0001664710-23-000021 | 10-K | XBRL Viewer

Common Stock

12 Months Ended

Dec. 31, 2022

COMMON STOCK

As of December 31, 2022, the Company’s amended and restated certificate of incorporation authorized the Company to issue 200,000,000 shares of common stock at a par value of $0.0001 per share.

On May 3, 2021, the Company entered into a Sales Agreement (the “ATM Sales Agreement”) with SVB Securities LLC (formerly SVB Leerink LLC) (“SVB Securities”), as agent, pursuant to which the Company may offer and sell, from time to time, shares of its common stock through SVB Securities (the “ATM Offering”). On May 3, 2021, the Company filed the Shelf Registration Statement, including a base prospectus and sales agreement prospectus, with the Securities and Exchange Commission (the “SEC”), which became effective immediately upon filing, for the issuance and sale of up to $150.0 million of shares of the Company’s common stock under the ATM Sales Agreement. On December 12, 2022, the Company filed a prospectus supplement to the Shelf Registration Statement for the issuance and sale, if any, of up to an additional $250.0 million of shares of its common stock under the ATM Sales Agreement.

For the year ended December 31, 2021, the Company raised gross proceeds of $28.6 million pursuant to the ATM Offering through the sale of 520,000 shares of common stock at a weighted average price of $55.00 per share. The net proceeds from the ATM Offering for the year ended December 31, 2021 were approximately $28.1 million after deducting sales agent commissions of $0.4 million and offering expenses of $0.1 million.

For the year ended December 31, 2022, the Company raised gross proceeds of $121.4 million pursuant to the ATM Offering through the sale of 3,410,384 shares of common stock at a weighted average price of $35.60 per share. The net proceeds from the ATM Offering for the year ended December 31, 2022 were approximately $119.4 million after deducting sales agent commissions of $1.8 million and offering expenses of $0.2 million.

As of December 31, 2022, the Company was eligible to offer and sell, from time to time, shares of its common stock for an aggregate offering amount of up to $250.0 million available under the ATM Offering.

The following is a summary of the rights and privileges of the holders of common stock as of December 31, 2022:

Liquidation Preference: In the event of liquidation, dissolution or winding up, holders of common stock will be entitled to share ratably in the net assets legally available for distribution to stockholders after the payment of all debts and other liabilities and the satisfaction of any liquidation preference granted to the holders of any then-outstanding shares of preferred stock.

Dividends: Subject to preferences that may be applicable to any then-outstanding preferred stock, holders of common stock are entitled to receive ratably those dividends, if any, as may be declared from time to time by the Board out of legally available funds. As of December 31, 2022, no cash dividends have been declared or paid.

Voting Rights: Each holder of common stock is entitled to one vote for each share on all matters submitted to a vote of the stockholders, including the election of directors. Under the Company's amended and restated certificate of incorporation and amended and restated bylaws, stockholders will not have cumulative voting rights. Because of this, the holders of a majority of the shares of common stock entitled to vote in any election of directors can elect all of the directors standing for election, if they should so choose.

Rights and Preferences: Holders of common stock have no preemptive, conversion or subscription rights and there are no redemption or sinking fund provisions applicable to the common stock. The rights, preferences and privileges of the holders of common stock are subject to, and may be adversely affected by, the rights of the holders of shares of any series of preferred stock that the Company may designate in the future.

As of December 31, 2022 and 2021, the Company has reserved the following shares of common stock for the potential exercise of stock options:



	DECEMBER 31,
	2022	2021


Options to purchase common stock	3,533,169	2,810,684
Total	3,533,169	2,810,684

The Company’s potentially dilutive securities have been excluded from the computation of diluted net loss per share, as the effect would be to reduce the net loss per share. 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.

- 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.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-URI https://asc.fasb.org/topic&trid=2208762

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section 50
-Paragraph 13
-Subparagraph (b)
-URI https://asc.fasb.org/extlink&oid=126973232&loc=SL123496158-112644

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section 50
-Paragraph 13
-URI https://asc.fasb.org/extlink&oid=126973232&loc=SL123496158-112644

Reference 4: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section 50
-Paragraph 14
-Subparagraph (c)
-URI https://asc.fasb.org/extlink&oid=126973232&loc=SL123496171-112644

Reference 5: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section 50
-Paragraph 14
-Subparagraph (b)
-URI https://asc.fasb.org/extlink&oid=126973232&loc=SL123496171-112644

Reference 6: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.3-04)
-URI https://asc.fasb.org/extlink&oid=120397183&loc=d3e187085-122770

Reference 7: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section 50
-Paragraph 18
-Subparagraph (d)
-URI https://asc.fasb.org/extlink&oid=126973232&loc=SL123496189-112644

Reference 8: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section 50
-Paragraph 13
-Subparagraph (g)
-URI https://asc.fasb.org/extlink&oid=126973232&loc=SL123496158-112644

Reference 9: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section 50
-Paragraph 18
-Subparagraph (a)
-URI https://asc.fasb.org/extlink&oid=126973232&loc=SL123496189-112644

Reference 10: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section 50
-Paragraph 13
-Subparagraph (h)
-URI https://asc.fasb.org/extlink&oid=126973232&loc=SL123496158-112644

Reference 11: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section 50
-Paragraph 14
-Subparagraph (a)
-URI https://asc.fasb.org/extlink&oid=126973232&loc=SL123496171-112644

Reference 12: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section 50
-Paragraph 18
-Subparagraph (b)
-URI https://asc.fasb.org/extlink&oid=126973232&loc=SL123496189-112644

Reference 13: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section 50
-Paragraph 16
-Subparagraph (b)
-URI https://asc.fasb.org/extlink&oid=126973232&loc=SL123496180-112644

Reference 14: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section 50
-Paragraph 13
-Subparagraph (i)
-URI https://asc.fasb.org/extlink&oid=126973232&loc=SL123496158-112644

Reference 15: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 235
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.4-08(e)(1))
-URI https://asc.fasb.org/extlink&oid=120395691&loc=d3e23780-122690

Reference 16: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 40
-Section 50
-Paragraph 6
-Subparagraph (a)
-URI https://asc.fasb.org/extlink&oid=126731327&loc=SL126733271-114008

+ Details

Prepaid Expenses and Other Current Assets (Tables)

12 Months Ended

Dec. 31, 2022

Deferred Costs, Capitalized, Prepaid, and Other Assets Disclosure [Abstract]

Schedule of Prepaid Expenses and Other Current Assets

Prepaid expenses and other current assets as of December 31, 2022 and 2021 consisted of the following (in thousands):



	DECEMBER 31,
	2022		2021
Prepaid service contracts	3,319		1,613
Income tax credit receivable	—		30
Prepaid sales tax	872		255
Prepaid rent	96		—
R&D payroll tax credit	—		167
Prepaid insurance	941		993
Prepaid subscriptions	470		130
Interest and dividend receivable	841		—
Other	180		210
Total prepaid expenses and other current assets	$	6,719	$	3,398

License Agreements	12 Months Ended
License Agreements	Dec. 31, 2022
Research and Development [Abstract]
License Agreements	LICENSE AGREEMENTS Massachusetts General Hospital On April 5, 2016, the Company entered into an exclusive patent license agreement with The General Hospital Corporation d/b/a Massachusetts General Hospital (“MGH”). Under the license agreement with MGH (as amended in May 2017 and February 2018, the “MGH Agreement”), the Company obtained an exclusive, worldwide license, with the right to sublicense, under certain patents and technical information of MGH, to make, have made, use, have used, sell, have sold, lease, have leased, import, have imported or otherwise transfer licensed products and processes for use in the treatment, diagnosis, palliation and prevention of diseases and disorders in humans and animals. The Company is required to use commercially reasonable efforts to develop and commercialize licensed products and processes and must achieve certain required diligence milestones. Under the terms of the MGH Agreement, the Company paid an initial license payment of $0.1 million in 2016, and reimbursed MGH approximately $0.3 million of prior patent prosecution expenses related to the licensed patents in 2017. The Company also issued MGH an aggregate of 358,674 shares of its common stock. Additionally, the Company is required to pay a low-five digit to mid-five digit annual maintenance fee prior to the first commercial sale of its first product or process, a mid-five digit annual maintenance fee after the first commercial sale of its first product or process that is creditable against royalties, certain clinical and regulatory milestone payments for the first three products or indications to achieve such milestones, which milestone payments are $8.6 million in the aggregate, and certain commercial milestone payments for the first three products or indications to achieve such milestones, which milestone payments are $18.0 million in the aggregate. The Company made payments of $50,000 and $300,000 in 2020 and 2021, respectively, for the achievement of the clinical and regulatory milestones of (i) filing of an IND in the first country and (ii) the completion of a Phase 1 clinical trial, respectively. The Company is also obligated to pay tiered royalties on net sales of licensed products ranging in the low-single digits to mid-single digits. The royalty rates are subject to up to a maximum 50% reduction for lack of a valid claim, in the event that it is necessary for the Company to obtain a license to any third-party intellectual property related to the licensed products, and generic competition. The obligation to pay royalties under the MGH Agreement expires on a licensed product-by-licensed product and country-by-country basis upon the later of expiry of the last valid claim of the licensed patents that cover such licensed product in such country or ten years from the first commercial sale of such product in such country. The Company is also obligated to pay a percentage of non-royalty-related payments received by it from sublicensees ranging in the low-double digits and a change of control fee equal to a low-single digit percentage of the payments received as part of any completed transaction up to a low seven-digit amount. The MGH Agreement expires upon expiry of the last remaining royalty obligation for a licensed product or process. Under the MGH Agreement, MGH may terminate the agreement upon the Company’s uncured material breach or insolvency, a challenge by the Company of the licensed patents and certain other specified breaches of the MGH Agreement. The Company may terminate the agreement for any reason upon specified prior written notice to MGH. Neurona Agreement On June 22, 2021, the Company entered into a license agreement with Neurona. Refer to Note 12, Revenue from Contracts with Customers, for more information regarding this agreement. Hansoh Agreement On December 12, 2021, the Company entered into a license agreement with Hansoh. Refer to Note 12, Revenue from Contracts with Customers, for more information regarding this agreement.

Fair Value Measurements

12 Months Ended

Dec. 31, 2022

Fair Value Disclosures [Abstract]

Fair Value Measurements

FAIR VALUE MEASUREMENTS

The following table presents information about the Company’s financial assets and liabilities measured at fair value on a recurring basis and indicates the level of the fair value hierarchy utilized to determine such fair values (in thousands):




DESCRIPTION	DECEMBER 31, 2022		QUOTED PRICES ACTIVE MARKETS FOR IDENTICAL ASSETS (LEVEL 1)		SIGNIFICANT OTHER OBSERVABLE INPUTS (LEVEL 2)		SIGNIFICANT OTHER OBSERVABLE INPUTS (LEVEL 3)
Asset
Money market funds	$	271,734	$	271,734	$	—	$	—
Total financial assets	$	271,734	$	271,734	$	—	$	—




DESCRIPTION	DECEMBER 31, 2021		QUOTED PRICES ACTIVE MARKETS FOR IDENTICAL ASSETS (LEVEL 1)		SIGNIFICANT OTHER OBSERVABLE INPUTS (LEVEL 2)		SIGNIFICANT OTHER OBSERVABLE INPUTS (LEVEL 3)
Asset
Money market funds	$	230,042	$	230,042	$	—	$	—
Total financial assets	$	230,042	$	230,042	$	—	$	—

There have been no transfers between fair value levels during the years ended December 31, 2022 and 2021. The carrying values of other current assets, accounts payable and accrued expenses approximate their fair values due to the short-term nature of these assets and liabilities.

- 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

Property and Equipment, Net

12 Months Ended

Dec. 31, 2022

Property, Plant and Equipment [Abstract]

Property and Equipment, Net

PROPERTY AND EQUIPMENT, NET

Property and equipment, net as of December 31, 2022 and 2021 consisted of the following (in thousands):



	DECEMBER 31,
	2022		2021
Computer equipment and software	$	35	$	41
Laboratory equipment	2,652		1,821
Office furniture	284		55
Leasehold improvements	213		264
Total	3,184		2,181
Less: accumulated depreciation	(1,163)		(846)
Property and equipment, net	$	2,021	$	1,335

Depreciation expense was $0.7 million and $0.4 million for each of the years ended December 31, 2022 and 2021, respectively.

Property and Equipment, Net (Tables)

12 Months Ended

Dec. 31, 2022

Property, Plant and Equipment [Abstract]

Schedule of Property and Equipment, Net

Depreciation is calculated using the straight-line method over the estimated useful lives of the related assets as follows:



			ESTIMATED USEFUL LIFE
Computer equipment and software			3 years
Laboratory equipment			5 years
Office furniture			5 years
Leasehold improvements			lesser of useful life or remaining lease term

Property and equipment, net as of December 31, 2022 and 2021 consisted of the following (in thousands):



	DECEMBER 31,
	2022		2021
Computer equipment and software	$	35	$	41
Laboratory equipment	2,652		1,821
Office furniture	284		55
Leasehold improvements	213		264
Total	3,184		2,181
Less: accumulated depreciation	(1,163)		(846)
Property and equipment, net	$	2,021	$	1,335

Stock-Based Compensation - Schedule of Stock-Based Compensation Expense (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Total stock-based compensation expense	$ 18,682	$ 11,722
Research and development
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Total stock-based compensation expense	8,205	4,258
General and administrative
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Total stock-based compensation expense	$ 10,477	$ 7,464

Subsequent Events	12 Months Ended
Subsequent Events	Dec. 31, 2022
Subsequent Events [Abstract]
Subsequent Events	Subsequent Events Leases In January 2023, the Company entered into a first amendment to the 1050 Waltham Lease (the “Lease Amendment”). Under the terms of the Lease Amendment, a phased delivery of the Premises by the Landlord was established as follows: (i) the Landlord will deliver approximately 31,991 square feet of the Premises (the “Phase A Premises”), on or before January 4, 2023 (the “Phase A Premises Commencement Date”) and (ii) the Landlord will deliver the additional approximately 3,671 rentable square feet of vivarium space (the “Phase B Premises”), when the Landlord substantially completes work on the Phase B Premises, which is estimated to be on or before May 1, 2023 (the “Phase B Premises Commencement Date”). Per the Lease Amendment, the term of the 1050 Waltham Lease will now commence on the Phase A Premises Commencement Date. The 1050 Waltham Lease has a term of eight years, measured from the Phase A Premises Commencement Date. The Company’s obligation for the payment of base rent for the Phase A Premises begins on the date which is earlier to occur of (i) eight months following the Phase B Premises Commencement Date or (ii) 11 months following the Phase A Premises Commencement Date (such earlier date, the “Phase A Rent Commencement Date”). The Company’s obligation for the payment of base rent for the Phase B Premises begins on the date which is eight months following the Phase B Premises Commencement Date (the “Phase B Rent Commencement Date”). Base rent will initially be fixed at $202,085 per month, which will increase by approximately 3% per annum. From and after the Phase A Rent Commencement Date and until the occurrence of the Phase B Rent Commencement Date, the Company will be obligated to pay base rent at the per square foot rent for the Phase A Premises only. Upon the Phase B Rent Commencement Date, the Company will be obligated to pay the base rent for the entirety of the Premises. The Company will be obligated to pay the Landlord for certain costs, taxes and operating expenses as specified in the Lease Amendment.

