<SEC-DOCUMENT>0001144204-15-044125-index.html : 20150724
<SEC-HEADER>0001144204-15-044125.hdr.sgml : 20150724
<ACCEPTANCE-DATETIME>20150724161446
ACCESSION NUMBER:		0001144204-15-044125
CONFORMED SUBMISSION TYPE:	4
PUBLIC DOCUMENT COUNT:		1
CONFORMED PERIOD OF REPORT:	20150722
FILED AS OF DATE:		20150724
DATE AS OF CHANGE:		20150724

ISSUER:		

	COMPANY DATA:	
		COMPANY CONFORMED NAME:			ALEXION PHARMACEUTICALS INC
		CENTRAL INDEX KEY:			0000899866
		STANDARD INDUSTRIAL CLASSIFICATION:	PHARMACEUTICAL PREPARATIONS [2834]
		IRS NUMBER:				133648318
		STATE OF INCORPORATION:			DE
		FISCAL YEAR END:			1231

	BUSINESS ADDRESS:	
		STREET 1:		352 KNOTTER DRIVE
		CITY:			CHESHIRE
		STATE:			CT
		ZIP:			06511
		BUSINESS PHONE:		2037761790

	MAIL ADDRESS:	
		STREET 1:		352 KNOTTER DRIVE
		CITY:			CHESHIRE
		STATE:			CT
		ZIP:			06511

REPORTING-OWNER:	

	OWNER DATA:	
		COMPANY CONFORMED NAME:			BAKER BROS. ADVISORS LP
		CENTRAL INDEX KEY:			0001263508
		STATE OF INCORPORATION:			DE
		FISCAL YEAR END:			1231

	FILING VALUES:
		FORM TYPE:		4
		SEC ACT:		1934 Act
		SEC FILE NUMBER:	000-27756
		FILM NUMBER:		151004783

	BUSINESS ADDRESS:	
		STREET 1:		667 MADISON AVE
		STREET 2:		21ST FLOOR
		CITY:			NEW YORK
		STATE:			NY
		ZIP:			10065
		BUSINESS PHONE:		2123395600

	MAIL ADDRESS:	
		STREET 1:		667 MADISON AVE
		STREET 2:		21ST FLOOR
		CITY:			NEW YORK
		STATE:			NY
		ZIP:			10065

	FORMER NAME:	
		FORMER CONFORMED NAME:	BAKER BROS ADVISORS LLC
		DATE OF NAME CHANGE:	20030911

REPORTING-OWNER:	

	OWNER DATA:	
		COMPANY CONFORMED NAME:			667, L.P.
		CENTRAL INDEX KEY:			0001551139
		STATE OF INCORPORATION:			DE
		FISCAL YEAR END:			1231

	FILING VALUES:
		FORM TYPE:		4
		SEC ACT:		1934 Act
		SEC FILE NUMBER:	000-27756
		FILM NUMBER:		151004785

	BUSINESS ADDRESS:	
		STREET 1:		667 MADISON AVE.
		STREET 2:		21ST FLOOR
		CITY:			NEW YORK
		STATE:			NY
		ZIP:			10065
		BUSINESS PHONE:		212-339-5600

	MAIL ADDRESS:	
		STREET 1:		667 MADISON AVE.
		STREET 2:		21ST FLOOR
		CITY:			NEW YORK
		STATE:			NY
		ZIP:			10065

REPORTING-OWNER:	

	OWNER DATA:	
		COMPANY CONFORMED NAME:			Baker Bros. Advisors (GP) LLC
		CENTRAL INDEX KEY:			0001580575
		STATE OF INCORPORATION:			E9
		FISCAL YEAR END:			1231

	FILING VALUES:
		FORM TYPE:		4
		SEC ACT:		1934 Act
		SEC FILE NUMBER:	000-27756
		FILM NUMBER:		151004786

	BUSINESS ADDRESS:	
		STREET 1:		667 MADISON AVENUE
		STREET 2:		21ST FLOOR
		CITY:			NEW YORK
		STATE:			NY
		ZIP:			10065
		BUSINESS PHONE:		(212)339-5600

	MAIL ADDRESS:	
		STREET 1:		667 MADISON AVENUE
		STREET 2:		21ST FLOOR
		CITY:			NEW YORK
		STATE:			NY
		ZIP:			10065

REPORTING-OWNER:	

	OWNER DATA:	
		COMPANY CONFORMED NAME:			BAKER JULIAN
		CENTRAL INDEX KEY:			0001087939

	FILING VALUES:
		FORM TYPE:		4
		SEC ACT:		1934 Act
		SEC FILE NUMBER:	000-27756
		FILM NUMBER:		151004787

	MAIL ADDRESS:	
		STREET 1:		BAKER BROTHERS ADVISORS
		STREET 2:		667 MADISON AVENUE, 21ST FLOOR
		CITY:			NEW YORK
		STATE:			NY
		ZIP:			10065

REPORTING-OWNER:	

	OWNER DATA:	
		COMPANY CONFORMED NAME:			BAKER FELIX
		CENTRAL INDEX KEY:			0001087940

	FILING VALUES:
		FORM TYPE:		4
		SEC ACT:		1934 Act
		SEC FILE NUMBER:	000-27756
		FILM NUMBER:		151004788

	MAIL ADDRESS:	
		STREET 1:		BAKER BROTHERS ADVISORS
		STREET 2:		667 MADISON AVENUE, 21ST FLOOR
		CITY:			NEW YORK
		STATE:			NY
		ZIP:			10065

REPORTING-OWNER:	

	OWNER DATA:	
		COMPANY CONFORMED NAME:			Baker Brothers Life Sciences LP
		CENTRAL INDEX KEY:			0001363364
		STATE OF INCORPORATION:			DE
		FISCAL YEAR END:			1231

	FILING VALUES:
		FORM TYPE:		4
		SEC ACT:		1934 Act
		SEC FILE NUMBER:	000-27756
		FILM NUMBER:		151004784

	BUSINESS ADDRESS:	
		STREET 1:		667 MADISON AVENUE
		STREET 2:		21ST FLOOR
		CITY:			NEW YORK
		STATE:			NY
		ZIP:			10065
		BUSINESS PHONE:		212-339-5633

	MAIL ADDRESS:	
		STREET 1:		667 MADISON AVENUE
		STREET 2:		21ST FLOOR
		CITY:			NEW YORK
		STATE:			NY
		ZIP:			10065
</SEC-HEADER>
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<TYPE>4
<SEQUENCE>1
<FILENAME>form475381_20150724041306-.xml
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Document 1 - file: form475381_20150724041306-.html

Document 1 - RAW XML: form475381_20150724041306-.xml

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