The Combination of Metformin and Valproic Acid Has a Greater Anti-tumoral Effect on Prostate Cancer Growth In Vivo than Either Drug Alone.

BACKGROUND/AIM: The hypoglycemic drug metformin (MET) and the anti-epileptic drug valproic acid (VPA) have individually shown anti-tumor effects in prostate cancer in vitro. The present study intended to investigate the efficacy of the combination of MET and VPA in prostate cancer treatment in a pre-clinical xenograft model. MATERIALS AND METHODS: Prostate cancer cell lines (LNCaP and PC-3) were inoculated under the skin of BALB/c nude mice. The mice were treated with 200 µl/ml MET and/or 0.4% (w/v) VPA diluted in drinking water, or with vehicle control, and were monitored until the tumor volume reached 2,000 mm3 Evaluation of toxicity of the drug combination was determined in liver and kidney by histology. RESULTS: In both LNCaP and PC-3 xenografts, MET combined with VPA significantly reduced tumor growth during the first 4 weeks following treatment, and delayed the time-to-tumor volume of 2,000 mm3 by 90 days, as compared to MET or to VPA alone, and to vehicle control. There was no significant difference in total mouse weight, liver or kidney morphology in response to combination treatment (MET+VPA) compared to MET or VPA alone and vehicle control. CONCLUSION: The combination treatment of MET with VPA is more effective at slowing prostate tumor growth in vivo compared to either drug alone, in mouse xenografts. These pre-clinical results support previous in vitro data and also demonstrate the low toxicity of the combination of these drugs, suggesting that this may be a potential new therapy to be investigated in clinical trials for prostate cancer.

Phase I study of BNC105P, carboplatin and gemcitabine in partially platinum-sensitive ovarian cancer patients in first or second relapse (ANZGOG-1103).

PURPOSE: The primary objective of this study was to determine the recommended dose of the vascular disrupting agent, BNC105P, in combination with gemcitabine and carboplatin in patients with ovarian cancer in first or second relapse with a minimum 4 month progression-free interval after last platinum. METHODS: Patients received carboplatin AUC4 on day 1 in combination with escalating doses of 800 or 1000 mg/m2 gemcitabine on days 1 and 8 and escalating doses of 12 or 16 mg/m2 BNC105P on days 2 and 9 every 21 days for a maximum for six cycles. Maintenance treatment with 16 mg/m2 BNC105P treatment continued for a maximum of six additional cycles. Patients were followed for safety and anti-tumor activity. RESULTS: Fifteen patients were enrolled in the study. Adverse events were most commonly of hematological origin. Dose-limiting toxicities (thrombocytopenia and neutropenia) occurred in two patients at the dose level of 800 mg/m2 gemcitabine, carboplatin AUC4 and 16 mg/m2 BNC105P. No dose-limiting toxicities were observed at a dose level of gemcitabine 1000 mg/m2, carboplatin AUC4 and BNC105P 12 mg/m2. BNC105P as a single agent was well tolerated at a dose of 16 mg/m2 in maintenance treatment. Ten patients (67%) achieved a complete or partial response according to CA125 and/or RECIST response criteria, four of 13 (31%) responded by RECIST alone. The median progression-free survival was 5.9 months. CONCLUSIONS: We have established that BNC105P 12 mg/m2 with gemcitabine 1000 mg/m2 and carboplatin AUC4 is the recommended dose level and has an acceptable toxicity profile. Further exploration of BNC105P in the ovarian cancer setting is planned.

The vascular disrupting agent BNC105 potentiates the efficacy of VEGF and mTOR inhibitors in renal and breast cancer.

BNC105 is a tubulin targeting compound that selectively disrupts vasculature within solid tumors. The severe tumor hypoxia and necrosis that ensues translates to short term tumor growth inhibition. We sought to identify the molecular and cellular events activated following BNC105 treatment that drives tumor recovery. We investigated tumor adaptation to BNC105-induced hypoxia in animal models of breast and renal cancer. HIF-1α and GLUT-1 were found to be strongly upregulated by BNC105 as was the VEGF signaling axis. Phosphorylation of mTOR, 4E-BP-1 and elF2α were upregulated, consistent with increased protein synthesis and increased expression of VEGF-A. We sought to investigate the potential therapeutic utility of combining BNC105 with agents targeting VEGF and mTOR signaling. Bevacizumab and pazopanib target the VEGF axis and have been approved for first line use in renal cancer. Everolimus targets mTOR and is currently approved in second line therapy of renal and particular breast cancers. We combined these agents with BNC105 to explore the effects on tumor vasculature, tumor growth inhibition and animal survival. Bevacizumab hindered tumor vascular recovery following BNC105 treatment leading to greater tumor growth inhibition in a breast cancer model. Consistent with this, addition of BNC105 to pazopanib treatment resulted in a significant increase in survival in an orthotopic renal cancer model. Combination treatment of BNC105 with everolimus also increased tumor growth inhibition. BNC105 is currently being evaluated in a randomized phase II clinical trial in combination with everolimus in renal cancer.

Discovery of 7-hydroxy-6-methoxy-2-methyl-3-(3,4,5-trimethoxybenzoyl)benzo[b]furan (BNC105), a tubulin polymerization inhibitor with potent antiproliferative and tumor vascular disrupting properties.

