Pharmacokinetics and Safety of Intramuscular Injectable Benzathine Penicillin G in Japanese Healthy Participants.

An intramuscular (IM) suspension of benzathine penicillin G (BPG) has been used as first-line therapy for the treatment of syphilis worldwide since its approval in the 1950s. However, there are limited reports about the pharmacokinetics of BPG. A Phase 1 study was conducted on eight Japanese healthy participants to investigate the pharmacokinetics (samples collected predose to 648 h post-dose) and safety of 2.4 million units of BPG after a single IM injection. Following administration, penicillin G, the active moiety of BPG, was absorbed slowly from the injection site with a median time to Cmax (tmax) of 48 h post-dose. After the achievement of Cmax, concentrations of penicillin G declined slowly in a monophasic fashion with a mean apparent terminal half-life of 189 h. Geometric mean AUCinf and Cmax were 50770 ng•h/mL and 259 ng/mL, respectively. Median time (range) above the well-accepted therapeutic concentration (18 ng/mL) for syphilis treatment was 561 h (439-608 h [18-25 days]), which reached and exceeded the necessary duration of 7-10 days for syphilis treatment. Two participants were underdosed with residual drug left in the syringe due to the high viscosity of the drug product. Only one (12.5%) participant reported a mild adverse event of nasopharyngitis, which was considered not related to the study treatment. The study results supported BPG approval in Japan as an option for syphilis treatment.

Assessment of the Utility of Physiologically-based Pharmacokinetic Model for prediction of Pharmacokinetics in Chinese and Japanese Populations.

The objective for the present analyses was to evaluate the utility of physiologically-based pharmacokinetic (PBPK) modeling for prediction of the pharmacokinetics (PK) in Chinese and Japanese populations with a panel of Pfizer internal compounds. Twelve compounds from Pfizer internal development pipeline with available Westerner PK data and available PK data in at least one of the subpopulations of Japanese and Chinese populations were identified and included in the current analysis. These selected compounds represent various elimination pathways across different therapeutic areas. The Simcyp® PBPK simulator was used to develop and verify the PBPK models of individual compounds. The developed models for these compounds were verified by using the clinical PK data in Westerners. The verified PBPK models were further used to predict the PK of these compounds in Chinese and Japanese populations and the predicted PK parameters were compared with the observed PK parameters. Ten of the 12 compounds had PK data in Chinese, and all the 12 compounds had PK data in Japanese. In general, the PBPK models performed well in predicting PK in Chinese and Japanese, with 8 of 10 drugs in Chinese and 7 of 12 drugs in Japanese has AAFE values less than 1.25-fold. PBPK-guided predictions of the relative PK difference were successful for 75% and 50%, respectively, between Chinese and Western and between Japanese and Western of the tested drugs using 0.8-1.25 as criteria. In conclusion, well verified PBPK models developed using data from Westerners can be used to predict the PK in Chinese and Japanese populations.

Identification of Appropriate Endogenous Biomarker for Risk Assessment of Multidrug and Toxin Extrusion Protein-Mediated Drug-Drug Interactions in Healthy Volunteers.

Endogenous biomarkers are emerging to advance clinical drug-drug interaction (DDI) risk assessment in drug development. Twelve healthy subjects received a multidrug and toxin exclusion protein (MATE) inhibitor (pyrimethamine, 10, 25, and 75 mg) in a crossover fashion to identify an appropriate endogenous biomarker to assess MATE1/2-K-mediated DDI in the kidneys. Metformin (500 mg) was also given as reference probe drug for MATE1/2-K. In addition to the previously reported endogenous biomarker candidates (creatinine and N1 -methylnicotinamide (1-NMN)), N1 -methyladenosine (m1 A) was included as novel biomarkers. 1-NMN and m1 A presented as superior MATE1/2-K biomarkers since changes in their renal clearance (CLr ) along with pyrimethamine dose were well-correlated with metformin CLr changes. The CLr of creatinine was reduced by pyrimethamine, however, its changes poorly correlated with metformin CLr changes. Nonlinear regression analysis (CLr vs. mean total concentration of pyrimethamine in plasma) yielded an estimate of the inhibition constant (Ki ) of pyrimethamine and the fraction of the clearance pathway sensitive to pyrimethamine. The in vivo Ki value thus obtained was further converted to unbound Ki using plasma unbound fraction of pyrimethamine, which was comparable to the in vitro Ki for MATE1 (1-NMN) and MATE2-K (1-NMN and m1 A). It is concluded that 1-NMN and m1 A CLr can be leveraged as quantitative MATE1/2-K biomarkers for DDI risk assessment in healthy volunteers.

Dose-Dependent Inhibition of OATP1B by Rifampicin in Healthy Volunteers: Comprehensive Evaluation of Candidate Biomarkers and OATP1B Probe Drugs.

