X0306 4/A 2018-10-06 2018-10-09 0 0001419600 Flexion Therapeutics Inc FLXN 0001369453 Wentworth Kerry C/O FLEXION THERAPEUTICS, INC. 10 MALL ROAD, SUITE 301 BURLINGTON MA 01803 0 1 0 0 Chief Regulatory Officer Common Stock 2018-10-06 4 M 0 3400 A 15878 D Common Stock 2018-10-08 4 F 0 1002 18.60 D 14876 D Common Stock 6000 I By Spouse Restricted Stock Unit Award 2018-10-06 4 M 0 3400 0.00 D 2019-10-06 Common Stock 3400 3400 D Each restricted stock unit award represents a contingent right to receive one share of the Issuer's common stock. Represents shares withheld by the Issuer to satisfy income tax obligations associated with the vesting of the restricted stock unit award. 3,400 shares subject to the restricted stock unit award vested as of October 6, 2018 and the remaining 3,400 shares vest as of October 6, 2019. /s/ Mark S. Levine, Attorney-in-Fact 2019-03-05