Itraconazole, a P-glycoprotein and CYP3A4 inhibitor, markedly raises the plasma concentrations and enhances the renin-inhibiting effect of aliskiren

In vitro identification of decreased function genetic variants of ABCB1

The efflux transporter ABCB1 (P-glycoprotein, P-gp) has an important role in drug disposition, and thus, genetic variants that lead to decreased transport function might increase drug exposure. Complete loss of function of ABCB1 is rare but a few nonfunctional variants have been found. We studied the transport activity of the common S893A/T (c.2677T>G/A) variants and a set of 14 other naturally occurring non-synonymous single nucleotide variants to find new decreased function variants. The reference ABCB1 (c.1236T, c.2677T, c.3435T haplotype) and variants (N21D, H61Y, Y116C, N183S, I261V, L305P, R580P, C717Y, S795C, I836V, Y853N, S893A, S893T, V907F, Y928S, and A980P) were expressed in Sf9 cells. These cells were then used to prepare membrane vesicles, which were used to study N-methyl-quinidine (NMQ) and aliskiren transport. Aliskiren kinetics were characterised, as it has not previously been used in vesicle transport assays. Compared to the reference, C717Y caused a complete loss of NMQ and aliskiren transport, and L305P and V907F decreased transport to <25 % of the reference. In addition, R580P and A980P decreased the transport of both substrates to ≤50 %, while S795C affected only NMQ transport. Based on our results, carriers of the C717Y, L305P, or V907F variants may experience altered distribution and exposure of ABCB1 substrate drugs.

Genetic variations of CYP3A4 on the metabolism of itraconazole in vitro

Itraconazole is a triazole anti-infective drug that has been proven to prevent and treat a variety of fungal and viral infections and has been considered to be a potential therapeutic remedy for COVID-19 treatment. In this study, we aimed to completely evaluate the impacts of Cytochrome P450 3A4 (CYP3A4) variant proteins and drug interactions on the metabolism of itraconazole in recombinant insect microsomes, and to characterize the potential mechanism of substrate selectivity. Incubations with itraconazole (0.2-15 μM) in the presence/absence of lopinavir or darunavir were assessed by CYP3A4 variants, and the metabolite hydroxyitraconazole concentrations were measured by UPLC-MS/MS. Our data showed that when compared with CYP3A4.1, 4 variants (CYP3A4.9, .10, .28 and .34) displayed no significant differences, and 3 variants (CYP3A4.14, .15 and .19) exhibited increased intrinsic clearance (CLint), whereas the remaining 17 variant proteins showed decreased enzyme activities for the catalysis of itraconazole. Moreover, the inhibitory effects of lopinavir and darunavir on itraconazole metabolism varied in different degrees. Furthermore, different changed trend of the kinetic parameters in ten variants (CYP3A4.5, .9, .10, .16, .19, .24, .28, .29, .31, and .33) were observed, especially CYP3A4.5 and CYP3A4.16, and this may be related to the metabolic site-heme iron atom distance. In the present study, we functionally analyzed the effects of 25 CYP3A4 protein variants on itraconazole metabolism for the first time, and provided comprehensive data on itraconazole metabolism in vitro. This may help to better assess the metabolism and elimination of itraconazole in clinic to improve the safety and efficacy of its clinical treatment and also provide new possibilities for the treatment of COVID-19.

Probiotics and their postbiotics for the control of opportunistic fungal pathogens: A review

During past twenty years the opportunistic fungal infections have been emerging, causing morbidity and mortality. The fungi belonging to Aspergillus, Mucor, Rhizopus, Candida, Fusarium, Penicillium, Dermatophytes and others cause severe opportunistic fungal infections. Among these Aspergillus and Candida spp cause majority of the diseases. The continuum of fungal infections will prolong to progress in the surroundings of the growing inhabitants of immunocompromised individuals. Presently many chemical-based drugs were used as prophylactic and therapeutic agents. Prolonged usage of antibiotics may lead to some severe effect on the human health. Also, one of the major threats is that the fungal pathogens are becoming the drug resistant. There are many physical, chemical, and mechanical methods to prevent the contamination or to control the disease. Owing to the limitations that are observed in such methods, biological methods are gaining more interest because of the use of natural products which have comparatively less side effects and environment friendly. In recent years, research on the possible use of natural products such as probiotics for clinical use is gaining importance. Probiotics, one of the well studied biological products, are safe upon consumption and are explored to treat various fungal infections. The antifungal potency of major groups of probiotic cultures such as Lactobacillus spp, Leuconostoc spp, Saccharomyces etc. and their metabolic byproducts which act as postbiotics like organic acids, short chain fatty acids, bacteriocin like metabolites, Hydrogen peroxide, cyclic dipeptides etc. to inhibit these opportunistic fungal pathogens have been discussed here.

Pitavastatin and Ivermectin Enhance the Efficacy of Paclitaxel in Chemoresistant High-Grade Serous Carcinoma

Simple Summary

The main challenge in high-grade serous carcinoma management is to unveil therapeutic approaches to overcome chemoresistance. Drug combinations and repurposing of non-oncological agents are attractive strategies that allow for higher efficacy, decreased toxicity, and the overcoming of chemoresistance. Several non-oncological drugs display an effective anti-cancer activity and have been studied to be repurposed in multi-drug resistant neoplasms. The purpose of our study was to explore whether combining Paclitaxel with repurposed drugs (Pitavastatin, Metformin, Ivermectin, Itraconazole and Alendronate) led to a therapeutic benefit. Our results showed that the combination of Paclitaxel with Pitavastatin or Ivermectin demonstrates the highest cytotoxic effect and the strongest synergism among all combinations for two chemoresistant cell lines. Thus, the combination of these repurposed drugs with Paclitaxel could be a particularly valuable strategy to treat ovarian cancer patients with intrinsic or acquired chemoresistance.

