X0306 4 2019-05-20 0 0001113481 MEDICINES CO /DE MDCO 0001361754 DENNER ALEXANDER J C/O SARISSA CAPITAL MANAGEMENT LP 660 STEAMBOAT ROAD GREENWICH CT 06830 1 0 0 0 Common Stock 2019-05-20 4 P 0 160000 34.50 A 3796000 I See footnote Common Stock 2019-05-21 4 P 0 132000 33.95 A 3928000 I See footnote Common Stock 2019-05-22 4 P 0 139000 33.13 A 4067000 I See footnote The shares reported herein as being indirectly beneficially owned by Dr. Denner are directly beneficially owned by funds managed and/or controlled by Sarissa Capital Management LP. Dr. Denner is the Chief Investment Officer of Sarissa Capital Management LP and controls the general partner of Sarissa Capital Management LP. By virtue of the foregoing, Dr. Denner may be deemed to indirectly beneficially own (as that term is defined in Rule 13d-3 of the Securities Exchange Act of 1934, as amended) these shares. Dr. Denner disclaims beneficial ownership of these shares except to the extent of his pecuniary interest therein. /s/ Stephen M. Rodin, Attorney-in-Fact for Alexander J. Denner 2019-05-22