Azido-PEG4-Val-Cit-PAB-MMAE is primarily used in the development of antibody-drug conjugates (ADCs), which are targeted cancer therapies. The chemical serves as a linker-payload component, connecting a monoclonal antibody to a potent cytotoxic agent, MMAE. The azide group enables site-specific conjugation to antibodies via click chemistry, ensuring precise and efficient coupling. The PEG4 spacer enhances solubility and stability, while the Val-Cit dipeptide acts as a cleavable linker, allowing the release of MMAE in the presence of lysosomal enzymes within cancer cells. This targeted approach minimizes damage to healthy tissues while maximizing the delivery of the cytotoxic payload to tumor cells, making it a critical component in advancing precision medicine for cancer treatment.