Corixa Announces Its Intent to File a Biological License Application With U.S. FDA On the Use of Its Melacine Vaccine for Treatment of Stage II Melanoma.

Business Editors/Health & Medical Writers

SEATTLE--(BW HealthWire)--Sept. 27, 2000

Preparation of Biological License Application To Begin Immediately

Corixa Corporation (Nasdaq:CRXA), a research and development-based biotechnology company, today announced its intent to file for regulatory approval of its Melacine(R) melanoma vaccine.

The biological license application (BLA) will be based predominantly on data from the recently completed Phase III study of the use of Melacine vaccine for the treatment of Stage II melanoma which started enrollment in April of 1992 and has followed patients through January of 2000. The filing will also contain data following the same group of patients through January of 2001.

The results of this study, conducted by the former Ribi Immunochem Research, Inc., (acquired by Corixa in October 1999), were initially reported by the Southwest Oncology Group (SWOG) in March 2000. This study examined the effects of Melacine vaccination vs. observation in a randomized, controlled trial of 689 Stage II melanoma patients. Patients in the study were randomized, following surgical excision of their primary tumor, to either observation, as per standard practice, or Melacine therapy, according to three pre-determined stratification factors including sex and tumor thickness. The study closed accrual in 1996 and initial results were reported when a pre-defined number of events (death or disease recurrence) occurred. Analysis of the data in March 2000 revealed a statistically significant improvement in disease free survival in patients treated with Melacine vaccine (p=0.04). The company noted that it cannot assure that the benefit of Melacine vaccine seen through January of 2000 will continue to be seen through January 2001. The BLA will also contain safety and clinical efficacy data from all other currently completed clinical studies of Melacine in Stage III and IV melanoma. It is expected that the submission of the BLA will occur in the 2nd quarter of 2001. A full review of the BLA is anticipated to take approximately 12 months.

"We look forward with enthusiasm to the preparation and filing of a BLA for Melacine vaccine," said Steven Gillis, Ph.D., chairman and chief executive officer of Corixa. "Although we have a significant amount of work ahead of us in terms of preparation for multiple final study reports and manufacturing information, we are excited by the task. Given that the SWOG trial in Phase II melanoma patients calls for annual follow-up of all surviving patients until death, we are confident in our ability to gather timely disease free survival data for the current calendar year that will yield up-to-date analysis of the vaccine's efficacy in the largest completed, randomized and controlled U.S. tumor vaccine clinical trial to date."

Gillis added, "We will also continue to discuss regulatory strategies regarding potential Melacine vaccine approval in Europe with Schering-Plough, Corixa's worldwide marketing partner for Melacine vaccine. However, the vast majority of regulatory effort in the short term will be focused squarely, as it should be, on BLA preparation. We are pleased to begin the process of BLA submission and subsequent regulatory review to address issues regarding the challenge of bringing tumor vaccines from a position of theoretical benefit, to one of approved clinical practice."

About Melanoma

Malignant melanoma is a highly metastatic and lethal form of skin cancer. It is the most common form of cancer in women between the ages of 25-29 and the second most common form of cancer in women ages 30-34. It is the third most common form of cancer in men ages 35-44. According to the American Cancer Society, cancer of the skin is the most common of all cancers. Melanoma accounts for about 4 percent of skin cancer cases, but causes about 79 percent of skin cancer deaths. The number of new cases of melanoma found in the United States is on the rise. The American Cancer Society predicts that, in the year 2000, there will be 47,700 new cases of melanoma in the United States and about 7,700 deaths resulting from melanoma.

About Melacine

Melacine melanoma vaccine consists of lysed (broken) cells from two human melanoma cell lines combined with Corixa's proprietary Detox(R) adjuvant. Detox adjuvant includes MPL(R) adjuvant (monophosphoryl lipid A) and mycobacterial cell wall skeleton, both of which activate the human immune system in the context of vaccination. Melacine, MPL and Detox were acquired by Corixa as part of its purchase of Ribi ImmunoChem Research, Inc., in October 1999.

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 diagnostics, 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, Mont. and Redwood City, Calif. For more information, please visit Corixa's website at www.corixa.com or call the company's investor relations information line at 877/4CORIXA or 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, the risk that Corixa may re-evaluate its decision to file the BLA as a result of Corixa's analysis of additional data collected in preparing the BLA, the risk that FDA may not accept the BLA as filed or may not approve Melacine vaccine for the labeled indication that Corixa will seek or at all, and the "Factors Affecting Our Operating Results, Our Business and Our Stock Price," described in our Quarterly Report on Form 10-Q filed on August 14, 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.