Securities and Exchange Commission (“SEC”) for interim financial information. Accordingly, they do not include all of the information and footnotes required by U.S. GAAP for complete financial statements. The December 31, 2020 condensed balance sheet was derived from the audited financial statements as of that date but does not include all of the information and footnotes required by U.S. GAAP for complete financial statements. The preparation of financial statements in conformity with U.S. GAAP requires management to make estimates and assumptions that affect the amounts reported in the financial statements and accompanying notes. The Company bases its estimates on historical experience and market-specific or other relevant assumptions that it believes are reasonable under the circumstances. The amounts of assets and liabilities reported in the Company’s condensed balance sheets and the amounts of expenses and income reported for each of the periods presented are affected by estimates and assumptions, which are used for, but are not limited to, determining research and development periods under collaboration arrangements, stock-based compensation expense, valuation of marketable securities, impairment of long-lived assets, income taxes and certain accrued liabilities. Actual results could differ from such estimates or assumptions. The full extent to which the COVID-19 pandemic will directly or indirectly impact the Company’s business, results of operations and financial condition, including revenue, expenses, manufacturing, clinical trials, research and development costs and employee-related amounts, will depend on future developments that are highly uncertain, including as a result of new information that may emerge concerning COVID-19 and the actions taken to contain or treat it, as well as the economic impact on local, regional, national and international customers, suppliers, service providers and markets. The Company has made estimates of the impact of COVID-19 within its financial statements and there may be changes to those estimates in future periods. Actual results could differ from such estimates or assumptions. The accompanying unaudited interim condensed financial statements have been prepared on the same basis as the audited financial statements and, in the opinion of management, reflect all adjustments of a normal recurring nature considered necessary to state fairly the Company ’ s financial position, results of operations , comprehensive loss, and cash flows for the interim periods. The interim results for the three and nine months ended September 30 , 20 2 1 are not necessarily indicative of the results that may be expected for the year ending December 31, 20 2 1 , or for any other future annual or interim period. The information included in this Quarterly Report on Form 10-Q should be read in conjunction with the Company’s audited financial statements included in the Annual Report on Form 10-K pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934, as amended, for the year ended December 31, 2020. Recently Adopted Accounting Pronouncements In June 2016, the Financial Accounting Standards Board (“FASB”) issued Accounting Standards Updates (“ASU”) 2016-13 (Topic 326), Financial Instruments Credit Losses. The guidance modifies the measurement and recognition of credit losses for most financial assets and certain other instruments. The amendment updates the guidance for measuring and recording credit losses on financial assets measured at amortized cost by replacing the “incurred loss” model with an “expected loss” model. The Company adopted ASU 2016-13 in the third quarter of 2021 using the modified retrospective adoption approach. As a result of this adoption, the Company presents these financial assets, which include the accounts receivable and available-for-sale debt securities, at the net amount the Company expects to collect. The amendment also requires the Company to record credit losses related to available-for-sale debt securities as an allowance through net income rather than reducing the carrying amount under the historical, other-than-temporary-impairment model. The adoption of ASU 2016-13 did not have a material impact on the Company’s financial statements and related disclosures for the quarter ended September 30, 2021. In February 2016, the FASB issued ASU 2016-02 (Topic 842), Leases (Accounting Standards Codification, or “ASC”, 842). ASC 842 supersedes the lease recognition requirements in ASC 840, Leases. ASC 842 clarifies the definition of a lease and requires lessees to recognize right-of-use assets and lease liabilities for all leases, including those classified as operating leases under previous lease accounting guidance. The Company adopted ASC 842 on July 1, 2021, effective as of January 1, 2021. There was no impact on the Company’s accumulated deficit as of January 1, 2021 as a result of the adoption of this standard. Results for the three and nine months ended September 30, 2021 are presented under Topic 842. Other prior period amounts are not adjusted and continue to be reported in accordance with our historic accounting under previous lease guidance, ASC Topic 840: Leases (“Topic 840”). The Company elected the package of practical expedients permitted under the transition guidance of the new standard, which allowed the Company to carry forward its historical assessment on whether a contract is or contains a lease, lease classification, and initial direct costs. Upon adoption on January 1, 2021, the Company recognized operating lease right-of-use (“ROU”) assets of $29.7 million, and current and non-current operating lease liabilities of $2.9 million and $27.8 million, respectively. In connection with the adoption of this standard, deferred rent of $1.3 million and prepaid rent of $0.3 million, which was previously recorded in prepaid expenses and other current assets on the balance sheet as of December 31, 2020, were derecognized. Finance lease assets and liabilities were not material. The adoption of ASC 842 did not have a material impact to the Company’s condensed statements of operations and condensed statements of cash flows. Please see Note 7 for additional information regarding the Company’s leases. Accounting policies Leases The Company determines if an arrangement is or contains a lease at contract inception by assessing whether the arrangement contains an identified asset and whether the lessee has the right to control such asset. The Company is required to classify leases as either finance or operating leases and to record a ROU asset and a lease liability for all leases with a term greater than 12 months regardless of the lease classification. The lease classification will determine whether the lease expense is recognized based on an effective interest rate method or on a straight-line basis over the term of the lease. The Company determines the initial classification and measurement of its ROU assets and lease liabilities at the lease commencement date and thereafter, if modified. The Company does not have material finance leases. For leases with a term greater than 12 months, the Company records the related ROU asset and lease liability at the present value of lease payments over the term of the lease. The term of the Company’s leases equals the non-cancellable period of the lease, including any rent-free periods provided by the lessor, and also includes options to extend or terminate the lease that the Company is reasonably certain to exercise. The ROU asset equals the carrying amount of the related lease liability, adjusted for any lease payments made prior to lease commencement and lease incentives provided by the lessor. Variable lease payments are expensed as incurred and do not factor into the measurement of the applicable ROU asset or lease liability. The Company has elected, for all classes of underlying assets, not to recognize ROU assets and lease liabilities for leases with a term of 12 months or less. Lease cost for short-term leases is recognized on a straight-line basis over the lease term. The Company has also elected to not separate lease and non-lease components for its leases and, as a result, accounts for lease and non-lease components as one component. The Company’s leases do not provide a readily determinable implicit rate. Therefore, the Company estimates its incremental borrowing rate to discount the lease payments based on information available at lease commencement. The Company determines its incremental borrowing rate based on the rate of interest that the Company would have to pay to borrow, on a collateralized basis over a similar term, an amount equal to the lease payments in a similar economic environment. Lease payments may be fixed or variable; however, only fixed payments are included in the Company’s lease liability calculation. Lease costs for the Company’s operating leases are recognized on a straight-line basis within operating expenses over the lease term. The Company’s lease agreements may contain variable non-lease components such as common area maintenance, operating expenses or other costs, which are expensed as incurred. Cash, Cash Equivalents and Restricted Cash The following table provides a reconciliation of cash, cash equivalents and restricted cash reported within the balance sheets that sum to the total of the same amounts shown in the statements of cash flows. September 30, 2021 2020 (in thousands) Cash and cash equivalents $ 30,707 $ 64,370 Restricted cash 872 872 Total cash, cash equivalents, and restricted cash shown in the statements of cash flows $ 31,579 $ 65,242 Investments in Equity Securities Subsequent to the closing of the initial public offering (“IPO”) of Vaxcyte, Inc. in June 2020, the fair value of Vaxcyte’s common stock became readily determinable. Fair Value Measurements Fair value is defined as the exchange price that would be received for an asset or paid to transfer a liability, or an exit price, in the principal or most advantageous market for that asset or liability in an orderly transaction between market participants on the measurement date and establishes a fair value hierarchy that requires an entity to maximize the use of observable inputs, where available, and minimize the use of unobservable inputs when measuring fair value. The Company determined the fair value of financial assets and liabilities using the fair value hierarchy that describes three levels of inputs that may be used to measure fair value, as follows: Level 1—Quoted prices in active markets for identical assets and liabilities; Level 2—Inputs other than Level 1 that are observable, either directly or indirectly, such as quoted prices for similar assets or liabilities, quoted prices in markets that are not active, or other inputs that are observable or can be corroborated by observable market data for substantially the full term of the assets or liabilities; and Level 3—Unobservable inputs that are supported by little or no market activity and that are significant to the fair value of the assets or liabilities. The carrying amounts of accounts receivable, prepaid expenses, accounts payable, accrued liabilities and accrued compensation and benefits approximate fair value due to the short-term nature of these items. The fair value of the Company’s outstanding loan (See Note 6) is estimated using the net present value of the payments, discounted at an interest rate that is consistent with market interest rate, which is a Level 2 input. The estimated fair value of the Company’s outstanding loan approximates the carrying amount, as the loan bears a floating rate that approximates the market interest rate. Revenue Recognition The Company has no products approved for commercial sale and has not generated any revenue from commercial product sales. The total revenue to date has been generated principally from collaboration and license agreements and to a lesser extent, from manufacturing, supply, services and materials the Company provides to its collaboration partners. Collaboration Revenue The Company derives revenue from collaboration arrangements, under which the Company may grant licenses to its collaboration partners to further develop and commercialize its proprietary product candidates. The Company may also perform research and development activities under the collaboration agreements. Consideration under these contracts generally includes a nonrefundable upfront payment, development, regulatory and commercial milestones and other contingent payments, and royalties based on net sales of approved products. Additionally, the collaborations may provide options for the customer to acquire from the Company materials and reagents, clinical product supply or additional research and development services under separate agreements. The Company assesses which activities in the collaboration agreements are considered distinct performance obligations that should be accounted for separately. The Company develops assumptions that require judgement to determine whether the license to the Company’s intellectual property is distinct from the research and development services or participation in activities under the collaboration agreements. At the inception of each agreement, the Company determines the arrangement transaction price, which includes variable consideration, based on the assessment of the probability of achievement of future milestones and contingent payments and other potential consideration. The Company recognizes revenue over time by measuring its progress towards the complete satisfaction of the relevant performance obligation using an appropriate input or output method based on the nature of the service promised to the customer. For arrangements that include multiple performance obligations, the Company allocates the transaction price to the identified performance obligations based on the standalone selling price, or SSP, of each distinct performance obligation. In instances where SSP is not directly observable, the Company develops assumptions that require judgment to determine the SSP for each performance obligation identified in the contract. These key assumptions may include FTE, personnel effort, estimated costs, discount rates and probabilities of clinical development and regulatory success. Upfront Payments : For collaboration arrangements that include a nonrefundable upfront payment, if the license fee and research and development services cannot be accounted for as separate performance obligations, the transaction price is deferred and recognized as revenue over the expected period of performance using a cost-based input methodology. The Company uses judgement to assess the pattern of delivery of the performance obligation. In addition, amounts paid in advance of services being rendered may result in an associated financing component to the upfront payment. Accordingly, the interest on such borrowing cost component will be recorded as interest expense and revenue, based on an appropriate borrowing rate applied to the value of services to be performed by the Company over the estimated service performance period. License Grants: For collaboration arrangements that include a grant of a license to the Company’s intellectual property, the Company considers whether the license grant is distinct from the other performance obligations included in the arrangement. For licenses that are distinct, the Company recognizes revenues from nonrefundable, upfront payments and other consideration allocated to the license when the license term has begun and the Company has provided all necessary information regarding the underlying intellectual property to the customer, which generally occurs at or near the inception of the arrangement. Milestone and Contingent Payments : At the inception of the arrangement and at each reporting date thereafter, the Company assesses whether it should include any milestone and contingent payments or other forms of variable consideration in the transaction price using the most likely amount method. If it is probable that a significant reversal of cumulative revenue would not occur upon resolution of the uncertainty, the associated milestone value is included in the transaction price. At the end of each subsequent reporting period, the Company re-evaluates the probability of achievement of each such milestone and any related constraint and , if necessary, adjusts its estimate of the overall transaction price. Since milestone and contingent payments may become payable to the Company upon the initiation of a clinical study or filing for or receipt of regulatory approval, the Company reviews the relevant facts and circumstances to determine when the Company should update the transaction price, which may occur before the triggering event. When the Company updates the transaction price for milestone and contingent payments, the Company allocates the changes in the total transaction price to each performance obligation in the agreement on the same basis as the initial allocation. Any such adjustments are recorded on a cumulative catch-up basis in the period of adjustment, which may result in recognizing revenue for previously satisfied performance obligations in such period. The Company’s collaborators generally pay milestones and contingent payments subsequent to achievement of the triggering event. Research and Development Services : For amounts allocated to the Company’s research and development obligations in a collaboration arrangement, the Company recognizes revenue over time using a cost-based input methodology, representing the transfer of goods or services as activities are performed over the term of the agreement. Materials Supply: The Company provides materials and reagents, clinical materials and services to certain of its collaborators under separate agreements. The consideration for such services is generally based on FTE personnel effort used to manufacture those materials reimbursed at an agreed upon rate in addition to agreed-upon pricing for the provided materials. The amounts billed are recognized as revenue as the performance obligations are met by the Company.

Fair Value Measurements

Fair Value Measurements	9 Months Ended
	Sep. 30, 2021
Fair Value Disclosures [Abstract]
Fair Value Measurements	3. Fair Value Measurements The following table sets forth the fair value of the Company’s financial assets and liabilities measured on a recurring basis by level within the fair value hierarchy: September 30, 2021 Total Level 1 Level 2 Level 3 (in thousands) Assets: Money market funds $ 30,108 $ 30,108 $ – $ – Commercial paper 56,568 – 56,568 – Corporate debt securities 70,276 – 70,276 – Equity securities 39,763 39,763 – – Asset-backed securities 37,595 – 37,595 – U.S. government securities 37,631 37,631 – – Supranational debt securities 21,440 – 21,440 – Total $ 293,381 $ 107,502 $ 185,879 $ - The following table sets forth the fair value of the Company’s financial assets and liabilities measured on a recurring basis by level within the fair value hierarchy: December 31, 2020 Total Level 1 Level 2 Level 3 (in thousands) Assets: Money market funds $ 204,632 $ 204,632 $ – $ – Commercial paper 42,208 – 42,208 – Corporate debt securities 25,716 – 25,716 – Equity securities 41,644 41,644 – – Asset-backed securities 12,632 – 12,632 – U.S. government securities 39,785 39,785 – – Total $ 366,617 $ 286,061 $ 80,556 $ – Where applicable, the Company uses quoted market prices in active markets for identical assets to determine fair value. This pricing methodology applies to Level 1 investments, which are comprised of money market funds, U.S. government securities and the Vaxcyte common stock shares held by the Company. If quoted prices in active markets for identical assets are not available, then the Company uses quoted prices for similar assets or inputs other than quoted prices that are observable, either directly or indirectly. These investments are included in Level 2 and consist of commercial paper, corporate debt securities, asset-backed securities and supranational debt securities. These assets are valued using market prices when available, adjusting for accretion of the purchase price to face value at maturity. A financial instrument’s categorization within the valuation hierarchy is based upon the lowest level of input that is significant to the fair value measurement. The Company’s assessment of the significance of a particular input to the fair value measurement in its entirety requires management to make judgments and consider factors specific to the asset or liability. In certain cases where there is limited activity or less transparency around inputs to valuation, securities are classified as Level 3 within the valuation hierarchy. As of September 30, 2021 and December 31, 2020, the Company did not hold any securities that were classified as Level 3 within the valuation hierarchy. Investments in Equity Securities Subsequent to the closing of the IPO of Vaxcyte in June 2020, the fair value of Vaxcyte’s common stock became readily determinable. As a result, beginning June 2020, Vaxcyte common stock held by the Company is measured at fair value at each reporting period based on the closing price of Vaxcyte’s common stock on the last trading day of each reporting period, with any unrealized gains and losses recorded in the Company’s statements of operations. As of September 30, 2021, the Company held 1,567,324 shares of Vaxcyte common stock with an estimated fair value of $39.8 million. Related to Vaxcyte common stock, the Company recognized an unrealized gain of $4.5 million for the three months ended September 30, 2021 and unrealized loss of $1.9 million for the nine months ended September 30, 2021.

