A Physiologically-Based Pharmacokinetic Framework for Prediction of Drug Exposure in Malnourished Children

Minimal Physiologically-Based Pharmacokinetic Modeling of Atenolol and Metoprolol Absorption in Malnourished Rats

BACKGROUND AND OBJECTIVE

The pharmacokinetics of drugs can be altered by pathophysiological changes in the body that result from malnutrition. The objective of this study was to evaluate the profiles derived from in vivo studies conducted on non-malnourished (control) and malnourished rats using minimal physiologically based pharmacokinetic (mPBPK) models.

METHODS

Single oral doses of atenolol (ATN) and metoprolol (MET) were administered to non-malnourished and malnourished rats. We demonstrate how plasma profiles can be evaluated using mPBPK models with high and low tissue-to-plasma partition coefficients (Kp) and elimination by either kidney or liver. A decrease in blood flow and cardiac output due to beta-blocker administration was assumed. Reference IV profiles from the literature were included to inform the mPBPK model and to help assess the absorption phases of individual oral profiles. Absorption was captured as two or three sequential zero-order processes for both drugs, and IV and oral profiles were assessed by joint fitting. Modeling was performed using both naïve pooling (ADAPT) and population (Monolix) analyses.

RESULTS

The experimental data show increased AUC values of MET and ATN in malnourished rats. Accordingly, an increased bioavailability (from 0.43 to 0.67) for ATN and an increased bioavailability (from 0.42 to 0.84) for MET in the malnourished group were related to higher absorption rates in both absorption phases.

CONCLUSIONS

This study demonstrated advantageous use of mPBPK modeling with malnutrition primarily altering drug absorption in this animal model. Also, our analysis offers a blend of known and assumed components assembled mechanistically to suggest a reasonable interpretation of the PK profiles.

Model-Informed Drug Development of a Sustained Release Formulation of Flucytosine in the Treatment of Cryptococcal Meningitis: A Case Study Using Physiologically Based Pharmacokinetic Modeling

This paper presents a case study demonstrating the application of model-informed drug development (MIDD) and early modeling integration in the development of a sustained release (SR) formulation of flucytosine for cryptococcal meningoencephalitis (CM) in HIV-infected patients. The study aimed to showcase the value of physiologically based pharmacokinetic (PBPK) modeling and physiologically based biopharmaceutics modeling (PBBM) in guiding decisions and optimizing therapeutic strategies throughout drug development. The MIDD strategy started with a PBPK model based on limited literature data, iteratively refined informed by data from two Phase 1 clinical studies with various flucytosine formulations under different prandial conditions in healthy participants, enhancing model reliability. The PBPK/PBBM model played a substantial role in guiding SR prototype formulation design, dose selection for studies in healthy participants, and dosage determination for an upcoming Phase 2 clinical study in patients, with a focus on low-weight patients. The flexibility of MIDD allowed quick assessments of ancillary questions during the program. Ad hoc simulations evaluated strategies such as adding a loading dose for SR treatment and assessing drug exposure in unconscious patients, contributing to optimized therapeutic approaches. In conclusion, this case study emphasizes the benefits of MIDD and early model integration in drug development. PBPK/PBBM modeling facilitated informed decisions, leading to successful design and dosing of an SR flucytosine formulation for CM treatment. Continuous knowledge integration within MIDD ensured model adaptability and reliability, demonstrating its value in addressing evolving challenges and optimizing therapeutic outcomes.

Physiologically-based pharmacokinetic modelling in sepsis: A tool to elucidate how pathophysiology affects meropenem pharmacokinetics

OBJECTIVES

Applying physiologically-based pharmacokinetic (PBPK) modelling in sepsis could help to better understand how PK changes are influenced by drug- and patient-related factors. We aimed to elucidate the influence of sepsis pathophysiology on the PK of meropenem by applying PBPK modelling.

METHODS

A whole-body meropenem PBPK model was developed and evaluated in healthy individuals, and renally impaired non-septic patients. Sepsis-induced physiological changes in body composition, organ blood flow, kidney function, albumin, and haematocrit were implemented according to a previously proposed PBPK sepsis model. Model performance was evaluated, and a local sensitivity analysis was conducted.

RESULTS

The model-predicted PK metrics (AUC, Cmax, CL, Vss) were within 1.33-fold-error margin of published data for 87.5% of the simulated profiles in healthy individuals. In sepsis, the model provided good predictions for literature-digitised average plasma and tissue exposure data, where the model-predicted AUC was within 1.33-fold-error margin for 9 out 11 simulated study profiles. Furthermore, the model was applied to individual plasma concentration data from 52 septic patients, where the model-predicted AUC, Cmax, and CL had a fold-error ratio range of 0.98-1.12, with alignment of the predicted and observed variability. For Vss, the fold-error ratio was 0.81, and the model underpredicted the population variability. CL was sensitive to renal plasma clearance, and kidney volume, whereas Vss was sensitive to the unbound fraction, organ volume fraction of the interstitial compartment, and the organ volume.

CONCLUSIONS

These findings may be extended to more diverse drug types and support a more mechanistic understanding of the effect of sepsis on drug exposure.