Consolidated Statements of Stockholders’ Equity - USD ($) $ in Thousands	Total	COMMON STOCK	ADDITIONAL PAID-IN CAPITAL	ACCUMULATED DEFICIT	At The Market Offering	At The Market Offering COMMON STOCK	At The Market Offering ADDITIONAL PAID-IN CAPITAL
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Ending balance (in shares)		23,192,866
Ending balance	$ 261,721	$ 2	$ 326,730	$ (65,011)
Beginning balance (in shares) at Dec. 31, 2020		23,192,866
Beginning balance at Dec. 31, 2020	261,721	$ 2	326,730	(65,011)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of common stock, net of underwriting discounts, commissions and offering costs (in shares)						520,000
Issuance of common stock, net of underwriting discounts, commissions and offering costs					$ 28,096		$ 28,096
Exercise of common stock options (in shares)		261,968
Exercise of common stock options	379		379
Stock-based compensation	11,722		11,722
Net loss	(58,744)			(58,744)
Ending balance (in shares)		23,974,834
Ending balance	243,174	$ 2	366,927	(123,755)
Beginning balance (in shares) at Dec. 31, 2021		23,974,834
Beginning balance at Dec. 31, 2021	$ 243,174	$ 2	366,927	(123,755)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of common stock, net of underwriting discounts, commissions and offering costs (in shares)						3,410,384
Issuance of common stock, net of underwriting discounts, commissions and offering costs					$ 119,428		$ 119,428
Exercise of common stock options (in shares)	158,235	158,235
Exercise of common stock options	$ 818		818
Stock-based compensation	18,682		18,682
Net loss	(104,679)			(104,679)
Ending balance (in shares)		27,543,453
Ending balance	$ 277,423	$ 2	$ 505,855	$ (228,434)

- Definition

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

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 220
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-04(22))
-URI https://asc.fasb.org/extlink&oid=120399700&loc=SL114874048-224260

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
-SubTopic 10
-Section 50
-Paragraph 32
-Subparagraph (f)
-URI https://asc.fasb.org/extlink&oid=126901519&loc=d3e8933-108599

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 250
-SubTopic 10
-Section 50
-Paragraph 4
-URI https://asc.fasb.org/extlink&oid=124431687&loc=d3e22595-107794

Reference 4: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 220
-Section S99
-Paragraph 1
-Subparagraph (SX 210.7-04(18))
-URI https://asc.fasb.org/extlink&oid=120400993&loc=SL114874131-224263

Reference 5: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 40
-Section 65
-Paragraph 1
-Subparagraph (f)
-URI https://asc.fasb.org/extlink&oid=126732423&loc=SL123482106-238011

Reference 6: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 220
-SubTopic 10
-Section 50
-Paragraph 6
-URI https://asc.fasb.org/extlink&oid=124431353&loc=SL124452729-227067

Reference 7: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 470
-SubTopic 10
-Section S99
-Paragraph 1B
-Subparagraph (SX 210.13-02(a)(5))
-URI https://asc.fasb.org/extlink&oid=126975872&loc=SL124442552-122756

Reference 8: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 220
-SubTopic 10
-Section S99
-Paragraph 2
-Subparagraph (SX 210.5-03(20))
-URI https://asc.fasb.org/extlink&oid=126953954&loc=SL114868664-224227

Reference 9: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 28
-URI https://asc.fasb.org/extlink&oid=126954810&loc=d3e3602-108585

Reference 10: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 250
-SubTopic 10
-Section 50
-Paragraph 1
-Subparagraph (b)(2)
-URI https://asc.fasb.org/extlink&oid=124431687&loc=d3e22499-107794

Reference 11: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 470
-SubTopic 10
-Section S99
-Paragraph 1A
-Subparagraph (SX 210.13-01(a)(4)(iv))
-URI https://asc.fasb.org/extlink&oid=126975872&loc=SL124442526-122756

Reference 12: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 470
-SubTopic 10
-Section S99
-Paragraph 1A
-Subparagraph (SX 210.13-01(a)(4)(iii)(A))
-URI https://asc.fasb.org/extlink&oid=126975872&loc=SL124442526-122756

Reference 13: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 470
-SubTopic 10
-Section S99
-Paragraph 1B
-Subparagraph (SX 210.13-02(a)(4)(i))
-URI https://asc.fasb.org/extlink&oid=126975872&loc=SL124442552-122756

Reference 14: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 470
-SubTopic 10
-Section S99
-Paragraph 1A
-Subparagraph (SX 210.13-01(a)(4)(i))
-URI https://asc.fasb.org/extlink&oid=126975872&loc=SL124442526-122756

Reference 15: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 250
-SubTopic 10
-Section 50
-Paragraph 9
-URI https://asc.fasb.org/extlink&oid=124431687&loc=d3e22663-107794

Reference 16: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 470
-SubTopic 10
-Section S99
-Paragraph 1B
-Subparagraph (SX 210.13-02(a)(4)(iv))
-URI https://asc.fasb.org/extlink&oid=126975872&loc=SL124442552-122756

Reference 17: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 470
-SubTopic 10
-Section S99
-Paragraph 1A
-Subparagraph (SX 210.13-01(a)(4)(ii))
-URI https://asc.fasb.org/extlink&oid=126975872&loc=SL124442526-122756

Reference 18: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 825
-SubTopic 10
-Section 50
-Paragraph 28
-Subparagraph (f)
-URI https://asc.fasb.org/extlink&oid=123596393&loc=d3e14064-108612

Reference 19: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 250
-SubTopic 10
-Section 50
-Paragraph 3
-URI https://asc.fasb.org/extlink&oid=124431687&loc=d3e22583-107794

Reference 20: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 235
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.4-08(g)(1)(ii))
-URI https://asc.fasb.org/extlink&oid=120395691&loc=d3e23780-122690

Reference 21: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 260
-SubTopic 10
-Section 45
-Paragraph 60B
-Subparagraph (a)
-URI https://asc.fasb.org/extlink&oid=126958026&loc=SL5780133-109256

Reference 22: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 323
-SubTopic 10
-Section 50
-Paragraph 3
-Subparagraph (c)
-URI https://asc.fasb.org/extlink&oid=114001798&loc=d3e33918-111571

Reference 23: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 250
-SubTopic 10
-Section 50
-Paragraph 8
-URI https://asc.fasb.org/extlink&oid=124431687&loc=d3e22658-107794

Reference 24: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 220
-SubTopic 10
-Section 45
-Paragraph 1A
-Subparagraph (a)
-URI https://asc.fasb.org/extlink&oid=126968391&loc=SL7669619-108580

Reference 25: http://www.xbrl.org/2003/role/exampleRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
-SubTopic 10
-Section 50
-Paragraph 31
-URI https://asc.fasb.org/extlink&oid=126901519&loc=d3e8924-108599

Reference 26: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 250
-SubTopic 10
-Section 50
-Paragraph 11
-Subparagraph (b)
-URI https://asc.fasb.org/extlink&oid=124431687&loc=d3e22694-107794

Reference 27: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 250
-SubTopic 10
-Section 50
-Paragraph 11
-Subparagraph (a)
-URI https://asc.fasb.org/extlink&oid=124431687&loc=d3e22694-107794

Reference 28: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 205
-SubTopic 20
-Section 50
-Paragraph 7
-URI https://asc.fasb.org/extlink&oid=109222650&loc=SL51721683-107760

Reference 29: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 220
-SubTopic 10
-Section 45
-Paragraph 1B
-Subparagraph (a)
-URI https://asc.fasb.org/extlink&oid=126968391&loc=SL7669625-108580

Reference 30: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
-SubTopic 10
-Section 50
-Paragraph 22
-URI https://asc.fasb.org/extlink&oid=126901519&loc=d3e8736-108599

Reference 31: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 470
-SubTopic 10
-Section S99
-Paragraph 1A
-Subparagraph (SX 210.13-01(a)(5))
-URI https://asc.fasb.org/extlink&oid=126975872&loc=SL124442526-122756

Reference 32: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 470
-SubTopic 10
-Section S99
-Paragraph 1B
-Subparagraph (SX 210.13-02(a)(4)(iii)(B))
-URI https://asc.fasb.org/extlink&oid=126975872&loc=SL124442552-122756

Reference 33: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 470
-SubTopic 10
-Section S99
-Paragraph 1B
-Subparagraph (SX 210.13-02(a)(4)(iii)(A))
-URI https://asc.fasb.org/extlink&oid=126975872&loc=SL124442552-122756

Reference 34: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
-SubTopic 10
-Section 50
-Paragraph 30
-Subparagraph (b)
-URI https://asc.fasb.org/extlink&oid=126901519&loc=d3e8906-108599

Reference 35: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
-SubTopic 10
-Section 50
-Paragraph 32
-Subparagraph (c)
-URI https://asc.fasb.org/extlink&oid=126901519&loc=d3e8933-108599

+ Details

- Definition

Total of all stockholders' equity (deficit) items, net of receivables from officers, directors, owners, and affiliates of the entity which are attributable to the parent. The amount of the economic entity's stockholders' equity attributable to the parent excludes the amount of stockholders' equity which is allocable to that ownership interest in subsidiary equity which is not attributable to the parent (noncontrolling interest, minority interest). This excludes temporary equity and is sometimes called permanent equity.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 235
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.4-08(g)(1)(ii))
-URI https://asc.fasb.org/extlink&oid=120395691&loc=d3e23780-122690

Reference 2: http://www.xbrl.org/2003/role/exampleRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 852
-SubTopic 10
-Section 55
-Paragraph 10
-URI https://asc.fasb.org/extlink&oid=84165509&loc=d3e56426-112766

Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section S99
-Paragraph 2
-Subparagraph (SAB Topic 4.E)
-URI https://asc.fasb.org/extlink&oid=122038336&loc=d3e74512-122707

Reference 4: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02(31))
-URI https://asc.fasb.org/extlink&oid=120391452&loc=d3e13212-122682

Reference 5: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02(29))
-URI https://asc.fasb.org/extlink&oid=120391452&loc=d3e13212-122682

Reference 6: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02(30))
-URI https://asc.fasb.org/extlink&oid=120391452&loc=d3e13212-122682

Reference 7: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 825
-SubTopic 10
-Section 50
-Paragraph 28
-Subparagraph (f)
-URI https://asc.fasb.org/extlink&oid=123596393&loc=d3e14064-108612

Reference 8: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 323
-SubTopic 10
-Section 50
-Paragraph 3
-Subparagraph (c)
-URI https://asc.fasb.org/extlink&oid=114001798&loc=d3e33918-111571

+ Details

Summary of Significant Accounting Policies (Tables)

12 Months Ended

Dec. 31, 2022

Accounting Policies [Abstract]

Schedule of Estimated Useful Lives

Depreciation is calculated using the straight-line method over the estimated useful lives of the related assets as follows:



			ESTIMATED USEFUL LIFE
Computer equipment and software			3 years
Laboratory equipment			5 years
Office furniture			5 years
Leasehold improvements			lesser of useful life or remaining lease term

Property and equipment, net as of December 31, 2022 and 2021 consisted of the following (in thousands):



	DECEMBER 31,
	2022		2021
Computer equipment and software	$	35	$	41
Laboratory equipment	2,652		1,821
Office furniture	284		55
Leasehold improvements	213		264
Total	3,184		2,181
Less: accumulated depreciation	(1,163)		(846)
Property and equipment, net	$	2,021	$	1,335

Schedule of Antidilutive Securities Excluded From Computation of Diluted Net Loss Per Share

The Company excluded the following from the computation of diluted net loss per share attributable to common stockholders as of December 31, 2022 and 2021, because including them would have had an anti-dilutive effect:



	DECEMBER 31,
	2022	2021


Options to purchase common stock	3,533,169	2,810,684
	3,533,169	2,810,684

Stock-Based Compensation - Schedule of Stock Option Activity (Details) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021
NUMBER OF OPTIONS
Outstanding as of beginning of period (in shares)	2,810,684
Granted (in shares)	1,086,458
Exercised (in shares)	(158,235)
Cancelled or forfeited (in shares)	(195,428)
Expired (in USD per share)	(10,310)
Outstanding as of end of period (in shares)	3,533,169	2,810,684
Options vested (in shares)	1,749,888
Option unvested (in shares)	1,783,281
WEIGHTED- AVERAGE EXERCISE PRICE
Outstanding as of beginning of period (in USD per share)	$ 24.62
Granted (in USD per share)	43.66
Exercised (in USD per share)	5.17
Cancelled or forfeited (in USD per share)	42.44
Expired (in USD per share)	(59.46)
Outstanding as of end of period (in USD per share)	30.26	$ 24.62
Options vested (in USD per share)	19.59
Option unvested (in USD per share)	$ 40.72
WEIGHTED-AVERAGE REMAINING CONTRACTUAL TERM (IN YEARS)
Outstanding	7 years 9 months 7 days	8 years 1 month 9 days
Options vested	6 years 11 months 4 days
AGGREGATE INTRINSIC VALUE
Outstanding	$ 72,434	$ 100,009
Exercised	5,637
Options vested	$ 53,895

Summary of Significant Accounting Policies - Narrative (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2022 USD ($) certificate operatingLease financialInstitution segment	Dec. 31, 2021 USD ($) financialInstitution
Accounting Policies [Abstract]
Money market funds	$ 279,000	$ 230,000
Number of certificates of deposits \| certificate	2
Number of operating leases \| operatingLease	2
Restricted cash	$ 1,327	$ 1,327
Number of financial institutions \| financialInstitution	3	3
Research and development incentive income	$ 7,081	$ 0
Number of operating segments \| segment	1

Prepaid Expenses and Other Current Assets (Details) - USD ($) $ in Thousands	Dec. 31, 2022	Dec. 31, 2021
Deferred Costs, Capitalized, Prepaid, and Other Assets Disclosure [Abstract]
Prepaid service contracts	$ 3,319	$ 1,613
Income tax credit receivable	0	30
Prepaid sales tax	872	255
Prepaid rent	96	0
R&D payroll tax credit	0	167
Prepaid insurance	941	993
Prepaid subscriptions	470	130
Interest and dividend receivable	841	0
Other	180	210
Total prepaid expenses and other current assets	$ 6,719	$ 3,398

Property and Equipment, Net - Narrative (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021
Property, Plant and Equipment [Abstract]
Depreciation expense	$ 0.7	$ 0.4

Income Taxes

12 Months Ended

Dec. 31, 2022

Income Tax Disclosure [Abstract]

Income Taxes

INCOME TAXES

Loss before provision from income taxes for the years ended December 31, 2022 and 2021 consisted of the following (in thousands):