Cash Equivalents and Marketable

Cash Equivalents and Marketable Securities	9 Months Ended
	Sep. 30, 2021
Cash And Cash Equivalents [Abstract]
Cash Equivalents and Marketable Securities	4. Cash Equivalents and Marketable Securities Cash equivalents and marketable securities consisted of the following: September 30, 2021 Amortized Cost Basis Unrealized Gains Unrealized (Losses) Fair Value (in thousands) Money market funds $ 30,108 $ – $ – $ 30,108 Commercial paper 56,568 – – 56,568 Corporate debt securities 70,290 7 (21 ) 70,276 Asset-based securities 37,607 2 (14 ) 37,595 U.S. government securities 37,624 7 – 37,631 Supranational debt securities 21,451 – (11 ) 21,440 Total 253,648 16 (46 ) 253,618 Less amounts classified as cash equivalents (30,108 ) – – (30,108 ) Total marketable securities $ 223,540 $ 16 $ (46 ) $ 223,510 December 31, 2020 Amortized Cost Basis Unrealized Gains Unrealized (Losses) Fair Value (in thousands) Money market funds $ 204,632 $ – $ – $ 204,632 Commercial paper 42,208 – – 42,208 Corporate debt securities 25,669 48 (1 ) 25,716 Asset-based securities 12,593 39 – 12,632 U.S. government securities 39,743 44 (2 ) 39,785 Total 324,845 131 (3 ) 324,973 Less amounts classified as cash equivalents (204,632 ) – – (204,632 ) Total marketable securities $ 120,213 $ 131 $ (3 ) $ 120,341 As of September 30, 2021 and December 31, 2020, $64.3 million and zero, respectively, of marketable securities had maturities of more than one year and are classified as long-term assets. There were $85.7 million and $14.7 million of investments in an unrealized loss position of $46,000 and $3,000 as of September 30, 2021 and December 31, 2020, respectively. During the three and nine months ended September 30, 2021 and 2020, the Company did not record any other-than-temporary impairment charges on its available-for-sale securities. Based on the Company’s procedures under the expected credit loss model, including an assessment of unrealized gains on the portfolio after September 30, 2021, the Company concluded that the unrealized losses for its marketable securities were not attributable to credit and therefore an allowance for credit losses for these securities has not been recorded as of September 30, 2021. Also, based on the scheduled maturities of the investments, the Company was more likely than not to hold these investments for a period of time sufficient for a recovery of the Company’s cost basis. The Company recognized no material gains or losses on its cash equivalents and current and non-current marketable securities as of September 30, 2021 and as a result, the Company did not reclassify any amounts out of accumulated other comprehensive income for the period then ended.

Collaboration and License Agree

Collaboration and License Agreements and Supply Agreements	9 Months Ended
	Sep. 30, 2021
Collaboration And License Agreements And Supply Agreements [Abstract]
Collaboration and License Agreements and Supply Agreements	5. Collaboration and License Agreements and Supply Agreements The Company has entered into collaboration and license agreements and supply agreements with various pharmaceutical and biotechnology companies. See “Note 5. Collaboration and License Agreements and Supply Agreements” to the Company’s Financial Statements included in the Annual Report on Form 10-K for the year ended December 31, 2020, or as further described below, for additional information on each of our collaboration agreements. The Company’s accounts receivable balances may contain billed and unbilled amounts from milestones and other contingent payments, as well as reimbursable costs from collaboration and license agreements and supply agreements. The Company performs a regular review of its customers’ credit risk and payment histories, including payments made after period end. Historically, the Company has not experienced credit loss from its accounts receivable and, therefore, has not recorded a reserve for estimated credit losses as of September 30, 2021. In accordance with the collaboration agreements, the Company recognized revenue as follows: Three Months Ended Nine Months Ended September 30, September 30, 2021 2020 2021 2020 (in thousands) (in thousands) Bristol Myers Squibb Company (“BMS”) $ 1,118 $ 7,119 $ 7,784 $ 10,673 Merck Sharp & Dohme Corporation (“Merck”) (1) 6,414 9,055 38,175 18,837 Merck KGaA, Darmstadt, Germany (operating in the United States and Canada under the name “EMD Serono”) 249 1,507 2,844 4,656 Vaxcyte (2) 736 142 2,423 278 Total revenue $ 8,517 $ 17,823 $ 51,226 $ 34,444 (1) Merck was a related party until the closing of the Company’s public offering on May 14, 2020. (2) Vaxcyte was a related party until the closing of its initial public offering on June 16, 2020. The Company’s balance of deferred revenue contains the transaction price from collaboration agreements allocated to performance obligations which are partially unsatisfied. The Company expects to recognize approximately $7.8 million of the deferred revenue over the next twelve months. The following table presents the changes in the Company’s deferred revenue balance from collaboration agreements during the nine months ended September 30, 2021: Nine Months Ended September 30, 2021 (in thousands) Deferred revenue—December 31, 2020 $ 20,703 Additions to deferred revenue 19,402 Recognition of revenue in current period (32,156 ) Deferred revenue—September 30, 2021 $ 7,949 There have been no material changes to the Company’s collaboration agreements in the three and nine months ended September 30, 2021, except as described below. Collaboration with BMS BMS Agreement In September 2014, the Company signed a Collaboration and License Agreement (the “BMS Agreement”) with BMS to discover and develop bispecific antibodies and/or antibody-drug conjugates (“ADCs”), focused primarily on the field of immuno-oncology, using the Company’s proprietary integrated cell-free protein synthesis platform, XpressCF ® In May 2019, the U.S. Food and Drug Administration cleared the investigational new drug (“IND”) application for the BCMA ADC, which was discovered and manufactured by the Company and is the first collaboration program IND. BMS has worldwide development and commercialization rights with respect to the BCMA ADC. The Company will continue to be responsible for clinical supply manufacturing and certain development services for the BCMA ADC and is eligible to receive from BMS aggregate development and regulatory contingent payments of up to $275.0 million, if approved in multiple indications, and tiered royalties ranging from mid to high single digit percentages on worldwide sales of any resulting commercial products. As of both September 30, 2021 and December 31, 2020, there was zero balance in deferred revenue related to payments received by the Company under the BMS Agreement. 2018 BMS Master Services Agreement In March 2018, the Company entered into a Master Development and Clinical Manufacturing Services Agreement (the “2018 BMS Master Services Agreement”) with BMS, wherein BMS requested the Company to provide development, manufacturing and supply chain management services, including clinical product supply. As of September 30, 2021, and December 31, 2020, there was $1.8 million and $1.2 million, respectively, of deferred revenue under the 2018 BMS Master Services Agreement. Revenues under the BMS Agreement and the 2018 BMS Master Services Agreement were as follows: Three Months Ended Nine Months Ended September 30, September 30, 2021 2020 2021 2020 (in thousands) (in thousands) Ongoing performance related to unsatisfied performance obligations $ – $ 1,000 $ – $ 2,974 Research and development services 249 246 762 646 Materials supply 869 5,873 7,022 7,053 Total revenue $ 1,118 $ 7,119 $ 7,784 $ 10,673 Collaboration with Merck 2018 Merck Agreement In July 2018, the Company entered into an agreement (the “2018 Merck Agreement”) with Merck to jointly develop up to three research programs focusing on cytokine derivatives for cancer and autoimmune disorders with an initial transaction price of $60.0 million. Under ASC 606, the Company determined there was a financing component associated with the $60.0 million upfront payment and has calculated total interest expense of $7.4 million as of September 30, 2021 on the unearned revenue portion beyond one year from the effective date of the agreement, which amount is expected to be recognized as interest expense and revenue over the estimated service period for the first and second target programs. In March 2020, Merck exercised its option to extend the research term of the collaboration’s first cytokine-derivative program by one year, which, pursuant to the terms of the 2018 Merck Agreement, triggered a payment of $5.0 million. The $5.0 million was, in prior periods, considered to be a fully constrained variable consideration. Removal of the constraint on this variable consideration resulted in a change to the total transaction price, from $60.0 million to $65.0 million. The Company allocated the updated transaction price to all identified performance obligations on the same basis as the initial allocation upon inception of the 2018 Merck Agreement, with any adjustments recorded as a cumulative catch-up in the current period. In the second quarter of 2021, the Company earned a $15.0 million contingent payment for the initiation by Merck of the first IND-enabling toxicology study under the first cytokine-derivative program in the collaboration. The $15.0 million was, in prior periods, considered to be a fully constrained variable consideration. Removal of the constraint on this variable consideration resulted in a change to the total transaction price, from $65.0 million to $80.0 million. The Company allocated the updated transaction price to all identified performance obligations on the same basis as the initial allocation upon inception of the 2018 Merck Agreement, with any adjustments recorded as a cumulative catch-up in the nine-month period ended September 30, 2021. Based upon the adjusted transaction price, revenue allocated to the access to intellectual property rights was $9.4 million and incremental revenue of $1.6 million was recognized in the nine-month period ended September 30, 2021 as this performance obligation was previously completed. Revenue allocated to the first and second target programs totaled $60.6 million, to be recognized on a proportion of performance basis, using the FTE cost as the basis of measurement, with such performance expected to occur over an estimated service period of three years for each target program. Incremental revenue of $9.1 million was recognized in the nine-month period ended September 30, 2021. In September 2021, the Company entered into an amendment to the 2018 Merck Agreement (the “2021 Amendment”) to extend the research term for the first program in the 2018 Merck Agreement to discover and develop novel cytokine derivative therapeutics for cancer and autoimmune disorders. Under the terms of the 2021 Amendment, the Company will receive a payment of $2.5 million and may receive up to an additional $7.5 million upon the achievement of certain developmental milestones. Pursuant to ASC 606, the Company concluded that the 2021 Amendment constitutes a contract modification which is to be accounted for as a separate contract from the 2018 Merck Agreement. The $7.5 million is considered to be a fully constrained variable consideration. The amount of $2.5 million was recorded within the Company’s accounts receivable and current deferred revenue as of September 30, 2021. The Company is eligible to receive aggregate contingent payments of up to approximately $0.5 billion for each of the target programs selected by Merck, assuming the development and sale of the therapeutic candidate and all possible indications identified under the collaboration. If one or more products from each of the target programs are developed for non-oncology or a single indication, the Company will be eligible for reduced aggregate milestone payments. In addition, the Company is eligible to receive tiered royalties ranging from mid-single digit to low teen percentages on the worldwide sales of any commercial products that may result from the collaboration. As of September 30, 2021 and December 31, 2020, there was a total of $5.1 million and $18.5 million, respectively, of deferred revenue related to the 2018 Merck Agreement and 2021 Amendment. 2020 Merck Master Services Agreement In August 2020, the Company entered into a Pre-Clinical and Clinical Supply Agreement (the “2020 Merck Master Services Agreement”) with Merck, wherein Merck requested the Company to provide development, manufacturing and supply chain management services, including clinical product supply, upon completion of the research programs under the 2018 Merck Agreement. As of both September 30, 2021 and December 31, 2020, there was no deferred revenue under the 2020 Merck Master Services Agreement. Revenues under the 2018 Merck Agreement and the 2020 Merck Master Services Agreement were as follows: Three Months Ended Nine Months Ended September 30, September 30, 2021 2020 2021 2020 (in thousands) (in thousands) Ongoing performance related to unsatisfied performance obligations $ 3,506 $ 6,907 $ 30,889 $ 13,048 Research and development services 419 1,732 2,328 4,245 Financing component on unearned revenue 149 416 561 1,544 Materials supply 2,340 – 4,397 – Total revenue $ 6,414 $ 9,055 $ 38,175 $ 18,837 There was no revenue recognized under the 2021 Amendment in the three-month and nine-month periods ended September 30, 2021. Collaboration with EMD Serono EMD Serono Agreements The Company signed a Collaboration Agreement and a License Agreement with EMD Serono in May 2014 and September 2014, respectively, which were entered into in contemplation of each other and therefore treated as a single agreement for accounting purposes. The Collaboration Agreement was subsumed into the License Agreement (the “MDA Agreement”), which agreement is to develop ADCs for multiple cancer targets. Under the MDA Agreement, a novel bispecific ADC product candidate targeting EGFR and MUC1, known as M1231, is undergoing development. The Company is eligible to receive up to $52.5 million for M1231 under the MDA Agreement, primarily from pre-commercial contingent payments. Relatedly, the Company earned a $2.0 million contingent payment in the second quarter of 2021 related to a patient enrollment achievement in the Phase 1 dose escalation portion of a study of M1231. In August 2020, the Company earned a $1.0 million clinical supply milestone payment under the MDA Agreement. In September 2019, the Company earned a $ 1.5 million contingent payment under the MDA Agreement upon designation by EMD Serono of a specific bispecific antibody drug conjugate as a clinical development candidate with their approval to advance it to IND-enabling studies. In addition, the Company is eligible to receive tiered royalties ranging from low-to-mid single digit percentages, along with certain additional one-time royalties, on worldwide sales of any commercial products that may result from the MDA Agreement. As of both September 30, 2021 and December 31, 2020, there was no deferred revenue related to payments received by the Company under the MDA Agreement. 2019 EMD Serono Supply Agreement In April 2019, the Company entered into an ADC Product Preclinical and Phase I Clinical Supply Agreement (the “2019 EMD Serono Supply Agreement”) with EMD Serono, wherein EMD Serono requested the Company to provide development, manufacturing and supply chain management services, including clinical product supply. As of both September 30, 2021 and December 31, 2020, there was $1.0 Revenues under the EMD Serono agreements were as follows: Three Months Ended Nine Months Ended September 30, September 30, 2021 2020 2021 2020 (in thousands) (in thousands) Contingent payment earned $ – $ 1,000 $ 2,000 $ 1,000 Research and development services 214 265 503 1,088 Materials supply 35 242 341 2,568 Total revenue $ 249 $ 1,507 $ 2,844 $ 4,656 Vaxcyte Supply Agreement In May 2018, the Company entered into a Supply Agreement (the “Supply Agreement”) with Vaxcyte, wherein Vaxcyte engaged the Company to supply extracts and custom reagents, as requested by Vaxcyte. The pricing is based on an agreed upon cost plus margin arrangement. During 2020, upon Vaxcyte’s request and their agreement to reimburse the related costs, the Company entered into agreements with third-party contract manufacturers (“CMOs”) to conduct process transfers to allow for such CMOs to manufacture and supply extract and custom reagents for Vaxcyte. The agreed-upon reimbursements by Vaxcyte of the costs associated with such arrangements, principally for pass-through costs from the CMOs, were accounted for by the Company as a reduction to research and development expense. Revenues under the Vaxcyte Supply Agreement Three Months Ended Nine Months Ended September 30, September 30, 2021 2020 2021 2020 (in thousands) (in thousands) Research and development services $ 247 $ – $ 716 $ – Materials supply 489 142 1,707 278 Total revenue $ 736 $ 142 $ 2,423 $ 278

