0001564590-21-016675 | 10-K | XBRL Viewer

Income Taxes - Schedule of Deferred Tax Assets and Liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Deferred tax assets:
Net operating loss carryforwards	$ 38,739	$ 15,650
Accrued liabilities and reserves	1,623	716
Stock-based compensation	1,434	253
Intangible assets	9,792	10,435
Operating lease liability	3,427	4,121
Research and development credits	10,471	4,991
Total deferred tax assets	65,486	36,166
Deferred tax liabilities:
Property and equipment	(269)	(167)
Right-of-use assets	(3,243)	(3,956)
Total deferred tax liabilities	(3,512)	(4,123)
Valuation allowance	$ (61,974)	$ (32,043)

Organization	12 Months Ended
Dec. 31, 2020
Organization Consolidation And Presentation Of Financial Statements [Abstract]
Organization	Note 1. Organization IGM Biosciences, Inc. (the Company) was incorporated in the state of Delaware in August 1993 under the name Palingen, Inc. and the name was subsequently changed to IGM Biosciences, Inc. in 2010. The Company’s headquarters are in Mountain View, California. The Company is a biotechnology company engaged in the development of IgM antibody therapeutics for the treatment of multiple diseases. In December 2017, the Company established a holding company (Holdco); in April 2019, Holdco was subsequently dissolved and equity interests in Holdco were converted into equity interests in the Company. The information included in these financial statements is consistently presented as if it is that of the Company, even during the interim period when investors held their equity interests in Holdco. Haldor Topsøe Holding A/S is a significant investor in the Company either through its direct equity ownership or indirectly as the majority owner of Holdco, until Holdco was dissolved in April 2019. Haldor Topsøe Holding A/S and Holdco represent a combined entity (Significant Investor) as referenced herein. Basis of Presentation These financial statements have been prepared in accordance with accounting principles generally accepted in the United States of America (U.S. GAAP). Reverse Stock Split In August 2019, the Company filed an amendment to the Company’s amended and restated certificate of incorporation to effect a reverse split of shares of the Company’s common stock, non-voting common stock and convertible preferred stock, each on a 6.6084-for-1 basis (Reverse Stock Split). The Reverse Stock Split also applied to any outstanding securities or rights convertible into, or exchangeable or exercisable for, common stock, non-voting common stock or convertible preferred stock. The par value of the common stock was not adjusted as a result of the Reverse Stock Split. All references to common stock, non-voting common stock, restricted stock, options to purchase common stock, share data, per share data, convertible preferred stock and related information contained in the financial statements and related footnotes have been retrospectively adjusted to reflect the effect of the Reverse Stock Split for all periods presented. The Reverse Stock Split was effected on August 30, 2019. Public Offerings On September 17, 2019, the Company’s registration statement on Form S-1 (File No. 333-233365) relating to its initial public offering (IPO) of common stock became effective. The IPO closed on September 20, 2019 at which time the Company issued an aggregate of 12,578,125 shares of its common stock at a price of $16.00 per share, including 1,640,625 shares issued in connection with the full exercise by the underwriters of their option to purchase additional shares of common stock. In addition, immediately prior to the closing of the IPO, all outstanding shares of the Company’s convertible preferred stock automatically converted into 10,787,861 shares of common stock and 6,431,205 shares of non-voting common stock. Proceeds from the IPO, net of underwriting discounts and commissions and offering costs, were approximately $183.0 million. On November 12, 2020, the Company’s registration statement on Form S-3 (File No. 333-249863) was declared effective by the Securities and Exchange Commission (the SEC). On December 11, 2020, pursuant to the Form S-3 that was filed, the Company completed a public offering (2020 Public Offering) of 1,221,224 shares of its common stock, which included the exercise of the underwriters’ option to purchase 333,333 shares in full, and pre-funded warrants to purchase an additional 1,334,332 shares of common stock (Pre-funded Warrants). The Pre-funded Warrants were issued to two separate related party affiliates. The public offering price of common stock was $90.00 per share and the public offering price of each pre-funded warrant was $89.99, with each pre-funded warrant having an exercise price of $0.01. After deducting underwriting discounts and commissions and offering costs paid or payable by the Company of approximately $14.6 million, the net proceeds from the Company’s 2020 Public Offering were approximately $215.4 million. Liquidity The Company has incurred net operating losses and negative cash flows from operations since its inception and had an accumulated deficit of $188.6 million as of December 31, 2020. As of December 31, 2020, the Company had cash and investments of $366.3 million. Management believes that the existing financial resources are sufficient to continue operating activities at least one year past the issuance date of these financial statements. The Company has historically financed its operations primarily through the sale of convertible preferred stock and common stock and the issuance of unsecured promissory notes. To date, none of the Company’s product candidates have been approved for sale, and the Company has not generated any revenue since inception. Management expects operating losses to continue and increase for the foreseeable future, as the Company progresses into clinical development activities for its lead product candidates. The Company’s prospects are subject to risks, expenses and uncertainties frequently encountered by companies in the biotechnology industry as discussed below. While the Company has been able to raise multiple rounds of financing, there can be no assurance that in the event the Company requires additional financing, such financing will be available on terms which are favorable or at all. Failure to generate sufficient cash flows from operations, raise additional capital or reduce certain discretionary spending would have a material adverse effect on the Company’s ability to achieve its intended business objectives.

Organization

12 Months Ended

Dec. 31, 2020

Organization Consolidation And Presentation Of Financial Statements [Abstract]

Organization

Note 1. Organization

IGM Biosciences, Inc. (the Company) was incorporated in the state of Delaware in August 1993 under the name Palingen, Inc. and the name was subsequently changed to IGM Biosciences, Inc. in 2010. The Company’s headquarters are in Mountain View, California. The Company is a biotechnology company engaged in the development of IgM antibody therapeutics for the treatment of multiple diseases.

In December 2017, the Company established a holding company (Holdco); in April 2019, Holdco was subsequently dissolved and equity interests in Holdco were converted into equity interests in the Company. The information included in these financial statements is consistently presented as if it is that of the Company, even during the interim period when investors held their equity interests in Holdco. Haldor Topsøe Holding A/S is a significant investor in the Company either through its direct equity ownership or indirectly as the majority owner of Holdco, until Holdco was dissolved in April 2019. Haldor Topsøe Holding A/S and Holdco represent a combined entity (Significant Investor) as referenced herein.

Basis of Presentation

These financial statements have been prepared in accordance with accounting principles generally accepted in the United States of America (U.S. GAAP).

Reverse Stock Split

In August 2019, the Company filed an amendment to the Company’s amended and restated certificate of incorporation to effect a reverse split of shares of the Company’s common stock, non-voting common stock and convertible preferred stock, each on a 6.6084-for-1 basis (Reverse Stock Split). The Reverse Stock Split also applied to any outstanding securities or rights convertible into, or exchangeable or exercisable for, common stock, non-voting common stock or convertible preferred stock. The par value of the common stock was not adjusted as a result of the Reverse Stock Split. All references to common stock, non-voting common stock, restricted stock, options to purchase common stock, share data, per share data, convertible preferred stock and related information contained in the financial statements and related footnotes have been retrospectively adjusted to reflect the effect of the Reverse Stock Split for all periods presented. The Reverse Stock Split was effected on August 30, 2019.

Public Offerings

On September 17, 2019, the Company’s registration statement on Form S-1 (File No. 333-233365) relating to its initial public offering (IPO) of common stock became effective. The IPO closed on September 20, 2019 at which time the Company issued an aggregate of 12,578,125 shares of its common stock at a price of $16.00 per share, including 1,640,625 shares issued in connection with the full exercise by the underwriters of their option to purchase additional shares of common stock. In addition, immediately prior to the closing of the IPO, all outstanding shares of the Company’s convertible preferred stock automatically converted into 10,787,861 shares of common stock and 6,431,205 shares of non-voting common stock. Proceeds from the IPO, net of underwriting discounts and commissions and offering costs, were approximately $183.0 million.

On November 12, 2020, the Company’s registration statement on Form S-3 (File No. 333-249863) was declared effective by the Securities and Exchange Commission (the SEC). On December 11, 2020, pursuant to the Form S-3 that was filed, the Company completed a public offering (2020 Public Offering) of 1,221,224 shares of its common stock, which included the exercise of the underwriters’ option to purchase 333,333 shares in full, and pre-funded warrants to purchase an additional 1,334,332 shares of common stock (Pre-funded Warrants). The Pre-funded Warrants were issued to two separate related party affiliates. The public offering price of common stock was $90.00 per share and the public offering price of each pre-funded warrant was $89.99, with each pre-funded warrant having an exercise price of $0.01. After deducting underwriting discounts and commissions and offering costs paid or payable by the Company of approximately $14.6 million, the net proceeds from the Company’s 2020 Public Offering were approximately $215.4 million.

Liquidity

The Company has incurred net operating losses and negative cash flows from operations since its inception and had an accumulated deficit of $188.6 million as of December 31, 2020. As of December 31, 2020, the Company had cash and investments of $366.3 million. Management believes that the existing financial resources are sufficient to continue operating activities at least one year past the issuance date of these financial statements. The Company has historically financed its operations primarily through the sale of convertible preferred stock and common stock and the issuance of unsecured promissory notes. To date, none of the Company’s product candidates have been approved for sale, and the Company has not generated any revenue since inception. Management expects operating losses to continue and increase for the foreseeable future, as the Company progresses into clinical development activities for its lead product candidates. The Company’s prospects are subject to risks, expenses and uncertainties frequently encountered by companies in the biotechnology industry as discussed below. While the Company has been able to raise multiple rounds of financing, there can be no assurance that in the event the Company requires additional financing, such financing will be available on terms which are favorable or at all. Failure to generate sufficient cash flows from operations, raise additional capital or reduce certain discretionary spending would have a material adverse effect on the Company’s ability to achieve its intended business objectives.

Stock-Based Compensation - Summary of Stock Option (Details) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Outstanding Options, Shares, Beginning balance	2,289,209
Outstanding Options, Shares, Granted	893,875
Outstanding Options, Shares, Exercised	(203,192)
Outstanding Options, Shares, Cancelled	(53,332)
Outstanding Options, Shares, Ending balance	2,926,560	2,289,209
Outstanding Options, Shares, Exercisable	1,462,376
Outstanding Options, Weighted-Average Exercise Price, Beginning balance	$ 3.36
Outstanding Options, Weighted-Average Exercise Price, Granted	44.66
Outstanding Options, Weighted-Average Exercise Price, Exercised	2.27
Outstanding Options, Weighted-Average Exercise Price, Canceled	31.44
Outstanding Options, Weighted-Average Exercise Price, Ending balance	15.54	$ 3.36
Outstanding Options, Weighted-Average Exercise Price, Exercisable	$ 6.60
Outstanding Options, Weighted Average Remaining Contractual Term (Years)	7 years 9 months 18 days	8 years 1 month 6 days
Outstanding Options, Weighted Average Remaining Contractual Term (Years), Exercisable	6 years 9 months 18 days
Outstanding Options, Aggregate Intrinsic Value, Beginning balance	$ 79,656
Outstanding Options, Aggregate Intrinsic Value, Ending balance	212,906	$ 79,656
Outstanding Options, Aggregate Intrinsic Value, Exercisable	$ 119,459

Selected Quarterly Financial Data (Unaudited) (Tables)

12 Months Ended

Dec. 31, 2020

Quarterly Financial Information Disclosure [Abstract]

Selected Quarterly Financial Data

The following tables provide the selected quarterly financial data for the years ended December 31, 2020 and 2019 (in thousands, except share and per share data):

	2020
	First Quarter			Second Quarter			Third Quarter			Fourth Quarter
Statements of Operations Data:
Operating expenses:
Research and development	$	14,583		$	15,019		$	15,829		$	19,599
General and administrative		3,990			4,388			4,732			5,140
Total operating expenses		18,573			19,407			20,561			24,739
Loss from operations		(18,573	)		(19,407	)		(20,561	)		(24,739	)
Other income (expense), net		949			568			291			117
Net loss	$	(17,624	)	$	(18,839	)	$	(20,270	)	$	(24,622	)
Net loss per share, basic and diluted	$	(0.58	)	$	(0.62	)	$	(0.66	)	$	(0.79	)
Weighted-average common shares outstanding, basic and diluted		30,491,463			30,551,736			30,646,729			31,298,264

	2019
	First Quarter			Second Quarter			Third Quarter			Fourth Quarter
Statements of Operations Data:
Operating expenses:
Research and development	$	5,912		$	8,303		$	8,279		$	12,763
General and administrative		1,445			2,228			2,394			3,174
Total operating expenses		7,357			10,531			10,673			15,937
Loss from operations		(7,357	)		(10,531	)		(10,673	)		(15,937	)
Other income (expense), net		(113	)		(145	)		501			1,122
Net loss	$	(7,470	)	$	(10,676	)	$	(10,172	)	$	(14,815	)
Net loss per share, basic and diluted	$	(16.86	)	$	(19.08	)	$	(2.41	)	$	(0.49	)
Weighted-average common shares outstanding, basic and diluted		443,118			559,671			4,222,259			30,478,980

Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
Statements of Cash Flows - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Cash flows from operating activities:
Net loss	$ (81,355)	$ (43,133)	$ (22,711)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation	1,025	597	278
Stock-based compensation expense	8,454	1,014	183
Accrued interest on related party loan			27
Net amortization of premiums and accretion of discounts on investments	(23)	(306)
Non-cash lease expense	2,551	1,736
Changes in assets and liabilities:
Prepaid expenses and other current assets	(252)	(5,412)	(262)
Other long-term assets	(290)	(258)	8
Income tax receivable	35		(35)
Accounts payable	2,198	1,961	(61)
Accrued liabilities	2,837	(25)	2,791
Income tax payable			(128)
Deferred rent			(134)
Lease liabilities	(2,483)	(1,254)
Other current liabilities		(9)	9
Other long-term liabilities		(27)	(9)
Net cash used in operating activities	(67,303)	(45,116)	(20,044)
Cash flows from investing activities:
Purchase of property, plant and equipment	(17,502)	(2,337)	(788)
Purchases of investments	(208,564)	(208,901)
Maturities of investments	283,777	8,000
Net cash provided by (used in) investing activities	57,711	(203,238)	(788)
Cash flows from financing activities:
Proceeds from common stock issuance		11
Proceeds from exercise of stock options and purchases under the employee stock purchase plan	821	179
Payment of employee taxes and exercise costs for shares withheld	(1,731)
Proceeds from issuance of initial public offering, net of underwriters' commission		187,162
Proceeds from issuance of common stock and pre-funded warrants, net of issuance costs	216,186
Net cash provided by financing activities	214,781	282,258	22,337
Net increase in cash, cash equivalents and restricted cash	205,189	33,904	1,505
Cash, cash equivalents, and restricted cash, beginning of year	35,891	1,987	482
Cash, cash equivalents, and restricted cash, end of year	241,080	35,891	1,987
Cash and cash equivalents	241,080	35,891	1,887
Restricted cash			100
Supplemental disclosure of cash flow information:
Cash paid for income taxes			167
Supplemental disclosure of non-cash investing and financing activities:
Acquisition of property, plant and equipment in accounts payable and accrued liabilities	3,829	962	292
Issuance costs for public offerings in accounts payable and accrued liabilities	279
Conversion of convertible preferred stock into common stock and non-voting common stock		162,553
IPO
Cash flows from financing activities:
Payment of issuance costs for public offerings	$ (495)	(4,320)
Series C Convertible Preferred Stock
Cash flows from financing activities:
Payment of issuance costs		(324)
Supplemental disclosure of non-cash investing and financing activities:
Issuance costs in accounts payable and accrued liabilities		40
New Investors \| Series B Convertible Preferred Stock
Cash flows from financing activities:
Proceeds from issuance of convertible preferred stock			17,337
New Investors \| Series C Convertible Preferred Stock
Cash flows from financing activities:
Proceeds from issuance of convertible preferred stock		72,000
Haldor Topsøe Holding A/S and Holdco
Cash flows from financing activities:
Proceeds from related party capital contribution		2,550
Proceeds from loan from related party		15,000	5,000
Supplemental disclosure of cash flow information:
Cash paid for interest on related party loan		297
Supplemental disclosure of non-cash investing and financing activities:
Settlement of related party loan through issuance of Series C convertible preferred stock		20,000
Related party equity transaction			34,625
Haldor Topsøe Holding A/S and Holdco \| Series B Convertible Preferred Stock
Supplemental disclosure of non-cash investing and financing activities:
Receivable from related party for Series B convertible preferred stock			$ 2,511
Haldor Topsøe Holding A/S and Holdco \| Series C Convertible Preferred Stock
Cash flows from financing activities:
Proceeds from issuance of convertible preferred stock		$ 10,000

