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Each of the Reporting Persons disclaims beneficial ownership of the securities reported herein for purposes of Rule 16a-1(a) under the Securities Exchange Act of 1934, as amended (the \"Exchange Act\"), except to the extent of its pecuniary interest therein, if any. The Reporting Persons have designated a representative, Carl L. Gordon, a member of OrbiMed Advisors, to serve on the Issuer's board of directors. 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Each of the Reporting Persons disclaims beneficial ownership of the securities reported herein for purposes of Rule 16a-1(a) under the Securities Exchange Act of 1934, as amended (the \"Exchange Act\"), except to the extent of its pecuniary interest therein, if any. The Reporting Persons have designated a representative, Carl L. Gordon, a member of OrbiMed Advisors, to serve on the Issuer's board of directors. 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OrbiMed Capital GP VII LLC (\"OrbiMed GP\") is the general partner of OPI VII and OrbiMed Advisors LLC (\"OrbiMed Advisors\") is the managing member of OrbiMed GP. By virtue of such relationships, OrbiMed GP and OrbiMed Advisors may be deemed to have voting power and investment power over the securities held by OPI VII and as a result, may be deemed to have beneficial ownership over such securities. OrbiMed Advisors exercises voting and investment power through a management committee comprised of the Reporting Person, Sven H. Borho, and W. 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The Reporting Person, a member of the board of directors of the Issuer, is a partner of Partners GP I and as a result, may be deemed to share voting and investment power with respect to the shares held by PIF I."}],"balance_after":150047,"source":{"system":"sec-edgar","filing":"0001808365-25-000005","document":"form4-12182025_041201.xml","document_sequence":1,"table":"nonDerivative","row_type":"transaction","position":1,"url":"https://www.sec.gov/Archives/edgar/data/1808365/000180836525000005/form4-12182025_041201.xml","form_type":"4"}},{"id":1016812,"issuer":{"id":6242,"kind":"organization","name":"Keros Therapeutics, Inc."},"owners":[{"id":74162,"kind":"organization","name":"Pontifax Management 4 G.P. (2015) Ltd.","position":1,"cik":"0001726334","reported_name":"Pontifax Management 4 G.P. 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(\"Late Stage\"). Pontifax Late Stage GP Ltd. (\"Late Stage GP\") is the general partner of Late Stage and the sole shareholder of Late Stage GP is Mr. Shlomo Karako. Pursuant to the Strategic Alliance Agreement, dated August 9, 2018, between Late Stage, Israel IV, Cayman IV and China IV (collectively the, \"Pontifax IV Funds\"), Late Stage invests side-by-side with the Pontifax IV Funds. By virtue of the strategic relationship, Management 4 and Tomer Kariv and Ran Nussbaum may be deemed to share voting and dispositive power with respect to the shares held by Late Stage in a manner similar to the voting and investment power with respect to the shares held by each of the Pontifax IV Funds. Each of the Reporting Persons disclaims beneficial ownership of the securities reported herein, except to the extent of his or its pecuniary interest therein."}],"balance_after":0,"source":{"system":"sec-edgar","filing":"0000921895-25-002765","document":"form414601002_10172025.xml","document_sequence":1,"table":"nonDerivative","row_type":"transaction","position":4,"url":"https://www.sec.gov/Archives/edgar/data/1726334/000092189525002765/form414601002_10172025.xml","form_type":"4"}},{"id":1016811,"issuer":{"id":6242,"kind":"organization","name":"Keros Therapeutics, Inc."},"owners":[{"id":74162,"kind":"organization","name":"Pontifax Management 4 G.P. (2015) Ltd.","position":1,"cik":"0001726334","reported_name":"Pontifax Management 4 G.P. 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(\"China IV\"). Management 4 is the ultimate general partner of China IV. As a result, Management 4 may be deemed to share voting and dispositive power with respect to the shares held by China IV. Each of Tomer Kariv and Ran Nussbaum is a Managing Partner of Management 4 and, as a result, Messrs. Kariv and Nussbaum may be deemed to share voting and investment power with respect to the shares held by China IV. Management 4 and Messrs. Kariv and Nussbaum disclaim beneficial ownership of such shares, except to the extent of his or its pecuniary interest therein, and the inclusion of the shares in this report shall not be deemed to be an admission of beneficial ownership of the reported shares for purposes of Section 16 of the Securities Exchange Act of 1934, as amended, or otherwise."}],"balance_after":0,"source":{"system":"sec-edgar","filing":"0000921895-25-002765","document":"form414601002_10172025.xml","document_sequence":1,"table":"nonDerivative","row_type":"transaction","position":3,"url":"https://www.sec.gov/Archives/edgar/data/1726334/000092189525002765/form414601002_10172025.xml","form_type":"4"}},{"id":1016810,"issuer":{"id":6242,"kind":"organization","name":"Keros Therapeutics, Inc."},"owners":[{"id":74162,"kind":"organization","name":"Pontifax Management 4 G.P. (2015) Ltd.","position":1,"cik":"0001726334","reported_name":"Pontifax Management 4 G.P. 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(\"Cayman IV\"). Management 4 is the ultimate general partner of Cayman IV. As a result, Management 4 may be deemed to share voting and dispositive power with respect to the shares held by Cayman IV. Each of Tomer Kariv and Ran Nussbaum is a Managing Partner of Management 4 and, as a result, Messrs. Kariv and Nussbaum may be deemed to share voting and investment power with respect to the shares held by Cayman IV. Management 4 and Messrs. Kariv and Nussbaum disclaim beneficial ownership of such shares, except to the extent of his or its pecuniary interest therein, and the inclusion of the shares in this report shall not be deemed to be an admission of beneficial ownership of the reported shares for purposes of Section 16 of the Securities Exchange Act of 1934, as amended, or otherwise."