La Jolla Pharmaceutical Scientists Present Positive Results for Thrombosis Candidate.

Business Editors and Health/Medical Writers

BIOWIRE2K

SAN DIEGO--(BW HealthWire)--Sept. 13, 2000

La Jolla Pharmaceutical Company (Nasdaq: LJPC) researchers presented positive preclinical results which showed that its clinical Toleragen(R) candidate, LJP 1082, reduced disease-causing antibodies involved in antibody-mediated thrombosis, a life-threatening blood-clotting disorder.

Company scientists presented two papers at the 9th International Symposium on Antiphospholipid Antibodies in Tours, France.

"These studies show that we can suppress the production of the targeted antibodies and B cells using a number of Toleragen molecules," said Mathew Linnik Ph.D., Executive Vice President of Research for La Jolla Pharmaceutical Company. "Based on these findings, we have selected LJP 1082 as our clinical candidate. This is a key step in developing a therapeutic molecule for this disease. Following the successful completion of toxicology studies, we plan to file an Investigational New Drug (IND) application and begin clinical studies."

Antibody-mediated thrombosis is an autoimmune disease afflicting more than two million patients in the U.S. and Europe. Patients have an increased risk of blood clots that can result in stroke, myocardial infarction, deep-vein thrombosis, recurrent fetal loss, and post-operative complications following cardiovascular surgery. Patients usually suffer recurrent thrombotic events for the rest of their lives at more than double the rate of individuals without these antibodies.

The disease, also known as Antiphospholipid Syndrome (APS), is often discovered in younger patients who may lack typical risk factors for stroke or heart attacks. Current therapy relies on anticoagulants, which are difficult to manage, and cause serious side effects -- such as an increased risk of life-threatening bleeding episodes -- and are not effective in many patients.

In this disorder, antibodies produced by disease-causing B cells target a key blood protein, beta 2 glycoprotein 1 (beta 2 GP1), which is involved in the formation of blood clots. When antibodies bind to this protein, inappropriate blood-clot formation is exacerbated.

In the first study, titled "Tolerance Activity and Pharmacokinetics of Multivalent beta 2 GP1 Domain One Conjugates in an Immunized Animal Model," LJP scientists presented data on the efficacy and pharmacokinetics of several thrombosis Toleragen drug candidates in mouse and rat models of the disease. In an immunized rat model, LJP 1082 drug treatment reduced the level of antibodies and the number of B cells producing these antibodies by approximately 90%. These findings suggest that the drug candidate effectively shut down or tolerized the targeted B cells responsible for producing these disease-associated antibodies.

In a second presentation, scientists explained how site-directed mutagenesis was used to identify where disease-causing antibodies bind to beta 2 GP1. Site-directed mutagenesis involves the systematic modification of individual amino acids in beta 2 GP1 to determine which amino acids are important in the binding between beta 2 GP1 and the antibodies. That information was used in the design of LJP 1082. This presentation was titled, "Use of Single Point Mutations in Domain 1 of beta 2 GP1 to determine Fine Antigenic Specificity of Antiphospholipid Autoantibodies."

La Jolla Pharmaceutical's Tolerance Technology(R) is designed to arrest the production of disease-causing antibodies without suppressing the healthy functions of the immune system. Its Tolerance Technology platform has been shown to reduce targeted disease-causing antibodies in five human clinical trials in lupus patients.

La Jolla Pharmaceutical Company (LJP) is a biotechnology company developing therapeutics for antibody-mediated diseases, such as lupus and stroke, which afflict several million people in the United States and Europe. The Company is preparing to initiate a Phase III trial of LJP 394 for patients with lupus kidney disease, a leading cause of sickness and death in these patients. The Company is also developing drugs for antibody-mediated stroke, heart attack, and deep-vein thrombosis, for xenotransplantation, and for other antibody-mediated diseases. The Company's common stock trades on The Nasdaq Stock Market under the symbol LJPC. For more information about the company, visit our website: www.ljpc.com.

Except for historical statements, this press release contains forward-looking statements, including without limitation statements regarding the analysis of results from preclinical and clinical studies and La Jolla Pharmaceutical's drug candidates and drug development plans. These forward-looking statements involve risks and uncertainties, and a number of factors, both foreseen and unforeseen, could cause actual results to differ materially from those anticipated. The Company's analysis of clinical results for LJP 394 is ongoing, and future analyses may not necessarily support conclusions to date. Clinical results for LJP 394 are derived from a trial that was terminated prior to completion, and certain data are incomplete.

The Company's blood test to measure binding affinity for LJP 394 is experimental and has not been validated by independent laboratories. Tolerance, or the specific inactivation of pathogenic B cells, is a new technology that has not been proven. The Company's ability to develop and sell its products in the future may be affected by the intellectual property rights of third parties. Future clinical trials of the Company's drug candidates may have negative or inconclusive results. Future clinical trials of the Company's drug candidates may not support results of preclinical or other prior trials and pre IND studies of the Company's new candidate for treating antibody-mediated thrombosis may reveal a potential safety issue requiring the development of a new candidate. Any delays in testing of the Company's drug candidates and/or termination of development by the Company would result in delays or lack of government approval to market the compounds. The development of drug candidates involves many risks and uncertainties, including, without limitation, whether the drug can provide a meaningful clinical benefit, and any positive results observed to date may not be indicative of future results. La Jolla Pharmaceutical's other potential drug candidates, including its Toleragen candidate for xenotransplantation, which has not progressed to clinical trials, involve comparable risks. Interested parties are urged to review the risks detailed from time to time in La Jolla Pharmaceutical Company's Securities and Exchange Commission (SEC) filings, including the report on Form 10-K for the year ended December 31, 1999 and on Form 10-Q for the quarter ended June 30, 2000.