The first HIV vaccine efficacy study to launch anywhere in 7 years is testing whether an experimental vaccine safely prevents HIV infection among South African adults.

According to an announcement by the National Institute of Allergy and Infectious Diseases, a cofunder of the trial and part of the U.S. National Institutes of Health, the study ( called HVTN 702 ) involves a new version of the only HIV vaccine candidate ever shown to provide some protection against the virus. HVTN 702 intends to enroll 5,400 men and women, which would make it the largest and most advanced HIV vaccine clinical trial to take place in South Africa.

“If deployed alongside our current armory of proven HIV prevention tools, a safe and effective vaccine could be the final nail in the coffin for HIV,” Anthony S. Fauci, MD, director of NIAID, said in a statement. “Even a moderately effective vaccine would significantly decrease the burden of HIV disease over time in countries and populations with high rates of HIV infection, such as South Africa.”

The experimental vaccine regimen being tested in HVTN 702 is based on one investigated in the RV144 clinical trial in Thailand, led by the U.S. Military HIV Research Program and the Thai Ministry of Health. In 2009, the Thai trial found for the first time that a vaccine could offer modest prevention against HIV infection. NIAID said the new regimen aims to provide “greater and more sustained protection” than the RV144 regimen and has been adapted to the HIV subtype that predominates in southern Africa.

The experimental vaccine regimen tested in the Thai trial was found to be 31.2 % effective at preventing HIV infection over the 3.5-year follow-up after vaccination. In the HVTN 702 study, the design, schedule, and components of the RV144 vaccine regimen have been modified in an attempt to increase the magnitude and duration of vaccine-elicited protective immune responses.

NIAID is responsible for all operational aspects of this phase IIb/III trial, which is enrolling HIV-uninfected, sexually active men and women aged 18-35 years. The NIAID-funded HIV Vaccine Trials Network is conducting the trial at 15 sites across South Africa, and expects results in late 2020. The study volunteers are being randomized to receive either the investigational vaccine regimen or a placebo. All study participants will receive a total of five injections over 1 year.

“If an HIV vaccine were found to work in South Africa, it could dramatically alter the course of the pandemic,” said HVTN 702 protocol chair Glenda Gray, MBBCH, president and CEO of the South African Medical Research Council and research professor of pediatrics at the University of the Witwatersrand, Johannesburg.

The HVTN 702 study begins just months after interim results were reported for HVTN 100, a predecessor clinical trial that found that the new vaccine regimen was safe for the 252 study participants and induced comparable immune responses to those reported in RV144, according to NIAID.

Both HVTN 100 and HVTN 702 are part of a larger HIV vaccine research endeavor led by the Pox-Protein Public-Private Partnership (P5), which includes NIAID, the Bill & Melinda Gates Foundation, the South African Medical Research Council, HVTN, Sanofi Pasteur, GSK, and the U.S. Military HIV Research Program.

NIAID said the HVTN 702 vaccine regimen consists of two experimental vaccines: a canarypox vector–based vaccine called ALVAC-HIV and a two-component gp120 protein subunit vaccine with an adjuvant to enhance the body’s immune response to the vaccine. Both ALVAC-HIV and the protein vaccine have been modified from the versions used in RV144 to be specific to HIV subtype C, the predominant HIV subtype in southern Africa.

In addition, NIAID said the protein subunit vaccine in HVTN 702 is combined with MF59, a different adjuvant than the one used in RV144, in the hope of generating a more robust immune response. The HVTN 702 vaccine regimen includes booster shots at the 1-year mark in an effort to prolong the early protective effect observed in RV144.

On Twitter @richpizzi


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