Population Pharmacokinetic Model Research Articles

Establishment and validation of a population pharmacokinetic model for apatinib in patients with tumors

ObjectiveThis study aimed to develop a population pharmacokinetic (PPK) model for oral apatinib in Chinese oncology patients and investigate the factors influencing the pharmacokinetics of apatinib.MethodsWe gathered 199 blood concentration monitoring data points from 91 inpatient oncology participants receiving oral apatinib at the Third Affiliated Hospital of Soochow University. Covariates, such as age, gender, body weight, and indices of liver and renal function, were examined to assess their influence on the pharmacokinetic parameters of apatinib. The PPK model was developed using the nonlinear mixed-effects modeling procedure (NONMEM), and model validation was conducted using the bootstrap method and normalized prediction distribution error (NPDE) method.ResultsThe structural model adopted a one-compartment structure with first-order elimination. Notably, aspartate aminotransferase (AST) and the co-administered drug type emerged as primary covariates affecting apatinib clearance (CL/F). The finalized model was expressed as CL/F (L/h) = 56.7 × (AST/26.6)−0.298 × θ, when apatinib was combined with monoclonal antibodies, θ was 1; when combined with paclitaxel, θ was 0.58; when combined with other drugs (e.g., platinum, capecitabine, or the combination of tegafur, gimeracil, and oteracil potassium), θ was 1.60; When used as monotherapy, θ was 1.38. V/F = 674 L, and the absorption rate constant (Ka) was fixed at 0.08 h−1. Bootstrap results affirmed the model’s reliability and stability, while NPDE outcomes attested to the model’s fit.ConclusionOur study successfully established a PPK model for apatinib in oncology patients, revealing that liver function status and co-administered drug types significantly impacted apatinib CL/F. This finding underscored the potential necessity for dose adjustments to optimize efficacy, particularly in patients undergoing different chemotherapy regimens involving apatinib.

Population pharmacokinetics of fluconazole for prevention or treatment of invasive candidiasis in Chinese young infants.

The dosing of fluconazole for young infants remains empirical because of the limited pharmacokinetic (PK) data. We aimed to establish a population PK model and assess the systematic exposure-response of commonly used regimens of fluconazole in Chinese infants.We included infants with a postnatal age of less than 120 days and received intravenous fluconazole. Both scheduled and scavenged plasma samples were collected, and fluconzaole concentration was determined by a validated ultra-performance liquid chromatography-tandem mass spectrometry assay. Population PK analysis was conducted using Phoenix NLME, and then Monte Carlo simulation was conducted to predict the probability of target attainment (PTA) of empirically used regimens of both prophylactic and therapeutic purposes.Based on 304 plasma samples from 183 young infants, fluconazole concentration data was best described by a one-compartment model with first-order elimination. Gestational Age (GA), postnatal age (PNA), and body weight (BW) were included in the final model as CL = 0.02*(GA/214)2.77*(PNA/13)0.24*exp(nCL); V = 1.56*(BW/1435)0.90*exp(nV). Model validation revealed the final model had qualified stability and acceptable predictive properties. Monte Carlo simulation indicated that under the same minimum inhibitory concentration (MIC) value and administration regimen, PTA decreased with GA and PNA. The commonly used prophylactic regimens can meet the clinical need, while higher doses might be needed for treatment of invasive candidiasis.This population PK model of fluconazole discriminated the impact of GA and PNA on CL and BW on V. Dosing adjustment was needed according to the GA and PNA of infants to achieve targeted exposures.

Population Pharmacokinetic Modeling and Exposure-Response Analysis for the Antibody-Drug Conjugate Enfortumab Vedotin in Locally Advanced or Metastatic Urothelial Carcinoma.

