Scientists Engineered Cancer-Fighting Cells Inside Patients’ Bodies—and Two Early Trials Show Promise

Two recent studies show the novel therapy works in people with multiple myeloma, but researchers are trying to minimize side effects

Sara Hashemi | Daily Correspondent

December 16, 2025

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CAR T-cell therapy can be a lifesaving treatment for blood cancers like leukemia and lymphoma. The gene therapy trains a patient’s T cells—white blood cells that play an important role in the immune system—to fight cancer by making them produce chimeric antigen receptor (CAR) proteins. These proteins help the T cells recognize diseased cells and destroy them.  

But the current process involves harvesting T cells, modifying them and putting them back into a patient’s body, which can be slow and expensive. That’s why scientists are working to engineer T cells within the body. So far, the novel practice shows promise.

Researchers presented preliminary results of an early-phase clinical trial exploring in vivo CAR T-cell therapy at the American Society of Hematology annual meeting earlier this month. This trial, along with another reported in July in the Lancet, is inspiring hope that the experimental treatment can be used for certain hard-to-treat cancers, though the researchers also noted some serious side effects.

“The question is no longer can you really do this,” says Yvonne Chen, a cancer immunotherapy researcher at the University of California, Los Angeles who was not involved in either study, to Mitch Leslie at Science. “The question now is can you reach the level of efficacy that’s expected and will the safety profile meet the target.”

To alter T cells inside the body, researchers behind the two new trials relied on genetically modified viruses. They carry the genetic code for CAR proteins to patients’ immune cells. This method could help doctors overcome some challenges of CAR T-cell therapy. For instance, the manufacturing process is so slow that patients’ cancers can progress while they wait. The therapy is also prohibitively expensive for many people.

“If I tell you that only 15 to 20 percent of patients nationally who should be getting CAR T are getting it, that is a really eye-opening number,” says Mazyar Shadman, a blood cancer specialist at the Fred Hutch Cancer Center, on a recent episode of the podcast From Bench to Bedside and Beyond. “That is concerning for us in the CAR T community. You have a treatment that’s lifesaving, yet we are looking at best 20 percent utilization in the country. And there’s a problem there.”

In the study reported in July, four patients with multiple myeloma were enrolled in a trial conducted in China. They received an experimental therapy developed by Belgian biotechnology company EsoBiotec and Chinese biopharmaceutical company Shenzhen Pregene Biopharma. Within a few months, two patients showed strong responses, and their tumors disappeared; the two other patients had partial responses, and their tumors shrank.

Still, after receiving an infusion with the experimental therapy, three of the patients experienced a drop in blood pressure that required treatment, and two of them needed supplemental oxygen. One patient also experienced a “mild disturbance of consciousness,” according to the paper.

The patients recovered, but Heng Mei, a study co-author and hematologist at the Huazhong University of Science and Technology in China, tells Science that these side effects don’t usually occur with conventional CAR T-cell therapy. However, lab-made CAR T cells often cause the immune system to become overactive, inducing fever, chills and other flu-like symptoms. All patients in the in vivo therapy trial experienced minor inflammatory reactions after receiving their infusions.

In the second trial, presented at the meeting in December, three patients with multiple myeloma received an experimental therapy developed by Boston-based biotechnology company Kelonia Therapeutics. All patients had a minimal amount of cancer cells at the one-month mark, and they’ve shown no disease progression since receiving the treatment. Side effects were milder than in the other study.

Still, “it’s very early. They’re only reporting on three patients, so we still have a lot more to learn,” Michael Rosenzweig, a hematologist-oncologist at City of Hope who was not involved with the trial, tells Mary Caffrey and Ryan Flinn at the American Journal of Managed Care. “But it’s definitely an exciting abstract that’s beginning, at least, to offer proof of principle that it’s possible to do this with some efficacy.”

Sara Hashemi | Read More

Sara Hashemi is a science writer and fact-checker currently based in New York City. Her work has appeared in Sierra, The Body, Maisonneuve magazine and more.