Abstract

Chemotherapy is a hallmark in high-grade serous carcinoma management; however, chemoresistance and side effects lead to therapeutic interruption. Combining repurposed drugs with chemotherapy has the potential to improve antineoplastic efficacy, since drugs can have independent mechanisms of action and suppress different pathways simultaneously. This study aimed to explore whether the combination of Paclitaxel with repurposed drugs led to a therapeutic benefit. Thus, we evaluated the cytotoxic effects of Paclitaxel alone and in combination with several repurposed drugs (Pitavastatin, Metformin, Ivermectin, Itraconazole and Alendronate) in two tumor chemoresistant (OVCAR8 and OVCAR8 PTX R P) and a non-tumoral (HOSE6.3) cell lines. Cellular viability was assessed using Presto Blue assay, and the synergistic interactions were evaluated using Chou–Talalay, Bliss Independence and Highest Single Agent reference models. The combination of Paclitaxel with Pitavastatin or Ivermectin showed the highest cytotoxic effect and the strongest synergism among all combinations for both chemoresistant cell lines, resulting in a chemotherapeutic effect superior to both drugs alone. Almost all the repurposed drugs in combination with Paclitaxel presented a safe pharmacological profile in non-tumoral cells. Overall, we suggest that Pitavastatin and Ivermectin could act synergistically in combination with Paclitaxel, being promising two-drug combinations for high-grade serous carcinoma management.

The Overview on the Pharmacokinetic and Pharmacodynamic Interactions of Triazoles

Second generation triazoles are widely used as first-line drugs for the treatment of invasive fungal infections, including aspergillosis and candidiasis. This class, along with itraconazole, voriconazole, posaconazole, and isavuconazole, is characterized by a broad range of activity, however, individual drugs vary considerably in safety, tolerability, pharmacokinetics profiles, and interactions with concomitant medications. The interaction may be encountered on the absorption, distribution, metabolism, and elimination (ADME) step. All triazoles as inhibitors or substrates of CYP isoenzymes can often interact with many drugs, which may result in the change of the activity of the drug and cause serious side effects. Drugs of this class should be used with caution with other agents, and an understanding of their pharmacokinetic profile, safety, and drug-drug interaction profiles is important to provide effective antifungal therapy. The manuscript reviews significant drug interactions of azoles with other medications, as well as with food. The PubMed and Google Scholar bases were searched to collect the literature data. The interactions with anticonvulsants, antibiotics, statins, kinase inhibitors, proton pump inhibitors, non-nucleoside reverse transcriptase inhibitors, opioid analgesics, benzodiazepines, cardiac glycosides, nonsteroidal anti-inflammatory drugs, immunosuppressants, antipsychotics, corticosteroids, biguanides, and anticoagulants are presented. We also paid attention to possible interactions with drugs during experimental therapies for the treatment of COVID-19.

Quantitative prediction of P-glycoprotein-mediated drug-drug interactions and intestinal absorption using humanized mice

BACKGROUND AND PURPOSE

P-glycoprotein (P-gp) exhibits a broad substrate specificity and affects pharmacokinetics, especially intestinal absorption. However, prediction, in vivo, of P-gp-mediated drug-drug interaction (DDI) and non-linear absorption at the preclinical stage, is challenging. Here we evaluate the use of human MDR1 mouse artificial chromosome (hMDR1-MAC) mice carrying human P-gp and lacking their own murine P-gp to quantitatively predict human P-gp-mediated DDI and non-linear absorption.

EXPERIMENTAL APPROACH

The P-gp substrates (aliskiren, betrixaban, celiprolol, digoxin, fexofenadine and talinolol) were administered orally to wild-type, Mdr1a/b-knockout (KO) and hMDR1-MAC mice, and their plasma concentrations were measured. We calculated the ratio of area under the curve (AUCR) in mice (AUC_Mdr1a/b-KO /AUC_wild-type or AUC_Mdr1a/b-KO /AUC_hMDR1-MAC ) estimated as attributable to complete P-gp inhibition and the human AUCR with and without P-gp inhibitor administration. The correlations of AUCR_human with AUCR_wild-type and AUCR_hMDR1-MAC were investigated. For aliskiren, betrixaban and celiprolol, the K_m and V_max values for P-gp in hMDR1-MAC mice and humans were optimized from different dosing studies using GastroPlus. The correlations of K_m and V_max for P-gp between human and hMDR1-MAC mice were investigated.

KEY RESULTS

A better correlation between AUCR_human and AUCR_hMDR1-MAC (R²  = 0.88) was observed. Moreover, good relationships of K_m (R²  = 1.00) and V_max (R²  = 0.98) for P-gp between humans and hMDR1-MAC mice were observed.

CONCLUSIONS AND IMPLICATIONS

These results suggest that P-gp-mediated DDI and non-linear absorption can be predicted using hMDR1-MAC mice. These mice are a useful in vivo tool for quantitatively predicting P-gp-mediated disposition in drug discovery and development.

Antiretroviral Treatment and Antihypertensive Therapy

The presence of hypertension among the population with human immunodeficiency virus (HIV) has become a new threat to the health and well-being of people living with this disease, in particular, among those who received antiretroviral therapy. The estimated prevalence of high blood pressure in HIV-infected patients is significantly higher than the rate observed in HIV-uninfected subjects. The approach to the HIV-positive patient requires the assessment of individual cardiovascular risk and its consideration when designing the individualized target. On the other hand, the numerous pharmacological interactions of antiretroviral (ARV) drugs are essential elements to take into account. Serum levels of any kind of antihypertensive drugs may be influenced by the coadministration of protease inhibitors, non-nucleoside reverse transcriptase inhibitor, or other antiretroviral. Similarly, plasma concentrations of antiretroviral drugs can be increased by the concomitant use of calcium channel blockers or diuretics. In this regard, the treatment of high blood pressure in HIV patients should be preferentially based on ACE inhibitors or thiazide/thiazide-like diuretics or their combination.

Associations between plasma hydroxylated metabolite of itraconazole and serum creatinine in patients with a hematopoietic or immune-related disorder

PURPOSE

Serum markers of renal function have not been characterized in patients treated with itraconazole (ITZ). This study aimed to evaluate the associations between plasma ITZ and its hydroxylated metabolite (OH-ITZ) concentrations and serum markers of renal function in patients with hematopoietic or immune-related disorder.