Enfortumab vedotin is a fully human monoclonal antibody directed to Nectin-4 and conjugated to monomethyl auristatin E (MMAE), approved for treatment of previously treated locally advanced or metastatic urothelial carcinoma (mUC). This population analysis characterized pharmacokinetics of enfortumab vedotin and free (unconjugated) MMAE, identified covariates affecting pharmacokinetics, and evaluated weight-based dosing for enfortumab vedotin. Exposure-response analyses characterized relationships between enfortumab vedotin and free MMAE exposures and efficacy/safety endpoints. Data from 748 patients with locally advanced or mUC in 5 clinical studies were analyzed using nonlinear mixed-effects modeling. Patients received enfortumab vedotin 0.50-1.25 mg/kg every 3 weeks or on days 1, 8, and 15 of a 28-day cycle. Relevant covariates retained in final models were evaluated for clinical relevance to enfortumab vedotin and free MMAE exposures. Although some covariates produced differences in exposure, the magnitude of changes was not clinically meaningful. Simulations indicated weight-based dosing yielded more consistent exposures across body weight groups vs. a hypothetical fixed-dose regimen of enfortumab vedotin 95 mg (calculated for median body weight, 75 kg). Exposure-response analysis showed average enfortumab vedotin concentrations were not a statistically significant predictor of overall survival (hazard ratio 0.91, 95% confidence interval: 0.72-1.14; P = 0.41); all exposure quartiles had a greater median overall survival than chemotherapy (11.0-12.6 vs. 9.0 months). Enfortumab vedotin and free MMAE exposures were statistically significant predictors of grade ≥ 3 treatment-related adverse events (both P < 0.0001). This analysis supports enfortumab vedotin 1.25 mg/kg on days 1, 8, and 15 of a 28-day cycle.

Dosing strategy of tacrolimus when co-administered with Wuzhi tablet in renal transplant recipients.

Tacrolimus (TAC) is a first-line immunosuppressant to prevent allograft rejection. Wuzhi tablet is widely used as a TAC-sparing agent in China that could significantly elevate TAC exposure. However, insufficient data support the dose recommendation of TAC when co-administered with Wuzhi. A total of 305 adult renal transplant patients with 2,541 TAC trough concentrations (C0) were enrolled for population pharmacokinetic (PPK) modeling. CYP3A5 polymorphism was genotyped, and corresponding clinical factors were recorded. Nonlinear mixed-effects modeling and Monte Carlo simulation were used for dose recommendation. PK parameters were calculated based on one-compartment model with first-order absorption and elimination. The estimated total clearance (CL/F) and volume of distribution (Vd/F) of TAC were 23.84 L/h and 1,075.96 L, respectively. Wuzhi, CYP3A5 genotype, hematocrit (HCT), and weight were found to have a significant influence on CL/F. CL/F was significantly lower in the individuals who were CYP3A5 non-expressers and received TAC together with Wuzhi. CYP3A5 genotype (expressers or non-expressers), body weight (40-80 kg), and hematocrit (20 - 40%) were selected as the specific clinical scenarios, and the starting dose of TAC ranged from 1.5 to 4.5 mg when co-administered with Wuzhi. We establish a TAC PPK model comprising Wuzhi as a covariate in renal transplant recipients and recommend an initial dose of TAC when co-administered with Wuzhi, which could provide reference for the individualized regimens of TAC.

Characterisation of the pharmacokinetic and pharmacodynamic relationship of milvexian in total knee replacement patients

Abstract Background Milvexian, an oral factor XIa inhibitor, is currently being evaluated in patients at risk for thrombotic events due to atrial fibrillation, ischaemic stroke, or acute coronary syndrome. The exposure-response relationship between clinical efficacy and safety endpoints and milvexian pharmacokinetic (PK) metrics was recently submitted as a separate publication. Characterisation of the relationship between the coagulation pharmacodynamic (PD) markers versus milvexian PK metrics at the patient level has yet to be reported. Purpose This analysis characterised the relationship between the coagulation biomarkers, activated partial thromboplastin time (aPTT) and prothrombin time (PT), and milvexian systemic exposure in patients undergoing total knee replacement (TKR) evaluated in the AXIOMATIC-TKR study. Methods A population pharmacokinetic (PopPK) model was previously developed and characterised the PK of milvexian in TKR patients well. The PK/PD relationships between observed aPTT and PT versus PopPK model estimated time-matched milvexian plasma concentrations via nonlinear mixed effects modeling. The relationship between key clinical safety endpoints (e.g., any bleeding or clinically relevant non-major bleeding) and individual PD marker change (e.g., aPTT ratio to baseline) was also explored. Results The aPTT increased with increasing plasma concentration of milvexian over the range of doses evaluated in the study (25mg QD to 200mg BID). An Emax type of model reasonably characterised the PK/PD relationship between the aPTT and model predicted time-matched milvexian plasma concentration, which is consistent with previously observed relationships in healthy volunteers. No change was observed in PT with increased milvexian exposure. No obvious relationship was identified between any (including clinically relevant non-major) bleeding and aPTT ratio to baseline. Conclusions Increased milvexian exposure is directly correlated with aPTT prolongation over the range of doses evaluated in the TKR study. There was no obvious relationship between any (including clinically relevant non-major) bleeding and aPTT ratio. The PK/PD relationship of aPTT without a parallel relationship in PT distinguishes milvexian, a FXIa inhibitor, from previously studied FXa inhibitors. These analyses were a complementary component in dose selection for the milvexian Phase 3 program. Figure 1. PK/PD relationship between aPTT (left) and PT (right) and estimated time-matched plasma concentration (AXIOMATIC-TKR study)

Population pharmacokinetic and pharmacodynamic model of evogliptin: Severe uremia increases the bioavailability ofevogliptin.

