Sera Prognostics (SERA) 10-Q 9 Nov 21 2021 Q3 Quarterly report Financial data

Cover

Cover - shares	9 Months Ended
	Sep. 30, 2021	Nov. 05, 2021
Document Information [Line Items]
Document Type	10-Q
Document Quarterly Report	true
Document Period End Date	Sep. 30, 2021
Document Transition Report	false
Entity File Number	001-40606
Entity Registrant Name	SERA PROGNOSTICS, INC.
Entity Incorporation, State or Country Code	DE
Entity Tax Identification Number	26-1911522
Entity Address, Address Line One	2749 East Parleys Way
Entity Address, Address Line Two	Suite 200
Entity Address, City or Town	Salt Lake City
Entity Address, State or Province	UT
Entity Address, Postal Zip Code	84109
City Area Code	801
Local Phone Number	990-0520
Title of 12(b) Security	Class A Common Stock, $0.0001 par value per share
Trading Symbol	SERA
Security Exchange Name	NASDAQ
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Non-accelerated Filer
Entity Small Business	true
Entity Emerging Growth Company	true
Entity Ex Transition Period	false
Entity Shell Company	false
Entity Central Index Key	0001534969
Current Fiscal Year End Date	--12-31
Document Fiscal Year Focus	2021
Document Fiscal Period Focus	Q3
Amendment Flag	false
Class A common stock
Document Information [Line Items]
Entity Common Stock, Shares Outstanding		29,293,831
Class B common stock
Document Information [Line Items]
Entity Common Stock, Shares Outstanding		1,405,259

Condensed Balance Sheets (unaud

Condensed Balance Sheets (unaudited) - USD ($) $ in Thousands	Sep. 30, 2021	Dec. 31, 2020
Current assets:
Cash and cash equivalents	$ 82,479	$ 13,533
Marketable securities	37,498	0
Accounts receivable	35	2
Prepaid expenses and other current assets	2,327	198
Total current assets	122,339	13,733
Property and equipment, net	1,185	965
Long-term marketable securities	29,997	0
Other assets	168	98
Total assets	153,689	14,796
Current liabilities:
Accounts payable	1,270	441
Accrued and other current liabilities	2,062	1,577
Accrued interest on convertible note	0	996
Deferred rent, current portion	139	130
Capital lease obligation, current portion	72	69
Convertible promissory note, current portion	0	4,353
Loans payable, current portion	0	3,676
Total current liabilities	3,543	11,242
Deferred rent	35	139
Loans payable, net of current portion	0	348
Preferred stock warrant liability	0	474
Capital lease obligation, net of current portion	73	127
Total liabilities	3,651	12,330
Commitments and contingencies
Stockholders' equity (deficit):
Common stock, $0.0001 par value; 150,000,000 and 55,000,000 Class A shares authorized as of September 30, 2021 and December 31, 2020, respectively; 29,293,831 and 1,700,625 Class A shares issued and outstanding as of September 30, 2021 and December 31, 2020, respectively; 1,500,000 and 0 Class B shares authorized as of September 30, 2021 and December 31, 2020, respectively; 1,405,259 and 0 Class B shares issued and outstanding as of September 30, 2021 and December 31, 2020, respectively	3	0
Additional paid-in capital	304,044	5,889
Accumulated other comprehensive loss	(25)	0
Accumulated deficit	(153,984)	(131,459)
Total stockholders' equity (deficit)	150,038	(125,570)
Total liabilities, convertible preferred stock, and stockholders' equity (deficit)	153,689	14,796
Junior Convertible Preferred Stock
Convertible preferred stock:
Convertible preferred stock	0	77,844
Senior Convertible Preferred Stock
Convertible preferred stock:
Convertible preferred stock	$ 0	$ 50,192

Condensed Balance Sheets (una_2

Condensed Balance Sheets (unaudited) (Parenthetical) - USD ($) $ in Thousands	Sep. 30, 2021	Dec. 31, 2020
Junior Convertible Preferred Stock
Convertible preferred stock, par value (in usd per share)	$ 0.0001	$ 0.0001
Convertible preferred stock, shares authorized (in shares)	0	20,537,294
Convertible preferred stock, shares issued (in shares)	0	9,819,480
Convertible preferred stock, shares outstanding (in shares)	0	9,819,480
Convertible preferred stock, liquidation preference	$ 0	$ 78,916
Senior Convertible Preferred Stock
Convertible preferred stock, par value (in usd per share)	$ 0.0001	$ 0.0001
Convertible preferred stock, shares authorized (in shares)	0	12,320,844
Convertible preferred stock, shares issued (in shares)	0	5,737,440
Convertible preferred stock, shares outstanding (in shares)	0	5,737,440
Convertible preferred stock, liquidation preference	$ 0	$ 102,535
Class A common stock
Common stock, par value (in shares)	$ 0.0001	$ 0.0001
Common stock, shares authorized (in shares)	150,000,000	55,000,000
Common stock, shares issued (in shares)	29,293,831	1,700,625
Common stock, shares outstanding (in shares)	29,293,831	1,700,625
Class B common stock
Common stock, par value (in shares)	$ 0.0001	$ 0.0001
Common stock, shares authorized (in shares)	1,500,000	0
Common stock, shares issued (in shares)	1,405,259	0
Common stock, shares outstanding (in shares)	1,405,259	0

Condensed Statements of Operati

Condensed Statements of Operations and Comprehensive Loss (unaudited) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Income Statement [Abstract]
Revenue	$ 23	$ 5	$ 56	$ 19
Operating expenses:
Cost of revenue	10	3	23	8
Research and development	2,724	1,888	7,944	5,690
Selling and marketing	2,690	1,054	5,780	2,634
General and administrative	4,041	1,704	9,157	4,904
Total operating expenses	9,465	4,649	22,904	13,236
Loss from operations	(9,442)	(4,644)	(22,848)	(13,217)
Interest expense	(439)	(425)	(744)	(1,282)
Other income (expense), net	22	(3)	1,067	26
Net loss	$ (9,859)	$ (5,072)	$ (22,525)	$ (14,473)
Net loss per share, diluted (in usd per share)	$ (0.39)	$ (3.30)	$ (2.32)	$ (9.46)
Net loss per share, basic (in usd per share)	$ (0.39)	$ (3.30)	$ (2.32)	$ (9.46)
Weighted-average shares of common stock outstanding, diluted (In shares)	25,085,013	1,536,483	9,707,254	1,529,182
Weighted-average shares of common stock outstanding, basic (in shares)	25,085,013	1,536,483	9,707,254	1,529,182
Other comprehensive loss:
Unrealized loss on available-for-sale debt securities	$ (25)	$ 0	$ (25)	$ 0
Total other comprehensive loss	(25)	0	(25)	0
Comprehensive loss	$ (9,884)	$ (5,072)	$ (22,550)	$ (14,473)

Condensed Statements of Convert

Condensed Statements of Convertible Preferred Stock and Stockholders’ Equity (Deficit) (unaudited) - USD ($) $ in Thousands	Total	Common Stock (Class A and B)	Additional Paid-In Capital	Accumulated Other Comprehensive Loss	Accumulated Deficit	Senior Convertible Preferred Stock	Junior Convertible Preferred Stock
Balance at the beginning (in shares) at Dec. 31, 2019						4,546,024	9,819,480
Balance at the beginning at Dec. 31, 2019						$ 39,506	$ 77,844
Increase (Decrease) in Temporary Equity [Roll Forward]
Issuance of senior convertible preferred stock, net of issuance costs (in shares)						1,191,416
Issuance of senior convertible preferred stock, net of issuance costs						$ 10,704
Balance at the ending (in shares) at Mar. 31, 2020						5,737,440	9,819,480
Balance at the ending at Mar. 31, 2020						$ 50,210	$ 77,844
Balance at the beginning (in shares) at Dec. 31, 2019		1,525,119
Balance at the beginning at Dec. 31, 2019	$ (106,624)	$ 0	$ 4,987		$ (111,611)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of common stock upon exercise of stock options (in shares)		529
Issuance of common stock upon exercise of stock options	1		1
Stock-based compensation expense	135		135
Net loss	(4,696)				(4,696)
Balance at the ending (in shares) at Mar. 31, 2020		1,525,648
Balance at the ending at Mar. 31, 2020	(111,184)	$ 0	5,123		(116,307)
Balance at the beginning (in shares) at Dec. 31, 2019						4,546,024	9,819,480
Balance at the beginning at Dec. 31, 2019						$ 39,506	$ 77,844
Balance at the ending (in shares) at Sep. 30, 2020						5,737,440	9,819,480
Balance at the ending at Sep. 30, 2020						$ 50,192	$ 77,844
Balance at the beginning (in shares) at Dec. 31, 2019		1,525,119
Balance at the beginning at Dec. 31, 2019	(106,624)	$ 0	4,987		(111,611)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Total other comprehensive loss	0
Net loss	(14,473)
Balance at the ending (in shares) at Sep. 30, 2020		1,568,741
Balance at the ending at Sep. 30, 2020	(120,487)	$ 0	5,597		(126,084)
Balance at the beginning (in shares) at Mar. 31, 2020						5,737,440	9,819,480
Balance at the beginning at Mar. 31, 2020						$ 50,210	$ 77,844
Increase (Decrease) in Temporary Equity [Roll Forward]
Issuance of senior convertible preferred stock, net of issuance costs						$ 18
Balance at the ending (in shares) at Jun. 30, 2020						5,737,440	9,819,480
Balance at the ending at Jun. 30, 2020						$ 50,192	$ 77,844
Balance at the beginning (in shares) at Mar. 31, 2020		1,525,648
Balance at the beginning at Mar. 31, 2020	(111,184)	$ 0	5,123		(116,307)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stock-based compensation expense	201		201
Net loss	(4,705)				(4,705)
Balance at the ending (in shares) at Jun. 30, 2020		1,525,648
Balance at the ending at Jun. 30, 2020	(115,688)	$ 0	5,324		(121,012)
Balance at the ending (in shares) at Sep. 30, 2020						5,737,440	9,819,480
Balance at the ending at Sep. 30, 2020						$ 50,192	$ 77,844
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of common stock upon exercise of stock options (in shares)		43,093
Issuance of common stock upon exercise of stock options	78		78
Stock-based compensation expense	195		195
Total other comprehensive loss	0
Net loss	(5,072)				(5,072)
Balance at the ending (in shares) at Sep. 30, 2020		1,568,741
Balance at the ending at Sep. 30, 2020	(120,487)	$ 0	5,597		(126,084)
Balance at the beginning (in shares) at Dec. 31, 2020						5,737,440	9,819,480
Balance at the beginning at Dec. 31, 2020						$ 50,192	$ 77,844
Increase (Decrease) in Temporary Equity [Roll Forward]
Issuance of senior convertible preferred stock, net of issuance costs (in shares)						4,938,482
Issuance of senior convertible preferred stock, net of issuance costs						$ 60,307
Balance at the ending (in shares) at Mar. 31, 2021						10,675,922	9,819,480
Balance at the ending at Mar. 31, 2021						$ 110,499	$ 77,844
Balance at the beginning (in shares) at Dec. 31, 2020		1,700,625
Balance at the beginning at Dec. 31, 2020	(125,570)	$ 0	5,889	$ 0	(131,459)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Fair value of warrants to purchase common stock issued to Series E investor	1,071		1,071
Issuance of common stock upon exercise of stock options (in shares)		281,458
Issuance of common stock upon exercise of stock options	229		229
Stock-based compensation expense	239		239
Net loss	(6,359)				(6,359)
Balance at the ending (in shares) at Mar. 31, 2021		1,982,083
Balance at the ending at Mar. 31, 2021	(130,390)	$ 0	7,428	0	(137,818)
Balance at the beginning (in shares) at Dec. 31, 2020						5,737,440	9,819,480
Balance at the beginning at Dec. 31, 2020						$ 50,192	$ 77,844
Balance at the ending (in shares) at Sep. 30, 2021						0	0
Balance at the ending at Sep. 30, 2021						$ 0	$ 0
Balance at the beginning (in shares) at Dec. 31, 2020		1,700,625
Balance at the beginning at Dec. 31, 2020	(125,570)	$ 0	5,889	0	(131,459)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Conversion of preferred stock warrants to common stock warrants	$ 929
Issuance of common stock upon exercise of stock options (in shares)	449,204
Total other comprehensive loss	$ (25)
Net loss	(22,525)
Balance at the ending (in shares) at Sep. 30, 2021		30,699,090
Balance at the ending at Sep. 30, 2021	150,038	$ 3	304,044	(25)	(153,984)
Balance at the beginning (in shares) at Mar. 31, 2021						10,675,922	9,819,480
Balance at the beginning at Mar. 31, 2021						$ 110,499	$ 77,844
Increase (Decrease) in Temporary Equity [Roll Forward]
Issuance of senior convertible preferred stock, net of issuance costs (in shares)						3,115,657
Issuance of senior convertible preferred stock, net of issuance costs						$ 38,645
Balance at the ending (in shares) at Jun. 30, 2021						13,791,579	9,819,480
Balance at the ending at Jun. 30, 2021						$ 149,144	$ 77,844
Balance at the beginning (in shares) at Mar. 31, 2021		1,982,083
Balance at the beginning at Mar. 31, 2021	(130,390)	$ 0	7,428	0	(137,818)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of common stock upon exercise of stock options (in shares)		22,872
Issuance of common stock upon exercise of stock options	35		35
Stock-based compensation expense	864		864
Net loss	(6,307)				(6,307)
Balance at the ending (in shares) at Jun. 30, 2021		2,004,955
Balance at the ending at Jun. 30, 2021	(135,798)	$ 0	8,327	0	(144,125)
Increase (Decrease) in Temporary Equity [Roll Forward]
Conversion of preferred stock to common stock (in shares)						(13,791,579)	(9,819,480)
Conversion of preferred stock to common stock						$ (149,144)	$ (77,844)
Balance at the ending (in shares) at Sep. 30, 2021						0	0
Balance at the ending at Sep. 30, 2021						$ 0	$ 0
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Conversion of preferred stock to common stock (in shares)		4,687,500
Common stock issuance for initial public offering, net of issuance costs	66,612	$ 1	66,611
Conversion of preferred stock to common stock (in shares)		23,839,389
Conversion of preferred stock to common stock	226,992	$ 2	226,990
Conversion of preferred stock warrants to common stock warrants	929
Issuance of common stock upon exercise of stock options (in shares)		144,874
Issuance of common stock upon exercise of stock options	273		273
Stock warrant exercises (in shares)		22,372
Stock-based compensation expense	914		914
Total other comprehensive loss	(25)			(25)
Net loss	(9,859)				(9,859)
Balance at the ending (in shares) at Sep. 30, 2021		30,699,090
Balance at the ending at Sep. 30, 2021	$ 150,038	$ 3	$ 304,044	$ (25)	$ (153,984)

