Engineered Immunotherapy Shows Extraordinary Efficacy Treating Leukemia

A recent study found genetically engineered T cells that fight B-cell acute lymphoblastic leukemia resulted in 27 out of 29 patients achieving remission.

Researchers from the Fred Hutchinson Cancer Center genetically engineered the T cells with a chimeric antigen receptor (CAR) that allows the T cells to recognize and kill cancer cells with CD19. The study looked to examine the safety of these engineered cells.

There were 39 adult patients enrolled with advanced disease who either relapsed or did not respond to other therapies.

Once T cells were extracted from the patients, a specialized virus delivered the DNA instructions for making the CAR into cells, which were then multiplied by the billions in the laboratory. After chemotherapy, the reengineered cells were infused back into the participants. A few weeks after the infusion, researchers evaluated the response using a high-sensitivity test.

The results of the study showed that the cancer in their bone marrow was undetectable in 27 out of 29 patients and the CAR T cells eliminated cancers in whichever parts of the body they appeared. Two participants did not achieve complete remission, but 1 patient did eventually reenroll in the trial and was able to go into complete remission after receiving a higher dose of cells.

“In early-phase trials, you're continually learning,” said senior study author David Maloney. “You don't expect results like these from early-phase trials. That's why these response rates are so extraordinary.”

However, not all of the patients stayed in complete remission, with some who relapsed and were retreated with CAR T cells. Two patients who relapsed with leukemia that was immune to the cells.

“Patients who come onto the trial have really limited options for treatment. They have refractory, acute leukemia,” said study leader Cameron Turtle. “So the fact that we're getting so many into remission is giving these people a way forward.”

Despite promising results more work needs to be done, the researchers concluded.

“This is just the beginning,” Turtle said. “It sounds fantastic to say that we get over 90% remissions, but there's so much more work to do make sure they're durable remissions, to work out who's going to benefit the most, and extend this work to other diseases.”

The study is the first to infuse patients with a defined ratio of killer and helper T cells. It includes the largest number of participants of any other published study using CD19 CAR T cells against this form of cancer.

The study was not designed to give definitive evidence of the efficacy of the therapy against cancer.