X0306 4 2021-01-05 0 0001419600 Flexion Therapeutics Inc FLXN 0001617236 Levine Mark S. C/O FLEXION THERAPEUTICS, INC. 10 MALL ROAD, SUITE 301 BURLINGTON MA 01803 0 1 0 0 General Counsel Common Stock 2021-01-05 4 S 0 6829 11.13 D 107431 D Sale of shares of common stock to cover tax withholding obligations associated with the vesting of restricted stock unit awards granted to the Reporting Person on February 1, 2018, March 1, 2019, and March 2, 2020. The weighted average sale price for the transaction reported was $11.13. The shares were sold at a range of prices between $11.12 and $11.55. Upon request by the SEC staff, the Issuer, or any security holder of the Issuer, full information regarding the number of shares sold at each separate price will be provided. /s/ Mark S. Levine 2021-01-07