Document And Entity Information - USD ($)	12 Months Ended
Document And Entity Information - USD ($)	Dec. 31, 2020	Mar. 24, 2021	Jun. 30, 2020
Document And Entity Information [Line Items]
Document Type	10-K
Amendment Flag	false
Document Period End Date	Dec. 31, 2020
Document Fiscal Year Focus	2020
Document Fiscal Period Focus	FY
Entity Registrant Name	IGM Biosciences, Inc.
Entity Central Index Key	0001496323
Entity Current Reporting Status	Yes
Entity Voluntary Filers	No
Entity Interactive Data Current	Yes
Current Fiscal Year End Date	--12-31
Entity Filer Category	Non-accelerated Filer
Entity Well-known Seasoned Issuer	No
Entity Public Float			$ 513,600,000
Entity Shell Company	false
Entity Small Business	false
Entity Emerging Growth Company	true
Entity Ex Transition Period	false
Title of 12(b) Security	Common Stock, par value $0.01 per share
Trading Symbol	IGMS
Security Exchange Name	NASDAQ
Entity File Number	001-39045
Entity Incorporation, State or Country Code	DE
Entity Tax Identification Number	77-0349194
Entity Address, Address Line One	325 E. Middlefield Road
Entity Address, City or Town	Mountain View
Entity Address, State or Province	CA
Entity Address, Postal Zip Code	94043
City Area Code	650
Local Phone Number	965-7873
Document Annual Report	true
Document Transition Report	false
Documents Incorporated by Reference	Certain sections of the Registrant’s definitive Proxy Statement to be filed in connection with the Registrant’s 2021 Annual Meeting of Stockholders are incorporated by reference into Part III of this Annual Report on Form 10-K where indicated. Such definitive Proxy Statement will be filed with the Securities and Exchange Commission pursuant to Regulation 14A within 120 days of the Registrant’s fiscal year ended December 31, 2020.
Common Stock
Document And Entity Information [Line Items]
Entity Common Stock, Shares Outstanding		25,574,983
Non-voting Common Stock
Document And Entity Information [Line Items]
Entity Common Stock, Shares Outstanding		6,431,205

Summary of Significant Accounting Policies - Additional Information (Details)	12 Months Ended
	Dec. 31, 2020 USD ($) Segment	Dec. 31, 2019 USD ($)	Dec. 31, 2018 USD ($)
Summary Of Significant Accounting Policies [Line Items]
Number of reportable segment \| Segment	1
Number of operating segment \| Segment	1
Impairment of long-lived assets	$ 0	$ 0	$ 0
Deferred offering costs	0	$ 0
Interest or penalties charged in relation to unrecognized tax benefits	$ 0
ASU No 2018-13
Summary Of Significant Accounting Policies [Line Items]
Change in accounting principle, accounting standards update, adopted	true
Change in accounting principle, accounting standards update, adoption date	Jan. 01, 2020
Change in accounting principle, accounting standards update, immaterial effect	true
Minimum
Summary Of Significant Accounting Policies [Line Items]
Property and equipment estimated useful life	3 years
Description of income tax contingencies, likely of being realized upon settlement	The Company measures the benefit by determining the amount that is greater than 50% likely of being realized upon settlement, presuming that the tax position is examined by the appropriate taxing authority that has full knowledge of all relevant information.
Maximum
Summary Of Significant Accounting Policies [Line Items]
Property and equipment estimated useful life	5 years

Balance Sheet Components (Tables)

12 Months Ended

Dec. 31, 2020

Balance Sheet Related Disclosures [Abstract]

Schedule of Property, Plant and Equipment, Net

Property, plant and equipment, net consists of the following (in thousands):

	December 31,			December 31,
	2020			2019
Laboratory equipment	$	7,125		$	3,800
Office equipment		212			150
Leasehold improvement		253			78
Construction in progress		17,925			1,118
Total property, plant and equipment, gross		25,515			5,146
Less: Accumulated depreciation		(2,289	)		(1,264	)
Total property, plant and equipment, net	$	23,226		$	3,882

Schedule of Accrued Liabilities

Accrued liabilities consisted of the following (in thousands):

	December 31,		December 31,
	2020		2019
Accrued research and development materials and services	$	1,509	$	906
Accrued professional services		163		360
Accrued compensation		4,925		2,030
Other		52		9
Total accrued liabilities	$	6,649	$	3,305

Common Stock and Non-Voting Common Stock (Tables)

12 Months Ended

Dec. 31, 2020

Stockholders Equity Note [Abstract]

Schedule of Number of Common Stock Reserved for Future Issuance

The Company had reserved common stock, on an as-converted basis, for future issuance as follows:

	December 31,		December 31,
	2020		2019
Stock options, issued and outstanding		2,926,560		2,289,209
Restricted stock units		667		—
Restricted stock, issued and outstanding		—		58,259
Stock options and restricted stock units, future issuance		3,054,127		2,669,264
Employee stock purchase plan, available for future grants		554,088		280,000
Pre-funded warrants		1,334,332		—
Total		7,869,774		5,296,732

Summary of Significant Accounting Policies (Policies)	12 Months Ended
Summary of Significant Accounting Policies (Policies)	Dec. 31, 2020
Accounting Policies [Abstract]
Basis of Presentation	Basis of Presentation These financial statements have been prepared in accordance with accounting principles generally accepted in the United States of America (U.S. GAAP).
Reverse Stock Split	Reverse Stock Split In August 2019, the Company filed an amendment to the Company’s amended and restated certificate of incorporation to effect a reverse split of shares of the Company’s common stock, non-voting common stock and convertible preferred stock, each on a 6.6084-for-1 basis (Reverse Stock Split). The Reverse Stock Split also applied to any outstanding securities or rights convertible into, or exchangeable or exercisable for, common stock, non-voting common stock or convertible preferred stock. The par value of the common stock was not adjusted as a result of the Reverse Stock Split. All references to common stock, non-voting common stock, restricted stock, options to purchase common stock, share data, per share data, convertible preferred stock and related information contained in the financial statements and related footnotes have been retrospectively adjusted to reflect the effect of the Reverse Stock Split for all periods presented. The Reverse Stock Split was effected on August 30, 2019.
Public Offerings	Public Offerings On September 17, 2019, the Company’s registration statement on Form S-1 (File No. 333-233365) relating to its initial public offering (IPO) of common stock became effective. The IPO closed on September 20, 2019 at which time the Company issued an aggregate of 12,578,125 shares of its common stock at a price of $16.00 per share, including 1,640,625 shares issued in connection with the full exercise by the underwriters of their option to purchase additional shares of common stock. In addition, immediately prior to the closing of the IPO, all outstanding shares of the Company’s convertible preferred stock automatically converted into 10,787,861 shares of common stock and 6,431,205 shares of non-voting common stock. Proceeds from the IPO, net of underwriting discounts and commissions and offering costs, were approximately $183.0 million. On November 12, 2020, the Company’s registration statement on Form S-3 (File No. 333-249863) was declared effective by the Securities and Exchange Commission (the SEC). On December 11, 2020, pursuant to the Form S-3 that was filed, the Company completed a public offering (2020 Public Offering) of 1,221,224 shares of its common stock, which included the exercise of the underwriters’ option to purchase 333,333 shares in full, and pre-funded warrants to purchase an additional 1,334,332 shares of common stock (Pre-funded Warrants). The Pre-funded Warrants were issued to two separate related party affiliates. The public offering price of common stock was $90.00 per share and the public offering price of each pre-funded warrant was $89.99, with each pre-funded warrant having an exercise price of $0.01. After deducting underwriting discounts and commissions and offering costs paid or payable by the Company of approximately $14.6 million, the net proceeds from the Company’s 2020 Public Offering were approximately $215.4 million.
Liquidity	Liquidity The Company has incurred net operating losses and negative cash flows from operations since its inception and had an accumulated deficit of $188.6 million as of December 31, 2020. As of December 31, 2020, the Company had cash and investments of $366.3 million. Management believes that the existing financial resources are sufficient to continue operating activities at least one year past the issuance date of these financial statements. The Company has historically financed its operations primarily through the sale of convertible preferred stock and common stock and the issuance of unsecured promissory notes. To date, none of the Company’s product candidates have been approved for sale, and the Company has not generated any revenue since inception. Management expects operating losses to continue and increase for the foreseeable future, as the Company progresses into clinical development activities for its lead product candidates. The Company’s prospects are subject to risks, expenses and uncertainties frequently encountered by companies in the biotechnology industry as discussed below. While the Company has been able to raise multiple rounds of financing, there can be no assurance that in the event the Company requires additional financing, such financing will be available on terms which are favorable or at all. Failure to generate sufficient cash flows from operations, raise additional capital or reduce certain discretionary spending would have a material adverse effect on the Company’s ability to achieve its intended business objectives.
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 amounts reported in the financial statements and accompanying notes. On an ongoing basis, the Company evaluates its estimates, including, but not limited to, those related to investments, manufacturing accruals, accrued research and development expenses, fair value of common stock, stock-based compensation, operating lease right-of-use (ROU) assets and liabilities, income tax uncertainties and the valuation of deferred tax assets. The Company bases its estimates on its historical experience and also on assumptions that it believes are reasonable; however, actual results could significantly differ from those estimates.
Segments	Segments The Company operates and manages its business as one reportable and operating segment, which is the business of developing engineered IgM antibodies for the treatment of multiple diseases. The Company’s chief executive officer, who is the chief operating decision maker, reviews financial information on an aggregate basis for allocating and evaluating financial performance. All long-lived assets are maintained in, and all losses are attributable to, the United States of America.
Concentration of Credit Risk and Other Risks and Uncertainties	Concentration of Credit Risk and Other Risks and Uncertainties Financial instruments that potentially subject the Company to a concentration of credit risk consist primarily of cash and investments. The Company invests in money market funds, U.S. Treasury securities, corporate bonds, commercial paper, and U.S. government agency securities. The Company maintains bank deposits in federally insured financial institutions and these deposits may exceed federally insured limits. The Company is exposed to credit risk in the event of a default by the financial institutions holding its cash and issuers of investments to the extent recorded on the balance sheets. The Company’s investment policy limits investments to money market funds, certain types of debt securities issued by the U.S. Government and its agencies, corporate debt, commercial paper, and places restrictions on the credit ratings, maturities and concentration by type and issuer. The Company has not experienced any losses on its deposits of cash and investments. The Company’s future results of operations involve a number of other risks and uncertainties. Factors that could affect the Company’s future operating results and cause actual results to vary materially from expectations include, but are not limited to, the Company’s early stages of clinical drug development; uncertainties related to the use of engineered IgM antibodies, which is a novel and unproven therapeutic approach; the Company’s ability to advance product candidates into, and successfully complete, clinical trials on the timelines it projects; the Company’s ability to adequately demonstrate sufficient safety and efficacy of its product candidates; the Company’s ability to enroll patients in its ongoing and future clinical trials; the Company’s ability to successfully manufacture and supply its product candidates for clinical trials; the Company’s ability to obtain additional capital to finance its operations; uncertainties related to the projections of the size of patient populations suffering from the diseases the Company is targeting; the Company’s ability to obtain, maintain, and protect its intellectual property rights; developments relating to the Company’s competitors and its industry, including competing product candidates and therapies; general economic and market conditions; and other risks and uncertainties, including those more fully described in the “Risk Factors” section of this Annual Report on Form 10-K. The Company’s product candidates will require approvals from the U.S. Food and Drug Administration and comparable foreign regulatory agencies prior to commercial sales in their respective jurisdictions. There can be no assurance that any product candidates will receive the necessary approvals. If the Company was denied approval, approval was delayed or the Company was unable to maintain approval for any product candidate, it could have a materially adverse impact on the Company.
Cash, Cash Equivalents and Restricted Cash	Cash, Cash Equivalents and Restricted Cash The Company considers all highly liquid investments with original maturities of three months or less from the date of purchase to be cash and cash equivalents. Cash equivalents consist primarily of amounts invested in money market accounts and are stated at fair value. Restricted cash consisted of a money market account, which was closed during 2019, that served as collateral for a credit card agreement at one of the Company’s financial institutions.
Investments	Investments The Company’s investments have been classified and accounted for as available-for-sale securities. Fixed income securities consist of U.S. Treasury securities, U.S. government agency securities, corporate debt, and commercial paper. The specific identification method is used to determine the cost basis of fixed income securities sold. These securities are recorded on the balance sheets at fair value. Unrealized gains and losses on these securities are included as a separate component of accumulated other comprehensive income. The cost of investment securities is adjusted for amortization of premiums and accretion of discounts to maturity. Such amortization and accretion are included in other income, net. Realized gains and losses and declines in fair value judged to be other-than-temporary, if any, are also included in other income, net. The Company evaluates securities for other-than-temporary impairment at the balance sheet date. Declines in fair value determined to be other-than-temporary are also included in other income, net. The Company classifies its investments as short or long term primarily based on the remaining contractual maturity of the securities.
Property, Plant and Equipment	Property, Plant and Equipment Property, plant and equipment are stated at cost, less accumulated depreciation and amortization. Depreciation is determined using the straight-line method over the estimated useful lives of the respective assets, generally three to five years. Leasehold improvements are amortized using the straight-line method over the shorter of the lease term or the estimated useful economic lives of the related assets. Upon retirement or sale of the assets, the cost and related accumulated depreciation and amortization are removed from the balance sheet and the resulting gain or loss are recorded to the statements of operations. Repairs and maintenance are charged to operations as incurred.
Impairment of Long-Lived Assets	Impairment of Long-Lived Assets Long-lived assets consist of property and equipment. The Company evaluates the carrying amount of its long-lived assets whenever events or changes in circumstances indicate that the assets may not be recoverable. An impairment loss would be recognized when estimated future cash flows expected to result from the use of the asset and its eventual disposition are less than the carrying amount of the asset. There was no impairment of long-lived assets in 2020, 2019 and 2018.
Research and Development Expenses	Research and Development Expenses The Company expenses research and development costs as they are incurred. Research and development expenses consist primarily of: (i) personnel-related expenses, including salaries, benefits and stock-based compensation expense, for personnel in the Company’s research and development functions; (ii) fees paid to third parties such as contractors, consultants and contract research organizations (CROs) for conducting clinical trials, animal studies, and other costs related to clinical and preclinical testing; (iii) costs related to acquiring and manufacturing research and clinical trial materials, including under agreements with third parties such as contract manufacturing organizations (CMOs), and other vendors; (iv) costs related to the preparation of regulatory submissions; (v) expenses related to laboratory supplies and services; and (vi) depreciation of equipment and facilities expenses.
Accrued Research and Development Expenses	Accrued Research and Development Expenses The Company records accruals for estimated costs of research, preclinical studies, clinical trials, and manufacturing, which are significant components of research and development expenses. A substantial portion of the Company’s ongoing research and development activities is conducted by third-party service providers, CROs and CMOs. The Company’s contracts with CROs generally include pass-through fees such as costs related to animal studies and safety tests, regulatory expenses, investigator fees, travel costs and other miscellaneous costs, including shipping and printing fees. The Company’s contracts with the CMOs generally include fees such as initiation fees, reservation fees, verification run costs, materials and reagents expenses, taxes, etc. The financial terms of these contracts are subject to negotiations, which vary from contract to contract and may result in payment flows that do not match the periods over which materials or services are provided to the Company under such contracts. The Company accrues the costs incurred under agreements with these third parties based on estimates of actual work completed in accordance with the respective agreements. The Company determines the estimated costs through discussions with internal personnel and external service providers as to the progress, or stage of completion or actual timeline (start-date and end-date) of the services and the agreed-upon fees to be paid for such services. In the event the Company makes advance payments, the payments are recorded as a prepaid expense and recognized as the services are performed. As actual costs become known, the Company adjusts its accruals. Although the Company does not expect its estimates to be materially different from amounts actually incurred, such estimates for the status and timing of services performed relative to the actual status and timing of services performed may vary and could result in the Company reporting amounts that are too high or too low in any particular period. The Company’s accrual is dependent, in part, upon the receipt of timely and accurate reporting from CROs and other third-party vendors. Variations in the assumptions used to estimate accruals including, but not limited to, the number of patients enrolled, the rate of patient enrollment and the actual services performed, may vary from the Company’s estimates, resulting in adjustments to clinical trial expenses in future periods. Changes in these estimates that result in material changes to the Company’s accruals could materially affect its financial condition and results of operations. Through December 31, 2020, there have been no material differences from the Company’s estimated accrued research and development expenses to actual expenses.
Stock-Based Compensation	Stock-Based Compensation The Company accounts for stock-based compensation by measuring and recognizing compensation expense for all share-based awards made to employees, non-employees and directors based on estimated grant-date fair values. The Company uses the straight-line method to allocate compensation cost to reporting periods over the requisite service period, which is generally the vesting period, and estimates the fair value of share-based awards to employees and directors using the Black-Scholes option-pricing model. If the service inception date precedes the grant date, the Company accrues for the stock-based compensation based on the fair value at the reporting date. The Company accounts for forfeitures as they occur. The fair value of each purchase under the employee stock purchase plan (ESPP) is estimated at the beginning of the offering period using the Black-Scholes option pricing model and recorded as expense over the service period using the straight-line method.
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 (including non-voting common stock and Pre-funded Warrants) outstanding during the period, without consideration for common stock equivalents. Shares of common stock into which the Pre-funded Warrants may be exercised are considered outstanding for the purposes of computing net loss per share because the shares may be issued for little or no consideration, are fully vested, and are exercisable after the original issuance date. Diluted net loss per share is the same as basic net loss per share, since the effects of potentially dilutive securities are antidilutive given the net loss for each period presented.
Deferred Offering Costs	Deferred Offering Costs Deferred offering costs, consisting of legal, accounting, and filing fees directly relating to the Company’s equity offerings, are capitalized and offset against the proceeds upon the completion of the offering. There were no deferred offering costs as of December 31, 2020 and 2019.
Leases	Leases During 2019, the Company elected to early adopt Accounting Standard Update (ASU) No. 2016-02, Leases (ASC 842) and its associated amendments as of January 1, 2019 using the modified retrospective transition approach. There was no cumulative-effect adjustment recorded to accumulated deficit upon adoption. Under ASC 842 and its associated amendments, the Company determines if an arrangement is a lease at inception. In addition, the Company determines whether leases meet the classification criteria of a finance or operating lease at the lease commencement date considering: (1) whether the lease transfers ownership of the underlying asset to the lessee at the end of the lease term, (2) whether the lease grants the lessee an option to purchase the underlying asset that the lessee is reasonably certain to exercise, (3) whether the lease term is for a major part of the remaining economic life of the underlying asset, (4) whether the present value of the sum of the lease payments and residual value guaranteed by the lessee equals or exceeds substantially all of the fair value of the underlying asset, and (5) whether the underlying asset is of such a specialized nature that it is expected to have no alternative use to the lessor at the end of the lease term. As of December 31, 2020, the Company's lease population consisted of real estate. As of the date of adoption of ASC 842, and as of December 31, 2020 and 2019, the Company did not have finance leases. Operating leases are included in operating lease right-of-use (ROU) assets, lease liabilities, current, and lease liabilities, non-current in the Company’s balance sheet. ROU assets represent the Company’s right to use an underlying asset for the lease term and lease liabilities represent the Company’s obligation to make lease payments arising from the lease. Operating lease ROU assets and liabilities are recognized at the lease commencement date based on the present value of lease payments over the lease term. In determining the present value of lease payments, the Company uses its incremental borrowing rate based on the information available at the lease commencement date if the rate implicit in the lease is not readily determinable. The Company determines the incremental borrowing rate based on an analysis of corporate bond yields with a credit rating similar to the Company. The determination of the Company’s incremental borrowing rate requires management judgment including the development of a synthetic credit rating and cost of debt as the Company currently does not carry any debt. The Company believes that the estimates used in determining the incremental borrowing rate are reasonable based upon current facts and circumstances. Applying different judgments to the same facts and circumstances could result in the estimated amounts to vary. The operating lease ROU assets also include adjustments for prepayments and accrued lease payments and exclude lease incentives. The Company’s lease terms may include options to extend or terminate the lease when it is reasonably certain that the Company will exercise such options. Operating lease cost is recognized on a straight-line basis over the expected lease term. Variable lease costs represent payments that are dependent on usage, a rate or index. Variable lease cost primarily relates to common area maintenance charges. Lease agreements that include lease and non-lease components are accounted for as a single lease component. Lease agreements with a noncancelable term of less than 12 months are not recorded on the Company’s balance sheet. For more information about the impact of adoption and disclosures on the Company’s leases, refer to “Note 10 – Commitments and Contingencies.”
Income Taxes	Income Taxes The Company accounts for income taxes using the liability method, whereby deferred tax asset and liability account balances are determined based on differences between the financial reporting and tax bases of assets and liabilities and are measured using the enacted tax rates and laws that will be in effect when the differences are expected to reverse. The Company provides a valuation allowance when it is more likely than not that some portion, or all of the Company’s deferred tax assets will not be realized. The Company accounts for income tax contingencies using a benefit recognition model. If it considers that a tax position is more likely than not to be sustained upon audit, based solely on the technical merits of the position, it recognizes the benefit. The Company measures the benefit by determining the amount that is greater than 50% likely of being realized upon settlement, presuming that the tax position is examined by the appropriate taxing authority that has full knowledge of all relevant information. The Company’s policy is to recognize interest and penalties related to the underpayment of income taxes as a component of income tax expense or benefit. To date, there have been no interest or penalties charged in relation to the unrecognized tax benefits.
Recently Adopted Accounting Standards and Accounting Pronouncements	Recently Adopted Accounting Standards In August 2018, the FASB issued ASU No. 2018-13, Disclosure Framework – Changes to the Disclosure Requirements for Fair Value Measurement, which amends ASC 820, Fair Value Measurement. This ASU modifies the disclosure requirements for fair value measurements by removing, modifying, or adding certain disclosures. The effective date was the first quarter of fiscal year 2020, with early adoption permitted for the removed disclosures and delayed adoption until fiscal year 2020 permitted for the new disclosures. The Company adopted this ASU as of January 1, 2020 and the adoption did not have a material impact on its financial statements and related disclosures. The removed and modified disclosures were adopted on a retrospective basis and the new disclosures were adopted on a prospective basis. Recently Issued Accounting Pronouncements In June 2016, the FASB issued ASU 2016-13, Financial Instruments – Credit Losses (Topic 326): Measurement of Credit Losses on Financial Instruments, which requires that financial assets measured at amortized cost be presented at the net amount expected to be collected. The measurement of expected credit losses is based on historical experience, current conditions, and reasonable and supportable forecasts that affect collectability. This ASU also eliminates the concept of “other-than-temporary” impairment when evaluating available-for-sale debt securities and instead focuses on determining whether any impairment is a result of a credit loss or other factors. An entity will recognize an allowance for credit losses on available-for-sale debt securities rather than an other-than-temporary impairment that reduces the cost basis of the investment. This ASU is effective for fiscal years beginning after December 15, 2022 and interim periods within those fiscal years. Early adoption is permitted. The Company is currently assessing the impact of this standard on its financial statements and related disclosures. In December 2019, the FASB issued ASU 2019-12, Income Taxes (Topic 740): Simplifying the Accounting for Income Taxes (“ASU 2019-12”), which is intended to simplify the accounting for income taxes. ASU 2019-12 removes certain exceptions to the general principles in Topic 740 and also clarifies and amends existing guidance to improve consistent application. The new standard will be effective beginning January 1, 2021. The Company is currently assessing the impact of this standard on its financial statements and related disclosures.

