Cell-permeable. A protein tyrosine kinase (PTK) inhibitor.  targeting KIT that is active, orally bioavailable in vivo, and has low toxicity. Masitinib also potently inhibited recombinant PDGFR and the intracellular kinase Lyn, and to a lesser extent, fibroblast growth factor receptor 3. In contrast, masitinib demonstrated weak inhibition of ABL and c-Fms and was inactive against a variety of other tyrosine and serine/threonine kinases.