METHODS

This study enrolled 40 patients with hematopoietic or immune-related disorder who are receiving oral ITZ solution. Plasma concentrations of ITZ and OH-ITZ at 12 h after dosing were determined at steady state. Their relationships with serum levels of creatinine and cystatin C and their estimated glomerular filtration rate (eGFR) were evaluated.

RESULTS

The free plasma concentration of ITZ had no correlation with serum creatinine and serum creatinine-based estimated glomerular filtration rate (eGFR-cre). The free plasma concentration of OH-ITZ was positively and negatively correlated with serum creatinine and eGFR-cre, respectively. The free plasma concentrations of ITZ and OH-ITZ had no association with serum cystatin C and serum cystatin C-based eGFR. Serum creatinine was higher by 16% after than before starting ITZ treatment, while eGFR-cre was lower by 9.3%. The serum creatinine ratio after/before ITZ treatment was positively correlated with the free plasma concentration of OH-ITZ. The patients co-treated with trimethoprim-sulfamethoxazole had higher serum creatinine. Concomitant glucocorticoid administration did not significantly alter serum cystatin C.

CONCLUSIONS

Patients with hematopoietic or immune-related disorder treated with oral ITZ had a higher level of serum creatinine. Although serum creatinine potentially increases in conjunction with the free plasma concentration of OH-ITZ, concomitant ITZ administration has a slight impact on the eGFR-cre level in clinical settings.

Cardiovascular Risk Management and Hepatitis C: Combining Drugs

Direct-acting antivirals (DAAs) are known victims (substrate) and perpetrators (cause) of drug–drug interactions (DDIs). These DAAs are used for the treatment of hepatitis C virus (HCV) infections and are highly effective drugs. Drugs used for cardiovascular risk management are frequently used by HCV-infected patients, whom also are treated with DAAs. Therefore, the aim of this review was to describe DDIs between cardiovascular drugs (CVDs) and DAAs. An extensive literature search was performed containing search terms for the marketed DAAs and CVDs (β-blocking agents, ACE inhibitors, angiotensin II antagonists, renin inhibitors, diuretics, calcium channel blockers, statins/ezetimibe, fibrates, platelet aggregation inhibitors, vitamin K antagonists, heparins, direct Xa inhibitors, nitrates, amiodarone, and digoxin). In particular, the drug labels from the European Medicines Agency and the US Food and Drug Administration were used. A main finding of this review is that CVDs are mostly victims of DDIs with DAAs. Therefore, when possible, monitoring of pharmacodynamics is recommended when coadministering these drugs with DAAs. Nevertheless, it is sometimes better to discontinue a drug on a temporary basis (statins, ezetimide). The DAAs are victims of DDIs in combination with bisoprolol, carvedilol, labetalol, verapamil, and gemfibrozil. Despite there are many DDIs predicted in this review, most of these DDIs can be managed by monitoring the efficacy and toxicity of the victim drug or by switching to another CVD/DAA.

Pharmacokinetic Drug Interactions of an Orally Available TRH Analog (Rovatirelin) With a CYP3A4/5 and P-Glycoprotein Inhibitor (Itraconazole)

The effects of itraconazole on the pharmacokinetics of rovatirelin were investigated in an open-label, single-sequence drug-drug interaction study in 16 healthy subjects. Subjects were administered a single oral dose of rovatirelin (1.6 mg) on day 1 and day 15. From day 8 through 16, subjects received daily oral doses of itraconazole (200 mg/day). Concentrations of rovatirelin and (thiazolylalanyl)methylpyrrolidine (TAMP), the major metabolite of rovatirelin formed by cytochrome P450 (CYP) 3A4/5, were determined in plasma and urine. Pharmacokinetic parameters were used to evaluate the drug-drug interaction potential of rovatirelin as a victim. With coadministration, maximum concentration (C_max ) and area under the concentration-time curve extrapolated to infinity (AUC_inf ) of rovatirelin increased 3.05-fold and 2.82-fold, respectively, and the 90% confidence intervals of the ratios for C_max (2.64-3.52) and AUC_inf (2.47-3.23) did not fall within the 0.8-1.25 boundaries. Urinary excretion of rovatirelin increased at almost the same ratio as the AUC_inf ratio with coadministration; however, renal clearance did not change. C_max , AUC_inf , and urinary excretion of TAMP were decreased by coadministration. Itraconazole has the potential to inhibit drug transport via intestinal P-glycoprotein (P-gp) and breast cancer resistance protein (BCRP); therefore, substrate assessments of rovatirelin for the 2 transporters were evaluated using Caco-2 cell monolayers. In vitro studies showed that rovatirelin is a substrate for P-gp but not for BCRP. The current study shows that itraconazole's effect on rovatirelin pharmacokinetics is mediated through inhibition of CYP3A4/5 and intestinal P-gp.

Progress in the Consideration of Possible Sex Differences in Drug Interaction Studies

Background:

Anecdotal evidence suggests that there may be sex differences in Drug-drug Interactions (DDI) involving specific drugs. Regulators have provided general guidance for the inclusion of females in clinical studies. Some clinical studies have reported sex differences in the Pharmacokinetics (PK) of CYP3A4 substrates, suggesting that DDI involving CYP3A4 substrates could potentially show sex differences.

Objective:

The aim of this review was to investigate whether recent prospective DDI studies have included both sexes and whether there was evidence for the presence or absence of sex differences with the DDIs.

Methods:

The relevant details from 156 drug interaction studies within 124 papers were extracted and evaluated.

Results:

Only eight studies (five papers) compared the outcome of the DDI between males and females. The majority of the studies had only male volunteers. Five studies had females only while 60 had males only, with 7.7% of the studies having an equal proportion of both sexes. Surprisingly, four studies did not specify the sex of the subjects.

:

Based on the limited number of studies comparing males and females, no specific trends or conclusions were evident. Sex differences in the interaction were reported between ketoconazole and midazolam as well as clarithromycin and midazolam. However, no sex difference was observed with the interaction between clarithromycin and triazolam or erythromycin and triazolam. No sex-related PK differences were observed with the interaction between ketoconazole and domperidone, although sex-related differences in QT prolongation were observed.

Conclusion:

This review has shown that only limited progress had been made with the inclusion of both sexes in DDI studies.

