Relative bioavailability of a newly developed 5-mg levomethadone hydrochloride IR tablet (L-Polamidon® 5 mg tablets) in comparison with the 5-mg levomethadone hydrochloride oral solution (L-Polamidon® solution for substitution) as reference product.

OBJECTIVES: To establish the relative bioavailability (rBA) between two p.o. 5-mg levomethadone hydrochloride formulations, i.e., L-Polamidon® 5 mg tablets (test) vs. L-Polamidon® solution for substitution (reference). To assess the safety and tolerability of both formulations. SUBJECT AND METHODS: A total of 33 healthy male subjects, aged 29 ± 6 years (BMI: 23.9 ± 2.5 kg/m2) completed this single center, open-label, randomized, 2-period cross-over study with single dose administrations under fasting conditions and coadministration with naltrexone for safety reasons. Administrations of both investigational products were separated by a washout period of at least 2 weeks, i.e., 13 treatmentfree days. The total dose for each subject was 2 x 5 mg resulting in 10 mg levomethadone hydrochloride. For pharmacokinetic evaluation, blood samples were withdrawn until 72 hours postdose. A validated non-stereoselective liquid chromatography-tandem mass spectroscopy method (LC-MS/MS) was applied for the determination of levomethadone in plasma. The lower limit of quantitation was 0.100 ng/mL. Adverse events were descriptively analyzed in the study population. RESULTS: The geometric means of the parameters related with the extent of total exposure of levomethadone, i.e., AUC(0-tlast) and AUC(0-∞), were 244.422 ng x h/mL and 332.999 ng x h/mL for test and 246.837 ng x h/mL and 329.467 ng×h/mL for reference, respectively. The geometric means of the peak exposure for levomethadone, i.e., Cmax, were 8.923 ng/mL for test and 8.635 ng/mL for reference. The point estimates (PEs) of the Test/Reference (T/R) adjusted geometric mean ratios of AUC(0-last), AUC(0-∞), and C(max) were 99.20%, 101.42%, and 104.11%, respectively, and all of them showed 90%-confidence intervals (CIs) within the range of 80.00 - 125.00% as suggested by regulatory requirements for bioequivalence assessment In total, 21 subjects experienced 55 AEs during the study, the most frequently reported AE, i.e., headache, accounted for 13 out of the total 55 AEs (23.6%) and no AEs of severe intensity were reported. CONCLUSIONS: Bioequivalence could be demonstrated in terms of rate and extent of absorption after administration of test and reference products under naltrexone protection. Concerning the safety evaluation, no negative implications on the possible use of the test formulation could be determined.

Genetic evidence for a tumor suppressor role of HIF-2alpha.

The hypoxia-inducible transcription factors HIF-1alpha and HIF-2alpha are activated in hypoxic tumor regions. However, their role in tumorigenesis remains controversial, as tumor growth promoter and suppressor activities have been ascribed to HIF-1alpha, while the role of HIF-2alpha remains largely unknown. Here, we show that overexpression of HIF-2alpha in rat glioma tumors enhances angiogenesis but reduces growth of these tumors, in part by increasing tumor cell apoptosis. Moreover, siRNA knockdown of HIF-2alpha reduced apoptosis in hypoxic human malignant glioblastoma cells. Furthermore, inhibition of HIF by overexpression of a dominant-negative HIF transgene in glioma cells or HIF-2alpha deficiency in teratomas reduced vascularization but accelerated growth of these tumor types. These findings urge careful consideration of using HIF inhibitors as cancer therapeutic strategies.

Cooperative interaction of hypoxia-inducible factor-2alpha (HIF-2alpha ) and Ets-1 in the transcriptional activation of vascular endothelial growth factor receptor-2 (Flk-1).

Interactions between Ets family members and a variety of other transcription factors serve important functions during development and differentiation processes, e.g. in the hematopoietic system. Here we show that the endothelial basic helix-loop-helix PAS domain transcription factor, hypoxia-inducible factor-2alpha (HIF-2alpha) (but not its close relative HIF-1alpha), cooperates with Ets-1 in activating transcription of the vascular endothelial growth factor receptor-2 (VEGF-2) gene (Flk-1). The receptor tyrosine kinase Flk-1 is indispensable for angiogenesis, and its expression is closely regulated during development. Consistent with the hypothesis that HIF-2alpha controls the expression of Flk-1 in vivo, we show here that HIF-2alpha and Flk-1 are co-regulated in postnatal mouse brain capillaries. A tandem HIF-2alpha/Ets binding site was identified within the Flk-1 promoter that acted as a strong enhancer element. Based on the analysis of transgenic mouse embryos, these motifs are essential for endothelial cell-specific reporter gene expression. A single HIF-2alpha/Ets element conferred strong cooperative induction by HIF-2alpha and Ets-1 when fused to a heterologous promoter and was most active in endothelial cells. The physical interaction of HIF-2alpha with Ets-1 was demonstrated and localized to the HIF-2alpha carboxyl terminus and the autoinhibitory exon VII domain of Ets-1, respectively. The deletion of the DNA binding and carboxyl-terminal transactivation domains of HIF-2alpha, respectively, created dominant negative mutants that suppressed transactivation by the wild type protein and failed to synergize with Ets-1. These results suggest that the interaction between HIF-2alpha and endothelial Ets factors is required for the full transcriptional activation of Flk-1 in endothelial cells and may therefore represent a future target for the manipulation of angiogenesis.