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SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES	6 Months Ended
SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES	Jun. 30, 2024
Accounting Policies [Abstract]
SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES	SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES Significant Accounting Policies The significant accounting policies and estimates used in preparation of the unaudited interim condensed consolidated financial statements are described in the Company’s audited consolidated financial statements as of and for the year ended December 31, 2023, and the notes thereto, which are included in the Annual Report. Except as detailed below, there have been no material changes to the Company’s significant accounting policies during the six months ended June 30, 2024. Stock-Based Compensation The Company accounts for all stock-based awards granted to employees and non-employees as stock-based compensation expense at fair value. The Company’s stock-based awards include stock options and performance-based stock options. The measurement date for employee and non-employee awards is the date of grant. For stock options that vest based on service conditions, stock-based compensation costs are recognized as expense over the requisite service period, which is the vesting period, on a straight-line basis. For stock options with performance conditions, stock-based compensation costs are recognized as expense using the accelerated attribution method when it is probable that the performance condition will be achieved. Stock-based compensation expense is classified in the accompanying consolidated statement of operations based on the function to which the related services are provided. 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 weighted with its own volatility for the period in which its stock has been publicly traded. 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. Recently Issued Accounting Pronouncements In November 2023, the FASB issued ASU 2023-07, Segment Reporting (Topic 280). The amendments in this update expand segment disclosure requirements, including new segment disclosure requirements for entities with a single reportable segment among other disclosure requirements. This update is effective for fiscal years beginning after December 15, 2023, and interim periods within fiscal years beginning after December 15, 2024. The Company is evaluating the impact of this standard on the Company’s consolidated financial statements. Risks and Uncertainties There have been significant disruptions to global financial markets that have contributed to a general global economic slowdown. While recent trends towards rising inflation have eased, prices continue to rise, which may materially affect the Company’s business and corresponding financial position and cash flows. Inflationary factors, such as increases in the cost of materials and supplies relating to the Company’s preclinical studies and clinical trials, interest rates and overhead costs may adversely affect its operating results. Rising interest rates present a recent challenge impacting the U.S. economy and could make it more difficult for the Company to obtain traditional financing on acceptable terms, if at all, in the future. Although the Company does not believe that inflation or higher interest rates have had a material impact on its financial position or results of operations to date, the Company may experience increases in the near future (especially if inflation rates rise more quickly) on its operating costs, including its labor costs and research and development costs, due to supply chain constraints, consequences associated with public health crises and global geopolitical tensions, such as the ongoing war between Russia and Ukraine and the war in Israel, worsening global macroeconomic conditions and employee availability and wage increases, which may result in additional stress on the Company’s working capital resources. 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.

Pay vs Performance Disclosure - USD ($) $ in Thousands	3 Months Ended				6 Months Ended
Pay vs Performance Disclosure - USD ($) $ in Thousands	Jun. 30, 2024	Mar. 31, 2024	Jun. 30, 2023	Mar. 31, 2023	Jun. 30, 2024	Jun. 30, 2023
Pay vs Performance Disclosure
Net loss	$ (45,257)	$ (43,114)	$ (37,505)	$ (35,804)	$ (88,371)	$ (73,309)

- Definition

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

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+ Details

Condensed Consolidated Balance Sheets - USD ($) $ in Thousands	Jun. 30, 2024	Dec. 31, 2023
CURRENT ASSETS:
Cash and cash equivalents	$ 405,863	$ 331,147
Accounts receivable	4	143
Prepaid expenses and other current assets	26,847	16,003
Total current assets	432,714	347,293
Operating lease right-of-use assets	14,649	15,334
Property and equipment, net	4,292	4,134
Restricted cash	1,212	1,212
Other long-term assets	2,155	2,052
TOTAL ASSETS	455,022	370,025
CURRENT LIABILITIES:
Accounts payable	6,535	5,450
Current portion of operating lease liabilities	1,096	1,005
Accrued expenses and other current liabilities	13,614	17,918
Total current liabilities	21,245	24,373
Operating lease liabilities, net of current portion	12,861	13,439
Total liabilities	34,106	37,812
STOCKHOLDERS' EQUITY:
Preferred stock, par value of $0.0001 per share; $10,000,000 shares authorized as of June 30, 2024 and December 31, 2023, respectively; no shares issued and outstanding	0	0
Common stock, par value of $0.0001 per share; 200,000,000 shares authorized as of June 30, 2024 and December 31, 2023; 36,169,558 and 31,841,084 shares issued and outstanding as of June 30, 2024 and December 31, 2023, respectively	3	3
Additional paid-in capital	890,710	713,636
Accumulated deficit	(469,797)	(381,426)
Total stockholders' equity	420,916	332,213
TOTAL LIABILITIES AND STOCKHOLDERS' EQUITY	$ 455,022	$ 370,025

