X0306 4 2017-09-05 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 2017-09-05 4 M 0 4300 1.5068 A 512463 D Common Stock 2017-09-05 4 S 0 4000 42.9755 D 508463 D Common Stock 2017-09-05 4 S 0 300 43.6717 D 508163 D Common Stock 181169 I By Reporting Person's Trust Stock Option (Right to Buy) 1.5068 2017-09-05 4 M 0 4300 0.00 D 2025-06-03 Common Stock 4300 166512 D This transaction was effected pursuant to a Rule 10b5-1 trading plan adopted by the Reporting Person. Represents the weighted average sale price of the shares sold ranging from $42.40 to $43.35 per share. The Reporting Person will provide, upon request by the Commission staff, the Issuer, or a security holder of the Issuer, full information regarding the number of shares sold at each separate price. Represents the weighted average sale price of the shares sold ranging from $43.45 to $43.80 per share. The Reporting Person will provide, upon request by the Commission staff, the Issuer, or a security holder of the Issuer, full information regarding the number of shares sold at each separate price. 25% of the shares subject to the option vested and became exercisable on June 4, 2016, and the remaining shares subject to this option vest and become exercisable in monthly installments through June 4, 2019. /s/ Jake Bauer, Attorney-in-Fact 2017-09-07