Commitments and Contingencies - Additional Information (Details) - Agreement	3 Months Ended	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2020
Lessee Lease Description [Line Items]
Number of lease agreements		2
Percentage of employees contribution to annual compensation plan		100.00%
Offices and Laboratory \| Mountain View, California
Lessee Lease Description [Line Items]
Sub-lease commenced date	Dec. 01, 2019
Sub-lease expiration period month and year	2024-09
Offices and Laboratory \| Mountain View, California \| Lease Agreements One
Lessee Lease Description [Line Items]
Lessee operating lease expiry month and year		2024-09
Offices and Laboratory \| Mountain View, California \| Lease Agreements Two
Lessee Lease Description [Line Items]
Lessee operating lease expiry month and year		2025-04

Stock-Based Compensation - Summary of Fair Value of Employee Stock Options Estimated Weighted-average Assumptions (Details) - Stock Options - $ / shares	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Expected term in years	6 years	6 years	5 years 10 months 24 days
Expected volatility	84.30%	79.30%	77.50%
Risk-free interest rate	1.00%	2.20%	2.90%
Weighted average fair value of share-based awards granted per share	$ 31.70	$ 4.36	$ 0.94

Net Loss Per Share Attributable to Common Stockholders - Summary of Potentially Dilutive Securities Not Included in the Diluted Per Share Calculations (Details) - shares	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Potentially dilutive securities not included in diluted per share calculations	2,930,281	2,357,655
Stock Options
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Potentially dilutive securities not included in diluted per share calculations	2,926,560	2,289,209
Estimated Shares Issuable Under Employee Stock Purchase Plan
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Potentially dilutive securities not included in diluted per share calculations	3,054	10,187
Restricted Stock Units
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Potentially dilutive securities not included in diluted per share calculations	667
Restricted Stock
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Potentially dilutive securities not included in diluted per share calculations		58,259

Common Stock and Non-Voting Common Stock - Schedule of Number of Common Stock Reserved for Future Issuance (Details) - shares	Dec. 31, 2020	Dec. 31, 2019
Stockholders Equity Note [Abstract]
Stock options, issued and outstanding	2,926,560	2,289,209
Restricted stock units	667
Restricted stock, issued and outstanding		58,259
Stock options and restricted stock units, future issuance	3,054,127	2,669,264
Employee stock purchase plan, available for future grants	554,088	280,000
Pre-funded warrants	1,334,332
Total	7,869,774	5,296,732

Balance Sheet Components - Schedule of Accrued Liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Balance Sheet Related Disclosures [Abstract]
Accrued research and development materials and services	$ 1,509	$ 906
Accrued professional services	163	360
Accrued compensation	4,925	2,030
Other	52	9
Total accrued liabilities	$ 6,649	$ 3,305

Fair Value Measurement - Summary of Contractual Maturities of Cash and Investments (Details) - Fair Value, Recurring $ in Thousands	Dec. 31, 2020 USD ($)
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Due in less than one year	$ 364,723
Total	$ 364,723

License Agreements - Additional Information (Details) - USD ($)	1 Months Ended		12 Months Ended
	Oct. 31, 2020	Jan. 31, 2017	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018	May 31, 2018
Research and Development Expenses \| LakePharma, Inc.
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
License expenses recognized			$ 300,000	$ 100,000	$ 300,000
Maximum \| LakePharma, Inc.
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Potential payments based on achievement of specified development and regulatory milestones						$ 10,300,000
Adimab \| Research and Development Expenses
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
License expenses recognized			200,000	$ 100,000	$ 300,000
Adimab \| Maximum
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
License fee		$ 1,000,000
Additional milestone payment		16,000,000
Adimab \| Minimum
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Additional milestone payment		$ 7,400,000
University of Texas
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Upfront payment	$ 100,000
University of Texas \| Research and Development Expenses
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
License expenses recognized			100,000
University of Texas \| Maximum
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
License fee	100,000
University of Texas \| Maximum \| Research and Development Expenses
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Potential payments based on achievement of specified development and regulatory milestones	2,800,000
AvantGen Inc.
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Upfront payment	200,000
AvantGen Inc. \| Research and Development Expenses
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
License expenses recognized			$ 200,000
AvantGen Inc. \| Maximum
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
License fee	300,000
AvantGen Inc. \| Maximum \| Research and Development Expenses
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Potential payments based on achievement of specified development and regulatory milestones	$ 8,400,000

Statements of Operations - USD ($)
$ in Thousands

3 Months Ended

12 Months Ended

Dec. 31, 2020

Sep. 30, 2020

Jun. 30, 2020

Mar. 31, 2020

Dec. 31, 2019

Sep. 30, 2019

Jun. 30, 2019

Mar. 31, 2019

Dec. 31, 2020

Dec. 31, 2019

Dec. 31, 2018

Operating expenses:

Research and development

$ 19,599

$ 15,829

$ 15,019

$ 14,583

$ 12,763

$ 8,279

$ 8,303

$ 5,912

$ 65,030

$ 35,257

$ 18,962

General and administrative

5,140

4,732

4,388

3,990

3,174

2,394

2,228

1,445

18,250

9,241

3,829

Total operating expenses

24,739

20,561

19,407

18,573

15,937

10,673

10,531

7,357

83,280

44,498

22,791

Loss from operations

(24,739)

(20,561)

(19,407)

(18,573)

(15,937)

(10,673)

(10,531)

(7,357)

(83,280)

(44,498)

(22,791)

Other income, net

117

291

568

949

1,122

501

(145)

(113)

1,925

1,365

Net loss

$ (24,622)

$ (20,270)

$ (18,839)

$ (17,624)

$ (14,815)

$ (10,172)

$ (10,676)

$ (7,470)

$ (81,355)

$ (43,133)

$ (22,711)

Net loss per share, basic and diluted

$ (0.79)

$ (0.66)

$ (0.62)

$ (0.58)

$ (0.49)

$ (2.41)

$ (19.08)

$ (16.86)

$ (2.65)

$ (4.80)

$ (51.84)

Weighted-average common shares outstanding, basic and diluted

31,298,264

30,646,729

30,551,736

30,491,463

30,478,980

4,222,259

559,671

443,118

30,748,280

^[1]

8,995,410

^[1]

438,074

^[1]

[1]	Includes shares of common stock into which Pre-Funded Warrants may be exercised. See Note 7 to our financial statements included in this Form 10-K.

- Definition

The portion of profit or loss for the period, net of income taxes, which is attributable to the parent.

+ References

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-URI http://asc.fasb.org/extlink&oid=120311839&loc=d3e8906-108599

Reference 18: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 250
-SubTopic 10
-Section 50
-Paragraph 3
-URI http://asc.fasb.org/extlink&oid=109234566&loc=d3e22583-107794

Reference 19: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 235
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.4-08(g)(1)(ii))
-URI http://asc.fasb.org/extlink&oid=120395691&loc=d3e23780-122690

Reference 20: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 260
-SubTopic 10
-Section 45
-Paragraph 60B
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=121326447&loc=SL5780133-109256

Reference 21: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 323
-SubTopic 10
-Section 50
-Paragraph 3
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=114001798&loc=d3e33918-111571

Reference 22: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
-SubTopic 10
-Section 50
-Paragraph 32
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=120311839&loc=d3e8933-108599

Reference 23: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 250
-SubTopic 10
-Section 50
-Paragraph 8
-URI http://asc.fasb.org/extlink&oid=109234566&loc=d3e22658-107794

+ Details

Net Loss Per Share Attributable to Common Stockholders

12 Months Ended

Dec. 31, 2020

Earnings Per Share [Abstract]

Net Loss Per Share Attributable to Common Stockholders

Note 12. Net Loss Per Share Attributable to Common Stockholders

Basic and diluted net loss per share is computed by dividing net loss by the weighted-average number of common stock and Pre-funded Warrants outstanding for the period. Shares of common stock into which the Pre-funded Warrants may be exercised are considered outstanding for the purposes of computing net loss per share because the shares may be issued for little or no consideration, are fully vested, and are exercisable after the original issuance date.

The following table sets forth the computation of the basic and diluted net loss per share (in thousands except share and per share data):

	Year Ended December 31,
	2020			2019			2018
Numerator:
Net loss	$	(81,355	)	$	(43,133	)	$	(22,711	)
Denominator:
Weighted average common shares outstanding used to compute net loss per share, basic and diluted ⁽¹⁾		30,748,280			8,995,410			438,074
Net loss per share attributable to common stockholders	$	(2.65	)	$	(4.80	)	$	(51.84	)

⁽¹⁾	Includes shares of common stock into which Pre-Funded Warrants may be exercised. See Note 7 to our financial statements included in this Form 10-K.

Since the Company was in a loss position for all periods presented, basic net loss per share is the same as diluted net loss per share for all periods as the inclusion of all common stock equivalents outstanding would have been anti-dilutive. Potentially dilutive securities that were not included in the diluted per share calculations because they would be anti-dilutive were as follows:

	December 31,
	2020		2019
Stock options		2,926,560		2,289,209
Estimated shares issuable under the employee stock purchase plan		3,054		10,187
Restricted stock units		667		—
Restricted stock		—		58,259
Total		2,930,281		2,357,655

Common Stock and Non-Voting Common Stock - Additional Information (Details)	12 Months Ended
	Dec. 31, 2020 USD ($) Vote $ / shares shares	Dec. 31, 2019 USD ($) $ / shares shares
Class Of Stock [Line Items]
Common stock, shares authorized	1,000,000,000	1,000,000,000
Preferred stock, shares authorized	200,000,000	200,000,000
Common stock, par value \| $ / shares	$ 0.01	$ 0.01
Preferred stock, par value \| $ / shares	$ 0.01	$ 0.01
Common stock, voting rights	Each share of common stock (excluding non-voting common stock) is entitled to one vote
Number of common stock voting rights held \| Vote	1
Common stock, dividends declared \| $	$ 0	$ 0
Common Stock Including Nonvoting Common Stock
Class Of Stock [Line Items]
Common stock, shares authorized	1,006,431,208	1,006,431,208
Non-voting Common Stock
Class Of Stock [Line Items]
Common stock, shares authorized	6,431,208	6,431,208
Common stock, par value \| $ / shares	$ 0.01	$ 0.01

Balance Sheet Components - Schedule of Property, Plant and Equipment, Net (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Property Plant And Equipment [Line Items]
Total property, plant and equipment, gross	$ 25,515	$ 5,146
Less: Accumulated depreciation	(2,289)	(1,264)
Total property, plant and equipment, net	23,226	3,882
Laboratory Equipment
Property Plant And Equipment [Line Items]
Total property, plant and equipment, gross	7,125	3,800
Office Equipment
Property Plant And Equipment [Line Items]
Total property, plant and equipment, gross	212	150
Leasehold Improvement
Property Plant And Equipment [Line Items]
Total property, plant and equipment, gross	253	78
Construction In Progress
Property Plant And Equipment [Line Items]
Total property, plant and equipment, gross	$ 17,925	$ 1,118

Income Taxes - Reconciliation of Statutory Federal Income Tax Rate (Details)	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Income Tax Disclosure [Abstract]
Federal tax (benefit) at statutory rate	21.00%	21.00%	21.00%
State tax (benefit), net of federal benefit	9.40%	6.70%	5.50%
Permanent differences and other	(0.00%)	(0.40%)	(0.80%)
Research and development credits	4.80%	4.30%	5.40%
Provision to return adjustments		(2.80%)
Stock-based compensation	1.70%
Change in valuation allowance	(36.90%)	(28.80%)	(31.10%)

Related Party Transactions

12 Months Ended

Dec. 31, 2020

Related Party Transactions

Note 11. Related Party Transactions

The following are transactions that occurred between the Company and related parties, including the Significant Investor, as defined in Note 1.

