CTSB and neoplasm: The integration of site-specific conjugation strategies enabling precise DAR control, tumor-selective linker systems responsive to proteases (e.g., cathepsin B, legumain) or acidic pH, payloads with optimized physicochemical properties to modulate membrane permeability and hydrophilicity, and conditional activation platforms such as protease-activated probody ADCs is driving the development of next-generation ADCs with improved plasma stability, reduced off-target cytotoxicity, and enhanced intratumoral drug release [27,163].