Joseph Schlessinger is currently the Chairman of the Department of Pharmacology and the William H. Prusoff Professor at Yale University School of Medicine. Schlessinger’s laboratory is pursuing research in field of signal transduction by receptor tyrosine kinases. Schlessinger showed how growth factor receptors with tyrosine kinase activity are activated by growth factor-induced receptor dimerization and how the signals are relayed intracellularly to regulate a variety of cellular processes. He also demonstrated that dysfunction of receptor tyrosine kinases cause various human cancers, such as those driven by mutations or amplification of the epidermal growth factor (EGF) receptor gene. The assembly of signaling molecules by activated EGF receptors serves as a prototype for interactions between different protein modules crucial for the control of every aspect of signal transduction. These studies provided the conceptual foundation for development of a new class of targeted cancer therapies directed against receptor tyrosine kinases and other kinases, leading to the discovery of a series of successful cancer drugs. To date 20 tyrosine kinase and other kinase inhibitors have been approved by FDA for clinical use in the treatment of cancer included three drugs developed by two companies that were co-founded by Schlessinger.