X0508 4 2025-10-31 1 0001733294 Generation Bio Co. GBIO 0001946316 Samayoa Phillip C/O GENERATION BIO CO. 301 BINNEY STREET, SUITE 401 CAMBRIDGE MA 02142 false true false false CHIEF SCIENTIFIC OFFICER 0 The reporting person will no longer serve as Generation Bio Co.'s chief scientific officer effective October 31, 2025. As a result, the reporting person is no longer subject to Section 16 in connection with his transactions in the equity securities of Generation Bio Co. and therefore will no longer report any such transactions on Form 4 or Form 5. /s/ Shawna-Gay White, Attorney-in-Fact 2025-10-31