Aura Biosciences (AURA) 10-Q 24 Nov 21 2021 Q3 Quarterly report Financial data

Document and Entity Information

Document and Entity Information - shares	9 Months Ended
	Sep. 30, 2021	Nov. 19, 2021
Cover [Abstract]
Document Type	10-Q
Amendment Flag	false
Document Period End Date	Sep. 30, 2021
Document Fiscal Year Focus	2021
Document Fiscal Period Focus	Q3
Entity Registrant Name	AURA BIOSCIENCES, INC.
Entity Central Index Key	0001501796
Entity File Number	001-40971
Entity Incorporation, State or Country Code	DE
Entity Tax Identification Number	32-0271970
Entity Address, Address Line One	85 Bolton Street
Entity Address, City or Town	Cambridge
Entity Address, State or Province	MA
Entity Address, Postal Zip Code	02140
City Area Code	617
Local Phone Number	500-8864
Entity Interactive Data Current	Yes
Entity Current Reporting Status	No
Current Fiscal Year End Date	--12-31
Entity Filer Category	Non-accelerated Filer
Entity Shell Company	false
Entity Small Business	true
Entity Emerging Growth Company	true
Entity Ex Transition Period	false
Title of 12(b) Security	Common Stock, par value $0.00001 per share
Trading Symbol	AURA
Security Exchange Name	NASDAQ
Document Quarterly Report	true
Document Transition Report	false
Entity Bankruptcy Proceedings, Reporting Current	true
Entity Common Stock, Shares Outstanding		29,210,549

Condensed Balance Sheets (Unaud

Condensed Balance Sheets (Unaudited) - USD ($) $ in Thousands	Sep. 30, 2021	Dec. 31, 2020
Current assets:
Cash and cash equivalents	$ 81,829	$ 17,393
Restricted cash and deposits	20	19
Prepaid expenses and other current assets	1,609	1,043
Total current assets	83,458	18,455
Restricted cash and deposits, net of current portion	125	75
Right of use assets - operating lease	1,096
Property and equipment, net	4,442	3,574
Deferred offering costs	1,583
Total Assets	90,704	22,104
Current liabilities:
Accounts payable	1,736	611
Current portion of operating lease liabilities	607
Accrued expenses and other current liabilities	3,488	2,050
Total current liabilities	5,831	2,661
Deferred rent		8
Operating lease liabilities, net of current portion	513
Warrant liability	71	72
Total Liabilities	6,415	2,741
Commitments and Contingencies (Note 12)
Stockholders’ Deficit:
Common stock, $0.00001 par value, 470,183,383 and 232,697,999 authorized at September 30, 2021 and December 31, 2020, and 442,717 and 381,123 shares issued and outstanding at September 30, 2021 and December 31, 2020, respectively
Additional paid-in capital	9,488	8,173
Accumulated deficit	(140,503)	(116,886)
Total Stockholders’ Deficit	(131,015)	(108,713)
Total Liabilities, Convertible Preferred Stock, and Stockholders’ Deficit	90,704	22,104
Series A Convertible Preferred Stock
Current liabilities:
Convertible preferred stock	3,368	3,368
Series A-1 Convertible Preferred Stock
Current liabilities:
Convertible preferred stock	7,837	7,837
Series A-2 Convertible Preferred Stock
Current liabilities:
Convertible preferred stock	5,373	5,373
Series B Convertible Preferred Stock
Current liabilities:
Convertible preferred stock	20,806	20,806
Series C-1 Convertible Preferred Stock
Current liabilities:
Convertible preferred stock	29,353	29,353
Series C-2 Convertible Preferred Stock
Current liabilities:
Convertible preferred stock	11,746	11,746
Series D-1 Convertible Preferred Stock
Current liabilities:
Convertible preferred stock	39,686	39,686
Series D-2 Convertible Preferred Stock
Current liabilities:
Convertible preferred stock	16,889	$ 9,907
Series E Convertible Preferred Stock
Current liabilities:
Convertible preferred stock	$ 80,246

Condensed Balance Sheets (Una_2

Condensed Balance Sheets (Unaudited) (Parenthetical) - USD ($) $ in Thousands	Sep. 30, 2021	Dec. 31, 2020
Convertible preferred stock, par value	$ 0.00001
Common stock, par value	$ 0.00001	$ 0.00001
Common stock, shares authorized	470,183,383	232,697,999
Common stock, shares issued	442,717	381,123
Common stock, shares outstanding	442,717	381,123
Series A Convertible Preferred Stock
Convertible preferred stock, par value	$ 0.00001	$ 0.00001
Convertible preferred stock, shares authorized	1,701,141	1,701,141
Convertible preferred stock, shares issued	1,701,141	1,701,141
Convertible preferred stock, shares outstanding	1,701,141	1,701,141
Convertible preferred stock, liquidation preference	$ 3,403	$ 3,403
Series A-1 Convertible Preferred Stock
Convertible preferred stock, par value	$ 0.00001	$ 0.00001
Convertible preferred stock, shares authorized	3,298,732	3,298,732
Convertible preferred stock, shares issued	3,298,732	3,298,732
Convertible preferred stock, shares outstanding	3,298,732	3,298,732
Convertible preferred stock, liquidation preference	$ 8,196	$ 8,196
Series A-2 Convertible Preferred Stock
Convertible preferred stock, par value	$ 0.00001	$ 0.00001
Convertible preferred stock, shares authorized	4,325,021	4,325,021
Convertible preferred stock, shares issued	4,324,998	4,324,998
Convertible preferred stock, shares outstanding	4,324,998	4,324,998
Convertible preferred stock, liquidation preference	$ 5,373	$ 5,373
Series B Convertible Preferred Stock
Convertible preferred stock, par value	$ 0.00001	$ 0.00001
Convertible preferred stock, shares authorized	22,705,646	22,705,646
Convertible preferred stock, shares issued	22,531,819	22,531,819
Convertible preferred stock, shares outstanding	22,531,819	22,531,819
Convertible preferred stock, liquidation preference	$ 38,894	$ 37,429
Series C-1 Convertible Preferred Stock
Convertible preferred stock, par value	$ 0.00001	$ 0.00001
Convertible preferred stock, shares authorized	58,109,711	58,109,711
Convertible preferred stock, shares issued	58,109,711	58,109,711
Convertible preferred stock, shares outstanding	58,109,711	58,109,711
Convertible preferred stock, liquidation preference	$ 37,736	$ 36,150
Series C-2 Convertible Preferred Stock
Convertible preferred stock, par value	$ 0.00001	$ 0.00001
Convertible preferred stock, shares authorized	33,218,192	33,218,192
Convertible preferred stock, shares issued	33,218,192	33,218,192
Convertible preferred stock, shares outstanding	33,218,192	33,218,192
Convertible preferred stock, liquidation preference	$ 15,332	$ 14,697
Series D-1 Convertible Preferred Stock
Convertible preferred stock, par value	$ 0.00001	$ 0.00001
Convertible preferred stock, shares authorized	57,878,742	57,878,742
Convertible preferred stock, shares issued	57,878,742	57,878,742
Convertible preferred stock, shares outstanding	57,878,742	57,878,742
Convertible preferred stock, liquidation preference	$ 46,003	$ 43,908
Series D-2 Convertible Preferred Stock
Convertible preferred stock, par value	$ 0.00001	$ 0.00001
Convertible preferred stock, shares authorized	24,598,481	24,598,481
Convertible preferred stock, shares issued	24,598,481	14,469,710
Convertible preferred stock, shares outstanding	24,598,481	14,469,710
Convertible preferred stock, liquidation preference	$ 17,982	$ 10,176
Series E Convertible Preferred Stock
Convertible preferred stock, par value	$ 0.00001	$ 0.00001
Convertible preferred stock, shares authorized	102,671,041	0
Convertible preferred stock, shares issued	102,671,041	0
Convertible preferred stock, shares outstanding	102,671,041	0
Convertible preferred stock, liquidation preference	$ 83,525

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
Operating Expenses:
Research and development	$ 6,365	$ 2,850	$ 17,182	$ 14,499
General and administrative	2,530	781	6,441	2,798
Total operating expenses	8,895	3,631	23,623	17,297
Total operating loss	8,895	3,631	23,623	17,297
Other income (expense):
Change in fair value of warrant liability			(1)
Change in fair value of derivative liability	52
Interest income (expense), including amortization of discount	5		8	(2)
Loss from disposal of assets			(3)
Total other income (expense)	57		6	(2)
Net loss and comprehensive loss	(8,838)	(3,631)	(23,617)	(17,299)
Net loss attributable to common stockholders - basic and diluted	$ (12,506)	$ (5,579)	$ (33,244)	$ (23,101)
Net loss per share attributable to common stockholders—basic and diluted	$ (28.33)	$ (14.81)	$ (77.93)	$ (63.69)
Weighted average common stock outstanding- basic and diluted	441,448	376,738	426,604	362,735

Condensed Statements of Convert

Condensed Statements of Convertible Preferred Stock and Stockholders' Deficit (Unaudited) - USD ($) $ in Thousands	Total	Common Stock	Additional Paid-in Capital	Accumulated Deficit	Series A Convertible Preferred Stock	Series A-1 Convertible Preferred Stock	Series A-2 Convertible Preferred Stock	Series B Convertible Preferred Stock	Series C-1 and C-2 Convertible Preferred Stock	Series D-1 and D-2 Convertible Preferred Stock	Series E Convertible Preferred Stock
Beginning Balance at Dec. 31, 2019	$ (87,406)		$ 7,274	$ (94,680)
Convertible preferred stock, Beginning Balance at Dec. 31, 2019					$ 3,368	$ 7,837	$ 5,373	$ 20,806	$ 41,099	$ 39,686
Convertible preferred stock, Beginning Balance, Shares at Dec. 31, 2019					1,701,141	3,298,732	4,324,998	22,531,819	91,327,903	57,878,742
Beginning Balance, Shares at Dec. 31, 2019		340,591
Stock-based compensation expense	177		177
Stock option exercises	33		33
Stock option exercises, Shares		7,880
Net loss	(7,512)			(7,512)
Ending Balance at Mar. 31, 2020	(94,708)		7,484	(102,192)
Convertible preferred stock, Ending Balance at Mar. 31, 2020					$ 3,368	$ 7,837	$ 5,373	$ 20,806	$ 41,099	$ 39,686
Convertible preferred stock, Ending Balance, Shares at Mar. 31, 2020					1,701,141	3,298,732	4,324,998	22,531,819	91,327,903	57,878,742
Ending Balance, Shares at Mar. 31, 2020		348,471
Beginning Balance at Dec. 31, 2019	(87,406)		7,274	(94,680)
Convertible preferred stock, Beginning Balance at Dec. 31, 2019					$ 3,368	$ 7,837	$ 5,373	$ 20,806	$ 41,099	$ 39,686
Convertible preferred stock, Beginning Balance, Shares at Dec. 31, 2019					1,701,141	3,298,732	4,324,998	22,531,819	91,327,903	57,878,742
Beginning Balance, Shares at Dec. 31, 2019		340,591
Net loss	(17,299)
Ending Balance at Sep. 30, 2020	(104,000)		7,979	(111,979)
Convertible preferred stock, Ending Balance at Sep. 30, 2020					$ 3,368	$ 7,837	$ 5,373	$ 20,806	$ 41,099	$ 39,686
Convertible preferred stock, Ending Balance, Shares at Sep. 30, 2020					1,701,141	3,298,732	4,324,998	22,531,819	91,327,903	57,878,742
Ending Balance, Shares at Sep. 30, 2020		379,902
Beginning Balance at Mar. 31, 2020	(94,708)		7,484	(102,192)
Convertible preferred stock, Beginning Balance at Mar. 31, 2020					$ 3,368	$ 7,837	$ 5,373	$ 20,806	$ 41,099	$ 39,686
Convertible preferred stock, Beginning Balance, Shares at Mar. 31, 2020					1,701,141	3,298,732	4,324,998	22,531,819	91,327,903	57,878,742
Beginning Balance, Shares at Mar. 31, 2020		348,471
Stock-based compensation expense	189		189
Stock option exercises	97		97
Stock option exercises, Shares		24,648
Net loss	(6,156)			(6,156)
Ending Balance at Jun. 30, 2020	(100,578)		7,770	(108,348)
Convertible preferred stock, Ending Balance at Jun. 30, 2020					$ 3,368	$ 7,837	$ 5,373	$ 20,806	$ 41,099	$ 39,686
Convertible preferred stock, Ending Balance, Shares at Jun. 30, 2020					1,701,141	3,298,732	4,324,998	22,531,819	91,327,903	57,878,742
Ending Balance, Shares at Jun. 30, 2020		373,119
Stock-based compensation expense	191		191
Stock option exercises	18		18
Stock option exercises, Shares		6,783
Net loss	(3,631)			(3,631)
Ending Balance at Sep. 30, 2020	(104,000)		7,979	(111,979)
Convertible preferred stock, Ending Balance at Sep. 30, 2020					$ 3,368	$ 7,837	$ 5,373	$ 20,806	$ 41,099	$ 39,686
Convertible preferred stock, Ending Balance, Shares at Sep. 30, 2020					1,701,141	3,298,732	4,324,998	22,531,819	91,327,903	57,878,742
Ending Balance, Shares at Sep. 30, 2020		379,902
Beginning Balance at Dec. 31, 2020	(108,713)		8,173	(116,886)
Convertible preferred stock, Beginning Balance at Dec. 31, 2020					$ 3,368	$ 7,837	$ 5,373	$ 20,806	$ 41,099	$ 49,593
Convertible preferred stock, Beginning Balance, Shares at Dec. 31, 2020					1,701,141	3,298,732	4,324,998	22,531,819	91,327,903	72,348,452	0
Beginning Balance, Shares at Dec. 31, 2020		381,123
Issuance of convertible preferred stock										$ 6,982	$ 80,246
Issuance of convertible preferred stock, Shares										10,128,771	102,671,041
Stock-based compensation expense	185		185
Stock option exercises	265		265
Stock option exercises, Shares		54,296
Net loss	(5,927)			(5,927)
Ending Balance at Mar. 31, 2021	(114,190)		8,623	(122,813)
Convertible preferred stock, Ending Balance at Mar. 31, 2021					$ 3,368	$ 7,837	$ 5,373	$ 20,806	$ 41,099	$ 56,575	$ 80,246
Convertible preferred stock, Ending Balance, Shares at Mar. 31, 2021					1,701,141	3,298,732	4,324,998	22,531,819	91,327,903	82,477,223	102,671,041
Ending Balance, Shares at Mar. 31, 2021		435,419
Beginning Balance at Dec. 31, 2020	(108,713)		8,173	(116,886)
Convertible preferred stock, Beginning Balance at Dec. 31, 2020					$ 3,368	$ 7,837	$ 5,373	$ 20,806	$ 41,099	$ 49,593
Convertible preferred stock, Beginning Balance, Shares at Dec. 31, 2020					1,701,141	3,298,732	4,324,998	22,531,819	91,327,903	72,348,452	0
Beginning Balance, Shares at Dec. 31, 2020		381,123
Net loss	(23,617)
Ending Balance at Sep. 30, 2021	(131,015)		9,488	(140,503)
Convertible preferred stock, Ending Balance at Sep. 30, 2021					$ 3,368	$ 7,837	$ 5,373	$ 20,806	$ 41,099	$ 56,575	$ 80,246
Convertible preferred stock, Ending Balance, Shares at Sep. 30, 2021					1,701,141	3,298,732	4,324,998	22,531,819	91,327,903	82,477,223	102,671,041
Ending Balance, Shares at Sep. 30, 2021		442,717
Beginning Balance at Mar. 31, 2021	(114,190)		8,623	(122,813)
Convertible preferred stock, Beginning Balance at Mar. 31, 2021					$ 3,368	$ 7,837	$ 5,373	$ 20,806	$ 41,099	$ 56,575	$ 80,246
Convertible preferred stock, Beginning Balance, Shares at Mar. 31, 2021					1,701,141	3,298,732	4,324,998	22,531,819	91,327,903	82,477,223	102,671,041
Beginning Balance, Shares at Mar. 31, 2021		435,419
Stock-based compensation expense	271		271
Stock option exercises	20		20
Stock option exercises, Shares		3,649
Net loss	(8,852)			(8,852)
Ending Balance at Jun. 30, 2021	(122,751)		8,914	(131,665)
Convertible preferred stock, Ending Balance at Jun. 30, 2021					$ 3,368	$ 7,837	$ 5,373	$ 20,806	$ 41,099	$ 56,575	$ 80,246
Convertible preferred stock, Ending Balance, Shares at Jun. 30, 2021					1,701,141	3,298,732	4,324,998	22,531,819	91,327,903	82,477,223	102,671,041
Ending Balance, Shares at Jun. 30, 2021		439,068
Stock-based compensation expense	554		554
Stock option exercises	20		20
Stock option exercises, Shares		3,649
Net loss	(8,838)			(8,838)
Ending Balance at Sep. 30, 2021	$ (131,015)		$ 9,488	$ (140,503)
Convertible preferred stock, Ending Balance at Sep. 30, 2021					$ 3,368	$ 7,837	$ 5,373	$ 20,806	$ 41,099	$ 56,575	$ 80,246
Convertible preferred stock, Ending Balance, Shares at Sep. 30, 2021					1,701,141	3,298,732	4,324,998	22,531,819	91,327,903	82,477,223	102,671,041
Ending Balance, Shares at Sep. 30, 2021		442,717