Condensed Statements of Conve_2

Condensed Statements of Convertible Preferred Stock and Stockholders’ Equity (Deficit) (unaudited) (Parenthetical) - USD ($) $ in Millions	3 Months Ended
	Jun. 30, 2021	Mar. 31, 2021	Jun. 30, 2020	Mar. 31, 2020
Series E Senior Convertible Preferred Stock
Issue price per share (in usd per share)	$ 12.46	$ 12.46
Stock issuance costs	$ 0.1	$ 0.1
Series D Senior Convertible Preferred Stock
Issue price per share (in usd per share)			$ 9.03	$ 9.03
Stock issuance costs			$ 0.5	$ 0.5

Condensed Statements of Cash Fl

Condensed Statements of Cash Flows (unaudited) - USD ($) $ in Thousands	3 Months Ended				9 Months Ended		12 Months Ended
	Sep. 30, 2021	Mar. 31, 2021	Sep. 30, 2020	Mar. 31, 2020	Sep. 30, 2021	Sep. 30, 2020	Dec. 31, 2020
Cash flows from operating activities
Net loss	$ (9,859)	$ (6,359)	$ (5,072)	$ (4,696)	$ (22,525)	$ (14,473)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation and amortization	100		200		514	693
Stock-based compensation					2,017	531
Non-cash interest expense					588	1,076
Gain on extinguishment of PPP loan	0		0		(1,050)	0
Other					32	13
Changes in operating assets and liabilities:
Accounts receivable					(33)	1
Prepaid expenses and other assets					(2,085)	0
Accounts payable					518	(166)
Deferred rent					(95)	(83)
Accrued and other current liabilities					(365)	(275)
Net cash used in operating activities					(22,484)	(12,683)
Cash flows from investing activities
Purchases of marketable securities					(67,572)	0
Purchases of property and equipment					(555)	(105)
Net cash used in investing activities					(68,127)	(105)
Cash flows from financing activities
Proceeds allocated to issuance of common stock warrants in connection with Series E					1,071	0
Proceeds from initial public offering of common stock, net of issuance costs					66,611	0
Proceeds from exercise of stock options					537	79
Proceeds from loan payable					0	1,050
Payment of convertible note payable					(4,494)	(1,667)
Payment of loan payable					(3,100)	0
Capital lease principal payments					(51)	(68)
Net cash provided by financing activities					159,557	10,080
Net increase (decrease) in cash and cash equivalents					68,946	(2,708)
Cash and cash equivalents at beginning of period		$ 13,533		$ 21,390	13,533	21,390	$ 21,390
Cash and cash equivalents at end of period	$ 82,479		$ 18,682		82,479	18,682	$ 13,533
Supplemental disclosure of cash flow information
Cash paid for interest					1,273	206
Supplemental disclosure of non-cash investing and financing information
Purchases of property and equipment in accounts payable and accruals					170	3
Series E senior convertible preferred stock offering costs prepaid and deferred in prior period and reclassified to Series E senior convertible preferred stock					26	0
Series D Senior Convertible Preferred Stock
Cash flows from financing activities
Proceeds from issuance of convertible preferred stock, net of issuance costs					0	10,686
Series E Senior Convertible Preferred Stock
Cash flows from financing activities
Proceeds from issuance of convertible preferred stock, net of issuance costs					$ 98,983	$ 0

Description of Business and Fin

Description of Business and Financial Condition	9 Months Ended
	Sep. 30, 2021
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Description of Business and Financial Condition	. Description of Business and Financial Condition Sera Prognostics, Inc. (the “Company”) is a women’s health diagnostic company utilizing its proprietary proteomics and bioinformatics platform to discover, develop, and commercialize biomarker tests with an initial focus on improving pregnancy outcomes. The Company was incorporated in the State of Delaware on January 17, 2008 and its operations are located in Salt Lake City, Utah, including a Clinical Laboratory Improvement Amendments (“CLIA”)-certified laboratory. Since its inception, the Company’s activities have consisted of performing research and development, conducting clinical studies, acquiring product rights, raising capital, establishing facilities, and organizing commercial operations to market the PreTRM test. Liquidity and Capital Resources The accompanying condensed financial statements have been prepared on a going concern basis, which contemplates the realization of assets and the satisfaction of liabilities and commitments in the normal course of business. The Company has incurred net losses and negative cash flows from operations since inception and had an accumulated deficit of $154.0 million as of September 30, 2021. The Company’s management expects the Company to incur significant additional operating losses and negative cash flows for the foreseeable future, principally as a result of the Company’s commercialization activities for the PreTRM test, and to support additional clinical and preclinical trials and anticipated research and development activities. The Company had no significant commercial product revenue for the three and nine months ended September 30, 2021 and has no recurring sources of licensing or other revenue. There can be no assurance that the Company will eventually achieve significant revenues or profitability to sustain operations, or if achieved, can sustain either on a continuing basis. If the Company is unable to achieve significant revenues or raise additional funds, when needed, it may not be able to continue the development or commercialization of its diagnostic products and could be required to delay, scale back, or abandon some or all of its development programs and other operations. No assurance can be given that the Company will be successful in raising the required capital on reasonable terms and at the required times, or at all. Any additional equity financing, if available to the Company, may not be available on favorable terms and may be dilutive to current stockholders, and any debt financing, if available, may involve restrictive covenants and dilutive financing instruments. The Company’s future operations are highly dependent on a combination of factors, including (i) the successful commercial launch and market acceptance of the PreTRM test; (ii) the success of clinical trials and other research and development programs; (iii) the development of competitive products by other biotechnology and laboratory companies; (iv) the Company’s ability to manage growth of the organization; (v) the Company’s ability to protect its intellectual property, technology, and products; and, ultimately (vi) the timely and successful completion of any additional financing. The principal sources of the Company’s working capital to date have been the proceeds from the sale and issuance of convertible preferred stock and convertible notes, bank loans, and the sale and issuance of Class A common stock in an initial public offering ("IPO"), which was completed in July 2021. See Note 10—Capital Structure for additional details about the IPO. As of September 30, 2021, the Company had approximately $82.5 million in cash and cash equivalents and $67.5 million of available-for-sale securities. See Note 3—Cash, Cash Equivalents and Marketable Securities. The Company believes that its existing financial resources are sufficient to continue operating activities at least 12 months from the issuance date of these unaudited condensed financial statements.

Significant Accounting Policies

Significant Accounting Policies	9 Months Ended
	Sep. 30, 2021
Accounting Policies [Abstract]
Significant Accounting Policies	Significant Accounting PoliciesThere have been no significant changes to the Company’s significant accounting policies during the three and nine months ended September 30, 2021 as compared to the significant accounting policies described in Note 2 of the “Notes to Financial Statements” in the Company’s audited financial statements included in its final prospectus dated as of July 14, 2021 and filed with the Securities and Exchange Commission (“SEC”) pursuant to Rule 424(b)(4) on July 16, 2021 (“Final Prospectus”). Basis of Presentation The accompanying unaudited condensed financial statements have been prepared in accordance with accounting principles generally accepted in the United States of America (“U.S. GAAP”) and applicable rules and regulations of the SEC regarding interim financial reporting. Certain information and note disclosures normally included in the financial statements prepared in accordance with U.S. GAAP have been condensed or omitted pursuant to such rules and regulations. As such, these unaudited condensed financial statements should be read in conjunction with the audited financial statements and accompanying notes as of and for the year ended December 31, 2020 included in the Final Prospectus. The unaudited interim condensed financial statements have been prepared on a basis consistent with the audited annual financial statements as of and for the year ended December 31, 2020, and, in the opinion of the Company’s management, reflect all adjustments, consisting solely of normal recurring adjustments, necessary for the fair presentation of the Company’s financial results. The results of the three and nine months ended September 30, 2021 are not necessarily indicative of the results to be expected for the full year ending December 31, 2021 or any other period. Any reference in these notes to applicable accounting guidance is meant to refer to the authoritative U.S. GAAP included in the Accounting Standards Codification (“ASC”), and Accounting Standards Updates (“ASU”) issued by the Financial Accounting Standards Board (“FASB”). Reverse Stock Split On June 30, 2021, the Company’s board of directors (the “Board of Directors”) approved a 1-for-2.079 reverse stock split of the Company’s common stock and redeemable convertible preferred stock, which was effective by amendment to the Company’s charter on July 7, 2021. The par value and authorized shares of the common stock and redeemable convertible preferred stock were not adjusted as a result of the reverse stock split. All issued and outstanding common stock, warrants, options to purchase common stock and per share amounts contained in the financial statements have been retroactively adjusted to give effect to the reverse stock split for all periods presented. Use of Estimates The preparation of the condensed financial statements in conformity with U.S. GAAP requires the Company’s management to make estimates and assumptions that affect the amounts reported in the condensed financial statements and accompanying notes. On an ongoing basis, the Company evaluates its estimates, including those related to the determination of fair value of its stock options, fair value of its common and preferred stock warrants, fair value of its marketable securities, valuation of deferred tax assets resulting from net operating losses, and useful lives of property and equipment. The Company bases these estimates on historical and anticipated results, trends, and various other assumptions that the Company believes are reasonable under the circumstances, including assumptions as to future events. Actual results could differ materially from those estimates. The COVID-19 pandemic and the rapidly evolving actions of governments, private sector participants and the public in an effort to contain the spread of the COVID-19 virus and address its impacts have intensified and have had significant direct and indirect effects on businesses and commerce. The extent to which the COVID-19 pandemic may impact the Company’s business, financial condition, cash flows, and results of operations, in particular, will depend on future developments that are highly uncertain, many of which are outside the Company’s control. Such developments include the availability and effectiveness of actions taken to contain or treat COVID-19, the ultimate geographic spread and duration of the pandemic, the extent and duration of a resurgence of the COVID-19 virus and variant strains thereof, new information concerning the severity of the COVID-19 virus, the effectiveness and intensity of measures to contain the COVID-19 virus and the economic impact of the pandemic and the reactions to it. Such developments, among others, depending on their nature, duration, and intensity, could have a significant adverse effect on the Company’s business, financial condition, cash flows, and results of operations. There were no significant estimates contained in the preparation of the Company’s condensed financial statements or impacts to the Company’s condensed financial statements for the three and nine months ended September 30, 2021 that were a direct result of the COVID-19 pandemic. The Company is not aware of any specific event or circumstance that would require an update to its estimates, judgments and assumptions or a revision of the carrying value of the Company’s assets or liabilities as of the date of the condensed financial statements. Recently Issued Accounting Pronouncements Not Yet Adopted In February 2016, the FASB issued ASU 2016-02, Leases (Topic 842). Under the new guidance, lessees will be required to recognize a lease liability and a right-of-use asset for all leases (with the exception of short-term leases) at the commencement date. The standard was effective for public entities for fiscal years beginning after December 15, 2018 and for private companies for fiscal years beginning after December 15, 2021. The Company is evaluating the effect that ASU 2016-02 will have on its interim financial statements and related disclosures. The Company is currently an emerging growth company and has elected to use the extended transition period for complying with new or revised accounting standards that have different effective dates for public and private companies. As such, the Company expects to adopt this new standard on January 1, 2022 and has not yet determined the effect of the standard on its ongoing financial reporting. In December 2019, the FASB issued ASU 2019-12, Income Taxes (Topic 740): Simplifying the Accounting for Income Taxes . This standard removes certain exceptions for investments, intra-period allocations and interim calculations, and adds guidance to reduce complexity in accounting for income taxes. This standard will be effective for the Company on January 1, 2022, with early adoption permitted. The Company is currently evaluating the potential impact this standard may have on its financial statements and disclosures. Other recent accounting pronouncements issued by the FASB (including its Emerging Issues Task Force), the American Institute of Certified Public Accountants, and the SEC did not, or are not believed by the Company’s management to, have a material impact on the Company’s financial position, results of operations or cash flows.

