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In children with a blood cancer called acute lymphoblastic leukemia, T-cell therapy has demonstrated unprecedented effectiveness. It eradicates the disease in 80 percent of cases, and about half of those remissions are lasting, based on Kymriah studies. The first child to be treated, Emily Whitehead of Philipsburg, Pa., now 12, is about to mark six years cancer free.

In contrast, only 26 percent of CLL patients have a complete remission, even though CLL launched Penn’s breakthrough in T-cell research. Almost eight years ago, two of the first three CLL patients to be treated with the therapy saw their end-stage disease disappear; the third had a partial remission.

Patient number one, Bill Ludwig, 73, of Bridgeton, N.J., went from expecting to die, to expecting miracles would be standard.

“I figured if they can cure me, they can cure everyone,” said the retired corrections officer.

Now, as he continues to enjoy family, travel, and hobbies, he hopes researchers can figure out the secret of his success. Ongoing check-ups show his engineered T cells are still in his body, killing B cells, the immune cells that turn malignant in CLL. Because the therapy also kills healthy B cells, he gets an infusion of an immune-boosting drug every seven weeks.

“They manipulated my immune system and activated the killer T cells. Those cells are still there, and they’re still eliminating B cells,” he said. “I have no side effects. It’s just three or four hours that I sit in a chair” for the infusion.

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How many of the newly discovered memory T cells are needed to ensure a good response? The answer is unclear, but in the validation study, researchers correctly predicted that if at least 29 percent of all T cells were memory cells, the patient’s cancer would be gone three months later.

Penn researcher Joseph A. Fraietta, lead author of the new study, said the findings open the door to using genetic engineering to create synthetic memory T cells.

“We are actively working on manufacturing improvements that could enrich the therapy for these memory cells,” he said. “It’s a work in progress, for sure.”