Role of P glycoprotein in absorption of novel antimalarial drugs

Chloroquine: Rapidly withdrawing from first-line treatment of COVID-19

The COVID-19 outbreak has garnered significant global attention due to its impact on human health. Despite its relatively low fatality rate, the virus affects multiple organ systems, resulting in various symptoms such as palpitations, headaches, muscle pain, and hearing loss among COVID-19 patients and those recovering from the disease. These symptoms impose a substantial physical, psychological, and social burden on affected individuals. On February 15, 2020, the Chinese government advised incorporating antimalarial drugs into the guidelines issued by the National Health Commission of China for preventing, diagnosing, and treating COVID-19 pneumonia. We examine the adverse effects of Chloroquine (CQ) in treating COVID-19 complications to understand why it is no longer the primary treatment for the disease.

Medicinal and mechanistic overview of artemisinin in the treatment of human diseases

Artemisinin (ART) is a bioactive compound isolated from the plant Artemisia annua and has been traditionally used to treat conditions such as malaria, cancer, viral infections, bacterial infections, and some cardiovascular diseases, especially in Asia, North America, Europe and other parts of the world. This comprehensive review aims to update the biomedical potential of ART and its derivatives for treating human diseases highlighting its pharmacokinetic and pharmacological properties based on the results of experimental pharmacological studies in vitro and in vivo. Cellular and molecular mechanisms of action, tested doses and toxic effects of artemisinin were also described. The analysis of data based on an up-to-date literature search showed that ART and its derivatives display anticancer effects along with a wide range of pharmacological activities such as antibacterial, antiviral, antimalarial, antioxidant and cardioprotective effects. These compounds have great potential for discovering new drugs used as adjunctive therapies in cancer and various other diseases. Detailed translational and experimental studies are however needed to fully understand the pharmacological effects of these compounds.

Physiologically-Based Pharmacokinetics Modeling for Hydroxychloroquine as a Treatment for Malaria and Optimized Dosing Regimens for Different Populations

Malaria is a severe parasite infectious disease with high fatality. As one of the approved treatments of this disease, hydroxychloroquine (HCQ) lacks clinical administration guidelines for patients with special health conditions and co-morbidities. This may result in improper dosing for different populations and lead them to suffer from severe side effects. One of the most important toxicities of HCQ overdose is cardiotoxicity. In this study, we built and validated a physiologically based pharmacokinetic modeling (PBPK) model for HCQ. With the full-PBPK model, we predicted the pharmacokinetic (PK) profile for malaria patients without other co-morbidities under the HCQ dosing regimen suggested by Food and Drug Administration (FDA) guidance. The PK profiles for different special populations were also predicted and compared to the normal population. Moreover, we proposed a series of adjusted dosing regimens for different populations with special health conditions and predicted the concentration-time (C-T) curve of the drug plasma concentration in these populations which include the pregnant population, elderly population, RA patients, and renal impairment populations. The recommended special population-dependent dosage regimens can maintain the similar drug levels observed in the virtual healthy population under the original dosing regimen provided by FDA. Last, we developed mathematic formulas for predicting dosage based on a patient’s body measurements and two indexes of renal function (glomerular filtration rate and serum creatine level) for the pediatric and morbidly obese populations. Those formulas can facilitate personalized treatment of this disease. We hope to provide some advice to clinical practice when taking HCQ as a treatment for malaria patients with special health conditions or co-morbidities so that they will not suffer from severe side effects due to higher drug plasma concentration, especially cardiotoxicity.

An update on pharmacogenetic factors influencing the metabolism and toxicity of artemisinin-based combination therapy in the treatment of malaria

INTRODUCTION

Artemisinin-based combination therapies (ACTs) are recommended first-line antimalarials for uncomplicated Plasmodium falciparum malaria. Pharmacokinetic/pharmacodynamic variation associated with ACT drugs and their effect is documented. It is accepted to an extent that inter-individual variation is genetically driven, and should be explored for optimized antimalarial use.

AREAS COVERED

We provide an update on the pharmacogenetics of ACT antimalarial disposition. Beyond presently used antimalarials, we also refer to information available for the most notable next-generation drugs under development. The bibliographic approach was based on multiple Boolean searches on PubMed covering all recent publications since our previous review.

EXPERT OPINION

The last 10 years have witnessed an increase in our knowledge of ACT pharmacogenetics, including the first clear examples of its contribution as an exacerbating factor for drug-drug interactions. This knowledge gap is still large and is likely to widen as a new wave of antimalarial drug is looming, with few studies addressing their pharmacogenetics. Clinically useful pharmacogenetic markers are still not available, in particular, from an individual precision medicine perspective. A better understanding of the genetic makeup of target populations can be valuable for aiding decisions on mass drug administration implementation concerning region-specific antimalarial drug and dosage options.