Condensed Statements of Conve_2

Condensed Statements of Convertible Preferred Stock and Stockholders' Deficit (Unaudited) (Parenthetical) $ in Thousands	3 Months Ended
	Mar. 31, 2021USD ($)
Series D Tranche 2 Convertible Preferred Stock
Stock issuance cost, net	$ 18
Series E Convertible Preferred Stock
Stock issuance cost, net	$ 237

Condensed Statements of Cash Fl

Condensed Statements of Cash Flows (Unaudited) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020
Cash flows from operating activities:
Net loss	$ (23,617)	$ (17,299)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation expense	601	605
Change in fair value of warrant liability	(1)
Stock-based compensation expense	1,010	557
Loss on disposal of property and equipment	(3)
Operating lease expense	4
Changes in operating assets and liabilities:
Prepaid expenses and other assets	(566)	(52)
Accounts payable	891	(1,837)
Accrued expenses and other liabilities	1,357	(2,538)
Net cash used in operating activities	(20,324)	(20,564)
Cash flows from investing activities:
Purchases of property and equipment	(1,306)	(639)
Net cash used in investing activities	(1,306)	(639)
Cash flows from financing activities:
Proceeds from exercise of stock options	305	148
Payments made for deferred offering/financing costs	(1,416)
Other		(25)
Net cash provided by financing activities	86,117	4,903
Net increase (decrease) in cash, cash equivalents and restricted cash	64,487	(16,300)
Cash, cash equivalents and restricted cash at beginning of period	17,487	32,543
Cash, cash equivalents and restricted cash at end of period	81,974	16,243
Supplemental Disclosure of Cash Flow Information:
Purchases of property and equipment in accounts payable and accrued expenses and other liabilities	159
Initial measurement of right-of-use assets and lease liabilities for operating lease	536
Remeasurement of right-of-use assets and lease liabilities for lease modification	390
Right-of-use assets obtained in exchange for operating lease liabilities	516
Series D Convertible Preferred Stock
Cash flows from financing activities:
Advanced proceeds from issuance of Series D convertible preferred stock, net of issuance costs		4,849
Proceeds from issuance of convertible preferred stock, net of issuance costs	6,982
Payments made for deferred offering/financing costs		$ (69)
Series E Convertible Preferred Stock
Cash flows from financing activities:
Proceeds from issuance of convertible preferred stock, net of issuance costs	$ 80,246

Condensed Statements of Cash _2

Condensed Statements of Cash Flows (Unaudited) (Parenthetical) - USD ($) $ in Thousands	Sep. 30, 2021	Sep. 30, 2020
Statement Of Cash Flows [Abstract]
Cash and cash equivalents, end of period	$ 81,829	$ 11,302
Short-term restricted cash, end of period	20	4,866
Long-term restricted cash, end of period	125	75
Cash, cash equivalents and restricted cash at end of period	$ 81,974	$ 16,243

Description of Business

Description of Business	9 Months Ended
	Sep. 30, 2021
Organization Consolidation And Presentation Of Financial Statements [Abstract]
Description of Business	1. Description of Business Aura Biosciences, Inc. is a clinical-stage biotechnology company leveraging its novel targeted oncology platform to develop a potential new standard of care across multiple cancer indications, with an initial focus on ocular and urologic oncology. Within these condensed financial statements, unless the context otherwise requires, references to the Company or Aura refer to Aura Biosciences, Inc. The Company’s proprietary platform enables the targeting of a broad range of solid tumors using Virus-Like Particles, or VLPs, that can be conjugated with drugs or loaded with nucleic acids to create Virus-Like Drug Conjugates, or VDCs. The Company’s VDCs are largely agnostic to tumor type and can recognize a surface marker, known as HSPGs, that are specifically modified and more broadly expressed on many tumors. The Company is developing AU-011, its first VDC product candidate for the first line treatment of primary choroidal melanoma, a rare disease with no drugs approved. The Company is also developing AU-011 for additional ocular oncology indications and in non-muscle invasive bladder cancer. Aura’s team combines expertise in cancer cell biology, ophthalmology, and targeted therapies together with experience in the development and commercialization of orphan products for significant unmet medical needs. Aura’s headquarters are located in Cambridge, Massachusetts. The Company’s operations to date have consisted primarily of conducting research and development and raising capital. The Company is subject to risks common to companies in the biotechnology industry, including, but not limited to, the successful development and commercialization of products, fluctuations in operating results and financial risks, need for additional financing or alternative means of financial support or both to fund its current operating plan, protection of proprietary technology and patent risks, compliance with government regulations, dependence on key personnel and collaborative partners, competition, customer demand, management of growth, and the effectiveness of marketing by the Company. Liquidity and Going Concern Through September 30, 2021, the Company has funded its operations primarily with proceeds from the initial closing and additional closings of its convertible preferred stock financings. The Company has incurred recurring losses and negative cash flows from operations since its inception, including net losses of $ 23.6 million and $ 17.3 million for the nine months ended September 30, 2021 and 2020, respectively. As of September 30, 2021, the Company had cash and cash equivalents of $ 82.0 million and an accumulated deficit of $ 140.5 million. The Company expects to continue to generate operating losses for the foreseeable future. On November 2, 2021, the Company completed its initial public offering, or the IPO, in which it issued and sold 6,210,000 shares of common stock, including the full exercise of the underwriters’ option to purchase additional shares at a price to the public of $ 14.00 per share for aggregate gross proceeds of $ 86.9 million . The Company received approximately $ 77.9 million in net proceeds after deducting underwriting discounts, commissions and estimated offering expenses. As of November 24, 2021, the issuance date of these condensed financial statements, the Company expects that its cash and cash equivalents and total net proceeds from the IPO of $ 77.9 million will be sufficient to fund its operating expenses and capital expenditure requirements through at least 12 months from the issuance of these condensed financial statements. The future viability of the Company beyond that point is dependent on its ability to raise additional capital to finance its operations. Impact of COVID-19 In December 2019, a novel strain of coronavirus, which causes the disease known as COVID-19, was reported to have surfaced. Since then, COVID-19 coronavirus has spread globally. In March 2020, the World Health Organization declared the COVID-19 outbreak a pandemic and the U.S. government- imposed travel restrictions on travel between the United States, Europe and certain other countries. The outbreak and government measures taken in response have had a significant impact, both direct and indirect, on businesses and commerce, as certain worker shortages have occurred, supply chains have been disrupted, and facilities and production have been suspended. The future progression of the pandemic and its effects on the Company’s business and operations are uncertain. The Company is monitoring the potential impact of COVID-19 on its business and condensed financial statements. The effects of the public health directives and the Company’s work-from-home policies may negatively impact productivity, disrupt its business, and delay clinical programs and timelines and future clinical trials, the magnitude of which will depend, in part, on the length and severity of the restrictions and other limitations on its ability to conduct business in the ordinary course. These and similar, and perhaps more severe, disruptions in the Company’s operations could negatively impact business, results of operations and financial condition, including its ability to obtain financing. To date, the Company has not incurred impairment losses in the carrying values of its assets as a result of the pandemic and are not aware of any specific related event or circumstance that would require the Company to revise its estimates reflected in the condensed financial statements. The Company cannot be certain what the overall impact of the COVID-19 pandemic will be on its business and prospects. The extent to which the COVID-19 pandemic will directly or indirectly impact its business, results of operations, financial condition, and liquidity, including planned and future clinical trials and research and development costs, will depend on future developments that are highly uncertain, including as a result of new information that may emerge concerning COVID-19, the actions taken to contain or treat it, and the duration and intensity of the related effects.

Summary of Significant Accounti

Summary of Significant Accounting Policies	9 Months Ended
	Sep. 30, 2021
Accounting Policies [Abstract]
Summary of Significant Accounting Policies	2. Summary of Significant Accounting Policies Basis of Presentation The accompanying unaudited condensed financial statements have been prepared in accordance with accounting principles generally accepted in the United States of America, or U.S. GAAP. In management’s opinion, the accompanying unaudited condensed financial statements include all adjustments, consisting of normal recurring adjustments, which are necessary to present fairly the Company’s financial position, results of operations, and cash flows. Unaudited Interim Financial Information The accompanying condensed balance sheet as of September 30, 2021, the condensed statements of operations and comprehensive loss, condensed statement of convertible preferred stock and stockholders’ deficit for the three and nine months ended September 30, 2021 and 2020, and the condensed statements of cash flows for the nine months ended September 30, 2021 and 2020 are unaudited. The unaudited interim financial statements have been prepared on the same basis as the audited annual financial statements and, in the opinion of management, reflect all adjustments, which include only normal recurring adjustments, necessary for the fair statement of the Company’s financial position as of September 30, 2021 and the results of its operations for the three and nine months ended September 30, 2021 and 2020 and its cash flows for the nine months ended September 30, 2021 and 2020. The financial data and other information disclosed in these notes related to the three and nine months ended September 30, 2021 and 2020 are also unaudited. The unaudited condensed results of operations are not necessarily indicative of the operating results that may occur for the full fiscal year ending December 31, 2021. Certain information and footnote disclosures normally included in annual financial statements prepared in accordance with U.S. GAAP have been omitted pursuant to instructions, rules, and regulations prescribed by the United States Securities and Exchange Commission, or the SEC. Management believes that the disclosures provided here are adequate to make the information presented not misleading when these unaudited condensed financial statements are read in conjunction with the audited financial statements and notes thereto as of and for the year ended December 31, 2020. The balance sheet data as of December 31, 2020 was derived from the Company’s audited financial statements included in the final prospectus filed pursuant to Rule 424(b)(4) under the Securities Act with the SEC on November 1, 2021. Significant Accounting Policies The Company’s significant accounting policies are disclosed in the audited financial statements for the year ended December 31, 2020, filed with the SEC as a part of the final prospectus filed pursuant to Rule 424(b)(4) under the Securities Act with the SEC on November 1, 2021. Since the date of those financial statements, there have been no changes to the Company's significant accounting policies except as noted below. Cash Equivalents Cash equivalents are highly liquid investments with an original maturity of 90 days or less at the date of purchase and consist of time deposits and investments in money market funds that invest in U.S. Treasury obligations and government funds with commercial banks and financial institutions. Leases Prior to January 1, 2021, the Company accounted for leases in accordance with ASC 840, Leases. At lease inception, the Company determined if an arrangement was an operating or capital lease. For operating leases, the Company recognized rent expense, inclusive of rent escalation, holidays and lease incentives, on a straight-line basis over the lease term. The difference between rent expense recorded and the amount paid was charged to deferred rent. The Company presented lease incentives as deferred rent and amortized the incentives as a reduction to rent expense on a straight-line basis over the lease term. The Company classified deferred rent as current and noncurrent liabilities based on the portion of the deferred rent that was scheduled to mature within the proceeding twelve months. Effective January 1, 2021, the Company accounts for leases in accordance with ASU No. 2016-02, Leases (Topic 842) (“ASC 842”) . At contract inception, the Company determines if an arrangement is or contains a lease. A lease conveys the right to control the use of an identified asset for a period of time in exchange for consideration. If determined to be or contain a lease, the lease is assessed for classification as either an operating or finance lease at the lease commencement date, defined as the date on which the leased asset is made available for use by the Company, based on the economic characteristics of the lease. For each lease with a term greater than twelve months, the Company records a right-of-use asset and lease liability. The Company adopted the n ew leasing standard effective January 1, 2021 , using the modified retrospective transition approach which uses the effective date, or January 1, 2021, as the date of initial application. As a result, prior periods are presented in accordance with the previous guidance in ASC 840. ASC 842 provides several optional practical expedients in transition. The Company has elected to apply the package of practical expedients requiring no reassessment of whether any expired or existing contracts are or contain leases, the lease classification of any expired or existing leases, or the capitalization of initial direct costs for any existing leases. A right-of-use asset represents the economic benefit conveyed to the Company by the right to use the underlying asset over the lease term. A lease liability represents the obligation to make lease payments arising from the lease. The Company elected the practical expedient to not separate lease and non-lease components for all classes of underlying assets and therefore measures each lease payment as the total of the fixed lease and associated non-lease components. Lease liabilities are measured at lease commencement and calculated as the present value of the future lease payments in the contract using the rate implicit in the contract, when available. If an implicit rate is not readily determinable, the Company uses an incremental borrowing rate measured as the rate at which the Company could borrow, on a fully collateralized basis, a commensurate loan in the same currency over a period consistent with the lease term at the commencement date. Right-of-use assets are measured as the lease liability plus initial direct costs and prepaid lease payments, less lease incentives granted by the lessor. The lease term is measured as the noncancelable period in the contract, adjusted for any options to extend or terminate when it is reasonably certain the Company will extend the lease term via such options based on an assessment of economic factors present as of the lease commencement date. The Company elected the practical expedient to not recognize leases with a lease term of twelve months or less. Components of a lease are split into three categories: lease components, non-lease components, and non-components. The fixed and in-substance fixed contract consideration (including any consideration related to non-components) are allocated, based on the respective relative fair values, to the lease components and non-lease components. The Company has elected to account for lease and non-lease components together as a single lease component for all underlying assets and allocate all of the contract consideration to the lease component only. The Company’s operating leases are presented in the condensed balance sheet as operating lease right-of-use assets, classified as noncurrent assets, and operating lease liabilities, classified as current and noncurrent liabilities. Operating lease expense is recognized on a straight-line basis over the lease term. Variable costs associated with a lease, such as maintenance and utilities, are not included in the measurement of the lease liabilities and right-of-use assets but rather are expensed when the events determining the amount of variable consideration to be paid have occurred. Deferred Offering Costs The Company capitalizes certain legal, professional accounting and other third-party fees that are directly associated with in-process preferred stock or common stock financings as deferred offering costs until such financings are consummated. After consummation of the equity financing, these costs are recorded as a reduction to the carrying value of convertible preferred stock or in stockholders’ equity (deficit) as a reduction of additional paid-in capital generated as a result of the offering. Should a planned equity financing be abandoned, the deferred offering costs will be expensed immediately as a charge to operating expenses in the statements of operations and comprehensive loss. As of September 30, 2021, the Company had deferred offering costs of $ 1.6 million. Recently Adopted Accounting Pronouncements Upon adoption of ASC 842, the Company recorded lease liabilities and their corresponding right-of-use assets based on the present value of lease payments over the remaining lease term. The adoption of ASC 842 resulted in the recognition of operating lease liabilities of $ 0.6 million and operating lease right-of-use assets of $ 0.5 million and the derecognition of deferred rent liabilities of $ 0.02 million on the Company’s balance sheet as of January 1, 2021. The adoption impact relates to the Company’s existing operating lease for operating and laboratory space. The adoption of ASC 842 did not have a material impact on the Company’s statements of operations and comprehensive loss or statements of cash flows.

