X0306 4/A 2018-01-02 2018-01-03 0 0001552451 MyoKardia Inc MYOK 0001654909 Bauer Jake C/O MYOKARDIA, INC. 333 ALLERTON AVENUE SOUTH SAN FRANCISCO CA 94080 0 1 0 0 Chief Business Officer Common Stock 2018-01-02 4 M 0 5000 12.25 A 71777 D Common Stock 2018-01-02 4 S 0 3900 42.7566 D 67877 D Common Stock 2018-01-02 4 S 0 1100 43.3773 D 66777 D Stock Option (Right to Buy) 12.25 2018-01-02 4 M 0 5000 0.00 D 2027-01-17 Common Stock 5000 54850 D This transaction was effective pursuant to a Rule 10b5-1 trading plan adopted by the Reporting Person. These shares were omitted from the Reporting Person's original Form 4, and also were omitted from the subsequent Form 4s filed by the Reporting Person through the date of this amendment Represents the weighted average sale price of the shares sold ranging from $42.20 to $43.15 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 $43.20 to $43.60 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. The shares underlying the option vest in 48 equal monthly installments from January 1, 2017, so long as the Reporting Person continues to be an employee of the Issuer through each vesting date. This option is subject to accelerated vesting upon termination without cause upon a change of control of the Issuer. The Reporting Person's title at the time of the filing of the original Form 4 was Senior Vice President, Finance and Corporate Development. /s/ Cynthia Ladd, as Attorney-in-Fact 2019-04-17