Chloroquine/Hydroxychloroquine Use and Suicide Risk: Hypotheses for Confluent Etiopathogenetic Mechanisms?

Chloroquine (CQ) and hydroxychloroquine (HCQ) are classical anti-malarial and anti-inflammatory treatments, which were used as first-line therapy at the beginning of the 2019 coronavirus disease (COVID-19) pandemic. Besides the emerging data on their lack of efficacy against COVID-19 infection, such treatments have been associated with some severe health concerns, including those of neuropsychiatric nature, such as a possible increase in suicide risk. Here we report a case of a patient with no history of psychiatric illnesses, who abruptly developed depression with melancholic features, severe suicidal ideation (SI), and attempted suicide (SA) shortly after receiving HCQ for his COVID-19 infection. The case was followed by a mini-review of the heterogeneous scientific literature on the hypothetical association between neuropsychiatric symptoms, with a focus on SI and suicidal behavior (SB, including SA and death by suicide), when CQ and HCQ are used in COVID-19, rheumatologic diseases, and malaria settings. Considering the anti-inflammatory properties of CQ and HCQ and the implications for neuroinflammation in suicide pathogenesis, the possible increase in suicide risk caused by these medications appears paradoxical and suggests that other underlying pathological trajectories might account for this eventuality. In this regard, some of these latter mechanistic postulates were proposed. Certainly the role and contribution of psycho-social factors that a COVID-19 patient had to face can neither be minimized nor excluded in the attempt to understand his suffering until the development of SI/SB. However, while this case report represents a rare scenario in clinical practice and no consensus exists in the literature on this topic, a psychiatric screening for suicide risk in patients using of CQ and HCQ could be carefully considered.

Starch Nanoparticles for Enhancement of Oral Bioavailability of a Newly Synthesized Thienopyrimidine Derivative with Anti-Proliferative Activity Against Pancreatic Cancer

Purpose

This research aimed to improve water solubility and oral bioavailability of a newly synthesized thienopyrimidine derivative (TPD) with anti-pancreatic cancer activity by loading on starch nanoparticles (SNPs).

Methods

TPD was synthesized, purified and its ADME behavior was predicted using Swiss ADME software. A UV spectroscopy method was developed and validated to measure TPD concentration at various dosage forms. SNPs loaded with TPD (SNPs-TPD) were prepared, characterized for particle size, polydispersity index, zeta potential, transmission electron microscopy, Fourier transform infrared spectroscopy (FT-IR), differential scanning calorimetry (DSC), entrapment efficiency, in-vitro release, and in-vivo animal study.

Results

The Swiss ADME results showed that TPD can be administered orally; however, it has low oral bioavailability (0.55) and poor water solubility. The significant regression coefficient of the calibration curve (r² = 0.9995), the precision (%RSD < 0.5%) and the accuracy (99.46−101.72%) confirmed the efficacy of the developed UV method. SNPs-TPD had a spherical monodispersed (PDI= 0.12) shape, nanoparticle size (22.98 ± 4.23) and good stability (−21 ± 4.72 mV). Moreover, FT-IR and DSC revealed changes in the physicochemical structure of starch resulting in SNPs formation. The entrapment efficiency was 97% ± 0.45%, and the in-vitro release showed that the SNPs enhanced the solubility of the TPD. The in-vivo animal study and histopathology showed that SNPs enhanced the oral bioavailability of TPD against solid Ehrlich carcinoma.

Conclusion

SNPs-TPD were superior in drug solubility and oral bioavailability than those obtained from TPD suspension.

Drug-induced Liver Injury in a Patient With Coronavirus Disease 2019: Potential Interaction of Remdesivir With P-Glycoprotein Inhibitors

We report a case of a man with COVID-19 who developed acute hepatotoxicity related to remdesivir with probable interaction of P-glycoprotein (P-gp) inhibitors. Until further details on this interaction become available, we recommend physicians to be cautious with the prescription of P-gp inhibitors in patients receiving remdesivir therapy.

Psychiatric Aspects of Chloroquine and Hydroxychloroquine Treatment in the Wake of Coronavirus Disease-2019: Psychopharmacological Interactions and Neuropsychiatric Sequelae

BACKGROUND

Chloroquine and hydroxychloroquine are among several experimental treatments being investigated in the urgent response to the coronavirus disease-2019. With increased use of these medications, physicians need to become knowledgeable of these drugs' neuropsychiatric side effects and interactions with psychiatric medications.

