AMENDMENT NO. 1 TO DEVELOPMENT AND COMMERCIALIZATION AGREEMENT

Exhibit 10.3

EXECUTION COPY

AMENDMENT NO. 1
TO
DEVELOPMENT AND COMMERCIALIZATION AGREEMENT

THIS AMENDMENT NO. 1 (the “ Amendment ”), dated January 16, 2009, amends that certain Development and Commercialization Agreement, dated as of January 4, 2009 (the “ Development Agreement ”), by and between La Jolla Pharmaceutical Company, a Delaware corporation (the “ Company ”), and BioMarin CF Limited, an Irish corporation (“ BioMarin CF ”).

RECITALS

A. WHEREAS, in connection with the Development Agreement, the Company and BioMarin Pharmaceutical Inc., a Delaware corporation (“ BioMarin Pharmaceutical ”), entered into that certain Securities Purchase Agreement, dated as of January 4, 2009 (the “ Securities Purchase Agreement ”);

B. WHEREAS, the Company and BioMarin Pharmaceutical have made certain changes to the Securities Purchase Agreement in the form of an amendment to the Securities Purchase Agreement (the “ Amendment to the Securities Purchase Agreement ”); and

C. WHEREAS, the Company and BioMarin CF desire to make conforming changes to the Development Agreement to reflect certain changes made by the Amendment to the Securities Purchase Agreement.

NOW, THEREFORE, in consideration of the foregoing, the parties agree as follows:

1. Section 1.41 of the Deve