X0609 4 2026-09-14 0001649904 RHYTHM PHARMACEUTICALS, INC. RYTM 0001385155 Meeker David P false C/O RHYTHM PHARMACEUTICALS, INC. 222 BERKELEY STREET, 12TH FLOOR BOSTON MA 02116 1 1 President and CEO 1 Common Stock 2026-09-14 4 M 0 50000 6.05 A 289258 D Common Stock 2026-09-14 4 S 0 6439 101.7464 D 282819 D Common Stock 2026-09-14 4 S 0 30746 102.347 D 252073 D Common Stock 2026-09-14 4 S 0 8698 103.43 D 243375 D Common Stock 2026-09-14 4 S 0 1817 104.5487 D 241558 D Common Stock 2026-09-14 4 S 0 2300 105.19 D 239258 D Employee Stock Option (Right to Buy) 6.05 2026-09-14 4 M 0 50000 0 D 2027-02-07 Common Stock 50000 15431 D The exercise and sales reported in this form 4 were effected pursuant to a Rule 10b5-1 trading plan adopted by the reporting person on June 15, 2026. Includes 242 shares acquired under the Rhythm Pharmaceuticals, Inc. employee stock purchase plan on 2-28-2026. The price reported in Column 4 is a weighted average price. The securities were sold in multiple transactions at prices ranging from $100.96 to $101.95 per common stock. The Reporting Person undertakes to provide to the Issuer, any security holder of the Issuer or the staff of the Securities and Exchange Commission, upon request, full information regarding the number of shares sold at each separate price within the range set forth in this footnote. The price reported in Column 4 is a weighted average price. The securities were sold in multiple transactions at prices ranging from $101.96 to $102.94 per common stock. The Reporting Person undertakes to provide to the Issuer, any security holder of the Issuer or the staff of the Securities and Exchange Commission, upon request, full information regarding the number of shares sold at each separate price within the range set forth in this footnote. The price reported in Column 4 is a weighted average price. The securities were sold in multiple transactions at prices ranging from $102.97 to $103.96 per common stock. The Reporting Person undertakes to provide to the Issuer, any security holder of the Issuer or the staff of the Securities and Exchange Commission, upon request, full information regarding the number of shares sold at each separate price within the range set forth in this footnote. The price reported in Column 4 is a weighted average price. The securities were sold in multiple transactions at prices ranging from $103.97 to $104.94 per common stock. The Reporting Person undertakes to provide to the Issuer, any security holder of the Issuer or the staff of the Securities and Exchange Commission, upon request, full information regarding the number of shares sold at each separate price within the range set forth in this footnote. The price reported in Column 4 is a weighted average price. The securities were sold in multiple transactions at prices ranging from $105.00 to $105.31 per common stock. The Reporting Person undertakes to provide to the Issuer, any security holder of the Issuer or the staff of the Securities and Exchange Commission, upon request, full information regarding the number of shares sold at each separate price within the range set forth in this footnote. The stock options were granted on February 8, 2017 and vested and became exercisable in three equal annual installments measured from January 6, 2017. /s/ Stephen Vander Stoep, attorney-in-fact for David P. Meeker 2026-09-14