Uremia, a condition characterized by the retention of uremic toxins due to impaired renal function, may affect drug metabolism mediated by CYP3A4 enzymes. Evogliptin is a dipeptidyl peptidase-4 (DPP-4) inhibitor diabetic drug that is primarily metabolized by CYP3A4. This study aimed to construct a population pharmacokinetic (PK) and pharmacodynamic (PD) model for evogliptin in patients with varying degrees of renal disease, including end-stage renal disease on hemodialysis. A total of 688 evogliptin concentration and 598 DPP-4 activity data were available from 46 subjects. PK and PD data analyses were performed using a nonlinear mixed-effects model. The PK of evogliptin was optimally described by a two-compartment model with first-order absorption. The significant covariates in the final model included blood amylase and triglyceride on F1 (relative bioavailability). The simulation findings, together with previously reported PK data, provided evidence of a significant inhibition of the first-pass effect of evogliptin in patients with renal impairment. A direct link sigmoidal Emax model was developed to describe the relationship between evogliptin concentration and DPP-4 inhibition. The PD model predicted significant inhibition of DPP-4 at maximum effect (Emax: 88.9%) and a low EC50 value (1.08 μg/L), indicating the high potency and efficacy of evogliptin. The developed PK/PD model accurately predicted exposure and the resulting DPP-4 activity of evogliptin in renal impairment. The findings of this study suggest that renal impairment and associated biochemical changes may impact the bioavailability of CYP3A4-metabolized drugs.

Population Pharmacokinetic Modelling of Norepinephrine in Healthy Volunteers Prior to and During General Anesthesia.

Intraoperation hypotension (IOH) is commonly observed in patients undergoing surgery under general anesthesia, and even a brief episode of IOH can lead to unfavorable outcomes. To reduce the risk, blood pressure is closely measured during general anesthesia, and norepinephrine (NE) is frequently administered if hypotension is detected. Despite its routine application, information on the dose-exposure-response relationship of NE remains limited. Additionally, quantification of the influence of general anesthesia on the pharmacokinetics (PK) of NE is lacking. In this study, we aimed to describe NE PK in healthy volunteers and the influence of general anesthesia on its PK. A single-center, cross-over study was conducted in healthy volunteers. The volunteers received a step-up NE dosing scheme (0.04, 0.08, 0.12, 0.16 and 0.20 mcg-1/kg-1/min-1) first in the awake state and then under general anesthesia. General anesthesia was administered using a propofol/remifentanil Eleveld target-controlled infusion. During general anesthesia, a 30-second electrical stimulus was given as surrogate for surgical incision to the volunteers at each dosage step. Blood samples were drawn before the initial dosing and after each dosing step, and plasma NE, propofol and remifentanil concentrations were subsequently determined. A population PK model was developed using non-linear mixed effects modelling. Simulations were conducted to predict the plasma NE concentration in patients at different measured propofol concentrations. A total of 1219 samples were analyzed from 36 volunteers. A two-compartment model with a first-order elimination best described the data. Weight, age, and session effect (awake vs general anesthesia) were identified as relevant covariates on the clearance (CL) of NE. A 10% decrease in NE CL was observed after general anesthesia induction. This difference between sessions is better explained by the measured concentration of propofol, rather than the anticipated impact of cardiac output. The estimated post-stimulation NE concentration is 0.66 nmol/L-1 (95% CI 0.06-1.20 nmol/L-1) lower than the pre-stimulation NE concentration. Model simulation indicates that patients at a higher measured propofol concentration (e.g., 6 mcg/mL-1) exhibited higher NE concentrations (95% PI 18.10-43.89 nmol/L-1) than patients at a lower measured propofol concentration (e.g., 3 mcg/mL-1) (95% PI 16.81-38.91 nmol L-1). The NE PK is well described with a two-compartment model with a first-order elimination. NE CL exhibiting a 10% decrease under general anesthesia, with this difference being attributed to the measured concentration of propofol. The impact of stimulation on NE PK under general anesthesia is very limited. NL9312.