Lease Guarantee

In February 2019, the Significant Investor entered into an agreement to lend its credit and creditworthiness to the Company by providing a guarantee in the form of a letter of credit to allow the Company to enter into the lease agreement for its facilities in Mountain View, California. The Company did not draw on the guarantee and in December 2019, the Company exercised its rights to substitute a security deposit in lieu of the letter of credit pursuant to the lease agreement. Accordingly, the letter of credit was returned to the Significant Investor and the guarantee was no longer outstanding as of December 31, 2019.

Settlement of Related Party Receivable

In April 2019, the Company received $2.5 million in cash from the Significant Investor in settlement of the outstanding note receivable as of December 31, 2018.

Related Party Loan

In January, February and April 2019, the Company issued an unsecured promissory note to the Significant Investor for proceeds of $15.0 million. In June 2019, the outstanding unsecured promissory note, amounting to $20.0 million, issued by the Significant Investor was settled as shares of Series C convertible preferred stock (see below). During the year ended December 31, 2019, the Company paid $0.3 million in interest related to the unsecured promissory note issued to the Significant Investor.

2019 Series C Issuance

In June 2019, the Company issued 2,269,838 shares of Series C convertible preferred stock to the Significant Investor for $30.0 million. A portion of the shares of Series C convertible preferred stock was issued to satisfy the settlement of the unsecured promissory note amounting to $20.0 million issued by the Significant Investor.

Public Offerings

Immediately prior to the closing of the IPO, all outstanding shares of the Company’s convertible preferred stock held by the Significant Investor automatically converted into common stock and non-voting common stock. In September 2019, the Significant Investor purchased an additional 1,250,000 shares of common stock in connection with the IPO. In December 2020, the Significant Investor purchased an additional 111,111 shares of common stock in connection with the Company’s public offering. As a result of these events, the Significant Investor owned 10,400,564 shares of common stock and 2,269,838 shares of non-voting common stock upon the closing of the December 2020 Public Offering.

Additionally, in connection with the 2020 Public Offering the Company issued Pre-funded Warrants to two separate related party affiliates. (See “Note 7 Pre-Funded Warrants”).

Common Stock and Non-Voting Common Stock

12 Months Ended

Dec. 31, 2020

Stockholders Equity Note [Abstract]

Common Stock and Non-Voting Common Stock

Note 6. Common Stock and Non-Voting Common Stock

As of December 31, 2020 and 2019, the Company’s certificate of incorporation authorized the Company to issue 1,006,431,208 shares of common stock (including 6,431,208 shares of non-voting common stock) and 200,000,000 shares of preferred stock, respectively, at a par value of $0.01 per share. Each share of common stock (excluding non-voting common stock) is entitled to one vote. The holders of common stock are also entitled to receive dividends whenever funds are legally available and when declared by the Company’s Board of Directors, subject to prior rights of the preferred stockholders. As of December 31, 2020 and 2019, no dividends have been declared.

The Company had reserved common stock, on an as-converted basis, for future issuance as follows:

	December 31,		December 31,
	2020		2019
Stock options, issued and outstanding		2,926,560		2,289,209
Restricted stock units		667		—
Restricted stock, issued and outstanding		—		58,259
Stock options and restricted stock units, future issuance		3,054,127		2,669,264
Employee stock purchase plan, available for future grants		554,088		280,000
Pre-funded warrants		1,334,332		—
Total		7,869,774		5,296,732

Stock-Based Compensation - Summary of Fair Value of Employee Stock Purchase Plan Estimated Weighted-average Assumptions (Details) - Employee Stock Purchase Plan	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Expected term in years	6 months	8 months 12 days
Expected volatility	85.50%	74.30%
Risk-free interest rate	0.10%	1.90%

Balance Sheet Components - Additional Information (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Balance Sheet Related Disclosures [Abstract]
Depreciation expense	$ 1,025	$ 597	$ 278

Statements of Comprehensive Loss - USD ($) $ in Thousands	12 Months Ended
Statements of Comprehensive Loss - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Statement Of Income And Comprehensive Income [Abstract]
Net loss	$ (81,355)	$ (43,133)	$ (22,711)
Other comprehensive income:
Unrealized gain (loss) on investments	(17)	43
Comprehensive loss	$ (81,372)	$ (43,090)	$ (22,711)

- Definition

The portion of profit or loss for the period, net of income taxes, which is attributable to the parent.

+ References

+ Details

Commitments and Contingencies - Schedule of ROU Assets and Related Lease Liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Assets And Liabilities Lessee [Abstract]
Lease liabilities, current	$ 2,667	$ 2,483
Non-current operating lease liabilities	$ 9,577	$ 12,244
Weighted average remaining lease term in years	4 years 1 month 6 days	5 years 1 month 6 days
Weighted average discount rate	3.80%	3.80%

Stock-Based Compensation (Tables)

12 Months Ended

Dec. 31, 2020

Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]

Summary of Stock-Based Compensation Expense

Total stock-based compensation expense recorded related to the 2010 Plan, 2018 Plan, and ESPP was recorded in the statements of operations and allocated as follows (in thousands):

	Year Ended December 31,
	2020		2019		2018
Research and development	$	4,160	$	522	$	51
General and administrative		4,294		492		132
Total stock-based compensation expense	$	8,454	$	1,014	$	183

Summary of Stock Option

The following table summarizes stock option activity:

	Outstanding Options
	Shares			Weighted- Average Exercise		Weighted- Average Remaining Contractual Term (Years)		Aggregate Intrinsic Value
								(in thousands)
Balance—December 31, 2019		2,289,209		$	3.36		8.1	$	79,656
Granted		893,875		$	44.66
Exercised		(203,192	)	$	2.27
Cancelled		(53,332	)	$	31.44
Balance—December 31, 2020		2,926,560		$	15.54		7.8	$	212,906
Exercisable—December 31, 2020		1,462,376		$	6.60		6.8	$	119,459

Summary of Fair Value of Employee Stock Options Estimated Weighted-average Assumptions

The fair value of employee stock options was estimated using the following weighted-average assumptions:

	Year Ended December 31,
	2020			2019			2018
Expected term in years		6.0			6.0			5.9
Expected volatility		84.3	%		79.3	%		77.5	%
Risk-free interest rate		1.0	%		2.2	%		2.9	%
Expected dividend yield		—			—			—
Weighted average fair value of share-based awards granted per share	$	31.70		$	4.36		$	0.94

Summary of Fair Value of Employee Stock Purchase Plan Estimated Weighted-average Assumptions

The fair value of ESPP was estimated using the following weighted-average assumptions:

	Year Ended December 31,
	2020			2019			2018
Expected term in years		0.5			0.7			—
Expected volatility		85.5	%		74.3	%		—
Risk-free interest rate		0.1	%		1.9	%		—
Expected dividend yield		—			—			—

Commitments and Contingencies (Tables)

12 Months Ended

Dec. 31, 2020

Commitments And Contingencies Disclosure [Abstract]

Summary of Cash Paid for Operating Lease Liabilities and Lease Costs Recognized in Statement of Operations

The following table summarizes the cash paid for operating lease liabilities and the lease costs recognized in the statements of operations:

	Year Ended December 31,
	2020		2019
Cash paid for operating lease liabilities	$	3,002	$	1,527
Operating lease cost		3,069		1,396
Variable lease cost		216		683

Schedule of ROU Assets and Related Lease Liabilities

Information related to the Company’s ROU assets and related lease liabilities was as follows (in thousands except for remaining lease term and discount rate):

	December 31, 2020			December 31, 2019
Current operating lease liabilities	$	2,667		$	2,483
Non-current operating lease liabilities		9,577			12,244
Weighted average remaining lease term in years		4.1			5.1
Weighted average discount rate		3.8	%		3.8	%

Schedule of Maturities of Lease Liabilities

Maturities of lease liabilities as of December 31, 2020 were as follows (in thousands):

	Operating
	Lease
Year Ending December	Commitments
2021	$	3,086
2022		3,172
2023		3,261
2024		3,008
2025		733
Thereafter		—
Total		13,260
Less imputed interest		(1,016	)
Total lease liabilities	$	12,244

Balance Sheets - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Current assets:
Cash and cash equivalents	$ 241,080	$ 35,891
Short-term investments	125,189	188,743
Prepaid expenses and other current assets	7,003	6,431
Income tax receivable		35
Total current assets	373,272	231,100
Property, plant and equipment, net	23,226	3,882
Long-term investments		11,973
Operating lease right-of-use asset	11,586	14,137
Other assets	548	258
Total assets	408,632	261,350
Current liabilities:
Accounts payable	7,924	3,087
Accrued liabilities	6,649	3,305
Lease liabilities, current	2,667	2,483
Total current liabilities	17,240	8,875
Lease liabilities, non-current	9,577	12,244
Total liabilities	26,817	21,119
Commitments and contingencies (Note 10)
Stockholders' equity:
Preferred stock
Common stock, value	255	240
Additional paid-in-capital	570,030	347,089
Accumulated other comprehensive income	26	43
Accumulated deficit	(188,560)	(107,205)
Total stockholders’ equity	381,815	240,231
Total liabilities and stockholders’ equity	408,632	261,350
Non-voting Common Stock
Stockholders' equity:
Common stock, value	64	64
Total stockholders’ equity	$ 64	$ 64

Pre Funded Warrants

12 Months Ended

Dec. 31, 2020

Stockholders Equity Note [Abstract]

Pre-Funded Warrants

Note 7. Pre-Funded Warrants

On December 11, 2020, the Company completed an underwritten public offering of 1,221,224 shares of its common stock, which included the exercise of the underwriters’ option to purchase 333,333 shares in full, and Pre-funded Warrants to purchase an additional 1,334,332 shares of common stock. The Pre-funded Warrants were issued to two separate related party affiliates. The public offering price of common stock was $90.00 per share and the public offering price of each Pre-funded Warrant was $89.99, with each Pre-funded Warrant having an exercise price of $0.01. After deducting underwriting discounts and commissions and offering costs paid or payable by the Company of approximately $14.6 million, the aggregate net proceeds from the 2020 Public Offering were approximately $215.4 million.

The public offering price for the Pre-funded Warrants was equal to the public offering price, less the $0.01 exercise price of each warrant. The Pre-funded Warrants were recorded as a component of stockholders’ equity within additional paid-in-capital and will expire on the date any such warrant is exercised in full.

Subject to applicable law, upon exercise of a Pre-funded Warrant, a holder may elect to receive the same number of shares of non-voting common stock as the shares of common stock for which the Pre-funded Warrant is exercisable, provided that (i) at the time of such election there is a sufficient number of authorized but unissued and otherwise unreserved shares of non-voting common stock and (ii) the Company consents to such election.

The outstanding Pre-funded Warrants to purchase shares of common stock are exercisable at any time after their original issuance. However, the Company may not effect the exercise of any Pre-funded Warrants, and a holder will not be entitled to exercise any portion of any Pre-funded Warrants that, upon giving effect to such exercise, would cause: (i) the aggregate number of shares of the Company’s common stock beneficially owned by such holder (together with its affiliates) to exceed 9.99% of the number of shares of the Company’s common stock outstanding immediately after giving effect to the exercise; or (ii) the combined voting power of the Company’s securities beneficially owned by such holder (together with its affiliates) to exceed 9.99% of the combined voting power of all of the Company’s securities outstanding immediately after giving effect to the exercise, as such percentage ownership is determined in accordance with the terms of the Pre-funded Warrants. However, any holder of a Pre-funded Warrant may increase or decrease such percentage to any other percentage not in excess of 19.99% upon at least 61 days’ prior notice from the holder to the Company. As of December 31, 2020, no shares underlying the Pre-funded Warrants had been exercised (see “Note 12 Net Loss Per Share Attributable to Common Stockholders”).

Income Taxes

12 Months Ended

Dec. 31, 2020

Income Tax Disclosure [Abstract]

Income Taxes

Note 9. Income Taxes

Income Taxes

The Company had no income tax expense for the years ended December 31, 2020, 2019 and 2018. The following is a reconciliation of the statutory federal income tax rate to the Company’s effective tax rate:

	Year Ended December 31,
	2020			2019			2018
Federal tax (benefit) at statutory rate		21.0	%		21.0	%		21.0	%
State tax (benefit), net of federal benefit		9.4			6.7			5.5
Permanent differences and other		(0.0	)		(0.4	)		(0.8	)
Research and development credits		4.8			4.3			5.4
Provision to return adjustments		—			(2.8	)		—
Stock-based compensation		1.7			—			—
Change in valuation allowance		(36.9	)		(28.8	)		(31.1	)
Effective income tax rate		—	%		—	%		—	%

Deferred tax assets and liabilities consist of the following (in thousands):

	December 31,
	2020			2019
Deferred tax assets:
Net operating loss carryforwards	$	38,739		$	15,650
Accrued liabilities and reserves		1,623			716
Stock-based compensation		1,434			253
Intangible assets		9,792			10,435
Operating lease liability		3,427			4,121
Research and development credits		10,471			4,991
Total deferred tax assets		65,486			36,166
Deferred tax liabilities:
Property and equipment		(269	)		(167	)
Right-of-use assets		(3,243	)		(3,956	)
Total deferred tax liabilities		(3,512	)		(4,123	)
Valuation allowance		(61,974	)		(32,043	)
Net deferred tax assets	$	—		$	—

The provisions of ASC Topic 740, Accounting for Income Taxes (ASC 740), require an assessment of both positive and negative evidence when determining whether it is more likely than not that deferred tax assets are recoverable. For the years ended December 31, 2020 and 2019, based on all available objective evidence, including the existence of cumulative losses, the Company determined that it was not more likely than not that the net deferred tax assets were fully realizable. Accordingly, the Company established a full valuation allowance against its deferred tax assets. The Company intends to maintain a full valuation allowance on net deferred tax assets until sufficient positive evidence exists to support reversal of the valuation allowance. During the years ended December 31, 2020 and 2019, the valuation allowance increased by $29.9 million and $12.4 million, respectively.

At December 31, 2020, the Company had net operating loss carryforwards available to reduce future taxable income, if any, for federal and California income tax purposes of approximately $141.2 million and $129.4 million, respectively. Of the federal net operating loss carryforwards at December 31, 2020, $4.4 million begins expiring in 2030 and $136.8 million can be carried forward indefinitely, subject to an annual limitation of 80% of taxable income. The California net operating loss carryforward begins expiring in 2037.

At December 31, 2020, the Company also had federal and California research and development tax credit carryforwards of $8.3 million and $5.4 million, respectively, available to offset future income tax, if any. The federal credit carryforwards begins expiring in 2032, and the California credits can be carried forward indefinitely.

Under Section 382 and 383 of the Internal Revenue Code of 1986, as amended, if a corporation undergoes an “ownership change,” the corporation's ability to use its pre-change net operating loss carryforwards and other pre-change attributes, such as research tax credits, to offset its post-change income may be limited. In general, an “ownership change” will occur if there is a cumulative change in the Company's ownership by “5-percent shareholders” that exceeds 50 percentage points over a rolling three-year period. Similar rules may apply under state tax laws. Therefore, certain of the Company's carryforward tax attributes may be subject to an annual limitation regarding their utilization against taxable income in future periods. The Company has completed a Section 382 study and believes it has experienced two changes in ownership. As a result, some of the federal and California NOL carryforwards and tax credit carryforwards may expire before being applied to reduce future income tax liabilities.

In response to the COVID-19 pandemic, the Coronavirus Aid, Relief and Economic Securities Act (CARES Act) was signed into law in the US in March 2020. The CARES Act adjusted a number of provisions in the tax code that could impact a business entity’s income taxes, including the calculation and eligibility of certain deductions and the treatment of net operating losses and tax credits. The enactment of the CARES Act did not result in any material adjustments to our income tax provision for the year ended December 31, 2020, or to our net deferred tax assets as of December 31, 2020. The CARES Act also provides for other non-income tax related benefits to assist those impacted by the COVID-19 pandemic, such as, Paycheck Protection Program loans, deferral of the employer portion of social security taxes, and employee retention credits (“ERC”). The Company elected to defer its portion of social security taxes and it claimed the Employee Retention Credit (“ERC”) as its operations were impacted by a Shelter in Place order issued by a governmental authority (Santa Clara County). The Company utilized approximately $548K of ERC’s during 2020 which will result in a cash benefit. The Company continues to monitor and evaluate the regulatory and interpretive guidance related to the CARES Act.

California Assembly Bill 85 (AB 85) was signed into law in June 2020. The legislation suspends the use of California Net Operating Loss deductions for 2020, 2021, and 2022 for certain taxpayers and imposes a limitation on the use of certain California Tax Credits for 2020, 2021, and 2022. The carryover periods for Net Operating Loss deductions disallowed by this provision will be extended. Given the Company’s net operating loss position in the current year, the new legislation will not impact the current year provision. The Company will continue to monitor possible California net operating loss and credit limitations in future periods.

Uncertain Tax Positions

The Company adopted the provisions of ASC 740, which requires companies to determine whether it is “more likely than not” that a tax position will be sustained upon examination by the appropriate taxing authorities before any tax benefit can be recorded in the financial statements. It also provides guidance on the recognition, measurement, classification and interest and penalties related to uncertain tax positions.

