A phase I study of high dose camostat mesylate in healthy adults provides a rationale to repurpose the TMPRSS2 inhibitor for the treatment of COVID-19.

Camostat mesylate, an oral serine protease inhibitor, is used to treat chronic pancreatitis and reflux esophagitis. Recently, camostat mesylate and its active metabolite 4-(4-guanidinobenzoyloxy)phenylacetic acid (GBPA) were reported to inhibit the infection of cells by severe acute respiratory syndrome coronavirus 2 by inhibiting type II transmembrane serine protease. We conducted a phase I study to investigate high-dose camostat mesylate as a treatment for coronavirus disease 2019. Camostat mesylate was orally administered to healthy adults at 600 mg 4 times daily under either of the following conditions: fasted state, after a meal, 30 min before a meal, or 1 h before a meal, and the pharmacokinetics and safety profiles were evaluated. In addition, the time of plasma GBPA concentration exceeding the effective concentration was estimated as the time above half-maximal effective concentration (EC50 ) by using pharmacokinetic/pharmacodynamic modeling and simulation. Camostat mesylate was safe and tolerated at all dosages. Compared with the fasted state, the exposure of GBPA after a meal and 30 min before a meal was significantly lower; however, no significant difference was observed at 1 h before a meal. The time above EC50 was 11.5 h when camostat mesylate 600 mg was administered 4 times daily in the fasted state or 1 h before a meal. Based on the results of this phase I study, we are currently conducting a phase III study.

Target-controlled infusion and population pharmacokinetics of landiolol hydrochloride in patients with peripheral arterial disease.

PURPOSE: We previously determined the pharmacokinetic (PK) parameters of landiolol in healthy male volunteers and gynecological patients. In this study, we determined the PK parameters of landiolol in patients with peripheral arterial disease. METHODS: Eight patients scheduled to undergo peripheral arterial surgery were enrolled in the study. After inducing anesthesia, landiolol hydrochloride was administered at target plasma concentrations of 500 and 1,000 ng/mL for 30 minutes each. A total of 112 data points of plasma concentration were collected from the patients and used for the population PK analysis. A population PK model was developed using a nonlinear mixed-effect modeling software program (NONMEM). RESULTS: The patients had markedly decreased heart rates at 2 minutes after initiation of landiolol hydrochloride administration; however, systolic blood pressures were lower than the baseline values at only five time points. The concentration time course of landiolol was best described by a two-compartment model with lag time. The estimates of PK parameters were as follows: total body clearance, 30.7 mL/min/kg; distribution volume of the central compartment, 65.0 mL/kg; intercompartmental clearance, 48.3 mL/min/kg; distribution volume of the peripheral compartment, 54.4 mL/kg; and lag time, 0.633 minutes. The predictive performance of this model was better than that of the previous model. CONCLUSION: The PK parameters of landiolol were best described by a two-compartment model with lag time. Distribution volume of the central compartment and total body clearance of landiolol in patients with peripheral arterial disease were approximately 64% and 84% of those in healthy volunteers, respectively.

Target-controlled infusion and population pharmacokinetics of landiolol hydrochloride in gynecologic patients.

PURPOSE: We previously determined the pharmacokinetic (PK) parameters of landiolol in healthy male volunteers. In this study, we evaluated the usefulness of target-controlled infusion (TCI) of landiolol hydrochloride and determined PK parameters of landiolol in gynecologic patients. METHODS: Nine patients who were scheduled to undergo gynecologic surgery were enrolled. After inducing anesthesia, landiolol hydrochloride was administered at the target plasma concentrations of 500 and 1,000 ng/mL for each 30 min. A total of 126 data points of plasma concentration were collected from the patients and used for the population PK analysis. Furthermore, a population PK model was developed using the nonlinear mixed-effect modeling software. RESULTS: The patients had markedly decreased heart rates (HRs) at 2 min after the initiation of landiolol hydrochloride administration; however, their blood pressures did not markedly change from the baseline value. The concentration time course of landiolol was best described by a 2-compartment model with lag time. The estimate of PK parameters were total body clearance (CL) 34.0 mL/min/kg, distribution volume of the central compartment (V 1) 74.9 mL/kg, inter-compartmental clearance (Q) 70.9 mL/min/kg, distribution volume of the peripheral compartment (V 2) 38.9 mL/kg, and lag time (ALAG) 0.634 min. The predictive performance of this model was better than that of the previous model. CONCLUSION: TCI of landiolol hydrochloride is useful for controlling HR, and the PK parameters of landiolol in gynecologic patients were similar to those in healthy male volunteers and best described by a 2-compartment model with lag time.

