Bolt Biotherapeutics (BOLT) 10-Q 13 May 21 2021 Q1 Quarterly report Financial data

Document and Entity Information

Document and Entity Information - shares	3 Months Ended
	Mar. 31, 2021	May 10, 2021
Cover [Abstract]
Document Type	10-Q
Amendment Flag	false
Document Period End Date	Mar. 31, 2021
Document Fiscal Year Focus	2021
Document Fiscal Period Focus	Q1
Entity Registrant Name	Bolt Biotherapeutics, Inc.
Entity Central Index Key	0001641281
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Current Fiscal Year End Date	--12-31
Entity Filer Category	Non-accelerated Filer
Entity Common Stock, Shares Outstanding		36,338,130
Entity Shell Company	false
Entity Small Business	true
Entity Emerging Growth Company	true
Entity Ex Transition Period	true
Title of 12(b) Security	Common Stock, $0.00001 par value
Trading Symbol	BOLT
Security Exchange Name	NASDAQ
Entity File Number	001-39988
Entity Incorporation, State or Country Code	DE
Entity Tax Identification Number	47-2804636
Entity Address, Address Line One	900 Chesapeake
Entity Address, Address Line Two	Drive
Entity Address, City or Town	Redwood City
Entity Address, State or Province	CA
Entity Address, Postal Zip Code	94063
City Area Code	650
Local Phone Number	665-9295
Document Quarterly Report	true
Document Transition Report	false

CONDENSED BALANCE SHEETS (Unaud

CONDENSED BALANCE SHEETS (Unaudited) - USD ($) $ in Thousands	Mar. 31, 2021	Dec. 31, 2020
Current assets:
Cash and cash equivalents	$ 95,481	$ 5,542
Short-term investments	171,188	17,296
Prepaid expenses and other current assets	4,541	2,523
Total current assets	271,210	25,361
Property and equipment, net	3,910	4,083
Operating lease right-of-use assets	11,478	12,267
Finance lease right-of-use assets	30	34
Restricted cash	1,565	1,565
Deferred offering costs		2,357
Long-term investments	36,236
Other assets	208	875
Total assets	324,637	46,542
Current liabilities:
Accounts payable	2,888	1,598
Accrued expenses and other current liabilities	5,994	6,663
Deferred revenue	1,502	1,502
Operating lease liabilities	1,628	1,501
Total current liabilities	12,012	11,264
Operating lease liabilities, net of current portion	9,056	9,376
Convertible preferred stock purchase right liability, non-current		25,224
Other long-term liabilities	321	329
Total liabilities	21,389	46,193
Commitments and contingencies (Note 7)
Convertible preferred stock		105,296
Stockholders' equity (deficit):
Additional paid-in capital	436,165	3,452
Accumulated other comprehensive income	(64)
Accumulated deficit	(132,853)	(108,399)
Total stockholders' equity (deficit):	303,248	(104,947)
Total liabilities, convertible preferred stock, and stockholders' equity (deficit)	$ 324,637	$ 46,542

CONDENSED BALANCE SHEETS (Una_2

CONDENSED BALANCE SHEETS (Unaudited) (Parenthetical) - $ / shares	Mar. 31, 2021	Dec. 31, 2020
Statement Of Financial Position [Abstract]
Common stock, par value per share	$ 0.00001	$ 0.00001
Common stock, shares authorized	200,000,000	198,000,000
Common stock, shares, issued	36,331,846	2,130,139
Common stock, shares, outstanding	36,331,846	2,130,139

CONDENSED STATEMENTS OF OPERATI

CONDENSED STATEMENTS OF OPERATIONS AND COMPREHENSIVE LOSS (Unaudited) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Income Statement [Abstract]
Collaboration revenue		$ 164
Operating expenses:
Research and development	$ 14,127	6,787
General and administrative	4,299	2,122
Total operating expense	18,426	8,909
Loss from operations	(18,426)	(8,745)
Other income (expense), net
Interest income, net	56	112
Change in fair value of preferred stock right liability	(6,084)
Total other income (expense), net	(6,028)	112
Net loss	(24,454)	(8,633)
Net unrealized loss on marketable securities	(64)	(10)
Comprehensive loss	$ (24,518)	$ (8,643)
Net loss per share, basic and diluted	$ (1.14)	$ (4.16)
Weighted-average shares outstanding, basic and diluted	21,498,306	2,077,365

CONDENSED STATEMENTS OF CONVERT

CONDENSED STATEMENTS OF CONVERTIBLE PREFERRED STOCK AND STOCKHOLDERS' EQUITY (DEFICIT) (Unaudited) - USD ($) $ in Thousands	Total	Convertible Preferred Stock	Common Stock	Additional Paid-In Capital	Accumulated Other Comprehensive Loss	Accumulated Deficit
Beginning Balance at Dec. 31, 2019	$ (45,846)			$ 1,825		$ (47,671)
Beginning Balance, Shares at Dec. 31, 2019			1,921,642
Beginning Balance at Dec. 31, 2019		$ 77,505
Beginning Balance, Shares at Dec. 31, 2019		10,070,102
Issuance of common stock upon exercise of stock options	34			34
Issuance of common stock upon exercise of stock options, Shares			16,161
Vesting of early exercised options and restricted stock awards	5			5
Stock-based compensation	225			225
Net unrealized loss on marketable securities	(10)				$ (10)
Net loss	(8,633)					(8,633)
Ending Balance at Mar. 31, 2020	(54,225)			2,089	(10)	(56,304)
Ending Balance, Shares at Mar. 31, 2020		10,070,102
Ending Balance at Mar. 31, 2020		$ 77,505
Ending Balance, Shares at Mar. 31, 2020			1,937,803
Beginning Balance at Dec. 31, 2020	(104,947)			3,452		(108,399)
Beginning Balance, Shares at Dec. 31, 2020			2,130,139
Beginning Balance at Dec. 31, 2020	105,296	$ 105,296
Beginning Balance, Shares at Dec. 31, 2020		15,232,275
Issuance of Series C-2 convertible preferred stock, net of issuance cost of $42		$ 51,902
Issuance of Series C-2 convertible preferred stock, net of issuance cost of $42, Shares		5,611,059
Reclassification of convertible preferred stock purchase right liability to equity upon issuance of convertible C-2 preferred stock		$ 31,308
Conversion of convertible preferred stock to common stock	188,506			188,506
Conversion of convertible preferred stock to common stock, Shares			20,843,334
Temporary equity, conversion of convertible preferred stock to common stock		$ (188,506)
Temporary equity, conversion of convertible preferred stock to common stock, Shares		(20,843,334)
Issuance of common stock upon initial public offering, net of issuance costs of $22,541	241,959			241,959
Issuance of common stock upon initial public offering, net of issuance costs of $22,541, Shares			13,225,000
Issuance of common stock upon exercise of common stock warrants, Shares			82,603
Issuance of common stock upon exercise of stock options	129			129
Issuance of common stock upon exercise of stock options, Shares			50,770
Vesting of early exercised options and restricted stock awards	10			10
Stock-based compensation	2,109			2,109
Net unrealized loss on marketable securities	(64)				(64)
Net loss	(24,454)					(24,454)
Ending Balance at Mar. 31, 2021	$ 303,248			$ 436,165	$ (64)	$ (132,853)
Ending Balance, Shares at Mar. 31, 2021			36,331,846

CONDENSED STATEMENTS OF CONVE_2

CONDENSED STATEMENTS OF CONVERTIBLE PREFERRED STOCK AND STOCKHOLDERS' EQUITY (DEFICIT) (Unaudited) (Parenthetical) $ in Thousands	3 Months Ended
	Mar. 31, 2021USD ($)
Common Stock
Stock issuance cost	$ 22,541
Convertible Preferred Stock
Stock issuance cost	$ 42