Application of Intestinal Epithelial Cells Differentiated from Human Induced Pluripotent Stem Cells for Studies of Prodrug Hydrolysis and Drug Absorption in the Small Intestine

Cell models to investigate intestinal absorption functions, such as those of transporters and metabolic enzymes, are essential for oral drug discovery and development. The purpose of this study was to generate intestinal epithelial cells from human induced pluripotent stem cells (hiPSC-IECs) and then clarify whether the functions of hydrolase and transporters in them reflect oral drug absorption in the small intestine. The hiPSC-IECs showed the transport activities of P-glycoprotein (P-gp), breast cancer resistance protein (BCRP), and peptide transporter 1 (PEPT1), revealed by using their probe substrates ([3H]digoxin, sulfasalazine, and [14C]glycylsarcosine), and the metabolic activities of CYP3A4, CES2, and CES1, which were clarified using their probe substrates (midazolam, irinotecan, and temocapril). The intrinsic clearance by hydrolysis of six ester prodrugs into the active form in hiPSC-IECs was correlated with the plasma exposure (Cmax , AUC, and bioavailability) of the active form after oral administration of these prodrugs to rats. Also, the permeability coefficients of 14 drugs, containing two substrates of P-gp (doxorubicin and [3H]digoxin), one substrate of BCRP (sulfasalazine), and 11 nonsubstrates of transporters (ganciclovir, [14C]mannitol, famotidine, sulpiride, atenolol, furosemide, ranitidine, hydrochlorothiazide, acetaminophen, propranolol, and antipyrine) in hiPSC-IECs were correlated with their values of the fraction of intestinal absorption (Fa) in human clinical studies. These findings suggest that hiPSC-IECs would be a useful cell model to investigate the hydrolysis of ester prodrugs and to predict drug absorption in the small intestine.

Clinical Drug-Drug Interaction Potential of BFE1224, Prodrug of Antifungal Ravuconazole, Using Two Types of Cocktails in Healthy Subjects

BFE1224, prodrug of ravuconazole, is a novel, once-daily, oral, triazole antifungal drug, and currently in development for the treatment of onychomycosis. The clinical drug-drug interaction (DDI) potential of BFE1224 with cytochrome P450 (CYP) and transporter was assessed by using two types of cocktails in healthy subjects in separate clinical studies. The CYP and transporter cocktails consisted of caffeine/tolbutamide/omeprazole/dextromethorphan/midazolam used in study 1 and digoxin/rosuvastatin used in study 2. In addition, repaglinide was separately administered to the same subjects in study 2. There were no major effects on the pharmacokinetics of CYP and transporter substrates, except for an approximate threefold increase in midazolam exposure after oral administration of BFE1224. The clinical DDIs of BFE1224 were mild for CYP3A and minor for other major CYPs (CYP1A2/2C8/2C9/2C19/2D6) as well as those of P-glycoprotein (P-gp), breast cancer resistance protein (BCRP), organic anion transporting polypeptide (OATP) 1B1, and OATP1B3.

Oral drug absorption in pediatrics: the intestinal wall, its developmental changes and current tools for predictions

The dissolution, intestinal absorption and presystemic metabolism of a drug depend on its physicochemical characteristics but also on numerous physiological (e.g. gastrointestinal pH, volume, transit time, morphology) and biochemical factors (e.g. luminal enzymes and flora, intestinal wall enzymes and transporters). Over the past decade, evidence has accumulated indicating that these factors may differ in children and adults resulting in age-related changes in drug exposure and drug response. Thus, drug dosage may require adjustment for the pediatric population to ensure the desired therapeutic outcome and to avoid side-effects. Although tremendous progress has been made in understanding the effects of age on intestinal physiology and function, significant knowledge gaps remain. Studying and predicting pharmacokinetics in pediatric patients remains challenging due to ethical concerns associated with clinical trials in this vulnerable population, and because of the paucity of predictive in vitro and in vivo animal assays. This review details the current knowledge related to developmental changes determining intestinal drug absorption and pre-systemic metabolism. Supporting experimental approaches as well as physiologically based pharmacokinetic modeling are also discussed together with their limitations and challenges. Copyright © 2016 John Wiley & Sons, Ltd.

Effects of Membrane PEGylation on Entry and Location of Antifungal Drug Itraconazole and Their Pharmacological Implications

Itraconazole (ITZ) is an antifungal agent used clinically to treat mycotic infections. However, its therapeutic effects are limited by low solubility in aqueous media. Liposome-based delivery systems (LDS) have been proposed as a delivery mechanism for ITZ to alleviate this problem. Furthermore, PEGylation, the inclusion in the formulation of a protective "stealth sheath" of poly(ethylene glycol) around carrier particles, is widely used to increase circulation time in the bloodstream and hence efficacy. Together, these themes highlight the importance of mechanistic and structural understanding of ITZ incorporation into liposomes both with and without PEGylation because it can provide a potential foundation for the rational design of LDS-based systems for delivery of ITZ, using alternate protective polymers or formulations. Here we have combined atomistic simulations, cryo-TEM, Langmuir film balance, and fluorescence quenching experiments to explore how ITZ interacts with both pristine and PEGylated liposomes. We found that the drug can be incorporated into conventional and PEGylated liposomes for drug concentrations up to 15 mol % without phase separation. We observed that, in addition to its protective properties, PEGylation significantly increases the stability of liposomes that host ITZ. In a 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC) bilayer without PEGylation, ITZ was found to reside inside the lipid bilayer between the glycerol and the double-bond regions of POPC, adopting a largely parallel orientation along the membrane surface. In a PEGylated liposome, ITZ partitions mainly to the PEG layer. The results provide a solid basis for further development of liposome-based delivery systems.

Projecting ADME Behavior and Drug-Drug Interactions in Early Discovery and Development: Application of the Extended Clearance Classification System

PURPOSE

To assess the utility of Extended Clearance Classification System (ECCS) in understanding absorption, distribution, metabolism, and elimination (ADME) attributes and enabling victim drug-drug interaction (DDI) predictions.

