0001564590-21-047532 | 10-Q | XBRL Viewer

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Document and Entity Information - shares	6 Months Ended
Document and Entity Information - shares	Jun. 30, 2021	Sep. 03, 2021
Cover [Abstract]
Document Type	10-Q
Amendment Flag	false
Document Period End Date	Jun. 30, 2021
Document Fiscal Year Focus	2021
Document Fiscal Period Focus	Q2
Entity Registrant Name	Omega Therapeutics, Inc.
Entity Central Index Key	0001850838
Entity Current Reporting Status	No
Entity Interactive Data Current	Yes
Current Fiscal Year End Date	--12-31
Entity Filer Category	Non-accelerated Filer
Entity Common Stock, Shares Outstanding		47,756,474
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 $0.001 per share
Trading Symbol	OMGA
Security Exchange Name	NASDAQ
Entity File Number	001-40657
Entity Incorporation, State or Country Code	DE
Entity Tax Identification Number	81-3247585
Entity Address, Address Line One	20 Acorn Park Drive
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	949-4360
Document Quarterly Report	true
Document Transition Report	false

Condensed Balance Sheets (Unaudited) - USD ($) $ in Thousands	Jun. 30, 2021	Dec. 31, 2020
Current assets:
Cash and cash equivalents	$ 122,411	$ 22,951
Prepaid expenses and other current assets	1,301	1,052
Deferred offering costs	1,585
Total current assets	125,297	24,003
Property and equipment, net	4,100	3,482
Restricted cash	341	341
Other assets	308	257
Total assets	130,046	28,083
Current liabilities:
Accounts payable	1,169	1,063
Accrued expenses	7,268	3,277
Other current liabilities	363	359
Long-term debt, current portion	3,000	3,000
Total current liabilities	11,800	7,699
Long-term debt, net	8,806	8,732
Other liabilities	1,331	1,055
Total liabilities	21,937	17,486
Commitments and contingencies (Note 8)
Redeemable convertible preferred stock:
Redeemable convertible preferred stock	200,593	75,225
Stockholders’ deficit:
Common stock, $0.001 par value; 175,000,000 and 137,700,000 shares authorized as of June 30, 2021 and December 31, 2020, respectively; 4,647,035 and 4,465,351 issued and outstanding as of June 30, 2021 and December 31, 2020, respectively	5	5
Additional paid-in capital	2,634	1,592
Accumulated deficit	(95,123)	(66,225)
Total stockholders’ deficit	(92,484)	(64,628)
Total liabilities, redeemable convertible preferred stock, and stockholders’ deficit	130,046	28,083
Series A Redeemable Convertible Preferred Stock
Redeemable convertible preferred stock:
Redeemable convertible preferred stock	26,708	26,708
Series B Redeemable Convertible Preferred Stock
Redeemable convertible preferred stock:
Redeemable convertible preferred stock	48,517	$ 48,517
Series C Redeemable Convertible Preferred Stock
Redeemable convertible preferred stock:
Redeemable convertible preferred stock	$ 125,368

Condensed Balance Sheets (Unaudited) (Parenthetical) - USD ($) $ in Thousands	Jun. 30, 2021	Dec. 31, 2020
Redeemable convertible preferred stock, shares authorized	132,858,564	107,125,232
Redeemable convertible preferred stock, shares issued	131,008,559	89,175,231
Redeemable convertible preferred stock, shares outstanding	131,008,559	89,175,231
Redeemable convertible preferred stock, liquidation value	$ 199,600	$ 74,100
Common stock, par value	$ 0.001	$ 0.001
Common stock, shares authorized	175,000,000	137,700,000
Common stock, shares issued	4,647,035	4,465,351
Common stock, shares outstanding	4,647,035	4,465,351
Series A Redeemable Convertible Preferred Stock
Redeemable convertible preferred stock, par value	$ 0.001	$ 0.001
Redeemable convertible preferred stock, shares authorized	57,125,232	57,125,232
Redeemable convertible preferred stock, shares issued	56,775,232	56,775,232
Redeemable convertible preferred stock, shares outstanding	56,775,232	56,775,232
Redeemable convertible preferred stock, liquidation value	$ 25,500	$ 25,500
Series B Redeemable Convertible Preferred Stock
Redeemable convertible preferred stock, par value	$ 0.001	$ 0.001
Redeemable convertible preferred stock, shares authorized	32,399,999	50,000,000
Redeemable convertible preferred stock, shares issued	32,399,999	32,399,999
Redeemable convertible preferred stock, shares outstanding	32,399,999	32,399,999
Redeemable convertible preferred stock, liquidation value	$ 48,600	$ 48,600
Series C Redeemable Convertible Preferred Stock
Redeemable convertible preferred stock, par value	$ 0.001
Redeemable convertible preferred stock, shares authorized	43,333,333
Redeemable convertible preferred stock, shares issued	41,833,328
Redeemable convertible preferred stock, shares outstanding	41,833,328
Redeemable convertible preferred stock, liquidation value	$ 125,500

Condensed Statements of Operations and Comprehensive Loss (Unaudited) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Operating expenses:
Research and development	$ 11,184	$ 4,895	$ 20,933	$ 8,416
General and administrative	3,637	1,010	6,452	2,375
Related party expense, net	384	225	763	567
Total operating expenses	15,205	6,130	28,148	11,358
Loss from operations	(15,205)	(6,130)	(28,148)	(11,358)
Other expense, net:
Interest expense, net	(190)	(194)	(402)	(387)
Change in fair value of warrant liability	(11)	1	(340)	4
Other expense, net	(4)		(8)
Total other expense, net	(205)	(193)	(750)	(383)
Net loss and comprehensive loss	$ (15,410)	$ (6,323)	$ (28,898)	$ (11,741)
Net loss per common stock attributable to common stockholders, basic and diluted	$ (3.36)	$ (1.58)	$ (6.36)	$ (2.99)
Weighted-average common stock used in net loss per share attributable to common stockholders, basic and diluted	4,588,500	4,007,606	4,542,832	3,929,900

Condensed Statements of Redeemable Convertible Preferred Stock and Stockholders' Deficit (Unaudited) - USD ($) $ in Thousands	Total	Preferred Stock - Series A	Preferred Stock - Series B	Preferred Stock - Series C	Common Stock	Additional Paid-in Capital	Accumulated Deficit
Balance at Dec. 31, 2019	$ (35,919)				$ 5	$ 854	$ (36,778)
Balance (in shares) at Dec. 31, 2019		56,775,232
Balance at Dec. 31, 2019		$ 26,708
Balance (in shares) at Dec. 31, 2019					3,775,292
Issuance of redeemable convertible preferred stock, shares			24,066,666
Issuance of redeemable convertible preferred stock			$ 36,038
Issuance of common stock for options exercised	7					7
Issuance of common stock for options exercised, shares					15,588
Vesting of restricted stock, shares					124,080
Stock-based compensation	145					145
Net loss	(5,418)						(5,418)
Balance at Mar. 31, 2020	(41,185)				$ 5	1,006	(42,196)
Balance (in shares) at Mar. 31, 2020		56,775,232	24,066,666
Balance at Mar. 31, 2020		$ 26,708	$ 36,038
Balance (in shares) at Mar. 31, 2020					3,914,960
Balance at Dec. 31, 2019	(35,919)				$ 5	854	(36,778)
Balance (in shares) at Dec. 31, 2019		56,775,232
Balance at Dec. 31, 2019		$ 26,708
Balance (in shares) at Dec. 31, 2019					3,775,292
Net loss	(11,741)
Balance at Jun. 30, 2020	(47,391)				$ 5	1,123	(48,519)
Balance (in shares) at Jun. 30, 2020		56,775,232	27,399,999
Balance at Jun. 30, 2020		$ 26,708	$ 41,027
Balance (in shares) at Jun. 30, 2020					4,062,409
Balance at Mar. 31, 2020	(41,185)				$ 5	1,006	(42,196)
Balance (in shares) at Mar. 31, 2020		56,775,232	24,066,666
Balance at Mar. 31, 2020		$ 26,708	$ 36,038
Balance (in shares) at Mar. 31, 2020					3,914,960
Issuance of redeemable convertible preferred stock, shares			3,333,333
Issuance of redeemable convertible preferred stock			$ 4,989
Issuance of common stock for options exercised	11					11
Issuance of common stock for options exercised, shares					25,933
Vesting of restricted stock, shares					124,080
Common stock repurchased	(1)					(1)
Common stock repurchased, shares					(2,564)
Stock-based compensation	107					107
Net loss	(6,323)						(6,323)
Balance at Jun. 30, 2020	(47,391)				$ 5	1,123	(48,519)
Balance (in shares) at Jun. 30, 2020		56,775,232	27,399,999
Balance at Jun. 30, 2020		$ 26,708	$ 41,027
Balance (in shares) at Jun. 30, 2020					4,062,409
Balance at Dec. 31, 2020	$ (64,628)				$ 5	1,592	(66,225)
Balance (in shares) at Dec. 31, 2020	89,175,231	56,775,232	32,399,999
Balance at Dec. 31, 2020	$ 75,225	$ 26,708	$ 48,517
Balance (in shares) at Dec. 31, 2020					4,465,351
Issuance of redeemable convertible preferred stock, shares				41,833,328
Issuance of redeemable convertible preferred stock				$ 125,368
Issuance of common stock for options exercised	45					45
Issuance of common stock for options exercised, shares					80,460
Stock-based compensation	194					194
Net loss	(13,488)						(13,488)
Balance at Mar. 31, 2021	(77,877)				$ 5	1,831	(79,713)
Balance (in shares) at Mar. 31, 2021		56,775,232	32,399,999	41,833,328
Balance at Mar. 31, 2021		$ 26,708	$ 48,517	$ 125,368
Balance (in shares) at Mar. 31, 2021					4,545,811
Balance at Dec. 31, 2020	$ (64,628)				$ 5	1,592	(66,225)
Balance (in shares) at Dec. 31, 2020	89,175,231	56,775,232	32,399,999
Balance at Dec. 31, 2020	$ 75,225	$ 26,708	$ 48,517
Balance (in shares) at Dec. 31, 2020					4,465,351
Net loss	(28,898)
Balance at Jun. 30, 2021	$ (92,484)				$ 5	2,634	(95,123)
Balance (in shares) at Jun. 30, 2021	131,008,559	56,775,232	32,399,999	41,833,328
Balance at Jun. 30, 2021	$ 200,593	$ 26,708	$ 48,517	$ 125,368
Balance (in shares) at Jun. 30, 2021					4,647,035
Balance at Mar. 31, 2021	(77,877)				$ 5	1,831	(79,713)
Balance (in shares) at Mar. 31, 2021		56,775,232	32,399,999	41,833,328
Balance at Mar. 31, 2021		$ 26,708	$ 48,517	$ 125,368
Balance (in shares) at Mar. 31, 2021					4,545,811
Issuance of common stock for options exercised	118					118
Issuance of common stock for options exercised, shares					101,224
Stock-based compensation	685					685
Net loss	(15,410)						(15,410)
Balance at Jun. 30, 2021	$ (92,484)				$ 5	$ 2,634	$ (95,123)
Balance (in shares) at Jun. 30, 2021	131,008,559	56,775,232	32,399,999	41,833,328
Balance at Jun. 30, 2021	$ 200,593	$ 26,708	$ 48,517	$ 125,368
Balance (in shares) at Jun. 30, 2021					4,647,035

Condensed Statements of Redeemable Convertible Preferred Stock and Stockholders' Deficit (Unaudited) (Parenthetical) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2021	Jun. 30, 2020	Mar. 31, 2020
Preferred Stock - Series B
Stock issuance costs		$ 11	$ 62
Preferred Stock - Series C
Stock issuance costs	$ 132

Condensed Statements of Cash Flows (Unaudited) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Operating activities
Net loss			$ (28,898)	$ (11,741)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation	$ 300	$ 200	639	441
Amortization of debt issuance costs and debt discount	33	12	74	24
Change in fair value of warrant liability	11	(1)	340	(4)
Change in fair value of success fee obligation			5
Stock-based compensation expense			879	252
Deferred rent			(62)	(54)
Changes in operating assets and liabilities:
Prepaid expenses and other current assets			(249)	165
Deferred offering costs			(904)
Other assets			(51)
Accounts payable			67	(146)
Accrued expenses and other current liabilities			3,007	(129)
Other liabilities			(4)
Net cash used in operating activities			(25,157)	(11,192)
Investing activities
Purchases of property and equipment			(914)	(239)
Net cash used in investing activities			(914)	(239)
Financing activities
Proceeds from issuance of redeemable convertible preferred stock			125,500	41,100
Equity issuance costs			(132)	(73)
Proceeds from exercise of stock options			163	17
Net cash provided by financing activities			125,531	41,044
Net increase in cash, cash equivalents and restricted cash			99,460	29,613
Cash, cash equivalents and restricted cash—beginning of period			23,292	2,615
Cash, cash equivalents and restricted cash—end of period	122,752	32,228	122,752	32,228
Reconciliation of cash, cash equivalents and restricted cash
Cash and cash equivalents	122,411	31,887	122,411	31,887
Restricted cash	341	341	341	341
Cash, cash equivalents and restricted cash—end of period	$ 122,752	$ 32,228	122,752	32,228
Supplemental disclosures of cash flow information
Cash paid for interest			348	366
Supplemental disclosure of noncash investing and financing activities
Deferred offering costs in accounts payable and accrued expenses			681
Purchase of property and equipment included accounts payable and accrued expenses			$ 343	$ 123

Nature of the Business and Basis of Presentation

6 Months Ended

Jun. 30, 2021

Nature Of Business And Basis Of Presentation [Abstract]

Nature of the Business and Basis of Presentation

1. Nature of the Business and Basis of Presentation

Organization

Omega Therapeutics, Inc. (the “Company” or “Omega”) is a development-stage biotechnology company pioneering a new systematic approach to use mRNA therapeutics as programmable epigenetic medicines by leveraging its OMEGA Epigenomic Programming platform (“OMEGA platform”). The OMEGA platform harnesses the power of epigenetics, the mechanism that controls gene expression and every aspect of an organism's life from cell genesis, growth and differentiation to cell death. The OMEGA platform enables control of fundamental epigenetic processes to correct the root cause of disease by returning aberrant gene expression to a normal range without altering native nucleic acid sequences. The Company was incorporated in July 2016 (“inception”) as a Delaware corporation and its offices are in Cambridge, Massachusetts.