Loan and Security Agreement

Loan and Security Agreement	9 Months Ended
	Sep. 30, 2021
Debt Disclosure [Abstract]
Loan and Security Agreement	6. Loan and Security Agreement The Company entered into loan and security agreements with Oxford Finance LLC (“Oxford”) and Silicon Valley Bank (“SVB”) in both August 2017 and February 2020. See “Note 7. Loan and Security Agreement” to the Company’s Financial Statements included in the Annual Report on Form 10-K for the year ended December 31, 2020, or as further described below, for additional information. In connection with entering into the loan and security agreement in February 2020, the Company issued to the lenders warrants exercisable for 81,257 shares of the Company’s common stock (the “2020 Warrants”). The 2020 Warrants are exercisable in whole or in part, immediately, and have a per share exercise price of $9.23, which is the closing price of the Company’s common stock reported on the Nasdaq Global Market on the day prior to the effective date of the February 2020 loan and security agreement. The 2020 Warrants will terminate on the earlier of February 28, 2030 or the closing of certain merger or consolidation transactions. The estimated fair value upon issuance of the Warrants of $0.6 million was recorded as a debt discount on the associated borrowings on the Company’s balance sheet. The debt discount is being amortized to interest expense over the expected repayment period of the loan using the effective-interest method. As of September 30, 2021, the Company has classified $6.3 million of the outstanding debt balance as current and $18.7 million as non-current, which reflects the scheduled repayment terms under the February 2020 loan and security agreement. As of both September 30, 2021 and December 31, 2020, accrued interest expense was $0.2 million. During the three and nine months ended September 30, 2021, the Company recorded interest expense related to loans outstanding of $0.7 million and $1.9 million, respectively, with average interest rates of 8.07% in both periods, and interest related to the accretion of debt discount of $0.1 million and $0.4 million, respectively. During the three and nine months ended September 30, 2020, the Company recorded interest expense related to loans outstanding of $0.7 million and $1.7 million, respectively, with average interest rates of 8.07% and 8.08%, respectively, and interest related to the accretion of debt discount of $0.1 million and $0.3 million, respectively.

Commitments and Contingencies

Commitments and Contingencies	9 Months Ended
	Sep. 30, 2021
Commitments And Contingencies Disclosure [Abstract]
Commitments and Contingencies	7. Commitments and Contingencies In June 2021, the Company entered into a third amendment (the “Third Amendment”) to its manufacturing facility lease, dated May 18, 2011, as amended, by and between Alemany Plaza LLC, located in San Carlos, California (the “San Carlos Lease”), as an extension to the term of the San Carlos Lease for a period of five years (the “Lease Extension Period”). Pursuant to the Third Amendment, the San Carlos Lease will expire on July 31, 2026, and it includes an option to renew the San Carlos Lease for an additional five years. The aggregate estimated base rent payments due over the Lease Extension Period is approximately $4.2 million, subject to certain terms contained in the San Carlos Lease. In June 2021, the Company entered into a first amendment (the “First Amendment”) to its manufacturing support facility lease, dated May 4, 2015, as amended, by and between 870 Industrial Road LLC, located in San Carlos, California (the “Industrial Lease”), as an extension to the term of the Industrial Lease for a period of five years (the “Industrial Lease Extension Period”). Pursuant to the first Amendment, the Industrial Lease will expire on June 30, 2026, and it includes an option to renew the Industrial Lease for an additional five years. The aggregate estimated base rent payments due over the Industrial Lease Extension Period is approximately $4.3 million, subject to certain terms contained in the Industrial Lease. In September 2020, the Company entered into a sublease agreement (the “Sublease”) with Five Prime Therapeutics, Inc. (the “Sublessor”), for approximately 115,466 square feet, located in South San Francisco, California (the “Premises”). The Company expects to use the Premises as its new corporate headquarters and to conduct (or expand) research and development activities. The commencement date for the first 85,755 square feet of the Premises (“Initial Premises”) per sublease was in July 2021, at which time the Company commenced making monthly payments under the Sublease, with occupancy of such space commencing in August 2021. The Company was provided early access to the Sublease commencing in the fourth quarter of 2020 to conduct certain planning and tenant improvement work. The Sublease is subordinate to the lease agreement, effective December 12, 2016, between the Sublessor and HCP Oyster Point III LLC (the “Landlord”). The commencement date for the remaining 29,711 square feet of the Premises (the “Expansion Premises”) is expected to be 24 months following the commencement date on the Initial Premises, although the Company has the right to accelerate the commencement date on the Expansion Premises to an earlier date upon six months’ prior written notice to the Sublessor. The Sublease for both the Initial Premises and Expansion Premises will expire on December 31, 2027. With a commencement date on the Initial Premises of July 1, 2021, the aggregate estimated base rent payments due over the term of the Sublease are approximately $39.1 million, including the approximately $5.2 million in potential financial benefit to the Company of base rent abatement to be provided by Sublessor, subject to certain terms contained in the Sublease. The Sublease contains customary provisions requiring the Company to pay its pro rata share of utilities and a portion of the operating expenses and certain taxes, assessments and fees of the Premises and provisions allowing the Sublessor to terminate the Sublease upon the termination of the lease with the Landlord or if the Company fails to remedy a breach of certain of its obligations within specified time periods. Additionally, the Company posted a security deposit of $ 0.9 million, which is reflected as restricted cash in non-current assets on the Company’s balance sheet as of September 3 0 , 202 1 and December 31, 2020 . The Company recognizes rent expense for these operating leases on a straight-line basis over the lease period. The components of lease costs, which the Company includes in operating expenses in the condensed statements of operations, were as follows (in thousands): Three Months Ended Nine Months Ended September 30, September 30, 2021 2021 Operating lease cost $ 2,266 $ 6,396 Short-term lease cost 22 73 Variable lease cost 754 1,513 Total lease costs $ 3,042 $ 7,982 During the nine months ended September 30, 2021, the Company recorded operating lease expense of $6.4 million and paid $4.0 million of operating lease payments related to the lease liabilities, which the Company includes in net cash used in operating activities in the condensed statements of cash flows. As of September 30, 2021, the weighted-average remaining lease term was 5.9 years and the weighted-average discount rate used to determine the operating lease liability was 10.8%. As of September 30, 2021, the maturities of the Company’s operating lease liabilities were as follows (in thousands): Year Ending December 31, Amount (in thousands) Remaining in 2021 $ 2,142 2022 (1) 1,643 2023 8,002 2024 9,219 2025 9,533 Thereafter 17,282 Total lease payments 47,821 Less: imputed interest (14,303 ) Operating lease liabilities 33,518 Less: current portion (1,445 ) Total lease liabilities, non-current $ 32,073 (1) Includes approximately $5.2 million in potential financial benefit to the Company of base rent abatement to be provided by sublessor for months 7 – 18 of the sublease period, subject to certain terms contained in the Sublease. Under the historical guidance of ASC 840, the deferred rent balance on December 31, 2020 totaled $1.3 million and our future minimum lease payments for our operating leases on December 31, 2020 were as follows (in thousands): Year Ending December 31, Amount (in thousands) 2021 $ 5,742 2022 (1) 5,183 2023 6,310 2024 7,476 2025 and thereafter 24,034 Total future minimum lease payments $ 48,745 (1) Excludes approximately $5.2 million in potential financial benefit to the Company of base rent abatement to be provided by sublessor for months 7 – 18 of the sublease period, subject to certain terms contained in the Sublease Rent expense was $0.9 million and $2.7 million for the three and nine months ended September 30, 2020, respectively. Indemnification & Other In the ordinary course of business, the Company may provide indemnifications of varying scope and terms to vendors, lessors, business partners, board members, officers, and other parties with respect to certain matters, including, but not limited to, losses arising out of breach of such agreements, services to be provided by the Company, negligence or willful misconduct of the Company, violations of law by the Company, or from intellectual property infringement claims made by third parties. In addition, the Company has entered into indemnification agreements with directors and certain officers and employees that will require the Company, among other things, to indemnify them against certain liabilities that may arise by reason of their status or service as directors, officers or employees. No demands have been made upon the Company to provide indemnification under such agreements, and thus, there are no claims that the Company is aware of that could have a material effect on the Company’s balance sheets, statements of operations, or statements of cash flows. The Company currently has directors’ and officers’ liability insurance. In addition, the Company enters into agreements in the normal course of business, including with contract research organizations for clinical trials, contract manufacturing organizations for certain manufacturing services, and vendors for preclinical studies and other services and products for operating purposes, which are generally cancelable upon written notice.

Related-Party Transactions

Related-Party Transactions	9 Months Ended
	Sep. 30, 2021
Related Party Transactions [Abstract]
Related-Party Transactions	8. Related-Party Transactions Upon the Company’s public offering on May 14, 2020, Merck’s ownership of the Company’s outstanding equity interest decreased to less than 10%. As a result, starting May 14, 2020, the Company ceased to reflect balances and transactions associated with Merck as being with a related party in its financial statements. Transactions with Merck for the three and nine months ended September 30, 2021 and 2020 are described in Note 5. As discussed in Note 2, Vaxcyte closed its IPO of its common stock on June 16, 2020, resulting in the Company’s ownership of Vaxcyte’s outstanding equity interest being less than 4.0%. As a result, starting on June 16, 2020, the Company ceased to reflect any balances and transactions associated with Vaxcyte as being with a related party in its financial statements. Transactions with Vaxcyte for the three and nine months ended September 30, 2021 and 2020 are described in Note 5.

Stockholders' Equity

Stockholders' Equity	9 Months Ended
	Sep. 30, 2021
Stockholders Equity Note [Abstract]
Stockholders' Equity	9. Stockholders’ Equity Common Stock Holders of common stock are entitled to one vote per share on all matters to be voted upon by the stockholders of the Company. The Company has reserved common stock, on an if-converted basis, for issuance as follows: September 30, December 31, 2021 2020 Common stock options issued and outstanding 6,533,772 5,439,295 Restricted common stock units issued and outstanding 2,262,776 666,375 Remaining shares reserved for issuance under 2004 and 2018 Equity Incentive Plan 1,681,651 1,710,824 Shares reserved for issuance under 2018 Employee Stock Purchase Plan 673,251 361,539 Warrants to purchase common stock 153,070 153,070 Total 11,304,520 8,331,103 Preferred Stock As of September 30, 2021 and December 31, 2020, the Company had 10,000,000 shares of preferred stock authorized with a par value of $0.001 per share. No shares of preferred stock were outstanding as of September 30, 2021 and December 31, 2020. Warrants In August 2017, the Company issued warrants to Oxford and SVB to purchase an aggregate of 682,230 shares of Series D-2 redeemable convertible preferred stock at an exercise price of $0.6596 per share in connection with the issuance of the August 2017 Loan. If there was a subsequent convertible preferred stock or other senior equity securities financing with a per share price less than the Series D-2 redeemable convertible preferred per share price, then the warrant would automatically convert to a warrant to purchase such class of shares, based on the per share price of such equity. Given that the price per share of the Series E redeemable convertible preferred stock was less than the price per share of the Series D-2 redeemable convertible preferred stock, the 2017 Warrant converted into a warrant to purchase a total of 1,682,871 shares of Series E redeemable convertible preferred stock at an exercise price of $0.2674 per share. The warrant is exercisable from the original date of issuance and has a 10-year term. The Company adjusted the warrant liability for changes in fair value until the completion of its IPO on October 1, 2018, at which time certain convertible preferred stock warrants were converted into warrants for the purchase of common stock and the related convertible preferred stock warrant liability was reclassified to additional paid-in capital and others expired. On October 1, 2018, 1,232,220 shares of the Series C redeemable convertible preferred warrants were canceled, and the remaining 687,928 shares were converted on a 1-for-0.0370 basis to warrants to purchase 25,454 shares of common stock. All Series E redeemable convertible preferred warrants were converted on a 1-for-0.0275 basis to warrants to purchase 46,359 shares of common stock. In February 2020, in connection with entering into a loan and security agreement, the Company issued to Oxford and SVB the 2020 Warrants, which are exercisable for 54,171 shares and 27,086 shares, respectively, of the Company’s common stock. The 2020 Warrants are exercisable in whole or in part, immediately, and have a per share exercise price of $9.23, which is the closing price of the Company’s common stock reported on the Nasdaq Global Market on the day prior to the effective date