The following table summarizes the activity related to the Company’s gross unrecognized tax benefits (in thousands):

	December 31,
	2020			2019		2018
Beginning balance	$	1,820		$	1,113	$	665
Decreases for tax positions related to prior years		(495	)		—		—
Additions for tax positions related to current year		1,104			707		448
Ending balance	$	2,429		$	1,820	$	1,113

The decrease in balance for tax positions taken in prior years relates to the completion of a research and development tax credit study for the years 2016-2019.

The unrecognized tax benefits, if recognized, would not affect the effective income tax rate due to the valuation allowance that currently offsets deferred tax assets. Interest and penalties were zero. The Company does not expect the unrecognized tax benefits to change significantly over the next twelve months.

The Company files federal and state income tax returns. All periods since inception are subject to examination by federal and state authorities, where applicable. There are currently no pending income tax examinations.

- Definition

The entire disclosure for income taxes. Disclosures may include net deferred tax liability or asset recognized in an enterprise's statement of financial position, net change during the year in the total valuation allowance, approximate tax effect of each type of temporary difference and carryforward that gives rise to a significant portion of deferred tax liabilities and deferred tax assets, utilization of a tax carryback, and tax uncertainties information.

+ References + Details

Selected Quarterly Financial Data (Unaudited) - Summary of Quarterly Financial Information (Details) - USD ($)
$ / shares in Units, $ in Thousands

3 Months Ended

12 Months Ended

Dec. 31, 2020

Sep. 30, 2020

Jun. 30, 2020

Mar. 31, 2020

Dec. 31, 2019

Sep. 30, 2019

Jun. 30, 2019

Mar. 31, 2019

Dec. 31, 2020

Dec. 31, 2019

Dec. 31, 2018

Operating expenses:

Research and development

$ 19,599

$ 15,829

$ 15,019

$ 14,583

$ 12,763

$ 8,279

$ 8,303

$ 5,912

$ 65,030

$ 35,257

$ 18,962

General and administrative

5,140

4,732

4,388

3,990

3,174

2,394

2,228

1,445

18,250

9,241

3,829

Total operating expenses

24,739

20,561

19,407

18,573

15,937

10,673

10,531

7,357

83,280

44,498

22,791

Loss from operations

(24,739)

(20,561)

(19,407)

(18,573)

(15,937)

(10,673)

(10,531)

(7,357)

(83,280)

(44,498)

(22,791)

Other income (expense), net

117

291

568

949

1,122

501

(145)

(113)

1,925

1,365

Net loss

$ (24,622)

$ (20,270)

$ (18,839)

$ (17,624)

$ (14,815)

$ (10,172)

$ (10,676)

$ (7,470)

$ (81,355)

$ (43,133)

$ (22,711)

Net loss per share, basic and diluted

$ (0.79)

$ (0.66)

$ (0.62)

$ (0.58)

$ (0.49)

$ (2.41)

$ (19.08)

$ (16.86)

$ (2.65)

$ (4.80)

$ (51.84)

Weighted-average common shares outstanding, basic and diluted

31,298,264

30,646,729

30,551,736

30,491,463

30,478,980

4,222,259

559,671

443,118

30,748,280

^[1]

8,995,410

^[1]

438,074

^[1]

[1]	Includes shares of common stock into which Pre-Funded Warrants may be exercised. See Note 7 to our financial statements included in this Form 10-K.

- Definition

The portion of profit or loss for the period, net of income taxes, which is attributable to the parent.

+ References

+ Details

Related Party Transactions - Additional Information (Details)		1 Months Ended			4 Months Ended	12 Months Ended
	Sep. 20, 2019 shares	Dec. 31, 2020 shares	Jun. 30, 2019 USD ($) shares	Apr. 30, 2019 USD ($)	Apr. 30, 2019 USD ($)	Dec. 31, 2020 RelatedParty shares	Dec. 31, 2019 USD ($) shares	Dec. 31, 2018 USD ($)
Related Party Transaction [Line Items]
Accrued interest on related party loan \| $								$ 27,000
IPO
Related Party Transaction [Line Items]
Issuance of common stock, shares	12,578,125
Common Stock
Related Party Transaction [Line Items]
Issuance of common stock, shares							7,566
Shares issued upon conversion of convertible preferred stock	10,787,861						10,787,861
Common Stock \| IPO
Related Party Transaction [Line Items]
Issuance of common stock, shares							12,578,125
Non-voting Common Stock
Related Party Transaction [Line Items]
Shares issued upon conversion of convertible preferred stock	6,431,205						6,431,205
Haldor Topsøe Holding A/S and Holdco
Related Party Transaction [Line Items]
Proceeds from related party notes receivable \| $				$ 2,500,000
Haldor Topsøe Holding A/S and Holdco \| Public Offering \| Pre-funded Warrant
Related Party Transaction [Line Items]
Number of related party to warrant issued \| RelatedParty						2
Haldor Topsøe Holding A/S and Holdco \| Common Stock \| IPO
Related Party Transaction [Line Items]
Issuance of common stock, shares	1,250,000
Haldor Topsøe Holding A/S and Holdco \| Common Stock \| Public Offering
Related Party Transaction [Line Items]
Issuance of common stock, shares		111,111				10,400,564
Haldor Topsøe Holding A/S and Holdco \| Series C Convertible Preferred Stock
Related Party Transaction [Line Items]
Preferred stock issued			2,269,838
Preferred stock issued, value \| $			$ 30,000,000
Debt settled \| $			20,000,000
Haldor Topsøe Holding A/S and Holdco \| Non-voting Common Stock \| Public Offering
Related Party Transaction [Line Items]
Shares issued upon conversion of convertible preferred stock	2,269,838
Haldor Topsøe Holding A/S and Holdco \| Unsecured Promissory Note
Related Party Transaction [Line Items]
Proceeds from loan from related party \| $					$ 15,000,000
Outstanding unsecured promissory note \| $			$ 20,000,000
Accrued interest on related party loan \| $							$ 300,000

Commitments and Contingencies - Summary of Cash Paid for Operating Lease Liabilities and Lease Costs Recognized in Statement of Operations (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Lease Cost [Abstract]
Cash paid for operating lease liabilities	$ 3,002	$ 1,527
Operating lease cost	3,069	1,396
Variable lease cost	$ 216	$ 683

Subsequent Events - Additional Information (Details) - Subsequent Events - USD ($) $ in Millions	1 Months Ended
	Mar. 30, 2021	Jan. 31, 2021
Offices and Laboratory \| Mountain View, California
Subsequent Event [Line Items]
Lessee operating lease commencement month and year	2021-03
Lessee operating lease expiry month and year	2023-08
Future rent payments under agreement	$ 1.9
Medivir AB \| License Agreement
Subsequent Event [Line Items]
Upfront payment		$ 1.0
Additional milestone payment		1.5
Medivir AB \| License Agreement \| Maximum
Subsequent Event [Line Items]
Milestone payment based on achievement of specified development		$ 350.0

Commitments and Contingencies - Schedule of Maturities of Lease Liabilities (Details) $ in Thousands	Dec. 31, 2020 USD ($)
Operating Lease Liabilities Payments Due [Abstract]
2021	$ 3,086
2022	3,172
2023	3,261
2024	3,008
2025	733
Total	13,260
Less imputed interest	(1,016)
Total lease liabilities	$ 12,244

Summary of Significant Accounting Policies

12 Months Ended

Dec. 31, 2020

Accounting Policies [Abstract]

Summary of Significant Accounting Policies

Note 2. Summary of Significant Accounting Policies

Use of Estimates

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. On an ongoing basis, the Company evaluates its estimates, including, but not limited to, those related to investments, manufacturing accruals, accrued research and development expenses, fair value of common stock, stock-based compensation, operating lease right-of-use (ROU) assets and liabilities, income tax uncertainties and the valuation of deferred tax assets. The Company bases its estimates on its historical experience and also on assumptions that it believes are reasonable; however, actual results could significantly differ from those estimates.

Segments

The Company operates and manages its business as one reportable and operating segment, which is the business of developing engineered IgM antibodies for the treatment of multiple diseases. The Company’s chief executive officer, who is the chief operating decision maker, reviews financial information on an aggregate basis for allocating and evaluating financial performance. All long-lived assets are maintained in, and all losses are attributable to, the United States of America.

Concentration of Credit Risk and Other Risks and Uncertainties

Financial instruments that potentially subject the Company to a concentration of credit risk consist primarily of cash and investments. The Company invests in money market funds, U.S. Treasury securities, corporate bonds, commercial paper, and U.S. government agency securities. The Company maintains bank deposits in federally insured financial institutions and these deposits may exceed federally insured limits. The Company is exposed to credit risk in the event of a default by the financial institutions holding its cash and issuers of investments to the extent recorded on the balance sheets. The Company’s investment policy limits investments to money market funds, certain types of debt securities issued by the U.S. Government and its agencies, corporate debt, commercial paper, and places restrictions on the credit ratings, maturities and concentration by type and issuer. The Company has not experienced any losses on its deposits of cash and investments.

The Company’s future results of operations involve a number of other risks and uncertainties. Factors that could affect the Company’s future operating results and cause actual results to vary materially from expectations include, but are not limited to, the Company’s early stages of clinical drug development; uncertainties related to the use of engineered IgM antibodies, which is a novel and unproven therapeutic approach; the Company’s ability to advance product candidates into, and successfully complete, clinical trials on the timelines it projects; the Company’s ability to adequately demonstrate sufficient safety and efficacy of its product candidates; the Company’s ability to enroll patients in its ongoing and future clinical trials; the Company’s ability to successfully manufacture and supply its product candidates for clinical trials; the Company’s ability to obtain additional capital to finance its operations; uncertainties related to the projections of the size of patient populations suffering from the diseases the Company is targeting; the Company’s ability to obtain, maintain, and protect its intellectual property rights; developments relating to the Company’s competitors and its industry, including competing product candidates and therapies; general economic and market conditions; and other risks and uncertainties, including those more fully described in the “Risk Factors” section of this Annual Report on Form 10-K.

The Company’s product candidates will require approvals from the U.S. Food and Drug Administration and comparable foreign regulatory agencies prior to commercial sales in their respective jurisdictions. There can be no assurance that any product candidates will receive the necessary approvals. If the Company was denied approval, approval was delayed or the Company was unable to maintain approval for any product candidate, it could have a materially adverse impact on the Company.

Cash, Cash Equivalents and Restricted Cash

The Company considers all highly liquid investments with original maturities of three months or less from the date of purchase to be cash and cash equivalents. Cash equivalents consist primarily of amounts invested in money market accounts and are stated at fair value. Restricted cash consisted of a money market account, which was closed during 2019, that served as collateral for a credit card agreement at one of the Company’s financial institutions.

Investments

The Company’s investments have been classified and accounted for as available-for-sale securities. Fixed income securities consist of U.S. Treasury securities, U.S. government agency securities, corporate debt, and commercial paper. The specific identification method is used to determine the cost basis of fixed income securities sold. These securities are recorded on the balance sheets at fair value. Unrealized gains and losses on these securities are included as a separate component of accumulated other comprehensive income. The cost of investment securities is adjusted for amortization of premiums and accretion of discounts to maturity. Such amortization and accretion are included in other income, net. Realized gains and losses and declines in fair value judged to be other-than-temporary, if any, are also included in other income, net. The Company evaluates securities for other-than-temporary impairment at the balance sheet date. Declines in fair value determined to be other-than-temporary are also included in other income, net. The Company classifies its investments as short or long term primarily based on the remaining contractual maturity of the securities.

Property, Plant and Equipment

Property, plant and equipment are stated at cost, less accumulated depreciation and amortization. Depreciation is determined using the straight-line method over the estimated useful lives of the respective assets, generally three to five years. Leasehold improvements are amortized using the straight-line method over the shorter of the lease term or the estimated useful economic lives of the related assets.

Upon retirement or sale of the assets, the cost and related accumulated depreciation and amortization are removed from the balance sheet and the resulting gain or loss are recorded to the statements of operations. Repairs and maintenance are charged to operations as incurred.

Impairment of Long-Lived Assets

Long-lived assets consist of property and equipment. The Company evaluates the carrying amount of its long-lived assets whenever events or changes in circumstances indicate that the assets may not be recoverable. An impairment loss would be recognized when estimated future cash flows expected to result from the use of the asset and its eventual disposition are less than the carrying amount of the asset. There was no impairment of long-lived assets in 2020, 2019 and 2018.

Research and Development Expenses

The Company expenses research and development costs as they are incurred. Research and development expenses consist primarily of: (i) personnel-related expenses, including salaries, benefits and stock-based compensation expense, for personnel in the Company’s research and development functions; (ii) fees paid to third parties such as contractors, consultants and contract research organizations (CROs) for conducting clinical trials, animal studies, and other costs related to clinical and preclinical testing; (iii) costs related to acquiring and manufacturing research and clinical trial materials, including under agreements with third parties such as contract manufacturing organizations (CMOs), and other vendors; (iv) costs related to the preparation of regulatory submissions; (v) expenses related to laboratory supplies and services; and (vi) depreciation of equipment and facilities expenses.

Accrued Research and Development Expenses

The Company records accruals for estimated costs of research, preclinical studies, clinical trials, and manufacturing, which are significant components of research and development expenses. A substantial portion of the Company’s ongoing research and development activities is conducted by third-party service providers, CROs and CMOs. The Company’s contracts with CROs generally include pass-through fees such as costs related to animal studies and safety tests, regulatory expenses, investigator fees, travel costs and other miscellaneous costs, including shipping and printing fees. The Company’s contracts with the CMOs generally include fees such as initiation fees, reservation fees, verification run costs, materials and reagents expenses, taxes, etc. The financial terms of these contracts are subject to negotiations, which vary from contract to contract and may result in payment flows that do not match the periods over which materials or services are provided to the Company under such contracts. The Company accrues the costs incurred under agreements with these third parties based on estimates of actual work completed in accordance with the respective agreements. The Company determines the estimated costs through discussions with internal personnel and external service providers as to the progress, or stage of completion or actual timeline (start-date and end-date) of the services and the agreed-upon fees to be paid for such services. In the event the Company makes advance payments, the payments are recorded as a prepaid expense and recognized as the services are performed.

As actual costs become known, the Company adjusts its accruals. Although the Company does not expect its estimates to be materially different from amounts actually incurred, such estimates for the status and timing of services performed relative to the actual status and timing of services performed may vary and could result in the Company reporting amounts that are too high or too low in any particular period. The Company’s accrual is dependent, in part, upon the receipt of timely and accurate reporting from CROs and other third-party vendors. Variations in the assumptions used to estimate accruals including, but not limited to, the number of patients enrolled, the rate of patient enrollment and the actual services performed, may vary from the Company’s estimates, resulting in adjustments to clinical trial expenses in future periods. Changes in these estimates that result in material changes to the Company’s accruals could materially affect its financial condition and results of operations. Through December 31, 2020, there have been no material differences from the Company’s estimated accrued research and development expenses to actual expenses.

Stock-Based Compensation

The Company accounts for stock-based compensation by measuring and recognizing compensation expense for all share-based awards made to employees, non-employees and directors based on estimated grant-date fair values. The Company uses the straight-line method to allocate compensation cost to reporting periods over the requisite service period, which is generally the vesting period, and estimates the fair value of share-based awards to employees and directors using the Black-Scholes option-pricing model. If the service inception date precedes the grant date, the Company accrues for the stock-based compensation based on the fair value at the reporting date. The Company accounts for forfeitures as they occur. The fair value of each purchase under the employee stock purchase plan (ESPP) is estimated at the beginning of the offering period using the Black-Scholes option pricing model and recorded as expense over the service period using the straight-line method.

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 (including non-voting common stock and Pre-funded Warrants) outstanding during the period, without consideration for common stock equivalents. Shares of common stock into which the Pre-funded Warrants may be exercised are considered outstanding for the purposes of computing net loss per share because the shares may be issued for little or no consideration, are fully vested, and are exercisable after the original issuance date. Diluted net loss per share is the same as basic net loss per share, since the effects of potentially dilutive securities are antidilutive given the net loss for each period presented.

Deferred Offering Costs

Deferred offering costs, consisting of legal, accounting, and filing fees directly relating to the Company’s equity offerings, are capitalized and offset against the proceeds upon the completion of the offering.

There were no deferred offering costs as of December 31, 2020 and 2019.

Leases

During 2019, the Company elected to early adopt Accounting Standard Update (ASU) No. 2016-02, Leases (ASC 842) and its associated amendments as of January 1, 2019 using the modified retrospective transition approach. There was no cumulative-effect adjustment recorded to accumulated deficit upon adoption.

Under ASC 842 and its associated amendments, the Company determines if an arrangement is a lease at inception. In addition, the Company determines whether leases meet the classification criteria of a finance or operating lease at the lease commencement date considering: (1) whether the lease transfers ownership of the underlying asset to the lessee at the end of the lease term, (2) whether the lease grants the lessee an option to purchase the underlying asset that the lessee is reasonably certain to exercise, (3) whether the lease term is for a major part of the remaining economic life of the underlying asset, (4) whether the present value of the sum of the lease payments and residual value guaranteed by the lessee equals or exceeds substantially all of the fair value of the underlying asset, and (5) whether the underlying asset is of such a specialized nature that it is expected to have no alternative use to the lessor at the end of the lease term. As of December 31, 2020, the Company's lease population consisted of real estate. As of the date of adoption of ASC 842, and as of December 31, 2020 and 2019, the Company did not have finance leases.

