144 0001839697 XXXXXXXX LIVE 0001293971 bluebird bio, Inc. 001-35966 c/o bluebird bio, Inc. 455 Grand Union Boulevard Somerville MA 02145 3394999300 Obenshain Andrew Officer Director Common Morgan Stanley

1500 - 600 3 Ave SW Calgary A0 T2P 0G5

971 436.95 194444345 12/10/2024 NASDAQ Common 11/02/2020 Vested restricted stock units under company equity plan; sale of shares due to withholding taxes Issuer N 2585 11/02/2024 Services rendered N Andrew Obenshain

c/o bluebird bio, Inc. 455 Grand Union Boulevard Somerville MA 02145

Common 09/30/2024 34780 18269.00 Shares to be sold to cover withholding taxes upon vesting of restricted stock unit awards pursuant to standing Rule 10b5-1 sell to cover instruction. 12/10/2024 05/10/2023 /s/ Sydney Gaylin, attorney-in-fact for Andrew Obenshain