An experimental therapy has brought prolonged remissions to a high proportion of patients who were facing death from advanced leukemia after standard treatments had failed, researchers are reporting.

The therapy involves genetically programming cells from the patient’s own immune system to fight the disease.

The research included 30 patients: five adults ages 26 to 60, and 25 children and young adults ages 5 to 22. All were severely ill, with acute lymphoblastic leukemia, and had relapsed several times or had never responded to typical therapies. In more than half, the disease had come back even after a stem-cell transplant, which usually gives patients the best hope of surviving. Their life expectancy was a few months, or in some cases just weeks.

Six months after being treated, 23 of the 30 patients were still alive, and 19 of them have remained in complete remission.