CONDENSED STATEMENTS OF CASH FL

CONDENSED STATEMENTS OF CASH FLOWS (Unaudited) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
CASH FLOWS FROM OPERATING ACTIVITIES:
Net loss	$ (24,454)	$ (8,633)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation and amortization	272	101
Stock-based compensation expense	2,109	225
Accretion of premium/discount on marketable securities	335	(23)
Unrealized loss on marketable securities, net	(64)	(10)
Change in fair value of convertible preferred stock purchase rights liabilities	6,084
Non-cash lease expense	530	426
Changes in operating assets and liabilities:
Prepaid expenses and other assets	(1,351)	33
Accounts payable and accrued expenses	(88)	(540)
Operating lease liabilities	66	(1,223)
Deferred revenue		(2)
Other long-term liabilities	2	8
Net cash used in operating activities	(16,559)	(9,638)
CASH FLOWS FROM INVESTING ACTIVITIES:
Purchase of property and equipment	(58)	(373)
Purchases of marketable securities	(198,069)	(13,235)
Maturities of marketable securities	7,606
Net cash used in investing activities	(190,521)	(13,608)
CASH FLOWS FROM FINANCING ACTIVITIES:
Proceeds from issuance of preferred stock, net of issuance cost	51,902
Proceeds from initial public offering, net of issuance cost	244,988
Proceeds from issuance of common stock	129	34
Net cash provided by financing activities	297,019	34
Net increase (decrease) in cash	89,939	(23,212)
Cash, cash equivalents and restricted cash at beginning of year	7,107	35,410
Cash, cash equivalents and restricted cash at end of period	97,046	12,198
Reconciliation of cash, cash equivalents and restricted cash:
Cash and cash equivalents	95,481	11,614
Restricted cash	1,565	584
Total cash, cash equivalents and restricted cash	97,046	12,198
Supplemental schedule of non-cash investing and financing activities:
Vesting of early exercised options	10	5
Purchases of property and equipment included in accounts payable and accrued liabilities	37	17
Deferred offering costs in accounts payable and accrued liabilities	$ 672
Right of use assets obtained in exchange for operating lease obligations		$ 254

Description of the Business

Description of the Business	3 Months Ended
	Mar. 31, 2021
Organization Consolidation And Presentation Of Financial Statements [Abstract]
Description of the Business	1. Description of the Business Bolt Biotherapeutics, Inc. (the “Company”) is a clinical-stage biotechnology company pioneering a new class of immuno-oncology agents that combine the targeting precision of antibodies with the power of both the innate and adaptive immune systems. Initial Public Offering and Related Transactions On February 9, 2021, the Company completed its initial public offering (“IPO”) pursuant to a registration statement on Form S-1 (File No. 333-252136) that was declared effective by the Securities and Exchange Commission (the “SEC”) on February 4, 2021 and sold an aggregate of 13,225,000 shares of its common stock, including the full exercise of the underwriters’ option to purchase 1,725,000 shares, at a price per share of $20.00. Proceeds from the IPO, net of underwriting discounts, commissions and offering costs, were approximately $242.0 million. In addition, each of the following occurred on February 4, 2021 in connection with the completion of the Company’s IPO: • the conversion of all outstanding shares of convertible preferred stock into 20,843,334 shares of the Company’s common stock; and • the amendment and restatement of the Company’s certificate of incorporation, authorizing 200,000,000 shares of common stock and 10,000,000 shares of undesignated preferred stock. Liquidity The Company has incurred operating losses and negative cash flows from operations since its inception and had an accumulated deficit of $132.9 million and $108.4 million as of March 31, 2021 and December 31, 2020, respectively. To date, none of the Company’s product candidates have been approved for sale and therefore the Company has not generated any revenue from product sales. The Company expects operating losses and negative cash flows from operations to continue for the foreseeable future. Based on the Company’s current business plan, management believes that the existing cash and cash equivalents, and marketable securities of $302.9 million as of March 31, 2021 will be sufficient to fund the Company’s obligations for at least 12 months after these financial statements are issued. Management plans to continue to incur substantial costs in order to conduct research and development activities and the Company will be required to raise additional capital. However, there can be no assurance as to whether additional financing will be available on terms acceptable to the Company, if at all. If sufficient funds on acceptable terms are not available when needed, it would have a negative impact on the Company’s financial condition and could force the Company to delay, limit, reduce or terminate product development or future commercialization efforts or grant rights to develop and market product candidates that the Company would otherwise plan to develop and market itself.

Summary of Significant Accounti

Summary of Significant Accounting Policies	3 Months Ended
	Mar. 31, 2021
Accounting Policies [Abstract]
Summary of Significant Accounting Policies	2. Summary of Significant Accounting Policies Basis of Presentation The accompanying unaudited condensed financial statements as of March 31, 2021 and for the three months ended March 31, 2021 and 2020 have been prepared in accordance with U.S. generally accepted accounting principles (“U.S. GAAP”) Reverse Stock Split On January 26, 2021, the Company amended and restated its amended and restated certificate of incorporation to effect a 1-for-7 reverse stock split of the Company’s outstanding common stock and convertible preferred stock. The par value and authorized shares of the common stock were not adjusted as a result of the reverse stock split. All issued and outstanding common stock, options to purchase common stock, early exercised options and per share amounts contained in the financial statements have been retroactively adjusted to give effect to the reverse stock split for all periods presented. Other Risks and Uncertainties The Company is subject to a number of risks similar to other early-stage biopharmaceutical companies, including, but not limited to, changes in any of the following areas that the Company believes could have a material adverse effect on its future financial position or results of operations: risks related to the successful discovery and development of its product candidates, ability to raise additional capital, development of new technological innovations by its competitors and delay or inability to obtain chemical or biological intermediates from such suppliers required for the synthesis of the Company’s product candidates, including due to the impact of the current COVID-19 pandemic, protection of intellectual property rights, litigation or claims against the Company based on intellectual property rights, and regulatory clearance and market acceptance of the Company’s products. The current COVID-19 pandemic, which is impacting worldwide economic activity, poses the risk that the Company or its employees, contractors, suppliers and other partners may be prevented from conducting business activities for an indefinite period of time, including due to shutdowns that may be requested or mandated by governmental authorities. The extent to which the COVID-19 pandemic will impact the Company’s business will depend on future developments that are highly uncertain and cannot be predicted at this time. The preparation of financial statements in conformity with generally accepted accounting principles requires management to make estimates and assumptions that affect the amounts reported in the financial statements and accompanying notes. The extent to which the COVID-19 pandemic may directly or indirectly impact the Company’s financial statements is highly uncertain and subject to change. Management considered the potential impact of the COVID-19 pandemic on its estimates and assumptions and there was not a material impact to the Company’s condensed financial statements as of and for the three months ended March 31, 2021; however, actual results could differ from those estimates and there may be changes to management’s estimates in future periods. The Company relies on single source manufacturers and suppliers for the supply of its product candidates. Disruption from these manufacturers or suppliers would have a negative impact on the Company’s business, financial position and results of operations. Use of Estimates The preparation of financial statements in conformity with U.S. GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities at the date of the financial statements and the reported amounts of expenses during the reporting period. On an ongoing basis, the Company evaluates its estimates and assumptions, including those related to revenue recognition, the valuation of common stock, stock-based compensation, convertible preferred stock purchase right liabilities and accrued liabilities. Management bases its estimates on historical experience and on various other assumptions that are believed to be reasonable under the circumstances, the results of which form the basis for making judgments about the carrying values of assets and liabilities that are not readily apparent from other sources. Actual results may differ materially from those estimates. Deferred Offering Costs The Company capitalized certain legal, accounting and other third-party fees that were directly related to the Company’s IPO. After the completion of the IPO in February 2021, the total deferred offering costs of $4.0 million were offset against the proceeds from the IPO and reclassified to additional paid-in capital in the accompanying the balance sheets. At December 31, 2020, deferred offering costs totaling $2.4 million were included as non-current assets in the accompanying balance sheet. Concentrations of Credit Risk Financial instruments that potentially subject the Company to concentration of credit risk consist of cash, cash equivalents and marketable securities. At March 31, 2021 and December 31, 2020, most of the Company’s funds are invested with a registered investment manager and custodied at one financial institution, with working capital kept at a separate financial institution, and account balances may at times exceed federally insured limits. Management believes that the Company is not exposed to significant credit risk due to the financial strength of the depository institutions where the funds are held. Cash and Cash Equivalents The Company considers all highly liquid investments purchased with an original maturity of three months or less to be cash equivalents. As of March 31, 2021 and December 31, 2020, cash and cash equivalents consisted primarily of bank deposits and money market funds, which were unrestricted as to withdrawal or use. Marketable Securities The Company classifies its marketable securities as available-for-sale and records such assets at estimated fair value in the balance sheets, with unrealized gains and losses that are determined to be temporary, if any, Restricted Cash As of March 31, 2021 and December 31, 2020, the Company had $1.6 million of long-term restricted cash deposited with a financial institution. The restricted cash is held in separate bank accounts to support letter of credit agreements related to the Company’s facility leases which expire in 2025 and 2031 (see Note 7). Fair Value Measurements Fair value is defined as the price that would be received to sell an asset or paid to transfer a liability in an orderly transaction between market participants at the measurement date. As such, fair value is a market-based measurement that should be determined based on assumptions that market participants would use in pricing an asset or liability. Cash and cash equivalents, restricted cash, marketable debt securities, accounts payable, accrued expenses and other current liabilities are reported at their respective fair values in our condensed balance sheets. The carrying amount of the remaining financial instruments approximate fair value due to their short-term nature. Refer to Note 3 for the methodologies and assumptions used in valuing financial instruments. Net Loss Per Share Basic net loss per share is calculated by dividing the net loss by the weighted-average number of shares of common stock outstanding during the period, without consideration for potentially dilutive securities. Diluted net loss per share is computed by dividing the net loss by the weighted-average number of common stock and potentially dilutive securities outstanding for the period. For purposes of the diluted net loss per share calculation, convertible preferred stock, stock options, common stock subject to repurchase related to unvested restricted stock awards and early exercise of stock options are considered to be potentially dilutive securities. Basic and diluted net loss per share is presented in conformity with the two-class method required for participating securities as the convertible preferred stock is considered a participating security because it participates in dividends with common stock. The Company also considers the shares issued upon the early exercise of stock options subject to repurchase to be participating securities because holders of such shares have non-forfeitable dividend rights in the event a dividend is paid on common stock. The holders of all series of convertible preferred stock and the holders of early exercised shares subject to repurchase do not have a contractual obligation to share in the Company’s losses. As such, the net loss was attributed entirely to common stockholders. Because the Company has reported a net loss for all periods presented, diluted net loss per share is the same as basic net loss per share for all periods presented as potentially dilutive securities were anti-dilutive. Recent Accounting Standards From time to time, new accounting standards are issued by the Financial Accounting Standards Board (the “FASB”), or other standard setting bodies and adopted by the Company as of the specified effective date. There have been no new accounting pronouncements issued nor adopted during the three months ended March 31, 2021 that are of significance to the Company’s financial position or results of operations.