OBJECTIVE

Clarify evidence base regarding the psychiatric side effects and psychiatric drug interactions of chloroquine and hydroxychloroquine.

METHODS

A literature review was performed in PubMed from 1950 to 2020 regarding psychiatric topics and targeted pharmacological properties of chloroquine and hydroxychloroquine.

RESULTS

First, chloroquine and hydroxychloroquine may mildly inhibit CYP2D6 metabolism of psychiatric medications, and psychiatric medications that interfere with CYP2D6 or CYP3A4 activity could alter chloroquine and hydroxychloroquine levels. Second, they may prolong the QT interval, warranting caution with concomitant prescription of other QT prolonging agents. Finally, neuropsychiatric side effects are very uncommon but possible and include a potentially prolonged phenomenon of "psychosis after chloroquine." Hydroxychloroquine has less information available about its neuropsychiatric side effects than chloroquine, with psychosis literature limited to several case reports. Weak evidence suggests a possible association of hydroxychloroquine exposure and increased suicidal ideation. It is not clear whether patients with psychiatric illness are more vulnerable to neuropsychiatric sequela of these medications; however, overdose of these medications by suicidal patients has high risk of mortality.

CONCLUSION

The risk of neuropsychiatric side effects of chloroquine and hydroxychloroquine when used for coronavirus disease-2019 treatment is not known. Best practice may include suicide risk assessment for patients treated with hydroxychloroquine. However, delirium is expected to be a more likely etiology of neuropsychiatric symptoms in critically ill patients treated for coronavirus disease-2019, and adjustment disorder is a much more likely etiology of anxiety and depression symptoms than the side effects of chloroquine or hydroxychloroquine.

Quantum Chemical Lipophilicities of Antimalarial Drugs in Relation to Terminal Half-Life

According to the WHO, artemisinin-based combination therapies (ACTs) have been integral to the recent reduction in deaths due to Plasmodium falciparum malaria. ACT-resistant strains are an emerging problem and have evolved altered developmental stages, reducing exposure of the most susceptible stages to artemisinin drugs in popular ACTs. Lipophilicity, log K ow, is a guide in understanding and predicting pharmacokinetic properties such as terminal half-life which alters drug exposure. Consistent log K ow values are not necessarily available for artemisinin derivatives designed to extend terminal half-life, increase bioavailability, and reduce neurotoxicity. For other drugs used in ACTs, an assortment of experimental and computational log K ow values are available in the literature and in some cases, do not account for subtle but important differences between closely related structures such as between diastereomers. Quantum chemical methods such as density functional theory (DFT) used with an implicit solvent model allow for consistent comparison of physical properties including log K ow and distinguish between closely related structures. To this end, DFT, B3LYP/6-31G(d), with an implicit solvent model (SMD) was used to compute ΔG ow o and ΔG vow o for 1-octanol-water and olive oil-water partitions, respectively, for 21 antimalarial drugs: 12 artemisinin-based, 4 4-aminoquinolines and structurally similar pyronaridine, and 4 amino alcohols. The computed ΔG ow o was close to ΔG ow o calculated from experimental log K ow values from the literature where available, with a mean signed error of 2.3 kJ/mol and mean unsigned error of 3.7 kJ/mol. The results allow assignment of log K ow for α-and β-diastereomers of arteether, and prediction of log K ow for β-DHA and five experimental drugs. Linear least square analysis of log K ow and log K vow versus terminal elimination half-life showed strong linear relationships, once the data points for the 4-aminoquinoline drugs, mefloquine and pyronaridine were found to follow their own linear relationship, which is consistent with their different plasma protein binding. The linear relationship between the computed log K vow and terminal elimination half-life was particularly strong, R 2 = 0.99 and F = 467, and can be interpreted in terms of a simple pharmacokinetic model. Terminal elimination half-life for β-DHA and four experimental artemisinin drugs were estimated based on this linear relationship between log K vow and terminal t 1/2. The computed log K ow and log K vow values for epimers α- and β-DHA and α and β-arteether provide physical data that may be helpful in understanding their different pharmacokinetics and activity based on their different molecular geometries. Relative solubility of quinine and quinidine are found to be sensitive to thermal corrections to enthalpy and to vibrational entropy and do not follow the general trend of longer terminal t 1/2 with greater predicted log K ow. Geometric relaxation of α- and β-DHA in solvent and inclusion of thermal correction for enthalpy and entropy results in correct prediction that α-DHA is favored in aqueous environments compared to β-DHA. Predictions made regarding experimental drugs have implications regarding their potential use in response to artemisinin drug-resistant strains.