}],"balance_after":0,"source":{"system":"sec-edgar","filing":"0000921895-25-002765","document":"form414601002_10172025.xml","document_sequence":1,"table":"nonDerivative","row_type":"transaction","position":2,"url":"https://www.sec.gov/Archives/edgar/data/1726334/000092189525002765/form414601002_10172025.xml","form_type":"4"}},{"id":1016809,"issuer":{"id":6242,"kind":"organization","name":"Keros Therapeutics, Inc."},"owners":[{"id":74162,"kind":"organization","name":"Pontifax Management 4 G.P. (2015) Ltd.","position":1,"cik":"0001726334","reported_name":"Pontifax Management 4 G.P. 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(\"Israel IV\"). Pontifax Management 4 G.P. (2015) Ltd. (\"Management 4\") is the ultimate general partner of Israel IV. As a result, Management 4 may be deemed to share voting and dispositive power with respect to the shares held by Israel IV. Each of Tomer Kariv and Ran Nussbaum is a Managing Partner of Management 4 and, as a result, Messrs. Kariv and Nussbaum may be deemed to share voting and investment power with respect to the shares held by Israel IV. Management 4 and Messrs. Kariv and Nussbaum disclaim beneficial ownership of such shares, except to the extent of his or its pecuniary interest therein, and the inclusion of the shares in this report shall not be deemed to be an admission of beneficial ownership of the reported shares for purposes of Section 16 of the Securities Exchange Act of 1934, as amended, or otherwise."}],"balance_after":0,"source":{"system":"sec-edgar","filing":"0000921895-25-002765","document":"form414601002_10172025.xml","document_sequence":1,"table":"nonDerivative","row_type":"transaction","position":1,"url":"https://www.sec.gov/Archives/edgar/data/1726334/000092189525002765/form414601002_10172025.xml","form_type":"4"}},{"id":1018729,"issuer":{"id":6242,"kind":"organization","name":"Keros Therapeutics, Inc."},"owners":[{"id":980,"kind":"organization","name":"ADAR1 Capital Management, LLC","position":1,"cik":"0001940272","reported_name":"ADAR1 Capital Management, LLC","relationship":{"director":false,"officer":false,"ten_percent_owner":true,"other":false}},{"id":74265,"kind":"organization","name":"ADAR1 Partners, LP","position":2,"cik":"0001758866","reported_name":"ADAR1 Partners, LP","relationship":{"director":false,"officer":false,"ten_percent_owner":true,"other":false}},{"id":74266,"kind":"organization","name":"ADAR1 Capital Management GP, LLC","position":3,"cik":"0001940267","reported_name":"ADAR1 Capital Management GP, LLC","relationship":{"director":false,"officer":false,"ten_percent_owner":true,"other":false}},{"id":981,"kind":"person","name":"Schneeberger Daniel","position":4,"cik":"0001861120","reported_name":"Schneeberger Daniel","relationship":{"director":false,"officer":false,"ten_percent_owner":true,"other":false}}],"security":"Common Stock","published_at":"2025-10-15T13:24:20.000Z","date":"2025-10-15","kind":"sale","planned":false,"acquired":false,"shares":743358,"price":17.75,"value":13194604.5,"ownership":{"direct":false,"nature":"By Spearhead Insurance Solutions IDF, LLC"},"footnotes":[{"field":"ownership.nature","element":"natureOfOwnership","label":"F1","text":"The securities to which this filing relates are held directly by ADAR1 Partners, LP, ADAR1 SPV I, LP and Spearhead Insurance Solutions IDF, LLC. As the investment manager of ADAR1 Partners, LP and ADAR1 SPV I, LP and as the sub-advisor of Spearhead Insurance Solutions IDF, LLC, ADAR1 Capital Management, LLC may be deemed to indirectly beneficially own securities held by ADAR1 Partners, LP, ADAR1 SPV I, LP and Spearhead Insurance Solutions IDF, LLC. As the general partner of ADAR1 Partners, LP and ADAR1 SPV I, LP, ADAR1 Capital Management GP, LLC may be deemed to indirectly beneficially own securities held by ADAR1 Partners, LP and ADAR1 SPV I, LP. As the manager of ADAR1 Capital Management, LLC and ADAR1 Capital Management GP, LLC, Daniel Schneeberger may be deemed to indirectly beneficially own securities held by ADAR1 Partners, LP, Spearhead Insurance Solutions IDF, LLC, and ADAR1 SPV I, LP."},{"field":"ownership.nature","element":"natureOfOwnership","label":"F2","text":"For purposes of Section 16 of the Securities Exchange Act of 1934, as amended, each Reporting Person disclaims beneficial ownership of any such securities, except to the extent of his/its pecuniary interest therein, if any, and this report shall not be deemed an admission that such Reporting Person is the beneficial owner of such securities for purposes of Section 16 or otherwise."}],"balance_after":0,"source":{"system":"sec-edgar","filing":"0000902664-25-004411","document":"ownership.xml","document_sequence":1,"table":"nonDerivative","row_type":"transaction","position":3,"url":"https://www.sec.gov/Archives/edgar/data/1940267/000090266425004411/ownership.xml","form_type":"4"}},{"id":1018728,"issuer":{"id":6242,"kind":"organization","name":"Keros Therapeutics, Inc."},"owners":[{"id":980,"kind":"organization","name":"ADAR1 Capital Management, LLC","position":1,"cik":"0001940272","reported_name":"ADAR1 Capital Management, LLC","relationship":{"director":false,"officer":false,"ten_percent_owner":true,"other":false}},{"id":74265,"kind":"organization","name":"ADAR1 Partners, LP","position":2,"cik":"0001758866","reported_name":"ADAR1 Partners, LP","relationship":{"director":false,"officer":false,"ten_percent_owner":true,"other":false}},{"id":74266,"kind":"organization","name":"ADAR1 Capital Management GP, LLC","position":3,"cik":"0001940267","reported_name":"ADAR1 Capital Management GP, LLC","relationship":{"director":false,"officer":false,"ten_percent_owner":true,"other":false}},{"id":981,"kind":"person","name":"Schneeberger Daniel","position":4,"cik":"0001861120","reported_name":"Schneeberger Daniel","relationship":{"director":false,"officer":false,"ten_percent_owner":true,"other":false}}],"security":"Common Stock","published_at":"2025-10-15T13:24:20.000Z","date":"2025-10-15","kind":"sale","planned":false,"acquired":false,"shares":254669,"price":17.75,"value":4520374.75,"ownership":{"direct":false,"nature":"By ADAR1 SPVI, LP"},"footnotes":[{"field":"ownership.nature","element":"natureOfOwnership","label":"F1","text":"The securities to which this filing relates are held directly by ADAR1 Partners, LP, ADAR1 SPV I, LP and Spearhead Insurance Solutions IDF, LLC. As the investment manager of ADAR1 Partners, LP and ADAR1 SPV I, LP and as the sub-advisor of Spearhead Insurance Solutions IDF, LLC, ADAR1 Capital Management, LLC may be deemed to indirectly beneficially own securities held by ADAR1 Partners, LP, ADAR1 SPV I, LP and Spearhead Insurance Solutions IDF, LLC. As the general partner of ADAR1 Partners, LP and ADAR1 SPV I, LP, ADAR1 Capital Management GP, LLC may be deemed to indirectly beneficially own securities held by ADAR1 Partners, LP and ADAR1 SPV I, LP. As the manager of ADAR1 Capital Management, LLC and ADAR1 Capital Management GP, LLC, Daniel Schneeberger may be deemed to indirectly beneficially own securities held by ADAR1 Partners, LP, Spearhead Insurance Solutions IDF, LLC, and ADAR1 SPV I, LP."