RYTM

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.

The option is fully vested and exercisable.

The sales reported in the Form 4 were effected pursuant to a Rule 10b5-1 instruction adopted on December 15, 2025.

The price reported is a weighted average price. The securities were sold in multiple transactions at per share prices ranging from $100.00 to $100.91. The Reporting Person undertakes to provide upon request the SEC staff, the Issuer, or any shareholder of the Issuer, full information regarding the number of securities sold at each separate price within the range set forth in this footnote.

The options are fully vested.

The stock options were granted on April 4, 2023. The options vest and become exercisable as to 25% of the total shares on March 20, 2024 and, thereafter, as to the remaining 75% of the total shares in twelve equal quarterly installments of 6.25% beginning June 20, 2024 and ending March 20, 2027, subject to the Reporting Person's continued service on each such vesting date.

The stock options were granted on February 14, 2025. 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 stock options were granted on February 16, 2024. 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.

Includes an aggregate of 201 shares of Common Stock purchased pursuant to the Rhythm Pharmaceuticals, Inc. Employee Stock Purchase Plan.

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 will vest as to 33% of the total shares on each of April 1, 2027, April 1, 2028, April 1, 2029. 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 vest or have vested as to 25% of the total shares on each of April 15, 2025, April 1, 2026, April 1, 2027 and April 1, 2028. 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 vest or have vested as to 25% of the total shares on each of April 14, 2024, April 14, 2025, April 1, 2026 and April 1, 2027. The restricted stock units have no expiration date.

The stock options were granted on April 1, 2026. The options vest and become exercisable in three substantially equal annual installments subject to the Reporting Person continuing in service through each such vesting date.

NEA Partners 13, L.P. ("NEA Partners 13") made a pro rata distribution for no consideration of shares of Common Stock of the Issuer to its limited partners on March 12, 2026. The Edward Timothy Mathers Revocable Trust (the "Mathers Trust") received 4,199 shares of Common Stock of the Issuer in the distribution by NEA Partners 13 on March 12, 2026.

The Reporting Person is the trustee of the Mathers Trust, which is the direct beneficial owner of the securities. The Reporting Person disclaims beneficial ownership within the meaning of Section 16 of the Securities Exchange Act of 1934, as amended, or otherwise of such portion of the securities held by the Mathers Trust in which the Reporting Person has no pecuniary interest.

Includes 21 shares of Common Stock purchased pursuant to the Rhythm Pharmaceuticals, Inc. Employee Stock Purchase Plan.

The stock options were granted on April 4, 2023. The options vest and become exercisable as to 25% of the total shares on March 20, 2024 and, thereafter, as to the remaining 75% of the total shares in twelve equal quarterly installments of 6.25% beginning June 20, 2024 and ending March 20, 2027, subject to the Reporting Person's continued service on each such vesting date.

NEA Partners 13, L.P. ("NEA Partners 13") made a pro rata distribution for no consideration of shares of Common Stock of the Issuer to its limited partners on March 2, 2026. The Edward Timothy Mathers Revocable Trust (the "Mathers Trust") received 4,198 shares of Common Stock of the Issuer in the distribution by NEA Partners 13 on March 2, 2026.

The Reporting Person is the trustee of the Mathers Trust, which is the direct beneficial owner of the securities. The Reporting Person disclaims beneficial ownership within the meaning of Section 16 of the Securities Exchange Act of 1934, as amended, or otherwise of such portion of the securities held by the Mathers Trust in which the Reporting Person has no pecuniary interest.

The stock options were granted on March 2, 2026. 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 options are fully vested.

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 shares on each of March 20, 2024, March 20, 2025, March 1, 2026 and March 1, 2027, subject to the Reporting Person's continued service on each such vesting date. The restricted stock units have no expiration date.