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

Pyronaridine: a review of its clinical pharmacology in the treatment of malaria

Pyronaridine-artesunate was recently strongly recommended in the 2022 update of the WHO Guidelines for the Treatment of Malaria, becoming the newest artemisinin-based combination therapy (ACT) for both uncomplicated Plasmodium falciparum and Plasmodium vivax malaria. Pyronaridine-artesunate, available as a tablet and paediatric granule formulations, is being adopted in regions where malaria treatment outcome is challenged by increasing chloroquine resistance. Pyronaridine is an old antimalarial agent that has been used for more than 50 years as a blood schizonticide, which exerts its antimalarial activity by interfering with the synthesis of the haemozoin pigment within the Plasmodium digestive vacuole. Pyronaridine exhibits a high blood-to-plasma distribution ratio due to its tendency to accumulate in blood cells. This feature is believed to play a crucial role in its pharmacokinetic (PK) properties and pharmacological activity. The PK characteristics of pyronaridine include rapid oral absorption, large volumes of distribution and low total body clearance, resulting in a long terminal apparent half-life. Moreover, differences in PK profiles have been observed between healthy volunteers and malaria-infected patients, indicating a potential disease-related impact on PK properties. Despite a long history, there is only limited knowledge of the clinical PK and pharmacodynamics of pyronaridine, particularly in special populations such as children and pregnant women. We here provide a comprehensive overview of the clinical pharmacology of pyronaridine in the treatment of malaria.

In Vitro Evaluation of P-gp-Mediated Drug-Drug Interactions Using the RPTEC/TERT1 Human Renal Cell Model

BACKGROUND AND OBJECTIVES

In vitro evaluation of the P-glycoprotein (P-gp) inhibitory potential is an important issue when predicting clinically relevant drug-drug interactions (DDIs). Located within all physiological barriers, including intestine, liver, and kidneys, P-gp plays a major role in the pharmacokinetics of various therapeutic classes. However, few data are available about DDIs involving renal transporters during the active tubular secretion of drugs. In this context, the present study was designed to investigate the application of the human renal cell line RPTEC/TERT1 to study drug interactions mediated by P-gp.

METHODS

The P-gp inhibitory potentials of a panel of drugs were first determined by measuring the intracellular accumulation of rhodamine 123 in RPTEC/TERT1 cells. Then four drugs were selected to assess the half-maximal inhibitor concentration (IC50) values by measuring the intracellular accumulation of two P-gp-substrate drugs, apixaban and rivaroxaban. Finally, according to the FDA guidelines, the [I₁]/IC50 ratio was calculated for each combination of drugs to assess the clinical relevance of the DDIs.

RESULTS

The data showed that drugs which are known P-gp inhibitors, including cyclosporin A, ketoconazole, and verapamil, caused great increases in rhodamine 123 retention, whereas noninhibitors did not affect the intracellular accumulation of the P-gp substrate. The determined IC50 values were in accordance with the inhibition profiles observed in the rhodamine 123 accumulation assays, confirming the reliability of the RPTEC/TERT1 model.

CONCLUSIONS

Taken together, the data demonstrate the feasibility of the application of the RPTEC/TERT1 model for evaluating the P-gp inhibitory potentials of drugs and consequently predicting renal drug interactions.

Association between ABCB1 Polymorphisms and Artesunate-Mefloquine Treatment Responses of Patients with Falciparum Malaria on the Thailand-Myanmar Border

A decrease in the clinical efficacy of a 3-day artesunate-mefloquine combination treatment was reported in the areas of multidrug-resistant Plasmodium falciparum along the Thailand-Myanmar border. The current study investigated the possible contribution of genetic polymorphisms of the three major genes encoding drug efflux transporters, ABCB1, ABCG2, and ABCC1, to responses to the aforementioned treatment in 91 patients with acute uncomplicated falciparum malaria residing along the Thailand-Myanmar border. Patients carrying homozygous mutant genotype ABCB1 c.1236C>T (TT) were found to have a three-times higher chance of successful treatment with this combination compared with other genotypes (CC and CT). Furthermore, whole blood mefloquine concentrations in these patients with the TT genotype were significantly lower than those of patients carrying the CC genotype. Patients with heterozygous mutant genotype (CT), however, were three-times more likely to experience treatment failure. No significant association was found with the ABCG2 and ABCC1 gene polymorphisms. The results suggest that ABCB1 c.1236CT polymorphisms could be useful genetic markers for predicting responses to the 3-day artesunate-mefloquine treatment; however, studies using larger sample sizes in different malaria-endemic areas are necessary to confirm this finding. This study highlights the impact of pharmacogenetic factors on antimalarial treatment responses and the basis for the application of control policies in various malaria-endemic areas.

