X0306 4 2019-09-20 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 2019-09-20 4 M 0 10000 9.08 A 76068 D Common Stock 2019-09-20 4 M 0 9700 12.25 A 85768 D Common Stock 2019-09-20 4 S 0 19700 60.0902 D 66068 D Stock Option (Right to Buy) 9.08 2019-09-20 4 M 0 10000 0.00 D 2026-02-01 Common Stock 10000 18748 D Stock Option (Right to Buy) 12.25 2019-09-20 4 M 0 9700 0.00 D 2027-01-17 Common Stock 9700 40150 D This transaction was effected pursuant to a Rule 10b5-1 trading plan that was previously adopted by the Reporting Person. Represents the weighted average sale price of the shares sold ranging from $60.00 to $60.27 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 subject to this option vest and become exercisable in 48 equal monthly installments from January 1, 2016, subject to the Reporting Person's continued service to the Issuer through each vesting date. The shares subject to this option vest and become exercisable in 48 equal monthly installments from January 1, 2017, subject to the Reporting Person's continued service to the Issuer through each vesting date. /s/ Cynthia Ladd, as Attorney-in-Fact 2019-09-23