EXHIBIT 99.1



Contact:

Ann Tanabe                    Hershel Berry                     Lacy Fitzpatrick
Texas Biotechnology          The Trout Group                    ICOS Corporation
(713) 796-8822               (415) 392-3385                      (425) 415-2207


FOR IMMEDIATE RELEASE


            TEXAS BIOTECHNOLOGY ACQUIRES ICOS CORPORATION'S INTEREST
                        IN ICOS-TEXAS BIOTECHNOLOGY, L.P.

        FULL DEVELOPMENT AND MARKETING RIGHTS TO SITAXSENTAN AND TBC3711
                         RETURNED TO TEXAS BIOTECHNOLOGY


HOUSTON, TX AND BOTHELL, WA - APRIL 23, 2003 - Texas Biotechnology Corporation
(NASDAQ: TXBI) and ICOS Corporation (NASDAQ: ICOS) today announced that Texas
Biotechnology has acquired ICOS' 50% interest in ICOS-Texas Biotechnology, L.P.
This effectively returns to Texas Biotechnology full ownership rights to the
endothelin receptor antagonist program, including the experimental pulmonary
arterial hypertension (PAH) drug, sitaxsentan, and TBC3711.

Under the terms of the agreement, Texas Biotechnology paid ICOS $4 million at
closing, and agreed to pay $4 million in 12 months and $2 million in 18 months,
plus interest.

"This agreement represents Texas Biotechnology's commitment to realizing the
full value of sitaxsentan for our shareholders," Bruce D. Given, M.D., President
and CEO of Texas Biotechnology said. "Sitaxsentan is an important program to
Texas Biotechnology and we are excited to have the full development and
marketing rights, and the flexibility to pursue potential agreements with future
partners. We thank ICOS for their considerable contributions."

"This agreement is part of our commitment to focusing ICOS' development
strategy," said Paul Clark, ICOS Chairman and CEO. "Dr. Given and his team at
Texas Biotechnology are well positioned to take this product forward and we wish
them much success in the future."

ABOUT SITAXSENTAN AND PAH

Sitaxsentan is a small molecule that blocks the action of endothelin, a potent
mediator of blood vessel constriction and growth of smooth muscle in vascular
walls. Endothelin receptor antagonists may prove to be effective in the
treatment of a variety of diseases where the regulation of vascular constriction
is important. Sitaxsentan is selective in the targeting of the endothelin A
receptor.

Pulmonary arterial hypertension is a condition that involves high blood pressure
and structural changes in the walls of the pulmonary arteries, which are the
blood vessels that connect the right side of the heart to the lungs. PAH causes
shortness of breath, limits activity, and is eventually


                                                                    EXHIBIT 99.1


fatal unless treated successfully with heart and lung transplant. Primary and
secondary pulmonary arterial hypertension are estimated to afflict up to 100,000
people worldwide, many of whom are children or young adults.

ABOUT TEXAS BIOTECHNOLOGY CORPORATION

Texas Biotechnology Corporation, a biopharmaceutical company focused on the
discovery, development and commercialization of novel drugs, is recognized for
its expertise in small molecule drug development and vascular biology.
Argatroban, its first FDA-approved product, is being marketed by GlaxoSmithKline
for heparin-induced thrombocytopenia. Texas Biotechnology is in Phase III
development of the endothelin antagonist, sitaxsentan, for pulmonary arterial
hypertension. Its majority owned affiliate, Revotar Biopharmaceuticals AG, is in
Phase II development with the selectin antagonist bimosiamose in asthma,
psoriasis and atopic dermatitis. Texas Biotechnology has several other research
and development programs ongoing for a range of cardiovascular and inflammatory
diseases. To learn more about Texas Biotechnology please visit our web site:
www.tbc.com.

ABOUT ICOS

ICOS is a product-driven company that has expertise in both protein-based and
small molecule therapeutics. ICOS combines its capabilities in molecular,
cellular and structural biology, high throughput drug screening, medicinal
chemistry and gene expression profiling to develop highly innovative products
expected to have significant commercial potential. ICOS applies its integrated
approach to erectile dysfunction and other urologic disorders, sepsis,
psoriasis, and other inflammatory diseases. ICOS' strategy targets multiple
therapeutic areas with drugs that act through distinct molecular mechanisms,
increasing opportunities to market breakthrough products.

This press release contains "forward-looking statements" within the meaning of
Section 27A of the Securities Act of 1933, as amended, and Section 21E of the
Securities Exchange Act of 1934, as amended. These forward-looking statements
are subject to certain risks, trends and uncertainties that could cause actual
results to differ materially from those projected. Among those risks, trends and
uncertainties are timing and cost of our clinical trials, attainment of research
and clinical goals and milestones of product candidates, attainment of required
governmental approvals, sales levels of our products and availability of
financing and revenues sufficient to fund development of product candidates and
operations. In particular, careful consideration should be given to cautionary
statements made in the various reports Texas Biotechnology and ICOS have filed
with the Securities and Exchange Commission. Texas Biotechnology and ICOS
undertake no duty to update or revise these forward-looking statements. The
biotechnology and pharmaceutical businesses are risky and there can be no
assurance that any particular product candidate will progress and become a
commercial product.

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