The 24 patients had undergone most standard therapies available to them and yet their chronic lymphocytic leukemia had come back strong. Almost all of them had been treated with a newly approved, targeted drug called ibrutinib; data from other studies show that most patients whose disease progresses after ibrutinib treatment do not survive long. The majority of the 24 had chromosomal markers in their leukemia cells that serve as[DAE1] “predictors of a bad response to most standard therapies,” said Dr. Cameron Turtle of Fred Hutchinson Cancer Research Center.
But most of these patients, who were enrolled in a small, early-phase trial, saw their advanced tumors shrink or even disappear after an infusion of genetically engineered immune cells. Turtle, one of the study’s leaders, presented the results on Saturday at the 2016 annual meeting of the American Society of Hematology in San Diego.
In the trial, participants’ disease-fighting T cells were removed from their blood and genetically engineered in a lab at Fred Hutch to produce an artificial receptor, called a CAR, or chimeric antigen receptor, that empowered them to recognize and destroy cancer cells bearing a target molecule called CD19. After patients received chemotherapy, the CAR T cells were infused back into their bloodstream to kill their CD19-positive cancers.
While all 24 patients with chronic lymphocytic leukemia, or CLL, received the experimental therapy, Turtle focused in his presentation on the results in a subgroup of 19 patients who received particular chemotherapy regimens and doses of CAR T cells the researchers now prefer, based on recent data in other groups of patients on the trial.
Fourteen of 19 experienced a partial or complete regression of their disease in their lymph nodes. And of the 17 who had leukemia in their bone marrow when they enrolled on the trial, the marrow became cancer-free in 15 after they received CAR T cells. (In his presentation, Turtle presented new results not reflected in the abstract available online.)
“It’s very pleasing to see patients with refractory disease respond like this,” Turtle said. The research team “had seen very good responses [to the same CAR T-cell therapy] in acute lymphoblastic leukemia and non-Hodgkin lymphoma, so we hoped responses would be good in CLL too.”