Used primarily as a linker in antibody-drug conjugates (ADCs), enabling targeted delivery of cytotoxic agents to cancer cells. The dipeptide Mc-Val-Cit is cleavable by cathepsin B, an enzyme overexpressed in tumor tissues, allowing selective release of the active drug inside cancer cells. The PAB (para-aminobenzyl) spacer facilitates efficient drug release upon cleavage, while the chloro group (Cl) acts as a reactive handle for attachment to payloads such as maytansinoids or other cytotoxic agents. This linker system enhances the therapeutic index of ADCs by minimizing off-target toxicity and improving plasma stability.