X0306 4 2019-01-03 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 2019-01-03 4 S 0 3278 12.36 D 66810 D Common Stock 314066 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 Sale of shares of common stock pursuant to Rule 10b5-1 arrangements to cover tax withholding obligations associated with the vesting of a Restricted Stock Unit Award granted to the Reporting Person on February 1, 2018. Includes 922 shares of Common Stock that were acquired by the Reporting Person on December 20, 2018 at $10.48 per share pursuant to the Issuer's Employee Stock Purchase Plan. 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 2019-01-04