The Fas pathway was shown to significantly contribute to DuoBody-CD3x5T4–induced T cell–mediated kill of 5T4+ tumor cells, in line with recent data implicating Fas and its ligand in antigen-specific T cell–mediated cytotoxicity, including T cell–mediated kill induced by the CD3xCD19 bsAb blinatumomab (Upadhyay et al, 2021). The gene discussed is FAS; the disease is neoplasm.