To address the most appropriate endogenous biomarker for drug-drug interaction risk assessment, eight healthy subjects received an organic anion transporting polypeptide 1B (OATP1B) inhibitor (rifampicin, 150, 300, and 600 mg), and a probe drug cocktail (atorvastatin, pitavastatin, rosuvastatin, and valsartan). In addition to coproporphyrin I, a widely studied OATP1B biomarker, we identified at least 4 out of 28 compounds (direct bilirubin, glycochenodeoxycholate-3-glucuronide, glycochenodeoxycholate-3-sulfate, and hexadecanedioate) that presented good sensitivity and dynamic range in terms of the rifampicin dose-dependent change in area under the plasma concentration-time curve ratio (AUCR). Their suitability as OATP1B biomarkers was also supported by the good correlation of AUC0-24h between the endogenous compounds and the probe drugs, and by nonlinear regression analysis (AUCR-1 vs. rifampicin plasma Cmax (maximum total concentration in plasma)) to yield an estimate of the inhibition constant of rifampicin. These endogenous substrates can complement existing OATP1B-mediated drug-drug interaction risk assessment approaches based on agency guidelines in early clinical trials.

Population pharmacokinetic analysis of voriconazole from a pharmacokinetic study with immunocompromised Japanese pediatric subjects.

A population pharmacokinetic (PK) analysis was conducted to characterize the voriconazole pharmacokinetic profiles in immunocompromised Japanese pediatric subjects and to compare them to those in immunocompromised non-Japanese pediatric subjects. A previously developed two-compartment pharmacokinetic model with first-order absorption and mixed linear and nonlinear elimination adequately described the voriconazole intravenous and oral data from Japanese pediatric subjects with few modifications. Bayesian priors were applied to this analysis by using the NONMEM routine NWPRI, which allowed priors for the fixed-effect parameter vector and variance matrix of the random-effect parameters to be a normal distribution and an inverse Wishart distribution, respectively. Large intersubject variabilities in oral bioavailability and voriconazole exposure were observed in these pediatric subjects. The mean oral bioavailability estimated in Japanese pediatric subjects was 73% (range, 17% to 99%), which is consistent with the reported estimates of 64% in the previous model and less than what was originally estimated for healthy adults-96%. Voriconazole exposures in Japanese pediatric subjects were generally comparable to those in non-Japanese pediatric subjects receiving the same dosing regimens, given the large intersubject variability. Consistent with the previous findings, the CYP2C19 genotyping status did not have a clinically relevant effect on voriconazole exposure in Japanese pediatric subjects, although it was identified as a covariate in the model to help explain the intersubject variability in voriconazole exposure. The CYP2C19 genotyping status alone does not warrant dose adjustment of voriconazole. No other factors besides age and weight were identified to explain the PK variability of voriconazole.

Pharmacokinetics and safety of voriconazole intravenous-to-oral switch regimens in immunocompromised Japanese pediatric patients.

The aim of this study was to investigate the pharmacokinetics, safety, and tolerability of voriconazole following intravenous-to-oral switch regimens used with immunocompromised Japanese pediatric subjects (age 2 to <15 years) at high risk for systemic fungal infection. Twenty-one patients received intravenous-to-oral switch regimens based on a recent population pharmacokinetic modeling; they were given 9 mg/kg of body weight followed by 8 mg/kg of intravenous (i.v.) voriconazole every 12 h (q12h), and 9 mg/kg (maximum, 350 mg) of oral voriconazole q12h (for patients age 2 to <12 or 12 to <15 years and <50 kg) or 6 mg/kg followed by 4 mg/kg of i.v. voriconazole q12h and 200 mg of oral voriconazole q12h (for patients age 12 to <15 years and ≥50 kg). The steady-state area under the curve over the 12-h dosing interval (AUC0-12,ss) was calculated using the noncompartmental method and compared with the predicted exposures in Western pediatric subjects based on the abovementioned modeling. The geometric mean (coefficient of variation) AUC0-12,ss values for the intravenous and oral regimens were 51.1 µg · h/ml (68%) and 45.8 µg·h/ml (90%), respectively; there was a high correlation between AUC0-12,ss and trough concentration. Although the average exposures were higher in the Japanese patients than those in the Western pediatric subjects, the overall voriconazole exposures were comparable between these two groups due to large interindividual variability. The exposures in the 2 cytochrome P450 2C19 poor metabolizers were among the highest. Voriconazole was well tolerated. The most common treatment-related adverse events were photophobia and abnormal hepatic function. These recommended doses derived from the modeling appear to be appropriate for Japanese pediatric patients, showing no additional safety risks compared to those with adult patients. (This study has been registered at ClinicalTrials.gov under registration no. NCT01383993.).

Population pharmacokinetics of ampicillin and sulbactam in patients with community-acquired pneumonia: evaluation of the impact of renal impairment.