Operating leases are included in operating lease right-of-use (ROU) assets, lease liabilities, current, and lease liabilities, non-current in the Company’s balance sheet. ROU assets represent the Company’s right to use an underlying asset for the lease term and lease liabilities represent the Company’s obligation to make lease payments arising from the lease. Operating lease ROU assets and liabilities are recognized at the lease commencement date based on the present value of lease payments over the lease term. In determining the present value of lease payments, the Company uses its incremental borrowing rate based on the information available at the lease commencement date if the rate implicit in the lease is not readily determinable. The Company determines the incremental borrowing rate based on an analysis of corporate bond yields with a credit rating similar to the Company. The determination of the Company’s incremental borrowing rate requires management judgment including the development of a synthetic credit rating and cost of debt as the Company currently does not carry any debt. The Company believes that the estimates used in determining the incremental borrowing rate are reasonable based upon current facts and circumstances. Applying different judgments to the same facts and circumstances could result in the estimated amounts to vary. The operating lease ROU assets also include adjustments for prepayments and accrued lease payments and exclude lease incentives. The Company’s lease terms may include options to extend or terminate the lease when it is reasonably certain that the Company will exercise such options. Operating lease cost is recognized on a straight-line basis over the expected lease term. Variable lease costs represent payments that are dependent on usage, a rate or index. Variable lease cost primarily relates to common area maintenance charges. Lease agreements that include lease and non-lease components are accounted for as a single lease component. Lease agreements with a noncancelable term of less than 12 months are not recorded on the Company’s balance sheet. For more information about the impact of adoption and disclosures on the Company’s leases, refer to “Note 10 – Commitments and Contingencies.”

Income Taxes

The Company accounts for income taxes using the liability method, whereby deferred tax asset and liability account balances are determined based on differences between the financial reporting and tax bases of assets and liabilities and are measured using the enacted tax rates and laws that will be in effect when the differences are expected to reverse. The Company provides a valuation allowance when it is more likely than not that some portion, or all of the Company’s deferred tax assets will not be realized.

The Company accounts for income tax contingencies using a benefit recognition model. If it considers that a tax position is more likely than not to be sustained upon audit, based solely on the technical merits of the position, it recognizes the benefit. The Company measures the benefit by determining the amount that is greater than 50% likely of being realized upon settlement, presuming that the tax position is examined by the appropriate taxing authority that has full knowledge of all relevant information. The Company’s policy is to recognize interest and penalties related to the underpayment of income taxes as a component of income tax expense or benefit. To date, there have been no interest or penalties charged in relation to the unrecognized tax benefits.

Recently Adopted Accounting Standards

In August 2018, the FASB issued ASU No. 2018-13, Disclosure Framework – Changes to the Disclosure Requirements for Fair Value Measurement, which amends ASC 820, Fair Value Measurement. This ASU modifies the disclosure requirements for fair value measurements by removing, modifying, or adding certain disclosures. The effective date was the first quarter of fiscal year 2020, with early adoption permitted for the removed disclosures and delayed adoption until fiscal year 2020 permitted for the new disclosures. The Company adopted this ASU as of January 1, 2020 and the adoption did not have a material impact on its financial statements and related disclosures. The removed and modified disclosures were adopted on a retrospective basis and the new disclosures were adopted on a prospective basis.

Recently Issued Accounting Pronouncements

In June 2016, the FASB issued ASU 2016-13, Financial Instruments – Credit Losses (Topic 326): Measurement of Credit Losses on Financial Instruments, which requires that financial assets measured at amortized cost be presented at the net amount expected to be collected. The measurement of expected credit losses is based on historical experience, current conditions, and reasonable and supportable forecasts that affect collectability. This ASU also eliminates the concept of “other-than-temporary” impairment when evaluating available-for-sale debt securities and instead focuses on determining whether any impairment is a result of a credit loss or other factors. An entity will recognize an allowance for credit losses on available-for-sale debt securities rather than an other-than-temporary impairment that reduces the cost basis of the investment. This ASU is effective for fiscal years beginning after December 15, 2022 and interim periods within those fiscal years. Early adoption is permitted. The Company is currently assessing the impact of this standard on its financial statements and related disclosures.

In December 2019, the FASB issued ASU 2019-12, Income Taxes (Topic 740): Simplifying the Accounting for Income Taxes (“ASU 2019-12”), which is intended to simplify the accounting for income taxes. ASU 2019-12 removes certain exceptions to the general principles in Topic 740 and also clarifies and amends existing guidance to improve consistent application. The new standard will be effective beginning January 1, 2021. The Company is currently assessing the impact of this standard on its financial statements and related disclosures.

Stock-Based Compensation

12 Months Ended

Dec. 31, 2020

Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]

Stock-Based Compensation

Note 8. Stock-Based Compensation

2018 Omnibus Incentive Plan (as Amended and Restated)

The Company’s Board of Directors adopted and the Company’s stockholders approved, effective on the day prior to the effectiveness of the registration statement on Form S-1 related to the IPO, an amendment and restatement of the 2018 Omnibus Incentive Plan (the 2018 Plan) which provides for the grant of incentive stock options, within the meaning of Section 422 of the Code to employees, and for the grant of nonstatutory stock options, restricted stock, restricted stock units (RSUs), stock appreciation rights, performance units, and performance shares to employees, directors, and consultants of the Company.

Options granted under the 2018 Plan expire no later than 10 years from the date of grant. The exercise price of options granted under the 2018 Plan must at least be equal to the fair market value of the Company’s common stock on the date of grant. With respect to any participant who owns more than 10% of the voting power of all classes of the Company’s outstanding stock, the term of an incentive stock option granted to such participant must not exceed five years and the exercise price must equal at least 110% of the fair market value on the grant date. Employee stock options generally vest 25% upon one year of continued service to the Company, with the remainder in monthly increments over three additional years.

Subject to an annual evergreen increase and adjustment in the case of certain capitalization events, the Company initially reserved 4,384,000 shares of the Company’s common stock for issuance pursuant to awards under the 2018 Plan. The 2018 Plan is administered by the Compensation Committee of the Company’s Board of Directors. The number of shares of the Company’s common stock available for issuance under the 2018 Plan will also include an annual increase on the first day of each fiscal year beginning with the 2020 fiscal year, equal to the least of (i) 8,768,800 shares, (ii) 4% of the Company’s common stock and non-voting common stock outstanding at December 31 of the immediately preceding year, or (iii) such number of shares as determined by the Company’s Board of Directors.

On July 30, 2020, the Company’s Board of Directors adopted and the Company’s stockholders approved an amendment and restatement of the 2018 Plan which clarified the number of outstanding shares of common stock used to calculate the annual evergreen provision to include both voting and non-voting shares of common stock. Upon adoption of the amended and restated 2018 Plan, the number of shares of common stock available under the 2018 Plan increased by 257,248 shares.

As of December 31, 2020, 3,054,127 shares of common stock remained available for issuance under the 2018 Plan. Effective January 1, 2021, the number of shares of common stock available under the 2018 Plan increased by 1,278,965 shares pursuant to the evergreen provision of the 2018 Plan.

2010 Stock Plan (as Amended and Restated)

The 2010 Stock Plan (the 2010 Plan) was originally adopted by the Company’s Board of Directors and approved by the Company’s stockholders in November 2010. The 2010 Plan was amended and restated in December 2017 and April 2019. The 2010 Plan allowed the Company to provide incentive stock options, within the meaning of Section 422 of the Code, nonstatutory stock options and stock purchase rights to eligible employees, consultants and directors and any parent or subsidiary of the Company. The 2010 Plan was terminated in 2019 and the Company will not grant any additional awards under the 2010 Plan. However, the 2010 Plan will continue to govern the terms and conditions of the outstanding awards previously granted under the 2010 Plan.

2019 Employee Stock Purchase Plan

The Company’s Board of Directors adopted and the Company’s stockholders approved, effective on the day prior to the effectiveness of the registration statement on Form S-1 related to the IPO, the 2019 Employee Stock Purchase Plan (ESPP). However, no offering period or purchase period under the ESPP will begin unless and until determined by the Company’s Board of Directors. The ESPP is intended to have two components: a component that is intended to qualify as an “employee stock purchase plan” under Section 423 of the Code (the 423 Component) and a component that is not intended to qualify (the Non-423 Component). The ESPP allows eligible employees to purchase shares of the Company’s common stock at a discount through payroll deductions of up to 15% of their eligible compensation. At the end of each offering period, employees are able to purchase shares at 85% of the lower of the fair market value of the Company’s common stock at the beginning of the offering period or at the end of each applicable purchase period.

Subject to adjustment in the case of certain capitalization events, a total of 280,000 common shares of the Company were available for purchase at adoption of the ESPP. Pursuant to the ESPP, the annual share increase pursuant to the evergreen provision is determined based on the least of (i) 560,000 shares, (ii) 1% of the Company’s common stock and non-voting common stock outstanding at December 31 of the immediately preceding year, or (iii) such number of shares as determined by the Company’s Board of Directors.

On July 30, 2020, the Company’s Board of Directors adopted and the Company’s stockholders approved an amendment and restatement of the ESPP which clarified the number of outstanding shares of common stock used to calculate the annual evergreen provision to include both voting and non-voting shares of common stock. Upon adoption of the amended and restated ESPP, the number of shares of common stock available under the ESPP was increased by 64,312 shares. During the year ended December 31, 2020, the Company issued 31,345 shares of common stock under the ESPP.

As of December 31, 2020, 554,088 shares of common stock remained available for issuance under the ESPP. Effective January 1, 2021, the number of shares of common stock available under the ESPP increased by 319,741 shares pursuant to the evergreen provision of the ESPP.

Stock-Based Compensation Expense

Total stock-based compensation expense recorded related to the 2010 Plan, 2018 Plan, and ESPP was recorded in the statements of operations and allocated as follows (in thousands):

	Year Ended December 31,
	2020		2019		2018
Research and development	$	4,160	$	522	$	51
General and administrative		4,294		492		132
Total stock-based compensation expense	$	8,454	$	1,014	$	183

Stock Options

The following table summarizes stock option activity:

	Outstanding Options
	Shares			Weighted- Average Exercise		Weighted- Average Remaining Contractual Term (Years)		Aggregate Intrinsic Value
								(in thousands)
Balance—December 31, 2019		2,289,209		$	3.36		8.1	$	79,656
Granted		893,875		$	44.66
Exercised		(203,192	)	$	2.27
Cancelled		(53,332	)	$	31.44
Balance—December 31, 2020		2,926,560		$	15.54		7.8	$	212,906
Exercisable—December 31, 2020		1,462,376		$	6.60		6.8	$	119,459

The fair value of employee stock options was estimated using the following weighted-average assumptions:

	Year Ended December 31,
	2020			2019			2018
Expected term in years		6.0			6.0			5.9
Expected volatility		84.3	%		79.3	%		77.5	%
Risk-free interest rate		1.0	%		2.2	%		2.9	%
Expected dividend yield		—			—			—
Weighted average fair value of share-based awards granted per share	$	31.70		$	4.36		$	0.94

As of December 31, 2020, there was $23.6 million of total unrecognized compensation cost related to stock options under the Plans. The unrecognized stock-based compensation cost is expected to be recognized over a weighted-average period of 2.5 years. The aggregate intrinsic value of options exercised for the years ended December 31, 2020 and December 31, 2019 was $12.5 million and $0.3 million, respectively. Intrinsic values are calculated as the difference between the exercise price of the underlying options and the fair value of the common stock on the date of exercise.

The fair value of ESPP was estimated using the following weighted-average assumptions:

	Year Ended December 31,
	2020			2019			2018
Expected term in years		0.5			0.7			—
Expected volatility		85.5	%		74.3	%		—
Risk-free interest rate		0.1	%		1.9	%		—
Expected dividend yield		—			—			—

Restricted Stock

During December 2018, the Company issued 116,518 shares of common stock to an executive officer under a restricted stock agreement at a grant date fair value of $1.39 per share that vested over two years. Any unvested shares were subject to forfeiture in the case that the grantee’s service terminated. As of December 31, 2020, all shares of restricted stock were vested. For the years ended December 31, 2020 and 2019, the related stock-based compensation was not material.

Restricted Stock Units

During the year ended December 31, 2020, the Company granted 8,312 shares of RSUs, of which 7,645 shares were issued upon vesting. These RSUs were granted to a consultant and certain members of the Company’s Board of Directors under the Company’s Outside Director Compensation Policy, as amended, and had a weighted-average fair value of $69.30 per share. The stock-based compensation expense related to these awards was $0.5 million, which was recognized over the service period of the awards. As of December 31, 2020, the remaining amount of unrecognized stock-based compensation related to these awards was not material. During the years ended December 31, 2020 and 2019, there were no RSUs cancelled.

Statements of Convertible Preferred Stock and Stockholders' Equity (Deficit) - USD ($) $ in Thousands	Total	IPO	Due To (From) Related Party	Convertible Preferred Stock	Non-voting Common Stock	Common Stock	Common Stock IPO	Additional Paid-In Capital	Additional Paid-In Capital IPO	Accumulated Other Comprehensive Income	Accumulated Deficit
Convertible preferred stock balance at Dec. 31, 2017				$ 40,783
Convertible preferred stock balance, shares at Dec. 31, 2017				6,384,797
Issuance of convertible preferred stock				$ 20,134
Issuance of convertible preferred stock, shares				3,116,823
Convertible preferred stock balance at Dec. 31, 2018				$ 60,917
Convertible preferred stock balance, shares at Dec. 31, 2018				9,501,620
Balance at Dec. 31, 2017	$ (40,503)		$ (34,625)			$ 4		$ 35,479			$ (41,361)
Balance, shares at Dec. 31, 2017						438,074
Issuance of common stock	(2,797)		(2,511)					(286)
Related party equity transaction			34,625					(34,625)
Stock-based compensation expense	183							183
Net loss	(22,711)										(22,711)
Balance at Dec. 31, 2018	(65,828)		(2,511)			$ 4		751			(64,072)
Balance, shares at Dec. 31, 2018						438,074
Issuance of convertible preferred stock				$ 101,636
Issuance of convertible preferred stock, shares				7,717,446
Conversion of convertible preferred stock into common stock and non-voting common stock				$ (162,553)
Conversion of convertible preferred stock into common stock and non-voting common stock, shares				(17,219,066)
Exercise of stock options	179					$ 2		177
Exercise of stock options, shares						184,036
Issuance of common stock	11	$ 182,842					$ 125	11	$ 182,717
Issuance of common stock, shares						7,566	12,578,125
Related party equity transaction	2,550		$ 2,511					39
Vesting of restricted stock						$ 1		(1)
Vesting of restricted stock, shares						58,259
Conversion of convertible preferred stock into common stock and non-voting common stock	162,553				$ 64	$ 108		162,381
Conversion of convertible preferred stock into common stock and non-voting common stock, shares					6,431,205	10,787,861
Unrealized gain (loss) on investments	43									$ 43
Stock-based compensation expense	1,014							1,014
Net loss	(43,133)										(43,133)
Balance at Dec. 31, 2019	240,231				$ 64	$ 240		347,089		43	(107,205)
Balance, shares at Dec. 31, 2019					6,431,205	24,053,921
Issuance of common stock and pre-funded warrants, net of offering costs	215,412					$ 12		215,400
Issuance of common stock and pre-funded warrants, net of offering costs, shares						1,221,224
Exercise of stock options, net of shares withheld for taxes and exercise costs	$ (1,593)					$ 2		(1,595)
Exercise of stock options, net of shares withheld for taxes and exercise costs, shares						170,537
Exercise of stock options, shares	203,192
Vesting of restricted stock						$ 1		(1)
Vesting of restricted stock, shares						58,259
Issuance of common stock upon restricted stock unit settlement, shares						7,645
Purchases under employee stock purchase plan	$ 683							683
Purchases under employee stock purchase plan, shares						31,345
Unrealized gain (loss) on investments	(17)									(17)
Stock-based compensation expense	8,454							8,454
Net loss	(81,355)										(81,355)
Balance at Dec. 31, 2020	$ 381,815				$ 64	$ 255		$ 570,030		$ 26	$ (188,560)
Balance, shares at Dec. 31, 2020					6,431,205	25,542,931

Net Loss Per Share Attributable to Common Stockholders (Tables)

12 Months Ended

Dec. 31, 2020

Earnings Per Share [Abstract]

Schedule of Computation of Basic and Diluted Net Loss Per Share

The following table sets forth the computation of the basic and diluted net loss per share (in thousands except share and per share data):

	Year Ended December 31,
	2020			2019			2018
Numerator:
Net loss	$	(81,355	)	$	(43,133	)	$	(22,711	)
Denominator:
Weighted average common shares outstanding used to compute net loss per share, basic and diluted ⁽¹⁾		30,748,280			8,995,410			438,074
Net loss per share attributable to common stockholders	$	(2.65	)	$	(4.80	)	$	(51.84	)

⁽¹⁾	Includes shares of common stock into which Pre-Funded Warrants may be exercised. See Note 7 to our financial statements included in this Form 10-K.

