Ownership Submission
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 OF SECURITIES

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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(Print or Type Responses)
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 (Month/Day/Year)
12/17/2018
(Street)

GREENWICH, CT 06830
4. If Amendment, Date Original Filed(Month/Day/Year)
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 (Month/Day/Year) 2A. Deemed Execution Date, if any (Month/Day/Year) 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 12/17/2018   P   20,000 A $ 17.91 2,761,000 I See footnote (1)
Common Stock 12/18/2018   P   10,000 A $ 18.18 2,771,000 I See footnote (1)
Common Stock               10,429 D  

Reminder: Report on a separate line for each class of securities beneficially owned directly or indirectly.
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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 (Month/Day/Year) 3A. Deemed Execution Date, if any (Month/Day/Year) 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
(Month/Day/Year)
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
3.50% Convertible Senior Notes due 2024 $ 25.19 12/18/2018   P   $ 20,000,000   10/15/2023(2) 01/14/2024(3) Common Stock 793,840 $ 20,000,000 $ 20,000,000 I See footnote (1)

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, CT 06830
  X      

Signatures

 /s/ Stephen M. Rodin, Attorney-in-Fact for Alexander J. Denner   12/18/2018
**Signature of Reporting Person Date

Explanation of Responses:

* If the form is filed by more than one reporting person, see Instruction 4(b)(v).
** Intentional misstatements or omissions of facts constitute Federal Criminal Violations. See 18 U.S.C. 1001 and 15 U.S.C. 78ff(a).
(1) All of the shares and notes reported herein as being indirectly beneficially owned by Dr. Denner are directly beneficially owned by funds managed by Sarissa Capital Management LP (such funds, the "Sarissa Funds"). Dr. Denner is the Chief Investment Officer of Sarissa Capital Management LP and the managing member of the general partner of the Sarissa Funds. 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 and notes that the Sarissa Funds directly beneficially own. Dr. Denner disclaims beneficial ownership of these shares and notes except to the extent of his pecuniary interest therein.
(2) Holders may convert the notes at any time prior to the close of business on the business day immediately preceding 10/15/23 only under the following circumstances: (1) during any calendar quarter commencing on or after 3/31/19 (and only during such calendar quarter), if the last reported sale price of our common stock for at least 20 trading days (whether or not consecutive) during a period of 30 consecutive trading days ending on the last trading day of the immediately preceding calendar quarter is greater than or equal to 130% of the conversion price on each applicable trading day; (2) during the 5 business day period after any 5 consecutive trading day period (the measurement period) in which the trading price per $1,000 principal amount of notes for each trading day of the measurement period was less than 98% of the product of the last reported sale price of our common stock and the conversion rate on each such trading day; or (3) upon the occurrence of specified corporate events.
(3) On or after October 15, 2023, until the close of business on the business day immediately preceding the maturity date (i.e., until and including January 14, 2024), holders may convert their notes at any time, regardless of the foregoing circumstances.

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