AG-490, also known as Tyrphostin B42, is primarily used in research settings as a selective inhibitor of the JAK2 tyrosine kinase. It is widely employed in studies focused on understanding cellular signaling pathways, particularly those involving the JAK-STAT pathway, which plays a critical role in immune response, cell growth, and differentiation. Researchers use AG-490 to investigate its potential in suppressing abnormal cell proliferation, making it a valuable tool in cancer research, especially for hematologic malignancies like leukemia and lymphoma. Additionally, it is utilized in studies exploring inflammatory diseases and autoimmune disorders, where JAK2 signaling is implicated. Its ability to modulate these pathways provides insights into therapeutic strategies targeting specific kinase activities.