RYTM · Rhythm Pharmaceuticals, Inc.

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 May 13, 2026.

The price reported in Column 4 is a weighted average price. The securities were sold in multiple transactions at prices ranging from $105.04 to $106.01 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 exercise and sales reported in this form 4 were effected pursuant to a Rule 10b5-1 trading plan adopted by the reporting person on May 13, 2026.

The price reported in Column 4 is a weighted average price. The securities were sold in multiple transactions at prices ranging from $106.05 to $106.88 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 exercise and sales reported in this form 4 were effected pursuant to a Rule 10b5-1 trading plan adopted by the reporting person on May 13, 2026.

The price reported in Column 4 is a weighted average price. The securities were sold in multiple transactions at prices ranging from $104.04 to $105.03 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 exercise and sales reported in this form 4 were effected pursuant to a Rule 10b5-1 trading plan adopted by the reporting person on May 13, 2026.

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 May 13, 2026.

This option was granted on February 14, 2018 and the shares underlying this option vested in sixteen equal quarterly installments.

The Restricted Stock Units vest as to 25% of the Restricted Stock Units on September 1 of each of 2027, 2028, 2029, and 2030, such that the Restricted Stock Units shall be fully vested on September 1, 2030, subject to the Reporting Person continuing in service through each such vesting date.

The restricted stock units have no expiration date.

The Stock Options vest and become exercisable as to 25% of the total number of shares subject to the option on the first anniversary of the grant date and as to 6.25% of the total number of shares subject to the option upon the Reporting Person's completion of each successive three months of service to the Corporation.

The sales reported in the Form 4 were effected pursuant to a Rule 10b5-1 trading plan adopted by the Reporting Person on May 14, 2026.

The price reported in Column 4 is a weighted average price. The securities were sold in multiple transactions at prices ranging from $117.73 to $118.71 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 Exercise and sale reported in this Form 4 were effected pursuant to a Rule 10b5-1 trading plan adopted by the Reporting Person on December 15, 2025.

The stock options were granted on February 9, 2022. The options vested and become exercisable in 16 substantially equal installments upon the Reporting Person's completion of each three full months of successive service to the Issuer following the grant date.

The exercises and sales reported in the Form 4 were effected pursuant to a Rule 10b5-1 trading plan adopted by the Reporting Person on May 14, 2026.

The stock options were granted on November 9, 2020. 25% of the shares subject to the option vested and become exercisable on November 9, 2021 and the remaining 75% of the shares subject to the option vested and become exercisable in 12 substantially equal installments upon the Reporting Person's completion of each three full months of successive service to the Issuer thereafter.

The sales reported in the Form 4 were effected pursuant to a Rule 10b5-1 trading plan adopted by the Reporting Person on May 14, 2026.

The price reported in Column 4 is a weighted average price. The securities were sold in multiple transactions at prices ranging from $116.72 to $117.66 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 Exercise and sale reported in this Form 4 were effected pursuant to a Rule 10b5-1 trading plan adopted by the Reporting Person on December 15, 2025.

The sales reported in the Form 4 were effected pursuant to a Rule 10b5-1 trading plan adopted by the Reporting Person on May 14, 2026.

The price reported in Column 4 is a weighted average price. The securities were sold in multiple transactions at prices ranging from $115.67 to $116.62 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 exercises and sales reported in the Form 4 were effected pursuant to a Rule 10b5-1 trading plan adopted by the Reporting Person on May 14, 2026.

The exercises and sales reported in the Form 4 were effected pursuant to a Rule 10b5-1 trading plan adopted by the Reporting Person on May 14, 2026.

The sales reported in the Form 4 were effected pursuant to a Rule 10b5-1 trading plan adopted by the Reporting Person on May 14, 2026.

The price reported in Column 4 is a weighted average price. The securities were sold in multiple transactions at prices ranging from $118.73 to $119.52 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 Exercise and sale reported in this Form 4 were effected pursuant to a Rule 10b5-1 trading plan adopted by the Reporting Person on December 15, 2025.

The exercises and sales reported in the Form 4 were effected pursuant to a Rule 10b5-1 trading plan adopted by the Reporting Person on May 14, 2026.

The stock options were granted on February 9, 2022. The options vested and became exercisable in 16 substantially equal installments upon the Reporting Person's completion of each three full months of successive service to the Issuer following the grant date.

The exercises and sales reported in the Form 4 were effected pursuant to a Rule 10b5-1 trading plan adopted by the Reporting Person on May 14, 2026.

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 May 13, 2026.

The price reported in Column 4 is a weighted average price. The securities were sold in multiple transactions at prices ranging from $114.01 to $115.00 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 exercise and sales reported in this Form 4 were effected pursuant to a Rule 10b5-1 trading plan adopted by the Reporting Person on May 13, 2026.

The price reported in Column 4 is a weighted average price. The securities were sold in multiple transactions at prices ranging from $112.84 to $112.92 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 exercise and sales reported in this Form 4 were effected pursuant to a Rule 10b5-1 trading plan adopted by the Reporting Person on May 13, 2026.

The price reported in Column 4 is a weighted average price. These shares were sold in multiple transactions at prices ranging from $117.01 to $117.60 per share. 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 exercise and sales reported in this Form 4 were effected pursuant to a Rule 10b5-1 trading plan adopted by the Reporting Person on May 13, 2026.

