Preclinical pharmacokinetic and pharmacodynamic evaluation of metronomic and conventional temozolomide dosing regimens
ABSTRACT Metronomic dosed (MD) chemotherapy as opposed to conventional dosed (CD) chemotherapy is considered an alternate strategy to target angiogenesis and limit host toxicity. Although this approach is promising, there has not been any attempt to define optimal metronomic dosing regimens by integrating pharmacokinetic (PK) with pharmacodynamic (PD) measurements. The aim of this study was to compare the pharmacokinetics and pharmacodynamics of temozolomide [TMZ, 8-carbamoyl-3-methylidazo(5,1-d)-1,2,3,5-terrazin-4(3H)-one] after MD and CD regimens. In vivo studies were carried out in xenografted athymic rats treated with either 18 mg/kg/day TMZ for 5 days or 3.23 mg/kg/day TMZ for 28 days. PK studies were performed on the first and last days of dosing. PD measurements consisted of gene and protein expression of various angiogenic markers, tumor size, tumor pH, and interstitial fluid pressure (IFP). The results demonstrated that the PK parameters (total clearance, volume of distribution, and tumor/plasma accumulation) were quite similar for MD and CD groups, consistent with the linear PK properties of TMZ. Both TMZ treatment schedules caused a significant decrease in IFP and tumor size compared with vehicle control treatment, demonstrating comparable effectiveness of MD and CD regimens. Using real-time polymerase chain reaction and Western blot analyses, some differences were noted in expression levels of vascular endothelial growth factor and hypoxia inducible factor-1alpha, suggesting that the MD regimen may be superior to the CD regimen by preventing tumors from progressing to a proangiogenic state. In conclusion, several PK/PD factors contributing to the antitumor activity of the MD TMZ therapy have been identified and form a foundation for further investigations of low-dose TMZ regimens.
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- "Fisher et al.  have shown that treatment of human GBM cells with TMZ activates stress mechanisms that include the angiogenesis-inducing proteins notably hypoxia-inducible factors such as HIF-1α and vascular endothelial growth factor (VEGF), leading therefore to proangiogenic signals . This is in contrast to previous antiangiogenic effects reported for the drug    . We recently demonstrated that TMZ increases galectin-1 expression in GBM cells both in vitro and in vivo  . "
ABSTRACT: The aims of the present work were to investigate the in vitro and in vivo antiangiogenic effects of chronic temozolomide treatment on various glioma models and to demonstrate whether bevacizumab (Avastin) increased the therapeutic benefits contributed by temozolomide in glioma. The expression levels of various antiangiogenic factors in four glioma cell lines were evaluated after chronic in vitro treatment with temozolomide by Western blot. Proliferation and migration assays were performed on human endothelial cells incubated with supernatants of glioma cells treated with and without temozolomide. Orthotopic glioma models were used to evaluate the antiangiogenic effects of temozolomide in vivo and the therapeutic benefits of different temozolomide treatment schedules used alone or in combination with bevacizumab. Temozolomide, a proautophagic and proapoptotic drug, decreased the expression levels of HIF-1alpha, ID-1, ID-2, and cMyc in the glioma models investigated, all of which playing major roles in angiogenesis and the switch to hypoxic metabolism. These changes could be, at least partly, responsible for the impairment of angiogenesis observed in vitro and in vivo. Moreover, combining bevacizumab with temozolomide increased the survival of glioma-bearing mice in comparison to each compound administered alone. In addition to the numerous mechanisms of action already identified for temozolomide, we report here that it also exerts antitumor effects by impairing angiogenic processes. We further emphasize that bevacizumab, which is an antiangiogenic drug with a different mechanism of action, could be useful in combination with temozolomide to increase the latter's therapeutic benefit in glioma patients.Neoplasia (New York, N.Y.) 01/2009; 10(12):1383-92. DOI:10.1593/neo.08928 · 5.40 Impact Factor
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ABSTRACT: Temozolomide is a novel cytotoxic agent for malignant gliomas. However, treatment failure occurs approximately in half of patients, and the optimal regimen in this setting has yet to be defined. In the present study, we assessed retrospectively the efficacy and toxicity of the combination of carboplatin and oral cyclophosphamide in temozolomide-resistant patients. We evaluated the medical records of 30 patients with malignant gliomas. After failure of temozolomide therapy, patients were treated with a combination of carboplatin and oral cyclophosphamide. Treatment consisted of intravenous carboplatin AUC 6 (based on the Calvert Formula) on day 1 and oral cyclophosphamide 75 mg/m2 daily on days 1 to 14, followed by 14 days of rest, with the treatment repeated every 4 weeks. All patients were evaluated for response and toxicity. The objective response rate was 30%, including 9 partial responses. Median time to disease progression and median overall survival was 7 months and 8 months, respectively. Clinically responsive patients had statistically significant longer progression-free survival and overall survival than unresponsive patients. Hematological side effects were commonly observed toxicities, with neutropenia the most frequent. Our data suggest that carboplatin and oral cyclophosphamide therapy is a convenient regimen after failure of temozolomide therapy in patients with malignant gliomas because of its activity, feasibility and tolerability. Further prospective studies are needed in this setting.Tumori 94(5):674-80. · 1.09 Impact Factor
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ABSTRACT: Prolonged, frequently administered low-dose metronomic chemotherapy (LDM) is being explored (pre)clinically as a promising antiangiogenic antitumor strategy. Although appealing because of a favorable side effect profile and mostly oral dosing, LDM involves new challenges different from conventional maximum tolerated dose chemotherapy. These include possible altered pharmacokinetic characteristics due to long-term drug exposure potentially resulting in acquired resistance and increased risk of unfavorable drug interactions. We therefore compared the antitumor and antivascular effects of LDM cyclophosphamide (CPA) given to mice that had been pretreated with either LDM CPA or normal saline, obtained blood 4-hydroxy-CPA (activated CPA) concentrations using either gas chromatography/mass spectrometry or liquid chromatography/tandem mass spectrometry in mice treated with LDM CPA, and measured hepatic and intratumoral activity of enzymes involved in the biotransformation of CPA and many other drugs [i.e., cytochrome P450 3A4 (CYP3A4) and aldehyde dehydrogenase]. Exposure of mice to LDM CPA for >or=8 weeks did not compromise subsequent activity of LDM CPA therapy, and biologically active 4-hydroxy-CPA levels were maintained during long-term LDM CPA administration. Whereas the effects on CYP3A4 were complex, aldehyde dehydrogenase activity was not affected. In summary, our findings suggest that acquired resistance to LDM CPA is unlikely accounted for by altered CPA biotransformation. In the absence of reliable pharmacodynamic surrogate markers, pharmacokinetic parameters might become helpful to individualize/optimize LDM CPA therapy. LDM CPA-associated changes of CYP3A4 activity point to a potential risk of unfavorable drug interactions when compounds that are metabolized by CYP3A4 are coadministered with LDM CPA.Molecular Cancer Therapeutics 08/2007; 6(8):2280-9. DOI:10.1158/1535-7163.MCT-07-0181 · 6.11 Impact Factor