Population pharmacokinetic model of ABL001/CTX-009 (anti-VEGF/DLL4) in adult cancer patients with solid tumor.

ABL001/CTX-009 is a bispecific antibody targeting delta-like ligand-4 and vascular endothelial growth factor A. In this study, we developed a population pharmacokinetic (PK) model of ABL001/CTX-009 in patients with solid tumors. A total of 712 plasma concentrations from 30 patients with relapsed or refractory solid tumors were collected from a phase 1 study (NCT03292783). A population PK model was developed using a nonlinear mixed-effect method and was evaluated by graphical and numerical methods. Using the model, the steady-state concentrations were simulated to compare weight-based and fixed-dose regimens and to find optimal dosing intervals. The PK of ABL001/CTX-009 was well described by a two-compartment model with a parallel first-order and Michaelis-Menten elimination kinetics. Body weight was selected as a significant covariate on V1. Model evaluation results suggested that the model was adequate and robust with good precision. Simulations after administrations of fixed or weight-based doses showed similar plasma concentrations. Additionally, 10 mg/kg for every other week and 15 mg/kg for every three-week administration showed comparable plasma concentrations. In conclusion, the model well described the plasma concentrations of ABL001/CTX-009 in patients with solid tumors. The simulation suggested that weight-based dose and fixed dose can provide equivalent systemic exposure.

Effects of food and ethnicity on the pharmacokinetics of venadaparib, a next-generation PARP inhibitor, in healthy Korean, Caucasian, and Chinese male subjects.

AIM: Venadaparib is a next-generation poly(ADP-ribose) polymerase inhibitor under development for treating gastric cancer. This study aimed to evaluate the effects of food and ethnicity on the pharmacokinetics (PKs) and safety of venadaparib after a single oral administration in healthy Korean, Caucasian, and Chinese male subjects. METHODS: In this randomized, open-label, single-dose, two-sequence, two-period, and crossover study, Korean and Caucasian subjects received venadaparib 80 mg in each period (fasted or fed state) with a seven-day washout. In an open-label, single-dose study, Chinese subjects received venadaparib 80 mg only in the fasted state. Serial blood samples were collected up to 72 h post-dosing. RESULTS: Twelve subjects from each ethnic group completed the study. The geometric mean ratios (90% confidence intervals) of the maximum plasma concentration (Cmax) and area under the plasma concentration-time curve from time zero to the last measurable time point (AUClast) of venadaparib for the fed to fasted state were 0.82 (0.7457-0.9094) and 1.02 (0.9088-1.1339) in Koreans, and 0.77 (0.6871-0.8609) and 0.96 (0.9017-1.0186) in Caucasians, respectively. No statistically significant differences were observed in Cmax (P-value = 0.45) or AUClast (P-value = 0.30) among the three ethnic groups. A single venadaparib dose was well-tolerated. CONCLUSION: The overall systemic exposure of venadaparib was not affected by the high-fat meal, despite delayed absorption with a decreased Cmax in the fed state. The PK profiles were comparable among the Korean, Caucasian, and Chinese subjects. A single venadaparib 80 mg dose was safe and well-tolerated in both fasted and fed states.

Pharmacokinetics, pharmacodynamics and safety of oral formulation (CG-750) of ivaltinostat, a histone deacetylase inhibitor, compared to IV formulation (CG-745).

AIMS: CG-750 is an oral formulation of ivaltinostat, a newly developing histone deacetylase (HDAC) inhibitor. This study aimed to evaluate the pharmacokinetics (PK), pharmacodynamics (PD) and safety of an oral formulation (CG-750) of ivaltinostat compared to an intravenous (IV) formulation (CG-745). METHODS: A randomized, double-blind, placebo-controlled study was conducted in three cohorts. Subjects received either CG-745 (Cohorts 1 and 3: 125 mg; Cohort 2: 250 mg) or placebo followed by CG-750 (Cohort 1: 125 mg; Cohort 2: 375 mg; Cohort 3: 750 mg) or placebo. Blood samples for PK and PD assessment were collected up to 72 h post-dose. Histone H3 acetylation at sites K9, K9/K14 and K27 was assessed for area under the % acetylation induction versus time curve (AUEC). RESULTS: A total of 25 subjects were randomized, and 23 subjects completed the study (Cohort 1, n = 6; Cohort 2, n = 6; Cohort 3, n = 6; placebo, n = 5). The mean bioavailability of CG-750 was 10.6% (range: 4.18%-21.33%) and displayed linear PK in the dose range of 125-750 mg. The comparison of AUEC between formulations and the evaluation of the dose-AUEC relationship were inconclusive, due to the small sample sizes and significant variability observed in PD markers. All adverse events (AEs) were transient and of mild or moderate intensity. CONCLUSIONS: The oral formulation of ivaltinostat (CG-750) was generally well tolerated after a single dose. CG-750 displayed a mean bioavailability of 10.6%.