The price reported in Column 4 is a weighted average price. The securities were sold in multiple transactions at prices ranging from $115.01 to $116.00 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 exercise and sales reported in this Form 4 were effected pursuant to a Rule 10b5-1 trading plan adopted by the Reporting Person on May 13, 2026.

The stock options were granted on February 9, 2022. The options vest and become exercisable in 16 substantially equal installments upon the Reporting Person's completion of each three full months of successive service to the Issuer following the grant date.

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 May 13, 2026.

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 May 13, 2026.

The price reported in Column 4 is a weighted average price. The securities were sold in multiple transactions at prices ranging from $111.58 to $112.30 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 exercise and sales reported in this Form 4 were effected pursuant to a Rule 10b5-1 trading plan adopted by the Reporting Person on May 13, 2026.

The price reported in Column 4 is a weighted average price. The securities were sold in multiple transactions at prices ranging from $116.01 to $117.00 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.

Each restricted stock unit represents a contingent right to receive one share of Issuer common stock.

These shares were withheld for payment of the withholding taxes upon the vesting of the restricted stock units reported herein.

Each restricted stock unit represents a contingent right to receive one share of Issuer common stock.

The restricted stock units vest as to 25% of the total restricted stock units on each of the first four anniversaries of July 1, 2024, subject to the Reporting Person's continued service on each such vesting date. The restricted stock units have no expiration date.

The options fully vest upon the earlier of (i) June 24, 2027 or (ii) the day immediately prior to the date of the Issuer's next annual meeting of the stockholders to be held in 2027, subject to the Reporting Person's continued service on such vesting date.

Each restricted stock unit represents a contingent right to receive one share of Issuer common stock.

The restricted stock units fully vest upon the earlier of (i) June 24, 2027 or (ii) the day immediately prior to the date of the Issuer's next annual meeting of the stockholders to be held in 2027, subject to the Reporting Person's continued service on such vesting date. The restricted stock units have no expiration date.

Each restricted stock unit represents a contingent right to receive one share of Issuer common stock.

The restricted stock units fully vest upon the earlier of (i) June 24, 2027 or (ii) the day immediately prior to the date of the Issuer's next annual meeting of the stockholders to be held in 2027, subject to the Reporting Person's continued service on such vesting date. The restricted stock units have no expiration date.

Each restricted stock unit represents a contingent right to receive one share of Issuer common stock.

The restricted stock units fully vest upon the earlier of (i) June 24, 2027 or (ii) the day immediately prior to the date of the Issuer's next annual meeting of the stockholders to be held in 2027, subject to the Reporting Person's continued service on such vesting date. The restricted stock units have no expiration date.

The options fully vest upon the earlier of (i) June 24, 2027 or (ii) the day immediately prior to the date of the Issuer's next annual meeting of the stockholders to be held in 2027, subject to the Reporting Person's continued service on such vesting date.

The options fully vest upon the earlier of (i) June 24, 2027 or (ii) the day immediately prior to the date of the Issuer's next annual meeting of the stockholders to be held in 2027, subject to the Reporting Person's continued service on such vesting date.

The options fully vest upon the earlier of (i) June 24, 2027 or (ii) the day immediately prior to the date of the Issuer's next annual meeting of the stockholders to be held in 2027, subject to the Reporting Person's continued service on such vesting date.

Each restricted stock unit represents a contingent right to receive one share of Issuer common stock.

The restricted stock units fully vest upon the earlier of (i) June 24, 2027 or (ii) the day immediately prior to the date of the Issuer's next annual meeting of the stockholders to be held in 2027, subject to the Reporting Person's continued service on such vesting date. The restricted stock units have no expiration date.

The options fully vest upon the earlier of (i) June 24, 2027 or (ii) the day immediately prior to the date of the Issuer's next annual meeting of the stockholders to be held in 2027, subject to the Reporting Person's continued service on such vesting date.

Each restricted stock unit represents a contingent right to receive one share of Issuer common stock.

The restricted stock units fully vest upon the earlier of (i) June 24, 2027 or (ii) the day immediately prior to the date of the Issuer's next annual meeting of the stockholders to be held in 2027, subject to the Reporting Person's continued service on such vesting date. The restricted stock units have no expiration date.

Each restricted stock unit represents a contingent right to receive one share of Issuer common stock.

The restricted stock units are fully vested. The restricted stock units have no expiration date.

Each restricted stock unit represents a contingent right to receive one share of Issuer common stock.

Each restricted stock unit represents a contingent right to receive one share of Issuer common stock.

The restricted stock units are fully vested. The restricted stock units have no expiration date.

Each restricted stock unit represents a contingent right to receive one share of Issuer common stock.

The restricted stock units are fully vested. The restricted stock units have no expiration date.

Each restricted stock unit represents a contingent right to receive one share of Issuer common stock.

The restricted stock units are fully vested. The restricted stock units have no expiration date.

Each restricted stock unit represents a contingent right to receive one share of Issuer common stock.

Each restricted stock unit represents a contingent right to receive one share of Issuer common stock.

Each restricted stock unit represents a contingent right to receive one share of Issuer common stock.

The restricted stock units are fully vested. The restricted stock units have no expiration date.

Each restricted stock unit represents a contingent right to receive one share of Issuer common stock.

Each restricted stock unit represents a contingent right to receive one share of Issuer common stock.