Fair Value of Assets and Liabil

Fair Value of Assets and Liabilities	9 Months Ended
	Sep. 30, 2021
Fair Value Disclosures [Abstract]
Fair Value of Assets and Liabilities	3. Fair Value of Assets and Liabilities The following table presents information about the Company’s financial assets and liabilities measured at fair value on a recurring basis and indicates the level of the fair value hierarchy utilized to determine such fair values as of September 30, 2021 and December 31, 2020 (in thousands): Description September 30, Quoted prices Significant Significant Assets Money market funds $ 79,829 $ 79,829 $ — $ — Total financial assets $ 79,829 $ 79,829 $ — $ — Liability Warrant liability $ 71 $ — $ — $ 71 Total financial liabilities $ 71 $ — $ — $ 71 Description December 31, Quoted prices Significant Significant Liability Warrant liability $ 72 $ — $ — $ 72 Total financial liabilities $ 72 $ — $ — $ 72 At September 30, 2021, the Company’s cash equivalents include investments in money market funds that invest in U.S. Treasury obligations and government funds, the fair value of which is valued using level 1 inputs. The fair value of the warrant liability was determined based on Level 3 inputs and utilizing the Black-Scholes option pricing model (see Note 10). Significant changes to these assumptions would result in increases or decreases to the fair value of the warrant liability. During the nine months ended September 30, 2021 and 202 0 , there were no transfers into or out of Level 3. The following table set forth a summary of changes in the fair value of the Series B Warrants, which represents a recurring fair value measurement that is classified within Level 3 of the fair value hierarchy. Changes in fair value are recognized in other (expense) income as “Change in fair value of warrant liability” in the Company’s condensed statements of operations and comprehensive loss (in thousands): Series B Warrants ( 173,827 warrants) Fair value at December 31, 2020 $ 72 Change in fair value ( 1 ) Fair value at September 30, 2021 $ 71

Property and Equipment, Net

Property and Equipment, Net	9 Months Ended
	Sep. 30, 2021
Property Plant And Equipment [Abstract]
Property and Equipment, Net	4. Property and Equipment, Net Property and equipment, net, consisted of the following (in thousands): September 30, 2021 December 31, 2020 Assets under construction $ 1,741 $ 1,154 IT equipment 73 — Leasehold improvements 13 — Lab equipment 5,085 4,708 Office furniture 63 64 Total property and equipment $ 6,975 $ 5,926 Less—accumulated depreciation ( 2,533 ) ( 2,352 ) Property and equipment, net $ 4,442 $ 3,574 Depreciation expense was $ 0.2 million for the three months ended September 30, 2021 and 2020, and was $ 0.6 million for the nine months ended September 30, 2021 and 2020.

Prepaid Expenses and Other Curr

Prepaid Expenses and Other Current Assets	9 Months Ended
	Sep. 30, 2021
Prepaid Expense and Other Assets, Current [Abstract]
Prepaid Expenses and Other Current Assets	5. Prepaid Expenses and Other Current Assets Prepaid expenses and other current assets consisted of the following (in thousands): September 30, 2021 December 31, 2020 Prepaid insurance $ 80 $ 51 Prepaid research and development expenses 1,474 976 Other 55 16 Prepaid expenses and other current assets $ 1,609 $ 1,043

Accrued Expenses and Other Curr

Accrued Expenses and Other Current Liabilities	9 Months Ended
	Sep. 30, 2021
Payables And Accruals [Abstract]
Accrued Expenses and Other Current Liabilities	6. Accrued Expenses and Other Current Liabilities Accrued expenses and other current liabilities consisted of the following (in thousands): September 30, 2021 December 31, 2020 Accrued research and development expenses $ 1,184 $ 750 Accrued compensation 1,569 1,023 Other 735 277 Accrued expenses and other current liabilities $ 3,488 $ 2,050

Convertible Preferred Stock

Convertible Preferred Stock	9 Months Ended
	Sep. 30, 2021
Temporary Equity Disclosure [Abstract]
Convertible Preferred Stock	7. Convertible Preferred Stock As of September 30, 2021, the Company had 1,701,141 authorized, issued and outstanding shares of Series A Preferred stock, par value $ 0.00001 , or the Series A, 3,298,732 authorized, issued and outstanding shares of Series A-1 Preferred stock, par value $ 0.00001 , or the Series A-1, 4,325,021 authorized shares and 4,324,998 issued and outstanding shares of Series A-2 Preferred stock, par value $ 0.00001 , or the Series A-2, and 22,705,646 authorized shares and 22,531,819 issued and outstanding shares of Series B Preferred stock, par value $ 0.00001 , or the Series B, 58,109,711 authorized, issued and outstanding shares of Series C-1 Preferred stock, par value $ 0.00001 , or the Series C-1, 33,218,192 authorized, issued and outstanding shares of Series C-2 Preferred stock, par value $ 0.00001 , or the Series C-2, together with Series C-1, the Series C, 57,878,742 authorized, issued and outstanding shares of Series D-1 Preferred stock, par value $ 0.00001 , or the Series D-1, and 24,598,481 authorized, issued and outstanding shares of Series D-2 Preferred stock, par value $ 0.00001 , or the Series D-2, together with the Series D-1, the Series D, 102,671,041 authorized, issued, and outstanding shares of Series E Preferred stock, par value $ 0.00001 , or the Series E, and together with the Series D, the Series C and the Series B, collectively the Senior Preferred Stock. All series of convertible preferred stock are collectively referred to as the Preferred Stock, each with a par value of $ 0.00001 per share. Series D-2 Offering On June 25, 2020, the Company entered into a Series D-2 Convertible Preferred Stock Purchase Agreement, or the Series D-2 Agreement, with certain investors to sell up to 24,598,481 shares of the Series D-2 stock at a purchase price of $ 0.6911 per share. The Series D-2 Agreement provides for two closings, the first on October 1, 2020, and the second upon the achievement or waiver of certain milestone events. The Company sold 14,469,710 shares of the Series D-2 on October 1, 2020, at the first tranche closing for gross proceeds of $ 10.0 million. On March 5, 2021, the Company completed the second tranche of the Series D-2 offering and issued 10,128,771 shares of the Series D-2 at a purchase price of $ 0.6911 per share for gross proceeds of $ 7.0 million. Costs incurred in connection with the Series D-2 offering totaled $ 0.1 million and were recorded as a reduction of proceeds from the Series D-2. The majority of offering costs were incurred during the year ended December 31, 2020. Offering costs incurred during the nine months ended September 30, 2021, were $ 0.02 million. Series E Offering On March 18, 2021, the Company completed its Series E offering and issued 102,671,041 shares of Series E stock, $ 0.00001 par value per share, at a purchase price of $ 0.7839 per share for gross proceeds of $ 80.5 million. Costs incurred in connection with the Series E offering totaled $ 0.2 million during the nine months September 30, 2021 and were recorded as a reduction to the Series E convertible preferred stock. The rights and privileges of the Company’s Preferred Stock are as follows: Voting Except as otherwise required by law or by other provisions, holders of the Preferred Stock vote together with the holders of common stock as a single class. Holders of the Preferred Stock may cast the number of votes equal to the number of shares of common stock to which such shares of the Preferred Stock are convertible into. Dividends Series C, D, and E Dividends: From and after the date of the issuance of any shares of the Series C-1, Series C-2, Series D-1, Series D-2, and Series E, dividends at the annual rate of seven percent ( 7 %) per annum of the original share price per share accrue on such shares of the Series C-1, Series C-2, Series D-1, Series D-2, and Series E. Dividends accrue from day to day, whether or not declared, and are cumulative, but not compounding. Such dividends are only payable when and if declared by the Board of Directors (the "Board") or in the event of a Deemed Liquidation Event (as defined in the amended and restated Certificate of Incorporation). No other dividends may be declared or paid on any other class of stock unless the holders of the shares of the Series E then outstanding first receive, or simultaneously receive, their applicable dividend. As of September 30, 2021, $ 7.4 million, $ 3.2 million, $ 6.0 million, $ 1.0 million, and $ 3.0 million of cumulative dividends on the Series C-1, Series C-2, Series D-1, Series D-2, and Series E respectively, are included in the liquidation preference amount indicated on the balance sheet. Series B Dividends: From and after the date of the issuance of any shares of the Series B, dividends at the annual rate of $ 0.0869645 per share accrue on such shares of the Series B. Dividends accrue from day to day, whether or not declared, and are cumulative, but not compounding. Such dividends are only payable when and if declared by the Company’s Board or in the event of a Deemed Liquidation Event (as defined in the amended and restated Certificate of Incorporation). No other dividends may be declared or paid on any other class of stock unless the holders of the shares of the Series B then outstanding first receive, or simultaneously receive, their applicable dividend. As of September 30, 2021, $ 10.9 million of cumulative dividends on the Series B are included in the liquidation preference amount indicated on the balance sheet. Series A Dividends From and after the date of the issuance of the Series A, Series A-1, and Series A-2, if the Company declares, pays or sets aside, on the same date, a dividend on shares of more than one class or series of capital stock of the Company, the dividend payable to the holders of the Series A, Series A-1, and Series A-2 convertible preferred stock shall be calculated based upon the dividend on the class or series of capital stock that would result in the highest dividend. No other dividends, or dividends on common stock payable in shares of common stock, may be declared or paid unless the holders of the Series A, Series A-1, and Series A-2 then outstanding first receive, or simultaneously receive, their applicable dividend. As of September 30, 2021, no dividends have been declared on the common stock or the Preferred Stock. Liquidation Rights In the event of a Deemed Liquidation Event, as defined in the Company’s amended and restated Certificate of Incorporation, the assets of the Company will be distributed first to the holders of the Series E. The holders of the Series E will receive, in preference to all other stockholders, an amount equal to the sum of the Series E original issue price (equal to the cash price paid per share of $ 0.783900 ), plus unpaid dividends on such shares. Next, the holders of the Series D will receive, in preference to all other stockholders other than the Series E, an amount equal to the sum of the Series D original issue price, plus unpaid dividends on such shares. Next, the holders of the Series C will receive, in preference to all stockholders other than the Series E and D holders, an amount equal to the sum of the Series C original issue price plus unpaid dividends on such shares. Next, the holders of the Series B will receive, in preference to the holders of the Series A, Series A-1, Series A-2 and common stock, an amount equal to the sum of the Series B original issue price plus unpaid dividends on such shares. Next, the holders of the Series A, Series A-1, and Series A-2 will receive, in preference to the holders of common stock, an amount equal to the greater of their applicable liquidation preference or what they would have received had their shares converted into common stock. If the proceeds available are not sufficient to satisfy the full liquidation preference, the entire proceeds are to be distributed pro-rata among the Series E holders in proportion to the full preferential amount the Series E holders are entitled to receive. Conversion The Senior Preferred Stock converts into common stock on a one-for- one basis . Each share of the Series B, Series C-1, Series C-2, Series D-1, Series D-2, and Series E is convertible into the number of shares of common stock as is determined by dividing the respective original issue price by the conversion price in effect at the time of conversion. The Series E conversion price is set at $ 0.7839 per share, the Series D-1 and Series D-2 conversion price is set at $ 0.6911 per share, the Series C-1 conversion price is set at $ 0.5213 per share, the Series C-2 conversion price is set at $ 0.36491 per share, and the Series B conversion price is set at $ 1.24235 per share; none represents a beneficial conversion feature. Subject to certain exceptions, the Senior Preferred Stock has the benefit of anti- dilution protection on a weighted-average basis in the event that the Company sells stock at less than the applicable conversion price per share. Each share of the Series A and Series A-1 was originally convertible into the number of shares of common stock determined by dividing the respective Series A and Series A-1 original issue price by the conversion price in effect at the time of conversion. The Series A conversion price was originally equal to $ 2.00 per share and the Series A-1 conversion price was originally equal to $ 2.4847 per share. As the Series A-2 was sold at $ 1.24235 per share, less than the per share prices of the Series A and Series A-1, anti-dilution protections were triggered. Pursuant to the anti-dilution protection terms, on February 24, 2015, the Series A conversion price was reduced from $2.00 to $ 1.8191 per share of common stock and the Series A-1 conversion price was reduced from $2.4847 to $ 2.1898 per share of common stock and, therefore, the Series A conversion ratio was changed from 1 to 1 to 1 to 1.099 and the Series A-1 conversion ratio was changed from 1 to 1 to 1 to 1.135 . The Company evaluated the Series A and Series A-1 with the updated conversion ratios and determined that there was no beneficial conversion feature. The Series A-2 converts into common stock on a one-for- one basis . The Series A-2 conversion price is set at $ 1.24235 per share and does not represent a beneficial conversion feature. According to the terms of the Company’s amended and restated Certificate of Incorporation, in the event that the applicable conversion price for any series of Senior Preferred Stock is reduced, then the applicable conversion price for each series of the Series A convertible preferred stock shall be uniformly and concurrently reduced. Each share of the Preferred Stock will automatically convert into common stock upon (a) the occurrence of an event, specified by vote or written consent of certain stockholders or (b) the completion of a public stock offering involving a price per share of common stock of not less than $ 1.554975 per share, subject to certain adjustments, where such offering results in aggregate gross proceeds to the Company of at least $ 50.0 million and the common stock is listed for trading on either the New York Stock Exchange or the Nasdaq Stock Market. The Company must reserve and keep available out of its authorized but unused capital stock such number of authorized shares of common stock to sufficiently effect the conversion of all outstanding Preferred Stock. In considering the features of the convertible preferred stock, the Company determined that none of the features, including the conversion features, requires bifurcation during the nine months ended September 30, 2021 and 2020. The conversion ratios for the Series A was changed to 13.700 to 1.099 , Series A-1 was changed to 13.7 to 1.135 , and the Series A-2 through the Series E was changed to 13.7 to 1 upon the Company’s filing of its amendment to its amended and restated Certificate of Incorporation on October 22, 2021 (see Note 16).