Equity Incentive Plans, Employe

Equity Incentive Plans, Employee Stock Purchase Plan and Stock-Based Compensation	9 Months Ended
	Sep. 30, 2021
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Equity Incentive Plans, Employee Stock Purchase Plan and Stock-Based Compensation	10. Equity Incentive Plans, Employee Stock Purchase Plan and Stock-Based Compensation 2004 Equity Incentive Plan, 2018 Equity Incentive Plan and 2021 Equity Inducement Plan In September 2018, the Company adopted the 2018 Equity Incentive Plan (“2018 Plan”), which became effective on September 25, 2018. As a result, the Company will not grant any additional awards under the 2004 Equity Incentive Plan (“2004 Plan”). The terms of the 2004 Plan and applicable award agreements will continue to govern any outstanding awards thereunder. In addition to the shares of common stock reserved for future issuance under the 2004 Plan that were added to the 2018 Plan upon its effective date, the Company initially reserved 2,300,000 shares of common stock for issuance under the 2018 Plan. In addition, the number of shares of common stock reserved for issuance under the 2018 Plan will automatically increase on the first day of January for a period of up to ten years, commencing on January 1, 2019, in an amount equal to 5% of the total number of shares of the Company’s capital stock outstanding on the last day of the preceding year (rounded to the nearest whole share), or a lesser number of shares determined by the Company’s board of directors. As a result, common stock reserved for issuance under the 2018 Plan was increased by 2,287,605 shares on January 1, 2021. In August 2021, the Company adopted the 2021 Equity Inducement Plan (“2021 Plan”), which became effective on August 4, 2021. Upon its effective date, the Company initially reserved 750,000 shares of common stock for issuance pursuant to non-qualified stock options and restricted stock units (“RSUs”) under the 2021 Plan. In accordance with Rule 5635(c)(4) of the Nasdaq listing rules, equity awards under the 2021 Plan may only be made to an employee if he or she is granted such equity awards in connection with his or her commencement of employment with the Company and such grant is an inducement material to his or her entering into employment with the Company or such subsidiary. In addition, awards under the 2021 Plan may only be made to employees who have not previously been an employee or member of the Board (or any parent or subsidiary of the Company) or following a bona fide period of non-employment of the employee by the Company (or a parent or subsidiary of the Company). At all times the Company will reserve and keep available a sufficient number of shares as will be required to satisfy the requirements of all outstanding awards granted under the 2021 Plan. As of September 30, 2021, the Company had a total of 1,681,651 shares available for grant under the 2018 Plan and the 2021 Plan. The following table summarizes option activity under the Company’s 2004 Plan, 2018 Plan and 2021 Plan: Shares Weighted- Average Exercise Price Weighted- Average Remaining Contract Term (Years) Aggregate Intrinsic Value (in thousands) Stock options outstanding at December 31, 2020 5,439,295 $ 11.93 7.75 $ 53,202 Granted 1,383,950 $ 20.40 Exercised (185,974 ) $ 10.60 Canceled and forfeited (103,499 ) $ 10.58 Stock options outstanding at September 30, 2021 6,533,772 $ 13.78 7.65 $ 35,715 Stock options exercisable at September 30, 2021 3,523,838 $ 12.73 6.80 $ 21,959 The aggregate intrinsic value was calculated as the difference between the exercise prices of the underlying stock option awards and the estimated fair value of the Company’s common stock on the date of exercise. For the three and nine months ended September 30, 2021, the aggregate intrinsic value of stock options exercised was $0.1 million and $2.3 million, respectively, determined at the date of the option exercise. For the three and nine months ended September 30, 2020, the aggregate intrinsic value of stock options exercised was $48,000 and $0.1 million, respectively, determined at the date of the option exercise. Employee Stock Options Valuation For determining stock-based compensation expense, the fair-value-based measurement of each employee stock option was estimated as of the date of grant using the Black-Scholes option-pricing model with assumptions as follows: Nine Months Ended September 30, 2021 2020 Expected term (in years) 5.3-6.1 5.1-7.0 Expected volatility 81.6%-84.9% 73.2%-84.2% Risk-free interest rate 0.6%-1.1% 0.2%-1.6% Expected dividend – – Using the Black-Scholes option-valuation model, the weighted-average estimated grant-date fair value of employee stock options granted during the three and nine months ended September 30, 2021 was $13.21 and $14.35 per share, respectively, and during the three and nine months ended September 30, 2020 was $5.69 and $5.09 per share, respectively. Restricted Stock Units During the nine months ended September 30, 2021, the Company granted 1,913,750 shares of restricted common stock units (“RSUs”) to certain employees. These RSUs A summary of the status and activity of non-vested RSUs during the nine months ended September 30, 2021 is as follows: Number of shares Weighted Average Grant-Date Fair Value Non-vested December 31, 2020 666,375 $ 9.83 Granted 1,913,750 $ 20.56 Vested and released (232,474 ) $ 11.06 Canceled and forfeited (84,875 ) $ 17.07 Non-vested September 30, 2021 2,262,776 $ 18.50 2018 Employee Stock Purchase Plan In September 2018, the Company adopted the 2018 Employee Stock Purchase Plan (“ESPP”), which became effective on September 26, 2018, in order to enable eligible employees to purchase shares of the Company’s common stock. The Company initially reserved 230,000 shares of common stock for sale under the ESPP. The aggregate number of shares reserved for sale under the ESPP will automatically increase on the first day of January for a period of up to ten years, commencing on January 1, 2019, in an amount equal to 1% of the total number of shares of the Company’s capital stock outstanding on the last day of the preceding year (rounded to the nearest whole share), or a lesser number of shares determined by the Company’s board of directors. As a result, common stock reserved for issuance under the ESPP was increased by 457,521 shares on January 1, 2021. The aggregate number of shares issued over the term of the Company’s ESPP, subject to stock-splits, recapitalizations or similar events, may not exceed 2,300,000 shares of the Company’s common stock. The fair value of the ESPP shares is estimated using the Black-Scholes option pricing model. For the nine months ended September 30, 2021 and 2020 Nine Months Ended September 30, 2021 2020 Expected term (in years) 0.5 0.5 Expected volatility 65.9-111.4% 94.1 % Risk-free interest rate 0.1 % 0.4 % Expected dividend – – As of September 30, 2021 Stock-Based Compensation Expense The Company believes that the fair value of the stock options, RSUs and ESPP shares is more reliably measurable than the fair value of services received. Total stock-based compensation expense recognized was as follows: Three Months Ended Nine Months Ended September 30, September 30, 2021 2020 2021 2020 (in thousands) (in thousands) Research and development expense: $ 1,933 $ 761 $ 4,882 $ 1,972 General and administrative expense: $ 4,562 2,351 11,472 6,858 Total $ 6,495 $ 3,112 $ 16,354 $ 8,830 As of September 30, 2021 unvested stock options and RSUs granted The remaining unrecognized compensation cost is expected to be recognized over a weighted-average period of 2.6 years and 3.4 years, respectively. September 30, 2021 $ As of September 30, 2020, unrecognized stock-based compensation expense related to the unvested stock options and RSUs granted was $18.5 million and $5.4 million, respectively. The remaining unrecognized compensation cost is expected to be recognized over a weighted-average period of 2.4 years and 2.7 years, respectively. As of September 30, 2020, there was Non-Employee Stock-Based Compensation Expense The fair value of options granted to non-employees was estimated using the Black-Scholes method. The stock-based compensation expense related to non-employees for the three and nine months ended September 30, 2021 and 2020 was immaterial. Call Option Plan In February 2017, the Company adopted a Call Option Plan to grant selected employees, officers, directors and consultants (collectively, the “Participants”) options to purchase shares of the common stock of Vaxcyte. As of September 30, 2021, the Company has reserved 266,724 shares of Vaxcyte common stock for issuance under the program, under which call options covering 248,944 and 17,780 shares were granted in February 2017 and August 2019, respectively. The call options granted in February 2017 vested 25% on each of January 1, 2017, 2018, 2019, and 2020, and expire one year from the vesting date. The call options granted in August 2019 vest 25% on each of January 1, 2019, 2020, 2021, and 2022, and expire one year from the vesting date. A summary of the status of the call options as of September 30, 2021 and December 31, 2020 is as follows: September 30, December 31, 2021 2020 Shares Shares Options vested and exercised 257,834 257,834 Options vested and outstanding 4,445 - Options unvested and outstanding 4,445 8,890 Total options granted 266,724 266,724 The amounts recognized as compensation expense related to the Call Option Plan for the three and nine months ended September 30, 2021 were $32,000 and $78,000, respectively. The amounts recognized as compensation expense related to the Call Option Plan for the three and nine months ended September 30, 2020 were $90,000 and $0.2 million, respectively. The amounts recognized as other expense or income related to the remeasurement of the vested call options for the three and nine months ended September 30, 2021 were $13,000 of other expense and $5,000 of other income, respectively. The amounts recognized as other expense related to the remeasurement of the vested call options for the three and nine months ended September 30, 2020 were $1.1 million and $3.1 million, respectively. As of September 30, 2021 and December 31, 2020, the liability attributable to the Call Option Plan was $182,000 and $109,000, respectively.

Net (Loss) Income Per Share

Net (Loss) Income Per Share	9 Months Ended
	Sep. 30, 2021
Earnings Per Share [Abstract]
Net (Loss) Income Per Share	11. Net (Loss) Income Per Share The following table sets forth the computation of the Company’s basic and diluted net (loss) income per share. Three Months Ended Nine Months Ended September 30, September 30, 2021 2020 2021 2020 (in thousands, except share and per share amounts) Numerator: Net (loss) income, basic and diluted $ (30,902 ) $ 17,139 $ (67,413 ) $ 27,416 Denominator: Weighted-average shares used to compute basic EPS 46,162,544 36,887,266 46,060,010 29,994,917 Dilutive effect of common stock options – 828,623 – 228,557 Dilutive effect of restricted stock units – 159,788 – 120,649 Dilutive effect of warrants to purchase common stock – 1,875 – 5,733 Weighted-average shares used to compute diluted EPS 46,162,544 37,877,552 46,060,010 30,349,856 Net (loss) income per share: Basic $ (0.67 ) $ 0.46 $ (1.46 ) $ 0.91 Diluted $ (0.67 ) $ 0.45 $ (1.46 ) $ 0.90 The following common stock equivalents were excluded from the computation of diluted net loss per share for the periods ended September 30, 2021, because including them would have been antidilutive: As of September 30, 2021 Common stock options issued and outstanding 6,533,772 Restricted stock units issued and outstanding 2,262,776 Warrants to purchase common stock 153,070 Employee stock purchase plan 6,663 Total 8,956,281

Subsequent Event

Subsequent Event	9 Months Ended
	Sep. 30, 2021
Subsequent Events [Abstract]
Subsequent Event	12. Subsequent Event On October 9, 2021, the Company entered into an option agreement with BioNova Pharmaceuticals Limited (“BioNova”) (the “BioNova Option Agreement”), to confer BioNova the option to obtain exclusive rights to develop and commercialize STRO-001 in the People’s Republic of China, Taiwan, Hong Kong, and Macau (“Greater China”). BioNova will pursue the clinical development, regulatory approval, and commercialization of STRO-001 in multiple indications, including non-Hodgkin's lymphoma, multiple myeloma, and leukemia in the licensed territory. The Company will retain development and commercial rights of STRO-001 globally outside of Greater China, including the United States. Under the BioNova Option Agreement, BioNova will pay to the Company an initial licensing option payment of $4 million, with potential payments totaling up to $200 million related to option exercise, development, regulatory, and commercial milestones. The Company will provide STRO-001 to BioNova under appropriate clinical and commercial supply service agreements. Upon commercialization, the Company is eligible to receive tiered royalties ranging from low- to mid-teen percentages based on annual net sales of STRO-001 in Greater China for at least ten years following the first commercial sale of STRO-001 in Greater China. BioNova has the right to terminate the BioNova Option Agreement for convenience or other reasons specified in the BioNova Option Agreement, upon prior written notice.

