FORM 4 UNITED STATES SECURITIES AND EXCHANGE COMMISSION
Washington, D.C. 20549

STATEMENT OF CHANGES IN BENEFICIAL OWNERSHIP

Filed pursuant to Section 16(a) of the Securities Exchange Act of 1934
or Section 30(h) of the Investment Company Act of 1940
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Check this box if no longer subject to Section 16. Form 4 or Form 5 obligations may continue. See Instruction 1(b).
1. Name and Address of Reporting Person *
GORDON CARL L

(Last) (First) (Middle)
C/O KEROS THERAPEUTICS, INC.
1050 WALTHAM STREET, SUITE 302

(Street)
LEXINGTON MA 02421

(City) (State) (Zip)
2. Issuer Name and Ticker or Trading Symbol
Keros Therapeutics, Inc. [ KROS ]
5. Relationship of Reporting Person(s) to Issuer
(Check all applicable)
X Director 10% Owner
Officer (give title below) Other (specify below)
3. Date of Earliest Transaction (Month/Day/Year)
06/04/2025
4. If Amendment, Date of Original Filed (Month/Day/Year)
6. Individual or Joint/Group Filing (Check Applicable Line)
X Form filed by One Reporting Person
Form filed by More than One Reporting Person
Table I - Non-Derivative Securities Acquired, Disposed of, or Beneficially Owned
1. Title of Security (Instr. 3) 2. Transaction Date (Month/Day/Year) 2A. Deemed Execution Date, if any (Month/Day/Year) 3. Transaction Code (Instr. 8) 4. Securities Acquired (A) or Disposed Of (D) (Instr. 3, 4 and 5) 5. Amount of Securities Beneficially Owned Following Reported Transaction(s) (Instr. 3 and 4) 6. Ownership Form: Direct (D) or Indirect (I) (Instr. 4) 7. Nature of Indirect Beneficial Ownership (Instr. 4)
Code V Amount (A) or (D) Price
Common Stock 06/04/2025   A   5,250 (1) (2) A $ 0 5,250 D  
Common Stock               899,212 I See footnotes (3) (4)
Common Stock               119,522 I See footnotes (4) (5)
Table II - Derivative Securities Acquired, Disposed of, or Beneficially Owned
(e.g., puts, calls, warrants, options, convertible securities)
1. Title of Derivative Security (Instr. 3) 2. Conversion or Exercise Price of Derivative Security 3. Transaction Date (Month/Day/Year) 3A. Deemed Execution Date, if any (Month/Day/Year) 4. Transaction Code (Instr. 8) 5. Number of Derivative Securities Acquired (A) or Disposed of (D) (Instr. 3, 4 and 5) 6. Date Exercisable and Expiration Date (Month/Day/Year) 7. Title and Amount of Securities Underlying Derivative Security (Instr. 3 and 4) 8. Price of Derivative Security (Instr. 5) 9. Number of derivative Securities Beneficially Owned Following Reported Transaction(s) (Instr. 4) 10. Ownership Form: Direct (D) or Indirect (I) (Instr. 4) 11. Nature of Indirect Beneficial Ownership (Instr. 4)
Code V (A) (D) Date Exercisable Expiration Date Title Amount or Number of Shares
Stock Option (right to buy) $ 14.82 06/04/2025   A   10,500     (6) 06/03/2035 Common Stock 10,500 $ 0 10,500 (2) D  
Explanation of Responses:
1. Represents a restricted stock unit ("RSU") award. The RSUs fully vest on the earlier of (A) June 4, 2026 and (B) the date of the Issuer's 2026 annual meeting of stockholders, subject to the Reporting Person continuing to provide service through each such date.
2. Pursuant to an agreement with OrbiMed Advisors LLC and OrbiMed Capital GP VII LLC, the Reporting Person is obligated to transfer any securities issued under any such stock options or other awards, or the economic benefit thereof, to OrbiMed Advisors LLC and OrbiMed Capital GP VII LLC, which will in turn ensure that such securities or economic benefits are provided to OrbiMed Private Investments VII, LP.
3. These securities are held of record by OrbiMed Private Investments VII, LP ("OPI VII"). 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. Carter Neild, each of whom disclaims beneficial ownership of the shares held by OPI VII.
4. Each of the Reporting Person, OrbiMed Advisors, OrbiMed GP, and Genesis GP 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 his or its pecuniary interest therein, if any. 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.
5. . These securities are held of record by OrbiMed Genesis Master Fund, L.P. ("Genesis"). OrbiMed Genesis GP LLC ("Genesis GP") is the general partner of Genesis and OrbiMed Advisors is the managing member of Genesis GP. By virtue of such relationships, Genesis GP and OrbiMed Advisors may be deemed to have voting power and investment power over the securities held by Genesis 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. Carter Neild, each of whom disclaims beneficial ownership of the shares held by Genesis.
6. The option shall vest in equal quarterly installments over the 12 months following the date of grant, provided that the grant will in any case be fully vested on the date of Issuer's 2026 annual meeting of stockholders, subject to the Reporting Person continuing to provide service through each such date.
/s/ Keith Regnante, Attorney-in-Fact 06/06/2025
** Signature of Reporting Person Date
Reminder: Report on a separate line for each class of securities beneficially owned directly or indirectly.
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