Photoswitchable CAR-T Cell Function In Vitro and In Vivo via a Cleavable Mediator.

Chimeric antigen receptor (CAR)-T-based therapeutics are a breakthrough in cancer treatment; however, they are hampered by constitutive activation, which leads to worrisome side effects. Engineering CAR-T cells to be as tightly controllable as possible remains a topic of ongoing investigation. Here, we report a photoswitchable approach that uses a mediator for the at-will regulation of CAR-T cells. This mediator carries dual folate and fluorescein isothiocyanate moieties tethered by an ortho-nitrobenzyl ester photocleavable linker. CAR-T cells were shown to be highly cytotoxic to targeted cells only in the presence of the mediator and acted in a dose-dependent manner. The toxicity of CAR-T cells can be rapidly terminated by cleavage of the mediator, and the effects of CAR-T cells can be activated again by resupplementation with the mediator without compromising tumor therapy. The approach described here provides a direction for enhancing the controllability of CAR-T cells and can likely be applied in other immunotherapies.