New cancer immunotherapies involve extracting a patient’s T cells and genetically engineering them so they will recognize and attack tumors. This technique is a true medical breakthrough, with an increasing number of leukemia and lymphoma patients experiencing complete remissions since CAR T therapy was FDA approved in 2017.

This type of therapy is not without challenges, however. Engineering a patient’s T cells is laborious and expensive. And when successful, the alterations to the immune system immediately make patients very sick for a short period of time, with symptoms including fever, nausea and neurological effects.

Now, University of Pennsylvania researchers have demonstrated a new engineering technique that, because it is less toxic to the T cells, could enable a different mechanism for altering the way they recognize cancer.