Concentration-QTc and cardiac safety analysis of single and multiple zavegepant nasal spray doses in healthy participants to support approval.

Zavegepant is a novel gepant administered as a nasal spray approved in the United States at a 10 mg dose for the acute treatment of migraine with or without aura in adults. The cardiovascular safety of zavegepant nasal spray was assessed in both single-ascending dose (SAD) and multiple-ascending dose (MAD) studies in healthy participants. The SAD study included 72 participants (54 active/18 placebo) who received 0.1-40 mg zavegepant or placebo. The MAD study included 72 participants (56 active/16 placebo) who received 5-40 mg zavegepant or placebo for 1-14 days. Plasma zavegepant pharmacokinetics and electrocardiographic (ECG) parameters (Fridericia-corrected QT interval [QTcF], heart rate, PR interval, ventricular depolarization [QRS], T-wave morphology, and U-wave presence) were analyzed pre- and post-zavegepant administration. Using pooled data from the SAD and MAD studies, the relationship between time-matched plasma zavegepant concentrations and QTc interval was assessed using a linear mixed-effects model to evaluate the potential for QTc interval prolongation. Results showed that single and multiple doses of zavegepant had no significant impact on ECG parameters versus placebo, and there was no concentration-dependent effect on QTcF interval. The estimated slope of the plasma zavegepant concentration-QTcF model was -0.053 ms per ng/mL with a 90% confidence interval of -0.0955 to -0.0110 (p = 0.0415), which is not considered clinically meaningful. At doses up to four times the recommended daily dose, zavegepant does not prolong the QT interval to any clinically relevant extent.

No clinically relevant electrocardiogram effects in a randomized TQT study of single therapeutic/supratherapeutic rimegepant doses in healthy adults.

A single-center, phase I, partially double-blind (double-blind regarding doses of rimegepant and placebo, and open label with respect to moxifloxacin), randomized, 12-sequence, four-period crossover study of therapeutic (75 mg) and supratherapeutic (300 mg) doses of rimegepant with placebo and moxifloxacin (400 mg) controls was designed to evaluate drug effect on the Fridericia corrected QT (QTcF) interval in healthy fasted adults. A total of 38 participants were randomized and dosed in the study. Electrocardiogram (ECG) data were available from 37 participants in the rimegepant 75-mg group, 38 participants in the rimegepant 300-mg group, and 36 participants in the moxifloxacin and placebo groups. Both the 75- and 300-mg doses of rimegepant had no clinically relevant effect on ECG parameters, including QTcF, heart rate, PR and QRS interval, T-wave morphology, and U-wave presence. All upper 90% confidence intervals for the QTcF effect with rimegepant were less than or equal to 4.69 ms, well below the 10-ms threshold for potential clinical significance. Assay sensitivity was demonstrated by the QT effect of moxifloxacin. Using both by-timepoint and concentration-QTc analysis, a placebo-corrected change-from-baseline QTcF greater than 10 ms could be excluded for rimegepant plasma concentrations up to ~10,000 ng/mL, representing concentrations at least 10.8-fold the maximum observed concentration of the 75-mg therapeutic dose of rimegepant.

Bioequivalence of rimegepant, a small molecule CGRP receptor antagonist, administered as an oral tablet, a sublingual orally disintegrating tablet, and a supralingual orally disintegrating tablet: two phase 1 randomized studies in healthy adults.

