Used in the synthesis of antibody-drug conjugates (ADCs), particularly as a linker-payload component. It facilitates the targeted delivery of cytotoxic agents to cancer cells, enhancing therapeutic efficacy while minimizing off-target effects. The Fmoc group protects the amino acid during synthesis, while the Val-Cit dipeptide sequence is cleavable by cathepsin B, an enzyme overexpressed in tumor cells. The PAB-OH moiety ensures stable attachment of the payload until it reaches the target site. This chemical is critical in developing precision cancer therapies, enabling controlled release of drugs within tumor environments.