Model-based prediction of effective target exposure for MEN1611 in combination with trastuzumab in HER2-positive advanced or metastatic breast cancer patients

MEN1611 is a novel orally bioavailable PI3K inhibitor currently in clinical development for patients with HER2-positive (HER2+) PI3KCA mutated advanced/metastatic breast cancer (BC) in combination with trastuzumab (TZB). In this work, a translational model-based approach to determine the minimum target exposure of MEN1611 in combination with TZB was applied. First, pharmacokinetic (PK) models for MEN1611 and TZB in mice were developed. Then, in vivo tumor growth inhibition (TGI) data from seven combination studies in mice xenograft models representative of the human HER2+ BC non-responsive to TZB (alterations of the PI3K/AkT/mTOR pathway) were analyzed using a PK-pharmacodynamic (PD) TGI model for co-administration of MEN1611 and TZB. The established PK-PD relationship was used to quantify the minimum effective MEN1611 concentration, as a function of TZB concentration, needed for tumor eradication in xenograft mice. Finally, a range of minimum effective exposures for MEN1611 were extrapolated to patients with BC, considering the typical steady-state TZB plasma levels in patients with BC following three alternative regimens (i.v. 4 mg/kg loading dose +2 mg/kg q1w, i.v. 8 mg/kg loading dose +6 mg/kg q3w or s.c. 600 mg q3w). A threshold of about 2000 ng·h/ml for MEN1611 exposure associated with a high likelihood of effective antitumor activity in a large majority of patients was identified for the 3-weekly and the weekly i.v. schedule for TZB. A slightly lower exposure (i.e., 25% lower) was found for the 3-weekly s.c. schedule. This important outcome confirmed the adequacy of the therapeutic dose administered in the ongoing phase 1b B-PRECISE-01 study in patients with HER2+ PI3KCA mutated advanced/metastatic BC.

Clinical Pharmacokinetic Characteristics of Cebranopadol, a Novel First-in-Class Analgesic

Background and Objectives

Cebranopadol is a novel first-in-class analgesic acting as a nociceptin/orphanin FQ peptide and opioid peptide receptor agonist with central analgesic activity. It is currently in clinical development for the treatment of chronic pain conditions. This trial focuses on the clinical pharmacokinetic (PK) properties of cebranopadol after oral single- and multiple-dose administration.

Methods

The basic PK properties of cebranopadol were assessed by means of noncompartmental methods in six phase I clinical trials in healthy subjects and patients. A population PK analysis included two further phase I and six phase II clinical trials.

Results

After oral administration of the immediate-release (IR) formulation, cebranopadol is characterized by a late time to reach maximum plasma concentration [C_max] (4–6 h), a long half-value duration [HVD] (14–15 h), and a terminal phase half-life in the range of 62–96 h. After multiple once-daily dosing in patients, an operational half-life (the dosing interval resulting in an accumulation factor [AF] of 2) of 24 h was found to be the relevant factor to describe the multiple-dose PKs of cebranopadol. The time to reach steady state was approximately 2 weeks, the AF was approximately 2, and peak-trough fluctuation (PTF) was low (70–80%). Dose proportionality at steady state was shown for a broad dose range of cebranopadol 200–1600 µg. A two-compartment disposition model with two lagged transition compartments and a first-order elimination process best describes cebranopadol data in healthy subjects and patients after single- and multiple-dose administration.

Conclusions

Cebranopadol formulated as an IR product can be used as a once-daily formulation; it reaches C_max after only 4–6 h, and has a long HVD and a low PTF. Therefore, from a PK perspective, cebranopadol is an attractive treatment option for patients with chronic pain.

Treatment of Malignant Gliomas: A New Approach

The aim of this study is to describe the authors’ experience with intra-arterial ACNU chemotherapy of malignant gliomas. The prognosis of cerebral malignant gliomas remains poor, whatever traditional therapy is applied. ACNU is a well tolerated nitrosourea with a strong antimitotic effect on neurogenic cells both in vitro and in vivo; this drug has enhanced efficacy when used at high concentrations, particularly as an intraarterial infusion. Seventy-six patients have been studied to date, 68 of whom are evaluable; these patients were treated by intraarterial infusion of ACNU (100 mg/m2) every 6 weeks, with a mean of 2.5 courses per patient. The objective response (OR) was 28% and analysis of pretreatment factors revealed that survival was influenced by histological grade, other types of therapy applied, and age. In general IAC is well tolerated and the response and survival appear to be better than with systemic chemotherapy.