},{"field":"ownership.nature","element":"natureOfOwnership","label":"F2","text":"For purposes of Section 16 of the Securities Exchange Act of 1934, as amended, each Reporting Person disclaims beneficial ownership of any such securities, except to the extent of his/its pecuniary interest therein, if any, and this report shall not be deemed an admission that such Reporting Person is the beneficial owner of such securities for purposes of Section 16 or otherwise."}],"balance_after":0,"source":{"system":"sec-edgar","filing":"0000902664-25-004411","document":"ownership.xml","document_sequence":1,"table":"nonDerivative","row_type":"transaction","position":2,"url":"https://www.sec.gov/Archives/edgar/data/1940267/000090266425004411/ownership.xml","form_type":"4"}},{"id":1018727,"issuer":{"id":6242,"kind":"organization","name":"Keros Therapeutics, Inc."},"owners":[{"id":980,"kind":"organization","name":"ADAR1 Capital Management, LLC","position":1,"cik":"0001940272","reported_name":"ADAR1 Capital Management, LLC","relationship":{"director":false,"officer":false,"ten_percent_owner":true,"other":false}},{"id":74265,"kind":"organization","name":"ADAR1 Partners, LP","position":2,"cik":"0001758866","reported_name":"ADAR1 Partners, LP","relationship":{"director":false,"officer":false,"ten_percent_owner":true,"other":false}},{"id":74266,"kind":"organization","name":"ADAR1 Capital Management GP, LLC","position":3,"cik":"0001940267","reported_name":"ADAR1 Capital Management GP, LLC","relationship":{"director":false,"officer":false,"ten_percent_owner":true,"other":false}},{"id":981,"kind":"person","name":"Schneeberger Daniel","position":4,"cik":"0001861120","reported_name":"Schneeberger Daniel","relationship":{"director":false,"officer":false,"ten_percent_owner":true,"other":false}}],"security":"Common Stock","published_at":"2025-10-15T13:24:20.000Z","date":"2025-10-15","kind":"sale","planned":false,"acquired":false,"shares":4391237,"price":17.75,"value":77944456.75,"ownership":{"direct":false,"nature":"By ADAR1 Partners, LP"},"footnotes":[{"field":"ownership.nature","element":"natureOfOwnership","label":"F1","text":"The securities to which this filing relates are held directly by ADAR1 Partners, LP, ADAR1 SPV I, LP and Spearhead Insurance Solutions IDF, LLC. 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As the manager of ADAR1 Capital Management, LLC and ADAR1 Capital Management GP, LLC, Daniel Schneeberger may be deemed to indirectly beneficially own securities held by ADAR1 Partners, LP, Spearhead Insurance Solutions IDF, LLC, and ADAR1 SPV I, LP."},{"field":"ownership.nature","element":"natureOfOwnership","label":"F2","text":"For purposes of Section 16 of the Securities Exchange Act of 1934, as amended, each Reporting Person disclaims beneficial ownership of any such securities, except to the extent of his/its pecuniary interest therein, if any, and this report shall not be deemed an admission that such Reporting Person is the beneficial owner of such securities for purposes of Section 16 or otherwise."}],"balance_after":0,"source":{"system":"sec-edgar","filing":"0000902664-25-004411","document":"ownership.xml","document_sequence":1,"table":"nonDerivative","row_type":"transaction","position":1,"url":"https://www.sec.gov/Archives/edgar/data/1940267/000090266425004411/ownership.xml","form_type":"4"}},{"id":1046642,"issuer":{"id":6242,"kind":"organization","name":"Keros Therapeutics, Inc."},"owners":[{"id":53564,"kind":"person","name":"Seehra Jasbir","position":1,"cik":"0001732369","reported_name":"Seehra Jasbir","relationship":{"director":true,"officer":true,"ten_percent_owner":false,"other":false,"officer_title":"CHIEF EXECUTIVE OFFICER"}}],"security":"Common Stock","published_at":"2025-09-05T20:10:08.000Z","date":"2025-09-03","kind":"grant","planned":false,"acquired":true,"shares":90500,"price":0,"value":0.0,"ownership":{"direct":true},"footnotes":[{"field":"shares","element":"transactionShares","label":"F1","text":"Represents a restricted stock unit (\"RSU\") award. 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As a result, the aggregate number of notional shares of Common Stock of the Issuer in the applicable basket after giving effect to such transactions is 50,000 shares."},{"field":"derivative.expiration_date","element":"expirationDate","label":"F7","text":"In connection with the purchase of 74,333 securities reported as being purchased in Table 1, ADAR1 Partners, LP and the counterparty to the cash-settled total equity swaps previously reported agreed to reduce the number of notional shares of Common Stock of the Issuer in the applicable basket by a corresponding number of 74,333 shares. As a result, the aggregate number of notional shares of Common Stock of the Issuer in the applicable basket after giving effect to such transactions is 50,000 shares."},{"field":"derivative.underlying_shares","element":"underlyingSecurityShares","label":"F7","text":"In connection with the purchase of 74,333 securities reported as being purchased in Table 1, ADAR1 Partners, LP and the counterparty to the cash-settled total equity swaps previously reported agreed to reduce the number of notional shares of Common Stock of the Issuer in the applicable basket by a corresponding number of 74,333 shares. As a result, the aggregate number of notional shares of Common Stock of the Issuer in the applicable basket after giving effect to such transactions is 50,000 shares."