Genesis Research and Corixa Provide PVAC Treatment Program Update; Brazil and Cebu PVAC Treatment Psoriasis Trials Indicate Clinical Activity and Safety.

Business Editors & Health/Medical Writers

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AUCKLAND, New Zealand & SEATTLE--(BUSINESS WIRE)--Nov. 7, 2002

Genesis Research and Development Corporation Ltd (NZSE:GEN) (ASX:GEN) and Corixa Corporation (Nasdaq:CRXA), a Seattle-based developer of immunotherapeutics, today provided a program update on the development of the companies' PVAC(TM) treatment for psoriasis.

Additional Completed Clinical Trials

The 165 patient Brazil study, conducted by Corixa, compared two doses of PVAC treatment (15 and 50 micrograms) with placebo, with each patient receiving two injections three weeks apart. The Psoriasis Area and Severity Index (PASI) score at baseline and after 12 weeks measured the clinical assessment of psoriasis improvement.

The patients, aged 18 to 69 years, had suffered psoriasis for an average of 12 years. Only 12 of the 165 patients had been previously untreated, most having received a number of different forms of treatment over the years. As was the case with the U.S. Phase II clinical trial completed in 2001, in the Brazil study the percentage of patients who exhibited a 75 percent reduction in PASI score at twelve weeks was not statistically different between PVAC treatment and control arms. However, the percentage of patients that manifested a 50 percent improvement in disease approached statistical significance vs. control for the highest PVAC treatment dose group (p=0.053). In addition, there was evidence of a dose response as the percentage of patients achieving a 50 percent improvement in disease at 12 weeks was lowest in placebo patients, intermediate in those receiving 15mcg of PVAC treatment and highest in those treated with 50mcg of PVAC treatment.

A smaller controlled study with 60 patients has also been completed in Cebu, Philippines. In the Cebu study, there was also evidence of a relationship between PVAC treatment dose and response as the percentage of patients showing 50 percent or more improvement in PASI score, increased from 25 percent of placebo patients, to 30 percent of those receiving 15mcg PVAC treatment, to just over 40 percent of patients treated with 50mcg of PVAC treatment.

Importantly there were no reported serious adverse events in PVAC treatment groups in either study, providing further evidence of PVAC's benign safety profile.

Ongoing Clinical Trials

The apparent dose response observed in both the Cebu and Brazil studies, suggests that greater exposure to PVAC treatment doses may be required to achieve an optimal effect. For an immune modulating agent such as PVAC treatment, a common way to increase dose is to increase the number of injections rather than increasing the dose per injection because the immune system response can accelerate with repeated challenge. The current blinded, controlled U.S. study that began accruing patients in mid-2002, is approximately 50 percent accrued at this time. The study is investigating four injections of 15mcg or 50mcg of PVAC treatment vs. placebo. In addition, given the safety profile of PVAC treatment, this study is testing the product in mild to moderate disease psoriasis patients, as opposed to studying efficacy in moderate to severe cases. The mild to moderate population represents the majority of psoriasis patients that customarily seek treatment for their disease. Finally, the U.S. study is assessing efficacy at 24 weeks from initial treatment. Patient response in all completed, randomized trials of PVAC treatment indicate that PASI scores were continuing to decline in treated patients when efficacy analysis was conducted at 12 weeks. Other immunomodulatory compounds under investigation have routinely relied on 24-week efficacy data in order to demonstrate statistically significant improvement of disease as opposed to the 12-week efficacy time point used in prior PVAC treatment clinical trials.

A further approach to exploring efficacy is to combine PVAC treatment with another proven therapy. In a current New Zealand PVAC treatment study, 60 patients are being evaluated for clinical response to the combination of PVAC treatment with ultra violet light, delivered in a controlled treatment schedule. This randomized, controlled study is based on anecdotal reports of unexpectedly high levels of response in several patients (from the U.S. Phase II study completed last year) who received ultraviolet light therapy following PVAC treatment. The trial is now fully recruited, and the results are expected in Q3 2003.

Medicis Pharmaceutical Corporation has acquired the USA and Canadian commercialization rights to PVAC(TM) treatment as a therapeutic for psoriasis and Zenyaku Kogyo Co Ltd has acquired the commercialization rights for the Japanese market.

Psoriasis Market Information

According to the U.S. National Psoriasis Foundation, psoriasis is a chronic skin disease affecting more than seven million Americans, or about 2.6 percent of the U.S. population. It is estimated that approximately 75 percent of the patient population suffer from mild to moderate forms of the disease. About 150,000 to 260,000 new cases of psoriasis are diagnosed each year. Annual outpatient costs for treating psoriasis are currently estimated at approximately $1.6 billion to $3.2 billion. Psoriasis occurs when new skin cells grow too rapidly, resulting in inflamed, scaly skin lesions. Although the cause of psoriasis is unknown, researchers believe the increased activation, adhesion and passage of T-cells to the skin contributes to the inflammation and abnormal skin cell proliferation. Most current psoriasis therapies are palliative in nature and provide temporary patient benefit, or have significant side effects.

About Genesis

Founded in 1994, Genesis is a New Zealand-based biotechnology company committed to the development of innovative products in health and plant biotechnology from its broad genomic platform. Genesis partners with industry leaders to develop products that have global market potential through the mining of its extensive microbe, plant and mammalian EST databases.

Genesis' Health Sciences Division focuses on signaling pathways involved in immune diseases and cancer and has an extensive patent portfolio. It has three programs in human clinical development utilizing PVAC(TM) treatment and AVAC(TM) for the treatment of psoriasis, atopic dermatitis (eczema) and asthma. Additional pre-clinical programs are developing YB-1, FGFR5 and Epigen as targets for treatment of cancer and immune mediated diseases. The patented BioStore solutions for storage of tissues and living cells are also in pre-clinical development. Collaborations are maintained with Amgen Inc. (Nasdaq: AMGN), Corixa Corporation (Nasdaq: CRXA), SR Pharma (LSE: SPA), and Jurox Pty Ltd.

The Plant Sciences division is focusing on key cell signaling genes -- novel hormones and transcription factors -- to control commercial traits including growth rates and wood fiber quality in trees, nutritional content of forage grasses, flowering control, salt and cold tolerance. It has developed comprehensive plant EST databases including the world's largest EST database for commercial forestry species. It has research collaborations with ArborGen LLC, Wrightson (NZSE: WRI), HortResearch, AgResearch and Landcare. Genesis is also undertaking significant unpartnered research programs in novel plant hormones. A number of patents are held including 12 steps in the production of lignin.

For more information, please visit www.genesis.co.nz

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 18 programs in clinical development.

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

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 failure of further clinical trials to evidence that PVAC(TM) treatment is safe and efficacious for the treatment of psoriasis, as well as the "Important Factors That May Affect Our Business, Our Results of Operations and Our Stock Price," described in Corixa's Quarterly Report on Form 10-Q for the quarter ended June 30, 2002, copies of which are available from Corixa's 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.