Cl-amidine is primarily used in research settings as a potent and selective inhibitor of protein arginine deiminases (PADs), particularly PAD4. It plays a significant role in studying the function of PAD enzymes in various biological processes, including gene regulation, immune response, and the development of certain diseases such as rheumatoid arthritis and cancer. By inhibiting PAD activity, it helps researchers understand the role of citrullination in autoimmune disorders and other pathological conditions. Additionally, it is explored as a potential therapeutic agent for diseases where PAD overactivity is implicated, offering insights into targeted treatment strategies.