Virax HIV trial data generates interest

Results from a Phase I/IIa study of an experimental HIV therapeutic vaccine developed by on Melbourne company Virax have generated interest from researchers at an international conference of HIV and AIDS researchers in San Francisco, according to the trial's coordinator.

The trial results were presented at the annual Conference on Retroviruses and Opportunistic Infections in San Francisco by Prof David Cooper, director of the University of NSW's National Centre in HIV Epidemiology and Clinical Research (NCHECR), which conducted the trial.

Assoc Prof Sean Emery, head of the NCHECR's therapeutic and vaccine research program, said the conference marked the first time that details of the study have been released, since the company announced the results last October.

The randomised, double-blinded and placebo controlled Phase I/IIa trial looked at the safety of Virax's therapeutic vaccine -- based on its Co-X-gene technology which uses a recombinant pox virus to deliver a viral gene alongside an immune system-stimulating gene -- as well as the ability of the vaccine to control the level of the virus in the blood (viral load) of the patients.

Patients enrolled in the Phase I trial were given the option to participate in an extension trial, to evaluate whether the immune response generated by Virax's VIR201 vaccine was sufficient to control the patient's viral load. 35 patients were given a fourth dose of the vaccine 12 months after they commenced the trial, and then ceased their anti-retroviral therapy. Viral load was then measured over a 20-week period.

Patients receiving VIR201 had a reduction in their viral load approximately 6.3 times lower than patients who received the placebo. The result suggests that Virax's vaccine may be a useful tool in controlling HIV viral load in patients. The vaccine was also shown to be well tolerated by patients.

But Emery cautioned that it is still very early days in the development of the vaccine, and further trials are required to fully evaluate its efficacy in statistically significant numbers of patients.

"I would estimate that there is a development program of 5-7 years from here on out," he said. "A bigger trial would be the logical next step. The first trial was very much exploratory -- we need to find out whether this was a real result or a fluke."

According to Cooper, the NCHECR is looking at setting up a larger trial of VIR201 with Virax.

Virax chairman Dr Tom Quirk said the results provided confirmation of the company's technology platform, which is also being applied to other diseases including hepatitis B. "It gives us a path forward," he said.

The market responded positively to the announcement with Virax's share price (ASX:VHL) reaching as high as AUD$1.01 on very heavy trading. At the time of writing the share price was 15.6 per cent up at $0.89.