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (Policies)	6 Months Ended
SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (Policies)	Jun. 30, 2024
Accounting Policies [Abstract]
Significant Accounting Policies	Significant Accounting Policies The significant accounting policies and estimates used in preparation of the unaudited interim condensed consolidated financial statements are described in the Company’s audited consolidated financial statements as of and for the year ended December 31, 2023, and the notes thereto, which are included in the Annual Report. Except as detailed below, there have been no material changes to the Company’s significant accounting policies during the six months ended June 30, 2024.
Stock-Based Compensation	Stock-Based Compensation The Company accounts for all stock-based awards granted to employees and non-employees as stock-based compensation expense at fair value. The Company’s stock-based awards include stock options and performance-based stock options. The measurement date for employee and non-employee awards is the date of grant. For stock options that vest based on service conditions, stock-based compensation costs are recognized as expense over the requisite service period, which is the vesting period, on a straight-line basis. For stock options with performance conditions, stock-based compensation costs are recognized as expense using the accelerated attribution method when it is probable that the performance condition will be achieved. Stock-based compensation expense is classified in the accompanying consolidated statement of operations based on the function to which the related services are provided. 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 weighted with its own volatility for the period in which its stock has been publicly traded. 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.
Recently Issued Accounting Pronouncements	Recently Issued Accounting Pronouncements In November 2023, the FASB issued ASU 2023-07, Segment Reporting (Topic 280). The amendments in this update expand segment disclosure requirements, including new segment disclosure requirements for entities with a single reportable segment among other disclosure requirements. This update is effective for fiscal years beginning after December 15, 2023, and interim periods within fiscal years beginning after December 15, 2024. The Company is evaluating the impact of this standard on the Company’s consolidated financial statements.

- Definition

Disclosure of accounting policy for award under share-based payment arrangement. Includes, but is not limited to, methodology and assumption used in measuring cost.

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+ Details

FAIR VALUE MEASUREMENTS

6 Months Ended

Jun. 30, 2024

Fair Value Disclosures [Abstract]

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	JUNE 30, 2024		QUOTED PRICES ACTIVE MARKETS FOR IDENTICAL ASSETS (LEVEL 1)		SIGNIFICANT OTHER OBSERVABLE INPUTS (LEVEL 2)		SIGNIFICANT OTHER OBSERVABLE INPUTS (LEVEL 3)
Assets
Money market funds	$	403,867	$	403,867	$	—	$	—
Total financial assets	$	403,867	$	403,867	$	—	$	—


DESCRIPTION	DECEMBER 31, 2023		QUOTED PRICES ACTIVE MARKETS FOR IDENTICAL ASSETS (LEVEL 1)		SIGNIFICANT OTHER OBSERVABLE INPUTS (LEVEL 2)		SIGNIFICANT OTHER OBSERVABLE INPUTS (LEVEL 3)
Assets
Money market funds	$	325,898	$	325,898	$	—	$	—
Total financial assets	$	325,898	$	325,898	$	—	$	—

There have been no transfers between fair value levels during the six months ended June 30, 2024. 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

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+ Details

PREPAID EXPENSES AND OTHER CURRENT ASSETS (Tables)

6 Months Ended

Jun. 30, 2024

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

Schedule of Prepaid Expenses and Other Current Assets

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


	JUNE 30, 2024		DECEMBER 31, 2023
Prepaid external R&D costs	$	18,374	$	10,116
Prepaid external manufacturing costs	3,720		2,303

Prepaid sales tax	776		429


Prepaid insurance	1,201		638
Prepaid subscriptions	853		568
Interest and dividend receivable	1,341		948
Other	582		1,001
Total prepaid expenses and other current assets	$	26,847	$	16,003

Condensed Consolidated Statements of Cash Flows - USD ($) $ in Thousands	3 Months Ended				6 Months Ended		12 Months Ended
	Jun. 30, 2024	Mar. 31, 2024	Jun. 30, 2023	Mar. 31, 2023	Jun. 30, 2024	Jun. 30, 2023	Dec. 31, 2023
CASH FLOWS FROM OPERATING ACTIVITIES:
Net loss	$ (45,257)	$ (43,114)	$ (37,505)	$ (35,804)	$ (88,371)	$ (73,309)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation expense					583	358
Loss on disposal of fixed asset					0	4
Stock-based compensation expense					16,855	12,728
Non-cash lease expense					685	876
Changes in operating assets and liabilities:
Accounts receivable					139	0
Prepaid expenses and other current assets					(10,844)	(5,563)
Other assets					(26)	0
Accounts payable					1,636	752
Right-to-use assets and operating lease liabilities					(564)	(109)
Accrued expenses and other current liabilities					(4,454)	(804)
Net cash used in operating activities					(84,361)	(65,067)
CASH FLOWS FROM INVESTING ACTIVITIES:
Purchase of property and equipment					(1,256)	(1,373)
Net cash used in investing activities					(1,256)	(1,373)
CASH FLOWS FROM FINANCING ACTIVITIES:
Payment of issuance costs					(283)	0
Proceeds from exercise of stock options					8,688	2,110
Net cash provided by financing activities					160,333	109,418
NET INCREASE IN CASH, CASH EQUIVALENTS AND RESTRICTED CASH					74,716	42,978
Cash, cash equivalents and restricted cash at beginning of period		$ 332,359		$ 280,375	332,359	280,375	$ 280,375
Cash, cash equivalents and restricted cash at end of period	407,075		323,353		407,075	323,353	332,359
SUPPLEMENTAL DISCLOSURE OF CASH FLOW INFORMATION:
Right-of-use assets obtained in exchange for operating lease obligation					0	1,338
Property and equipment purchases in accounts payable and accrued expenses					84	55
Issuance costs associated with the ATM agreement in accounts payable and accrued expenses					114	0
Reconciliation of cash, cash equivalents and restricted cash
Cash and cash equivalents	405,863		322,026		405,863	322,026	331,147
Restricted cash	1,212		1,327		1,212	1,327
Total cash, cash equivalents and restricted cash	$ 407,075		$ 323,353		407,075	323,353	$ 332,359
At the Market Offering
CASH FLOWS FROM FINANCING ACTIVITIES:
Proceeds from issuance of common stock, net of underwriting discounts					629	107,308
Payment of issuance costs associated with issuance of common stock under the ATM agreement					(41)	0
Common Stock Offering
CASH FLOWS FROM FINANCING ACTIVITIES:
Proceeds from issuance of common stock, net of underwriting discounts					$ 151,340	$ 0

