Integrated Exposure-Response of Dupilumab in Children, Adolescents, and Adults With Atopic Dermatitis Using Categorical and Continuous Efficacy Assessments: A Population Analysis.

BACKGROUND: While the majority of patients with atopic dermatitis (AD) achieve disease control with dupilumab treatment, there is variability in which patients achieve clear disease. The predictors of these responses are currently unclear. Integrated models were developed to evaluate the exposure-response (E-R) relationship of dupilumab in children, adolescents, and adults with AD. METHODS: Data from six Phase II and III clinical studies were pooled (2,366 adults [> 18 years], 243 adolescents [≥ 12 to < 18 years] and 359 children [≥ 6 to < 12 years]) for model development. Efficacy was assessed using the Eczema Area and Severity Index (EASI) and Investigator's Global Assessment (IGA). Indirect response models were applied to link measures of efficacy and functional serum dupilumab concentrations. The covariates on individual placebo-corrected response were assessed. Clinical trial scenarios were simulated to compare E-R relationships across age groups. Safety was not explored. RESULTS: After correcting for differences in placebo response and dupilumab exposure: 1) older age, higher body weight, lower baseline thymus and activation-regulated chemokine, and Asian race were associated with slightly lower EASI response, and no clear covariates were identified on IGA response; 2) clinical trial simulations generally showed slightly higher response at a given dupilumab concentration in children compared to adults and adolescents with severe and moderate AD. CONCLUSIONS: The collectively tested covariates explain some of the variability in dupilumab response in patients with AD. Patients in all age groups showed adequate response to dupilumab; however, children showed slightly higher drug effects compared to adults and adolescents at equivalent concentrations.

Population pharmacokinetic and pharmacokinetic-pharmacodynamic modeling of bempedoic acid and low-density lipoprotein cholesterol in healthy subjects and patients with dyslipidemia.

Population pharmacokinetics (popPK) of bempedoic acid and the popPK/pharmacodynamic (popPK/PD) relationship between bempedoic acid concentrations and serum low-density lipoprotein cholesterol (LDL-C) from baseline were characterized. A two-compartment disposition model with a transit absorption compartment and linear elimination best described bempedoic acid oral pharmacokinetics (PK). Multiple covariates, including renal function, sex, and weight, had statistically significant effects on the predicted steady-state area under the curve. Mild (estimated glomerular filtration rate (eGFR) 60 to < 90 mL/min vs. ≥ 90 mL/min) and moderate (eGFR 30 to < 60 mL/min vs. ≥ 90 mL/min) renal impairment, female sex, low (< 70 kg vs. 70-100 kg) and high (> 100 kg vs. 70-100 kg) body weight were predicted to have a 1.36-fold (90% confidence interval (CI) 1.32, 1.41), 1.85-fold (90% CI 1.74, 2.00), 1.39-fold (90% CI 1.34, 1.47), 1.35-fold (90% CI 1.30, 1.41), and 0.75-fold (90% CI 0.72, 0.79) exposure difference relative to their reference populations, respectively. An indirect response model described changes in serum LDL-C with a model-predicted 35% maximal reduction and bempedoic acid IC50 of 3.17 µg/mL. A 28% reduction from LDL-C baseline was predicted for a steady-state average concentration of 12.5 µg/mL after bempedoic acid (180 mg/day) dosing, accounting for approximately 80% of the predicted maximal LDL-C reduction. Concurrent statin therapy, regardless of intensity, reduced the maximal effect of bempedoic acid but resulted in similar steady-state LDL-C levels. While multiple covariates had statistically significant effects on PK and LDL-C lowering, none were predicted to warrant bempedoic acid dose adjustment.

A Time-to-Event Exposure-Response Model for Amyloid-Related Imaging Abnormalities Following Administration of Aducanumab to Subjects With Early Alzheimer Disease.