Common Stock

Common Stock	9 Months Ended
	Sep. 30, 2021
Equity [Abstract]
Common Stock	8. Common Stock The Company had 470,183,383 and 232,697,999 authorized shares of common stock, par value $ 0.00001 per share, of which 442,717 and 381,123 shares were issued and outstanding as of September 30, 2021 and December 31, 2020, respectively.

Stock-Based Compensation

Stock-Based Compensation	9 Months Ended
	Sep. 30, 2021
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Stock-Based Compensation	9. Stock-Based Compensation On January 15, 2009, the Company’s Board adopted the 2009 Long-Term Incentive Stock Option Plan (the “2009 Plan”) for the issuance of stock-based compensation to both employees and non- employees. The awards under this plan typically vest over a 24, 36 or 48-month period, depending on the option agreement and have a 10-year term. On December 12, 2018 , the 2009 Plan expired, and the Company adopted the Aura Biosciences, Inc. 2018 Equity Incentive Plan (the “2018 Plan” and collectively with the 2009 Plan, the "Plans”). No options were modified in conjunction with the expiration of the 2009 Plan. The options granted under the 2009 Plan continue to be outstanding in accordance with their original terms. The 2018 Plan will expire in 2028. Under the 2018 Plan, Aura may grant incentive stock options, non-qualified stock options, restricted and unrestricted stock awards and stock rights. The Board is authorized to administer the 2018 Plan. In accordance with the provisions of the 2018 Plan, the Board determines the terms of Aura options and other awards issued pursuant thereto, including the following:  which employees, directors and consultants shall be granted awards;  the number of shares of common stock subject to options and other awards;  the exercise price of each option, which generally shall not be less than fair market value of the common stock on the date of grant;  the termination or cancellation provisions applicable to options;  the terms and conditions of other awards, including conditions for repurchase, termination or cancellation, issue price and repurchase price; and  all other terms and conditions upon which each award may be granted in accordance with the 2018 Plan. In addition, the Board or any committee to which the Board delegates authority may, with the consent of the affected plan participants, re-price or otherwise amend outstanding awards consistent with the terms of the 2018 Plan. On March 18, 2021, the Board approved an increase to the 2018 Plan available option pool of 2,346,228 options. With this increase and the transfer of the available options from the 2009 Plan, there were 650,795 options available for grant under the 2018 Plan at September 30, 2021. The following table summarizes the combined stock option activity under the 2009 and the 2018 Plan for the nine months ended September 30, 2021: Options Weighted- Weighted- Aggregate Outstanding at December 31, 2020 1,512,129 $ 3.84 7.77 $ 1,174 Granted 1,883,480 6.13 - - Exercised ( 61,594 ) 4.95 - - Cancelled or forfeited ( 169,066 ) 4.50 - - Outstanding at September 30, 2021 3,164,949 $ 5.15 8.60 $ 14,053 Exercisable at September 30, 2021 1,024,453 $ 3.85 6.75 $ 5,849 The weighted-average grant date fair value of stock options granted during the nine months ended September 30, 2021 and 2020 is $ 3.97 and $ 2.74 per share, respectively. The total intrinsic value of options exercised was $ 0.01 million and $ 0.02 million for the nine months ended September 30, 2021 and 2020, respectively. The Company has elected to use the Black-Scholes option pricing model to determine the fair value of options granted and generally recognizes the compensation cost of stock-based awards on a straight-line basis over the vesting period of the award. The determination of the fair value of stock-based payment awards utilizing the Black-Scholes option pricing model is affected by the estimated fair value of the Company’s common stock and a number of other assumptions, including expected volatility, expected life, risk-free interest rate, and expected dividends. The fair value of the stock options issued for the three and nine months ended September 30, 2021 and 2020 was measured with the following weighted-average assumptions: Three Months Ended Nine Months Ended 2021 2020 2021 2020 Weighted average risk-free interest rate 1.00 % 0.33 % 1.06 % 0.58 % Expected term (years) 6.06 5.67 6.02 6.03 Expected volatility 73.36 % 73.71 % 74.21 % 74.16 % Expected dividend yield 0.00 % 0.00 % 0.00 % 0.00 % The Company recorded stock-based compensation expense as follows (in thousands): Three Months Ended Nine Months Ended 2021 2020 2021 2020 Research and development $ 157 $ 47 $ 263 $ 153 General and administrative 397 144 747 404 Total $ 554 $ 191 $ 1,010 $ 557 As of September 30, 2021, there was $ 7.9 million of unrecognized compensation expense related to stock options, which is expected to be recognized over a weighted-average period of 2.61 years.

Series B Warrants

Series B Warrants	9 Months Ended
	Sep. 30, 2021
Equity [Abstract]
Series B Warrants	10. Series B Warrants In February 2015 and May 2015, the Company issued warrants to purchase 1,650,098 and 887,536 shares of the Series B convertible preferred stock, respectively, at an exercise price of $ 1.24235 per share. Each Series B Warrant was immediately exercisable and expires in ten years from the original date of issuance. Pursuant to FASB ASC Topic 480, Distinguishing Liabilities from Equity , the Series B Warrants were classified as a liability and are re-measured to fair value at each balance sheet date and immediately prior to exercise. The Series B Warrants were converted into warrants to purchase 12,686 shares of common stock upon the completion of the IPO in November 2021. A total of 173,827 of the Series B Warrants remained outstanding at September 30, 2021 and December 31, 2020. The warrants were valued using the Black-Scholes option pricing model. The estimated fair value of the warrants and the significant assumptions used were as follows: Series B Warrants September 30, 2021 December 30, 2021 Series B estimated fair value $ 1.12 $ 1.17 Volatility 79.50 % 74.07 % Expected term (years) 3.5 4.2 Risk free rate 0.76 % 0.27 % Dividend yield 7.00 % 7.00 % During the nine months ended September 30, 2021, the change in fair value of the warrant liability was deemed immaterial.

Compensation

Compensation	9 Months Ended
	Sep. 30, 2021
Compensation And Retirement Disclosure [Abstract]
Compensation	11. Compensation In January 2012, the Company adopted the Aura Biosciences 401(k) Profit Sharing Plan and Trust (the “401(k) Plan”) for its employees, which is designed to be qualified under Section 401(k) of the Internal Revenue Code. Eligible employees are permitted to contribute to the 401(k) Plan within statutory and 401(k) Plan limits. The Company makes matching contributions of 100 % of the first 6 % of employee contributions. The Company made matching contributions in the amount of $ 0.2 million and $ 0.1 million for the nine months ended September 30, 2021 and 2020, respectively.

