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Camille Leahy stands outside Princess Margaret Hospital after an appointment in Toronto, on Feb. 16.Galit Rodan/The Globe and Mail

A new method of treating cancer has given Camille Leahy the chance to live. After she was diagnosed in 2020 with acute lymphoblastic leukemia, an aggressive form of cancer of the blood, the single mother from Newmarket, Ont., underwent chemotherapy and a gruelling stem cell transplant. But her cancer kept returning.

Just as she thought she had run out of treatment options, she received an experimental form of immunotherapy in September, 2021, as part of a clinical trial at the Ottawa Hospital – one the researchers believe could help transform cancer care across the country.

Since then, Ms. Leahy, 38, has been cancer-free. Last summer, feeling better than she has in a long time, she attended a Blue Jays game with her daughter, went treetop trekking and even participated in a five-kilometre running race.

“I don’t think we could have expected anything better to come out of it,” Ms. Leahy said.

The experimental treatment is a made-in-Canada CAR-T (chimeric antigen receptor T-cell) therapy. Principal investigator Natasha Kekre, a hematologist at the Ottawa Hospital and associate professor at the University of Ottawa, said the goal of her team is to see their work taken up at health care centres across Canada. Last month, they received a $4-million federal grant, allowing the researchers to conduct further clinical trials, starting with Ottawa, Toronto and Winnipeg.

CAR-T therapy involves modifying a patient’s own immune cells, called T-cells, to recognize and attack their cancer. A patient’s immune cells are collected and brought to a lab, where the T-cells are genetically engineered to produce a receptor on their surface that targets a specific protein on cancer cells. These cells are then delivered back into the patient’s bloodstream.

Existing CAR-T therapies require either having the patients travel out of country or sending their cells to facilities in the United States, a process that can take more time than severely ill patients have, Dr. Kekre said. It is also very expensive, and is restricted to patients with specific types of leukemia and lymphoma. Under their Canadian-led Immunotherapies in Cancer program, Dr. Kekre and her colleagues developed a method of making CAR T-cells in Canada, which they believe will make the treatment less expensive and easier to access.

Currently, one of the major bottlenecks in this field is it relies on biotech companies to make the viruses that contain the genetic material used to manufacture CAR T-cells, she explained. Their program instead takes advantage of an existing academic facility that can make viruses for use in academic medicine through the Ottawa Hospital Research Institute.

“This is just the beginning of a huge pipeline of what we want to build for the country,” she said.

Combined with the expertise of researchers at BC Cancer and the BioCanRx research network, they’ve developed a process to then use those viruses to manufacture CAR T-cells, using a machine made by the international company Miltenyi Biotec that can be set up in multiple sites across the country, thus shortening the time and distance it takes to receive and deliver them to patients, Dr. Kekre said.

“You put on the cells into the machine, you put a bunch of reagents and liquid that helps the cells grow, and then, at the end of 12 days, I mean it sounds very simplistic, but it pops out your product” she said.

Having a made-in-Canada approach also allows researchers to conduct their own trials to test new CAR-T therapies, instead of exporting their ideas to be tested elsewhere and waiting for them to eventually be made available to Canadians, she said. “We can run trials in Canada with our own science.”

So far, Dr. Kekre said, the program has treated more than 60 patients in Ottawa and Vancouver, using CAR T-cells they manufactured in Victoria. Initial results from an early trial of 30 patients, for whom other treatments have not worked, showed long-term, progression-free survival among 40 per cent of them, meaning the patients did not have a recurrence of their cancer and were alive and well, she said. Currently, CAR-T therapy is only used for patients for whom traditional lines of therapy have not worked.

“That number will only get better as we learn more and we treat more patients,” Dr. Kekre said.

The treatment is not without the risk of serious side effects, including cytokine-release syndrome, which is an overactivation of the immune system, and a kind of neurotoxicity that can result in seizures or coma.

Hamilton Health Sciences’ Juravinski Hospital and Cancer Centre has been treating patients with commercial CAR-T therapy since January, 2020. The treatment, which is covered by the province, relies on pharmaceutical company facilities in New Jersey and California to manufacture CAR T-cells.

Amaris Balitsky, a malignant hematologist at Juravinski who is not involved in Dr. Kekre’s research, said there have been major advances in CAR-T therapy over the past five years, and there will likely be more to come in the next five, particularly when it comes to addressing the complexities of delivering the therapy.

Dr. Balitsky also expects that as more studies emerge, the patients and conditions for which CAR-T therapy can be used will expand.

“Every advance in this science will be helpful,” she said.