Impact of disease, drug and patient adherence on the effectiveness of antiviral therapy in pediatric HIV

INTRODUCTION

Maintaining effective antiretroviral treatment for life is a major problem in both resource-limited and resource-rich countries. Despite the progress observed in paediatric antiretroviral therapy, approximately 12% of children still experience treatment failure due to drug resistance, inadequate dosing and poor adherence. We explore the current status of antiretroviral therapy in children with focus on the interaction between disease, drug pharmacokinetics and patient behavior, all of which are strongly interconnected and determine treatment outcome. Areas covered: An overview is provided of the viral characteristics and available drug combinations aimed at the prevention of resistance. In this context, the role of patient adherence is scrutinized. A detailed assessment of factors affecting adherence is presented together with the main strategies to enhance treatment response in children. Expert opinion: Using modeling and simulation, a framework for characterizing the forgiveness of non-adherence for specific antiretroviral drugs in children is proposed in which information on pharmacokinetics, pharmacokinetic-pharmacodynamic relationships and viral dynamics is integrated. This approach represents an opportunity for the simplification of dosing regimens taking into account the interaction between these factors. Based on clinical trial simulation scenarios, we envisage the possibility of assessing the impact of variable adherence to antiretroviral drug combinations in HIV-infected children.

Influence of covariate distribution on the predictive performance of pharmacokinetic models in paediatric research

AIMS

The accuracy of model-based predictions often reported in paediatric research has not been thoroughly characterized. The aim of this exercise is therefore to evaluate the role of covariate distributions when a pharmacokinetic model is used for simulation purposes.

METHODS

Plasma concentrations of a hypothetical drug were simulated in a paediatric population using a pharmacokinetic model in which body weight was correlated with clearance and volume of distribution. Two subgroups of children were then selected from the overall population according to a typical study design, in which pre-specified body weight ranges (10-15 kg and 30-40 kg) were used as inclusion criteria. The simulated data sets were then analyzed using non-linear mixed effects modelling. Model performance was assessed by comparing the accuracy of AUC predictions obtained for each subgroup, based on the model derived from the overall population and by extrapolation of the model parameters across subgroups.

RESULTS

Our findings show that systemic exposure as well as pharmacokinetic parameters cannot be accurately predicted from the pharmacokinetic model obtained from a population with a different covariate range from the one explored during model building. Predictions were accurate only when a model was used for prediction in a subgroup of the initial population.

CONCLUSIONS

In contrast to current practice, the use of pharmacokinetic modelling in children should be limited to interpolations within the range of values observed during model building. Furthermore, the covariate point estimate must be kept in the model even when predictions refer to a subset different from the original population.

Busulfan dosing algorithm and sampling strategy in stem cell transplantation patients

AIM

The aim of this investigation was to develop a model-based dosing algorithm for busulfan and identify an optimal sampling scheme for use in routine clinical practice.

METHODS

Clinical data from an ongoing study (n = 29) in stem cell transplantation patients were used for the purposes our analysis. A one compartment model was selected as basis for sampling optimization and subsequent evaluation of a suitable dosing algorithm. Internal and external model validation procedures were performed prior to the optimization steps using ED-optimality criteria. Using systemic exposure as parameter of interest, dosing algorithms were considered for individual patients with the scope of minimizing the deviation from target range as determined by AUC(0,6 h).

RESULTS

Busulfan exposure after oral administration was best predicted after the inclusion of adjusted ideal body weight and alanine transferase as covariates on clearance. Population parameter estimates were 3.98 h(-1), 48.8 l and 12.3 l h(-1) for the absorption rate constant, volume of distribution and oral clearance, respectively. Inter-occasion variability was used to describe the differences between test dose and treatment. Based on simulation scenarios, a dosing algorithm was identified, which ensures target exposure values are attained after a test dose. Moreover, our findings show that a sparse sampling scheme with five samples per patient is sufficient to characterize the pharmacokinetics of busulfan in individual patients.

