Toronto man’s HIV no longer detectable after bone marrow transplant

Walmsley, who has been the Toronto patient’s doctor since he was diagnosed with HIV and an aggressive lymphoma in 1999, said it was a miracle he survived at the time.

To think that less than three decades later he’d be in “sustained remission” with HIV undetected for almost a year would have been inconceivable, she said.

“It’s really an incredible journey.”

THE TORONTO PATIENT

In July 2020, Walmsley noticed the patient’s blood counts were abnormal when he came in for a routine test.

“I knew that something wasn’t right,” she said, so she sent him to Princess Margaret Cancer Centre, where an oncologist diagnosed him with acute myelogenous leukemia and determined he needed a bone marrow transplant.

The search began to find the best bone marrow match. The ideal donor would also have a CCR5 gene mutation resistant to HIV.

CCR5 is a protein on the surface of an immune cell that acts as the door that HIV enters to infect the body, but about one per cent of the population, primarily of northern European descent, are deficient of this gene.

That means there is no door for the virus to enter, “and so the virus can’t get into the cells,” said Dr. Mario Ostrowski, a clinician-scientist at St. Michael’s Hospital who co-led the case with Walmsley. The new donor cells could also attack and eliminate the reservoir of virus-infected cells.

In March 2021, the transplant took place at Princess Margaret Cancer Centre. The patient had several complications afterward, such as pneumonia, which is not unusual after such a significant transformation of the immune system.

Ostrowski took samples of the patient’s cells to assess if the virus was disappearing. Once HIV was undetectable, the patient was clinically stable and his leukemia was in remission, the medical team took him off of anti-HIV therapy (ART) in July 2025 for the first time in almost three decades.

WHY DO WE NEED A CURE?

Many people living with HIV take ART once a day and have a near-normal life expectancy.

“And so people say, ‘Well, why do you need a cure then?’” Walmsley said.

“Well, because HIV can still cause comorbidity. People living with HIV, even when it’s well controlled, may have more heart disease or lung disease or kidney disease than the general population,” Walmsley said.

And the other big reason is stigma, which she said has not gone away.

When Ostrowski lectures students at the University of Toronto, he asks if they would rather have HIV, take a pill once a day for the rest of your life, and never get AIDS – or be diabetic and take insulin four times a day, monitor sugar levels, and face many risks of complications.

“One hundred per cent of people will always say they’d rather have diabetes. And that just shows you how potent the stigma of being HIV infected is. It affects people emotionally. It’s associated with a lot of violence and a lot of trauma that people are unaware of. And so there’s a lot of interest in HIV infected people to develop a cure,” he said.

Transplants are too medically risky, complicated and expensive to be used as a standard treatment for HIV, but Ostrowski said clinicians can learn clues about how to kill the virus from these patients.

There’s also steps that can be taken sooner, such as developing a standardized transplant program across Canada that identifies matches for HIV patients.

“Because this is going to happen again and again.”

This report by The Canadian Press was first published April 25, 2026.

Canadian Press health coverage receives support through a partnership with the Canadian Medical Association. CP is solely responsible for this content.

Hannah Alberga, The Canadian Press

by The Canadian Press

Toronto man’s HIV no longer detectable after bone marrow transplant

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