Coadministration of Voriconazole and Rifabutin Can Increase the Risk of Adverse Drug Reactions in Patients with Multiple Infections.

BACKGROUND: Coinfection of tuberculosis or nontuberculous mycobacteria and Aspergillus presents a challenge in medication selection because of the pharmacokinetic interactions between rifampin and voriconazole. Some researchers have suggested the use of rifabutin as an alternative to rifampin because of its lower hepatic cytochrome P450 enzyme induction potency despite its contraindication to drug labels. This study presents clinical cases of voriconazole and rifabutin coadministration and their potential risks. METHODS: This retrospective study was conducted using clinical data from patients who met the following criteria: (1) admitted to Seoul National University Hospital between July 2014 and August 2023 and (2) concurrently administered rifabutin and voriconazole for more than 5 days. RESULTS: Among the 6 patients analyzed, 4 experienced adverse drug reactions (ADRs). Three patients experienced visual and auditory hallucinations, lower extremity numbness, or delirious behavior. Two patients had prolonged the time from the start of the Q wave to the end of the T wave intervals, and 1 had elevated aspartate aminotransferase and alanine aminotransferase levels. In addition, 2 patients experienced severe nausea, poor oral intake, and weight loss. Despite receiving 1.81-fold the recommended voriconazole dosage, a therapeutic concentration (1.0-5.5 mg/L) was not achieved because of cytochrome P450 induction by rifabutin. However, during septic shock, the voriconazole concentration increased by 13.7- to 36-fold. CONCLUSIONS: Concurrent use of rifabutin and voriconazole was associated with ADRs, including the time from the start of the Q wave to the end of the T wave prolongation, hallucinations, and severe nausea. Moreover, initially, there was a significant decrease in voriconazole concentrations; however, these concentrations substantially increased during septic shock. Therefore, it is essential to monitor drug concentrations and ADRs during concurrent use of voriconazole and rifabutin.

Pharmacokinetic and pharmacodynamic interaction between DWP16001, an sodium-glucose cotransporter 2 inhibitor and metformin in healthy subjects.

AIMS: DWP16001 is a novel sodium-glucose cotransporter 2 inhibitor for the treatment of type 2 diabetes with selective and sustained sodium-glucose cotransporter 2 inhibition. We aimed to evaluate whether the coadministration of DWP16001 and metformin causes any changes in pharmacokinetics (PK) or pharmacodynamics (PD). METHODS: A randomized, open-label, single- and multiple-dose, 2-sequence, crossover study was conducted in healthy male subjects. Subjects received the following treatments: a single oral dose of DWP16001 (DWP) 2 mg, metformin immediate release 1000 mg (MET) twice daily for 7 days and a single oral dose of DWP and MET at steady-state for metformin (DWP+MET). Serial blood and interval urine were collected for PK and PD analyses. Safety and tolerability profiles were assessed throughout the study. RESULTS: DWP+MET displayed increased peak concentration and area under the concentration-time curve from time 0 to time of the last quantifiable concentration compared with DWP (per standard bioequivalence boundaries, 0.8-1.25); the geometric mean ratios (GMRs) and their 90% confidence intervals (CIs) were 1.22 (1.13-1.31) and 1.09 (1.05-1.14), respectively. DWP+MET and MET showed similar peak concentration and area under the concentration-time curve within a dosing interval at steady state for metformin; the GMRs and 90% CIs were 0.98 (0.90-1.06) and 1.05 (0.98-1.13), respectively. The amount of urinary glucose excretion from time 0 to 144 h was also comparable between DWP+MET and DWP (GMR and 90% CI; 0.99, 0.94-1.05). CONCLUSION: The results suggest that DWP16001 and metformin could be coadministered without clinically relevant PK and PD interactions.

Effects of CYP2C19 genetic polymorphisms on the pharmacokinetics of lacosamide in Korean patients with epilepsy.

