X0306 4 2018-02-05 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 2018-02-05 4 M 0 3000 1.5068 A 77390 D Common Stock 2018-02-05 4 S 0 954 49.7806 D 76436 D Common Stock 2018-02-05 4 S 0 699 50.9109 D 75737 D Common Stock 2018-02-05 4 S 0 1147 51.9151 D 74590 D Common Stock 2018-02-05 4 S 0 200 52.575 D 74390 D Common Stock 12200 I By The Alexander Gianakakos 2015 Irrevocable Trust dtd 9/26/2015 Common Stock 12200 I By The Emmanuel Gianakakos 2015 Irrevocable Trust Dtd 9/26/2015 Common Stock 12200 I By The James Gianakakos 2015 Irrevocable Trust Dtd 9/26/2015 Common Stock 85973 I By The Gianakakos Family Revocable Trust DTD 11/02/2006 Common Stock 500000 I By The Tassos Gianakakos 2018 Annuity Trust dtd 1/6/2018 Stock Option (Right to Buy) 1.5068 2018-02-05 4 M 0 3000 0.00 D 2025-06-03 Common Stock 3000 137235 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 $49.35 to $50.20 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 $50.50 to $51.40 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 $51.50 to $52.45 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 $52.50 to $52.65 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 2018-02-07