Fair Value Measurements and Fai

Fair Value Measurements and Fair Value of Financial Instruments	3 Months Ended
	Mar. 31, 2021
Fair Value Disclosures [Abstract]
Fair Value Measurements and Fair Value of Financial Instruments	3. Fair Value Measurements and Fair Value of Financial Instruments The authoritative guidance on fair value measurements establishes a three-tier fair value hierarchy for disclosure of fair value measurements as follows: Level 1 —Quoted prices in active markets for identical assets or liabilities. Level 2 —Observable inputs other than Level 1 prices, such as quoted prices for similar assets or liabilities, quoted prices in markets that are not active or other inputs that are observable or can be corroborated by observable market data for substantially the full term of the assets or liabilities. Level 3 —Unobservable inputs that are supported by little or no market activity and that are significant to the fair value of the assets or liabilities. Assets and liabilities measured at fair value are classified in their entirety based on the lowest level of input that is significant to the fair value measurement. The Company’s assessment of the significance of a particular input to the fair value measurement in its entirety requires management to make judgments and consider factors specific to the asset or liability. During the three months ended March 31, 2021, financial assets measured on a recurring basis consist of cash invested in money market accounts, short-term investments, and long-term investments. The fair value of short-term and long-term investments is based upon market prices quoted on the last day of the fiscal period or other observable market inputs. The Company obtains pricing information from its investment manager and generally determines the fair value of investment securities using standard observable inputs, including reported trades, broker/dealer quotes, bids and/or offers. Financial liabilities measured at fair value on a recurring basis include the convertible preferred stock purchase rights liabilities described below. There were no transfers within the hierarchy during the three months ended March 31, 2021 and 2020. Marketable securities, all of which are classified as available-for-sale securities, consisted of the following at March 31, 2021 and December 31, 2020 (in thousands): March 31, 2021 Amortized Unrealized Unrealized Estimated Cost Gains Losses Fair Value Asset backed securities $ 28,614 $ 1 $ (4 ) $ 28,611 Other government agency securities 5,113 — (7 ) 5,106 Commercial paper 91,976 — — 91,976 Corporate debt securities 81,784 — (53 ) 81,731 Total $ 207,487 $ 1 $ (64 ) $ 207,424 December 31, 2020 Amortized Unrealized Unrealized Estimated Cost Gains Losses Fair Value Asset backed securities $ 2,639 $ — $ — $ 2,639 U.S. treasury securities 1,300 — — 1,300 Commercial paper 6,795 — — 6,795 Corporate debt securities 6,562 1 (1 ) 6,562 Total $ 17,296 $ 1 $ (1 ) $ 17,296 At March 31, 2021 and December 31, 2020, the fair values of the Company’s assets and liabilities, which are measured at fair value on a recurring basis, were determined using the following inputs (in thousands): March 31, 2021 Total (Level 1) (Level 2) (Level 3) Money market funds $ 93,270 $ 93,270 $ — $ — Asset backed securities 28,611 — 28,611 — Other government agency securities 5,106 — 5,106 — Commercial paper 91,976 — 91,976 — Corporate debt securities 81,731 — 81,731 — Total $ 300,694 $ 93,270 $ 207,424 $ — December 31, 2020 Total (Level 1) (Level 2) (Level 3) Money market funds $ 3,921 $ 3,921 $ — $ — U.S. treasury securities 1,300 1,300 — — Asset backed securities 2,640 — 2,640 — Commercial paper 6,795 — 6,795 — Corporate debt securities 6,561 — 6,561 — Total $ 21,217 $ 5,221 $ 15,996 $ — Liabilities: Preferred stock purchase rights liability $ 25,224 $ — $ — $ 25,224 Level 3 liabilities that are measured at fair value on a recurring basis consist of the convertible preferred stock purchase right liabilities. The following table provides a summary of changes in the estimated fair value of the financial instruments using significant Level 3 inputs (in thousands): Series C Convertible Preferred Stock Purchase Right Liability Balance at December 31, 2020 $ 25,224 Change in fair value 6,084 Reclassification to equity (31,308 ) Balance at March 31, 2021 $ — The fair value of the convertible preferred stock purchase right liabilities is estimated using an income-based approach incorporating probability considerations for different scenarios. The main assumptions include the probability and timing of the tranche closing, and the estimated value of the Company’s equity at that time. In January 2021, the Company issued the additional shares of Series C-2 convertible preferred stock and accordingly, this contractual obligation was settled and the preferred stock purchase right liability was remeasured to its fair value and reclassified to permanent equity. The fair value of the convertible preferred stock purchase right liability immediately prior to settlement was increased to $31.3 million as a result of the estimated probability of the occurrence of the second closing of Series C convertible preferred stock increasing to 80%, timing related to the occurrence of the second closing decreasing to 0.06 years and the increase in the future expected value of the Series C preferred shares to $16.25 per share.

License and Equity Agreement

License and Equity Agreement	3 Months Ended
	Mar. 31, 2021
License And Equity Agreement [Abstract]
License and Equity Agreement	4. License and Equity Agreement License and Equity Agreement with Related Party In May 2015 and June 2018, the Company entered into license agreements (the “Stanford Agreement”), as amended, with The Board of Trustees of the Leland Stanford Junior University (“Stanford”). The Stanford Agreement provides the Company exclusive licenses to certain inventions. As consideration, the Company issued Stanford shares of its common stock and a limited right to purchase equity in future financing. Dr. Engleman, a founder and member of the board of directors of the Company, who is a professor at Stanford, was issued shares of common stock as part of the Company’s Series A financing in September 2016. Additionally, the Company has been and is required by the Stanford Agreement to make milestone payments up to an aggregate of $0.4 million for the first licensed product that meets certain patent issuance, clinical and regulatory milestones, and an additional milestone payment of $0.2 million for each additional regulatory approval. The Company also agreed in the Stanford Agreement to pay Stanford tiered royalties on the Company’s and its sublicensees’ net sales of licensed products, if any, at low single-digit percentage rates, subject to certain reductions. Dr. Engleman is entitled to receive a share of any royalties that the Company pays to Stanford under the Stanford Agreement with respect to the covered intellectual property. No royalty payments have been made to date.

