What happens when the wrong cell is reprogrammed with CAR-T

One patient’s CAR-T therapy went terribly awry, and scientists are now using it as a cautionary tale on how cancers might become resistant to this groundbreaking new therapy.

As reported in Nature Medicine, the CAR gene meant to turn a patient’s T cells into cancer-fighting mercenaries was inadvertently inserted in a patient’s cancerous blood cell. This wound up allowing the patient’s leukemia to hide away from the therapeutic CAR-T cells — because the lymphoma cells began expressing the chimeric antigen receptors as well. The cancer spread, and the patient ultimately died.

The case appears to be exceedingly rare, and happened five years back in an early clinical trial. But similar problems could arise again as cellular therapies become more widely used, experts caution.