CONCLUSION

The use of the proposed dosing algorithm in conjunction with a sparse sampling scheme may contribute to considerable improvement in the safety and efficacy profile of patients undergoing treatment for stem cell transplantation.

Covariate effects and population pharmacokinetics of lamivudine in HIV-infected children

AIM

Lamivudine is used as first line therapy in HIV-infected children. Yet, like many other paediatric drugs, its dose rationale has been based on limited clinical data, without thorough understanding of the effects of growth on drug disposition. Here we use lamivudine to show how a comprehensive population pharmacokinetic model can account for the influence of demographic covariates on exposure (i.e. AUC and Cmax ).

METHODS

Data from three paediatric trials were used to describe the pharmacokinetics across the overall population. Modelling was based on a non-linear mixed effects approach. A stepwise procedure was used for covariate model building.

RESULTS

A one compartment model with first order elimination best described the pharmacokinetics of lamivudine in children. The effect of weight on clearance (CL) and volume of distribution (V) was characterized by an exponential function, with exponents of 0.705 and 0.635, respectively. For a child with median body weight (17.6 kg), CL and V were 16.5 (95% CI 15.2, 17.7) l h⁻¹ and 46.0 (95% CI 42.4, 49.5) l, respectively. There were no differences between formulations (tablet and solution). The predicted AUC(0,12 h) after twice daily doses of 4 mg kg⁻¹ ranged from 4.44 mg l⁻¹  h for children <14 kg to 7.25 mg l⁻¹  h for children >30 kg.

CONCLUSIONS

The use of meta-analysis is critical to identify the correct covariate-parameter relationships, which must be assessed before a model is applied for predictive purposes (e.g. defining dosing recommendations for children). In contrast to prior modelling efforts, we show that the covariate distribution in the target population must be considered.

A model-based approach for the evaluation of once daily dosing of lamivudine in HIV-infected children

AIM

Little attention has been paid to the effects of compliance and prescription practice on treatment outcome in HIV-infected children. In this context, an evaluation of the role of covariates on pharmacokinetics is required to establish the impact of differences in dosing regimens. Here we investigate whether a once daily dosing regimen of lamivudine provides comparable exposure to the currently approved paediatric regimen.

METHODS

A hypothetical group of 180 patients between 3 months and 12 years old was used to evaluate the impact of body weight on systemic exposure to lamivudine. Simulation scenarios were evaluated using AUC and Cmax as parameters of interest. The analysis was performed using a population pharmacokinetic model previously implemented in nonmem v.6.2.

RESULTS

The simulations show that once daily dosing of lamivudine yields comparable exposure to historical values observed in children and adults, both for liquid and solid dosage forms. Simulated steady-state AUC(0-24 h) and Cmax values after once daily doses ranged respectively from 9.9  mg l⁻¹  h and 1.9 mg l⁻¹ for children lighter than 14 kg to 13.75 mg l⁻¹  h and 3.0 mg l⁻¹ for children heavier than 30 kg. These values are comparable or higher than historical values observed after once daily dosing in children and adults.

CONCLUSIONS

Our findings illustrate how dosing regimens can be evaluated taking into account the effects of developmental growth on drug disposition. Most importantly, they suggest that the reduction in dosing frequency to once daily leads to comparable lamivudine exposure, as observed after administration of a twice daily dosing regimen.

Implications of pharmacogenetics for the therapeutic use of antiepileptic drugs

INTRODUCTION

Epilepsy is a chronic neurological disease manifesting as recurrent seizures. Despite the availability of numerous antiepileptic drugs (AEDs), one-third of the patients are not responsive to treatment. Such inter-individual variability in the response to AEDs may be partly explained by genetic differences. This review summarizes the pharmacogenetics (PGx) of AEDs. In addition, a model-based approach is presented that enables the integration of PGx data with other relevant sources of variability, such as demographic characteristics and co-medications.

AREAS COVERED

A comprehensive overview is provided of the data available in the literature on the evidence for correlations between genetic mutations and pharmacokinetic (PK) and/or pharmacodynamics (PD) of AEDs. This information is then used in an integrated manner in the second part, where PGx differences are parameterized as covariates in PK and PKPD models.

