X0306 4 2019-01-01 0 0001552451 MyoKardia Inc MYOK 0001691494 Semigran Marc C/O MYOKARDIA, INC. 333 ALLERTON AVENUE SOUTH SAN FRANCISCO CA 94080 0 1 0 0 Chief Medical Officer Common Stock 2019-01-01 4 M 0 1325 A 1627 D Restricted Stock Units 2019-01-01 4 M 0 1325 0.00 D Common Stock 1325 3975 D Restricted stock units convert into common stock on a one-for-one basis. Each Restricted Stock Unit ("RSU") represents a contingent right to receive one share of Issuer's Common Stock. The shares of Common Stock underlying the RSUs vest in equal annual installments over 4 years from January 1, 2018, so that all of the underlying shares shall be vested on January 1, 2022, subject to the Reporting Person's continued employment with the Issuer through each vesting date. The RSUs are subject to accelerated vesting upon termination without cause after a change of control of the Issuer. /s/ Cynthia Ladd Attorney-in-Fact 2019-01-03