X0306 4 2020-03-01 0 0001597264 Blueprint Medicines Corp BPMC 0001663022 Haviland Kate C/O BLUEPRINT MEDICINES CORPORATION 45 SIDNEY STREET CAMBRIDGE MA 02139 0 1 0 0 Chief Operating Officer Common Stock 2020-03-01 4 A 0 14250 0 A 38865 D Common Stock 2020-03-03 4 M 0 4644 16.28 A 43509 D Stock Option (Right to Buy) 54.13 2020-03-01 4 A 0 28500 0 A 2030-03-01 Common Stock 28500 28500 D Stock Option (Right to Buy) 16.28 2020-03-03 4 M 0 4644 0 D 2026-02-01 Common Stock 4644 3145 D The reported transaction involved the Reporting Person's receipt of a grant of 14,250 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 14,250 newly awarded restricted stock units, 8,750 previously reported restricted stock units, 2,188 of which vested on March 1, 2020, and 15,865 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. This option was granted on February 1, 2016. This option vested with respect to 25% of the shares underlying the option on January 5, 2017 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