Pregnancy and CYP3A5 Genotype Affect Day 7 Plasma Lumefantrine Concentrations

Pregnancy and pharmacogenetics variation alter drug disposition and treatment outcome. The objective of this study was to investigate the effect of pregnancy and pharmacogenetics variation on day 7 lumefantrine (LF) plasma concentration and therapeutic responses in malaria-infected women treated with artemether-lumefantrine (ALu) in Tanzania. A total of 277 (205 pregnant and 72 nonpregnant) women with uncomplicated Plasmodium falciparum malaria were enrolled. Patients were treated with ALu and followed up for 28 days. CYP3A4, CYP3A5, and ABCB1 genotyping were done. Day 7 plasma LF concentration and the polymerase chain reaction (PCR) - corrected adequate clinical and parasitological response (ACPR) at day 28 were determined. The mean day 7 plasma LF concentrations were significantly lower in pregnant women than nonpregnant women [geometric mean ratio = 1.40; 95% confidence interval (CI) of geometric mean ratio (1.119-1.1745), P < 0.003]. Pregnancy, low body weight, and CYP3A5*1/*1 genotype were significantly associated with low day 7 LF plasma concentration (P < 0.01). PCR-corrected ACPR was 93% (95% CI = 89.4-96.6) in pregnant women and 95.7% (95% CI = 90.7-100) in nonpregnant women. Patients with lower day 7 LF concentration had a high risk of treatment failure (mean 652 vs. 232 ng/ml, P < 0.001). In conclusion, pregnancy, low body weight, and CYP3A5*1 allele are significant predictors of low day 7 LF plasma exposure. In turn, lower day 7 LF concentration is associated with a higher risk of recrudescence. SIGNIFICANCE STATEMENT: This study reports a number of factors contributing to the lower day 7 lumefantrine (LF) concentration in women, which includes pregnancy, body weight, and CYP3A5*1/*1 genotype. It also shows that day 7 LF concentration is a main predictor of malaria treatment. These findings highlight the need to look into artemether-LF dosage adjustment in pregnant women so as to be able to maintain adequate drug concentration, which is required to reduce treatment failure rates in pregnant women.

Reversible inhibition of efflux transporters by hydrogel microdevices

Oral drug delivery is a preferred administration route due to its low cost, high patient compliance and fewer adverse events compared to intravenous administration. However, many pharmaceuticals suffer from poor solubility and low oral bioavailability. One major factor that contributes to low bioavailability are efflux transporters which prevent drug absorption through intestinal epithelial cells. P-glycoprotein (P-gp) and Breast Cancer Resistance Protein (BCRP) are two important efflux transporters in the intestine functioning to prevent toxic materials from entering systemic circulation. However, due to its broad substrate specificity, P-gp limits the absorption of many therapeutics, including chemotherapeutics and antibacterial agents. Methods to inhibit P-gp with competitive inhibitors have not been clinically successful. Here, we show that micron scale devices (microdevices) made from a commonly used biomaterial, polyethylene glycol (PEG), inhibit P-gp through a biosimilar mucus in Caco-2 cells and that transporter function is restored when the microdevices are removed. Microdevices were shown to inhibit P-gp mediated transport of calcein AM, doxorubicin, and rhodamine 123 (R123) and BCRP mediated transport of BODIPY-FL-prazosin. When in contact with Caco-2 cells, microdevices decrease the cell surface amount of P-gp without affecting the passive transport. Moreover, there was an increase in mucosal to serosal transport of R123 with microdevices in an ex-vivo mouse model and increased absorption in vivo. This biomaterial-based approach to inhibit efflux transporters can be applied to a range of drug delivery systems and allows for a nonpharmacologic method to increase intestinal drug absorption while limiting toxic effects.

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.