Amyloid-related imaging abnormalities with edema (ARIA-E) have been reported in patients with early Alzheimer disease treated with aducanumab. ARIA-E incidence has been observed to be dependent on both dose and apolipoprotein E4 carrier status. A time-to-event (TTE) approach applying data from 2 phase 3 studies (studies 301 and 302) was used to describe the effect of aducanumab serum exposure on the instantaneous risk of 2 end points: the first incidence of ARIA-E and time to ARIA-E resolution. A total of 3251 subjects with 826 events supported the TTE model to characterize the first ARIA-E event. The TTE resolution model was supported by data from 768 of 826 subjects who had ARIA-E resolved. Relationships between drug concentrations and ARIA-E events were modeled with a hazard function dependent on time, aducanumab serum concentrations, attenuation of aducanumab exposure effects with time (ie, potential for tolerance to aducanumab exposure), study, and apolipoprotein E4 carrier status. The TTE model showed that ARIA-E incidence rates were higher during the first 200 days, followed by a reduction in rates. The change in event rate reflects the attenuation of drug effect, thereby providing support for the current proposed titration regimen. Time to ARIA-E resolution was characterized by a constant baseline hazard with a probability to resolution affected by baseline ARIA-E severity and aducanumab concentration. ARIA-E resolution was found to be driven primarily by baseline hazard and time and suggested that aducanumab concentration effect is a minor contributor to the time to resolution of ARIA-E.

Development of a Population Pharmacokinetic Model for the Diroximel Fumarate Metabolites Monomethyl Fumarate and 2-Hydroxyethyl Succinimide Following Oral Administration of Diroximel Fumarate in Healthy Participants and Patients with Multiple Sclerosis.

INTRODUCTION: Diroximel fumarate (DRF) is a next-generation oral fumarate that is indicated in the USA for relapsing forms of multiple sclerosis (MS). A joint population pharmacokinetic model was developed for the major active metabolite (monomethyl fumarate, MMF) and the major inactive metabolite (2-hydroxyethyl succinimide, HES) of DRF. METHODS: MMF and HES data were included from 341 healthy volunteers and 48 patients with MS across 11 phase I and III studies in which DRF was administered as single or multiple doses. Population modeling was performed with NONMEM version 7.3 with the first-order conditional estimation method. RESULTS: Estimated MMF clearance (CLMMF), volume of distribution, and absorption rate constant (Ka) were 13.5 L/h, 30.4 L, and 5.04 h-1, respectively. CLMMF and HES clearance (CLHES) increased with increasing body weight. CLHES decreased with decreasing renal function. CLMMF and CLHES were 28% and 12% lower in patients with MS than in healthy volunteers, respectively. Ka was reduced in the presence of low-, medium-, and high-fat meals by 37%, 51%, and 67%, respectively, for MMF; and by 34%, 49%, and 62%, respectively, for HES. CONCLUSIONS: Age, sex, race, and baseline liver function parameters such as total bilirubin, albumin, and aspartate aminotransferase were not considered to be significant predictors of MMF or HES disposition.

Pharmacodynamic effect of bempedoic acid and statin combinations: predictions from a dose-response model.

AIMS: Many patients are unable to achieve guideline-recommended LDL cholesterol (LDL-C) targets, despite taking maximally tolerated lipid-lowering therapy. Bempedoic acid, a competitive inhibitor of ATP citrate lyase, significantly lowers LDL-C with or without background statin therapy in diverse populations. Because pharmacodynamic interaction between statins and bempedoic acid is complex, a dose-response model was developed to predict LDL-C pharmacodynamics following administration of statins combined with bempedoic acid. METHODS AND RESULTS: Bempedoic acid and statin dosing and LDL-C data were pooled from 14 phase 1-3 clinical studies. Dose-response models were developed for bempedoic acid monotherapy and bempedoic acid-statin combinations using previously published statin parameters. Simulations were performed using these models to predict change in LDL-C levels following treatment with bempedoic acid combined with clinically relevant doses of atorvastatin, rosuvastatin, simvastatin, and pravastatin. Dose-response models predicted that combining bempedoic acid with the lowest statin dose of commonly used statins would achieve a similar degree of LDL-C lowering as quadrupling that statin dose; for example, the predicted LDL-C lowering was 54% with atorvastatin 80 mg compared with 54% with atorvastatin 20 mg + bempedoic acid 180 mg, and 42% with simvastatin 40 mg compared with 46% with simvastatin 10 mg + bempedoic acid 180 mg. CONCLUSION: These findings suggest bempedoic acid combined with lower statin doses offers similar LDL-C lowering compared with statin monotherapy at higher doses, potentially sparing patients requiring additional lipid-lowering therapies from the adverse events associated with higher statin doses.

