X0202 SCHEDULE 13G/A 0001224962 XXXXXXXX LIVE 2 Common Stock, $0.001 par value per share 03/31/2026 0001649904 RHYTHM PHARMACEUTICALS, INC. 76243J105 222 BERKELEY STREET, 12TH FLOOR Suite 1200 BOSTON MA 02116 Rule 13d-1(c) Perceptive Advisors LLC b DE 0 3519626 0 3519626 3519626 N 5.1 IA Joseph Edelman b X1 0 3519626 0 3519626 3519626 N 5.1 IN Perceptive Life Sciences Master Fund, Ltd. b E9 0 2790461 0 2790461 2790461 N 4.1 CO Perceptive Capital Solutions Holdings LP b DE 0 729165 0 729165 729165 N 1.1 PN RHYTHM PHARMACEUTICALS, INC. 222 BERKELEY STREET, 12TH FLOOR, BOSTON, MA 02116 The names of the persons filing this report (collectively, the "Reporting Persons") with respect to shares of Common Stock, $0.001 par value per share (the "Common Stock") of RHYTHM PHARMACEUTICALS, INC. (the "Issuer") are: (i) Perceptive Advisors LLC ("Perceptive Advisors") (ii) Joseph Edelman ("Mr. Edelman") (iii) Perceptive Life Sciences Master Fund, Ltd. (the "Master Fund") (iv) Perceptive Capital Solutions Holdings LP ("Capital Solutions Holdings") The address of the principal business office of each of the Reporting Persons is: 51 Astor Place, 10th Floor, New York, NY 10003 Perceptive Advisors is a Delaware limited liability company. Mr. Edelman is a United States citizen. The Master Fund is a Cayman Islands corporation. Capital Solutions Holdings is a Delaware Limited Liability Company. Y The information required by this item with respect to each Reporting Person is set forth in Rows 5 through 9 of the cover pages to this Schedule 13G. The ownership percentages reported are based on 68,532,607 shares of Common Stock outstanding as of May 1, 2026, as reported by the Issuer in its Quarterly Report on Form 10-Q filed with the Securities and Exchange Commission on May 5, 2026, and give effect to the conversion of shares of the Issuer's Series A Convertible Preferred Stock, par value $0.001 per share (the "Series A Convertible Preferred Stock"), held by the Reporting Persons at the current conversion rate of 20.8333 shares of Common Stock issuable upon the conversion of each $1,000 of liquidation preference. The Master Fund directly holds 2,373,795 shares of Common Stock. The Master Fund holds Series A Convertible Preferred Stock convertible into 416,666 shares of Common Stock. Capital Solutions Holdings holds Series A Convertible Preferred Stock convertible into 729,165 shares of Common Stock. Perceptive Advisors serves as the investment manager to the Master Fund and may be deemed to beneficially own the shares held by the Master Fund. Perceptive Capital Solutions Advisors LP serves as the investment manager to Capital Solutions Holdings and may be deemed to beneficially own the shares held by Capital Solutions Holdings. Perceptive Capital Solutions GP LLC is the general partner of Capital Solutions Holdings and is managed by Perceptive Capital Solutions Advisors LP, a relying adviser of Perceptive Advisors. Mr. Edelman is the managing member of Perceptive Advisors and may be deemed to beneficially own the shares held by the Master Fund and Capital Solutions Holdings. Perceptive Advisors: 5.1% Mr. Edelman: 5.1% Master Fund: 4.1% Capital Solutions Holdings: 1.1% Perceptive Advisors: 0 Mr. Edelman: 0 Master Fund: 0 Capital Solutions Holdings: 0 Perceptive Advisors: 3,519,626 Mr. Edelman: 3,519,626 Master Fund: 2,790,461 Capital Solutions Holdings: 729,165 Perceptive Advisors: 0 Mr. Edelman: 0 Master Fund: 0 Capital Solutions Holdings: 0 Perceptive Advisors: 3,519,626 Mr. Edelman: 3,519,626 Master Fund: 2,790,461 Capital Solutions Holdings: 729,165 Y Y Y Y Y N By signing below I certify that, to the best of my knowledge and belief, the securities referred to above were not acquired and are not held for the purpose of or with the effect of changing or influencing the control of the issuer of the securities and were not acquired and are not held in connection with or as a participant in any transaction having that purpose or effect, other than activities solely in connection with a nomination under ?? 240.14a-11. Perceptive Advisors LLC /s/ Joseph Edelman 05/15/2026 Joseph Edelman /s/ Joseph Edelman 05/15/2026 Perceptive Life Sciences Master Fund, Ltd. /s/ Joseph Edelman 05/15/2026 Perceptive Capital Solutions Holdings LP /s/ Joseph Edelman 05/15/2026