An asymptotic description of a basic FcRn-regulated clearance mechanism and its implications for PBPK modelling of large antibodies.

A basic FcRn-regulated clearance mechanism is investigated using the method of matched asymptotic expansions. The broader aim of the work is to obtain further insight on the mechanism, thereby providing theoretical support for future pharmacologically-based pharmacokinetic modelling efforts. The corresponding governing equations are first non-dimensionalised and the order of magnitudes of the model parameters are assessed based on their values reported in the literature.

OSWG Recommended Approaches to the Nonclinical Pharmacokinetic (ADME) Characterization of Therapeutic Oligonucleotides.

This white paper summarizes the recommendations of the absorption, distribution, metabolism, and excretion (ADME) Subcommittee of the Oligonucleotide Safety Working Group for the characterization of absorption, distribution, metabolism, and excretion of oligonucleotide (ON) therapeutics in nonclinical studies. In general, the recommended approach is similar to that for small molecule drugs. However, some differences in timing and/or scope may be warranted due to the greater consistency of results across ON classes as compared with the diversity among small molecule classes.

Preclinical anti-tumour activity of HexaBody-CD38, a next-generation CD38 antibody with superior complement-dependent cytotoxic activity.

Background: HexaBody®-CD38 (GEN3014) is a hexamerization-enhanced human IgG1 that binds CD38 with high affinity. The E430G mutation in its Fc domain facilitates the natural process of antibody hexamer formation upon binding to the cell surface, resulting in increased binding of C1q and potentiated complement-dependent cytotoxicity (CDC).

Methods: Co-crystallization studies were performed to identify the binding interface of HexaBody-CD38 and CD38.

Next Generation Exon 51 Skipping Antisense Oligonucleotides for Duchenne Muscular Dystrophy.

In the last two decades, antisense oligonucleotides (AONs) that induce corrective exon skipping have matured as promising therapies aimed at tackling the dystrophin deficiency that underlies the severe and progressive muscle fiber degeneration in Duchenne muscular dystrophy (DMD) patients. Pioneering first generation exon 51 skipping AONs like drisapersen and eteplirsen have more recently been followed up by AONs for exons 53 and 45, with, to date, a total of four exon skipping AON drugs having reached (conditional) regulatory US Food and Drug Administration (FDA) approval for DMD. Nonetheless, considering the limited efficacy of these drugs, there is room for improvement.

The Pharmacokinetics of 2'--Methyl Phosphorothioate Antisense Oligonucleotides: Experiences from Developing Exon Skipping Therapies for Duchenne Muscular Dystrophy.

Delivery to the target site and adversities related to off-target exposure have made the road to clinical success and approval of antisense oligonucleotide (AON) therapies challenging. Various classes of AONs have distinct chemical features and pharmacological properties. Understanding the similarities and differences in pharmacokinetics (PKs) among AON classes is important to make future development more efficient and may facilitate regulatory guidance of AON development programs.

Suppression of Mutant Protein Expression in SCA3 and SCA1 Mice Using a CAG Repeat-Targeting Antisense Oligonucleotide.

Spinocerebellar ataxia type 3 (SCA3) and type 1 (SCA1) are dominantly inherited neurodegenerative disorders that are currently incurable. Both diseases are caused by a CAG-repeat expansion in exon 10 of the Ataxin-3 and exon 8 of the Ataxin-1 gene, respectively, encoding an elongated polyglutamine tract that confers toxic properties to the resulting proteins. We have previously shown lowering of the pathogenic polyglutamine protein in Huntington's disease mouse models using (CUG)7, a CAG repeat-targeting antisense oligonucleotide.

Nonclinical Exon Skipping Studies with 2'-O-Methyl Phosphorothioate Antisense Oligonucleotides in mdx and mdx-utrn-/- Mice Inspired by Clinical Trial Results.

Duchenne muscular dystrophy is a severe, progressive muscle-wasting disease that is caused by mutations that abolish the production of functional dystrophin protein. The exon skipping approach aims to restore the disrupted dystrophin reading frame, to allow the production of partially functional dystrophins, such as found in the less severe Becker muscular dystrophy. Exon skipping is achieved by antisense oligonucleotides (AONs).

Assessment of Dermal Absorption of Aluminum from a Representative Antiperspirant Formulation Using a Al Microtracer Approach.