	YEAR ENDED DECEMBER 31,
	2022		2021
United States	$	(112,240)	$	(55,961)
Foreign	7,561		(772)
Loss before provision from income taxes	$	(104,679)	$	(56,733)

The components of income tax provision (benefit) for the years ended December 31, 2022 and 2021 consisted of the following (in thousands):



	YEAR ENDED DECEMBER 31,
	2022		2021
Current income tax provision (benefit):
Federal	$	—	$	—
State	—		11
Foreign	—		2,000
Total current income tax provision (benefit)	$	—	$	2,011
Total deferred income tax benefit	$	—	$	—
Total income tax provision (benefit)	$	—	$	2,011

A reconciliation of the U.S. federal statutory income tax rate to the Company’s effective income tax rate for the years ended December 31, 2022 and 2021 was as follows:



	YEAR ENDED DECEMBER 31,
	2022		2021
Federal income tax at statutory rate	21.0	%	21.0	%
State income tax, net of federal benefit	5.2		6.7
Stock compensation	(2.8)		(1.5)
Permanent differences	(1.4)		—

Research and development credits	2.5		4.8
Impact of foreign operations	(0.3)		(0.6)
Foreign withholding taxes	—		(2.8)
Other	(3.3)		(0.3)
Tax credits	3.2		—
Change in valuation allowance	(24.1)		(30.9)
Effective tax rate	—	%	(3.5)	%

Net deferred tax assets as of December 31, 2022 and 2021 consisted of the following (in thousands):



	YEAR ENDED DECEMBER 31,
	2022		2021
Net operating loss carryforwards	$	37,687	$	27,833
Research and development credits	10,459		6,315
Capitalized research and development expenses	10,822		—
Operating lease liability	3,602		298
Accrueds	1,275		597


Intangibles	115		127
Other	$	908	$	558
Total deferred tax assets	$	64,868	$	35,728
Valuation allowance	(60,650)		(35,445)
Net deferred tax assets	$	4,218	$	283
Deferred tax liability
Operating lease right-of-use asset	(4,218)		(283)

Net deferred tax assets (liability)	$	—	$	—

As of December 31, 2022, the Company had U.S. federal, state and foreign net operating loss (“NOL”) carryforwards of $138.7 million, $137.8 million and $0 million, respectively. Of the $138.7 million federal NOLs, $0.2 million will expire in 2035 and the remaining $138.5 million can be carried forward indefinitely. The previously reported foreign tax loss carryforwards were fully absorbed in 2022. The state NOL carryforwards expire in 2039.

As of December 31, 2022, the Company had U.S. federal and state research and development tax credit carryforwards of $6.0 million and $3.5 million, respectively. As of December 31, 2021, the Company had U.S. federal and state research and development tax credit carryforwards of $4.3 million and $2.5 million, respectively. The tax credits begin to expire in 2031. As of December 31, 2022, the Company had foreign research and development tax credit carry forward of $1.6 million.

Under the provisions of the Internal Revenue Code of 1986, as amended (the “Code”), the NOL and tax credit carryforwards are subject to review and potential adjustments by the Internal Revenue Services and state tax authorities. Under Section 382 of the Code (“Section 382”), certain substantial changes in the Company’s ownership, including the sale of the Company or significant changes in ownership due to sales of equity, may have limited, or may limit in the future, the amount of NOL carryforwards or tax credits which could be used annually to offset future taxable income. The Company completed an analysis under Section 382 through November 17, 2020 and determined that on April 15, 2016 and April 13, 2020, ownership changes had occurred. Based on the Company’s analysis, the Company has determined that $0.3 million and $0.3 million of its federal and state NOL carryforwards, respectively, are limited by Section 382 as of December 31, 2022 and have been written off in the prior period. The remaining unused carryforwards remain available for future periods. The Company may also experience ownership changes in the future as a result of subsequent shifts in the Company’s stock ownership, some of which may be outside the Company’s control. As a result, its ability to use its pre-change NOLs or tax credits to offset U.S. federal taxable income may be subject to limitations, which could potentially result in increased future tax liability. In addition, at the state level, there may be periods during which the use of NOLs is suspended or otherwise limited, which could accelerate or permanently increase state taxes owed.

Management of the Company has evaluated the positive and negative evidence bearing upon the realizability of its deferred tax assets, which are comprised principally of research and development credits and NOLs. Under the applicable accounting standards, management has considered the Company’s history of losses and concluded that it is more likely than not that the Company will not recognize the benefits of federal and state deferred tax assets. Accordingly, a full valuation allowance was maintained as of December 31, 2022 and 2021. A change in the Company’s valuation allowance was recorded in 2022 and 2021, in the amount of $25.2 million and $17.5 million, respectively, due primarily to the generation of additional net deferred tax assets.

The Tax Cuts and Jobs Act resulted in significant changes to the treatment of research and developmental (“R&D”) expenditures under Section 174. For tax years beginning after December 31, 2021, taxpayers are required to capitalize and amortize all R&D expenditures that are paid or incurred in connection with their trade or business. Specifically, costs for U.S.-based R&D activities must be amortized over five years and costs for foreign R&D activities must be amortized over 15 years – both using a midyear convention. During the year ended December 31, 2022, the Company capitalized $44.3 million of R&D expenses.

The calculation of the Company’s tax liabilities involves dealing with uncertainties in the application of complex tax laws and regulations for both federal taxes and the many states in which it operates or does business in. A tax benefit from an

uncertain tax position may be recognized when it is more likely than not that the position will be sustained upon examination, including resolutions of any related appeals or litigation processes, on the basis of the technical merits.

The Company records tax positions as liabilities and adjusts these liabilities when its judgement changes as a result of the evaluation of new information not previously available. Because of the complexity of some of these uncertainties, the ultimate resolution may result in a payment that is materially different from the Company’s current estimate of the recognized tax benefit liabilities. These differences will be reflected as increases or decreases to income tax expense in the period in which new information is available. As of December 31, 2022 and 2021, the Company has not recorded any uncertain tax positions in its financial statements.

The Company recognizes interest and penalties related to unrecognized tax benefits on the income tax expense line in the accompanying consolidated statement of operations. As of December 31, 2022 and 2021, no accrued interest or penalties are included on the related tax liability line in the consolidated balance sheet.

The Company files tax returns as prescribed by the tax laws of the jurisdictions in which it operates. In the normal course of business, the Company is subject to examination by federal and state jurisdictions, where applicable. There are currently no pending tax examinations. The Company’s tax years are still open under statute from December 31, 2016, to the present. There are currently no pending income tax examinations. To the extent the Company has tax attribute carryforwards, the tax years in which the attribute was generated may still be adjusted upon examination by the Internal Revenue Service and state tax authorities to the extent utilized in a future period.

- Definition

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

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-SubTopic 10
-Section 50
-Paragraph 21
-URI https://asc.fasb.org/extlink&oid=121826272&loc=d3e32857-109319

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-SubTopic 10
-Section S99
-Paragraph 2
-Subparagraph (SAB Topic 11.C)
-URI https://asc.fasb.org/extlink&oid=122134291&loc=d3e330215-122817

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-SubTopic 10
-Section 50
-Paragraph 17
-Subparagraph (b)
-URI https://asc.fasb.org/extlink&oid=121826272&loc=d3e32809-109319

Reference 4: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SAB TOPIC 6.I.5.Q1)
-URI https://asc.fasb.org/extlink&oid=122134291&loc=d3e330036-122817

Reference 5: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-SubTopic 10
-Section 50
-Paragraph 14
-URI https://asc.fasb.org/extlink&oid=121826272&loc=d3e32705-109319

Reference 6: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-SubTopic 270
-Section 50
-Paragraph 1
-URI https://asc.fasb.org/extlink&oid=6424409&loc=d3e44925-109338

Reference 7: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-URI https://asc.fasb.org/topic&trid=2144680

Reference 8: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-SubTopic 30
-Section 50
-Paragraph 2
-Subparagraph (a)
-URI https://asc.fasb.org/extlink&oid=6424122&loc=d3e41874-109331

Reference 9: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 235
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.4-08(h)(2))
-URI https://asc.fasb.org/extlink&oid=120395691&loc=d3e23780-122690

+ Details

Summary of Significant Accounting Policies

12 Months Ended

Dec. 31, 2022

Accounting Policies [Abstract]

Summary of Significant Accounting Policies

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES

Principles of Consolidation

The accompanying consolidated financial statements include the accounts of the Company, Keros Australia and Keros Security Corporation. All intercompany accounts and transactions have been eliminated in consolidation.

Use of Estimates

may result in actual results differing materially from those estimated amounts used in the preparation of the financial statements if these results differ from historical experience, or other assumptions do not turn out to be substantially accurate, even if such assumptions are reasonable when made. Significant estimates and assumptions reflected in these consolidated financial statements include, but are not limited to, useful lives assigned to property and equipment, the fair values of common and preferred stock and the fair value of the preferred stock tranche obligation. The Company assesses estimates on an ongoing basis; however, actual results could materially differ from those estimates.

Fair Value Measurements

Certain assets and liabilities are reported on a recurring basis at fair value. Fair value is defined as the exchange price that would be received for an asset or paid to transfer a liability (an exit price) in the principal or most advantageous market for the asset or liability in an orderly transaction between market participants on the measurement date. Valuation techniques used to measure fair value must maximize the use of observable inputs and minimize the use of unobservable inputs. Financial assets and liabilities carried at fair value are to be classified and disclosed in one of the following three levels of the fair value hierarchy, of which the first two are considered observable and the last is considered unobservable:

Level 1—Quoted prices in active markets for identical assets or liabilities.

Level 2—Observable inputs (other than Level 1 quoted prices), such as quoted prices in active markets for similar assets or liabilities, quoted prices in markets that are not active for identical or similar assets or liabilities, or other inputs that are observable or can be corroborated by observable market data.

Level 3—Unobservable inputs that are supported by little or no market activity and that are significant to determining the fair value of the assets or liabilities, including pricing models, discounted cash flow methodologies and similar techniques.

To the extent that the valuation is based on models or inputs that are less observable or unobservable in the market, the determination of fair value requires more judgment. Accordingly, the degree of judgment exercised by the Company in determining fair value is greatest for instruments categorized in Level 3. A financial instrument’s level within the fair value hierarchy is based on the lowest level of any input that is significant to the fair value measurement.

An entity may choose to measure many financial instruments and certain other items at fair value at specified election dates. Subsequent unrealized gains and losses on items for which the fair value option has been elected will be reported in earnings. The Company had no financial instruments measured at level 3 as of December 31, 2022.

Cash, Cash Equivalents, and Restricted Cash

Cash and cash equivalents consist of standard checking accounts and money market funds. The Company considers all highly liquid investments with an original maturity of 90 days or less at the date of purchase to be cash equivalents.

The Company’s cash equivalents, which are funds held in a money market account, are measured at fair value on a recurring basis. The carrying amount of cash equivalents was $279.0 million and $230.0 million as of December 31, 2022 and 2021, respectively, which approximates fair value and was determined based upon Level 1 inputs. The money market account is valued using quoted market prices with no valuation adjustments applied and is categorized as Level 1.

The Company had restricted cash in the form of two certificates of deposit related to its two operating leases in Lexington, Massachusetts of $1.3 million each as of December 31, 2022 and 2021.

Concentrations of Credit Risk

Financial instruments that potentially subject the Company to significant concentration of credit risk consist primarily of cash and cash equivalents. The Company may maintain deposits in financial institutions in excess of government insured limits. The Company believes that it is not exposed to significant credit risk as its deposits are held at financial institutions that management believes to be of high credit quality and the Company has not experienced any losses on these deposits. As of December 31, 2022 and 2021, the Company’s cash and cash equivalents were held with three financial institutions. The Company believes that the market risk arising from its holdings of these financial instruments is mitigated based on the fact that many of these securities are either government-backed or of high credit rating.

Property and Equipment

Property and equipment are recorded at cost. Expenditures for repairs and maintenance are expensed as incurred. When assets are retired or disposed of, the assets and related accumulated depreciation are written off from the accounts, and any

resulting gain or loss is included in the determination of net loss. Depreciation is calculated using the straight-line method over the estimated useful lives of the related assets as follows:



			ESTIMATED USEFUL LIFE
Computer equipment and software			3 years
Laboratory equipment			5 years
Office furniture			5 years
Leasehold improvements			lesser of useful life or remaining lease term

Impairment of Long-Lived Assets

The Company evaluates its long-lived assets for impairment whenever events or changes in circumstances indicate that the carrying amount of an asset may not be recoverable. Recoverability of assets to be held and used is measured by a comparison of the carrying amount of an asset to future undiscounted net cash flows expected to be generated by the asset. If such assets are considered to be impaired, the impairment to be recognized is measured by the amount by which the carrying amount of the assets exceed the fair value of the assets. Assets to be disposed of are reported at the lower of the carrying amount or fair value less costs to sell. To date, no impairments have been recognized for these assets.

Leases

The Company accounts for its leases under Accounting Standards Codification (“ASC”) Topic 842, Leases (“ASC 842”). At the inception of an arrangement, the Company determines whether the arrangement is or contains a lease based on the unique facts and circumstances present in the arrangement. Leases with a term greater than 12 months are recognized on the balance sheet as ROU assets and current and non-current lease liabilities, as applicable. The Company has elected not to recognize on the balance sheet leases with terms of 12 months or less. The Company typically only includes an initial lease term in its assessment of a lease arrangement. Options to renew a lease are not included in the Company’s assessment unless there is reasonable certainty that the Company will renew. The Company monitors its material leases on a quarterly basis.

Operating lease liabilities and their corresponding ROU assets are recorded based on the present value of future lease payments over the expected remaining lease term. Lease cost for operating leases is recognized on a straight-line basis over the lease term as an operating expense. Certain adjustments to the ROU asset may be required for items such as lease prepayments or incentives received. The interest rate implicit in lease contracts is typically not readily determinable. As a result, the Company utilizes its incremental borrowing rate, which reflects the fixed rate at which the Company could borrow on a collateralized basis the amount of the lease payments in the same currency, for a similar term, in a similar economic environment. In transition to ASC 842, the Company utilized the remaining lease term of its lease in determining the appropriate incremental borrowing rate.

For all asset classes of its leases, the Company has elected to account for the lease and non-lease components together for existing classes of underlying assets.

Guarantees and Indemnifications

As permitted under Delaware law, the Company indemnifies its officers, directors, consultants and employees for certain events or occurrences that happen by reason of the relationship with, or position held at, the Company. Through December 31, 2022, the Company had not experienced any losses related to these indemnification obligations, and no claims were outstanding. The Company does not expect significant claims related to these indemnification obligations and, consequently, concluded that the fair value of these obligations is negligible, and no related liabilities have been established.

Research and Development Costs

Research and development costs are charged to expense as incurred. Research and development costs consist of expenses incurred in performing research and development activities, including salaries and benefits, materials and supplies, preclinical expenses, stock-based compensation expense, depreciation of equipment, contract services, facilities, and other outside expenses. Costs for external development activities are recognized based on an evaluation of the progress to completion of specific tasks using information provided to the Company by its vendors. Payments for these activities are based on the terms of the individual arrangements, which may differ from the pattern of costs incurred, and are reflected in the consolidated financial statements as prepaid expense or accrued research and development expense.

