X0206 3 2015-10-28 0 0001552451 MyoKardia Inc MYOK 0001413822 GIANAKAKOS ANASTASIOS C/O MYOKARDIA, INC. 333 ALLERTON AVENUE SOUTH SAN FRANCISCO CA 94080 1 1 0 0 CEO, President Common Stock 480815 D Common Stock 204081 I Trust Stock Option (Right to Buy) 1.51 2025-06-03 Common Stock 208162 D Stock Option (Right to Buy) 1.51 2025-06-03 Common Stock 111564 D These shares of Common Stock are subject to the Issuer's right of repurchase, which lapsed with respect to 25% of the shares on October 7, 2014, and lapses in 36 equal monthly installments thereafter. The shares of Common Stock held indirectly in the reporting person's trust are fully vested. 25% of the shares subject to this option shall vest and become exercisable on June 4, 2016, and the remaining shares subject to this option shall vest and become exercisable in 36 equal monthly installments thereafter. The shares subject to this option shall vest and become exercisable with respect to all of the underlying shares upon achievement of specified market capitalization of the company. Exhibit List: Exhibit 24.1 - Power of Attorney /s/ Steven Chan, attorney-in-fact 2015-10-28