Summary of Significant Accoun_2

Summary of Significant Accounting Policies (Policies)	9 Months Ended
	Sep. 30, 2021
Accounting Policies [Abstract]
Basis of Presentation and Use of Estimates	Basis of Presentation and Use of Estimates The accompanying interim condensed financial statements of the Company are unaudited. These interim condensed financial statements have been prepared in accordance with generally accepted accounting principles in the United States of America (“U.S. GAAP”) and the applicable rules and regulations of the Securities and Exchange Commission (“SEC”) for interim financial information. Accordingly, they do not include all of the information and footnotes required by U.S. GAAP for complete financial statements. The December 31, 2020 condensed balance sheet was derived from the audited financial statements as of that date but does not include all of the information and footnotes required by U.S. GAAP for complete financial statements. The preparation of financial statements in conformity with U.S. GAAP requires management to make estimates and assumptions that affect the amounts reported in the financial statements and accompanying notes. The Company bases its estimates on historical experience and market-specific or other relevant assumptions that it believes are reasonable under the circumstances. The amounts of assets and liabilities reported in the Company’s condensed balance sheets and the amounts of expenses and income reported for each of the periods presented are affected by estimates and assumptions, which are used for, but are not limited to, determining research and development periods under collaboration arrangements, stock-based compensation expense, valuation of marketable securities, impairment of long-lived assets, income taxes and certain accrued liabilities. Actual results could differ from such estimates or assumptions. The full extent to which the COVID-19 pandemic will directly or indirectly impact the Company’s business, results of operations and financial condition, including revenue, expenses, manufacturing, clinical trials, research and development costs and employee-related amounts, will depend on future developments that are highly uncertain, including as a result of new information that may emerge concerning COVID-19 and the actions taken to contain or treat it, as well as the economic impact on local, regional, national and international customers, suppliers, service providers and markets. The Company has made estimates of the impact of COVID-19 within its financial statements and there may be changes to those estimates in future periods. Actual results could differ from such estimates or assumptions. The accompanying unaudited interim condensed financial statements have been prepared on the same basis as the audited financial statements and, in the opinion of management, reflect all adjustments of a normal recurring nature considered necessary to state fairly the Company ’ s financial position, results of operations , comprehensive loss, and cash flows for the interim periods. The interim results for the three and nine months ended September 30 , 20 2 1 are not necessarily indicative of the results that may be expected for the year ending December 31, 20 2 1 , or for any other future annual or interim period. The information included in this Quarterly Report on Form 10-Q should be read in conjunction with the Company’s audited financial statements included in the Annual Report on Form 10-K pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934, as amended, for the year ended December 31, 2020.
Recently Adopted Accounting Pronouncements	Recently Adopted Accounting Pronouncements In June 2016, the Financial Accounting Standards Board (“FASB”) issued Accounting Standards Updates (“ASU”) 2016-13 (Topic 326), Financial Instruments Credit Losses. The guidance modifies the measurement and recognition of credit losses for most financial assets and certain other instruments. The amendment updates the guidance for measuring and recording credit losses on financial assets measured at amortized cost by replacing the “incurred loss” model with an “expected loss” model. The Company adopted ASU 2016-13 in the third quarter of 2021 using the modified retrospective adoption approach. As a result of this adoption, the Company presents these financial assets, which include the accounts receivable and available-for-sale debt securities, at the net amount the Company expects to collect. The amendment also requires the Company to record credit losses related to available-for-sale debt securities as an allowance through net income rather than reducing the carrying amount under the historical, other-than-temporary-impairment model. The adoption of ASU 2016-13 did not have a material impact on the Company’s financial statements and related disclosures for the quarter ended September 30, 2021. In February 2016, the FASB issued ASU 2016-02 (Topic 842), Leases (Accounting Standards Codification, or “ASC”, 842). ASC 842 supersedes the lease recognition requirements in ASC 840, Leases. ASC 842 clarifies the definition of a lease and requires lessees to recognize right-of-use assets and lease liabilities for all leases, including those classified as operating leases under previous lease accounting guidance. The Company adopted ASC 842 on July 1, 2021, effective as of January 1, 2021. There was no impact on the Company’s accumulated deficit as of January 1, 2021 as a result of the adoption of this standard. Results for the three and nine months ended September 30, 2021 are presented under Topic 842. Other prior period amounts are not adjusted and continue to be reported in accordance with our historic accounting under previous lease guidance, ASC Topic 840: Leases (“Topic 840”). The Company elected the package of practical expedients permitted under the transition guidance of the new standard, which allowed the Company to carry forward its historical assessment on whether a contract is or contains a lease, lease classification, and initial direct costs. Upon adoption on January 1, 2021, the Company recognized operating lease right-of-use (“ROU”) assets of $29.7 million, and current and non-current operating lease liabilities of $2.9 million and $27.8 million, respectively. In connection with the adoption of this standard, deferred rent of $1.3 million and prepaid rent of $0.3 million, which was previously recorded in prepaid expenses and other current assets on the balance sheet as of December 31, 2020, were derecognized. Finance lease assets and liabilities were not material. The adoption of ASC 842 did not have a material impact to the Company’s condensed statements of operations and condensed statements of cash flows. Please see Note 7 for additional information regarding the Company’s leases.
Leases	Leases The Company determines if an arrangement is or contains a lease at contract inception by assessing whether the arrangement contains an identified asset and whether the lessee has the right to control such asset. The Company is required to classify leases as either finance or operating leases and to record a ROU asset and a lease liability for all leases with a term greater than 12 months regardless of the lease classification. The lease classification will determine whether the lease expense is recognized based on an effective interest rate method or on a straight-line basis over the term of the lease. The Company determines the initial classification and measurement of its ROU assets and lease liabilities at the lease commencement date and thereafter, if modified. The Company does not have material finance leases. For leases with a term greater than 12 months, the Company records the related ROU asset and lease liability at the present value of lease payments over the term of the lease. The term of the Company’s leases equals the non-cancellable period of the lease, including any rent-free periods provided by the lessor, and also includes options to extend or terminate the lease that the Company is reasonably certain to exercise. The ROU asset equals the carrying amount of the related lease liability, adjusted for any lease payments made prior to lease commencement and lease incentives provided by the lessor. Variable lease payments are expensed as incurred and do not factor into the measurement of the applicable ROU asset or lease liability. The Company has elected, for all classes of underlying assets, not to recognize ROU assets and lease liabilities for leases with a term of 12 months or less. Lease cost for short-term leases is recognized on a straight-line basis over the lease term. The Company has also elected to not separate lease and non-lease components for its leases and, as a result, accounts for lease and non-lease components as one component. The Company’s leases do not provide a readily determinable implicit rate. Therefore, the Company estimates its incremental borrowing rate to discount the lease payments based on information available at lease commencement. The Company determines its incremental borrowing rate based on the rate of interest that the Company would have to pay to borrow, on a collateralized basis over a similar term, an amount equal to the lease payments in a similar economic environment. Lease payments may be fixed or variable; however, only fixed payments are included in the Company’s lease liability calculation. Lease costs for the Company’s operating leases are recognized on a straight-line basis within operating expenses over the lease term. The Company’s lease agreements may contain variable non-lease components such as common area maintenance, operating expenses or other costs, which are expensed as incurred.
Cash, Cash Equivalents and Restricted Cash	Cash, Cash Equivalents and Restricted Cash The following table provides a reconciliation of cash, cash equivalents and restricted cash reported within the balance sheets that sum to the total of the same amounts shown in the statements of cash flows. September 30, 2021 2020 (in thousands) Cash and cash equivalents $ 30,707 $ 64,370 Restricted cash 872 872 Total cash, cash equivalents, and restricted cash shown in the statements of cash flows $ 31,579 $ 65,242
Investments in Equity Securities	Investments in Equity Securities Subsequent to the closing of the initial public offering (“IPO”) of Vaxcyte, Inc. in June 2020, the fair value of Vaxcyte’s common stock became readily determinable.
Fair Value Measurements	Fair Value Measurements Fair value is defined as the exchange price that would be received for an asset or paid to transfer a liability, or an exit price, in the principal or most advantageous market for that asset or liability in an orderly transaction between market participants on the measurement date and establishes a fair value hierarchy that requires an entity to maximize the use of observable inputs, where available, and minimize the use of unobservable inputs when measuring fair value. The Company determined the fair value of financial assets and liabilities using the fair value hierarchy that describes three levels of inputs that may be used to measure fair value, as follows: Level 1—Quoted prices in active markets for identical assets and liabilities; Level 2—Inputs other than Level 1 that are observable, either directly or indirectly, such as quoted prices for similar assets or liabilities, quoted prices in markets that are not active, or other inputs that are observable or can be corroborated by observable market data for substantially the full term of the assets or liabilities; and Level 3—Unobservable inputs that are supported by little or no market activity and that are significant to the fair value of the assets or liabilities. The carrying amounts of accounts receivable, prepaid expenses, accounts payable, accrued liabilities and accrued compensation and benefits approximate fair value due to the short-term nature of these items. The fair value of the Company’s outstanding loan (See Note 6) is estimated using the net present value of the payments, discounted at an interest rate that is consistent with market interest rate, which is a Level 2 input. The estimated fair value of the Company’s outstanding loan approximates the carrying amount, as the loan bears a floating rate that approximates the market interest rate.
Revenue Recognition	Revenue Recognition The Company has no products approved for commercial sale and has not generated any revenue from commercial product sales. The total revenue to date has been generated principally from collaboration and license agreements and to a lesser extent, from manufacturing, supply, services and materials the Company provides to its collaboration partners. Collaboration Revenue The Company derives revenue from collaboration arrangements, under which the Company may grant licenses to its collaboration partners to further develop and commercialize its proprietary product candidates. The Company may also perform research and development activities under the collaboration agreements. Consideration under these contracts generally includes a nonrefundable upfront payment, development, regulatory and commercial milestones and other contingent payments, and royalties based on net sales of approved products. Additionally, the collaborations may provide options for the customer to acquire from the Company materials and reagents, clinical product supply or additional research and development services under separate agreements. The Company assesses which activities in the collaboration agreements are considered distinct performance obligations that should be accounted for separately. The Company develops assumptions that require judgement to determine whether the license to the Company’s intellectual property is distinct from the research and development services or participation in activities under the collaboration agreements. At the inception of each agreement, the Company determines the arrangement transaction price, which includes variable consideration, based on the assessment of the probability of achievement of future milestones and contingent payments and other potential consideration. The Company recognizes revenue over time by measuring its progress towards the complete satisfaction of the relevant performance obligation using an appropriate input or output method based on the nature of the service promised to the customer. For arrangements that include multiple performance obligations, the Company allocates the transaction price to the identified performance obligations based on the standalone selling price, or SSP, of each distinct performance obligation. In instances where SSP is not directly observable, the Company develops assumptions that require judgment to determine the SSP for each performance obligation identified in the contract. These key assumptions may include FTE, personnel effort, estimated costs, discount rates and probabilities of clinical development and regulatory success. Upfront Payments : For collaboration arrangements that include a nonrefundable upfront payment, if the license fee and research and development services cannot be accounted for as separate performance obligations, the transaction price is deferred and recognized as revenue over the expected period of performance using a cost-based input methodology. The Company uses judgement to assess the pattern of delivery of the performance obligation. In addition, amounts paid in advance of services being rendered may result in an associated financing component to the upfront payment. Accordingly, the interest on such borrowing cost component will be recorded as interest expense and revenue, based on an appropriate borrowing rate applied to the value of services to be performed by the Company over the estimated service performance period. License Grants: For collaboration arrangements that include a grant of a license to the Company’s intellectual property, the Company considers whether the license grant is distinct from the other performance obligations included in the arrangement. For licenses that are distinct, the Company recognizes revenues from nonrefundable, upfront payments and other consideration allocated to the license when the license term has begun and the Company has provided all necessary information regarding the underlying intellectual property to the customer, which generally occurs at or near the inception of the arrangement. Milestone and Contingent Payments : At the inception of the arrangement and at each reporting date thereafter, the Company assesses whether it should include any milestone and contingent payments or other forms of variable consideration in the transaction price using the most likely amount method. If it is probable that a significant reversal of cumulative revenue would not occur upon resolution of the uncertainty, the associated milestone value is included in the transaction price. At the end of each subsequent reporting period, the Company re-evaluates the probability of achievement of each such milestone and any related constraint and , if necessary, adjusts its estimate of the overall transaction price. Since milestone and contingent payments may become payable to the Company upon the initiation of a clinical study or filing for or receipt of regulatory approval, the Company reviews the relevant facts and circumstances to determine when the Company should update the transaction price, which may occur before the triggering event. When the Company updates the transaction price for milestone and contingent payments, the Company allocates the changes in the total transaction price to each performance obligation in the agreement on the same basis as the initial allocation. Any such adjustments are recorded on a cumulative catch-up basis in the period of adjustment, which may result in recognizing revenue for previously satisfied performance obligations in such period. The Company’s collaborators generally pay milestones and contingent payments subsequent to achievement of the triggering event. Research and Development Services : For amounts allocated to the Company’s research and development obligations in a collaboration arrangement, the Company recognizes revenue over time using a cost-based input methodology, representing the transfer of goods or services as activities are performed over the term of the agreement. Materials Supply: The Company provides materials and reagents, clinical materials and services to certain of its collaborators under separate agreements. The consideration for such services is generally based on FTE personnel effort used to manufacture those materials reimbursed at an agreed upon rate in addition to agreed-upon pricing for the provided materials. The amounts billed are recognized as revenue as the performance obligations are met by the Company.

Summary of Significant Accoun_3

Summary of Significant Accounting Policies (Tables)	9 Months Ended
	Sep. 30, 2021
Accounting Policies [Abstract]
Schedule of Reconciliation of Cash, Cash Equivalents, and Restricted Cash	The following table provides a reconciliation of cash, cash equivalents and restricted cash reported within the balance sheets that sum to the total of the same amounts shown in the statements of cash flows. September 30, 2021 2020 (in thousands) Cash and cash equivalents $ 30,707 $ 64,370 Restricted cash 872 872 Total cash, cash equivalents, and restricted cash shown in the statements of cash flows $ 31,579 $ 65,242

Fair Value Measurements (Tables

Fair Value Measurements (Tables)	9 Months Ended
	Sep. 30, 2021
Fair Value Disclosures [Abstract]
Fair Value of Financial Assets and Liabilities Measured on Recurring Basis	The following table sets forth the fair value of the Company’s financial assets and liabilities measured on a recurring basis by level within the fair value hierarchy: September 30, 2021 Total Level 1 Level 2 Level 3 (in thousands) Assets: Money market funds $ 30,108 $ 30,108 $ – $ – Commercial paper 56,568 – 56,568 – Corporate debt securities 70,276 – 70,276 – Equity securities 39,763 39,763 – – Asset-backed securities 37,595 – 37,595 – U.S. government securities 37,631 37,631 – – Supranational debt securities 21,440 – 21,440 – Total $ 293,381 $ 107,502 $ 185,879 $ - The following table sets forth the fair value of the Company’s financial assets and liabilities measured on a recurring basis by level within the fair value hierarchy: December 31, 2020 Total Level 1 Level 2 Level 3 (in thousands) Assets: Money market funds $ 204,632 $ 204,632 $ – $ – Commercial paper 42,208 – 42,208 – Corporate debt securities 25,716 – 25,716 – Equity securities 41,644 41,644 – – Asset-backed securities 12,632 – 12,632 – U.S. government securities 39,785 39,785 – – Total $ 366,617 $ 286,061 $ 80,556 $ –

Cash Equivalents and Marketab_2

Cash Equivalents and Marketable Securities (Tables)	9 Months Ended
	Sep. 30, 2021
Cash And Cash Equivalents [Abstract]
Schedule of Cash Equivalents and Marketable Securities	Cash equivalents and marketable securities consisted of the following: September 30, 2021 Amortized Cost Basis Unrealized Gains Unrealized (Losses) Fair Value (in thousands) Money market funds $ 30,108 $ – $ – $ 30,108 Commercial paper 56,568 – – 56,568 Corporate debt securities 70,290 7 (21 ) 70,276 Asset-based securities 37,607 2 (14 ) 37,595 U.S. government securities 37,624 7 – 37,631 Supranational debt securities 21,451 – (11 ) 21,440 Total 253,648 16 (46 ) 253,618 Less amounts classified as cash equivalents (30,108 ) – – (30,108 ) Total marketable securities $ 223,540 $ 16 $ (46 ) $ 223,510 December 31, 2020 Amortized Cost Basis Unrealized Gains Unrealized (Losses) Fair Value (in thousands) Money market funds $ 204,632 $ – $ – $ 204,632 Commercial paper 42,208 – – 42,208 Corporate debt securities 25,669 48 (1 ) 25,716 Asset-based securities 12,593 39 – 12,632 U.S. government securities 39,743 44 (2 ) 39,785 Total 324,845 131 (3 ) 324,973 Less amounts classified as cash equivalents (204,632 ) – – (204,632 ) Total marketable securities $ 120,213 $ 131 $ (3 ) $ 120,341

Collaboration and License Agr_2

Collaboration and License Agreements and Supply Agreements (Tables)	9 Months Ended
	Sep. 30, 2021
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Summary of Recognized Revenue	In accordance with the collaboration agreements, the Company recognized revenue as follows: Three Months Ended Nine Months Ended September 30, September 30, 2021 2020 2021 2020 (in thousands) (in thousands) Bristol Myers Squibb Company (“BMS”) $ 1,118 $ 7,119 $ 7,784 $ 10,673 Merck Sharp & Dohme Corporation (“Merck”) (1) 6,414 9,055 38,175 18,837 Merck KGaA, Darmstadt, Germany (operating in the United States and Canada under the name “EMD Serono”) 249 1,507 2,844 4,656 Vaxcyte (2) 736 142 2,423 278 Total revenue $ 8,517 $ 17,823 $ 51,226 $ 34,444 (1) Merck was a related party until the closing of the Company’s public offering on May 14, 2020. (2) Vaxcyte was a related party until the closing of its initial public offering on June 16, 2020.
Summary of Deferred Revenue Balance	The following table presents the changes in the Company’s deferred revenue balance from collaboration agreements during the nine months ended September 30, 2021: Nine Months Ended September 30, 2021 (in thousands) Deferred revenue—December 31, 2020 $ 20,703 Additions to deferred revenue 19,402 Recognition of revenue in current period (32,156 ) Deferred revenue—September 30, 2021 $ 7,949
2018 BMS Master Services Agreement
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Summary of Recognized Revenue	Revenues under the BMS Agreement and the 2018 BMS Master Services Agreement were as follows: Three Months Ended Nine Months Ended September 30, September 30, 2021 2020 2021 2020 (in thousands) (in thousands) Ongoing performance related to unsatisfied performance obligations $ – $ 1,000 $ – $ 2,974 Research and development services 249 246 762 646 Materials supply 869 5,873 7,022 7,053 Total revenue $ 1,118 $ 7,119 $ 7,784 $ 10,673
2020 Merck Master Services Agreement
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Summary of Recognized Revenue	Revenues under the 2018 Merck Agreement and the 2020 Merck Master Services Agreement were as follows: Three Months Ended Nine Months Ended September 30, September 30, 2021 2020 2021 2020 (in thousands) (in thousands) Ongoing performance related to unsatisfied performance obligations $ 3,506 $ 6,907 $ 30,889 $ 13,048 Research and development services 419 1,732 2,328 4,245 Financing component on unearned revenue 149 416 561 1,544 Materials supply 2,340 – 4,397 – Total revenue $ 6,414 $ 9,055 $ 38,175 $ 18,837
2019 EMD Serono Supply Agreement
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Summary of Recognized Revenue	Revenues under the EMD Serono agreements were as follows: Three Months Ended Nine Months Ended September 30, September 30, 2021 2020 2021 2020 (in thousands) (in thousands) Contingent payment earned $ – $ 1,000 $ 2,000 $ 1,000 Research and development services 214 265 503 1,088 Materials supply 35 242 341 2,568 Total revenue $ 249 $ 1,507 $ 2,844 $ 4,656
Supply Agreement | Vaxcyte
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Summary of Recognized Revenue	Revenues under the Vaxcyte Supply Agreement Three Months Ended Nine Months Ended September 30, September 30, 2021 2020 2021 2020 (in thousands) (in thousands) Research and development services $ 247 $ – $ 716 $ – Materials supply 489 142 1,707 278 Total revenue $ 736 $ 142 $ 2,423 $ 278