METHODS

A database of 368 drugs with relevant ADME parameters, main metabolizing enzymes, uptake transporters, efflux transporters, and highest change in exposure (%AUC) in presence of inhibitors was developed using published literature. Drugs were characterized according to ECCS using ionization, molecular weight and estimated permeability.

RESULTS

Analyses suggested that ECCS class 1A drugs are well absorbed and systemic clearance is determined by metabolism mediated by CYP2C, esterases, and UGTs. For class 1B drugs, oral absorption is high and the predominant clearance mechanism is hepatic uptake mediated by OATP transporters. High permeability neutral/basic drugs (class 2) showed high oral absorption, with metabolism mediated generally by CYP3A, CYP2D6 and UGTs as the predominant clearance mechanism. Class 3A/4 drugs showed moderate absorption with dominant renal clearance involving OAT/OCT2 transporters. Class 3B drugs showed low to moderate absorption with hepatic uptake (OATPs) and/or renal clearance as primary clearance mechanisms. The highest DDI risk is typically seen with class 2/1B/3B compounds manifested by inhibition of either CYP metabolism or active hepatic uptake. Class 2 showed a wider range in AUC change likely due to a variety of enzymes involved. DDI risk for class 3A/4 is small and associated with inhibition of renal transporters.

CONCLUSIONS

ECCS provides a framework to project ADME profiles and further enables prediction of victim DDI liabilities in drug discovery and development.

Quantitative Targeted Absolute Proteomics of Transporters and Pharmacoproteomics-Based Reconstruction of P-Glycoprotein Function in Mouse Small Intestine

The purpose of this study was to investigate whether a pharmacokinetic model integrating in vitro mdr1a efflux activity (which we previously reported) with in vitro/in vivo differences in protein expression level can reconstruct intestinal mdr1a function. In situ intestinal permeability-surface area product ratio between wild-type and mdr1a/1b (-/-) mice is one of the parameters used to describe intestinal mdr1a function. The reconstructed ratios of six mdr1a substrates (dexamethasone, digoxin, loperamide, quinidine, verapamil, vinblastine) and one nonsubstrate (diazepam) were consistent with the observed values reported by Adachi et al. within 2.1-fold difference. Thus, intestinal mdr1a function can be reconstructed by our pharmacoproteomic modeling approach. Furthermore, we evaluated regional differences in protein expression levels of mouse intestinal transporters. Sixteen (mdr1a, mrp4, bcrp, abcg5, abcg8, glut1, 4f2hc, sglt1, lat2, pept1, mct1, slc22a18, ostβ, villin1, Na(+)/K(+)-ATPase, γ-gtp) out of 46 target molecules were detected by employing our established quantitative targeted absolute proteomics technique. The protein expression amounts of mdr1a and bcrp increased progressively from duodenum to ileum. Sglt1, lat2, and 4f2hc were highly expressed in jejunum and ileum. Mct1 and ostβ were highly expressed in ileum. The quantitative expression profiles established here should be helpful to understand and predict intestinal transporter functions.

BDDCS Predictions, Self-Correcting Aspects of BDDCS Assignments, BDDCS Assignment Corrections, and Classification for more than 175 Additional Drugs

The biopharmaceutics drug disposition classification system was developed in 2005 by Wu and Benet as a tool to predict metabolizing enzyme and drug transporter effects on drug disposition. The system was modified from the biopharmaceutics classification system and classifies drugs according to their extent of metabolism and their water solubility. By 2010, Benet et al. had classified over 900 drugs. In this paper, we incorporate more than 175 drugs into the system and amend the classification of 13 drugs. We discuss current and additional applications of BDDCS, which include predicting drug-drug and endogenous substrate interactions, pharmacogenomic effects, food effects, elimination routes, central nervous system exposure, toxicity, and environmental impacts of drugs. When predictions and classes are not aligned, the system detects an error and is able to self-correct, generally indicating a problem with initial class assignment and/or measurements determining such assignments.

Pharmacokinetics of cyclosporine a conversion from twice-daily infusion to oral administration in allogeneic hematopoietic stem cell transplantation

Twice-daily administration of cyclosporine A (CyA) has often been used for prophylaxis of acute graft versus host disease in allogeneic hematopoietic stem cell transplantation (allo-HSCT). But there have not been any reports that calculated the conversion ratio of the switch from twice-daily intravenous infusion to oral administration of CyA in adult patients. To establish the conversion ratio and the best strategy of twice-daily administration of CyA, the authors investigated the serial changes in the blood CyA concentration during the switch from twice-daily intravenous infusion to oral administration while maintaining high-peak concentration (over 1000 ng/mL) and calculated the bioavailability of Neoral, a micro emulsion cyclosporine, in 11 patients. All the patients underwent allo-HSCT with graft versus host disease prophylaxis consisting of CyA at a high-peak concentration of twice-daily infusion with short-term methotrexate and oral administration. Neoral was started at an oral dose, 2 times daily, at twice the latest dose of intravenous dose according to the bioavailability of healthy volunteers. Micafungin, a mild inhibitor of CYP3A4, was administered for prophylaxis against fungal infection. The total area under the concentration-time curve during oral administration (AUCpo) was nearly the same as AUC during intravenous infusion (AUCiv) (mean ± SD, 7206 ± 1557 ng·h·mL and 7783 ± 897.7 ng·h·mL, respectively). The bioavailability of Neoral, defined as F = AUCpo × DOSEiv/AUCiv × DOSEpo was 0.58 ± 0.15 (mean ± SD, range: 0.41-0.94). When patients were switched from twice-daily infusion to oral administration, the dose conversion ratio of 1:2 seemed to be appropriate. At that time, the target trough level of Neoral was nearly the same as that of the infusion.

