CEACAM5 and neoplasm: Recent late-stage clinical failures of CEACAM5 mono-targeting therapeutics including the T-cell engager Cibisatamab and the ADC Tusamitamab ravtansine, were likely driven in part by high CEACAM5 target expression in normal GI tissues relative to tumor, resulting in toxicities that prevent achievement of clinically meaningful doses (8, 9).