Virax to extend trials for HIV/AIDS therapy

Melbourne-based immune therapies company Virax Holdings (ASX: VHL) has announced an extension to its Phase I/IIA clinical trial to further assess the potential of its HIV/AIDS therapy.

The current study has been evaluating safety and immune responses in HIV positive patients, who continued to take their anti-retroviral medications during the trial. The additional study will examine the impact of Virax's VIR201 therapy in patients when anti-retroviral drugs are stopped, to see if it will work as an independent therapy.

"It's very significant because the Phase I/IIA trial we've been running was to demonstrate safety and immunogenicity, or immune response, but this one allows us to look at the efficacy as anti-retrovirals are removed," explained CEO David Beames.

Beames said that anti-retroviral medications kept the level of virus, or viral load, in patients very low. When medication is stopped, typically the virus titres rebound, as shown in a number of studies around the world.

"We are particularly excited about this development as very few interruption studies have been undertaken in conjunction with immune-based drugs," said Prof David Cooper, Director of the National Centre in HIV Epidemiology and Clinical Research at the University of NSW.

The Centre is conducting the trial in conjunction with the St Vincent's Hospital in Sydney and the Alfred Hospital in Melbourne.

Virax's therapy is based on its Co-X-Gene platform technology, which uses a modified fowlpox virus to deliver two HIV genes plus a gene for the cytokine gamma interferon.

Beames said, "it causes the immune system to produce T-cells specific for both HIV infected cells and HIV." He explained that a strong cell mediated immune response involving T-cells was thought to be critically important in an antiviral therapy of this kind.

According to a statement released by Virax, patients for the new study will be recruited from patients completing the current study, and will take an additional dose of VIR201, before ceasing to take anti-retroviral medications. Viral loads and T-cell counts will be measured and if there are concerns about the wellbeing of the patient, anti-retroviral medications will be reintroduced.

The additional study is expected to take an further 20 weeks for each patient after they complete the first study. As patients in the initial study were recruited over a period of 10 months, results from the new trial are not likely to be known until late in 2003.

Beames said that the company hopes to begin a larger Phase II trial towards the end of 2003.

Hepatitis B project

In addition to it's HIV project, Virax announced recently that it had entered into a collaboration with the New York Blood Centre (NYBC) to develop a therapeutic treatment for hepatitis B (HBV) infection based on its Co-X-Gene technology.

"We're very excited about that agreement. The New York Blood Centre is a very large and competent organisation," said Beames. He noted that Dr Alfred Prince, who will be leading the study at the NYBC, is an internationally renowned expert in hepatitis B research.

Beames said that the HBV Co-X-Gene vector is being developed in Melbourne at present and should be completed later this year. Pre-clinical work in mice and monkeys will begin early next year at the NYBC and at a primate facility in Africa, and clinical trials might commence in the US as early as late 2003.

While commercial terms were not disclosed, Virax will retain the rights to commercially develop the most promising leads.

At the time of writing the share price for Virax had risen 7.7 per cent to 56 cents.