BACKGROUND: Rimegepant is an orally administered small molecule calcitonin gene-related peptide receptor antagonist indicated for the acute and preventive treatment of migraine. METHODS: Two single-center, phase 1, open-label, randomized bioequivalence studies were conducted in healthy adult non-smokers, aged 18-55 years. One study compared the rate and extent of absorption of the marketed formulation of rimegepant 75 mg orally disintegrating tablet (ODT) administered sublingually with rimegepant 75 mg oral tablet, an earlier development formulation; the second compared the rate and extent of absorption of 75 mg rimegepant ODT administered supralingually with rimegepant oral tablet. RESULTS: The ln-transformed geometric mean ratios for the area under the curve (AUC) from time 0 to the last available concentration time point (time t) (AUC0-t), AUC from time 0 to infinity (AUC0-inf), and maximum observed concentration (Cmax) of sublingual rimegepant ODT vs. rimegepant tablet were 97, 97, and 105%, respectively, and the 90% confidence intervals (CIs) were all within the predefined range (80-125%) for bioequivalence. The ln-transformed geometric mean ratios for the AUC0-t and AUC0-inf of supralingual rimegepant ODT vs. rimegepant tablet were 98%, the 90% CIs were within the predefined range (80-125%), and the geometric mean ratio for Cmax was 103% with the 95% upper confidence bound for the scaled average bioequivalence criterion of -0.0575 (within-participant coefficient of variation for the reference for Cmax > 30%) for bioequivalence. CONCLUSIONS: Rimegepant 75 mg ODT, administered sublingually or supralingually, and rimegepant 75 mg oral tablet were bioequivalent.

A Drug-Drug Interaction Study to Evaluate the Impact of Rimegepant on OCT2- and MATE1-Mediated Transport of Metformin in Healthy Participants.

Rimegepant is a calcitonin gene-related peptide receptor antagonist approved for migraine treatment. This phase 1, open-label, single-center, fixed-sequence study evaluated the effect of rimegepant on the pharmacokinetics (PK) of metformin. Twenty-eight healthy participants received metformin 500 mg twice daily from Days 1 to 4 and Days 7 to 10, and once daily on Days 5 and 11. Rimegepant, 75 mg tablet, was administered once daily from Days 9 to 12. At pre-specified time points, plasma metformin concentration, serum glucose levels, and safety and tolerability were evaluated. A 16% increase in the area under the plasma metformin concentration-time curve (AUC) for 1 dosing interval (AUC0-τ,ss), a statistically insignificant increase in maximum and minimum steady-state metformin concentration (Cmax,ss and Cmin,ss), and a decrease in metformin renal clearance were observed on Day 11 following metformin-rimegepant coadministration compared with metformin alone; however, the changes were not clinically relevant. Additionally, coadministration of rimegepant with metformin did not induce clinically meaningful change in the maximum observed glucose concentration (Gmax) or AUCgluc compared with metformin alone. Overall, rimegepant and metformin coadministration did not result in clinically relevant changes in metformin PK, renal clearance, or the antihyperglycemic effects of metformin. Rimegepant is considered safe for use with metformin.

The Pharmacokinetics, Safety, and Tolerability of Rimegepant 75 mg Are Similar in Elderly and Nonelderly Adults: A Phase 1, Open-Label, Parallel-Group, Single-Dose Study.

Rimegepant is a small-molecule calcitonin gene-related peptide receptor antagonist approved for the acute treatment of migraine ± aura and preventive treatment of migraine in adults. The pharmacokinetics of rimegepant in elderly and nonelderly subjects were evaluated. In an open-label Phase 1 study, 14 elderly (aged 65 years or older) and 14 nonelderly (aged 18 to less than 45 years) subjects each received a single oral dose of rimegepant 75 mg. Blood samples were collected before dosing and through 96 hours after dosing. The pharmacokinetic parameters of rimegepant after a single dose were similar in both age groups. Geometric least-squares mean ratios (elderly/nonelderly) of the natural log-transformed maximum observed plasma concentration and natural log-transformed area under the plasma concentration-time curve from time 0 extrapolated to infinity were 96.6 and 104.6, respectively. Eight (28.6%) subjects (4 elderly, 4 nonelderly) experienced 1 or more adverse events (AEs); all AEs were mild in intensity, and no serious AEs or AEs leading to discontinuation were reported. Following a single 75-mg dose of oral rimegepant, pharmacokinetic parameters were similar in elderly and nonelderly adults; no dose adjustment is warranted in elderly subjects.

A placebo-controlled, randomized, single and multiple dose study to evaluate the safety, tolerability, and pharmacokinetics of rimegepant in healthy participants.

