X0306 4 2017-03-23 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) 1.51 2017-03-23 4 A 0 27891 0.00 A 2017-03-23 2025-06-03 Common Stock 27891 55782 D On June 4, 2015, the Reporting Person was granted an option to purchase 111,565 shares of Common Stock under the issuer's 2012 Equity Incentive Plan, the vesting of which was subject to various conditions (other than the passage of time and continued employment) that were not tied to the market price of the issuer's securities. On March 23, 2017, one of the conditions was deemed to be achieved, resulting in the vesting and exercisability of 27,891 of the shares underlying such option. /s/ Jake Bauer, as Attorney-in-Fact 2017-03-27