EXPERT OPINION

Polymorphisms are profuse in the PK and PD of AEDs. However, understanding of their clinical implication remains limited due to the lack of methodologies that discriminate the contribution of other sources of variability in CNS exposure to drugs. A model-based approach, in which other intrinsic (e.g., demographic covariates) and extrinsic (e.g., drug-drug interactions) factors are evaluated concurrently is needed to ensure optimization and individualization of treatment in epileptic patients.

Population pharmacokinetics of abacavir in infants, toddlers and children

AIMS

To characterize the pharmacokinetics of abacavir in infants, toddlers and children and to assess the influence of covariates on drug disposition across these populations.

METHODS

Abacavir concentration data from three clinical studies in human immunodeficiency virus-infected children (n = 69) were used for model building. The children received either a weight-normalized dose of 16 mg kg(-1) day(-1) or the World Health Organization recommended dose based on weight bands. A population pharmacokinetic analysis was performed using nonlinear mixed effects modelling VI. The influence of age, gender, bodyweight and formulation was evaluated. The final model was selected according to graphical and statistical criteria.

RESULTS

A two-compartmental model with first-order absorption and first-order elimination best described the pharmacokinetics of abacavir. Bodyweight was identified as significant covariate influencing the apparent oral clearance and volume of distribution. Predicted steady-state maximal plasma concentration and area under the concentration-time curve from 0 to 12 h of the standard twice daily regimen were 2.5 mg l(-1) and 6.1 mg h l(-1) for toddlers and infants, and 3.6 mg l(-1) and 8.7 mg h l(-1) for children, respectively. Model-based predictions showed that equivalent systemic exposure was achieved after once and twice daily dosing regimens. There were no pharmacokinetic differences between the two formulations (tablet and solution). The model demonstrated good predictive performance for dosing prediction in individual patients and, as such, can be used to support therapeutic drug monitoring in conjunction with sparse sampling.

CONCLUSIONS

The disposition of abacavir in children appears to be affected only by differences in size, irrespective of the patient's age. Maturation processes of abacavir metabolism in younger infants should be evaluated in further studies to demonstrate the potential impact of ontogeny.

Lack of compliance of European Public Assessment Reports to guidelines for paediatric drug development before the introduction of paediatric investigation plans

Background

According to the International Conference on Harmonisation (ICH) and Food and Drug Administration (FDA) guidelines for paediatric clinical trials, bridging procedures can be used if disease progression, exposure–response relationships, and clinical endpoints are similar in adults and children. In these circumstances, confirmatory efficacy trials are not necessary; the evaluation of pharmacokinetics and safety ought to be sufficient for drug approval.

Purpose

The aim of this study was to assess whether the clinical trials and strategy for market approval authorisation (MAAs) in paediatric indications reflect the guidelines for bridging of adult data.

Methods

A total of 95 European Public Assessment Reports (EPARs) published between 1995 and 2007 were reviewed. From every report, data extraction was performed according to the phase of development, scope of analysis, number of dose levels, dosage form, and demographics of the subjects enrolled in the trial. Data analysis consisted of an initial grouping of the studies by the degree of compliance to bridging guidelines.

Results

Our analysis reveals that only 66% of the trials (n = 174) can be classified as needed, while 22% of the trials (n = 59) could have been designed and performed differently from the approved protocol (partially required). Moreover, 12% (n = 30) of the studies were deemed completely unnecessary.

Limitations

A potential limitation in our study was that the dates of start and completion of the clinical studies were not available. Therefore, some EPARs have been included that may reflect common practice in the period that precedes the introduction of the ICH E11 guidelines. Yet, this should not obscure the points identified with regard to the lack of compliance to guidelines before the introduction of the paediatric legislation and the requirements for a paediatric investigation plan.

Conclusions

Paediatric trials are desirable and necessary to address important unmet medical needs. However, the types of studies supporting regulatory approval do not always reflect the recommendations available in paediatric guidelines, which allow for extrapolation and bridging approaches. This situation may be explained by the lack of awareness about the prerequisites for the use of bridging concepts and of a clear process for evaluating different strategies in paediatric development.

