The translational challenge in Chagas disease drug development

Chagas disease is a neglected tropical disease caused by the protozoan parasite Trypanosoma cruzi. There is an urgent need for safe, effective, and accessible new treatments since the currently approved drugs have serious limitations. Drug development for Chagas disease has historically been hampered by the complexity of the disease, critical knowledge gaps, and lack of coordinated R&D efforts. This review covers some of the translational challenges associated with the progression of new chemical entities from preclinical to clinical phases of development, and discusses how recent technological advances might allow the research community to answer key questions relevant to the disease and to overcome hurdles in R&D for Chagas disease.

Pharmacokinetic/pharmacodynamic modeling of the antitumor action of bispecific CD3/EpCAM antibody M701 in human colorectal cancer xenograft mice / 药学学报

M701 is a bispecific CD3/EpCAM T-cell engager antibody for the treatment of malignant ascites. We developed a population pharmacokinetic/pharmacodynamic (PK/PD) model to quantitatively describe and predict the antitumor effect of M701 in human colorectal cancer xenograft mice. We developed the M701 PK model based on plasma concentration data after i.v. administration. A tumor growth model for human colorectal cancer xenograft was developed to evaluate the antitumor effect of M701. We additionally simulated the inhibitory effect of M701 on tumor volume under different dose regimens based on a PK/PD model. A two-compartment model was developed to predict the PK in human colorectal cancer xenograft mice. The relationship between the M701 concentration and tumor growth inhibition was characterized by a combined Simeoni tumor growth/transit compartment model. The estimated pharmacodynamic parameters were related to the tumor growth characteristics λ0 (0.212 d-1) and λ1 (0.044 7 cm3·d-1), to the drug potency k2 (0.071 5 mL·ng-1·d-1), and to the kinetics of tumor cell death k1 (2×10-5 d-1). A model visual predictive check showed that both the PK model and the tumor growth model closely fit the observed data. Simulated tumor growth after administration of M701 (0.5 mg·kg-1 every 6 days and 0.25 mg·kg-1 every 3 days) could be effectively inhibited. This population PK/PD model of M701 provides insight into the antitumor effect of M701 and supports the further therapeutic development of M701.

Progress in Application of Population Pharmacokinetic and Pharmacodynamic Models in Research on Traditional Chinese Medicine / 中国实验方剂学杂志

In recent years， the role of quantitative pharmacological models in applicable population of drugs and dose optimization has been widely recognized. In order to improve the efficiency of clinical development and optimize clinical rational drug use， quantitative pharmacological models are being gradually introduced into the research of traditional Chinese medicine （TCM）. There are various types of quantitative pharmacological models， among which the following three models are commonly used：①Population pharmacokinetic （PPK） model， which is mainly used to explore the pharmacokinetic characteristics in different populations.②Pharmacokinetic-pharmacodynamic （PK-PD） model， which is used to reveal the internal relationship among dose， time and efficacy. ③PPK-PD model， which integrates both the characteristics of PPK model and PK-PD model. The paper summarizes the application of the above three models in TCM， and extracts the main ideas and methods of TCM model research， in order to provide reference for clinical research and rational use of TCM.

Application of physiologically based pharmacokinetic model in drug development and several questions being thought / 中国临床药理学与治疗学

Physiologically based pharmacokinetic (PBPK) model is based on physiology, anatomy, enzymes for drug metabolism, characteristic of drug transport, physicochemical property of drug and drug-body interaction. Thus, PBPK model may quantitatively predict: concentration-time profiles of drug and its metabolites in plasma and tissues; pharmacokinetics of drug under disease status; pharmacokinetics of drug in special population; pharmacokinetics of drugs in human derived from experimental animals; in vivo pharmacokinetics of drugs based on in vitro parameters for metabolism and transport; pharmacokinetics of drugs from different formations; pharmacodynamics or toxicity of drugs based on in vitro parameters for metabolism, transport, activity or toxicity of drug; drug-drug interaction; individual contributions of enzymes and transporters to in vivo drug disposition. Here, we would review applications of PBPK model in drug development and several questions which should be thought through a series of examples.

