Infectious Disease

Another HIV vaccine fails to provide protection in discontinued trial

January 18, 2023

2 min read

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Janssen on Wednesday announced it has stopped the phase 3 Mosaico trial because the investigational HIV vaccine regimen it was testing was not effective in preventing HIV infection compared with placebo.

No safety issues were identified, but the study’s independent data and safety monitoring board determined the study would not reach its primary endpoint of preventing HIV.

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“We are disappointed with this outcome and stand in solidarity with the people and communities vulnerable and affected by HIV,” Penny Heaton, MD, global therapeutic area head for vaccines in Janssen’s research and development unit, said in a press release.

It was the latest HIV vaccine trial to be stopped because the experimental regimen being tested did not work. Janssen discontinued the phase 2 Imbokodo trial — which tested a similar vaccine regimen as Mosaico — in 2021, and the National Institute of Allergy and Infectious Diseases held a phase 2b/3 clinical trial in early 2020 that was testing a regimen based on the only investigational HIV vaccine combination ever to demonstrate efficacy in a large clinical study.

Stephaun E. Wallace, PhD, MS, director of external relations at the HIV Vaccine Trials Network (HVTN), which conducted the study, told Healio that the organization “does not have any HIV vaccine efficacy trials currently in the field that are recruiting. ”

Both the Mosaico and Imbokodo studies are in follow-up, Wallace said.

“In the coming weeks, (Mosaico) study participants will have a final study visit, at which they will learn which study arm they were assigned to, have blood specimens taken for HIV diagnostic testing, receive information regarding vaccine-induced seropositivity and seroreactivity, and again receive counseling regarding HIV prevention options and [be] provided with appropriate referrals,” Wallace said.

The study included approximately 3,900 cisgender men and transgender people who have sex with cisgender men, transgender people or both at more than 50 trial sites in Argentina, Brazil, Italy, Mexico, Peru, Poland, Puerto Rico, Spain and the United States.

Beginning in 2019, and with vaccinations complete in October 2022, participants received either placebo or a vaccine regimen containing a mosaic-based adenovirus serotype 26 vector administered in four doses over 1 year, with the second two doses including a mix of soluble proteins.

Since completion of the study vaccine series, “the number of HIV infections were equivalent between the vaccine and placebo arms of the study,” the NIAID said in a statement, adding that “the Mosaico findings track with developments in the phase 2b Imbokodo clinical trial .”

In the Imbokodo study, which enrolled 2,637 women aged 18 to 35 years from Malawi, Mozambique, South Africa, Zambia and Zimbabwe, the vaccine being tested was estimated to be 25.2% efficacious.

“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,” Heaton said.

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Paul A Volberding, MD)

Paul A Volberding, MD

Forty years after the discovery of HIV, and despite a tremendous international effort and public and private support, we are still searching for an effective vaccine. These results are, again, disappointing.

Yet each step we take teaches us more and paves the path to what we still so clearly need — an effective and inexpensive vaccine that might end the HIV epidemic. Despite that, we remain thankful that so much progress continues in the availability of treatment regimens that can block transmission, drugs to stop transmission such as PrEP and after potential exposure such as PEP.

Our vaccine programs will continue, but meanwhile, we should acknowledge our success in various prevention strategies and seek to make them even more available to millions worldwide who remain at risk for HIV infection.

Paul A Volberding, MD

Chief Medical Editor, Infectious Disease News

Professor emeritus of medicine

University of California, San Francisco

Disclosures: Volberding reports serving on a data safety and monitoring board for Gilead Science for PrEP.

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