A clinical pharmacokinetic study was performed in 12 healthy women to evaluate systemic exposure to aluminum following topical application of a representative antiperspirant formulation under real-life use conditions. A simple roll-on formulation containing an extremely rare isotope of aluminum ( Al) chlorohydrate (ACH) was prepared to commercial specifications. A Al radio-microtracer was used to distinguish dosed aluminum from natural background, using accelerated mass spectroscopy.

Fingerprinting of neurotoxic compounds using a mouse embryonic stem cell dual luminescence reporter assay.

Identification of neurotoxic drugs and environmental chemicals is an important challenge. However, only few tools to address this topic are available. The aim of this study was to develop a neurotoxicity/developmental neurotoxicity (DNT) test system, using the pluripotent mouse embryonic stem cell line CGR8 (ESCs).

To Apply Microdosing or Not? Recommendations to Single Out Compounds with Non-Linear Pharmacokinetics.

Microdosing studies allow clinical investigation of pharmacokinetics earlier in drug development, before all high-dose safety concerns have been sorted out. Furthermore, microdosing allows inclusion of target groups that are inadmissible in high-dose phase I trials. A potential concern when considering a microdosing study is that a particular drug candidate may display non-linear pharmacokinetics.

Toxicokinetic Triage for Environmental Chemicals.

Toxicokinetic (TK) models link administered doses to plasma, blood, and tissue concentrations. High-throughput TK (HTTK) performs in vitro to in vivo extrapolation to predict TK from rapid in vitro measurements and chemical structure-based properties. A significant toxicological application of HTTK has been "reverse dosimetry," in which bioactive concentrations from in vitro screening studies are converted into in vivo doses (mg/kg BW/day).

Interpreting in vitro developmental toxicity test battery results: The consideration of toxicokinetics.

In the EU collaborative project ChemScreen an alternative, in vitro assay-based test strategy was developed to screen compounds for reproductive toxicity. A toxicokinetic modeling approach was used to allow quantitative comparison between effective concentrations in the in vitro test battery and observations of developmental toxicity in vivo. This modeling strategy is based on (1) the definition of relevant observations of toxicity in vivo, (2) simulation of the corresponding systemic concentrations in vivo by toxicokinetic modeling, and (3) correction for differences in protein binding and lipid partitioning between plasma and in vitro test media.

Evaluation of an alternative in vitro test battery for detecting reproductive toxicants in a grouping context.

Previously we showed a battery consisting of CALUX transcriptional activation assays, the ReProGlo assay, and the embryonic stem cell test, and zebrafish embryotoxicity assay as 'apical' tests to correctly predict developmental toxicity for 11 out of 12 compounds, and to explain the one false negative [7]. Here we report on applying this battery within the context of grouping and read across, put forward as a potential tool to fill data gaps and avoid animal testing, to distinguish in vivo non- or weak developmental toxicants from potent developmental toxicants within groups of structural analogs. The battery correctly distinguished 2-methylhexanoic acid, monomethyl phthalate, and monobutyltin trichloride as non- or weak developmental toxicants from structurally related developmental toxicants valproic acid, mono-ethylhexyl phthalate, and tributyltin chloride, respectively, and, therefore, holds promise as a biological verification model in grouping and read across approaches.

Predicting carrier-mediated hepatic disposition of rosuvastatin in man by scaling from individual transfected cell-lines in vitro using absolute transporter protein quantification and PBPK modeling.

In contrast to primary hepatocytes, estimating carrier-mediated hepatic disposition by using a panel of single transfected cell-lines provides direct information on the contribution of the individual transporters to the net disposition. The most direct way to correct for differences in transporter abundance between cell-lines and tissue is by using absolute protein quantification. In the present study, the performance of this strategy to predict human hepatic uptake transport was investigated and compared with traditional scaling from primary human hepatocytes.

Prediction of in vivo developmental toxicity of all-trans-retinoic acid based on in vitro toxicity data and in silico physiologically based kinetic modeling.

The use of laboratory animals for toxicity testing in chemical safety assessment meets increasing ethical, economic and legislative constraints. The development, validation and application of reliable alternatives for in vivo toxicity testing are therefore urgently needed. In order to use toxicity data obtained from in vitro assays for risk assessment, in vitro concentration-response data need to be translated into in vivo dose-response data that are needed to obtain points of departure for risk assessment, like a benchmark dose (BMD).

