EXHIBIT 99.1

    LA JOLLA PHARMACEUTICAL TO PRESENT AT UBS GLOBAL LIFE SCIENCES CONFERENCE

SAN DIEGO, SEPTEMBER 22, 2004 - La Jolla Pharmaceutical Company (Nasdaq: LJPC)
today announced that Steven B. Engle, Chairman and CEO of La Jolla
Pharmaceutical, will present Thursday, September 30th at 11:30 a.m. Eastern Time
during the UBS Global Life Sciences Conference. The conference will take place
at The Grand Hyatt New York hotel in New York City. An audio webcast of the
presentation will be available through the Company's Web site:
http://www.ljpc.com.

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.

The forward-looking statements in this press release and made by Mr. Engle
during his presentation 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. The 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"), 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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