},{"field":"balance_after","element":"sharesOwnedFollowingTransaction","label":"F7","text":"In connection with the purchase of 74,333 securities reported as being purchased in Table 1, ADAR1 Partners, LP and the counterparty to the cash-settled total equity swaps previously reported agreed to reduce the number of notional shares of Common Stock of the Issuer in the applicable basket by a corresponding number of 74,333 shares. As a result, the aggregate number of notional shares of Common Stock of the Issuer in the applicable basket after giving effect to such transactions is 50,000 shares."},{"field":"ownership.nature","element":"natureOfOwnership","label":"F1","text":"As the investment manager of ADAR1 Partners, LP and ADAR1 SPV I, LP and as the sub-advisor of Spearhead Insurance Solutions IDF, LLC, ADAR1 Capital Management, LLC may be deemed to indirectly beneficially own securities held by ADAR1 Partners, LP, ADAR1 SPV I, LP and Spearhead Insurance Solutions IDF, LLC. As the general partner of ADAR1 Partners, LP and ADAR1 SPV I, LP, ADAR1 Capital Management GP, LLC may be deemed to indirectly beneficially own securities held by ADAR1 Partners, LP and ADAR1 SPV I, LP. As the manager of ADAR1 Capital Management, LLC and ADAR1 Capital Management GP, LLC, Mr. Schneeberger may be deemed to indirectly beneficially own securities held by ADAR1 Partners, LP, Spearhead Insurance Solutions IDF, LLC, and ADAR1 SPV I, LP."},{"field":"ownership.nature","element":"natureOfOwnership","label":"F8","text":"For purposes of Section 16 of the Securities Exchange Act of 1934, as amended, each Reporting Person disclaims beneficial ownership of any such securities, except to the extent of his/its pecuniary interest therein, if any, and this report shall not be deemed an admission that such Reporting Person is the beneficial owner of such securities for purposes of Section 16 or otherwise."}],"balance_after":50000,"derivative":{"underlying":"Common Stock","underlying_shares":74333},"source":{"system":"sec-edgar","filing":"0001104659-25-034321","document":"tm2512234-2_4seq1.xml","document_sequence":1,"table":"derivative","row_type":"transaction","position":9,"url":"https://www.sec.gov/Archives/edgar/data/1940267/000110465925034321/tm2512234-2_4seq1.xml","form_type":"4"}},{"id":1173472,"issuer":{"id":6242,"kind":"organization","name":"Keros Therapeutics, Inc."},"owners":[{"id":980,"kind":"organization","name":"ADAR1 Capital Management, LLC","position":1,"cik":"0001940272","reported_name":"ADAR1 Capital Management, LLC","relationship":{"director":false,"officer":false,"ten_percent_owner":true,"other":false}},{"id":74265,"kind":"organization","name":"ADAR1 Partners, LP","position":2,"cik":"0001758866","reported_name":"ADAR1 Partners, LP","relationship":{"director":false,"officer":false,"ten_percent_owner":true,"other":false}},{"id":74266,"kind":"organization","name":"ADAR1 Capital Management GP, LLC","position":3,"cik":"0001940267","reported_name":"ADAR1 Capital Management GP, LLC","relationship":{"director":false,"officer":false,"ten_percent_owner":true,"other":false}},{"id":981,"kind":"person","name":"Schneeberger Daniel","position":4,"cik":"0001861120","reported_name":"Schneeberger Daniel","relationship":{"director":false,"officer":false,"ten_percent_owner":true,"other":false}}],"security":"Cash-Settled Total Return Swaps","published_at":"2025-04-11T21:57:19.000Z","date":"2025-04-09","kind":"other","planned":false,"acquired":false,"shares":500000,"ownership":{"direct":false,"nature":"By ADAR1 Partners, LP"},"footnotes":[{"field":"derivative.exercise_price","element":"conversionOrExercisePrice","label":"F6","text":"In connection with the purchase of 500,000 securities reported as being purchased in Table 1, ADAR1 Partners, LP and the counterparty to the cash-settled total equity swaps previously reported agreed to reduce the number of notional shares of Common Stock of the Issuer in the applicable basket by a corresponding number of 500,000 shares. As a result, the aggregate number of notional shares of Common Stock of the Issuer in the applicable basket after giving effect to such transactions is 124,333 shares."},{"field":"kind","element":"transactionCoding","label":"F6","text":"In connection with the purchase of 500,000 securities reported as being purchased in Table 1, ADAR1 Partners, LP and the counterparty to the cash-settled total equity swaps previously reported agreed to reduce the number of notional shares of Common Stock of the Issuer in the applicable basket by a corresponding number of 500,000 shares. As a result, the aggregate number of notional shares of Common Stock of the Issuer in the applicable basket after giving effect to such transactions is 124,333 shares."},{"field":"shares","element":"transactionShares","label":"F6","text":"In connection with the purchase of 500,000 securities reported as being purchased in Table 1, ADAR1 Partners, LP and the counterparty to the cash-settled total equity swaps previously reported agreed to reduce the number of notional shares of Common Stock of the Issuer in the applicable basket by a corresponding number of 500,000 shares. As a result, the aggregate number of notional shares of Common Stock of the Issuer in the applicable basket after giving effect to such transactions is 124,333 shares."},{"field":"price","element":"transactionPricePerShare","label":"F6","text":"In connection with the purchase of 500,000 securities reported as being purchased in Table 1, ADAR1 Partners, LP and the counterparty to the cash-settled total equity swaps previously reported agreed to reduce the number of notional shares of Common Stock of the Issuer in the applicable basket by a corresponding number of 500,000 shares. As a result, the aggregate number of notional shares of Common Stock of the Issuer in the applicable basket after giving effect to such transactions is 124,333 shares."},{"field":"derivative.exercise_date","element":"exerciseDate","label":"F6","text":"In connection with the purchase of 500,000 securities reported as being purchased in Table 1, ADAR1 Partners, LP and the counterparty to the cash-settled total equity swaps previously reported agreed to reduce the number of notional shares of Common Stock of the Issuer in the applicable basket by a corresponding number of 500,000 shares. As a result, the aggregate number of notional shares of Common Stock of the Issuer in the applicable basket after giving effect to such transactions is 124,333 shares."