EXHIBIT 99.1

  LA JOLLA PHARMACEUTICAL REACHES AGREEMENT WITH CARDIO-RENAL DIVISION OF FDA
        REGARDING PHASE 4 TRIAL DESIGN UNDER SPECIAL PROTOCOL ASSESSMENT

SAN DIEGO, AUGUST 2, 2004 - La Jolla Pharmaceutical Company (Nasdaq: LJPC) today
announced that it has reached a written agreement with the Cardio-Renal Division
of the United States Food and Drug Administration (FDA) concerning a clinical
trial that is designed to fulfill the Company's obligation to conduct a Phase 4
post-marketing clinical trial if its lupus drug candidate, Riquent(R) (abetimus
sodium), is approved under the FDA's accelerated approval regulation, also
called Subpart H. The trial protocol was evaluated and agreed to under the
Special Protocol Assessment (SPA) process. The Company has initiated the study
and expects to screen the first patient in August 2004.

The Cardio-Renal Division is currently reviewing the Company's New Drug
Application for Riquent and the Company expects to learn of a decision
concerning its application on or about October 16, 2004. Although the Company
has reached an agreement concerning the Phase 4 trial design and has initiated
the trial, there can be no guarantee that the FDA will approve Riquent, under
Subpart H or otherwise.

"We are pleased to have an agreement on the design of this trial. We have chosen
to begin the trial now to demonstrate our commitment to the study and to speed
its conduct. We believe our last two studies generated important information
that demonstrates the need to reduce antibodies to double-stranded DNA in
patients with lupus renal disease. We look forward to continuing to develop a
drug that is specifically designed to treat lupus and to working with physicians
and patients to increase our knowledge about this disease and Riquent," said
Steve Engle, Chairman and CEO of La Jolla Pharmaceutical Company.

CLINICAL TRIAL DESIGN

The Phase 4 trial is a randomized double-blind placebo-controlled international
study of lupus patients with a history of renal disease. The design of the study
builds on previous Riquent clinical studies with several enhancements, including
twice as many patients receiving Riquent compared with placebo, increased
patient enrollment of approximately 500 to 600 patients, more control of
immunosuppressive drugs at baseline, higher doses of Riquent in some treatment
groups, and a 12 month treatment duration for each patient. The primary endpoint
for the trial is time to renal flare, a serious increase in inflammation of the
kidneys. The trial is expected to take several years to complete.

To be eligible for enrollment in the trial, patients must have antibodies to
double-stranded DNA (dsDNA) and a history of renal flare within the last four
years, and must not be receiving high doses of immunosuppressive agents.
Patients will be randomized to one of four dosing groups: placebo, 100 mg of
Riquent per week, 300 mg of Riquent per week, and 100 mg of Riquent per week
shifting to 300 mg of Riquent per week at week 12.

"While 100 mg per week of Riquent appears to be sufficient for most patients, we
continue to believe that some patients may benefit from higher doses," added
Engle. "This study will allow us to assess if higher doses result in further
reductions in antibodies to dsDNA and increases in the percentage of patients
with sustained reductions in these antibodies. Higher doses may also show an
increased impact on clinical endpoints and will provide additional safety data."

SUBPART H AND SPECIAL PROTOCOL ASSESSMENTS

Drugs in development for serious, life-threatening diseases with an unmet
medical need such as lupus may be approved under the Subpart H regulation on an
accelerated basis if the FDA determines that the effect of the drug on a
surrogate endpoint is reasonably likely to predict clinical benefit. Under
Subpart H, a post-marketing clinical trial to confirm clinical benefit may be
initiated prior to approval, but would not need to be completed until after
approval. The SPA process is a formal procedure that results in a binding
written agreement between a company and the FDA concerning the design of a
clinical trial or other study.

Lupus, systemic lupus erythematosus or SLE, is a chronic, potentially
life-threatening autoimmune disease. About 90% of lupus patients are female, and
many develop the disease during their childbearing years. Approximately 50% of
lupus patients have renal disease, which can lead to irreversible kidney damage,
kidney failure and the need for dialysis, and is a leading cause of death in
lupus patients. Latinos, African Americans and Asians face an increased risk of
serious renal disease associated with lupus. The current standard of care for
lupus renal disease often involves treatment with high doses of corticosteroids
and immunosuppressive drugs that can cause severe side effects including
diabetes, hypertension and sterility, and may leave patients vulnerable to
opportunistic infections.

La Jolla Pharmaceutical Company is a biotechnology company developing
therapeutics for antibody-mediated autoimmune diseases and inflammation
afflicting several million people in the United States and Europe. The Company
is developing Riquent(R) for the treatment of lupus kidney disease, a leading
cause of sickness and death in patients with lupus. The Company is also
developing LJP 1082 for the treatment of antibody-mediated thrombosis, a
condition in which patients suffer from recurrent stroke, deep-vein thrombosis,
miscarriage and other thrombotic events, and is in the early stage of developing
small molecules to treat various other autoimmune and inflammatory conditions.
The Company's common stock is traded on The Nasdaq Stock Market under the symbol
LJPC. For more information about the Company, visit its Web site:
http://www.ljpc.com.

The forward-looking statements in this press release involve significant risks
and uncertainties, and a number of factors, both foreseen and unforeseen, could
cause actual results to differ materially from our current expectations.
Forward-looking statements include those that express a plan, belief,
expectation, estimation, anticipation, intent, contingency, future development
or similar expression. Even though our New Drug Application ("NDA") for
Riquent(R) has been accepted by the United States

Food and Drug Administration (the "FDA") for review, and even though we have
agreed with the FDA regarding the design of a potential Phase 4 trial and we
have initiated the trial, there is no guarantee that the FDA will approve
Riquent in a timely manner, or at all. Our analyses of clinical results of
Riquent, previously known as 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 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. The analysis of
the data from our Phase 3 trial of Riquent showed that the trial did not reach
statistical significance with respect to its primary endpoint, time to renal
flare, or with respect to the secondary endpoint, time to treatment with
high-dose corticosteroids or cyclophosphamide. Although our NDA for Riquent has
been accepted for review by the FDA, the results from our clinical trials of
Riquent may not ultimately be sufficient to obtain regulatory clearance to
market Riquent either in the United States or Europe, and we may be required to
conduct additional clinical studies to demonstrate the safety and efficacy of
Riquent in order to obtain marketing approval. There is no guarantee, however,
that we will have the necessary resources to complete any additional trial or
that any additional trial will sufficiently demonstrate the safety and efficacy
of Riquent. Our blood test to measure the binding affinity for Riquent is
experimental, has not been validated by independent laboratories and will likely
be reviewed as part of the Riquent approval process. 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. In
any event, regulatory authorities may require additional clinical trials, or may
not approve our drugs. Our ability to develop and sell our products in the
future may be adversely affected by the intellectual property rights of third
parties. Additional risk factors include the uncertainty and timing of:
obtaining required regulatory approvals, including delays associated with any
approvals that we may obtain; the clear need for additional financing; our
ability to pass all necessary FDA inspections; the increase in capacity of our
manufacturing capabilities for possible commercialization; successfully
marketing and selling our products; our lack of manufacturing, marketing and
sales experience; our ability to make use of the orphan drug designation for
Riquent; generating future revenue from product sales or other sources such as
collaborative relationships; future profitability; and our dependence on patents
and other proprietary rights. 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 Annual Report on Form 10-K for the year
ended December 31, 2003, and in other reports and registration statements that
we file with the Securities and Exchange Commission from time to time.

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