Liquidity

Since its inception, the Company has devoted substantially all of the resources to building its platform and advancing development of its portfolio of programs, establishing and protecting its intellectual property, conducting research and development activities, organizing and staffing the Company, business planning, raising capital and providing general and administrative support for these operations. The Company is subject to risks and uncertainties common to early-stage companies in the biotechnology industry including, but not limited to, technical risks associated with the successful research, development and manufacturing of product candidates, development by competitors of new technological innovations, dependence on key personnel, protection of proprietary technology, compliance with government regulations and the ability to secure additional capital to fund operations. Current and future programs will require significant research and development efforts, including extensive preclinical and clinical testing and regulatory approval prior to commercialization. These efforts require significant amounts of additional capital, adequate personnel and infrastructure. Even if the Company’s drug development efforts are successful, it is uncertain when, if ever, the Company will realize significant revenue from product sales.

On August 3, 2021, the Company closed its initial public offering (“IPO”) of 7,400,000 shares of the Company’s common stock at a public offering price of $17.00 per share. The gross proceeds from the IPO were $125.8 million and the net proceeds were approximately $113.4 million, after deducting underwriting discounts and commissions and other offering expenses payable by the Company. Upon completion of the Company’s IPO, all of the Company’s then outstanding redeemable convertible preferred stock was automatically converted into an aggregate of 34,678,733 shares of common stock. On August 17, 2021, the Company issued and sold 900,976 shares of its common stock pursuant to the partial exercise of the underwriters’ option to purchase additional shares, at a public offering price of $17.00 per share, for aggregate gross proceeds of $15.3 million. The Company received appropriately $14.2 million in net proceeds after deducting underwriting discounts and commissions.

As presented in the unaudited condensed financial statements, the Company had cash and cash equivalents of $122.4 million at June 30, 2021. The Company expects that its cash and cash equivalents, including the net proceeds from its IPO, will enable it to fund its operating expenses and capital expenditure requirements for at least twelve months from September 10, 2021, the filing date of this Quarterly Report on Form 10-Q. However, additional funding will be necessary beyond this point to fund future preclinical and clinical activities and to develop new product candidates. The Company expects to finance its future cash needs through a combination of equity offerings, debt financings, marketing and distribution arrangements and other collaborations, strategic alliances and licensing arrangements, or other sources.

COVID-19-Related Significant Risks and Uncertainties

With the global COVID-19 pandemic continuing throughout 2021, the Company is following, and plans to continue to follow, recommendations from federal, state and local governments regarding workplace policies, practices and procedures. In response to the direction from state and local governmental authorities, the Company has restricted access to its facility to those individuals who must perform critical research and laboratory support activities that must be completed on site, limited the number of such people that can be present at its facility at any one time and required that certain employees work remotely if possible. The Company expects to continue incurring additional costs to ensure it adheres to the guidelines instituted by the federal, state and local governments and to provide a safe working environment to its onsite employees.

The extent to which the COVID-19 pandemic and variants of the virus impacts the Company’s business, its corporate development objectives, results of operations and financial condition, and the fair value of and market for its common stock, will depend on future developments that are highly uncertain and cannot be predicted with confidence at this time, such as the ultimate duration of the pandemic, travel restrictions, quarantines, social distancing and business closure requirements, and the effectiveness of actions taken globally to contain and treat the disease. Disruptions to the global economy, disruption of global healthcare systems, and other significant impacts of the COVID-19 pandemic could have a material adverse effect on the Company’s business, financial condition, results of operations and growth prospects.

While the COVID-19 pandemic did not significantly impact the Company’s business or results of operations during the six months ended June 30, 2021, the length and extent of the pandemic, its consequences, and containment efforts will determine the future impact on the Company’s operations and financial condition.

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 (“GAAP”). Any reference in these notes to applicable guidance is meant to refer to the authoritative GAAP as found in the Accounting Standards Codification (“ASC”), and Accounting Standards Update (“ASU”), of the Financial Accounting Standards Board (“FASB”). All amounts herein are expressed in U.S. dollars (“USD”) unless otherwise noted.

Summary of Significant Accounting Policies

6 Months Ended

Jun. 30, 2021

Accounting Policies [Abstract]

Summary of Significant Accounting Policies

2. Summary of Significant Accounting Policies

Unaudited Condensed Financial Information

The accompanying unaudited condensed financial statements included herein have been prepared, without audit, pursuant to the rules and regulations of the Securities and Exchange Commission (the “SEC”). The unaudited condensed financial statements have been prepared on the same basis as audited financial statements, except certain information and footnote disclosures normally included in financial statements prepared in accordance with GAAP have been condensed or omitted from this report, as is permitted by such rules and regulations. In the opinion of management, the information furnished reflects all adjustments, all of which are of a normal and recurring nature, necessary for a fair representation of the results for the reported periods. These unaudited condensed financial statements should be read in conjunction with the audited financial statements and notes thereto contained in the Company’s final prospectus for its IPO dated August 2, 2021 and filed with the SEC pursuant to Rule 424(b)(4) under the Securities Act of 1933, as amended (the “Prospectus”).

The results for the six months ended June 30, 2021 are not necessarily indicative of results to be expected for the year ending December 31, 2021, any other interim periods, or any future year or period.

Use of Estimates

The preparation of the unaudited condensed financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the reported amounts of assets, liabilities and expenses, and the disclosure of contingent assets and liabilities as of and during the reporting period. The Company bases its estimates and assumptions on historical experience when available and on various factors that it believes to be reasonable under the circumstances.

Significant estimates and assumptions reflected in these unaudited condensed financial statements include, but are not limited to, the selection of useful lives of property and equipment, the fair values of common stock, redeemable convertible preferred stock, warrants, success fee obligation, and stock-based compensation. Actual results could differ from these estimates. Changes in estimates are reflected in reported results in the period in which they become known.

Summary of Significant Accounting Policies

The Company’s significant accounting policies are described in Note 2, “Summary of significant accounting policies,” to the Company’s audited financial statements included in the Prospectus. Except as detailed below, there have been no material changes to the significant accounting policies during the six months ended June 30, 2021.

Deferred Offering Costs

The Company capitalizes certain legal, professional accounting and other third-party fees that are directly associated with in-process equity financings as deferred offering costs until such financings are consummated. After consummation of the equity financing, these costs are recorded in stockholders’ deficit as a reduction of proceeds generated as a result of the offering. Should a planned equity financing be abandoned, the deferred offering costs would be expensed immediately as a charge to operating expenses in the unaudited condensed consolidated statement of operations. The Company recorded deferred offering costs, related to the IPO, of approximately $1.6 million as of June 30, 2021. Upon closing the IPO in August 2021, deferred offering costs were derecognized and recorded against the IPO proceeds as a reduction to additional paid-in capital.

Recently Issued Accounting Pronouncements

In February 2016, the FASB issued ASU No. 2016-02, Leases (Topic 842) (“ASU 2016-02”), which sets out the principles for the recognition, measurement, presentation and disclosure of leases for both parties to a contract (i.e., lessees and lessors). The new standard requires lessees to apply a dual approach, classifying leases as either finance or operating leases based on the principle of whether or not the lease is effectively a financed purchase by the lessee. This classification will determine whether lease expense is recognized based on an effective interest method or on a straight- line basis over the term of the lease. A lessee is also required to record a right-of-use asset and a lease liability for all leases with a term of greater than 12 months regardless of their classification. Leases with a term of 12 months or less may be accounted for similar to existing guidance for operating leases today. As the Company has elected to use the extended transition period for complying with new or revised accounting standards as available under the Jumpstart Our Business Startups Act (“JOBS Act”), the standard is effective for the Company beginning January 1, 2022, with early adoption permitted. The Company is currently evaluating the impact that the adoption of ASU 2016-02 will have on its financial statements.

In December 2019, the FASB issued ASU No. 2019-12, Income Taxes-Simplifying the Accounting for Income Taxes (“ASU 2019-12”). ASU 2019-12 eliminates certain exceptions related to the approach for intraperiod tax allocation, the methodology for calculating income taxes in an interim period and the recognition of deferred tax liabilities for outside basis differences. The new guidance also simplifies aspects of the accounting for franchise taxes, enacted changes in tax laws or rates and clarifies the accounting for transactions that result in a step-up in the tax basis of goodwill. Adoption of the standard requires certain changes to be made prospectively and certain others to be made retrospectively. As the Company has elected to use the extended transition period for complying with new or revised accounting standards as available under the JOBS Act, the standard is effective for the Company beginning January 1, 2022, with early adoption permitted. The Company does not expect ASU 2019-12 to have a material effect on the Company’s financial statements.

Prepaid Expenses and Other Current Assets

6 Months Ended

Jun. 30, 2021

Prepaid Expense And Other Assets Current [Abstract]

Prepaid Expenses and Other Current Assets

3. Prepaid Expenses and Other Current Assets

Prepaid expenses and other current assets consisted of the following (in thousands):

	June 30,		December 31,
	2021		2020
Prepaid software	$	33	$	78
Prepaid research and development		953		653
Prepaid other		275		128
Other receivables		40		193
Prepaid expenses and other current assets	$	1,301	$	1,052

Property and Equipment, Net

6 Months Ended

Jun. 30, 2021

Property Plant And Equipment [Abstract]

Property and Equipment, Net

4. Property and Equipment, Net

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

	June 30,			December 31,
	2021			2020
Leasehold improvements	$	1,378		$	1,378
Lab equipment		4,225			3,444
Furniture and fixtures		1,047			985
Computer equipment		129			129
Construction in process		429			16
Total property and equipment		7,208			5,952
Less accumulated depreciation		(3,108	)		(2,470	)
Property and equipment, net	$	4,100		$	3,482

Depreciation expense for the three months ended June 30, 2021 and 2020 was $0.3 million and $0.2 million, respectively; depreciation expense for the six months ended June 30, 2021 and 2020 was $0.6 million and $0.4 million, respectively.

Accrued Expenses

6 Months Ended

Jun. 30, 2021

Accrued Liabilities Current [Abstract]

Accrued Expenses

5. Accrued Expenses

Accrued expenses consist of the following (in thousands):

	June 30,		December 31,
	2021		2020
Employee related expenses	$	1,094	$	1,124
Research costs		4,377		1,724
Consulting fees		122		165
Interest		58		44
Other		1,617		220
Total	$	7,268	$	3,277

Term Loan

6 Months Ended

Jun. 30, 2021

Debt Disclosure [Abstract]

Term Loan

6. Term Loan

On March 9, 2018 (“Closing Date”), the Company entered into the loan and security agreement (“Loan Agreement”) with Pacific Western Bank (“PWB”), a California state-chartered bank. Under the Loan Agreement, the Company may borrow amounts not to exceed $8.0 million, consisted of Tranche I and Tranche II, with the Tranche I funded on the Closing Date and Tranche II funded no later than 18 months from the Closing Date. The Company borrowed $3.5 million under Tranche I on the Closing Date and $4.5 million under Tranche II in August 2018, and the full amount of $8.0 million was to be repaid beginning 18 months from the Closing Date in thirty equal installments, including interest at a floating annual rate equal to the greater of (i) 0.75% above the prime rate then in effect and (ii) 5.00%, due monthly starting the first month after the Closing Date.

In conjunction with the Loan Agreement, under Tranche I, the Company issued a warrant to PWB to purchase 87,500 shares of Series A redeemable convertible preferred stock (“Series A Preferred Stock”) at the initial strike price of $0.50 per share. The warrant is exercisable for a 10-year period. Additionally, the warrant shall be exercisable for an additional number of shares of Series A Preferred Stock equal to the amount borrowed under Tranche II multiplied by 0.0125. In no event shall the warrant be exercisable for more than 200,000 shares of Series A Preferred Stock. Upon closing of Tranche II, the warrant was not exercised for additional number of shares of Series A Preferred Stock. In lieu of exercising the warrant, PWB may, in whole or in part, convert the warrant into a number of shares of Series A Preferred Stock, determined by (a) dividing the aggregate fair market value of the Series A Preferred Stock shares minus the aggregate warrant price of such shares by (b) the fair market value of one share of Series A Preferred Stock. The fair market value of the Series A Preferred Stock shares shall be determined based upon either the publicly traded closing price on the date of the conversion or, if not publicly traded, a value deemed appropriate by the Company’s board of directors. Refer to Note 7, Fair value of financial instruments, for further discussion on the valuation methodology and inputs for the determination of the fair value of the warrants.

