Sec Form 4 Filing - Mazabraud Yann @ RHYTHM PHARMACEUTICALS, INC. - 2024-04-14

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 Mazabraud Yann 2. Issuer Name and Ticker or Trading Symbol RHYTHM PHARMACEUTICALS, INC. [ RYTM] 5. Relationship of Reporting Person(s) to Issuer (Check all applicable) _____ Director _____ 10% Owner X __ Officer (give title below) _____ Other (specify below) EVP, Head of International (Last) (First) (Middle) 222 BERKELEY STREET, 12TH FLOOR 3. Date of Earliest Transaction (MM/DD/YY) 04/14/2024 (Street) BOSTON, MA02116 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 04/14/2024 M 10,375 D 34,870 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 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 Restricted Stock Units ( 1 ) 04/14/2024 M 10,375 ( 2 ) ( 2 ) Common Stock 10,375 $ 0 31,125 D Restricted Stock Units ( 1 ) 04/15/2024 D( 3 ) 2,031 ( 4 ) ( 4 ) Common Stock 2,031 $ 0 0 D Restricted Stock Units ( 1 ) 04/15/2024 D( 5 ) 6,874 ( 6 ) ( 6 ) Common Stock 6,874 $ 0 0 D Restricted Stock Units ( 1 ) 04/15/2024 A 8,905 ( 7 ) ( 7 ) Common Stock 8,905 $ 0 8,905 D Restricted Stock Units ( 1 ) 04/15/2024 A 10,000 ( 8 ) ( 8 ) Common Stock 10,000 $ 0 10,000 D

Reporting Owners Reporting Owner Name / Address Relationships Director 10% Owner Officer Other Mazabraud Yann 222 BERKELEY STREET, 12TH FLOOR BOSTON, MA02116 EVP, Head of International Signatures /s/ Hunter Smith, attorney-in-fact for Yann Mazabraud 04/16/2024 Signature of Reporting Person Date

Explanation of Responses:

( 1 )Each restricted stock unit represents a contingent right to receive one share of Issuer common stock. ( 2 )The restricted stock units vest or have vested as to 25% of the total shares on each of April 14, 2024, April 14, 2025, April 14, 2026 and April 14, 2027. The restricted stock units have no expiration date. ( 3 )The restricted stock units were rescinded and cancelled by mutual agreement of the reporting person and Issuer. The reporting person received French-qualified restricted stock units on April 15, 2024 as consideration for the recission and cancellation of the unvested portion of the restricted stock previously received on February 11, 2021. ( 4 )The restricted stock units vest or have vested as to 25% of the total shares on each of February 11, 2022, February 11, 2023, February 11, 2024 and February 11, 2025. The restricted stock units have no expiration date. ( 5 )The restricted stock units were rescinded and cancelled by mutual agreement of the reporting person and Issuer. The reporting person received French-qualified restricted stock units on April 15, 2024 as consideration for the recission and cancellation of the unvested portion of the restricted stock previously received on February 9, 2022. ( 6 )The restricted stock units vest or have vested as to 25% of the total shares on each of February 9, 2023, February 9, 2024, February 9, 2025 and February 9, 2026. The restricted stock units have no expiration date. ( 7 )The restricted stock units vest in full on April 15, 2025. The restricted stock units have no expiration date. ( 8 )The restricted stock units vest or have vested as to 25% of the total shares on each of April 15, 2025, April 15, 2026, April 15, 2027 and April 15, 2028. The restricted stock units have no expiration date.

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).

** Intentional misstatements or omissions of facts constitute Federal Criminal Violations. See 18 U.S.C. 1001 and 15 U.S.C. 78ff(a).

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