Nonrefundable advance payments for goods or services to be received in the future for use in research and development activities are recorded as prepaid expenses and expensed as the related goods are delivered or the services are performed.

Research and Development Incentive

Research and development incentive income includes payments under the Research and Development Tax Incentive (the “R&D Incentive”) from the Australian government. The R&D Incentive is one of the key elements of the Australian government’s support for Australia’s innovation system and was developed to assist businesses recover some of the costs of

undertaking research and development. Since July 1, 2021, the R&D Incentive has provided a non-refundable tax offset up to 16.5% above the Company’s underlying income tax rate, as the Company qualified as an eligible company with an aggregated turnover of more than $20.0 million per annum that engages in research and development activities.

The Company has assessed its research and development activities and expenditures to determine which activities and expenditures are likely to be eligible under the R&D Incentive. The Company estimates the non-refundable tax offset available to it based on available information at the time. This estimate is also reviewed by the Company’s external tax advisors on an annual basis.

Revenue Recognition

To date, the Company has earned revenue under the license agreement with Novo Nordisk A/S, which was terminated in October 2020, the license agreement with Neurona Therapeutics, Inc. (“Neurona”) (see Note 12) and the license agreement with Hansoh (Shanghai) Healthtech Co., Ltd. (“Hansoh”) (see Note 12).

The Company recognizes revenue in accordance with ASC Topic 606, Revenue from Contracts with Customers (“ASC 606”). The Company enters into certain agreements that are within the scope of ASC 606, under which the Company licenses, may license or grants an option to license rights to certain of the Company’s product candidates and performs research and development services in connection with such arrangements. The terms of these arrangements typically include payment of one or more of the following: non-refundable, upfront fees; reimbursement of research and development costs; development, clinical, regulatory and commercial sales milestone payments, and royalties on net sales of licensed products.

Under ASC 606, an entity recognizes revenue when its customer obtains control of promised goods or services, in an amount that reflects the consideration which the entity expects to receive in exchange for those goods or services. To determine the appropriate amount of revenue to be recognized for arrangements determined to be within the scope of ASC 606, the Company performs the following five steps: (i) identification of the promised goods or services in the contract; (ii) determination of whether the promised goods or services are performance obligations including whether they are distinct; (iii) measurement of the transaction price, including the constraint on variable consideration; (iv) allocation of the transaction price to the performance obligations; and (v) recognition of revenue when (or as) the Company satisfies each performance obligation. The Company only applies the five-step model to contracts when it is probable that the entity will collect consideration it is entitled to in exchange for the goods or services it transfers to the customer.

The promised goods or services in the Company’s arrangements typically consist of a license, or option to license, rights to the Company’s intellectual property or research and development services. The Company provides options to additional items in such arrangements, which are accounted for as separate contracts when the customer elects to exercise such options, unless the option provides a material right to the customer. Performance obligations are promised goods or services in a contract to transfer a distinct good or service to the customer and are considered distinct when (i) the customer can benefit from the good or service on its own or together with other readily available resources and (ii) the promised good or service is separately identifiable from other promises in the contract. In assessing whether promised goods or services are distinct, the Company considers factors such as the stage of development of the underlying intellectual property, the capabilities of the customer to develop the intellectual property on its own or whether the required expertise is readily available and whether the goods or services are integral or dependent to other goods or services in the contract.

The Company estimates the transaction price based on the amount expected to be received for transferring the promised goods or services in the contract. The consideration may include fixed consideration and variable consideration. At the inception of each arrangement that includes variable consideration, the Company evaluates the amount of potential payment and the likelihood that the payments will be received. The Company utilizes either the most likely amount method or expected value method to estimate the amount expected to be received based on which method best predicts the amount expected to be received. The amount of variable consideration that is included in the transaction price may be constrained and is included in the transaction price only to the extent that it is probable that a significant reversal in the amount of the cumulative revenue recognized will not occur in a future period.

The Company’s contracts often include development and regulatory milestone payments that are assessed under the most likely amount method and constrained if it is probable that a significant revenue reversal would occur. Milestone payments that are not within the Company’s control or the licensee’s control, such as regulatory approvals, are not considered probable of being achieved until those approvals are received. At the end of each reporting period, the Company re-evaluates the probability of achievement of such development and clinical milestones and any related constraint, and if necessary, adjusts

its estimate of the overall transaction price. Any such adjustments are recorded on a cumulative catch-up basis, which would affect collaboration and other research and development revenue in the period of adjustment.

For arrangements that include sales-based royalties, including milestone payments based on the level of sales, and the license is deemed to be the predominant item to which the royalties relate, the Company recognizes revenue at the later of (i) when the related sales occur, or (ii) when the performance obligation to which some or all of the royalty has been allocated has been satisfied (or partially satisfied). To date, the Company has not recognized any royalty revenue resulting from any of the Company’s collaboration or strategic alliance arrangements.

The Company allocates the transaction price based on the estimated standalone selling price. The Company must develop assumptions that require judgment to determine the stand-alone selling price for each performance obligation identified in the contract. The Company utilizes key assumptions to determine the stand-alone selling price, which may include other comparable transactions, pricing considered in negotiating the transaction and the estimated costs. Variable consideration is allocated specifically to one or more performance obligations in a contract when the terms of the variable consideration relate to the satisfaction of the performance obligation and the resulting amounts allocated are consistent with the amounts the Company would expect to receive for the satisfaction of each performance obligation.

The consideration allocated to each performance obligation is recognized as revenue when control is transferred for the related goods or services. For performance obligations which consist of licenses and other promises, the Company utilizes judgment to assess the nature of the combined performance obligation to determine whether the combined performance obligation is satisfied over time or at a point in time and, if over time, the appropriate method of measuring progress. The Company evaluates the measure of progress each reporting period and, if necessary, adjusts the measure of performance and related revenue recognition.

The Company receives payments from its customers based on billing schedules established in each contract. Upfront payments and fees are recorded as deferred revenue upon receipt or when due until the Company performs its obligations under these arrangements. Amounts are recorded as accounts receivable when the Company’s right to consideration is unconditional.

Foreign Currency Transactions

The functional currency for the Company’s wholly owned foreign subsidiary, Keros Australia, is the United States dollar. All foreign currency transaction gains and losses are recognized in the consolidated statement of operations.

Segment Information

Operating segments are identified as components of an enterprise about which separate discrete financial information is made available for evaluation by the chief operating decision maker (“CODM”) in making decisions regarding resource allocation and assessing performance. The CODM is the Company’s chief executive officer. The Company manages its operations as a single segment for the purposes of assessing performance and making operating decisions. The Company’s singular concentration is focused on the discovery and development of breakthrough therapeutics for hematological, pulmonary and cardiovascular disorders with high unmet medical need.

Stock-Based Compensation

The Company accounts for all stock-based payment awards granted to employees and non-employees as stock-based compensation expense at fair value. The Company’s stock-based payments include stock options and grants of common stock, including common stock subject to vesting. The measurement date for employee awards is the date of grant, and stock-based compensation costs are recognized as expense over the employees’ requisite service period, which is the vesting period, on a straight-line basis. Stock-based compensation costs for non-employees are recognized as expense over the vesting period on a straight-line basis. Stock-based compensation expense is classified in the accompanying consolidated statement of operations based on the function to which the related services are provided. The Company recognizes stock-based compensation expense for the portion of awards that have vested. Forfeitures are recorded as they occur.

The fair value of each stock option grant is estimated on the date of grant using the Black-Scholes option-pricing model. The Company lacks company-specific historical and implied volatility information. Therefore, it estimates its expected stock volatility based on the historical volatility of a publicly traded set of peer companies and expects to continue to do so until such time as it has adequate historical data regarding the volatility of its own traded stock price. The expected term of the Company’s stock options has been determined utilizing the “simplified” method for awards that qualify as “plain-vanilla” options. The risk-free interest rate is determined by reference to the U.S. Treasury yield curve in effect at the time of grant of the award for time periods approximately equal to the expected term of the award. Expected dividend yield is based on the fact that the Company has never paid cash dividends on common stock and does not expect to pay any cash dividends in the foreseeable future.

Income Taxes

The Company recognizes deferred tax assets and liabilities for the expected future tax consequences of events that have been included in the Company’s consolidated financial statements and tax returns. Deferred tax assets and liabilities are determined based upon the differences between the financial statement carrying amounts and the tax bases of existing assets and liabilities and for loss and credit carryforwards, using enacted tax rates expected to be in effect in the year in which the differences are expected to reverse. Deferred tax assets are reduced by a valuation allowance if it is more likely than not that these assets may not be realized. The Company determines whether it is more likely than not that a tax position will be sustained upon examination. If it is not more likely than not that a position will be sustained, none of the benefit attributable to the position is recognized. The tax benefit to be recognized for any tax position that meets the more-likely-than-not recognition threshold is calculated as the largest amount that is more than 50% likely of being realized upon resolution of the contingency. The Company accounts for interest and penalties related to uncertain tax positions as part of its provision for income taxes.

Comprehensive Loss

Comprehensive loss is defined as the change in equity of a business enterprise during a period from transactions and other events and circumstances from non-owner sources. Comprehensive loss is equal to net loss for all periods presented.

Net Loss Per Share

Basic net loss per share and diluted net loss per share are computed using the weighted-average number of shares of common stock outstanding for the period. Net loss per share attributable to common stockholders is calculated using the two-class method, which is an earnings allocation formula that determines net loss per share for the holders of shares of the Company’s common stock and participating securities. The Company’s preferred stock contains participation rights in any dividend paid by the Company and is deemed to be a participating security. The participating securities do not include a contractual obligation to share in losses of the Company and are not included in the calculation of net loss per share in the periods in which a net loss is recorded.

Diluted net loss per share is computed using the more dilutive of (a) the two-class method or (b) the if-converted method. The Company allocates earnings first to preferred stockholders based on dividend rights and then to common and preferred stockholders based on ownership interests. The weighted-average number of shares of common stock included in the computation of diluted net loss gives effect to all potentially dilutive common stock equivalent shares, including outstanding stock options and preferred stock.

The Company’s potentially dilutive securities, which include stock options, have been excluded from the computation of diluted net loss per share as the effect would be to reduce the net loss per share. Therefore, the weighted-average number of common shares outstanding used to calculate both basic and diluted net loss per share attributable to common stockholders is the same. The Company excluded the following from the computation of diluted net loss per share attributable to common stockholders as of December 31, 2022 and 2021, because including them would have had an anti-dilutive effect:



	DECEMBER 31,
	2022	2021


Options to purchase common stock	3,533,169	2,810,684
	3,533,169	2,810,684

Recently Adopted Accounting Pronouncements

On January 1, 2021, the Company adopted Financial Accounting Standards Board Accounting Standards Update No. 2019-12, Income Taxes Simplifying the Accounting for Income Taxes ("ASU No. 2019-12"). ASU No. 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. ASU No. 2019-12 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. The adoption of this standard did not have an impact on the Company’s consolidated financial statements and related disclosures.

Risks and Uncertainties

As a result of the continuing global COVID-19 pandemic, the Company has implemented business continuity plans designed to address and mitigate the impact of the COVID-19 pandemic on its employees and its business operations, including its preclinical studies and clinical trials, supply chains and third-party providers. The Company anticipates that the COVID-19 pandemic will continue to have an impact on the development timelines for several of its preclinical and clinical programs. The extent to which the COVID-19 pandemic impacts the Company’s business, its clinical development and regulatory efforts, its corporate development objectives and the value of and market for its common stock will depend on future developments which are highly uncertain and cannot be predicted with confidence at this time, such as the ultimate duration of the pandemic, particularly in light of variant strains of the COVID-19 virus, travel restrictions, quarantines, social distancing

and business closure requirements in the United States, Australia, New Zealand, Europe, the United Kingdom, South Korea and other countries and the effectiveness of actions taken globally to contain and treat the disease. The global economic slowdown, manufacturing and supply chain issues, the overall disruption of global healthcare systems and the other risks and uncertainties associated with the pandemic could have a material adverse effect on the Company’s business, financial condition, results of operations and growth prospects. As of the date of issuance of these financial statements, the Company is not aware of any specific event or circumstance that would require the Company to update its estimates, assumptions and judgments or revise the carrying value of its assets or liabilities. Actual results could differ from those estimates, and any such differences may be material to the Company’s financial statements.

In addition, the Company is subject to other challenges and risks specific to its business and its ability to execute on its business plan and strategy, as well as risks and uncertainties common to companies in the biopharmaceutical industry with research and development operations, including, without limitation, risks and uncertainties associated with: obtaining regulatory approval of its product candidates; delays or problems in obtaining clinical supply, loss of single source suppliers or failure to comply with manufacturing regulations; product development and the inherent uncertainty of clinical success; the challenges of protecting and enhancing its intellectual property rights; the challenges of complying with applicable regulatory requirements; and identifying, acquiring or in-licensing additional products or product candidates. In addition, to the extent the ongoing COVID-19 pandemic adversely affects the Company’s business and results of operations, it may also have the effect of heightening many of the other risks and uncertainties discussed above.

Stock-Based Compensation

12 Months Ended

Dec. 31, 2022

Share-Based Payment Arrangement [Abstract]

Stock-Based Compensation

STOCK-BASED COMPENSATION

2017 Stock Incentive Plan

The Board adopted the 2017 Stock Incentive Plan (the "2017 Plan") in February 2017, and the stockholders approved the 2017 Plan in March 2017. The 2017 Plan was most recently amended in March 2020.

As of December 31, 2022, there were an aggregate of 584,646 shares of common stock issuable upon the exercise of outstanding options under the 2017 Plan. Any options or awards outstanding under the 2017 Plan remain outstanding and effective.

2020 Equity Incentive Plan

In April 2020, the 2020 Equity Incentive Plan (the "2020 Plan") became effective, and, as a result, no further awards will be made under the 2017 Plan. The 2020 Plan provides for the grant of stock options qualifying as incentive stock options ("ISOs"), to employees and for the grant of nonstatutory stock options ("NSOs"), restricted stock awards, restricted stock unit awards, stock appreciation rights, performance stock awards and other forms of stock compensation to employees, consultants and directors. The 2020 Plan also provides for the grant of performance cash awards to employees, consultants and directors. Any previously granted awards under the 2017 Plan will remain outstanding in accordance with their respective terms.

Under the 2020 Plan, there is an annual increase on January 1 of each year from January 1, 2021 continuing through January 1, 2030, by 4.0% of the total number of shares of common stock outstanding on December 31 of the preceding calendar year, or a lesser number of shares as may be determined by the Board. On January 1, 2022, the Company increased the number of shares available for future grant under the 2020 Plan by 958,993 shares. On January 1, 2023, the Company increased the number of shares available for future grant under the 2020 Plan by 1,101,738 shares. The awards granted under the 2020 Plan typically vest over a four-year period and have a 10-year contractual term.