ACCRUED EXPENSES AND OTHER CURRENT LIABILITIES

6 Months Ended

Jun. 30, 2024

Payables and Accruals [Abstract]

ACCRUED EXPENSES AND OTHER CURRENT LIABILITIES

Accrued expenses and other current liabilities consisted of the following (in thousands):


	JUNE 30, 2024		DECEMBER 31, 2023
Accrued external R&D costs	$	3,478	$	3,904
Accrued external manufacturing costs	3,545		5,288
Accrued compensation and benefits	5,313		7,542

Accrued legal and consulting fees	812		519
Other	466		665
Total accrued expenses and other current liabilities	$	13,614	$	17,918

Accrued compensation and benefits consisted primarily of accrued payroll and accrued vacation

STOCK-BASED COMPENSATION

6 Months Ended

Jun. 30, 2024

Share-Based Payment Arrangement [Abstract]

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 June 30, 2024, there was an aggregate of 500,485 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, 2024, the Company increased the number of shares available for future grant under the 2020 Plan by 1,273,643 shares. The awards granted under the 2020 Plan typically vest over a four-year period and have a 10-year contractual term.

As of June 30, 2024, there was an aggregate of 4,740,187 shares of common stock issuable upon the exercise of outstanding options under the 2020 Plan. Additionally, there were an aggregate of 1,114,824 shares reserved for future issuance under the 2020 Plan, including shares forfeited from the 2017 Plan.

Stock Options

A summary of option activity during the six months ended June 30, 2024 is as follows (in thousands except share and per share data):


	NUMBER OF OPTIONS	WEIGHTED-AVERAGE EXERCISE PRICE
Outstanding as of December 31, 2023	4,394,807	$	36.08
Granted	1,340,000	56.93
Exercised	(289,406)	30.02
Cancelled or Forfeited	(190,679)	50.00
Expired	(14,050)	$	59.13
Outstanding as of June 30, 2024	5,240,672	$	41.18

Options exercisable as of June 30, 2024	2,666,117	$	30.38

The summary of option activity includes performance-based stock options granted during the first quarter of 2024. There were no performance-based stock options granted during the second quarter of 2024. As of June 30, 2024, there has been no expense recognized for the performance-based stock options. The weighted-average grant date fair value price per share of options granted during the six months ended June 30, 2024 and 2023 was $40.62 and $36.96, respectively. As of June 30, 2024, there was $88.5 million of unrecognized stock-based compensation expense related to unvested stock options, including $4.9 million of unrecognized stock-based compensation expense related to unvested performance-based stock options. The unrecognized stock-based compensation expense is estimated to be recognized over a period of 2.7 years.

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 aggregate intrinsic value of the stock options outstanding and stock options exercisable was $54.4 million and $51.0 million as of June 30, 2024, respectively. The aggregate intrinsic value of stock options exercised was $7.3 million and $3.7 million during the six months ended June 30, 2024 and 2023, respectively.

Stock-Based Compensation Expense

Total stock-based compensation expense recorded for employees, directors and non-employees during the three and six months ended June 30, 2024 and 2023 was as follows (in thousands):


	THREE MONTHS ENDED JUNE 30,				SIX MONTHS ENDED JUNE 30,
	2024		2023		2024		2023
Research and development	$	4,624	$	3,363	$	8,526	$	6,021
General and administrative	4,161		3,678		8,329		6,707
Total stock-based compensation expense	$	8,785	$	7,041	$	16,855	$	12,728

Cover - shares	6 Months Ended
Cover - shares	Jun. 30, 2024	Jul. 31, 2024
Cover [Abstract]
Document Type	10-Q
Document Quarterly Report	true
Document Period End Date	Jun. 30, 2024
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 Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Large Accelerated Filer
Entity Small Business	false
Entity Emerging Growth Company	false
Entity Shell Company	false
Entity Common Stock, Shares Outstanding (in shares)		37,522,097
Amendment Flag	false
Document Fiscal Year Focus	2024
Document Fiscal Period Focus	Q2
Current Fiscal Year End Date	--12-31
Entity Central Index Key	0001664710

