The only vaccine against HIV currently undergoing testing, known as Mosaico, has been deemed ineffective, according to an announcement from its manufacturer. This trial was developed through a public-private partnership involving the US government and Janssen Pharmaceuticals. HIV is a virus that progressively attacks the immune system, which serves as the body’s natural defense against illness, while AIDS is the syndrome caused by the HIV virus. The failure of this latest vaccine candidate highlights the significant challenges faced in designing an effective HIV vaccine.
The announcement, posted on Johnson & Johnson’s website, indicated that the independent Data and Safety Monitoring Board (DSMB) determined the vaccine regimen was not effective in preventing HIV infection compared to a placebo among study participants. However, the announcement also noted that no safety issues with the vaccine regimen were identified. Consequently, the Mosaico clinical trial will be discontinued, and participant notifications, along with further data analyses, are currently underway. Throughout the trial, investigators ensured that individuals who contracted HIV received prompt treatment and care.
Penny Heaton, the Global Therapeutic Area Head for Vaccines at Janssen Research & Development, LLC, expressed disappointment over the trial’s outcome, stating, “We stand in solidarity with the people and communities vulnerable to and affected by HIV.” She emphasized that despite significant advances in prevention since the onset of the global epidemic, 1.5 million people acquired HIV in 2021 alone, highlighting the urgent need for new options. Heaton reaffirmed the commitment to advancing innovation in HIV research and expressed hope that the data from Mosaico would provide valuable insights for future vaccine development. She also extended gratitude to the Mosaico partners, study investigators, staff, and participants.
In 2020, the United States National Institutes of Health announced the termination of its HVTN 702 clinical trial of an HIV vaccine. Although no safety concerns were reported during that trial, the independent data and safety monitoring board concluded that the vaccine was ineffective in preventing HIV transmission. Similarly, in 2021, an investigational HIV vaccine tested in the “Imbokodo” clinical trial in sub-Saharan Africa posed no safety concerns but failed to provide sufficient protection against HIV infection, according to a primary analysis of the study data.
The Mosaico trial, a Phase three study of Janssen’s investigational HIV vaccine regimen, began in 2019 and completed vaccinations in October 2022. The study involved approximately 3,900 cisgender men and transgender individuals who have sex with cisgender men and/or transgender individuals, representing populations vulnerable to HIV. The trial took place at over 50 sites across Argentina, Brazil, Italy, Mexico, Peru, Poland, Puerto Rico, Spain, and the United States.
The study evaluated an investigational vaccine regimen that included a mosaic-based adenovirus serotype 26 vector (Ad26.Mos4.HIV), administered during four vaccination visits over one year. Additionally, a mix of soluble proteins (Clade C/Mosaic gp140, adjuvanted with aluminum phosphate) was administered during the third and fourth visits. The DSMB’s analysis of the available data indicated that the regimen does not protect against HIV and is not expected to meet its primary endpoint. Following this determination, the study will be discontinued, and further analyses are underway.
This DSMB determination follows the primary analysis of the Phase 2b Imbokodo study, announced in August 2021, which found that a similar investigational HIV vaccine regimen did not provide sufficient protection against HIV in a population of young women in sub-Saharan Africa. The investigational vaccine regimen used in the Imbokodo study was reported to have a favorable safety profile.
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