Washington Editor

Disappointing results from a Phase II trial for the psoriasis candidate PVAC caused Corixa Corp. and partner Genesis Research and Development Corp. Ltd. to abandon all development of the injectable treatment.

While PVAC had demonstrated poor efficacy in previous Phase II trials, the final decision stems from a double-blind, randomized, placebo-controlled study of 240 patients in the U.S.

Corixa, a Seattle-based company, said the trial confirmed that PVAC therapy failed to provide a statistically significant increase in the percentage of patients achieving a 75 percent reduction in the psoriasis area and severity index (PASI) score, as compared to placebo-treated patients. Also, results from a smaller, 60-patient New Zealand trial in which PVAC treatment was provided in advance of standard ultraviolet light therapy and failed to demonstrate a clinical benefit.

Jim DeNike, Corixa's senior director of corporate communications, told BioWorld Today there are no plans to move PVAC forward. Corixa discovered PVAC, an immunotherapeutic based on a process and formulation derived from heat-killed Mycobacterium vaccae.

Of the failure, Steven Gillis, Corixa's chairman and CEO, said in a prepared statement that the results of the trials do not justify further investment of resources in PVAC.

"While we would have preferred a different outcome, we thoroughly explored the potential utility of PVAC in this indication and we are confident that we made the right decision," he said.

Indeed, PVAC has been a challenge for some time. Corixa's stock fell 22 percent (to close at $19.43) about two years ago when a 241-patient Phase II trial missed its primary endpoint of at least a 50 percent reduction in the PASI score. Nevertheless, the dose approached statistical significance and there was a belief that a later observation point might make a difference, so Corixa marched on. (See BioWorld Today, Feb. 16, 2001.)

Then, a 165-patient Phase II study designed to compare two doses of PVAC with placebo failed to demonstrate a statistical difference between the two arms in those patients who exhibited a 75 percent reduction in the PASI score at 12 weeks. (See BioWorld Today, Nov. 8, 2002.)

Corixa and Genesis, of Auckland, New Zealand, entered a development partnership in 1998 for PVAC. DeNike said the companies were sharing the costs of development and had planned to share potential revenues. Specific financial terms were not disclosed.

Beyond that, Corixa had signed two marketing partners. Zenyaku Kogyo Co. Ltd. has commercialization rights in Japan, and Medicis Pharmaceutical Group, of Phoenix, has other rights. On signing the deal with Medicis in August 2000, Corixa received a nonrefundable $17 million up-front payment and was in line for hefty milestones. (See BioWorld Today, Aug. 17, 2002.)

Corixa's stock (NASDAQ:CRXA) closed Monday at $5.68, down 22 cents.