Integration of pharmacogenetics and pharmacogenomics in drug development: implications for regulatory and medical decision making in pediatric diseases

This article aims to provide an overview of the current situation regarding pharmacogenetic and pharmacogenomic (PG) studies in pediatrics, with a special focus on the role of PG data in the regulatory decision-making process. Despite the gap in pharmacogenetic research due to the lack of translational studies in adults and children, several technologies exist in drug development and biomarkers validation, which could supply valuable information concerning labeling and dosing recommendations. If performed under strict good clinical practice quality criteria, such findings could be included in the submission package of new chemical entities and used as additional information for prescribers, supporting further evaluation and understanding of the efficacy and safety profile of new medicines. Even though regulatory authorities may be aware of the potential role of PG in medical practice and guidances are available about the integration of PG in drug development, most data obtained from PG studies are not used by prescribers. The challenge is to better understand whether PG markers can be used to assess potential differences in drug response during the clinical program, so PG data can be integrated into the regulatory decision-making process, enabling the introduction of labeling information that promotes optimal dosing in the pediatric population.

The role of population PK-PD modelling in paediatric clinical research

Children differ from adults in their response to drugs. While this may be the result of changes in dose exposure (pharmacokinetics [PK]) and/or exposure response (pharmacodynamics [PD]) relationships, the magnitude of these changes may not be solely reflected by differences in body weight. As a consequence, dosing recommendations empirically derived from adults dosing regimens using linear extrapolations based on body weight, can result in therapeutic failure, occurrence of adverse effect or even fatalities. In order to define rational, patient-tailored dosing schemes, population PK-PD studies in children are needed. For the analysis of the data, population modelling using non-linear mixed effect modelling is the preferred tool since this approach allows for the analysis of sparse and unbalanced datasets. Additionally, it permits the exploration of the influence of different covariates such as body weight and age to explain the variability in drug response. Finally, using this approach, these PK-PD studies can be designed in the most efficient manner in order to obtain the maximum information on the PK-PD parameters with the highest precision. Once a population PK-PD model is developed, internal and external validations should be performed. If the model performs well in these validation procedures, model simulations can be used to define a dosing regimen, which in turn needs to be tested and challenged in a prospective clinical trial. This methodology will improve the efficacy/safety balance of dosing guidelines, which will be of benefit to the individual child.

Comparison between chondroprotective effects of glucosamine, curcumin, and diacerein in IL-1beta-stimulated C-28/I2 chondrocytes

OBJECTIVE

To compare the effects of glucosamine (GlcN), curcumin, and diacerein in immortalized human C-28/I2 chondrocytes at the cellular and the gene expression level. This study aimed to provide insights into the proposed beneficial effects of these agents and to assess the applicability of the C-28/I2 cell line as a model for the evaluation of chondroprotective action.

METHODS

Interleukin-1beta (IL-1beta)-stimulated C-28/I2 cells were cultured in the presence of GlcN, curcumin, and diacerein prior to the evaluation of parameters such as viability, morphology and proliferation. The impact of GlcN, curcumin, and diacerein on gene expression was determined using quantitative real-time RT-PCR (qPCR).

RESULTS

At the transcriptional level, 5 mM GlcN and 50 microM diacerein increased the expression of cartilage-specific genes such as aggrecan (AGC) and collagen type II (COL2), while reducing collagen type I (COL1) mRNA levels. Moreover, the IL-1beta-mediated shift in gene expression pattern was antagonized by GlcN and diacerein. These effects were associated with a significant reduction in cellular proliferation and the development of chondrocyte-specific cell morphology. In contrast, curcumin was not effective at lower concentrations but even damaged the cells at higher amounts.

CONCLUSIONS

Both GlcN and diacerein promoted a differentiated chondrocytic phenotype of immortalized human C-28/I2 chondrocytes by altering proliferation, morphology, and COL2/COL1 mRNA ratios. Moreover, both agents antagonized inhibitory effects of IL-1beta by enhancing AGC and COL2 as well as by reducing COL1 mRNA levels.