BACKGROUND: Rimegepant is an oral, small molecule calcitonin gene-related peptide receptor antagonist for acute treatment of migraine and migraine prevention. METHODS: This was a single-site, placebo-controlled, sequential, single and multiple ascending dose study in healthy males and females, aged 18-55 years, with no clinically significant medical history. The objectives were to assess the safety, tolerability, and pharmacokinetics of the oral capsule free-base formulation. Single oral doses of rimegepant from 25-1500 mg were evaluated in the single ascending dose phase, and 75-600 mg/day doses administered for 14 days were evaluated in the multiple ascending dose phase. RESULTS: No dose-related trends were observed in orthostatic systolic and diastolic blood pressure or heart rate after rimegepant administration. Rimegepant was rapidly absorbed with the median time of maximum observed plasma concentration from 1-3.5 hours. Rimegepant showed a more than dose-proportional increase in exposure from 25-1500 mg following a single dose and from 75-600 mg/day following multiple doses. CONCLUSIONS: Rimegepant was safe and generally well tolerated at single oral doses up to 1500 mg and multiple doses up to 600 mg/day for 14 days in healthy participants in this study. Median terminal half-life ranged from 8-12 hours across the wide range of single doses studied.

Effects of rimegepant 75 mg daily on the pharmacokinetics of a combined oral contraceptive containing ethinyl estradiol and norgestimate in healthy female participants.

OBJECTIVE: To assess the effect of single and multiple doses of rimegepant 75 mg dose on the pharmacokinetics of an oral contraceptive containing ethinyl estradiol (EE)/norgestimate (NGM) in healthy females of childbearing potential or non-menopausal females with tubal ligation. BACKGROUND: Females of childbearing age experience the highest prevalence of migraine and frequently inquire about the concomitant use of anti-migraine medications and contraceptives. Rimegepant, a calcitonin gene-related peptide receptor antagonist, demonstrated efficacy and safety for treating an acute migraine attack and preventing migraine. METHODS: This open-label, single-center, phase 1, drug-drug interaction study explored the effects of rimegepant 75 mg daily dose on the pharmacokinetics of an oral contraceptive containing EE/NGM 0.035 mg/0.25 mg in healthy females of childbearing potential or non-menopausal females with tubal ligation. During cycles 1 and 2, participants received EE/NGM once daily for 21 days followed by placebo tablets with inactive ingredients for 7 days. Rimegepant was administered during only cycle 2 for 8 days, from days 12 through 19. The primary endpoint was the effect of single and multiple doses of rimegepant on the pharmacokinetics of EE and norelgestromin (NGMN), an active metabolite of NGM, at steady state, including area under the concentration-time curve for 1 dosing interval (AUC0-τ,ss ) and maximum observed concentration (Css[max] ). RESULTS: The study enrolled 25 participants, with pharmacokinetic data assessed for 20 participants. A single 75 mg dose of rimegepant co-administered with EE/NGM increased exposures of EE and NGMN by ≤16% (geometric mean ratio [GMR], 1.03; 90% confidence interval [CI], 1.01-1.06; and GMR, 1.16; 90% CI, 1.13-1.20, respectively). After 8 days of co-administering EE/NGM with rimegepant, EE pharmacokinetic parameters, AUC0-τ,ss and Css(max) , increased by 20% (GMR, 1.20; 90% CI, 1.16-1.25) and 34% (GMR, 1.34; 90% CI, 1.23-1.46), respectively, and NGMN pharmacokinetic parameters increased by 46% (GMR, 1.46; 90% CI, 1.39-1.52) and 40% (GMR, 1.40; 90% CI, 1.30-1.51), respectively. CONCLUSIONS: The study identified modest elevations in overall EE and NGMN exposures after multiple doses of rimegepant, but these elevations are unlikely to be clinically relevant in healthy females with migraine.

Rimegepant 75 mg in Subjects With Hepatic Impairment: Results of a Phase 1, Open-Label, Single-Dose, Parallel-Group Study.