Improved Malaria Therapy with Cationic Nanocapsules Demonstrated in Plasmodium berghei-Infected Rodents Using Whole Blood Surrogate Population PK/PD Modeling

Objectives: Investigating how nanoparticle systems interact in whole blood (WB) is critical to evaluating the effectiveness of malaria therapy. Methods: We decided to establish a pharmacokinetic/pharmacodynamic (PK/PD) model of the quinine population in WB using Plasmodium berghei-infected mice, with a subsequent model comparison for nanocapsules coated with polysorbate (NCP80) or prepared with Eudragit® RS (NCEUD). The WB quinine population pharmacokinetic model in rats was developed using plasma and partition coefficients for rat erythrocytes. Mouse WB quinine population PK/PD modeling was developed using allometrically scaled literature-free mouse quinine pharmacokinetic data and covariate values to obtain a WB population pharmacokinetic model for quinine and nanocapsules in mice. This allowed for PK/PD modeling of the quinine population with the WB concentration and parasitemia data in mice. All models were built in NONMEN. Results: The WB quinine concentration profiles in rats were characterized using a two-compartment model. Nanoencapsulation reduced clearance and central compartment volume and increased peripherical compartimental volume. A maximum effect model described the PK/PD of the quinine WB population in mice, demonstrating that NCEUD enhances the antimalarial effect. Conclusions: Quinine WB is a good surrogate for describing the response to exposure in malaria. NCEUD outperformed NCP80 and free quinine, suggesting that cationic surfaces improve the potential for treating malaria.

Population pharmacokinetic modeling study and discovery of covariates for the antidepressant sertraline, a serotonin selective reuptake inhibitor

The purpose of this study was to discover effective covariates related to explanation of inter-individual pharmacokinetic (PK) variations through population pharmacokinetic (Pop-PK) modeling for sertraline and to provide insight into establishing scientific regimen. The bioequivalence results of sertraline performed on 24 healthy Korean men and the physiological and biochemical parameters derived from each individual were used as data to develop a Pop-PK model of sertraline for Koreans. And the relevant effectiveness of ∗10 allele polymorphisms of CYP2D6 in sertraline PK polymorphisms was further confirmed through a modeling approach. The Pop-PK profiles of sertraline were explained by the basic structure of sequential 2-absorption with 1-compartment, and in terms of inter-individual PK diversity, the volume of distribution could be significantly correlated with estimated glomerular filtration rate (eGFR) and clearance with total protein levels. CYP2D6∗10 allele was not significant in interpreting sertraline PK diversity. As a result of model simulation, the concentration of sertraline in serum significantly increased as total protein and eGFR levels became higher and lower, respectively. The mean serum concentrations of sertraline at steady-state differed by up to 2.12 times from 10.36 to 22.02 ng/mL depending on changes in total protein and eGFR levels, and the fluctuations between the maximum and minimum concentration values ranged from 2.02 to 29.51 to 4.31–63.78 ng/mL. The factor that significantly influenced change in mean serum concentration of sertraline at steady-state was the total protein level, which was interpreted to be closely related to the change in clearance due to the high serum protein binding of sertraline.

Identification of vancomycin exposure target in neonates: how much is enough?

Vancomycin is commonly used in neonates with the same pharmacokinetics/pharmacodynamics (PK/PD) target as adults. However, no evidence supports this practice, and the association between trough concentrations and treatment outcomes has been widely questioned. This study aimed to identify the optimal PK/PD predictor and assess the correlation between AUC/MIC, trough concentration and the vancomycin efficacy in neonates. This study retrospectively collected neonates who used vancomycin and constructed a population pharmacokinetic (PPK) model to estimate the AUC. Logistic analyses were used to identify the variables related to efficacy. Classification and regression tree analysis was used to explore thresholds. The correlation between trough concentration and AUC/MIC on the first day was analysed using a linear regression model. PPK modelling involved 131 neonates. Postmenstrual age and current weight were included in the covariate analysis. Forty-eight patients were included in the efficacy analysis, 13 of whom were infected with MRSA. The best-performance PK/PD target for efficacy was AUC0-24 h/MIC ≥ 331. The trough concentration was correlated with AUC0-24 h/MIC (r2 = 0.32), but individual differences existed. AUC0-24 h/MIC ranged up to 2.5-fold for a given trough concentration. AUC0-24 h/MIC ≥ 331 was the optimal target of vancomycin efficacy in neonates. The trough concentration was not a reliable predictor of efficacy and AUC0-24 h/MIC. AUC-guided dosage adjustments are more valuable in clinical applications.

