Infectious Disease Research Institute Receives $15 Million Donation from the Bill & Melinda Gates Foundation

SEATTLE -- A vaccine for leishmaniasis—a parasitic disease that kills up to 500,000 adults and children every year—is one step closer to reality. The Infectious Disease Research Institute (IDRI) today announced receipt of a $15 million grant from the Bill & Melinda Gates Foundation to fund their ongoing effort with Corixa Corporation (Nasdaq: CRXA) to develop a vaccine to prevent leishmaniasis.

Leishmaniasis is a skin and visceral disease endemic in the Indian sub-continent, Africa, South America, and the Middle East. According to the World Health Organization (WHO), an estimated 15 million new cases of the disease appear each year. Leishmaniasis is caused by the parasite leishmania, which is carried by sand flies.

"We are excited to receive funding for our leishmaniasis program from the Bill & Melinda Gates Foundation," stated Cynthia Healy, Ph.D., chair of the board of IDRI. "This generous donation represents a serious commitment to treating and preventing diseases of developing countries. IDRI and Corixa have been collaborating on leishmaniasis research for the past several years, which has resulted in a promising candidate vaccine. Support from the Bill & Melinda Gates Foundation will allow us to optimize the vaccine and begin applying it in areas of the world where it is needed most.

"IDRI's mission is to develop vaccines for diseases of developing countries, and our collaboration with Corixa has been instrumental in these efforts. Our aim is to produce the world's first successful vaccine against a parasitic disease."

Already in Phase I clinical trials in Brazil, IDRI has tested a prototype leishmaniasis vaccine comprising Corixa's novel antigens on a compassionate-use basis on a small number of leishmaniasis patients. The funding will allow IDRI to pursue additional studies, including advanced clinical trials in several countries. As part of the collaboration, Corixa anticipates the company will manufacture and supply product formulations for further clinical studies. They also will manage required, multi-site clinical trials and product registration efforts. Corixa's adjuvant technology also is expected to be a key component of the vaccine.

"Corixa's collaboration with IDRI brings complementary skills, resources and technology together to attempt to resolve diseases that affect major patient populations in less developed nations," said Steven Reed, Ph.D., chief scientific officer and executive vice president of Corixa. "A vaccine powered by both Corixa's antigens and adjuvants, combined with IDRI's efforts to conduct vaccine testing in developing countries, will be a dramatic breakthrough for this important unmet medical need."

Corixa has developed a prototype vaccine for leishmaniasis, which has been tested in patients in Brazil. A similar vaccine has been licensed to Heska, Inc., for vaccination of dogs against Leishmania infection. Dogs can serve as a host for the sand fly that harbors the parasite responsible for the disease.

About IDRI
IDRI is a not-for-profit corporation dedicated to the study of infectious diseases and cancer and to the development of vaccines, therapeutics and diagnostics for their treatment and prevention. IDRI's mission is to promote such research through its internal programs and, occasionally, by supporting research at other organizations with expertise in infectious disease and cancer research consistent with these purposes and with its tax exempt status under Section 501(c)(3) of the Internal Revenue Code. IDRI research is supported by the National Institutes of Health.

About Corixa
Corixa is a research- and development-based biotechnology company committed 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 vaccine components on a standalone basis. The company partners with numerous developers and marketers of pharmaceuticals and diagnostic products with the goal of making its potential products, Powered by Corixa, available to patients around the world. Corixa was founded in 1994 and is headquartered in Seattle, Wash., with additional operations in Hamilton, Mont. and Redwood City, Calif. For more information, call the company's investor relations information line at 1-877-4CORIXA or 1.877.426.7492 or visit Corixa's website.

Forward-Looking Statements
Except for the historical information presented, certain matters discussed in this press release are forward-looking statements that 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. Such risks and uncertainties include adverse events resulting from further clinical trials of the leishmaniasis vaccine being developed by IDRI and Corixa and other risks detailed from time to time in Corixa's public disclosure filings with the U.S. Securities and Exchange Commission (SEC), including the Annual Report on Form 10-K for the fiscal year ended December 31, 1999, and the Company's Registration Statement on Form S-3, filed on March 7, 2000. Copies of Corixa's public disclosure filings with the SEC are available from its investor relations department.