WHI-P258 is primarily used in research settings as a selective inhibitor of the JAK3 kinase enzyme. It plays a significant role in studying cellular signaling pathways, particularly those involved in immune system regulation. Researchers utilize WHI-P258 to investigate the effects of JAK3 inhibition on lymphocyte development and function, which can provide insights into autoimmune diseases and potential therapeutic strategies. Additionally, it is employed in preclinical studies to explore its efficacy in modulating immune responses and its potential application in treating conditions like rheumatoid arthritis and other inflammatory disorders.