Best practices for the use of itraconazole as a replacement for ketoconazole in drug-drug interaction studies

Ketoconazole has been widely used as a strong cytochrome P450 (CYP) 3A (CYP3A) inhibitor in drug-drug interaction (DDI) studies. However, the US Food and Drug Administration has recommended limiting the use of ketoconazole to cases in which no alternative therapies exist, and the European Medicines Agency has recommended the suspension of its marketing authorizations because of the potential for serious safety concerns. In this review, the Innovation and Quality in Pharmaceutical Development's Clinical Pharmacology Leadership Group (CPLG) provides a compelling rationale for the use of itraconazole as a replacement for ketoconazole in clinical DDI studies and provides recommendations on the best practices for the use of itraconazole in such studies. Various factors considered in the recommendations include the choice of itraconazole dosage form, administration in the fasted or fed state, the dose and duration of itraconazole administration, the timing of substrate and itraconazole coadministration, and measurement of itraconazole and metabolite plasma concentrations, among others. The CPLG's recommendations are based on careful review of available literature and internal industry experiences.

CUSP9* treatment protocol for recurrent glioblastoma: aprepitant, artesunate, auranofin, captopril, celecoxib, disulfiram, itraconazole, ritonavir, sertraline augmenting continuous low dose temozolomide

CUSP9 treatment protocol for recurrent glioblastoma was published one year ago. We now present a slight modification, designated CUSP9*. CUSP9* drugs--aprepitant, artesunate, auranofin, captopril, celecoxib, disulfiram, itraconazole, sertraline, ritonavir, are all widely approved by regulatory authorities, marketed for non-cancer indications. Each drug inhibits one or more important growth-enhancing pathways used by glioblastoma. By blocking survival paths, the aim is to render temozolomide, the current standard cytotoxic drug used in primary glioblastoma treatment, more effective. Although esthetically unpleasing to use so many drugs at once, the closely similar drugs of the original CUSP9 used together have been well-tolerated when given on a compassionate-use basis in the cases that have come to our attention so far. We expect similarly good tolerability for CUSP9*. The combined action of this suite of drugs blocks signaling at, or the activity of, AKT phosphorylation, aldehyde dehydrogenase, angiotensin converting enzyme, carbonic anhydrase -2,- 9, -12, cyclooxygenase-1 and -2, cathepsin B, Hedgehog, interleukin-6, 5-lipoxygenase, matrix metalloproteinase -2 and -9, mammalian target of rapamycin, neurokinin-1, p-gp efflux pump, thioredoxin reductase, tissue factor, 20 kDa translationally controlled tumor protein, and vascular endothelial growth factor. We believe that given the current prognosis after a glioblastoma has recurred, a trial of CUSP9* is warranted.

Ritonavir is the best alternative to ketoconazole as an index inhibitor of cytochrome P450-3A in drug-drug interaction studies

AIMS

The regulatory prohibition of ketoconazole as a CYP3A index inhibitor in drug-drug interaction (DDI) studies has compelled consideration of alternative inhibitors.

METHODS

The biomedical literature was searched to identify DDI studies in which oral midazolam (MDZ) was the victim, and the inhibitory perpetrator was either ketoconazole, itraconazole, clarithromycin, or ritonavir. The ratios (RAUC ) of total area under the curve (AUC) for MDZ with inhibitor divided by MDZ AUC in the control condition were aggregated across individual studies for each inhibitor.

RESULTS

Mean (± SE) RAUC values were: ketoconazole (15 studies, 131 subjects), 11.5 (±1.2); itraconazole (five studies, 48 subjects), 7.3 (±1.0); clarithromycin (five studies, 73 subjects), 6.5 (±10.9); and ritonavir (13 studies, 159 subjects), 14.5 (±2.0). Differences among inhibitors were significant (F = 5.31, P < 0.005). RAUC values were not significantly related to inhibitor dosage or to duration of inhibitor pre-exposure prior to administration of MDZ.

CONCLUSIONS

Ritonavir produces CYP3A inhibition equivalent to or greater than ketoconazole, and is the best index CYP3A inhibitor alternative to ketoconazole. Cobicistat closely resembles ritonavir in structure and function, and can also be considered. Itraconazole and clarithromycin are not suitable alternatives since they do not produce inhibition comparable with ketoconazole or ritonavir, and have other significant disadvantages as well.

Therapeutic drug monitoring for triazoles: A needs assessment review and recommendations from a Canadian perspective

Invasive fungal infections cause significant morbidity and mortality in patients with concomitant underlying immunosuppressive diseases. The recent addition of new triazoles to the antifungal armamentarium has allowed for extended-spectrum activity and flexibility of administration. Over the years, clinical use has raised concerns about the degree of drug exposure following standard approved drug dosing, questioning the need for therapeutic drug monitoring (TDM). Accordingly, the present guidelines focus on TDM of triazole antifungal agents. A review of the rationale for triazole TDM, the targeted patient populations and available laboratory methods, as well as practical recommendations based on current evidence from an extended literature review are provided in the present document.

Effects of the inhibition of intestinal P-glycoprotein on aliskiren pharmacokinetics in cynomolgus monkeys

Aliskiren is a substrate for P-glycoprotein (P-gp) and is metabolized via cytochrome P450 3A4 (CYP3A4). The aim of the present study was to assess whether P-gp influenced the pharmacokinetics of aliskiren and also if drug-drug interactions (DDIs) mediated through P-gp could be reproduced in cynomolgus monkeys. The study investigated the pharmacokinetics of aliskiren in mdr1a/1b gene-deficient (P-gp KO) and wild-type (WT) mice. The area under the plasma concentration-time curve (AUC) following the oral administration of aliskiren was 6.9-fold higher in P-gp KO mice than in WT mice, while no significant differences were observed in the AUC or total plasma clearance following the intravenous administration of aliskiren to P-gp KO mice. Then the pharmacokinetics of aliskiren were evaluated and DDIs between aliskiren and P-gp inhibitors, such as cyclosporin A (CsA) and zosuquidar, examined in cynomolgus monkeys. The AUC for aliskiren were 8.3- and 42.1-fold higher after the oral administration of aliskiren with the concomitant oral administration of zosuquidar and CsA at doses of 10 and 30 mg/kg, respectively. In contrast, the AUC after the intravenous and oral administration of aliskiren was not significantly affected by the oral administration of zosuquidar or intravenous administration of CsA, respectively. These results indicated that P-gp strictly limited the intestinal absorption of aliskiren in mice and monkeys, and also that the effects of intestinal P-gp inhibition by CsA or zosuquidar on the pharmacokinetics of aliskiren were sensitively reproduced in monkeys. In conclusion, aliskiren can be used as a sensitive substrate to evaluate intestinal P-gp inhibition in monkeys.