Balance Sheet Components

Balance Sheet Components	3 Months Ended
	Mar. 31, 2021
Balance Sheet Related Disclosures [Abstract]
Balance Sheet Components	5. Balance Sheet Components Property and Equipment, net Property and equipment, net, consist of the following (in thousands): March 31, 2021 December 31, 2020 Laboratory equipment $ 5,348 $ 5,253 Office equipment 69 69 Total property and equipment 5,417 5,322 Less accumulated depreciation and amortization (1,507 ) (1,239 ) Total $ 3,910 $ 4,083 Depreciation expense related to property and equipment was $0.3 million and $0.1 million for the three months ended March 31, 2021 and 2020, respectively. Accrued Expenses and Other Current Liabilities Accrued expenses and other current liabilities consist of the following (in thousands): March 31, 2021 December 31, 2020 Accrued research and development $ 3,522 $ 3,199 Accrued compensation 1,658 2,885 Accrued other 814 579 Total $ 5,994 $ 6,663

Collaborations

Collaborations	3 Months Ended
	Mar. 31, 2021
Organization Consolidation And Presentation Of Financial Statements [Abstract]
Collaborations	6. Collaborations Joint Development and License Agreement with Toray Industries, Inc. In March 2019, the Company entered into a Joint Development and License Agreement (the “Toray Development Agreement”) with Toray Industries, Inc. (“Toray”) to jointly develop and commercialize a Boltbody immune stimulating antibody conjugate (“ISAC”) containing Toray’s proprietary antibody to treat cancer. The Company determined that the Toray Development Agreement is a contract with a customer and should be accounted for under ASC 606. In conjunction with the Toray Development Agreement, the Company entered into a Series T Convertible Preferred Stock Purchase Agreement (the “Series T Agreement”) for the issuance of 717,514 shares of Series T convertible preferred stock to Toray. These contracts have been evaluated together and the consideration in excess of the fair value of the Series T convertible preferred stock of $1.5 million has been allocated to the Toray Development agreement and included in the total consideration for collaboration revenue. In February 2021, in connection with the Company’s IPO, all outstanding shares of Series T convertible preferred stock were converted into shares of the Company’s common stock. In the Toray Development Agreement, the Company has identified one bundled performance obligation which includes the license rights, research and development services and services associated with participation on a joint steering committee. Collaboration revenue is recognized over time proportionate to the costs that the Company has incurred to perform the services using an input method as a measure of progress towards satisfying the performance obligation, which is based on project hours. Amounts are billed based on estimated variable consideration in the quarter ahead of performance and are trued up on the subsequent quarter’s invoice following the work performed. The cumulative effect of revisions to estimated hours to complete the Company’s performance obligation will be recorded in the period in which changes are identified and amounts can be reasonably estimated. Deferred revenue allocated to the unsatisfied performance obligation is recorded as a contract liability on the balance sheet and will be recognized over time as the services are performed, which is expected to take place through the first quarter of 2022. As of March 31, 2021 and December 31, 2020, contract liabilities totaling $1.5 million at each period-end were recorded in deferred revenue in current liabilities on the balance sheet. The Toray Development Agreement includes optional additional items which will be accounted for as contract modifications when development advances past certain milestones and the parties both exercise their opt-in rights.

Commitment and Contingencies

Commitment and Contingencies	3 Months Ended
	Mar. 31, 2021
Commitments And Contingencies Disclosure [Abstract]
Commitments and Contingencies	7. Commitments and Contingencies Leases The Company has operating leases for its corporate office, laboratory and vivarium space in Redwood City, California. eight-year As of March 31, 2021, the operating lease right-of-use assets and operating lease liabilities were $3.6 million and $4.0 million, respectively, which represents the portion of the Chesapeake Master Lease that was controlled by the Company. As the Company had not taken control of the remaining space and the lease term had not yet commenced, no operating lease right-of-use assets or operating lease liabilities for the remaining space have been recorded. In connection with the execution of the Chesapeake Master Lease, the Company entered into two operating lease agreements to sublease portions of the premises to two unrelated third parties. The first sublease agreement is to sublease 10,000 square feet which commenced on August 7, 2020 and expires on July 31, 2022. Rent is subject to scheduled annual increases and the subtenant (“Subtenant A”) is responsible for certain operating expenses and taxes throughout the term under the first sublease agreement. Subtenant A has no option to extend the sublease term. Sublease income under the first sublease agreement for the three months ended March 31, 2021, was approximately $0.1 million. The second sublease agreement is to sublease 10,500 square feet, is expected to commence in the second quarter of 2021 and will expire approximately 26 months thereafter. Rent is subject to scheduled annual increases and the subtenant (“Subtenant B”) is responsible for certain operating expenses and taxes throughout the term under the second sublease agreement. Subtenant B has no option to extend the sublease term. No sublease income under the second sublease agreement was recognized for the three months ended March 31, 2021 as the lease term had not yet commenced. At March 31, 2021 and December 31, 2020, finance right-of-use leases are used to finance capital equipment such as printers or ozone generators. The weighted-average remaining lease term and discount rate related to the Company’s lease liabilities as of March 31, 2021 were 6.2 years and 9.6%, respectively, for the operating leases. The weighted-average remaining lease term and discount rate related to the Company’s lease liabilities as of December 31, 2020 were 6.3 years and 9.5%, respectively, for the operating leases. The Company lease discount rates are based on estimates of its incremental borrowing rate, as the discount rates implicit in the Company’s leases cannot be readily determined. As the Company does not have any outstanding debt, the Company estimates the incremental borrowing rate based on its estimated credit rating and available market information. The components of lease expense were as follows (in thousands): Three Months Ended March 31, 2021 2020 Total operating lease cost $ 664 $ 593 Supplemental cash flow information related to leases was as follows (in thousands): Three Months Ended March 31, 2021 2020 Operating cash flows from operating leases $ 172 $ 1,390 The following is a schedule by year for future maturities of the Company’s operating lease liabilities and sublease income to be received as of March 31, 2021 (in thousands): Operating Leases Sublease Income 2021 $ 1,867 $ 409 2022 2,701 362 2023 2,239 — 2024 2,317 — 2025 1,685 — Thereafter 4,254 — Total minimum lease payments/sublease income 15,063 771 Less imputed interest (4,379 ) — Total $ 10,684 $ 771 Supply Agreement The Company has entered into a supply agreement with a contract manufacturer pursuant to which the Company may be required to pay milestone payments upon the achievement of specified regulatory milestones. The agreement is cancelable by the Company upon delivering the appropriate prior written notice. At March 31, 2021, potential future milestone payments under this agreement were up to $2.0 million. Guarantees and Indemnifications In the normal course of business, the Company enters into agreements that contain a variety of representations and provide for general indemnification. The Company’s exposure under these agreements is unknown because it involves claims that may be made against the Company in the future. To date, the Company has not paid any claims or been required to defend any action related to its indemnification obligations. As of March 31, 2021, the Company does not have any material indemnification claims that were probable or reasonably possible and consequently has not recorded related liabilities. Legal Proceedings The Company is subject to claims and assessments from time to time in the ordinary course of business but is not aware of any such matters, individually or in the aggregate, that will have a material adverse effect on the Company’s financial position, results of operations or cash flows.

Convertible Preferred Stock

Convertible Preferred Stock	3 Months Ended
	Mar. 31, 2021
Equity [Abstract]
Convertible Preferred Stock	8. Convertible Preferred Stock Issuance of Series C-1 and Series C-2 Convertible Preferred Stock In June 2020, the Company entered into a preferred stock purchase agreement (the “Series C Agreement”) with existing and new investors to raise up to $93.5 million in two separate tranches. The first tranche closed in June 2020 and the Company raised $41.3 million, net of issuance costs of $0.2 million, and issued 5,162,173 shares of Series C-1 convertible preferred stock at $8.05 per share. In addition, the investors agreed to buy and the Company agreed to sell up to 5,611,065 shares of Series C-2 convertible preferred stock at a price per share of $9.2575, for potential additional gross proceeds of $51.9 million, upon the achievement of certain milestones as defined in the agreement. The commitment made by the investors to invest in the second tranche of the Series C Agreement was considered a separate freestanding financial instrument and was recorded as a Convertible Preferred Stock Purchase Right Liability in the amount of $13.5 million upon the issuance of the first tranche of the Series C-1 convertible preferred stock in June 2020. The commitment was accounted for at fair value during the period it was outstanding with changes in fair value recorded as other income (expense) in the statement of operations and comprehensive loss. During the three months ended March 31, 2021, changes in fair value of this liability totaling $6.1 million have been recorded in other income (expense) in the statement of operations and comprehensive loss. In January 2021, the Company issued the additional 5,611,059 shares of Series C-2 convertible preferred stock for net proceeds of $51.9 million and accordingly, this contractual obligation was settled and the preferred stock purchase right liability was remeasured to its fair value and reclassified to permanent equity. In February 2021, all outstanding shares of convertible preferred stock were converted into the Company’s common stock in connection with the IPO.