Estimation of Pediatric Dosage of Antimalarial Drugs, Using Pharmacokinetic and Physiological Approach

Most of the individuals who die of malaria in sub-Saharan Africa are children. It is, therefore, important for this age group to have access to the right treatment and correct dose. Artemether-lumefantrine is one of the fixed dose combination therapies that was approved by the World Health Organization to treat malaria. However, the current recommended dose has been reported to cause underexposure or overexposure in some children. The aim of this article was, therefore, to estimate the doses that can mimic adult exposure. The availability of more and reliable pharmacokinetic data is essential to accurately estimate appropriate dosage regimens. The doses in this study were estimated using the physiological information from children and some pharmacokinetic data from adults due to the lack of pediatric pharmacokinetic data in the literature. Depending on the approach that was used to calculate the dose, the results showed that some children were underexposed, and others were overexposed. This can lead to treatment failure, toxicity, and even death. Therefore, when designing a dosage regimen, it is important to know and include the distinctions in physiology at various phases of development that influence the pharmacokinetics of various drugs in order to estimate the dose in young children. The physiology at each time point during the growth of a child may influence how the drug is absorbed, gets distributed, metabolized, and eliminated. From the results, there is a very clear need to conduct a clinical study to further verify if the suggested (i.e., 0.34 mg/kg for artemether and 6 mg/kg for lumefantrine) doses could be clinically efficacious.

Predicting the correct dose in children: Role of computational Pediatric Physiological-based pharmacokinetics modeling tools

The pharmacokinetics (PKs) and safety of medications in particular groups can be predicted using the physiologically-based pharmacokinetic (PBPK) model. Using the PBPK model may enable safe pediatric clinical trials and speed up the process of new drug research and development, especially for children, a population in which it is relatively difficult to conduct clinical trials. This review summarizes the role of pediatric PBPK (P-PBPK) modeling software in dose prediction over the past 6 years and briefly introduces the process of general P-PBPK modeling. We summarized the theories and applications of this software and discussed the application trends and future perspectives in the area. The modeling software's extensive use will undoubtedly make it easier to predict dose prediction for young patients.

Renal Transporter-Mediated Drug-Biomarker Interactions of the Endogenous Substrates Creatinine and N1 -Methylnicotinamide: A PBPK Modeling Approach

Endogenous biomarkers for transporter-mediated drug-drug interaction (DDI) predictions represent a promising approach to facilitate and improve conventional DDI investigations in clinical studies. This approach requires high sensitivity and specificity of biomarkers for the targets of interest (e.g., transport proteins), as well as rigorous characterization of their kinetics, which can be accomplished utilizing physiologically-based pharmacokinetic (PBPK) modeling. Therefore, the objective of this study was to develop PBPK models of the endogenous organic cation transporter (OCT)2 and multidrug and toxin extrusion protein (MATE)1 substrates creatinine and N¹ -methylnicotinamide (NMN). Additionally, this study aimed to predict kinetic changes of the biomarkers during administration of the OCT2 and MATE1 perpetrator drugs trimethoprim, pyrimethamine, and cimetidine. Whole-body PBPK models of creatinine and NMN were developed utilizing studies investigating creatinine or NMN exogenous administration and endogenous synthesis. The newly developed models accurately describe and predict observed plasma concentration-time profiles and urinary excretion of both biomarkers. Subsequently, models were coupled to the previously built and evaluated perpetrator models of trimethoprim, pyrimethamine, and cimetidine for interaction predictions. Increased creatinine plasma concentrations and decreased urinary excretion during the drug-biomarker interactions with trimethoprim, pyrimethamine, and cimetidine were well-described. An additional inhibition of NMN synthesis by trimethoprim and pyrimethamine was hypothesized, improving NMN plasma and urine interaction predictions. To summarize, whole-body PBPK models of creatinine and NMN were built and evaluated to better assess creatinine and NMN kinetics while uncovering knowledge gaps for future research. The models can support investigations of renal transporter-mediated DDIs during drug development.

Evaluation of Physiologically Based Pharmacokinetic Models to Predict the Absorption of BCS Class I Drugs in Different Pediatric Age Groups

Age-related changes in many parameters affecting drug absorption remain poorly characterized. The objective of this study was to apply physiologically based pharmacokinetic (PBPK) models in pediatric patients to investigate the absorption and pharmacokinetics of 4 drugs belonging to the Biopharmaceutics Classification System (BCS) class I administered as oral liquid formulations. Pediatric PBPK models built with PK-Sim/MoBi were used to predict the pharmacokinetics of acetaminophen, emtricitabine, theophylline, and zolpidem in different pediatric populations. The model performance for predicting drug absorption and pharmacokinetics was assessed by comparing the predicted absorption profile with the deconvoluted dose fraction absorbed over time and predicted with observed plasma concentration-time profiles. Sensitivity analyses were performed to analyze the effects of changes in relevant input parameters on the model output. Overall, most pharmacokinetic parameters were predicted within a 2-fold error range. The absorption profiles were generally reasonably predicted, but relatively large differences were observed for acetaminophen. Sensitivity analyses showed that the predicted absorption profile was most sensitive to changes in the gastric emptying time (GET) and the specific intestinal permeability. The drug's solubility played only a minor role. These findings confirm that gastric emptying time, more than intestinal permeability or solubility, is a key factor affecting BCS class I drug absorption in children. As gastric emptying time is prolonged in the fed state, a better understanding of the interplay between food intake and gastric emptying time in children is needed, especially in the very young in whom the (semi)fed condition is the prevailing prandial state, and hence prolonged gastric emptying time seems more plausible than the fasting state.