On September 30, 2019, the Company entered into an amendment to the Loan Agreement (the “First Amendment”), in which PWB made an additional term loan pursuant to a new Tranche III to the Company in an aggregate principal amount of $12.0 million. The proceeds of the term loan pursuant to Tranche III were first applied to the repayment in full of all outstanding principal and accrued interest on the outstanding term loan of $8.0 million borrowed pursuant to Tranche I and Tranche II; the remaining cash proceeds of $4.0 million was used for general working capital and for capital expenditures purposes. The maturity date of the additional term loan was initially March 9, 2022, and it would have been repaid beginning on January 9, 2020 in twenty-seven equal installments. However, the first closing of the Company’s Series B redeemable convertible preferred stock (“Series B Preferred Stock”) financing in January 2020 satisfied the cash proceeds milestone noted in the First Amendment, in which the maturity date of the amended term loan was extended to June 9, 2023, and the term loan was to be repaid beginning in January 2021 in thirty equal installments, including interest at a floating annual rate equal to the greater of (i) 0.75% above the prime rate then in effect and (ii) 6.00%, due monthly starting the first month after September 30, 2019. The Company incurred $15 thousand of debt issuance costs, which was recorded as a direct reduction against the additional term loan and amortized over the life of the associated term loan as a component of interest expense using the effective interest method.

In conjunction with the First Amendment, the Company also issued a warrant to purchase 350,000 shares of Series A Preferred Stock, which effectively restated and replaced the original warrant agreement. The strike price of the amended warrant is $0.50 per share, and the term remains unchanged, expiring in March 2028. No warrants have been exercised as of June 30, 2021. Refer to Note 7, Fair value of financial instruments, for further discussion on the valuation methodology and inputs for the determination of the fair value of the warrants. Upon the closing of the IPO, the Company’s outstanding warrants to purchase Series A Preferred Stock automatically became warrants to purchase an aggregate of 92,647 shares of common stock.

As the warrants issued are freestanding financial instruments that are exercisable for contingently redeemable shares, they were initially recorded at fair value on the date of issuance as a liability, with a corresponding discount recorded against the face value of the term loan. The discount was accreted against the face value of the term loan over its remaining term as additional interest expense. At the end of each reporting period, the change in estimated fair value of the warrants during the period is recognized as a component of other income (expense), net in the statements of operations and comprehensive loss.

On January 22, 2020, the Loan Agreement was further amended (the “Second Amendment”) to extend the principal repayment start date, from January 9, 2020 as noted in the First Amendment to February 9, 2020; the number of repayment installments was also amended from twenty-seven equal installments to twenty-six equal installments. No additional proceeds were taken under the Second Amendment, and there were no other material amendments to the terms and conditions.

On December 30, 2020, the Loan Agreement was further amended (the “Third Amendment”) to extend the principal repayment date. No additional proceeds were taken under the Third Amendment. The maturity date of the term loan was extended to June 30, 2023, and it is to be repaid beginning on June 30, 2021 in twenty-four equal installments, including interest at a floating annual rate equal to the greater of (i) 0.75% above the prime rate then in effect and (ii) 6.00%, due monthly starting the first month after December 30, 2020. The Company incurred $15 thousand of debt issuance costs, which have been recorded as a direct reduction against the term loan and amortized over the life of the associated term loan as a component of interest expense using the effective interest method.

Borrowings under the Loan agreement, as amended, are collateralized by substantially all of the Company’s personal property, other than its intellectual property. There are no financial covenants associated with the Loan Agreement, as amended; however, the Company is subject to certain affirmative and negative covenants to which the Company will remain subject until maturity.

As a result of the closing of Series C redeemable convertible preferred stock (“Series C Preferred Stock”) in March 2021, as further discussed in Note 10, Redeemable convertible preferred stock, the Company satisfied the cash proceeds milestone as defined in the Third Amendment, in which the Company received gross cash proceeds of more than $50.0 million from the issuance of new preferred stock prior to June 30, 2021. Accordingly, the principal repayment date of the term loan was extended to December 31, 2021 and the maturity date was extended to December 31, 2023. There are no other changes to the terms as a result of the achievement of the cash proceeds milestone.

Additionally, the Company is required to pay a success fee of $0.2 million upon the occurrence of a specified liquidity event, as described in the Loan Agreement, which includes an IPO. The Company determined that this obligation represented a freestanding financial instrument. Accordingly, the success fee obligation was classified as a liability on the

Company’s balance sheets and initially recorded at fair value, with changes in fair value for each reporting period recognized in other income (expense), net in the statements of operations and comprehensive loss. The fair value of such obligation is remeasured at the end of each reporting period until the liability is settled, for which it was settled and paid in August 2021 upon the completion of the IPO.

As of June 30, 2021 and December 31, 2020, the long-term debt, current portion was $3.0 million, and the long-term debt was $9.0 million. The Company’s outstanding term loan balance was comprised of the following (in thousands):

	June 30,			December 31,
	2021			2020
Principal	$	12,000		$	12,000
Unamortized debt discount		(194	)		(268	)
Net carrying amount	$	11,806		$	11,732

The Company determined that the expected life of the debt was equal to the term on the term loan. The effective interest rate on the liability component ranged from 5.53% to 7.51% for the period from the date of issuance through June 30, 2021. The following table sets forth total interest expense recognized related to the term loan (in thousands):

	Three months ended June 30,				Six months ended June 30,
	2021		2020		2021		2020
Contractual interest expense	$	182	$	182	$	362	$	364
Amortization of debt issuance costs and debt discount		33		12		74		24
Total interest expense	$	215	$	194	$	436	$	388

At June 30, 2021 and December 31, 2020, accrued interest on the term loan was $58 thousand and $44 thousand, respectively.

The Company is required to repay the following principal amounts in connection with its term loan (in thousands):

2021 (remaining 6 months)	$	—
2022		6,000
2023		6,000
	$	12,000

- Definition

The entire disclosure for information about short-term and long-term debt arrangements, which includes amounts of borrowings under each line of credit, note payable, commercial paper issue, bonds indenture, debenture issue, own-share lending arrangements and any other contractual agreement to repay funds, and about the underlying arrangements, rationale for a classification as long-term, including repayment terms, interest rates, collateral provided, restrictions on use of assets and activities, whether or not in compliance with debt covenants, and other matters important to users of the financial statements, such as the effects of refinancing and noncompliance with debt covenants.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 470
-URI http://asc.fasb.org/topic&trid=2208564

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 470
-SubTopic 20
-Section 50
-Paragraph 1B
-Subparagraph (h)
-URI http://asc.fasb.org/extlink&oid=123466505&loc=SL123495323-112611

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
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Reference 4: http://www.xbrl.org/2003/role/disclosureRef
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Reference 5: http://www.xbrl.org/2003/role/disclosureRef
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Reference 6: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
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-Topic 235
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-Section S99
-Paragraph 1
-Subparagraph (SX 210.4-08(c))
-URI http://asc.fasb.org/extlink&oid=120395691&loc=d3e23780-122690

Reference 7: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
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-SubTopic 20
-Section 50
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Reference 8: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
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Reference 9: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
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-URI http://asc.fasb.org/extlink&oid=123466505&loc=SL123495334-112611

Reference 10: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
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-Publisher FASB
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Reference 12: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 470
-SubTopic 20
-Section 50
-Paragraph 1I
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=123466505&loc=SL123495371-112611

Reference 13: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 470
-SubTopic 20
-Section 50
-Paragraph 1B
-Subparagraph (i)
-URI http://asc.fasb.org/extlink&oid=123466505&loc=SL123495323-112611

+ Details

Fair Value of Financial Instruments

6 Months Ended

Jun. 30, 2021

Fair Value Disclosures [Abstract]

Fair Value of Financial Instruments

7. Fair Value of Financial Instruments

The fair value of the Company’s financial instruments is summarized in the tables below (in thousands):

	June 30, 2021
	Level 1		Level 2		Level 3		Total
Financial Liabilities
Warrant liability	$	—	$	—	$	464	$	464
Success fee obligation		—		—		199		199
Total	$	—	$	—	$	663	$	663

	December 31, 2020
	Level 1		Level 2		Level 3		Total
Financial Liabilities
Warrant liability	$	—	$	—	$	124	$	124
Success fee obligation		—		—		194		194
Total	$	—	$	—	$	318	$	318

The Company’s warrant liability and success fee obligation contain unobservable inputs that reflected the Company’s own assumptions in which there is little, if any, market activity at the measurement date. Accordingly, the Company’s warrant liability and success fee obligation are measured at fair value on a recurring basis using unobservable

inputs at each reporting period and are classified as Level 3 inputs. The warrant liability is recorded as other liabilities on the balance sheets as they are deemed more probable than not by the Company to be settled in longer than one year.

The fair values of the warrants are estimated using the Black-Scholes option-pricing model. The expected terms represent the remaining contractual term of the warrants. The risk-free interest rate is determined by reference to the U.S. Treasury yield curve for time periods approximately equal to the remaining contractual term of the warrants. The expected dividend is zero as the Company has not paid nor does it anticipate paying any dividends on its common stock in the foreseeable future. The Company historically has been a private company and lacks company-specific historical and implied volatility information of its stock. Therefore, it estimates its expected stock volatility based on the historical volatility of publicly traded peer companies for a term equal to the remaining contractual term of the warrants.

The assumptions used in the Black-Scholes option-pricing model for the warrants were as follows:

	Six months ended June 30,
	2021	2020
Expected volatility	77.42 - 77.62%	73.09 - 74.06%
Risk-free interest rate	1.21 - 1.40%	0.58 - 0.63%
Expected dividend yield	0.00%	0.00%
Expected term (in years)	6.7 - 6.9	7.7 - 7.9

The fair value of the warrants will be remeasured at each reporting period, with changes in fair value recognized in the statements of operations and comprehensive loss. The change in the fair value of the warrant liability during the three and six months ended June 30, 2021 was less than $0.1 million and $0.3 million, respectively; and there was an immaterial change in the fair value of the warrant liability for both of the three months and six months ended June 30, 2020.

The fair value of the success fee obligation was determined using the probability-weighted expected return method. The key estimates and assumptions impacting the fair value include the probability of achieving a specified liquidity event, the expected timing of achieving a liquidity event and discount rate. The fair value of the success fee obligation is remeasured at each reporting period, with changes in fair value recognized in the statement of operations and comprehensive loss, until such liability is settled. During the three and six months ended June 30, 2021, the change in the fair value of the success fee obligation was immaterial. The success fee obligation is recorded as other current liabilities on the balance sheets as it is deemed more probable than not by the Company to be settled in less than one year; such obligation was settled in August 2021 upon the closing of the IPO.

The following reflects the significant quantitative inputs used to determine the valuation of the success fee obligation during the six months ended June 30, 2021:

Discount rate		6.0	%
Expected timing of achieving liquidity events (years)		0.11
Probability of achieving liquidity events	1% -99%

The following table provides a roll-forward of the fair values of the Company’s warrant liability and the success fee obligation for which fair value is determined by Level 3 inputs (in thousands):

	Warrant liability		Success fee obligation
Fair value at January 1, 2021	$	124	$	194
Change in fair value		340		5
Fair value at June 30, 2021	$	464	$	199

	Warrant liability			Success fee obligation
Fair value at January 1, 2020	$	127		$	—
Change in fair value		(4	)		—
Fair value at June 30, 2020	$	123		$	—

- Definition

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

+ References + Details

Commitments and Contingencies

6 Months Ended

Jun. 30, 2021

Commitments And Contingencies Disclosure [Abstract]

Commitments and Contingencies

8. Commitments and Contingencies

Operating Leases

In 2017, the Company entered a noncancelable operating lease agreement to lease its office space at 325 Vassar Street, Cambridge, Massachusetts, which will expire in September 2024. The Company is required to pay property taxes, insurance, and normal maintenance costs. The operating lease contains predetermined fixed escalations of minimum rentals during the lease term. During 2018, the Company received $1.1 million of landlord-funded leasehold improvements related to the leased office space. The landlord-funded leasehold improvements were recorded as property and equipment, net and deferred rent in the balance sheets and are being amortized as a reduction to rent expense over the life of the lease. In 2019 and 2020, the Company entered into sublease agreements with two related parties to sublease this office and laboratory space. Refer to Note 15, Related party transactions, for further details.

On July 13, 2020, the Company entered into a Shared Space Arrangement (“the Arrangement”) with Senda Biosciences, Inc. (“Senda”, also formerly known as Kintai Therapeutics, Inc.) to share one-third of Senda’s 69,867 square feet of leased space at 20 Acorn Park Drive, Cambridge, Massachusetts. Senda is a related party as it is an affiliate of Flagship Pioneering (“Flagship”). The Arrangement commenced on August 1, 2020 and continues through July 31, 2022 with two options to extend the term of the Arrangement for a period of 24 months each. The operating lease contains predetermined fixed escalations of minimum rentals during the lease term, and the Company is required to pay property taxes, insurance, and normal maintenance costs. During the three and six months ended June 30, 2021, the Company incurred $0.6 million and $1.2 million for rental expenses. As of June 30, 2021 and December 31, 2020, the Company did not have any outstanding payments due to Senda.

The Company recognizes the rental expense on a straight-line basis over the life of the respective lease from the date the Company takes possession of the office and records the difference between amounts charged to operations and amounts paid as deferred rent. Rent expense under both lease agreements for the three months ended June 30, 2021 and 2020 was $0.8 million and $0.4 million, respectively; rent expense under both lease agreements for the six months ended June 30, 2021 and 2020 was $1.6 million and $0.7 million, respectively.

As of June 30, 2021, the future minimum lease payments for the Company’s facility operating leases were as follows (in thousands):

2021 (remaining 6 months)	$	1,678
2022		2,618
2023		1,563
2024		1,205
Total minimum lease payments	$	7,064

License Agreements

6 Months Ended

Jun. 30, 2021

License Agreements [Abstract]

License Agreements

9. License Agreements

Flagship Pioneering Innovations V, Inc.

