X0306 4 2016-10-31 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 Common Stock 2016-10-31 4 A 0 898 10.03 A 508254 D Common Stock 181169 I Trust Stock Option (Right to Buy) 1.51 2016-11-01 4 A 0 27891 0.00 A 2016-11-01 2025-06-03 Common Stock 27891 27891 D Shares acquired pursuant to the Issuer's 2015 Employee Stock Purchase Plan. On October 10, 2016, the Tassos Gianakakos 2015 Annuity Trust, dated September 25, 2015 (the "Trust") transferred 22,912 shares to the Reporting Person. The Reporting Person as trustee has sole dispositive power over the shares held in the Trust. 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 November 1, 2016, 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/ Steven Chan, as Attorney-in-Fact 2016-11-02