Alexion Pharmaceuticals, Inc.
Leonard Bell, M.D.
Chief Executive Officer
(203) 272-2596

Media
Makovsky + Company
David Patti (Media)
(212) 508-9623

Investors
Rx Communications
Rhonda Chiger (Investors)
(917) 322-2569

Alexion To Present At The William Blair 27th Annual Growth Stock Conference

Cheshire, CT, June 13, 2007 — Alexion Pharmaceuticals, Inc. (Nasdaq: ALXN) today announced that Vikas Sinha, Senior Vice President and Chief Financial Officer of Alexion Pharmaceuticals, will present at the William Blair 27th Annual Growth Stock Conference in Chicago at 3:00 p.m., local time (4:00 p.m., eastern) on Wednesday, June 20, 2007.

An audio webcast of Mr. Sinha's remarks will be available live. You can access the webcast at: www.alexionpharm.com. An archived version of the remarks will also be available through the Company's web site for a limited time following the conference.