Cash, Cash Equivalents and Mark

Cash, Cash Equivalents and Marketable Securities	9 Months Ended
	Sep. 30, 2021
Cash and Cash Equivalents [Abstract]
Cash, Cash Equivalents and Marketable Securities	Cash, Cash Equivalents and Marketable Securities The Company has classified its marketable securities as available-for-sale. These securities are carried at fair value with unrealized gains and losses included in accumulated other comprehensive loss. Gains and losses on marketable security transactions are reported on the specific-identification method. The Company's cash, cash equivalents and marketable securities by major security type as of September 30, 2021 were as follows (in thousands): September 30, 2021 Amortized Cost Gross Unrealized Gains Gross Unrealized Losses Fair Value Cash and cash equivalents: Cash $ 330 $ — $ — $ 330 Money market funds 2,642 — — 2,642 Commercial paper 79,510 — (3) 79,507 Total cash and cash equivalents 82,482 — (3) 82,479 Current marketable securities: Commercial paper 30,992 — (4) 30,988 Corporate debt securities 6,513 — (3) 6,510 Total current marketable securities 37,505 — (7) 37,498 Long-term marketable securities: U.S. federal agency securities 25,797 — (13) 25,784 U.S. government securities 3,696 — (2) 3,694 Corporate debt securities 519 — — 519 Total long-term marketable securities 30,012 — (15) 29,997 Total cash, cash equivalents and marketable securities $ 149,999 $ — $ (25) $ 149,974 The Company had no marketable securities as of December 31, 2020. As of September 30, 2021, the Company had no available-for-sale debt securities that had been in a continuous unrealized loss position for a period greater than 12 months. The Company determined that no available-for-sale securities were other-than-temporarily impaired as of September 30, 2021. The Company's marketable securities classified by contractual maturities as of September 30, 2021 were as follows (in thousands): Amortized Cost Fair Value Due within one year $ 37,505 $ 37,498 Due after one year through five years 30,012 29,997 Total $ 67,517 $ 67,495

Property and Equipment

Property and Equipment	9 Months Ended
	Sep. 30, 2021
Property, Plant and Equipment [Abstract]
Property and Equipment	Property and Equipment The following table presents the components of property and equipment, net, as of September 30, 2021 and December 31, 2020 (in thousands): September 30, December 31, Laboratory equipment $ 4,615 $ 4,194 Computer equipment 1,009 767 Leasehold improvements 701 701 Software 373 373 Furniture and fixtures 309 292 Total property and equipment 7,007 6,327 Less accumulated depreciation and amortization (5,822) (5,362) Property and equipment, net $ 1,185 $ 965 As of September 30, 2021 and December 31, 2020, $3.0 million of the Company’s laboratory equipment was subject to capital leases, which had recorded accumulated amortization of $2.9 million and $2.6 million, respectively. Associated amortization expense, included with depreciation expense, for the three months ended September 30, 2021 and September 30, 2020 totaled $0.1 million and $0.2 million, respectively. Associated amortization expense for the nine months ended September 30, 2021 and September 30, 2020 totaled $0.3 million and $0.5 million, respectively. Depreciation and amortization expense was $0.1 million and $0.2 million for the three months ended September 30, 2021 and 2020, respectively. Depreciation and amortization expense was $0.5 million and $0.7 million for the nine months ended September 30, 2021 and 2020, respectively.

Accrued and Other Current Liabi

Accrued and Other Current Liabilities	9 Months Ended
	Sep. 30, 2021
Accounts Payable and Accrued Liabilities, Current [Abstract]
Accrued and Other Current Liabilities	Accrued and Other Current Liabilities The following table presents the components of accrued and other current liabilities as of September 30, 2021 and December 31, 2020 (in thousands): September 30, December 31, Accrued compensation $ 1,507 $ 996 Accrued paid time off 422 290 Bank loan final payment fee — 100 Other current liabilities 133 191 Total accrued and other current liabilities $ 2,062 $ 1,577

Other Income (Expense), net

Other Income (Expense), net	9 Months Ended
	Sep. 30, 2021
Other Income and Expenses [Abstract]
Other Income (Expense), net	Other Income (Expense), net The following table presents the components of other income (expense), net, for the three and nine months ended September 30, 2021 and 2020 (in thousands): Three Months Ended Nine Months Ended 2021 2020 2021 2020 Interest income $ 32 $ 5 $ 53 $ 39 Fair value remeasurements (9) (8) (15) (13) Gain on extinguishment of PPP loan — — 1,050 — Other losses, net (1) — (21) — Other income (expense), net $ 22 $ (3) $ 1,067 $ 26

Loans and Convertible Promissor

Loans and Convertible Promissory Notes	9 Months Ended
	Sep. 30, 2021
Debt Disclosure [Abstract]
Loans and Convertible Promissory Notes	Loans and Convertible Promissory Notes Bank Loan In 2014, through a Loan and Security Agreement (the “Loan Agreement”) with Pacific Western Bank (the “Bank”) the Company obtained a term loan for $10.0 million. The Loan Agreement, as amended, had a final repayment date of September 1, 2021. Repayment of amounts borrowed were paid in equal monthly installments of principal, plus all accrued interest. The loan bore interest, on the outstanding daily balance, equal to the greater of 1.0% above the Prime Rate then in effect, or 4.75%. In addition, the Loan Agreement required a Final Payment Fee (as defined in the Loan Agreement) equal to one-percent of the aggregate principal amount borrowed, or $0.1 million. In March 2021, the Company repaid the outstanding principal of $2.0 million, accrued interest of $6 thousand, and the Final Payment Fee of $0.1 million related to this loan. Convertible Promissory Note In February 2019, the Company authorized the issuance of a $6.4 million subordinated convertible promissory note (the “February 2019 Convertible Note”) to a current stockholder, bearing 12% interest and a maturity date of February 26, 2021, to provide liquidity and additional working capital. On February 15, 2021, the maturity date was extended to March 28, 2021. The February 2019 Convertible Note was convertible at the option of the holder into shares of Series D Convertible Preferred Stock at a conversion price equal to 80% of the issuance price of the Series D Convertible Preferred Stock of $9.03 per share. In July 2019, $1.9 million of the $6.4 million February 2019 Convertible Note’s principal and $0.1 million of accrued interest were converted into 277,507 shares of the Company’s Series D Preferred Stock. The conversion feature of the February 2019 Convertible Note met the requirements for separate accounting and was recognized as a liability at the measurement date fair value of $2.4 million, subject to remeasurement to fair value, with any changes in estimated fair value recognized as a component of other income (expense), net. A corresponding discount, which reduced the carrying value of the February 2019 Convertible Note, was also recorded. The unamortized discount was written off in proportion to the partial conversion, with the remaining discount accreted to interest expense until maturity. The Company recognized additional interest expense of $0.1 million and $0.6 million from accretion of the discount during the nine months ended September 30, 2021 and 2020, respectively. On March 24, 2021, the Company repaid the outstanding principal of $4.5 million and accrued interest of $1.1 million related to the February 2019 Convertible Note. Paycheck Protection Loan In April 2020, the Company obtained a $1.1 million loan through the Bank under the Paycheck Protection Program (“PPP”) under the Coronavirus Aid, Relief, and Economic Security Act (“CARES Act”), as amended. The loan’s purpose was to maintain payroll and make rent and utilities payments as specified under the terms of the PPP. Under the PPP, borrowers may apply for loan forgiveness if the funds are used for payroll costs, mortgage interest, rent, and utilities payments over a specified term following receipt of the loan funds. During the term of the agreement, the Company utilized the loan funds for forgivable purposes and applied for forgiveness. On June 26, 2021, the outstanding $1.1 million PPP loan was forgiven and removed from the Company’s balance sheet in the second quarter of 2021. As a result of the forgiveness of the PPP loan, a $1.1 million gain on extinguishment was recorded in other income (expense), net for the nine months ended September 30, 2021.

Fair Value Measurements

Fair Value Measurements	9 Months Ended
	Sep. 30, 2021
Fair Value Disclosures [Abstract]
Fair Value Measurements	Fair Value Measurements As of September 30, 2021 and December 31, 2020, the carrying amounts of the Company’s receivables, prepaid and other current assets, accounts payable, and accrued and other current liabilities approximate their fair values, principally due to the short-term nature of the assets and liabilities. The recorded values of the loan payable and capital leases approximate fair value as the interest rates approximate market interest rates. The Company follows a fair value hierarchy that prioritizes the inputs to valuation techniques used to measure fair value. Fair value is defined as an exit price, representing the amount that would be received to sell an asset or paid to transfer a liability in an orderly transaction between market participants. As such, fair value is a market-based measurement that should be determined based on assumptions that market participants would use in pricing an asset or liability. The three levels of the fair value hierarchy are as follows: Level 1 inputs are observable, quoted prices (unadjusted) in active markets for identical assets or liabilities that the Company can access at the measurement date. Level 2 inputs are observable inputs other than quoted prices included in Level 1 that are observable either directly or indirectly or 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 inputs are unobservable inputs in which there is little or no market data, which require the Company to develop its own assumptions. Concurrent with the Company's IPO, the outstanding preferred stock warrants were converted to common stock warrants. As such, there were no preferred stock warrants outstanding at September 30, 2021. Immediately prior to the conversion, the Company adjusted the fair value of the preferred stock warrants using the Black-Scholes option pricing model based on the publicly available fair value of the Company's common stock on the pricing date of the Company's IPO along with other significant unobservable inputs. The fair value of the preferred stock warrant liability was then reclassified to equity upon conversion. In prior periods, the Company’s convertible preferred stock warrant liability was valued using Level 3 inputs in a Black-Scholes option pricing model (see Note 12 — Warrants). The Company, utilizing a third-party valuation firm to assist with the estimation of the fair value of common stock, employed a hybrid method of option-pricing model (OPM) and Probability-Weighted Expected Return Method (“PWERM”). Under the hybrid OPM and PWERM approach, the per share value calculated under OPM and PWERM were weighted based on expected exit outcomes and the quality of the information specific to each allocation methodology to arrive at a final estimated fair value per share of the common stock before a discount for lack of marketability was applied. This model also calculated the fair value of the other classes of equity, including preferred shares. This estimated preferred stock value, along with other significant unobservable inputs, was an input into a Black-Scholes option pricing model, which calculated the fair value of the preferred stock warrant liability. The other significant unobservable inputs in this calculation were the remaining expected term, which considered the timing of a liquidation event that would net settle the awards before their contractual term expired, and the expected equity volatility, which is a statistical measure of the dispersion of returns for a given security. Volatility was determined based on select comparable public guideline companies in the same business sector. The following table summarizes the significant unobservable inputs used to value the Company’s preferred stock warrant liability: As of December 31, 2020 Range Weighted-Average Fair value per share of common stock $3.41 - $7.35 $ 4.56 Expected term (in years) 1.7 - 9.1 5.3 Expected volatility 59.5% - 72.5% 63.6% Significant increases (decreases) in the term would have resulted in significantly higher (lower) fair value measurements. Significant increases (decreases) in the volatility would have resulted in significantly higher (lower) fair value measurements. The following table shows the Company’s assets measured at fair value on a recurring basis by level within the fair value hierarchy (in thousands) as of September 30, 2021: Level 1 Level 2 Level 3 Assets: Cash equivalents: Money market funds $ 2,642 $ — $ — Commercial paper — 79,507 — Marketable securities: Commercial paper — 30,988 — Corporate debt securities — 7,029 — U.S. federal agency securities — 25,784 — U.S. government securities — 3,694 — Total assets $ 2,642 $ 147,002 $ — The following table shows the Company’s assets and liabilities measured at fair value on a recurring basis by level within the fair value hierarchy (in thousands) as of December 31, 2020: Level 1 Level 2 Level 3 Assets: Cash equivalents $ 13,533 $ — $ — Liabilities: Warrant liability — — 474 A table providing a roll forward of the fair value of the Company’s convertible preferred stock warrant liability for the nine months ended September 30, 2021 is included in Note 12 — Warrants.

Related Party Transactions

Related Party Transactions	9 Months Ended
	Sep. 30, 2021
Related Party Transactions [Abstract]
Related Party Transactions	Related Party TransactionsIn January 2017, Laboratory Corporation of America (“LabCorp”) and the Company entered into a strategic commercialization agreement contemporaneously with LabCorp’s participation in the Company’s sale of Series C Convertible Preferred Stock, par value $0.0001 per share. Under the agreement with LabCorp, amended in 2018, LabCorp is a non-exclusive distributor of the PreTRM test and performs certain sample collection, processing and shipping services, for a fee. The Company paid fees related to this agreement of less than $0.1 million for each of the three and nine-month periods ended September 30, 2021 and 2020. In July 2019, the Company entered into a consulting agreement with Blue Ox Healthcare Partners, LLC (“Blue Ox”) to advise the Company on development of strategies with the goal to obtain widespread insurance coverage for the PreTRM test. Contemporaneously with the consulting agreement, Blue Ox participated in the initial closing of the Series D Convertible Preferred Stock financing in July 2019 and appointed its designee to the Board of Directors. The Company paid consulting fees related to the consulting agreement of $0.3 million and $0.1 million for the three months ended September 30, 2021 and 2020, respectively, and $0.6 million and $0.3 million for the nine months ended September 30, 2021 and 2020, respectively. In June 2019, the Company entered into a master services agreement with Healthcore Inc., a wholly-owned subsidiary of Anthem Inc. (“Anthem”). This agreement covers a range of research projects, including Healthcore’s role as a contract research organization for the P rematurity R isk Assessment Combined With Clinical I nterventions for Improving Neonatal outco ME s (“PRIME”) study. The Company paid fees related to this agreement of $0.4 million and $0.1 million for the three months ended September 30, 2021 and 2020, respectively, and $1.1 million and $0.6 million for the nine months ended September 30, 2021 and 2020, respectively. In November 2020, the Company entered into a Laboratory Services Agreement with Anthem related to the PRIME study. This agreement provides a contracted rate for certain tests performed pursuant to the study. The Company recognized revenues related to this agreement of $17 thousand and $41 thousand for the three and nine months ended September 30, 2021, respectively. In February 2021, the Company entered into a Commercial Collaboration Agreement with Anthem and its affiliates (the “Commercial Collaboration Agreement”). The Commercial Collaboration Agreement provides defined reimbursement within a defined period for use of the PreTRM test within Anthem’s network of covered members. Pursuant to the Commercial Collaboration Agreement, Anthem will purchase a certain minimum number of tests for each of the first three years of the term of the Commercial Collaboration Agreement. Additionally, Anthem has agreed to pay a certain minimum amount per year for the first three years of the term of the Commercial Collaboration Agreement. The Company has also agreed to develop a sales, marketing, and customer service program, and to provide training and marketing to duly licensed physicians specializing in obstetrics and gynecology or family medicine, or licensed nurse midwives, at the reasonable request of Anthem. Anthem has further agreed to develop appropriate care management programs that incorporate the use of the PreTRM test. The Company and Anthem have also agreed to form a Joint Operating Committee to oversee the relationship, comprised of two voting members each from Anthem and the Company. The Company will submit monthly invoices to Anthem for the sale of the PreTRM test at the negotiated rates. Anthem has been participating in the Company’s PRIME study and at the conclusion of the PRIME study, under the Commercial Collaboration Agreement, the Company has agreed to enter into Anthem’s standard lab provider agreement. Unless earlier terminated due to breach, the Commercial Collaboration Agreement will remain in effect until the later of (a) the third anniversary of the effective date or (b) the date on which Anthem has purchased a fixed number of PreTRM tests as agreed by the parties. The Commercial Collaboration Agreement with Anthem is considered to be within the scope of ASC Topic 808, Collaborative Arrangements (“ASC 808”), as the parties are active participants and exposed to the risks and rewards of the collaborative activity. The Company determined the PreTRM tests to be a performance obligation for which Anthem is a customer and a unit of account within the scope of ASC 606. The associated transaction price is based on the contractual minimum number of tests and the agreed upon defined reimbursement amount per test. The transaction price was allocated to this single performance obligation, which will be recognized upon delivery of test results expected to occur over the term of the agreement. All other items promised to Anthem are immaterial in the context of the Commercial Collaboration Agreement. There were no material revenues or cash receipts related to the Commercial Collaboration Agreement for the three and nine months ended September 30, 2021.