A structure-activity relationship (SAR) guided design of novel tubulin polymerization inhibitors has resulted in a series of benzo[b]furans with exceptional potency toward cancer cells and activated endothelial cells. The potency of early lead compounds has been substantially improved through the synergistic effect of introducing a conformational bias and additional hydrogen bond donor to the pharmacophore. Screening of a focused library of potent tubulin polymerization inhibitors for selectivity against cancer cells and activated endothelial cells over quiescent endothelial cells has afforded 7-hydroxy-6-methoxy-2-methyl-3-(3,4,5-trimethoxybenzoyl)benzo[b]furan (BNC105, 8) as a potent and selective antiproliferative. Because of poor solubility, 8 is administered as its disodium phosphate ester prodrug 9 (BNC105P), which is rapidly cleaved in vivo to return the active 8. 9 exhibits both superior vascular disrupting and tumor growth inhibitory properties compared with the benchmark agent combretastatin A-4 disodium phosphate 5 (CA4P).

BNC105: a novel tubulin polymerization inhibitor that selectively disrupts tumor vasculature and displays single-agent antitumor efficacy.

Vascular disruption agents (VDA) cause occlusion of tumor vasculature, resulting in hypoxia-driven tumor cell necrosis. Tumor vascular disruption is a therapeutic strategy of great potential; however, VDAs currently under development display a narrow therapeutic margin, with cardiovascular toxicity posing a dose-limiting obstacle. Discovery of new VDAs, which display a wider therapeutic margin, may allow attainment of improved clinical outcomes. To identify such compounds, we used an in vitro selectivity screening approach that exploits the fact that tumor endothelial cells are in a constant state of activation and angiogenesis and do not undergo senescence. Our effort yielded the compound BNC105. This compound acts as a tubulin polymerization inhibitor and displays 80-fold higher potency against endothelial cells that are actively proliferating or are engaged in the formation of in vitro capillaries compared with nonproliferating endothelial cells or endothelium found in stable capillaries. This selectivity was not observed with CA4, a VDA currently under evaluation in phase III clinical trials. BNC105 is more potent and offers a wider therapeutic window. CA4 produces 90% vascular disruption at its no observed adverse event level (NOAEL), whereas BNC105 causes 95% vascular disruption at 1/8th of its NOAEL. Tissue distribution analysis of BNC105 in tumor-bearing mice showed that while the drug is cleared from all tissues 24 hours after administration, it is still present at high concentrations within the solid tumor mass. Furthermore, BNC105 treatment causes tumor regressions with complete tumor clearance in 20% of treated animals.

Discovery and validation of drug targets for tumour angiogenesis.

The formation of blood vessels is a key process in the progression of solid tumours, providing the means for tumour growth and metastasis. A number of drugs are currently being developed to exploit inhibition of angiogenesis in the therapy of cancer. An even greater number of genes that are regulated in models of in vitro angiogenesis have been identified. These genes present potential drug targets for the development of novel, more efficient, drugs that will enable the judicious design of drug cocktails that may be able to account for the many different cancer pathologies and their drug resistance properties. Dealing with the validation of hundreds of potential angiogenesis drug targets requires the utilisation of experimental technology platforms that enable concomitant and dynamic target selection filtering and validation. Such platforms should act as a funnel-like medium-to-low throughput processes that enable the sequential short-listing of hundreds of candidates culminating in the selection of only a small number of well-validated targets that are manageable by drug screening regimes.

Effects of the insecticide amitraz, an alpha2-adrenergic receptor agonist, on human luteinized granulosa cells.

BACKGROUND: Amitraz, an insecticide used to prevent tick and mite infestation of cattle, crops and dogs, is an alpha2-adrenergic receptor agonist that inhibits GnRH release and the ovulatory LH surge in rats. Noradrenalin, the physiological ligand for adrenergic receptors, inhibits progesterone production by IVF-derived granulosa cells, but the effects of amitraz are unknown. METHODS: Luteinized granulosa cells obtained from women undergoing ovarian stimulation were exposed to amitraz (1, 10, 50, 100 microg/ml) for 2-72 h, and to amitraz (50 microg/ml) +/- hCG or the specific alpha2-adrenergic receptor antagonist yohimbine, for 6 h. Cell numbers were determined by 3-(4, 5-dimethylthiazol-(2)-yl)-2, 5-diphenyl tetrazolium bromide(MTT) assay and hormone production by radioimmunoassay. RESULTS: Amitraz 10 microg/ml did not affect cell numbers or estrogen production, but reduced progesterone production to 58 +/- 8% (p < 0.01, 24 h, n = 6) of control values. Amitraz (100 microg/ml) was cytotoxic and caused a corresponding reduction in hormone production. Amitraz 50 microg/ml did not affect cell numbers or estrogen production, but reduced progesterone per cell production to 82 +/- 6% of control values after 6 h. This was prevented by 0.2 mmol/l yohimbine. Exposure to amitraz 50 microg/ml for 6 h exposure abolished hCG-stimulated progesterone production but not estrogen production. CONCLUSIONS: Amitraz inhibited basal and hCG-stimulated progesterone but not estrogen production. The inhibitory action of amitraz and its antagonism by yohimbine suggest that alpha2-adrenergic receptors are expressed by luteinized human granulosa cells.