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 * Moriarty John B   2. Issuer Name and Ticker or Trading Symbol ALEXION PHARMACEUTICALS INC [ALXN] 5. Relationship of Reporting Person(s) to Issuer (Check all applicable) _____ Director _____ 10% Owner __X__ Officer (give title below) _____ Other (specify below) EVP & General Counsel (Last) (First) (Middle) C/O ALEXION PHARMACEUTICALS, INC, 100 COLLEGE STREET 3. Date of Earliest Transaction (Month/Day/Year) 02/06/2018 (Street) NEW HAVEN, CT 06510 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, par value $.0001 per share 02/06/2018   A   21,489 (1) A $ 0 71,400 D   Common Stock, par value $.0001 per share 02/06/2018   A   6,500 (2) A $ 0 77,900 D   Common Stock, par value $.0001 per share 02/08/2018   S   2,163 (3) D $ 115.7 (4) 75,737 D   Common Stock, par value $.0001 per share 02/08/2018   S   1,200 (3) D $ 115.7 (5) 74,537 D

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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

Reporting Owners

Reporting Owner Name / Address	Relationships
	Director	10% Owner	Officer	Other
Moriarty John B C/O ALEXION PHARMACEUTICALS, INC 100 COLLEGE STREET NEW HAVEN, CT 06510			EVP & General Counsel

Signatures

/s/ Michael Greco, Attorney-in-Fact for John B. Moriarty		02/08/2018
**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)	On February 6, 2018, the Leadership and Compensation Committee determined that the reporting person earned 21,489 Performance Share Units upon achievement of certain performance targets previously established by the Committee. 1/3 of such shares vested on February 6, 2018 and 1/3 vest on each subsequent anniversary.
(2)	On February 6, 2018, the Leadership and Compensation Committee determined that the reporting person earned 6,500 Performance Share Units upon achievement of certain performance targets previously established by the Committee. 1/4 of such shares vested on February 6, 2018 and 1/4 vest on each subsequent anniversary.
(3)	This sale was made to cover withholding taxes immediately following the vesting of previously granted Performance Stock Units.
(4)	This transaction was executed in multiple trades through a broker-dealer at prices ranging from $115.20 - $116.20. The price reported in this column reflects the weighted average sales price. Upon request, the reporting person will provide to the SEC staff full information regarding the number of shares sold at each price.
(5)	This transaction was executed in multiple trades through a broker-dealer at prices ranging from $116.25 - $117.25. The price reported in this column reflects the weighted average sales price. Upon request, the reporting person will provide to the SEC staff full information regarding the number of shares sold at each price.

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