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Unlocking the promise of CAR-T


Health

Unlocking the promise of CAR-T

June 30, 2025


long read

Research across multiple fronts seeks to expand impact of a cancer therapy that has left patients and doctors awestruck

David Avigan doesn’t like to use the word “miracle” to describe CAR-T-cell therapy, but he knows what people mean when they do. He also remembers the first time it happened with one of his patients.

“As a field, we’re always a little cautious — our patients are on a roller coaster,” said Avigan, director of the Cancer Center at Beth Israel Deaconess and the Theodore W. and Evelyn G. Berenson Professor of Medicine for the Study of Oncology at Harvard Medical School. “But frankly, we’ve seen very dramatic responses in patients with advanced disease.”

First approved by the FDA in 2017, CAR-T-cell therapy enlists the body’s immune system in the fight against cancer. It has triggered rapid improvement in some of the sickest patients, those whose hopes had faded with the failure of one treatment after another. Physicians report astonishing results: tumors melting away over weeks or even just days and people who appeared to be on death’s door getting up and reclaiming their lives.

“They had received every other known therapy and experimental therapy — nothing worked — and after CAR-T therapy they would go into remission and just a week later, be walking around like they were totally normal, even if they got really sick during the therapy,” said Robbie Majzner, an associate professor of pediatrics at the Medical School and director of the Pediatric and Young Adult Cancer Cell Therapy Program at the Dana-Farber/Boston Children’s Cancer and Blood Disorders Center. “We had one patient who almost died during the therapy and two weeks later he was leukemia-free and snowboarding. It was just unbelievable.”

Eric Smith, an assistant professor of medicine at the Medical School and Dana-Farber’s director of translational research, immune effector cell therapies, describes CAR-T as a “platform” rather than a specific treatment. Its weapon is one of the body’s most potent fighters — the T-cell, refined over millions of years to destroy bacteria, viruses, fungi, and other invaders. The CAR, or chimeric antigen receptor, is the T-cell’s targeting system, which can be tuned by bioengineers to different targets. That tuning ability allowed Smith and others to engineer a therapy originally effective against leukemia and lymphoma into a weapon against a third blood cancer, multiple myeloma. It also underlies excitement around the therapy’s potential to treat not just other cancers but also noncancerous conditions such as autoimmune diseases and chronic infections.

“The platform is just so amenable to further engineering — the different things we can do to increase efficacy — that we’re very enthusiastic,” Smith said. “We’ll be curing a higher percentage of patients with the next iteration.”

Eric Smith said he’s seen many amazing recoveries. One of his first was the second patient ever to receive the CD-19 directed CAR-T-cell therapy, during his oncology fellowship at the Memorial Sloan Kettering Cancer Center in New York City.

“We were shocked to see such an amazing clinical response,” Smith said. “We published a case report of a patient who had such rapidly progressive myeloma that in between starting on conditioning therapy and getting her CAR-T-cells, she developed paralysis from the myeloma in her spine. Then, with the CAR-T-cells, she was able to recover from that and do well for over a year. So yeah, that’s one of the things that does really make it different from other therapies.”

Prior to the development of CAR-T and other immunotherapies, cancer cells were protected from immune attack because they arise from the patient’s own tissues and aren’t recognized as an invader by the immune system.

In CAR-T therapy, physicians extract T-cells from the patient and send them to a cell manufacturing facility, where the CAR is added to the cell surface. The engineered cells are multiplied, frozen, and shipped back to the medical facility to be infused into the patient. Once in the body, the CAR attaches to a molecule — the antigen — on the cancer cell surface, signaling that the T-cell should attack.

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