KIT and systemic mastocytosis: Greater than 80% of the patients with SM have a KIT D816V mutation which drives the disease.27 Midostaurin, a multikinase small molecule inhibitor has been shown to have in vitro activity against D816V KIT mutants.28 The results of an open-label phase 2 study (CPKC412D2201) using midostaurin in patients with ASM were promising; the overall response rate was 60%, with 45% of the patients demonstrating complete resolution of mastocytosis-related damage in at least one organ system.