Sec Form 4 Filing - Lazarus Alon @ Keros Therapeutics, Inc. - 2020-04-13

FORM 4 Check this box if no longer subject to Section 16. Form 4 or Form 5 obligations may continue. See Instruction 1(b).

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, Section 17(a) of the Public Utility Holding Company Act of 1935 or Section 30(h) of the Investment Company Act of 1940

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1. Name and Address of Reporting Person Lazarus Alon 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 X __ 10% Owner _____ Officer (give title below) _____ Other (specify below) (Last) (First) (Middle) C/O KEROS THERAPEUTICS, INC., 99 HAYDEN AVENUE, SUITE 120, BUILDING E 3. Date of Earliest Transaction (MM/DD/YY) 04/13/2020 (Street) LEXINGTON, MA02421 4. If Amendment, Date Original Filed (MM/DD/YY) 6. Individual or Joint/Group Filing (Check Applicable Line) __ X __ Form filed by One Reporting Person _____ Form filed by More than One Reporting Person (City) (State) (Zip)

Table I - Non-Derivative Securities Acquired, Disposed of, or Beneficially Owned 1.Title of Security (Instr. 3) 2. Transaction Date (MM/DD/YY) 2A. Deemed Execution Date, if any (MM/DD/YY) 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 04/13/2020 C 1,382,295 A 1,382,295 I See footnote ( 2 ) Common Stock 04/13/2020 C 343,270 A 1,725,565 I See footnote ( 2 ) Common Stock 04/13/2020 C 167,537 A 1,893,102 I See footnote ( 2 ) Common Stock 04/13/2020 P 120,000 A $ 16 2,013,102 I See footnote ( 2 ) Common Stock 23,038 D

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 (MM/DD/YY) 3A. Deemed Execution Date, if any (MM/DD/YY) 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 (MM/DD/YY) 7. Title and Amou nt of Underlying Securities (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 of Derivative Security: 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 Series A Preferred Stock ( 1 ) 04/13/2020 C 1,382,295 ( 1 ) ( 1 ) Common Stock 1,382,295 $ 0 0 I See footnote ( 2 ) Series B-1 Preferred Stock ( 1 ) 04/13/2020 C 343,270 ( 1 ) ( 1 ) Common Stock 343,270 $ 0 0 I See footnote ( 2 ) Series C Preferred Stock ( 1 ) 04/13/2020 C 167,537 ( 1 ) ( 1 ) Common Stock 167,537 $ 0 0 I See footnote ( 2 )

Reporting Owners Reporting Owner Name / Address Relationships Director 10% Owner Officer Other Lazarus Alon C/O KEROS THERAPEUTICS, INC. 99 HAYDEN AVENUE, SUITE 120, BUILDING E LEXINGTON, MA02421 X X Signatures /s/ Keith Regnante, Attorney-in-Fact 04/13/2020 Signature of Reporting Person Date

Explanation of Responses:

( 1 )Each share of Series A Preferred Stock, Series B-1 Preferred Stock and Series C Preferred Stock converted into shares of Common Stock upon the closing of the Issuer's initial public offering, on a one-for-one basis, and had no expiration date. ( 2 )The securities are held by Arkin Bio Ventures Limited Partnership ("Arkin Bio"). Arkin Bio Venture Partners Ltd. is the general partner of Arkin Bio. The Reporting Person, a member of the board of directors of the Issuer, is the Biotech Investment Manager of the Pharma Division of Arkin Holdings, and, as a result, may be deemed to share voting and investment power with respect to the shares held by Arkin Bio. The Reporting Person disclaims beneficial ownership of the shares held by Arkin Bio, except to the extent of his pecuniary interest therein.

Reminder: Report on a separate line for each class of securities beneficially owned directly or indirectly.

* If the form is filed by more than one reporting person, see Instruction 4(b)(v).

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