Rimegepant is a small-molecule calcitonin gene-related peptide receptor antagonist (gepant) with demonstrated efficacy and safety in the acute and preventive treatment of migraine. Here, we report the pharmacokinetics and safety of a single 75-mg oral dose of rimegepant in subjects with severe, moderate, or mild hepatic impairment and matched healthy subjects from an open-label, single-dose, 4-group phase 1 study. Thirty-six subjects aged 41-71 years were enrolled, including 6 each with severe, moderate, or mild hepatic impairment and 18 healthy subjects. All subjects completed the study. A <20% increase in total and unbound pharmacokinetics was observed in subjects with mild hepatic impairment and ≤65% increase with moderate hepatic impairment versus matched healthy controls. Total and unbound systemic exposure increased 2.0- and 3.9-fold in the severe hepatic impairment group. In subjects with severe hepatic impairment, geometric mean ratios (severe impairment/controls) for total concentrations were 202.2% for area under the plasma concentration-time curve from time 0 to the last quantifiable concentration, 202.2% for area under the plasma concentration-time curve from time 0 to infinity, and 189.1% for maximum observed plasma concentration. Corresponding geometric mean ratios using unbound concentrations were 388.8% and 388.7%, respectively. Three (8.3%) subjects reported 4 treatment-emergent adverse events. Rimegepant is not recommended for use in adults with severe hepatic impairment.

P-Glycoprotein and Breast Cancer Resistance Protein Transporter Inhibition by Cyclosporine and Quinidine on the Pharmacokinetics of Oral Rimegepant in Healthy Subjects.

Rimegepant (Nurtec ODT)-an orally administered, small-molecule calcitonin gene-related peptide receptor antagonist indicated for the acute and preventive treatment of migraine-is a substrate for both the P-glycoprotein and breast cancer resistance protein transporters in vitro. We evaluated the effects of concomitant administration of strong inhibitors of these transporters on the pharmacokinetics of rimegepant in healthy subjects. This single-center, open-label, randomized study was conducted in 2 parts, both of which were 2-period, 2-sequence, crossover studies. Part 1 (n = 15) evaluated the effect of a single oral dose of 200-mg cyclosporine, a strong inhibitor of the P-glycoprotein and breast cancer resistance protein transporters, on the pharmacokinetics of rimegepant 75 mg. Part 2 (n = 12) evaluated the effect of a single oral dose of 600-mg quinidine, a strong selective P-glycoprotein transporter, on the pharmacokinetics of rimegepant 75 mg. Coadministration with cyclosporine showed an increase in rimegepant area under the plasma concentration-time curve from time 0 to infinity and maximum observed concentration based on geometric mean ratios (90% confidence intervals [CIs]) of 1.6 (1.49-1.72) and 1.41 (1.27-1.57), respectively, versus rimegepant alone. Coadministration with quinidine showed an increase in rimegepant area under the plasma concentration-time curve from time 0 to infinity and maximum observed concentration geometric mean ratios (90% CIs) of 1.55 (1.40-1.72) and 1.67 (1.46-1.91), respectively, versus rimegepant alone. Strong P-glycoprotein inhibitors (cyclosporine, quinidine) increased rimegepant exposures (>50%, <2-fold). In parts 1 and 2, rimegepant coadministration was well tolerated and safe. The similar effect of cyclosporine and quinidine coadministration on rimegepant exposure suggests that inhibition of breast cancer resistance protein inhibition may have less influence on rimegepant exposure.

Human Milk and Plasma Pharmacokinetics of Single-Dose Rimegepant 75 mg in Healthy Lactating Women.

