X0306 4 2018-06-28 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 2018-06-28 4 A 0 6250 0.00 A 2018-06-28 2026-11-30 Common Stock 6250 6250 D On December 1, 2016, the Reporting Person was granted an option to purchase 25,000 shares of Common Stock under the issuer's 2015 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 June 28, 2018, one of the conditions was deemed to be achieved, resulting in the vesting and exercisability of 6,250 of the shares underlying such option. Exhibit 24.1 - Power of Attorney /s/ Jake Bauer, Attorney-in-Fact 2018-06-29