OBJECTIVE: Many pharmacokinetic studies of lacosamide (LCM) have been reported, but no large-scale clinical study has been conducted on genetic polymorphisms that affect the metabolism of LCM. Therefore, we designed a pharmacogenetic study of LCM to explore the effect of genetic polymorphisms on serum LCM concentration. We evaluated the pharmacodynamic characteristics of LCM, including clinical efficacy and toxicity. METHODS: Adult patients with epilepsy who received LCM at Seoul National University Hospital were enrolled. Blood samples were obtained from 115 patients taking LCM for more than 1 month with unchanged doses and were used to analyze the serum LCM concentration, the concentration/dose (C/D) ratio and the single nucleotide polymorphisms (SNPs) of the cytochrome P450 (CYP)2C9 and CYP2C19 genes. In addition, clinical information-including efficacy, toxicity, and concomitant drugs-was collected. RESULTS: The serum LCM concentration showed a linear correlation with the daily dose (r = .66, p < .001). In genetic analysis, 43 patients (38.7%) were extensive metabolizers (EMs), 51 (45.9%) were intermediate metabolizers (IMs), and 17 (15.3%) were poor metabolizers (PMs). In the group comparison, mean serum concentrations and the C/D ratio showed significant differences between the three groups (p = .01 and p < .001, respectively). The C/D ratios of IM (27.78) and PM (35.6) were 13% and 39% higher than those of EM (25.58), respectively. In the pharmacodynamic subgroup analysis, patients in the ineffective LCM group had significantly lower serum concentrations (6.39 ± 3.25 vs. 8.44 ± 3.68 µg/ml, p = .024), whereas patients with adverse events had higher serum concentrations than those without adverse events (11.03 ± 4.32 vs. 7.4 ± 3.1 µg/ml, p < .001). Based on this, we suggest a reference range for LCM in the Korean population (6-9 µg/ml). SIGNIFICANCE: Genetic polymorphisms of the CYP2C19 gene affect the serum LCM concentration. Because efficacy and toxicity are apparently related to serum LCM levels, the genetic phenotype of CYP2C19 should be considered when prescribing LCM for patients with epilepsy.

Dose-dependent glucosuria of DWP16001, a novel selective sodium-glucose cotransporter-2 inhibitor, in healthy subjects.

AIMS: DWP16001 is a novel sodium-glucose cotransporter-2 inhibitor under development for the treatment of type 2 diabetes mellitus. This study was conducted to evaluate the pharmacokinetics, pharmacodynamics and safety of DWP16001 after single and multiple doses in healthy subjects. METHODS: A randomized, double-blind, placebo- and active-controlled, single- and multiple-dose study was conducted. Twelve subjects in each dose group received a single dose (0.2, 0.5, 1.0, 2.0 or 5.0 mg) or multiple doses (0.1, 0.3, 0.5, 1.0 or 2.0 mg once daily for 15 consecutive days) of DWP16001, dapagliflozin 10 mg or placebo at a ratio of 8:2:2. Serial blood and interval urine samples were collected for the pharmacokinetic and pharmacodynamic analyses. The safety and tolerability of DWP16001 were also assessed. RESULTS: A dose-dependent increase in the urinary glucose excretion was observed after a single dose, and the steady state urinary glucose excretion was 50-60 g/d after multiple doses in the dose range of 0.3-2.0 mg. DWP16001 was rapidly absorbed with the time to peak plasma concentration of 1.0-3.0 hours, and it exhibited a mean elimination half-life of 13-29 hours. The systemic exposure to DWP16001 increased proportionally with multiple dose administrations in the range of 0.1-2.0 mg. DWP16001 was well tolerated in all dose groups. CONCLUSION: DWP16001 induced glucosuria in a dose-dependent manner, and systemic exposure was observed after multiple doses. DWP16001 was well tolerated in single oral doses of up to 5.0 mg and in multiple oral doses of up to 2.0 mg.

Evaluation of safety and pharmacokinetics of bismuth-containing quadruple therapy with either vonoprazan or lansoprazole for Helicobacter pylori eradication.