In March 2019, the Company entered into an exclusive license agreement with Flagship Pioneering Innovations V, Inc., an affiliate of one of the Company’s principal stockholders, under which the Company was granted an exclusive, worldwide, royalty-bearing, sublicensable, transferable license under specified patent rights to develop, manufacture and commercialize licensed products (the “Flagship License”). Under the terms of the Flagship License, the Company is obligated to pay low single digit percentage royalties on net sales of licensed products by the Company. Royalties shall be paid by the Company on a country-by-country basis until expiration or abandonment of the last valid patent claim covering such licensed product in such country. The Company is also obligated to reimburse Flagship for patent prosecution costs.

The royalty payment is contingent upon sales of licensed products under the Flagship License. As such, when such expense is considered probable and estimable at the commencement of sales, the Company will account for the royalty expense as cost of sales for the amount it is obligated.

Whitehead Institute for Biomedical Research

In May 2019, the Company entered into an exclusive license agreement with the Whitehead Institute for Biomedical Research (“WIBR”), an affiliate of one of the Company’s board members, under which the Company was granted an exclusive, worldwide, royalty-bearing, sublicensable license under specified patent rights to research, make,

have made, use, sell, offer to sell, lease and import products and to perform and have performed licensed processes (the “WIBR Exclusive License”). Under the terms of the WIBR Exclusive License, the Company paid a nonrefundable upfront fee of less than $0.1 million upon the commencement of the exclusive license agreement. The Company is obligated to pay WIBR annual license maintenance fees of less than $0.1 million and low single digit percentage royalties on net sales of licensed products by the Company and its affiliates and sublicensees. Additionally, the Company is required to make milestone payments of up to $1.7 million in the aggregate for each of the first three licensed products (excluding backup products) upon the achievement of specified clinical, regulatory, and sublicensing milestones. In addition, the Company is required to pay to WIBR a percentage of the non-royalty payments that it receives from sublicensees of the WIBR Exclusive License. This percentage ranges from zero to low double-digits and will be based upon the stage of development of the licensed product at the time such sublicense is executed.

In May 2019, the Company also entered into a co-exclusive license agreement with WIBR under which the Company was granted a co-exclusive, worldwide, royalty-bearing, sublicensable license under specified patent rights to research, make, have made, use, sell, offer to sell, lease and import products and to perform and have performed licensed processes (the “WIBR Co-Exclusive License”). Under the terms of the WIBR Co-Exclusive License, the Company paid a nonrefundable upfront fee of less than $0.1 million upon the commencement of the co-exclusive license agreement. The Company is obligated to pay WIBR annual license maintenance fees of less than $0.1 million and sub single digit percentage royalties on net sales of licensed products by the Company and its affiliates and sublicensees as well as low single digit percentage royalties on licensed service income received by the Company and its affiliates. Additionally, the Company is required to make milestone payments of up to $1.9 million in the aggregate for each of the first three licensed products (excluding backup products) upon the achievement of specified clinical and regulatory milestones. In addition, the Company is required to pay to WIBR annual fees of less than $0.1 million for each sublicense agreement.

For both of the three-month periods ended June 30, 2021 and 2020, the Company recognized expenses of less than $0.1 million for the reimbursable patent costs related to the licenses under the agreements. During both of the six months ended June 30, 2021 and 2020, the Company recognized expenses for the license maintenances fees and the reimbursable patent costs in the amount of $0.1 million. There was no outstanding payment due to WIBR as of June 30, 2021 and December 31, 2020.

The annual maintenance fees will be recorded as an expense on an annual basis based on the stated amount for the applicable year. Upon determination that a milestone payment is probable to occur, the amount due will be recorded as research and development. As the triggering of these milestone payments was not considered probable during both of the three-month periods and six-month periods ended June 30, 2021 and 2020, no expense has been recorded for these milestones during these periods. Lastly, the royalty payments and the sublicense non-royalty payments are contingent upon sales of licensed products or execution of a sublicence agreement under the WIBR Exclusive and Co-Exclusive Licenses. As such, when such expenses are considered probable and estimable at the commencement of sales or execution of a sublicense agreement, the Company will accrue royalty expense and sublicence non-royalty payments, as applicable, for the amount the Company is obligated.

Acuitas Therapeutics, Inc.

In October 2020, the Company entered into a development and option agreement (the “Development and Option Agreement”) with Acuitas Therapeutics, Inc. (“Acuitas”). Under the terms of the Development and Option Agreement, the parties agreed to jointly develop certain products combining the Company’s gene modulating therapeutics with Acuitas’s lipid nanoparticles. Additionally, in accordance with the Development and Option Agreement, the Company has options to obtain non-exclusive, worldwide, sublicensable licenses under Acuitas’s patents and know-how related to lipid nanoparticle technology (“Acuitas LNP Technology”) with respect to two specified targets (e.g., OEC constructs) (“Reserved Targets”) to develop and commercialize one or more therapeutic products relating to such targets. For each option and Reserved Target, the Company is obligated to pay an annual technology access fee and target reservation and maintenance fees collectively in the low-mid six figures until such Reserved Target is removed from the Reserved Target list or until the Company exercises an option with respect to such Reserved Target. In the event that the Company exercises the options, the Company will pay $1.5 million for the first non-exclusive license and $1.75 million for the second non-exclusive license. Under the terms of the Development and Option Agreement, the Company is also responsible for the FTE funding obligations and reimbursements to Acuitas for certain development and material costs incurred by them, which is currently approximately $0.4 million per year.

In March 2021, the Company exercised the first option under the Development and Option Agreement and entered into a non-exclusive license agreement with Acuitas (the “Acuitas License Agreement”) under which the Company was granted a non-exclusive, worldwide, sublicensable license under the Acuitas LNP Technology to research, develop, manufacture, and commercially exploit products consisting of the Company’s gene modulating therapeutics and Acuitas’s lipid nanoparticles. In connection with the option exercise, the Company paid Acuitas an option exercise fee of $1.5 million. Under the Acuitas License Agreement, the Company is required to pay Acuitas an annual license maintenance fee in the high six figures until the Company achieves a particular development milestone. Acuitas is entitled to receive potential clinical and regulatory milestone payments of up to $18.0 million in the aggregate. With respect to the sale of each licensed products, the Company is also obligated to pay Acuitas low single digit percentage royalties on net sales of the licensed products by the Company and its affiliates and sublicensees in a given country until the last to occur, in such country, of (i) the expiration or abandonment of all licensed patent rights covering the licensed product, (ii) expiration of any regulatory exclusivity for the licensed product, or (iii) ten years from the first commercial sale of the licensed product.

During the three and six months ended June 30, 2021, the Company recorded an aggregate of $0.4 million and $2.0 million of research and development expenses, consisting of the option exercise fee, the costs of services performed by Acuitas, the material costs and the reimbursable costs incurred.

The option exercise fee under the Development and Option Agreement was recorded as research and development expense upon the Company’s exercise of the first option. Additionally, the technology access fees, target reservation and maintenance fees, expenses associated with the FTE funding obligations and reimbursements for development and material costs incurred by Acuitas are recorded as research and development expense when incurred. The annual maintenance fee will be recorded as an expense on an annual basis based on the stated amount for the applicable year. Upon determination that a milestone payment is probable to occur, the amount due will be recorded as research and development expense. As the triggering of these milestone payments was not considered probable during the three and six months ended June 30, 2021, no expense has been recorded for these milestones during the periods. Lastly, the royalty payment is contingent upon sales of licensed products under the Acuitas License Agreement. As such, when such expenses are considered probable and estimable at the commencement of sales, the Company will accrue royalty expense for the amount the Company is obligated.

Redeemable Convertible Preferred Stock

6 Months Ended

Jun. 30, 2021

Equity [Abstract]

Redeemable Convertible Preferred Stock

10. Redeemable Convertible Preferred Stock

During August 2017 and March 2021, the Company issued Series A, Series B and Series C Preferred Stock (collectively the “Preferred Stock”) to investors in private placements. Upon completion of the Company’s IPO, all of the Company’s then outstanding Preferred Stock was automatically converted into an aggregate of 34,678,733 shares of common stock.

Series A Redeemable Convertible Preferred Stock

During 2017 and 2019, the Company issued an aggregate of 56,775,232 shares of Series A Preferred Stock at a purchase price of $0.50 per share in exchange for cash proceeds of $25.5 million and the exchange of approximately $2.8 million in outstanding promissory notes, including $54 thousand in accrued interest. In connection with the issuance of Series A Preferred Stock during 2017 and 2019, the Company incurred less than $0.1 million of issuance costs. No additional shares of Series A Preferred Stock were issued after 2019.

Series B Redeemable Convertible Preferred Stock

On January 27, 2020, the Company issued 24,066,666 shares of Series B Preferred Stock at a purchase price of $1.50 per share for aggregate proceeds of $36.1 million. On June 2, 2020, the Company issued an additional 3,333,333 shares of Series B Preferred Stock at the purchase price of $1.50 per share for aggregate proceeds of $5.0 million. On August 3, 2020, the Company issued 5,000,000 shares of Series B Preferred Stock at the purchase price of $1.50 per share for aggregate proceeds of $7.5 million. No additional shares of Series B Preferred Stock were issued after August 2020. In connection with the issuance of Series B Preferred Stock in 2020, the Company incurred $83 thousand of issuance costs.

Series C Redeemable Convertible Preferred Stock

In March 2021, the Company issued an aggregate of 41,833,328 shares of Series C Preferred Stock, at a price of $3.00 per share, for gross proceeds of $125.5 million. The terms of the Series C Preferred Stock are substantially the same as the terms of the Series A and Series B Preferred Stock. No additional shares of Series C Preferred Stock were issued after March 2021. In connection with the issuance of Series C Preferred Stock in March 2021, the Company incurred $0.1 million of issuance costs. The Company further amended its Amended and Restated Certificate of Incorporation to increase the authorized preferred stock issuable from 107,125,232 shares to 132,858,564 shares.

The Preferred Stock consisted of the following (in thousands, except for share data):

	June 30, 2021
	Preferred Stock Authorized		Preferred stock issued and outstanding		Carrying value		Liquidation preference		Common stock issuable upon conversion
Series A Preferred Stock		57,125,232		56,775,232	$	26,708	$	25,500		15,028,741
Series B Preferred Stock		32,399,999		32,399,999		48,517		48,600		8,576,470
Series C Preferred Stock		43,333,333		41,833,328		125,368		125,500		11,073,522
		132,858,564		131,008,559	$	200,593	$	199,600		34,678,733

	December 31, 2020
	Preferred Stock Authorized		Preferred stock issued and outstanding		Carrying value		Liquidation preference		Common stock issuable upon conversion
Series A Preferred Stock		57,125,232		56,775,232	$	26,708	$	25,500		15,028,741
Series B Preferred Stock		50,000,000		32,399,999		48,517		48,600		8,576,470
		107,125,232		89,175,231	$	75,225	$	74,100		23,605,211

The following is a summary of the rights and preferences of the Preferred Stock as of June 30, 2021 and December 31, 2020:

Conversion— Each share of Preferred Stock is convertible, at the option of the holder into an equal amount of fully paid and non-assessable shares of common stock as is determined by dividing the respective original Preferred Stock issue price by the respective Preferred Stock Conversion Price in effect at the time of conversion. The Series A, Series B and Series C Conversion Price shall be equal to $0.50, $1.50 and $3.00, respectively, subject to appropriate adjustment as set forth in the Company’s Amended and Restated Certificate of Incorporation, as amended and restated. As such, the shares of Preferred Stock currently convert on a one-for-one basis. No fractional shares of common stock will be issued.

Upon either (a) the closing of the sale of shares of common stock, in a firm-commitment underwritten public offering with at least $35,000,000 of gross proceeds to the Company or (b) the date and time, or the occurrence of an event, specified by vote or written consent of the holders of a majority in voting power of the then-outstanding shares of Preferred Stock, then (i) all outstanding shares of Preferred Stock shall automatically be converted into shares of common stock, at the applicable conversion ratio then in effect, and (ii) such shares may not be reissued by the Company.

Dividends— The holders of Preferred Stock are entitled to receive noncumulative dividends if and when declared by the Company’s board of directors. The Company may not declare, pay or set aside any dividends on shares of any other series of capital stock of the Company, other than dividends on common stock payable in common stock, unless the holders of the Preferred Stock first receive, or simultaneously receive, a dividend on each outstanding share of Preferred Stock. No dividends were declared as of June 30, 2021 and December 31, 2020 or paid during the three and six months ended June 30, 2021 and 2020.

Voting Rights— The holders of Preferred Stock are entitled to vote, together with the holders of common stock as a single class, on matters submitted to stockholders for a vote. The holders of Preferred Stock are entitled to the number of votes equal to the number of shares of common stock into which each such share of Preferred Stock could convert.

Liquidation Preference— While the Preferred Stock is not redeemable at the option of the holders, the shares are redeemable for cash in certain change of control events that are beyond the control of the Company. In the event of any voluntary or involuntary liquidation, dissolution, or winding up of the Company, or deemed liquidation event (as

described below), the holders of the Preferred Stock are entitled to receive a liquidation preference in priority over the holders of common stock, at an amount per share equal to the greater of i) the respective original Preferred Stock issue price plus any declared but unpaid dividends, or ii) the amount per share payable had all shares of Preferred Stock been converted to common stock immediately prior to such liquidation. If assets available for distribution are insufficient to satisfy the liquidation payment to holders in full, assets available for distribution will be allocated among holders based on their pro rata shareholdings. When holders are satisfied in full, any excess assets available for distribution will be allocated ratably among common stockholders based on their pro rata shareholdings.

Unless the holders of a majority of the then-outstanding shares of Preferred Stock, consenting or voting together as a single class, elect otherwise, a deemed liquidation event shall include a merger or consolidation (other than one in which stockholders of the Company own a majority by voting power of the outstanding shares of the surviving or acquiring corporation) or a sale, lease, transfer, exclusive license or other disposition of all or substantially all of the assets of the Company.