As of December 31, 2022, there were an aggregate of 2,948,523 shares of common stock issuable upon the exercise of outstanding options under the 2020 Plan. Additionally, there were an aggregate of 972,377 shares reserved for future issuance under the 2020 Plan, including shares forfeited from the 2017 Plan.

Stock Option Valuation

The assumptions that the Company used in the Black-Scholes option-pricing model to determine the grant-date fair value of stock options granted for the years ended December 31, 2022 and 2021 were as follows:



	YEAR ENDED DECEMBER 31,
	2022			2021
Weighted-average risk-free interest rate	2.24		%	0.88		%
Expected term (in years)	6.06			6.05
Expected volatility	83.03		%	83.00		%
Expected dividend yield	0.00		%	0.00		%
Fair value of underlying common stock	$	31.18		$	42.29

A summary of option activity during the years ended December 31, 2022 and 2021 is as follows (in thousands except share and per share data):



	NUMBER OF OPTIONS	WEIGHTED- AVERAGE EXERCISE PRICE		WEIGHTED-AVERAGE REMAINING CONTRACTUAL TERM (IN YEARS)	AGGREGATE INTRINSIC VALUE
Outstanding as of January 1, 2022	2,810,684	$	24.62	8.11	$	100,009
Granted	1,086,458	43.66
Exercised	(158,235)	5.17			$	5,637
Cancelled or forfeited	(195,428)	42.44
Expired	(10,310)	(59.46)
Outstanding as of December 31, 2022	3,533,169	$	30.26	7.77	$	72,434

Options vested as of December 31, 2022	1,749,888	$	19.59	6.93	$	53,895
Options unvested as of December 31, 2022	1,783,281	$	40.72

The aggregate intrinsic value of stock options is calculated as the difference between the exercise price of the stock options and the fair value of the Company’s common stock for those stock options that had exercise prices lower than the fair value of the Company’s common stock.

The weighted-average grant date fair value price per share of options granted during each of the years ended December 31, 2022 and 2021 was $31.18 and $42.29, respectively. As of December 31, 2022, there was $44.4 million of unrecognized stock-based compensation expense related to unvested stock options. The unrecognized stock-based compensation expense is estimated to be recognized over a period of 2.51 years.

The total fair value of options vested during the years ended December 31, 2022 and 2021 was $16.5 million and $10.1 million, respectively.

Stock-Based Compensation Expense

Total stock-based compensation expense recorded as research and development and general and administrative expenses, respectively, for employees, directors and non-employees during the years ended December 31, 2022 and 2021 is as follows (in thousands):



	YEAR ENDED DECEMBER 31,
	2022		2021
Research and development	$	8,205	$	4,258
General and administrative	10,477		7,464
Total stock-based compensation expense	$	18,682	$	11,722

Summary of Significant Accounting Policies - Schedule of Property and Equipment (Details)	12 Months Ended
	Dec. 31, 2022
Computer equipment and software
Property, Plant and Equipment [Line Items]
Estimated useful life	3 years
Laboratory equipment
Property, Plant and Equipment [Line Items]
Estimated useful life	5 years
Office furniture
Property, Plant and Equipment [Line Items]
Estimated useful life	5 years

Fair Value Measurements - Schedule of Fair Value, Assets and Liabilities Measured on Recurring Basis (Details) - USD ($) $ in Thousands	Dec. 31, 2022	Dec. 31, 2021
Asset
Money market funds	$ 279,000	$ 230,000
Fair Value, Recurring
Asset
Money market funds	271,734	230,042
Total financial assets	271,734	230,042
Fair Value, Recurring \| QUOTED PRICES ACTIVE MARKETS FOR IDENTICAL ASSETS (LEVEL 1)
Asset
Money market funds	271,734	230,042
Total financial assets	271,734	230,042
Fair Value, Recurring \| SIGNIFICANT OTHER OBSERVABLE INPUTS (LEVEL 2)
Asset
Money market funds	0	0
Total financial assets	0	0
Fair Value, Recurring \| SIGNIFICANT OTHER OBSERVABLE INPUTS (LEVEL 3)
Asset
Money market funds	0	0
Total financial assets	$ 0	$ 0

Income Taxes (Tables)

12 Months Ended

Dec. 31, 2022

Income Tax Disclosure [Abstract]

Schedule of Loss Before Provision For (Benefit From) Income Taxes

Loss before provision from income taxes for the years ended December 31, 2022 and 2021 consisted of the following (in thousands):



	YEAR ENDED DECEMBER 31,
	2022		2021
United States	$	(112,240)	$	(55,961)
Foreign	7,561		(772)
Loss before provision from income taxes	$	(104,679)	$	(56,733)

Schedule of Components of Income Tax Expense (Benefit)

The components of income tax provision (benefit) for the years ended December 31, 2022 and 2021 consisted of the following (in thousands):



	YEAR ENDED DECEMBER 31,
	2022		2021
Current income tax provision (benefit):
Federal	$	—	$	—
State	—		11
Foreign	—		2,000
Total current income tax provision (benefit)	$	—	$	2,011
Total deferred income tax benefit	$	—	$	—
Total income tax provision (benefit)	$	—	$	2,011

Schedule of Reconciliation of U.S. Federal Statutory Income Tax Rate to Effective Income Tax Rate

A reconciliation of the U.S. federal statutory income tax rate to the Company’s effective income tax rate for the years ended December 31, 2022 and 2021 was as follows:



	YEAR ENDED DECEMBER 31,
	2022		2021
Federal income tax at statutory rate	21.0	%	21.0	%
State income tax, net of federal benefit	5.2		6.7
Stock compensation	(2.8)		(1.5)
Permanent differences	(1.4)		—

Research and development credits	2.5		4.8
Impact of foreign operations	(0.3)		(0.6)
Foreign withholding taxes	—		(2.8)
Other	(3.3)		(0.3)
Tax credits	3.2		—
Change in valuation allowance	(24.1)		(30.9)
Effective tax rate	—	%	(3.5)	%

Schedule of Net Deferred Tax Assets

Net deferred tax assets as of December 31, 2022 and 2021 consisted of the following (in thousands):



	YEAR ENDED DECEMBER 31,
	2022		2021
Net operating loss carryforwards	$	37,687	$	27,833
Research and development credits	10,459		6,315
Capitalized research and development expenses	10,822		—
Operating lease liability	3,602		298
Accrueds	1,275		597


Intangibles	115		127
Other	$	908	$	558
Total deferred tax assets	$	64,868	$	35,728
Valuation allowance	(60,650)		(35,445)
Net deferred tax assets	$	4,218	$	283
Deferred tax liability
Operating lease right-of-use asset	(4,218)		(283)

Net deferred tax assets (liability)	$	—	$	—

Commitments and Contingencies - Schedule of Maturity of Lease Liability (Details) - USD ($) $ in Thousands	Dec. 31, 2022	Dec. 31, 2021	Sep. 07, 2021
MATURITY OF LEASE LIABILITY
2023	$ 1,741
2024	2,202
2025	2,269
2026	2,337
2027	2,407
2028	2,479
2029	2,553
2030	2,630
2031	1,561
Total lease payments	20,179
Less: imputed interest	(6,913)
Total operating lease liabilities	13,266		$ 12,900
Included in the consolidated balance sheet:
Current portion of lease liabilities	455	$ 862
Lease liabilities	12,811	$ 231
Total operating lease liabilities	$ 13,266		$ 12,900

Prepaid Expenses and Other Current Assets

12 Months Ended

Dec. 31, 2022

Deferred Costs, Capitalized, Prepaid, and Other Assets Disclosure [Abstract]

Prepaid Expenses and Other Current Assets

PREPAID EXPENSES AND OTHER CURRENT ASSETS

Prepaid expenses and other current assets as of December 31, 2022 and 2021 consisted of the following (in thousands):



	DECEMBER 31,
	2022		2021
Prepaid service contracts	3,319		1,613
Income tax credit receivable	—		30
Prepaid sales tax	872		255
Prepaid rent	96		—
R&D payroll tax credit	—		167
Prepaid insurance	941		993
Prepaid subscriptions	470		130
Interest and dividend receivable	841		—
Other	180		210
Total prepaid expenses and other current assets	$	6,719	$	3,398

Consolidated Statements of Stockholders’ Equity (Parenthetical) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021
Preferred stock, par value (in USD per share)	$ 0.0001	$ 0.0001
At The Market Offering
Commissions and offering cost	$ 1,971	$ 475

Property and Equipment, Net - Schedule of Property and Equipment, Net (Details) - USD ($) $ in Thousands	Dec. 31, 2022	Dec. 31, 2021
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	$ 3,184	$ 2,181
Less: accumulated depreciation	(1,163)	(846)
Property and equipment, net	2,021	1,335
Computer equipment and software
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	35	41
Laboratory equipment
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	2,652	1,821
Office furniture
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	284	55
Leasehold improvements
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	$ 213	$ 264

Consolidated Balance Sheets - USD ($) $ in Thousands	Dec. 31, 2022	Dec. 31, 2021
CURRENT ASSETS:
Cash and cash equivalents	$ 279,048	$ 230,042
Accounts receivable	0	18,000
Prepaid expenses and other current assets	6,719	3,398
Total current assets	285,767	251,440
Operating lease right-of-use assets	15,548	1,067
Property and equipment, net	2,021	1,335
Restricted cash	1,327	1,327
Other long term assets	2,118	82
TOTAL ASSETS	306,781	255,251
CURRENT LIABILITIES:
Accounts payable	3,339	3,645
Current portion of operating lease liabilities	455	862
Accrued expenses and other current liabilities	12,753	7,339
Total current liabilities	16,547	11,846
Operating lease liabilities, net of current portion	12,811	231
Total liabilities	29,358	12,077
COMMITMENTS AND CONTINGENCIES (Note 11)
STOCKHOLDERS’ EQUITY:
Preferred stock, par value of $0.0001 per share; 10,000,000 shares authorized as of December 31, 2022 and December 31, 2021, respectively; no shares issued and outstanding	0	0
Common stock, par value of $0.0001 per share; 200,000,000 and 200,000,000 shares authorized as of December 31, 2022 and December 31, 2021, respectively; 27,543,453 and 23,974,834 shares issued and outstanding as of December 31, 2022 and December 31, 2021, respectively	2	2
Additional paid-in capital	505,855	366,927
Accumulated deficit	(228,434)	(123,755)
Total stockholders’ equity	277,423	243,174
TOTAL LIABILITIES AND STOCKHOLDERS’ EQUITY	$ 306,781	$ 255,251

Summary of Significant Accounting Policies (Policies)

12 Months Ended

Dec. 31, 2022

Accounting Policies [Abstract]

Basis of Accounting

The accompanying consolidated financial statements are prepared in conformity with accounting principles generally accepted in the United States of America (“U.S. GAAP”) and include the accounts of the Company and its wholly owned subsidiaries, Keros Therapeutics Australia Pty Ltd (“Keros Australia”) and Keros Security Corporation, a Massachusetts securities corporation.

Principles of Consolidation

Use of Estimates

The preparation of financial statements in conformity with U.S. GAAP requires management to make estimates and assumptions that affect the reported amounts of assets, liabilities, revenue, 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. This process may result in actual results differing materially from those estimated amounts used in the preparation of the financial statements if these results differ from historical experience, or other assumptions do not turn out to be substantially accurate, even if such assumptions are reasonable when made. Significant estimates and assumptions reflected in these consolidated financial statements include, but are not limited to, useful lives assigned to property and equipment, the fair values of common and preferred stock and the fair value of the preferred stock tranche obligation. The Company assesses estimates on an ongoing basis; however, actual results could materially differ from those estimates.

Fair Value Measurements

Level 1—Quoted prices in active markets for identical assets or liabilities.

Cash, Cash Equivalents, and Restricted Cash

Concentrations of Credit Risk

Property and Equipment

resulting gain or loss is included in the determination of net loss. Depreciation is calculated using the straight-line method over the estimated useful lives of the related assets as follows:



			ESTIMATED USEFUL LIFE
Computer equipment and software			3 years
Laboratory equipment			5 years
Office furniture			5 years
Leasehold improvements			lesser of useful life or remaining lease term

Impairment of Long-Lived Assets

Leases

For all asset classes of its leases, the Company has elected to account for the lease and non-lease components together for existing classes of underlying assets.

Guarantees and Indemnifications

Research and Development Costs

Research and Development Incentive and Income Taxes

The Company’s estimate of the cash refund it expects to receive related to the R&D Incentive is included in other assets in the accompanying consolidated balance sheet and such amounts are recorded as research and development incentive income in the statement of operations. The Company recognizes research and development incentive income when there is reasonable assurance that the income will be received, the relevant expenditure has been incurred, and the consideration can be reliably measured.The Company recognizes deferred tax assets and liabilities for the expected future tax consequences of events that have been included in the Company’s consolidated financial statements and tax returns. Deferred tax assets and liabilities are determined based upon the differences between the financial statement carrying amounts and the tax bases of existing assets and liabilities and for loss and credit carryforwards, using enacted tax rates expected to be in effect in the year in which the differences are expected to reverse. Deferred tax assets are reduced by a valuation allowance if it is more likely than not that these assets may not be realized. The Company determines whether it is more likely than not that a tax position will be sustained upon examination. If it is not more likely than not that a position will be sustained, none of the benefit attributable to the position is recognized. The tax benefit to be recognized for any tax position that meets the more-likely-than-not recognition threshold is calculated as the largest amount that is more than 50% likely of being realized upon resolution of the contingency. The Company accounts for interest and penalties related to uncertain tax positions as part of its provision for income taxes.

