X0306 4 2020-03-01 0 0001597264 Blueprint Medicines Corp BPMC 0001638474 Albers Jeffrey W. C/O BLUEPRINT MEDICINES CORPORATION 45 SIDNEY STREET CAMBRIDGE MA 02139 1 1 0 0 CEO and President Common Stock 2020-03-01 4 A 0 45000 0 A 123711 D Stock Option (Right to Buy) 54.13 2020-03-01 4 A 0 90000 0 A 2030-03-01 Common Stock 90000 90000 D The reported transaction involved the Reporting Person's receipt of a grant of 45,000 restricted stock units under Issuer's 2015 Stock Option and Incentive Plan. The Reporting Person has reported prior awards of restricted stock units in Table II of Form 4. The total reported in Column 5 includes the 45,000 newly awarded restricted stock units, 29,750 previously reported restricted stock units, 7,438 of which vested on March 1, 2020, and 48,961 shares of common stock. This option vests with respect to 1/48th of the shares underlying the option on April 1, 2020 and as to an additional 1/48th of the shares underlying the option each month thereafter. /s/ Christopher Frankenfield, Attorney-in-Fact 2020-03-03