X0306 4 2017-07-20 0 0001552451 MyoKardia Inc MYOK 0001654909 Bauer Jake C/O MYOKARDIA, INC. 333 ALLERTON AVENUE SOUTH SAN FRANCISCO CA 94080 0 1 0 0 See Remarks Stock Option (Right to Buy) 13.90 2017-07-20 4 A 0 15000 0.00 A 2027-07-19 Common Stock 15000 15000 D The shares subject to this option shall vest and become exercisable in two annual installments after the date of grant. This option is subject to accelerated vesting upon termination without cause upon a change of control of the Issuer. Senior Vice President, Finance and Corporate Development /s/ Jake Bauer 2017-07-24