Population pharmacokinetics and exposure-response relationship of a muscarinic receptor antagonist, imidafenacin.

This study was designed to update the population pharmacokinetic model and investigate the exposure-response (efficacy and safety) and concentration-QT relationships for imidafenacin, a synthetic orally active muscarinic receptor antagonist. The population pharmacokinetic model was updated using data from 90 healthy subjects and 852 patients with an overactive bladder. Plasma concentration data from nine clinical studies were used, including new data from a long-term dose escalation study. The updated population pharmacokinetic model for imidafenacin adequately described the plasma concentration profile. The results were generally consistent with those obtained from the previous population pharmacokinetic analysis, indicating that no new covariates were found to influence the pharmacokinetics of imidafenacin. Exposure-response relationships in the long-term dose escalation study were investigated using a regression analysis with efficacy and safety endpoints as dependent variables. There was no clear relationship between exposure and any endpoint. The concentration-QT relationship was also evaluated to assess whether imidafenacin prolonged the concentration-dependent QT interval. There was no clear relationship between the plasma concentration of imidafenacin and QTc, indicating that concentration-dependent QTc interval prolongation was not observed.

The prediction of human response to ONO-4641, a sphingosine 1-phosphate receptor modulator, from preclinical data based on pharmacokinetic-pharmacodynamic modeling.

The pharmacokinetic (PK) and pharmacodynamic (PD) parameters of ONO-4641 in humans were estimated using preclinical data in order to provide essential information to better design future clinical studies. The characterization of PK/PD was measured in terms of decreased lymphocyte counts in blood after administration of ONO-4641, a sphingosine 1-phosphate receptor modulator. Using a two-compartment model, human PK parameters were estimated from preclinical PK data of cynomolgus monkey and in vitro human metabolism data. To estimate human PD parameters, the relationship between lymphocyte counts and plasma concentrations of ONO-4641 in cynomolgus monkeys was determined. The relationship between lymphocyte counts and plasma concentrations of ONO-4641 was described by an indirect-response model. The indirect-response model had an I(max) value of 0.828 and an IC(50) value of 1.29 ng/ml based on the cynomolgus monkey data. These parameters were used to represent human PD parameters for the simulation of lymphocyte counts. Other human PD parameters such as input and output rate constants for lymphocytes were obtained from the literature. Based on these estimated human PK and PD parameters, human lymphocyte counts after administration of ONO-4641 were simulated. In conclusion, the simulation of human lymphocyte counts based on preclinical data led to the acquisition of useful information for designing future clinical studies.

Impact of pharmacokinetics and pharmacogenetics on the efficacy of pranlukast in Japanese asthmatics.

BACKGROUND AND OBJECTIVE: Wide inter-individual variability in therapeutic effects limits the efficacy of leukotriene (LT) receptor antagonists in the treatment of asthma. We have reported that genetic variability in the expression of LTC(4) synthase is associated with responsiveness to pranlukast in Japanese asthmatic patients. However, the effects of pharmacokinetic variability are less well known. This was an analysis of the pharmacokinetics of pranlukast in a population of adult asthmatics, and its effect on clinical responses. Other factors that may be related to the therapeutic effects of pranlukast, including LTC(4) synthase gene polymorphisms, were also investigated. METHODS: The population pharmacokinetics of pranlukast was analysed in a one-compartment model, using data collected in 50 Japanese adults with moderate to severe asthma, who were treated with pranlukast, 225 mg bd for 4 days. In 32 of these patients, in whom the clinical response to pranlukast (increase in FEV(1) after 4 weeks of treatment) was measured in a previous study, a combined pharmacokinetic and pharmacogenetic analysis was performed. RESULTS: Using the population pharmacokinetic model, the estimated the mean oral clearance (CL/F) of pranlukast was 16.4 L/h, and the inter-individual variability was 30.1%. Univariate and multivariate analyses showed that LTC(4) synthase polymorphisms, but not the CL/F of the drug, predicted an improvement in pulmonary function with pranlukast treatment (P < 0.05). CONCLUSIONS: There was marked inter-individual variability in the pharmacokinetics of pranlukast among adult asthmatics, but this had little impact on the clinical effectiveness of the drug.

