X0306 4 2017-01-18 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) 12.25 2017-01-18 4 A 0 303500 0.00 A 2027-01-17 Common Stock 303500 303500 D The shares underlying the option vest in 48 equal monthly installments from January 1, 2017, 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. /s/ Steven Chan, as Attorney-in-Fact 2017-01-20