A model-based approach to predict individual weight loss with semaglutide in people with overweight or obesity.

AIMS: To determine the relationship between exposure and weight-loss trajectories for the glucagon-like peptide-1 analogue semaglutide for weight management. MATERIALS AND METHODS: Data from one 52-week, phase 2, dose-ranging trial (once-daily subcutaneous semaglutide 0.05-0.4 mg) and two 68-week phase 3 trials (once-weekly subcutaneous semaglutide 2.4 mg) for weight management in people with overweight or obesity with or without type 2 diabetes were used to develop a population pharmacokinetic (PK) model describing semaglutide exposure. An exposure-response model describing weight change was then developed using baseline demographics, glycated haemoglobin and PK data during treatment. The ability of the exposure-response model to predict 1-year weight loss based on weight data collected at baseline and after up to 28 weeks of treatment, was assessed using three independent phase 3 trials. RESULTS: Based on population PK, exposure levels over time consistently explained the weight-loss trajectories across trials and dosing regimens. The exposure-response model had high precision and limited bias for predicting body weight loss at 1 year in independent datasets, with increased precision when data from later time points were included in the prediction. CONCLUSION: An exposure-response model has been established that quantitatively describes the relationship between systemic semaglutide exposure and weight loss and predicts weight-loss trajectories for people with overweight or obesity who are receiving semaglutide doses up to 2.4 mg once weekly.

Population Pharmacokinetics of Tralokinumab in Adult Subjects With Moderate to Severe Atopic Dermatitis.

Tralokinumab is the first biologic therapy for moderate-to-severe atopic dermatitis (AD) that specifically neutralizes interleukin-13 activity, a key driver of AD signs and symptoms. Tralokinumab is a human immunoglobulin G4 monoclonal antibody administered subcutaneously every 2 weeks (with possibility of maintenance dosing every 4 weeks). This population pharmacokinetic (PK) analysis aimed to identify sources of PK variability and relevant predictors of tralokinumab exposure in adults with moderate to severe AD. Nonlinear mixed-effect modeling, including covariate analysis, was used on a data set including 2561 subjects (AD, asthma, healthy) from 10 clinical trials. A 2-compartment model with first-order absorption and elimination adequately described the tralokinumab PK. Body weight was identified as a relevant predictor of tralokinumab exposure; other covariates including age, sex, race, ethnicity, disease type, AD severity, and renal and hepatic impairment were not. For body weight, the difference in exposure between the upper- and lower-weight quartiles in patients with AD was <2-fold, supporting the appropriateness of flat dosing (300 mg). Given the reduced exposure associated with higher body weight, coupled with the reduced exposure provided by dosing every 4 weeks, it is uncertain whether higher-weight patients will achieve sufficient exposure to maintain efficacy if dosed every 4 weeks instead of the standard every 2 weeks.

Rotational thromboelastometry can predict the probability of bleeding events in a translational rat model of haemophilia A following gene-based FVIIa prophylaxis.

INTRODUCTION: Monitoring of clinical effectiveness of bypassing agents in haemophilia patients is hampered by the lack of validated laboratory assays. Thromboelastography (TEG) and rotational thromboelastometry (ROTEM) have been evaluated for predicting clinical effectiveness of bypassing agents, however, with limited success. AIM: Application of a longitudinal model-based approach may allow for a quantitative characterization of the link between ROTEM parameters and the probability of bleeding events. METHODS: We analyse longitudinal data from haemophilia A rats receiving gene-based FVIIa prophylaxis in terms of total circulatory levels of FVII/FVIIa, clotting time (CT) measured using ROTEM and the probability of bleeding events. RESULTS: Using population pharmacokinetic-pharmacodynamic (PKPD) modelling, a PK-CT-repeated time-to-event (RTTE) model was developed composed of three submodels (a) a FVII/FVIIa PK model, (b) a PK-CT model describing the relationship between predicted FVIIa expression and CT and (c) a RTTE model describing the probability of bleeding events as a function of CT. The developed PK-CT-RTTE model accurately described the vector dose-dependent plasma concentration-time profile of total FVII/FVIIa and the exposure-response relationship between AAV-derived FVIIa expression and CT. Importantly, the developed model accurately described the occurrence of bleeding events over time in a quantitative manner, revealing a linear relationship between predicted change from baseline CT and the probability of bleeding events. CONCLUSION: Using PK-CT-RTTE modelling, we demonstrated that ROTEM parameters can accurately predict the probability of bleeding events in a translational animal model of haemophilia A.