Objective: Investigate whether rimegepant-an oral small molecule calcitonin gene-related peptide receptor antagonist for the treatment of migraine-is excreted in human milk after a single 75 mg dose and characterize its concentration-time profile in the plasma and milk of healthy lactating women to determine the relative infant dose (RID). Methods: This open-label, single-center study enrolled healthy lactating women aged 18-40 years with a gestation of 37-42 weeks and uncomplicated delivery of a single healthy child ≥2 weeks (14 days) and ≤6 months before study drug administration. Plasma samples were collected 0, 1, 2, 4, and 8 hours postdose; human milk samples were collected at 0, 1, 2, 4, 8, 12, 16, 24, 32, and 36 hours. The milk:plasma drug concentration ratio was estimated as the ratio of the human milk:plasma areas under the curve. The RID (%) was calculated as 100 times the quotient of the body weight-normalized infant and maternal doses. Results: Subjects (N = 12) were enrolled between 25 January and 15 September 2020. The mean (standard deviation [SD]) age was 29.8 (3.6) years; mean (SD) body mass index was 26.8 (4.9) kg/m2. The mean (SD) RID of rimegepant was 0.51% (0.14). The mean (SD) body-weight normalized infant dose was 0.005 (0.001) mg/kg/day, the mean (SD) body-weight normalized maternal dose was 1.04 (0.18) mg/kg/day, and mean (SD) maternal body weight was 74.0 (13.3) kg. Conclusion: On a weight-adjusted basis, the mean RID of rimegepant was <1% of the maternal dose.

Dosing regimen optimisation for oseltamivir in immunocompromised paediatric patients with influenza: Extrapolation of efficacy.

AIMS: To optimise the dosing regimen of oseltamivir for immunocompromised (IC) paediatric patients (<18 years) with influenza, we used an extrapolation approach alongside clinical data. METHODS: Efficacy was extrapolated from adult IC patients to paediatric IC patients by leveraging existing efficacy, safety, pharmacokinetic (PK)/pharmacodynamic (PD), and disease-progression models of oseltamivir and oseltamivir carboxylate (OC). Data of IC paediatric patients from two studies (NV25719 and NV20234) were included in the population PK (n = 30), PK/PD analysis (n = 22) and disease modelling approach (n = 36). Simulations were performed to identify the optimal dosing regimen. RESULTS: Clearance of oseltamivir (CL) and OC (CLM ) were similar in IC and otherwise-healthy (OwH) patients <10 years, but decreased by 44.4% (95% CI: 26.8-62.0) and 49.1% (95% CI: 34.5-63.8), respectively, in IC patients aged 10-17 years versus OwH patients. There were no notable exposure-response relationships for any of the virologic PD analyses. Thus, no additional benefit was seen with oseltamivir carboxylate exposures higher than achieved with the conventional dose (75 mg twice daily, age- and weight-adjusted for children <13 years). The disease model illustrated that doses above the conventional oseltamivir dose had limited impact on viral kinetics in IC paediatric patients and a prolonged treatment duration of 10 days was favoured to limit potential viral rebound. CONCLUSION: An oseltamivir dosage recommendation (conventional dose, twice daily for 10 days) was established in IC paediatric patients with influenza, based on extrapolation of efficacy from IC adults, leveraging population PK, PK/PD, and disease modelling, whilst taking resistance and safety data into account.

Pharmacologic effects of oseltamivir in immunocompromised adult patients as assessed by population PK/PD analysis and drug-disease modelling for dosing regimen optimization.

AIM: Pharmacologic effects were analysed to determine a dose recommendation for oseltamivir in immunocompromised (IC) adults with influenza. METHODS: Quantitative clinical pharmacology methods were applied to data from 160 adult IC patients (aged 18-78 years) from two studies (NV20234, 150 patients; NV25118, 10 patients) who received oseltamivir 75-200 mg twice daily for up to 10 days. An established population-pharmacokinetic (PK) model with additional effects on oseltamivir and oseltamivir carboxylate (OC) clearance described the PK characteristics of oseltamivir in IC patients versus otherwise healthy (OwH) patients from previous clinical trials. Estimated PK parameters were used to evaluate exposure-response relationships for virologic endpoints (time to cessation of viral shedding, viral load measures and treatment-emergent resistance). A drug-disease model characterized the viral kinetics of influenza accounting for the effect of OC on viral production. RESULTS: Oseltamivir clearance was 32.5% lower (95% confidence interval [CI], 26.1-38.8) and OC clearance was 33.7% lower (95% CI, 23.2-44.1) in IC versus OwH patients. No notable exposure-response relationships were identified for exposures higher than those achieved after conventional dose oseltamivir 75 mg, which appeared to be close to the maximum effect of oseltamivir. Simulations of the drug-disease model predicted that initiating treatment within 48 hours of symptom onset had maximum impact, and a treatment duration of 10 days was favourable over 3-5 days to limit viral rebound. CONCLUSIONS: Our findings support the use of conventional-dose oseltamivir 75 mg twice daily for 10 days in the treatment of IC adult patients with influenza.