Commitment and Contingencies

Commitment and Contingencies	9 Months Ended
	Sep. 30, 2021
Commitments And Contingencies Disclosure [Abstract]
Commitments and Contingencies	12. Commitments and Contingencies Lease Commitments The Company has historically entered into lease arrangements for its facilities. As of December 31, 2020, the Company had one operating lease for its office and laboratory facility with required future minimum payments. The lease does not contain any options to renew, terminate, or purchase the underlying asset, and was set to expire on July 31, 2022 . As part of its adoption of ASC 842, the Company recorded a right-of-use asset and operating lease liability for this lease as of the effective date. On March 31, 2021, the Company executed an amendment to the facility lease which included an extension of the expiration date of the original leased premises, the addition of 4,516 square feet of laboratory space with an expected commencement date of May 1, 2021 , and the addition of 1,000 square feet of laboratory space with an expected commencement date of June 15, 2021 . The lease term for the original and new spaces will expire on July 31, 2023 , with an option to renew for an additional 12 months . Upon the execution of the amendment, which was deemed to be a lease modification, the Company re-evaluated the assumptions made at the original lease commencement date. The Company determined the amendment consists of two separate contracts under ASC 842. One contract is related to the modification of term for the original space, and the other is related to a new right-of-use for the two additional spaces, which are to be accounted for as new leases. The Company remeasured the lease liability and corresponding right-of-use asset for the original space as of the effective date of the amendment to reflect the extended term and recorded in the second quarter of 2021 an additional right-of-use asset and lease liability upon lease commencement of each of the additional space. The Company also leases office and laboratory equipment for which the related expense is immaterial. The following table contains a summary of the lease costs recognized under ASC 842 and other information pertaining to the Company’s leases for the three and nine months ended September 30, 2021 (in thousands): Three Months Ended Nine Months Ended Lease Cost Financing lease costs: Amortization of finance right-of-use assets $ - $ 11 Operating lease costs 154 370 Variable lease costs 90 233 Total lease costs $ 244 $ 614 Cash paid for amounts included in the measurement of lease liability—finance leases $ 15 Cash paid for amounts included in the measurement of lease liability—operating leases $ 367 Weighted-average remaining lease term—operating leases (years) 1.83 Weighted-average discount rate—finance leases 7.94 % Weighted-average discount rate—operating leases 3.51 % The following table reconciles the future minimum commitments to the Company’s operating lease liabilities at September 30, 2021 (in thousands): Operating lease payments as of September 30, 2021 2021 (excluding nine months ended September 30, 2021) $ 153 2022 625 2023 377 Total lease payments 1,155 Less: interest ( 35 ) Total operating lease liabilities at September 30, 2021 1,120 Less: current portion of lease liabilities 607 Lease liabilities, net of current portion $ 513 In May 2021, the Company paid in full its finance lease. Laser Purchasing Commitment On April 5, 2019, the Company entered into a purchase agreement for equipment with future commitments payable in three installments of € 0.2 million each. The first two installments of € 0.2 million were paid by the Company in April 2019 and August 2019. Upon receipt of the laser systems, the Company will assess whether the laser systems have an alternative future use and, if so, will capitalize the lasers as a component of fixed assets. License Agreements The Company has entered into the following key agreements that relate to the core technology under development: LI-COR Exclusive License and Supply Agreement In January 2014, the Company entered into an Exclusive License and Supply Agreement, or the LI-COR Exclusive License Agreement, with LI-COR, Inc., or LI-COR, for the license of IRDye 700DX and related licensed patents for the treatment and diagnosis of ocular cancers in humans, and as amended in January 2016, July 2017, April 2018 and April 2019. LI-COR is a related party owning shares of the Company’s capital stock. The LI-COR Exclusive License Agreement required a one-time upfront license issue fee of $ 0.1 million and requires aggregate milestone payments of up to $ 0.2 million upon certain regulatory and development milestones. The Company is also required to pay LI-COR low-single digit royalties on net sales. The term of the LI-COR Exclusive Agreement expires on a country-by-country basis, until the longer of (i) ten years from the first commercial sale of a licensed product in such country and (ii) the last to expire valid claim in such country. The Company recognized no expenses related to this agreement and related amendments for the nine months ended September 30, 2021 and 2020, respectively. LI-COR Non-Exclusive License and Supply Agreement In December 2014, the Company entered into a Non-Exclusive License Agreement, or the 2014 Non-Exclusive Agreement, for LI-COR to supply IRDye 700DX to the Company for the treatment and diagnosis of non-ocular cancers in humans. Under the 2014 Non-Exclusive Agreement, the Company paid a license issue fee of $ 0.03 million on the effective date. The Company must also pay LI-COR a non-refundable, non-creditable fee of $ 0.03 million per each licensed product upon pre-IND designation, as defined, of such licensed product. During the term, the Company must pay LI-COR low-single digit royalties on net sales. LI-COR receives 10% of all sublicensee income within 30 days of the Company’s receipt from the sublicensee. The 2014 Non-Exclusive Agreement also required the Company to make certain payments upon the achievement of specified development and commercial milestones of up to $ 0.4 million in the aggregate. Life Technologies Corporation In December 2014, the Company entered into a non-exclusive, perpetual license agreement with Life Technologies Corporation, or Life Technologies, which allows the use of their HEK293 cell lines to manufacture Aura’s products. Under this agreement the Company is required to pay an initial license fee of $ 0.1 million for each product. An annual development fee of $ 0.1 million is due within a year from the payment of the initial license fee and due annually until the earlier of (i) payment of a commercialization fee or (ii) all development work is terminated. The commercialization fee is a one-time, non-refundable, non-creditable fee of $ 0.3 million due upon receipt of approval of a licensed product. In the event of a change of control of an above 50 % change in voting share, there will be a change of control fee of $ 0.2 million. The Company recorded a derivative liability due an increased probability of payment assessed in June 2021 to account for the change of control fee. Such amount was reduced to nil during the three months ended September 30, 2021 as the probability of a change of ownership above 50 % of voting shares for the pending IPO was deemed probable not to occur. During the nine months ended September 30, 2021 and 2020, the Company recognized $ 0.03 million of expenses related to this agreement. National Institute of Health (NIH)-Biologic Materials License Agreement In December 2010, the Company entered into a Biologic Materials License Agreement with National Institutes of Health, or the NIH, for a non-exclusive right to use materials described in Schiller et al., Virology 2004 Apr.10, 321(2):205-16, which required a one-time non-refundable license issuance fee of $ 0.02 million. No future milestone payments or royalties are due under this agreement. National Institute of Health (NIH)-Collaboration Research and Development Agreement In July 2011, the Company entered into a Collaboration Research and Development Agreement, or CRADA, with Dr. John Schiller at the NIH, for a period of two years with the rights to an exclusive license to all technology generated within the collaboration. Under the agreement, the Company was required to make annual payments each year to fund the research activities, with the first payment due within 30 days of the effective date and subsequent payments due within 30 days of the anniversary date. This agreement was further amended in 2012, 2013, 2014, 2015, 2016, 2018 and most recently in September of 2020. During 2011-2020, the Company paid an aggregate of $ 0.3 million in research collaboration fees, $ 0.04 million of which was paid in 2020. In September 2020, the Company executed the seventh amendment to the CRADA agreement. In this amendment the term of this agreement is extended until September 30, 2022, and the Company paid $ 0.03 million on the tenth anniversary of the CRADA agreement which occurred in July of 2021. National Institute of Health (NIH)-Exclusive Patent License Agreement In 2013, the Company entered into an exclusive patent license agreement that required the Company to pay a license issue royalty fee of $ 0.1 million and reimburse the NIH for any patent expenses incurred. Under the agreement, the Company is required to make low single-digit percentage royalty payments based on specified levels of annual net sales of licensed products subject to certain specified reductions. The Company is required to make development and regulatory milestone payments up to $ 0.7 million in the aggregate and sales milestone payments up to $ 0.6 million in the aggregate. The Company is also required to pay NIH a mid-single to low teen-digit percentage of any sublicensing revenue the Company receives. Additionally, the Company’s payment obligations to NIH are subject to an annual minimum royalty payment of low five figures. As of September 30, 2021, the Company has paid NIH approximately $ 0.4 million in aggregate milestones under the NIH license agreement. In addition to milestones under the agreement, the Company reimburses the NIH for any patent filing costs incurred. As of September 30, 2021, the Company has reimbursed the NIH approximately $ 0.3 million in aggregate. The Company accrued $ 0.03 million and $ 0.02 million in patent licensing reimbursement fees as of September 30, 2021 and December 31, 2020. In 2015, 2018 and 2019, the Company amended its exclusive patent license to include updates on the status of the commercial development and update/expand the list of licensed patents and patent applications. Each of those amendments required a $ 0.03 million payment that the Company paid. Inserm In November 2009, the Company entered into an exclusive, royalty-bearing license agreement with Inserm-Transfert of France for use of its patents. The agreement expires on a country by country basis based on the last to expire of any patent encompassed within the scope of the patent rights or 10 years from the date of the first commercial sale by the Company, whichever is later. There are potential milestone payments of € 0.5 million ($ 0.5 million at December 31, 2020) in the aggregate associated with this agreement. The IND filing milestone of € 0.01 million was accrued in 2016 and paid in 2017 by the Company. The milestones for the successful Phase I, II and III clinical trials are based on receiving a final report and achieving the primary endpoints defined in that trial and those milestones have not been achieved as of September 30, 2021. Upon the sublicense by the Company of a product for which royalties are payable under this agreement, low- to mid-single-digit royalty payments would be due by the Company. If Aura sublicenses the delivery platform for use with multiple drugs, low- to mid-teen payments on receipts would be due by the Company . The non-milestone payments in this agreement are subject to an anti-stacking clause. The Company did no t incur any expense in the period ended September 30, 2021 and 2020. Clearside In July 2019, the Company entered into an exclusive license agreement with Clearside Biomedical, Inc., or Clearside, for the license of Clearside’s Suprachoroidal Microneedle Technology for use in the treatment of indeterminate lesions, and choroidal tumors. Upon execution of the license agreement, the Company paid Clearside an upfront payment of $ 0.1 million which was expensed as incurred. Under the Clearside license agreement, the Company is required to pay milestones up to $ 21.0 million in the aggregate to Clearside upon the achievement of specified regulatory and development milestones, and upon the achievement of certain commercial sales milestones The Company is also required to pay low single digit royalties on net sales. If the Company sublicenses a product for which royalties are payable, then the Company is required to pay the greater of 20 % received or low single digit royalties on net sales. The Company has made no milestone or royalty payments as of September 30, 2021. The Clearside license agreement expires on a country-by-country basis upon the later of the last to expire patent or ten years from the date of the first commercial sale of a product.

Net Loss Per Share

Net Loss Per Share	9 Months Ended
	Sep. 30, 2021
Earnings Per Share [Abstract]
Net Loss Per Share	13. Net Loss Per Share Basic net loss per share is calculated by dividing the net loss attributable to common stockholders by the weighted average number of shares of common stock outstanding during the period, without consideration for potentially dilutive securities. Diluted net loss per share is the same as basic net loss per share for the periods presented since the effects of potentially dilutive securities are antidilutive given the net loss of the Company. The Company has calculated basic and diluted net loss per share for the three and nine months ended September 30, 2021 and 2020 as follows (in thousands, except share and per share data): Three Months Ended Nine Months Ended 2021 2020 2021 2020 Numerator: Net loss $ ( 8,838 ) $ ( 3,631 ) $ ( 23,617 ) $ ( 17,299 ) Less: Accruals of dividends of preferred stock ( 3,668 ) ( 1,948 ) ( 9,627 ) ( 5,802 ) Net loss attributable to common stockholders—basic and $ ( 12,506 ) $ ( 5,579 ) $ ( 33,244 ) $ ( 23,101 ) Denominator: Weighted-average common stock outstanding 441,448 376,738 426,604 362,735 Net loss per share attributable to common stockholders— ( 28.33 ) ( 14.81 ) ( 77.93 ) ( 63.69 ) The following potentially dilutive securities were excluded from the computation of the diluted net loss per share for the periods presented because their effect would have been antidilutive: Three Months Ended Nine Months Ended 2021 2020 2021 2020 Convertible preferred stock on as if converted basis 22,550,561 13,260,868 22,550,561 13,260,868 Stock options to purchase common stock 3,164,949 1,412,791 3,164,949 1,412,791 Warrants to purchase preferred stock 12,686 12,686 12,686 12,686 Total potential dilutive shares 25,728,196 14,686,345 25,728,196 14,686,345

Income Taxes

Income Taxes	9 Months Ended
	Sep. 30, 2021
Income Tax Disclosure [Abstract]
Income Taxes	14. Income Taxes The Company estimates an annual effective tax rate of 0 % for the year ending December 31, 2021 as the Company incurred losses for the nine months ended September 30, 2021, and is forecasting additional losses through the remainder of fiscal year ending December 31, 2021, resulting in an estimated net loss for both financial statement and tax purposes for the year ending December 31, 2021. Therefore, no federal or state income taxes are expected and none have been recorded at this time. Income taxes have been accounted for using the liability method. Due to the Company’s history of losses since inception, there is not enough evidence at this time to support that the Company will generate future income of a sufficient amount and nature to utilize the benefits of its net deferred tax assets. Accordingly, the deferred tax assets have been reduced by a full valuation allowance, since the Company does not currently believe that realization of its deferred tax assets is more likely than not. As of September 30, 2021, the Company had no unrecognized income tax benefits that would reduce the Company’s effective tax rate if recognized.

Related Parties

Related Parties	9 Months Ended
	Sep. 30, 2021
Related Party Transactions [Abstract]
Related Parties	15. Related Parties During the nine months ended September 30, 2021 and 2020, the Company incurred $ 0.4 million and $ 0.3 million in expenses to a stockholder that provided research and development related services. Of these amounts, $ 0.01 and $ 0.1 million were in accrued expenses as of September 30, 2021 and 2020.

Subsequent Events

Subsequent Events	9 Months Ended
	Sep. 30, 2021
Subsequent Events [Abstract]
Subsequent Events	16. Subsequent Events Subsequent events have been evaluated through the date of filing of the unaudited condensed financial statements. The Company has identified the following subsequent events that require disclosure: A. Election of Automatic Conversion of Preferred Stock On October 7, 2021, the required convertible preferred stockholders authorized the automatic conversion of all shares of convertible preferred stock in an initial public offering, subject to the price per share of the common stock in the Company’s sale of shares of common stock to the public in a firm commitment underwritten public offering pursuant to an effective registration statement under the Securities Act of 1933, as amended, resulting in at least $ 75.0 million of gross proceeds to the Company and such shares being listed on the Nasdaq Stock Market, or a Public Offering, being at least $ 0.94068 (subject to appropriate adjustment in the event of any stock dividend, stock split, combination or other similar recapitalization with respect to the common stock), (ii) subject to and effective upon the closing of the Public Offering and (iii) subject to the Public Offering being consummated no later than February 28, 2022 . B. Reverse Stock Split On October 22, 2021, the Company effected a reverse stock split of the Company’s common stock on a 1-for-13.7 basis, or the Reverse Stock Split. In connection with the Reverse Stock Split, the conversion ratio for the Company’s convertible preferred stock was proportionately adjusted such that the common stock issuable upon conversion of such preferred stock was decreased in proportion to the Reverse Stock Split. Accordingly, all common stock share and per share amounts, for all periods presented in these condensed financial statements, have been retroactively adjusted, to reflect this reverse stock split and adjustment of the convertible preferred stock conversion ratios. C. Initial Public Offering On November 2, 2021, the Company completed its IPO, in which it issued and sold 6,210,000 shares of common stock, including the full exercise of the underwriters’ option to purchase additional shares at a price to the public of $ 14.00 per share for aggregate gross proceeds of $ 86.9 million. The Company received approximately $ 77.9 million in net proceeds after deducting underwriting discounts, commissions and estimated offering expenses. D. 2021 Stock Option and Incentive Plan The 2021 Stock Option and Incentive Plan, or the 2021 Plan, was adopted by the Board on October 7, 2021, approved by the Company’s stockholders on October 22, 2021 and became effective on November 1, 2021. The 2021 Plan permits the granting of both options to purchase common stock intended to qualify as incentive stock options under Section 422 of the Code and options that do not so qualify. The number of shares initially reserved for issuance under the 2021 Plan was 3,352,166 , which will automatically increase on January 1, 2022 and each January 1 thereafter, by 5 % of the outstanding number of shares of common stock on the immediately preceding December 31 or such lesser number of shares as determined by the Company’s compensation committee. The maximum number of shares of common stock that may be issued in the form of incentive stock options shall not exceed the initial limit, cumulatively increased on January 1, 2022 and on each January 1 thereafter by the lesser of the annual increase for such year or 3,352,166 shares of common stock. E. 2021 Employee Stock Purchase Plan The 2021 Employee Stock Purchase Plan, or the ESPP, was adopted by the Board on October 7, 2021, approved by the Company’s stockholders on October 22, 2021 and became effective on November 1, 2021. A total of 335,217 shares of common stock were initially reserved for issuance under this plan, which will automatically increase on January 1, 2022 and each January 1 thereafter through January 1, 2031, by the least of (i) 335,217 shares of common stock, (ii) 1 % of the outstanding number of shares of common stock on the immediately preceding December 31 or (iii) such lesser number of shares of common stock as determined by the administrator of the ESPP.