Development and application progress of physiologically based pharmacokinetic modeling and its combined use with other modeling methods / 中国临床药理学与治疗学

Physiologically based pharmacokinetics (PBPK) is one of the main research fields of pharmacometrics, and it plays an important role at all the stages of drug development and clinical practice. In early drug discovery and development, human pharmacokinetics (PK) could be predicted by PBPK modeling using in silico, in vitro and preclinical in vivo data. During clinical studies, PBPK model could be used to investigate the effects of various physiological and pathological factors on PK, such as age, gender, liver/kidney impairment, and to guide dose adjustment of special population (pregnant women, children, etc.). Furthermore, PBPK modeling is now becoming more appealing with the ability to predict drug-drug interaction (DDI) in the case of co-administration of multiple drugs. In recent years, the application of PBPK modeling in industry has increased widely. Also, regulatory agencies have recognized the potential of PBPK and its impact on labeling recommendations. As the popularity of model-informed drug development, the combination of PBPK modeling with other commonly used modeling methods, such as population pharmacokinetics (PopPK), pharmacokinetic/pharmacodynamic (PK/PD) modeling and model-based meta-analysis (MBMA), has shown attractive advantages. In this paper, the origin and development, as well as the application status of PBPK are introduced briefly, and the application of PBPK modeling merged with PopPK, PK/PD and MBMA is reviewed.

Evolving role of modeling and simulation in drug development

Pharmacokinetic-pharmacodynamic model is a kind of language that quantitatively describes the drug-related outcomes in the form of mathematical formula. Various outcomes can be subjected to modeling analysis if they can be expressed in numbers. Empirical models have been widely and successfully applied in drug development and research. However, a more competitive drug development environment requires more accurate and predictive models in the early stages of drug development. Accordingly, the subjects of PK-PD modeling have been extended from clinical data to preclinical and in vitro data in the discovery stage. More mechanistic and predictive models, such as physiologically based pharmacokinetic and quantitative system-based pharmacology models, are being increasingly used owing to the growing need to characterize drugs more accurately at the earliest. This tutorial briefly introduces the essential concepts of PK-PD modeling and simulation and describes the recent changing roles of PK-PD model for application in novel drug development process.

A review of three years' experience of the first pharmacometrics company in Korea

As the pharmaceutical industry in Korea is reaching the golden era of drug discovery due to increased investments in research and development and government funds, the need for a more efficient tool for the quantitative analysis has emerged. Therefore, the demand for pharmacometrics (PMx) consultancy services increased. Higher quality service suitable for regulatory submission and out-licensing deals were desired. In this analysis, we compiled and summarized 3 years of experiences of Q-fitter, the first PMx consultancy service company providing PMx analysis to the pharmaceutical industry in Korea. The projects were organized by companies, company types, indications, therapeutic areas, drug development stages, purposes, and scope of services. Within each category, we subcategorized the sections and assessed proportions and a year-over-year trend. As a result, we observed an increase in the number of projects in an average of ~170% per year, with the most frequent types of companies collaborated being the domestic pharmaceutical companies. Among the projects, ~72% involved modeling and simulation using population pharmacokinetic (PK) models, and the other included non-compartmental analysis (NCA), drug-drug interaction (DDI) prediction, and interpretation of the modeling results. The most sought-after purpose in PMx analysis was first-in-human (FIH) dose prediction followed by PK analysis, next clinical trial prediction, and scenario-based simulation. Oncology has been the top therapeutic area of interest every year consisting of ~38% of total projects, followed by Neurology (~13%). From this review, we were able to characterize the PMx service needs and spot the trend of current PMx practices in Korea.

Influence of CYP2D6 Polymorphism on the Pharmacokinetic/Pharmacodynamic Characteristics of Carvedilol in Healthy Korean Volunteers

