SCHEDULE 13G/A 0000902664-25-002239 0001535978 XXXXXXXX LIVE 2 Ordinary shares, nominal value 0.002 GBP per share 09/30/2025 0001847903 Centessa Pharmaceuticals plc 152309100 3RD FLOOR 1 ASHLEY ROAD ALTRINCHAM, CHESHIRE X0 WA14 2DT Rule 13d-1(b) Adage Capital Management, L.P. DE 0.00 10035000.00 0.00 10035000.00 10035000.00 N 7.48 IA PN Robert Atchinson X1 0.00 10035000.00 0.00 10035000.00 10035000.00 N 7.48 HC IN Phillip Gross X1 0.00 10035000.00 0.00 10035000.00 10035000.00 N 7.48 HC IN Centessa Pharmaceuticals plc 3rd Floor, 1 Ashley Road, Altrincham, Cheshire WA14 2DT, United Kingdom This statement is filed by: (i) Adage Capital Management, L.P., a Delaware limited partnership ("ACM"), as the investment manager of Adage Capital Partners, L.P., a Delaware limited partnership ("ACP"), with respect to the American Depositary Shares, each representing one ordinary share, nominal value (pound)0.002 per share ("Ordinary Shares") of Centessa Pharmaceuticals PLC, a limited liability company incorporated under the laws of England and Wales (the "Company") underlying the ADSs (as defined below) directly held by ACP; (ii) Robert Atchinson ("Mr. Atchinson"), as (1) managing member of Adage Capital Advisors, L.L.C., a limited liability company organized under the laws of the State of Delaware ("ACA"), managing member of Adage Capital Partners GP, L.L.C., a limited liability company organized under the laws of the State of Delaware ("ACPGP"), general partner of ACP and (2) managing member of Adage Capital Partners LLC, a Delaware limited liability company ("ACPLLC"), general partner of ACM, with respect to the Ordinary Shares underlying the ADSs directly held by ACP; and (iii) Phillip Gross ("Mr. Gross"), as (1) managing member of ACA, managing member of ACPGP and (2) managing member of ACPLLC, general partner of ACM, with respect to the Ordinary Shares underlying the ADSs directly held by ACP. The foregoing persons are hereinafter sometimes collectively referred to as the "Reporting Persons." Any disclosures herein with respect to persons other than the Reporting Persons are made on information and belief after making inquiry to the appropriate party. The filing of this statement should not be construed in and of itself as an admission by any Reporting Person as to beneficial ownership of the securities reported herein. There is no CUSIP number assigned to the Ordinary Shares. The CUSIP number 152309100 has been assigned to the American Depositary Shares ("ADSs") of the Company, which are quoted on Nasdaq under the symbol "CNTA." Each ADS represents one Ordinary Share. The address of the business office of each of the Reporting Persons is 200 Clarendon Street, 52nd Floor, Boston, Massachusetts 02116. ACM is a limited partnership organized under the laws of the State of Delaware. Messrs. Gross and Atchinson are citizens of the United States. N IA HC The information required by Item 4(a) is set forth in Row 9 of the cover page for each of the Reporting Persons and is incorporated herein by reference. The percentage set forth in this Schedule 13G is calculated based upon an aggregate of 134,073,436 Ordinary Shares outstanding as of August 1, 2025 as reported in the Company's Quarterly Report on Form 10-Q for the quarterly period ended June 30, 2025, filed with the Securities and Exchange Commission on August 12, 2025. 7.48% The information required by Item 4(c)(i) is set forth in Row 5 of the cover page for each of the Reporting Persons and is incorporated herein by reference. The information required by Item 4(c)(ii) is set forth in Row 6 of the cover page for each of the Reporting Persons and is incorporated herein by reference. The information required by Item 4(c)(iii) is set forth in Row 7 of the cover page for each of the Reporting Persons and is incorporated herein by reference. The information required by Item 4(c)(iv) is set forth in Row 8 of the cover page for each of the Reporting Persons and is incorporated herein by reference. Y N See Item 2(a). Y Y Y N By signing below I certify that, to the best of my knowledge and belief, the securities referred to above were acquired and are held in the ordinary course of business and 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. Adage Capital Management, L.P. /s/ Robert Atchinson 11/13/2025 Robert Atchinson /s/ Robert Atchinson 11/13/2025 Phillip Gross /s/ Phillip Gross 11/13/2025