A B7-H3-targeted CD28 bispecific antibody enhances the activity of anti-PD1 and CD3 T-cell engager immunotherapies.

T-cell activation is a multistep process requiring T-cell receptor engagement by peptide-major histocompatibility complexes (Signal 1) coupled with CD28-mediated costimulation (Signal 2). Tumors typically lack expression of CD28 ligands, so tumor-specific Signal 1 (e.g.