Predictive factors of biochemical recurrence after radical prostatectomy for high-risk prostate cancer.

OBJECTIVE: To identify risk factors of biochemical recurrence after radical prostatectomy in high-risk patients. METHODS: A total of 191 high-risk prostate cancer patients according to the D'Amico classification treated with radical prostatectomy at a single institution between April 2000 and December 2013 were enrolled. The pathological evaluation including intraductal carcinoma of prostate was reassessed, and the clinical and pathological risk factors of biochemical recurrence were analyzed. RESULTS: The median follow up after radical prostatectomy was 49 months. The 5-year biochemical recurrence-free survival rate after radical prostatectomy in high-risk prostate cancer patients was 41.6%. Initial prostate-specific antigen, pathological Gleason score, seminal vesicle invasion, extraprostatic extension and intraductal carcinoma of the prostate were significantly associated with biochemical recurrence-free survival. The 5-year biochemical recurrence-free survival rates in patients with zero, one, two and three of these risk factors were 92.9%, 70.7%, 38.3% and 28.8%, respectively. In patients with four or more factors, the biochemical recurrence-free survival rate was 6.1% after 18 months. CONCLUSIONS: In D'Amico high-risk patients treated with radical prostatectomy, risk factors for biochemical recurrence can be identified. Patients with fewer risk factors have longer biochemical recurrence-free survival, even among these high-risk cases.

Substrate- and dose-dependent drug interactions with grapefruit juice caused by multiple binding sites on OATP2B1.

PURPOSE: OATP2B1-mediated grapefruit juice (GFJ)-drug interactions are substrate-dependent; for example, GFJ ingestion significantly reduces bioavailability of fexofenadine, but not pravastatin. In the present study, we aimed to establish whether this observation can be explained by the presence of multiple binding sites (MBS) on OATP2B1. METHODS: OATP2B1-mediated drug uptake was evaluated using a Xenopus oocyte expression system. Drug concentration was quantified by LC/MS/MS analysis. RESULTS: OATP2B1-mediated uptake of pravastatin and fexofenadine exhibited biphasic saturation kinetics, indicating the presence of MBS on OATP2B1. GFJ strongly inhibited pravastatin uptake mediated by the high-affinity site on OATP2B1, while no significant inhibition of the low-affinity site was observed. In contrast, high-affinity transport of fexofenadine was only modestly inhibited by GFJ, while significant inhibition of the low-affinity site was observed. Contribution analysis indicated that both drugs are transported via the low-affinity site on OATP2B1 at therapeutically relevant concentrations. These findings indicate that only fexofenadine is expected to interact with GFJ on OATP2B1 at therapeutic concentrations, in accordance with the clinical observations. CONCLUSION: Substrate- and dose-dependent GFJ-drug interactions mediated by OATP2B1 might be explained in terms of the presence of MBS: interaction occurs only when drug and GFJ components share the same binding site on OATP2B1.

Long-lasting inhibitory effect of apple and orange juices, but not grapefruit juice, on OATP2B1-mediated drug absorption.

Enzyme-based grapefruit juice (GFJ)-drug interactions are mainly due to mechanism-based irreversible inhibition of metabolizing enzyme CYP3A4 by GFJ components, but the transporter organic anion transporting polypeptide (OATP)2B1 is also a putative site of interaction between drugs and fruit juices (FJ) in the absorption process. Here we aimed to investigate the effect of preincubation with FJ on OATP2B1-mediated transport of drugs in vitro. When OATP2B1-expressing Xenopus oocytes were preincubated with GFJ, orange juice (OJ), or apple juice (AJ), AJ induced a remarkable decrease in OATP2B1-mediated estrone-3-sulfate uptake in a concentration-dependent manner (IC(50) = 1.5%). A similar but less potent effect was observed with OJ (IC(50) = 21%), whereas GFJ had no effect. Similar results were obtained in preincubation studies using fexofenadine. Preincubation with OJ and AJ resulted in time-dependent inhibition of OATP2B1. Again, AJ had the more potent effect; its action lasted for at least 240 minutes, suggesting that AJ irreversibly inhibits OATP2B1-mediated drug uptake. Kinetic analysis revealed that coincubation and preincubation with AJ reduced OATP2B1-mediated estrone-3-sulfate uptake via competitive and noncompetitive mechanisms, respectively. Thus, OATP2B1 is functionally impaired through both competitive and long-lasting inhibition mechanisms by AJ and OJ, but not GFJ. Interestingly, although GFJ but not AJ is able to irreversibly inhibit CYP3A4, in the case of OATP2B1, AJ but not GFJ has a long-lasting inhibitory effect. Accordingly, complex FJ-drug interactions may occur in vivo, and their clinical significance should be examined.

In Vitro to In Vivo Extrapolation Linked to Physiologically Based Pharmacokinetic Models for Assessing the Brain Drug Disposition.

Drug development for the central nervous system (CNS) is a complex endeavour with low success rates, as the structural complexity of the brain and specifically the blood-brain barrier (BBB) poses tremendous challenges. Several in vitro brain systems have been evaluated, but the ultimate use of these data in terms of translation to human brain concentration profiles remains to be fully developed. Thus, linking up in vitro-to-in vivo extrapolation (IVIVE) strategies to physiologically based pharmacokinetic (PBPK) models of brain is a useful effort that allows better prediction of drug concentrations in CNS components. Such models may overcome some known aspects of inter-species differences in CNS drug disposition. Required physiological (i.e. systems) parameters in the model are derived from quantitative values in each organ. However, due to the inability to directly measure brain concentrations in humans, compound-specific (drug) parameters are often obtained from in silico or in vitro studies. Such data are translated through IVIVE which could be also applied to preclinical in vivo observations. In such exercises, the limitations of the assays and inter-species differences should be adequately understood in order to verify these predictions with the observed concentration data. This report summarizes the state of IVIVE-PBPK-linked models and discusses shortcomings and areas of further research for better prediction of CNS drug disposition. Graphical abstract.