Summary of Significant Accoun_2

Summary of 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, or U.S. GAAP. In management’s opinion, the accompanying unaudited condensed financial statements include all adjustments, consisting of normal recurring adjustments, which are necessary to present fairly the Company’s financial position, results of operations, and cash flows.
Unaudited Interim Financial Information	Unaudited Interim Financial Information The accompanying condensed balance sheet as of September 30, 2021, the condensed statements of operations and comprehensive loss, condensed statement of convertible preferred stock and stockholders’ deficit for the three and nine months ended September 30, 2021 and 2020, and the condensed statements of cash flows for the nine months ended September 30, 2021 and 2020 are unaudited. The unaudited interim financial statements have been prepared on the same basis as the audited annual financial statements and, in the opinion of management, reflect all adjustments, which include only normal recurring adjustments, necessary for the fair statement of the Company’s financial position as of September 30, 2021 and the results of its operations for the three and nine months ended September 30, 2021 and 2020 and its cash flows for the nine months ended September 30, 2021 and 2020. The financial data and other information disclosed in these notes related to the three and nine months ended September 30, 2021 and 2020 are also unaudited. The unaudited condensed results of operations are not necessarily indicative of the operating results that may occur for the full fiscal year ending December 31, 2021. Certain information and footnote disclosures normally included in annual financial statements prepared in accordance with U.S. GAAP have been omitted pursuant to instructions, rules, and regulations prescribed by the United States Securities and Exchange Commission, or the SEC. Management believes that the disclosures provided here are adequate to make the information presented not misleading when these unaudited condensed financial statements are read in conjunction with the audited financial statements and notes thereto as of and for the year ended December 31, 2020. The balance sheet data as of December 31, 2020 was derived from the Company’s audited financial statements included in the final prospectus filed pursuant to Rule 424(b)(4) under the Securities Act with the SEC on November 1, 2021.
Significant Accounting Policies	Significant Accounting Policies The Company’s significant accounting policies are disclosed in the audited financial statements for the year ended December 31, 2020, filed with the SEC as a part of the final prospectus filed pursuant to Rule 424(b)(4) under the Securities Act with the SEC on November 1, 2021. Since the date of those financial statements, there have been no changes to the Company's significant accounting policies except as noted below.
Cash Equivalents	Cash Equivalents Cash equivalents are highly liquid investments with an original maturity of 90 days or less at the date of purchase and consist of time deposits and investments in money market funds that invest in U.S. Treasury obligations and government funds with commercial banks and financial institutions.
Leases	Leases Prior to January 1, 2021, the Company accounted for leases in accordance with ASC 840, Leases. At lease inception, the Company determined if an arrangement was an operating or capital lease. For operating leases, the Company recognized rent expense, inclusive of rent escalation, holidays and lease incentives, on a straight-line basis over the lease term. The difference between rent expense recorded and the amount paid was charged to deferred rent. The Company presented lease incentives as deferred rent and amortized the incentives as a reduction to rent expense on a straight-line basis over the lease term. The Company classified deferred rent as current and noncurrent liabilities based on the portion of the deferred rent that was scheduled to mature within the proceeding twelve months. Effective January 1, 2021, the Company accounts for leases in accordance with ASU No. 2016-02, Leases (Topic 842) (“ASC 842”) . At contract inception, the Company determines if an arrangement is or contains a lease. A lease conveys the right to control the use of an identified asset for a period of time in exchange for consideration. If determined to be or contain a lease, the lease is assessed for classification as either an operating or finance lease at the lease commencement date, defined as the date on which the leased asset is made available for use by the Company, based on the economic characteristics of the lease. For each lease with a term greater than twelve months, the Company records a right-of-use asset and lease liability. The Company adopted the n ew leasing standard effective January 1, 2021 , using the modified retrospective transition approach which uses the effective date, or January 1, 2021, as the date of initial application. As a result, prior periods are presented in accordance with the previous guidance in ASC 840. ASC 842 provides several optional practical expedients in transition. The Company has elected to apply the package of practical expedients requiring no reassessment of whether any expired or existing contracts are or contain leases, the lease classification of any expired or existing leases, or the capitalization of initial direct costs for any existing leases. A right-of-use asset represents the economic benefit conveyed to the Company by the right to use the underlying asset over the lease term. A lease liability represents the obligation to make lease payments arising from the lease. The Company elected the practical expedient to not separate lease and non-lease components for all classes of underlying assets and therefore measures each lease payment as the total of the fixed lease and associated non-lease components. Lease liabilities are measured at lease commencement and calculated as the present value of the future lease payments in the contract using the rate implicit in the contract, when available. If an implicit rate is not readily determinable, the Company uses an incremental borrowing rate measured as the rate at which the Company could borrow, on a fully collateralized basis, a commensurate loan in the same currency over a period consistent with the lease term at the commencement date. Right-of-use assets are measured as the lease liability plus initial direct costs and prepaid lease payments, less lease incentives granted by the lessor. The lease term is measured as the noncancelable period in the contract, adjusted for any options to extend or terminate when it is reasonably certain the Company will extend the lease term via such options based on an assessment of economic factors present as of the lease commencement date. The Company elected the practical expedient to not recognize leases with a lease term of twelve months or less. Components of a lease are split into three categories: lease components, non-lease components, and non-components. The fixed and in-substance fixed contract consideration (including any consideration related to non-components) are allocated, based on the respective relative fair values, to the lease components and non-lease components. The Company has elected to account for lease and non-lease components together as a single lease component for all underlying assets and allocate all of the contract consideration to the lease component only. The Company’s operating leases are presented in the condensed balance sheet as operating lease right-of-use assets, classified as noncurrent assets, and operating lease liabilities, classified as current and noncurrent liabilities. Operating lease expense is recognized on a straight-line basis over the lease term. Variable costs associated with a lease, such as maintenance and utilities, are not included in the measurement of the lease liabilities and right-of-use assets but rather are expensed when the events determining the amount of variable consideration to be paid have occurred.
Deferred Offering Costs	Deferred Offering Costs The Company capitalizes certain legal, professional accounting and other third-party fees that are directly associated with in-process preferred stock or common stock financings as deferred offering costs until such financings are consummated. After consummation of the equity financing, these costs are recorded as a reduction to the carrying value of convertible preferred stock or in stockholders’ equity (deficit) as a reduction of additional paid-in capital generated as a result of the offering. Should a planned equity financing be abandoned, the deferred offering costs will be expensed immediately as a charge to operating expenses in the statements of operations and comprehensive loss. As of September 30, 2021, the Company had deferred offering costs of $ 1.6 million.
Recently Adopted Accounting Pronouncements	Recently Adopted Accounting Pronouncements Upon adoption of ASC 842, the Company recorded lease liabilities and their corresponding right-of-use assets based on the present value of lease payments over the remaining lease term. The adoption of ASC 842 resulted in the recognition of operating lease liabilities of $ 0.6 million and operating lease right-of-use assets of $ 0.5 million and the derecognition of deferred rent liabilities of $ 0.02 million on the Company’s balance sheet as of January 1, 2021. The adoption impact relates to the Company’s existing operating lease for operating and laboratory space. The adoption of ASC 842 did not have a material impact on the Company’s statements of operations and comprehensive loss or statements of cash flows.

Fair Value of Assets and Liab_2

Fair Value of Assets and Liabilities (Tables)	9 Months Ended
	Sep. 30, 2021
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Financial Assets and Liabilities Measured at Fair Value on Recurring Basis	The following table presents information about the Company’s financial assets and liabilities measured at fair value on a recurring basis and indicates the level of the fair value hierarchy utilized to determine such fair values as of September 30, 2021 and December 31, 2020 (in thousands): Description September 30, Quoted prices Significant Significant Assets Money market funds $ 79,829 $ 79,829 $ — $ — Total financial assets $ 79,829 $ 79,829 $ — $ — Liability Warrant liability $ 71 $ — $ — $ 71 Total financial liabilities $ 71 $ — $ — $ 71 Description December 31, Quoted prices Significant Significant Liability Warrant liability $ 72 $ — $ — $ 72 Total financial liabilities $ 72 $ — $ — $ 72
Summary of Changes in Fair Value of Warrants	The following table set forth a summary of changes in the fair value of the Series B Warrants, which represents a recurring fair value measurement that is classified within Level 3 of the fair value hierarchy. Changes in fair value are recognized in other (expense) income as “Change in fair value of warrant liability” in the Company’s condensed statements of operations and comprehensive loss (in thousands): Series B Warrants ( 173,827 warrants) Fair value at December 31, 2020 $ 72 Change in fair value ( 1 ) Fair value at September 30, 2021 $ 71

Property and Equipment, Net (Ta

Property and Equipment, Net (Tables)	9 Months Ended
	Sep. 30, 2021
Property Plant And Equipment [Abstract]
Schedule of Property and Equipment, Net	Property and equipment, net, consisted of the following (in thousands): September 30, 2021 December 31, 2020 Assets under construction $ 1,741 $ 1,154 IT equipment 73 — Leasehold improvements 13 — Lab equipment 5,085 4,708 Office furniture 63 64 Total property and equipment $ 6,975 $ 5,926 Less—accumulated depreciation ( 2,533 ) ( 2,352 ) Property and equipment, net $ 4,442 $ 3,574

Prepaid Expenses and Other Cu_2

Prepaid Expenses and Other Current Assets (Tables)	9 Months Ended
	Sep. 30, 2021
Prepaid Expense and Other Assets, Current [Abstract]
Schedule of Prepaid Expenses and Other Current Assets	Prepaid expenses and other current assets consisted of the following (in thousands): September 30, 2021 December 31, 2020 Prepaid insurance $ 80 $ 51 Prepaid research and development expenses 1,474 976 Other 55 16 Prepaid expenses and other current assets $ 1,609 $ 1,043

Accrued Expenses and Other Cu_2

Accrued Expenses and Other Current Liabilities (Tables)	9 Months Ended
	Sep. 30, 2021
Payables And Accruals [Abstract]
Summary of Accrued Expenses and Other Current Liabilities	Accrued expenses and other current liabilities consisted of the following (in thousands): September 30, 2021 December 31, 2020 Accrued research and development expenses $ 1,184 $ 750 Accrued compensation 1,569 1,023 Other 735 277 Accrued expenses and other current liabilities $ 3,488 $ 2,050

Stock-Based Compensation (Table

Stock-Based Compensation (Tables)	9 Months Ended
	Sep. 30, 2021
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Summary of Combined Stock Option Activity under 2009 and 2018 Plan	The following table summarizes the combined stock option activity under the 2009 and the 2018 Plan for the nine months ended September 30, 2021: Options Weighted- Weighted- Aggregate Outstanding at December 31, 2020 1,512,129 $ 3.84 7.77 $ 1,174 Granted 1,883,480 6.13 - - Exercised ( 61,594 ) 4.95 - - Cancelled or forfeited ( 169,066 ) 4.50 - - Outstanding at September 30, 2021 3,164,949 $ 5.15 8.60 $ 14,053 Exercisable at September 30, 2021 1,024,453 $ 3.85 6.75 $ 5,849
Schedule of Fair Value of Stock Options, Valuation Assumptions	The fair value of the stock options issued for the three and nine months ended September 30, 2021 and 2020 was measured with the following weighted-average assumptions: Three Months Ended Nine Months Ended 2021 2020 2021 2020 Weighted average risk-free interest rate 1.00 % 0.33 % 1.06 % 0.58 % Expected term (years) 6.06 5.67 6.02 6.03 Expected volatility 73.36 % 73.71 % 74.21 % 74.16 % Expected dividend yield 0.00 % 0.00 % 0.00 % 0.00 %
Summary of Stock-Based Compensation Expense	The Company recorded stock-based compensation expense as follows (in thousands): Three Months Ended Nine Months Ended 2021 2020 2021 2020 Research and development $ 157 $ 47 $ 263 $ 153 General and administrative 397 144 747 404 Total $ 554 $ 191 $ 1,010 $ 557

Series B Warrants (Tables)

Series B Warrants (Tables)	9 Months Ended
	Sep. 30, 2021
Equity [Abstract]
Summary of Estimated Fair Value of Warrants and Significant Assumptions	The warrants were valued using the Black-Scholes option pricing model. The estimated fair value of the warrants and the significant assumptions used were as follows: Series B Warrants September 30, 2021 December 30, 2021 Series B estimated fair value $ 1.12 $ 1.17 Volatility 79.50 % 74.07 % Expected term (years) 3.5 4.2 Risk free rate 0.76 % 0.27 % Dividend yield 7.00 % 7.00 %

Commitments and Contingencies (

Commitments and Contingencies (Tables)	9 Months Ended
	Sep. 30, 2021
Leases [Abstract]
Summary of Lease Costs	The following table contains a summary of the lease costs recognized under ASC 842 and other information pertaining to the Company’s leases for the three and nine months ended September 30, 2021 (in thousands): Three Months Ended Nine Months Ended Lease Cost Financing lease costs: Amortization of finance right-of-use assets $ - $ 11 Operating lease costs 154 370 Variable lease costs 90 233 Total lease costs $ 244 $ 614 Cash paid for amounts included in the measurement of lease liability—finance leases $ 15 Cash paid for amounts included in the measurement of lease liability—operating leases $ 367 Weighted-average remaining lease term—operating leases (years) 1.83 Weighted-average discount rate—finance leases 7.94 % Weighted-average discount rate—operating leases 3.51 %
Summary of Future Minimum Commitments of Operating Lease Liabilities	The following table reconciles the future minimum commitments to the Company’s operating lease liabilities at September 30, 2021 (in thousands): Operating lease payments as of September 30, 2021 2021 (excluding nine months ended September 30, 2021) $ 153 2022 625 2023 377 Total lease payments 1,155 Less: interest ( 35 ) Total operating lease liabilities at September 30, 2021 1,120 Less: current portion of lease liabilities 607 Lease liabilities, net of current portion $ 513

Net Loss Per Share (Tables)

Net Loss Per Share (Tables)	9 Months Ended
	Sep. 30, 2021
Earnings Per Share [Abstract]
Summary of Basic and Diluted Net Loss Per Share	The Company has calculated basic and diluted net loss per share for the three and nine months ended September 30, 2021 and 2020 as follows (in thousands, except share and per share data): Three Months Ended Nine Months Ended 2021 2020 2021 2020 Numerator: Net loss $ ( 8,838 ) $ ( 3,631 ) $ ( 23,617 ) $ ( 17,299 ) Less: Accruals of dividends of preferred stock ( 3,668 ) ( 1,948 ) ( 9,627 ) ( 5,802 ) Net loss attributable to common stockholders—basic and $ ( 12,506 ) $ ( 5,579 ) $ ( 33,244 ) $ ( 23,101 ) Denominator: Weighted-average common stock outstanding 441,448 376,738 426,604 362,735 Net loss per share attributable to common stockholders— ( 28.33 ) ( 14.81 ) ( 77.93 ) ( 63.69 )
Summary of Dilutive Securities Excluded from Computation of Diluted Net Loss Per Share	The following potentially dilutive securities were excluded from the computation of the diluted net loss per share for the periods presented because their effect would have been antidilutive: Three Months Ended Nine Months Ended 2021 2020 2021 2020 Convertible preferred stock on as if converted basis 22,550,561 13,260,868 22,550,561 13,260,868 Stock options to purchase common stock 3,164,949 1,412,791 3,164,949 1,412,791 Warrants to purchase preferred stock 12,686 12,686 12,686 12,686 Total potential dilutive shares 25,728,196 14,686,345 25,728,196 14,686,345

Description of Business - Addit

Description of Business - Additional Information (Details) - USD ($) $ / shares in Units, $ in Thousands	Nov. 02, 2021	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	Dec. 31, 2019
Description Of Business [Line Items]
Net losses		$ 8,838	$ 8,852	$ 5,927	$ 3,631	$ 6,156	$ 7,512	$ 23,617	$ 17,299
Cash and cash equivalents		81,974			$ 16,243			81,974	$ 16,243	$ 17,487	$ 32,543
Accumulated deficit		$ 140,503						$ 140,503		$ 116,886
Initial Public Offering | Subsequent Event
Description Of Business [Line Items]
Share price	$ 14
Aggregate gross proceeds from IPO	$ 86,900
Net proceeds from the IPO	$ 77,900
Common Stock | Initial Public Offering | Subsequent Event
Description Of Business [Line Items]
Shares issued and sold	6,210,000