},{"field":"derivative.expiration_date","element":"expirationDate","label":"F6","text":"In connection with the purchase of 500,000 securities reported as being purchased in Table 1, ADAR1 Partners, LP and the counterparty to the cash-settled total equity swaps previously reported agreed to reduce the number of notional shares of Common Stock of the Issuer in the applicable basket by a corresponding number of 500,000 shares. As a result, the aggregate number of notional shares of Common Stock of the Issuer in the applicable basket after giving effect to such transactions is 124,333 shares."},{"field":"derivative.underlying_shares","element":"underlyingSecurityShares","label":"F6","text":"In connection with the purchase of 500,000 securities reported as being purchased in Table 1, ADAR1 Partners, LP and the counterparty to the cash-settled total equity swaps previously reported agreed to reduce the number of notional shares of Common Stock of the Issuer in the applicable basket by a corresponding number of 500,000 shares. As a result, the aggregate number of notional shares of Common Stock of the Issuer in the applicable basket after giving effect to such transactions is 124,333 shares."},{"field":"balance_after","element":"sharesOwnedFollowingTransaction","label":"F6","text":"In connection with the purchase of 500,000 securities reported as being purchased in Table 1, ADAR1 Partners, LP and the counterparty to the cash-settled total equity swaps previously reported agreed to reduce the number of notional shares of Common Stock of the Issuer in the applicable basket by a corresponding number of 500,000 shares. As a result, the aggregate number of notional shares of Common Stock of the Issuer in the applicable basket after giving effect to such transactions is 124,333 shares."},{"field":"ownership.nature","element":"natureOfOwnership","label":"F1","text":"As the investment manager of ADAR1 Partners, LP and ADAR1 SPV I, LP and as the sub-advisor of Spearhead Insurance Solutions IDF, LLC, ADAR1 Capital Management, LLC may be deemed to indirectly beneficially own securities held by ADAR1 Partners, LP, ADAR1 SPV I, LP and Spearhead Insurance Solutions IDF, LLC. As the general partner of ADAR1 Partners, LP and ADAR1 SPV I, LP, ADAR1 Capital Management GP, LLC may be deemed to indirectly beneficially own securities held by ADAR1 Partners, LP and ADAR1 SPV I, LP. As the manager of ADAR1 Capital Management, LLC and ADAR1 Capital Management GP, LLC, Mr. Schneeberger may be deemed to indirectly beneficially own securities held by ADAR1 Partners, LP, Spearhead Insurance Solutions IDF, LLC, and ADAR1 SPV I, LP."},{"field":"ownership.nature","element":"natureOfOwnership","label":"F8","text":"For purposes of Section 16 of the Securities Exchange Act of 1934, as amended, each Reporting Person disclaims beneficial ownership of any such securities, except to the extent of his/its pecuniary interest therein, if any, and this report shall not be deemed an admission that such Reporting Person is the beneficial owner of such securities for purposes of Section 16 or otherwise."}],"balance_after":124333,"derivative":{"underlying":"Common Stock","underlying_shares":500000},"source":{"system":"sec-edgar","filing":"0001104659-25-034321","document":"tm2512234-2_4seq1.xml","document_sequence":1,"table":"derivative","row_type":"transaction","position":8,"url":"https://www.sec.gov/Archives/edgar/data/1940267/000110465925034321/tm2512234-2_4seq1.xml","form_type":"4"}},{"id":1173471,"issuer":{"id":6242,"kind":"organization","name":"Keros Therapeutics, Inc."},"owners":[{"id":980,"kind":"organization","name":"ADAR1 Capital Management, LLC","position":1,"cik":"0001940272","reported_name":"ADAR1 Capital Management, LLC","relationship":{"director":false,"officer":false,"ten_percent_owner":true,"other":false}},{"id":74265,"kind":"organization","name":"ADAR1 Partners, LP","position":2,"cik":"0001758866","reported_name":"ADAR1 Partners, LP","relationship":{"director":false,"officer":false,"ten_percent_owner":true,"other":false}},{"id":74266,"kind":"organization","name":"ADAR1 Capital Management GP, LLC","position":3,"cik":"0001940267","reported_name":"ADAR1 Capital Management GP, LLC","relationship":{"director":false,"officer":false,"ten_percent_owner":true,"other":false}},{"id":981,"kind":"person","name":"Schneeberger Daniel","position":4,"cik":"0001861120","reported_name":"Schneeberger Daniel","relationship":{"director":false,"officer":false,"ten_percent_owner":true,"other":false}}],"security":"Cash-Settled Total Return Swaps","published_at":"2025-04-11T21:57:19.000Z","date":"2025-04-09","kind":"other","planned":false,"acquired":false,"shares":325000,"ownership":{"direct":false,"nature":"By ADAR1 Partners, LP"},"footnotes":[{"field":"derivative.exercise_price","element":"conversionOrExercisePrice","label":"F5","text":"In connection with the purchase of 325,000 securities reported as being purchased in Table 1, ADAR1 Partners, LP and the counterparty to the cash-settled total equity swaps previously reported agreed to reduce the number of notional shares of Common Stock of the Issuer in the applicable basket by a corresponding number of 325,000 shares. As a result, the aggregate number of notional shares of Common Stock of the Issuer in the applicable basket after giving effect to such transactions is 624,333 shares."},{"field":"kind","element":"transactionCoding","label":"F5","text":"In connection with the purchase of 325,000 securities reported as being purchased in Table 1, ADAR1 Partners, LP and the counterparty to the cash-settled total equity swaps previously reported agreed to reduce the number of notional shares of Common Stock of the Issuer in the applicable basket by a corresponding number of 325,000 shares. As a result, the aggregate number of notional shares of Common Stock of the Issuer in the applicable basket after giving effect to such transactions is 624,333 shares."},{"field":"shares","element":"transactionShares","label":"F5","text":"In connection with the purchase of 325,000 securities reported as being purchased in Table 1, ADAR1 Partners, LP and the counterparty to the cash-settled total equity swaps previously reported agreed to reduce the number of notional shares of Common Stock of the Issuer in the applicable basket by a corresponding number of 325,000 shares. As a result, the aggregate number of notional shares of Common Stock of the Issuer in the applicable basket after giving effect to such transactions is 624,333 shares."