Multi-dimensional orchestration of binders for improved CAR-T immunotherapy.

The design of antigen-binding domains (binders) is emerging as a decisive frontier in chimeric antigen receptor (CAR)-T cell engineering. Rather than serving as passive recognition elements, binders actively shape antigen selectivity, signaling thresholds, exhaustion propensity, persistence, and toxicity. We propose that optimal CAR performance requires a multidimensional design strategy. Success cannot be achieved by maximizing a single variable like affinity. Designers must instead integrate epitope position, binding kinetics, avidity, molecular geometry, and biophysical stability. In this review, we synthesize recent advances showing how these parameters collectively govern immunological synapse formation, antigen-density discrimination, and functional durability. Importantly, we highlight that the consequences of binder design are increasingly evident not only in mechanistic and preclinical studies, but also in real-world clinical translation and commercial trajectories. We further examine how the binder landscape has expanded beyond conventional scFvs to include VHHs, monobodies, DARPins, D-domains, peptides, natural ligands, TCR-mimic binders, and de novo AI-designed proteins. Together, these advances support a shift from empirical binder selection to rational binder orchestration as a foundational principle for next-generation CAR-T immunotherapy.