LA JOLLA PHARMACEUTICAL PRESENTS AT BIOCENTURY NEWSMAKERS CONFERENCE

SAN DIEGO, September 5, 2002 -- La Jolla Pharmaceutical Company (Nasdaq: LJPC) announced that Steven B. Engle, Chairman and CEO, will provide an update on the Company's progress at the "NewsMakers in the Biotech Industry" investor conference sponsored by BioCentury. The presentation will take place today at the Millennium Broadway Hotel in New York City.

"Approximately 280 lupus patients with a history of renal disease have been enrolled in our Phase III clinical trial of LJP 394," said Mr. Engle. "The study is being conducted at more than 70 trial sites in North America and Europe."

The double-blinded, placebo-controlled Phase III study is designed to confirm data from a previous Phase II/III trial in which time to renal flare, the primary endpoint, and time to treatment with high doses of corticosteroids and/or cyclophosphamide were significantly increased in patients with high-affinity antibodies to LJP 394. Completion of the Phase III trial is based on reaching a targeted number of renal flares in patients with high-affinity antibodies for LJP 394. Patient enrollment will continue until the targeted number of renal flares is reached. Patients will remain in the study until its conclusion or until they have completed 22 months of treatment. The Company expects the average time patients will remain in the Phase III trial to be about 12 months, which is similar to the average time in the Phase II/III trial.

"The first patients have completed 22 months in the Phase III trial. All of these patients have enrolled in an open-label follow-on clinical trial in which they will receive 100 mg of LJP 394 weekly," said Mr. Engle. "This follow-on trial is designed to provide LJP 394 treatment to patients after they complete the Phase III protocol and collect longer-term safety data."

Regarding the Phase I/II clinical trial of its candidate for antibody-mediated thrombosis, Mr. Engle stated, "We are currently dosing the last patient group in this study of LJP 1082."

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. Patients interested in the Phase III lupus trial may call 1-888-30-LUPUS for information.

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.