Exhibit 99.1

    PDL TO ADJUST PURCHASE PRICE FOR ESP PHARMA, INC. FOLLOWING ESP PHARMA'S
                      ACQUISITION OF RIGHTS TO RETAVASE(R)

FREMONT, Calif., Feb. 1 /PRNewswire-FirstCall/ -- Protein Design Labs,
Inc. (PDL) (Nasdaq: PDLI) today said that it will amend its definitive
agreement to acquire ESP Pharma, Inc. (ESP) to reflect that company's
acquisition of exclusive rights to Retavase(R) in the United States and
Canada.

On January 25, 2005, PDL and ESP announced that they had entered into a
definitive agreement under which PDL will acquire ESP for $300 million
in cash and approximately $175 million in PDL common stock, or an
aggregate value of approximately $475 million. PDL and ESP have agreed
to increase the purchase price payable to the ESP shareholders at the
closing of the ESP acquisition by $25 million in cash in connection with
the Retavase transaction announced today by ESP. The closing of the
acquisition of ESP is subject to various conditions, including the
receipt of antitrust and other regulatory approvals, and is not
anticipated to close until late in the first quarter of 2005.

"We are extremely pleased by the addition of Retavase to ESP Pharma's
portfolio of proprietary products," said Mark McDade, Chief Executive
Officer, PDL. "We see a strong strategic fit with their hospital-focused
presence in cardiovascular medicine. We also believe that the addition
of Retavase could also help expand sales of Cardene(R) IV, ESP's product
for the short-term reduction of hypertension, due to an increased
presence in hospital emergency rooms." Mr. McDade added, "Overall,
following closing of both ESP and the Retavase transactions, these steps
should accelerate PDL's revenue growth and further enhance the value of
this strategic combination."

ESP Pharma, a specialty pharmaceutical company focused on the
acquisition, marketing, and late-stage development of life-saving
acute-care therapeutics, today announced its acquisition of exclusive
North American rights to Retavase(R) (reteplase) from Centocor, a
biopharmaceutical operating company of Johnson & Johnson. The product
currently is marketed on behalf of Centocor Inc. by Scios, Inc., another
Johnson & Johnson company. ESP Pharma noted that its acquisition of
Retavase included distribution, manufacturing, development and marketing
rights, all relevant intellectual property, and approximately two years
supply of inventory plus certain manufacturing equipment.

First introduced into the U.S. market in 1997, Retavase belongs to the
fibrinolytic or thrombolytic class of pharmaceutical agents used in the
acute-care setting to dissolve coronary blood clots and improve blood
flow in heart attack patients. Each year, in the U.S., more than one
million people suffer a heart attack (acute myocardial infarction or
AMI).



Retavase is indicated for use in the management of AMI in adults for the
improvement of ventricular function following AMI, the reduction of the
incidence of congestive heart failure, and the reduction of mortality
associated with AMI. The product can be administered within a 30-minute
time window by a double-bolus injection without dose adjustment for
patient weight compared to other thrombolytics requiring longer duration
intravenous infusions or dosing adjustments based on weight.

About ESP Pharma, Inc.

ESP Pharma is committed to Excellence in Specialty Pharmaceuticals and
to helping physicians improve patient outcomes and survival in the
acute-care setting. Under the leadership of a highly experienced
management team, ESP focuses its "Buy and Build, Search and Develop"
strategy on identifying opportunities to selectively acquire and enhance
the market potential of novel, commercially available therapeutics and
late-stage development compounds to fulfill unmet market needs.
Additional information about ESP is available at
http://www.ESPPharma.com .

About PDL

Protein Design Labs is a leader in the development of humanized
antibodies to prevent or treat various disease conditions. PDL currently
has antibodies under development for autoimmune and inflammatory
conditions, asthma and cancer. PDL holds fundamental patents for its
antibody humanization technology. Further information on PDL is
available at www.pdl.com.

The foregoing contains forward-looking statements involving risks and
uncertainties and PDL's actual results may differ materially from those,
express or implied, in the forward-looking statements. The
forward-looking statements contained herein include statements about the
consummation of the pending acquisition of ESP, and of Retavase assets
by ESP, and the benefits of the pending transactions, including their
potential effect upon PDL's future financial performance. These
statements are subject to inherent risks and uncertainties that could
cause actual results to differ materially from those expressed or
implied. Such risks and uncertainties include, among others, the
possibility that regulatory or other closing conditions will not be
satisfied, whether the combined company will be able to realize the
anticipated benefits or synergies of the transactions in a timely manner
or at all, and the future revenues from ESP Pharma products. Other
factors that may cause our actual results to differ materially from
those, express or implied, in the forward- looking statements in this
press release are discussed in our Annual Report on Form 10-K for the
year ended December 31, 2003, in our quarterly report on Form 10-Q for
the period ended September 30, 2004, and in other filings with the
Securities and Exchange Commission.

NOTE: Protein Design Labs and the PDL logo are registered U.S.
trademarks of Protein Design Labs, Inc. Cardene IV is a registered
trademark of ESP Pharma, Inc. Retavase is a registered trademark of
Centocor.

SOURCE  Protein Design Labs, Inc.
    -0-                             02/01/2005
    /CONTACT:  James R. Goff Senior Director, Corporate Communications of
Protein Design Labs +1-510-574-1421, or jgoff@pdl.com/
    /Web site:  http://www.pdl.com/