The HIV candidate was developed using the same AdVac viral vector platform as the company’s COVID-19 vaccine. Although a Phase 2b trial for the vaccine last year only showed efficacy of 25.2%, Janssen and its partners had hoped a different regimen in different populations would prove successful in the Phase 3 trial.
In a scheduled data review, however, the independent Data and Safety Monitoring Board (DSMB) for the Phase 3 study has found that the number of HIV infections were equivalent between the vaccine and placebo arms of the study. In light of these results, Janssen announced yesterday that ‘the regiment does not protect against HIV and the study is not expected to meet its primary endpoint… in light of this, the study will be discontinued.”
Further analyses are underway to see what can be learned from the data.
Mosaic immunogens
The Phase 3 study evaluated an investigational vaccine regimen containing a mosaic-based adenovirus serotype 26 vector (Ad26.Mos4.HIV) administered during four vaccination visits over one year. A mix of soluble proteins (Clade C/Mosaic gp140, adjuvanted with aluminum phosphate) was also administered at visits three and four.
The hope had been that the ‘mosaic’ immunogens – featuring elements of multiple HIV subtypes – could induce immune responses against a wide variety of global HIV strains.
The Mosaico study began in 2019 and completed vaccinations in October last year. The study included approximately 3,900 cisgender men and transgender people who have sex with cisgender men and/or transgender people, who represent groups and populations vulnerable to HIV, at over 50 trial sites in Argentina, Brazil, Italy, Mexico, Peru, Poland, Puerto Rico, Spain and the US.
The previous Phase 2b Imbokodo study, which announced its results in August last year, assessed the vaccine in a population of young women in sub-Saharan Africa.
Both studies failed to show the vaccine was effective at preventing infections.
“We are disappointed with this outcome and stand in solidarity with the people and communities vulnerable to and affected by HIV,” said Penny Heaton, M.D., Global Therapeutic Area Head, Vaccines, Janssen Research & Development, LLC, speaking as the company announced it would discontinue the Phase 3 study.
“Though there have been significant advances in prevention since the beginning of the global epidemic, 1.5 million people acquired HIV in 2021 alone, underscoring the high unmet need for new options and why we have long worked to tackle this global health challenge.
"We remain steadfast in our commitment to advancing innovation in HIV, and we hope the data from Mosaico will provide insights for future efforts to develop a safe and effective vaccine. We are grateful to our Mosaico partners and the study investigators, staff and participants.”
The Mosaico study was led by a global public-private partnership including the National Institute of Allergy and Infectious Diseases (NIAID), part of the National Institutes of Health (NIH), the HIV Vaccine Trials Network (HVTN), the U.S. Army Medical Research and Development Command (USAMRDC), and Janssen Vaccines & Prevention B.V.