BACKGROUND: Carvedilol is commonly used to treat hypertension as a β- and α1-adrenoreceptor blocker, but it is metabolized by CYP2D6, and CYP2D6*10 allele is dominant in Asian population. The objective of this study was to assess the influence of CYP2D6 polymorphisms on the pharmacokinetic (PK) and pharmacodynamic (PD) characteristics of carvedilol in healthy Korean volunteers. METHODS: A PK/PD study for a single and multiple dosing of carvedilol were conducted. All volunteers in 3 genotypic groups received single oral dose of carvedilol 12.5 mg for 3 days, then 25 mg QD for 5 days, and 12.5 mg QD for another 3 days. PK parameters for carvedilol and its three metabolites were determined using non-compartmental analysis. For PD properties, blood pressure, heart rate, and the chronotropic dose 25 (CD25) value were obtained. RESULTS: The IM_2 group with two *10 alleles (intermediate metabolizers) exhibited lower clearance of carvedilol as well as higher area under the curve (AUC) for O-desmethyl carvedilol. The ratio of CD25 to baseline at multiple dosing was significantly higher in the combined IM group (IM_1 and IM_2) than in the EM group, however, the ratio of CD25 after single and multiple dosing and the other PD markers were not significantly different between the 3 genotypic groups compared with the baseline. CONCLUSION: These findings showed that CYP2D6 genotype influenced the PK characteristics of carvedilol and no differences in PD response were observed in Korean healthy volunteers. Registered at the ClinicalTrials.gov, NCT02286934.

Pharmacokinetic-pharmacodynamic study on antipyreticeffects of coptisine on endotoxin-induced pyrexia of rats / 中国药理学通报

Aim To establish the pharmacokinetic-pharmacodynamic(PK-PD) modeling to characterize the antipyretic effects of coptisine, an active component in coptis chinensis on rats.Methods Nine healthy male Sprague-Dawley(SD) rats were randomly divided into three groups, each with three.The rats in the first group were injected intravenously with lipopolysaccharide(LPS,100 μg·kg-1) alone.The second and third group rats were given coptisine high-dose(3.87 mg·kg-1) and coptisine low-dose(1.93 mg·kg-1) by tail vein injection at 30 min after LPS injection, respectively.Body temperature was measured at different time points, and blood samples from tail vein were collected simultaneously.The blood concentration of coptisine was determined by ultra performance liquid chromatography.Monolix software was used to model PK-PD of coptisine mean plasma concentration and temperature effects,by population computation with non-covariates.Besides.the model with advantage was selected by the fitting goodness.Results Coptisine could inhibit body temperature of endotoxin-induced fever in rats significantly.Two-compartment linear elimination model was used to describe the final PK model.Gaussian function, an input function of body temperature changes, which was used to depict PD model, the PK and PD models were connected by the Emax model.At last, the final model was fitted better;the fitting results indicated that the EC50 of antipyretic effect of coptisine was 89.7 μg·L-1, and the Emax was 1.88℃.Conclusions Coptisine has a powerful anti-pyretic effect on endotoxin-induced pyrexia of rats with high potency, Low in vivo distribution and quick clearance.

Discussion on research status and development ideas of biopotency for Chinese materia medica / 中草药

The quality control of Chinese materia medica (CMM) has been the focus of CMM modernization, and how to demonstrate the consistency of product quality and clinical efficacy has become an important research aspect of development and innovation of CMM. Due to the heterogeneity of CMM, it is necessary to combine biopotency with other detection methods to guarantee the quality of medicines. This article reviewed the research status of CMM biopotency, analyzed the global local government regulations about biopotency and the difficulties of development in CMM, and discussed development ideas of biopotency based on PK-PD for CMM. Its main aim is to provide reference for the construction of the follow-up quality evaluation system, and to promote recognition from the international drug administration management on CMM quality standard.

Evaluation of the protective effect of salvianolic acid A on ischemic heart failure by a multi-target pharmacokinetic-pharmacodynamic model / 中国药科大学学报

@#The aim of this study was to develop a multi-target pharmacokinetic-pharmacodynamic(PK-PD)model for the evaluation of the protective effect of salvianolic acid A(Sal A)on ischemic heart failure based on a metabolic balance model. The rats were assigned to 3 groups: sham-operated group(saline), ischemic heart failure group(saline)and Sal A-treated group(Sal A, 1 mg/(kg ·d), ip). The concentrations of brain natriuretic peptide(BNP), angiotensin II(Ang II), malondialdehyde(MDA), asymmetric dimethylarginine(ADMA)and the activity of glutathione peroxidase(GSH-Px)in rat plasma were determined before and at 1, 2, 3, and 4 weeks after ligation in all the groups. A multi-target PK-PD model was developed based on the change rate of metabolic disruption parameter k and was eventually used to integrally evaluate the protective effect of Sal A on ischemic heart failure. Sal A showed improvement effects on multiple biomarkers and the correlation study demonstrated a good relationship between dynamic parameter k and left ventricular ejection fraction(LVEF). More importantly, the multi-target model well fitted the relationship between AUC and the change rate. The multi-target PK-PD model provides a novel method to integrally evaluate the protective effect of Sal A, which might offer a new strategy for the establishment of a PK-PD model that embodies the characteristics of traditional Chinese medicine.