Lefamulin dosing optimization using population pharmacokinetic and pharmacokinetic/pharmacodynamic assessment in Chinese patients with community-acquired bacterial pneumonia

PurposeLefamulin is the first pleuromutilin antibiotic approved for the treatment of community-acquired bacterial pneumonia (CABP). However, the pharmacokinetic/pharmacodynamic (PK/PD) characteristics in Chinese CABP patients are not fully understood. This study aimed to evaluate its microbiological efficacy against Streptococcus pneumoniae and Staphylococcus aureus via PK/PD analysis.MethodsThe population PK (PopPK) model, established with foreign data was validated using data from Chinese CABP patients. PK/PD analysis was conducted for the intravenous administration of 150 mg q12 h for 1-h, 1.5-h and extended 2-h infusion. Oral administrations of 600 mg q12 h were assessed, considering original and higher plasma protein binding.ResultsLefamulin displayed similar PK characteristics in both Chinese and Western populations. The PopPK model effectively predicted lefamulin concentrations in Chinese CABP patients. Under the dosage regimen of 150 mg q12 h via intravenous infusion for 1/1.5/2 h, the probability of target attainments reached 98% at the minimum inhibitory concentration for both 90% S. pneumoniae and S. aureus, considering both original and higher protein binding rates. It is advisable to extend the infusion duration from 1/1.5 h–2 h to minimize the risk of adverse effects at the infusion site. Regardless of fasted or fed conditions, the PTAs for 600 mg q12 h lefamulin via oral administration proved comparable to those for intravenous administration.ConclusionThis study proved that intravenous and oral administrations of lefamulin can reach preclinical PK/PD targets of S. pneumoniae and S. aureus. These findings support the optimal use of lefamulin for the safe and effective treatment of Chinese CABP patients.

Impact of Continuous Infusion Meropenem PK/PD Target Attainment on C-Reactive Protein Dynamics in Critically Ill Patients With Documented Gram-Negative Hospital-Acquired or Ventilator-Associated Pneumonia.

Population pharmacokinetic/pharmacodynamic (PK/PD) modelling of antibiotics including C-reactive protein (C-RP) dynamics could be helpful in predicting the efficacy of antimicrobials. We developed a PK/PD model for assessing the impact of continuous infusion (CI) meropenem PK/PD target attainment on C-RP dynamics in critically ill patients with documented Gram-negative hospital- (HAP) or ventilator-acquired pneumonia (VAP). Patients were grouped according to the type of antibiotic treatment received [meropenem monotherapy; meropenem plus empirical anti-MRSA (methicillin-resistant Staphylococcus aureus) therapy; meropenem in combination with another anti-Gram-negative active agent; meropenem plus a targeted anti-MRSA therapy]. A one-compartment population PK model of CI meropenem was developed by including all patients. A full C-RP production inhibition model was developed for fitting the PD data by including only patients receiving meropenem monotherapy or meropenem plus empirical anti-MRSA therapy. Monte Carlo simulations explored the relationship between the type of PK/PD target attainment of CI meropenem, defined as optimal (steady-state plasma concentration [Css] to minimum inhibitory concentration [MIC] ratio = 4-8), quasi-optimal (Css/MIC = 1-4) and sub-optimal (Css/MIC < 1) and the magnitude of C-RP production inhibition over time. A total of 64 patients providing 211 meropenem concentrations were included in the PK analysis, whereas 47 patients providing 328 C-RP data were included in the PD model. Simulations showed that optimal PK/PD target attainment was associated with the highest and most rapid C-RP production inhibition (44% and 56% at days 2 and 4, respectively). Conversely, sub-optimal PK/PD target attainment was shown to be almost ineffective (< 5% at day 4 and < 10% at day 10). Our PK/PD model predicted that attaining optimal PK/PD target with CI meropenem may grant prompt and intense C-RP decrease among critically ill patients receiving targeted monotherapy for Gram-negative HAP/VAP, thus anticipating efficacy.

Recombinant Erwinia asparaginase (JZP458) in ALL/LBL: Complete follow-Up of the Children’s Oncology Group AALL1931 study

