X0609 4 2026-06-02 0 0001253689 CRESCENT BIOPHARMA, INC. CBIO 0001802528 Fairmount Funds Management LLC false 200 BARR HARBOR DRIVE, SUITE 400 WEST CONSHOHOCKEN PA 19428 1 0 1 0 0001769651 Fairmount Healthcare Fund II L.P. false 200 BARR HARBOR DRIVE, SUITE 400 WEST CONSHOHOCKEN PA 19428 1 0 1 0 0001663607 Harwin Peter Evan false 200 BARR HARBOR DRIVE, SUITE 400 WEST CONSHOHOCKEN PA 19428 1 0 1 0 0001830177 Kiselak Tomas false 200 BARR HARBOR DRIVE, SUITE 400 WEST CONSHOHOCKEN PA 19428 1 0 1 0 0 Stock Option (Right to Buy) 17.01 2026-06-02 4 A 0 11050 0 A 2036-06-02 Ordinary Shares 11050 11050 I By: Peter Harwin This option represents a right to purchase 11,050 of the Issuer's ordinary shares and vests in full on the earlier of (i) June 2, 2027 or (ii) the date of the Issuer's next annual meeting of shareholders, in each case, subject to the Reporting Person's continued service to the Issuer. Fairmount Funds Management LLC ("Fairmount") is the investment manager for Fairmount Healthcare Fund II LP ("Fund II"). Peter Harwin and Tomas Kiselak are the managers of Fairmount. Under Mr. Harwin's arrangement with Fairmount, Mr. Harwin holds the option for one or more investment vehicles managed by Fairmount (each, a "Fairmount Fund"). Mr. Harwin is obligated to turn over to Fairmount any net cash or stock received from the option for the benefit of such Fairmount Fund. Fairmount, Mr. Harwin, and Mr. Kiselak disclaim beneficial ownership of any of the reported securities, except to the extent of their pecuniary interest therein. Fairmount and Fund II may each be deemed a director by deputization of the Issuer by virtue of the fact that Peter Harwin serves on the board of directors of the Issuer and is a manager of Fairmount. /s/ Tomas Kiselak, Managing Member of Fairmount Funds Management LLC 2026-06-03 /s/ Tomas Kiselak, Managing Member of Fairmount Healthcare Fund II L.P. 2026-06-03 /s/ Tomas Kiselak 2026-06-03 /s/ Peter Harwin 2026-06-03