Common Stock

Common Stock	3 Months Ended
	Mar. 31, 2021
Equity [Abstract]
Common Stock	9. COMMON STOCK Common Stock Warrants In July 2018, the Company issued 249,218 warrants to purchase common stock to the Series B investors in the first tranche. The warrants were deemed to be freestanding instruments indexed to the Company’s common stock and also met the requirements for equity classification. The warrants had an expiration date of July 26, 2028 and were exercisable at the option of the warrant holder for $0.07 per share. In February 2021, all outstanding warrants were exercised to purchase 82,603 shares of the Company’s common stock in connection with the IPO.

Stock-Based Compensation

Stock-Based Compensation	3 Months Ended
	Mar. 31, 2021
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Stock-Based Compensation	10. STOCK-BASED COMPENSATION Approval of 2021 Equity Incentive Plan and 2021 Employee Stock Purchase Plan In January 2021, the Company’s board of directors adopted the 2021 Equity Incentive Plan (the “2021 Plan”) and the Company’s stockholders approved the 2021 Plan. The 2021 Plan authorized issuance of up to 8,075,000 shares of common stock and it became effective upon the execution of the underwriting agreement for the Company’s IPO. In addition, in January 2021, the Company’s board of directors and stockholders adopted the 2021 Employee Stock Purchase Plan (the “ESPP”). The ESPP authorized issuance of up to 840,000 shares of common stock and it became effective upon the execution of the underwriting agreement for the Company’s IPO. The 2021 ESPP permits participants to purchase common stock through payroll deductions of up to 15% of their eligible compensation. Employees purchase shares of common stock at a price per share equal to 85% of the lower of the fair market value at the start or end of the six-month purchase periods within the two-year Performance and Service Based Stock Options In September 2020, the compensation committee of the Company’s board of directors granted 526,018 options to employees that would commence vesting upon the closing of the Series C-2 financing and generally vest monthly over 48 months (the “Performance Awards”). The Company recognizes expense based on the fair value of the Performance Awards over the estimated service period (under the graded vesting method) to the extent the achievement of the related performance criteria is estimated to be probable. The Company determined that the financing milestone was achieved during the three months ended March 31, 2021 and accordingly recognized stock-based compensation expense related to the Performance Awards of approximately $0.5 million for this quarter. The weighted-average grant date fair value of the Performance Awards was $3.24 per share. Stock-Based Compensation Expense The following table summarizes the components of stock-based compensation expense recognized in the Company’s statement of operations and comprehensive loss (in thousands): Three Months Ended March 31, 2021 2020 Research and development $ 1,020 $ 100 General and administrative 1,089 125 Total $ 2,109 $ 225 Early Exercise Liability Some of the options granted under the 2015 Plan may be exercised prior to the time that the options have vested, provided that such shares remain subject to repurchase until such time as they have vested. The right to repurchase these shares lapses over the vesting periods, which are generally four years. As of March 31, 2021 and December 31, 2020, there were 42,822 and 47,180, respectively, unvested shares representing an early exercise liability of approximately $0.1 million at each period-end. The unvested shares purchased by the employees are not deemed, for accounting purposes, to be outstanding.

Net Loss Per Share

Net Loss Per Share	3 Months Ended
	Mar. 31, 2021
Earnings Per Share [Abstract]
Net Loss Per Share	11. Net Loss Per Share The following table sets forth the computation of the Company’s basic and diluted net loss per share attributable to common stockholders, which excludes shares which are legally outstanding, but subject to repurchase by the Company (in thousands, except share and per share amounts): Three Months Ended March 31, 2021 2020 Numerator: Net loss $ (24,454 ) $ (8,633 ) Denominator: Weighted average common shares outstanding 21,507,171 1,933,639 Common stock outstanding subject to repurchase related to unvested early exercised stock options and restricted stock awards (44,952 ) (28,589 ) Warrants to purchase common stock 36,087 172,315 Weighted average common shares outstanding - basic and diluted 21,498,306 2,077,365 Net loss per share attributable to common stockholders, basic and diluted $ (1.14 ) $ (4.16 ) Potentially dilutive securities not included in the calculation of diluted net loss per share because to do so would be anti-dilutive are as follows (in common stock equivalent shares): Three Months Ended March 31, 2021 2020 Convertible preferred stock — 10,070,102 Common stock options issued and outstanding 5,003,518 1,999,430 Common stock outstanding subject to repurchase related to unvested early exercised stock options and restricted stock awards 42,822 24,508 Total 5,046,340 12,094,040 The ESPP did not exist in 2020, and the potentially dilutive shares to be issued under the ESPP as of March 31, 2021 were not included in the calculation of dilutive net loss per share because they would be anti-dilutive and were immaterial.

Summary of Significant Accoun_2

Summary of Significant Accounting Policies (Policies)	3 Months Ended
	Mar. 31, 2021
Accounting Policies [Abstract]
Basis of Presentation	Basis of Presentation The accompanying unaudited condensed financial statements as of March 31, 2021 and for the three months ended March 31, 2021 and 2020 have been prepared in accordance with U.S. generally accepted accounting principles (“U.S. GAAP”)
Reverse Stock Split	Reverse Stock Split On January 26, 2021, the Company amended and restated its amended and restated certificate of incorporation to effect a 1-for-7 reverse stock split of the Company’s outstanding common stock and convertible preferred stock. The par value and authorized shares of the common stock were not adjusted as a result of the reverse stock split. All issued and outstanding common stock, options to purchase common stock, early exercised options and per share amounts contained in the financial statements have been retroactively adjusted to give effect to the reverse stock split for all periods presented.
Other Risks and Uncertainties	Other Risks and Uncertainties The Company is subject to a number of risks similar to other early-stage biopharmaceutical companies, including, but not limited to, changes in any of the following areas that the Company believes could have a material adverse effect on its future financial position or results of operations: risks related to the successful discovery and development of its product candidates, ability to raise additional capital, development of new technological innovations by its competitors and delay or inability to obtain chemical or biological intermediates from such suppliers required for the synthesis of the Company’s product candidates, including due to the impact of the current COVID-19 pandemic, protection of intellectual property rights, litigation or claims against the Company based on intellectual property rights, and regulatory clearance and market acceptance of the Company’s products. The current COVID-19 pandemic, which is impacting worldwide economic activity, poses the risk that the Company or its employees, contractors, suppliers and other partners may be prevented from conducting business activities for an indefinite period of time, including due to shutdowns that may be requested or mandated by governmental authorities. The extent to which the COVID-19 pandemic will impact the Company’s business will depend on future developments that are highly uncertain and cannot be predicted at this time. The preparation of financial statements in conformity with generally accepted accounting principles requires management to make estimates and assumptions that affect the amounts reported in the financial statements and accompanying notes. The extent to which the COVID-19 pandemic may directly or indirectly impact the Company’s financial statements is highly uncertain and subject to change. Management considered the potential impact of the COVID-19 pandemic on its estimates and assumptions and there was not a material impact to the Company’s condensed financial statements as of and for the three months ended March 31, 2021; however, actual results could differ from those estimates and there may be changes to management’s estimates in future periods. The Company relies on single source manufacturers and suppliers for the supply of its product candidates. Disruption from these manufacturers or suppliers would have a negative impact on the Company’s business, financial position and results of operations.
Use of Estimates	Use of Estimates The preparation of financial statements in conformity with U.S. GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities at the date of the financial statements and the reported amounts of expenses during the reporting period. On an ongoing basis, the Company evaluates its estimates and assumptions, including those related to revenue recognition, the valuation of common stock, stock-based compensation, convertible preferred stock purchase right liabilities and accrued liabilities. Management bases its estimates on historical experience and on various other assumptions that are believed to be reasonable under the circumstances, the results of which form the basis for making judgments about the carrying values of assets and liabilities that are not readily apparent from other sources. Actual results may differ materially from those estimates.
Deferred Offering Costs	Deferred Offering Costs The Company capitalized certain legal, accounting and other third-party fees that were directly related to the Company’s IPO. After the completion of the IPO in February 2021, the total deferred offering costs of $4.0 million were offset against the proceeds from the IPO and reclassified to additional paid-in capital in the accompanying the balance sheets. At December 31, 2020, deferred offering costs totaling $2.4 million were included as non-current assets in the accompanying balance sheet.
Concentrations of Credit Risk	Concentrations of Credit Risk Financial instruments that potentially subject the Company to concentration of credit risk consist of cash, cash equivalents and marketable securities. At March 31, 2021 and December 31, 2020, most of the Company’s funds are invested with a registered investment manager and custodied at one financial institution, with working capital kept at a separate financial institution, and account balances may at times exceed federally insured limits. Management believes that the Company is not exposed to significant credit risk due to the financial strength of the depository institutions where the funds are held.
Cash and Cash Equivalents	Cash and Cash Equivalents The Company considers all highly liquid investments purchased with an original maturity of three months or less to be cash equivalents. As of March 31, 2021 and December 31, 2020, cash and cash equivalents consisted primarily of bank deposits and money market funds, which were unrestricted as to withdrawal or use.
Marketable Securities	Marketable Securities The Company classifies its marketable securities as available-for-sale and records such assets at estimated fair value in the balance sheets, with unrealized gains and losses that are determined to be temporary, if any,
Restricted Cash	Restricted Cash As of March 31, 2021 and December 31, 2020, the Company had $1.6 million of long-term restricted cash deposited with a financial institution. The restricted cash is held in separate bank accounts to support letter of credit agreements related to the Company’s facility leases which expire in 2025 and 2031 (see Note 7).
Fair Value Measurements	Fair Value Measurements Fair value is defined as the price that would be received to sell an asset or paid to transfer a liability in an orderly transaction between market participants at the measurement date. As such, fair value is a market-based measurement that should be determined based on assumptions that market participants would use in pricing an asset or liability. Cash and cash equivalents, restricted cash, marketable debt securities, accounts payable, accrued expenses and other current liabilities are reported at their respective fair values in our condensed balance sheets. The carrying amount of the remaining financial instruments approximate fair value due to their short-term nature. Refer to Note 3 for the methodologies and assumptions used in valuing financial instruments.
Net Loss Per Share	Net Loss Per Share Basic net loss per share is calculated by dividing the net loss by the weighted-average number of shares of common stock outstanding during the period, without consideration for potentially dilutive securities. Diluted net loss per share is computed by dividing the net loss by the weighted-average number of common stock and potentially dilutive securities outstanding for the period. For purposes of the diluted net loss per share calculation, convertible preferred stock, stock options, common stock subject to repurchase related to unvested restricted stock awards and early exercise of stock options are considered to be potentially dilutive securities. Basic and diluted net loss per share is presented in conformity with the two-class method required for participating securities as the convertible preferred stock is considered a participating security because it participates in dividends with common stock. The Company also considers the shares issued upon the early exercise of stock options subject to repurchase to be participating securities because holders of such shares have non-forfeitable dividend rights in the event a dividend is paid on common stock. The holders of all series of convertible preferred stock and the holders of early exercised shares subject to repurchase do not have a contractual obligation to share in the Company’s losses. As such, the net loss was attributed entirely to common stockholders. Because the Company has reported a net loss for all periods presented, diluted net loss per share is the same as basic net loss per share for all periods presented as potentially dilutive securities were anti-dilutive.
Recent Accounting Standards	Recent Accounting Standards From time to time, new accounting standards are issued by the Financial Accounting Standards Board (the “FASB”), or other standard setting bodies and adopted by the Company as of the specified effective date. There have been no new accounting pronouncements issued nor adopted during the three months ended March 31, 2021 that are of significance to the Company’s financial position or results of operations.

