X0306 4 2020-07-02 0 0001552451 MyoKardia, Inc. MYOK 0001413822 GIANAKAKOS ANASTASIOS C/O MYOKARDIA, INC. 1000 SIERRA POINT PARKWAY BRISBANE CA 94005 1 1 0 0 President and CEO Common Stock 2020-07-02 4 S 0 1776 93.5485 D 22346 D Common Stock 2020-07-02 4 S 0 3224 94.2205 D 19122 D Common Stock 129407 I By Reporting Person's Trust 2 Common Stock 300000 I By Reporting Person's Trust 4 Common Stock 7000 I By Reporting Person's Trust 5 Common Stock 10000 I By reporting Person's Trust 6 Common Stock 53087 I By Trust 1 Common Stock 53087 I By Trust 2 Common Stock 53087 I By Trust 3 This transaction was effected pursuant to a Rule 10b5-1 trading plan adopted by the Reporting Person on June 3, 2019. Represents the weighted average sale price of the shares sold ranging from $92.98 to $93.93 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 within the ranges set forth in footnotes 2 and 3. Represents the weighted average price of the shares sold ranging from $94.01 to $94.75 per share. /s/ Cynthia J. Ladd, as Attorney-in-Fact 2020-07-07