Commitments and Contingencies (

Commitments and Contingencies (Tables)	9 Months Ended
	Sep. 30, 2021
Commitments And Contingencies Disclosure [Abstract]
Schedule of Components of Lease Costs	The components of lease costs, which the Company includes in operating expenses in the condensed statements of operations, were as follows (in thousands): Three Months Ended Nine Months Ended September 30, September 30, 2021 2021 Operating lease cost $ 2,266 $ 6,396 Short-term lease cost 22 73 Variable lease cost 754 1,513 Total lease costs $ 3,042 $ 7,982
Schedule of Maturities of Operating Lease Liabilities	As of September 30, 2021, the maturities of the Company’s operating lease liabilities were as follows (in thousands): Year Ending December 31, Amount (in thousands) Remaining in 2021 $ 2,142 2022 (1) 1,643 2023 8,002 2024 9,219 2025 9,533 Thereafter 17,282 Total lease payments 47,821 Less: imputed interest (14,303 ) Operating lease liabilities 33,518 Less: current portion (1,445 ) Total lease liabilities, non-current $ 32,073 (1) Includes approximately $5.2 million in potential financial benefit to the Company of base rent abatement to be provided by sublessor for months 7 – 18 of the sublease period, subject to certain terms contained in the Sublease. Under the historical guidance of ASC 840, the deferred rent balance on December 31, 2020 totaled $1.3 million and our future minimum lease payments for our operating leases on December 31, 2020 were as follows (in thousands): Year Ending December 31, Amount (in thousands) 2021 $ 5,742 2022 (1) 5,183 2023 6,310 2024 7,476 2025 and thereafter 24,034 Total future minimum lease payments $ 48,745 (1) Excludes approximately $5.2 million in potential financial benefit to the Company of base rent abatement to be provided by sublessor for months 7 – 18 of the sublease period, subject to certain terms contained in the Sublease

Stockholders' Equity (Tables)

Stockholders' Equity (Tables)	9 Months Ended
	Sep. 30, 2021
Stockholders Equity Note [Abstract]
Schedule of Common Stock Reserved for Future Issuance	The Company has reserved common stock, on an if-converted basis, for issuance as follows: September 30, December 31, 2021 2020 Common stock options issued and outstanding 6,533,772 5,439,295 Restricted common stock units issued and outstanding 2,262,776 666,375 Remaining shares reserved for issuance under 2004 and 2018 Equity Incentive Plan 1,681,651 1,710,824 Shares reserved for issuance under 2018 Employee Stock Purchase Plan 673,251 361,539 Warrants to purchase common stock 153,070 153,070 Total 11,304,520 8,331,103

Equity Incentive Plans, Emplo_2

Equity Incentive Plans, Employee Stock Purchase Plan and Stock-Based Compensation (Tables)	9 Months Ended
	Sep. 30, 2021
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Summary of Option Activity	The following table summarizes option activity under the Company’s 2004 Plan, 2018 Plan and 2021 Plan: Shares Weighted- Average Exercise Price Weighted- Average Remaining Contract Term (Years) Aggregate Intrinsic Value (in thousands) Stock options outstanding at December 31, 2020 5,439,295 $ 11.93 7.75 $ 53,202 Granted 1,383,950 $ 20.40 Exercised (185,974 ) $ 10.60 Canceled and forfeited (103,499 ) $ 10.58 Stock options outstanding at September 30, 2021 6,533,772 $ 13.78 7.65 $ 35,715 Stock options exercisable at September 30, 2021 3,523,838 $ 12.73 6.80 $ 21,959
Schedule of Employee Stock Options Valuation	For determining stock-based compensation expense, the fair-value-based measurement of each employee stock option was estimated as of the date of grant using the Black-Scholes option-pricing model with assumptions as follows: Nine Months Ended September 30, 2021 2020 Expected term (in years) 5.3-6.1 5.1-7.0 Expected volatility 81.6%-84.9% 73.2%-84.2% Risk-free interest rate 0.6%-1.1% 0.2%-1.6% Expected dividend – –
Summary of Status and Activity of Non-vested RSUs	A summary of the status and activity of non-vested RSUs during the nine months ended September 30, 2021 is as follows: Number of shares Weighted Average Grant-Date Fair Value Non-vested December 31, 2020 666,375 $ 9.83 Granted 1,913,750 $ 20.56 Vested and released (232,474 ) $ 11.06 Canceled and forfeited (84,875 ) $ 17.07 Non-vested September 30, 2021 2,262,776 $ 18.50
Schedule of Fair Value of ESPP Shares Using Option Pricing Model	For the nine months ended September 30, 2021 and 2020 Nine Months Ended September 30, 2021 2020 Expected term (in years) 0.5 0.5 Expected volatility 65.9-111.4% 94.1 % Risk-free interest rate 0.1 % 0.4 % Expected dividend – –
Schedule of Stock-Based Compensation Expense Recognized	Total stock-based compensation expense recognized was as follows: Three Months Ended Nine Months Ended September 30, September 30, 2021 2020 2021 2020 (in thousands) (in thousands) Research and development expense: $ 1,933 $ 761 $ 4,882 $ 1,972 General and administrative expense: $ 4,562 2,351 11,472 6,858 Total $ 6,495 $ 3,112 $ 16,354 $ 8,830
Summary of the Status of Call Options	A summary of the status of the call options as of September 30, 2021 and December 31, 2020 is as follows: September 30, December 31, 2021 2020 Shares Shares Options vested and exercised 257,834 257,834 Options vested and outstanding 4,445 - Options unvested and outstanding 4,445 8,890 Total options granted 266,724 266,724

Net (Loss) Income Per Share (Ta

Net (Loss) Income Per Share (Tables)	9 Months Ended
	Sep. 30, 2021
Earnings Per Share [Abstract]
Summary of Computation of Company's Basic and Diluted Net (Loss) Income per Share	The following table sets forth the computation of the Company’s basic and diluted net (loss) income per share. Three Months Ended Nine Months Ended September 30, September 30, 2021 2020 2021 2020 (in thousands, except share and per share amounts) Numerator: Net (loss) income, basic and diluted $ (30,902 ) $ 17,139 $ (67,413 ) $ 27,416 Denominator: Weighted-average shares used to compute basic EPS 46,162,544 36,887,266 46,060,010 29,994,917 Dilutive effect of common stock options – 828,623 – 228,557 Dilutive effect of restricted stock units – 159,788 – 120,649 Dilutive effect of warrants to purchase common stock – 1,875 – 5,733 Weighted-average shares used to compute diluted EPS 46,162,544 37,877,552 46,060,010 30,349,856 Net (loss) income per share: Basic $ (0.67 ) $ 0.46 $ (1.46 ) $ 0.91 Diluted $ (0.67 ) $ 0.45 $ (1.46 ) $ 0.90
Summary of Common Stock Equivalents of Antidilutive Securities Excluded from Computation of Diluted Net Loss per Share	The following common stock equivalents were excluded from the computation of diluted net loss per share for the periods ended September 30, 2021, because including them would have been antidilutive: As of September 30, 2021 Common stock options issued and outstanding 6,533,772 Restricted stock units issued and outstanding 2,262,776 Warrants to purchase common stock 153,070 Employee stock purchase plan 6,663 Total 8,956,281

Organization and Principal Ac_2

Organization and Principal Activities - Additional Information (Details) $ in Thousands	9 Months Ended
	Sep. 30, 2021USD ($)Segment	Dec. 31, 2020USD ($)
Organization Consolidation And Presentation Of Financial Statements [Line Items]
Date of incorporation	Apr. 21, 2003
Headquartered in	South San Francisco
Headquartered in state	CA
Number of operating segments | Segment	1
Accumulated deficit	$ 295,286	$ 227,873
Unrestricted cash, cash equivalents and marketable securities	$ 254,200
Substantial doubt about going concern, within one year	false
Minimum
Organization Consolidation And Presentation Of Financial Statements [Line Items]
Period from issuance date of unaudited interim condensed financial statements	12 months

Summary of Significant Accoun_4

Summary of Significant Accounting Policies - Additional Information (Details) - USD ($) $ in Thousands	Sep. 30, 2021	Jan. 01, 2021
Summary Of Significant Accounting Policies [Line Items]
Operating lease right-of-use assets	$ 30,129	$ 29,700
Operating lease liabilities current	1,445	2,900
Operating lease liabilities non-current	$ 32,073	27,800
Accounting Standards Update 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	Jun. 1, 2021
Change in accounting principle, accounting standards update, immaterial effect [true false]	true
Accounting Standards Update 2016-02
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	Jul. 1, 2021
Change in accounting principle, accounting standards update, immaterial effect [true false]	true
Deferred rent derecognized		1,300
Prepaid rent derecognized		$ 300

Summary of Significant Accoun_5

Summary of Significant Accounting Policies - Schedule of Reconciliation of Cash, Cash Equivalents, and Restricted Cash (Details) - USD ($) $ in Thousands	Sep. 30, 2021	Dec. 31, 2020	Sep. 30, 2020
Accounting Policies [Abstract]
Cash and cash equivalents	$ 30,707	$ 206,152	$ 64,370
Restricted cash	872	$ 872	872
Total cash, cash equivalents, and restricted cash shown in the statements of cash flows	$ 31,579		$ 65,242

Fair Value Measurements - Fair

Fair Value Measurements - Fair Value of Financial Assets and Liabilities Measured on Recurring Basis (Details) - Fair Value Measurements Recurring - USD ($)	Sep. 30, 2021	Dec. 31, 2020
Assets:
Total	$ 293,381,000	$ 366,617,000
Level 1
Assets:
Total	107,502,000	286,061,000
Level 2
Assets:
Total	185,879,000	80,556,000
Level 3
Assets:
Total	0	0
Money Market Funds
Assets:
Total	30,108,000	204,632,000
Money Market Funds | Level 1
Assets:
Total	30,108,000	204,632,000
Commercial Paper
Assets:
Total	56,568,000	42,208,000
Commercial Paper | Level 2
Assets:
Total	56,568,000	42,208,000
Corporate Debt Securities
Assets:
Total	70,276,000	25,716,000
Corporate Debt Securities | Level 2
Assets:
Total	70,276,000	25,716,000
Equity Securities
Assets:
Total	39,763,000	41,644,000
Equity Securities | Level 1
Assets:
Total	39,763,000	41,644,000
Asset-backed Securities
Assets:
Total	37,595,000	12,632,000
Asset-backed Securities | Level 2
Assets:
Total	37,595,000	12,632,000
U.S. Government Securities
Assets:
Total	37,631,000	39,785,000
U.S. Government Securities | Level 1
Assets:
Total	37,631,000	$ 39,785,000
Supranational Debt Securities
Assets:
Total	21,440,000
Supranational Debt Securities | Level 2
Assets:
Total	$ 21,440,000

Fair Value Measurements - Addit

Fair Value Measurements - Additional Information (Details) - USD ($)	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020	Dec. 31, 2020
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Estimated fair value of equity securities	$ 39,763,000		$ 39,763,000		$ 41,644,000
Unrealized gain (loss) on equity securities	4,483,000	$ 29,778,000	(1,881,000)	$ 78,638,000
Vaxcyte, Inc. | Vaxcyte Common Stock
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Estimated fair value of equity securities	39,800,000		39,800,000
Unrealized gain (loss) on equity securities	$ 4,500,000		$ (1,900,000)
Equity Securities | Vaxcyte, Inc. | Vaxcyte Common Stock
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Number of shares held	1,567,324		1,567,324
Fair Value Measurements Recurring
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Securities held	$ 293,381,000		$ 293,381,000		366,617,000
Fair Value Measurements Recurring | Level 3
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Securities held	$ 0		$ 0		$ 0

Cash Equivalents and Marketab_3

Cash Equivalents and Marketable Securities - Schedule of Cash Equivalents and Marketable Securities (Details) - USD ($) $ in Thousands	Sep. 30, 2021	Dec. 31, 2020	Sep. 30, 2020
Cash And Cash Equivalents [Line Items]
Amortized Cost Basis	$ 253,648	$ 324,845
Unrealized Gains	16	131
Unrealized (Losses)	(46)	(3)
Fair Value	253,618	324,973
Less amounts classified as cash equivalents, Amortized Cost Basis	(30,707)	(206,152)	$ (64,370)
Marketable Securities
Cash And Cash Equivalents [Line Items]
Amortized Cost Basis	223,540	120,213
Unrealized Gains	16	131
Unrealized (Losses)	(46)	(3)
Fair Value	223,510	120,341
Cash Equivalents
Cash And Cash Equivalents [Line Items]
Less amounts classified as cash equivalents, Amortized Cost Basis	(30,108)	(204,632)
Less amounts classified as cash equivalents, Fair Value	(30,108)	(204,632)
Money Market Funds
Cash And Cash Equivalents [Line Items]
Amortized Cost Basis	30,108	204,632
Unrealized Gains	0	0
Unrealized (Losses)	0	0
Fair Value	30,108	204,632
Commercial Paper
Cash And Cash Equivalents [Line Items]
Amortized Cost Basis	56,568	42,208
Unrealized Gains	0	0
Unrealized (Losses)	0	0
Fair Value	56,568	42,208
Corporate Debt Securities
Cash And Cash Equivalents [Line Items]
Amortized Cost Basis	70,290	25,669
Unrealized Gains	7	48
Unrealized (Losses)	(21)	(1)
Fair Value	70,276	25,716
Asset-backed Securities
Cash And Cash Equivalents [Line Items]
Amortized Cost Basis	37,607	12,593
Unrealized Gains	2	39
Unrealized (Losses)	(14)	0
Fair Value	37,595	12,632
U.S. Government Securities
Cash And Cash Equivalents [Line Items]
Amortized Cost Basis	37,624	39,743
Unrealized Gains	7	44
Unrealized (Losses)	0	(2)
Fair Value	37,631	$ 39,785
Supranational Debt Securities
Cash And Cash Equivalents [Line Items]
Amortized Cost Basis	21,451
Unrealized Gains	0
Unrealized (Losses)	(11)
Fair Value	$ 21,440

