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Global Phase 3 Study Will Determine Efficacy of HIV Prevention Vaccine

Jaime Rosenberg
The HPX3002/HVTN, or Mosaico, trial will determine if the vaccine regimen can induce immune responses against various global HIV strains among 3800 men who have sex with men and transgender people aged between 18 and 60 years.
Janssen, in collaboration with the National Institutes of Health (NIH) and the HIV Vaccine Trials Network (HVTN), is launching a phase 3 study to explore whether an investigational HIV vaccine regimen is effective against different strains of the virus seen across the globe. The HPX3002/HVTN or Mosaico trial will determine if the regimen can induce immune responses against various HIV strains among 3800 men who have sex with men and transgender people aged between 18 and 60 years.

The trial will occur alongside the ongoing phase 2b HPX2008/HVTN 705 or Imbokodo trial, which launched in 2017 and is evaluating the regimen among 2600 sexually active women aged between 18 and 35 years in southern Africa.

United States enrollment for Mosaico is expected to begin later this year, and clinical research sites in Argentina, Brazil, Italy, Mexico, Peru, Poland, and Spain will partake in the study.

“We are committed to developing a safe and effective preventive HIV vaccine suitable for the global populations most vulnerable to HIV acquisition,” said Anthony S. Fauci, MD, director of NIH’s National Institute of Allergy and Infectious Diseases, in a statement. “Ensuring that investigational vaccines are evaluated in diverse populations is critical to achieving this goal."

The experimental vaccine includes 4 components targeting multiple strains of HIV in order to address varying predominant subtypes of HIV based on geographic location. For example, clade C HIV is common in southern Africa, where Imbokodo is taking place, while clade B is predominant in regions of Europe and the Americas where Mosaic will enroll. All participants will also be offered pre-exposure prophylaxis and will be randomly assigned to either receive the vaccine regimen or placebo.

Those receiving the vaccine regimen will receive a total of 6 shots over 4 sessions. The first 4 vaccinations will include Ad26.Mos4.HIV, which uses an engineered common-cold virus, in order to deliver the 4 mosaic immunogens. The final 2 vaccinations will be administered together with a 2-component HIV envelope protein formulation, combining clade C gp140 and mosaic gp140 envelope proteins, and an adjuvant to boost immune response.

The regimen being utilized in Imbokodo is essentially the same; however, the final 2 vaccinations do not include mosaic gp140 and instead include Ad26.Mos4.HIV and clade c gp140.

Mosaic and Imbokodo represent 2 of the 3 ongoing efficacy trials for HIV vaccines worldwide. Initial results from Imbokodo, which completed enrollment in May, are expected in 2021. In addition to these 2 trials, the ongoing phase 2b/3 HVTN 702 study is examining whether a new version of the experimental regimen that was first tested in RV144 is effective among 5000 men and women in South Africa.

To date, RV144, also known as the Thai trial, is the only vaccine candidate to show protection against HIV. The results of more than 10,000 people in Thailand were on the border of being statistically significant, with the vaccine demonstrating a protective efficacy of 31% over 3.5 years. Analyses have indicated that the protective efficacy reached 60% in the first 12 months, leading researchers to try and build upon that efficacy and maintain it. The vaccine regimen being used in HVTN 702 consists of 2 vaccines: a canarypox vector-based vaccine called ALVAC-HIV and a 2-component gp120 protein subunit vaccine with an adjuvant. Participants will receive 5 injections over the course of a year. The study completed enrollment in June.

 
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