X0206 3 2020-06-11 0 0001733294 Generation Bio Co. GBIO 0001814189 Kerr Douglas C/O GENERATION BIO CO., 301 BINNEY STREET CAMBRIDGE MA 02142 0 1 0 0 Chief Development Officer Common Stock 326558 D Stock Option (right to buy) 4.60 2028-04-01 Common Stock 123760 D Stock Option (right to buy) 5.16 2030-03-04 Common Stock 56289 D Stock Option (right to buy) 5.16 2030-03-04 Common Stock 56289 D The option was granted on April 2, 2018. The shares underlying the option vest over four years, with 25% of the shares vested on April 2, 2019 and the remaining shares vesting in equal quarterly installments thereafter. The option was granted on March 5, 2020. The shares underlying the option vest in full upon the date on which the Board of Directors of the Issuer determines that the Issuer has dosed the initial patient in its first clinical trial, provided that such event occurs on or before July 1, 2023. The option was granted on March 5, 2020. The shares underlying the option vest over four years, with 25% of the shares vesting on March 5, 2021 and the remaining shares vesting in equal quarterly installments thereafter. Exhibit Index: 24.1 Power of Attorney /s/ Jennifer Elliott, Attorney-in-Fact 2020-06-11