Mechanistic Population Pharmacokinetic Model of Oseltamivir and Oseltamivir Carboxylate Accounting for Physiological Changes to Predict Exposures in Neonates and Infants.

A mechanistic population-pharmacokinetic model was developed to predict oseltamivir exposures in neonates and infants accounting for physiological changes during the first 2 years of life. The model included data from 13 studies, comprising 436 subjects with normal renal function (317 pediatric subjects (≥ 38 weeks postmenstrual age (PMA), ≥ 13 days old) and 119 adult subjects < 40 years). Concentration-time profiles of oseltamivir and its active metabolite, oseltamivir carboxylate (OC), were characterized by a four-compartment model, with absorption described by three additional compartments. Renal maturational changes were implemented by description of OC clearance with allometric function of weight and Hill function of PMA. Clearance of OC increased with weight up to 43 kg (allometric coefficient 0.75). Half the adult OC clearance was reached at a PMA of 45.6 weeks (95% confidence interval (CI) 41.6-49.6) with a Hill coefficient of 2.35 (95% CI 1.67-3.04). The model supports the European Union/United States-approved 3 mg/kg twice-daily oseltamivir dose for infants < 1 year (PMA ≥ 38 weeks) and allows prediction of exposures in preterm neonates.

Prevalence and Antibiogram study of Rhodococcus equi in equines of Jammu and Kashmir, India.

The present study was conducted to determine the prevalence of Rhodococcus equi infection in equines of Jammu and Kashmir, India, and evaluate the zoonotic threat posed by this organism to equine owners and tourists. One hundred and forty-one samples (98 samples from adult animals ≥5 years old and 43 samples from foals less than 6 months old) were collected in duplicate from nasopharyngeal tract of equines for isolation and direct PCR. A total of 12 isolates of R. equi were recovered, of which 9 were from foals and 3 from adult animals. Therefore, the present study recorded prevalence rates of 20.93% and 3.06% among foals and adult equines respectively. The prevalence rates were found to be 25.58% and 4.08% by 16S rRNA species-specific PCR among foals and adult animals respectively. Thus, the PCR-based assay was found to be more sensitive and helped in quick detection of R. equi than the culture based method which is time consuming and laborious. However, the culture-based method is still preferred due to some limitations of PCR. The antibiogram of the isolates revealed that erythromycin and rifampicin were the most effective antimicrobials with 100% sensitivity, followed by amoxicillin (66.67%), lincomycin (58.3%) and kanamycin (58.3%). The results also revealed that resistance was highest for penicillin G (50%), followed by kanamycin (25%) and streptomycin (25%).

cis-1-Oxo-heterocyclyl-4-amido cyclohexane derivatives as NPY5 receptor antagonists.

The NPY5 receptor binding and pharmacokinetic properties of a novel series of cis-1-oxo-heterocyclyl-4-amido-cyclohexane derivatives are described.

The functional evaluation of human peptide/histidine transporter 1 (hPHT1) in transiently transfected COS-7 cells.

