X0306 4 2021-07-19 0 0001419600 Flexion Therapeutics Inc FLXN 0001597407 Clayman Michael D. C/O FLEXION THERAPEUTICS, INC. 10 MALL ROAD, SUITE 301 BURLINGTON MA 01803 1 1 0 0 President and CEO Common Stock 2021-07-19 4 F 0 13859 D 334981 D Common Stock 373769 I By the Michael D.Clayman 2006 Revocable Trust Common Stock 24600 I By the Michael D. Clayman Irrevocable Trust Common Stock 388683 I By Versant Development Fund III, LLC Withholding of shares by the Issuer to satisfy income tax obligations associated with the vesting of a restricted stock unit award granted to the Reporting Person on July 16, 2020. Shares held by Versant Development Fund III, LLC. The Reporting Person is a manager and minority member of Versant Development Fund III, LLC. The Reporting Person disclaims any beneficial ownership of the shares held by Versant Development Fund III, LLC except to the extent of his pecuniary interest in these shares. /s/ Mark S. Levine, Attorney-in-Fact 2021-07-20