Certain Common Stock of bluebird bio, Inc. are subject to a Lock-Up Agreement Ending on 26-JAN-2018. These Common Stock will be under lockup for 45 days starting from 12-DEC-2017 to 26-JAN-2018. Details: Shares and securities convertible into or exchangeable for shares held by the directors and executive officers of the company will be under lock up for a period of 45 days after the date of this prospectus supplement.