Certain Common Stock of Synthorx, Inc. are subject to a Lock-Up Agreement Ending on 5-JUN-2019. These Common Stock will be under lockup for 181 days starting from 6-DEC-2018 to 5-JUN-2019. Details: The officers, directors and holders have entered into a lock up agreement pursuant to which, they will not directly or indirectly, offer, sell, contract to sell, pledge, grant or dispose of or hedge any common stock or securities convertible into or exchangeable or exercisable for common stock, for a period of 180 days after the date of the prospectus.