},{"field":"price","element":"transactionPricePerShare","label":"F5","text":"In connection with the purchase of 325,000 securities reported as being purchased in Table 1, ADAR1 Partners, LP and the counterparty to the cash-settled total equity swaps previously reported agreed to reduce the number of notional shares of Common Stock of the Issuer in the applicable basket by a corresponding number of 325,000 shares. As a result, the aggregate number of notional shares of Common Stock of the Issuer in the applicable basket after giving effect to such transactions is 624,333 shares."},{"field":"derivative.exercise_date","element":"exerciseDate","label":"F5","text":"In connection with the purchase of 325,000 securities reported as being purchased in Table 1, ADAR1 Partners, LP and the counterparty to the cash-settled total equity swaps previously reported agreed to reduce the number of notional shares of Common Stock of the Issuer in the applicable basket by a corresponding number of 325,000 shares. As a result, the aggregate number of notional shares of Common Stock of the Issuer in the applicable basket after giving effect to such transactions is 624,333 shares."},{"field":"derivative.expiration_date","element":"expirationDate","label":"F5","text":"In connection with the purchase of 325,000 securities reported as being purchased in Table 1, ADAR1 Partners, LP and the counterparty to the cash-settled total equity swaps previously reported agreed to reduce the number of notional shares of Common Stock of the Issuer in the applicable basket by a corresponding number of 325,000 shares. As a result, the aggregate number of notional shares of Common Stock of the Issuer in the applicable basket after giving effect to such transactions is 624,333 shares."},{"field":"derivative.underlying_shares","element":"underlyingSecurityShares","label":"F5","text":"In connection with the purchase of 325,000 securities reported as being purchased in Table 1, ADAR1 Partners, LP and the counterparty to the cash-settled total equity swaps previously reported agreed to reduce the number of notional shares of Common Stock of the Issuer in the applicable basket by a corresponding number of 325,000 shares. As a result, the aggregate number of notional shares of Common Stock of the Issuer in the applicable basket after giving effect to such transactions is 624,333 shares."},{"field":"balance_after","element":"sharesOwnedFollowingTransaction","label":"F5","text":"In connection with the purchase of 325,000 securities reported as being purchased in Table 1, ADAR1 Partners, LP and the counterparty to the cash-settled total equity swaps previously reported agreed to reduce the number of notional shares of Common Stock of the Issuer in the applicable basket by a corresponding number of 325,000 shares. As a result, the aggregate number of notional shares of Common Stock of the Issuer in the applicable basket after giving effect to such transactions is 624,333 shares."},{"field":"ownership.nature","element":"natureOfOwnership","label":"F1","text":"As the investment manager of ADAR1 Partners, LP and ADAR1 SPV I, LP and as the sub-advisor of Spearhead Insurance Solutions IDF, LLC, ADAR1 Capital Management, LLC may be deemed to indirectly beneficially own securities held by ADAR1 Partners, LP, ADAR1 SPV I, LP and Spearhead Insurance Solutions IDF, LLC. As the general partner of ADAR1 Partners, LP and ADAR1 SPV I, LP, ADAR1 Capital Management GP, LLC may be deemed to indirectly beneficially own securities held by ADAR1 Partners, LP and ADAR1 SPV I, LP. As the manager of ADAR1 Capital Management, LLC and ADAR1 Capital Management GP, LLC, Mr. Schneeberger may be deemed to indirectly beneficially own securities held by ADAR1 Partners, LP, Spearhead Insurance Solutions IDF, LLC, and ADAR1 SPV I, LP."},{"field":"ownership.nature","element":"natureOfOwnership","label":"F8","text":"For purposes of Section 16 of the Securities Exchange Act of 1934, as amended, each Reporting Person disclaims beneficial ownership of any such securities, except to the extent of his/its pecuniary interest therein, if any, and this report shall not be deemed an admission that such Reporting Person is the beneficial owner of such securities for purposes of Section 16 or otherwise."}],"balance_after":624333,"derivative":{"underlying":"Common Stock","underlying_shares":325000},"source":{"system":"sec-edgar","filing":"0001104659-25-034321","document":"tm2512234-2_4seq1.xml","document_sequence":1,"table":"derivative","row_type":"transaction","position":7,"url":"https://www.sec.gov/Archives/edgar/data/1940267/000110465925034321/tm2512234-2_4seq1.xml","form_type":"4"}},{"id":1173470,"issuer":{"id":6242,"kind":"organization","name":"Keros Therapeutics, Inc."},"owners":[{"id":980,"kind":"organization","name":"ADAR1 Capital Management, LLC","position":1,"cik":"0001940272","reported_name":"ADAR1 Capital Management, LLC","relationship":{"director":false,"officer":false,"ten_percent_owner":true,"other":false}},{"id":74265,"kind":"organization","name":"ADAR1 Partners, LP","position":2,"cik":"0001758866","reported_name":"ADAR1 Partners, LP","relationship":{"director":false,"officer":false,"ten_percent_owner":true,"other":false}},{"id":74266,"kind":"organization","name":"ADAR1 Capital Management GP, LLC","position":3,"cik":"0001940267","reported_name":"ADAR1 Capital Management GP, LLC","relationship":{"director":false,"officer":false,"ten_percent_owner":true,"other":false}},{"id":981,"kind":"person","name":"Schneeberger Daniel","position":4,"cik":"0001861120","reported_name":"Schneeberger Daniel","relationship":{"director":false,"officer":false,"ten_percent_owner":true,"other":false}}],"security":"Common Stock","published_at":"2025-04-11T21:57:19.000Z","date":"2025-04-09","kind":"purchase","planned":false,"acquired":true,"shares":74333,"price":10.33,"value":767859.89,"ownership":{"direct":false,"nature":"By ADAR1 Partners, LP"},"footnotes":[{"field":"ownership.nature","element":"natureOfOwnership","label":"F1","text":"As the investment manager of ADAR1 Partners, LP and ADAR1 SPV I, LP and as the sub-advisor of Spearhead Insurance Solutions IDF, LLC, ADAR1 Capital Management, LLC may be deemed to indirectly beneficially own securities held by ADAR1 Partners, LP, ADAR1 SPV I, LP and Spearhead Insurance Solutions IDF, LLC. As the general partner of ADAR1 Partners, LP and ADAR1 SPV I, LP, ADAR1 Capital Management GP, LLC may be deemed to indirectly beneficially own securities held by ADAR1 Partners, LP and ADAR1 SPV I, LP. As the manager of ADAR1 Capital Management, LLC and ADAR1 Capital Management GP, LLC, Mr. Schneeberger may be deemed to indirectly beneficially own securities held by ADAR1 Partners, LP, Spearhead Insurance Solutions IDF, LLC, and ADAR1 SPV I, LP."