Capital Structure

Capital Structure	9 Months Ended
	Sep. 30, 2021
Stockholders' Equity Note [Abstract]
Capital Structure	Capital StructureOn July 19, 2021, the Company completed its IPO and issued 4,687,500 shares of its Class A common stock at a price of $16.00 per share for net proceeds of approximately $66.6 million, after deducting underwriting discounts and commissions and offering expenses payable by the Company. In connection with the IPO, all shares of convertible preferred stock converted into 22,434,130 shares of Class A common stock and 1,405,259 shares of Class B common stock. Common Stock The Company has two authorized classes of common stock, Class A and Class B. The rights of the holders of Class A and Class B common stock are identical, except with respect to voting and conversion. Each share of Class A common stock is entitled to one vote and shares of Class B common stock are non-voting. Each share of Class B common stock may be converted at any time to one share of Class A common stock at the option of its holder, subject to the ownership limitations provided for in the Company's amended and restated certificate of incorporation. The following shares of Class A common stock were reserved for future issuance: September 30, 2021 December 31, 2020 Senior convertible preferred stock — 5,737,440 Junior convertible preferred stock — 9,819,480 Shares issuable under convertible note — 665,699 Warrants to purchase convertible preferred stock — 81,543 Warrants to purchase Class A common stock 2,788,484 2,019,590 Options to purchase Class A common stock 6,018,350 4,096,722 Class A common stock available for future grants under the 2011 Equity Incentive Plan 668,772 388,505 Class A common stock available for future grants under the 2021 Equity Incentive Plan 3,480,549 — Class A common stock available for future grants under the 2021 Employee Stock Purchase Plan 305,089 — Total 13,261,244 22,808,979 As of September 30, 2021, all deferred offering costs related to the Company's IPO, totaling $3.1 million, had been reclassified to additional paid-in capital. As of December 31, 2020, approximately $26 thousand of deferred offering costs related to an equity offering were recorded within other assets. Convertible Preferred Stock In connection with the IPO, all shares of convertible preferred stock converted into 22,434,130 shares of Class A common stock and 1,405,259 shares of Class B common stock. No new convertible preferred stock has been issued since the IPO, and as such, there was no convertible preferred stock outstanding as of September 30, 2021. Authorized, issued and outstanding convertible preferred stock and its principal terms as of December 31, 2020 were as follows (in thousands, except share and per share amounts): Series Shares Shares Issued Original Aggregate Proceeds, Series A-1 Junior Preferred Stock 1,390 667 $ 2,079.00 $ 1,390 $ 1,390 Series A-2 Junior Preferred Stock 7,941,499 3,803,878 5.20 19,771 19,595 Series B-1 Junior Preferred Stock 2,060,000 961,994 5.20 5,000 4,914 Series B-2 Junior Preferred Stock 5,012,500 2,404,995 8.32 20,000 19,984 Series C-1 Junior Preferred Stock 5,521,905 2,647,946 12.38 32,755 32,653 Series C-2 Junior Preferred Stock 1,510,000 — 17.22 — — Series D Senior Preferred Stock 12,320,844 5,737,440 9.03 102,535 50,415 Total Convertible Preferred Stock 34,368,138 15,556,920 $ 181,451 $ 128,951 In connection with various preferred stock financings, the Company issued warrants to purchase common stock and warrants to purchase preferred stock. See Note 12 — Warrants for additional details.

Stock-Based Compensation

Stock-Based Compensation	9 Months Ended
	Sep. 30, 2021
Share-based Payment Arrangement [Abstract]
Stock-Based Compensation	Stock-Based Compensation Equity Incentive Plans In November 2011, the Company established the 2011 Employee, Director and Consultant Equity Incentive Plan (the “2011 Plan”) and reserved shares of the Company’s common stock for sale and issuance under the 2011 Plan. The 2011 Plan provides for the grant of incentive and non-statutory stock options as well as restricted stock to employees, non employee directors, and consultants of the Company, which are to be granted at a price that is not less than 100% of the fair value of the stock at the date of grant. Options and restricted stock generally vest over a four-year period and options generally expire ten years from the date of grant. Options are exercisable only to the extent vested. As of September 30, 2021, there were 668,772 shares of the Company's Class A common stock that were available for future grants under the 2011 Plan. The 2021 Equity Incentive Plan (the “2021 Plan”) was adopted by the Board of Directors on June 30, 2021, approved by the Company’s stockholders in July 2021 and became effective in connection with the closing of the IPO. A total of 3,966,162 shares of Class A common stock were initially reserved for issuance under the 2021 Plan. The number of shares of Class A common stock reserved for issuance under the 2021 Plan will also be increased pursuant to provisions for annual automatic evergreen increases. As of September 30, 2021, there were 3,480,549 shares of the Company's Class A common stock that were available for future grants under the 2021 Plan. The 2021 Employee Stock Purchase Plan (the “2021 ESPP”) was adopted by the Board of Directors on June 30, 2021, approved by the Company’s stockholders in July 2021 and became effective in connection with the closing of the IPO. A total of 305,089 shares of Class A common stock were initially reserved for issuance under the 2021 ESPP. In addition, the number of shares reserved for future issuance under the 2021 ESPP will be increased pursuant to provisions for annual automatic evergreen increases. As of September 30, 2021, no shares had been granted under the 2021 ESPP. Stock Options Unless otherwise noted, references to “options” in the subsequent disclosures, refers to the combined incentive and non-statutory stock options issued as employee and non-employee stock-based compensation, and authorized under the 2011 Plan and the 2021 Plan. The following table summarizes information about these options granted and outstanding: Number of Weighted- Weighted- Aggregate Intrinsic Value (In Thousands) Outstanding — December 31, 2020 4,096,722 $ 1.64 7.0 $ 13,328 Granted 2,395,956 7.38 Expired (63) 207.90 Cancelled (25,061) 3.52 Exercised (449,204) 1.20 Outstanding — September 30, 2021 6,018,350 $ 3.95 7.8 $ 43,113 Vested and expected to vest at September 30, 2021 5,679,528 $ 3.82 7.7 $ 41,411 Vested and exercisable at September 30, 2021 2,643,188 $ 1.98 6.0 $ 24,122 The following table presents the impact of stock-based compensation expense in the statements of operations for the periods indicated (in thousands): Three Months Ended Nine Months Ended 2021 2020 2021 2020 Research and development expense $ 283 $ 62 $ 717 $ 184 Sales and marketing expense 179 38 358 102 General and administrative expense 452 95 942 245 Total employee stock-based compensation $ 914 $ 195 $ 2,017 $ 531 At September 30, 2021, there was $11.2 million of unrecognized stock-based compensation cost related to unvested stock options which is expected to be recognized over a weighted average period of 3.3 years.

Warrants

Warrants	9 Months Ended
	Sep. 30, 2021
Warrants and Rights Note Disclosure [Abstract]
Warrants	Warrants Warrants to purchase common stock A certain investor of Series E Convertible Preferred Stock also received 722,223 warrants to purchase shares of Class A common stock of the Company at a price of $20.77 per share. Because these warrants are equity classified, the Company allocated the relative fair value of the cash proceeds between the Series E Convertible Preferred Stock and the warrants. Proceeds allocated to these common stock warrants on a relative fair value basis, calculated using the Black-Scholes option pricing model, were $1.1 million and were recognized as a component of additional paid-in capital in the accompanying condensed financial statements. As an equity instrument, these warrants are not required to be remeasured to their fair value each reporting period. Concurrent with the Company's IPO, all outstanding preferred stock warrants were converted to an equal number of common stock warrants. Converted warrants retained the same exercise prices. All outstanding common stock warrants were exercisable immediately when granted. All outstanding common stock warrants are exercisable for shares of Class A common stock. The Company's common stock warrants outstanding were as follows: Number of Warrants Outstanding as of: Exercise Price September 30, 2021 December 31, 2020 $ 5.20 15,979 — 9.03 1,032,404 1,009,795 10.84 1,009,795 1,009,795 12.38 8,083 — 20.77 722,223 — 2,788,484 2,019,590 The following is a summary of the Company's common stock warrant activity for the nine months ended September 30, 2021: Number of Warrants Outstanding — December 31, 2020 2,019,590 Issued in connection with sale of Series E convertible preferred stock 722,223 Conversion of outstanding preferred stock warrants to common stock warrants 81,543 Exercised, net shares issued (22,372) Cancelled for net exercise (12,500) Outstanding — September 30, 2021 2,788,484 Warrants to purchase preferred stock In connection with the issuance of Series D Convertible Preferred Stock, the Company issued warrants to purchase shares of Series D Convertible Preferred Stock. These warrants were exercisable for cash immediately when granted, and had a ten-year expiration. The initial fair value of these warrants was calculated using the Black-Scholes option pricing model and recorded as a reduction to additional paid-in capital and a corresponding preferred stock warrant liability. During each reporting period, any changes in the fair value of this warrant liability are recorded in other income (expense), net. Total adjustments to the fair value of this warrant liability resulted in other expense of $9 thousand and $8 thousand during the three months ended September 30, 2021 and 2020, respectively. Total adjustments to the fair value of this warrant liability resulted in other expense of $15 thousand and $13 thousand during the nine months ended September 30, 2021 and 2020, respectively. In connection with various debt financings, refinancing, and amendments to the Loan Agreement with the Bank, the Company has, from time to time, issued warrants to purchase shares of convertible preferred stock. Each of these warrants were exercisable for cash immediately when granted and had a ten-year expiration. The initial fair value of each these warrants was calculated using the Black-Scholes option pricing model and recorded as a reduction to the carrying value of the bank loan payable and a corresponding preferred stock liability in the year of issuance. During each reporting period, any changes in the fair value of these warrant liabilities are recorded in interest expense. Total adjustments to the fair value of these warrant liabilities during the three months ended September 30, 2021 and 2020 resulted in $0.4 million and $11 thousand of interest expense, respectively. Total adjustments to the fair value of these warrant liabilities during the nine months ended September 30, 2021 and 2020 resulted in $0.4 million and $7 thousand of interest expense, respectively. Concurrent with the Company's IPO, all outstanding preferred stock warrants were converted to an equal number of common stock warrants. Immediately prior to the conversion, the Company adjusted the preferred stock warrant liability to fair value. See Note 8—Fair Value Measurements. The fair value of the preferred stock warrant liability was then reclassified to equity upon conversion to common stock warrants. As such, there were no outstanding warrants to purchase convertible preferred stock as of September 30, 2021, and no corresponding preferred stock warrant liability. The following table summarizes the warrants to purchase convertible preferred stock and the fair value as of December 31, 2020 (in thousands, except share and per share amounts): Fair Value as of Series Grant Date Number of Exercise December 31, Series A-2 Sep 2012 12,506 $ 5.20 $ 41 Series A-2 Sep 2014 3,473 5.20 13 Series B-1 Dec 2014 28,860 5.20 113 Series B-2 Dec 2015 6,012 8.32 22 Series C-1 Mar 2017 8,083 12.38 31 Series D Feb 2020 22,609 9.03 254 Total 81,543 $ 474 As of December 31, 2020, the fair value of preferred stock warrants outstanding was $0.5 million and was recorded in warrant liability as a long-term liability in the accompanying condensed balance sheets. The following is a summary of the Company’s preferred stock warrant liability activity for the nine months ended September 30, 2021 (in thousands): Warrant Liability Outstanding — December 31, 2020 $ 474 Net increase in fair value of preferred stock warrants — recognized in other income (expense), net 15 Net increase in fair value of preferred stock warrants — recognized in interest expense 440 Recorded in equity upon conversion of preferred stock warrants to common stock warrants (929) Outstanding — September 30, 2021 $ —