AIMS: Helicobacter pylori (Hp) eradication plays a key role in the treatment and prevention of peptic ulcer diseases. Increasing clarithromycin resistance in Hp necessitates more effective treatments for eradication, such as bismuth-containing quadruple therapy. We aimed to compare the safety and pharmacokinetics (PK) of bismuth between vonoprazan- and lansoprazole-containing quadruple therapy in Hp-positive subjects. METHODS: In this randomised, double-blind, parallel-group study, Hp-positive subjects were randomised to receive vonoprazan- or lansoprazole-containing quadruple therapy. Each subject received vonoprazan 20 mg or lansoprazole 30 mg combined with bismuth 220 mg, clarithromycin 500 mg and amoxicillin 1000 mg twice daily for 14 days. Blood sampling and urine collection for bismuth PK were conducted predose and up to 12 hours postdose at steady-state. The PK parameters of bismuth were derived using a noncompartmental method and compared between treatments. An exploratory breath test for Hp was conducted at screening and at the follow-up visit on day 42. Safety was assessed by adverse event monitoring, physical examinations, vital signs, 12-lead electrocardiograms and clinical laboratory tests. RESULTS: A total of 30 subjects were randomised and 26 subjects completed the study (12 in the vonoprazan group and 14 in the lansoprazole group). The systemic exposure of bismuth in the 2 treatments was comparable (~5% difference). All subjects turned negative for Hp at the follow-up visit. No significant difference in safety profiles was noted between the 2 treatments. CONCLUSION: The systemic exposure of bismuth was similar between vonoprazan- and lansoprazole-containing quadruple therapy. Vonoprazan-containing quadruple therapy was safe and well tolerated.

Night-time gastric acid suppression by tegoprazan compared to vonoprazan or esomeprazole.

AIMS: Nocturnal acid breakthrough has been considered an unmet need of proton-pump inhibitors. Tegoprazan, a novel potassium-competitive acid blocker, is expected to show improved properties for this unmet need. This study was aimed to compare night-time acid suppression by tegoprazan with that by vonoprazan or esomeprazole, and to explore the effect of CYP2C19 phenotypes on acid-suppressive effects. METHODS: A randomized, open-label, 3-period, 6-sequence crossover study was conducted. A single oral dose of tegoprazan 50 mg, vonoprazan 20 mg or esomeprazole 40 mg was administered at night in each period. Continuous intragastric pH was monitored at baseline and after each dosing. RESULTS: Sixteen healthy subjects (6 CYP2C19 extensive metabolizers, 5 intermediate metabolizers, 5 poor metabolizers) completed the study. After a single dose of tegoprazan, intragastric pH increased more rapidly to over 4 at approximately 1 hour compared to the other treatments, and elevated intragastric pH was maintained stably at night. Tegoprazan exhibited night-time acid suppression for slightly but not significantly longer than vonoprazan, and greater than esomeprazole; % time at pH ≥ 4 at night was 66.0%, 60.5% and 36.1% for tegoprazan, vonoprazan and esomeprazole, respectively. Night-time acid suppression by tegoprazan and vonoprazan was not dependent on CYP2C19 phenotypes, while that by esomeprazole tended to be influenced by CYP2C19 phenotypes. CONCLUSION: Tegoprazan produced more rapid, potent and well sustained night-time acid suppression vs. vonoprazan or esomeprazole when administered at night. Furthermore, tegoprazan showed no CYP2C19 phenotype dependency in acid suppression. It suggests the potential of tegoprazan, especially in preventing nocturnal acid breakthrough.

A pilot study to investigate the utility of NAT2 genotype-guided isoniazid monotherapy regimens in NAT2 slow acetylators.

Isoniazid is a therapeutic agent for the treatment of latent tuberculosis infection. Genetic variants in the N-acetyltransferase 2 (NAT2) are associated with the safety and pharmacokinetics of isoniazid. The study aimed to evaluate the safety and pharmacokinetics of a NAT2 genotype-guided regimen of isoniazid monotherapy. A randomized, open-label, parallel-group and multiple-dosing study was performed in healthy subjects. The subjects received isoniazid for 29 days. The NAT2 slow acetylators (NAT2*5/*5, -*5/*6, -*5/*7, -*6/*6, -*6/*7, -*7/*7) randomly received standard dose (300 mg, standard-treatment group) or reduced dose (200 mg, PGx-treatment group) of isoniazid. Also, all the NAT2 rapid acetylators (NAT2*4/*4) received isoniazid 300 mg (reference group). The safety and pharmacokinetics were evaluated during the study. The PGx-treatment group showed a more stable serum liver enzyme profile and a lower incidence of adverse drug reactions (ADRs) than the standard-treatment group. The emergence rates of ADRs were 12.5, 60 and 33.3% in the reference, standard-treatment and PGx-treatment groups, respectively. The PGx-treatment group showed higher plasma isoniazid concentrations than the reference group, although the PGx-treatment group received a reduced dose of isoniazid. Our results showed that a NAT2 genotype-guided regimen may reduce ADRs during isoniazid monotherapy without concern over insufficient drug exposure.