Revenue Recognition

Foreign Currency Transactions

Segment Information

Stock-Based Compensation

Comprehensive Loss

Net Loss Per Share



	DECEMBER 31,
	2022	2021


Options to purchase common stock	3,533,169	2,810,684
	3,533,169	2,810,684

Recently Adopted Accounting Pronouncements

Common Stock - Narrative (Details)			1 Months Ended	12 Months Ended
Common Stock - Narrative (Details)	Dec. 12, 2022 shares	May 03, 2021 USD ($)	May 31, 2021 USD ($)	Dec. 31, 2022 USD ($) vote $ / shares shares	Dec. 31, 2021 USD ($) $ / shares shares
Class of Stock [Line Items]
Common stock, shares authorized (in shares) \| shares				200,000,000	200,000,000
Common stock, par value (in USD per share) \| $ / shares				$ 0.0001	$ 0.0001
Number of votes per common share held \| vote				1
At The Market Offering
Class of Stock [Line Items]
Stock sales agreement, maximum amount authorized to be issued		$ 150,000,000	$ 150,000,000
Stock sales agreement, additional (in shares) \| shares	250,000,000
Issuance of common stock				$ 119,578,000	$ 28,171,000
Issuance costs				87,000	0
Common Stock \| At The Market Offering
Class of Stock [Line Items]
Proceeds from initial public offering, net of discounts and offering costs				$ 121,400,000	$ 28,600,000
Sale of stock, number of shares issued in transaction (in shares) \| shares				3,410,384	520,000
Sale of stock, price per share (in USD per share) \| $ / shares				$ 35.60	$ 55.00
Issuance of common stock				$ 119,400,000	$ 28,100,000
Sales agent commissions				1,800,000	400,000
Issuance costs				200,000	$ 100,000
Sale of stock, remaining authorized amount				250,000,000.0
Dividend Declared \| Common Stock
Class of Stock [Line Items]
Dividends payable				$ 0

Nature of Business and Basis of Presentation	12 Months Ended
Nature of Business and Basis of Presentation	Dec. 31, 2022
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Nature of Business and Basis of Presentation	Keros Therapeutics, Inc. (“Keros” or the “Company”) was incorporated in 2015 as a Delaware corporation. Its principal offices are in Lexington, Massachusetts. The Company is a clinical-stage biopharmaceutical company focused on the discovery, development and commercialization of novel treatments for patients suffering from hematological, pulmonary and cardiovascular disorders with high unmet medical need. The Company’s lead protein therapeutic product candidate, KER-050, is an engineered ligand trap comprised of a modified ligand-binding domain of the transforming growth factor-beta (“TGF-ß”) receptor known as activin receptor type IIA that is fused to the portion of the human antibody known as the Fc domain. KER-050 is being developed for the treatment of low blood cell counts (“cytopenias”), including anemia and thrombocytopenia, in patients with myelodysplastic syndromes (“MDS”) and in patients with myelofibrosis. The Company’s lead small molecule product candidate, KER-047, is designed to selectively and potently inhibit activin receptor-like kinase-2 (“ALK2”), a TGF-ß receptor. KER-047 is being developed for the treatment of functional iron deficiency which is a consequence of elevated ALK2 signaling, including the Company’s initial target, iron-refractory iron deficiency anemia (“IRIDA”). The Company’s third product candidate, KER-012, is designed to bind to and inhibit the signaling of TGF-ß ligands that stimulate smooth muscle hypertrophy and fibrosis, including activin A, activin B and myostatin (GDF8). KER-012 is being developed for the treatment of pulmonary arterial hypertension (“PAH”) and for the treatment of cardiovascular disorders. Since its inception in 2015, the Company has devoted the majority of its resources to business planning, research and development of its product candidates, including conducting clinical trials and preclinical studies, raising capital and recruiting management and technical staff to support these operations. To date, the Company has not generated any revenue from product sales as none of its product candidates have been approved for commercialization. In May 2021, the Company filed a registration statement on Form S-3, which was automatically effective upon filing (the “Shelf Registration Statement”). Pursuant to the Shelf Registration Statement, the Company could issue up to $150.0 million in common stock in sales deemed to be an “at the market offering,” as defined by the Securities Act, and, so long as the Company qualifies as a “well-known seasoned issuer” as defined in Rule 405 of the Securities Act, an unspecified amount of shares of the Company common stock, preferred stock, debt securities and warrants. In December 2022, the Company filed a prospectus supplement to the Shelf Registration Statement for the issuance and sale, if any, of up to an additional $250.0 million in common stock in sales deemed to be an “at the market offering,” as defined by the Securities Act. Liquidity and Capital Resources The Company’s consolidated financial statements have been prepared on the basis of the Company continuing as a going concern for the next 12 months. Management believes that the Company’s existing $279.0 million in cash and cash equivalents, will allow the Company to continue its operations for at least the next 12 months. In the absence of a significant source of recurring revenue, the continued viability of the Company beyond that point is dependent on its ability to continue to raise additional capital to finance its operations. If the Company is unable to obtain additional funding, the Company may be forced to delay, reduce or eliminate some or all of its research and development programs, product portfolio expansion or commercialization efforts, which could adversely affect its business prospects, or the Company may be unable to continue operations. The accompanying consolidated financial statements are prepared in conformity with accounting principles generally accepted in the United States of America (“U.S. GAAP”) and include the accounts of the Company and its wholly owned subsidiaries, Keros Therapeutics Australia Pty Ltd (“Keros Australia”) and Keros Security Corporation, a Massachusetts securities corporation.

Income Taxes - Schedule of Net Deferred Tax Assets (Details) - USD ($) $ in Thousands	Dec. 31, 2022	Dec. 31, 2021
Income Tax Disclosure [Abstract]
Net operating loss carryforwards	$ 37,687	$ 27,833
Research and development credits	10,459	6,315
Capitalized research and development expenses	10,822	0
Operating lease liability	3,602	298
Accrueds	1,275	597
Intangibles	115	127
Other	908	558
Total deferred tax assets	64,868	35,728
Valuation allowance	(60,650)	(35,445)
Net deferred tax assets	4,218	283
Deferred tax liability
Operating lease right-of-use asset	(4,218)	(283)
Net deferred tax assets (liability)	$ 0	$ 0

Cover - USD ($) $ in Millions	12 Months Ended
Cover - USD ($) $ in Millions	Dec. 31, 2022	Feb. 23, 2023	Jun. 30, 2022
Cover [Abstract]
Document Type	10-K
Document Annual Report	true
Document Period End Date	Dec. 31, 2022
Current Fiscal Year End Date	--12-31
Document Transition Report	false
Entity File Number	001-39264
Entity Registrant Name	KEROS THERAPEUTICS, INC.
Entity Incorporation, State or Country Code	DE
Entity Tax Identification Number	81-1173868
Entity Address, Address Line One	1050 Waltham Street,
Entity Address, Address Line Two	Suite 302
Entity Address, City or Town	Lexington,
Entity Address, State or Province	MA
Entity Address, Postal Zip Code	02421
City Area Code	617
Local Phone Number	314-6297
Title of 12(b) Security	Common Stock, $0.0001 par value per share
Trading Symbol	KROS
Security Exchange Name	NASDAQ
Entity Well-known Seasoned Issuer	No
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Accelerated Filer
Entity Small Business	false
Entity Emerging Growth Company	true
Entity Ex Transition Period	false
ICFR Auditor Attestation Flag	false
Entity Shell Company	false
Entity Public Float			$ 470.7
Entity Common Stock, Shares Outstanding		28,535,536
Documents Incorporated by Reference	DOCUMENTS INCORPORATED BY REFERENCE Portions of the registrant’s proxy statement to be filed with the Securities and Exchange Commission pursuant to Regulation 14A in connection with the registrant’s 2023 Annual Meeting of Stockholders, which will be filed subsequent to the date hereof, are incorporated by reference into Part III of this Form 10-K. Such proxy statement will be filed with the Securities and Exchange Commission not later than 120 days following the end of the registrant’s fiscal year ended December 31, 2022.
Entity Central Index Key	0001664710
Amendment Flag	false
Document Fiscal Year Period	FY
Document Fiscal Year Focus	2022

Subsequent Events (Details)	1 Months Ended	12 Months Ended
Subsequent Events (Details)	Jan. 31, 2023 USD ($) ft²	Dec. 31, 2022 USD ($)	May 01, 2023 ft²	Sep. 07, 2021 ft²
Waltham Lease
Subsequent Event [Line Items]
Area of rental space (sqft)				35,662
Operating lease term		8 years 4 months
Lessee, operating lease, monthly base rent \| $		$ 200,000
Percentage of annual increase in operating lease		3.00%
Subsequent Event \| Minimum
Subsequent Event [Line Items]
Lessee, operating lease, period after commencement date for which base rent is due	8 months
Subsequent Event \| Maximum
Subsequent Event [Line Items]
Lessee, operating lease, period after commencement date for which base rent is due	11 months
Subsequent Event \| Waltham Lease
Subsequent Event [Line Items]
Area of rental space (sqft)	31,991
Lessee, operating lease, monthly base rent \| $	$ 202,085
Percentage of annual increase in operating lease	3.00%
Lessee, operating lease, term of contract	8 years
Subsequent Event \| Waltham Lease \| Forecast
Subsequent Event [Line Items]
Area of rental space (sqft)			3,671

Consolidated Statements of Operations - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021
REVENUE:
Total revenue	$ 0	$ 20,100
OPERATING EXPENSES:
Research and development	(87,265)	(55,143)
General and administrative	(27,525)	(21,330)
Total operating expenses	(114,790)	(76,473)
LOSS FROM OPERATIONS	(114,790)	(56,373)
OTHER INCOME (EXPENSE), NET:
Interest expense, net	(1)	(4)
Research and development incentive income	7,081	0
Other income (expense), net	3,031	(356)
Total other income (expense), net	10,111	(360)
Loss before income taxes	(104,679)	(56,733)
Income tax provision	0	(2,011)
Net loss	(104,679)	(58,744)
Net loss attributable to common stockholders - basic	(104,679)	(58,744)
Net loss attributable to common stockholders - diluted	$ (104,679)	$ (58,744)
Net loss per share attributable to common stockholders - diluted (in dollars per share)	$ (4.15)	$ (2.52)
Net loss per share attributable to common stockholders - basic (in dollars per share)	$ (4.15)	$ (2.52)
Weighted-average common stock outstanding - basic (in shares)	25,241,030	23,333,914
Weighted-average common stock outstanding - diluted (in shares)	25,241,030	23,333,914

Stock-Based Compensation - Schedule of Stock Option Valuation (Details) - Stock Options - $ / shares	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Weighted-average risk-free interest rate	2.24%	0.88%
Expected term (in years)	6 years 21 days	6 years 18 days
Expected volatility	83.03%	83.00%
Expected dividend yield	0.00%	0.00%
Fair value of underlying common stock (in dollars per share)	$ 31.18	$ 42.29

Fair Value Measurements (Tables)

12 Months Ended

Dec. 31, 2022

Fair Value Disclosures [Abstract]

Schedule of Fair Value, Assets and Liabilities Measured on Recurring Basis




DESCRIPTION	DECEMBER 31, 2022		QUOTED PRICES ACTIVE MARKETS FOR IDENTICAL ASSETS (LEVEL 1)		SIGNIFICANT OTHER OBSERVABLE INPUTS (LEVEL 2)		SIGNIFICANT OTHER OBSERVABLE INPUTS (LEVEL 3)
Asset
Money market funds	$	271,734	$	271,734	$	—	$	—
Total financial assets	$	271,734	$	271,734	$	—	$	—




DESCRIPTION	DECEMBER 31, 2021		QUOTED PRICES ACTIVE MARKETS FOR IDENTICAL ASSETS (LEVEL 1)		SIGNIFICANT OTHER OBSERVABLE INPUTS (LEVEL 2)		SIGNIFICANT OTHER OBSERVABLE INPUTS (LEVEL 3)
Asset
Money market funds	$	230,042	$	230,042	$	—	$	—
Total financial assets	$	230,042	$	230,042	$	—	$	—

Revenue from Contracts with Customers (Details) - USD ($) $ in Thousands		3 Months Ended	12 Months Ended
	Apr. 05, 2016	Mar. 31, 2022	Dec. 31, 2022	Dec. 31, 2021
Disaggregation of Revenue [Line Items]
Research collaboration revenue			$ 0	$ 20,100
MGH \| License Agreement
Disaggregation of Revenue [Line Items]
Expiration period	10 years		10 years
License \| Neurona Therapeutics, Inc.
Disaggregation of Revenue [Line Items]
Research collaboration revenue				100
License \| Hansoh Shanghai Healthtech Co Ltd
Disaggregation of Revenue [Line Items]
Research collaboration revenue		$ 18,000
Revenue, remaining performance obligation, development milestones, variable consideration			$ 26,500
Revenue, remaining performance obligation, sales milestones, variable consideration amount			$ 144,000
Withholding taxes from upfront fee				2,000
Revenue from Contract with Customer, Including Assessed Tax				$ 20,000

Stock-Based Compensation - Narrative (Details) - USD ($) $ / shares in Units, $ in Millions			12 Months Ended
	Jan. 01, 2023	Jan. 01, 2022	Dec. 31, 2022	Dec. 31, 2021
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Options granted in period (in shares)			1,086,458
Fair value of underlying common stock (in shares)			$ 31.18	$ 42.29
Unrecognized stock-based compensation expense related to unvested stock options			$ 44.4
Total fair value of options vested during period			$ 16.5	$ 10.1
Stock Options
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unvested award, period for recognition			2 years 6 months 3 days
2017 Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of shares authorized (in shares)			584,646
2020 Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of shares authorized (in shares)			2,948,523
Annual percentage increase in shares authorized			4.00%
Number of additional shares authorized (in shares)		958,993
Vesting period		4 years
Contractual term		10 years
Number of shares available for future grants (in shares)			972,377
2020 Plan \| Subsequent Event
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of additional shares authorized (in shares)	1,101,738

Summary of Significant Accounting Policies - Schedule of Antidilutive Securities (Details) - shares	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of earnings per share (in shares)	3,533,169	2,810,684
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 (in shares)	3,533,169	2,810,684

Accrued Expenses and Other Current Liabilities

12 Months Ended

Dec. 31, 2022

Payables and Accruals [Abstract]

Accrued Expenses and Other Current Liabilities

ACCRUED EXPENSES AND OTHER CURRENT LIABILITIES

Accrued expenses and other current liabilities as of December 31, 2022 and 2021 consisted of the following (in thousands):



	DECEMBER 31,
	2022		2021
Accrued external R&D costs	$	2,429	$	861
Accrued external manufacturing costs	4,240		3,259
Accrued compensation and benefits	4,811		2,373
Accrued tax	50		110
Accrued legal and consultants	523		532
Other	700		204
Total accrued expenses and other current liabilities	$	12,753	$	7,339

Stock-Based Compensation (Tables)

12 Months Ended

Dec. 31, 2022

Share-Based Payment Arrangement [Abstract]

Schedule of Stock Option Valuation Assumptions



	YEAR ENDED DECEMBER 31,
	2022			2021
Weighted-average risk-free interest rate	2.24		%	0.88		%
Expected term (in years)	6.06			6.05
Expected volatility	83.03		%	83.00		%
Expected dividend yield	0.00		%	0.00		%
Fair value of underlying common stock	$	31.18		$	42.29

Schedule of Option Activity

A summary of option activity during the years ended December 31, 2022 and 2021 is as follows (in thousands except share and per share data):



	NUMBER OF OPTIONS	WEIGHTED- AVERAGE EXERCISE PRICE		WEIGHTED-AVERAGE REMAINING CONTRACTUAL TERM (IN YEARS)	AGGREGATE INTRINSIC VALUE
Outstanding as of January 1, 2022	2,810,684	$	24.62	8.11	$	100,009
Granted	1,086,458	43.66
Exercised	(158,235)	5.17			$	5,637
Cancelled or forfeited	(195,428)	42.44
Expired	(10,310)	(59.46)
Outstanding as of December 31, 2022	3,533,169	$	30.26	7.77	$	72,434

Options vested as of December 31, 2022	1,749,888	$	19.59	6.93	$	53,895
Options unvested as of December 31, 2022	1,783,281	$	40.72