Population Pharmacokinetics of Vixotrigine in Healthy Volunteers and Subjects with Trigeminal Neuralgia, Painful Lumbosacral Radiculopathy and Erythromelalgia.

BACKGROUND: Vixotrigine is a voltage and use dependent sodium channel blocker currently under development for treatment of various neuropathic pain indications. OBJECTIVE: The objective of this work was to develop a population pharmacokinetic model and assess effects of various covariates on pharmacokinetic parameters of vixotrigine. METHOD: Plasma concentration-time data from 12 Phase 1 or 2 studies were included in the analyses. The data were obtained following administration of single or multiple doses of vixotrigine in healthy volunteers and patients. One- and two-compartment pharmacokinetic models were evaluated as base structural pharmacokinetic models. The inclusion of selected covariates was assessed using a stepwise backward elimination approach (α = 0.001) once the base/full model was developed. The predictive ability of the model was evaluated using a visual predictive check (VPC). The final model was used to evaluate effect of covariates on exposure of vixotrigine. RESULTS: A total of 10,263 pharmacokinetic samples collected from 465 subjects were included in the analyses. The pharmacokinetics of vixotrigine was adequately described by a two-compartment model with two transit absorption compartments and first-order elimination. Predictability of the model was also established by VPC. The final model included covariates of age, weight and carbamazepine co-administration on clearance, weight on central volume of distribution, food on absorption rate constant and formulation and Japanese race on bioavailability. None of the covariates identified had a clinically relevant effect, as impact on area under the plasma concentration-time curve (AUC) and maximum plasma concentration (Cmax) was within ± 25%. CONCLUSION: The model characterizes the pharmacokinetics of vixotrigine well, and the exposure of vixotrigine was comparable between healthy subjects and patients. None of the covariates evaluated have a clinically relevant impact on the pharmacokinetics of vixotrigine.

Population pharmacokinetic analysis of apomorphine sublingual film or subcutaneous apomorphine in healthy subjects and patients with Parkinson's disease.

Apomorphine is an on-demand treatment of "OFF" episodes in patients with Parkinson's disease (PD). A joint parent-metabolite population pharmacokinetic (PK) model characterized apomorphine and apomorphine-sulfate following administration of apomorphine sublingual film (APL) and two formulations of subcutaneous apomorphine. Overall, 2485 samples from 87 healthy subjects and 71 patients with PD and "OFF" episodes were analyzed using nonlinear mixed-effects modeling. Apomorphine PK was adequately described by a two-compartment model with first-order transit absorption via both routes of administration and first-order metabolism to apomorphine-sulfate with one-compartment disposition and first-order elimination. Bioavailability of apomorphine sublingual film was ~ 18% relative to subcutaneous apomorphine. Among covariates tested, only body weight had a large effect on apomorphine exposure (maximum plasma concentration and area under the concentration-time curve [AUC0-∞ ]), with greater weight resulting in lower exposure. Model-predicted apomorphine exposure was similar between apomorphine sublingual film 30 mg and subcutaneous apomorphine 5 mg (median AUC0-24 , 66.7 ng•h/mL, geometric mean ratio of 0.99; 90% confidence interval [CI], 0.96-1.03) and was comparable between apomorphine sublingual film 35 mg and subcutaneous apomorphine 6 mg (median AUC0-24 , 75.4 and 80.0 ng•h/mL, respectively; geometric mean ratio of 0.94; 90% CI, 0.90-0.97) administered every 2 h for a maximum of 5 doses per day. In a typical patient with PD, predicted apomorphine exposure increased with increasing doses of apomorphine sublingual film; however, the increase was less than dose proportional. Similar apomorphine exposure was predicted in patients with mild renal impairment versus normal renal function. PK properties of apomorphine sublingual film support its administration for a wide range of patients with PD and "OFF" episodes, regardless of demographic and clinical characteristics.

Concentration-QTc Modeling of Ozanimod's Major Active Metabolites in Adult Healthy Subjects.

