Corixa Announces First Approval of an Infectious Disease Vaccine Containing the Company's RC-529 Adjuvant; Berna Biotech's SUPERVAX Approved for Sale in Argentina.

Business Editors/Health/Medical Writers

SEATTLE--(BUSINESS WIRE)--Sept. 8, 2003

Corixa Corporation (Nasdaq:CRXA) today announced the Argentinean approval of SUPERVAX, Berna Biotech's prophylactic vaccine containing Corixa's synthetic RC-529(TM) adjuvant, for the prevention of Hepatitis B infection. Developed by Berna Biotech, the vaccine combines Berna Biotech's Hansenula polymorpha-based recombinant Hepatitis B antigen with Corixa's RC-529 adjuvant. An adjuvant is a formulated compound or additive that, when combined with a vaccine, boosts the body's immune response to the antigen(s).

Clinical results for SUPERVAX showed seroprotection of more than 95 percent of the individuals vaccinated with SUPERVAX containing Corixa's RC-529 adjuvant after only two vaccinations, one month apart. Berna Biotech expects to launch SUPERVAX in Argentina next year.

"We are pleased to announce continued product commercialization progress with the approval of SUPERVAX containing our RC-529 adjuvant," said Steven Gillis, Ph.D., chairman and chief executive officer at Corixa. "This milestone -- soon after the filing for approval of GlaxoSmithKline's Fendrix containing Corixa's MPL adjuvant -- is further evidence of our strong commitment to aggressively move more products through clinical testing and on to product approval. The strength of our adjuvant technology and its potential contribution to Corixa's future product sales and royalty income is a distinguishing characteristic of our vaccine development efforts."

About Corixa's Adjuvant Business

Corixa's adjuvant technology is based on the knowledge that certain microbial products long have been recognized as potent immune system regulators and have been shown to induce a broad range of known cytokines, a class of substances that are produced by cells of the immune system and can affect the immune response. Modifications of these microbial products and their physical and biological delivery to the immune system can influence the way cytokines are expressed, as well as the recipient's own physiological responses. Such responses mimic the normal, protective responses that are initiated during microbial infection or injury.

With its partners, Corixa is evaluating its adjuvants in adult and pediatric vaccines that are designed to be safe and more effective in protecting against a broad range of diseases.

In addition to RC-529 adjuvant, Corixa's adjuvant portfolio also includes MPL, a derivative of the lipid A molecule found in gram-negative bacteria, one of the most potent immune system stimulants. Corixa also owns patented technology for extracting MPL adjuvant from bacterial cell walls. Several of Corixa's partners are evaluating MPL adjuvant in vaccines for development in allergy, cancer and infectious disease targets. MPL adjuvant has been administered to more than 12,000 patients in more than 33,000 doses as a vaccine adjuvant.

About Corixa

Corixa is a developer of immunotherapeutics with a commitment to treating and preventing autoimmune diseases, cancer and infectious diseases by understanding and directing the immune system. On June 30, 2003, Corixa announced that the FDA approved BEXXAR(R) for the treatment of patients with CD20 positive, follicular, NHL, with and without transformation, whose disease is refractory to Rituximab and has relapsed following chemotherapy.

Corixa is focused on immunotherapeutic products and has a broad technology platform enabling both fully integrated vaccine design and the use of its separate, proprietary product components on a standalone basis. In addition to BEXXAR, Corixa currently has multiple programs in clinical development, including several product candidates that have advanced to and through late stage clinical trials. The company partners with numerous developers and marketers of pharmaceuticals, targeting products that are Powered by Corixa(TM) technology with the goal of making its potential products available to patients around the world. Corixa was founded in 1994 and is headquartered in Seattle, with additional operations in Hamilton, Mont., and South San Francisco. For more information, please visit Corixa's Web site at http://www.corixa.com/.

Corixa Forward-Looking Statements

This press release contains forward-looking statements, including statements regarding the commercialization of our RC-529 adjuvant, statements regarding potential future sales and royalty income from our adjuvant technology and other statements about our plans, objectives, intentions and expectations. Forward-looking statements are based on the opinions and estimates of management at the time the statements are made. They are subject to certain risks and uncertainties that could cause actual results to differ materially from any future results, performance or achievements expressed or implied by such statements. Factors that could affect Corixa's actual results include, but are not limited to, the risk that we are unable to commercialize our RC-529 adjuvant or other products incorporating our adjuvant technology, the risk that royalties from our RC-529 adjuvant do not grow as we expect or that we do not achieve the royalty income from future products incorporating our adjuvant technology that we expect and the "Factors Affecting Our Operating Results, Our Business and Our Stock Price," described in our Quarterly Report on Form 10-Q for the quarter ended June 30, 2003, copies of which are available from our investor relations department. Readers are cautioned not to place undue reliance on these forward-looking statements, which speak only as of the date of this release.