Ketoconazole and the modulation of multidrug resistance-mediated transport in Caco-2 and MDCKII-MDR1 drug transport models

Impact of Composition and Morphology of Ketoconazole-Loaded Solid Lipid Nanoparticles on Intestinal Permeation and Gastroplus-Based Prediction Studies

Ketoconazole (KTZ) is a potential oral antifungal agent to control systemic and local infections. This study addresses the impact of composition (tween 80 and compritol as CATO) and morphology on permeation (stomach, jejunum, and ileum) profiles of KTZ-loaded solid lipid nanoparticles (SLNs) in rats followed by in vivo pharmacokinetic prediction and simulation using GastroPlus. The selected formulations were characterized for size, size distribution, zeta potential, entrapment efficiency, total drug content, morphology, in vitro drug release, ex vivo permeation and drug deposition, penetration potential, and GastroPlus-based in vivo prediction in rats. The results showed that there was considerable impact of pH, composition (CATO and tween 80), size, total drug content, and entrapment efficiency on in vitro drug release and permeation across the stomach, jejunum, and ileum. Ex vivo findings suggested pH, composition, size, and permeability coefficient-dependent permeation of SLNs across the stomach, jejunum, and ileum. Confocal laser scanning microscopy (CLSM) confirmed a relatively high degree of penetration of the optimized formulation "K-SLN4" (66.1% across the stomach, 51.5% across the jejunum, and 47.9% across the ileum) as compared to KSUS (corresponding values of 21.7%, 18.2%, and 17.4%). Finally, GastroPlus predicted in vivo dissolution/absorption as 0.012 μg/mL of K-SLN4 as compared to KSUS (the drug suspension with 0.0058 μg/mL) and a total regional absorption of 80.0% by K-SLN4 as compared to 60.1% of KSUS. There was only an impact of dose on C _max (maximum plasma concentration) and area under the curve (AUC) in rats. Thus, the present strategy could be a promising alternative to parenteral and topical delivery systems for long-term therapy against systemic and local mycoses with high patient compliance.

Relevance of ABC Transporters in Drug Development

ATP-binding cassette (ABC) transporters play a critical role in protecting vital organs such as the brain and placenta against xenobiotics, as well as in modulating the pharmacological and toxicological profile of several drug candidates by restricting their penetration through cellular and tissue barriers. This review paper provides a description of the structure and function of ABC transporters as well as the role of P-glycoprotein, multidrug resistance-associated protein 2 and breast cancer resistance protein in the disposition of drugs. Furthermore, a review of the in vitro and in vivo techniques for evaluating the interaction between drugs and ABC transporters are provided.

Interactions between artemisinin derivatives and P-glycoprotein

BACKGROUND

Artemisinin was isolated and identified in 1972, which was the starting point for a new era in antimalarial drug therapy. Furthermore, numerous studies have demonstrated that artemisinin and its derivatives exhibit considerable anticancer activity both in vitro, in vivo, and even in clinical Phase I/II trials. P-glycoprotein (P-gp) mediated multi-drug resistance (MDR) is one of the most serious causes of chemotherapy failure in cancer treatment. Interestingly, many artemisinin derivatives exhibit excellent ability to overcome P-gp mediated MDR and even show collateral sensitivity against MDR cancer cells. Furthermore, some artemisinin derivatives show P-gp-mediated MDR reversal activity. Therefore, the interaction between P-gp and artemisinin derivatives is important to develop novel combination treatment protocols with artemisinin derivatives and established anticancer drugs that are P-gp substrates.

PURPOSE

This systematic review provides an updated overview on the interaction between artemisinin derivatives and P-gp and the effect of artemisinin derivatives on the P-gp expression level.

RESULTS

Artemisinin derivatives exhibit multi-specific interactions with P-gp. The currently used artemisinin derivatives are not transported by P-gp. However, some of novel synthetized artemisinin derivatives exhibit P-gp substrate properties. Furthermore, many artemisinin derivatives act as P-gp inhibitors, which exhibit the potential to reverse MDR towards clinically used anticancer drugs.

CONCLUSION

Therefore, studies on the interaction between artemisinin derivatives and P-gp provide important information for the development of novel anti-cancer artemisinin derivatives to reverse P-gp mediated MDR and for the design of rational artemisinin-based combination therapies against cancer.

Enhanced anti-metastatic and anti-tumorigenic efficacy of Berbamine loaded lipid nanoparticles in vivo

Research on metastasis is gaining momentum for effective cancer management. Berbamine (BBM) has the potency to act as a therapeutic in multiple cancers and cancer metastasis. However, the major limitation of the compound includes poor bioavailability at the tumor site due to short plasma half-life. Here, our major objective involved development of lipid based nanoparticles (NPs) loaded with BBM with an aim to circumvent the above problem. Moreover its, therapeutic potentiality was evaluated through various in vitro cellular studies and in vivo melanoma primary and experimental lung metastatic tumor model in C57BL/6 mice. Results of different cellular experiments demonstrated enhanced therapeutic efficacy of BBM-NPs in inhibiting metastasis, cell proliferation and growth as compared to native BBM in highly metastatic cancer cell lines. Further, in vivo results demonstrated suppression of primary B16F10 melanoma tumor growth in C57BL/6 mice model treated with BBM-NPs than that of native BBM. Importantly, a moderately cytotoxic dose of BBM-NPs was able to significantly suppress the incidence of B16F10 cells lung metastasis in vivo. Results indicated development of an effective approach for aggressive metastatic cancer.