Summary of Potentially Dilutive Securities Not Included in the Diluted Per Share Calculations

Potentially dilutive securities that were not included in the diluted per share calculations because they would be anti-dilutive were as follows:

	December 31,
	2020		2019
Stock options		2,926,560		2,289,209
Estimated shares issuable under the employee stock purchase plan		3,054		10,187
Restricted stock units		667		—
Restricted stock		—		58,259
Total		2,930,281		2,357,655

Balance Sheet Components

12 Months Ended

Dec. 31, 2020

Balance Sheet Related Disclosures [Abstract]

Balance Sheet Components

Note 4. Balance Sheet Components

Property, Plant and Equipment, Net

Property, plant and equipment, net consists of the following (in thousands):

	December 31,			December 31,
	2020			2019
Laboratory equipment	$	7,125		$	3,800
Office equipment		212			150
Leasehold improvement		253			78
Construction in progress		17,925			1,118
Total property, plant and equipment, gross		25,515			5,146
Less: Accumulated depreciation		(2,289	)		(1,264	)
Total property, plant and equipment, net	$	23,226		$	3,882

Depreciation expense was approximately $1.0 million, $0.6 million and $0.3 million for the years ended December 31, 2020, 2019 and 2018, respectively.

Accrued Liabilities

Accrued liabilities consisted of the following (in thousands):

	December 31,		December 31,
	2020		2019
Accrued research and development materials and services	$	1,509	$	906
Accrued professional services		163		360
Accrued compensation		4,925		2,030
Other		52		9
Total accrued liabilities	$	6,649	$	3,305

Income Taxes - Additional Information (Details) - USD ($)	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Income Tax [Line Items]
Income tax expense	$ 0	$ 0	$ 0
Increase in valuation allowance amount	$ 29,900,000	12,400,000
Operating loss carryforwards limitations on use, percentage of taxable income	80.00%
Research and development credits	$ 10,471,000	$ 4,991,000
ERC cash benefit	548,000
Interest or penalties charged in relation to unrecognized tax benefits	0
Federal
Income Tax [Line Items]
Operating loss carryforwards	141,200,000
Operating loss carryforwards, subject to expiration	$ 4,400,000
Operating loss carryforwards expiration year	2030
Operating loss carryforwards, not subject to expiration	$ 136,800,000
Research and development credits	$ 8,300,000
Federal credit carryforwards expiration period	2032
California
Income Tax [Line Items]
Operating loss carryforwards	$ 129,400,000
Operating loss carryforwards expiration year	2037
Research and development credits	$ 5,400,000

Balance Sheets (Parenthetical) - $ / shares	Dec. 31, 2020	Dec. 31, 2019
Common stock, par value	$ 0.01	$ 0.01
Common stock, shares authorized	1,000,000,000	1,000,000,000
Common stock, shares issued	25,542,931	24,053,921
Common stock, shares outstanding	25,542,931	24,053,921
Non-voting Common Stock
Common stock, par value	$ 0.01	$ 0.01
Common stock, shares authorized	6,431,208	6,431,208
Common stock, shares issued	6,431,205	6,431,205
Common stock, shares outstanding	6,431,205	6,431,205

Stock-Based Compensation - Additional Information (Details) - USD ($) $ / shares in Units, $ in Millions	1 Months Ended	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2020	Dec. 31, 2019	Jan. 01, 2021
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Shares reserved for issuance		7,869,774	5,296,732
Stock Options
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Unrecognized stock-based compensation		$ 23.6
Expects to recognize over a remaining weighted-average period		2 years 6 months
Aggregate intrinsic value of options exercised		$ 12.5	$ 0.3
Restricted Stock Units
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Stock-based compensation expense related to awards		$ 0.5
Shares cancelled		0	0
Executive Officer \| Restricted Stock
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Vesting period	2 years
Issued of common stock	116,518
Grant date fair value per share	$ 1.39
Board of Directors \| Restricted Stock Units
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Issued of common stock		7,645
Grant date fair value per share		$ 69.30
Granted of common stock		8,312
2018 Plan
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Percentage of exercise price of stock option on estimated fair value of shares		110.00%
Vesting period		3 years
Shares reserved for issuance		4,384,000
Increase in number of shares		257,248
Outstanding stock including non-voting common stock, percent		4.00%
Shares available for issuance		3,054,127
2018 Plan \| Subsequent Event
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Increase in number of shares				1,278,965
2018 Plan \| Maximum
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Term of options		10 years
Increase in number of shares		8,768,800
2018 Plan \| Share-based Compensation Award, Tranche One
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Vesting percentage		25.00%
Vesting period		1 year
2018 Plan \| 10% Stockholder \| Maximum
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Term of options		5 years
2018 Plan \| 10% Stockholder \| Minimum
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Percentage of voting power		10.00%
ESPP
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Increase in number of shares		64,312
Outstanding stock including non-voting common stock, percent		1.00%
Shares available for issuance		554,088	280,000
Percentage of exercise price of stock option on estimated fair value of shares		85.00%
Issued of common stock		31,345
ESPP \| Subsequent Event
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Increase in number of shares				319,741
ESPP \| Maximum
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Increase in number of shares		560,000
Discount rate		15.00%

Statements of Convertible Preferred Stock and Stockholders' Equity (Deficit) (Parenthetical) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Stock issuance cost	$ 0.8
IPO
Stock issuance cost		$ 4.3
Series B Convertible Preferred Stock
Stock issuance cost			$ 0.5
Series C Convertible Preferred Stock
Stock issuance cost		$ 0.4

Commitments and Contingencies

12 Months Ended

Dec. 31, 2020

Commitments And Contingencies Disclosure [Abstract]

Commitments and Contingencies

Note 10. Commitments and Contingencies

Operating Leases

The Company leases its headquarters with its main offices and laboratory facilities in Mountain View, California under two lease agreements that end in September 2024 and April 2025. During the three months ended December 31, 2019, the Company entered into a sub-lease agreement for additional office and laboratory space in Mountain View, California, which commenced on December 1, 2019 and expires in September 2024. The Company determined the incremental borrowing rate for this sub-lease agreement based on an analysis of corporate bond yields with a credit rating similar to the Company.

Variable lease cost primarily relates to common area maintenance charges for its real estate leases, which is dependent on usage. Because the rate implicit in each lease is not readily determinable, the Company uses its incremental borrowing rate to determine the present value of the lease payments. As noted in “Note 11 - Related Party Transactions,” the Company entered into an agreement with the Significant Investor in February 2019 whereby the Significant Investor lent its credit and creditworthiness to the Company which applied to the Company’s leases that transitioned upon the adoption of ASC 842. At the time of adoption, the Company determined the incremental borrowing rates for its leases by adjusting the observable risk-free interest rate with a credit risk premium corresponding to the Significant Investor’s credit rating.

The following table summarizes the cash paid for operating lease liabilities and the lease costs recognized in the statements of operations:

	Year Ended December 31,
	2020		2019
Cash paid for operating lease liabilities	$	3,002	$	1,527
Operating lease cost		3,069		1,396
Variable lease cost		216		683

Information related to the Company’s ROU assets and related lease liabilities was as follows (in thousands except for remaining lease term and discount rate):

	December 31, 2020			December 31, 2019
Current operating lease liabilities	$	2,667		$	2,483
Non-current operating lease liabilities		9,577			12,244
Weighted average remaining lease term in years		4.1			5.1
Weighted average discount rate		3.8	%		3.8	%

Maturities of lease liabilities as of December 31, 2020 were as follows (in thousands):

	Operating
	Lease
Year Ending December	Commitments
2021	$	3,086
2022		3,172
2023		3,261
2024		3,008
2025		733
Thereafter		—
Total		13,260
Less imputed interest		(1,016	)
Total lease liabilities	$	12,244

Employee Benefit Plan

The Company sponsors a 401(k) defined contribution plan for its employees. This plan provides for tax-deferred salary deductions for all employees. Employee contributions are voluntary. Employees may contribute up to 100% of their annual compensation to this plan, as limited by an annual maximum amount as determined by the IRS. The Company does not make matching contributions under its 401(k) plan.

Legal Proceedings

The Company, from time to time, may be party to litigation arising in the ordinary course of business. The Company was not subject to any material legal proceedings during the years ended December 31, 2020 and 2019, and, to the best of its knowledge, no material legal proceedings are currently pending or threatened.

Indemnification

The Company enters into standard indemnification agreements in the ordinary course of business. Pursuant to these arrangements, the Company indemnifies, holds harmless and agrees to reimburse the indemnified parties for losses suffered or incurred by the indemnified party, in connection with any trade secret, copyright, patent or other intellectual property infringement claim by any third party with respect to its technology. The term of these indemnification agreements is generally perpetual any time after the execution of the agreement. The maximum potential amount of future payments the Company could be required to make under these arrangements is not determinable. The Company has never incurred costs to defend lawsuits or settle claims related to these indemnification agreements. As a result, the Company believes the fair value of these agreements is not material.

The Company has also entered into indemnification agreements with its directors and officers that may require the Company to indemnify its directors and officers against liabilities that may arise by reason of their status or service as directors or officers to the fullest extent permitted by Delaware corporate law. The Company currently has directors’ and officers’ insurance.

Fair Value Measurement (Tables)

12 Months Ended

Dec. 31, 2020

Fair Value Disclosures [Abstract]

Summary of Investments Measured and Recognized at Fair Value

The following tables set forth the fair value of the Company’s financial assets, which consist of investments measured and recognized at fair value (in thousands):

		December 31, 2020
	Fair Value Hierarchy Level	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses			Fair Value
Assets
Financial assets included within cash and cash equivalents:
Money market funds	Level 1	$	135,257	$	—	$	—		$	135,257
U.S. Treasury securities	Level 1		73,494		1		—			73,495
U.S. government agency securities	Level 2		30,783		—		(1	)		30,782
Financial assets included within short-term investments:
U.S. Treasury securities	Level 1		71,795		2		—			71,797
Corporate bonds	Level 2		6,876		1		—			6,877
Commercial paper	Level 2		2,997		—		—			2,997
U.S. government agency securities	Level 2		43,495		23		—			43,518
Total		$	364,697	$	27	$	(1	)	$	364,723

		December 31, 2019
	Fair Value Hierarchy Level	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses			Fair Value
Assets
Financial assets included within cash and cash equivalents:
Money market funds	Level 1	$	12,854	$	—	$	—		$	12,854
Commercial paper	Level 2		21,677		—		(2	)		21,675
Financial assets included within short-term investments:
U.S. Treasury securities	Level 1		66,244		48		—			66,292
Corporate bonds	Level 2		39,953		3		—			39,956
Commercial paper	Level 2		74,507		—		(9	)		74,498
U.S. government agency securities	Level 2		7,995		2		—			7,997
Financial assets included within long-term investments:
U.S. government agency securities	Level 2		11,974		—		(1	)		11,973
Total		$	235,204	$	53	$	(12	)	$	235,245

Summary of Contractual Maturities of Cash and Investments

The following table presents the contractual maturities of the Company’s cash and investments as of December 31, 2020 (in thousands):

	December 31, 2020
Due in less than one year	$	364,723
Due in more than one year		—
Total	$	364,723

License Agreements

12 Months Ended

Dec. 31, 2020

Organization Consolidation And Presentation Of Financial Statements [Abstract]

License Agreements

Note 5. License Agreements

Adimab Agreement

In January 2017, the Company entered into an option and license agreement with Adimab LLC (Adimab) pursuant to which the Company acquired a non-exclusive license to conduct research to evaluate certain Adimab antibodies in the context of the Company’s proprietary platform constructs directed to selected targets, and an option to be granted a non-exclusive license to develop and commercialize antibody products incorporating or derived from such Adimab antibodies. The Company may exercise such option on a research program-by-research program basis during a specified period after the expiration of the discovery and evaluation term. The Company is obligated to pay license fees of up to approximately $1.0 million in the aggregate to Adimab under this agreement during the evaluation term. Upon exercise of the Company’s option for an antibody covered by the agreement, it will be required to pay additional amounts aggregating up to either $7.4 million or $16.0 million per product incorporating each such antibody upon the option exercise and subsequent achievement of specified development and regulatory milestones, depending on the nature of the Adimab antibody incorporated in such product. In addition, the Company is obligated to pay Adimab either low or mid single-digit royalties based on net sales of each optioned antibody by the Company and its affiliates and sublicensees, subject to specified reductions. During the years ended December 31, 2020, 2019 and 2018, the Company recognized $0.2 million, $0.1 million and $0.3 million, respectively, in research and development expenses incurred under this agreement in its statements of operations.

LakePharma Agreement

In May 2018, the Company and LakePharma, Inc. (LakePharma) entered into an agreement for screening services aimed towards discovering certain antibodies. If the Company elects to enter into a license to develop and commercialize one or more of the antibodies discovered under this agreement, the Company will be obligated to make payments to LakePharma aggregating up to $10.3 million based on achieving specified development and regulatory milestones for each such antibody. During the years ended December 31, 2020, 2019 and 2018, the Company recognized $0.3 million, $0.1 million and $0.3 million, respectively, in research and development expenses incurred under this agreement in its statements of operations.

AbCellera Agreement

In September 2020, the Company entered into a multi-year, multi-target strategic research and license agreement with AbCellera Biologics Inc. (AbCellera) to facilitate the discovery and development of novel IgM antibodies. The Company may exercise an option to obtain ownership of all rights, title, and interests in the antibodies discovered and developed under the agreement for a selected target. Upon exercise of the option, the Company may be required to pay research and development fees, amounts related to achievement of downstream milestones, and royalties on net sales.

University of Texas Agreement

In October 2020, the Company entered into a multi-year patent and materials license agreement with the Board of Regents of the University of Texas System on behalf of the University of Texas Health Science Center at Houston for certain antibodies against the SARS-CoV-2 virus. Under the terms of the agreement, the Company is obligated to pay an upfront payment of $0.1 million, an annual license fee of up to $0.1 million, research and development fees aggregating up to $2.8 million upon the achievement of clinical and regulatory milestones and single digit royalties on future net sales of antibody products stemming from this agreement. During the year ended December 31, 2020, the Company recognized $0.1 million in research and development expenses incurred under this agreement in its statements of operations.

AvantGen Agreement

In December 2020, the Company entered into a multi-year patent and license agreement with AvantGen Inc. for certain antibodies against the SARS-CoV-2 virus. Under the terms of the agreement, the Company is obligated to pay an upfront payment of $0.2 million, an annual fee of up to $0.3 million upon the first and second anniversaries of the agreement, research and development fees aggregating up to $8.4 million upon the achievement of clinical and regulatory milestones and single digit royalties on future net sales of antibody products stemming from this agreement. During the year ended December 31, 2020, the Company recognized $0.2 million in research and development expenses incurred under this agreement in its statements of operations.

Income Taxes - Summary of Gross Unrecognized Tax Benefits (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Income Tax Disclosure [Abstract]
Beginning balance	$ 1,820	$ 1,113	$ 665
Decreases for tax positions related to prior years	(495)
Additions for tax positions related to current year	1,104	707	448
Ending balance	$ 2,429	$ 1,820	$ 1,113

Selected Quarterly Financial Data (Unaudited)

12 Months Ended

Dec. 31, 2020

Quarterly Financial Information Disclosure [Abstract]

Selected Quarterly Financial Data (Unaudited)

13. Selected Quarterly Financial Data (Unaudited)

The following tables provide the selected quarterly financial data for the years ended December 31, 2020 and 2019 (in thousands, except share and per share data):

	2020
	First Quarter			Second Quarter			Third Quarter			Fourth Quarter
Statements of Operations Data:
Operating expenses:
Research and development	$	14,583		$	15,019		$	15,829		$	19,599
General and administrative		3,990			4,388			4,732			5,140
Total operating expenses		18,573			19,407			20,561			24,739
Loss from operations		(18,573	)		(19,407	)		(20,561	)		(24,739	)
Other income (expense), net		949			568			291			117
Net loss	$	(17,624	)	$	(18,839	)	$	(20,270	)	$	(24,622	)
Net loss per share, basic and diluted	$	(0.58	)	$	(0.62	)	$	(0.66	)	$	(0.79	)
Weighted-average common shares outstanding, basic and diluted		30,491,463			30,551,736			30,646,729			31,298,264

	2019
	First Quarter			Second Quarter			Third Quarter			Fourth Quarter
Statements of Operations Data:
Operating expenses:
Research and development	$	5,912		$	8,303		$	8,279		$	12,763
General and administrative		1,445			2,228			2,394			3,174
Total operating expenses		7,357			10,531			10,673			15,937
Loss from operations		(7,357	)		(10,531	)		(10,673	)		(15,937	)
Other income (expense), net		(113	)		(145	)		501			1,122
Net loss	$	(7,470	)	$	(10,676	)	$	(10,172	)	$	(14,815	)
Net loss per share, basic and diluted	$	(16.86	)	$	(19.08	)	$	(2.41	)	$	(0.49	)
Weighted-average common shares outstanding, basic and diluted		443,118			559,671			4,222,259			30,478,980

