Characteristics of ADCs. The components of the ADC and its target antigen influence the efficacy and safety profile. Preferably, target antigens should only be found on malignant cells, be abundantly expressed, be capable of internalization, and not be shed from the cellular membrane. The cytotoxic drug (payload or warhead) is the ultimate effector component, inducing direct cell killing either by inhibiting microtubule formation or directly damaging cellular DNA. It should be highly potent in the subnanomolar range and preferably nonpermeable to avoid damage to surrounding tissues. The linker connects the warhead to the antibody. These should be stable in circulation and cleavable upon lysosomal degradation. The conjugation chemistry of the linker determines the drug:antibody ratio, which critically influences the ADC potency. ADCC, antibody-dependent T-cellular cytotoxicity, Fab, fragment antigen-binding region.