Tips for the choice of initial estimates in NONMEM

The importance of precise information and knowledge on the initial estimates (IEs) in modeling has not been paid its due attention so far. By focusing on the IE, this tutorial may serve as a practical guide for beginners in pharmacometrics. A 'good' set of IEs rather than arbitrary values is required because the IEs where NONMEM kicks off its estimation may influence the subsequent objective function minimization. To provide NONMEM with acceptable IEs, modelers should understand the exact meaning of THETA, OMEGA and SIGMA based on physiology. In practice, problems related to the value of the IE are more likely to occur for THETAs rather than the random-effect terms. Because it is almost impossible for a modeler to give a precise IE for OMEGAs at the beginning, it may be a good practice to start at relatively small IEs for them. NONMEM may fail to converge when too small IEs are provided for residual error parameters; thus, it is recommended to give sufficiently large values for them. The understandings on the roles, meanings and implications of IEs even help modelers in troubleshooting situations which frequently occur over the whole modeling process.

Study on PK-PD combination of ligustrazine in cerebral ischemia reperfusion rats after ig administration of effective parts in compatibility of Chuanxiong Rhizoma and Astragali Radix / 中草药

Objective: To research the pharmacokinetic-pharmacodynamic (PK-PD) model of ligustrazine in cerebral ischemia reperfusion (I/R) rats. Methods: To build the middle cerebral artery embolization (MCAO) model. The blood 0.5 mL was collected from orbital venous plexus at 0.083, 0.25, 0.5, 0.75, 1.0, 1.5, 2.0, 3.0, 4.0, and 6.0 h time points after ig administration of effective parts in compatibility prescription of Chuanxiong Rhizoma and Astragali Radix. The concentration of ligustrazine in serum was determined by RP-HPLC, and then the concentration-time curves were drawn. Meanwhile, the activities of LDH in serum were determined with ELISA Kit. PK-PD modeling was fitted with DAS 3.2.6 software. The PK-PD model parameters were calculated. Results: The effect of ligustrazine on inducing LDH release did not relate directly with the concentration but lagged behind the concentration of ligustrazine in serum. The relationship between effect and serum concentration fits Emax model. Conclusion: This study successfully establishes the combined PK-PD model of ligustrazine after ig administration of different combinations of the active parts in Chinese materia medica (CMM) to rats. This research can be effectively applied to predict PK- PD studies on the main effective components in other compatibility of CMM.

Effect of vertebral canal opening on pharmacodynamics of local anesthesia in epidural space / 中国中西医结合急救杂志

Objective To investigate the pharmacodynamic changes in local epidural anesthetic and correlated factors before and after epidural space opening during vertebral canal surgery. Methods 120 patients who underwent vertebral canal operation under epidural anesthesia from January 2008 to December 2010 in Anyang City People's Hospital in Henan Provincial were selected. A self control study method was applied to persistently monitor the patients' vital signs〔heart rate variance(HRV),mean arterial pressure(MAP),heart rate(HR),saturation of blood oxygen(SpO2)〕,and the subjective manifestations of patients,the appraisal of surgeon about the surgical local situation(the degree of skeletal muscle relaxation,neural reflex,the ooze blood and so on),the changes in movement (primarily Aαnerve fiber),feeling(primarily Aδnerve fiber),skin temperature(primarily non-myelinated nerve fiber C)within the scope of anesthesia,the dosage of local anesthetic used and the incidence of local anesthetic toxicity were record before and after epidural cavity opening. Results There were no statistical significant differences in vital signs before and after epidural cavity opening in this group of patients. After the opening of epidural space,the local use of anesthetic dosage and the incidence of local anesthetic toxicity were obviously higher than those before the opening〔lidocaine(mg/h):911.23±15.58 vs. 460.19±10.82,ropivacaine(mg/h):13.35±0.19 vs. 5.24±0.17, the incidence of local anesthetic toxicity:67.5%vs. 1.2%,all P<0.01〕,the anesthesia plane(skeletal muscle laxity, feeling,skin temperature)was poorer than that before the opening of epidural space〔the anesthetic plane before the opening was(4.0±1.7),(10.7±1.5),(12.0±1.6)segments respectively,after opening was(2.0±1.8),(10.2±1.3), (12.6±1.9)segments〕,after epidural space opening,the correlations among the three planes(movement sensation disjointed)were worse than those before the epidural space opening(good). Conclusion The opening of vertebral canal can change the action of local epidural anesthetic,decrease its therapeutic effect and increase its incidence of toxicity,therefore,it is necessary to further discuss the application of epidural anesthesia in vertebral canal operation.