Ozanimod, approved by regulatory agencies in multiple countries for the treatment of adults with relapsing multiple sclerosis, is a sphingosine 1-phosphate (S1P) receptor modulator, which binds with high affinity selectively to S1P receptor subtypes 1 and 5. The relationships between plasma concentrations of ozanimod and its major active metabolites, CC112273 and CC1084037, and the QTc interval (C-QTc) from a phase I multiple-dose study in healthy subjects were analyzed using nonlinear mixed effects modeling. QTc was modeled linearly as the sum of a sex-related fixed effect, baseline, and concentration-related random effects that incorporated interindividual and residual variability. Common linear, power, and maximum effect (Emax ) functions were assessed for characterizing the relationship of QTc with concentrations. Model goodness-of-fit and performance were evaluated by standard diagnostic tools, including a visual predictive check. The placebo-corrected change from baseline in QTc (ΔΔQTc) was estimated based on the developed C-QTc model using a nonparametric bootstrapping approach. QTc was better derived using a study-specific population formula (QTcP). Among the investigated functions, an Emax function most adequately described the relationship of QTcP with concentrations. Separate models for individual analytes characterized the C-QTcP relationship better than combined analytes models. Attributing QT prolongation independently to CC1084037 or CC112273, the upper bound of the 95% confidence interval of the predicted ΔΔQTcP was ~ 4 msec at the plateau of the Emax curves. Therefore, ΔΔQTcP is predicted to remain below 10 msec at the supratherapeutic concentrations of the major active metabolites.

Cabozantinib exposure-response analyses of efficacy and safety in patients with advanced hepatocellular carcinoma.

Cabozantinib, a multi-kinase inhibitor, is approved in the United States and European Union for treatment of patients with hepatocellular carcinoma following prior sorafenib treatment. In the Phase III CELESTIAL trial, hepatocellular carcinoma patients receiving cabozantinib showed longer overall survival (OS) and progression-free survival (PFS) than those receiving placebo. The approved cabozantinib (Cabometyx®) dose is 60 mg once daily with allowable dose modifications to manage adverse events (AE). Time-to-event Cox proportional hazard exposure-response (ER) models were developed to characterize the relationship between predicted cabozantinib exposure and the likelihood of various efficacy and safety endpoints. The ER models were used to predict hazard ratios (HR) for efficacy and safety endpoints for starting doses of 60, 40, or 20 mg daily. Statistically significant relationships between cabozantinib exposure and efficacy and safety endpoints were observed. For efficacy endpoints, predicted HR were lower for OS and PFS at 40 and 60 mg relative to the 20 mg dose: HR for death (OS) are 0.84 (40 mg) and 0.70 (60 mg); HR for disease progression/death (PFS) are 0.73 (40 mg) and 0.62 (60 mg). For safety endpoints, predicted HR were lower for palmar-plantar erythrodysaesthesia (PPE), diarrhea, and hypertension at 20 or 40 mg relative to the 60 mg dose: HR for PPE are 0.31 (20 mg) and 0.66 (40 mg); HR for diarrhea are 0.61 (20 mg) and 0.86 (40 mg); HR for hypertension are 0.46 (20 mg) and 0.76 (40 mg). The rate of dose modifications was predicted to increase in patients with lower cabozantinib apparent clearance. OS and PFS showed the greatest benefit at the 60 mg dose. However, higher cabozantinib exposure was predicted to increase the likelihood of AE and subsequent dose reductions appeared to decrease these risks.

Population Pharmacokinetics of Pregabalin Extended-Release in Healthy Volunteers and Patients With Postherpetic Neuralgia, Fibromyalgia, and Partial-Onset Seizures.

A population pharmacokinetic (PK) model was developed to characterize the properties of pregabalin extended-release (ER) in healthy volunteers and was subsequently applied to patient data from efficacy/safety studies investigating pregabalin ER for postherpetic neuralgia, fibromyalgia, and partial-onset seizures. The impact of demographic and other covariates on PK was assessed, and various dosing scenarios were simulated to inform pregabalin ER dosing/administration instructions. Phase 1 and 3 models were developed using data from 14 phase 1 studies (12 627 samples from 335 participants receiving pregabalin immediate-release [IR] or ER) and 3 phase 3 studies (2591 samples from 1235 patients receiving pregabalin ER), respectively. Final phase 1 and 3 models adequately characterized the data. Several covariates were statistically significant, but renal function (creatinine clearance) was considered the only clinically relevant covariate. The relationship between creatinine clearance and pregabalin clearance was reasonably consistent between phase 1 and 3 models and with that reported previously with pregabalin IR data alone. Patients with moderate renal impairment who received pregabalin ER 82.5 mg once daily (QD) had similar predicted area under the plasma concentration-time curve and peak plasma concentration values as patients with normal/mild renal impairment who received 165 mg QD. Ranges in predicted PK parameters after switching from pregabalin IR administered in the morning to ER after a meal at 3, 6, or 9 pm were similar. Administration of a missed evening dose at bedtime with food or the next morning with food did not result in clinically important changes in predicted PK parameters.

