X0306 4 2019-02-08 0 0001552451 MyoKardia Inc MYOK 0001413822 GIANAKAKOS ANASTASIOS C/O MYOKARDIA, INC. 333 ALLERTON AVENUE SOUTH SAN FRANCISCO CA 94080 1 1 0 0 President and CEO Stock Option (Right to Buy) 40.11 2019-02-08 4 A 0 236500 0.00 A 2029-02-07 Common Stock 236500 236500 D Restricted Stock Units 2019-02-08 4 A 0 81200 0.00 A Common Stock 81200 81200 D The shares underlying the option vest in 48 equal monthly installments from January 1, 2019, so long as the Reporting Person continues to be an employee of the Issuer through each vesting date. This option is subject to accelerated vesting upon termination without cause upon a change of control of the Issuer. 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, 2019, so that all of the underlying shares shall be vested on January 1, 2023, 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, as Attorney-in-Fact 2019-02-12