The Children's Oncology Group study AALL1931 investigated the efficacy and safety of recombinant Erwinia asparaginase (JZP458) in patients with acute lymphoblastic leukemia/lymphoblastic lymphoma and hypersensitivity reactions/silent inactivation to Escherichia coli-derived asparaginases. Each pegylated Escherichia coli asparaginase dose remaining in a patient's treatment plan was replaced by intramuscular (IM) or intravenous (IV) JZP458 (6 doses) administered Monday/Wednesday/Friday (MWF). Three IM cohorts (1a [25 mg/m2 MWF], n=33; 1b [37.5 mg/m2 MWF], n=83; 1c [25/25/50 mg/m2 MWF], n=51) and 1 IV cohort (25/25/50 mg/m2 MWF, n=62) were evaluated. The proportion (95% confidence interval) of patients maintaining nadir serum asparaginase activity (NSAA) levels ≥0.1 IU/mL at the last 72 (primary endpoint) and 48 hours during course 1 was 90% (81, 98) and 96% (90, 100) in IM cohort 1c, respectively, and 40% (26, 54) and 90% (82, 98) in the IV cohort. Population pharmacokinetic modeling results were comparable with observed data, predicting the vast majority of patients would maintain therapeutic NSAA levels when JZP458 is administered IM or IV 25 mg/m2 every 48 hours, or IM 25/25/50 mg/m2 MWF, or with mixed administration of IM and IV (IV/IV/IM 25/25/50 mg/m2 MWF). Drug discontinuation occurred in 23% and 56% of patients in the IM and IV cohorts, respectively; 13% and 33% due to treatment-related adverse events (mainly allergic reactions and pancreatitis). JZP458 achieves therapeutic NSAA levels via multiple IM and IV dosing schedules based on a combination of observed and modeled data with a safety profile consistent with other asparaginases. Clinicaltrials.gov Identifier: NCT04145531.

Effect of poly(ε-caprolactone) microspheres on population pharmacokinetic/pharmacodynamic model of a simple coumarin

This study aims to evaluated the impact of poly(ε-caprolactone) (PCL) microspheres on the pharmacokinetics and pharmacodynamics (PopPK/PD) of 6-methylcoumarin (6MC). For this, PCL microspheres loaded with 6MC were prepared using the emulsification-evaporation method. Particle size, zeta potential, drug loading, and entrapment efficiency were characterised by dynamic light scattering and UV spectrophotometry. In vitro release and pharmacokinetics in Wistar rats were assessed for free and encapsulated 6MC. Anti-inflammatory activity was evaluated using the carrageenan-induced paw edoema model, with PopPK and PopPK/PD models developed. Microspheres showed diameters between 2.9 and 7.1 µm, zeta potentials of −10 to −15 mV, and drug loading of 0.24 mg/mg. Encapsulation efficiency was 45.5% to 75.9%. PopPK models showed enhanced absorption and distribution, with increased anti-inflammatory potency of encapsulated 6MC. PCL microspheres significantly improved the pharmacokinetic and pharmacodynamic profiles of 6MC, enhancing its therapeutic potential for lipophilic drugs.

Population Pharmacokinetic Quantification of CYP2D6 Activity in Codeine Metabolism in Ambulatory Surgical Patients for Model-Informed Precision Dosing.

Codeine metabolism in humans is complex due to the involvement of multiple cytochrome P450 (CYP) enzymes, and has a strong genetic underpinning, which determines the levels of relevant CYP450 enzyme expression in vivo. Polymorphic CYP2D6 metabolises codeine to morphine via O-demethylation, while a strong correlation between CYP2D6 phenotype and opioidergic adverse effects of codeine is well documented. The aim of this study was to quantify the effect of CYP2D6 genotype on the biotransformation of codeine. We conducted a prospective clinical trial with 1000 patients, during which ambulatory patients were administered 60 mg of codeine preoperatively and the association between CYP2D6 activity and morphine exposure across various CYP2D6 genotypes was quantified using a population pharmacokinetic model. Plasma concentration data for codeine and its primary metabolites were obtained from 997 patients and CYP2D6 genotype was screened for study subjects, and respective sums of activity scores assigned for each CYP2D6 allele were used as covariates in model development. Our final model predicts the disposition of codeine and the formation of morphine, codeine-6-glucuronide and morphine-3-glucuronide adequately while accounting for variability in morphine exposure on the basis of CYP2D6 genotype. In agreement with previous results, patients with decreased function alleles (CYP2D6*10 and *41) showed varying levels of decrease in CYP2D6 activity that were inconsistent with increasing activity scores. Model simulations demonstrate that morphine concentrations in ultrarapid CYP2D6 metabolisers reach systemic concentrations that can potentially cause respiratory depression (over 9.1 ng/mL), and have 218% higher exposure (19 versus 8.7 µg · h/L, p < 0.001) to morphine than normal metabolisers. Similarly, poor and intermediate metabolisers had significantly reduced morphine exposure (1.0 and 3.7 versus 8.7 µg · h/L, p < 0.001) as compared with normal metabolisers. Our final model leads the way in implementing model-informed precision dosing in codeine therapy and identifies the use of genetic testing as an integral component in the effort to implement rational pharmacotherapy with codeine.