Updated Population Pharmacokinetic Model of Cabozantinib Integrating Various Cancer Types Including Hepatocellular Carcinoma.

An integrated population pharmacokinetic (PPK) model was used to evaluate the effects of liver dysfunction on the pharmacokinetics (PK) of cabozantinib in patients with hepatocellular carcinoma and to determine whether clinical dosage adjustment may be necessary in this population. An integrated PPK model previously developed in healthy volunteers and patients with various cancer types was updated with cabozantinib concentration data from hepatocellular carcinoma patients in phase 2 and 3 studies (total 2023; hepatocellular carcinoma 489 patients). Covariate effects of cancer type including hepatocellular carcinoma population and liver dysfunction per the National Cancer Institute Organ Dysfunction Working Group criteria were evaluated (normal 1425; mild liver dysfunction 558; moderate/severe liver dysfunction 15/1 patients). With hepatocellular carcinoma patients, PK parameter estimates and covariate effects were similar to the previous PPK model (2 compartments with first- and zero-order absorption and first-order elimination). Only medullary thyroid cancer had appreciable PK differences from healthy volunteers. PK parameter estimates were similar with and without addition of liver dysfunction covariates. Patients with mild liver dysfunction were predicted to have minimal differences in apparent clearance of cabozantinib relative to patients with normal liver function. Therefore, no initial cabozantinib dosage adjustment is recommended for cancer patients with mild liver dysfunction. The small sample size for patients with moderate and severe liver dysfunction limited dosing recommendations in these subpopulations. The results from this PPK analysis were different from those of the single-dose hepatic impairment study in healthy volunteers and more reflective of exposure in cancer patients following daily cabozantinib dosing.

Clinical Pharmacokinetics and Pharmacodynamics of Dalcetrapib.

The cholesterol ester transfer protein (CETP) inhibitor dalcetrapib has been under evaluation for its potential to prevent cardiovascular (CV) events for almost two decades. The current clinical development program, representing new advances in precision medicine and focused on a genetically defined population with acute coronary syndrome (ACS), is supported by a large body of pharmacokinetic and pharmacodynamic data as well as substantial clinical experience in over 13,000 patients and volunteers. Dalcetrapib treatment of 600 mg/day produces significant inhibition of CETP activity, and has been utilized in phase II and III studies, including CV endpoint trials. Numerous studies have investigated the interactions between dalcetrapib and most drugs commonly prescribed to CV patients and have not demonstrated any clinically significant effects. Evaluations in patients with renal and hepatic impairment demonstrate a greater exposure to dalcetrapib than in the non-impaired population, but long-term clinical studies including patients with mild to moderate hepatic and renal dysfunction demonstrate no increase in adverse events. Safety pharmacology and toxicology studies as well as the clinical safety experience support the continuing development of dalcetrapib as an adjunct to 'standard of care' for the ACS population. This article provides a full review of the pharmacokinetics, as well as pharmacodynamics and pharmacology, of dalcetrapib in the context of a large clinical program.

Population Pharmacokinetics Analysis To Inform Efavirenz Dosing Recommendations in Pediatric HIV Patients Aged 3 Months to 3 Years.