Dihydroartemisinin-Loaded Magnetic Nanoparticles for Enhanced Chemodynamic Therapy

Recently, chemodynamic therapy (CDT) has represented a new approach for cancer treatment with low toxicity and side effects. Nonetheless, it has been a challenge to improve the therapeutic effect through increasing the amount of reactive oxygen species (ROS). Herein, we increased the amount of ROS agents in the Fenton-like reaction by loading dihydroartemisinin (DHA) which was an artemisinin (ART) derivative containing peroxide groups, into magnetic nanoparticles (MNP), thereby improving the therapeutic effect of CDT. Blank MNP were almost non-cytotoxic, whereas three MNP loading ART-based drugs, MNP-ART, MNP-DHA, and MNP-artesunate (MNP-AS), all showed significant killing effect on breast cancer cells (MCF-7 cells), in which MNP-DHA were the most potent. What's more, the MNP-DHA showed high toxicity to drug-resistant breast cancer cells (MCF-7/ADR cells), demonstrating its ability to overcome multidrug resistance (MDR). The study revealed that MNP could produce ferrous ions under the acidic condition of tumor microenvironment, which catalyzed DHA to produce large amounts of ROS, leading to cell death. Further experiments also showed that the MNP-DHA had significant inhibitory effect on another two aggressive breast cancer cell lines (MDA-MB-231 and MDA-MB-453 cells), which indicated that the great potential of MNP-DHA for the treatment of intractable breast cancers.

An in vitro toolbox to accelerate anti-malarial drug discovery and development

Background

Modelling and simulation are being increasingly utilized to support the discovery and development of new anti-malarial drugs. These approaches require reliable in vitro data for physicochemical properties, permeability, binding, intrinsic clearance and cytochrome P450 inhibition. This work was conducted to generate an in vitro data toolbox using standardized methods for a set of 45 anti-malarial drugs and to assess changes in physicochemical properties in relation to changing target product and candidate profiles.

Methods

Ionization constants were determined by potentiometric titration and partition coefficients were measured using a shake-flask method. Solubility was assessed in biorelevant media and permeability coefficients and efflux ratios were determined using Caco-2 cell monolayers. Binding to plasma and media proteins was measured using either ultracentrifugation or rapid equilibrium dialysis. Metabolic stability and cytochrome P450 inhibition were assessed using human liver microsomes. Sample analysis was conducted by LC–MS/MS.

Results

Both solubility and fraction unbound decreased, and permeability and unbound intrinsic clearance increased, with increasing Log D_7.4. In general, development compounds were somewhat more lipophilic than legacy drugs. For many compounds, permeability and protein binding were challenging to assess and both required the use of experimental conditions that minimized the impact of non-specific binding. Intrinsic clearance in human liver microsomes was varied across the data set and several compounds exhibited no measurable substrate loss under the conditions used. Inhibition of cytochrome P450 enzymes was minimal for most compounds.

Conclusions

This is the first data set to describe in vitro properties for 45 legacy and development anti-malarial drugs. The studies identified several practical methodological issues common to many of the more lipophilic compounds and highlighted areas which require more work to customize experimental conditions for compounds being designed to meet the new target product profiles. The dataset will be a valuable tool for malaria researchers aiming to develop PBPK models for the prediction of human PK properties and/or drug–drug interactions. Furthermore, generation of this comprehensive data set within a single laboratory allows direct comparison of properties across a large dataset and evaluation of changing property trends that have occurred over time with changing target product and candidate profiles.

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.

SLCO1A2, SLCO1B1 and SLCO2B1 polymorphisms influences chloroquine and primaquine treatment in Plasmodium vivax malaria

AIM

The association of transporters gene polymorphisms with chloroquine/primaquine malaria treatment response was investigated in a Brazilian population.

PATIENTS & METHODS

Totally, 164 Plasmodium vivax malaria infected patients were included. Generalized estimating equations were performed to determine gene influences on parasitemia and/or gametocytemia clearance over treatment time.

RESULTS

Significant interaction between SLCO2B1 genotypes and treatment over time for parasitemia clearance rate on day 2 were observed (p FDR = 0.002). SLCO1A2 and SLCO1B1 gene treatment over time interactions were associated with gametocytemia clearance rate (p FDR = 0.018 and p FDR = 0.024). ABCB1, ABCC4 and SLCO1B3 were not associated with treatment response.

CONCLUSION

The present work presents the first pharmacogenetic report of an association between chloroquine/primaquine responses with OATP transporters.