Condensed Consolidated Statements of Stockholders’ Equity - USD ($) $ in Thousands	Total	At the Market Offering	COMMON STOCK	COMMON STOCK At the Market Offering	ADDITIONAL PAID-IN CAPITAL	ADDITIONAL PAID-IN CAPITAL At the Market Offering	ACCUMULATED DEFICIT
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Ending balance (in shares)			27,543,453
Ending balance	$ 277,423		$ 2		$ 505,855		$ (228,434)
Beginning balance (in shares) at Dec. 31, 2022			27,543,453
Beginning balance at Dec. 31, 2022	277,423		$ 2		505,855		(228,434)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of common stock under the ATM agreement, net of commissions and offering costs (in shares)				1,990,927
Issuance of common stock under the ATM agreement, net of commissions and offering costs		$ 107,308		$ 1		$ 107,307
Exercise of common stock options (in shares)			14,269
Exercise of common stock options	370				370
Stock-based compensation	5,687				5,687
Net loss	(35,804)						(35,804)
Beginning balance (in shares) at Dec. 31, 2022			27,543,453
Beginning balance at Dec. 31, 2022	277,423		$ 2		505,855		(228,434)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net loss	(73,309)
Ending balance (in shares)			29,548,649
Ending balance	354,984		$ 3		619,219		(264,238)
Beginning balance (in shares) at Mar. 31, 2023			29,548,649
Beginning balance at Mar. 31, 2023	354,984		$ 3		619,219		(264,238)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Exercise of common stock options (in shares)			112,356
Exercise of common stock options	1,740				1,740
Stock-based compensation	7,041				7,041
Net loss	(37,505)						(37,505)
Ending balance (in shares)			29,661,005
Ending balance	326,260		$ 3		628,000		(301,743)
Ending balance (in shares)			31,841,084
Ending balance	332,213		$ 3		713,636		(381,426)
Beginning balance (in shares) at Dec. 31, 2023			31,841,084
Beginning balance at Dec. 31, 2023	332,213		$ 3		713,636		(381,426)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of common stock under the ATM agreement, net of commissions and offering costs (in shares)				4,025,000
Issuance of common stock under the ATM agreement, net of commissions and offering costs		151,057				151,057
Exercise of common stock options (in shares)			201,702
Exercise of common stock options	5,721				5,721
Stock-based compensation	8,070				8,070
Net loss	(43,114)						(43,114)
Beginning balance (in shares) at Dec. 31, 2023			31,841,084
Beginning balance at Dec. 31, 2023	$ 332,213		$ 3		713,636		(381,426)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Exercise of common stock options (in shares)	289,406
Net loss	$ (88,371)
Ending balance (in shares)			36,067,786
Ending balance	453,947		$ 3		878,484		(424,540)
Beginning balance (in shares) at Mar. 31, 2024			36,067,786
Beginning balance at Mar. 31, 2024	453,947		$ 3		878,484		(424,540)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of common stock under the ATM agreement, net of commissions and offering costs (in shares)				14,068
Issuance of common stock under the ATM agreement, net of commissions and offering costs		$ 474				$ 474
Exercise of common stock options (in shares)			87,704
Exercise of common stock options	2,967				2,967
Stock-based compensation	8,785				8,785
Net loss	(45,257)						(45,257)
Ending balance (in shares)			36,169,558
Ending balance	$ 420,916		$ 3		$ 890,710		$ (469,797)

- Definition

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

+ References

+ Details

- Definition

Equity impact of the value of new stock issued during the period. Includes shares issued in an initial public offering or a secondary public offering.

+ References + Details

- Definition

Amount of equity (deficit) attributable to parent. Excludes temporary equity and equity attributable to noncontrolling interest.

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+ Details

NATURE OF BUSINESS AND BASIS OF PRESENTATION (Details) - USD ($)		1 Months Ended
	May 03, 2021	Dec. 31, 2022	May 31, 2021	Jun. 30, 2024	Dec. 31, 2023	Jun. 30, 2023
Class of Stock [Line Items]
Cash and cash equivalents				$ 405,863,000	$ 331,147,000	$ 322,026,000
At the Market Offering
Class of Stock [Line Items]
Stock sales agreement, maximum amount authorized to be issued	$ 150,000,000	$ 250,000,000	$ 150,000,000.0

- Definition

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Reference 8: http://www.xbrl.org/2003/role/disclosureRef
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Reference 9: http://www.xbrl.org/2003/role/disclosureRef
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Reference 11: http://www.xbrl.org/2003/role/disclosureRef
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Reference 14: http://www.xbrl.org/2003/role/disclosureRef
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Reference 18: http://www.xbrl.org/2003/role/disclosureRef
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+ Details

Insider Trading Arrangements	3 Months Ended
Insider Trading Arrangements	Jun. 30, 2024
Trading Arrangements, by Individual
Rule 10b5-1 Arrangement Adopted	false
Non-Rule 10b5-1 Arrangement Adopted	false
Rule 10b5-1 Arrangement Terminated	false
Non-Rule 10b5-1 Arrangement Terminated	false

COMMON STOCK - Narrative (Details) - USD ($)					1 Months Ended		3 Months Ended			6 Months Ended		12 Months Ended
COMMON STOCK - Narrative (Details) - USD ($)	Jun. 17, 2024	Jan. 08, 2024	Dec. 12, 2022	May 03, 2021	Dec. 31, 2022	May 31, 2021	Jun. 30, 2024	Mar. 31, 2024	Mar. 31, 2023	Jun. 30, 2024	Jun. 30, 2023	Dec. 31, 2023
Class of Stock [Line Items]
Common stock, shares authorized (in shares)							200,000,000			200,000,000		200,000,000
Common stock, par value (in USD per share)							$ 0.0001			$ 0.0001	$ 0.0001	$ 0.0001
Common stock
Class of Stock [Line Items]
Sale of stock, number of shares issued in transaction (in shares)		4,025,000
Sale of stock, price per share (in USD per share)		$ 40.00
Proceeds from issuance of common stock, net of underwriting discounts		$ 151,100,000
At the Market Offering
Class of Stock [Line Items]
Stock sales agreement, maximum amount authorized to be issued				$ 150,000,000	$ 250,000,000	$ 150,000,000.0
Stock sales agreement, additional (in shares)	350,000,000.0		250,000,000
Proceeds from issuance of common stock, net of underwriting discounts										$ 629,000	$ 107,308,000
Commissions and offering cost							$ 164,000	$ 9,943,000	$ 1,665,000	200,000
At the Market Offering \| Common stock
Class of Stock [Line Items]
Proceeds from initial public offering, net of discounts and offering costs										$ 600,000		$ 178,500,000
Sale of stock, number of shares issued in transaction (in shares)										14,068		4,061,606
Sale of stock, price per share (in USD per share)							$ 45.39			$ 45.39		$ 43.95
Proceeds from issuance of common stock, net of underwriting discounts										$ 500,000		$ 175,800,000
Sales agent commissions										9,600		$ 2,700,000
ATM offering
Class of Stock [Line Items]
Sale of stock, remaining authorized amount							$ 349,400,000			$ 349,400,000
Over-Allotment Option \| Common stock
Class of Stock [Line Items]
Sale of stock, number of shares issued in transaction (in shares)		525,000