},{"field":"ownership.nature","element":"natureOfOwnership","label":"F8","text":"For purposes of Section 16 of the Securities Exchange Act of 1934, as amended, each Reporting Person disclaims beneficial ownership of any such securities, except to the extent of his/its pecuniary interest therein, if any, and this report shall not be deemed an admission that such Reporting Person is the beneficial owner of such securities for purposes of Section 16 or otherwise."}],"balance_after":4392737,"source":{"system":"sec-edgar","filing":"0001104659-25-034321","document":"tm2512234-2_4seq1.xml","document_sequence":1,"table":"nonDerivative","row_type":"transaction","position":5,"url":"https://www.sec.gov/Archives/edgar/data/1940267/000110465925034321/tm2512234-2_4seq1.xml","form_type":"4"}},{"id":1173469,"issuer":{"id":6242,"kind":"organization","name":"Keros Therapeutics, Inc."},"owners":[{"id":980,"kind":"organization","name":"ADAR1 Capital Management, LLC","position":1,"cik":"0001940272","reported_name":"ADAR1 Capital Management, LLC","relationship":{"director":false,"officer":false,"ten_percent_owner":true,"other":false}},{"id":74265,"kind":"organization","name":"ADAR1 Partners, LP","position":2,"cik":"0001758866","reported_name":"ADAR1 Partners, LP","relationship":{"director":false,"officer":false,"ten_percent_owner":true,"other":false}},{"id":74266,"kind":"organization","name":"ADAR1 Capital Management GP, LLC","position":3,"cik":"0001940267","reported_name":"ADAR1 Capital Management GP, LLC","relationship":{"director":false,"officer":false,"ten_percent_owner":true,"other":false}},{"id":981,"kind":"person","name":"Schneeberger Daniel","position":4,"cik":"0001861120","reported_name":"Schneeberger Daniel","relationship":{"director":false,"officer":false,"ten_percent_owner":true,"other":false}}],"security":"Common Stock","published_at":"2025-04-11T21:57:19.000Z","date":"2025-04-09","kind":"purchase","planned":false,"acquired":true,"shares":500000,"price":10.33,"value":5165000.0,"ownership":{"direct":false,"nature":"By ADAR1 Partners, LP"},"footnotes":[{"field":"ownership.nature","element":"natureOfOwnership","label":"F1","text":"As the investment manager of ADAR1 Partners, LP and ADAR1 SPV I, LP and as the sub-advisor of Spearhead Insurance Solutions IDF, LLC, ADAR1 Capital Management, LLC may be deemed to indirectly beneficially own securities held by ADAR1 Partners, LP, ADAR1 SPV I, LP and Spearhead Insurance Solutions IDF, LLC. As the general partner of ADAR1 Partners, LP and ADAR1 SPV I, LP, ADAR1 Capital Management GP, LLC may be deemed to indirectly beneficially own securities held by ADAR1 Partners, LP and ADAR1 SPV I, LP. As the manager of ADAR1 Capital Management, LLC and ADAR1 Capital Management GP, LLC, Mr. Schneeberger may be deemed to indirectly beneficially own securities held by ADAR1 Partners, LP, Spearhead Insurance Solutions IDF, LLC, and ADAR1 SPV I, LP."},{"field":"ownership.nature","element":"natureOfOwnership","label":"F8","text":"For purposes of Section 16 of the Securities Exchange Act of 1934, as amended, each Reporting Person disclaims beneficial ownership of any such securities, except to the extent of his/its pecuniary interest therein, if any, and this report shall not be deemed an admission that such Reporting Person is the beneficial owner of such securities for purposes of Section 16 or otherwise."}],"balance_after":4318404,"source":{"system":"sec-edgar","filing":"0001104659-25-034321","document":"tm2512234-2_4seq1.xml","document_sequence":1,"table":"nonDerivative","row_type":"transaction","position":4,"url":"https://www.sec.gov/Archives/edgar/data/1940267/000110465925034321/tm2512234-2_4seq1.xml","form_type":"4"}},{"id":1173468,"issuer":{"id":6242,"kind":"organization","name":"Keros Therapeutics, Inc."},"owners":[{"id":980,"kind":"organization","name":"ADAR1 Capital Management, LLC","position":1,"cik":"0001940272","reported_name":"ADAR1 Capital Management, LLC","relationship":{"director":false,"officer":false,"ten_percent_owner":true,"other":false}},{"id":74265,"kind":"organization","name":"ADAR1 Partners, LP","position":2,"cik":"0001758866","reported_name":"ADAR1 Partners, LP","relationship":{"director":false,"officer":false,"ten_percent_owner":true,"other":false}},{"id":74266,"kind":"organization","name":"ADAR1 Capital Management GP, LLC","position":3,"cik":"0001940267","reported_name":"ADAR1 Capital Management GP, LLC","relationship":{"director":false,"officer":false,"ten_percent_owner":true,"other":false}},{"id":981,"kind":"person","name":"Schneeberger Daniel","position":4,"cik":"0001861120","reported_name":"Schneeberger Daniel","relationship":{"director":false,"officer":false,"ten_percent_owner":true,"other":false}}],"security":"Common Stock","published_at":"2025-04-11T21:57:19.000Z","date":"2025-04-09","kind":"purchase","planned":false,"acquired":true,"shares":325000,"price":9.857,"value":3203525.0,"ownership":{"direct":false,"nature":"By ADAR1 Partners, LP"},"footnotes":[{"field":"price","element":"transactionPricePerShare","label":"F4","text":"The reported price is a weighted average price. These shares were purchased in multiple transactions at prices ranging from $9.13 to $10.60, inclusive."