Optimization and validation of a fluorogenic dipeptidyl peptidase 4 enzymatic assay in human plasma.

During the development of a specific dipeptidyl peptidase 4 (DPP4) inhibitor to treat type 2 diabetes, a fluorogenic kinetic analysis for DPP4 enzymatic activity using Gly-Pro-Aminomethylcoumarin (AMC) as a substrate was optimized and validated for recombinant DPP4 and human plasma samples. The sensitivity, calibration curve, detection range, accuracy, precision, recovery efficiency, Km constant, short/long-term stability, and stability after freezing-thawing cycles were analyzed. DPP4 enzymatic activity (mU/min) was measured as the initial velocity (Vo) of the enzymatic reaction over time. The sensitivity of the Vo value was 14,488 mU/min for recombinant DPP4 and 17,995 mU/min for human plasma samples. The dynamic ranges of the calibration curve were linear and reliable between 1.11 × 104-1.86 × 106 mU/min of the mean Vo value and in the DPP4 concentration range of 23.4-3,000 ng/mL. The assay's accuracy and precision met acceptance criteria for all samples. Plasma DPP4 was stable under various storage temperatures, even after three freeze-thaw cycles. Our optimized, validated bioanalytic method for measuring DPP4 activity in plasma samples was successfully employed to evaluate the effect of evogliptin (DA-1229) tartrate, which irreversibly and dose-dependently inhibits DPP4 enzymatic activity, without the dilution effect of human plasma samples and irrespective of the co-treated metformin.

Tolerability of lacosamide rapid dose titration: A randomized, multicenter, prospective, open-label study.

OBJECTIVE: Currently recommended dosing of lacosamide often necessitates long titration periods. However, the use of a regimen consisting of initial loading dose of 200 mg followed by a maintenance dose of 200 mg/day in practice suggests tolerability of more rapid titration schedules. We aimed to clarify whether the shortened titration schedule affects tolerability of lacosamide. METHODS: We evaluated the safety of two rapid titration protocols designed to reach the target dose of 400 mg/day within 1 week, and the conventional weekly titration protocol (reaching the target dose of 400 mg/day in three weeks). The ≥50% responder rate and steady-state plasma concentration of lacosamide were also analyzed. Adverse events were assessed at 1 week and 5 weeks after reaching the target dose. RESULTS: Seventy-five patients with epilepsy were enrolled and evenly distributed to three titration protocols, from which 5 patients were lost to follow-up and excluded from the safety analysis. Discontinuation of lacosamide or dose reductions due to adverse events occurred in 32 patients (46%), of whom a large majority (74%) had experienced adverse events after reaching 400 mg/day, demonstrating apparent dose-dependency. There was no difference in safety outcomes among the three titration groups. Concomitant use of sodium channel blockers significantly increased the risk of adverse events. CONCLUSION: Rapid titration protocols for lacosamide were not associated with an increased risk of adverse events compared to the conventional weekly titration protocol. Uptitration of lacosamide at shorter intervals to an effective target dosage may be feasible in appropriate clinical situations.

Effects of perampanel on cognition and quantitative electroencephalography in patients with epilepsy.

Antiepileptic drugs are well known for their effects on cognition and electrophysiologic changes. However, perampanel is yet to be evaluated for its effects on cognitive function and electroencephalography (EEG). The purpose of the present study was to identify the effect of perampanel on neuropsychological (NP) tests and quantitative EEG (QEEG) and their relationship with the level of the drug in blood. Seventeen patients with epilepsy were enrolled in the study. Electroencephalographic recordings were obtained, and NP tests were conducted before perampanel intake and 6 months after treatment. The relative frequency band power, peak alpha frequency, and NP test scores were compared before and after drug administration. The serum concentration of perampanel was correlated with the QEEG changes. Delayed recall of the Rey Complex Figure showed significant improvement (20.03 vs. 22.94; P = 0.004) following perampanel administration. Other cognitive function tests showed no significant differences before and after drug administration. Theta frequency band power increased in all brain regions (P = 0.001-0.01), and alpha frequency power decreased in all brain regions (P = 0.006-0.03). The theta/alpha ratio, which represents background EEG slowing, increased in all brain areas (P = 0.003-0.02). The peak frequency of the alpha rhythm decreased after perampanel intake (t = 2.45, P = 0.03). Difference of relative alpha power in the central region positively correlated with the blood level of perampanel (r = 0.53, P = 0.03). Perampanel induced electrophysiological slowing, but cognitive decline was not observed. Because the controls were not compared in the study, the results of cognitive function tests should be interpreted conservatively. Background EEG slowing correlated with the serum concentration of perampanel. Our results show the effect of perampanel on cognitive function and background EEG in adult patients with epilepsy.

