Phase I Trial of Novel Prime-boost Regimen Starts in Africa

A Phase I clinical trial known as B002, which started in February, will test the safety and immune responses induced by two HIV vaccine candidates administered either sequentially, in a prime-boost regimen, or simultaneously. One of the candidates is based on a non-infectious adenovirus serotype 35 (Ad35) vector that is used as a vehicle to deliver non-infectious fragments of HIV to the immune system. The other candidate consists of a protein administered along with an adjuvant that is intended to boost the immune responses.

Vaccinations already began at a clinical research center run by the Kenya AIDS Vaccine initiative (KAVI) in Nairobi. IAVI, the trial’s sponsor and the developer of the Ad35 candidate, has also applied for regulatory approval to conduct additional arms of the B002 trial in Lusaka, Zambia, and in Entebbe and Masaka, Uganda, and plans to enroll approximately 140 HIV-uninfected volunteers between the ages of 18 and 40. The trial is being conducted in partnership with GlaxoSmithKline (GSK; the pharmaceutical company that developed and manufactured the protein vaccine candidate), KAVI, and other partners in Africa, pending approvals.

Researchers will measure immune responses in blood samples from volunteers, as well as in genital and oral mucosal fluids collected from volunteers who agree to provide such samples. The mucosal work will be done at the clinical research center in Nairobi, says Patricia Fast, chief medical officer at IAVI.

Previous Phase I trials have shown that separately, both the Ad35 and protein candidates have acceptable safety profiles and induce immune responses against HIV. The B002 trial is the first time these two vaccine candidates will be tested in combination. “There is a lot of interest in combining vectors and proteins following on the success of RV144,” says Fast, referring to the trial conducted in Thailand that showed that a different viral vector-based/protein prime-boost regimen provided a modest 31% protection against HIV infection. —Andreas von Bubnoff