An improved model to predict physiologically based model parameters and their inter-individual variability from anthropometry.

We developed a population physiology model, physB, which provides a statistical description of the physiological characteristics in the human population, in terms of the physiological parameters that are needed in physiologically based pharmacokinetic modelling. The model predicts individual organ weights, blood flows and some respiratory parameters from anthropometric properties (body height and weight, age and gender). It draws on two existing models, PK-Pop and P(3)M, but various changes and improvements were made.

An expert consortium review of the EC-commissioned report "alternative (Non-Animal) methods for cosmetics testing: current status and future prospects - 2010".

The European cosmetics legislation foresees a review in 2011 and possible postponement of the 2013 marketing ban to enforce the testing ban for systemic and repeated-dose animal tests. For this purpose, a 119-page report commissioned by the European Commission was published recently. Here, a group of 17 independent experts from the US, Europe, and Japan was brought together to evaluate the report.

Probabilistic cumulative risk assessment of anti-androgenic pesticides in food.

In this paper, we present a cumulative risk assessment of three anti-androgenic pesticides (vinclozolin, procymidone and prochloraz) using the relative potency factor (RPF) approach and an integrated probabilistic risk assessment (IPRA) model. RPFs for each substance were estimated for three reproductive endpoints (ano-genital distance, and weights of the seminal vesicles and the musculus levator ani/bulbocavernosus) in male rat foetuses exposed in utero. The cumulative dietary intake was estimated based on consumption data and residue data from the Netherlands.

Dose addition and the isobole method as approaches for predicting the cumulative effect of non-interacting chemicals: a critical evaluation.

The prediction of the effect of cumulative exposure to similarly acting chemicals is commonly done by dose addition, such as in the relative potency factor approach. This can only be done under the assumption of zero interaction between the chemicals. The related, but not equivalent, isobole method is the most common criterion to judge whether interactions between similarly acting chemicals have taken place in a mixture experiment.

Toxicodynamic analysis of the inhibition of isolated human acetylcholinesterase by combinations of methamidophos and methomyl in vitro.

The applicability of dose addition to combinations of OP-esters and carbamates has been questioned based on theoretical considerations, but these have not been well supported by experimental findings. In the present study, the inhibition of AChE by combinations of methamidophos (an OP-ester) and methomyl (a carbamate) was examined in vitro. AChE inhibition was measured by the Ellman assay.

Toxicodynamic analysis of the combined cholinesterase inhibition by paraoxon and methamidophos in human whole blood.

Theoretical work has shown that the isobole method is not generally valid as a method for testing the absence or presence of interaction (in the biochemical sense) between chemicals. The present study illustrates how interaction can be tested by fitting a toxicodynamic model to the results of a mixture experiment. The inhibition of cholinesterases (ChE) in human whole blood by various dose combinations of paraoxon and methamidophos was measured in vitro.

An integrated probabilistic framework for cumulative risk assessment of common mechanism chemicals in food: an example with organophosphorus pesticides.

This paper presents a framework for integrated probabilistic risk assessment of chemicals in the diet which accounts for the possibility of cumulative exposure to chemicals with a common mechanism of action. Variability between individuals in the population with respect to food consumption, concentrations of chemicals in the consumed foods, food processing habits and sensitivity towards the chemicals is addressed by Monte Carlo simulations. A large number of individuals are simulated, for which the individual exposure (iEXP), the individual critical effect dose (iCED) and the ratio between these values (the individual margin of exposure, iMoE) are calculated by drawing random values for all variable parameters from databases or specified distributions.

A model for probabilistic health impact assessment of exposure to food chemicals.

A statistical model is presented extending the integrated probabilistic risk assessment (IPRA) model of van der Voet and Slob [van der Voet, H., Slob, W., 2007.

Probabilistic risk characterization: an example with di(2-ethylhexyl) phthalate.

While probabilistic methods gain attention in hazard characterization and are increasingly used in exposure assessment, full use of the available probabilistic information in risk characterization is still uncommon. Usually, after probabilistic hazard characterization and/or exposure assessment, percentiles from the obtained distributions are used as point estimates in risk characterization. In this way, all information on variability and uncertainty is lost, while these aspects are crucial in any risk assessment.