In vitro metabolism and inhibitory effects of pranlukast in human liver microsomes.

We investigated the metabolism of pranlukast, a selective leukotriene agonist, and the potential for drug-drug interactions. Although cytochrome P450 (CYP) 3A4 appeared to be the major cytochrome P450 isoform involved in the metabolism of pranlukast, the results suggested that pranlukast metabolism was inhibited less than 50% by ketoconazole, a reversible CYP3A4 inhibitor, or by anti-CYP3A4 antibodies. Irreversible macrolide CYP3A4 inhibitors, clarithromycin, erythromycin and roxithromycin, exhibited little effect on pranlukast metabolism. On the other hand, pranlukast reversibly inhibited CYP2C8 and/or 2C9, and CYP3A4, with K(i) values of 3.9 and 4.1 micromol/l, respectively. The [I](in,max,u)/K(i) ratios were 0.004 and 0.003, respectively. The K(i) values were about 300-fold greater than the [I](in,max,u), therefore it is suggested that, at clinical doses, pranlukast will not affect the pharmacokinetics of concomitantly administered drugs that are primarily metabolized by CYP2C8 and/or 2C9 or CYP3A4.

Development and validation of an on-line two-dimensional reversed-phase liquid chromatography-tandem mass spectrometry method for the simultaneous determination of prostaglandins E(2) and F(2alpha) and 13,14-dihydro-15-keto prostaglandin F(2alpha) levels in human plasma.

We developed and validated an on-line reverse-phase two-dimensional LC/MS/MS (2D-LC/MS/MS) system for simultaneous determination of the levels of prostaglandin (PG) E(2) as well as PGF(2alpha) and its metabolite 13,14-dihydro-15-keto PGF(2alpha) (F(2alpha)-M) in human plasma. Analytes were extracted by a three-step solid-phase extraction. Samples were then analyzed by on-line 2D-LC/MS/MS with electrospray ionization in negative mode. The 2D-LC system is composed of two reverse-phase analytical columns with a trapping column linking the two analytical columns. While an acidic buffer was used for both separation dimensions, differing organic solvents were employed for each dimension: methanol for the first and acetonitrile for the second to increase resolving power. The 2D-LC/MS/MS method was highly selective and sensitive with a significantly lower limit of quantitation (0.5 pg/mL for PGE(2) and 2.5 pg/mL for PGF(2alpha) and F(2alpha)-M, respectively). Linearity of the 2D-LC/MS/MS system was demonstrated for the calibration ranges of 0.5-50 pg/mL for PGE(2) and 2.5-500 pg/mL for PGF(2alpha) and F(2alpha)-M, respectively. Acceptable precision and accuracy were obtained throughout the calibration curve ranges. This highly selective and sensitive method was successfully utilized to determine the endogenous levels of PGE(2), PGF(2alpha), and F(2alpha)-M in plasma samples from six (four male and two female) normal volunteers. The mean concentrations for each analyte were 0.755 pg/mL for PGE(2), 5.70 pg/mL for PGF(2alpha) and 9.48 pg/mL for F(2alpha)-M.

Validation and application of a 96-well format solid-phase extraction and liquid chromatography-tandem mass spectrometry method for the quantitation of digoxin in human plasma.

To evaluate the pharmacokinetics of digoxin in humans, a sensitive and specific LC/MS/MS method was developed and validated for the determination of digoxin concentrations in human plasma. The method was shown to be more sensitive, specific, accurate, and reproducible than common techniques such as RIA. For detection, a LC/MS/MS system with electro spray ionization tandem mass spectrometry in the positive ion-multiple reaction-monitoring (MRM) mode was used to monitor precursor to product ions of m/z 798.5-51.5 for digoxin and m/z 782.5-35.5 for the internal standard, digitoxin. The method was validated over a concentration range of 0.02-5 ng/mL and was found to have acceptable accuracy, precision, linearity, and selectivity. The mean extraction recovery from spiked plasma samples was above 80%. Imidafenacin, coadministered in a drug-drug interaction study, had no detectable influence on the determination of digoxin in human plasma. The novel method was applied to a drug-drug interaction study of digoxin and imidafenacin and the characterization of steady-state pharmacokinetics of digoxin in humans after oral administration at a dose of 0.25 mg on days 1 and 2 followed by 0.125 mg daily doses on days 3 through 8.