FAIR VALUE MEASUREMENTS -Schedule of Fair Value, Assets and Liabilities Measured on Recurring Basis (Details) - Fair Value, Recurring - USD ($) $ in Thousands	Jun. 30, 2024	Dec. 31, 2023
Assets
Money market funds	$ 403,867	$ 325,898
Total financial assets	403,867	325,898
QUOTED PRICES ACTIVE MARKETS FOR IDENTICAL ASSETS (LEVEL 1)
Assets
Money market funds	403,867	325,898
Total financial assets	403,867	325,898
SIGNIFICANT OTHER OBSERVABLE INPUTS (LEVEL 2)
Assets
Money market funds	0	0
Total financial assets	0	0
SIGNIFICANT OTHER OBSERVABLE INPUTS (LEVEL 3)
Assets
Money market funds	0	0
Total financial assets	$ 0	$ 0

STOCK-BASED COMPENSATION - Schedule of Option Activity (Details) - $ / shares	6 Months Ended
	Jun. 30, 2024
NUMBER OF OPTIONS
Outstanding as of beginning of period (in shares)	4,394,807
Granted (in shares)	1,340,000
Exercised (in shares)	(289,406)
Cancelled or Forfeited (in shares)	(190,679)
Expired (in shares)	(14,050)
Outstanding as of end of period (in shares)	5,240,672
Exercisable (in shares)	2,666,117
WEIGHTED-AVERAGE EXERCISE PRICE
Outstanding as of beginning of period (in USD per share)	$ 36.08
Granted (in USD per share)	56.93
Exercised (in USD per share)	30.02
Cancelled or Forfeited (in USD per share)	50.00
Expired (in USD per share)	59.13
Outstanding as of end of period (in USD per share)	41.18
Exercisable (in USD per share)	$ 30.38

REVENUE FROM CONTRACTS WITH CUSTOMERS	6 Months Ended
REVENUE FROM CONTRACTS WITH CUSTOMERS	Jun. 30, 2024
Revenue from Contract with Customer [Abstract]
REVENUE FROM CONTRACTS WITH CUSTOMERS	REVENUE FROM CONTRACTS WITH CUSTOMERS Hansoh License Agreement On December 12, 2021, the Company entered into a license agreement (the “Hansoh Agreement”) with Hansoh (Shanghai) Healthtech Co., Ltd. (“Hansoh”). Under the Hansoh Agreement, the Company granted to Hansoh the exclusive right to develop, manufacture and commercialize elritercept and licensed products containing elritercept 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 elritercept 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 one-time, net $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 nor 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 elritercept and licensed products containing elritercept 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, the Company recognized a one-time, upfront license fee of $20.0 million as revenue and $2.0 million in withholding tax expense during the year ended December 31, 2021. The Company received the net payment of $18.0 million during the three months ended March 31, 2022. 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. No milestones have been achieved as of June 30, 2024. In connection with the Hansoh Agreement, the Company entered into a manufacturing technology transfer agreement (the “Tech Transfer Agreement”) with Hansoh, effective in June 2023. The Tech Transfer Agreement governs the transfer to Hansoh, by the Company of all documents and information required to complete the manufacturing technology transfer. Under the Tech Transfer Agreement, Hansoh is obligated to make certain payments to the Company, at the rates set forth in the Tech Transfer Agreement, as manufacturing technology transfer services are provided over the term of the Tech Transfer Agreement. The Tech Transfer Agreement is set to expire on December 30, 2024, unless extended pursuant to its terms. As of June 30, 2024, work under the Tech Transfer Agreement has begun. The Company recognized $0.1 million of service revenue during the six months ended June 30, 2024.

- 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
-Topic 606
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-Section 50
-Paragraph 9
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-URI https://asc.fasb.org/1943274/2147479806/606-10-50-9

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
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Reference 3: http://www.xbrl.org/2003/role/disclosureRef
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Reference 4: http://www.xbrl.org/2003/role/disclosureRef
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Reference 8: http://www.xbrl.org/2003/role/disclosureRef
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Reference 10: http://www.xbrl.org/2003/role/disclosureRef
-Name Accounting Standards Codification
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+ Details

ACCRUED EXPENSES AND OTHER CURRENT LIABILITIES (Tables)

6 Months Ended

Jun. 30, 2024

Payables and Accruals [Abstract]

Schedule of of Accrued Expenses and Other Current Liabilities

Accrued expenses and other current liabilities consisted of the following (in thousands):


	JUNE 30, 2024		DECEMBER 31, 2023
Accrued external R&D costs	$	3,478	$	3,904
Accrued external manufacturing costs	3,545		5,288
Accrued compensation and benefits	5,313		7,542

Accrued legal and consulting fees	812		519
Other	466		665
Total accrued expenses and other current liabilities	$	13,614	$	17,918

