The CAR T-cell treatment, manufactured by the drug company Novartis, initially would be available only for the small number of children and young adults whose leukemia does not respond to standard care. Those patients typically have a grim prognosis, but in the pivotal trial testing the therapy in almost a dozen countries, 83 percent of patients went into remission. A year later, two-thirds remained so.

And childhood leukemia is just the start for a field that has attracted intense interest in academia and industry. Kite Pharma of Santa Monica, Calif., has applied for FDA approval to treat aggressive non-Hodgkin’s lymphoma, and a similar Novartis application is close behind. Researchers also are exploring CAR T-cell therapy’s use for multiple myeloma and chronic lymphocytic leukemia, the disease that afflicted Ludwig. They are also tackling a far more difficult challenge — using the therapy for solid tumors in the lungs or brain, for example.