Recently, the expression of the human peptide/histidine transporter (hPHT1, SLC15A4) mRNA was observed in the GI tract and in Caco-2 cells, suggesting that it may participate in the intestinal absorption of peptide-based agents. This study aims to elucidate the: (i) protein expression pattern of hPHT1 (SLC15A4) in human small intestine; (ii) cloning of the hPHT1 full-length sequence; (iii) functional characterization of hPHT1 in transiently transfected COS-7 cells. The expression of hPHT1 was measured using Western blot and immunohistochemical analysis. The hPHT1 full-sequence was amplified from BeWo cells, inserted into the pcDNA3.1-V5/His TOPO plasmid and transiently transfected into COS-7 cells to investigate the uptake kinetics of [3H]histidine and [3H]carnosine. Time, pH and sodium-dependent uptake studies were performed in mock (empty vector) and hPHT1-COS-7 cells. Results demonstrated hPHT1 protein expression in different intestinal regions. Histidine and carnosine uptake was linear in hPHT1-COS-7 cells over 15 min and was found to be pH-dependent. These substrates and valacyclovir showed significantly higher uptake at pH 5.0 in the hPHT1 transients when contrasted to the mock COS-7 cells, whereas glycylsarcosine uptake was significantly lower and unaffected by pH. Other di- and tripeptides also showed affinity for hPHT1. This study presents the initial functional characterization, the protein expression of the hPHT1 transporter and provides insight into a potentially different route for increasing peptide and peptide-based drug transport.

Delineation of human peptide transporter 1 (hPepT1)-mediated uptake and transport of substrates with varying transporter affinities utilizing stably transfected hPepT1/Madin-Darby canine kidney clones and Caco-2 cells.

In the present investigation, the uptake and transport kinetics of valacyclovir (VACV), 5-aminolevulinic acid (5-ALA), and benzylpenicillin (BENZ) were studied in stably transfected Madin-Darby canine kidney (MDCK)/human peptide transporter 1 (hPepT1)-V5&His clonal cell lines expressing varying levels of epitope-tagged hPepT1 protein (low, medium, and high expression) and in Caco-2 cells to delineate hPepT1-mediated transport kinetics. These compounds were selected due to the fact that they are known PepT1 substrates, yet also have affinity for other transporters. Caco-2 cells, traditionally used for studying peptide-based drug transport, were included for comparison purposes. The time, pH, sodium, and concentration dependence of cellular uptake and permeability were measured using mock, clonal hPepT1-MDCK, and Caco-2 cells. A pH-dependent effect was observed in the hPepT1-expressing clones and Caco-2 cells, with an increase of 1.96-, 1.84-, and 2.05-fold for VACV, 5-ALA, and BENZ uptake, respectively, at pH 6 versus 7.4 in the high-expressing hPepT1 cells. BENZ uptake was significantly decreased in Caco-2 and MDCK cells in Na(+)-depleted buffer, whereas VACV uptake only decreased in Caco-2 cells. Concentration-dependent uptake studies in the mock-corrected hPepT1-MDCK and Caco-2 cells demonstrated hPepT1 affinity ranking of VACV > 5-ALA > BENZ. The apical-to-basal apparent permeability coefficient (P(app)) values of VACV, 5-ALA, and BENZ in mock-corrected hPepT1-MDCK cells showed solely hPepT1-mediated transport in contrast to Caco-2 cells. Lower K(m) values and higher P(app) in Caco-2 cells compared with hPepT1-MDCK cells suggested the involvement of multiple transporters in Caco-2 cells. Thus, hPepT1-MDCK cells corrected for endogenous transporter expression may be a more appropriate model for screening compounds for their affinity to hPepT1.

A novel hPepT1 stably transfected cell line: establishing a correlation between expression and function.

Stably transfected MDCK/hPepT1-V5&His clonal cell lines expressing varying levels of epitope-tagged hPepT1 protein were established to quantify the relationship between transgene hPepT1 expression levels and its functional kinetics in facilitating peptide and peptide-like drug uptake and transport in vitro. The hPepT1 sequence was amplified from Caco-2 cell mRNA, inserted into the pcDNA3.1 -V5&His TOPO plasmid, and transfected into MDCK cells. Transgene protein levels were quantified by Western Blot analysis utilizing a standard curve generated with a positive control protein containing a V5&His epitope. Three clones expressing different levels of the hPepT1 fusion protein (low, medium, and high) were selected for the functional characterization with [14C]Gly-Sar and [3H]carnosine. The MDCK/hPepT1 cells expressed a novel hPepT1/epitope tag protein with an apparent molecular mass of 110 kDa. The [14C]Gly-Sar uptake in the transfected cells was sodium-independent and pH-dependent, demonstrating enhanced uptake, the rate of which increased significantly from the weakly to strongly expressing hPepT1 MDCK/hPepT1 -V5&His clones as compared to the mock cell line at pH 6.0. The uptake and permeability of [14C]Gly-Sar and [3H]carnosine demonstrated a direct correlation between the hPepT1 level of expression, uptake, and transport capabilities. Molecular and functional characterization of the MDCK/hPepT1-V5&His cell line confirmed a directly proportional relationship between Vmax and Papp versus the molar levels of hPepT1 transgene expression. This stably transfected hPepT1 cell line may serve as a useful in vitro model for screening and quantifying peptide and peptide-like drug transport as a function of hPepT1 expression in drug discovery.