Impact of capacity-limited binding on recombinant factor VIII and von Willebrand factor pharmacokinetics in hemophilia A rats.

Essentials Knowledge of the interplay between FVIII and VWF pharmacokinetics (PK) is lacking. We characterized the capacity-limited PK of FVIII and VWF. The PK model described the PK of FVIII and VWF over a broad range of rFVIII doses. High-dose rFVIII treatment can reduce the endogenous VWF levels. BACKGROUND: Understanding of the pharmacokinetics (PK) interplay between factor VIII (FVIII) and von Willebrand factor (VWF) following high-dose FVIII treatment is lacking. OBJECTIVES: To characterize the PK of recombinant FVIII (rFVIII), VWF, and the rFVIII:VWF complex in hemophilia A rats following intravenous administration of rFVIII using PK modeling. A second aim was to investigate the effect of high daily dosing and constant expression of rFVIII on VWF exposure using PK simulations. METHODS: We developed a population PK model based on the principles of target-mediated drug disposition modeling, using data on total rFVIII and VWF plasma concentrations, and the rFVIII:VWF complex luminescent oxygen channeling immunoassay signal in hemophilia A rats following intravenous administration of rFVIII (17.5, 100, 1000, and 5000 IU kg-1 ). Additionally, we evaluated the influence of high-dose rFVIII treatment on the exposure of VWF using PK simulations. RESULTS: The plasma concentration-time profiles of total rFVIII and VWF, and the luminescent oxygen channeling immunoassay signal-time profiles of the rFVIII:VWF complex were adequately described using a two-compartment quasi-steady-state target-mediated drug disposition model (Kss  = 0.14 nmol L-1 ). The elimination half-life of the rFVIII:VWF complex was dependent on the unbound plasma concentration of rFVIII. Additionally, we showed that high-dose rFVIII treatment may significantly reduce the endogenous VWF levels. CONCLUSIONS: We developed a population-based PK model describing the time-course of total rFVIII, total VWF, and the rFVIII:VWF complex over a broad range of rFVIII doses in hemophilia A rats.

Impact of trial design on the estimation of drug potency and power in clinical trials of haemophilia with inhibitors.

Historically, clinical trials of haemophilia with inhibitors (HwI) have been challenged by the small patient population. New approaches to clinical trial methodology and statistical modelling could potentially be used for study optimization. The aim of this work was to evaluate the impact of different trial designs and study conditions on the estimated drug potency and power, and compare traditional statistical methods with repeated time-to-event (RTTE) modelling in terms of power. Bleeding information from a clinical trial of 23 haemophilia patients with inhibitors treated on-demand was used to develop a baseline RTTE model using NONMEM. Clinical trial simulations for a hypothetical anti-haemophilic drug were performed, by adding a drug effect and a literature-derived placebo effect to the baseline RTTE model, using different trial designs (parallel-group, placebo-controlled parallel-group, crossover and placebo-controlled crossover designs) and study conditions, including sample size, study duration and doses. The precision and accuracy of the estimated drug potency (EC50) and power for different trial designs, study conditions and statistical methods (RTTE modelling, t-test and negative binomial regression) were evaluated. The developed baseline RTTE model accurately described the clinical data. The crossover designs displayed up to four-fold higher precision of the estimated EC50 and three-fold higher power relative to the parallel-group trial designs. Furthermore, RTTE modelling provided a higher power relative to the traditional statistical tests. We found that crossover designs in combination with RTTE modelling can reduce the required sample size and study duration, while ensuring high power and precise estimation of EC50, in clinical trials of HwI.

Prediction of human pharmacokinetics of activated recombinant factor VII and B-domain truncated factor VIII from animal population pharmacokinetic models of haemophilia.

