South African trial renews hopes in failed HIV vaccine combo

An HIV vaccine regimen that failed in a notable clinical trial conducted in Thailand has been given a new chance to prove itself.

In a trial in South Africa, the two experimental vaccines in the famous 2009 "Thai trial"--one from Sanofi ($SNY) and another developed by VaxGen--passed a key hurdle, eliciting robust immune responses in 100 healthy adults.

The findings are significant considering participants in the two trials varied in ethnicity, body mass index, gender and age--all factors that were previously shown to impact the protective effect of the vaccines.

Known as RV144, after the original Thai trial, the vaccine combo has been the only such regimen to show any promise against HIV. Even then, the candidate only demonstrated a modest level of protection in a study of more than 16,000 adults.

The investigational HIV vaccine combo combines Sanofi Pasteur's ALVAC-HIV vaccine, a modified canarypox vaccine, and AIDSVAX B/E vaccine, a glycoprotein 120 vaccine developed by VaxGen and now owned by the San Francisco nonprofit Global Solutions for Infectious Diseases. The regimen, originally designed to protect against two common strains of HIV in Thailand, is a prime-boost approach that uses ALVAC-HIV to prime and AIDSVAX B/E to boost immune response.

In 2009, the candidate was only 31% effective at reducing the risk of HIV transmission among trial participants. Researchers think the vaccine may have provided better protection against HIV sooner after vaccination and the effect waned over time.

The results from the South African trial, called HVTN 097, bode well for researchers hoping to test an improved version of the experimental vaccine regimen in South Africa beginning next year. The findings were presented at the HIV Research for Prevention conference this week in Cape Town.

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