Atovaquone and quinine anti-malarials inhibit ATP binding cassette transporter activity

Background

Therapeutic blood plasma concentrations of anti-malarial drugs are essential for successful treatment. Pharmacokinetics of pharmaceutical compounds are dependent of adsorption, distribution, metabolism, and excretion. ATP binding cassette (ABC) transport proteins are particularly involved in drug deposition, as they are located at membranes of many uptake and excretory organs and at protective barriers, where they export endogenous and xenobiotic compounds, including pharmaceuticals. In this study, a panel of well-established anti-malarial drugs which may affect drug plasma concentrations was tested for interactions with human ABC transport proteins.

Methods

The interaction of chloroquine, quinine, artemisinin, mefloquine, lumefantrine, atovaquone, dihydroartemisinin and proguanil, with transport activity of P-glycoprotein (P-gp), breast cancer resistance protein (BCRP), bile salt export pump (BSEP) and multidrug resistance-associated proteins (MRP) 1–4 were analysed. The effect of the anti-malarials on the ATP-dependent uptake of radio-labelled substrates was measured in membrane vesicles isolated from HEK293 cells overexpressing the ABC transport proteins.

Results

A strong and previously undescribed inhibition of BCRP-mediated transport by atovaquone with a 50% inhibitory concentration (IC₅₀) of 0.23 μM (95% CI 0.17-0.29 μM) and inhibition of P-gp-mediated transport by quinine with an IC₅₀ of 6.8 μM (95% CI 5.9-7.8 μM) was observed. Furthermore, chloroquine and mefloquine were found to significantly inhibit P-gp-mediated transport. BCRP transport activity was significantly inhibited by all anti-malarials tested, whereas BSEP-mediated transport was not inhibited by any of the compounds. Both MRP1- and MRP3-mediated transport were significantly inhibited by mefloquine.

Conclusions

Atovaquone and quinine significantly inhibit BCRP- and P-gp- mediated transport at concentrations within the clinically relevant prophylactic and therapeutic range. Co-administration of these established anti-malarials with drugs that are BCRP or P-gp substrates may potentially lead to drug-drug interactions.

Investigation of the functional role of P-glycoprotein in limiting the oral bioavailability of lumefantrine

In the quest to explore the reason for the low and variable bioavailability of lumefantrine, we investigated the possible role of P-glycoprotein (P-gp) in lumefantrine intestinal absorption. An in situ single-pass intestinal perfusion study in rats with the P-gp inhibitor verapamil or quinidine and an ATPase assay with human P-gp membranes indicated that lumefantrine is a substrate of P-gp which limits its intestinal absorption. To confirm these findings, an in vivo pharmacokinetic study was performed in rats. The oral administration of verapamil (10 mg/kg of body weight) along with lumefantrine caused a significant increase in its bioavailability with a concomitant decrease in clearance. The increase in bioavailability of lumefantrine could be due to inhibition of P-gp and/or cytochrome P450 3A in the intestine/liver by verapamil. However, in a rat intestinal microsomal stability study, lumefantrine was found to be resistant to oxidative metabolism. Further, an in situ permeation study clearly showed a significant role of P-gp in limiting the oral absorption of lumefantrine. Thus, the increase in lumefantrine bioavailability with verapamil is attributed in part to the P-gp-inhibitory ability of verapamil. In conclusion, lumefantrine is a substrate of P-gp, and active efflux by P-gp across the intestine partly contributed to the low/variable bioavailability of lumefantrine.

Potential P-glycoprotein-mediated drug-drug interactions of antimalarial agents in Caco-2 cells

Antimalarials are widely used in African and Southeast Asian countries, where they are combined with other drugs for the treatment of concurrent ailments. The potential for P-glycoprotein (P-gp)-mediated drug-drug interactions (DDIs) between antimalarials and P-gp substrates was examined using a Caco-2 cell-based model. Selected antimalarials were initially screened for their interaction with P-gp based on the inhibition of rhodamine-123 (Rho-123) transport in Caco-2 cells. Verapamil (100 μM) and quinidine (1 μM) were used as positive inhibition controls. Lumefantrine, amodiaquin, and artesunate all showed blockade of Rho-123 transport. Subsequently, the inhibitory effect of these antimalarials on the bi-directional passage of digoxin (DIG) was examined. All of the drugs decreased basal-to-apical (B-A) P-gp-mediated DIG transport at concentrations of 100 μM and 1 mM. These concentrations may reflect therapeutic doses for amodiaquin and artesunate. Therefore, clinically relevant DDIs may occur between certain antimalarials and P-gp substrates in general.

Computational prediction of CNS drug exposure based on a novel in vivo dataset

PURPOSE

To develop a computational model for predicting CNS drug exposure using a novel in vivo dataset.