Pharmacokinetics and pharmacodynamics of antifungals in children and their clinical implications

Invasive fungal infections are a significant cause of morbidity and mortality in children. Successful management of these systemic infections requires identification of the causative pathogen, appropriate antifungal selection, and optimisation of its pharmacokinetic and pharmacodynamic properties to maximise its antifungal activity and minimise toxicity and the emergence of resistance. This review highlights salient scientific advancements in paediatric antifungal pharmacotherapies and focuses on pharmacokinetic and pharmacodynamic studies that underpin current clinical decision making. Four classes of drugs are widely used in the treatment of invasive fungal infections in children, including the polyenes, triazoles, pyrimidine analogues and echinocandins. Several lipidic formulations of the polyene amphotericin B have substantially reduced the toxicity associated with the traditional amphotericin B formulation. Monotherapy with the pyrimidine analogue flucytosine rapidly promotes the emergence of resistance and cannot be recommended. However, when used in combination with other antifungal agents, therapeutic drug monitoring of flucytosine has been shown to reduce high peak flucytosine concentrations, which are strongly associated with toxicity. The triazoles feature large inter-individual pharmacokinetic variability, although this pattern is less pronounced with fluconazole. In clinical trials, posaconazole was associated with fewer adverse effects than other members of the triazole family, though both posaconazole and itraconazole display erratic absorption that is influenced by gastric pH and the gastric emptying rate. Limited data suggest that the clinical response to therapy may be improved with higher plasma posaconazole and itraconazole concentrations. For voriconazole, pharmacokinetic studies among children have revealed that children require twice the recommended adult dose to achieve comparable blood concentrations. Voriconazole clearance is also affected by the cytochrome P450 (CYP) 2C19 genotype and hepatic impairment. Therapeutic drug monitoring is recommended as voriconazole pharmacokinetics are highly variable and small dose increases can result in marked changes in plasma concentrations. For the echinocandins, the primary source of pharmacokinetic variability stems from an age-dependent decrease in clearance with increasing age. Consequently, young children require larger doses per kilogram of body weight than older children and adults. Routine therapeutic drug monitoring for the echinocandins is not recommended. The effectiveness of many systemic antifungal agents has been correlated with pharmacodynamic targets in in vitro and in murine models of invasive candidiasis and aspergillosis. Further study is needed to translate these findings into optimal dosing regimens for children and to understand how these agents interact when multiple antifungal agents are used in combination.

Aliskiren toxicity in juvenile rats is determined by ontogenic regulation of intestinal P-glycoprotein expression

Juvenile rat toxicity studies with the direct renin inhibitor aliskiren were initiated to support treatment in the pediatric population. In Study 1, aliskiren was administered orally to juvenile rats at doses of 0, 30, 100 or 300 mg/kg/day with repeated dosing from postpartum day (PPD) 8 to PPD 35/36. In-life, clinical pathology, anatomic pathology, and toxicokinetics evaluations were performed. In Study 2, single oral doses of aliskiren (0, 100 or 300 mg/kg) were given to 14-, 21-, 24-, 28-, 31- or 36-day-old rats; in-life data and toxicokinetics were evaluated. Study 3 was a single dose (3 mg/kg i.v.) pharmacokinetic study in juvenile rats on PPD 8, 14, 21 and 28. In Study 4, naïve rats were used to investigate ontogenic changes of the multidrug-resistant protein 1 (MDR1) and the organic anion transporting polypeptide (OATP) mRNA in several organs. Oral administration of aliskiren at 100 and 300 mg/kg caused unexpected mortality and severe morbidity in 8-day-old rats. Aliskiren plasma and tissue concentrations were increased in rats aged 21days and younger. Expression of MDR1 and OATP mRNA in the intestine, liver and brain was significantly lower in very young rats. In conclusion, severe toxicity and increased exposure in very young rats after oral administration of aliskiren are considered to be the result of immature drug transporter systems. Immaturity of MDR1 in enterocytes appears to be the most important mechanism responsible for the high exposure.

SLCO2B1 c.935G>A single nucleotide polymorphism has no effect on the pharmacokinetics of montelukast and aliskiren

OBJECTIVE

A nonsynonymous single nucleotide polymorphism (SNP) in the SLCO2B1 gene encoding organic anion transporting polypeptide 2B1 (OATP2B1), c.935G>A (p.R312Q; rs12422149), has been associated with reduced plasma concentrations of montelukast in patients with asthma. Our aim was to examine the possible effects of the SLCO2B1 c.935G>A SNP on the single-dose pharmacokinetics of the suggested OATP2B1 substrates montelukast and aliskiren.

METHODS

Sixteen healthy volunteers with the SLCO2B1 c.935GG genotype, 12 with the c.935GA genotype, and five with the c.935AA genotype ingested a single 10 mg dose of montelukast or a 150 mg dose of aliskiren, with a washout period of 1 week. Plasma montelukast concentrations were measured up to 24 h. Plasma and urine aliskiren concentrations were measured up to 72 and 12 h, respectively, and plasma renin activity up to 24 h after aliskiren intake.

RESULTS

The SLCO2B1 genotypes had no significant effect on the pharmacokinetics of montelukast or aliskiren. The geometric mean ratios with 90% confidence intervals of montelukast area under the plasma concentration-time curve from 0 h to infinity (AUC(0-∞)) in participants with the c.935GA or the c.935AA genotype to those with the c.935GG genotype were 1.02 (0.87, 1.21) or 0.88 (0.71, 1.10), respectively (P=0.557). The geometric mean ratios (90% confidence interval) of aliskiren AUC(0-∞) in participants with the c.935GA or the c.935AA genotype to those with the c.935GG genotype were 0.98 (0.74, 1.30) or 1.24 (0.85, 1.80), respectively (P=0.576).

CONCLUSION

These data do not support the suggested functional significance of the SLCO2B1 c.935G>A SNP on OATP2B1 activity in vivo.