Various experimental animal models are used in haemophilia research, however, little is known about how well the different species predict pharmacokinetic (PK) profiles in haemophilia patients. The aim of the current study was to describe the plasma concentration-time profile of recombinant activated factor VII (rFVIIa) and recombinant factor VIII (rFVIII) in several experimental animal models using population PK modelling, and apply a simulation-based approach to evaluate how well the developed animal population PK models predict human PK. PK models were developed for rFVIIa and rFVIII in mice, rats, monkeys, and dogs using nonlinear mixed-effects modelling, accounting for inter-individual variability, nonlinear kinetics and covariate effects. Three scaling principles were applied to predict human PK: proportional scaling to body weight from single species, scaling with fixed theory-based allometric exponents from single species, and allometric interspecies scaling with estimated allometric coefficients and exponents. The plasma concentration-time profile of rFVIIa and rFVIII in mice, rats, monkeys and dogs were accurately described by the developed species-specific PK models, accounting for nonlinear kinetics and gender-specific difference in clearance for rFVIII. The predictive performance of the animal population PK models of rFVIIa and rFVIII revealed significant species-variation. The developed PK models of rFVIIa and rFVIII in monkeys and dogs along with allometric interspecies scaling revealed high predictive performance for human PK, and may promote rational decision-making in future first-in-human trials for rFVIIa and rFVIII variants.

Pharmacokinetic/Pharmacodynamic Relationship of Gabapentin in a CFA-induced Inflammatory Hyperalgesia Rat Model.

PURPOSE: Gabapentin displays non-linear drug disposition, which complicates dosing for optimal therapeutic effect. Thus, the current study was performed to elucidate the pharmacokinetic/pharmacodynamic (PKPD) relationship of gabapentin's effect on mechanical hypersensitivity in a rat model of CFA-induced inflammatory hyperalgesia. METHODS: A semi-mechanistic population-based PKPD model was developed using nonlinear mixed-effects modelling, based on gabapentin plasma and brain extracellular fluid (ECF) time-concentration data and measurements of CFA-evoked mechanical hyperalgesia following administration of a range of gabapentin doses (oral and intravenous). RESULTS: The plasma/brain ECF concentration-time profiles of gabapentin were adequately described with a two-compartment plasma model with saturable intestinal absorption rate (K m = 44.1 mg/kg, V max = 41.9 mg/h∙kg) and dose-dependent oral bioavailability linked to brain ECF concentration through a transit compartment. Brain ECF concentration was directly linked to a sigmoid E max function describing reversal of hyperalgesia (EC 50, plasma = 16.7 µg/mL, EC 50, brain = 3.3 µg/mL). CONCLUSIONS: The proposed semi-mechanistic population-based PKPD model provides further knowledge into the understanding of gabapentin's non-linear pharmacokinetics and the link between plasma/brain disposition and anti-hyperalgesic effects. The model suggests that intestinal absorption is the primary source of non-linearity and that the investigated rat model provides reasonable predictions of clinically effective plasma concentrations for gabapentin.

In vivo and in vitro evaluations of intestinal gabapentin absorption: effect of dose and inhibitors on carrier-mediated transport.

PURPOSE: Gabapentin exhibits saturable absorption kinetics, however, it remains unclear which transporters that are involved in the intestinal transport of gabapentin. Thus, the aim of the current study was to explore the mechanistic influence of transporters on the intestinal absorption of gabapentin by both in vivo and in vitro investigations METHODS: Pharmacokinetic parameters were determined following a range of intravenous (5-100 mg/kg) and oral doses (10-200 mg/kg) in rats. Transepithelial transport (50 µM-50 mM) and apical uptake of gabapentin (0.01-50 mM) were investigated in Caco-2 cells. The effect of co-application of the LAT-inhibitor, BCH, and the b(0,+)-substrate, L-lysine, on intestinal transport of gabapentin was evaluated in vivo and in vitro. RESULTS: Gabapentin showed dose-dependent oral absorption kinetics and dose-independent disposition kinetics. Co-application of BCH inhibited intestinal absorption in vivo and apical uptake in vitro, whereas no effect was observed following co-application of L-lysine. CONCLUSIONS: The present study shows for the first time that BCH was capable of inhibiting intestinal absorption of gabapentin in vivo. Furthermore, in Caco-2 cell experiments BCH inhibited apical uptake of gabapentin. These findings may imply that a BCH-sensitive transport-system was involved in the apical and possibly the basolateral transport of gabapentin across the intestinal wall.