No effect of imidafenacin, a novel antimuscarinic drug, on digoxin pharmacokinetics in healthy subjects.

Plasma digoxin concentrations are increased by the coadministration of anticholinergic drugs, such as propantheline, which decrease gastrointestinal motility. The present study evaluated the effect of imidafenacin, a novel anticholinergic drug, on the pharmacokinetics of digoxin. The effect of imidafenacin on the pharmacokinetics of digoxin was examined in 14 healthy Japanese male subjects in a single-centre, open-label, randomized, two-way crossover study. Subjects received a daily oral dose of digoxin 0.25 mg on days 1 and 2 and digoxin 0.125 mg on days 3 to 8 (period 1). Following a 2-week washout period, digoxin was administered orally for 8 days in a similar manner (period 2). A twice daily dose of imidafenacin 0.1 mg was concomitantly administered with digoxin for 8 days either in period 1 or 2. The geometric mean ratios [GMR] (90% confidence intervals [CIs]) for digoxin C(max) and AUC(0-24) (with/without imidafenacin) at steady state were 0.88 (0.74, 1.04) and 1.00 (0.90, 1.10), respectively. The 90% CIs of GMR for digoxin trough concentration, urinary excretion amount and renal clearance at steady state fell within the range of 0.8 to 1.25. The steady-state pharmacokinetics of digoxin is not affected by concomitant administration of imidafenacin in healthy subjects.

Population pharmacokinetics of aprepitant and dexamethasone in the prevention of chemotherapy-induced nausea and vomiting.

PURPOSE: To develop a population pharmacokinetic model of aprepitant and dexamethasone in Japanese patients with cancer, explore the factors that affect the pharmacokinetics of aprepitant, and evaluate the effect of aprepitant on the clearance of intravenous dexamethasone. METHODS: A total of 897 aprepitant concentration measurements were obtained from 290 cancer patients and 25 healthy volunteers. For dexamethasone, a total of 847 measurements were obtained from 440 patients who were co-administered aprepitant (40, 125 mg, or placebo). Plasma concentration of aprepitant and dexamethasone were determined by liquid chromatography connected with a tandem mass spectrometer and analyzed by a population approach using NONMEM software. RESULTS: The plasma concentration time course of aprepitant was described using a one-compartment model with first-order absorption and lag time. Oral clearance (CL/F) of aprepitant was changed by aprepitant dose at doses of 40 or 125 mg. Body weight was the most influential intrinsic factor to CL/F of aprepitant. Age, ALT, and BUN also had mild effects on the CL/F. Typical population estimates of CL/F, apparent distribution volume (V(d)/F), absorption constant (K(a)) and absorption lag time were 1.54 L/h, 72.1 L, 0.893/h and 0.295 h, respectively. Inter-individual variability in CL/F, V(d)/F and K(a) were 53.9, 21.0, and 141%, respectively; intra-individual variability was 27.7%. The plasma concentration time course of intravenous dexamethasone was also described using a one-compartment model. Clearance of dexamethasone was decreased 24.7 and 47.5% by co-administration of aprepitant 40 and 125 mg. All final model estimates of aprepitant and dexamethasone fell within 10% of the bootstrapped mean. CONCLUSIONS: A pharmacokinetic model for aprepitant has been developed that incorporates body weight, age, ALT, BUN and aprepitant dose to predict the CL/F. The results of population pharmacokinetic analysis of dexamethasone support dose adjustment of dexamethasone in the case of co-administration with aprepitant.

Absolute bioavailability of imidafenacin after oral administration to healthy subjects.