},{"field":"ownership.nature","element":"natureOfOwnership","label":"F1","text":"As the investment manager of ADAR1 Partners, LP and ADAR1 SPV I, LP and as the sub-advisor of Spearhead Insurance Solutions IDF, LLC, ADAR1 Capital Management, LLC may be deemed to indirectly beneficially own securities held by ADAR1 Partners, LP, ADAR1 SPV I, LP and Spearhead Insurance Solutions IDF, LLC. As the general partner of ADAR1 Partners, LP and ADAR1 SPV I, LP, ADAR1 Capital Management GP, LLC may be deemed to indirectly beneficially own securities held by ADAR1 Partners, LP and ADAR1 SPV I, LP. As the manager of ADAR1 Capital Management, LLC and ADAR1 Capital Management GP, LLC, Mr. Schneeberger may be deemed to indirectly beneficially own securities held by ADAR1 Partners, LP, Spearhead Insurance Solutions IDF, LLC, and ADAR1 SPV I, LP."},{"field":"ownership.nature","element":"natureOfOwnership","label":"F8","text":"For purposes of Section 16 of the Securities Exchange Act of 1934, as amended, each Reporting Person disclaims beneficial ownership of any such securities, except to the extent of his/its pecuniary interest therein, if any, and this report shall not be deemed an admission that such Reporting Person is the beneficial owner of such securities for purposes of Section 16 or otherwise."}],"balance_after":3818404,"source":{"system":"sec-edgar","filing":"0001104659-25-034321","document":"tm2512234-2_4seq1.xml","document_sequence":1,"table":"nonDerivative","row_type":"transaction","position":3,"url":"https://www.sec.gov/Archives/edgar/data/1940267/000110465925034321/tm2512234-2_4seq1.xml","form_type":"4"}},{"id":1173467,"issuer":{"id":6242,"kind":"organization","name":"Keros Therapeutics, Inc."},"owners":[{"id":980,"kind":"organization","name":"ADAR1 Capital Management, LLC","position":1,"cik":"0001940272","reported_name":"ADAR1 Capital Management, LLC","relationship":{"director":false,"officer":false,"ten_percent_owner":true,"other":false}},{"id":74265,"kind":"organization","name":"ADAR1 Partners, LP","position":2,"cik":"0001758866","reported_name":"ADAR1 Partners, LP","relationship":{"director":false,"officer":false,"ten_percent_owner":true,"other":false}},{"id":74266,"kind":"organization","name":"ADAR1 Capital Management GP, LLC","position":3,"cik":"0001940267","reported_name":"ADAR1 Capital Management GP, LLC","relationship":{"director":false,"officer":false,"ten_percent_owner":true,"other":false}},{"id":981,"kind":"person","name":"Schneeberger Daniel","position":4,"cik":"0001861120","reported_name":"Schneeberger Daniel","relationship":{"director":false,"officer":false,"ten_percent_owner":true,"other":false}}],"security":"Common Stock","published_at":"2025-04-11T21:57:19.000Z","date":"2025-04-09","kind":"purchase","planned":false,"acquired":true,"shares":16365,"price":9.3952,"value":153752.448,"ownership":{"direct":false,"nature":"By Spearhead Insurance Solutions IDF, LLC"},"footnotes":[{"field":"price","element":"transactionPricePerShare","label":"F3","text":"The reported price is a weighted average price. These shares were purchased in multiple transactions at prices ranging from $9.21 to $9.56, inclusive."},{"field":"ownership.nature","element":"natureOfOwnership","label":"F1","text":"As the investment manager of ADAR1 Partners, LP and ADAR1 SPV I, LP and as the sub-advisor of Spearhead Insurance Solutions IDF, LLC, ADAR1 Capital Management, LLC may be deemed to indirectly beneficially own securities held by ADAR1 Partners, LP, ADAR1 SPV I, LP and Spearhead Insurance Solutions IDF, LLC. As the general partner of ADAR1 Partners, LP and ADAR1 SPV I, LP, ADAR1 Capital Management GP, LLC may be deemed to indirectly beneficially own securities held by ADAR1 Partners, LP and ADAR1 SPV I, LP. 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OrbiMed Capital GP VII LLC (\"OrbiMed GP\") is the general partner of OPI VII and OrbiMed Advisors LLC (\"OrbiMed Advisors\") is the managing member of OrbiMed GP. By virtue of such relationships, OrbiMed GP and OrbiMed Advisors may be deemed to have voting power and investment power over the securities held by OPI VII and as a result, may be deemed to have beneficial ownership over such securities. OrbiMed Advisors exercises voting and investment power through a management committee comprised of the Reporting Person, Sven H. Borho, and W. 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Each of the Reporting Persons disclaims beneficial ownership of the securities reported herein for purposes of Rule 16a-1(a) under the Securities Exchange Act of 1934, as amended (the \"Exchange Act\"), except to the extent of its pecuniary interest therein, if any. The Reporting Persons have designated a representative, Carl L. Gordon, a member of OrbiMed Advisors, to serve on the Issuer's board of directors. 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OrbiMed Capital GP VII LLC (\"OrbiMed GP\") is the general partner of OPI VII and OrbiMed Advisors LLC (\"OrbiMed Advisors\") is the managing member of OrbiMed GP. By virtue of such relationships, OrbiMed GP and OrbiMed Advisors may be deemed to have voting power and investment power over the securities held by OPI VII and as a result, may be deemed to have beneficial ownership over such securities. OrbiMed Advisors exercises voting and investment power through a management committee comprised of Carl L. Gordon, Sven H. Borho, and W. Carter Neild, each of whom disclaims beneficial ownership of the shares held by OPI VII."},{"field":"ownership.nature","element":"natureOfOwnership","label":"F3","text":"This report on Form 4 is jointly filed by OrbiMed Advisors, OrbiMed GP, and Genesis GP. Each of the Reporting Persons disclaims beneficial ownership of the securities reported herein for purposes of Rule 16a-1(a) under the Securities Exchange Act of 1934, as amended (the \"Exchange Act\"), except to the extent of its pecuniary interest therein, if any. The Reporting Persons have designated a representative, Carl L. Gordon, a member of OrbiMed Advisors, to serve on the Issuer's board of directors. This report shall not be deemed an admission that any such entity or person is a beneficial owner of such securities for purposes of Section 16 of the Exchange Act, or for any other purpose."}],"balance_after":899212,"source":{"system":"sec-edgar","filing":"0000947871-24-000702","document":"ownership.xml","document_sequence":1,"table":"nonDerivative","row_type":"transaction","position":1,"url":"https://www.sec.gov/Archives/edgar/data/1055951/000094787124000702/ownership.xml","form_type":"4"}}],"next_cursor":"2024-08-15T21:01:28.000000Z,1432829"}