Antifungal activity of Lactobacillus against Microsporum canis, Microsporum gypseum and Epidermophyton floccosum

A total of 220 lactic acid bacteria isolates were screened for antifungal activity using Aspergillus fumigatus and Aspergillus niger as the target strains. Four Lactobacillus strains exhibited strong inhibitory activity on agar surfaces. All four were also identified as having strong inhibitory activity against the human pathogenic fungi Microsporum canis, Microsporum gypseum and Epidermophyton floccosum. One of the four lactobacilli, namely Lb. reuteri ee1p exhibited the most inhibition against dermatophytes. Cell-free culture supernatants of Lb. reuteri ee1p and of the non-antifungal Lb. reuteri M13 were freeze-dried and used to access and compare antifungal activity in agar plate assays and microtiter plate assays. Addition of the Lb. reuteri ee1p freeze-dried cell-free supernatant powder into the agar medium at concentrations greater than 2% inhibited all fungal colony growth. Addition of the powder at 5% to liquid cultures caused complete inhibition of fungal growth on the basis of turbidity. Freeze-dried supernatant of the non-antifungal Lb. reuteri M13 at the same concentrations had a much lesser effect. As Lb. reuteri M13 is very similar to the antifungal strain ee1p in terms of growth rate and final pH in liquid culture, and as it has little antifungal activity, it is clear that other antifungal compounds must be specifically produced (or produced at higher levels) by the anti-dermatophyte strain Lb. reuteri ee1p. Reuterin was undetectable in all four antifungal strains. The cell free supernatant of Lb. reuteri ee1p was analyzed by LC-FTMS using an Accela LC coupled to an LTQ Orbitrap XL mass spectrometer. The high mass accuracy spectrum produced by compounds in the Lb. reuteri ee1p strain was compared with both a multianalyte chromatogram and individual spectra of standard anti-fungal compounds, which are known to be produced by lactic acid bacteria. Ten antifungal metabolites were detected.

Top Three Pharmacogenomics and Personalized Medicine Applications at the Nexus of Renal Pathophysiology and Cardiovascular Medicine

Pharmacogenomics is a field with origins in the study of monogenic variations in drug metabolism in the 1950s. Perhaps because of these historical underpinnings, there has been an intensive investigation of 'hepatic pharmacogenes' such as CYP450s and liver drug metabolism using pharmacogenomics approaches over the past five decades. Surprisingly, kidney pathophysiology, attendant diseases and treatment outcomes have been vastly under-studied and under-theorized despite their central importance in maintenance of health, susceptibility to disease and rational personalized therapeutics. Indeed, chronic kidney disease (CKD) represents an increasing public health burden worldwide, both in developed and developing countries. Patients with CKD suffer from high cardiovascular morbidity and mortality, which is mainly attributable to cardiovascular events before reaching end-stage renal disease. In this paper, we focus our analyses on renal function before end-stage renal disease, as seen through the lens of pharmacogenomics and human genomic variation. We herein synthesize the recent evidence linking selected Very Important Pharmacogenes (VIP) to renal function, blood pressure and salt-sensitivity in humans, and ways in which these insights might inform rational personalized therapeutics. Notably, we highlight and present the rationale for three applications that we consider as important and actionable therapeutic and preventive focus areas in renal pharmacogenomics: 1) ACE inhibitors, as a confirmed application, 2) VDR agonists, as a promising application, and 3) moderate dietary salt intake, as a suggested novel application. Additionally, we emphasize the putative contributions of gene-environment interactions, discuss the implications of these findings to treat and prevent hypertension and CKD. Finally, we conclude with a strategic agenda and vision required to accelerate advances in this under-studied field of renal pharmacogenomics with vast significance for global public health.

Transporter-mediated drug-drug interactions

Drug-drug interactions are a serious clinical issue. An important mechanism underlying drug-drug interactions is induction or inhibition of drug transporters that mediate the cellular uptake and efflux of xenobiotics. Especially drug transporters of the small intestine, liver and kidney are major determinants of the pharmacokinetic profile of drugs. Transporter-mediated drug-drug interactions in these three organs can considerably influence the pharmacokinetics and clinical effects of drugs. In this article, we focus on probe drugs lacking significant metabolism to highlight mechanisms of interactions of selected intestinal, hepatic and renal drug transporters (e.g., organic anion transporting polypeptide [OATP] 1A2, OATP2B1, OATP1B1, OATP1B3, P-gp, organic anion transporter [OAT] 1, OAT3, breast cancer resistance protein [BCRP], organic cation transporter [OCT] 2 and multidrug and toxin extrusion protein [MATE] 1). Genotype-dependent drug-drug interactions are also discussed.

Orange and apple juice greatly reduce the plasma concentrations of the OATP2B1 substrate aliskiren

AIM

The aim of this study was to investigate the effects of orange juice and apple juice on the pharmacokinetics and pharmacodynamics of aliskiren.

METHODS

In a randomized crossover study, 12 healthy volunteers ingested 200 ml of orange juice, apple juice or water three times daily for 5 days. On day 3, they ingested a single 150-mg dose of aliskiren. Plasma aliskiren concentrations were measured up to 72 h, its excretion into urine up to 12 h and plasma renin activity up to 24 h.

RESULTS

Orange and apple juice reduced aliskiren peak plasma concentrations by 80% (95% CI 63%, 89%, P < 0.001) and 84% (95% CI 72%, 91%, P < 0.001), and the area under the plasma aliskiren concentration-time curve (AUC) by 62% (95% CI 47%, 72%, P < 0.001) and 63% (95% CI 46%, 74%, P < 0.001), respectively, but had no significant effect on its elimination half-life or renal clearance. The decreases in aliskiren AUC by orange and apple juice correlated with aliskiren AUC during the water phase (r= 0.98, P < 0.001). Plasma renin activity was 87% and 67% higher at 24 h after aliskiren during the orange juice and apple juice phases, respectively, than during the water phase (P < 0.05).

CONCLUSIONS

Orange juice and apple juice greatly reduce the plasma concentrations and renin-inhibiting effect of aliskiren, probably by inhibiting its OATP2B1-mediated influx in the small intestine. Concomitant intake of aliskiren with orange or apple juice is best avoided.