STOCK-BASED COMPENSATION (Tables)

6 Months Ended

Jun. 30, 2024

Share-Based Payment Arrangement [Abstract]

Schedule of Option Activity

A summary of option activity during the six months ended June 30, 2024 is as follows (in thousands except share and per share data):


	NUMBER OF OPTIONS	WEIGHTED-AVERAGE EXERCISE PRICE
Outstanding as of December 31, 2023	4,394,807	$	36.08
Granted	1,340,000	56.93
Exercised	(289,406)	30.02
Cancelled or Forfeited	(190,679)	50.00
Expired	(14,050)	$	59.13
Outstanding as of June 30, 2024	5,240,672	$	41.18

Options exercisable as of June 30, 2024	2,666,117	$	30.38

Schedule of Stock-based Compensation Expense

Total stock-based compensation expense recorded for employees, directors and non-employees during the three and six months ended June 30, 2024 and 2023 was as follows (in thousands):


	THREE MONTHS ENDED JUNE 30,				SIX MONTHS ENDED JUNE 30,
	2024		2023		2024		2023
Research and development	$	4,624	$	3,363	$	8,526	$	6,021
General and administrative	4,161		3,678		8,329		6,707
Total stock-based compensation expense	$	8,785	$	7,041	$	16,855	$	12,728

COMMON STOCK	6 Months Ended
COMMON STOCK	Jun. 30, 2024
Equity [Abstract]
COMMON STOCK	COMMON STOCK As of June 30, 2024, 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 (doing business as Leerink Partners LLC) (“Leerink”), as agent, pursuant to which the Company may offer and sell, from time to time, shares of its common stock through Leerink (the “ATM Offering”). On May 3, 2021, the Company filed the Prior Shelf Registration Statement, including a base prospectus and sales agreement prospectus, with 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 Prior 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. On May 3, 2024, the Company filed the New Registration Statement to replace the Prior Shelf Registration Statement that was set to expire, including a base prospectus, which became effective immediately upon filing, under which the Company could issue an unspecified amount of shares of the Company common stock, preferred stock, debt securities and warrants. On June 17, 2024, the Company filed a prospectus supplement to the New Shelf Registration Statement for the issuance and sale, if any, of up to an additional $350.0 million of shares of its common stock under the ATM Sales Agreement. For the year ended December 31, 2023, the Company raised gross proceeds of $178.5 million pursuant to the ATM Offering through the sale of 4,061,606 shares of common stock at a weighted average price of $43.95 per share. The net proceeds from the ATM Offering for the year ended December 31, 2023 were approximately $175.8 million after deducting sales agent commissions of $2.7 million. During the six months ended June 30, 2024, the Company raised gross proceeds of $0.6 million pursuant to the ATM Offering through the sale of 14,068 shares of common stock at a weighted average price of $45.39 per share. The net proceeds from the ATM Offering during this period were approximately $0.5 million after deducting sales agent commissions of $9.6 thousand and offering expense of less than $0.2 million. As of June 30, 2024, 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 the remaining $349.4 million (less any sales agent commissions) available under the ATM Offering. On January 8, 2024, the Company closed an underwritten public offering in which 4,025,000 shares of common stock were issued and sold, which included 525,000 shares of common stock issued and sold pursuant to the full exercise of the underwriters’ option to purchase additional shares, at a public offering price of $40.00 per share. The aggregate net proceeds to the Company from the public offering were approximately $151.1 million, after deducting underwriting discount, commissions and offering expenses.

- Definition

The entire disclosure for equity.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 505
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-URI https://asc.fasb.org/1943274/2147481112/505-10-50-18

+ Details

Subsequent Events (Details) - Subsequent Event ft² in Thousands, $ in Millions	Jul. 01, 2024 USD ($)	Jul. 31, 2024 USD ($)	Jul. 30, 2024 ft²
Subsequent Event [Line Items]
Lessee, area of sublease \| ft²			20
Lessee, operating lease, term of contract	5 years 3 months
Lease obligation incurred	$ 7.5
Accent Therapeutics, Inc
Subsequent Event [Line Items]
Letters of credit outstanding, amount		$ 0.2

REVENUE FROM CONTRACTS WITH CUSTOMERS (Details) - USD ($) $ in Thousands	3 Months Ended			6 Months Ended		12 Months Ended
	Jun. 30, 2024	Jun. 30, 2023	Mar. 31, 2022	Jun. 30, 2024	Jun. 30, 2023	Dec. 31, 2021
Disaggregation of Revenue [Line Items]
Research collaboration revenue	$ 37	$ 0		$ 120	$ 0
Service revenue				$ 100
The General Hospital Corporation \| License Agreement
Disaggregation of Revenue [Line Items]
Expiration period				10 years
License revenue \| 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
Upfront license fee						$ 20,000
Withholding taxes from upfront fee						$ 2,000

Condensed Consolidated Balance Sheets (Parenthetical) - $ / shares	Jun. 30, 2024	Dec. 31, 2023
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)	36,169,558	31,841,084
Common stock, shares outstanding (in shares)	36,169,558	31,841,084

Condensed Consolidated Statements of Stockholders’ Equity (Parenthetical) - USD ($) $ in Thousands	3 Months Ended			6 Months Ended
	Jun. 30, 2024	Mar. 31, 2024	Mar. 31, 2023	Jun. 30, 2024	Dec. 31, 2023	Jun. 30, 2023
Common stock, par value (in USD per share)	$ 0.0001			$ 0.0001	$ 0.0001	$ 0.0001
At the Market Offering
Commissions and offering cost	$ 164	$ 9,943	$ 1,665	$ 200
At the Market Offering \| Common stock
Issuance of common stock under the ATM agreement, net of commissions and offering costs (in shares)	14,068	4,025,000	1,990,927