Cash Equivalents and Marketab_4

Cash Equivalents and Marketable Securities - Additional Information (Details) - USD ($)	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020	Dec. 31, 2020
Cash And Cash Equivalents [Line Items]
Long-term marketable securities	$ 64,279,000		$ 64,279,000		$ 0
Investments in an unrealized loss position	85,700,000		85,700,000		14,700,000
Unrealized losses	46,000		46,000		$ 3,000
Recognition of other-than-temporary impairment	$ 0	$ 0	$ 0	$ 0
Maximum
Cash And Cash Equivalents [Line Items]
Marketable securities maturity period			1 year		1 year

Collaboration and License Agr_3

Collaboration and License Agreements and Supply Agreements - Additional Information (Details)	Mar. 31, 2021USD ($)	May 31, 2019USD ($)	Aug. 31, 2020USD ($)	Mar. 31, 2020USD ($)	Feb. 29, 2020USD ($)	Sep. 30, 2019USD ($)	Jul. 31, 2018USD ($)Program	Aug. 31, 2017Program	Jun. 30, 2021USD ($)	Sep. 30, 2021USD ($)	Dec. 31, 2020USD ($)
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Accounts receivable, reserve for credit losses										$ 0
Accounts receivable										12,330,000	$ 5,559,000
2019 EMD Serono Supply Agreement
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Deferred revenue										1,000,000	1,000,000
BMS Agreement
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Number of programs advancing through preclinical development | Program								4
Contingent payments		$ 275,000,000
Deferred revenue										0	0
2018 BMS Master Services Agreement
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Deferred revenue										1,800,000	1,200,000
2018 Merck Agreement
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Deferred revenue										5,100,000	18,500,000
Milestone payment receivable upon initiation of IND enabling toxicology study									$ 15,000,000
Recognition of up front payment										60,600,000
Incremental revenue recognized										9,100,000
2018 Merck Agreement | Future Services on Collaboration Joint Steering Committee ("JSC")
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Incremental transaction price allocation resulted in additional revenue recognized										100,000
Contingent payment received									15,000,000
2018 Merck Agreement | Merck Sharp & Dohme Corp
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Deferred revenue										2,500,000
Number of research programs | Program							3
Initial transaction price							$ 60,000,000
Upfront payment received										60,000,000
Constrained variable consideration										7,500,000
Milestone payment received										2,500,000
Additional milestone payment received										7,500,000
Accounts receivable										2,500,000
Revenue recognition aggregate contingent payments eligible to receive										$ 500,000,000
Milestone Method Revenue Recognition Description										If one or more products from each of the target programs are developed for non-oncology or a single indication, the Company will be eligible for reduced aggregate milestone payments. In addition, the Company is eligible to receive tiered royalties ranging from mid-single digit to low teen percentages on the worldwide sales of any commercial products that may result from the collaboration
2018 Merck Agreement | Merck Sharp & Dohme Corp | Accounting Standards Update 2014-09
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Total interest of unearned revenue										$ 7,400,000
First Cytokine-Derivative Program | Merck Sharp & Dohme Corp
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Upfront payment received				$ 5,000,000
Extended research term				1 year
Transaction price	$ 65,000,000			$ 65,000,000	$ 60,000,000				80,000,000
Constrained variable consideration					$ 5,000,000				15,000,000
Revenue reallocated property rights										9,400,000
Incremental revenue recognized reallocated target programs										$ 1,600,000
Estimated service period										3 years
Incremental revenue recognized										$ 3,200,000
Adjustments to transaction price										9,100,000
Cumulative catch-up in revenue										14,000,000
2020 Merck Master Services Agreement
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Deferred revenue										0	0
MDA Agreement | EMD Serono
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Deferred revenue										0	$ 0
Contingent payment received						$ 1,500,000			$ 2,000,000
Milestone payment received			$ 1,000,000
Maximum amount eligible to receive for each product developed										$ 52,500,000

Collaboration and License Agr_4

Collaboration and License Agreements and Supply Agreements - Summary of Recognized Revenue (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Revenue Recognition Multiple Deliverable Arrangements [Line Items]
Total revenue	$ 8,517	$ 17,823	$ 51,226	$ 34,444
Collaboration and License Agreements and Supply Agreements
Revenue Recognition Multiple Deliverable Arrangements [Line Items]
Total revenue	8,517	17,823	51,226	34,444
Collaboration and License Agreements and Supply Agreements | Bristol-Myers Squibb Company ("BMS")
Revenue Recognition Multiple Deliverable Arrangements [Line Items]
Total revenue	1,118	7,119	7,784	10,673
Collaboration and License Agreements and Supply Agreements | Merck Sharp & Dohme Corporation (“Merck”)
Revenue Recognition Multiple Deliverable Arrangements [Line Items]
Total revenue	6,414	9,055	38,175	18,837
Collaboration and License Agreements and Supply Agreements | Merck KGaA, Darmstadt, Germany "EMD Serono")
Revenue Recognition Multiple Deliverable Arrangements [Line Items]
Total revenue	249	1,507	2,844	4,656
Collaboration and License Agreements and Supply Agreements | Vaxcyte, Inc.
Revenue Recognition Multiple Deliverable Arrangements [Line Items]
Total revenue	736	142	2,423	278
BMS Agreement and the 2018 BMS Master Services Agreement
Revenue Recognition Multiple Deliverable Arrangements [Line Items]
Revenues	1,118	7,119	7,784	10,673
BMS Agreement and the 2018 BMS Master Services Agreement | Ongoing Performance Related to Unsatisfied Performance Obligations
Revenue Recognition Multiple Deliverable Arrangements [Line Items]
Revenues		1,000		2,974
BMS Agreement and the 2018 BMS Master Services Agreement | Research and Development Services
Revenue Recognition Multiple Deliverable Arrangements [Line Items]
Revenues	249	246	762	646
BMS Agreement and the 2018 BMS Master Services Agreement | Materials Supply
Revenue Recognition Multiple Deliverable Arrangements [Line Items]
Revenues	869	5,873	7,022	7,053
2020 Merck Master Services Agreement
Revenue Recognition Multiple Deliverable Arrangements [Line Items]
Total revenue	6,414	9,055	38,175	18,837
2020 Merck Master Services Agreement | Ongoing Performance Related to Unsatisfied Performance Obligations
Revenue Recognition Multiple Deliverable Arrangements [Line Items]
Total revenue	3,506	6,907	30,889	13,048
2020 Merck Master Services Agreement | Research and Development Services
Revenue Recognition Multiple Deliverable Arrangements [Line Items]
Total revenue	419	1,732	2,328	4,245
2020 Merck Master Services Agreement | Financing Component on Unearned Revenue
Revenue Recognition Multiple Deliverable Arrangements [Line Items]
Total revenue	149	416	561	1,544
2020 Merck Master Services Agreement | Materials Supply
Revenue Recognition Multiple Deliverable Arrangements [Line Items]
Total revenue	2,340		4,397
2019 EMD Serono Supply Agreement
Revenue Recognition Multiple Deliverable Arrangements [Line Items]
Total revenue	249	1,507	2,844	4,656
2019 EMD Serono Supply Agreement | Contingent Payment Earned
Revenue Recognition Multiple Deliverable Arrangements [Line Items]
Total revenue		1,000	2,000	1,000
2019 EMD Serono Supply Agreement | Research and Development Services
Revenue Recognition Multiple Deliverable Arrangements [Line Items]
Total revenue	214	265	503	1,088
2019 EMD Serono Supply Agreement | Materials Supply
Revenue Recognition Multiple Deliverable Arrangements [Line Items]
Total revenue	35	242	341	2,568
Supply Agreement | Vaxcyte, Inc.
Revenue Recognition Multiple Deliverable Arrangements [Line Items]
Total revenue	736	142	2,423	278
Supply Agreement | Vaxcyte, Inc. | Research and Development Services
Revenue Recognition Multiple Deliverable Arrangements [Line Items]
Total revenue	247		716
Supply Agreement | Vaxcyte, Inc. | Materials Supply
Revenue Recognition Multiple Deliverable Arrangements [Line Items]
Total revenue	$ 489	$ 142	$ 1,707	$ 278

Collaboration and License Agr_5

Collaboration and License Agreements and Supply Agreements - Performance Obligations - Additional Information (Details) - Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date: 2021-10-01 $ in Millions	Sep. 30, 2021USD ($)
Revenue Remaining Performance Obligation Expected Timing Of Satisfaction [Line Items]
Revenue, remaining performance obligation, amount	$ 7.8
Revenue, remaining performance obligation, expected timing of satisfaction, period	12 months

Collaboration and License Agr_6

Collaboration and License Agreements and Supply Agreements - Summary of Deferred Revenue Balance (Details) - Collaboration and License Agreements and Supply Agreements $ in Thousands	9 Months Ended
	Sep. 30, 2021USD ($)
Revenue Recognition Multiple Deliverable Arrangements [Line Items]
Deferred revenue	$ 20,703
Additions to deferred revenue	19,402
Recognition of revenue in current period	(32,156)
Deferred revenue	$ 7,949

Loan and Security Agreement - A

Loan and Security Agreement - Additional Information (Details) - USD ($) $ / shares in Units, $ in Thousands	Feb. 28, 2020	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020	Dec. 31, 2020
Debt Instrument [Line Items]
Debt, non-current		$ 18,714		$ 18,714		$ 24,545
Interest payable		200		200		$ 200
Loan and accretion of debt discount		100	$ 100	400	$ 300
Interest expense, debt		$ 700	$ 700	$ 1,900	$ 1,700
Average interest rate		8.07%	8.07%	8.07%	8.08%
Loan and Security Agreement | Oxford Finance LLC and Silicon Valley Bank
Debt Instrument [Line Items]
Warrant to purchase stock	81,257
Exercise price per share	$ 9.23
Estimated fair value upon issuance of warrants	$ 600
Debt, current		$ 6,300		$ 6,300
Debt, non-current		$ 18,700		$ 18,700

Commitments and Contingencies -

Commitments and Contingencies - Additional Information (Details) $ in Thousands	1 Months Ended		3 Months Ended	9 Months Ended
	Jun. 30, 2021USD ($)	Sep. 30, 2020USD ($)ft²	Sep. 30, 2020USD ($)ft²	Sep. 30, 2021USD ($)	Sep. 30, 2020USD ($)ft²	Jul. 31, 2021ft²	Dec. 31, 2020USD ($)
Loss Contingencies [Line Items]
Aggregate estimated base rent payments due				$ 47,821
Operating lease expense				6,400
Operating lease payments				$ 4,000
Operating lease, weighted average remaining lease term				5 years 10 months 24 days
Operating lease, weighted average discount rate, percent				10.80%
Deferred rent							$ 1,340
Rent expense			$ 900		$ 2,700
Sublease Agreement
Loss Contingencies [Line Items]
Security deposit				$ 900			$ 900
Sublease Agreement | Five Prime Therapeutics, Inc. (the "Sublessor")
Loss Contingencies [Line Items]
Lease expiration Date		Dec. 31, 2027
Aggregate estimated base rent payments due		$ 39,100	$ 39,100		$ 39,100
Area of Sublease Premises | ft²		115,466	115,466		115,466
Lease base rent abatement		$ 5,200	$ 5,200		$ 5,200
San Carlos Lease | California
Loss Contingencies [Line Items]
Lease extension period	5 years
Lease expiration Date	Jul. 31, 2026
Lease renewal term	5 years
Aggregate estimated base rent payments due	$ 4,200
Industrial Lease | California
Loss Contingencies [Line Items]
Lease extension period	5 years
Lease expiration Date	Jun. 30, 2026
Lease renewal term	5 years
Aggregate estimated base rent payments due	$ 4,300
Initial Premises | Sublease Agreement | Five Prime Therapeutics, Inc. (the "Sublessor")
Loss Contingencies [Line Items]
Area of Sublease Premises | ft²						85,755
Expansion Premises | Sublease Agreement | Five Prime Therapeutics, Inc. (the "Sublessor")
Loss Contingencies [Line Items]
Area of Sublease Premises | ft²		29,711	29,711		29,711

Commitments and Contingencies_2

Commitments and Contingencies - Schedule of Components of Lease Costs (Details) - USD ($) $ in Thousands	3 Months Ended	9 Months Ended
	Sep. 30, 2021	Sep. 30, 2021
Commitments And Contingencies Disclosure [Abstract]
Operating lease cost	$ 2,266	$ 6,396
Short-term lease cost	22	73
Variable lease cost	754	1,513
Total lease costs	$ 3,042	$ 7,982

Commitments and Contingencies_3

Commitments and Contingencies - Schedule of Maturities of Operating Lease Liabilities (Details) - USD ($) $ in Thousands	Sep. 30, 2021	Jan. 01, 2021	Dec. 31, 2020
Commitments And Contingencies Disclosure [Abstract]
Remaining in 2021	$ 2,142
2022 (1)	1,643
2023	8,002
2024	9,219
2025	9,533
Thereafter	17,282
Total lease payments	47,821
Less: imputed interest	(14,303)
Operating lease liabilities	33,518
Less: current portion	(1,445)	$ (2,900)
Operating lease liability - non-current	$ 32,073	$ 27,800
2021			$ 5,742
2022 (1)			5,183
2023			6,310
2024			7,476
2025 and thereafter			24,034
Total future minimum lease payments			$ 48,745

Commitments and Contingencies_4

Commitments and Contingencies - Schedule of Maturities of Operating Lease Liabilities (Parenthetical) (Details) - USD ($) $ in Millions	9 Months Ended	12 Months Ended
	Sep. 30, 2021	Dec. 31, 2020
Loss Contingencies [Line Items]
Potential financial benefit base rent abatement	$ 5.2	$ 5.2
Minimum
Loss Contingencies [Line Items]
Base rent abatement sublease period	7 months	7 months
Maximum
Loss Contingencies [Line Items]
Base rent abatement sublease period	18 months	18 months

