Corixa Provides Update on Diagnostic Patent Issuance.

Health/Medical Writers

SEATTLE--(BW HealthWire)--April 30, 2001

Corixa Corporation (Nasdaq:CRXA), a developer of immunotherapeutics, today announced that the United States Patent and Trademark Office (USPTO) has issued the Company patents covering certain of its discoveries potentially useful in the diagnosis and treatment of Babesia microti (B. microti) and Ehrlichia infections, as well as claims covering the use of certain gene sequences for the detection of lung cancer.

U.S. Patents 6,183,976, 6,207,169 and 6,214,971 cover compositions of matter and methods for the diagnosis and treatment of B. microti infection and Ehrlichia infection, particularly human granulocytic ehrlichiosis (HGE). Both are flu-like illnesses caused by a rodent bacterium generally transmitted to humans by the same tick responsible for the transmission of Lyme disease. A single tick bite can lead to co-infection with all three diseases.

While the number of reported cases of B. microti and HGE infections in the United States and Europe is on the rise, detection of these illnesses is difficult. Accurate and early diagnosis is critical because the preferred treatments for Lyme disease, ehrlichiosis and babesiosis are different. The issued patents cover composition of matter and utility claims for antigens that Corixa believes may be useful in performing rapid diagnosis and potential prevention of babesia or HGE infection.

U.S. Patent No. 6,210,883 relates to the use of several gene sequences in nucleic acid hybridization assays for detection of lung cancer. The patent also provides coverage on the use of such sequences in diagnostic kits for detection of lung cancer. Early detection of lung cancer is key to increasing survival rates, however, diagnosis can be difficult since clinical symptoms often are not seen until the disease has reached an advanced stage. Corixa's invention may help in the early detection of lung cancer as well as in monitoring the progression or reappearance of disease following treatment.

"We are pleased to add these patents to our expanding array of proprietary innovations in the fields of oncology, autoimmune and infectious diseases," said Steven Gillis, Ph.D., chairman and chief executive officer at Corixa. "The protection of Corixa's intellectual property remains a critical priority for the company as we continue to use the power of immunology and genomics to discover and develop immunotherapeutic solutions to the diagnosis and treatment of disease."

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. 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. Corixa currently has 16 programs in clinical development and 22 programs in preclinical development, including its most advanced product candidate, Bexxar(TM), a monoclonal antibody conjugated to a radioisotope.

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, Wash., with additional operations in Hamilton, Montana and Redwood City, California and South San Francisco, California. For more information, please visit Corixa's website at www.corixa.com or call the company's investor relations information line at 1-877-4CORIXA or 1-877-426-7492.

Forward-Looking Statements

Except for the historical information presented, certain matters discussed in this press release are forward-looking statements. 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 failure of the patented technology to prove useful in diagnosing lung cancer, or diagnosing or treating B. microti and HGE infections, and the "Factors Affecting Our Operating Results, Our Business and Our Stock Price," described in our Annual Report on Form 10-K for the year ended December 31, 2000, 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.