Fair Value Measurements and F_2

Fair Value Measurements and Fair Value of Financial Instruments (Tables)	3 Months Ended
	Mar. 31, 2021
Fair Value Disclosures [Abstract]
Schedule of Marketable Securities Classified as Available-for-sale Securities	Marketable securities, all of which are classified as available-for-sale securities, consisted of the following at March 31, 2021 and December 31, 2020 (in thousands): March 31, 2021 Amortized Unrealized Unrealized Estimated Cost Gains Losses Fair Value Asset backed securities $ 28,614 $ 1 $ (4 ) $ 28,611 Other government agency securities 5,113 — (7 ) 5,106 Commercial paper 91,976 — — 91,976 Corporate debt securities 81,784 — (53 ) 81,731 Total $ 207,487 $ 1 $ (64 ) $ 207,424 December 31, 2020 Amortized Unrealized Unrealized Estimated Cost Gains Losses Fair Value Asset backed securities $ 2,639 $ — $ — $ 2,639 U.S. treasury securities 1,300 — — 1,300 Commercial paper 6,795 — — 6,795 Corporate debt securities 6,562 1 (1 ) 6,562 Total $ 17,296 $ 1 $ (1 ) $ 17,296
Schedule of Fair Values of Assets and Liabilities Measured at Fair Value on Recurring Basis	At March 31, 2021 and December 31, 2020, the fair values of the Company’s assets and liabilities, which are measured at fair value on a recurring basis, were determined using the following inputs (in thousands): March 31, 2021 Total (Level 1) (Level 2) (Level 3) Money market funds $ 93,270 $ 93,270 $ — $ — Asset backed securities 28,611 — 28,611 — Other government agency securities 5,106 — 5,106 — Commercial paper 91,976 — 91,976 — Corporate debt securities 81,731 — 81,731 — Total $ 300,694 $ 93,270 $ 207,424 $ — December 31, 2020 Total (Level 1) (Level 2) (Level 3) Money market funds $ 3,921 $ 3,921 $ — $ — U.S. treasury securities 1,300 1,300 — — Asset backed securities 2,640 — 2,640 — Commercial paper 6,795 — 6,795 — Corporate debt securities 6,561 — 6,561 — Total $ 21,217 $ 5,221 $ 15,996 $ — Liabilities: Preferred stock purchase rights liability $ 25,224 $ — $ — $ 25,224
Schedule of Changes in Estimated Fair Value of Financial Instruments	The following table provides a summary of changes in the estimated fair value of the financial instruments using significant Level 3 inputs (in thousands): Series C Convertible Preferred Stock Purchase Right Liability Balance at December 31, 2020 $ 25,224 Change in fair value 6,084 Reclassification to equity (31,308 ) Balance at March 31, 2021 $ —

Balance Sheet Components (Table

Balance Sheet Components (Tables)	3 Months Ended
	Mar. 31, 2021
Balance Sheet Related Disclosures [Abstract]
Property and Equipment, Net	Property and equipment, net, consist of the following (in thousands): March 31, 2021 December 31, 2020 Laboratory equipment $ 5,348 $ 5,253 Office equipment 69 69 Total property and equipment 5,417 5,322 Less accumulated depreciation and amortization (1,507 ) (1,239 ) Total $ 3,910 $ 4,083
Accrued Expenses and Other Current Liabilities	Accrued expenses and other current liabilities consist of the following (in thousands): March 31, 2021 December 31, 2020 Accrued research and development $ 3,522 $ 3,199 Accrued compensation 1,658 2,885 Accrued other 814 579 Total $ 5,994 $ 6,663

Commitment and Contingencies (T

Commitment and Contingencies (Tables)	3 Months Ended
	Mar. 31, 2021
Commitments And Contingencies Disclosure [Abstract]
Components of Lease Expense	The components of lease expense were as follows (in thousands): Three Months Ended March 31, 2021 2020 Total operating lease cost $ 664 $ 593
Supplemental Cash Flow Information Related to Leases	Supplemental cash flow information related to leases was as follows (in thousands): Three Months Ended March 31, 2021 2020 Operating cash flows from operating leases $ 172 $ 1,390
Schedule by Year for Future Maturities of Operating Lease Liabilities and Sublease Income to be Received	The following is a schedule by year for future maturities of the Company’s operating lease liabilities and sublease income to be received as of March 31, 2021 (in thousands): Operating Leases Sublease Income 2021 $ 1,867 $ 409 2022 2,701 362 2023 2,239 — 2024 2,317 — 2025 1,685 — Thereafter 4,254 — Total minimum lease payments/sublease income 15,063 771 Less imputed interest (4,379 ) — Total $ 10,684 $ 771

Stock-Based Compensation (Table

Stock-Based Compensation (Tables)	3 Months Ended
	Mar. 31, 2021
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Summary of Components of Stock-Based Compensation Expense Recognized	The following table summarizes the components of stock-based compensation expense recognized in the Company’s statement of operations and comprehensive loss (in thousands): Three Months Ended March 31, 2021 2020 Research and development $ 1,020 $ 100 General and administrative 1,089 125 Total $ 2,109 $ 225

Net Loss Per Share (Tables)

