LA JOLLA PHARMACEUTICAL TO COMPLETE ENROLLMENT OF PHASE III LUPUS CLINICAL TRIAL

SAN DIEGO, October 22, 2002 - La Jolla Pharmaceutical Company (Nasdaq: LJPC) announced today that it would complete enrollment in its Phase III clinical trial of LJP 394 for the treatment of lupus renal disease by November 11, 2002. After the completion of enrollment, study physicians will conduct final patient visits during the next few weeks, at which point the Phase III trial will be finished. Then, the Company will collect and audit final data from the trial sites prior to unblinding and analysis. The Company currently plans to report initial results in early 2003.

Serum samples from approximately 90% of the patients enrolled to date have been analyzed. About 94% of the tested patient samples have high-affinity antibodies to LJP 394. In three previous clinical trials, the percentage of patients who had high-affinity antibodies to LJP 394 was 89%, 90% and 94%, respectively. The Company believes that lupus patients with high-affinity antibodies to LJP 394 are more likely to benefit from treatment with LJP 394.

"As planned, we have reached the targeted number of renal flares in high-affinity patients," said Steven B. Engle, Chairman and Chief Executive Officer. The primary endpoint in the Phase III trial is time to renal flare in patients with high-affinity antibodies to LJP 394, and completion of the trial is based on reaching a targeted number of renal flares. In the samples tested to date, the Company has observed that approximately 90% of patients who experienced a renal flare were high-affinity. Until all patients have been fully evaluated and the resulting data have been extensively analyzed, conclusions should not be drawn regarding the outcome of the study.

The Phase III trial is a randomized, double-blind, placebo-controlled study and is designed to confirm data observed in the Phase II/III trial. In the Phase II/III trial, LJP 394-treated patients who had high-affinity antibodies to the drug had fewer renal flares and fewer treatments with high-dose corticosteroids and/or cyclophosphamide than placebo-treated patients.

Lupus is an autoimmune disease that results in a wide variety of chronic, progressive symptoms including episodes of life-threatening kidney inflammation known as "renal flares." The current standard of care for lupus - treatment with steroids and chemotherapy drugs - can cause severe side effects including diabetes, hypertension and sterility, and may leave patients vulnerable to lethal opportunistic infections. LJP 394 is designed to specifically prevent the production of antibodies responsible for lupus kidney disease without suppressing the normal functions of the immune system.

La Jolla Pharmaceutical Company is a biotechnology company leading the development of therapeutics for antibody-mediated autoimmune diseases afflicting several million people in the United States and Europe. The Company is conducting a Phase III trial of LJP 394 in patients with lupus kidney disease, a leading cause of sickness and death in these patients. The Company is also conducting a Phase I/II trial of LJP 1082 for the treatment of antibody-mediated thrombosis, a condition in which patients suffer from recurrent stroke, deep-vein thrombosis and other thrombotic events. The Company's common stock is traded on The Nasdaq Stock Market under the symbol LJPC. For more information about the Company, visit our Web site: http://www.ljpc.com.

Except for historical statements, this press release contains forward-looking statements involving significant risks and uncertainties, and a number of factors, both foreseen and unforeseen, could cause actual results to differ materially from our current expectations. Our analyses of clinical results of LJP 394, our drug candidate for the treatment of systemic lupus erythematosus ("lupus"), and LJP 1082, our drug candidate for the treatment of antibody-mediated thrombosis ("thrombosis"), are ongoing and future analyses could result in a finding that these drug candidates are not effective in large patient populations, do not provide a meaningful clinical benefit or may reveal a potential safety issue requiring us to develop new candidates. Our blood test to measure the binding affinity for LJP 394 is experimental, has not been validated by independent laboratories, may require regulatory approval and may be necessary for the approval and the commercialization of LJP 394. Our other potential drug candidates are at earlier stages of development and involve comparable risks. Analysis of our clinical trials could have negative or inconclusive results. Any positive results observed to date may not be indicative of future results. Even if results are promising, the U.S. Food and Drug Administration ("FDA") may require additional clinical trials. The Company's ability to develop and sell its products in the future may be affected by the intellectual property rights of third parties. Additional risk factors include the uncertainty of: obtaining required regulatory approvals; successfully marketing products; receiving future revenue from product sales or other sources such as collaborative relationships; future profitability; the need for additional financing; our dependence on patents and other proprietary rights; FDA approval of our manufacturing facilities; the increase in capacity of our manufacturing capabilities for possible commercialization; and our lack of marketing experience. Readers are cautioned to not place undue reliance upon forward-looking statements, which speak only as of the date hereof, and we undertake no obligation to update forward-looking statements to reflect events or circumstances occurring after the date hereof. Interested parties are urged to review the risks described in our other reports and registration statements filed with the Securities and Exchange Commission from time to time, including the report on Form 10-K for the year ended December 31, 2001.