Thinking on pharmacokinetic studies of therapeutic antibody drugs / 中国药学杂志

Antibody drugs have experienced development for nearly 30 years. There are varieties of therapeutic antibody drugs successfully used in clinical practice. The design of pre-clinical and clinical pharmacokinetic studies for antibody drugs has achieved some progress. This article analyzed the issues in the pharmacokinetic studies of therapeutic antibody drugs from four aspects, including challenges for pharmacokinetic studies, pharmacokinetic characteristics, pharmacokinetic-pharmacodynamic research and some examples of pharmacokinetic studies. As for the prospects for future development, one of challenges is the establishment of bio-analytical methods, which ensure the reliability of the basic findings. Another challenge is the PK and PK/PD analysis. For antibody drugs displaying obvious targeting ability, target distribution is the key point of their pharmacokinetic studies. PK/PD model for data analysis, exposure-response assessment, and release of targeted drug delivery face more prominent challenges.

Pharmacokinetic-pharmacodynamic study on antipyretic effects of baicalin on carrageenan-induced pyrexia of rats / 中草药

Objective: Pharmacokinetic-pharmacodynamic (PK-PD) modeling is used to characterize the antipyretic effects of baicalin (BA) in rats. Methods: Twelve healthy male Sprague-Dawley (SD) rats were randomly divided into two groups, each with six. The rats in the first group were sc injected with carrageenan (1 mL per rat) alone to make the inflammation model. The rats in the second group were given BA (180 mg/kg) by ig administration after carrageenan injection. Body temperature was measured while orbital sinus blood sample was collected at different time points. The blood concentration of BA was determined by high performance liquid chromatography-mass spectrometry. PK-PD modelings were fitted with ADAPT 5.1 software. The model with advantage was selected by the fitting goodness. Results: The concentration-time curve was best and fitted by double-site absorption with enterohepatic circulaion of Pk model and the antipyretic responses of Sigmoid-Imax PD model could be well confirmed. The PK and PD models were reconnected by the antipyretogenetic inhibition with effect compartment. The fitting results indicated that the Imax of antipyretic effect by BA was 0.56 °C and shape parameter (H) for PD was 10.67. Conclusion: The dose-effect relationship range in the antipyretic activity of BA on carrageenan-induced pyrexia of rats is narrow and its efficiency is low.

Pharmacokinetic and pharmacodynamic modeling in anesthetic field

Models are simplified descriptions of true biological processes. Pharmacokinetic/pharmacodynamic (PK/PD) modeling is a mathematical description on the relationship between pharmacokinetics and pharmacodynamics. The PK/PD modeling allows estimation of PK/PD parameters and it can establish dose-concentration-response relationships which describe and predict the effect-time courses of a drug. PK/PD modeling has recently emerged as a major tool in clinical pharmacology in order to optimize drug uses by designing rational dosage forms. Population analysis is used to estimate the variability in the population and also to establish guidelines for the individualization of drug dosage regimen. Non-linear mixed effect model is the basis of population approach. This approach permits the simultaneous analysis for all the data of the studied population, by using either PK or PD models to describe the typical trends (population means) and individual profiles. The target controlled infusion system is based on the population PK models which describe the inter-individual PK variability by individualizing the PK parameters according to the patient's covariate. The PK/PD modeling is highly useful for the development of drugs as well as for pharmacotherapy.