Expression of multiple drug resistance conferring proteins in normal Chinese and Caucasian small and large intestinal tissue samples.

Multidrug resistance conferring proteins (MDRCP) are ATP-binding cassette (ABC) transporters known to significantly influence the absorption, distribution, metabolism, and elimination (ADME) and toxic behavior of many therapeutic agents. Research in the pharmacogenomics area has suggested that mutations and variable expression patterns of these MDCRPs may exist in tissue samples from different ethnic groups. The goal of this study was to examine the expression of P-glycoprotein (PGP), sister of PGP (S-PGP), multidrug resistance protein 3 (Mdr3), multidrug resistance like proteins 1-5 (MRP 1-5), and lung resistance associated protein (LRP) in tissue slides and protein lysates derived from normal adult small or large intestines of Caucasian or Chinese origin. Our results demonstrated ubiquitous expression of PGP, MRP 1, MRP 4, and LRP in the small and large intestinal epitheliums originating from both Caucasian and Chinese origin. S-PGP, Mdr3, MRP 2, and MRP 3 exhibited variable expression in the tissue slides and protein lysates derived from the Chinese and Caucasian small and large intestines. MRP 5 was not observed in any of the samples studied. The results suggest that MDCRPs may have distinct expression profiles in the small and large intestines that potentially vary with genetic background. These studies provide a foundation for further investigations to verify these findings across a wider number of patients of different ethnic backgrounds.

Piperine, a major constituent of black pepper, inhibits human P-glycoprotein and CYP3A4.

Dietary constituents (e.g., in grapefruit juice; NaCl) and phytochemicals (e.g., St. John's wort) are important agents modifying drug metabolism and transport and thereby contribute to interindividual variability in drug disposition. Most of these drug-food interactions are due to induction or inhibition of P-glycoprotein and/or CYP3A4. Preliminary data indicate that piperine, a major component of black pepper, inhibits drug-metabolizing enzymes in rodents and increases plasma concentrations of several drugs, including P-glycoprotein substrates (phenytoin and rifampin) in humans. However, there are no direct data whether piperine is an inhibitor of human P-glycoprotein and/or CYP3A4. We therefore investigated the influence of piperine on P-glycoprotein-mediated, polarized transport of digoxin and cyclosporine in monolayers of Caco-2 cells. Moreover, by using human liver microsomes we determined the effect of piperine on CYP3A4-mediated formation of the verapamil metabolites D-617 and norverapamil. Piperine inhibited digoxin and cyclosporine A transport in Caco-2 cells with IC(50) values of 15.5 and 74.1 microM, respectively. CYP3A4-catalyzed formation of D-617 and norverapamil was inhibited in a mixed fashion, with K(i) values of 36 +/- 8 (liver 1)/49 +/- 6 (liver 2) and 44 +/- 10 (liver 1)/77 +/- 10 microM (liver 2), respectively. In summary, we showed that piperine inhibits both the drug transporter P-glycoprotein and the major drug-metabolizing enzyme CYP3A4. Because both proteins are expressed in enterocytes and hepatocytes and contribute to a major extent to first-pass elimination of many drugs, our data indicate that dietary piperine could affect plasma concentrations of P-glycoprotein and CYP3A4 substrates in humans, in particular if these drugs are administered orally.