PREPAID EXPENSES AND OTHER CURRENT ASSETS

6 Months Ended

Jun. 30, 2024

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

PREPAID EXPENSES AND OTHER CURRENT ASSETS

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


	JUNE 30, 2024		DECEMBER 31, 2023
Prepaid external R&D costs	$	18,374	$	10,116
Prepaid external manufacturing costs	3,720		2,303

Prepaid sales tax	776		429


Prepaid insurance	1,201		638
Prepaid subscriptions	853		568
Interest and dividend receivable	1,341		948
Other	582		1,001
Total prepaid expenses and other current assets	$	26,847	$	16,003

LOSS PER SHARE (Tables)

6 Months Ended

Jun. 30, 2024

Earnings Per Share [Abstract]

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 at June 30, 2024 and 2023 because including them would have had an anti-dilutive effect:


	JUNE 30, 2024	JUNE 30, 2023
Options to purchase common stock	5,240,672	4,451,522

STOCK-BASED COMPENSATION - Schedule of Stock-based Compensation Expense (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2024	Jun. 30, 2023	Jun. 30, 2024	Jun. 30, 2023
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Total stock-based compensation expense	$ 8,785	$ 7,041	$ 16,855	$ 12,728
Research and development
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Total stock-based compensation expense	4,624	3,363	8,526	6,021
General and administrative
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Total stock-based compensation expense	$ 4,161	$ 3,678	$ 8,329	$ 6,707

LOSS PER SHARE

6 Months Ended

Jun. 30, 2024

Earnings Per Share [Abstract]

LOSS PER SHARE

The Company’s potentially dilutive securities, which includes 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 shares of common stock 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 at June 30, 2024 and 2023 because including them would have had an anti-dilutive effect:


	JUNE 30, 2024	JUNE 30, 2023
Options to purchase common stock	5,240,672	4,451,522

FAIR VALUE MEASUREMENTS (Tables)

6 Months Ended

Jun. 30, 2024

Fair Value Disclosures [Abstract]

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


DESCRIPTION	JUNE 30, 2024		QUOTED PRICES ACTIVE MARKETS FOR IDENTICAL ASSETS (LEVEL 1)		SIGNIFICANT OTHER OBSERVABLE INPUTS (LEVEL 2)		SIGNIFICANT OTHER OBSERVABLE INPUTS (LEVEL 3)
Assets
Money market funds	$	403,867	$	403,867	$	—	$	—
Total financial assets	$	403,867	$	403,867	$	—	$	—


DESCRIPTION	DECEMBER 31, 2023		QUOTED PRICES ACTIVE MARKETS FOR IDENTICAL ASSETS (LEVEL 1)		SIGNIFICANT OTHER OBSERVABLE INPUTS (LEVEL 2)		SIGNIFICANT OTHER OBSERVABLE INPUTS (LEVEL 3)
Assets
Money market funds	$	325,898	$	325,898	$	—	$	—
Total financial assets	$	325,898	$	325,898	$	—	$	—

STOCK-BASED COMPENSATION - Narrative (Details) - USD ($) $ / shares in Units, $ in Millions		6 Months Ended
	Jan. 01, 2024	Jun. 30, 2024	Jun. 30, 2023
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Options granted in period (in shares)		1,340,000
Weighted-average grant date fair value of options granted during the period (in dollars per share)		$ 40.62	$ 36.96
Options outstanding, value		$ 54.4
Options exercisable, value		51.0
Aggregate intrinsic value of stock options exercised		$ 7.3	$ 3.7
Employee Stock Option
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unvested award, period for recognition		2 years 8 months 12 days
Unvested Stock Options
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unrecognized stock-based compensation expense related to unvested stock options		$ 88.5
Performance Based Stock Options
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unrecognized stock-based compensation expense related to unvested stock options		$ 4.9
2017 Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of shares authorized (in shares)		500,485
2020 Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Annual percentage increase in shares authorized		4.00%
Number of additional shares authorized (in shares)	1,273,643
Vesting period		4 years
Contractual term		10 years
Options granted in period (in shares)		4,740,187
Number of shares available for future grants (in shares)		1,114,824

ACCRUED EXPENSES AND OTHER CURRENT LIABILITIES - Schedule of of Accrued Expenses and Other Current Liabilities (Details) - USD ($) $ in Thousands	Jun. 30, 2024	Dec. 31, 2023
Payables and Accruals [Abstract]
Accrued external R&D costs	$ 3,478	$ 3,904
Accrued external manufacturing costs	3,545	5,288
Accrued compensation and benefits	5,313	7,542
Accrued legal and consulting fees	812	519
Other	466	665
Total accrued expenses and other current liabilities	$ 13,614	$ 17,918