Commitments and Contingences

Commitments and Contingences	9 Months Ended
	Sep. 30, 2021
Commitments and Contingencies Disclosure [Abstract]
Commitments and Contingences	Commitments and Contingencies Operating Leases The Company leases a total of approximately 24,100 square feet of office and laboratory space under a single non-cancelable operating lease with a termination date of December 31, 2022. Under the terms of the lease agreement, the Company has an option to renew the lease for one additional five-year rental period. The lease included a tenant improvement allowance from the landlord for structural and cosmetic changes to the new space. The tenant improvements were completed and delivery of possession occurred on September 1, 2018. The tenant improvement allowance has been accounted for as a liability of the Company within deferred rent and is amortized monthly as a reduction to rent expense. A corresponding leasehold improvement asset has been recorded with monthly depreciation being recorded as depreciation expense. Scheduled base rent increases of 3% occur annually each August. The Company recognizes rent expense on a straight-line basis over the term of the operating lease. The difference in actual amounts paid and amounts recorded as rent expense during the period was recorded as deferred rent on the accompanying balance sheets. For the three months ended September 30, 2021 and 2020, the Company recognized rent expense of $0.1 million. For the nine months ended September 30, 2021 and 2020, the Company recognized rent expense of $0.3 million. Amounts classified as deferred rent at September 30, 2021 and December 31, 2020 totaled $0.2 million and $0.3 million, respectively. Capital Leases The full value of all leased equipment, including advance payments, are classified as assets on the Company’s balance sheets. The portion of the future payments designated as principal repayment are classified as a capital lease obligation. As of September 30, 2021, the Company classified the aggregate amount of scheduled capital lease obligation payments due within twelve months of the date of the condensed financial statements, $0.1 million, as a current liability, and the remaining $0.1 million due thereafter, in other liabilities. Indemnification The Company has agreed to indemnify its officers and directors for certain events or occurrences, while the officer or director is or was serving at the Company’s request in such capacity. The maximum amount of potential future indemnification is unlimited; however, the Company purchases director and officer insurance coverage that provides for corporate reimbursements of covered obligations that limits the Company’s exposure and enables it to recover a portion of potential future amounts paid. The Company is unable to reasonably estimate the maximum amount that could be payable under these arrangements since these obligations are not capped but are conditional to the unique facts and circumstances involved. Accordingly, the Company has no liabilities recorded for these agreements as of September 30, 2021 and December 31, 2020. The Company has never incurred costs to defend lawsuits or settle claims related to these indemnification agreements. Employee Agreements The Company has signed various employment agreements with key executives pursuant to which if their employment is terminated by the Company without cause or by the employees for good reason, or following a change of control of the Company, the employees are entitled to receive certain benefits, including severance payments, accelerated vesting of stock and stock options, and certain insurance benefits. Legal Matters The Company is not currently a party to any material litigation or other material legal proceedings. The Company may, from time to time, be involved in various legal proceedings arising from the normal course of business activities, and an unfavorable resolution of any of these matters could materially affect the Company’s future results of operations, cash flows, or financial position.

Net Loss Per Share

Net Loss Per Share	9 Months Ended
	Sep. 30, 2021
Earnings Per Share [Abstract]
Net Loss Per Share	Net loss per share For the three and nine months ended September 30, 2021, the Company calculated net loss per share of Class A and Class B common stock using the two-class method. For periods in which the Company reports a net loss, all potentially dilutive shares are anti-dilutive and are therefore excluded from the calculation of diluted net loss per share. For the three and nine months ended September 30, 2021, the Company reported a net loss and as such, basic and diluted net loss per share are the same. The rights, including the liquidation and dividend rights, of the holders of the Company's Class A and Class B common stock are identical, except with respect to voting and conversion. The undistributed earnings for each period are allocated based on the contractual participation rights of the Class A and Class B common shares as if the earnings for the period had been distributed. As the liquidation and dividend rights are identical, the undistributed earnings are allocated on a proportionate basis and the resulting amount per share for Class A and Class B common stock was the same for the three and nine months ended September 30, 2021. The Company issued certain shares of convertible preferred stock that were outstanding until the Company's IPO and were concluded to be participating securities. For the three and nine months ended September 30, 2020, there was only one class of common stock outstanding. Due to the presence of participating securities, the Company calculated net loss per share for the three and nine months ending September 30, 2020 using the more dilutive of the treasury stock or the two-class method. For periods presented in which the Company reports a net loss, the losses are not allocated to the participating securities. As the Company reported a net loss during the three and nine months ending September 30, 2020, diluted net loss per share was the same as basic net loss per share, since dilutive common shares are not assumed to have been issued if their effect is anti-dilutive. The preferred stock converted to common stock in July 2021 as part of the Company's IPO. See Note 10—Capital Structure for additional details. The following table sets forth the computation of basic and diluted net loss per share of Class A and Class B common stock during 2021 (in thousands, except share and per share amounts): Three Months Ended Nine Months Ended Class A Class B Class A Class B Net loss $ (9,415) $ (444) $ (21,641) $ (884) Weighted average common stock outstanding, basic and diluted 23,954,696 1,130,317 9,326,341 380,913 Net loss per share — basic and diluted $ (0.39) $ (0.39) $ (2.32) $ (2.32) The following table sets forth the computation of the basic and diluted net loss per share during 2020 (in thousands, except share and per share amounts): Three Months Ended Nine Months Ended Net loss $ (5,072) $ (14,473) Weighted average common stock outstanding, basic and diluted 1,536,483 1,529,182 Net loss per share — basic and diluted $ (3.30) $ (9.46) The Company excluded the following potentially dilutive securities, presented based on amounts outstanding at each period end, from the computation of diluted net loss per share for the periods indicated because their impact would have been anti-dilutive: September 30, 2021 2020 Junior convertible preferred stock — 9,819,480 Senior convertible preferred stock — 5,737,440 Shares issuable under convertible note — 649,216 Warrants to purchase convertible preferred stock — 81,543 Warrants to purchase Class A common stock 2,788,484 2,019,590 Options to purchase Class A common stock 6,018,350 4,373,578 Total 8,806,834 22,680,847

Significant Accounting Polici_2

Significant Accounting Policies (Policies)	9 Months Ended
	Sep. 30, 2021
Accounting Policies [Abstract]
Basis of Presentation	Basis of Presentation The accompanying unaudited condensed financial statements have been prepared in accordance with accounting principles generally accepted in the United States of America (“U.S. GAAP”) and applicable rules and regulations of the SEC regarding interim financial reporting. Certain information and note disclosures normally included in the financial statements prepared in accordance with U.S. GAAP have been condensed or omitted pursuant to such rules and regulations. As such, these unaudited condensed financial statements should be read in conjunction with the audited financial statements and accompanying notes as of and for the year ended December 31, 2020 included in the Final Prospectus. The unaudited interim condensed financial statements have been prepared on a basis consistent with the audited annual financial statements as of and for the year ended December 31, 2020, and, in the opinion of the Company’s management, reflect all adjustments, consisting solely of normal recurring adjustments, necessary for the fair presentation of the Company’s financial results. The results of the three and nine months ended September 30, 2021 are not necessarily indicative of the results to be expected for the full year ending December 31, 2021 or any other period. Any reference in these notes to applicable accounting guidance is meant to refer to the authoritative U.S. GAAP included in the Accounting Standards Codification (“ASC”), and Accounting Standards Updates (“ASU”) issued by the Financial Accounting Standards Board (“FASB”).
Reverse Stock Split	Reverse Stock Split On June 30, 2021, the Company’s board of directors (the “Board of Directors”) approved a 1-for-2.079 reverse stock split of the Company’s common stock and redeemable convertible preferred stock, which was effective by amendment to the Company’s charter on July 7, 2021. The par value and authorized shares of the common stock and redeemable convertible preferred stock were not adjusted as a result of the reverse stock split. All issued and outstanding common stock, warrants, options to purchase common stock and per share amounts contained in the financial statements have been retroactively adjusted to give effect to the reverse stock split for all periods presented.
Use of Estimates	Use of Estimates The preparation of the condensed financial statements in conformity with U.S. GAAP requires the Company’s management to make estimates and assumptions that affect the amounts reported in the condensed financial statements and accompanying notes. On an ongoing basis, the Company evaluates its estimates, including those related to the determination of fair value of its stock options, fair value of its common and preferred stock warrants, fair value of its marketable securities, valuation of deferred tax assets resulting from net operating losses, and useful lives of property and equipment. The Company bases these estimates on historical and anticipated results, trends, and various other assumptions that the Company believes are reasonable under the circumstances, including assumptions as to future events. Actual results could differ materially from those estimates. The COVID-19 pandemic and the rapidly evolving actions of governments, private sector participants and the public in an effort to contain the spread of the COVID-19 virus and address its impacts have intensified and have had significant direct and indirect effects on businesses and commerce. The extent to which the COVID-19 pandemic may impact the Company’s business, financial condition, cash flows, and results of operations, in particular, will depend on future developments that are highly uncertain, many of which are outside the Company’s control. Such developments include the availability and effectiveness of actions taken to contain or treat COVID-19, the ultimate geographic spread and duration of the pandemic, the extent and duration of a resurgence of the COVID-19 virus and variant strains thereof, new information concerning the severity of the COVID-19 virus, the effectiveness and intensity of measures to contain the COVID-19 virus and the economic impact of the pandemic and the reactions to it. Such developments, among others, depending on their nature, duration, and intensity, could have a significant adverse effect on the Company’s business, financial condition, cash flows, and results of operations. There were no significant estimates contained in the preparation of the Company’s condensed financial statements or impacts to the Company’s condensed financial statements for the three and nine months ended September 30, 2021 that were a direct result of the COVID-19 pandemic. The Company is not aware of any specific event or circumstance that would require an update to its estimates, judgments and assumptions or a revision of the carrying value of the Company’s assets or liabilities as of the date of the condensed financial statements.
Recently Issued Accounting Pronouncements Not Yet Adopted	Recently Issued Accounting Pronouncements Not Yet Adopted In February 2016, the FASB issued ASU 2016-02, Leases (Topic 842). Under the new guidance, lessees will be required to recognize a lease liability and a right-of-use asset for all leases (with the exception of short-term leases) at the commencement date. The standard was effective for public entities for fiscal years beginning after December 15, 2018 and for private companies for fiscal years beginning after December 15, 2021. The Company is evaluating the effect that ASU 2016-02 will have on its interim financial statements and related disclosures. The Company is currently an emerging growth company and has elected to use the extended transition period for complying with new or revised accounting standards that have different effective dates for public and private companies. As such, the Company expects to adopt this new standard on January 1, 2022 and has not yet determined the effect of the standard on its ongoing financial reporting. In December 2019, the FASB issued ASU 2019-12, Income Taxes (Topic 740): Simplifying the Accounting for Income Taxes . This standard removes certain exceptions for investments, intra-period allocations and interim calculations, and adds guidance to reduce complexity in accounting for income taxes. This standard will be effective for the Company on January 1, 2022, with early adoption permitted. The Company is currently evaluating the potential impact this standard may have on its financial statements and disclosures. Other recent accounting pronouncements issued by the FASB (including its Emerging Issues Task Force), the American Institute of Certified Public Accountants, and the SEC did not, or are not believed by the Company’s management to, have a material impact on the Company’s financial position, results of operations or cash flows.

Cash, Cash Equivalents and Ma_2

Cash, Cash Equivalents and Marketable Securities (Tables)	9 Months Ended
	Sep. 30, 2021
Cash and Cash Equivalents [Abstract]
Schedule of Cash, Cash Equivalents and Marketable Securities by Major Security Type	The Company's cash, cash equivalents and marketable securities by major security type as of September 30, 2021 were as follows (in thousands): September 30, 2021 Amortized Cost Gross Unrealized Gains Gross Unrealized Losses Fair Value Cash and cash equivalents: Cash $ 330 $ — $ — $ 330 Money market funds 2,642 — — 2,642 Commercial paper 79,510 — (3) 79,507 Total cash and cash equivalents 82,482 — (3) 82,479 Current marketable securities: Commercial paper 30,992 — (4) 30,988 Corporate debt securities 6,513 — (3) 6,510 Total current marketable securities 37,505 — (7) 37,498 Long-term marketable securities: U.S. federal agency securities 25,797 — (13) 25,784 U.S. government securities 3,696 — (2) 3,694 Corporate debt securities 519 — — 519 Total long-term marketable securities 30,012 — (15) 29,997 Total cash, cash equivalents and marketable securities $ 149,999 $ — $ (25) $ 149,974
Schedule of Marketable Securities Classified by Contractual Maturities	The Company's marketable securities classified by contractual maturities as of September 30, 2021 were as follows (in thousands): Amortized Cost Fair Value Due within one year $ 37,505 $ 37,498 Due after one year through five years 30,012 29,997 Total $ 67,517 $ 67,495

Property and Equipment (Tables)

Property and Equipment (Tables)	9 Months Ended
	Sep. 30, 2021
Property, Plant and Equipment [Abstract]
Schedule of Components of Property and Equipment, Net	The following table presents the components of property and equipment, net, as of September 30, 2021 and December 31, 2020 (in thousands): September 30, December 31, Laboratory equipment $ 4,615 $ 4,194 Computer equipment 1,009 767 Leasehold improvements 701 701 Software 373 373 Furniture and fixtures 309 292 Total property and equipment 7,007 6,327 Less accumulated depreciation and amortization (5,822) (5,362) Property and equipment, net $ 1,185 $ 965

Accrued and Other Current Lia_2

Accrued and Other Current Liabilities (Tables)	9 Months Ended
	Sep. 30, 2021
Accounts Payable and Accrued Liabilities, Current [Abstract]
Schedule of Components of Accrued and Other Current Liabilities	The following table presents the components of accrued and other current liabilities as of September 30, 2021 and December 31, 2020 (in thousands): September 30, December 31, Accrued compensation $ 1,507 $ 996 Accrued paid time off 422 290 Bank loan final payment fee — 100 Other current liabilities 133 191 Total accrued and other current liabilities $ 2,062 $ 1,577