Summary of Significant Accoun_3

Summary of Significant Accounting Policies - Additional Information (Details) - USD ($) $ in Thousands	Sep. 30, 2021	Jan. 01, 2021	Dec. 31, 2020
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Deferred offering costs	$ 1,600
Operating lease liabilities	1,120
Operating lease right of use assets	$ 1,096
Deferred rent			$ 8
ASU 2016-02
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Change in accounting principle, accounting standards update, adopted [true false]			true
Change in accounting principle, accounting standards update, adoption date	Jan. 1, 2021
Operating lease liabilities		$ 600
Operating lease right of use assets		500
Deferred rent		$ 20
Change in accounting principle, accounting standards update, immaterial effect [true false]		true

Fair Value of Assets and Liab_3

Fair Value of Assets and Liabilities - Financial Assets and Liabilities Measured at Fair Value on Recurring Basis (Details) - Fair Value, Recurring - USD ($) $ in Thousands	Sep. 30, 2021	Dec. 31, 2020
Assets
Financial assets	$ 79,829
Liability
Financial liabilities	71	$ 72
Money Market Funds
Assets
Financial assets	79,829
Warrant Liability
Liability
Financial liabilities	71	72
Level 1
Assets
Financial assets	79,829
Level 1 | Money Market Funds
Assets
Financial assets	79,829
Level 3
Liability
Financial liabilities	71	72
Level 3 | Warrant Liability
Liability
Financial liabilities	$ 71	$ 72

Fair Value of Assets and Liab_4

Fair Value of Assets and Liabilities - Additional Information (Details) - USD ($)	9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020
Fair Value Disclosures [Abstract]
Assets transfers into Level 3	$ 0	$ 0
Assets, transfers out of Level 3	0	0
Liability, transfers into Level 3	0	0
Liability, transfers out of Level 3	$ 0	$ 0

Fair Value of Assets and Liab_5

Fair Value of Assets and Liabilities - Summary of Changes in Fair Value of Series B Warrants (Details) - Series B Warrants $ in Thousands	9 Months Ended
	Sep. 30, 2021USD ($)
Fair Value Liabilities Measured On Recurring Basis Unobservable Input Reconciliation [Line Items]
Beginning Balance	$ 72
Change in fair value	(1)
Ending Balance	$ 71

Fair Value of Assets and Liab_6

Fair Value of Assets and Liabilities - Summary of Changes in Fair Value of Series B Warrants (Parenthetical) (Details) - shares	Sep. 30, 2021	Dec. 31, 2020
Series B Warrants
Fair Value Liabilities Measured On Recurring Basis Unobservable Input Reconciliation [Line Items]
Warrants outstanding	173,827	173,827

Property and Equipment, Net - S

Property and Equipment, Net - Schedule of Property and Equipment, Net (Details) - USD ($) $ in Thousands	Sep. 30, 2021	Dec. 31, 2020
Property Plant And Equipment [Line Items]
Property and equipment, gross	$ 6,975	$ 5,926
Less—accumulated depreciation	(2,533)	(2,352)
Property and equipment, net	4,442	3,574
Assets Under Construction
Property Plant And Equipment [Line Items]
Property and equipment, gross	1,741	1,154
IT Equipment
Property Plant And Equipment [Line Items]
Property and equipment, gross	73
Leasehold Improvements
Property Plant And Equipment [Line Items]
Property and equipment, gross	13
Lab Equipment
Property Plant And Equipment [Line Items]
Property and equipment, gross	5,085	4,708
Office Furniture
Property Plant And Equipment [Line Items]
Property and equipment, gross	$ 63	$ 64

Property and Equipment, Net - A

Property and Equipment, Net - Additional Information (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Property Plant And Equipment [Abstract]
Depreciation expense	$ 200	$ 200	$ 601	$ 605

Prepaid Expenses and Other Cu_3

Prepaid Expenses and Other Current Assets - Schedule of Prepaid Expenses and Other Current Assets (Details) - USD ($) $ in Thousands	Sep. 30, 2021	Dec. 31, 2020
Prepaid Expense and Other Assets, Current [Abstract]
Prepaid insurance	$ 80	$ 51
Prepaid research and development expenses	1,474	976
Other	55	16
Prepaid expenses and other current assets	$ 1,609	$ 1,043

Accrued Expenses and Other Cu_3

Accrued Expenses and Other Current Liabilities - Summary of Accrued Expenses and Other Current Liabilities (Details) - USD ($) $ in Thousands	Sep. 30, 2021	Dec. 31, 2020
Payables And Accruals [Abstract]
Accrued research and development expenses	$ 1,184	$ 750
Accrued compensation	1,569	1,023
Other	735	277
Accrued expenses and other current liabilities	$ 3,488	$ 2,050

Convertible Preferred Stock - A

Convertible Preferred Stock - Additional Information (Details)	Mar. 18, 2021USD ($)$ / sharesshares	Mar. 05, 2021USD ($)$ / sharesshares	Oct. 01, 2020USD ($)shares	Mar. 31, 2021USD ($)shares	Sep. 30, 2021USD ($)$ / sharesshares	Dec. 31, 2020USD ($)$ / sharesshares	Oct. 22, 2021	Jun. 30, 2021shares	Sep. 30, 2020shares	Jun. 30, 2020shares	Jun. 25, 2020$ / sharesshares	Mar. 31, 2020shares	Dec. 31, 2019shares
Temporary Equity [Line Items]
Convertible preferred stock, par value | $ / shares					$ 0.00001
Common stock dividends declared | $					$ 0
Preferred stock liquidation rights description					In the event of a Deemed Liquidation Event, as defined in the Company’s amended and restated Certificate of Incorporation, the assets of the Company will be distributed first to the holders of the Series E. The holders of the Series E will receive, in preference to all other stockholders, an amount equal to the sum of the Series E original issue price (equal to the cash price paid per share of $0.783900), plus unpaid dividends on such shares. Next, the holders of the Series D will receive, in preference to all other stockholders other than the Series E, an amount equal to the sum of the Series D original issue price, plus unpaid dividends on such shares. Next, the holders of the Series C will receive, in preference to all stockholders other than the Series E and D holders, an amount equal to the sum of the Series C original issue price plus unpaid dividends on such shares. Next, the holders of the Series B will receive, in preference to the holders of the Series A, Series A-1, Series A-2 and common stock, an amount equal to the sum of the Series B original issue price plus unpaid dividends on such shares. Next, the holders of the Series A, Series A-1, and Series A-2 will receive, in preference to the holders of common stock, an amount equal to the greater of their applicable liquidation preference or what they would have received had their shares converted into common stock. If the proceeds available are not sufficient to satisfy the full liquidation preference, the entire proceeds are to be distributed pro-rata among the Series E holders in proportion to the full preferential amount the Series E holders are entitled to receive.
Preferred stock, conversion basis					one-for-one basis
Preferred stock, conversion ratio					1
Common Stock
Temporary Equity [Line Items]
Proceeds from issuance of convertible preferred stock | $					$ 50,000,000
Preferred stock, conversion price | $ / shares					$ 1.554975
Series A Convertible Preferred Stock
Temporary Equity [Line Items]
Convertible preferred stock, shares authorized					1,701,141	1,701,141
Convertible preferred stock, shares issued					1,701,141	1,701,141
Convertible preferred stock, shares outstanding				1,701,141	1,701,141	1,701,141		1,701,141	1,701,141	1,701,141		1,701,141	1,701,141
Convertible preferred stock, par value | $ / shares					$ 0.00001	$ 0.00001
Preferred stock dividends declared | $					$ 0
Preferred stock, conversion price | $ / shares					$ 2
Preferred Stock, conversion price due to anti-dilution protection terms | $ / shares					$ 1.8191
Preferred stock, conversion ratio					1.099
Series A Convertible Preferred Stock | Subsequent Event
Temporary Equity [Line Items]
Preferred stock, conversion ratio							12.47
Series A-1 Convertible Preferred Stock
Temporary Equity [Line Items]
Convertible preferred stock, shares authorized					3,298,732	3,298,732
Convertible preferred stock, shares issued					3,298,732	3,298,732
Convertible preferred stock, shares outstanding				3,298,732	3,298,732	3,298,732		3,298,732	3,298,732	3,298,732		3,298,732	3,298,732
Convertible preferred stock, par value | $ / shares					$ 0.00001	$ 0.00001
Preferred stock, conversion price | $ / shares					2.4847
Preferred Stock, conversion price due to anti-dilution protection terms | $ / shares					$ 2.1898
Preferred stock, conversion ratio					1.135
Series A-1 Convertible Preferred Stock | Subsequent Event
Temporary Equity [Line Items]
Preferred stock, conversion ratio							12.07
Series A-2 Convertible Preferred Stock
Temporary Equity [Line Items]
Convertible preferred stock, shares authorized					4,325,021	4,325,021
Convertible preferred stock, shares issued					4,324,998	4,324,998
Convertible preferred stock, shares outstanding				4,324,998	4,324,998	4,324,998		4,324,998	4,324,998	4,324,998		4,324,998	4,324,998
Convertible preferred stock, par value | $ / shares					$ 0.00001	$ 0.00001
Purchase price per share | $ / shares					$ 1.24235
Preferred stock, conversion basis					one-for-one basis
Preferred stock, conversion price | $ / shares					$ 1.24235
Preferred stock, conversion ratio					1
Series A-2 Convertible Preferred Stock | Subsequent Event
Temporary Equity [Line Items]
Preferred stock, conversion ratio							13.7
Series B Convertible Preferred Stock
Temporary Equity [Line Items]
Convertible preferred stock, shares authorized					22,705,646	22,705,646
Convertible preferred stock, shares issued					22,531,819	22,531,819
Convertible preferred stock, shares outstanding				22,531,819	22,531,819	22,531,819		22,531,819	22,531,819	22,531,819		22,531,819	22,531,819
Convertible preferred stock, par value | $ / shares					$ 0.00001	$ 0.00001
Cumulative dividends | $					$ 10,900,000
Preferred stock annual dividend rate per share | $ / shares					$ 0.0869645
Preferred stock, conversion price | $ / shares					$ 1.24235
Series B Convertible Preferred Stock | Subsequent Event
Temporary Equity [Line Items]
Preferred stock, conversion ratio							13.7
Series C-1 Convertible Preferred Stock
Temporary Equity [Line Items]
Convertible preferred stock, shares authorized					58,109,711	58,109,711
Convertible preferred stock, shares issued					58,109,711	58,109,711
Convertible preferred stock, shares outstanding					58,109,711	58,109,711
Convertible preferred stock, par value | $ / shares					$ 0.00001	$ 0.00001
Convertible preferred stock dividend percentage					7.00%
Cumulative dividends | $					$ 7,400,000
Preferred stock, conversion price | $ / shares					$ 0.5213
Series C-1 Convertible Preferred Stock | Subsequent Event
Temporary Equity [Line Items]
Preferred stock, conversion ratio							13.7
Series C-2 Convertible Preferred Stock
Temporary Equity [Line Items]
Convertible preferred stock, shares authorized					33,218,192	33,218,192
Convertible preferred stock, shares issued					33,218,192	33,218,192
Convertible preferred stock, shares outstanding					33,218,192	33,218,192
Convertible preferred stock, par value | $ / shares					$ 0.00001	$ 0.00001
Convertible preferred stock dividend percentage					7.00%
Cumulative dividends | $					$ 3,200,000
Preferred stock, conversion price | $ / shares					$ 0.36491
Series C-2 Convertible Preferred Stock | Subsequent Event
Temporary Equity [Line Items]
Preferred stock, conversion ratio							13.7
Series D-1 Convertible Preferred Stock
Temporary Equity [Line Items]
Convertible preferred stock, shares authorized					57,878,742	57,878,742
Convertible preferred stock, shares issued					57,878,742	57,878,742
Convertible preferred stock, shares outstanding					57,878,742	57,878,742
Convertible preferred stock, par value | $ / shares					$ 0.00001	$ 0.00001
Convertible preferred stock dividend percentage					7.00%
Cumulative dividends | $					$ 6,000,000
Preferred stock, conversion price | $ / shares					$ 0.6911
Series D-1 Convertible Preferred Stock | Subsequent Event
Temporary Equity [Line Items]
Preferred stock, conversion ratio							13.7
Series D-2 Convertible Preferred Stock
Temporary Equity [Line Items]
Convertible preferred stock, shares authorized					24,598,481	24,598,481					24,598,481
Convertible preferred stock, shares issued					24,598,481	14,469,710
Convertible preferred stock, shares outstanding					24,598,481	14,469,710
Convertible preferred stock, par value | $ / shares					$ 0.00001	$ 0.00001
Purchase price per share | $ / shares		$ 0.6911									$ 0.6911
Issuance of convertible preferred stock, Shares		10,128,771	14,469,710
Proceeds from issuance of convertible preferred stock | $		$ 7,000,000	$ 10,000,000
Offering costs | $					$ 20,000	$ 100,000
Convertible preferred stock dividend percentage					7.00%
Cumulative dividends | $					$ 1,000,000
Preferred stock, conversion price | $ / shares					$ 0.6911
Series D-2 Convertible Preferred Stock | Subsequent Event
Temporary Equity [Line Items]
Preferred stock, conversion ratio							13.7
Series E Convertible Preferred Stock
Temporary Equity [Line Items]
Convertible preferred stock, shares authorized					102,671,041	0
Convertible preferred stock, shares issued					102,671,041	0
Convertible preferred stock, shares outstanding				102,671,041	102,671,041	0		102,671,041
Convertible preferred stock, par value | $ / shares	$ 0.00001				$ 0.00001	$ 0.00001
Purchase price per share | $ / shares	$ 0.7839
Issuance of convertible preferred stock, Shares	102,671,041			102,671,041
Proceeds from issuance of convertible preferred stock | $	$ 80,500,000				$ 80,246,000
Offering costs | $				$ 237,000	$ 200,000
Convertible preferred stock dividend percentage					7.00%
Cumulative dividends | $					$ 3,000,000
Convertible preferred stock liquidation preference | $ / shares					$ 0.783900
Preferred stock, conversion price | $ / shares					$ 0.7839
Series E Convertible Preferred Stock | Subsequent Event
Temporary Equity [Line Items]
Preferred stock, conversion ratio							13.7