Net Loss Per Share (Tables)	3 Months Ended
	Mar. 31, 2021
Earnings Per Share [Abstract]
Computation of Basic and Diluted Net Loss per Share Attributable to Common Stockholders, which excludes Shares Legally Outstanding	The following table sets forth the computation of the Company’s basic and diluted net loss per share attributable to common stockholders, which excludes shares which are legally outstanding, but subject to repurchase by the Company (in thousands, except share and per share amounts): Three Months Ended March 31, 2021 2020 Numerator: Net loss $ (24,454 ) $ (8,633 ) Denominator: Weighted average common shares outstanding 21,507,171 1,933,639 Common stock outstanding subject to repurchase related to unvested early exercised stock options and restricted stock awards (44,952 ) (28,589 ) Warrants to purchase common stock 36,087 172,315 Weighted average common shares outstanding - basic and diluted 21,498,306 2,077,365 Net loss per share attributable to common stockholders, basic and diluted $ (1.14 ) $ (4.16 )
Potentially Dilutive Securities not Included in the Calculation of Diluted Net Loss per Share	Potentially dilutive securities not included in the calculation of diluted net loss per share because to do so would be anti-dilutive are as follows (in common stock equivalent shares): Three Months Ended March 31, 2021 2020 Convertible preferred stock — 10,070,102 Common stock options issued and outstanding 5,003,518 1,999,430 Common stock outstanding subject to repurchase related to unvested early exercised stock options and restricted stock awards 42,822 24,508 Total 5,046,340 12,094,040

Description of the Business - A

Description of the Business - Additional Information (Details) - USD ($) $ / shares in Units, $ in Thousands	Feb. 09, 2021	Feb. 04, 2021	Mar. 31, 2021	Dec. 31, 2020
Subsidiary Sale Of Stock [Line Items]
Proceeds from stock sold, net of underwriting discounts, commissions and offering costs			$ 244,988
Common stock, shares authorized		200,000,000	200,000,000	198,000,000
Preferred stock, shares authorized		10,000,000
Accumulated deficit			$ 132,853	$ 108,399
Cash and cash equivalents, and marketable securities			$ 302,900
Common Stock
Subsidiary Sale Of Stock [Line Items]
Aggregate stock sold			13,225,000
Outstanding shares of convertible preferred stock converted into common stock		20,843,334	20,843,334
IPO | Common Stock
Subsidiary Sale Of Stock [Line Items]
Aggregate stock sold	13,225,000
Sale of stock, price per share	$ 20
Proceeds from stock sold, net of underwriting discounts, commissions and offering costs	$ 242,000
Underwriters’ Option | Common Stock
Subsidiary Sale Of Stock [Line Items]
Aggregate stock sold	1,725,000

Summary of Significant Accoun_3

Summary of Significant Accounting Policies - Additional Information (Details) $ in Thousands	Jan. 26, 2021	Mar. 31, 2021USD ($)	Feb. 28, 2021USD ($)	Dec. 31, 2020USD ($)
Summary Of Significant Accounting Policies [Line Items]
Deferred offering costs noncurrent				$ 2,400
Deferred offering costs to offset against proceeds from IPO			$ 4,000
Restricted cash		$ 1,565		$ 1,565
Common Stock and Convertible Preferred Stock
Summary Of Significant Accounting Policies [Line Items]
Reverse stock split		1-for-7
Reverse stock split ratio	0.142857

Fair Value Measurements and F_3

Fair Value Measurements and Fair Value of Financial Instruments - Additional Information (Details) - USD ($)	1 Months Ended	3 Months Ended	12 Months Ended
	Jan. 31, 2021	Mar. 31, 2021	Dec. 31, 2020
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Fair value, assets, level 1 to level 2 transfers		$ 0	$ 0
Fair value, assets, level 2 to level 1 transfers		0	0
Fair value, liabilities, level 1 to level 2 transfers		0	0
Fair value, liabilities, level 2 to level 1 transfers		0	0
Fair value, asset, transfers into level 3		0	0
Fair value, asset, transfers out of level 3		0	0
Fair value, liability, transfers into level 3		0	0
Fair value, liability, transfers out of level 3		$ 0	$ 0
Series C-2 Convertible Preferred Stock
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Fair value of convertible preferred stock purchase right liability	$ 31,300,000
Percentage of increase in convertible preferred stock	80.00%
Period of timing related to occurrence	21 days
Increase in future expected value of share	$ 16.25

Fair Value Measurements and F_4

Fair Value Measurements and Fair Value of Financial Instruments - Schedule of Marketable Securities Classified as Available-for-sale Securities (Details) - USD ($) $ in Thousands	Mar. 31, 2021	Dec. 31, 2020
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Amortized Cost	$ 207,487	$ 17,296
Unrealized Gains	1	1
Unrealized Losses	(64)	(1)
Estimated Fair Value	207,424	17,296
Asset Backed Securities
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Amortized Cost	28,614	2,639
Unrealized Gains	1
Unrealized Losses	(4)
Estimated Fair Value	28,611	2,639
U.S. Treasury Securities
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Amortized Cost		1,300
Estimated Fair Value		1,300
Other Government Agency Securities
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Amortized Cost	5,113
Unrealized Losses	(7)
Estimated Fair Value	5,106
Commercial Paper
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Amortized Cost	91,976	6,795
Estimated Fair Value	91,976	6,795
Corporate Debt Securities
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Amortized Cost	81,784	6,562
Unrealized Gains		1
Unrealized Losses	(53)	(1)
Estimated Fair Value	$ 81,731	$ 6,562

Fair Value Measurements and F_5

Fair Value Measurements and Fair Value of Financial Instruments - Schedule of Fair Values of Assets and Liabilities Measured at Fair Value on Recurring Basis (Details) - Recurring Basis - USD ($) $ in Thousands	Mar. 31, 2021	Dec. 31, 2020
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Total asset	$ 300,694	$ 21,217
Liabilities:
Preferred stock purchase rights liability		25,224
Money Market Funds
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Total asset	93,270	3,921
U.S. Treasury Securities
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Total asset		1,300
Asset Backed Securities
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Total asset	28,611	2,640
Other Government Agency Securities
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Total asset	5,106
Commercial Paper
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Total asset	91,976	6,795
Corporate Debt Securities
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Total asset	81,731	6,561
Level 1
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Total asset	93,270	5,221
Level 1 | Money Market Funds
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Total asset	93,270	3,921
Level 1 | U.S. Treasury Securities
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Total asset		1,300
Level 2
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Total asset	207,424	15,996
Level 2 | Asset Backed Securities
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Total asset	28,611	2,640
Level 2 | Other Government Agency Securities
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Total asset	5,106
Level 2 | Commercial Paper
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Total asset	91,976	6,795
Level 2 | Corporate Debt Securities
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Total asset	$ 81,731	6,561
Level 3
Liabilities:
Preferred stock purchase rights liability		$ 25,224

Fair Value Measurements and F_6

Fair Value Measurements and Fair Value of Financial Instruments - Schedule of Changes in Estimated Fair Value of Financial Instruments (Details) - Recurring Basis $ in Thousands	3 Months Ended
	Mar. 31, 2021USD ($)
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Balance at December 31, 2020	$ 25,224
Change in fair value	6,084
Reclassification to equity	$ (31,308)

License and Equity Agreement -

License and Equity Agreement - Additional Information (Details) - Stanford Agreement	71 Months Ended
	Mar. 31, 2021USD ($)
License And Equity Agreement [Line Items]
Additional milestone payment	$ 200,000
Royalty payments	0
Maximum
License And Equity Agreement [Line Items]
Aggregate millstone payments	$ 400,000

Balance Sheet Components - Prop

Balance Sheet Components - Property and Equipment, Net (Details) - USD ($) $ in Thousands	Mar. 31, 2021	Dec. 31, 2020
Property Plant And Equipment [Line Items]
Property and equipment, gross	$ 5,417	$ 5,322
Less accumulated depreciation and amortization	(1,507)	(1,239)
Total	3,910	4,083
Equipment
Property Plant And Equipment [Line Items]
Property and equipment, gross	5,348	5,253
Office Equipment
Property Plant And Equipment [Line Items]
Property and equipment, gross	$ 69	$ 69

Balance Sheet Components - Addi

Balance Sheet Components - Additional Information (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Balance Sheet Related Disclosures [Abstract]
Depreciation expense	$ 0.3	$ 0.1

Balance Sheet Components - Accr

Balance Sheet Components - Accrued Expenses and Other Current Liabilities (Details) - USD ($) $ in Thousands	Mar. 31, 2021	Dec. 31, 2020
Balance Sheet Related Disclosures [Abstract]
Accrued research and development	$ 3,522	$ 3,199
Accrued compensation	1,658	2,885
Accrued other	814	579
Total	$ 5,994	$ 6,663

Collaborations - Additional Inf

Collaborations - Additional Information (Details) - USD ($) $ in Thousands	1 Months Ended	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2021	Dec. 31, 2020
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Consideration in excess of fair value		$ 241,959
Toray Development Agreement
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Contract liability		$ 1,500	$ 1,500
Series T Convertible Preferred Stock | Toray Development Agreement
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Issuance of shares	717,514
Consideration in excess of fair value	$ 1,500

