Sec Form 3 Filing - MARAGANORE JOHN @ Hemab Therapeutics Holdings, Inc. - 2026-04-30

FORM 3 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 MARAGANORE JOHN 2. Issuer Name and Ticker or Trading Symbol Hemab Therapeutics Holdings, Inc. [ COAG] 5. Relationship of Reporting Person(s) to Issuer (Check all applicable) X __ Director _____ 10% Owner _____ Officer (give title below) _____ Other (specify below) (Last) (First) (Middle) C/O HEMAB THERAPEUTICS HOLDINGS, INC., 101 MAIN STREET, SUITE 1220 3. Date of Earliest Transaction (MM/DD/YY) 04/30/2026 (Street) CAMBRIDGE, MA02142 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

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 Amount 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 B Preferred Stock ( 1 ) ( 1 ) ( 1 ) Common Stock 17,974 D Series C Preferred Stock ( 1 ) ( 1 ) ( 1 ) Common Stock 17,974 D Warrants (Right to Buy) $ 2.16 ( 2 ) 03/20/2032 Common Stock 47,476 D Warrants (Right to Buy) $ 7.07 ( 3 ) 08/13/2033 Common Stock 90,222 D Warrants (Right to Buy) $ 6 ( 4 ) 01/28/2036 Common Stock 107,338 D

Reporting Owners Reporting Owner Name / Address Relationships Director 10% Owner Officer Other MARAGANORE JOHN C/O HEMAB THERAPEUTICS HOLDINGS, INC. 101 MAIN STREET, SUITE 1220 CAMBRIDGE, MA02142 X Signatures /s/ Mads Nikolaj Behrndt-Eriksen, as Attorney-in-Fact 04/30/2026 Signature of Reporting Person Date

Explanation of Responses:

( 1 )Each share of Series B Preferred Stock and Series C Preferred Stock is convertible into 22 shares of common stock without payment of further consideration at the holder's election or upon closing of the initial public offering of the Issuer's common stock. The shares have no expiration date. ( 2 )The warrant was granted on March 21, 2022 and is fully vested. ( 3 )The warrant was granted on August 14, 2023 and is fully vested. ( 4 )The warrant was granted on January 29, 2026. The shares underlying the warrant vest over three years in equal monthly installments from January 1, 2026 through January 1, 2029.

Remarks: 24.1 Power of Attorney

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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