Analysis and strategy on pharmacokinetic/pharmacodynamic correlation of Chinese materia medica based on multi-components and multi-targets / 中草药

To analyze the correlation of pharmacokinetic/pharmacodynamic (PK/PD) of Chinese materia medica (CMM) based on the multi-components and multi-targets, through the example of demonstrative research, we brought forward some innovative strategies. The research requires to use a medicated serum in parallel at a pathologic state. The experiments included the determination of multi-components PK parameters, the establishment of serum dynamic fingerprints and multi-targets PD models, the research on PK/PD binding model, the selection of the analytic program, the representation of internal relations among the concentration, time, and effect in the effective component group, the analyses on the correlation between fingerprint and PD, the tracing of the rule of PD from the chemical fingerprints and metabolic fingerprints, and the construction of a spectrum which could represent the characterization of the correlation between the retention time and the effect and the characterization of dose-effect fingerprint spectrum of the correlation between peak area growth and effects. The multi-dimensional characteristics of fingerprint-pharmacophore fingerprints (feature effect peak and dose-effect fingerprint spectrum)-fingerprint spectrum of PK are integrated, processed, and edited and a multi-dimensional image of "active integration fingerprint" in the active component group was built. A new research method on the combination of the PK/PD of CMM was explored. Only by this way, we will really understand the interaction in active component group in vivo and clearly explain the material base which truly works.

Neuromuscular blockade and pharmacokinetic-pharmacodynamic modeling

A major goal in pharmacokinetic-pharmacodynamic (PK/PD) modeling of neuromuscular blockade (NMB) is to quantitatively estimate the dose-response relationship.Our PK/PD model consists of three submodels:PK, link kinetics, and PD.A virtual effect compartment in which the drug concentration is in equilibrium with the observed concentration is used to extract the kinetic component (keo) from the pharmacodynamic data alone.Parameters of this model are keo, Ce(50), and gamma.The underlying structural pharmacokinetics and pharmacodynamics for NMB have been well understood, and new novel PK/PD models have been substituted for the gold standard PK/PD model for NMB.The purpose of this review was to describe progress in the field of PK/PD modeling of NMB from the first model, a simultaneous PK/PD model developed by Sheiner et al in the 1970s, to some of the more complicated models.Specific PK/PD models, which accurately described the behaviors of rocuronium, mivacurium, atracurium, and cisatracurium, include the recirculatory model, the peripheral link model, the peripheral elimination model, and a nonparametric model for link kinetics.

Modelado farmacocinético-farmacodinámico de fármacos antihipertensivos: su aplicación en la práctica clínica / Pharmacokinetic-Pharmacodynamic Modelling of Antihypertensive Drugs: Its Application to Clinical Practice

El conocimiento de las propiedades farmacocinéticas-farmacodinámicas (PK/PD) de los fármacos puede optimizar la terapia antihipertensiva. El modelado PK/PD en la investigación clínica podría contribuir en el desarrollo del fármaco y en la práctica clínica en varios aspectos, entre ellos la evaluación de eficacia y seguridad de los antihipertensivos, mayor información durante el proceso del desarrollo, identificación de factores de variabilidad de la respuesta farmacológica, y permitir además una identificación rápida de malos respondedores o no respondedores y ayudar a determinar requerimientos óptimos del fármaco y dosis en cada paciente hipertenso. Hay algunas limitaciones en el modelado PK/PD de los antihipertensivos en la práctica clínica, entre las que se incluyen el uso de modelos farmacodinámicos inadecuados y la incapacidad de estudiar dosis elevadas de antihipertensivos para determinar el rango farmacodinámico completo del efecto antihipertensivo. El propósito de esta revisión es describir el conocimiento actual del modelado PK/PD de los fármacos antihipertensivos en la investigación clínica y sus usos futuros.

Knowing the pharmacokinetic-pharmacodynamic properties (PK/PD) of drugs might optimize antihypertensive therapy. PK/PD modelling might not only contribute to develop the drug but might also help in clinical practice assessing the efficacy and safety of antihypertensive drugs, bringing more information during the developing process, identifying factors responsible for the variability in pharmacologic response, bad responders or non-responders, and determining the optimal requisites of the drug and doses in each patient with hypertension. There are some limitations in PK/ PD modelling of antihypertensive drugs in clinical practice, such as inadequate pharmacodynamic models and the inability to study high doses of antihypertensive drugs to determine the whole pharmacodynamic range of the antihypertensive effect. The aim of this review is to describe the current knowledge on PK/PD modelling of antihypertensive drugs in clinical research, and its further uses.