Pharmacokinetic comparison between tablet of varenicline tartrate and orally disintegrating film of varenicline salicylate in healthy subjects.

OBJECTIVE: Varenicline is an efficacious aid for smoking cessation. In this study, the pharmacokinetics and safety were compared between film-coated tablets of varenicline tartrate (reference drug) and the newly developed orally disintegrating films of varenicline salicylate (test drug), both of them contained 1 mg of varenicline. MATERIALS AND METHODS: A randomized, open-label, single-dose, two-sequence, two-period crossover study was conducted in healthy male subjects. Serial blood samples were obtained for up to 72 hours in each period, with a washout period of 7 days or more. The pharmacokinetic parameters were calculated using the noncompartmental method. Safety profiles were assessed throughout the study. RESULTS: A total of 28 subjects completed the study. The plasma varenicline concentration-time profiles were similar for the two study drugs. The maximum plasma varenicline concentration (Cmax) was 5,768.95 ng/L (mean) and 5,780.55 ng/L for the test drug and reference drug, respectively. The areas under the concentration-time curve from time 0 to the last measurable time point (AUC0-t) were 94,086.30 h×ng/L and 89,958.55 h×ng/L for the test drug and reference drug, respectively. The geometric mean ratios (90% confidence intervals) of the test drug to the reference drug for Cmax and AUC0-t were 0.9955 (0.9488 - 1.0444) and 1.0449 (0.9848 - 1.1088), respectively, which fell within the bioequivalence range of 0.8 - 1.25. There was no difference in safety between the study drugs. CONCLUSION: The pharmacokinetics and safety profiles were similar between the two study drugs. The orally disintegrating film of varenicline salicylate can be an alternative to varenicline tartrate tablets.

Oral absorption of voriconazole is affected by SLCO2B1 c.*396T>C genetic polymorphism in CYP2C19 poor metabolizers.

High pharmacokinetic variability of voriconazole is mainly explained by CYP2C19 phenotype, but there are still unknown factors affecting the variability. In this study, the effect of solute carrier organic anion transporter family member 2B1 (SLCO2B1) genotype on the pharmacokinetics (PKs) of voriconazole was evaluated in 12 healthy CYP2C19 poor metabolizers after a single administration of voriconazole 200 mg intravenously and orally. In addition, the influence of CYP3A4 enzyme activity was also explored. The oral absorption of voriconazole was decreased and delayed in the subjects with the SLCO2B1 c.*396T>C variant compared to the subjects with wild type. However, the CYP3A activity markers measured in this study did not show significant association with metabolism of voriconazole. The results suggest that the SLCO2B1 c.*396T>C may be associated with the decreased function of intestinal OATP2B1, and it could contribute to interindividual PK variability of voriconazole.

Usefulness of saliva for perampanel therapeutic drug monitoring.

OBJECTIVE: Therapeutic drug monitoring (TDM) of antiepileptic drugs (AEDs) helps optimize drug management for patients with epilepsy. Salivary testing is both noninvasive and easy, and has several other advantages. Due to technical advances, salivary TDM has become feasible for several drugs, including AEDs, and its value has been investigated. Until recently, saliva TDM of perampanel (PER) had not been reported. The purpose of our study was to confirm whether saliva is a biological substitute for plasma in PER TDM. METHODS: Adult patients diagnosed with epilepsy who received PER from August 2018 to March 2019 at Seoul National University Hospital were enrolled. Total and free PER were measured in simultaneously obtained plasma and saliva samples using liquid chromatography-tandem mass spectrometry (LC-MS/MS) and high-performance liquid chromatographic (HPLC). We examined the correlations between saliva and plasma PER concentrations and whether the use of concomitant medications classified as cytochrome P450 (CYP)3A4 inducers affected the correlations. RESULTS: Thirty patients were enrolled, aged 16 to 60; 10 (33%) were women. Patients received 2 to 12 mg (mean, 6 mg) of PER. The average total and free concentrations of PER were 343.02 (46.6-818.0) and 1.53 (0.51-2.92) ng/mL in plasma and 9.74 (2.21-33.0) and 2.83 (1.01-6.8) ng/mL in saliva, respectively. A linear relationship was observed between the total PER concentrations in saliva and the total and free PER concentrations in plasma (both P < .001; r = .678 and r = .619, respectively). The change in the PER concentration caused by the CYP3A4 inducer did not affect the correlation between saliva and plasma concentrations (all P < .001). SIGNIFICANCE: The PER concentration in saliva was correlated with that in plasma. This correlation was not affected by CYP3A4 inducers. Our results demonstrate for the first time that PER is measurable in saliva and suggest the potential for the clinical application of the saliva PER TDM matrix.