METHODS

The brain-to-plasma (B:P) ratio of 43 diverse compounds was assessed following intravenous administration to Swiss Outbred mice. B:P ratios were subjected to PLS modeling using calculated molecular descriptors. The obtained results were transferred to a qualitative setting in which compounds predicted to have a B:P ratio > 0.3 were sorted as high CNS exposure compounds and those below this value were sorted as low CNS exposure compounds. The model was challenged with an external test set consisting of 251 compounds for which semi-quantitative values of CNS exposure were available in the literature.

RESULTS

The dataset ranged more than 1700-fold in B:P ratio, with 16 and 27 compounds being sorted as low and high CNS exposure drugs, respectively. The model was a one principal component model based on five descriptors reflecting molecular shape, electronegativity, polarisability and charge transfer, and allowed 74% of the compounds in the training set and 76% of the test set to be predicted correctly.

CONCLUSION

A qualitative computational model has been developed which accurately classifies compounds as being high or low CNS exposure drugs based on rapidly calculated molecular descriptors.

ABCB1 (P-glycoprotein) reduces bacterial attachment to human gastrointestinal LS174T epithelial cells

The aim of this project was to show elevated P-glycoprotein (P-gp) expression decreasing bacterial association with LS174T human gastrointestinal cells, and that this effect could be reversed upon blocking functional P-gp efflux. Staphylococcus aureus, Klebsiella pneumoniae, Pseudomonas aeruginosa, Lactobacillus acidophilus and numerous strains of Escherichia coli, from commensal to enteropathogenic and enterohaemorrhagic strains (O157:H7) were fluorescently labelled and incubated on LS174T cultures either with or without P-gp amplification using rifampicin. PSC-833 was used as a potent functional P-gp blocking agent. Staphylococcus and Pseudomonas displayed the greatest association with the LS174T cells. Surprisingly, lactobacilli retained more fluorescence than enteropathogenic-E. coli in this system. Irrespective of attachment differences between the bacterial species, the increase in P-gp protein expression decreased bacterial fluorescence by 25-30%. This included the GFP-labelled E. coli, and enterohaemorrhagic E. coli (O157:H7). Blocking P-gp function through the co-administration of PSC-833 increased the amount of bacteria associated with P-gp expressing LS174T cells back to control levels. As most bacteria were affected to the same degree, irrespective of pathogenicity, it is unlikely that P-gp has a direct influence on adhesion of bacteria, and instead P-gp may be playing an indirect role by secreting a bank of endogenous factors or changing the local environment to one less suited to bacterial growth in general.

Artemisinin-naphthoquine combination therapy for uncomplicated pediatric malaria: a pharmacokinetic study

Artemisinin-naphthoquine (ART-NQ) is a coformulated antimalarial therapy marketed as a single-dose treatment in Papua New Guinea and other tropical countries. To build on limited knowledge of the pharmacokinetic properties of the components, especially the tetra-aminoquinoline NQ, we studied ART-NQ disposition in Papua New Guinea children aged 5 to 12 years with uncomplicated malaria, comparing a single dose (15 and 6 mg/kg of body weight) administered with water (group 1; n = 13), a single dose (22 and 9 mg/kg) with milk (group 2) (n = 17), and two daily doses of 22 and 9 mg/kg with water (group 3; n = 16). The plasma NQ concentration was assayed by high-performance liquid chromatography, and the plasma ART concentration was assayed using liquid chromatography-mass spectrometry. Population-based multicompartment pharmacokinetic models for NQ and ART were developed. NQ disposition was best characterized by a three-compartment model with a mean absorption half-life (t(1/2)) of 1.0 h and predicted median maximum plasma concentrations that ranged as high as 57 μg/liter after the second dose in group 3. The mean NQ elimination t(1/2) was 22.8 days; clearance relative to bioavailability (CL/F) was 1.1 liters/h/kg; and volume at steady state relative to bioavailability (V(ss)/F) was 710 liters/kg. Administration of NQ with fat (8.5 g; 615 kJ) versus water was associated with 25% increased bioavailability. ART disposition was best characterized by a two-compartment model with a mean CL/F (4.1 liters/h/kg) and V/F (21 liters/kg) similar to those of previous studies. There was a 77% reduction in the bioavailability of the second ART dose (group 3). NQ has pharmacokinetic properties that confirm its potential as an artemisinin partner drug for treatment of uncomplicated pediatric malaria.

The role of P-glycoprotein and breast cancer resistance protein (BCRP) in bacterial attachment to human gastrointestinal cells

BACKGROUND AND AIMS

Active efflux proteins such as P-glycoprotein (P-gp) are thought to have a protective role in the intestinal tract by preventing xenotoxin absorption. Some bacteria also need to adhere to the intestinal tract before causing disease through adhesin secretion. Thus, this study was initiated to examine whether any association exists between bacterial adhesion.