Effects of Cytochrome P450 3A4 Inhibitors-Ketoconazole and Erythromycin-on Bitopertin Pharmacokinetics and Comparison with Physiologically Based Modelling Predictions

OBJECTIVE

To assess the effect of strong and moderate cytochrome P450 (CYP) 3A4 inhibition on exposure of bitopertin, a glycine reuptake inhibitor primarily metabolized by CYP3A4, and to compare the results with predictions based on physiologically based pharmacokinetic (PBPK) modelling.

METHODS

The effects of ketoconazole and erythromycin were assessed in two male volunteer studies with open-label, two-period, fixed-sequence designs. Twelve subjects were enrolled in each of the studies. In period 1, a single dose of bitopertin was administered; in period 2, 400 mg ketoconazole was administered once daily for 17 days or 500 mg erythromycin was administered twice daily for 21 days. A single dose of bitopertin was coadministered on day 5. Pharmacokinetic parameters were derived by non-compartmental methods. Simulated bitopertin profiles using dynamic PBPK modelling for a typical healthy volunteer in GastroPlus(®) were used to predict changes in pharmacokinetic parameters.

RESULTS

In healthy volunteers, coadministration of ketoconazole increased the bitopertin area under the plasma concentration-time curve (AUC) from 0 to 312 h (AUC0-312h) 4.2-fold (90 % confidence interval [CI] 3.5-5.0) and erythromycin increased the AUC from time zero to infinity (AUC0-inf) 2.1-fold (90 % CI 1.9-2.3). The peak concentration (C max) increased by <25 % in both studies. Simulated bitopertin profiles using PBPK modelling showed good agreement with the observed AUC ratios in both studies. The predicted AUC0-inf ratios for the interaction with ketoconazole and erythromycin were 7.7 and 1.9, respectively.

CONCLUSION

Strong CYP3A4 inhibitors increase AUC0-inf of bitopertin 7- to 8-fold and hence should not be administered concomitantly with bitopertin. Moderate CYP3A4 inhibitors double AUC0-inf.

The Bitter Chemodiversity of Hops (Humulus lupulus L.)

To map the chemodiversity of key bitter compounds in hops, a total of 75 different samples collected from the global hop market were analyzed for 117 key bitter tastants by means of a multiparametric HPLC-MS/MSMRM method. Among the compounds detected, 2'',3''-epoxyxanthohumol was detected for the first time in hops and iso¬xantho¬humol M was identified as a marker compound for varieties grown in Germany. Hop ageing experiments in the absence and presence of air oxygen, respectively, were conducted to address the stability of hop-derived compounds during long-term storage.

Pharmacological profile of xanthohumol, a prenylated flavonoid from hops (Humulus lupulus)

The female inflorescences of hops (Humulus lupulus L.), a well-known bittering agent used in the brewing industry, have long been used in traditional medicines. Xanthohumol (XN) is one of the bioactive substances contributing to its medical applications. Among foodstuffs XN is found primarily in beer and its natural occurrence is surveyed. In recent years, XN has received much attention for its biological effects. The present review describes the pharmacological aspects of XN and summarizes the most interesting findings obtained in the preclinical research related to this compound, including the pharmacological activity, the pharmacokinetics, and the safety of XN. Furthermore, the potential use of XN as a food additive considering its many positive biological effects is discussed.

Phase 0 and phase III transport in various organs: combined concept of phases in xenobiotic transport and metabolism

The historical phasing concept of drug metabolism and elimination was introduced to comprise the two phases of metabolism: phase I metabolism for oxidations, reductions and hydrolyses, and phase II metabolism for synthesis. With this concept, biological membrane barriers obstructing the accessibility of metabolism sites in the cells for drugs were not considered. The concept of two phases was extended to a concept of four phases when drug transporters were detected that guided drugs and drug metabolites in and out of the cells. In particular, water soluble or charged drugs are virtually not able to overcome the phospholipid membrane barrier. Drug transporters belong to two main clusters of transporter families: the solute carrier (SLC) families and the ATP binding cassette (ABC) carriers. The ABC transporters comprise seven families with about 20 carriers involved in drug transport. All of them operate as pumps at the expense of ATP splitting. Embedded in the former phase concept, the term "phase III" was introduced by Ishikawa in 1992 for drug export by ABC efflux pumps. SLC comprise 52 families, from which many carriers are drug uptake transporters. Later on, this uptake process was referred to as the "phase 0 transport" of drugs. Transporters for xenobiotics in man and animal are most expressed in liver, but they are also present in extra-hepatic tissues such as in the kidney, the adrenal gland and lung. This review deals with the function of drug carriers in various organs and their impact on drug metabolism and elimination.

