Population pharmacokinetics of total and unbound valemetostat and platelet dynamics in healthy volunteers and patients with non-Hodgkin lymphoma.

Valemetostat is an EZH2/1 inhibitor that has been approved in Japan for the treatment of patients with relapsed/refractory adult T-cell leukemia/lymphoma, based mainly on results from a single-arm phase II trial. It is currently under investigation worldwide for the treatment of other non-Hodgkin lymphomas (NHLs), including peripheral T-cell lymphoma, and for solid tumors. Semi-mechanistic population pharmacokinetic modeling of total and unbound valemetostat and an analysis of the platelet time course during treatment with valemetostat were conducted using data from five clinical trials (two in patients with NHL and three in healthy volunteers). Pharmacokinetic data, including 3162 total/1871 unbound valemetostat observations from 102 patients and 72 healthy volunteers, were described by a three-compartment model with sequential zero-/first-order absorption and saturable binding in the central compartment. Alpha-1-acid glycoprotein (AAG) was the most influential covariate for total valemetostat exposure, yet had little impact on unbound exposure, meaning no dose adjustment was warranted based on AAG levels. The longitudinal platelet data from 101 patients (2313 observations) were adequately described by a modified Friberg model with two proliferation compartments, which characterized unique spontaneous recovery of platelet counts without dose modifications. A model-based simulation quantitatively assessed the proposed dose-adjustment guidance in case of platelet count decreased by comparing the probability of treatment discontinuation due to platelet count decreased with or without the dose adjustment. In summary, the models described observed total and unbound valemetostat concentrations and a unique time course of platelets during treatment, which can justify the clinical dose and provide dose-adjustment guidance.

gPKPDviz: A flexible R shiny tool for pharmacokinetic/pharmacodynamic simulations using mrgsolve.

GPKPDviz is a Shiny application (app) dedicated to real-time simulation, visualization, and assessment of the pharmacokinetic/pharmacodynamic (PK/PD) models. Within the app, gPKPDviz is capable of generating virtual populations and complex dosing and sampling scenarios, which, together with the streamlined workflow, is designed to efficiently assess the impact of covariates and dosing regimens on PK/PD end points. The actual population data from clinical trials can be loaded into the app for simulation if desired. The app-generated dosing regimens include single or multiple dosing, and more complex regimens, such as loading doses or intermittent dosing. When necessary, the dosing regimens can be defined externally and loaded to the app for simulation. Using mrgsolve as the simulation engine, gPKPDviz is typically used for population simulation, however, with a slight modification of the mrgsolve model, gPKPDviz is capable of performing individual simulations with individual post hoc parameters, individual dosing logs, and individual sampling timepoints through an external dataset. A built-in text editor has a debugging feature for the mrgsolve model, providing the same error messages as model compilation in R. GPKPDviz has had stringent validation by comparing simulation results between the app and using mrgsolve in R. GPKPDviz is a member of the suite of Modeling and Simulation Shiny apps developed at Genentech to facilitate the typical modeling work in Clinical Pharmacology. For broader access to the Pharmacometric community, gPKPDviz has been published as an open-source application in GitHub under the terms of GNU General Public License.

A model-based analysis to guide gonadotropin-releasing hormone receptor antagonist use for management of endometriosis.

AIMS: To identify linzagolix doses, an oral GnRH receptor antagonist, that effectively lower oestradiol (E2) to relieve endometriosis-related pelvic pain without compromising bone health. METHODS: Integrated statistical, pharmacokinetic-pharmacodynamic and systems pharmacology models were developed from Phase 1 and 2 clinical trial data in healthy volunteers and patients, receiving linzagolix 25-200 mg daily or placebo, and analysed simultaneously. The main outcome measures were pelvic pain scores for dysmenorrhoea, nonmenstrual pelvic pain (NMPP), uterine bleeding and lumbar spine bone mineral density (BMD). RESULTS: Linzagolix pharmacokinetics were described by a 2-compartment model with sequential zero/first-order absorption process (CL/F: 0.422 L/h). E2 changes over time were well described as a function of linzagolix 24-hour AUC (AUC50 : 1.68 × 105 ng h/mL). For a Caucasian reference patient, a change in E2 from 50-20 pg/mL at 24 weeks increased the odds of relief of dysmenorrhoea 1.33-fold and NMPP 1.07-fold (95% CI: 1.22-1.47 and 1.02-1.12, respectively) and decreased bleeding days by 1.55 (95% CI: 1.39-1.72). A previously validated quantitative systems pharmacology BMD model was adjusted to the clinical data. The mean week 24 lumbar spine BMD change from baseline ranged from -0.092% in the 50 mg dose, -1.30% in the 100 mg dose group and -2.67% in the 200 mg dose group. DISCUSSION: The previously-reported E2 target range (20-50 pg/mL) to balance efficacy and safety endpoints was confirmed. Linzagolix once daily doses between 75-125 mg daily were expected to meet endometriosis-associated pain, efficacy, and BMD loss targets in Caucasian patients.