WHAT IS ALREADY KNOWN ABOUT THIS SUBJECT: The absolute bioavailability of imidafenacin in rats and dogs is 5.6% and 36.1%, respectively. The pharmacokinetic profiles of imidafenacin after oral administration have been revealed. Imidafenacin is primarily metabolized to metabolites by CYP3A4 and UGT1A4. WHAT THIS STUDY ADDS: The absolute bioavailability of imidafenacin in human is 57.8%. The pharmacokinetic profiles of imidafenacin after intravenous administration are revealed. The formation of metabolites in the plasma is caused mainly by first-pass effects. AIMS: To investigate the absolute bioavailability of imidafenacin, a new muscarinic receptor antagonist, a single oral dose of 0.1 mg imidafenacin was compared with an intravenous (i.v.) infusion dose of 0.028 mg of the drug in healthy subjects. METHODS: Fourteen healthy male subjects, aged 21-45 years, received a single oral dose of 0.1 mg imidafenacin or an i.v. infusion dose of 0.028 mg imidafenacin over 15 min at two treatment sessions separated by a 1-week wash-out period. Plasma concentrations of imidafenacin and the major metabolites M-2 and imidafenacin-N-glucuronide (N-Glu) were determined. The urinary excretion of imidafenacin was also evaluated. Analytes in biological samples were measured by liquid chromatography tandem mass spectrometry. RESULTS: The absolute oral bioavailability of imidafenacin was 57.8% (95% confidence interval 54.1, 61.4) with a total clearance of 29.5 +/- 6.3 l h(-1). The steady-state volume of distribution was 122 +/- 28 l, suggesting that imidafenacin distributes to tissues. Renal clearance after i.v. infusion was 3.44 +/- 1.08 l h(-1), demonstrating that renal clearance plays only a minor role in the elimination of imidafenacin. The ratio of AUC(t) of both M-2 and N-Glu to that of imidafenacin was reduced after i.v. infusion from that seen after oral administration, suggesting that M-2 and N-Glu in plasma after oral administration were generated primarily due to first-pass metabolism. No serious adverse events were reported during the study. CONCLUSIONS: The absolute mean oral bioavailability of imidafenacin was determined to be 57.8%. Imidafenacin was well tolerated following both oral administration and i.v. infusion.

Effect of itraconazole on the pharmacokinetics of imidafenacin in healthy subjects.

The effect of itraconazole, a potent inhibitor of the CYP3A isoenzyme family, on the pharmacokinetics of imidafenacin, a novel synthetic muscarinic receptor antagonist, was investigated. Twelve healthy subjects participated in this open-label, self-controlled study. In period I, subjects received a single oral dose of 0.1 mg imidafenacin. In period II, they received multiple oral doses of 200 mg itraconazole for 9 days and a single oral dose of 0.1 mg imidafenacin on day 8. Plasma concentrations of imidafenacin and M-2, the major metabolite of imidafenacin metabolized by CYP3A4, were determined. Analytes were measured by liquid chromatography tandem mass spectrometry. Following coadministration with itraconazole, the maximum plasma concentration (C(max)) of imidafenacin increased 1.32-fold (90% confidence intervals [CIs]: 1.12-1.56), and the area under the plasma concentration-time curve from time 0 to infinity (AUC(0-infinity)) increased 1.78-fold (90% CI: 1.47-2.16). In conclusion, itraconazole increases the plasma concentrations of imidafenacin by inhibiting CYP3A4. Therefore, itraconazole or potent CYP3A4 inhibitors should be carefully added to imidafenacin drug regimens.

Effect of clarithromycin on the pharmacokinetics of pranlukast in healthy volunteers.

Pranlukast is a cysteinyl leukotriene receptor antagonist that has been used to treat bronchial asthma and allergic rhinitis. In vitro data suggest that pranlukast is a substrate of CYP3A4. Thus, the effect of clarithromycin, a potent CYP3A4 inhibitor, on the pharmacokinetics of pranlukast was examined in an open-label, randomized, two-way crossover study in 16 healthy male volunteers. In treatment A, volunteers received a single, 225 mg dose of pranlukast. In treatment B, 200 mg of clarithromycin was administered twice daily for 7 days and a single, 225 mg dose of pranlukast was coadministered on day 7. Blood samples were collected up to 24 hours after treatment, and pranlukast concentrations in the plasma were measured. The geometric mean ratios [GMR] (90% confidence intervals [CIs]) for pranlukast AUC(0-infinity) and C(max) (with/without clarithromycin) were 1.06 (0.91, 1.24) and 1.17 (0.95, 1.45), respectively. In conclusion, clarithromycin and pranlukast could be coadministered without dose adjustment because clarithromycin minimally affected the pharmacokinetics of pranlukast.

