JAK3-IN-9 is a potent and orally active inhibitor of the Janus kinase 3 (JAK3) enzyme, displaying an impressive IC50 value of 1.7 nM. It exhibits high selectivity towards the JAK3 signaling pathway, making it a valuable tool for studying autoimmune diseases. Additionally, JAK3-IN-9 possesses desirable characteristics such as low toxicity and excellent oral bioavailability. It also demonstrates promising anti-arthritis activity, thus enhancing its potential as a therapeutic agent [1].