Dasatinib (BMS-354825) inhibits KITD816V, an imatinib-resistant activating mutation that triggers neoplastic growth in most patients with systemic mastocytosis

Abstract

Mastocytosis is associated with an activating mutation in the KIT oncoprotein (KIT D816V ) that results in autophosphorylation of the KIT receptor in a ligandindependent manner. This mutation is inherently resistant to imatinib and, to date, there remains no effective curative therapy for systemic mastocytosis associated with KIT D816V . Dasatinib (BMS-354825) is a novel orally bioavailable SRC/ ABL inhibitor that has activity against multiple imatinib-resistant BCR-ABL isoforms in vitro that is presently showing considerable promise in early-phase clinical trials of chronic myeloid leukemia (CML). Pharmacokinetic analysis suggests that high nanomolar concentrations of dasatinib can be achieved safely in humans. In this study, we demonstrate significant inhibitory activity of dasatinib against both wild-type KIT and the KIT D816V mutation in the nanomolar range in in vitro and cell-based kinase assays. Additionally, dasatinib leads to growth inhibition of a KIT D816V -harboring human mastocytosis cell line. Significantly, dasatinib selectively kills primary neoplastic bone marrow mast cells from patients with systemic mastocytosis while sparing other hematopoietic cells. Computer modeling suggests that the KIT D816V mutation destabilizes the inactive conformation of the KIT activation loop to which imatinib binds, but it is not predicted to impair binding of KIT IntroductionSystemic mastocytosis and mast-cell leukemia are relatively rare conditions that are characterized by a pathologic accumulation of mast cells in various tissues. 1 Previous work has demonstrated the clonal nature of the disorder as evidenced by an activating point mutation in the KIT receptor tyrosine kinase. 2,3 This mutation, KIT D816V , occurs near the activation loop of the kinase and can be identified in more than 80% of systemic mastocytosis cases and thus represents an attractive target for this disorder, for which few effective therapeutic options exist. 1 Although a small molecule tyrosine kinase inhibitor of KIT, imatinib mesylate, has been available to patients recently, both preclinical and clinical studies have demonstrated convincingly that the KIT D816V mutation is inherently resistant to imatinib. [4][5][6] The crystal structure of the wild-type KIT kinase domain has been solved in an autoinhibited state, with the activation loop of the kinase in a closed conformation, 7 similar to the cocrystal structure of imatinib bound to the ABL kinase domain. 7,8 These structural studies suggest that substitution of valine for aspartic acid at position 816 in KIT may alter the conformation of the activation loop and thus prevent imatinib from efficiently binding to KIT D816V .Inhibition of KIT D816V has thus become the focus of recent studies aiming to find a curative therapy for mast-cell disease, and several potential drug candidates with an ability to inhibit KIT D816V have been identified. [9][10][11][12][13][14][15] Dasatinib (BMS-354825) is a novel, potent, oral, multitargeted kinase inhibitor that targets ABL, SRC, KIT, PDGFR, ...

Target interaction profiling of midostaurin and its metabolites in neoplastic mast cells predicts distinct effects on activation and growth

“…During the past few years, several promising new drugs, potentially useful as cytoreductive agents in ASM and MCL, have been developed and tested in preclinical studies. One of these agents is the multi-kinase blocker midostaurin (20)(21)(22)(23)(24). However, although mediator-related symptoms often improve, hematologic responses are usually short-lived (20,24,30).…”

“…A novel promising strategy is to use KIT-targeting tyrosine kinase inhibitors (TKI) (19)(20)(21)(22)(23)(24)(25). However, the KIT D816V mutant is resistant against several of these TKI, including imatinib (21,25,26).…”

Systemic mastocytosis in adults: 2015 update on diagnosis, risk stratification, and management

“…1) Dasatinib has shown efficacy in vitro against various KIT mutants including D816V [112,113]. Furthermore, dasatinib may synergize with PKC412 and chemotherapy in this regard [114][115][116].…”

The Antitumor Activity of Homoharringtonine against Human Mast Cells Harboring the KIT D816V Mutation

“…Hence, novel strategies or compounds to override this resistance are needed. Small-molecule compounds PKC412 (6), dasatinib (12), and EXEL-0862 (13) have recently been shown to kill human mast cells expressing D816V KIT, clinical trials of PKC412 and dasatinib are going on in patients with aggressive SM (ASM)/ mast cell leukemia (MCL), whereas the long-term clinical benefit has not yet been determined. Lowering the expression of oncoprotein KIT that is essential for tumorigenesis by heat shock protein 90 inhibitor 17-allylamino-17-demethoxygeldanamycin, transcription inhibitor flavopiridol, and triptolide was recently found to be an effective strategy (14)(15)(16).…”

“…HMC-1.1 and HMC-1.2 differ only in the presence of the D816V mutation, making them ideal models for the study of novel agents against this mutation. The murine P815 mastocytoma cell line, which harbors the homologous D814Y mutation (4), is also relatively resistant to imatinib (12,29). The cells were monitored every month for the presence of the point mutations as previously described (4,12).…”