Common Contracts

3,000,000 SHARES ALEXION PHARMACEUTICALS, INC. COMMON STOCK, PAR VALUE $0.0001 PER SHARE UNDERWRITING AGREEMENT November 15, 2006

Underwriting Agreement • November 17th, 2006 • Alexion Pharmaceuticals Inc • Pharmaceutical preparations • New York

• Contract Type
  Underwriting Agreement
• Filed
  November 17th, 2006
• Company
  Alexion Pharmaceuticals Inc
• Industry
  Pharmaceutical preparations
• Jurisdiction
  New York

Alexion Pharmaceuticals, Inc., a Delaware corporation (the “Company”), proposes to issue and sell to the Underwriters named in Schedule I hereto (the “Underwriters”) an aggregate of 3,000,000 shares (the “Firm Shares”) and, at the election of the Underwriters, up to 450,000 additional shares (the “Optional Shares”) of its Common Stock, par value $0.0001. The shares of Common Stock, par value $0.0001 per share, of the Company to be outstanding after giving effect to the sales contemplated hereby are hereinafter referred to as the “Common Stock.” The Firm Shares and the Optional Shares that the Underwriters elect to purchase pursuant to Section 2 hereof are collectively called the Shares.

2,500,000 Shares ALEXION PHARMACEUTICALS, INC. COMMON STOCK, PAR VALUE $0.0001 PER SHARE UNDERWRITING AGREEMENT

Underwriting Agreement • August 15th, 2005 • Alexion Pharmaceuticals Inc • Pharmaceutical preparations • New York

• Contract Type
  Underwriting Agreement
• Filed
  August 15th, 2005
• Company
  Alexion Pharmaceuticals Inc
• Industry
  Pharmaceutical preparations
• Jurisdiction
  New York

Alexion Pharmaceuticals, Inc., a Delaware corporation (the “Company”), proposes to issue and sell to Morgan Stanley & Co. Incorporated (“Morgan Stanley” or the “Underwriter”) 2,500,000 shares of its Common Stock, par value $0.0001 per share (the “Shares”). The shares of Common Stock, par value $0.0001 per share, of the Company to be outstanding after giving effect to the sales contemplated hereby are hereinafter referred to as the “Common Stock.”