X0306 4 2019-06-13 0 0001552451 MyoKardia Inc MYOK 0001616640 AGARWAL SUNIL C/O MYOKARDIA, INC. 333 ALLERTON AVENUE SOUTH SAN FRANCISCO CA 94080 1 0 0 0 Stock Option (Right to Buy) 47.17 2019-06-13 4 A 0 6600 0.00 A 2029-06-12 Common Stock 6600 6600 D Restricted Stock Units 2019-06-13 4 A 0 2300 0.00 A Common Stock 2300 2300 D The shares subject to this option shall vest and become exercisable in 12 equal monthly installments with the first installment on July 13, 2019, such that all of the underlying shares shall be vested on June 13, 2020, subject to the Reporting Person's continued service on the Issuer's Board of Directors. This option is subject to full acceleration of vesting with respect to all then-unvested shares upon the consummation of a Sale Event (as defined in the Issuer's 2015 Stock Option and Incentive Plan, as amended). Each Restricted Stock Unit ("RSU") represents a contingent right to receive one share of the Issuer's Common Stock. The shares of Common Stock underlying the RSUs vest in a single installment on the first anniversary of the grant date, such that all of the underlying shares shall be vested on June 13, 2020, subject to the Reporting Person's continued service on the Issuer's Board of Directors. The shares of Common Stock underlying the RSUs are subject to full acceleration of vesting with respect to all then-unvested shares upon the consummation of a Sale Event (as defined in the Issuer's 2015 Stock Option and Incentive Plan, as amended). /s/ Cynthia Ladd, as Attorney-in-Fact 2019-06-17