A molecular 'remote control' could enable researchers to make a powerful cancer therapy safer.

The therapy relies on engineered immune-system cells called T cells that recognize and kill tumours, and has shown promise in clinical trials. But the T cells can also attack and damage healthy cells. James Onuffer and Wendell Lim at the University of California, San Francisco, and their colleagues designed an approach in which the T-cell receptors that recognize cancer cells are split in two, and will only assemble and function when triggered by a compound similar to the drug rapamycin.

T cells engineered in this manner only attacked their target cells in mice when the compound was present. The approach could provide a way to modulate the timing and intensity of engineered T-cell responses in humans.

Science http://doi.org/7v4 (2015)