For people living with HIV, the prospect of a functional cure — one that keeps the virus suppressed without daily antiretroviral therapy — hinges on whether immune-based interventions can hold viral rebound at bay after treatment stops. The RIO trial offers a rigorous Phase II look at whether broadly neutralizing antibodies (bNAbs) can serve that role, and the findings carry meaningful implications for the HIV remission research agenda.
The RIO trial enrolled adult males living with HIV and subjected them to analytical treatment interruption (ATI) — a controlled pause of antiretroviral therapy used to measure how well an immune intervention suppresses rebound viremia. Participants received two long-acting broadly neutralizing antibodies, 3BNC117-LS and 10-1074-LS, which target distinct epitopes on the HIV-1 envelope. The combination produced a measurable delay in viral rebound compared to controls. Critically, however, the trial also documented the emergence of antibody resistance mutations in rebounding virus, and found that the sensitivity of each participant's viral reservoir to their own autologous antibodies at baseline was a significant predictor of how long rebound took to occur — underscoring the heterogeneity of reservoir composition as a key variable.
These results fit into a growing body of evidence showing that bNAb combinations can meaningfully extend time-to-rebound during ATI, but rarely achieve durable suppression on their own. The resistance finding is a familiar challenge from both antiretroviral and monoclonal antibody research: monotherapy or even dual-antibody regimens create selective pressure that resistant variants can exploit. The reservoir-sensitivity association is arguably the most clinically actionable insight — it suggests that pre-ATI reservoir phenotyping could predict bNAb responders, enabling precision patient selection in future trials. This is an important confirmatory and mechanistically clarifying study, though its male-only cohort limits generalizability, and Phase III evidence with broader populations remains necessary before clinical translation.