Common Stock

6 Months Ended

Jun. 30, 2021

Equity [Abstract]

Common Stock

11. Common Stock

The Company was authorized to issue up to 137,700,000 shares of common stock with a $0.001 par value per share as of December 31, 2020. In March 2021, the Company increased the authorized common stock shares issuable to 175,000,000.

The holders of common stock are entitled to one vote for each share of common stock. Subject to the payment in full of all preferential dividends to which the holders of the preferred stock are entitled, the holders of common stock shall be entitled to receive dividends out of funds legally available. In the event of any voluntary or involuntary liquidation, dissolution, or winding up of the Company, after the payment or provision for payment of all debts and liabilities of the Company and all preferential amounts to which the holders of preferred stock are entitled with respect to the distribution of assets in liquidation, the holders of common stock shall be entitled to share ratably in the remaining assets of the Company available for distribution.

As of June 30, 2021, the Company has reserved an aggregate of 34,678,733 shares of common stock for the potential conversion of Series A, Series B and Series C Preferred Stock, which was automatically converted into common stock upon completion of the Company’s IPO, and 5,085,523 shares of common stock for the potential exercise of outstanding stock options under the 2017 Equity Incentive Plan (“2017 Plan”). Upon the effectiveness of the 2021 Incentive Award Plan (“2021 Plan”), the Company ceased granting awards under the 2017 Plan, and the 5,085,523 shares of common stock subject to outstanding stock options issued under the 2017 Plan may become available for future issuance under the 2021 Plan to the extent such stock options are forfeited.

- Definition

The entire disclosure for shareholders' equity comprised of portions attributable to the parent entity and noncontrolling interest, including other comprehensive income. Includes, but is not limited to, balances of common stock, preferred stock, additional paid-in capital, other capital and retained earnings, accumulated balance for each classification of other comprehensive income and amount of comprehensive income.

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+ Details

Equity Incentive Plan

6 Months Ended

Jun. 30, 2021

Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]

Equity Incentive Plan

12. Equity Incentive Plan

2017 Equity Incentive Plan

In June 2017, the Company’s board of directors adopted the 2017 Plan, which provided for the grant of qualified incentive stock options and nonqualified stock options, restricted stock or other awards to the Company’s employees and non-employees for the issuance or purchase of shares of the Company’s common stock. As of June 30, 2021, there were 855,627 shares of common stock available for future grants under the 2017 Plan and a total of 5,085,523 shares of the Company’s common stock were subject to outstanding stock options issued under the 2017 Plan.

The 2017 Plan is administered by the Company’s board of directors or a committee thereof to the extent the Company’s board of directors has delegated its power or authority under the 2017 Plan. The exercise prices, vesting and other restrictions are determined at the discretion of the board of directors, except that the exercise price per share of stock options may not be less than 100% of the fair market value of the common stock on the date of grant. Stock options awarded under the 2017 Plan expire 10 years after the grant date unless the board of directors sets a shorter term. Incentive stock options and nonqualified stock options granted to employees and non-employees typically vest over four years. Certain stock options provide for accelerated vesting if there is a change in control, as defined in the 2017 Plan.

The Company recorded stock-based compensation expense as research and development and general and administrative expenses in the statements of operations and comprehensive loss as follows (in thousands):

	Three months ended June 30,				Six months ended June 30,
	2021		2020		2021		2020
Research and development	$	212	$	66	$	275	$	141
General and administrative		473		41		604		111
Total stock-based compensation expense	$	685	$	107	$	879	$	252

Stock Options

A summary of option activity under the 2017 Plan during the six months ended June 30, 2021 was as follows:

	Number of options			Weighted average exercise price		Weighted average remaining contractual life (years)		Aggregate intrinsic value (1) (in thousands)
Outstanding as of January 1, 2021		3,049,875		$	1.10		8.86	$	4,467
Granted		2,314,823			5.72
Exercised		(181,684	)		0.90
Forfeitures		(97,491	)		3.10
Outstanding at June 30, 2021		5,085,523			3.17		9.02		17,127
Vested and expected to vest as of June 30, 2021		5,085,523			3.17		9.02		17,127
Exercisable as of June 30, 2021		1,000,934			0.81		8.18		5,737

(1)	The aggregate intrinsic value is calculated as the difference between the exercise price of the underlying options and the estimated fair value of the common stock for the options that were in the money as of June 30, 2021.

The weighted-average grant date fair value per share of stock options granted during the six months ended June 30, 2021 was $3.93. The aggregate intrinsic value of stock options exercised during the six months ended June 30, 2021 was $1.0 million.

As of June 30, 2021, there was $9.7 million of unrecognized compensation cost related to unvested stock options, which is expected to be recognized over a weighted-average period of approximately 3.6 years.

Restricted Stock

In 2017, the Company issued 1,985,295 shares of restricted common stock to certain scientific founders, having a fair value of $0.8 million, and subject to vesting over a period of 4 years.

If the holders of restricted common stock cease to have a service relationship with the Company prior to the vesting of such shares, the Company may reacquire any unvested shares of common stock held by these individuals for the original purchase price, and in certain instances for no consideration. The unvested shares of restricted common stock are not considered outstanding shares for accounting purposes until the shares vest.

As the restricted stock was fully vested in 2020, there was no remaining unrecognized stock-based compensation expense related to restricted stock as of June 30, 2021.

Net Loss Per Share Attributable to Common Stockholders

6 Months Ended

Jun. 30, 2021

Earnings Per Share [Abstract]

Net Loss Per Share Attributable to Common Stockholders

13. Net Loss per Share Attributable to Common Stockholders

For periods in which the Company reports a net loss attributable to common stockholders, potentially dilutive securities have been excluded from the computation of diluted net loss per share as their effects would be anti-dilutive. Therefore, the weighted average number of shares of common stock outstanding used to calculate both basic and diluted net loss per share attributable to common stockholders is the same.

The following table summarizes the computation of basic and diluted net loss per share attributable to common stockholders of the Company (in thousands except share and per share amounts):

	Three months ended June 30,						Six months ended June 30,
	2021			2020			2021			2020
Numerator:
Net loss attributable to common stockholders	$	(15,410	)	$	(6,323	)	$	(28,898	)	$	(11,741	)
Denominator:
Weighted average number of common stock, basic and diluted		4,588,500			4,007,606			4,542,832			3,929,900
Net loss per common stock attributable to common stockholders, basic and diluted	$	(3.36	)	$	(1.58	)	$	(6.36	)	$	(2.99	)

The Company excluded the following potential common stock, presented based on amounts outstanding at period end, from the computation of diluted net loss per share attributable to common stockholders because including them would have had an anti-dilutive effect:

	As of June 30,
	2021		2020
Redeemable convertible preferred stock		34,678,733		22,374,328
Unvested restricted stock		—		248,162
Outstanding options to purchase common stock		5,085,523		2,468,791
Warrants		92,647		92,647
Total		39,856,903		25,183,928

Income Taxes

6 Months Ended

Jun. 30, 2021

Income Tax Disclosure [Abstract]

Income Taxes

14. Income Taxes

During the three and months ended June 30, 2021 and 2020, the Company recorded a full valuation allowance on federal and state deferred tax assets since management does not forecast the Company to be in a taxable position in the near future.

- Definition

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

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+ Details

Related Party Transactions

6 Months Ended

Jun. 30, 2021

Related Party Transactions

15. Related Party Transactions

The majority ownership of the Company is held by Flagship. Fully diluted Flagship ownership was 54.5% and 70.9% as of June 30, 2021 and December 31, 2020, respectively. Flagship provides management services (accounting, human resources, information technology, legal and consultation) to the Company. Flagship is also reimbursed for certain expenses, including insurance and benefits, partner and related fees, and software licenses incurred on the Company’s behalf. For the three months ended June 30, 2021 and 2020, the Company incurred $0.3 million and $0.2 million, respectively, for the management services fees and other reimbursements that Flagship incurred on the Company’s behalf. For the six months ended June 30, 2021 and 2020, the Company incurred $0.4 million and $0.5 million, respectively, for the management services fees and other reimbursements that Flagship incurred on the Company’s behalf. These expenses are recorded as related party expense in the accompanying statements of operations and comprehensive loss. As of June 30, 2021 and December 31, 2020, the Company did not have any outstanding payments due to Flagship.

In September 2020, the Company sublet the entire space of its 325 Vassar Street facility, approximately 19,404 square feet, to LARONDE, Inc. (“LARONDE”, formerly known as VL50, Inc.), which is an affiliate of Flagship. The sublease term will expire at the end of the Company’s lease agreement with the landlord in September 2024. The rental rate for the sublease arrangement is equal to the Company’s rental obligation per the agreement with BMR-325 Vassar Street LLC, reduced by the sublease income received from Cygnal Therapeutics, Inc. (“Cygnal”), approximating $1.3 million per year. The sublessee is obligated to pay all real estate taxes and costs related to the subleased premises, including cost of operations, maintenance, repair, replacement and property management. Under the sublease agreement, the Company received rental income, which was recorded as a reduction of rental expenses, of $0.5 million and $1.0 million during the three and six months ended June 30, 2021, respectively. Such rental income was reflected as a reduction of related party expense in the accompanying statements of operations and comprehensive loss. There was no outstanding receivable due from LARONDE as of June 30, 2021 and December 31, 2020.

In September 2019, the Company sublet approximately 1,445 square feet of its 325 Vassar Street facility to Cygnal, which is an affiliate of Flagship, for two years. The rental rate for the sublease arrangement is equal to the Company’s rental obligation per the agreement with BMR-325 Vassar Street LLC, approximating $0.1 million per year. The sublessee is obligated to pay all real estate taxes and costs related to the subleased premises, including cost of operations, maintenance, repair, replacement and property management. Under the sublease agreement, the Company received rental income of less than $0.1 million during both of the three-month periods and six-month periods ended June 30, 2021 and 2020, which was recorded as a reduction of rental expenses. Such rental income was reflected as a reduction of related party expense in the accompanying statements of operations and comprehensive loss. There was an immaterial amount of outstanding receivable due from Cygnal as of June 30, 2021, which was recorded as prepaid expenses and other current assets in the accompanying balance sheet. There was no outstanding receivable due from Cygnal as of December 31, 2020.

Subsequent Events

6 Months Ended

Jun. 30, 2021

Subsequent Events [Abstract]

Subsequent Events

16. Subsequent Events

Reverse stock split

In July 2021, the Company’s board of directors and stockholders approved an amendment to the Company’s certificate of incorporation, which became effective on July 23, 2021. The amendment, among other things, effected a 1-for-3.777776 reverse stock split of the Company’s issued and outstanding common stock, a proportional adjustment to the conversion price for each series of Preferred Stock and to the exercise prices and number of shares of common stock underlying the outstanding stock options. All share, per share and additional paid in capital amounts for all periods presented in the accompanying unaudited condensed financial statements and notes thereto have been retroactively adjusted, where applicable, to reflect the reverse stock split.

Amendments to Articles of Incorporation

In connection with the completion of the IPO, the board of directors and stockholders approved the amended and restated certificate of incorporation to, among other things, provide for 200,000,000 authorized shares of common stock with a par value of $0.001 per share and 10,000,000 authorized shares of preferred stock with a par value of $0.001 per share.

Stock Plans

The Company's board of directors adopted and the Company's stockholders approved the 2021 Plan in July 2021. The 2021 Plan provides for the grant of incentive stock options, non-statutory stock options, restricted stock awards, restricted stock units, stock appreciation rights and other stock-based awards, and subsequent to the IPO, all equity-based awards are granted under the 2021 Plan. The Company has reserved 2,960,000 shares of its common stock for future issuance under the 2021 Plan. Additionally, the Company's board of directors adopted and the Company's stockholders approved the 2021 employee stock purchase plan (“2021 ESPP”) in July 2021; a total of 480,000 shares of the Company’s common stock is reserved for future issuance under the 2021 ESPP.

Initial Public Offering

On August 3, 2021, the Company completed its IPO pursuant to which it issued and sold 7,400,000 shares of its common stock at a public offering price of $17.00 per share. The gross proceeds from the IPO were $125.8 million and the net proceeds were approximately $113.4 million, after deducting underwriting discounts and commissions and other offering expenses payable by the Company. Upon the closing of the Company’s IPO, all of the Company’s then outstanding Preferred Stock was automatically converted into an aggregate of 34,678,733 shares of common stock. Additionally, the Company’s outstanding warrants to purchase Series A Preferred Stock automatically became warrants to purchase an aggregate of 92,647 shares of common stock. On August 17, 2021, the Company issued and sold 900,976 shares of its common stock pursuant to the partial exercise of the underwriters’ option to purchase additional shares, at a public offering price of $17.00 per share, for aggregate gross proceeds of $15.3 million. The Company received appropriately $14.2 million in net proceeds after deducting underwriting discounts and commissions.