Organization - Additional Information (Details) $ / shares in Units, $ in Thousands			1 Months Ended	12 Months Ended
	Dec. 11, 2020 USD ($) $ / shares shares	Sep. 20, 2019 USD ($) $ / shares shares	Aug. 31, 2019	Dec. 31, 2020 USD ($)	Dec. 31, 2019 USD ($) shares
Subsidiary Sale Of Stock [Line Items]
Reverse stock split ratio			6.6084
Reverse stock split ratio, description				6.6084-for-1
Proceeds from IPO, net of underwriting discounts and commission and offering costs \| $					$ 187,162
Pre-funded warrant, exercise price \| $ / shares	$ 0.01
Proceeds from common stock issuance \| $					11
Accumulated deficit \| $				$ 188,560	$ 107,205
Cash, and investments \| $				$ 366,300
Non-voting Common Stock
Subsidiary Sale Of Stock [Line Items]
Conversion of convertible preferred stock into common stock, shares		6,431,205			6,431,205
Common Stock
Subsidiary Sale Of Stock [Line Items]
Common stock, shares issued					7,566
Conversion of convertible preferred stock into common stock, shares		10,787,861			10,787,861
IPO
Subsidiary Sale Of Stock [Line Items]
Common stock, shares issued		12,578,125
Common stock, price per share \| $ / shares		$ 16.00
Common stock, exercised by underwriters		1,640,625
Proceeds from IPO, net of underwriting discounts and commission and offering costs \| $		$ 183,000
IPO \| Common Stock
Subsidiary Sale Of Stock [Line Items]
Common stock, shares issued					12,578,125
Underwritten Public Offering
Subsidiary Sale Of Stock [Line Items]
Common stock, exercised by underwriters	333,333
Pre-funded warrant, exercise price \| $ / shares	$ 0.01
Offering costs \| $	$ 14,600
Proceeds from common stock issuance \| $	$ 215,400
Underwritten Public Offering \| Pre-funded Warrant
Subsidiary Sale Of Stock [Line Items]
Common stock, price per share \| $ / shares	$ 89.99
Pre-funded warrants to purchase an additional shares of common stock	1,334,332
Pre-funded warrant, exercise price \| $ / shares	$ 0.01
Underwritten Public Offering \| Common Stock
Subsidiary Sale Of Stock [Line Items]
Common stock, shares issued	1,221,224
Common stock, price per share \| $ / shares	$ 90.00

Stock-Based Compensation - Summary of Stock-Based Compensation Expense (Details) - 2010 Plan, 2018 Plan and ESPP - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Total stock-based compensation expense	$ 8,454	$ 1,014	$ 183
Research and Development
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Total stock-based compensation expense	4,160	522	51
General and Administrative
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Total stock-based compensation expense	$ 4,294	$ 492	$ 132

Fair Value Measurement - Summary of Investments Measured and Recognized at Fair Value (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Amortized Cost	$ 364,697	$ 235,204
Gross Unrealized Gains	27	53
Gross Unrealized Losses	(1)	(12)
Fair Value	364,723	235,245
Fair Value, Recurring \| Financial Assets Included Within Cash and Cash Equivalents \| U.S. Treasury Securities \| Level 1
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Financial assets included within cash and cash equivalents, Amortized Cost	73,494
Financial assets included within cash and cash equivalents, Gross Unrealized Gains	1
Financial assets included within cash and cash equivalents, Fair Value	73,495
Fair Value, Recurring \| Financial Assets Included Within Cash and Cash Equivalents \| Money Market Funds \| Level 1
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Financial assets included within cash and cash equivalents, Amortized Cost	135,257	12,854
Financial assets included within cash and cash equivalents, Fair Value	135,257	12,854
Fair Value, Recurring \| Financial Assets Included Within Cash and Cash Equivalents \| Commercial Paper \| Level 2
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Financial assets included within cash and cash equivalents, Amortized Cost		21,677
Financial assets included within cash and cash equivalents, Gross Unrealized Losses		(2)
Financial assets included within cash and cash equivalents, Fair Value		21,675
Fair Value, Recurring \| Financial Assets Included Within Cash and Cash Equivalents \| U.S. Government Agency Securities \| Level 2
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Financial assets included within cash and cash equivalents, Amortized Cost	30,783
Financial assets included within cash and cash equivalents, Gross Unrealized Losses	(1)
Financial assets included within cash and cash equivalents, Fair Value	30,782
Fair Value, Recurring \| Financial Assets Included Within Short-Term Investments \| U.S. Treasury Securities \| Level 1
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Financial assets included within short-term/long-term investments, Amortized Cost	71,795	66,244
Financial assets included within short-term/long-term investments, Gross Unrealized Gains	2	48
Financial assets included within short-term/long-term investments, Fair Value	71,797	66,292
Fair Value, Recurring \| Financial Assets Included Within Short-Term Investments \| Corporate Bonds \| Level 2
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Financial assets included within short-term/long-term investments, Amortized Cost	6,876	39,953
Financial assets included within short-term/long-term investments, Gross Unrealized Gains	1	3
Financial assets included within short-term/long-term investments, Fair Value	6,877	39,956
Fair Value, Recurring \| Financial Assets Included Within Short-Term Investments \| Commercial Paper \| Level 2
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Financial assets included within short-term/long-term investments, Amortized Cost	2,997	74,507
Financial assets included within short-term/long-term investments, Gross Unrealized Losses		(9)
Financial assets included within short-term/long-term investments, Fair Value	2,997	74,498
Fair Value, Recurring \| Financial Assets Included Within Short-Term Investments \| U.S. Government Agency Securities \| Level 2
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Financial assets included within short-term/long-term investments, Amortized Cost	43,495	7,995
Financial assets included within short-term/long-term investments, Gross Unrealized Gains	23	2
Financial assets included within short-term/long-term investments, Fair Value	$ 43,518	7,997
Fair Value, Recurring \| Financial Assets Included Within Long-Term Investments \| U.S. Government Agency Securities \| Level 2
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Financial assets included within short-term/long-term investments, Amortized Cost		11,974
Financial assets included within short-term/long-term investments, Gross Unrealized Losses		(1)
Financial assets included within short-term/long-term investments, Fair Value		$ 11,973

Fair Value Measurement - Additional Information (Details) - Instrument	Dec. 31, 2020	Dec. 31, 2019
Fair Value Disclosures [Abstract]
Number of financial instruments classified as level 3	0	0

Income Taxes (Tables)

12 Months Ended

Dec. 31, 2020

Income Tax Disclosure [Abstract]

Reconciliation of Statutory Federal Income Tax Rate

The following is a reconciliation of the statutory federal income tax rate to the Company’s effective tax rate:

	Year Ended December 31,
	2020			2019			2018
Federal tax (benefit) at statutory rate		21.0	%		21.0	%		21.0	%
State tax (benefit), net of federal benefit		9.4			6.7			5.5
Permanent differences and other		(0.0	)		(0.4	)		(0.8	)
Research and development credits		4.8			4.3			5.4
Provision to return adjustments		—			(2.8	)		—
Stock-based compensation		1.7			—			—
Change in valuation allowance		(36.9	)		(28.8	)		(31.1	)
Effective income tax rate		—	%		—	%		—	%

Schedule of Deferred Tax Assets and Liabilities

Deferred tax assets and liabilities consist of the following (in thousands):

	December 31,
	2020			2019
Deferred tax assets:
Net operating loss carryforwards	$	38,739		$	15,650
Accrued liabilities and reserves		1,623			716
Stock-based compensation		1,434			253
Intangible assets		9,792			10,435
Operating lease liability		3,427			4,121
Research and development credits		10,471			4,991
Total deferred tax assets		65,486			36,166
Deferred tax liabilities:
Property and equipment		(269	)		(167	)
Right-of-use assets		(3,243	)		(3,956	)
Total deferred tax liabilities		(3,512	)		(4,123	)
Valuation allowance		(61,974	)		(32,043	)
Net deferred tax assets	$	—		$	—

Summary of Gross Unrecognized Tax Benefits

The following table summarizes the activity related to the Company’s gross unrecognized tax benefits (in thousands):

	December 31,
	2020			2019		2018
Beginning balance	$	1,820		$	1,113	$	665
Decreases for tax positions related to prior years		(495	)		—		—
Additions for tax positions related to current year		1,104			707		448
Ending balance	$	2,429		$	1,820	$	1,113

Fair Value Measurement

12 Months Ended

Dec. 31, 2020

Fair Value Disclosures [Abstract]

Fair Value Measurement

Note 3. Fair Value Measurement

The Company applies fair value accounting for all financial assets and liabilities and non-financial assets and liabilities that are recognized or disclosed at fair value in the financial statements on a recurring basis. Fair value is an exit price, representing the amount that would be received to sell an asset or paid to transfer a liability in an orderly transaction between market participants. As such, fair value is a market-based measurement that should be determined based on assumptions that market participants would use in pricing an asset or liability. As a basis for considering such assumptions, a three-tier fair value hierarchy has been established, which prioritizes the inputs used in measuring fair value as follows:

Level 1—Observable inputs, such as quoted prices in active markets for identical assets or liabilities at the measurement date.

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 which reflect management’s best estimate of what market participants would use in pricing the asset or liability at the measurement date. Consideration is given to the risk inherent in the valuation technique and the risk inherent in the inputs to the model.

In determining fair value, the Company utilizes valuation techniques that maximize the use of observable inputs and minimize the use of unobservable inputs to the extent possible as well as considers counterparty credit risk in its assessment of fair value.

Financial instruments classified within Level 2 of the fair value hierarchy are valued based on other observable inputs, including broker or dealer quotations or alternative pricing sources. When quoted prices in active markets for identical assets or liabilities are not available, the Company relies on non-binding quotes from its investment managers, which are based on proprietary valuation models of independent pricing services. These models generally use inputs such as observable market data, quoted market prices for similar instruments, or historical pricing trends of a security relative to its peers. To validate the fair value determination provided by its investment managers, the Company reviews the pricing movement in the context of overall market trends and trading information from its investment managers. In addition, the Company assesses the inputs and methods used in determining the fair value in order to determine the classification of securities in the fair value hierarchy. As of December 31, 2020 and 2019, there were no financial instruments classified as Level 3.

The following tables set forth the fair value of the Company’s financial assets, which consist of investments measured and recognized at fair value (in thousands):

		December 31, 2020
	Fair Value Hierarchy Level	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses			Fair Value
Assets
Financial assets included within cash and cash equivalents:
Money market funds	Level 1	$	135,257	$	—	$	—		$	135,257
U.S. Treasury securities	Level 1		73,494		1		—			73,495
U.S. government agency securities	Level 2		30,783		—		(1	)		30,782
Financial assets included within short-term investments:
U.S. Treasury securities	Level 1		71,795		2		—			71,797
Corporate bonds	Level 2		6,876		1		—			6,877
Commercial paper	Level 2		2,997		—		—			2,997
U.S. government agency securities	Level 2		43,495		23		—			43,518
Total		$	364,697	$	27	$	(1	)	$	364,723

		December 31, 2019
	Fair Value Hierarchy Level	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses			Fair Value
Assets
Financial assets included within cash and cash equivalents:
Money market funds	Level 1	$	12,854	$	—	$	—		$	12,854
Commercial paper	Level 2		21,677		—		(2	)		21,675
Financial assets included within short-term investments:
U.S. Treasury securities	Level 1		66,244		48		—			66,292
Corporate bonds	Level 2		39,953		3		—			39,956
Commercial paper	Level 2		74,507		—		(9	)		74,498
U.S. government agency securities	Level 2		7,995		2		—			7,997
Financial assets included within long-term investments:
U.S. government agency securities	Level 2		11,974		—		(1	)		11,973
Total		$	235,204	$	53	$	(12	)	$	235,245

The following table presents the contractual maturities of the Company’s cash and investments as of December 31, 2020 (in thousands):

	December 31, 2020
Due in less than one year	$	364,723
Due in more than one year		—
Total	$	364,723

- Definition

The entire disclosure for the fair value of financial instruments (as defined), including financial assets and financial liabilities (collectively, as defined), and the measurements of those instruments as well as disclosures related to the fair value of non-financial assets and liabilities. Such disclosures about the financial instruments, assets, and liabilities would include: (1) the fair value of the required items together with their carrying amounts (as appropriate); (2) for items for which it is not practicable to estimate fair value, disclosure would include: (a) information pertinent to estimating fair value (including, carrying amount, effective interest rate, and maturity, and (b) the reasons why it is not practicable to estimate fair value; (3) significant concentrations of credit risk including: (a) information about the activity, region, or economic characteristics identifying a concentration, (b) the maximum amount of loss the entity is exposed to based on the gross fair value of the related item, (c) policy for requiring collateral or other security and information as to accessing such collateral or security, and (d) the nature and brief description of such collateral or security; (4) quantitative information about market risks and how such risks are managed; (5) for items measured on both a recurring and nonrecurring basis information regarding the inputs used to develop the fair value measurement; and (6) for items presented in the financial statement for which fair value measurement is elected: (a) information necessary to understand the reasons for the election, (b) discussion of the effect of fair value changes on earnings, (c) a description of [similar groups] items for which the election is made and the relation thereof to the balance sheet, the aggregate carrying value of items included in the balance sheet that are not eligible for the election; (7) all other required (as defined) and desired information.

+ References + Details

Subsequent Events

12 Months Ended

Dec. 31, 2020

Subsequent Events [Abstract]

Subsequent Events

Note 14. Subsequent Events

In January 2021, the Company entered into an exclusive license agreement with Medivir AB (Medivir) through which the Company received global, exclusive development and commercialization rights for birinapant, a clinical-stage Second Mitochondrial-derived Activator of Caspases (SMAC) mimetic. Under terms of the agreement, the Company made an upfront payment of $1.0 million upon signing the agreement, to be followed by an additional $1.5 million payment when birinapant is included by the Company in its clinical Phase I studies. Under the terms of the agreement, should birinapant be successfully developed and approved, the Company is obligated to make milestone payments up to a total of approximately $350.0 million, plus tiered royalties from the mid-single digits up to mid-teens on net sales.

In March 2021, the Company entered into a lease agreement for additional office and laboratory space in Mountain View, California which commenced in March 2021 and expires in August 2023. Total future rent payments under the agreement amount to approximately $1.9 million.

In March 2021, the Company entered into a license agreement with Ablexis, Inc. through which the Company received rights to use AlivaMab^® Mouse technology for antibody drug discovery. Under terms of the license agreement, the Company will pay annual fees, and per product developed, royalty payments based on a percentage of sales and milestone payments based on milestone events set forth in the agreement.

Pre Funded Warrants - Additional Information (Details) $ / shares in Units, $ in Thousands		12 Months Ended
	Dec. 11, 2020 USD ($) RelatedParty $ / shares shares	Dec. 31, 2019 USD ($) shares	Dec. 31, 2020 shares
Class Of Warrant Or Right [Line Items]
Pre-funded warrant, exercise price \| $ / shares	$ 0.01
Proceeds from common stock issuance \| $		$ 11
Maximum allowed holding percentage of shares after exercise of warrants	9.99%
Maximum allowed combined voting percentage of shares after exercise of warrants	9.99%
Maximum allowed percentage of pre-funded warrants to exercise	19.99%
Minimum notice term to increase or decrease the holding percentage of pre-funded warrants	61 days
Number of warrants exercised \| shares			0
Common Stock
Class Of Warrant Or Right [Line Items]
Issuance of common stock, shares \| shares		7,566
Underwritten Public Offering
Class Of Warrant Or Right [Line Items]
Common stock, exercised by underwriters \| shares	333,333
Pre-funded warrant, exercise price \| $ / shares	$ 0.01
Offering costs \| $	$ 14,600
Proceeds from common stock issuance \| $	$ 215,400
Underwritten Public Offering \| Common Stock
Class Of Warrant Or Right [Line Items]
Issuance of common stock, shares \| shares	1,221,224
Common stock, price per share \| $ / shares	$ 90.00
Underwritten Public Offering \| Pre-funded Warrant
Class Of Warrant Or Right [Line Items]
Warrants to purchase an additional shares of common stock \| shares	1,334,332
Common stock, price per share \| $ / shares	$ 89.99
Pre-funded warrant, exercise price \| $ / shares	$ 0.01
Number of related party to warrant issued \| RelatedParty	2

Net Loss Per Share Attributable to Common Stockholders - Schedule of Computation of Basic and Diluted Net Loss Per Share (Details) - USD ($)
$ / shares in Units, $ in Thousands

3 Months Ended

12 Months Ended

Dec. 31, 2020

Sep. 30, 2020

Jun. 30, 2020

Mar. 31, 2020

Dec. 31, 2019

Sep. 30, 2019

Jun. 30, 2019

Mar. 31, 2019

Dec. 31, 2020

Dec. 31, 2019

Dec. 31, 2018

Numerator:

Net loss

$ (24,622)

$ (20,270)

$ (18,839)

$ (17,624)

$ (14,815)

$ (10,172)

$ (10,676)

$ (7,470)

$ (81,355)

$ (43,133)

$ (22,711)

Denominator:

Weighted average common shares outstanding used to compute net loss per share, basic and diluted

31,298,264

30,646,729

30,551,736

30,491,463

30,478,980

4,222,259

559,671

443,118

30,748,280

^[1]

8,995,410

^[1]

438,074

^[1]

Net loss per share attributable to common stockholders

$ (0.79)

$ (0.66)

$ (0.62)

$ (0.58)

$ (0.49)

$ (2.41)

$ (19.08)

$ (16.86)

$ (2.65)

$ (4.80)

$ (51.84)

[1]	Includes shares of common stock into which Pre-Funded Warrants may be exercised. See Note 7 to our financial statements included in this Form 10-K.

- Definition

The portion of profit or loss for the period, net of income taxes, which is attributable to the parent.

+ References

+ Details