Other Income (Expense), net (Ta

Other Income (Expense), net (Tables)	9 Months Ended
	Sep. 30, 2021
Other Income and Expenses [Abstract]
Schedule of Components of Other Income (Expense), Net	The following table presents the components of other income (expense), net, for the three and nine months ended September 30, 2021 and 2020 (in thousands): Three Months Ended Nine Months Ended 2021 2020 2021 2020 Interest income $ 32 $ 5 $ 53 $ 39 Fair value remeasurements (9) (8) (15) (13) Gain on extinguishment of PPP loan — — 1,050 — Other losses, net (1) — (21) — Other income (expense), net $ 22 $ (3) $ 1,067 $ 26

Fair Value Measurements (Tables

Fair Value Measurements (Tables)	9 Months Ended
	Sep. 30, 2021
Fair Value Disclosures [Abstract]
Schedule of Significant Unobservable Inputs Used to Value the Preferred Stock Warrant Liability	The following table summarizes the significant unobservable inputs used to value the Company’s preferred stock warrant liability: As of December 31, 2020 Range Weighted-Average Fair value per share of common stock $3.41 - $7.35 $ 4.56 Expected term (in years) 1.7 - 9.1 5.3 Expected volatility 59.5% - 72.5% 63.6%
Schedule of Financial Assets that are Measured at Fair Value on a Recurring basis	The following table shows the Company’s assets measured at fair value on a recurring basis by level within the fair value hierarchy (in thousands) as of September 30, 2021: Level 1 Level 2 Level 3 Assets: Cash equivalents: Money market funds $ 2,642 $ — $ — Commercial paper — 79,507 — Marketable securities: Commercial paper — 30,988 — Corporate debt securities — 7,029 — U.S. federal agency securities — 25,784 — U.S. government securities — 3,694 — Total assets $ 2,642 $ 147,002 $ — The following table shows the Company’s assets and liabilities measured at fair value on a recurring basis by level within the fair value hierarchy (in thousands) as of December 31, 2020: Level 1 Level 2 Level 3 Assets: Cash equivalents $ 13,533 $ — $ — Liabilities: Warrant liability — — 474

Capital Structure (Tables)

Capital Structure (Tables)	9 Months Ended
	Sep. 30, 2021
Stockholders' Equity Note [Abstract]
Schedule of Common Stock Reserved for Future Issuance	The following shares of Class A common stock were reserved for future issuance: September 30, 2021 December 31, 2020 Senior convertible preferred stock — 5,737,440 Junior convertible preferred stock — 9,819,480 Shares issuable under convertible note — 665,699 Warrants to purchase convertible preferred stock — 81,543 Warrants to purchase Class A common stock 2,788,484 2,019,590 Options to purchase Class A common stock 6,018,350 4,096,722 Class A common stock available for future grants under the 2011 Equity Incentive Plan 668,772 388,505 Class A common stock available for future grants under the 2021 Equity Incentive Plan 3,480,549 — Class A common stock available for future grants under the 2021 Employee Stock Purchase Plan 305,089 — Total 13,261,244 22,808,979
Schedule of Authorized, Issued and Outstanding Convertible Preferred Stock and its Principal Terms	Authorized, issued and outstanding convertible preferred stock and its principal terms as of December 31, 2020 were as follows (in thousands, except share and per share amounts): Series Shares Shares Issued Original Aggregate Proceeds, Series A-1 Junior Preferred Stock 1,390 667 $ 2,079.00 $ 1,390 $ 1,390 Series A-2 Junior Preferred Stock 7,941,499 3,803,878 5.20 19,771 19,595 Series B-1 Junior Preferred Stock 2,060,000 961,994 5.20 5,000 4,914 Series B-2 Junior Preferred Stock 5,012,500 2,404,995 8.32 20,000 19,984 Series C-1 Junior Preferred Stock 5,521,905 2,647,946 12.38 32,755 32,653 Series C-2 Junior Preferred Stock 1,510,000 — 17.22 — — Series D Senior Preferred Stock 12,320,844 5,737,440 9.03 102,535 50,415 Total Convertible Preferred Stock 34,368,138 15,556,920 $ 181,451 $ 128,951

Stock-Based Compensation (Table

Stock-Based Compensation (Tables)	9 Months Ended
	Sep. 30, 2021
Share-based Payment Arrangement [Abstract]
Summary of Options Granted and Outstanding	The following table summarizes information about these options granted and outstanding: Number of Weighted- Weighted- Aggregate Intrinsic Value (In Thousands) Outstanding — December 31, 2020 4,096,722 $ 1.64 7.0 $ 13,328 Granted 2,395,956 7.38 Expired (63) 207.90 Cancelled (25,061) 3.52 Exercised (449,204) 1.20 Outstanding — September 30, 2021 6,018,350 $ 3.95 7.8 $ 43,113 Vested and expected to vest at September 30, 2021 5,679,528 $ 3.82 7.7 $ 41,411 Vested and exercisable at September 30, 2021 2,643,188 $ 1.98 6.0 $ 24,122
Schedule of Impact of Stock-based Compensation Expense in the Statements of Operations	The following table presents the impact of stock-based compensation expense in the statements of operations for the periods indicated (in thousands): Three Months Ended Nine Months Ended 2021 2020 2021 2020 Research and development expense $ 283 $ 62 $ 717 $ 184 Sales and marketing expense 179 38 358 102 General and administrative expense 452 95 942 245 Total employee stock-based compensation $ 914 $ 195 $ 2,017 $ 531

Warrants (Tables)

Warrants (Tables)	9 Months Ended
	Sep. 30, 2021
Warrants and Rights Note Disclosure [Abstract]
Schedule of Warrants or Rights	The Company's common stock warrants outstanding were as follows: Number of Warrants Outstanding as of: Exercise Price September 30, 2021 December 31, 2020 $ 5.20 15,979 — 9.03 1,032,404 1,009,795 10.84 1,009,795 1,009,795 12.38 8,083 — 20.77 722,223 — 2,788,484 2,019,590 The following is a summary of the Company's common stock warrant activity for the nine months ended September 30, 2021: Number of Warrants Outstanding — December 31, 2020 2,019,590 Issued in connection with sale of Series E convertible preferred stock 722,223 Conversion of outstanding preferred stock warrants to common stock warrants 81,543 Exercised, net shares issued (22,372) Cancelled for net exercise (12,500) Outstanding — September 30, 2021 2,788,484 The following is a summary of the Company’s preferred stock warrant liability activity for the nine months ended September 30, 2021 (in thousands): Warrant Liability Outstanding — December 31, 2020 $ 474 Net increase in fair value of preferred stock warrants — recognized in other income (expense), net 15 Net increase in fair value of preferred stock warrants — recognized in interest expense 440 Recorded in equity upon conversion of preferred stock warrants to common stock warrants (929) Outstanding — September 30, 2021 $ —
Schedule of Warrants to Purchase Convertible Preferred Stock Including Fair Value	The following table summarizes the warrants to purchase convertible preferred stock and the fair value as of December 31, 2020 (in thousands, except share and per share amounts): Fair Value as of Series Grant Date Number of Exercise December 31, Series A-2 Sep 2012 12,506 $ 5.20 $ 41 Series A-2 Sep 2014 3,473 5.20 13 Series B-1 Dec 2014 28,860 5.20 113 Series B-2 Dec 2015 6,012 8.32 22 Series C-1 Mar 2017 8,083 12.38 31 Series D Feb 2020 22,609 9.03 254 Total 81,543 $ 474

Net Loss Per Share (Tables)

Net Loss Per Share (Tables)	9 Months Ended
	Sep. 30, 2021
Earnings Per Share [Abstract]
Schedule of Computation of Basic and Diluted Net Loss per Share	The following table sets forth the computation of basic and diluted net loss per share of Class A and Class B common stock during 2021 (in thousands, except share and per share amounts): Three Months Ended Nine Months Ended Class A Class B Class A Class B Net loss $ (9,415) $ (444) $ (21,641) $ (884) Weighted average common stock outstanding, basic and diluted 23,954,696 1,130,317 9,326,341 380,913 Net loss per share — basic and diluted $ (0.39) $ (0.39) $ (2.32) $ (2.32) The following table sets forth the computation of the basic and diluted net loss per share during 2020 (in thousands, except share and per share amounts): Three Months Ended Nine Months Ended Net loss $ (5,072) $ (14,473) Weighted average common stock outstanding, basic and diluted 1,536,483 1,529,182 Net loss per share — basic and diluted $ (3.30) $ (9.46)
Schedule of Anti-dilutive Securities Excluded from the Computation of Earnings per Share	The Company excluded the following potentially dilutive securities, presented based on amounts outstanding at each period end, from the computation of diluted net loss per share for the periods indicated because their impact would have been anti-dilutive: September 30, 2021 2020 Junior convertible preferred stock — 9,819,480 Senior convertible preferred stock — 5,737,440 Shares issuable under convertible note — 649,216 Warrants to purchase convertible preferred stock — 81,543 Warrants to purchase Class A common stock 2,788,484 2,019,590 Options to purchase Class A common stock 6,018,350 4,373,578 Total 8,806,834 22,680,847

Description of Business and F_2

Description of Business and Financial Condition (Details) - USD ($) $ in Thousands	Sep. 30, 2021	Dec. 31, 2020
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Accumulated deficit	$ (153,984)	$ (131,459)
Cash and cash equivalents	82,479	$ 13,533
Available-for-sale securities	$ 67,495

Significant Accounting Polici_3

Significant Accounting Policies (Details)	Jul. 07, 2021
Accounting Policies [Abstract]
Reverse stock split conversion ratio	0.48

Cash, Cash Equivalents and Ma_3

Cash, Cash Equivalents and Marketable Securities - Cash, Cash Equivalents and Marketable Securities by Major Security Type (Details) - USD ($)	Sep. 30, 2021	Dec. 31, 2020
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	$ 67,517,000	$ 0
Fair Value	67,495,000
Amortized Cost	149,999,000
Gross Unrealized Gains	0
Gross Unrealized Losses	(25,000)
Fair Value	149,974,000
Cash and cash equivalents:
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	82,482,000
Gross Unrealized Gains	0
Gross Unrealized Losses	(3,000)
Cash equivalents	82,479,000
Cash and cash equivalents: | Cash
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	330,000
Gross Unrealized Gains	0
Gross Unrealized Losses	0
Cash equivalents	330,000
Cash and cash equivalents: | Money market funds
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	2,642,000
Gross Unrealized Gains	0
Gross Unrealized Losses	0
Cash equivalents	2,642,000
Cash and cash equivalents: | Commercial paper
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	79,510,000
Gross Unrealized Gains	0
Gross Unrealized Losses	(3,000)
Cash equivalents	79,507,000
Current marketable securities:
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	37,505,000
Gross Unrealized Gains	0
Gross Unrealized Losses	(7,000)
Fair Value	37,498,000
Current marketable securities: | Commercial paper
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	30,992,000
Gross Unrealized Gains	0
Gross Unrealized Losses	(4,000)
Fair Value	30,988,000
Current marketable securities: | Corporate debt securities
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	6,513,000
Gross Unrealized Gains	0
Gross Unrealized Losses	(3,000)
Fair Value	6,510,000
Long-term marketable securities:
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	30,012,000
Gross Unrealized Gains	0
Gross Unrealized Losses	(15,000)
Fair Value	29,997,000
Long-term marketable securities: | U.S. federal agency securities
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	25,797,000
Gross Unrealized Gains	0
Gross Unrealized Losses	(13,000)
Fair Value	25,784,000
Long-term marketable securities: | U.S. government securities
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	3,696,000
Gross Unrealized Gains	0
Gross Unrealized Losses	(2,000)
Fair Value	3,694,000
Long-term marketable securities: | Corporate debt securities
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	519,000
Gross Unrealized Gains	0
Gross Unrealized Losses	0
Fair Value	$ 519,000

Cash, Cash Equivalents and Ma_4

Cash, Cash Equivalents and Marketable Securities - Narrative (Details) - USD ($)	Sep. 30, 2021	Dec. 31, 2020
Cash and Cash Equivalents [Abstract]
Amortized Cost	$ 67,517,000	$ 0
Debt securities, available-for-sale, continuous unrealized loss position, 12 months or longer	0
Debt securities, available-for-sale, other than temporary impairment	$ 0

Cash, Cash Equivalents and Ma_5

Cash, Cash Equivalents and Marketable Securities - Marketable Securities Classified by Contractual Maturities (Details) - USD ($)	Sep. 30, 2021	Dec. 31, 2020
Amortized Cost
Due within one year	$ 37,505,000
Due after one year through five years	30,012,000
Amortized Cost	67,517,000	$ 0
Fair Value
Due within one year	37,498,000
Due after one year through five years	29,997,000
Fair Value	$ 67,495,000

Property and Equipment (Details

Property and Equipment (Details) - USD ($) $ in Thousands	Sep. 30, 2021	Dec. 31, 2020
Property, Plant and Equipment [Line Items]
Total property and equipment	$ 7,007	$ 6,327
Less accumulated depreciation and amortization	(5,822)	(5,362)
Property and equipment, net	1,185	965
Laboratory equipment
Property, Plant and Equipment [Line Items]
Total property and equipment	4,615	4,194
Computer equipment
Property, Plant and Equipment [Line Items]
Total property and equipment	1,009	767
Leasehold improvements
Property, Plant and Equipment [Line Items]
Total property and equipment	701	701
Software
Property, Plant and Equipment [Line Items]
Total property and equipment	373	373
Furniture and fixtures
Property, Plant and Equipment [Line Items]
Total property and equipment	$ 309	$ 292

Property and Equipment - Additi

Property and Equipment - Additional Information (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020	Dec. 31, 2020
Property, Plant and Equipment [Line Items]
Depreciation and amortization	$ 100	$ 200	$ 514	$ 693
Laboratory equipment
Property, Plant and Equipment [Line Items]
Assets subject to capital leases	3,000		3,000		$ 3,000
Capital lease assets accumulated amortization	2,900		2,900		$ 2,600
Capital lease amortization expense	$ 100	$ 200	$ 300	$ 500