Summary of Significant Accounting Policies (Policies)	6 Months Ended
Summary of Significant Accounting Policies (Policies)	Jun. 30, 2021
Accounting Policies [Abstract]
Use of Estimates	Use of Estimates The preparation of the unaudited condensed financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the reported amounts of assets, liabilities and expenses, and the disclosure of contingent assets and liabilities as of and during the reporting period. The Company bases its estimates and assumptions on historical experience when available and on various factors that it believes to be reasonable under the circumstances. Significant estimates and assumptions reflected in these unaudited condensed financial statements include, but are not limited to, the selection of useful lives of property and equipment, the fair values of common stock, redeemable convertible preferred stock, warrants, success fee obligation, and stock-based compensation. Actual results could differ from these estimates. Changes in estimates are reflected in reported results in the period in which they become known.
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 equity financings as deferred offering costs until such financings are consummated. After consummation of the equity financing, these costs are recorded in stockholders’ deficit as a reduction of proceeds generated as a result of the offering. Should a planned equity financing be abandoned, the deferred offering costs would be expensed immediately as a charge to operating expenses in the unaudited condensed consolidated statement of operations. The Company recorded deferred offering costs, related to the IPO, of approximately $1.6 million as of June 30, 2021. Upon closing the IPO in August 2021, deferred offering costs were derecognized and recorded against the IPO proceeds as a reduction to additional paid-in capital.
Recently Issued Accounting Pronouncements	Recently Issued Accounting Pronouncements In February 2016, the FASB issued ASU No. 2016-02, Leases (Topic 842) (“ASU 2016-02”), which sets out the principles for the recognition, measurement, presentation and disclosure of leases for both parties to a contract (i.e., lessees and lessors). The new standard requires lessees to apply a dual approach, classifying leases as either finance or operating leases based on the principle of whether or not the lease is effectively a financed purchase by the lessee. This classification will determine whether lease expense is recognized based on an effective interest method or on a straight- line basis over the term of the lease. A lessee is also required to record a right-of-use asset and a lease liability for all leases with a term of greater than 12 months regardless of their classification. Leases with a term of 12 months or less may be accounted for similar to existing guidance for operating leases today. As the Company has elected to use the extended transition period for complying with new or revised accounting standards as available under the Jumpstart Our Business Startups Act (“JOBS Act”), the standard is effective for the Company beginning January 1, 2022, with early adoption permitted. The Company is currently evaluating the impact that the adoption of ASU 2016-02 will have on its financial statements. In December 2019, the FASB issued ASU No. 2019-12, Income Taxes-Simplifying the Accounting for Income Taxes (“ASU 2019-12”). ASU 2019-12 eliminates certain exceptions related to the approach for intraperiod tax allocation, the methodology for calculating income taxes in an interim period and the recognition of deferred tax liabilities for outside basis differences. The new guidance also simplifies aspects of the accounting for franchise taxes, enacted changes in tax laws or rates and clarifies the accounting for transactions that result in a step-up in the tax basis of goodwill. Adoption of the standard requires certain changes to be made prospectively and certain others to be made retrospectively. As the Company has elected to use the extended transition period for complying with new or revised accounting standards as available under the JOBS Act, the standard is effective for the Company beginning January 1, 2022, with early adoption permitted. The Company does not expect ASU 2019-12 to have a material effect on the Company’s financial statements.

Prepaid Expenses and Other Current Assets (Tables)

6 Months Ended

Jun. 30, 2021

Prepaid Expense And Other Assets Current [Abstract]

Summary of Prepaid Expenses and other Current Assets

Prepaid expenses and other current assets consisted of the following (in thousands):

	June 30,		December 31,
	2021		2020
Prepaid software	$	33	$	78
Prepaid research and development		953		653
Prepaid other		275		128
Other receivables		40		193
Prepaid expenses and other current assets	$	1,301	$	1,052

Property and Equipment, Net (Tables)

6 Months Ended

Jun. 30, 2021

Property Plant And Equipment [Abstract]

Summary of Property and Equipment, Net

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

	June 30,			December 31,
	2021			2020
Leasehold improvements	$	1,378		$	1,378
Lab equipment		4,225			3,444
Furniture and fixtures		1,047			985
Computer equipment		129			129
Construction in process		429			16
Total property and equipment		7,208			5,952
Less accumulated depreciation		(3,108	)		(2,470	)
Property and equipment, net	$	4,100		$	3,482

Accrued Expenses (Tables)

6 Months Ended

Jun. 30, 2021

Accrued Liabilities Current [Abstract]

Summary of Accrued Expenses

Accrued expenses consist of the following (in thousands):

	June 30,		December 31,
	2021		2020
Employee related expenses	$	1,094	$	1,124
Research costs		4,377		1,724
Consulting fees		122		165
Interest		58		44
Other		1,617		220
Total	$	7,268	$	3,277

Term Loan (Tables)

6 Months Ended

Jun. 30, 2021

Debt Disclosure [Abstract]

Summary of Outstanding Term Loan Balance

The Company’s outstanding term loan balance was comprised of the following (in thousands):

	June 30,			December 31,
	2021			2020
Principal	$	12,000		$	12,000
Unamortized debt discount		(194	)		(268	)
Net carrying amount	$	11,806		$	11,732

Summary of Interest Expense Recognized Related to Term loan

The following table sets forth total interest expense recognized related to the term loan (in thousands):

	Three months ended June 30,				Six months ended June 30,
	2021		2020		2021		2020
Contractual interest expense	$	182	$	182	$	362	$	364
Amortization of debt issuance costs and debt discount		33		12		74		24
Total interest expense	$	215	$	194	$	436	$	388

Schedule of Principal Amount in Connection With Term Loan

The Company is required to repay the following principal amounts in connection with its term loan (in thousands):

2021 (remaining 6 months)	$	—
2022		6,000
2023		6,000
	$	12,000

Fair Value of Financial Instruments (Tables)

6 Months Ended

Jun. 30, 2021

Fair Value Disclosures [Abstract]

Summary of Fair Value of Financial Instruments

The fair value of the Company’s financial instruments is summarized in the tables below (in thousands):

	June 30, 2021
	Level 1		Level 2		Level 3		Total
Financial Liabilities
Warrant liability	$	—	$	—	$	464	$	464
Success fee obligation		—		—		199		199
Total	$	—	$	—	$	663	$	663

	December 31, 2020
	Level 1		Level 2		Level 3		Total
Financial Liabilities
Warrant liability	$	—	$	—	$	124	$	124
Success fee obligation		—		—		194		194
Total	$	—	$	—	$	318	$	318

Summary of Assumptions Used in Black-Scholes Option-Pricing Model for Warrants

The assumptions used in the Black-Scholes option-pricing model for the warrants were as follows:

	Six months ended June 30,
	2021	2020
Expected volatility	77.42 - 77.62%	73.09 - 74.06%
Risk-free interest rate	1.21 - 1.40%	0.58 - 0.63%
Expected dividend yield	0.00%	0.00%
Expected term (in years)	6.7 - 6.9	7.7 - 7.9

Summary of Significant Quantitative Inputs Used to Determine Valuation of Success Fee Obligation

The following reflects the significant quantitative inputs used to determine the valuation of the success fee obligation during the six months ended June 30, 2021:

Discount rate		6.0	%
Expected timing of achieving liquidity events (years)		0.11
Probability of achieving liquidity events	1% -99%

Summary of Fair Values of Warrant Liability and Success Fee Obligation

The following table provides a roll-forward of the fair values of the Company’s warrant liability and the success fee obligation for which fair value is determined by Level 3 inputs (in thousands):

	Warrant liability		Success fee obligation
Fair value at January 1, 2021	$	124	$	194
Change in fair value		340		5
Fair value at June 30, 2021	$	464	$	199

	Warrant liability			Success fee obligation
Fair value at January 1, 2020	$	127		$	—
Change in fair value		(4	)		—
Fair value at June 30, 2020	$	123		$	—

Commitments and Contingencies (Tables)

6 Months Ended

Jun. 30, 2021

Commitments And Contingencies Disclosure [Abstract]

Summary of Future Minimum Lease Payments

As of June 30, 2021, the future minimum lease payments for the Company’s facility operating leases were as follows (in thousands):

2021 (remaining 6 months)	$	1,678
2022		2,618
2023		1,563
2024		1,205
Total minimum lease payments	$	7,064

Equity Incentive Plan (Tables)

6 Months Ended

Jun. 30, 2021

Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]

Summary of Stock-based Compensation Expense

	Three months ended June 30,				Six months ended June 30,
	2021		2020		2021		2020
Research and development	$	212	$	66	$	275	$	141
General and administrative		473		41		604		111
Total stock-based compensation expense	$	685	$	107	$	879	$	252

Summary of Option Activity

A summary of option activity under the 2017 Plan during the six months ended June 30, 2021 was as follows:

	Number of options			Weighted average exercise price		Weighted average remaining contractual life (years)		Aggregate intrinsic value (1) (in thousands)
Outstanding as of January 1, 2021		3,049,875		$	1.10		8.86	$	4,467
Granted		2,314,823			5.72
Exercised		(181,684	)		0.90
Forfeitures		(97,491	)		3.10
Outstanding at June 30, 2021		5,085,523			3.17		9.02		17,127
Vested and expected to vest as of June 30, 2021		5,085,523			3.17		9.02		17,127
Exercisable as of June 30, 2021		1,000,934			0.81		8.18		5,737

(1)	The aggregate intrinsic value is calculated as the difference between the exercise price of the underlying options and the estimated fair value of the common stock for the options that were in the money as of June 30, 2021.

Net Loss Per Share Attributable to Common Stockholders (Tables)

6 Months Ended

Jun. 30, 2021

Earnings Per Share [Abstract]

Summary of the Computation of Basic and Diluted Net Loss Per Share Attributable to Common Stockholders

The following table summarizes the computation of basic and diluted net loss per share attributable to common stockholders of the Company (in thousands except share and per share amounts):

	Three months ended June 30,						Six months ended June 30,
	2021			2020			2021			2020
Numerator:
Net loss attributable to common stockholders	$	(15,410	)	$	(6,323	)	$	(28,898	)	$	(11,741	)
Denominator:
Weighted average number of common stock, basic and diluted		4,588,500			4,007,606			4,542,832			3,929,900
Net loss per common stock attributable to common stockholders, basic and diluted	$	(3.36	)	$	(1.58	)	$	(6.36	)	$	(2.99	)

Schedule of Anti-Dilutive Securities Excluded from Computation of Earnings Per Share

	As of June 30,
	2021		2020
Redeemable convertible preferred stock		34,678,733		22,374,328
Unvested restricted stock		—		248,162
Outstanding options to purchase common stock		5,085,523		2,468,791
Warrants		92,647		92,647
Total		39,856,903		25,183,928

Nature of the Business and Basis of Presentation - Additional Information (Details) - USD ($) $ / shares in Units, $ in Thousands	Aug. 17, 2021	Aug. 03, 2021	Jun. 30, 2021	Dec. 31, 2020	Jun. 30, 2020
Nature Of Business And Basis Of Presentation [Line Items]
Common stock, shares issued			4,647,035	4,465,351
Conversion of preferred stock to common stock			34,678,733	23,605,211
Cash and cash equivalents			$ 122,411	$ 22,951	$ 31,887
Subsequent Event
Nature Of Business And Basis Of Presentation [Line Items]
Conversion of preferred stock to common stock		34,678,733
IPO \| Subsequent Event
Nature Of Business And Basis Of Presentation [Line Items]
Common stock, shares issued		7,400,000
Offering price per share		$ 17.00
Gross proceeds from IPO		$ 125,800
Net proceeds		$ 113,400
Underwriters’ Option to Purchase Additional Shares \| Subsequent Event
Nature Of Business And Basis Of Presentation [Line Items]
Common stock, shares issued	900,976
Offering price per share	$ 17.00
Gross proceeds	$ 15,300
Net proceeds	$ 14,200

Summary of Significant Accounting Policies - Additional Information (Details) $ in Thousands	Jun. 30, 2021 USD ($)
Accounting Policies [Abstract]
Deferred offering costs	$ 1,585

Prepaid Expenses and Other Current Assets - Summary of Prepaid Expenses and other Current Assets (Details) - USD ($) $ in Thousands	Jun. 30, 2021	Dec. 31, 2020
Prepaid Expense And Other Assets Current [Abstract]
Prepaid software	$ 33	$ 78
Prepaid research and development	953	653
Prepaid other	275	128
Other receivables	40	193
Prepaid expenses and other current assets	$ 1,301	$ 1,052

Property and Equipment, Net - Summary of Property and Equipment, Net (Details) - USD ($) $ in Thousands	Jun. 30, 2021	Dec. 31, 2020
Property Plant And Equipment [Line Items]
Total property and equipment	$ 7,208	$ 5,952
Less accumulated depreciation	(3,108)	(2,470)
Property and equipment, net	4,100	3,482
Leasehold Improvements
Property Plant And Equipment [Line Items]
Total property and equipment	1,378	1,378
Lab Equipment
Property Plant And Equipment [Line Items]
Total property and equipment	4,225	3,444
Furniture and Fixtures
Property Plant And Equipment [Line Items]
Total property and equipment	1,047	985
Computer Equipment
Property Plant And Equipment [Line Items]
Total property and equipment	129	129
Construction in Process
Property Plant And Equipment [Line Items]
Total property and equipment	$ 429	$ 16

Property and Equipment, Net - Additional Information (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Property Plant And Equipment [Abstract]
Depreciation	$ 300	$ 200	$ 639	$ 441

Accrued Expenses - Summary of Accrued Expenses (Details) - USD ($) $ in Thousands	Jun. 30, 2021	Dec. 31, 2020
Accrued Liabilities Current [Abstract]
Employee related expenses	$ 1,094	$ 1,124
Research costs	4,377	1,724
Consulting fees	122	165
Interest	58	44
Other	1,617	220
Total	$ 7,268	$ 3,277

