The Modular CAR: Adapting T Cells without Reengineering Them.

The therapeutic potential of chimeric antigen receptor (CAR) T cells has long been limited by the static nature of the engineered receptor; once manufactured, the cell is committed to a single antigen, unable to respond to the immune evasion and antigen heterogeneity that define solid tumors. Although solutions such as bispecific constructs and logic-gated circuits have been proposed, each encodes additional complexity into the cell product at the time of manufacture, with no capacity for post-infusion reprogramming. In this issue, Kuo and colleagues report a fundamentally different strategy-the meditope-enabled CAR-in which a small, structurally orthogonal peptide-docking interface is embedded into the extracellular domain of the CAR, converting a fixed cellular product into a programmable platform that can be redirected, selectively expanded, or precisely tracked by administering a modular adapter molecule. See related article by Kuo et al., p. XX.