KIT and mastocytosis: In contrast to clinical data in mastocytosis patients treated with other TKIs such as imatinib, the response rate to midostaurin in D816V-positive AdvSM was even higher than that found in patients with wild-type KIT or unknown KIT mutational status (63% vs. 44%), which is consistent with the results of prior in vitro investigations showing that midostaurin potently inhibits the imatinib-resistant D816V- and D816Y-mutated KIT forms (Gleixner, 2006).