Meesha Patel, 27 May 2026, Imperial College London
RIO trial shows a new HIV treatment (broadly neutralising antibody therapy) enables three quarters of participants to safely control HIV without daily medication
Summary
A randomised placebo-controlled clinical trial led by Imperial College London has shown that an immune-based treatment called broadly neutralising antibodies (bNAbs) enabled 75% (three quarters) of participants living with HIV to safely stop their usual HIV treatment (antiretroviral therapy, or ART) for at least 20 weeks. A proportion of people were able to remain off ART for considerably longer, up to 2 years. The results are published in Lancet HIV on 27th May 2026.
Why new HIV treatments are needed
ART has transformed survival for people living with HIV and is safe and highly effective at preventing HIV-related complications. However, it must be taken for life. This places a huge burden for people living with HIV as well as health care systems. If ART is stopped, HIV viral load rapidly returns in the body, (rebounds) to detectable levels and can cause serious health problems and risks passing virus on to partners and infants. The reason ART cannot cure HIV is because ART cannot eliminate virus from a group of resting cells called the HIV reservoir. ART can treat HIV but cannot cure it. New approaches that could safely control HIV without the need for daily medication are therefore an important area of research.
About the RIO Trial
The RIO trial is a clinical study that is designed to the test a new treatment for HIV to the highest level of evidence; a randomised, double-blinded, placebo-controlled clinical trial. Double-blinding means that neither the researchers nor the study participants know whether they have received the active new treatment or a placebo, and a computer randomly allocates which people receive which treatment or placebo. The study is sponsored by Imperial College London and co-led by researchers at Imperial College London, the University of Oxford and the Rockefeller University, New York, USA. The trial is funded by the Gates Foundation (and receives additional support from National Institute for Health and Care Research (NIHR) Biomedical Research Centres (BRCs) at Imperial College London and the University of Oxford.
Sixty-eight participants living with HIV were randomly assigned to receive either bNAb infusions or a placebo, recruited across sites in the UK and Denmark between 2021 and 2024.
Primary Outcome Results
Among participants who received bNAbs, three quarters (75%) of participants, were able to safely control HIV viral load for 20 weeks without ART. Of these, approximately half maintained viral control for one year and a quarter for two years. By comparison, only two participants who received placebo demonstrated viral control without ART. These findings suggest that bNAb-based therapies, were much more effective than placebo, and bNAb treatment could offer a new approach to controlling HIV viral load without needing to continue with lifelong, daily ART.
Investigator and Community Representative Comments
Professor Sarah Fidler, Chief Investigator and Professor of HIV Medicine at Imperial College London, said:
“This is the first time a bNAb-based therapy has demonstrated viral load control of this duration and magnitude in a randomised placebo-controlled trial. These results open new possibilities for HIV treatment and bring us closer to our goal of finding a cure.”
Professor John Frater, Professor of HIV Medicine at the University of Oxford and co-lead investigator, said:
“These bNAbs appear to function in two ways — first, by directly targeting HIV, and second, by working alongside the body’s existing immune defences. These data, from the largest placebo-controlled dataset of its kind, represent an important step forward in our understanding of how immune-based therapies could complement existing HIV treatment strategies.”
Professors Michel Nussenzweig and Marina Caskey, Rockefeller University, New York, said:
“The RIO trial is a landmark study showing that antibodies can control viremia for prolonged periods of time in the absence of traditional ART therapy. The challenge now is to find ways of further enhancing host immunity to increase the number of individuals that can benefit from this type of therapy”, said Nussenzweig. “By carefully studying individuals who maintained control of the virus for extended periods of time, we hope to design better therapies with long lasting effects”, said Caskey.
The RIO trial was designed with meaningful input from the HIV community from the outset.
Simon Collins, HIV community advocate, said:
“RIO is the first study to let so many people safely stay off ART for so long. These are exciting results for a study that is still ongoing.”
Looking Ahead
The results of the RIO trial represent an important step forward in HIV treatment research. Long-acting bNAbs have demonstrated that ART-free viral control is an achievable goal, and further work is underway to build on these findings.
The RIO trial is ongoing. A new open-label arm, called RIO Arm C, has recently completed recruitment and is investigating the optimal timing of bNAb administration. This arm will ask participants to interrupt ART on several occasions to measure how long HIV viral load remains undetectable without treatment. Blood samples will also be collected to examine what happens to HIV and the immune system during these treatment interruptions. ART will be restarted when HIV becomes detectable above a pre-specified level.
Further analyses from the RIO trial are also planned, including exploratory work examining changes in the HIV reservoir and immune responses over time, as well as remaining secondary endpoint analyses including long-term viral control and bNAb pharmacokinetics. These findings will be reported in future publications and will help build a more complete picture of how bNAb-based therapies work and which patients are most likely to benefit.
Read the Imperial press release in full: https://www.imperial.ac.uk/news/articles/2026/new-hiv-treatment-could-enable-people-to-safely-stop-daily-medication-/
The RIO trial is sponsored by Imperial College London.
The primary outcome results which have been published in Lancet HIV: https://www.sciencedirect.com/science/article/pii/S2352301826000597
The trial is managed by Imperial Clinical Trials Unit
