X0306 4 2015-10-28 0 0001552451 MyoKardia Inc MYOK 0001190270 PERRY MARK L C/O MYOKARDIA, INC. 333 ALLERTON AVENUE SOUTH SAN FRANCISCO CA 94080 1 0 0 0 Stock Option (Right to Buy) 10.00 2015-10-28 4 A 0 21800 A 2025-10-28 Common Stock 21800 21800 D The shares subject to this option shall vest and become exercisable in 48 equal monthly installments with the first installment on November 28, 2015, such that this option is fully exercisable on October 28, 2019. This option is subject to accelerated vesting upon a change of control of the Issuer. Not applicable. /s/ Steven Chan, as Attorney-in-Fact 2015-10-30