Cl-amidine is primarily used as a potent and selective inhibitor of protein arginine deiminases (PADs), a family of enzymes involved in post-translational modifications through citrullination. This compound is widely applied in biochemical and biomedical research to study the role of PAD enzymes in various cellular processes and disease mechanisms. It has been instrumental in investigating conditions such as rheumatoid arthritis, multiple sclerosis, and certain cancers, where abnormal citrullination is implicated. Due to its cell permeability and stability, Cl-amidine is used in cell-based assays and animal models to modulate PAD activity and assess therapeutic potential. Its application supports the development of targeted therapies aimed at PAD-related pathologies.