Schedule of Stock-based Compensation Expense



	YEAR ENDED DECEMBER 31,
	2022		2021
Research and development	$	8,205	$	4,258
General and administrative	10,477		7,464
Total stock-based compensation expense	$	18,682	$	11,722

Accrued Expenses and Other Current Liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2022	Dec. 31, 2021
Payables and Accruals [Abstract]
Accrued external R&D costs	$ 2,429	$ 861
Accrued external manufacturing costs	4,240	3,259
Accrued compensation and benefits	4,811	2,373
Accrued tax	50	110
Accrued legal and consultants	523	532
Other	700	204
Total accrued expenses and other current liabilities	$ 12,753	$ 7,339

Commitments and Contingencies - Narrative (Details)	1 Months Ended	3 Months Ended	12 Months Ended
Commitments and Contingencies - Narrative (Details)	Mar. 31, 2017 USD ($)	Mar. 31, 2023	Dec. 31, 2022 USD ($)	Dec. 31, 2021 USD ($)	Sep. 30, 2021 USD ($)	Sep. 07, 2021 USD ($) ft²	Aug. 31, 2021 ft²	Aug. 31, 2019 ft²
Lessee, Lease, Description [Line Items]
Operating lease right-of-use assets			$ 15,548,000	$ 1,067,000		$ 15,400,000
Operating lease liability			13,266,000			$ 12,900,000
Restricted cash			1,327,000	1,327,000
Tenant improvements			$ 400,000
Renewal term			5 years
Total lease cost			$ 1,100,000	600,000
Cash paid for operating leases			$ 900,000	600,000
Weighted average remaining lease term			4 years
Weighted average discount rate			10.00%
Short-term expenses			$ 23,627	5,089
Certificates of Deposit
Lessee, Lease, Description [Line Items]
Restricted cash			100,000	$ 100,000
99 Hayden Lease
Lessee, Lease, Description [Line Items]
Area of rental space (sqft) \| ft²							15,622	10,417
Operating lease right-of-use assets					$ 700,000
Operating lease liability					$ 700,000
99 Hayden Lease \| Loans Payable
Lessee, Lease, Description [Line Items]
Loan from landlord	$ 200,000
Interest rate	8.00%
Repayments related to loan			65,000
99 Hayden Lease \| Loans Payable \| Interest Only
Lessee, Lease, Description [Line Items]
Debt instrument, term	18 months
99 Hayden Lease \| Loans Payable \| Principal and Interest
Lessee, Lease, Description [Line Items]
Debt instrument, term	3 years 6 months
Waltham Lease
Lessee, Lease, Description [Line Items]
Area of rental space (sqft) \| ft²						35,662
Lessee, operating lease, monthly base rent			$ 200,000
Percentage of annual increase in operating lease			3.00%
Letters of credit outstanding, amount			$ 1,200,000
Operating lease, period for improvement			8 years 4 months
Operating lease not yet commenced			$ 2,200,000
Vivarium Premises \| Forecast
Lessee, Lease, Description [Line Items]
Lessee, operating lease, period after commencement date for which base rent is due		4 months

Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021
CASH FLOWS FROM OPERATING ACTIVITIES:
Net loss	$ (104,679)	$ (58,744)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation expense	674	378
Loss on disposal of fixed asset	12	46
Stock-based compensation expense	18,682	11,722
Non-cash lease expense	941	520
Changes in operating assets and liabilities:
Accounts receivable	18,000	(18,000)
Prepaid expenses and other current assets	(3,321)	(1,548)
Other assets	(1,574)	0
Accounts payable	(408)	1,485
Right-of-use assets and operating lease liabilities	(3,711)	(597)
Accrued expenses and other current liabilities	5,322	2,652
Other liabilities	0	(62)
Net cash used in operating activities	(70,062)	(62,148)
CASH FLOWS FROM INVESTING ACTIVITIES:
Purchase of property and equipment	(1,241)	(1,024)
Net cash used in investing activities	(1,241)	(1,024)
CASH FLOWS FROM FINANCING ACTIVITIES:
Proceeds from exercise of stock options	818	379
Net cash provided by financing activities	120,309	28,550
NET (DECREASE) INCREASE IN CASH, CASH EQUIVALENTS AND RESTRICTED CASH	49,006	(34,622)
Cash, cash equivalents and restricted cash at beginning of year	231,369	265,991
Cash, cash equivalents and restricted cash at end of year	280,375	231,369
SUPPLEMENTAL DISCLOSURE OF CASH FLOW INFORMATION:
Property and equipment purchases still in accounts payable	75	11
Issuance cost still in accrued and accounts payable	63	75
Right-of-use assets obtained in exchange for operating lease obligation	15,423	0
Reconciliation of cash, cash equivalents and restricted cash
Cash and cash equivalents	279,048	230,042
Restricted cash	1,327	1,327
Total cash, cash equivalents and restricted cash	280,375	231,369
At The Market Offering
CASH FLOWS FROM FINANCING ACTIVITIES:
Proceeds from issuance of common stock, net of offering cost	119,578	28,171
Payment of issuance costs	$ (87)	$ 0

Common Stock (Tables)

12 Months Ended

Dec. 31, 2022

Equity [Abstract]

Schedule of Preferred Stock

As of December 31, 2022 and 2021, the Company has reserved the following shares of common stock for the potential exercise of stock options:



	DECEMBER 31,
	2022	2021


Options to purchase common stock	3,533,169	2,810,684
Total	3,533,169	2,810,684

- Definition

Tabular disclosure of an entity's stock, including par or stated value per share, number and dollar amount of share subscriptions, shares authorized, shares issued, shares outstanding, number and dollar amount of shares held in an employee trust, dividend per share, total dividends, share conversion features, par value plus additional paid in capital, the value of treasury stock and other information necessary to a fair presentation, and EPS information. Stock by class includes common, convertible, and preferred stocks which are not redeemable or redeemable solely at the option of the issuer. Includes preferred stock with redemption features that are solely within the control of the issuer and mandatorily redeemable stock if redemption is required to occur only upon liquidation or termination of the reporting entity. If more than one issue is outstanding, state the title of each issue and the corresponding dollar amount; dollar amount of any shares subscribed but unissued and the deduction of subscriptions receivable there from; number of shares authorized, issued, and outstanding.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section 45
-Paragraph 2
-URI https://asc.fasb.org/extlink&oid=65888546&loc=d3e21300-112643

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02(28))
-URI https://asc.fasb.org/extlink&oid=120391452&loc=d3e13212-122682

Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section 50
-Paragraph 10
-URI https://asc.fasb.org/extlink&oid=126973232&loc=d3e21553-112644

Reference 4: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 480
-SubTopic 10
-Section S99
-Paragraph 1
-URI https://asc.fasb.org/extlink&oid=122040564&loc=d3e177068-122764

Reference 5: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section 50
-Paragraph 8
-URI https://asc.fasb.org/extlink&oid=126973232&loc=d3e21538-112644

Reference 6: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section 50
-Paragraph 7
-URI https://asc.fasb.org/extlink&oid=126973232&loc=d3e21521-112644

Reference 7: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02(29))
-URI https://asc.fasb.org/extlink&oid=120391452&loc=d3e13212-122682

Reference 8: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section 50
-Paragraph 5
-URI https://asc.fasb.org/extlink&oid=126973232&loc=d3e21488-112644

Reference 9: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.3-04)
-URI https://asc.fasb.org/extlink&oid=120397183&loc=d3e187085-122770

Reference 10: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section 50
-Paragraph 6
-URI https://asc.fasb.org/extlink&oid=126973232&loc=d3e21506-112644

Reference 11: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02(27))
-URI https://asc.fasb.org/extlink&oid=120391452&loc=d3e13212-122682

Reference 12: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section 50
-Paragraph 4
-URI https://asc.fasb.org/extlink&oid=126973232&loc=d3e21484-112644

Reference 13: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section 50
-Paragraph 3
-URI https://asc.fasb.org/extlink&oid=126973232&loc=d3e21475-112644

+ Details

Income Taxes - Schedule of Components of Income Tax Expense (Benefit) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021
Current income tax provision (benefit):
Federal	$ 0	$ 0
State	0	11
Foreign	0	2,000
Total current income tax provision (benefit)	0	2,011
Total deferred income tax benefit	0	0
Total income tax provision (benefit)	$ 0	$ 2,011

- Definition

Amount of current income tax expense (benefit) and deferred income tax expense (benefit) pertaining to continuing operations.

+ References + Details

Nature of Business and Basis of Presentation (Details) - USD ($)		1 Months Ended
	May 03, 2021	Dec. 31, 2022	May 31, 2021	Dec. 31, 2021
Class of Stock [Line Items]
Cash and cash equivalents		$ 279,048,000		$ 230,042,000
At The Market Offering
Class of Stock [Line Items]
Stock sales agreement, maximum amount authorized to be issued	$ 150,000,000		$ 150,000,000
Additional common shares		250,000,000

Commitments and Contingencies

12 Months Ended

Dec. 31, 2022

Commitments and Contingencies Disclosure [Abstract]

Commitments and Contingencies

COMMITMENTS AND CONTINGENCIES

Operating Leases

Operating lease liabilities are measured based on the present value of future lease payments over the expected remaining lease term. Right-of-use (“ROU”) assets represent the Company’s right to use an underlying asset for the lease term and are initially equal to their corresponding lease liabilities, subject to certain adjustments such as prepaid lease payments, initial direct costs and lease incentives. When the rate implicit in the lease is not readily determinable, the Company uses an incremental borrowing rate based on information available at the commencement date in determining the present value of lease payments. The incremental borrowing rate represents the rate of interest that the Company would have to pay to borrow on a collateralized basis over a similar term at an amount equal to the lease payments in a similar economic environment. The Company estimates this rate based on prevailing market conditions, comparable company and credit analyses, the impact of collateralization, and the term of each of the Company’s lease agreements.

In March 2017, the Company entered into a lease agreement (the “99 Hayden Lease”) with 99 Hayden LLC for its prior headquarters located in Lexington, Massachusetts. In July and August 2019, the Company entered into the first and second amendment, respectively, to its 99 Hayden Lease to expand the rental space to 10,417 square feet. In August 2021, the Company entered into a third amendment to its 99 Hayden Lease (the "Third Amendment") to extend the lease term through March 31, 2023 and to further expand the rental space to 15,622 square feet. The lease modification from the Third Amendment resulted in a non-cash increase to the Company's operating lease liabilities and right-of-use assets of $0.7 million in the quarter ended September 30, 2021. As required under the term of the 99 Hayden Lease as collateral for the 99 Hayden Lease, the Company had restricted cash of $0.1 million in the form of a certificate of deposit as of December 31, 2022 and 2021. The 99 Hayden Lease provides for scheduled annual rent increases throughout the lease term and does not include termination or purchase options. As part of the 99 Hayden Lease, the Company is obligated to pay certain variable payments related to its pro rata share of operating costs including taxes, utilities, and insurance premiums.

On September 7, 2021, the Company entered into an indenture of lease (the “1050 Waltham Lease”) with Revolution Labs Owner LLC (the “Landlord”), pursuant to which the Company is leasing approximately 35,662 square feet of office, laboratory and vivarium space located at 1050 Waltham Street, Lexington, Massachusetts (the “Premises”) for its new principal executive office. In December 2022, the Company received access to a portion of the Premises pertaining to the office and laboratory space (the “Initial Premises”) in order to begin getting it ready for use. Accordingly, the 1050 Waltham Lease for the Initial Premises, which is considered a distinct lease component, was determined to be classified as an operating lease and the Company recorded an ROU asset of $15.4 million and a lease liability of $12.9 million on the consolidated balance sheets. The portion of the Premises pertaining to the vivarium space (the “Vivarium Premises”) was not made available for use by the Landlord as improvement work was still in progress.The Company’s obligation for the payment of base rent for the Premises begins four months after the Landlord reaches substantial completion of all agreed upon improvements to the Premises (the “Rent Commencement Date”), which is currently expected to occur in the first quarter of 2023. Costs incurred for tenant improvements of $0.4 million are recorded as other long term assets on the consolidated balance sheets as they have been incurred prior to the Rent Commencement Date. Base rent will initially be fixed at $0.2 million per month and will increase by approximately 3% per annum. In connection with its entry into the 1050 Waltham Lease, the Company has provided the Landlord a letter of credit in the amount of approximately $1.2 million, which is recognized as restricted cash within other assets on the consolidated balance sheets. In accordance with the 1050 Waltham Lease, the Company is obligated to reimburse the Landlord for certain variable costs, including its proportional share of taxes and operating expenses which are not included in the measurement of the 1050 Waltham Lease. The 1050 Waltham Lease has a non-cancelable term of eight years and four months, measured from the date of completion of all Landlord required

improvements, and therefore, the 1050 Waltham Lease is currently expected to expire on July 31, 2031. The Company has the option to extend the term of the 1050 Waltham Lease for a period of an additional five years. As of December 31, 2022, the Company has no reasonable certainty that this option to extend will be exercised.

Total lease costs were $1.1 million and $0.6 million for the years ended December 31, 2022 and 2021, respectively. Cash paid for operating leases was $0.9 million and $0.6 million for the years ended December 31, 2022 and 2021, respectively. The weighted average remaining lease term is 4.0 years at December 31, 2022. The weighted average discount rate is 10.0%.

Maturities of operating lease liabilities at December 31, 2022 are as follows (in thousands):



MATURITY OF LEASE LIABILITY
2023	$	1,741
2024	2,202
2025	2,269
2026	2,337
2027	2,407
2028	2,479
2029	2,553
2030	2,630
2031	1,561
Total lease payments	20,179
Less: imputed interest	(6,913)
Total operating lease liabilities	$	13,266
Included in the consolidated balance sheet:
Current portion of lease liabilities	$	455
Lease liabilities	12,811
Total operating lease liabilities	$	13,266

The Vivarium Premises had not yet been made available to the Company as of December 31, 2022, therefore the commitment of $2.2 million, undiscounted, associated with this 1050 Waltham Lease component is not included in the table or values above. This Vivarium Premises component of the 1050 Waltham Lease is currently expected to commence in first half of 2023.

Short-term Leases

The Company enters into short-term leasing arrangements related to storage of clinical trial materials. For the year ended December 31, 2022, the Company engaged with a third-party vendor for master cell bank storage for various program trials, as well as extra space for additional storage for the Company’s lab equipment. The Company incurred $23,627 and $5,089 related to lease expense for the years ended December 31, 2022 and 2021, respectively.

Legal Proceedings

The Company is not a party to any litigation and does not have contingency reserves established for any litigation liabilities.

Other

In connection with the 99 Hayden Lease entered into in March 2017, the Company received a loan from the landlord of $0.2 million related to its tenant improvement allowance, which is recorded as a non-current liability in the Company’s consolidated balance sheets. The Company is required to repay interest only on the loan of 8.0% for the first 18 months of the 99 Hayden Lease and will then repay the full amount plus interest in installments over the remaining 3.5 year term of the 99 Hayden Lease. This loan expired in December 2022. The Company made payments totaling $65,000 related to the loan in 2022. There is no future payment obligation as of December 31, 2022.

