Fmoc-Val-Cit-OH is primarily used in solid-phase peptide synthesis (SPPS) as a building block for constructing peptide chains. It plays a critical role in the synthesis of peptide-drug conjugates, particularly in the development of antibody-drug conjugates (ADCs). The valine-citrulline dipeptide sequence is a key component in designing linkers that are cleavable by specific enzymes, such as cathepsin B, which is overexpressed in certain cancer cells. This enables targeted drug delivery, minimizing off-target effects and enhancing therapeutic efficacy. Additionally, the Fmoc group provides temporary protection for the amine group during synthesis, ensuring precise control over peptide assembly. Its application is essential in advancing cancer therapeutics and other targeted drug delivery systems.