Accrued and Other Current Lia_3

Accrued and Other Current Liabilities (Details) - USD ($) $ in Thousands	Sep. 30, 2021	Dec. 31, 2020
Accounts Payable and Accrued Liabilities, Current [Abstract]
Accrued compensation	$ 1,507	$ 996
Accrued paid time off	422	290
Bank loan final payment fee	0	100
Other current liabilities	133	191
Total accrued and other current liabilities	$ 2,062	$ 1,577

Other Income (Expense), net (De

Other Income (Expense), net (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Other Income and Expenses [Abstract]
Interest income	$ 32	$ 5	$ 53	$ 39
Fair value remeasurements	(9)	(8)	(15)	(13)
Gain on extinguishment of PPP loan	0	0	1,050	0
Other losses, net	(1)	0	(21)	0
Other income (expense), net	$ 22	$ (3)	$ 1,067	$ 26

Loans and Convertible Promiss_2

Loans and Convertible Promissory Notes - Bank Loan (Details) - Loan and Security Agreement - USD ($) $ in Thousands	1 Months Ended	12 Months Ended
	Mar. 31, 2021	Dec. 31, 2014
Debt Instrument [Line Items]
Term loan		$ 10,000
Long term debt, Interest rate		4.75%
Percentage of amount borrowed from bank loan		1.00%
Final payment fee	$ 100	$ 100
Repayment of outstanding principal	2,000
Repayment of accrued interest	$ 6
Prime Rate
Debt Instrument [Line Items]
Long term debt, spread on base interest rate		1.00%

Loans and Convertible Promiss_3

Loans and Convertible Promissory Notes - Convertible Promissory Notes (Details) - February 2019 Convertible Note $ / shares in Units, $ in Millions	Mar. 24, 2021USD ($)	Jul. 31, 2019USD ($)shares	Feb. 28, 2019USD ($)$ / shares	Sep. 30, 2021USD ($)	Sep. 30, 2020USD ($)
Debt Instrument [Line Items]
Aggregate principal amount			$ 6.4
Debt instrument, stated interest rate			12.00%
Debt instrument, convertible, conversion price (in usd per share) | $ / shares			$ 9.03
Interest expense		$ 0.1
Liability at the measurement date fair value			$ 2.4
Accretion of discount				$ 0.1	$ 0.6
Repayment of outstanding principal	$ 4.5
Repayment of accrued interest	$ 1.1
Series D Convertible Preferred Stock
Debt Instrument [Line Items]
Debt instrument, conversion price percentage			0.80
Amount of original debt converted		$ 1.9
Debt conversion, converted instrument, shares issued (in shares) | shares		277,507

Loans and Convertible Promiss_4

Loans and Convertible Promissory Notes - Paycheck Protection Loan (Details) - USD ($) $ in Thousands	Jun. 26, 2021	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020	Apr. 30, 2020
Debt Instrument [Line Items]
Gain on extinguishment of PPP loan		$ 0	$ 0	$ 1,050	$ 0
Paycheck Protection Program Loan
Debt Instrument [Line Items]
Aggregate principal amount						$ 1,100
Amount of debt outstanding	$ 1,100
Gain on extinguishment of PPP loan				$ 1,100

Fair Value Measurements - Narra

Fair Value Measurements - Narrative (Details) - shares	Sep. 30, 2021	Dec. 31, 2020
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Number of warrants outstanding (in shares)	2,788,484	2,019,590
Preferred Stock
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Number of warrants outstanding (in shares)	0

Fair Value Measurements - Signi

Fair Value Measurements - Significant Unobservable Inputs (Details) - Level 3	Dec. 31, 2020$ / sharesyear
Minimum | Fair value per share of common stock
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Measurement input | $ / shares	3.41
Minimum | Expected term (in years)
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Measurement input | year	1.7
Minimum | Expected volatility
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Measurement input	0.595
Maximum | Fair value per share of common stock
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Measurement input | $ / shares	7.35
Maximum | Expected term (in years)
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Measurement input | year	9.1
Maximum | Expected volatility
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Measurement input	0.725
Weighted-Average | Fair value per share of common stock
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Measurement input | $ / shares	4.56
Weighted-Average | Expected term (in years)
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Measurement input | year	5.3
Weighted-Average | Expected volatility
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Measurement input	0.636

Fair Value Measurements - Finan

Fair Value Measurements - Financial Assets that are Measured at Fair Value on a Recurring Basis (Details) - USD ($) $ in Thousands	Sep. 30, 2021	Dec. 31, 2020
Assets:
Marketable securities:	$ 67,495
Level 1 | Recurring
Assets:
Cash equivalents		$ 13,533
Total assets	2,642
Liabilities:
Warrant liability		0
Level 1 | Recurring | Commercial paper
Assets:
Marketable securities:	0
Level 1 | Recurring | Corporate debt securities
Assets:
Marketable securities:	0
Level 1 | Recurring | U.S. federal agency securities
Assets:
Marketable securities:	0
Level 1 | Recurring | U.S. government securities
Assets:
Marketable securities:	0
Level 1 | Recurring | Money market funds
Assets:
Cash equivalents	2,642
Level 1 | Recurring | Commercial paper
Assets:
Cash equivalents	0
Level 2 | Recurring
Assets:
Cash equivalents		0
Total assets	147,002
Liabilities:
Warrant liability		0
Level 2 | Recurring | Commercial paper
Assets:
Marketable securities:	30,988
Level 2 | Recurring | Corporate debt securities
Assets:
Marketable securities:	7,029
Level 2 | Recurring | U.S. federal agency securities
Assets:
Marketable securities:	25,784
Level 2 | Recurring | U.S. government securities
Assets:
Marketable securities:	3,694
Level 2 | Recurring | Money market funds
Assets:
Cash equivalents	0
Level 2 | Recurring | Commercial paper
Assets:
Cash equivalents	79,507
Level 3 | Recurring
Assets:
Cash equivalents		0
Total assets	0
Liabilities:
Warrant liability		$ 474
Level 3 | Recurring | Commercial paper
Assets:
Marketable securities:	0
Level 3 | Recurring | Corporate debt securities
Assets:
Marketable securities:	0
Level 3 | Recurring | U.S. federal agency securities
Assets:
Marketable securities:	0
Level 3 | Recurring | U.S. government securities
Assets:
Marketable securities:	0
Level 3 | Recurring | Money market funds
Assets:
Cash equivalents	0
Level 3 | Recurring | Commercial paper
Assets:
Cash equivalents	$ 0

Related Party Transactions (Det

Related Party Transactions (Details) $ / shares in Units, $ in Thousands	1 Months Ended	3 Months Ended		9 Months Ended
	Feb. 28, 2021	Sep. 30, 2021USD ($)	Sep. 30, 2020USD ($)	Sep. 30, 2021USD ($)voting_member	Sep. 30, 2020USD ($)	Jan. 31, 2017$ / shares
Commercial Collaboration Agreement
Related Party Transaction [Line Items]
Number of voting members from each party | voting_member				2
LabCorp | Strategic commercialization agreement | Maximum
Related Party Transaction [Line Items]
Fees paid		$ 100	$ 100	$ 100	$ 100
LabCorp | Strategic commercialization agreement | Series C Convertible Preferred Stock
Related Party Transaction [Line Items]
Preferred stock, par value (in usd per share) | $ / shares						$ 0.0001
Blue Ox | Consulting agreement
Related Party Transaction [Line Items]
Fees paid		300	100	600	300
Healthcore Inc | Master services agreement
Related Party Transaction [Line Items]
Fees paid		400	$ 100	1,100	$ 600
Anthem | Laboratory Services Agreement
Related Party Transaction [Line Items]
Recognized revenue		$ 17		$ 41
Anthem | Commercial Collaboration Agreement
Related Party Transaction [Line Items]
Term of agreement	3 years

Capital Structure - Narrative (

Capital Structure - Narrative (Details) $ / shares in Units, $ in Thousands	Jul. 19, 2021USD ($)$ / sharesshares	Sep. 30, 2021USD ($)votecommon_stock_classshares	Sep. 30, 2020USD ($)	Jul. 20, 2021shares	Dec. 31, 2020USD ($)
Class of Stock [Line Items]
Net proceeds from issuance of common stock | $		$ 66,611	$ 0
Number of common stock classes authorized | common_stock_class		2
Common stock, conversion ratio		1
Deferred offering costs related to an equity offering | $		$ 3,100			$ 26
Initial Public Offering
Class of Stock [Line Items]
Issue price per share (in usd per share) | $ / shares	$ 16
Net proceeds from issuance of common stock | $	$ 66,600
Class A common stock
Class of Stock [Line Items]
Common stock issued from conversion of convertible securities (in shares)	22,434,130
Number of votes per share | vote		1
Class A common stock | Initial Public Offering
Class of Stock [Line Items]
Number of shares of common stock issued (in shares)	4,687,500
Class B common stock
Class of Stock [Line Items]
Common stock issued from conversion of convertible securities (in shares)	1,405,259
Convertible Preferred Stock
Class of Stock [Line Items]
Preferred stock issued (in shares)				0
Preferred stock outstanding (in shares)		0

Capital Structure - Common Stoc

Capital Structure - Common Stock (Details) - Class A common stock - shares	Sep. 30, 2021	Dec. 31, 2020
Class of Stock [Line Items]
Shares reserved for future issuance (in shares)	13,261,244	22,808,979
Senior Convertible Preferred Stock
Class of Stock [Line Items]
Shares reserved for future issuance (in shares)	0	5,737,440
Junior Convertible Preferred Stock
Class of Stock [Line Items]
Shares reserved for future issuance (in shares)	0	9,819,480
Shares issuable under convertible note
Class of Stock [Line Items]
Shares reserved for future issuance (in shares)	0	665,699
Warrants to purchase convertible preferred stock
Class of Stock [Line Items]
Shares reserved for future issuance (in shares)	0	81,543
Warrants to purchase Class A common stock
Class of Stock [Line Items]
Shares reserved for future issuance (in shares)	2,788,484	2,019,590
Options to purchase Class A common stock
Class of Stock [Line Items]
Shares reserved for future issuance (in shares)	6,018,350	4,096,722
Class A common stock available for future grants under the 2011 Equity Incentive Plan
Class of Stock [Line Items]
Shares reserved for future issuance (in shares)	668,772	388,505
Class A common stock available for future grants under the 2021 Equity Incentive Plan
Class of Stock [Line Items]
Shares reserved for future issuance (in shares)	3,480,549	0
Class A common stock available for future grants under the 2021 Employee Stock Purchase Plan
Class of Stock [Line Items]
Shares reserved for future issuance (in shares)	305,089	0

Capital Structure - Convertible

Capital Structure - Convertible Preferred Stock (Details) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2020USD ($)$ / sharesshares
Total Convertible Preferred Stock
Temporary Equity [Line Items]
Shares authorized (in shares) | shares	34,368,138
Shares issued and outstanding (in shares) | shares	15,556,920
Aggregate Liquidation Preference | $	$ 181,451
Proceeds, net of issuance costs | $	$ 128,951
Series A-1 Junior Preferred Stock
Temporary Equity [Line Items]
Shares authorized (in shares) | shares	1,390
Shares issued and outstanding (in shares) | shares	667
Original issue price per share (in usd per share) | $ / shares	$ 2,079
Aggregate Liquidation Preference | $	$ 1,390
Proceeds, net of issuance costs | $	$ 1,390
Series A-2 Junior Preferred Stock
Temporary Equity [Line Items]
Shares authorized (in shares) | shares	7,941,499
Shares issued and outstanding (in shares) | shares	3,803,878
Original issue price per share (in usd per share) | $ / shares	$ 5.20
Aggregate Liquidation Preference | $	$ 19,771
Proceeds, net of issuance costs | $	$ 19,595
Series B-1 Junior Preferred Stock
Temporary Equity [Line Items]
Shares authorized (in shares) | shares	2,060,000
Shares issued and outstanding (in shares) | shares	961,994
Original issue price per share (in usd per share) | $ / shares	$ 5.20
Aggregate Liquidation Preference | $	$ 5,000
Proceeds, net of issuance costs | $	$ 4,914
Series B-2 Junior Preferred Stock
Temporary Equity [Line Items]
Shares authorized (in shares) | shares	5,012,500
Shares issued and outstanding (in shares) | shares	2,404,995
Original issue price per share (in usd per share) | $ / shares	$ 8.32
Aggregate Liquidation Preference | $	$ 20,000
Proceeds, net of issuance costs | $	$ 19,984
Series C-1 Junior Preferred Stock
Temporary Equity [Line Items]
Shares authorized (in shares) | shares	5,521,905
Shares issued and outstanding (in shares) | shares	2,647,946
Original issue price per share (in usd per share) | $ / shares	$ 12.38
Aggregate Liquidation Preference | $	$ 32,755
Proceeds, net of issuance costs | $	$ 32,653
Series C-2 Junior Preferred Stock
Temporary Equity [Line Items]
Shares authorized (in shares) | shares	1,510,000
Shares issued and outstanding (in shares) | shares	0
Original issue price per share (in usd per share) | $ / shares	$ 17.22
Aggregate Liquidation Preference | $	$ 0
Proceeds, net of issuance costs | $	$ 0
Series D Senior Preferred Stock
Temporary Equity [Line Items]
Shares authorized (in shares) | shares	12,320,844
Shares issued and outstanding (in shares) | shares	5,737,440
Original issue price per share (in usd per share) | $ / shares	$ 9.03
Aggregate Liquidation Preference | $	$ 102,535
Proceeds, net of issuance costs | $	$ 50,415

