EGFR and fibrosarcoma: In our model of mixed tumor cell spheroids close contacts between carcinoma and fibrosarcoma cells are expected to occur that might even lead to a minor degree of plasma membrane exchange and bystander killing of cells not expressing the TAA targeted by the αTAA–αCD3 BiMAb as demonstrated in Supplementary Figure 5C and previously shown for EGFR/CD3 BiTEs (37).