LA JOLLA PHARMACEUTICAL COMPANY ANNOUNCES FINANCING OF UP TO $16.3 MILLION

La Jolla Pharmaceutical Company (OTCBB: LJPC) (the “Company”) announced today that the Company has entered into definitive agreements with institutional investors and affiliates for a private placement of common stock, convertible preferred stock and warrants to purchase convertible preferred stock totaling up to $16.3 million in gross proceeds. The transaction is expected to close on or about May 25, 2010, subject to customary closing conditions. Proceeds of the financing will be used to evaluate potential pharmaceutical products for in-licensing or acquisition and to pursue potential development opportunities for Riquent in light of recent renewed interest in pharmaceutical products being developed by other companies for the treatment of Systemic Lupus Erythematosus (SLE), among other uses.

Summary of Financial Terms

The Company is selling approximately 29.0 million shares of common stock and 5,134 shares of convertible preferred stock in the initial closing, for aggregate gross proceeds of approximately $6.0 million. The investors will also receive a three-year warrant to purchase, for cash, an additional 10,268 shares of convertible preferred stock for an aggregate exercise price of approximately $10.3 million. The investors will be required to exercise the warrants and purchase the additional shares of convertible preferred stock in the event that the Company consummates a strategic transaction approved by the investors.

Each share of convertible preferred stock will be initially convertible into shares of the Company’s common stock at a conversion rate of 66,667 shares of common stock per share of preferred stock that is converted. This conversion rate will be subject to upward adjustment under certain circumstances. The convertible preferred stock will bear a dividend of 15% per annum, payable semi-annually in additional shares of convertible preferred stock. The convertible preferred stock is subject to redemption if the Company does not consummate a strategic transaction approved by the investors within nine months of the initial closing. The Company will be required to obtain the vote of the holders of the convertible preferred stock prior to taking certain corporate actions.