Pharmacokinetics of human antithrombin III concentrate in the immediate postoperative period after liver transplantation.

AIMS: Antithrombin III (AT-III) concentrates have been used to prevent critical thrombosis in the immediate post-liver transplantation period without clear evidence regarding the optimal dose or administration scheme. The relationship between the AT-III dosage and the plasma activity levels during the period was evaluated in this study. METHODS: The plasma AT-III activity levels and clinical data obtained from patients who received liver transplantation from January 2017 to September 2018 were retrospectively analysed. A population pharmacokinetic (PK) model was developed using nonlinear mixed-effects method and externally validated thereafter. Several dosing scenarios were simulated to maintain the plasma AT-III activity level within the normal range using the developed PK model to search for an optimal AT-III dosing regimen. RESULTS: The plasma AT-III activity levels were best described by a single compartment model with first order elimination kinetics. The recovery of endogenous AT-III level during the postoperative days was modelled using an Emax model. The typical values (95% confidence interval) of volume of distribution and clearance were 3.86 (3.40-4.32) L, and 0.129 (0.111-0.147) L h-1 , respectively. Serum albumin and body weight had significant effect on clearance and were included in the model. External validation of the proposed model demonstrated adequate prediction performance. Furthermore, simulation of previously suggested or modified dosing scenarios showed successful maintenance of AT-III activity level within the normal range. CONCLUSION: A population PK model of AT-III concentrate was developed using data from liver recipients. Dosing scenarios simulated in our study may help establish a practical guide for AT-III concentrate titration after liver transplantation.

Comparative pharmacokinetics of a montelukast/levocetirizine fixed-dose combination chewable tablet versus individual administration of montelukast and levocetirizine after a single oral administration in healthy Korean male subjects
.

OBJECTIVE: Asthma patients often have co-existing symptoms of allergic rhinitis and are often prescribed with both asthma and rhinitis treatments such as montelukast and levocetirizine. The objective of this study was to compare the pharmacokinetic profiles of a montelukast/levocetirizine fixed-dose combination chewable tablet with individual administration of montelukast and levocetirizine in healthy subjects. MATERIALS AND METHODS: A randomized, open-label, single-dose crossover study was conducted in healthy male subjects. One of the following treatments was administered in each period: co-administration of 1 chewable tablet of montelukast 5 mg and 1 tablet of levocetirizine 5 mg or administration of 1 chewable tablet of montelukast/levocetirizine 5/5 mg fixed-dose combination. Serial blood samples were collected up to 48 hours post dose. Plasma drug concentrations were measured by liquid chromatography/tandem mass spectrometry. Pharmacokinetic parameters, including maximum plasma concentration (Cmax) and area under the plasma concentration versus time curve from dosing to the last measurable concentration (AUClast), were determined by non-compartmental analysis. The geometric least-square mean (GLSM) ratios and associated 90% confidence intervals (CIs) of Cmax and AUClast were calculated to evaluate pharmacokinetic equivalence. RESULTS: A total of 22 subjects were included in pharmacokinetic analysis. The GLSM ratios and 90% CIs of Cmax and AUClast were 1.0054 (0.9535 - 1.0601) and 1.0628 (1.0013 - 1.1281) for montelukast and 1.0105 (0.9488 - 1.0764) and 1.0396 (0.9935 - 1.0879) for levocetirizine, respectively. CONCLUSION: The pharmacokinetic parameters of montelukast and levocetirizine when administered as separate tablets or as a fixed-dose combination were compared, and the parameters met the pharmacokinetic equivalence criteria. (ClinicalTrials.gov Identifier: NCT03371849).

The Impact of COVID-19 on the Conduct of Clinical Trials for Medical Products in Korea.