Effect of five novel 5-substituted tetrandrine derivatives on P-glycoprotein-mediated inhibition and transport in Caco-2 cells

Tetrandrine (Tet) is a potent inhibitor that reverses P-glycoprotein-mediated multidrug resistance (MDR). A number of novel 5-substituted tetrandrine derivatives were synthesized by the authors. The present study aimed at identifying potential P-gp inhibitor candidates, and intracellular uptake and efflux experiments and Caco-2 cell-based Transwell transport studies were performed. It was demonstrated that all five test compounds were able to inhibit efflux and increase intracellular uptake of the P-gp substrate, rhodamine-123 (Rho-123); the test compounds were P-gp inhibitors. The transepithelial transport experiment indicated that the secretory (basolateral-to-apical) of Rho-123 decreased, the absorption (apical-to-basolateral) increased and the transport efflux ratio (ER) reduced in the presence of the five compounds. Among the compounds, fluobenzene-Tet (TF) exhibited similar inhibitory effect as Tet. Although the other four test compounds exhibited weaker inhibitory effects than Tet and TF, the compounds exhibited stronger inhibitory effects compared with the reference compound verapamil. The study demonstrated that the five novel 5-substituted tetrandrine derivatives are able to act as inhibitors of P-gp to overcome P-gp-mediated drug resistance.

The drug transporter ABCB1 c.3435C>T SNP influences artemether-lumefantrine treatment outcome

Malaria treatment performance is potentially influenced by pharmacogenetic factors. This study reports an association study between the ABCB1 c.3435C>T, CYP3A4*1B (g.-392A>G), CYP3A5*3 (g.6986A>G) SNPs and artemether + lumefantrine treatment outcome in 103 uncomplicated malaria patients from Angola. No significant associations with the CYP3A4*1B and CYP3A5*3 were observed, while a significant predominance of the ABCB1 c.3435CC genotype was found among the recurrent infection-free patients (p < 0.01), suggesting a role for this transporter in AL inter-individual performance.

The Interactions of P-Glycoprotein with Antimalarial Drugs, Including Substrate Affinity, Inhibition and Regulation

The combination of passive drug permeability, affinity for uptake and efflux transporters as well as gastrointestinal metabolism defines net drug absorption. Efflux mechanisms are often overlooked when examining the absorption phase of drug bioavailability. Knowing the affinity of antimalarials for efflux transporters such as P-glycoprotein (P-gp) may assist in the determination of drug absorption and pharmacokinetic drug interactions during oral absorption in drug combination therapies. Concurrent administration of P-gp inhibitors and P-gp substrate drugs may also result in alterations in the bioavailability of some antimalarials. In-vitro Caco-2 cell monolayers were used here as a model for potential drug absorption related problems and P-gp mediated transport of drugs. Artemisone had the highest permeability at around 50 x 10(-6) cm/sec, followed by amodiaquine around 20 x 10(-6) cm/sec; both mefloquine and artesunate were around 10 x 10(-6) cm/sec. Methylene blue was between 2 and 6 x 10(-6) cm/sec depending on the direction of transport. This 3 fold difference was able to be halved by use of P-gp inhibition. MRP inhibition also assisted the consolidation of the methylene blue transport. Mefloquine was shown to be a P-gp inhibitor affecting our P-gp substrate, Rhodamine 123, although none of the other drugs impacted upon rhodamine123 transport rates. In conclusion, mefloquine is a P-gp inhibitor and methylene blue is a partial substrate; methylene blue may have increased absorption if co-administered with such P-gp inhibitors. An upregulation of P-gp was observed when artemisone and dihydroartemisinin were co-incubated with mefloquine and amodiaquine.

CYP2B6*6 genotype and high efavirenz plasma concentration but not nevirapine are associated with low lumefantrine plasma exposure and poor treatment response in HIV-malaria-coinfected patients

We investigated the influence of efavirenz (EFV)- or nevirapine (NVP)-based antiretroviral therapy (ART) on lumefantrine plasma exposure in HIV-malaria-coinfected patients and implication of pharmacogenetic variations. A total of 269 HIV patients with uncomplicated falciparum malaria on NVP-based ART (NVP-arm), EFV-based ART (EFV-arm) or not receiving ART (control-arm) were enrolled and treated with artemether-lumefantrine. Day-7 lumefantrine, baseline EFV and NVP plasma concentrations, and CYP2B6*6,*18, CYP3A4*1B, CYP3A5*3,*6,*7, ABCB1 c.3435C>T and ABCB1 c.4036A>G genotypes were determined. The median day-7 lumefantrine plasma concentration was significantly lower in the EFV-arm compared with that in NVP- and control-arm. High EFV plasma concentrations and CYP2B6*6/*6 genotype significantly correlated with low lumefantrine plasma concentrations and high rate of recurrent parasitemia. No significant effect of NVP-based ART on lumefantrine exposure was observed. In conclusion, owing to long-term CYP3A induction, EFV-based ART cotreatment significantly reduces lumefantrine plasma exposure leading to poor malaria treatment response, which is more pronounced in CYP2B6 slow metabolizers.

