Fig. 8: Regulation of XPAT protein activity.

a, Mechanism for XPAT protein binding to cells (left) and promoting T-cell engagement. Binding of XPAT protein to cells is a bimolecular event in which equilibrium should be directly proportional to the binding affinities of the component molecules. In contrast, synapse formation (right) is a high-order molecular process that involves many individual binding events. b, Proposed mechanisms for differential regulation of XPAT protein activity in different tissue compartments are depicted. By harnessing the potency of bispecific TCEs with an enhanced therapeutic window, XPAT proteins may provide an opportunity to improve clinical outcomes beyond those achieved with TAA-targeted monoclonal antibodies or antibody–drug conjugates, enabling patients to safely mobilize T cells independent of their antigen specificity.