Sec Form 4 Filing - DENNER ALEXANDER J @ MEDICINES CO /DE - 2017-08-31

FORM 4 Check this box if no longer subject to Section 16. Form 4 or Form 5 obligations may continue. See Instruction 1(b).

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 STATEMENT OF CHANGES IN BENEFICIAL OWNERSHIP Filed pursuant to Section 16(a) of the Securities Exchange Act of 1934, Section 17(a) of the Public Utility Holding Company Act of 1935 or Section 30(h) of the Investment Company Act of 1940

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1. Name and Address of Reporting Person DENNER ALEXANDER J 2. Issuer Name and Ticker or Trading Symbol MEDICINES CO /DE [ MDCO] 5. Relationship of Reporting Person(s) to Issuer (Check all applicable) X __ Director _____ 10% Owner _____ Officer (give title below) _____ Other (specify below) (Last) (First) (Middle) C/O SARISSA CAPITAL MANAGEMENT LP, 660 STEAMBOAT ROAD 3. Date of Earliest Transaction (MM/DD/YY) 08/31/2017 (Street) GREENWICH, CT06830 4. If Amendment, Date Original Filed (MM/DD/YY) 6. Individual or Joint/Group Filing (Check Applicable Line) __ X __ Form filed by One Reporting Person _____ Form filed by More than One Reporting Person (City) (State) (Zip)

Table I - Non-Derivative Securities Acquired, Disposed of, or Beneficially Owned 1.Title of Security (Instr. 3) 2. Transaction Date (MM/DD/YY) 2A. Deemed Execution Date, if any (MM/DD/YY) 3. Transaction Code (Instr. 8) 4. Securities Acquired (A) or Disposed of (D) (Instr. 3, 4 and 5) 5. Amount of Securities Beneficially Owned Following Reported Transaction(s) (Instr. 3 and 4) 6. Ownership Form: Direct (D) or Indirect (I) (Instr. 4) 7. Nature of Indirect Beneficial Ownership (Instr. 4) Code V Amount (A) or (D) Price Common Stock 08/31/2017 A 7,146 ( 1 ) A $ 36.69 1,752,000 I See Footnotes ( 1 ) ( 2 ) Common Stock 6,663 D

Table II - Derivative Securities Acquired, Disposed of, or Beneficially Owned ( e.g. , puts, calls, warrants, options, convertible securities) 1. Title of Derivative Security (Instr. 3) 2. Conversion or Exercise Price of Derivative Security 3. Transaction Date (MM/DD/YY) 3A. Deemed Execution Date, if any (MM/DD/YY) 4. Transaction Code (Instr. 8) 5. Number of Derivative Securities Acquired (A) or Disposed of (D) (Instr. 3, 4, and 5) 6. Date Exercisable and Expiration Date (MM/DD/YY) 7. Title and Amount of Underlying Securities (Instr. 3 and 4) 8. Price of Derivative Security (Instr. 5) 9. Number of Derivative Securities Beneficially Owned Following Reported Transaction(s) (Instr. 4) 10. Ownership Form of Derivative Security: Direct (D) or Indirect (I) (Instr. 4) 11. Nature of Indirect Beneficial Ownership (Instr. 4) Code V (A) (D) Date Exercisable Expiration Date Title Amount or Number of Shares Stock Option (right to buy) $ 0 08/31/2017 08/31/2017 Common Stock 0 8.577 D

Reporting Owners Reporting Owner Name / Address Relationships Director 10% Owner Officer Other DENNER ALEXANDER J C/O SARISSA CAPITAL MANAGEMENT LP 660 STEAMBOAT ROAD GREENWICH, CT06830 X Signatures /s/ Alexander J. Denner 08/31/2017 Signature of Reporting Person Date

Explanation of Responses:

( 1 )On August 31, 2017, in connection with a private transaction with Sarissa Capital Master Offshore Fund LP, a Cayman Island exempted limited partnership ("Sarissa Offshore"), and Sarissa Capital Domestic Fund LP, a Delaware limited partnership ("Sarissa Domestic"), Dr. Alexander Denner increased his pecuniary interest in shares of common stock of The Medicines Company through his direct interest in Sarissa Domestic and his indirect interest in Sarissa Offshore. ( 2 )All shares reported herein as of August 31, 2017 are beneficially owned by Sarissa Offshore. Sarissa Capital Management GP LLC, a Delaware limited liability company ("Sarissa Capital GP"), is the general partner of Sarissa Capital Management LP, a Delaware limited partnership ("Sarissa Capital"), the investment advisor to Sarissa Offshore. Dr. Denner is the Chief Investment Officer of Sarissa Capital and the managing member of Sarissa Capital GP. 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) the shares that Sarissa Offshore directly beneficially owns. Dr. Denner disclaims beneficial ownership of these shares except to the extent of any pecuniary interest therein.

Reminder: Report on a separate line for each class of securities beneficially owned directly or indirectly.

* If the form is filed by more than one reporting person, see Instruction 4(b)(v).

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