BACKGROUND: The number of clinical trials conducted in Korea continues to increase and an increasing proportion focus on severe and rare incurable diseases. After the start of the severe acute respiratory syndrome, coronavirus disease 2019 (COVID-19), Korea Centers for Disease Control and Prevention (KCDC) developed guidelines to prevent the spread of infection. This study evaluated the impact of COVID-19 and the KCDC guideline on the conduct of clinical research in Korea. The purpose was to develop recommendations on how to minimize the risk of infection while enabling subjects to take part in the trials if no better alternative treatment options were available. METHODS: The impact on subject's scheduled visits and major milestones of clinical trials in Korea were measured by conducting a survey among clinical project manager (CPMs) working at global clinical research organization. The policy on monitor's access to hospital and site initiation meetings was investigated through correspondence with clinical trial center of 39 hospitals. The Top 25 pharmaceutical companies' official press and public clinical trial registry database were used to analyze companies' trial strategy during the pandemic and COVID-19 clinical research status, respectively. RESULTS: Of 85 CPMs, 12% reported that trial subjects' scheduled visits had been affected in their project. Monitors' access to hospital for source data verification was restricted at all sites in February 2020. Accordingly, 43% of 105 CPMs reported that the COVID-19 epidemic had an effect on study major milestones and data cleaning and database lock accounted for > 60% of milestones affected. In addition, 87% sites advised not to have site initiation meetings and 52% pharmaceutical companies suspended recruitment or new study start-up due to the pandemic. On the other hands, the number of COVID-19 related clinical trials increased rapidly in Korea and worldwide, with investigator-initiated trials accounting for 47% and 63% of all trials locally and globally, respectively. Most trials were phase 2 and were in the recruitment stage. CONCLUSION: The COVID-19 and the KCDC guideline influenced all parties involved in clinical trials in Korea. In order to ensure the safety and well-being of trial subjects during the pandemic, new approaches are required for clinical trials to respond to the impact actively. Method of non-contact is developed to replace and supplement the face-to-face contact and alternatives to reduce the travel is introduced to decrease the risk of infection for all trial participants in whole trial process. The relevant regulations should be developed and the guidelines for foreign countries need to be adopted in accordance with the situation in Korea. COVID-19 trial is rapidly increasing worldwide and continuous support of health authorities, regulation, and facilities is required for developing the treatments with protecting all trial participants.

Identification of a quadruple mutation that confers tenofovir resistance in chronic hepatitis B patients.

BACKGROUND & AIMS: Tenofovir disoproxil fumarate (TDF) is one the most potent nucleot(s)ide analogues for treating chronic hepatitis B virus (HBV) infection. Phenotypic resistance caused by genotypic resistance to TDF has not been reported. This study aimed to characterize HBV mutations that confer tenofovir resistance. METHODS: Two patients with viral breakthrough during treatment with TDF-containing regimens were prospectively enrolled. The gene encoding HBV reverse transcriptase was sequenced. Eleven HBV clones harboring a series of mutations in the reverse transcriptase gene were constructed by site-directed mutagenesis. Drug susceptibility of each clone was determined by Southern blot analysis and real-time PCR. The relative frequency of mutants was evaluated by ultra-deep sequencing and clonal analysis. RESULTS: Five mutations (rtS106C [C], rtH126Y [Y], rtD134E [E], rtM204I/V, and rtL269I [I]) were commonly found in viral isolates from 2 patients. The novel mutations C, Y, and E were associated with drug resistance. In assays for drug susceptibility, the IC50 value for wild-type HBV was 3.8 ±â€¯0.6 µM, whereas the IC50 values for CYE and CYEI mutants were 14.1 ±â€¯1.8 and 58.1 ±â€¯0.9 µM, respectively. The IC90 value for wild-type HBV was 30 ±â€¯0.5 µM, whereas the IC90 values for CYE and CYEI mutants were 185 ±â€¯0.5 and 790 ±â€¯0.2 µM, respectively. Both tenofovir-resistant mutants and wild-type HBV had similar susceptibility to the capsid assembly modulator NVR 3-778 (IC50 <0.4 µM vs. IC50 = 0.4 µM, respectively). CONCLUSIONS: Our study reveals that the quadruple (CYEI) mutation increases the amount of tenofovir required to inhibit HBV by 15.3-fold in IC50 and 26.3-fold in IC90. These results demonstrate that tenofovir-resistant HBV mutants can emerge, although the genetic barrier is high. LAY SUMMARY: Tenofovir is the most potent nucleotide analogue for the treatment of chronic hepatitis B virus infection and there has been no hepatitis B virus mutation that confers >10-fold resistance to tenofovir up to 8 years. Herein, we identified, for the first time, a quadruple mutation that conferred 15.3-fold (IC50) and 26.3-fold (IC90) resistance to tenofovir in 2 patients who experienced viral breakthrough during tenofovir treatment.