Unlike patients with HER2+ tumors, there is an unmet clinical need for patients with HER2-low expression cancers, which are refractory to trastuzumab. Sanofi SA has developed TPP-45142, a T-cell engager consisting of two nanobody domains targeting HER2 and T-cell receptor (TCR) fused to an Fc region harboring the F234A and L235A mutations to inhibit effector function.