Efavirenz (EFV) is a nonnucleoside reverse transcriptase inhibitor approved worldwide for the treatment of HIV in adults and children over 3 years of age or weighing over 10 kg. Only recently EFV was approved in children over 3 months and weighing at least 3.5 kg in the United States and the European Union. The objective of this analysis was to support the selection of an appropriate dose for this younger pediatric population and to explore the impact of CYP2B6 genetic polymorphisms on EFV systemic exposures. A population pharmacokinetic (PPK) model was developed using data from three studies in HIV-1-infected pediatric subjects (n = 168) and one study in healthy adults (n = 24). The EFV concentration-time profile was best described by a two-compartment model with first-order absorption and elimination. Body weight was identified as a significant predictor of efavirenz apparent clearance (CL), oral central volume of distribution (VC), and absorption rate constant (Ka). The typical values of efavirenz apparent CL, VC, oral peripheral volume of distribution (VP), and Ka for a reference pediatric patient were 4.8 liters/h (4.5 to 5.1 liters/h), 84.9 liters (76.8 to 93.0 liters), 287 liters (252.6 to 321.4 liters), and 0.414 h(-1) (0.375 to 0.453 h(-1)), respectively. The final model was used to simulate steady-state efavirenz concentrations in pediatric patients weighing <10 kg to identify EFV doses that produce comparable exposure to adult and pediatric patients weighing ≥10 kg. Results suggest that administration of EFV doses of 100 mg once daily (QD) to children weighing ≥3.5 to <5 kg, 150 mg QD to children weighing ≥5 to <7.5 kg, and 200 mg QD to children weighing ≥7.5 to <10 kg produce exposures within the target range. Further evaluation of the impact of CYP2B6 polymorphisms on EFV PK showed that the identification of CYP2B6 genetic status is not predictive of EFV exposure and thus not informative to guide pediatric dosing regimens.

Lurasidone Dose Response in Bipolar Depression: A Population Dose-response Analysis.

PURPOSE: Characterization of dose-response relationships for psychotropic agents may be difficult to determine based on results of individual clinical studies, particularly those with a flexible dose design. The goal of this pharmacometric analysis was to characterize the dose-response profile for lurasidone in patients with bipolar depression. METHODS: The statistical modeling and simulation analyses reported here were derived from 2 randomized, 6-week, double-blind, placebo-controlled, flexible-dose studies (20-60 mg/d or 80-120 mg/d of lurasidone as monotherapy or 20-120 mg/d adjunct to lithium or valproate) in patients with bipolar depression. Pooled data included 5245 Montgomery-Åsberg Depression Rating Scale (MADRS) observations from 825 patients who had received lurasidone or placebo treatments, with or without lithium or valproate background medication. FINDINGS: The time course of placebo effect on the MADRS score was adequately described by an exponential asymptotic placebo model. A linear dose-response model best described the effect of lurasidone. The net improvement in MADRS score due to lurasidone treatment (the drug effect) was significant (P < 0.001), and a positive dose response was detected. Net drug effect after 6 weeks of treatment was estimated to be a 6.0-point decrease in MADRS score per 100 mg of lurasidone. Covariate effects (for age and lithium or valproate use) were significant only for placebo effect parameters; thus, no dose adjustment was necessary related to demographic covariates. IMPLICATIONS: This population dose-response modeling analysis indicates that higher doses of lurasidone are likely to produce greater therapeutic effects in patients with bipolar depression. The linear dose response was consistent for both lurasidone monotherapy and adjunctive therapy in patients with bipolar depression. ClinicalTrials.gov identifiers: NCT00868452, NCT00868699.

Population pharmacokinetics of naloxegol in a population of 1247 healthy subjects and patients.

AIMS: Naloxegol, a polyethylene glycol conjugated derivative of the opioid antagonist naloxone, is in clinical development for treatment of opioid-induced constipation (OIC). The aim of the study was to develop a population pharmacokinetic model describing the concentration vs. time profile of orally administered naloxegol, and determine the impact of pre-specified demographic and clinical factors and concomitant medication on population estimates of apparent clearance (CL/F) and apparent central compartment volume of distribution (Vc /F). METHODS: Analysis included 12,844 naloxegol plasma concentrations obtained from 1247 healthy subjects, patients with non-OIC and patients with OIC in 14 phase 1, 2b and 3 clinical studies. Pharmacokinetic analysis used the non-linear mixed effects modelling program. Goodness of fit plots and posterior predictive checks were conducted to confirm concordance with observed data. RESULTS: The final model was a two compartment disposition model with dual absorptions, comprising one first order absorption (ka1 4.56 h(-1) ) and one more complex absorption with a transit compartment (ktr 2.78 h(-1) ). Mean (SE) parameter estimates for CL/F and Vc /F, the parameters assessed for covariate effects, were 115 (3.41) l h(-1) and 160 (27.4) l, respectively. Inter-individual variability was 48% and 51%, respectively. Phase of study, gender, race, concomitant strong or moderate CYP3A4 inhibitors, strong CYP3A4 inducers, P-glycoprotein inhibitors or inducers, naloxegol formulation, baseline creatinine clearance and baseline opioid dose had a significant effect on at least one pharmacokinetic parameter. Simulations indicated concomitant strong CYP3A4 inhibitors or inducers had relevant effects on naloxegol exposure. CONCLUSIONS: Administration of strong CYP3A4 inhibitors or inducers had a clinically relevant influence on naloxegol pharmacokinetics.