Term Loan - Additional Information (Details)				1 Months Ended		6 Months Ended	12 Months Ended
Term Loan - Additional Information (Details)	Dec. 30, 2020 USD ($)	Jan. 22, 2020 USD ($)	Mar. 09, 2018 USD ($) $ / shares shares	Jan. 31, 2020	Sep. 30, 2019 USD ($) $ / shares shares	Jun. 30, 2021 USD ($) shares	Dec. 31, 2020 USD ($)	Aug. 03, 2021 shares	Sep. 29, 2019 USD ($)	Aug. 31, 2018 USD ($)
Debt [Line Items]
Aggregate principal amount						$ 12,000,000	$ 12,000,000
Long-term debt, current portion						3,000,000	3,000,000
Long-term debt						9,000,000.0	9,000,000.0
Accrued interest on term loan						$ 58,000	$ 44,000
Maximum
Debt [Line Items]
Effective interest rate on the liability component						7.51%
Minimum [Member]
Debt [Line Items]
Effective interest rate on the liability component						5.53%
Pacific Western Bank
Debt [Line Items]
Maturity date of term loan						Dec. 31, 2023
Principal repayment date						Dec. 31, 2021
Pacific Western Bank \| Minimum [Member]
Debt [Line Items]
Cash proceeds received						$ 50,000,000.0
Loan Agreement \| Pacific Western Bank
Debt [Line Items]
Tranche I funded date as Closing date						Mar. 09, 2018
Tranche II funded date						no later than 18 months from the Closing Date
Line of credit facility, Floating annual interest rate						0.75%
Line of credit facility, Interest rate during period						5.00%
Loan Agreement \| Pacific Western Bank \| IPO
Debt [Line Items]
Success fee payable						$ 200,000
Loan Agreement \| Pacific Western Bank \| Series A Redeemable Convertible Preferred Stock
Debt [Line Items]
Shares, Issued \| shares			87,500
Shares issued, Price per share \| $ / shares			$ 0.50
Warrant exercisable period			10 years
Loan Agreement \| Pacific Western Bank \| Series A Redeemable Convertible Preferred Stock \| Maximum
Debt [Line Items]
Warrant exercisable for number of shares \| shares			200,000
Loan Agreement \| Pacific Western Bank \| Tranche I and Tranche II
Debt [Line Items]
Maximum borrowing capacity			$ 8,000,000.0
Borrowed loan									$ 8,000,000.0
Loan Agreement \| Pacific Western Bank \| Tranche I
Debt [Line Items]
Borrowed loan			$ 3,500,000
Loan Agreement \| Pacific Western Bank \| Tranche II
Debt [Line Items]
Borrowed loan										$ 4,500,000
Loan Agreement \| Pacific Western Bank \| Tranche II \| Series A Redeemable Convertible Preferred Stock
Debt [Line Items]
Warrant exercisable multiplication rate			0.0125
First Amendment \| Pacific Western Bank
Debt [Line Items]
Warrants exercisable, expiration date					2028-03
Warrants exercised \| shares						0
First Amendment \| Pacific Western Bank \| Series A Redeemable Convertible Preferred Stock
Debt [Line Items]
Shares, Issued \| shares					350,000
Shares issued, Price per share \| $ / shares					$ 0.50
First Amendment \| Pacific Western Bank \| Common Stock \| IPO \| Subsequent Event
Debt [Line Items]
Shares, Issued \| shares								92,647
First Amendment \| Pacific Western Bank \| Tranche I and Tranche II
Debt [Line Items]
Debt extinguished					$ 8,000,000.0
First Amendment \| Pacific Western Bank \| Tranche III
Debt [Line Items]
Line of credit facility, Floating annual interest rate					0.75%
Line of credit facility, Interest rate during period					6.00%
Aggregate principal amount					$ 12,000,000.0
Remaining cash proceeds					$ 4,000,000.0
Maturity date of term loan				Jun. 09, 2023	Mar. 09, 2022
Debt issuance costs					$ 15,000
Second Amendment \| Pacific Western Bank
Debt [Line Items]
Proceeds from debt		$ 0
Third Amendment \| Pacific Western Bank
Debt [Line Items]
Line of credit facility, Floating annual interest rate	0.75%
Line of credit facility, Interest rate during period	6.00%
Maturity date of term loan	Jun. 30, 2023
Debt issuance costs	$ 15,000
Proceeds from debt	$ 0

Term Loan - Summary of Outstanding Term Loan Balance (Details) - USD ($) $ in Thousands	Jun. 30, 2021	Dec. 31, 2020
Debt Disclosure [Abstract]
Principal	$ 12,000	$ 12,000
Unamortized debt discount	(194)	(268)
Net carrying amount	$ 11,806	$ 11,732

- Definition

Amount, after unamortized (discount) premium and debt issuance costs, of long-term debt. Includes, but not limited to, notes payable, bonds payable, debentures, mortgage loans and commercial paper. Excludes capital lease obligations.

+ References + Details

Term Loan - Summary of Interest Expense Recognized Related to Term loan (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Debt Disclosure [Abstract]
Contractual interest expense	$ 182	$ 182	$ 362	$ 364
Amortization of debt issuance costs and debt discount	33	12	74	24
Total interest expense	$ 215	$ 194	$ 436	$ 388

Term Loan - Schedule of Principal Amount in Connection With Term Loan (Details) - USD ($) $ in Thousands	Jun. 30, 2021	Dec. 31, 2020
Debt Disclosure [Abstract]
2022	$ 6,000
2023	6,000
Long-term Debt	$ 12,000	$ 12,000

Fair Value of Financial Instruments - Summary of Fair Value of Financial Instruments (Details) - USD ($) $ in Thousands	Jun. 30, 2021	Dec. 31, 2020
Financial Liabilities
Total financial liabilities	$ 663	$ 318
Warrant Liability
Financial Liabilities
Total financial liabilities	464	124
Success Fee Obligation
Financial Liabilities
Total financial liabilities	199	194
Level 3
Financial Liabilities
Total financial liabilities	663	318
Level 3 \| Warrant Liability
Financial Liabilities
Total financial liabilities	464	124
Level 3 \| Success Fee Obligation
Financial Liabilities
Total financial liabilities	$ 199	$ 194

Fair Value of Financial Instruments - Additional Information (Details)	3 Months Ended		6 Months Ended
	Jun. 30, 2021 USD ($)	Jun. 30, 2020 USD ($)	Jun. 30, 2021 USD ($)	Jun. 30, 2020 USD ($)
Fair Value Liabilities Measured On Recurring Basis [Line Items]
Description of warrant liability			The warrant liability is recorded as other liabilities on the balance sheets as they are deemed more probable than not by the Company to be settled in longer than one year.
Change in fair value of warrant liability	$ 11,000	$ (1,000)	$ 340,000	$ (4,000)
Description of fair value of success fee obligation			During the three and six months ended June 30, 2021, the change in the fair value of the success fee obligation was immaterial. The success fee obligation is recorded as other current liabilities on the balance sheets as it is deemed more probable than not by the Company to be settled in less than one year; such obligation was settled in August 2021 upon the closing of the IPO.
Maximum
Fair Value Liabilities Measured On Recurring Basis [Line Items]
Change in fair value of warrant liability	$ 100,000		$ 300,000
Expected Dividend Yield
Fair Value Liabilities Measured On Recurring Basis [Line Items]
Warrants, measurement input	0	0.00	0	0.00

Fair Value of Financial Instruments - Summary of Assumptions Used in Black-Scholes Option-Pricing Model for Warrants (Details)	Jun. 30, 2021 yr	Jun. 30, 2020 yr
Expected Volatility \| Minimum [Member]
Fair Value Liabilities Measured On Recurring Basis [Line Items]
Warrants, measurement input	77.42	73.09
Expected Volatility \| Maximum
Fair Value Liabilities Measured On Recurring Basis [Line Items]
Warrants, measurement input	77.62	74.06
Risk-free Interest Rate \| Minimum [Member]
Fair Value Liabilities Measured On Recurring Basis [Line Items]
Warrants, measurement input	1.21	0.58
Risk-free Interest Rate \| Maximum
Fair Value Liabilities Measured On Recurring Basis [Line Items]
Warrants, measurement input	1.40	0.63
Expected Dividend Yield
Fair Value Liabilities Measured On Recurring Basis [Line Items]
Warrants, measurement input	0	0.00
Expected Term (in years) \| Minimum [Member]
Fair Value Liabilities Measured On Recurring Basis [Line Items]
Warrants, measurement input	6.7	7.7
Expected Term (in years) \| Maximum
Fair Value Liabilities Measured On Recurring Basis [Line Items]
Warrants, measurement input	6.9	7.9

Fair Value of Financial Instruments - Summary of Significant Quantitative Inputs Used to Determine Valuation of Success Fee Obligation (Details)	Jun. 30, 2021 yr
Discount Rate
Fair Value Liabilities Measured On Recurring Basis [Line Items]
Success fee, measurement input	6.0
Expected Timing of Achieving Liquidity Events (years)
Fair Value Liabilities Measured On Recurring Basis [Line Items]
Success fee, measurement input	0.11
Probability of Achieving Liquidity Events \| Minimum [Member]
Fair Value Liabilities Measured On Recurring Basis [Line Items]
Success fee, measurement input	1
Probability of Achieving Liquidity Events \| Maximum
Fair Value Liabilities Measured On Recurring Basis [Line Items]
Success fee, measurement input	99

Fair Value of Financial Instruments - Summary of Fair Values of Warrant Liability and Success Fee Obligation (Details) - Level 3 - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020
Warrant Liability
Fair Value Liabilities Measured On Recurring Basis Unobservable Input Reconciliation [Line Items]
Beginning balance	$ 124	$ 127
Change in fair value	340	(4)
Ending balance	464	$ 123
Success Fee Obligation
Fair Value Liabilities Measured On Recurring Basis Unobservable Input Reconciliation [Line Items]
Beginning balance	194
Change in fair value	5
Ending balance	$ 199

Commitments and Contingencies - Additional Information (Details)	3 Months Ended		6 Months Ended		12 Months Ended
	Jun. 30, 2021 USD ($)	Jun. 30, 2020 USD ($)	Jun. 30, 2021 USD ($) ft² Option	Jun. 30, 2020 USD ($)	Dec. 31, 2020 USD ($) Sublease	Dec. 31, 2019 Sublease	Dec. 31, 2018 USD ($)
Leases [Line Items]
Lease expiration date			Sep. 30, 2024
Landlord-funded leasehold improvements							$ 1,100,000
Number of sublease agreements with related parties \| Sublease					2	2
Rent expenses incurred	$ 600,000		$ 1,200,000
Rent expense	800,000	$ 400,000	$ 1,600,000	$ 700,000
Senda Biosciences, Inc
Leases [Line Items]
Lessee operating lease, description			share one-third of Senda’s 69,867 square feet of leased space at 20 Acorn Park Drive, Cambridge, Massachusetts.
Number of options to extend terms \| Option			2
Term of lease arrangement period			24 months
Lease arrangement description			The Arrangement commenced on August 1, 2020 and continues through July 31, 2022 with two options to extend the term of the Arrangement for a period of 24 months each.
Area of leased space \| ft²			69,867
Accrued rent	$ 0		$ 0		$ 0

Commitments and Contingencies - Summary of Future Minimum Lease Payments (Details) $ in Thousands	Jun. 30, 2021 USD ($)
Leases [Abstract]
2021 (remaining 6 months)	$ 1,678
2022	2,618
2023	1,563
2024	1,205
Total minimum lease payments	$ 7,064

License Agreements - Additional Information (Details)	1 Months Ended			3 Months Ended		6 Months Ended
License Agreements - Additional Information (Details)	Mar. 31, 2021 USD ($)	Oct. 31, 2020 USD ($)	May 31, 2019 USD ($) Product	Jun. 30, 2021 USD ($)	Jun. 30, 2020 USD ($)	Jun. 30, 2021 USD ($)	Jun. 30, 2020 USD ($)	Dec. 31, 2020 USD ($)
License Agreements [Line Items]
License maintenances fees and reimbursable patent costs						$ 100,000	$ 100,000
Outstanding payment due to WIBR				$ 0		0		$ 0
Annual maintenance fees recorded as expense for milestones				0	$ 0	0	0
Research and development				11,184,000	4,895,000	$ 20,933,000	$ 8,416,000
Maximum
License Agreements [Line Items]
Reimbursable patent costs recognized				100,000	$ 100,000
WIBR Exclusive License Agreement
License Agreements [Line Items]
Number of licensed products \| Product			3
Percentage of non-royalty payments description						This percentage ranges from zero to low double-digits and will be based upon the stage of development of the licensed product at the time such sublicense is executed.
WIBR Exclusive License Agreement \| Maximum
License Agreements [Line Items]
Nonrefundable upfront fee paid.			$ 100,000
Annual license maintenance fees			100,000
Milestone payments in the aggregate for each of the first three licensed products			$ 1,700,000
WIBR Co-Exclusive License Agreement
License Agreements [Line Items]
Number of licensed products \| Product			3
WIBR Co-Exclusive License Agreement \| Maximum
License Agreements [Line Items]
Nonrefundable upfront fee paid.			$ 100,000
Annual license maintenance fees			100,000
Milestone payments in the aggregate for each of the first three licensed products			1,900,000
Annual fees for each sublicense agreement			$ 100,000
Development and Option Agreement
License Agreements [Line Items]
Reimbursements for development and material costs incurred by Acuitas		$ 400,000
Development and Option Agreement \| First Non-exclusive License
License Agreements [Line Items]
Annual technology access fee		1,500,000
Development and Option Agreement \| Second Non-exclusive License
License Agreements [Line Items]
Annual technology access fee		$ 1,750,000
Acuitas License Agreement
License Agreements [Line Items]
Annual maintenance fees recorded as expense for milestones				0		$ 0
Option exercise fee	$ 1,500,000
Potential clinical and regulatory milestone payments aggregate amount entitled to receive Acuitas	$ 18,000,000.0
Research and development				$ 400,000		$ 2,000,000.0