METHODS

Three human cell lines (Caco2, RKO, and MCF7), and 6 species of bacteria were used in this study (Escherichia coli, Staphylococcus aureus, Salmonella typhimurium, Klebsiella pneumoniae, Clostridium sporogenes and Pseudomonas aeruginosa). Following incubation of our cells with active efflux inhibitors, bacteria incubated with a stable fluorescent dye were co-incubated at 37°C for various times up to 240min. Fluorescence intensity was used to compare bacterial attachment to these cell lines with either normal efflux protein expression or with induction or inhibition of efflux proteins.

RESULTS

P-gp inhibition by either PSC-833 or GF120918 resulted in a significant increase of all bacterial attachment to Caco2 cells up to 3 fold. RKO cells and MCF7 cells did not alter their bacterial attachment with PSC-833. Fumitremorgen C, a dedicated BCRP inhibitor had no effect. In addition, rifampicin, a P-gp inducer, resulted in some limited reduction in Salmonella and Klebsiella attachment only.

CONCLUSIONS

These results indicate P-gp expression may contribute to the resistance of potential bacterial toxicity, by preventing them adhering to human enterocytes cells in the gastrointestinal tract, which may reduce the risk or intensity of gastrointestinal disorders.

The pharmacogenetics of antimalaria artemisinin combination therapy

INTRODUCTION

Plasmodium falciparum malaria is one of the world's most lethal infectious diseases, commanding millions of drug administrations per year. The pharmacogenetics of these drugs is poorly known, although its application can be pivotal for the optimized management of this disease.

AREAS COVERED

The main components of artemisinin combination therapy (ACT), the worldwide main antimalarial strategy, are metabolized by the polymorphic CYP3A4 (mefloquine, artemether, lumefantrine), CYP2C8 (amodiaquine), CYP2A6 (artesunate) and CYP1A1/2 (amodiaquine/desethylamodiaquine), with dihydroartemisinin being acted by Phase II UDP-glucuronosyltransferases. The worldwide adoption of ACT is leading to a large number of antimalarial treatments. Simultaneously, the feared development of parasite drug resistance might drive dosing increases. In these scenarios of increased drug exposure, pharmacogenetics can be a key tool supporting evidence-based medicine aiming for the longest possible useful lifespan of this important chemotherapy.

EXPERT OPINION

Translation in this moment is not operationally possible at an individual level, but large population studies are achievable for: i) the development of robust pharmacogenetics markers; and ii) the parallel development of a pharmacogenetic cartography of malaria settings. Advances in the understanding of antimalarial pharmacogenetics are urgent in order to protect the exposed populations, enhance the effectiveness of ACT and, consequently, contributing for the long aimed elimination of the disease.

Absence of association between piperaquine in vitro responses and polymorphisms in the pfcrt, pfmdr1, pfmrp, and pfnhe genes in Plasmodium falciparum

We have analyzed the profiles of 23 of Plasmodium falciparum strains for their in vitro chemosusceptibilities to piperaquine (PPQ), dihydroartemisinin (DHA), chloroquine, monodesethylamodiaquine, quinine, mefloquine, lumefantrine, atovaquone, pyrimethamine, and doxycycline (DOX) in association with polymorphisms in genes involved in quinoline resistance (Plasmodium falciparum crt [pfcrt], pfmdr1, pfmrp, and pfnhe). The 50% inhibitory concentrations (IC(50)s) for PPQ ranged from 29 to 98 nM (geometric mean = 57.8 nM, 95% confidence interval [CI] = 51 to 65) and from 0.4 to 5.8 nM for DHA (geometric mean = 1.8 nM, 95% CI = 1.4 to 2.3). We found a significant positive correlation between the responses to PPQ and DHA (r(2) = 0.17; P = 0.0495) and between the responses to PPQ and DOX (r(2) = 0.41; P = 0.001). We did not find a significant association between the PPQ IC(50) (0.0525 < P < 0.9247) or the DHA IC(50) (0.0138 < P < 0.9018) and polymorphisms in the pfcrt, pfmdr1, pfmrp, and pfnhe-1 genes. There was an absence of cross-resistance with quinolines, and the IC(50)s for PPQ and DHA were found to be unrelated to mutations in the pfcrt, pfmdr1, pfmrp, and pfnhe-1 transport protein genes, which are involved in quinoline antimalarial drug resistance. These results confirm the interest in and the efficacy of the combination of PPQ and DHA for areas in which parasites are resistant to chloroquine or other quinolines.