A comparison of the pharmacokinetics and pharmacodynamics of pregabalin and gabapentin.

Pregabalin and gabapentin share a similar mechanism of action, inhibiting calcium influx and subsequent release of excitatory neurotransmitters; however, the compounds differ in their pharmacokinetic and pharmacodynamic characteristics. Gabapentin is absorbed slowly after oral administration, with maximum plasma concentrations attained within 3-4 hours. Orally administered gabapentin exhibits saturable absorption--a nonlinear (zero-order) process--making its pharmacokinetics less predictable. Plasma concentrations of gabapentin do not increase proportionally with increasing dose. In contrast, orally administered pregabalin is absorbed more rapidly, with maximum plasma concentrations attained within 1 hour. Absorption is linear (first order), with plasma concentrations increasing proportionately with increasing dose. The absolute bioavailability of gabapentin drops from 60% to 33% as the dosage increases from 900 to 3600 mg/day, while the absolute bioavailability of pregabalin remains at > or = 90% irrespective of the dosage. Both drugs can be given without regard to meals. Neither drug binds to plasma proteins. Neither drug is metabolized by nor inhibits hepatic enzymes that are responsible for the metabolism of other drugs. Both drugs are excreted renally, with elimination half-lives of approximately 6 hours. Pregabalin and gabapentin both show dose-response relationships in the treatment of postherpetic neuralgia and partial seizures. For neuropathic pain, a pregabalin dosage of 450 mg/day appears to reduce pain comparably to the predicted maximum effect of gabapentin. As an antiepileptic, pregabalin may be more effective than gabapentin, on the basis of the magnitude of the reduction in the seizure frequency. In conclusion, pregabalin appears to have some distinct pharmacokinetic advantages over gabapentin that may translate into an improved pharmacodynamic effect.

Exposure-response analysis in patients with schizophrenia to assess the effect of asenapine on QTc prolongation.

An exposure-response (E-R) analysis using linear mixed effects modeling was conducted on data from a thorough QTc trial for asenapine in 148 patients with schizophrenia. In a parallel design, patients received asenapine 5 mg twice daily (BID) for 10 days (10d) followed by 10 mg BID (6d), asenapine 15 mg BID (10d) followed by 20 mg BID (6d), quetiapine 375 mg BID (for assay sensitivity; 16d) or placebo (16d). Triplicate 12-lead electrocardiograms and concentration measurements were obtained on day -1 (baseline), 1, 10, and 16 at 8 scheduled times on each day. At mean C(max) for all asenapine doses, the E-R model predicted that the mean QTcF increase was less than 5 milliseconds, the International Conference on Harmonisation-established threshold for clinical concern. The model predicted a mean increase of 7 to 8 milliseconds for quetiapine. The corresponding upper bounds of the 95% confidence intervals were 7.5 milliseconds and 11.2 milliseconds for asenapine and quetiapine, respectively.

Performance characteristics for some typical QT study designs under the ICH E-14 guidance.

The International Conference on Harmonization (ICH) guidance for clinical evaluation of QT prolongation (E14) affected drug development by advocating that a thorough QT study (TQT) be conducted during development to assess the QT prolongation liability of a compound. The ICH E14 Statistics Group shortly thereafter recommended that a noninferiority intersection-union test (IUT) be used to exclude a clinically worrisome QT prolongation. Recent analyses have indicated that the IUT might be overly conservative with respect to excluding QT prolongation. This report assesses the IUT false positive rate for 4 recently conducted TQT trials using simple simulation experiments. Positive TQT study rates ranged from negligible to nearly 60% depending on study design, sample size, and patient status, despite no drug effect. Addition of clinically nonmeaningful QT prolongations (up to 5 milliseconds) increased the positive study rate to 80% for 1 particular study design. Ultimately, these results reveal significant limitations of the IUT with respect to excluding an effect and study interpretation for certain trial designs.

