Experimental immunotherapy shows promise for common adult leukemia in trial

WASHINGTON, July 17 (Xinhua) -- An experimental treatment that involves the use of patients' own immune cells, known as immunotherapy, has shown promise in treating patients with the most common adult leukemia in an early-phase clinical trial, according to a study published Monday.

About 70 percent of the 24 patients with chronic lymphocytic leukemia (CLL) who had failed other treatments had their tumors shrink or disappear following an experimental chimeric antigen receptor (CAR) T-cell immunotherapy, results of the Phase 1/2 clinical trial showed.

"It was not known whether CAR T-cells could be used to treat these high risk CLL patients," said Cameron Turtle, an immunotherapy researcher at Fred Hutchinson Cancer Research Center and lead author of the study published by the Journal of Clinical Oncology.

"Our study shows that CD19 CAR T-cells are a highly promising treatment for CLL patients who have failed ibrutinib," a targeted cancer drug approved in 2014 for CLL by the U.S. Food and Drug Administration.

CD19 CAR T-cells are a type of immunotherapy in which a patient's T cells are extracted from their blood and modified in a lab to recognize CD19, a target on the surface of leukemia cells. The engineered T cells are then infused back into the patient where they multiply and hunt down and kill cancer cells.

In CLL, bone marrow makes too many abnormal lymphocytes, which are a type of white blood cell. The American Cancer Society estimated that in the U.S., there will be about 20,000 new cases and 4,600 deaths from CLL in 2017.

Tests of blood, bone marrow and lymph nodes -- where lymphocytes congregate to fight infection -- reveal the disease.

The 24 patients participating in the study ranged in age from 40 to 73 years, with a median age of 61. They had received a median of five other therapies with as few as three and as many as nine, but most of them had seen their cancer progress despite these treatments.

Researchers found that 17 of the patients, or 71 percent, saw their tumors shrink or disappear following CAR T-cell therapy using the standard measure of lymph node size by CT scans four weeks after treatment.

Of side effects of CAR-T cell therapy, 20 of the 24 patients, or 83 percent, experienced cytokine release syndrome and eight patients, or 33 percent, developed neurotoxicity.

For the most part the side effects were reversible, but two patients had side effects severe enough to require being admitted to the intensive care unit and one of those patients died.

In addition, the researchers found that measuring genetic traces of cancer cells taken from bone marrow biopsies might be a better indicator of prognosis than the standard lymph node scan.

Turtle and his collaborators did the sequencing analysis in 12 of the patients, seven of whom had no malignant copies.

They found that all the patients without malignant copies were alive and free of disease at a median follow-up of 6.6 months after CAR T-cell infusion.

CAR T-cell therapy is being studied in the treatment of some types of cancer.

Last week, a U.S. Food and Drug Administration advisory committee recommended that the agency approve Novartis' CAR T-cell therapy CTL019 as a treatment for children and young adults with relapsed or refractory B-cell acute lymphoblastic leukemia.