La Jolla Pharmaceutical Company Selects Stroke Drug Candidate.

Business Editors & Health/Medical Writers

BIOWIRE2K

SAN DIEGO--(BW HealthWire)--July 11, 2000

La Jolla Pharmaceutical Company (Nasdaq:LJPC) today announced the nomination of a clinical drug candidate, LJP 1082, to treat antibody-mediated thrombosis, a life-threatening blood-clotting disorder. Based on positive preclinical results in mice, rats and primates, the Company has chosen this candidate for planned toxicology studies required for the filing of an Investigational New Drug Application (IND).

"We are excited about the selection of a clinical candidate for this deadly autoimmune disease," said Steven Engle, Chairman and CEO of La Jolla Pharmaceutical Company. "Based on positive toxicology results for LJP 1082, we plan to file an IND in the first half of 2001 and will begin clinical trials to assess the safety and efficacy of the candidate."

Antibody-mediated thrombosis afflicts more than 2 million patients in the U.S. and Europe. Patients have an increased risk of stroke, myocardial infarction, deep-vein thrombosis, recurrent fetal loss, and post-operative complications following cardiovascular surgery. In this autoimmune disorder, antibodies produced by disease-causing B cells target a key blood protein called beta 2 glycoprotein 1, which is involved in the formation of blood clots. When antibodies bind to this protein, inappropriate blood-clot formation is exacerbated.

The disease, known as Antiphospholipid Syndrome (APS), is often discovered in younger patients who may lack typical risk factors. Patients usually suffer recurrent thrombotic events for the rest of their lives at more than double the rate of individuals without these antibodies. Current therapy relies on anticoagulants, which are difficult to manage, may cause serious side effects - such as an increased risk of life-threatening bleeding episodes - and are not effective in many patients.

The Company has identified several antibody-mediated thrombosis drug-candidate molecules, called Toleragens(R), that have been shown to reduce the levels of disease-causing antibodies and their related B cells in a dose-dependent manner in both mouse and rat models. A Toleragen is a treatment agent that is designed to bind to antibody receptors on the cell surface of targeted B cells and to send a signal that arrests the production of disease-causing antibodies. These molecules are based on La Jolla Pharmaceutical's patented Tolerance Technology(R) that is designed to arrest the production of disease-causing antibodies without suppressing the healthy functions of the immune system.

Previously, the Company reported that disease-related antibodies from patients bind to a particular region, called domain-1, on beta 2-glycoprotein 1. These antibodies in APS are believed to increase blood-clot formation by interfering with the natural breakdown of a blood component - Factor Va - that accelerates clotting. In the Company's animal models of disease, the production of disease-causing antibodies results in a delay in the inactivation of Factor Va similar to that seen in humans.

Using this same Tolerance Technology, the Company announced positive clinical trial results earlier this year regarding its lupus Toleragen, LJP 394. LJP 394 is designed to arrest the production of antibodies to double-stranded DNA (dsDNA) in lupus patients. Antibodies to dsDNA are believed to be responsible for lupus renal disease, the leading cause of morbidity and mortality in lupus. In an 18-month Phase II/III clinical trial involving more than 200 patients, drug-treated patients with high-affinity antibodies for LJP 394 experienced one-third as many renal flares and less than one-half as many treatments with high-dose corticosteroids and/or cyclophosphamide as placebo-treated patients.

La Jolla Pharmaceutical is focused on the research and development of therapeutic compounds to treat antibody-mediated diseases such as lupus, antibody-mediated thrombosis and organ rejection in xenotransplantation. The Company develops disease-specific therapeutics using its proprietary Tolerance Technology for major diseases and conditions caused by antibodies. By treating the underlying cause of disease, the Company believes that Tolerance Technology will lead to products with improved therapeutic benefit and fewer side effects than currently available treatments. The Company's common stock trades on The Nasdaq Stock Market under the symbol LJPC. For more information about the Company, visit our Web site: www.ljpc.com.

Statements regarding the analysis of results from preclinical and clinical studies, as well as La Jolla Pharmaceutical's drug candidates and drug development plans, are forward-looking statements involving 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 may be 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. Future clinical trials of the Company's drug candidates may have negative or inconclusive results. Clinical trials of the Company's new drug candidate for treating antibody-mediated thrombosis may not support results of preclinical trials or pre IND studies 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 compound. 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.