A Canadian man appears to be free of HIV after a stem cell transplant using cells from an HIV-resistant donor, potentially making him the eleventh person to be cured after the procedure, researchers reported this week at the Canadian Association of HIV Research Conference.
Stem cell transplants are too risky for people living with HIV who do not have advanced cancer, but each new case offers clues that could help scientists develop an accessible functional cure, or long-term remission without antiretroviral treatment.
“The small but growing number of these cases prove an HIV cure is possible,” Professor Sharon Walmsley, director of the HIV clinic at the University of Toronto’s University Health Network, said in a press release. “Cases such as these provide important information for researchers to find ways to eradicate HIV from the body.”
Dubbed the Toronto Patient, the anonymous 62-year-old man has been under Walmsley’s care since 1999, when he was diagnosed with stage 4 Burkitt lymphoma, an opportunistic malignancy that prompted an HIV test. His CD4 count was 188, indicating an AIDS diagnosis. He achieved cancer remission with strong chemotherapy and viral suppression after starting antiretroviral treatment in 2000; by 2015, his CD4 count had reached 500.
Two decades later, the man developed myelodysplastic syndrome – possibly due to the prior chemotherapy – which progressed to acute myelogenous leukaemia in late 2020. He was treated with chemotherapy, but his care was complicated by bacterial sepsis and invasive fungal pneumonia.
In November 2021, after a reduced-intensity conditioning regimen to kill malignant cells and make room for new ones, he underwent an allogeneic haematopoietic stem cell transplant. His doctors searched a global registry to find a matched donor with two copies of a mutation known as CCR5-delta-32, which disables a receptor HIV uses to enter cells.
Despite preventive immune-suppressing medications, the man developed graft-versus-host disease, which occurs when donor immune cells attack the recipient’s body. His recovery was further complicated by febrile neutropenia (low white blood cells with fever), acute kidney injury, various infections and a broken hip, but the transplant put his leukaemia into remission.
The man stopped his antiretroviral treatment in July 2025 and remains in sustained remission ten months later, with an undetectable viral load according to highly sensitive tests. During the five years since the transplant, Professor Mario Ostrowski of St. Michael’s Hospital and colleagues have observed a continual decline in HIV DNA in the man’s blood cells – an indicator of the latent viral reservoir of HIV – and have been unable to isolate viable virus from his CD4 cells. What’s more, he no longer has detectable HIV-specific T-cell responses, suggesting there may be no remaining virus to trigger the immune system.
In short, the Toronto Patient appears to be in long-term remission with no detectable HIV, despite being in poor health with several complications. Follow-up is ongoing. In general, people are considered cured once they have been in remission without antiretrovirals for about two years, but some researchers have been more cautious than others in making such a determination.
Prior cure cases
The first person cured of HIV – Timothy Ray Brown, the original Berlin Patient – received two transplants to treat leukaemia from a donor with two copies of the CCR5-delta-32 mutation. As first reported in 2008, he stopped antiretroviral treatment but his viral load did not rebound. Over the years, scientists tested his blood, gut and other tissues, finding no evidence of intact HIV. At the time of his death in September 2020, Brown had been free of HIV for more than 13 years.
Six other people have also been cured after receiving stem cell transplants from donors with the double CCR5-delta32 mutation: Adam Castillejo (the London Patient), Marc Franke (the Düsseldorf Patient), Paul Edmonds (the City of Hope Patient), a woman in Marseille (the French Patient), the Chicago Patient and the Oslo Patient. (The Oslo case, first presented at last year’s Conference on Retroviruses and Opportunistic Infections, was recently published in Nature Microbiology.) All remain off antiretrovirals without viral rebound.
Scientists initially assumed Brown’s cure was attributable to the double mutation. But in 2022, researchers described the New York Patient, a woman with leukaemia who received a combination of umbilical cord blood cells with the CCR5-delta-32 mutation and partially matched adult stem cells without the mutation. The next Berlin Patient has a single copy of the mutation himself and received a transplant from a donor who also has a single copy. And Romuald, the Geneva Patient, was cured after a transplant using wild-type stem cells with no copies of the mutation.
Researchers are still trying to figure out why these people were cured with stem cell transplants while other attempts have failed, and there does not seem to be a single decisive factor common to all the cases.
Some of the patients received intensive pre-transplant conditioning with chemotherapy and, in some cases, radiation, while others received gentler regimens. They had varying severity of graft-versus-host disease, which might help clear residual HIV. The Geneva Patient used an immune-modulating drug (ruxolitinib) that may help shrink the viral reservoir.
“It’s not all about CCR5-delta-32,” cure expert Professor Sharon Lewin of the University of Melbourne said at a previous media briefing about the Next Berlin Patient. It’s likely that “multiple factors play a role in remission,” and these may differ from patient to patient.
While stem cell transplantation is an arduous and expensive procedure that is not safe for people without life-threatening cancer, each successful case provides further information that could help scientists develop more widely applicable functional cure approaches.
“Transplant provides clues to develop similar, less toxic and less expensive therapies by studying these individuals,” Ostrowski said in a University Health Network press release.
Dr Tommy Alfaro Moya of UHN’s Princess Margaret Cancer Centre, who was involved in the Toronto Patient’s post‑transplant care, added, “This case offers critical insight into how HIV can be eliminated from the body, informing safer approaches in the future.”
References
Walmsley S et al. The “Toronto Patient”: HIV sustained remission and possible cure in a 62-year-old male after allogeneic CCR5-delta-32 stem cell transplant. Canadian Association of HIV Research Conference, Winnipeg, 2026.