Phorbol 12-myristate 13-acetate inhibits P-glycoprotein-mediated efflux of digoxin in MDCKII-MDR1 and Caco-2 cell monolayer models

AIM

To investigate the effects of phorbol 12-myristate 13-acetate (PMA), a PKC activator, on P-glycoprotein-mediated efflux of digoxin in two cell transport models.

METHODS

Caco-2 cells, wild MDCKII cells (MDCKII-WT) and MDCKII cells transfected stably with human MDR1-gene encoding P-gp (MDCKII-MDR1) were examined. Cell viability was evaluated with MTT assay. Bidirectional transport of digoxin was evaluated in these cells. Intracellular ATP level was measured using ATP assay. P-gp ATPase activity was analyzed using a Pgp-Glo(TM) assay.

RESULTS

PMA (10 μmol/L) did not reduce the viability of the 3 types of cells. In Caco-2 and MDCKII-MDR1 cell monolayers, PMA (1, 10 and 100 nmol/L) dose-dependently inhibited the basolateral to apical transport of digoxin, but did not change the apical to basolateral transport. In addition, PMA did not affect both the basolateral to apical and apical to basolateral transport of digoxin in MDCKII-WT cell monolayer. In agreement with the above results, PMA dose-dependently reduced intracellular ATP level and stimulated P-gp ATPase activity in both Caco-2 and MDCKII-MDR1 cells. Verapamil (a positive control, 100 μmol/L) caused similar inhibition on digoxin efflux as PMA did, whereas 4α-PMA (a negative control, 100 nmol/L) had no effect.

CONCLUSION

PMA significantly inhibited P-gp-mediated efflux of digoxin in both Caco-2 and MDCKII-MDR1 cell monolayers via PKC activation.

Capsaicin pretreatment increased the bioavailability of cyclosporin in rats: involvement of P-glycoprotein and CYP 3A inhibition

Capsaicin (CAP), the main ingredient responsible for the hot pungent taste of chilli peppers. This study investigated the effect of CAP on the pharmacokinetics of Cyclosporin A (CyA) in rats and the mechanism of this food-drug interaction. The results indicated that after 7 days of low or middle dose of CAP (0.3 or 1.0 mg/kg), the blood concentration of CyA was not significantly changed compared with that of vehicle-treated rats, whereas the blood concentration of CyA in high dose group (3.0 mg/kg) was significantly increased. The total clearance (CL/F) of CyA was decreased, and the bioavailability was significantly increased to about 1.44-fold of that in vehicle-treated rats after 7 days of high dose CAP treatment. At this time, the P-gp and CYP3A1/2 in the liver and intestine were decreased at both the mRNA and protein levels. These results demonstrated that chronic ingestion of high doses of CAP will increase the bioavailability of CyA to a significant extent in rats and the food-drug interaction between CAP and CyA appears to be due to modulation of P-gp and CYP3A gene expression by CAP, with differential dose-dependence.

TFPI-2 downregulates multidrug resistance protein in 5-FU-resistant human hepatocellular carcinoma BEL-7402/5-FU cells

Tissue factor pathway inhibitor-2 (TFPI-2) is known to induce apoptosis and to suppress tumor metastasis in several types of cancer cells. However, there is little known about its reversal effect on chemoresistant tumor cells. This study investigated the effect of TFPI-2 in 5-fluorouracil (5-FU)-resistant human hepatocellular cancer BEL-7402/5-FU cells in vitro. We constructed TFPI-2 overexpression BEL-7402/5-FU cell lines and explored resistance index (RI) of 5-FU, function of the P-glycoprotein (P-gp) efflux pump, and the mRNA and protein expression of drug resistance gene, including multidrug resistance gene (MDR1), lung-resistance protein (LRP), multidrug resistance-associated protein (MRP1), glutathione-S-transferase-π (GST-π), excision repair cross-complementing gene 1 (ERCC1), and p38 phosphorylation. We found that TFPI-2 improved the RI of 5-FU and inhibited P-gp function. Western blotting and real-time PCR revealed that TFPI-2 also decreased mRNA and protein expression of MDR1, LRP, MRP1, GST-π, and ERCC1, whereas p38 phosphorylation was increased. We considered that TFPI-2 reduces 5-FU resistance in BEL-7402/5-FU cells, and the mechanism appears to involve p38-mediated downregulation of drug resistance gene expression such as MDR1, LRP, MRP1, GST-π, and ERCC1.