Used as a linker in antibody-drug conjugates (ADCs), particularly in the construction of prodrugs for targeted cancer therapy. The PAB (para-aminobenzyloxycarbonyl) group serves as a self-immolative spacer that enables the release of active cytotoxic agents upon enzymatic cleavage in the target cells. The Fmoc-protected dipeptide (Val-Ala) enhances solubility and stability during synthesis and acts as a substrate for lysosomal proteases, facilitating selective drug release inside tumor cells. Commonly employed in the development of ADCs where controlled, intracellular activation of the payload is required.