A pair of immune-modulating drugs may delay—but not prevent—viral rebound after stopping antiretroviral treatment. Researchers are exploring many approaches to keep HIV in remission, known as a functional cure. One is anti-PD-1 immune checkpoint inhibitors, which are widely used for cancer immunotherapy and might also reinvigorate exhausted T cells to fight HIV. A Phase II trial tested the PD-1 checkpoint inhibitor budigalimab plus trosunilimab, an antibody that binds to a different receptor. The study enrolled 142 adults on antiretroviral therapy with an undetectable viral load; they stopped their antiretrovirals at the start of the trial. At 24 weeks, 24% of people assigned to budigalimab plus low-dose trosunilimab maintained a viral load below 1,000 versus 5% in the placebo group. Viral control decreased with further follow-up, however, and the median peak viral load and the time to viral rebound did not differ significantly between the active treatment and placebo groups. What’s more, side effects were common and sometimes serious, casting doubt on this approach.