KIT and mastocytosis: An in vitro assay has shown that masitinib inhibits WT KIT (IC50 200 nm) with greater potency compared with D816V KIT (IC50 5.0 μm) (42) and has demonstrated activity in a phase II study of patients with systemic or cutaneous mastocytosis who had at least two organs confirmed to have mast cell infiltration, one or both of which had to have no detectable mutations in KIT (43).