X0306 4 2016-12-01 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 Stock Option (Right to Buy) 15.95 2016-12-01 4 A 0 175000 0.00 A 2026-11-30 Common Stock 175000 175000 D 25% of the shares subject to this option shall vest and become exercisable on December 1, 2017, and the remaining shares subject to this option shall vest and become exercisable in 36 equal monthly installments thereafter. This option is subject to full acceleration of vesting with respect to all then-unvested shares in the event the reporting person's service relationship is terminated by the issuer or any successor without Cause (as defined in the issuer's 2015 Stock Option and Incentive Plan) within one year following the consummation of a Sale Event (as defined in the issuer's 2015 Stock Option and Incentive Plan). /s/ Steven Chan, as Attorney-in-Fact 2016-12-05