Pharmacokinetics and metabolism of the antimalarial piperaquine after intravenous and oral single doses to the rat

This study aimed to evaluate the pharmacokinetic properties of piperaquine in the rat after intravenous and oral administration, and to identify and characterize the main piperaquine metabolites in rat plasma, urine, faeces and bile after intravenous administration. Male Sprague-Dawley rats were administered piperaquine as an emulsion orally or as a short-term intravenous infusion. Venous blood for pharmacokinetic evaluation was frequently withdrawn up to 90 h after dose. Urine, bile and faeces were collected after an infusion in rats kept in metabolic cages or in anesthetized rats. Pharmacokinetic characterization was done by compartmental modeling and non-compartmental analysis using WinNonlin. Piperaquine disposition was best described by a 3-compartment model with a rapid initial distribution phase after intravenous administration. The pharmacokinetics of piperaquine was characterized by a low clearance, a large volume of distribution and a long terminal half-life. Piperaquine displayed a low biliary clearance and less than 1% of the total dose was recovered in urine. The absolute oral bioavailability was approximately 50%. The main metabolite after intravenous administration of piperaquine was a carboxylic acid product identical to that reported in humans. The similarity with results in humans indicates the rat to be a suitable species for nonclinical in vivo piperaquine studies.

Fexofenadine hydrochloride in the treatment of allergic disease: a review

Fexofenadine is a selective, non-sedating H1 receptor antagonist, marketed in the United States since 2000. The FDA approved an oral suspension in 2006, for the treatment of seasonal allergic rhinitis and chronic idiopathic urticaria in children. The tablet, capsule, and oral suspension are bioequivalent. Although fexofenadine does not use P450 CYP 3A4 it does interact with a number of drugs at P-glycoprotein and organic anion transporter polypeptides. The risk of toxicity from other drugs may increase with the administration of fexofenadine. Orange and grapefruit juices reduce the bioavailability of fexofenadine. Fexofenadine has been shown to have an impact on inflammatory mediators, other than histamine, such as decreasing the production of LTC₄, LTD₄, LTE₄, PGE₂, and PGF_2α; inhibiting cyclo-oxygenase 2, thromboxane; limiting iNOS generation of NO; decreasing cytokine levels (ICAM-1, ELAM-1, VCAM-1, RANTES, I-TAC, MDC, TARC, MMP-2, MMP-9, tryptase); and diminishing eosinophil adherence, chemotaxis, and opsonization of particles. These effects may provide benefit to some of the inflammatory responses of an acute allergic reaction and provide a basis for future development of H1 antagonists with stronger anti-inflammatory effects. These studies also support the contention that fexofenadine is effective for the treatment of allergic rhinits and chronic idiopathic urticaria.

Polymorphism of antimalaria drug metabolizing, nuclear receptor, and drug transport genes among malaria patients in Zanzibar, East Africa

Artemisinin-based combination therapy is a main strategy for malaria control in Africa. Zanzibar introduced this new treatment policy in 2003. The authors have studied the prevalence of a number of functional single nucleotide polymorphisms (SNPs) in genes associated with the elimination of the artemisinin-based combination therapy compounds in use in Zanzibar to investigate the frequencies of subgroups potentially at higher drug exposure and therefore possible higher risk of toxicity. One hundred three unrelated children with uncomplicated malaria from the Unguja and Pemba islands of Zanzibar were enrolled. With use of polymerase chain reaction (PCR)-restriction fragment length polymorphism and real-time PCR-based allele discrimination methods, the CYP2B6 (G15631T), CYP3A4 (A-392G), CYP3A5 (A6986G, G14690A, 27131-132 insT, C3699T) SNPs and MDR1 SNPs C3435T, G2677T/A, and T-129C were analyzed. PCR product sequencing was applied to regulatory regions of MDR1, the CYP3A4 proximal promoter, and to exons 2 and 5 of PXR, a gene coding for a nuclear factor activated by artemisinin antimalarials and associated with the transcription induction of most of the studied genes. Homozygous subjects for alleles coding for low activity proteins were found at the following frequencies: 1) MDR1: 2.9%; 2) CYP2B6: 9.7%; 3) CYP3A5: 14.1%; and 4) CYP3A4: 49.5%. No functionally relevant allele was found in the analyzed regions of PXR. A new MDR1 SNP was found (T-158C), located in a putative antigen recognition element. Ten (10.1%) subjects were predicted to be low metabolizers simultaneously for CYP3A4 and CYP3A5. This fraction of the population is suggested to be under higher exposure to certain antimalarials, including lumefantrine and quinine.