Audit Information	12 Months Ended
Audit Information	Dec. 31, 2022
Audit Information [Abstract]
Auditor Firm ID	34
Auditor Name	Deloitte & Touche LLP
Auditor Location	Boston, Massachusetts

Commitments and Contingencies (Tables)

12 Months Ended

Dec. 31, 2022

Commitments and Contingencies Disclosure [Abstract]

Schedule of Maturity of Lease Liability

Maturities of operating lease liabilities at December 31, 2022 are as follows (in thousands):



MATURITY OF LEASE LIABILITY
2023	$	1,741
2024	2,202
2025	2,269
2026	2,337
2027	2,407
2028	2,479
2029	2,553
2030	2,630
2031	1,561
Total lease payments	20,179
Less: imputed interest	(6,913)
Total operating lease liabilities	$	13,266
Included in the consolidated balance sheet:
Current portion of lease liabilities	$	455
Lease liabilities	12,811
Total operating lease liabilities	$	13,266

Income Taxes - Schedule of Loss Before Provision For (Benefit From) Income Taxes (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021
Income Tax Disclosure [Abstract]
United States	$ (112,240)	$ (55,961)
Foreign	7,561	(772)
Loss before income taxes	$ (104,679)	$ (56,733)

- Definition

Amount of income (loss) from continuing operations, including income (loss) from equity method investments, before deduction of income tax expense (benefit), and income (loss) attributable to noncontrolling interest.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
-SubTopic 10
-Section 50
-Paragraph 32
-Subparagraph (c)
-URI https://asc.fasb.org/extlink&oid=126901519&loc=d3e8933-108599

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
-SubTopic 10
-Section 50
-Paragraph 30
-Subparagraph (b)
-URI https://asc.fasb.org/extlink&oid=126901519&loc=d3e8906-108599

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
-SubTopic 10
-Section 50
-Paragraph 32
-Subparagraph (f)
-URI https://asc.fasb.org/extlink&oid=126901519&loc=d3e8933-108599

Reference 4: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 940
-SubTopic 20
-Section 25
-Paragraph 1
-URI https://asc.fasb.org/extlink&oid=126941158&loc=d3e41242-110953

Reference 5: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
-SubTopic 10
-Section 50
-Paragraph 22
-URI https://asc.fasb.org/extlink&oid=126901519&loc=d3e8736-108599

Reference 6: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 220
-SubTopic 10
-Section S99
-Paragraph 2
-Subparagraph (SX 210.5-03(10))
-URI https://asc.fasb.org/extlink&oid=126953954&loc=SL114868664-224227

Reference 7: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 220
-Section S99
-Paragraph 1
-Subparagraph (SX 210.7-04(8))
-URI https://asc.fasb.org/extlink&oid=120400993&loc=SL114874131-224263

Reference 8: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 235
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-05(b)(2))
-URI https://asc.fasb.org/extlink&oid=120399901&loc=d3e537907-122884

Reference 9: http://www.xbrl.org/2003/role/exampleRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
-SubTopic 10
-Section 50
-Paragraph 31
-URI https://asc.fasb.org/extlink&oid=126901519&loc=d3e8924-108599

Reference 10: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 220
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-04(15))
-URI https://asc.fasb.org/extlink&oid=120399700&loc=SL114874048-224260

+ Details

Revenue from Contracts with Customers	12 Months Ended
Revenue from Contracts with Customers	Dec. 31, 2022
Revenue from Contract with Customer [Abstract]
Revenue from Contracts with Customers	REVENUE FROM CONTRACTS WITH CUSTOMERS Neurona License Agreement On June 22, 2021, the Company entered into a license agreement (the "Neurona Agreement") with Neurona. Under the Neurona Agreement, the Company granted Neurona a non-exclusive license to use LDN-193189, an early-stage research compound, which the Company licenses from a third party, solely as a reagent in connection with the manufacturing of diagnostic and/or therapeutic products to make, have made, use, import, offer for sale and sell products and services arising therefrom, and to make, have made, acquire, transfer, import and export the compound for such use. The license excludes Neurona from any rights to use, sell or distribute the compound for any therapeutic or diagnostic purpose. Unless terminated by either party for breach of contract or insolvency, the Neurona Agreement, which commenced on the execution date, will continue in perpetuity until the last patent expires. Under the Neurona Agreement, the Company was paid a one-time, upfront license payment of $0.1 million from Neurona as of December 31, 2021. In accordance with the Company's ASC 606 assessment, Neurona is considered to be a customer. The Company identified a single performance obligation, the non-exclusive license, that was satisfied on the date of the execution of the Neurona Agreement when control of the license was transferred. The Company determined that the upfront license fee of $0.1 million constitutes the entire transaction price and does not require further allocation as there was only one performance obligation. The Company determined that the $0.1 million represented the point at which the licensee was able to use and benefit from the license and recognized revenue from upfront license fees when the license was transferred to Neurona upon execution of the Neurona Agreement. The Company recognized the upfront fee as revenue on its consolidated statement of operations for the year ended December 31, 2021. Hansoh License Agreement In December 2021, the Company entered into a license agreement with Hansoh (the “Hansoh Agreement”). Under the Hansoh Agreement, the Company granted to Hansoh the exclusive right to develop, manufacture and commercialize KER-050 and licensed products containing KER-050 within the territories of mainland China, Hong Kong and Macau (the “Territory”). In connection with the Hansoh Agreement, Hansoh will purchase clinical trial supply of KER-050 from the Company, and the parties will also negotiate in good faith to enter into an agreement for commercial supply prior to any anticipated commercialization in the Territory. In addition, Hansoh will use commercially reasonable efforts to develop, obtain regulatory approval for, and commercialize licensed products in any region in the Territory. Pursuant to the Hansoh Agreement, the Company received a net one-time $18.0 million upfront license payment and will also be eligible to receive up to an aggregate of (i) $26.5 million upon the achievement of specified development milestones and (ii) $144.0 million upon the achievement of specified net sales thresholds for all licensed products in the Territory. If a licensed product is approved for marketing in the Territory, the Company will be entitled to receive royalty payments based on a tiered percentage of annual net sales in each region within the Territory, with such percentage ranging from the low double digit to high teens, subject to specified potential royalty reductions. Hansoh’s obligation to pay royalties for a given licensed product in a given region in the Territory will begin on the date of the first commercial sale for such licensed product in such region and continue until the latest of (i) 10 years from the date of the first commercial sale for such licensed product in such region, (ii) the expiration of the last valid claim of certain licensed patents or joint patents, and (iii) expiration of regulatory exclusivity in such region. During the royalty term, neither party will directly or indirectly commercialize a competing product in the Territory. The Hansoh Agreement will continue in force on a region-by-region basis until the expiration of the royalty term. Hansoh may terminate the Agreement in its entirety for convenience, with notice. The Company may terminate the Hansoh Agreement in its entirety for a patent challenge brought by Hansoh or its affiliates or their sublicensees. Either party may terminate the Hansoh Agreement in its entirety (i) if the other party materially breaches the Hansoh Agreement and fails to cure such breach or (ii) upon the bankruptcy of the other party. The Company evaluated the Hansoh Agreement and concluded that it was subject to ASC 606, as the Company viewed the Hansoh Agreement as a contract with a customer. As such, the Company assessed the terms of the Hansoh Agreement and identified a single performance obligation for the Company to provide Hansoh an exclusive license to develop, manufacture and commercialize KER-050 and licensed products containing KER-050 in the Territory, including the underlying know-how related to such licenses. All other promised goods/services were deemed immaterial in the context of the Hansoh Agreement. Under the Hansoh Agreement, Hansoh was obligated to pay a one-time, net $18.0 million payment to the Company, which was paid in the first quarter of 2022. The Company recognized a gross upfront fee of $20.0 million as revenue and $2.0 million in withholding tax on its consolidated statement of operations for the year ended December 31, 2021, and a receivable, net of withholding tax on its consolidated balance sheet as of December 31, 2021. The Company will recognize development milestone payments as revenue at the point in time when it is determined that it is probable such milestones will be achieved as all performance obligations will have been satisfied at the point which a milestone might occur (i.e., Hansoh will have assumed all responsibility for the activities under the Hansoh Agreement). The Company will recognize royalty payments and commercial milestone payments as the associated sales of licensed products are recorded by Hansoh, as they predominantly relate to the license granted with the Hansoh Agreement.

- Definition

The entire disclosure of revenue from contract with customer to transfer good or service and to transfer nonfinancial asset. Includes, but is not limited to, disaggregation of revenue, credit loss recognized from contract with customer, judgment and change in judgment related to contract with customer, and asset recognized from cost incurred to obtain or fulfill contract with customer. Excludes insurance and lease contracts.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-URI https://asc.fasb.org/topic&trid=49130388

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-SubTopic 10
-Section 50
-Paragraph 10
-URI https://asc.fasb.org/extlink&oid=126920106&loc=SL49130551-203045

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-SubTopic 10
-Section 50
-Paragraph 13
-Subparagraph (b)(2)
-URI https://asc.fasb.org/extlink&oid=126920106&loc=SL49130556-203045

Reference 4: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-SubTopic 10
-Section 50
-Paragraph 12
-Subparagraph (b)
-URI https://asc.fasb.org/extlink&oid=126920106&loc=SL49130554-203045

Reference 5: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-SubTopic 10
-Section 50
-Paragraph 9
-URI https://asc.fasb.org/extlink&oid=126920106&loc=SL49130550-203045

Reference 6: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-SubTopic 10
-Section 50
-Paragraph 12
-Subparagraph (e)
-URI https://asc.fasb.org/extlink&oid=126920106&loc=SL49130554-203045

Reference 7: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-SubTopic 10
-Section 50
-Paragraph 12
-Subparagraph (a)
-URI https://asc.fasb.org/extlink&oid=126920106&loc=SL49130554-203045

Reference 8: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-SubTopic 10
-Section 50
-Paragraph 12
-Subparagraph (d)
-URI https://asc.fasb.org/extlink&oid=126920106&loc=SL49130554-203045

Reference 9: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-SubTopic 10
-Section 50
-Paragraph 15
-URI https://asc.fasb.org/extlink&oid=126920106&loc=SL49130558-203045

Reference 10: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-SubTopic 10
-Section 50
-Paragraph 12
-Subparagraph (c)
-URI https://asc.fasb.org/extlink&oid=126920106&loc=SL49130554-203045

+ Details

Common Stock - Schedule of Preferred Stock (Details) - shares	Dec. 31, 2022	Dec. 31, 2021
Class of Stock [Line Items]
Common stock, reserved for future issuance (in shares)	3,533,169	2,810,684
Options to purchase common stock
Class of Stock [Line Items]
Common stock, reserved for future issuance (in shares)	3,533,169	2,810,684

Accrued Expenses and Other Current Liabilities (Tables)

12 Months Ended

Dec. 31, 2022

Payables and Accruals [Abstract]

Schedule of Accrued Expenses and Other Current Liabilities

Accrued expenses and other current liabilities as of December 31, 2022 and 2021 consisted of the following (in thousands):



	DECEMBER 31,
	2022		2021
Accrued external R&D costs	$	2,429	$	861
Accrued external manufacturing costs	4,240		3,259
Accrued compensation and benefits	4,811		2,373
Accrued tax	50		110
Accrued legal and consultants	523		532
Other	700		204
Total accrued expenses and other current liabilities	$	12,753	$	7,339

Consolidated Balance Sheets (Parenthetical) - $ / shares	Dec. 31, 2022	Dec. 31, 2021
Statement of Financial Position [Abstract]
Preferred stock, par value (in USD per share)	$ 0.0001	$ 0.0001
Preferred stock, shares authorized (in shares)	10,000,000	10,000,000
Preferred stock, shares issued (in shares)	0	0
Preferred stock, shares outstanding (in shares)	0	0
Common stock, par value (in USD per share)	$ 0.0001	$ 0.0001
Common stock, shares authorized (in shares)	200,000,000	200,000,000
Common stock, shares issued (in shares)	27,543,453	23,974,834
Common stock, shares outstanding (in shares)	27,543,453	23,974,834

Income Taxes - Schedule of Reconciliation of U.S. Federal Statutory Income Tax Rate to Effective Income Tax Rate (Details)	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021
Income Tax Disclosure [Abstract]
Federal income tax at statutory rate	21.00%	21.00%
State income tax, net of federal benefit	5.20%	6.70%
Stock compensation	(2.80%)	(1.50%)
Permanent differences	(1.40%)	0.00%
Research and development credits	2.50%	4.80%
Impact of foreign operations	(0.30%)	(0.60%)
Foreign withholding taxes	0.00%	(2.80%)
Other	(3.30%)	(0.30%)
Tax credits	3.20%	0.00%
Change in valuation allowance	(24.10%)	(30.90%)
Effective tax rate	0.00%	(3.50%)

License Agreements (Details) $ in Thousands		12 Months Ended
License Agreements (Details) $ in Thousands	Apr. 05, 2016 USD ($) shares	Dec. 31, 2022 product	Dec. 31, 2021 USD ($)	Dec. 31, 2020 USD ($)	Dec. 31, 2017 USD ($)	Dec. 31, 2016 USD ($)
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Payment for achievement of clinical and regulatory milestones			$ 300	$ 50
MGH \| License Agreement
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Initial license payment						$ 100
Reimbursement of prior patent prosecution expenses					$ 300
Sale of stock, number of shares issued in transaction (in shares) \| shares	358,674
Number of products \| product		3
Clinical and regulatory milestone payments	$ 8,600
Commercial milestone payments	$ 18,000
Royalty rate, maximum reduction	50.00%
Expiration period	10 years	10 years

Income Taxes - Narrative (Details) - USD ($) $ in Millions	12 Months Ended
Income Taxes - Narrative (Details) - USD ($) $ in Millions	Dec. 31, 2022	Dec. 31, 2021
Tax Credit Carryforward [Line Items]
Change in valuation allowance	$ 25.2	$ 17.5
In Process Research and Development
Tax Credit Carryforward [Line Items]
Research and development capitalized	44.3
Federal
Operating Loss Carryforwards [Line Items]
Net operating loss carryforwards	138.7
Tax Credit Carryforward [Line Items]
Net operating loss carryforwards written off in the current period	0.2
Operating loss carryforwards not subject to limitation	138.5
Operating loss carryforward, written off	0.3
Federal \| Research and Development Tax Credit
Tax Credit Carryforward [Line Items]
Tax credit carryforwards	6.0	4.3
State
Operating Loss Carryforwards [Line Items]
Net operating loss carryforwards	137.8
Tax Credit Carryforward [Line Items]
Operating loss carryforward, written off	0.3
State \| Research and Development Tax Credit
Tax Credit Carryforward [Line Items]
Tax credit carryforwards	3.5	$ 2.5
Foreign
Operating Loss Carryforwards [Line Items]
Net operating loss carryforwards	0.0
Foreign \| Research and Development Tax Credit
Tax Credit Carryforward [Line Items]
Tax credit carryforwards	$ 1.6