AIMS: The aims of this study were to develop a population pharmacokinetic (PK) model of ampicillin and sulbactam, to identify patient characteristics influencing the PK, and to explore the relationship between dose regimen and degree of renal impairment with exposure and time above minimum inhibitory concentration (MIC). METHODS: This analysis was performed on PK data for ampicillin and sulbactam and MIC data from a clinical trial in Japanese patients with community acquired pneumonia. Simulations were performed to investigate the effects of different dosing intervals on exposure and time above MIC in various degrees of renal impairment. RESULTS: The plasma concentrations from 47 patients were adequately described by a two compartment model with simultaneous fit of ampicillin and sulbactam PK data, where creatinine clearance on clearance and body weight on volume in the peripheral compartment were identified as covariates for both drugs. Creatinine clearance contributed to reducing inter-individual variability of clearance by 16%. Mean clearance (inter-individual variability) for ampicillin and sulbactam was estimated to be 10.7 l h(-1) (14.8%) and 10.4 l h(-1) (15.2%), respectively. The time above MIC for each pathogen was generally > 50% of the treatment period. Simulations for exposure and time above MIC supported currently recommended dose adjustments. CONCLUSIONS: This study provided a PK model for ampicillin and sulbactam, the time above MICs for identified pathogens and associated simulation results. These findings provide useful information and augment evidence for the established dosage regimens in patients with various degrees of renal impairment.

The pharmacokinetics and pharmacodynamics of PF-00734200, a DPP-IV inhibitor, in healthy Japanese subjects.

OBJECTIVE: To evaluate the pharmacokinetics, pharmacodynamics, safety, and tolerability of PF-00734200, a potent dipeptidyl peptidase-IV (DPP-IV) inhibitor, in Japanese subjects, and compare the results with those in Western subjects. MATERIALS AND METHODS: Eight healthy Japanese subjects received a single dose of PF-00734200 10 mg, 100 mg, or placebo. Another 8 subjects received PF-00734200 20 mg or placebo single dose once daily for 6 days. Serum and urine PK, plasma DPP-IV activity, and plasma glucagon-like peptide 1 (GLP-1) levels were measured. RESULTS: Linear pharmacokinetics was observed over the single dose range 10 - 100 mg. Following multiple-dose administration, 37.3 ± 4.33% of the unchanged PF-00734200 was excreted in the urine and renal clearance was calculated as 33.9 ± 6.56 ml/min. After the standardized meals, GLP- 1 levels increased ~ 2-fold compared with placebo, and no further increase in GLP-1 levels was observed at doses above 10 mg. The steady state DPP-IV inhibition at 24 h was ~ 75%. CONCLUSION: Pharmacokinetics of PF-00734200, inhibition of DPP-IV, and non-linear increases in GLP-1 were similar between healthy Japanese and Western subjects.

Population pharmacokinetic and pharmacodynamic modeling of pegvisomant in asian and Western acromegaly patients.

Pegvisomant is a growth hormone (GH) receptor antagonist that normalizes insulin-like growth factor I (IGF-I) levels in patients with acromegaly. Although the dose of pegvisomant is determined by the IGF-I level, the pharmacokinetic and pharmacodynamic (PK/PD) model for pegvisomant concentration and IGF-I reduction has not been established. This study was conducted to characterize PK/PD of pegvisomant, and to determine the influence of covariates on the pegvisomant PK/PD. Based on the data from 5 phase III studies in 168 acromegaly patients, models were developed to characterize the PK/PD of pegvisomant. The PD variables were IGF-I serum concentrations. The modeling was performed with a nonlinear mixed-effects approach using NONMEM. After subcutaneous dosing, the PK of pegvisomant was described by a steady state PK model with dose- dependent clearance. Baseline GH and age were significant covariates for the clearance. A sigmoid E(max) model adequately described the relationship between IGF-I and pegvisomant concentrations. Baseline GH was found to be a significant covariate for the baseline effect (E(0)) and IC(50). The PK/PD properties of pegvisomant were not significantly different between Asian and Western patients.

Pharmacokinetic-pharmacodynamic analysis of azithromycin extended release in Japanese patients with common respiratory tract infectious disease.

OBJECTIVES: it is known that the efficacy of azithromycin, in animal infection models, is best correlated with AUC/MIC. The pharmacokinetic-pharmacodynamic (PK-PD) relationship for azithromycin, however, has not been previously confirmed with clinical data. The objectives of this PK-PD analysis were to characterize exposure-response relationships for the efficacy and safety of azithromycin extended release (ER) in Japanese patients, and to evaluate the effects of potential covariates on the prediction of response. METHODS: sparse serum azithromycin concentration, MIC, efficacy and safety data were collected from three Japanese Phase 3 studies of a 2 g single dose of azithromycin-ER for respiratory tract infections. These sparse concentration data were combined with data from eight Phase 1 PK studies in Japanese and Western populations, to develop a robust population PK model using a non-linear mixed effects approach. The exposure-response relationships for efficacy and safety were evaluated using logistic regression. RESULTS: a two-compartment model with first-order absorption and first-order elimination with a lag time adequately described the PK of azithromycin-ER, without any significant ethnic differences in AUC. The percentage of bacteriological and clinical success in patients with AUC/MIC  >  5 (95.8% and 100%, respectively) was much higher than in those with AUC/MIC  ≤  5 (60.0% and 83.3%, respectively). CONCLUSIONS: as expected, the probabilities of success in the clinical and bacteriological responses were positively associated with AUC/MIC, but not with AUC. For the exposure-safety relationship, the incidence of treatment-related diarrhoea was inversely associated with azithromycin exposure.