NATURE OF BUSINESS AND BASIS OF PRESENTATION	6 Months Ended
NATURE OF BUSINESS AND BASIS OF PRESENTATION	Jun. 30, 2024
Organization, Consolidation and Presentation of Financial Statements [Abstract]
NATURE OF BUSINESS AND BASIS OF PRESENTATION	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 developing and commercializing novel therapeutics to treat a wide range of patients with disorders that are linked to dysfunctional signaling of the transforming growth factor-beta (“TGF-ß”) family of proteins. The Company’s lead product candidate, elritercept (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 second product candidate, cibotercept (KER-012), is being developed for the treatment of pulmonary arterial hypertension (“PAH”) and for the treatment of cardiovascular disorders. The Company's third product candidate, KER-065, is being developed for the treatment of obesity and for the treatment of neuromuscular diseases. 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 “Prior Shelf Registration Statement”). Pursuant to the Prior 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 of 1933, as amended (“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 Prior 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. In May 2024, the Company filed a registration statement on Form S-3 to replace the Prior Shelf Registration Statement, which became effective immediately upon filing (the “New Shelf Registration Statement”). The New Shelf Registration Statement included a base prospectus under which the Company could issue, 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 June 2024, the Company filed a prospectus supplement to the New Shelf Registration Statement for the issuance and sale, if any, of up to an additional $350.0 million of shares of its 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 condensed 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 $405.9 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 unaudited interim condensed consolidated financial statements as of June 30, 2024 and for the three and six months ended June 30, 2024 and 2023 have been prepared by the Company in conformity with generally accepted accounting principles in the United States of America (“U.S. GAAP”) and, pursuant to the rules and regulations of Article 10 of Regulation S-X of the Securities Act published by the Securities and Exchange Commission (“SEC”) for interim financial statements. Certain information and footnote disclosures normally included in financial statements prepared in accordance with U.S. GAAP have been condensed or omitted pursuant to such rules and regulations. However, the Company believes the disclosures are adequate to make the information presented not misleading. These unaudited interim condensed consolidated financial statements should be read in conjunction with the Company’s audited financial statements and notes thereto for the year ended December 31, 2023 included in the Company’s Annual Report on Form 10-K for the year ended December 31, 2023 filed with the SEC on February 28, 2024 (the “Annual Report”).

LOSS PER SHARE - Schedule of Antidilutive Securities Excluded From Computation of Diluted Net Loss Per Share (Details) - shares	6 Months Ended
	Jun. 30, 2024	Jun. 30, 2023
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)	5,240,672	4,451,522

Subsequent Events	6 Months Ended
Subsequent Events	Jun. 30, 2024
Subsequent Events [Abstract]
Subsequent Events	Subsequent Events Leases In July 2024, the Company entered into a sublease (the “Sublease Agreement”) with Accent Therapeutics, Inc. ("Accent Therapeutics"), pursuant to which the Company will sublease approximately 20,000 square feet of office and laboratory space located at 1050 Waltham Street, Lexington, Massachusetts, expanding the Company's existing headquarters. The term of the sublease commenced on July 1, 2024 (the "Sublease Commencement Date"). The Sublease Agreement has a term of 5 years and 3 months, measured from the Sublease Commencement Date. The Company’s obligation for the payment of base rent for the premises begins on the Sublease Commencement Date. The Company's obligation is approximately $7.5 million over the sublease term. In connection with its entry into the Sublease Agreement and as a security deposit, the Company has provided Accent Therapeutics a letter of credit in the amount of approximately $0.2 million upon the Sublease Commencement Date.

PREPAID EXPENSES AND OTHER CURRENT ASSETS - Schedule of Prepaid Expenses and Other Current Assets (Details) - USD ($) $ in Thousands	Jun. 30, 2024	Dec. 31, 2023
Deferred Costs, Capitalized, Prepaid, and Other Assets Disclosure [Abstract]
Prepaid external R&D costs	$ 18,374	$ 10,116
Prepaid external manufacturing costs	3,720	2,303
Prepaid sales tax	776	429
Prepaid insurance	1,201	638
Prepaid subscriptions	853	568
Interest and dividend receivable	1,341	948
Other	582	1,001
Total prepaid expenses and other current assets	$ 26,847	$ 16,003

Condensed Consolidated Statements of Operations - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2024	Jun. 30, 2023	Jun. 30, 2024	Jun. 30, 2023
Revenues [Abstract]
Total revenue	$ 37	$ 0	$ 120	$ 0
OPERATING EXPENSES:
Research and development	(40,515)	(32,534)	(78,773)	(63,625)
General and administrative	(9,961)	(8,803)	(20,269)	(16,581)
Total operating expenses	(50,476)	(41,337)	(99,042)	(80,206)
LOSS FROM OPERATIONS	(50,439)	(41,337)	(98,922)	(80,206)
OTHER INCOME (EXPENSE), NET
Dividend income	5,378	3,987	11,184	7,093
Other expense, net	(196)	(155)	(633)	(196)
Total other income, net	5,182	3,832	10,551	6,897
Net loss	(45,257)	(37,505)	(88,371)	(73,309)
Net loss attributable to common stockholders—basic	(45,257)	(37,505)	(88,371)	(73,309)
Net loss attributable to common stockholders— diluted	$ (45,257)	$ (37,505)	$ (88,371)	$ (73,309)
Net loss per share attributable to common stockholders - basic (in USD per share)	$ (1.25)	$ (1.27)	$ (2.46)	$ (2.53)
Net loss per share attributable to common stockholders - diluted (in USD per share)	$ (1.25)	$ (1.27)	$ (2.46)	$ (2.53)
Weighted-average common stock outstanding - basic (in shares)	36,103,187	29,602,458	35,894,305	28,989,361
Weighted-average common stock outstanding - diluted (in shares)	36,103,187	29,602,458	35,894,305	28,989,361
Revenue, Product and Service [Extensible Enumeration]	License revenue	License revenue
Service and other revenue
Revenues [Abstract]
Total revenue	$ 37	$ 0	$ 120	$ 0