X0306 4/A 2018-03-31 2018-04-03 0 0001367920 CONCERT PHARMACEUTICALS, INC. CNCE 0001353528 Cassella James V C/O CONCERT PHARMACEUTICALS, INC. 99 HAYDEN AVENUE, SUITE 500 LEXINGTON MA 02421 0 1 0 0 Chief Development Officer Common Stock 2018-03-31 4 F 0 4418 22.90 D 40582 D Transaction represents withholding of shares to satisfy tax withholding obligations upon the vesting of restricted stock units. This amendment is being filed to reduce the number of securities beneficially owned by the reporting person by 15,000 shares of common stock due to the failure to achieve certain performance criteria set forth in the restricted stock unit grant agreement with the reporting person dated July 6, 2017. /s/ James V. Cassella 2018-04-13