Topoisomerase I inhibitors in the treatment of primary CNS malignancies: an update on recent trends.
ABSTRACT High grade primary CNS gliomas hold some of the worst prognoses of any malignancy, with the vast majority of patients dying within two years of diagnosis, even with aggressive modern treatments. Surgical resection and radiotherapy are cornerstones of treatment when possible. In spite of many years of research, only recently has management with chemotherapy been able to prolong survival in patients with high grade gliomas, albeit only modestly at best. Topoisomerase I (TOP1) inhibitors target an enzyme critical for DNA replication and cell-cycle progression; they cross the blood-brain barrier and have antitumor activity against glioblastoma cells in vitro. The most frequently associated toxicities are neutropenia and diarrhea, but are often manageable. The two most used agents are irinotecan and topotecan. Due to enhanced cytochrome CY3A4/5 enzyme activity, irinotecan dose must be adjusted with concomitant enzyme-inducing antiepileptic drug usage; the data is less clear regarding the effects on topotecan. Clinical trials in patients with recurrent malignant glioma have evaluated TOP1 inhibitors as monotherapy and in combination with other agents. There is evidence for using topotecan with radiotherapy. Irinotecan has limited efficacy as monotherapy, but shows promise in combination with other agents, particularly temozolomide and bevacizumab. Newer generation TOP1 inhibitors are currently being evaluated in phase I trials. TOP1 inhibitors show promising activity in patients with primary CNS malignancies and warrant further study.
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ABSTRACT: PURPOSE: The current treatment strategies for glioblastoma have limited health and survival benefits for the patients. A common obstacle in the treatment is chemoresistance. A possible strategy to evade this problem may be to combine chemotherapeutic drugs with agents inhibiting resistance mechanisms. The aim with this study was to identify molecular pathways influencing drug resistance in glioblastoma-derived cells and to evaluate the potential of pharmacological interference with these pathways to identify synergistic drug combinations. METHODS: Global gene expressions and drug sensitivities to three chemotherapeutic drugs (imatinib, camptothecin and temozolomide) were measured in six human glioblastoma-derived cell lines. Gene expressions that correlated to drug sensitivity or resistance were identified and mapped to specific pathways. Selective inhibitors of these pathways were identified. The effects of six combinations of inhibitors and chemotherapeutic drugs were evaluated in glioblastoma-derived cell lines. Drug combinations with synergistic effects were also evaluated in non-cancerous epithelial cells. RESULTS: Four drug combinations had synergistic effects in at least one of the tested glioblastoma-derived cell lines; camptothecin combined with gefitinib (epidermal growth factor receptor inhibitor) or NSC 23766 (ras-related C3 botulinum toxin substrate 1 inhibitor) and imatinib combined with DAPT (Notch signaling inhibitor) or NSC 23766. Of these, imatinib combined with DAPT or NSC 23766 did not have synergistic effects in non-cancerous epithelial cells. Two drug combinations had at least additive effects in one of the tested glioblastoma-derived cell lines; temozolomide combined with gefitinib or PF-573228 (focal adhesion kinase inhibitor). CONCLUSION: Four synergistic and two at least additive drug combinations were identified in glioblastoma-derived cells. Pathways targeted by these drug combinations may serve as targets for future drug development with the potential to increase efficacy of currently used/evaluated chemotherapy.Cancer Chemotherapy and Pharmacology 06/2013; · 2.80 Impact Factor
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ABSTRACT: Various in-vitro chemosensitivity and resistance assays (CSRAs) have been demonstrated to be helpful decision aids for non-neurological tumors. Here, we evaluated the performance characteristics of two CSRAs for glioblastoma (GB) cells. The chemoresponse of fresh GB cells from 30 patients was studied in vitro using the ATP tumor chemoresponse assay and the chemotherapy resistance assay (CTR-Test). Both assay platforms provided comparable results. Of seven different chemotherapeutic drugs and drug combinations tested in vitro, treosulfan plus cytarabine (TARA) was the most effective, followed by nimustine (ACNU) plus teniposide (VM26) and temozolomide (TMZ). Whereas ACNU/VM26 and TMZ have proven their clinical value for malignant gliomas in large randomized studies, TARA has not been successful in newly diagnosed gliomas. This seeming discrepancy between in vitro and clinical result might be explained by the pharmacological behavior of treosulfan. Our results show reasonable agreement between two cell-based CSRAs. They appear to confirm the clinical effectiveness of drugs used in GB treatment as long as pharmacological preconditions such as overcoming the blood-brain barrier are properly considered.Anti-cancer drugs 01/2014; · 2.23 Impact Factor
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ABSTRACT: Background The aim of this study was to assess the objective response rate (ORR) of children and young adults with recurrent medulloblastoma/primitive neuroectodermal tumor (MB/PNET) treated with temozolomide (TMZ). The secondary purpose was to analyze the toxicity profile of TMZ when administered orally for 5 days in 3 divided daily doses every 28 days.Methods Forty-two patients with recurrent MB/PNET, aged 21 years and younger, were recruited. Patients were treated with oral TMZ. Starting doses ranged from 120 to 200 mg/m(2)/day based on previous treatments. A craniospinal MRI was performed prior to the first cycle of TMZ and following every 2 cycles of treatment.ResultsMedian age was 10 years (range, 2-21 years). Forty of 42 patients were assessed for response and toxicity. The objective response rate was 42.5%: 6 patients achieved a complete response, 11 had a partial response, and 10 had stable disease. Progression-free survival rates for all patients at 6 and 12 months were 30% and 7.5%, respectively. Their median overall survival rates at 6 and 12 months were 42.5% and 17.5%, respectively. No major extrahematological effects or life-threatening events were reported. The most common grade 3/4 toxicity included thrombocytopenia (17.5%), neutropenia (7.5%), and anemia (2.5%).ConclusionsTMZ proved to be an effective agent in children and young adults with MB/PNET, heavily pre-treated, with a tolerable toxicity profile.Neuro-Oncology 01/2014; · 5.29 Impact Factor