Population pharmacokinetics of landiolol hydrochloride in healthy subjects.

Landiolol hydrochloride is a newly developed cardioselective, ultra short-acting beta(1)-adrenergic receptor blocking agent used for perioperative arrhythmia control. The objective of this study was to characterize the population pharmacokinetics of landiolol hydrochloride in healthy male subjects. A total of 420 blood concentration data points collected from 47 healthy male subjects were used for the population pharmacokinetic analysis. NONMEM was used for population pharmacokinetic analysis. In addition, the final pharmacokinetic model was evaluated using a bootstrap method and a leave-one-out cross validation method. The concentration time course of landiolol hydrochloride was best described by a two-compartment model with lag time. The final parameters were total body clearance (CL: 36.6 mL/min/kg), distribution volume of the central compartment (V1: 101 mL/kg), inter-compartmental clearance (16.1 mL/min/kg), distribution volume of the peripheral compartment (55.6 mL/kg), and lag time (0.82 min). The inter-individual variability in the CL and V1 were 21.8% and 46.3%, respectively. The residual variability was 22.1%. Model evaluation by the two different methods indicated that the final model was robust and parameter estimates were reasonable. The population pharmacokinetic model for landiolol hydrochloride in healthy subjects was developed and was shown to be appropriate by both bootstrap and leave-one-out cross validation methods.

Population pharmacokinetic analysis of a novel muscarinic receptor antagonist, imidafenacin, in healthy volunteers and overactive bladder patients.

The objectives of this study were to develop a population pharmacokinetic model of imidafenacin and to explore the factors that affect the pharmacokinetics of imidafenecin. A total of 2406 plasma samples were collected from 90 healthy volunteers and 457 patients with overactive bladder. We determined the plasma concentrations of imidafenacin by liquid chromatography with tandem mass spectrometry; resultant data were analyzed by a population approach using NONMEM software. The imidafenacin plasma concentration time course was described using a two-compartment model with first-order absorption and lag time. The robustness of the population pharmacokinetic model was evaluated by bootstrap resampling. The results of the population pharmacokinetic analysis demonstrated that oral clearance was decreased with advancing age, increasing hepatic function parameters (AST and ALP), food intake, and itraconazole coadministration, while the first-order absorption rate constant was decreased with food intake. All parameter estimates from the final model fell within 20% of the bootstrapped mean. In conclusion, we developed a population pharmacokinetic model for imidafenacin that well-described plasma concentration profiles. We also identified the factors affecting imidafenacin pharmacokinetics.

Application of the correlation of in vitro dissolution behavior and in vivo plasma concentration profile (IVIVC) for soft-gel capsules--a pointless pursuit?

Plasma concentration profiles of arundic acid ((R)-(-)-2-propyloctanoic acid), an oil-like medicine, administered as soft-gel capsules in human clinical tests were predicted from the dissolution test data of the soft-gel capsules with different storage terms (short- and long-term stored drugs) by applying the in vitro-in vivo correlation (IVIVC). We established two linear-regression IVIVCs, which were characterized by either the in vitro dissolution behaviors against the pH 8.0 dissolution medium or the pH 6.8 dissolution medium containing 2% sodium dodecyl sulfate (SDS), in this study. Also, the prediction accuracies for the in vivo plasma profiles in humans for these two IVIVCs were compared. Regarding dissolution from the long-term stored capsule in pH 8.0 dissolution medium without surfactant, the prediction accuracies of the in vivo plasma profiles in humans were not satisfactory for the obtained IVIVC. The use of pH 6.8 dissolution medium containing 2% SDS, according to the Japanese guideline, improved the dissolution of the long-term stored capsule. Furthermore, the prediction accuracies for the in vivo plasma profiles in humans for these two IVIVCs were compared. The IVIVC established by the in vitro dissolution data obtained with the dissolution medium containing surfactant more effectively predicted the plasma drug concentration profiles following oral administrations of the soft-gel capsules under both storage conditions.