Redeemable Convertible Preferred Stock - Additional Information (Details) - USD ($)					1 Months Ended	3 Months Ended		6 Months Ended		12 Months Ended
	Aug. 03, 2021	Aug. 03, 2020	Jun. 02, 2020	Jan. 27, 2020	Mar. 31, 2021	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2017	Apr. 01, 2021	Sep. 01, 2020	Jan. 01, 2020
Class Of Stock [Line Items]
Redeemable convertible preferred stock, shares issued						131,008,559		131,008,559		89,175,231
Redeemable convertible preferred stock, shares authorized						132,858,564		132,858,564		107,125,232
Dividends declared								$ 0		$ 0
Dividends paid						$ 0	$ 0	$ 0	$ 0
Minimum [Member]
Class Of Stock [Line Items]
Gross proceeds								$ 35,000,000
Series A Redeemable Convertible Preferred Stock
Class Of Stock [Line Items]
Redeemable convertible preferred stock, shares issued						56,775,232		56,775,232		56,775,232	56,775,232	56,775,232			0
Purchase price per share											$ 0.50	$ 0.50
Cash proceeds from issuance of convertible preferred stock											$ 25,500,000	$ 25,500,000
Proceeds from outstanding promissory notes											2,800,000	2,800,000
Accrued interest on outstanding promissory notes											54,000	54,000
Redeemable convertible preferred stock, shares authorized						57,125,232		57,125,232		57,125,232
Conversion price						$ 0.50		$ 0.50
Series A Redeemable Convertible Preferred Stock \| Maximum
Class Of Stock [Line Items]
Stock issuance costs											$ 100,000	$ 100,000
Series B Redeemable Convertible Preferred Stock
Class Of Stock [Line Items]
Redeemable convertible preferred stock, shares issued		5,000,000	3,333,333	24,066,666		32,399,999		32,399,999		32,399,999				0
Purchase price per share		$ 1.50	$ 1.50	$ 1.50
Cash proceeds from issuance of convertible preferred stock		$ 7,500,000	$ 5,000,000.0	$ 36,100,000
Stock issuance costs		$ 83,000	$ 83,000	$ 83,000
Redeemable convertible preferred stock, shares authorized						32,399,999		32,399,999		50,000,000
Conversion price						$ 1.50		$ 1.50
Series C Redeemable Convertible Preferred Stock
Class Of Stock [Line Items]
Redeemable convertible preferred stock, shares issued					41,833,328	41,833,328		41,833,328					0
Purchase price per share					$ 3.00
Cash proceeds from issuance of convertible preferred stock					$ 125,500,000
Stock issuance costs					$ 100,000
Redeemable convertible preferred stock, shares authorized						43,333,333		43,333,333
Conversion price						$ 3.00		$ 3.00
Subsequent Event
Class Of Stock [Line Items]
Number of preferred stock converted into common stock	34,678,733

Redeemable Convertible Preferred Stock - Summary of Preferred Stock (Details) - USD ($) $ in Thousands	Jun. 30, 2021	Apr. 01, 2021	Mar. 31, 2021	Dec. 31, 2020	Sep. 01, 2020	Aug. 03, 2020	Jun. 30, 2020	Jun. 02, 2020	Mar. 31, 2020	Jan. 27, 2020	Jan. 01, 2020	Dec. 31, 2019	Dec. 31, 2017
Class Of Stock [Line Items]
Preferred Stock Authorized	132,858,564			107,125,232
Preferred stock issued	131,008,559			89,175,231
Preferred stock outstanding	131,008,559			89,175,231
Carrying value	$ 200,593			$ 75,225
Liquidation preference	$ 199,600			$ 74,100
Common stock issuable upon conversion	34,678,733			23,605,211
Series A Redeemable Convertible Preferred Stock
Class Of Stock [Line Items]
Preferred Stock Authorized	57,125,232			57,125,232
Preferred stock issued	56,775,232			56,775,232							0	56,775,232	56,775,232
Preferred stock outstanding	56,775,232		56,775,232	56,775,232			56,775,232		56,775,232			56,775,232
Carrying value	$ 26,708		$ 26,708	$ 26,708			$ 26,708		$ 26,708			$ 26,708
Liquidation preference	$ 25,500			$ 25,500
Common stock issuable upon conversion	15,028,741			15,028,741
Series B Redeemable Convertible Preferred Stock
Class Of Stock [Line Items]
Preferred Stock Authorized	32,399,999			50,000,000
Preferred stock issued	32,399,999			32,399,999	0	5,000,000		3,333,333		24,066,666
Preferred stock outstanding	32,399,999		32,399,999	32,399,999			27,399,999		24,066,666
Carrying value	$ 48,517		$ 48,517	$ 48,517			$ 41,027		$ 36,038
Liquidation preference	$ 48,600			$ 48,600
Common stock issuable upon conversion	8,576,470			8,576,470
Series C Redeemable Convertible Preferred Stock
Class Of Stock [Line Items]
Preferred Stock Authorized	43,333,333
Preferred stock issued	41,833,328	0	41,833,328
Preferred stock outstanding	41,833,328		41,833,328
Carrying value	$ 125,368		$ 125,368
Liquidation preference	$ 125,500
Common stock issuable upon conversion	11,073,522

Common Stock - Additional Information (Details) - $ / shares	Jun. 30, 2021	Mar. 31, 2021	Dec. 31, 2020
Class Of Stock [Line Items]
Common stock, shares authorized	175,000,000	175,000,000	137,700,000
Common stock, par value	$ 0.001		$ 0.001
2017 Equity Incentive Plan
Class Of Stock [Line Items]
Common stock, aggregate shares reserved for conversion	5,085,523
IPO
Class Of Stock [Line Items]
Common stock, aggregate shares reserved for conversion	34,678,733
IPO \| 2017 Equity Incentive Plan
Class Of Stock [Line Items]
Common stock, aggregate shares reserved for conversion	5,085,523
IPO \| 2021 Incentive Award Plan
Class Of Stock [Line Items]
Common stock, aggregate shares reserved for conversion	5,085,523

Equity Incentive Plan - Additional Information (Details) - 2017 Equity Incentive Plan - USD ($)	1 Months Ended	6 Months Ended	12 Months Ended
	Jun. 30, 2017	Jun. 30, 2021	Dec. 31, 2017
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Number of shares available for future grant		855,627
Common stock, aggregate shares reserved for conversion		5,085,523
Stock Options
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Expiration period	10 years
Vesting period	4 years
Weighted average grant date fair value per share of stock options granted		$ 3.93
Intrinsic value of stock options exercised		$ 1,000,000.0
Unrecognized compensation cost related to unvested stock options		$ 9,700,000
Unrecognized compensation cost, weighted-average period of recognition		3 years 7 months 6 days
Stock Options \| Minimum [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Purchase price of common stock percentage	100.00%
Restricted Stock
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Vesting period			4 years
Restricted common stock issued			1,985,295
Fair value of restricted common stock			$ 800,000
Unrecognized stock-based compensation expense related to restricted stock		$ 0

Equity Incentive Plan - Summary of Stock-based Compensation Expense (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Total stock-based compensation expense	$ 685	$ 107	$ 879	$ 252
Research and Development
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Total stock-based compensation expense	212	66	275	141
General and Administrative
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Total stock-based compensation expense	$ 473	$ 41	$ 604	$ 111

Equity Incentive Plan - Summary of Option Activity (Details) - 2017 Equity Incentive Plan $ / shares in Units, $ in Thousands	6 Months Ended	12 Months Ended
	Jun. 30, 2021 USD ($) $ / shares shares	Dec. 31, 2020 USD ($) $ / shares shares
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Number of options Outstanding, Beginning balance \| shares	3,049,875
Number of options, Granted \| shares	2,314,823
Number of options, Exercised \| shares	(181,684)
Number of options, Forfeitures \| shares	(97,491)
Number of options Outstanding, Ending balance \| shares	5,085,523	3,049,875
Number of options, Vested and expected to vest \| shares	5,085,523
Number of options, Exercisable \| shares	1,000,934
Weighted average exercise price Outstanding, Beginning balance \| $ / shares	$ 1.10
Weighted average exercise price, Granted \| $ / shares	5.72
Weighted average exercise price, Exercised \| $ / shares	0.90
Weighted average exercise price, Forfeitures \| $ / shares	3.10
Weighted average exercise price Outstanding, Ending balance \| $ / shares	3.17	$ 1.10
Weighted average exercise price, Vested and expected to vest \| $ / shares	3.17
Weighted average exercise price, Exercisable \| $ / shares	$ 0.81
Weighted average remaining contractual life (years), Outstanding	9 years 7 days	8 years 10 months 9 days
Weighted average remaining contractual life (years), Vested and expected to vest	9 years 7 days
Weighted average remaining contractual life (years), Exercisable	8 years 2 months 4 days
Aggregate intrinsic value, Outstanding \| $	$ 17,127	$ 4,467
Aggregate intrinsic value, Vested and expected to vest \| $	17,127
Aggregate intrinsic value, Exercisable \| $	$ 5,737

Net Loss Per Share Attributable to Common Stockholders - Summary of the Computation of Basic and Diluted Net Loss Per Share Attributable to Common Stockholders (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended				6 Months Ended
	Jun. 30, 2021	Mar. 31, 2021	Jun. 30, 2020	Mar. 31, 2020	Jun. 30, 2021	Jun. 30, 2020
Numerator:
Net loss	$ (15,410)	$ (13,488)	$ (6,323)	$ (5,418)	$ (28,898)	$ (11,741)
Denominator:
Weighted-average common stock used in net loss per share attributable to common stockholders, basic and diluted	4,588,500		4,007,606		4,542,832	3,929,900
Net loss per common stock attributable to common stockholders, basic and diluted	$ (3.36)		$ (1.58)		$ (6.36)	$ (2.99)

- Definition

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

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+ Details

Net Loss Per Share Attributable to Common Stockholders - Schedule of Anti-Dilutive Securities Excluded from Computation of Earnings Per Share (Details) - shares	6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of earnings per share	39,856,903	25,183,928
Redeemable Convertible Preferred Stock
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of earnings per share	34,678,733	22,374,328
Unvested Restricted Stock
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of earnings per share		248,162
Outstanding Options to Purchase Common Stock
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of earnings per share	5,085,523	2,468,791
Warrants
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of earnings per share	92,647	92,647

Related Party Transactions - Additional Information (Details)	3 Months Ended		6 Months Ended
	Jun. 30, 2021 USD ($)	Jun. 30, 2020 USD ($)	Jun. 30, 2021 USD ($)	Jun. 30, 2020 USD ($)	Dec. 31, 2020 USD ($)	Sep. 30, 2020 ft²	Sep. 30, 2019 ft²
LARONDE, Inc.
Related Party Transaction [Line Items]
Area of real estate property \| ft²						19,404
Sublease income			$ 1,300,000
Outstanding receivable	$ 0		0		$ 0
Cygnal
Related Party Transaction [Line Items]
Area of real estate property \| ft²							1,445
Sublease income			$ 100,000
Outstanding receivable					0
Sublease term			2 years
Related Party Expense \| LARONDE, Inc.
Related Party Transaction [Line Items]
Sublease rental income received	500,000		$ 1,000,000.0
Related Party Expense \| Cygnal \| Maximum
Related Party Transaction [Line Items]
Sublease rental income received	100,000	$ 100,000	100,000	$ 100,000
Flagship
Related Party Transaction [Line Items]
Outstanding payments	0		0		$ 0
Flagship \| Related Party Expense \| Management Services Fees and Other Reimbursements
Related Party Transaction [Line Items]
Related party expenses for management service	$ 300,000	$ 200,000	$ 400,000	$ 500,000
Omega Therapeutics, Inc. \| Flagship
Related Party Transaction [Line Items]
Ownership percentage	54.50%		54.50%		70.90%

Subsequent Events - Additional Information (Details) - USD ($) $ / shares in Units, $ in Millions			6 Months Ended
	Aug. 17, 2021	Aug. 03, 2021	Jun. 30, 2021	Jul. 31, 2021	Mar. 31, 2021	Dec. 31, 2020
Subsequent Event [Line Items]
Shares of common stock authorized			175,000,000		175,000,000	137,700,000
Common stock, par value			$ 0.001			$ 0.001
Common stock, shares issued			4,647,035			4,465,351
Conversion of preferred stock to common stock			34,678,733			23,605,211
IPO
Subsequent Event [Line Items]
Common stock reserved for future issuance			34,678,733
2021 Incentive Award Plan \| IPO
Subsequent Event [Line Items]
Common stock reserved for future issuance			5,085,523
Subsequent Event
Subsequent Event [Line Items]
Conversion of preferred stock to common stock		34,678,733
Warrants to purchase common stock	92,647
Subsequent Event \| IPO
Subsequent Event [Line Items]
Common stock, shares issued		7,400,000
Offering price per share		$ 17.00
Gross proceeds from IPO		$ 125.8
Net proceeds		$ 113.4
Subsequent Event \| Underwriters’ Option to Purchase Additional Shares
Subsequent Event [Line Items]
Common stock, shares issued	900,976
Offering price per share	$ 17.00
Gross proceeds	$ 15.3
Net proceeds	$ 14.2
Subsequent Event \| 2021 Incentive Award Plan
Subsequent Event [Line Items]
Common stock reserved for future issuance				2,960,000
Subsequent Event \| 2021 ESPP
Subsequent Event [Line Items]
Common stock reserved for future issuance				480,000
Amended and Restated Certificate of Incorporation
Subsequent Event [Line Items]
Reverse stock split description			1-for-3.777776
Amended and Restated Certificate of Incorporation \| Subsequent Event
Subsequent Event [Line Items]
Shares of common stock authorized		200,000,000
Common stock, par value		$ 0.001
Shares of preferred stock authorized		10,000,000
Preferred stock, par value		$ 0.001