Pharmacodynamic analysis of the microbiological efficacy of telithromycin in patients with community-acquired pneumonia.

BACKGROUND AND OBJECTIVE: Telithromycin, a ketolide antibacterial, demonstrates concentration-dependent bactericidal activity against the major pathogens causing community-acquired respiratory tract infections. The objective of this study was to explore the relationships between pharmacokinetic/pharmacodynamic predictor variables, such as area under the plasma concentration-time curve (AUC) over minimum inhibitory concentration (MIC) [AUC/MIC], maximum plasma concentration (C(max)) over MIC (C(max)/MIC) and microbiological outcome from telithromycin therapy for community-acquired pneumonia (CAP). PATIENTS AND METHODS: Data were pooled from five phase III studies of oral telithromycin (800 mg once daily for 7-10 days) for the outpatient treatment of adults with CAP. Only subjects with a single pathogen isolated at baseline, a telithromycin MIC determination and at least one plasma pharmacokinetic sample were included. Bacteriologically modified intent-to-treat (bmITT) and bacteriologically evaluable per protocol (PPb) populations were analysed. Individual AUC and C(max) Bayesian estimates were obtained with a population pharmacokinetic model. Logistic regression, nonparametric smoothing, and classification analysis and regression tree (CART) were used to assess the relationship between AUC/MIC and C(max)/MIC and microbiological outcome by pathogen. RESULTS: The bmITT population included 224 patients (Streptococcus pneumoniae in 113, Haemophilus influenzae in 89 and Staphylococcus aureus in 22). Median telithromycin MIC was 0.015 microg/mL for S. pneumoniae, 2.0 microg/mL for H. influenzae and 0.12 microg/mL for S. aureus, with median AUC/MIC of 907.1, 6.9 and 98.4, and median C(max)/MIC of 172.0, 1.3 and 20.4 for the three pathogens, respectively. Both logistic regression and nonparametric smoothing showed the probability of microbiological cure to be consistently greater than 90% over the observed range of predictor variables. No reliable AUC/MIC or C(max)/MIC breakpoints were identified by CART. CONCLUSION: Telithromycin exhibits near-maximal efficacy against three major pathogens causing CAP at a dose of 800 mg once daily.

Posttransfusion recovery of stored red blood cells in very low birth weight infants using a hemoglobin balance model.

BACKGROUND: A Hb balance model was used in very low birth weight (VLBW) infants to predict posttransfusion Hb levels from which we inferred allogeneic RBC recovery after transfusion of RBCs stored for varying periods of time. STUDY DESIGN AND METHODS: Premature VLBW infants receiving RBC transfusions during the 1st month of life were evaluated retrospectively for RBC survival of stored donor blood. Actual Hb levels measured in infant blood 1 and 2 days after RBC transfusions were compared to those predicted using a Hb balance model based on factors affecting blood Hb loss and gain. Transfusions were subgrouped according to whether or not infants were clinically stable at the time of RBC transfusion. Model-predicted RBC recovery was also evaluated relative to duration of RBC storage. RESULTS: Model-predicted mean (+/- SD) Hb levels 2 days after transfusion among the 30 VLBW infants receiving a total of 57 RBC transfusions were only 4 percent higher than actual values observed (15.2 +/- 1.2 g/dL vs. 14.7 +/- 1.4, respectively; p < 0.05). The infant's clinical status at the time of transfusion did not affect predicted 1- and 2-day posttransfusion RBC recovery. Model-predicted recovery of transfused RBCs was modestly, but significantly, decreased with increasing duration of donor RBC storage (i.e., 10% lower by 42 days-the maximal allowed storage period for donor blood [p < 0.01]). CONCLUSIONS: Our model-predicted RBC survival results are consistent with-but not direct evidence of-hemolysis of donor blood after RBC transfusion. Although observed post-RBC Hb levels 2 days after transfusion averaged only 4 percent less than predicted, model-predicted survival of donor RBCs at 42 days suggested a modest decrease (i.e., by 10%).