Certain Common Stock of Editas Medicine, Inc. are subject to a Lock-Up Agreement Ending on 4-JAN-2018. These Common Stock will be under lockup for 30 days starting from 5-DEC-2017 to 4-JAN-2018. Details: Each of the executive directors and officers, and certain holders of common stock have agreed that, without the prior written consent of Morgan Stanley & Co. LLC, they will not, subject to limited exceptions, during the period ending 30 days after the date of this prospectus supplement, offer, pledge, sell, contract to sell, sell any option or contract to purchase, purchase any option or contract to sell, grant any option, right or warrant to purchase, lend, or otherwise transfer or dispose of, directly or indirectly, any shares of common stock beneficially owned by them or any other securities so owned convertible into or exercisable or exchangeable for common stock