Quantitative Systems Pharmacology and Physiologically-Based Pharmacokinetic Modeling With mrgsolve: A Hands-On Tutorial.

mrgsolve is an open-source R package available on the Comprehensive R Archive Network. It combines R and C++ coding for simulation from hierarchical, ordinary differential equation-based models. Its efficient simulation engine and integration into a parallelizable, R-based workflow makes mrgsolve a convenient tool both for simple and complex models and thus is ideal for physiologically-based pharmacokinetic (PBPK) and quantitative systems pharmacology (QSP) model. This tutorial will first introduce the basics of the mrgsolve simulation workflow, including model specification, the introduction of interventions (dosing events) into the simulation, and simulated results postprocessing. An applied simulation example is then presented using a PBPK model for voriconazole, including a model validation step against adult and pediatric data sets. A final simulation example is then presented using a previously published QSP model for mitogen-activated protein kinase signaling in colorectal cancer, illustrating population simulation of different combination therapies.

Population Pharmacokinetics and Exposure-Response (Efficacy and Safety/Tolerability) of Empagliflozin in Patients with Type 2 Diabetes.

INTRODUCTION: The aim of the analysis was to characterize the population pharmacokinetics (PKs) and exposure-response (E-R) for efficacy (fasting plasma glucose, glycated hemoglobin) and safety/tolerability [hypoglycemia, genital infections, urinary tract infection (UTI), and volume depletion] of the sodium glucose cotransporter 2 inhibitor, empagliflozin, in patients with type 2 diabetes mellitus. This study extends the findings of previous analyses which described the PK and pharmacodynamics (PD) using early clinical studies of up to 12 weeks in duration. METHODS: Population pharmacokinetic and E-R models were developed based on two Phase I, four Phase II, and four Phase III studies. RESULTS: Variability in empagliflozin exposure was primarily affected by estimated glomerular filtration rate (eGFR) (less than twofold increase in exposure in patients with severe renal impairment). Consistent with its mode of action, the efficacy of empagliflozin was increased with elevated baseline plasma glucose levels and attenuated with decreasing renal function, but was still maintained to nearly half the maximal effect with eGFR as low as 30 mL/min/1.73 m(2). All other investigated covariates, including sex, body mass index, race, and age did not alter the PK or efficacy of empagliflozin to a clinically relevant extent. Compared with placebo, empagliflozin administration was associated with an exposure-independent increase in the incidence of genital infections and no significant change in the risk of UTI, hypoglycemia, or volume depletion. CONCLUSION: Based on the results from the PK and E-R analysis, no dose adjustment is required for empagliflozin in the patient population for which the drug is approved. FUNDING: Boehringer Ingelheim.

Bayesian approach to estimate AUC, partition coefficient and drug targeting index for studies with serial sacrifice design.

PURPOSE: The current study presents a Bayesian approach to non-compartmental analysis (NCA), which provides the accurate and precise estimate of AUC 0 (∞) and any AUC 0 (∞) -based NCA parameter or derivation. METHODS: In order to assess the performance of the proposed method, 1,000 simulated datasets were generated in different scenarios. A Bayesian method was used to estimate the tissue and plasma AUC 0 (∞) s and the tissue-to-plasma AUC 0 (∞) ratio. The posterior medians and the coverage of 95% credible intervals for the true parameter values were examined. The method was applied to laboratory data from a mice brain distribution study with serial sacrifice design for illustration. RESULTS: Bayesian NCA approach is accurate and precise in point estimation of the AUC 0 (∞) and the partition coefficient under a serial sacrifice design. It also provides a consistently good variance estimate, even considering the variability of the data and the physiological structure of the pharmacokinetic model. The application in the case study obtained a physiologically reasonable posterior distribution of AUC, with a posterior median close to the value estimated by classic Bailer-type methods. CONCLUSIONS: This Bayesian NCA approach for sparse data analysis provides statistical inference on the variability of AUC 0 (∞) -based parameters such as partition coefficient and drug targeting index, so that the comparison of these parameters following destructive sampling becomes statistically feasible.

NMDA-evoked consumption and recovery of mitochondrially targeted aequorin suggests increased Ca2+ uptake by a subset of mitochondria in hippocampal neurons.

Activation of NMDA receptors produces large increases in cytosolic Ca(2+) that are taken up into mitochondria. We used recombinant aequorin targeted to mitochondria to report changes in matrix Ca(2+) in rat hippocampal neurons in culture. Upon binding Ca(2+), aequorin emits a photon in a one-shot reaction that consumes the indicator. Here we show that stimulation with NMDA produced a mitochondrial Ca(2+) response that rapidly inactivated. However, following a 30-min recovery period the response was restored, suggesting the presence of a pool of indicator that was not exposed to high Ca(2+) during the initial stimulus. We speculate that aequorin distant from the Ca(2+) source was protected from microdomains of high Ca(2+) near the plasmalemma and that this aequorin moved, either by movement of individual mitochondria or via the mitochondrial tubular network, to replenish consumed indicator during the recovery time. A large Ca(2+) increase in a subset of mitochondria could produce local changes in energy metabolism, regional Ca(2+) buffering, and foci that initiate neurotoxic processes.