Common Stock - Additional Infor

Common Stock - Additional Information (Details) - $ / shares	Sep. 30, 2021	Dec. 31, 2020
Equity [Abstract]
Common stock, shares authorized	470,183,383	232,697,999
Common stock, par value	$ 0.00001	$ 0.00001
Common stock, shares issued	442,717	381,123
Common stock, shares outstanding	442,717	381,123

Stock-Based Compensation - Addi

Stock-Based Compensation - Additional Information (Details) - USD ($) $ / shares in Units, $ in Thousands	9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Mar. 18, 2021
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Weighted-average grant date fair value of stock options granted	$ 3.97	$ 2.74
Total intrinsic value of options exercised	$ 10	$ 20
Unrecognized compensation expense related to stock options	$ 7,900
Unrecognized compensation expense weighted average period	2 years 7 months 9 days
2009 Plan
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Vesting description	The awards under this plan typically vest over a 24, 36 or 48-month period, depending on the option agreement
Expiration period	10 years
Expiration date	Dec. 12, 2018
2018 Plan
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Number of shares authorized			2,346,228
Number of shares available for future issuance	650,795

Stock-Based Compensation - Summ

Stock-Based Compensation - Summary of Combined Stock Option Activity under 2009 and 2018 Plan (Details) - 2009 and 2018 Plan $ / shares in Units, $ in Thousands	9 Months Ended	12 Months Ended
	Sep. 30, 2021USD ($)$ / sharesshares	Dec. 31, 2020USD ($)$ / sharesshares
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Options Outstanding, Beginning balance | shares	1,512,129
Options, Granted | shares	1,883,480
Options, Exercised | shares	(61,594)
Options, Cancelled or forfeited | shares	(169,066)
Options Outstanding, Ending balance | shares	3,164,949	1,512,129
Options, Exercisable at September 30, 2021 | shares	1,024,453
Weighted Average Exercise Price, Beginning balance | $ / shares	$ 3.84
Weighted Average Exercise Price, Granted | $ / shares	6.13
Weighted Average Exercise Price, Exercised | $ / shares	4.95
Weighted Average Exercise Price, Cancelled or forfeited | $ / shares	4.50
Weighted Average Exercise Price, Ending balance | $ / shares	5.15	$ 3.84
Weighted Average Exercise Price, Exercisable at September 30, 2021 | $ / shares	$ 3.85
Weighted Average Remaining Contractual Term (years)	8 years 7 months 6 days	7 years 9 months 7 days
Weighted Average Remaining Contractual Term (years), Exercisable	6 years 9 months
Aggregate Intrinsic Value, Outstanding | $	$ 14,053	$ 1,174
Aggregate Intrinsic Value, Exercisable at September 30, 2021 | $	$ 5,849

Stock-Based Compensation - Sche

Stock-Based Compensation - Schedule of Fair Value of Stock Options, Valuation Assumptions (Details)	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Weighted average risk-free interest rate	1.00%	0.33%	1.06%	0.58%
Expected term (years)	6 years 21 days	5 years 8 months 1 day	6 years 7 days	6 years 10 days
Expected volatility	73.36%	73.71%	74.21%	74.16%
Expected dividend yield	0.00%	0.00%	0.00%	0.00%

Stock-Based Compensation - Su_2

Stock-Based Compensation - Summary of 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
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Stock-based compensation expense	$ 554	$ 191	$ 1,010	$ 557
Research and Development
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Stock-based compensation expense	157	47	263	153
General and Administrative
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Stock-based compensation expense	$ 397	$ 144	$ 747	$ 404

Series B Warrants - Additional

Series B Warrants - Additional Information (Details) - Series B Warrants - $ / shares	1 Months Ended
	May 31, 2015	Feb. 28, 2015	Nov. 02, 2021	Sep. 30, 2021	Dec. 31, 2020
Class Of Warrant Or Right [Line Items]
Warrants outstanding				173,827	173,827
Common Stock Warrants | Subsequent Event
Class Of Warrant Or Right [Line Items]
Number of Warrants converted			12,686
Series B Convertible Preferred Stock
Class Of Warrant Or Right [Line Items]
Number of Warrants converted	887,536	1,650,098
Exercise price of warrants	$ 1.24235	$ 1.24235
Warrants expiration period	10 years	10 years

Series B Warrants - Summary of

Series B Warrants - Summary of Estimated Fair Value of Warrants and Significant Assumptions (Details) - Series B Warrants	Dec. 30, 2021	Sep. 30, 2021
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Expected term (years)		3 years 6 months
Scenario Forecast
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Expected term (years)	4 years 2 months 12 days
Series B Estimated Fair Value
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Warrants measurement input		1.12
Series B Estimated Fair Value | Scenario Forecast
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Warrants measurement input	1.17
Volatility
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Warrants measurement input		79.50
Volatility | Scenario Forecast
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Warrants measurement input	74.07
Risk Free Rate
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Warrants measurement input		0.76
Risk Free Rate | Scenario Forecast
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Warrants measurement input	0.27
Dividend yield
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Warrants measurement input		7
Dividend yield | Scenario Forecast
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Warrants measurement input	7

Compensation - Additional Infor

Compensation - Additional Information (Details) - 401(k) Plan - USD ($) $ in Millions	9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020
Defined Contribution Plan Disclosure [Line Items]
Matching contribution by employer, percentage	100.00%
Employer matching contribution, percent of employees contribution	6.00%
Matching contributions from employer	$ 0.2	$ 0.1

Commitments and Contingencies -

Commitments and Contingencies - Additional Information (Details) € in Thousands

Mar. 31, 2021ft²

Apr. 05, 2019EUR (€)Installment

Jul. 31, 2021USD ($)

Aug. 31, 2019EUR (€)

Jul. 31, 2019USD ($)

Apr. 30, 2019EUR (€)

Dec. 31, 2014USD ($)

Jul. 31, 2011

Dec. 31, 2010USD ($)

Nov. 30, 2009

Sep. 30, 2021USD ($)

Sep. 30, 2021USD ($)

Sep. 30, 2021EUR (€)

Sep. 30, 2020USD ($)

Dec. 31, 2020USD ($)OperatingLease

Dec. 31, 2016EUR (€)

Dec. 31, 2013USD ($)

Jan. 31, 2014USD ($)

Lessee Lease Description [Line Items]

Operating lease termination date

Jul. 31, 2023

Area of space leased | ft²

4,516

Lease commencement date

May 1, 2021

Additional square feet of laboratory space | ft²

1,000

Additional leased space commencement date

Jun. 15, 2021

Lease existence of option to extend

true

Operating lease, option to extend term

12 months

Expense related to agreement and amendments

$ 4,000

Licensed patents and patent applications

30,000

Upfront payment

$ 100,000

Aggregate milestones payment

$ 21,000,000

Royalties on net sales

20.00%

Biologic Materials License Agreement

Lessee Lease Description [Line Items]

One time non refundable license issuance fee

$ 20,000

Milestone payments or royalties

$ 0

Collaboration Research and Development Agreement

Lessee Lease Description [Line Items]

Expenses

$ 30,000

National Institute of Health

Lessee Lease Description [Line Items]

License issue royalty fee

$ 100,000

Sales milestone payments

600,000

Development and regulatory milestone payments

$ 700,000

Aggregate milestones

400,000

Patent licensing reimbursement fees

30,000

$ 20,000

Aggregate reimbursed

300,000

Royalty Bearing License Agreement

Lessee Lease Description [Line Items]

Expenses

0

$ 0

License agreement term

10 years

Potential milestone payments

€ 500

500,000

€ 10

LI-COR | LI-COR Exclusive License Agreement

Lessee Lease Description [Line Items]

License issue fee

$ 100,000

Aggregate milestone payments

$ 200,000

Expense related to agreement and amendments

0

0

LI-COR | 2014 Non- Exclusive Agreement

Lessee Lease Description [Line Items]

License issue fee

$ 30,000

Non-refundable, Non- creditable fee

30,000

LI-COR | 2014 Non- Exclusive Agreement | Maximum

Lessee Lease Description [Line Items]

Payments for development and commercial milestones

400,000

Life Technologies Corporation

Lessee Lease Description [Line Items]

Derivative liability

Non-refundable, Non- creditable fee

300,000

Initial license fee

100,000

Annual development fee

100,000

Change of control fees

$ 200,000

Percentage of change in ownership of voting shares

50.00%

Expenses

30,000

$ 30,000

Dr. John Schiller | Collaboration Research and Development Agreement

Lessee Lease Description [Line Items]

Agreement term

2 years

First payment due

30 days

Subsequent payments due

30 days

Aggregate research collaboration fees

$ 300,000

Research collaboration fees

$ 40,000

Office and Laboratory Facility

Lessee Lease Description [Line Items]

Number of operating lease | OperatingLease

1

Operating lease termination date

Jul. 31, 2022

Laser System

Lessee Lease Description [Line Items]

Purchase agreement, commitments payable in each installment | €

€ 200

Purchase agreement, number of payment installments | Installment

3

Laser System | Installment One

Lessee Lease Description [Line Items]

Purchase agreement, installment amount paid | €

€ 200

Laser System | Installment Two

Lessee Lease Description [Line Items]

Purchase agreement, installment amount paid | €

€ 200

Commitments and Contingencies_2

Commitments and Contingencies - Summary of Lease Costs (Details) $ in Thousands	3 Months Ended	9 Months Ended
	Sep. 30, 2021USD ($)	Sep. 30, 2021USD ($)
Leases [Abstract]
Amortization of finance right-of-use assets		$ 11
Operating lease costs	$ 154	370
Variable lease costs	90	233
Total lease costs	$ 244	614
Cash paid for amounts included in the measurement of lease liability—finance leases		15
Cash paid for amounts included in the measurement of lease liability—operating leases		$ 367
Weighted-average remaining lease term—operating leases (years)	1 year 9 months 29 days	1 year 9 months 29 days
Weighted-average discount rate—finance leases	7.94%	7.94%
Weighted-average discount rate—operating leases	3.51%	3.51%

Commitments and Contingencies-

Commitments and Contingencies- Schedule of Fair Value of Financial Assets and Liabilities (Details) $ in Thousands	Sep. 30, 2021USD ($)
Leases [Abstract]
2021 (excluding nine months ended September 30, 2021)	$ 153
2022	625
2023	377
Total lease payments	1,155
Less: interest	(35)
Total operating lease liabilities at September 30, 2021	1,120
Less: current portion of lease liabilities	607
Lease liabilities, net of current portion	$ 513

Net Loss Per Share - Summary of

Net Loss Per Share - Summary of 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
Numerator:
Net loss	$ (8,838)	$ (8,852)	$ (5,927)	$ (3,631)	$ (6,156)	$ (7,512)	$ (23,617)	$ (17,299)
Less: Accruals of dividends of preferred stock	(3,668)			(1,948)			(9,627)	(5,802)
Net loss attributable to common stockholders - basic and diluted	$ (12,506)			$ (5,579)			$ (33,244)	$ (23,101)
Denominator:
Weighted average common stock outstanding	441,448			376,738			426,604	362,735
Net loss per share attributable to common stockholders—basic and diluted	$ (28.33)			$ (14.81)			$ (77.93)	$ (63.69)

Net Loss Per Share - Summary _2

Net Loss Per Share - Summary of Dilutive Securities Excluded from Computation of Diluted Net Loss Per Share (Details) - shares	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Total potential dilutive shares	25,728,196	14,686,345	25,728,196	14,686,345
Convertible Preferred Stock on as if Converted Basis
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Total potential dilutive shares	22,550,561	13,260,868	22,550,561	13,260,868
Stock Options to Purchase Common Stock
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Total potential dilutive shares	3,164,949	1,412,791	3,164,949	1,412,791
Warrants to Purchase Preferred Stock
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Total potential dilutive shares	12,686	12,686	12,686	12,686

Income Taxes - Additional Infor

Income Taxes - Additional Information (Details)	9 Months Ended
	Sep. 30, 2021USD ($)
Income Tax Disclosure [Abstract]
Effective tax rate	0.00%
Unrecognized income tax benefits that would reduce effective tax rate if recognized	$ 0

Related Parties - Additional In

Related Parties - Additional Information (Details) - Stockholder - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020
Related Party Transaction [Line Items]
Expenses incurred for research and development related services	$ 400	$ 300
Accrued expense, related party	$ 10	$ 100

Subsequent Events - Additional

Subsequent Events - Additional Information (Details) $ / shares in Units, $ in Millions	Nov. 02, 2021USD ($)$ / sharesshares	Oct. 22, 2021	Oct. 07, 2021USD ($)$ / sharesshares	Sep. 30, 2021USD ($)	Jan. 01, 2022shares
Scenario Forecast | 2021 Stock Option and Incentive Plan
Subsequent Event [Line Items]
Cumulative increase in shares of common stock					3,352,166
Scenario Forecast | 2021 Employee Stock Purchase Plan
Subsequent Event [Line Items]
Cumulative increase in shares of common stock					335,217
Common Stock
Subsequent Event [Line Items]
Gross proceeds from issuance of convertible preferred stock | $				$ 50
Subsequent Event
Subsequent Event [Line Items]
Reverse stock split, conversion ratio		0.072993
Reverse stock split description		On October 22, 2021, the Company effected a reverse stock split of the Company’s common stock on a 1-for-13.7 basis, or the Reverse Stock Split.
Subsequent Event | 2021 Stock Option and Incentive Plan
Subsequent Event [Line Items]
Number of shares reserved for issuance			3,352,166
Common stock outstanding percentage			5.00%
Subsequent Event | 2021 Employee Stock Purchase Plan
Subsequent Event [Line Items]
Number of shares reserved for issuance			335,217
Common stock outstanding percentage			1.00%
Subsequent Event | Conversion of Preferred Stock
Subsequent Event [Line Items]
Share price | $ / shares			$ 0.94068
Public offering consummated date			Feb. 28, 2022
Subsequent Event | Conversion of Preferred Stock | Minimum
Subsequent Event [Line Items]
Gross proceeds from issuance of convertible preferred stock | $			$ 75
Initial Public Offering | Subsequent Event
Subsequent Event [Line Items]
Share price | $ / shares	$ 14
Aggregate gross proceeds from IPO | $	$ 86.9
Net proceeds from the IPO | $	$ 77.9
Initial Public Offering | Subsequent Event | Common Stock
Subsequent Event [Line Items]
Shares issued and sold	6,210,000