PGP and neoplasm: Further strategies include the design of payloads engineered to evade efflux pumps (e.g., P-gp) (137); the exploration of combination regimens with efflux pump inhibitors, although still under clinical investigation due to potential toxicity concerns; and the development of ADCs with potent bystander effects (e.g., DS-8201) to eliminate adjacent antigen-negative tumor cells and address tumor heterogeneity (138).