Used in antibody-drug conjugates (ADCs) as a linker-payload component, enabling targeted delivery of cytotoxic agents to cancer cells. The PAB group serves as a self-immolative spacer that releases the active drug upon intracellular cleavage, typically by cathepsin B after proteolytic degradation of the peptide sequence. The Fmoc-Gly3-Val-Cit segment enhances solubility and acts as a substrate for lysosomal enzymes, improving the efficiency of drug release inside tumor cells. This construct is particularly valuable in the development of highly specific anticancer therapies with reduced systemic toxicity.