Population pharmacokinetics of cabotegravir following intramuscular thigh injections in adults with and without HIV.

Cabotegravir intramuscular gluteal injection is approved for HIV treatment (with rilpivirine) and prevention. Thigh muscle is a potential alternative injection site. We aim to characterize cabotegravir pharmacokinetics and its association with demographics following intramuscular thigh injection in comparison with gluteal injection using population pharmacokinetic (PPK) analysis. Fourteen HIV-negative participants received 600 mg single thigh injection in phase 1 study 208832 and 118 participants with HIV received thigh injections 400 mg monthly 4× or 600 mg once-every-2-months 2× after ≥3 years of gluteal injections in phase 3b study ATLAS-2M provided 1,249 cabotegravir concentrations from 366 thigh injections and 1,998 concentrations from 1,618 gluteal injections. The established gluteal PPK model was modified by adding thigh injection compartment and fit to pharmacokinetic data following both gluteal and thigh injections, enabling within-person comparison in ATLAS-2M. Gluteal parameters were fixed. Similar to the gluteal absorption rate constant (KAgluteal), the thigh absorption rate constant (KAthigh) was slower in females than males and in participants with higher BMI. KAthigh was strongly correlated with KAgluteal (correlation coefficient 0.766), best described by the additive linear relationship KAthigh = KAgluteal + 0.0002527 h-1. Terminal half-life of thigh injection was 26% (male) and 39% (female) shorter than gluteal injection. Relative bioavailability of thigh to gluteal was estimated to be 89.9%. The impact of covariates on cabotegravir exposure following thigh injections was ≤35%. In conclusion, cabotegravir absorption following thigh injection was correlated with, faster than, and 10% less bioavailable than gluteal injection, and correlated with sex and BMI. The cabotegravir thigh PPK model can inform dosing strategies and future study design.

A Sequential Population Pharmacokinetic Model of Zilovertamab Vedotin in Patients with Hematologic Malignancies Extrapolated to the Pediatric Population.

Recently a number of antibody-drug conjugate (ADC) pharmacometric models have been reported in the literature, describing one or two ADC-related analytes. The objective of this analysis was to build a population pharmacokinetic (popPK) three-analyte ADC model to describe efficacy and safety of zilovertamab vedotin, an ROR1-targeting ADC conjugated to monomethyl auristatin E (MMAE). Data from a phase 1 study of zilovertamab vedotin in subjects with hematologic malignancies was used in a stepwise ADC modeling strategy based on the simplified ADC popPK model proposed by Gibiansky. This choice provided opportunity to model three analytes: conjugated monomethyl auristatin E (acMMAE), total monoclonal antibody (total mAb), and free MMAE. The model was extrapolated to the pediatric population using a clearance maturation function and accounting for weight dependent pharmacokinetic (PK) changes. The simplified model provided a good structure to fit the adult acMMAE, total mAb, and free MMAE data. Analysis showed that MMAE was released through deconjugation of the payload and full proteolytic degradation of the acMMAE. Deconjugation was associated with an immediate release of MMAE, proteolytic clearance introduced a delay in the release of MMAE. Simulation of the model extrapolated to the pediatric population was the basis for pediatric dosing strategies forzilovertamab vedotinthat were approved in the United States and European Union. The total mAb, acMMAE, and free MMAE model showed a good fit to the data. The pediatric population can match the acMMAE adult exposure at the same weight-based dose regimen without concerns that the toxic MMAE concentration will reach higher levelsthan found in adults.

Therapeutic drug monitoring (TDM) of β-lactam/β-lactamase inhibitor (BL/BLI) drug combinations: insights from a pharmacometric simulation study.

The emergence of β-lactamase-producing bacteria has led to the use of β-lactam (BL) antibiotic and β-lactamase inhibitor (BLI) drug combinations. Despite therapeutic drug monitoring (TDM) being endorsed for BLs, the impact of TDM on BLIs remains unclear. Evaluate whether BLIs are available in effective exposures at the site of infection and assess if TDM of BLIs could be of interest. Population pharmacokinetic models for 9 BL and BLI compounds were used to simulate drug concentrations at infection sites following EMA-approved dose regimens, considering plasma protein binding and tissue penetration. Predicted target site concentrations were used for probability of target attainment (PTA) analysis. Using EUCAST targets, satisfactory (≥90%) PTA was observed for BLs in patients with typical renal clearance (CrCL of 80 mL/min) across various sites of infection. However, results varied for BLIs. Avibactam achieved satisfactory PTA only in plasma, with reduced PTAs in abdomen (78%), lung (73%) and prostate (23%). Similarly, tazobactam resulted in unsatisfactory PTAs in intra-abdominal infections (79%), urinary tract infections (64%) and prostatitis (34%). Imipenem-relebactam and meropenem-vaborbactam achieved overall satisfactory PTAs, except in prostatitis and high-MIC infections for the latter combination. This study highlights the risk of solely relying on TDM of BLs, as this can indicate acceptable exposures of the BL while the BLI concentration, and consequently the combination, can result in suboptimal performance in terms of bacterial killing. Thus, dose adjustments also based on plasma concentration measurements of BLIs, in particular for avibactam and tazobactam, can be valuable in clinical practice to obtain effective exposures at the target site.

