An investigational HIV vaccine regimen tested among men who have sex with men (MSM) and transgender people is safe but does not protect against HIV acquisition, an independent Data and Safety Monitoring Board (DSMB) has found.
The HPX3002/HVTN 706, or “Mosaico,” phase 3 clinical trial began in 2019 and enrolled 3,900 volunteers aged 18 to 60 in Europe, North America and South America. Based on the recommendation of the DSMB, the study will be terminated. Participants are being notified of the findings and further analyzes of the study data are planned.
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Janssen Vaccines & Prevention BV, part of Johnson & Johnson’s Janssen Pharmaceutical Companies, sponsored the Mosaico study with financial support from the National Institute of Allergy and Infectious Diseases (NIAID), part of the National Institutes of Health. The trial was conducted by the NIAID-funded HIV Vaccine Clinical Trials Network based at the Fred Hutchinson Cancer Research Center in Seattle. The US Army Medical Research and Development Command provided additional support for the study.
The experimental vaccine schedule was developed by Janssen. It relies on “mosaic” immunogens – vaccine components incorporating elements from multiple HIV subtypes – to induce an immune response against a wide variety of global HIV strains. The vaccine regimen studied consisted of four injections over one year of Ad26.Mos4.HIV. This vaccine candidate uses a common cold virus (adenovirus serotype 26 or Ad26) to deliver the mosaic immunogens. The last two vaccinations were accompanied by a bivalent (two-component) HIV envelope protein formulation combining clade C envelope proteins gp140 and mosaic gp140, adjuvanted with aluminum phosphate to enhance immune responses. All study vaccinations were completed in October 2022.
In its planned review of the data, the DSMB determined that there were no safety issues with the experimental vaccine regimen. However, the number of HIV infections was equivalent between the vaccine and placebo arms of the study. During the clinical trial, all participants were offered comprehensive HIV prevention tools, including pre-exposure prophylaxis, or PrEP. Study staff ensured that participants who became infected with HIV during the trial were immediately referred for medical care and treatment.
Mosaico’s findings follow the development of the phase 2b “Imbokodo” (HPX2008/HVTN 705) clinical trial, which tested a similar HIV vaccine regimen in young women in sub-Saharan Africa. The DSMB determined in 2021 that the experimental vaccine schedule in this study was also safe but ineffective in protecting against HIV infection.
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