[show abstract][hide abstract] ABSTRACT: Patients with systemic mastocytosis (SM) can suffer from disabling symptoms related to mast cell mediator release or mast cell infiltration, requiring mast cell eradication. In the present absence of any curative therapy, a recent case report describing the efficacy of cladribine showed promising results. In a pilot study, the efficacy of cladribine (0.10-0.13 mg/kg in a 2-hour infusion, days 1-5; repeated at 4-8 weeks until 6 cycles) was studied. Ten patients with SM with severe symptoms were treated. Four patients were classified as having indolent or smoldering mastocytosis, 3 as having aggressive systemic mastocytosis, and 3 as having SM with an accompanying hematologic malignancy. Nine patients received 6 courses, 1 patient stopped because of toxicodermia. All responded concerning signs, symptoms, and mast cell parameters (serum tryptase and urinary histamine metabolite excretion), although none achieved a complete remission. Prolonged follow-up is required, as response is ongoing in most cases. One patient relapsed within 11 months and showed a second response. Side effects were mainly related to bone marrow suppression. Single-agent cladribine is an effective and relatively safe treatment for severe systemic mastocytosis. The optimal dose and schedule need to be explored.
[show abstract][hide abstract] ABSTRACT: Mutations of c-KIT causing spontaneous activation of the KIT receptor kinase are associated with sporadic adult human mastocytosis (SAHM) and with human gastrointestinal stromal tumors. We have classified KIT-activating mutations as either "enzymatic site" type (EST) mutations, affecting the structure of the catalytic portion of the kinase, or as "regulatory" type (RT) mutations, affecting regulation of an otherwise normal catalytic site. Using COS cells expressing wild-type or mutant KIT, 2 compounds, STI571 and SU9529, inhibited wild-type and RT mutant KIT at 0.1 to 1 microM but did not significantly inhibit the Asp816Val EST mutant associated with SAHM, even at 10 microM. Using 2 subclones of the HMC1 mast cell line, which both express KIT with an identical RT mutation but which differ in that one also expresses the Asp816Val EST mutation, both compounds inhibited the RT mutant KIT, thereby suppressing proliferation and producing apoptosis in the RT mutant-only cell line. Neither compound suppressed activation of Asp816Val EST mutant KIT, and neither produced apoptosis or significantly suppressed proliferation of the cell line expressing the Asp816Val mutation. These studies suggest that currently available KIT inhibitors may be useful in treating neoplastic cells expressing KIT activated by its natural ligand or by RT activating mutations such as gastrointestinal stromal tumors but that neither compound is likely to be effective against SAHM. Furthermore, these results help establish a general paradigm whereby classification of mutations affecting oncogenic enzymes as RT or EST may be useful in predicting tumor sensitivity or resistance to inhibitory drugs.
[show abstract][hide abstract] ABSTRACT: Imatinib has shown to be effective against malignant disease driven by ckit. We prospectively treated 12 adults with symptomatic systemic mast-cell disease at a dose of either 100 mg or 400 mg per day. Of the ten patients who we could assess for response, five (50%) had a measurable response to the drug, four of whom had important mast-cell cytoreduction and two who had complete clinical and histological remission. In the five patients with eosinophilia, three had complete clinical and haematological remission. The other two, who did not respond to treatment, were the only patients with the ckit D816V mutation. Our results suggest that imatinib either inhibits the growth-promoting role of wild type ckit, or targets an oncogenic kinase.
The Lancet 09/2003; 362(9383):535-6. · 39.06 Impact Factor
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