Toward a Clinical Decision Support System for Monitoring Therapeutic Antituberculosis Medical Drugs in Tanzania (Project TuberXpert): Protocol for an Algorithm' Development and Implementation.

The end tuberculosis (TB) strategy requires a novel patient treatment approach contrary to the one-size-fits-all model. It is well known that each patient's physiology is different and leads to various rates of drug elimination. Therapeutic drug monitoring (TDM) offers a way to manage drug dosage adaptation but requires trained pharmacologists, which is scarce in resource-limited settings. We will develop an automated clinical decision support system (CDSS) to help practitioners with the dosage adaptation of rifampicin, one of the essential medical drugs targeting TB, that is known for large pharmacokinetic variability and frequent suboptimal blood exposure. Such an advanced system will encourage the spread of a dosage-individualization culture, including among practitioners not specialized in pharmacology. Thus, the objectives of this project are to (1) develop the appropriate population pharmacokinetic (popPK) model for rifampicin for Tanzanian patients, (2) optimize the reporting of relevant information to practitioners for drug dosage adjustment, (3) automate the delivery of the report in line with the measurement of drug concentration, and (4) validate and implement the final system in the field. A total of 3 teams will combine their efforts to deliver the first automated TDM CDSS for TB. A cross-sectional study will be conducted to define the best way to display information to clinicians. In parallel, a rifampicin popPK model will be developed taking advantage of the published literature, complemented with data provided by existing literature data from the Pan-African Consortium for the Evaluation of Antituberculosis Antibiotics (panACEA), and samples collected within this project. A decision tree will be designed and implemented as a CDSS, and an automated report generation will be developed and validated through selected case studies. Expert pharmacologists will validate the CDSS, and finally, field implementation in Tanzania will occur, coupled with a prospective study to assess clinicians' adherence to the CDSS recommendations. The TuberXpert project started in November 2022. In July 2024, the clinical study in Tanzania was completed with the enrollment of 50 patients to gather the required data to build a popPK model for rifampicin, together with a qualitative study defining the report design, as well as the CDSS general architecture definition. At the end of the TuberXpert project, Tanzania will possess a new tool to help the practitioners with the adaptation of drug dosage targeting complicated TB cases (TB or HIV, TB or diabetes mellitus, and TB or malnutrition). This automated system will be validated and used in the field and will be proposed to other countries affected by endemic TB. In addition, this approach will serve as proof of concept regarding the feasibility and suitability of CDSS-assisted TDM for further anti-TB drugs in TB-burdened areas deprived of TDM experts, including second-line treatments considered important to monitor. DERR1-10.2196/58720.

Pharmacokinetics of Vancomycin in Healthy Korean Volunteers and Monte Carlo Simulations to Explore Optimal Dosage Regimens in Patients with Normal Renal Function.

Background/Objectives: To date, population pharmacokinetic (PK) studies of vancomycin on healthy Korean adults have not been conducted. This study aimed to investigate the PK properties of vancomycin in healthy volunteers and to identify optimal dosing regimens based on the area under the concentration-time curve (AUC) in adult patients with normal renal function. Methods: We conducted a prospective clinical study, analysing PK samples from 12 healthy participants using noncompartmental analysis and non-linear mixed-effects modelling. The population PK parameters derived were employed in Monte Carlo simulations to evaluate the adequacy of the current dosing regimen and to formulate dosing recommendations. Results: The PK profiles were optimally described by a two-compartment model, with body weight and age as significant covariates affecting total clearance. The simulations indicated that to achieve a therapeutic target-defined as an AUC at steady-state over 24 h of 400-600 mg·h/L-daily doses ranging from 60 to 70 mg/kg are necessary in adults with normal renal function. Conclusions: This study underscores the need to actively adjust dosage and administration based on a vancomycin PK model that adequately reflects the demographic characteristics of patients to meet both safety and efficacy standards.