Related-Party Transactions - Ad

Related-Party Transactions - Additional Information (Details) - Maximum	Jun. 16, 2020	May 14, 2020
Merck Sharp & Dohme Corp | Sutro Biopharma
Related Party Transaction [Line Items]
Equity interest percentage		10.00%
Vaxcyte
Related Party Transaction [Line Items]
Percentage common stock ownership interest	4.00%

Stockholders' Equity - Addition

Stockholders' Equity - Additional Information (Details) - $ / shares	Oct. 01, 2018	Aug. 31, 2017	Sep. 30, 2021	Dec. 31, 2020	Feb. 28, 2020
Stockholders Equity [Line Items]
Voting rights per share			one vote per share
Preferred stock shares authorized			10,000,000	10,000,000
Preferred stock, par value			$ 0.001	$ 0.001
Preferred stock, outstanding			0	0
Loan and Security Agreement | Oxford Finance LLC
Stockholders Equity [Line Items]
Issuance of warrants to purchase shares					54,171
Loan and Security Agreement | Silicon Valley Bank
Stockholders Equity [Line Items]
Issuance of warrants to purchase shares					27,086
Loan and Security Agreement | Oxford Finance LLC and Silicon Valley Bank
Stockholders Equity [Line Items]
Issuance of warrants to purchase shares					81,257
Exercise price per share					$ 9.23
Series E Redeemable Convertible Preferred Stock
Stockholders Equity [Line Items]
Issuance of warrants to purchase shares	46,359
Preferred stock, conversion basis	1-for-0.0275
Series C Redeemable Convertible Preferred Stock
Stockholders Equity [Line Items]
Issuance of warrants to purchase shares	25,454
Preferred stock, conversion basis	1-for-0.0370
Cancellation of redeemable convertible preferred warrants	1,232,220
Conversion of warrants to purchase of shares of common stock	687,928
Oxford Finance LLC and Silicon Valley Bank | Series D Two Redeemable Convertible Preferred Stock | Loan and Security Agreement
Stockholders Equity [Line Items]
Issuance of warrants to purchase shares		682,230
Exercise price per share		$ 0.6596
Oxford Finance LLC and Silicon Valley Bank | Series E Redeemable Convertible Preferred Stock | Loan and Security Agreement
Stockholders Equity [Line Items]
Issuance of warrants to purchase shares		1,682,871
Exercise price per share		$ 0.2674
Term of warrant exercisable		10 years

Stockholders' Equity - Schedule

Stockholders' Equity - Schedule of Common Stock Reserved for Future Issuance (Details) - shares	Sep. 30, 2021	Dec. 31, 2020
Stockholders Equity [Line Items]
Reserved common stock	11,304,520	8,331,103
Common Stock Options Issued and Outstanding
Stockholders Equity [Line Items]
Reserved common stock	6,533,772	5,439,295
Restricted Common Stock Units Issued and Outstanding
Stockholders Equity [Line Items]
Reserved common stock	2,262,776	666,375
Remaining Shares Reserved for Issuance Under 2004 and 2018 Equity Incentive Plan
Stockholders Equity [Line Items]
Reserved common stock	1,681,651	1,710,824
Shares Reserved for Issuance Under 2018 Employee Stock Purchase Plan
Stockholders Equity [Line Items]
Reserved common stock	673,251	361,539
Warrants to Purchase Common Stock
Stockholders Equity [Line Items]
Reserved common stock	153,070	153,070

Equity Incentive Plans, Emplo_3

Equity Incentive Plans, Employee Stock Purchase Plan and Stock-Based Compensation - Additional Information (Details) - USD ($)	Sep. 26, 2018	Sep. 25, 2018	Aug. 31, 2019	Feb. 28, 2017	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020	Dec. 31, 2020	Aug. 04, 2021	Jan. 01, 2021
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Reserved common stock					11,304,520		11,304,520		8,331,103
Aggregate intrinsic value of stock options exercised					$ 100,000	$ 48,000	$ 2,300,000	$ 100,000
Weighted-average estimated grant-date fair value of employee stock options granted					$ 13.21	$ 5.69	$ 14.35	$ 5.09
Share-based compensation arrangement by share-based payment award options, shares granted							266,724		266,724
Stock-based compensation expense					$ 6,495,000	$ 3,112,000	$ 16,354,000	$ 8,830,000
Liability attributable to call option plan					182,000		$ 182,000		$ 109,000
Restricted Stock Units
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Restricted common stock granted							1,913,750
Shares vesting period							4 years
2018 Equity Incentive Plan
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Reserved common stock		2,300,000
Annual increase period of common stock reserved for issuance		10 years
Maximum number of shares issuable											2,287,605
2018 Equity Incentive Plan | Restricted Stock Units
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Total unrecognized compensation cost related to unvested granted					36,600,000	5,400,000	$ 36,600,000	$ 5,400,000
Remaining unrecognized compensation cost expected to be recognized over weighted-average period							3 years 4 months 24 days	2 years 8 months 12 days
2018 Equity Incentive Plan | Employee Stock Options
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Total unrecognized compensation cost related to unvested granted					28,100,000	18,500,000	$ 28,100,000	$ 18,500,000
Remaining unrecognized compensation cost expected to be recognized over weighted-average period							2 years 7 months 6 days	2 years 4 months 24 days
2018 Equity Incentive Plan | Employee Stock Purchase Plan
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Unrecognized stock-based compensation expense					$ 300,000	300,000	$ 300,000	$ 300,000
2018 Equity Incentive Plan | Maximum
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Increase in stock reserved for issuance as percentage of capital stock outstanding on last day of preceding year		5.00%
2021 Equity Inducement Plan
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Reserved common stock										750,000
2018 Equity Incentive Plan and 2021 Equity Inducement Plan
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Shares available for grant					1,681,651		1,681,651
2018 Employee Stock Purchase Plan
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Reserved common stock	230,000
Annual increase period of common stock reserved for issuance	10 years
Increase in stock reserved for issuance as percentage of capital stock outstanding on last day of preceding year	1.00%
Maximum number of shares issuable	2,300,000				673,251		673,251
Shares available for grant					473,740		473,740
Shares available for grant, increase											457,521
Call Option Plan
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Stock-based compensation expense					$ 32,000	90,000	$ 78,000	200,000
Other income (expense)					$ (13,000)	$ (1,100,000)	$ 5,000	$ (3,100,000)
Call Option Plan | Option Granted in February 2017
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Share-based compensation arrangement by share-based payment award options, shares granted				248,944
Call options expiration period				1 year
Call Option Plan | Option Granted in February 2017 | January 1 , 2017
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Call options vesting percentage				25.00%
Call Option Plan | Option Granted in February 2017 | January 1 , 2018
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Call options vesting percentage				25.00%
Call Option Plan | Option Granted in February 2017 | January 1 , 2019
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Call options vesting percentage				25.00%
Call Option Plan | Option Granted in February 2017 | January 1 , 2020
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Call options vesting percentage				25.00%
Call Option Plan | Option Granted in August 2019
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Share-based compensation arrangement by share-based payment award options, shares granted			17,780
Call options expiration period			1 year
Call Option Plan | Option Granted in August 2019 | January 1 , 2019
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Call options vesting percentage			25.00%
Call Option Plan | Option Granted in August 2019 | January 1 , 2020
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Call options vesting percentage			25.00%
Call Option Plan | Option Granted in August 2019 | January 1 , 2021
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Call options vesting percentage			25.00%
Call Option Plan | Option Granted in August 2019 | January 1 , 2022
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Call options vesting percentage			25.00%
Call Option Plan | Vaxcyte, Inc.
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Reserved common stock					266,724		266,724

Equity Incentive Plans, Emplo_4

Equity Incentive Plans, Employee Stock Purchase Plan and Stock-Based Compensation - Summary of Option Activity (Details) $ / shares in Units, $ in Thousands	9 Months Ended	12 Months Ended
	Sep. 30, 2021USD ($)$ / sharesshares	Dec. 31, 2020USD ($)$ / sharesshares
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Granted, Shares	266,724	266,724
Exercised, Shares	(257,834)	(257,834)
Stock options outstanding, Ending Balance, Shares	4,445
2004 Plan, 2018 Plan and 2021 Plan
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Stock options outstanding, Beginning Balance, Shares	5,439,295
Granted, Shares	1,383,950
Exercised, Shares	(185,974)
Canceled and forfeited, Shares	(103,499)
Stock options outstanding, Ending Balance, Shares	6,533,772	5,439,295
Stock options exercisable, Shares	3,523,838
Stock options outstanding, Weighted - Average Exercise Price, Beginning Balance | $ / shares	$ 11.93
Weighted - Average Exercise Price, Granted | $ / shares	20.40
Weighted - Average Exercise Price, Exercised | $ / shares	10.60
Weighted - Average Exercise Price, Canceled and forfeited | $ / shares	10.58
Stock options outstanding, Weighted - Average Exercise Price, Ending Balance | $ / shares	13.78	$ 11.93
Stock options exercisable, Weighted - Average Exercise Price, Exercisable | $ / shares	$ 12.73
Weighted - Average Remaining Contract Term	7 years 7 months 24 days	7 years 9 months
Weighted - Average Remaining Contract Term, Exercisable	6 years 9 months 18 days
Aggregate Intrinsic Value, Balance | $	$ 35,715	$ 53,202
Aggregate Intrinsic Value, Exercisable | $	$ 21,959

Equity Incentive Plans, Emplo_5

Equity Incentive Plans, Employee Stock Purchase Plan and Stock-Based Compensation - Schedule of Employee Stock Options Valuation (Details)	9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020
Share Based Compensation Arrangement By Share Based Payment Award Fair Value Assumptions And Methodology [Line Items]
Expected volatility, Minimum	81.60%	73.20%
Expected volatility, Maximum	84.90%	84.20%
Risk-free interest rate, Minimum	0.60%	0.20%
Risk-free interest rate, Maximum	1.10%	1.60%
Minimum
Share Based Compensation Arrangement By Share Based Payment Award Fair Value Assumptions And Methodology [Line Items]
Expected term (in years)	5 years 3 months 18 days	5 years 1 month 6 days
Maximum
Share Based Compensation Arrangement By Share Based Payment Award Fair Value Assumptions And Methodology [Line Items]
Expected term (in years)	6 years 1 month 6 days	7 years

Equity Incentive Plans, Emplo_6

Equity Incentive Plans, Employee Stock Purchase Plan and Stock-Based Compensation - Summary of Status and Activity of Non-vested RSUs (Details) - Restricted Stock Units	9 Months Ended
	Sep. 30, 2021$ / sharesshares
Number of shares
Non-vested, Beginning Balance | shares	666,375
Granted | shares	1,913,750
Vested and released | shares	(232,474)
Canceled and forfeited | shares	(84,875)
Non-vested, Ending balance | shares	2,262,776
Weighted Average Grant-Date Fair Value
Non-vested, Beginning Balance | $ / shares	$ 9.83
Granted | $ / shares	20.56
Vested and released | $ / shares	11.06
Canceled and forfeited | $ / shares	17.07
Non-vested, Ending balance | $ / shares	$ 18.50

Equity Incentive Plans, Emplo_7

Equity Incentive Plans, Employee Stock Purchase Plan and Stock-Based Compensation - Schedule of Fair Value of ESPP Shares Using Option Pricing Model (Details)	9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Expected volatility, Minimum	81.60%	73.20%
Expected volatility, Maximum	84.90%	84.20%
2018 Employee Stock Purchase Plan
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Expected term (in years)	6 months	6 months
Expected volatility		94.10%
Expected volatility, Minimum	65.90%
Expected volatility, Maximum	111.40%
Risk-free interest rate	0.10%	0.40%

Equity Incentive Plans, Emplo_8

Equity Incentive Plans, Employee Stock Purchase Plan and Stock-Based Compensation - Schedule of Stock-Based Compensation Expense Recognized (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Total stock-based compensation expense	$ 6,495	$ 3,112	$ 16,354	$ 8,830
Research and Development Expense
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Total stock-based compensation expense	1,933	761	4,882	1,972
General and Administrative Expense
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Total stock-based compensation expense	$ 4,562	$ 2,351	$ 11,472	$ 6,858

Equity Incentive Plans, Emplo_9

Equity Incentive Plans, Employee Stock Purchase Plan and Stock-Based Compensation - Summary of the Status of Call Options (Details) - shares	9 Months Ended	12 Months Ended
	Sep. 30, 2021	Dec. 31, 2020
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Options vested and exercised	257,834	257,834
Options vested and outstanding	4,445
Options unvested and outstanding	4,445	8,890
Total options granted	266,724	266,724

Net (Loss) Income Per Share - S

Net (Loss) Income Per Share - Summary of Computation of Company's Basic and Diluted Net (Loss) Income per Share (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended						9 Months Ended
	Sep. 30, 2021	Jun. 30, 2021	Mar. 31, 2021	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Sep. 30, 2021	Sep. 30, 2020
Numerator:
Net (loss) income, basic and diluted	$ (30,902)	$ (6,152)	$ (30,359)	$ 17,139	$ 29,872	$ (19,595)	$ (67,413)	$ 27,416
Denominator:
Weighted-average shares used in computing basic net (loss) income per share	46,162,544			36,887,266			46,060,010	29,994,917
Weighted-average shares used to compute diluted EPS	46,162,544			37,877,552			46,060,010	30,349,856
Net (loss) income per share:
Basic	$ (0.67)			$ 0.46			$ (1.46)	$ 0.91
Diluted	$ (0.67)			$ 0.45			$ (1.46)	$ 0.90
Stock Options
Denominator:
Dilutive effect of share based payment arrangements				828,623				228,557
Restricted Stock Units
Denominator:
Dilutive effect of share based payment arrangements				159,788				120,649
Warrants to Purchase Common Stock
Denominator:
Dilutive effect of share based payment arrangements				1,875				5,733

Net (Loss) Income Per Share -_2

Net (Loss) Income Per Share - Summary of Common Stock Equivalents of Antidilutive Securities Excluded from Computation of Diluted Net Loss per Share (Details)	9 Months Ended
	Sep. 30, 2021shares
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of net loss per share	8,956,281
Common Stock Options Issued and Outstanding
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of net loss per share	6,533,772
Restricted Stock Units Issued and Outstanding
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of net loss per share	2,262,776
Warrants to Purchase Common Stock
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of net loss per share	153,070
Employee Stock Purchase Plan
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of net loss per share	6,663

Subsequent Event - Additional I

Subsequent Event - Additional Information (Details) - BioNova Option Agreement - Subsequent Event	Oct. 09, 2021USD ($)
Subsequent Event [Line Items]
Initial Licensing Option Payment	$ 4,000,000
Maximum potential payments related to option exercise, development, regulatory, and commercial milestones	$ 200,000,000
Minimum term of royalties receivable based on annual net sales	10 years