Commitments and Contingencies -

Commitments and Contingencies - Additional Information (Details)	Aug. 07, 2020USD ($)ft²	Jun. 30, 2021USD ($)ft²	Mar. 31, 2021USD ($)	Dec. 31, 2020USD ($)
Commitments And Contingencies [Line Items]
Operating lease right-of-use assets			$ 11,478,000	$ 12,267,000
Operating lease liabilities			10,684,000
Sublease income			$ 771,000
Weighted-average remaining lease term			6 years 2 months 12 days	6 years 3 months 18 days
Weighted-average discount rate			9.60%	9.50%
Maximum
Commitments And Contingencies [Line Items]
Potential future milestone payments			$ 2,000,000
Forecast
Commitments And Contingencies [Line Items]
Operating sublease, option to extend, description		Subtenant B has no option to extend the sublease term.
Operating sublease, option to extend		false
Sublease income		$ 0
Sublease, area of property expected to be leased | ft²		10,500
Chesapeake Master Lease
Commitments And Contingencies [Line Items]
Operating lease, area of property available | ft²	71,646
Operating lease, area of property, additional space available | ft²	45,690
Operating lease, area of property, extension space available | ft²	25,956
Operating lease, initial term of contract	10 years
Operating lease, option to extend	true
Operating lease, extended additional term	8 years
Tenant improvement allowance	$ 4,800,000
Operating lease, area of property subleased | ft²	10,000
Operating lease right-of-use assets			3,600,000
Operating lease liabilities			$ 4,000,000
Sublease, area of property leased | ft²	10,000
Sublease expiration date	Jul. 31, 2022
Operating sublease, option to extend, description			Subtenant A has no option to extend the sublease term.
Operating sublease, option to extend	false
Sublease income			$ 100,000
Chesapeake Master Lease | Forecast
Commitments And Contingencies [Line Items]
Operating lease, area of property, extension space available | ft²		25,956
Operating lease, area of property, additional space remaining | ft²		35,690

Commitments and Contingencies_2

Commitments and Contingencies - Components of Lease Expense (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Commitments And Contingencies Disclosure [Abstract]
Total operating lease cost	$ 664	$ 593

Commitments and Contingencies_3

Commitments and Contingencies - Supplemental Cash Flow Information Related to Leases (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Commitments And Contingencies Disclosure [Abstract]
Operating cash flows from operating leases	$ 172	$ 1,390

Commitments and Contingencies_4

Commitments and Contingencies - Schedule by Year for Future Maturities of Operating Lease Liabilities and Sublease Income to be Received (Details) $ in Thousands	3 Months Ended
	Mar. 31, 2021USD ($)
Operating Leases
Operating Leases, 2021	$ 1,867
Operating Leases, 2022	2,701
Operating Leases, 2023	2,239
Operating Leases, 2024	2,317
Operating Leases, 2025	1,685
Operating Leases, Thereafter	4,254
Operating Leases, Total minimum lease payments	15,063
Operating lease liabilities	10,684
Less imputed interest	(4,379)
Sublease Income
Sublease Income, 2021	409
Sublease Income, 2022	362
Total Sublease Income	771
Sublease Income, Total	$ 771

Convertible Preferred Stock - A

Convertible Preferred Stock - Additional Information (Details)	1 Months Ended		3 Months Ended
	Jan. 31, 2021USD ($)shares	Jun. 30, 2020USD ($)Tranche$ / sharesshares	Mar. 31, 2021USD ($)	Dec. 31, 2020USD ($)
Class Of Stock [Line Items]
Convertible preferred stock value				$ 105,296,000
Proceeds from issuance of preferred stock, net of issuance cost			$ 51,902,000
Series C-2 Convertible Preferred Stock
Class Of Stock [Line Items]
Fair value of convertible preferred stock purchase right liability	$ 31,300,000
Series C Agreement
Class Of Stock [Line Items]
Convertible preferred stock, authorized amount		$ 93,500,000
Number of tranches | Tranche		2
First Tranche Series C Agreement
Class Of Stock [Line Items]
Convertible preferred stock value		$ 41,300,000
Net of issuance costs		$ 200,000
First Tranche Series C Agreement | Series C-1 Convertible Preferred Stock
Class Of Stock [Line Items]
Convertible preferred stock, shares issued | shares		5,162,173
Stock issued, price per share | $ / shares		$ 8.05
First Tranche Series C Agreement | Series C-2 Convertible Preferred Stock
Class Of Stock [Line Items]
Convertible preferred stock, shares issuable | shares		5,611,065
Stock price per share | $ / shares		$ 9.2575
Potential gross proceeds from issuance		$ 51,900,000
Second Tranche Series C Agreement
Class Of Stock [Line Items]
Changes in fair value of this liability			$ 6,100,000
Second Tranche Series C Agreement | Series C-1 Convertible Preferred Stock
Class Of Stock [Line Items]
Fair value of convertible preferred stock purchase right liability		$ 13,500,000
Second Tranche Series C Agreement | Series C-2 Convertible Preferred Stock
Class Of Stock [Line Items]
Convertible preferred stock, shares issued | shares	5,611,059
Proceeds from issuance of preferred stock, net of issuance cost	$ 51,900,000

Common Stock - Additional Infor

Common Stock - Additional Information (Details) - $ / shares	1 Months Ended
	Jul. 31, 2018	Feb. 28, 2021
Class Of Warrant Or Right [Line Items]
Warrants issued to purchase common stock	249,218
Warrants expiration date	Jul. 26, 2028
Warrant exercise price	$ 0.07
Common Stock
Class Of Warrant Or Right [Line Items]
Number of common stock purchased upon exercise of warrants		82,603

Stock-Based Compensation - Addi

Stock-Based Compensation - Additional Information (Details) - USD ($) $ / shares in Units, $ in Thousands	1 Months Ended		3 Months Ended
	Jan. 31, 2021	Sep. 30, 2020	Mar. 31, 2021	Mar. 31, 2020	Dec. 31, 2020
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Stock-based compensation expense			$ 2,109	$ 225
Performance and Service Based Stock Options
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Shares granted		526,018
Vesting period		48 months
Stock-based compensation expense			$ 500
Weighted-average grant date fair value of awards		$ 3.24
2021 Plan | Common Stock
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Shares authorized for issuance	8,075,000
2021 Employee Stock Purchase Plan
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Purchase price of stock as percentage of fair market value	85.00%
2021 Employee Stock Purchase Plan | Common Stock
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Shares authorized for issuance	840,000
Plan offering period	2 years
Shares issued			0
2021 Employee Stock Purchase Plan | Common Stock | Maximum
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Percentage of eligible compensation for payroll deductions to purchase stock	15.00%
2015 Plan | Employee Stock Option
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Unvested shares			42,822		47,180
Repurchase right vesting period			4 years
Early exercise liability			$ 100

Stock-Based Compensation - Summ

Stock-Based Compensation - Summary of Components of Stock-Based Compensation Expense Recognized (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Stock-based compensation expense	$ 2,109	$ 225
Research and Development
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Stock-based compensation expense	1,020	100
General and Administrative
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Stock-based compensation expense	$ 1,089	$ 125

Net Loss Per Share - Computatio

Net Loss Per Share - Computation of Basic and Diluted Net Loss per Share Attributable to Common Stockholders, which excludes Shares Legally Outstanding (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Numerator:
Net loss	$ (24,454)	$ (8,633)
Denominator:
Weighted average common shares outstanding	21,507,171	1,933,639
Common stock outstanding subject to repurchase related to unvested early exercised stock options and restricted stock awards	(44,952)	(28,589)
Warrants to purchase common stock	36,087	172,315
Weighted average common shares outstanding - basic and diluted	21,498,306	2,077,365
Net loss per share attributable to common stockholders, basic and diluted	$ (1.14)	$ (4.16)

Net Loss Per Share - Potentiall

Net Loss Per Share - Potentially Dilutive Securities not Included in the Calculation of Diluted Net Loss per Share (Details) - shares	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Potentially dilutive securities not included in the calculation of diluted net loss per share	5,046,340	12,094,040
Convertible Preferred Stock
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Potentially dilutive securities not included in the calculation of diluted net loss per share		10,070,102
Common Stock Options Issued and Outstanding
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Potentially dilutive securities not included in the calculation of diluted net loss per share	5,003,518	1,999,430
Common Stock Outstanding Subject to Repurchase Related to Unvested Early Exercised Stock Options and Restricted Stock Awards
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Potentially dilutive securities not included in the calculation of diluted net loss per share	42,822	24,508