Tyrphostin 9 is a synthetic inhibitor of protein tyrosine kinase (PTK) that displays characteristics of a potent reversible inhibitor of platelet-derived growth factor (PDGF)-induced mitogenesis via inhibition of tyrosine kinase activity of the PDGFR (PDGF receptor) and other signaling cascades. These studies suggest that Tyrphostin 9 could potentially be used to inhibit cell proliferations which depend on protein tyrosine kinase for replication. This compound was also reported to inhibit actin ring formation and bone resorption in murine osteoclasts. Tyrphostin A9 is a calcium channel protein inhibitor of Calcium Channel Protein (calcium release-activated calcium (CRAC) channels)