[Simultaneous ultrasonography and arthroscopy for the study of the joint environment: indications and limits]

Arthroscopy is a mini-invasive technique that allows the direct observation of the joint cavity and the execution of diagnostic and therapeutic procedures; arthroscopy needs a very long learning-time curve as well as dedicated spaces and instruments. Ultrasonography is an imaging technique that enables to perform an immediate extension of the standard physical examination. The opportunity to visualize soft tissues, to obtain multiplanar and dynamic images in real time makes this practice easy repeatable at low costs. Ultrasonography allows to detect a variety of changes during inflammatory processes. The wide experience in arthroscopy of rheumatic patients acquired through the years by our team at the G. Pini Institute led us to study in vivo, during arthroscopy, the correspondence between arthroscopic and ultrasonographic images. Up to now three knee arthroscopies have been conducted with the double equipment (ultrasonographic and arthroscopic devices) in operating room. In our experience, the combination of the two methods in operating room may improve the validation of ultrasonography with arthroscopy as gold standard, helps to train the ultrasonographer to give immediate answers in order to clear the doubts aroused by ultrasonographic images; it also allows the arthroscopist to visualize the deeper layers of the synovial membrane making double guided targeted biopsies possible. Limits are the complexity of the procedure (instruments, operators, spaces, training of the doctors), the loose of power-doppler signal with the blood tourniquet and the always difficult evaluation of cartilage.

An amperometric glucose biosensor prototype fabricated by thermal inkjet printing

The prototype of an amperometric glucose biosensor was realized by thermal inkjet printing using biological and electronic water-based inks, containing a glucose oxidase (GOD) from Aspergillus niger and the conducting polymer blend poly(3,4-ethylenedioxythiophene/polystyrene sulfonic acid) (PEDOT/PSS), respectively. The biosensor was fabricated microdepositing PEDOT/PSS and GOD, in sequence, on ITO-glass, by a commercial inkjet printer, with the help of a commercial software. High density microdots matrices were so-realized, with a calculated resolution of about 221 x 221 dpi (dot per inch). By means of a rapid and easy assay it was demonstrated that no activity loss occurred upon the printing of GOD, despite of the use of a thermal printhead. The device was encapsulated in a semipermeable membrane of cellulose acetate, applied by dip-coating, in order to prevent dissolution of the enzyme and/or PEDOT/PSS in water. The preliminary response of the electrode was measured in an aqueous glucose solution in the presence of ferrocenemethanol (FeMeOH) as a mediator, and resulted linear up to 60 mM in glucose. The best sensitivity value achieved was 6.43 microAM(-1) cm(-2) (447 nAM(-1) U(-1) cm(-2)). The characteristics of the device, and the possible performance improvements have been analyzed and discussed. The reported findings indicate that inkjet printing could be a viable instrument for the easy construction of a working biosensor via direct digital design using biological and conductive polymer based inks. Such an approach may be seen as an example of "biopolytronics".

Transcranial Doppler sonographic monitoring during cerebral aneurysm embolization: a preliminary report

BACKGROUND AND PURPOSE

The wide application of embolization in the treatment of aneurysms has created the need for an intraprocedural means to anticipate a poor outcome by monitoring hemodynamic changes in the brain.

METHODS

Transcranial Doppler sonography was used to monitor flow velocity in the middle cerebral artery (MCA) in 23 patients undergoing embolization with Guglielmi detachable coils (GDCs) of either incidental or symptomatic intracranial aneurysms. Sonographic values were recorded from the ipsilateral MCA at the beginning, middle, and end of the interventional procedure and 24 hours afterward.

RESULTS

No complications occurred in 15 patients. In these cases, sonography showed an average decrease in MCA flow velocity of 2.7% after GDC application, returning to baseline at the end of treatment and then increasing by about 17% 24 hours later. In four patients with vasospasm on posttreatment angiograms, MCA flow velocity increased to values higher than 120 cm/s after GDC application, returning to baseline after 24 hours. In four patients with ischemic complications (two transient ischemic attacks, one stroke, one vascular death), MCA flow velocity decreased more than 30% and did not return to preoperative values within 24 hours.

CONCLUSION

The application of transcranial Doppler sonographic monitoring during endovascular treatment may help to identify patients at risk for posttreatment cerebral ischemia.