Novel in vitro-in vivo extrapolation (IVIVE) method to predict hepatic organ clearance in rat

PURPOSE

Drug elimination in the liver consists of uptake, metabolism, biliary excretion, and sinusoidal efflux from the hepatocytes to the blood. We aimed to establish an accurate prediction method for liver clearance in rats, considering these four elimination processes. In vitro assays were combined to achieve improved predictions.

METHODS

In vitro clearances for uptake, metabolism, biliary excretion and sinusoidal efflux were determined for 13 selected compounds with various physicochemical and pharmacokinetic properties. Suspended hepatocytes, liver microsomes and sandwich-cultured hepatocytes were evaluated as in vitro models. Based on the individual processes, in vivo hepatic clearance was calculated. Subsequently, the predicted clearances were compared with the corresponding in vivo values from literature.

RESULTS

Using this in vitro-in vivo extrapolation method good linear correlation was observed between predicted and reported clearances. Linear regression analysis revealed much improved prediction for the novel method (r(2) = 0.928) as compared to parameter analysis using hepatocyte uptake only (r(2) = 0.600), microsomal metabolism only (r(2) = 0.687) or overall hepatobiliary excretion in sandwich-cultured hepatocytes (r(2) = 0.321).

CONCLUSIONS

In this new attempt to predict hepatic elimination under consideration of multiple clearance processes, in vivo hepatic clearances of 13 compounds in rats were well predicted using an IVIVE analysis method based on in vitro assays.

The stabilisation of purified, reconstituted P-glycoprotein by freeze drying with disaccharides

The drug efflux pump P-glycoprotein (P-gp) (ABCB1) confers multidrug resistance, a major cause of failure in the chemotherapy of tumours, exacerbated by a shortage of potent and selective inhibitors. A high throughput assay using purified P-gp to screen and characterise potential inhibitors would greatly accelerate their development. However, long-term stability of purified reconstituted ABCB1 can only be reliably achieved with storage at -80 degrees C. For example, at 20 degrees C, the activity of ABCB1 was abrogated with a half-life of <1 day. The aim of this investigation was to stabilise purified, reconstituted ABCB1 to enable storage at higher temperatures and thereby enable design of a high throughput assay system. The ABCB1 purification procedure was optimised to allow successful freeze drying by substitution of glycerol with the disaccharides trehalose or maltose. Addition of disaccharides resulted in ATPase activity being retained immediately following lyophilisation with no significant difference between the two disaccharides. However, during storage trehalose preserved ATPase activity for several months regardless of the temperature (e.g. 60% retention at 150 days), whereas ATPase activity in maltose purified P-gp was affected by both storage time and temperature. The data provide an effective mechanism for the production of resilient purified, reconstituted ABCB1.

Intestinal absorption mechanisms of prenylated flavonoids present in the heat-processed Epimedium koreanum Nakai (Yin Yanghuo)

PURPOSE

The purpose is to determine absorption mechanism of five bioactive prenylated flavonoids (baohuoside I, icariin, epimedine A, B, and C) present in heat-processed Epimedium koreanum Nakai (Yin Yanghuo).

METHODS

Transport of five prenylated flavonoids present in heat-processed herbs were studied in the human intestinal Caco-2 model and the perfused rat intestinal model.

RESULTS

In the perfused rat intestinal model, prenylated flavonoids with a monoglucosidic bond (e.g., icariin) was rapidly hydrolyzed into corresponding metabolites (e.g., baohuoside I). In the Caco-2 model, apical to basolateral permeability of a monoglycoside baohuoside I (1.46 x 10(-6) cm/sec) was more than 2 folds greater than four prenylated flavonoids with 2 or more sugar moieties (<0.6 x 10(-6) cm/sec). The slow apical to basolateral transport of baohuoside I was the result of efflux. This efflux was carrier-mediated and active since its transport was vectorial, concentration- and temperature-dependent with activation energies greater than 15 kcal/mol. Efflux of baohuoside I was significantly suppressed by inhibitors of BCRP and MRP2, whereas efflux of icariin was significantly inhibited only by p-glycoprotein inhibitor verapamil. Because YHH is often heat-processed for better efficacy, we determined and found the optimal condition for increasing contents of more bioavailable flavonoids (i.e., baohuoside I) to be 160-170 degrees C for 5-7 min.

CONCLUSIONS

Poor bioavailability of prenylated flavonoids results from their poor intrinsic permeation and transporter-mediated efflux. Heat processing parameters may be optimized to preserve the herb's bioavailable flavonoids, which help retain and improve its efficacy during processing.