Virax begins prostate cancer vaccine trial

Melbourne immunotherapy developer Virax Holdings (ASX:VHL) has begun a pre-clinical trial of its novel candidate vaccine for late-stage prostate cancer at the Royal Adelaide Hospital Cancer Centre.

Virax CEO Dr David Beames said that, based on the recent results of pre-clinical trials of the company's HIV-AIDS and hepatitis B therapeutic vaccines, which employ the same patented Co-X-Gene technology, the company expects to take the novel prostate-cancer therapeutic into clinical trials next year.

Beames said it was the third of Virax's pipeline products to achieve this milestone in the past six months.

The vaccine has been developed as a potential treatment for late-stage prostate cancer that has failed to respond to standard hormone therapy -- no effective therapy exists for prostate cancer that has progressed to this stage.

Some 2500 men die in Australia every year from hormone-refractory prostate cancer. In the US, the annual toll is 30,000.

Virax's Co-X-Gene expression uses a non-infectious fowlpox virus as a vector. It is genetically engineered to express genes for key antigens associated with particular diseases, along with genes that boost the patient's immune response to those antigens, particularly the cell-killing arm of the immune system, cytotoxic T-cells.

Conventional vaccines tend to elicit only antibody-mediated immunity. The cytotoxic T-cell response is essential to eliminate cells in which viruses are already replicating, or to kill cancerous cells, particularly those that have escaped surgery or conventional therapies, and have the potential to cause secondary, metastatic tumours.

Beames said that the Virax vaccines, unlike conventional vaccines, were therapeutics -- designed not to prevent infection or cancer, but to treat intractable infections and cancers that do not respond to conventional treatments.

The company has not disclosed which antigen it has targeted with its new prostate-cancer therapeutic -- only that it is already in the public domain, and is specific to late-stage prostate cancer.

The Adelaide trial is supervised by Dr Michael Brown, a medical oncologist with expertise in the immunological aspects of prostate cancer.

Brown, a recipient of a New Investigator Award from the US Department of Defence's prostate cancer research program, said there was an urgent need for an effective treatment for hormone-refractory prostate cancer. Immunotherapeutic vaccines were "a very promising new approach to cancer treatment", he said.