JAK3-IN-1 is primarily used in research settings to study the role of JAK3 kinase in cellular signaling pathways. It is a selective inhibitor, making it valuable for investigating the function of JAK3 in immune cell regulation and its involvement in autoimmune diseases, such as rheumatoid arthritis and psoriasis. Researchers utilize this compound to explore potential therapeutic targets for conditions driven by JAK3 activity. Additionally, it aids in understanding the mechanisms of JAK-STAT signaling, which is critical in immune responses and hematopoiesis. Its application extends to preclinical studies aimed at developing novel treatments for JAK3-related disorders.