Stock-Based Compensation - Narr

Stock-Based Compensation - Narrative (Details) - USD ($) $ in Millions	1 Months Ended	9 Months Ended
	Nov. 30, 2011	Sep. 30, 2021	Jul. 19, 2021	Dec. 31, 2020
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unamortized stock-based compensation cost		$ 11.2
Unamortized stock-based compensation cost expected to be recognized over a weighted average period		3 years 3 months 18 days
Class A common stock
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares available for future issuance (in shares)		13,261,244		22,808,979
2011 Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Grant price as a percentage of fair value of the stock (not less than)	100.00%
Vesting period	4 years
Expiration term	10 years
2011 Plan | Class A common stock
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares available for future issuance (in shares)		668,772
2021 Plan | Class A common stock
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares available for future issuance (in shares)		3,480,549	3,966,162
2021 ESPP
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares granted (in shares)		0
2021 ESPP | Class A common stock
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares available for future issuance (in shares)			305,089

Stock-Based Compensation - Stoc

Stock-Based Compensation - Stock Options (Details) $ / shares in Units, $ in Thousands	9 Months Ended	12 Months Ended
	Sep. 30, 2021USD ($)$ / sharesshares	Dec. 31, 2020USD ($)$ / sharesshares
Number of Shares Subject to Options Outstanding
Outstanding at the beginning (in shares) | shares	4,096,722
Granted (in shares) | shares	2,395,956
Expired (in shares) | shares	(63)
Cancelled (in shares) | shares	(25,061)
Exercised (in shares) | shares	(449,204)
Outstanding at the end (in shares) | shares	6,018,350	4,096,722
Number of shares subject to options outstanding, vested and expected to vest at the end (in shares) | shares	5,679,528
Number of shares subject to options outstanding, vested and exercisable at the end | shares	2,643,188
Weighted- Average Exercise Price Per Share
Outstanding at the beginning (in usd per share) | $ / shares	$ 1.64
Granted (in usd per share) | $ / shares	7.38
Expired (in usd per share) | $ / shares	207.90
Cancelled (in usd per share) | $ / shares	3.52
Exercised (in usd per share) | $ / shares	1.20
Outstanding at the end (in usd per share) | $ / shares	3.95	$ 1.64
Weighted average exercise price per share, vested and expected to vest at the end (in usd per share) | $ / shares	3.82
Weighted average exercise price per share, vested and exercisable at the end (in usd per share) | $ / shares	$ 1.98
Share-based Compensation Arrangement by Share-based Payment Award, Options, Additional Disclosures [Abstract]
Weighted average remaining contractual life, outstanding	7 years 9 months 18 days	7 years
Weighted average remaining contractual life, vested and expected to vest at the end	7 years 8 months 12 days
Weighted average remaining contractual life, vested and exercisable at the end	6 years
Aggregate intrinsic value, outstanding | $	$ 43,113	$ 13,328
Aggregate intrinsic value, vested and expected to vest at the end | $	41,411
Aggregate intrinsic value, vested and exercisable at the end | $	$ 24,122

Stock-Based Compensation - Expe

Stock-Based Compensation - Expense (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Total employee stock-based compensation	$ 914	$ 195	$ 2,017	$ 531
Research and development expense
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Total employee stock-based compensation	283	62	717	184
Sales and marketing expense
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Total employee stock-based compensation	179	38	358	102
General and administrative expense
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Total employee stock-based compensation	$ 452	$ 95	$ 942	$ 245

Warrants - Narrative (Details)

Warrants - Narrative (Details) - USD ($)	3 Months Ended						9 Months Ended
	Sep. 30, 2021	Jun. 30, 2021	Mar. 31, 2021	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Sep. 30, 2021	Sep. 30, 2020	Dec. 31, 2020
Class of Warrant or Right [Line Items]
Issued warrants to purchase shares of common stock (in shares)									81,543
Additional paid-in capital	$ 914,000	$ 864,000	$ 239,000	$ 195,000	$ 201,000	$ 135,000
Other expense	22,000			(3,000)			$ 1,067,000	$ 26,000
Warrants outstanding	$ 0						$ 0		$ 474,000
2019 Warrant
Class of Warrant or Right [Line Items]
Warrant term	10 years						10 years
Warrant to purchase common stock at $20.77 per share
Class of Warrant or Right [Line Items]
Warrant, exercise price (in usd per share)	$ 20.77						$ 20.77
Warrant to purchase convertible preferred stock | Loan Agreement
Class of Warrant or Right [Line Items]
Vesting period							10 years
Interest expense	$ 400,000			11,000			$ 400,000	7,000
Series E Convertible Preferred Stock | Warrant to purchase common stock at $20.77 per share
Class of Warrant or Right [Line Items]
Issued warrants to purchase shares of common stock (in shares)	722,223						722,223
Warrant, exercise price (in usd per share)	$ 20.77						$ 20.77
Series E Convertible Preferred Stock | Warrant to purchase common stock at $20.77 per share | Black-Scholes option pricing model
Class of Warrant or Right [Line Items]
Additional paid-in capital							$ 1,100,000
Series D Convertible Preferred Stock
Class of Warrant or Right [Line Items]
Issued warrants to purchase shares of common stock (in shares)									22,609
Warrant, exercise price (in usd per share)									$ 9.03
Warrants outstanding									$ 254,000
Series D Convertible Preferred Stock | 2019 Warrant
Class of Warrant or Right [Line Items]
Other expense	$ (9,000)			$ (8,000)			$ (15,000)	$ (13,000)
Total Convertible Preferred Stock
Class of Warrant or Right [Line Items]
Warrants outstanding									$ 500,000

Warrants - Common Stock Warrant

Warrants - Common Stock Warrants Outstanding (Details) - $ / shares	Sep. 30, 2021	Dec. 31, 2020
Class of Warrant or Right [Line Items]
Number of warrants outstanding (in shares)	2,788,484	2,019,590
5.20
Class of Warrant or Right [Line Items]
Exercise price (in usd per share)	$ 5.20
Number of warrants outstanding (in shares)	15,979	0
9.03
Class of Warrant or Right [Line Items]
Exercise price (in usd per share)	$ 9.03
Number of warrants outstanding (in shares)	1,032,404	1,009,795
10.84
Class of Warrant or Right [Line Items]
Exercise price (in usd per share)	$ 10.84
Number of warrants outstanding (in shares)	1,009,795	1,009,795
12.38
Class of Warrant or Right [Line Items]
Exercise price (in usd per share)	$ 12.38
Number of warrants outstanding (in shares)	8,083	0
20.77
Class of Warrant or Right [Line Items]
Exercise price (in usd per share)	$ 20.77
Number of warrants outstanding (in shares)	722,223	0

Warrants - Common Stock Warra_2

Warrants - Common Stock Warrants Roll Forward (Details)	9 Months Ended
	Sep. 30, 2021shares
Common Stock Warrants [Roll Forward]
Number of warrants outstanding, beginning balance (in shares)	2,019,590
Issued in connection with Series E financing (in shares)	722,223
Conversion of outstanding preferred stock warrants to common stock warrants (in shares)	81,543
Exercised, net shares issued (in shares)	(22,372)
Cancelled for net exercise (in shares)	(12,500)
Number of warrants outstanding, ending balance (in shares)	2,788,484

Warrants - Warrants to Purchase

Warrants - Warrants to Purchase Convertible Preferred Stock (Details) - USD ($)	Sep. 30, 2021	Dec. 31, 2020
Class of Warrant or Right [Line Items]
Number of warrants (in shares)		81,543
Fair Value	$ 0	$ 474,000
Series A-2 Convertible Preferred Stock Grant Date Sep 2012
Class of Warrant or Right [Line Items]
Number of warrants (in shares)		12,506
Exercise price (in usd per share)		$ 5.20
Fair Value		$ 41,000
Series A-2 Convertible Preferred Stock Grant Date Sep 2014
Class of Warrant or Right [Line Items]
Number of warrants (in shares)		3,473
Exercise price (in usd per share)		$ 5.20
Fair Value		$ 13,000
Series B-1 Convertible Preferred Stock Grant Date Dec 2014
Class of Warrant or Right [Line Items]
Number of warrants (in shares)		28,860
Exercise price (in usd per share)		$ 5.20
Fair Value		$ 113,000
Series B-2 Convertible Preferred Stock Grant Date Dec 2015
Class of Warrant or Right [Line Items]
Number of warrants (in shares)		6,012
Exercise price (in usd per share)		$ 8.32
Fair Value		$ 22,000
Series C-1 Convertible Preferred Stock Grant Date Mar 2017
Class of Warrant or Right [Line Items]
Number of warrants (in shares)		8,083
Exercise price (in usd per share)		$ 12.38
Fair Value		$ 31,000
Series D Convertible Preferred Stock Grant Date Feb 2020
Class of Warrant or Right [Line Items]
Number of warrants (in shares)		22,609
Exercise price (in usd per share)		$ 9.03
Fair Value		$ 254,000

Warrants - Preferred Stock Warr

Warrants - Preferred Stock Warrant Liability Activity (Details) - USD ($)	3 Months Ended	9 Months Ended
	Sep. 30, 2021	Sep. 30, 2021
Warrant Liability Outstanding
Outstanding, beginning of period		$ 474,000
Recorded in equity upon conversion of preferred stock warrants to common stock warrants	$ (929,000)	(929,000)
Outstanding, end of period	0	0
Preferred stock warrant liability
Warrant Liability Outstanding
Outstanding, beginning of period		474,000
Outstanding, end of period	$ 0	0
Preferred stock warrant liability | Other income (expense), net
Warrant Liability Outstanding
Net increase in fair value of preferred stock warrants		15,000
Preferred stock warrant liability | Interest expense
Warrant Liability Outstanding
Net increase in fair value of preferred stock warrants		$ 440,000

Commitments and Contingences (D

Commitments and Contingences (Details)	3 Months Ended		9 Months Ended
	Sep. 30, 2021USD ($)ft²	Sep. 30, 2020USD ($)	Sep. 30, 2021USD ($)ft²	Sep. 30, 2020USD ($)	Dec. 31, 2020USD ($)
Commitments And Contingencies [Line Items]
Renewal period of lease	5 years		5 years
Percentage of increase in base rent annually			3.00%
Lease rent expense	$ 100,000	$ 100,000	$ 300,000	$ 300,000
Deferred rent	200,000		200,000		$ 300,000
Indemnification liability	0		0		$ 0
Current Liabilities
Commitments And Contingencies [Line Items]
Capital lease obligation payments due	100,000		100,000
Other Liabilities
Commitments And Contingencies [Line Items]
Capital lease obligation payments due	$ 100,000		$ 100,000
Office and laboratory space
Commitments And Contingencies [Line Items]
Number of square feet under lease | ft²	24,100		24,100

Net Loss Per Share - Computatio

Net Loss Per Share - Computation of the Basic and Diluted Net Loss Per Share (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended						9 Months Ended
	Sep. 30, 2021	Jun. 30, 2021	Mar. 31, 2021	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Sep. 30, 2021	Sep. 30, 2020
Impairment Effects on Earnings Per Share [Line Items]
Net loss	$ (9,859)	$ (6,307)	$ (6,359)	$ (5,072)	$ (4,705)	$ (4,696)	$ (22,525)	$ (14,473)
Weighted-average shares of common stock outstanding, basic (in shares)	25,085,013			1,536,483			9,707,254	1,529,182
Weighted-average shares of common stock outstanding, diluted (In shares)	25,085,013			1,536,483			9,707,254	1,529,182
Net loss per share, basic (in usd per share)	$ (0.39)			$ (3.30)			$ (2.32)	$ (9.46)
Net loss per share, diluted (in usd per share)	$ (0.39)			$ (3.30)			$ (2.32)	$ (9.46)
Class A common stock
Impairment Effects on Earnings Per Share [Line Items]
Net loss	$ (9,415)						$ (21,641)
Weighted-average shares of common stock outstanding, basic (in shares)	23,954,696						9,326,341
Weighted-average shares of common stock outstanding, diluted (In shares)	23,954,696						9,326,341
Net loss per share, basic (in usd per share)	$ (0.39)						$ (2.32)
Net loss per share, diluted (in usd per share)	$ (0.39)						$ (2.32)
Class B common stock
Impairment Effects on Earnings Per Share [Line Items]
Net loss	$ (444)						$ (884)
Weighted-average shares of common stock outstanding, basic (in shares)	1,130,317						380,913
Weighted-average shares of common stock outstanding, diluted (In shares)	1,130,317						380,913
Net loss per share, basic (in usd per share)	$ (0.39)						$ (2.32)
Net loss per share, diluted (in usd per share)	$ (0.39)						$ (2.32)

Net Loss Per Share - Anti-Dilut

Net Loss Per Share - Anti-Dilutive Securities Excluded from the Computation of Diluted Net Loss Per Share (Details) - shares	9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Anti-dilutive securities excluded from the computation of earnings per share (in shares)	8,806,834	22,680,847
Junior Convertible Preferred Stock
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Anti-dilutive securities excluded from the computation of earnings per share (in shares)	0	9,819,480
Senior Convertible Preferred Stock
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Anti-dilutive securities excluded from the computation of earnings per share (in shares)	0	5,737,440
Shares issuable under convertible note
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Anti-dilutive securities excluded from the computation of earnings per share (in shares)	0	649,216
Warrants to purchase convertible preferred stock
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Anti-dilutive securities excluded from the computation of earnings per share (in shares)	0	81,543
Warrants to purchase Class A common stock
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Anti-dilutive securities excluded from the computation of earnings per share (in shares)	2,788,484	2,019,590
Options to purchase Class A common stock
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Anti-dilutive securities excluded from the computation of earnings per share (in shares)	6,018,350	4,373,578