Evaluation of novel acute urinary rat kidney toxicity biomarker for subacute toxicity studies in preclinical trials.

Novel urinary protein biomarkers for the detection of acute renal damage, recently accepted by the U.S. Food and Drug Administration, European Medicines Agency, and Pharmaceuticals and Medical Devices Agency (Japan), now have to be validated in practice. Limited data regarding the performance of these acute markers after subacute or subchronic treatment are publicly available. To increase the area of applicability of these markers, it is important to evaluate the ability to detect them after 28 days of treatment or even longer. Wistar rats were treated with three doses of cisplatin, vancomycin, or puromycin to induce renal damage. Twelve candidate proteins were measured by Luminex xMAP-based WideScreen assays, MesoScale Discovery-based MULTI-SPOT technology, or RENA-strip dipstick assay after 28 days. Treatment with all three model compounds resulted in a dose-dependent increase in urinary biomarkers, specific for the observed areas within the nephron, determined histopathologically. The most promising biomarkers in this study were NGAL, Kim-1, osteopontin, clusterin, RPA-1, and GSTYb1, detected by multiplexing technologies. The RENA-strip dipstick assay delivered good diagnostic results for vancomycin-treated but not for cisplatin- or puromycin-treated rats. Taken together, the data show that these new biomarkers are robust and measurable for longer term studies to predict different types of kidney toxicities.

Simple-to-use, reference criteria for revealing drug-induced QT interval prolongation in conscious dogs.

Electrocardiogram (ECG) QT interval prolongation produced by drugs in certain animal models is currently believed to be predictive of cardiac proarrhythmic effects in humans. For this reason, nonclinical assessment of the effects of novel drugs on cardiac repolarization is a regulatory prerequisite for progressing such agents to clinical evaluation. The present investigation was carried out to develop reliable, simple-to-use reference criteria for identifying individual animals as responders to drugs that prolong the QT interval. ECG were recorded for 30 s at 0 (8 am), 2, 4, 6 and 24 h in 6 trained, conscious, beagle dogs during 5 control experimental sessions. QT intervals were measured and corrected for heart rate by applying the Van de Water algorithm (QTc). The maximal (QTc(max)) and minimal (QTc(min)) values of QTc observed in each of the five control recording sessions were noted. Two reference (R) criteria were used to designate an individual animal as a responder to drug treatment: 1) QTc(maxR) which was obtained by adding 10 ms to the largest value of QTc(max) observed during the five control recording sessions and 2) (QTc(max)-QTc(min))(maxR) which was obtained by increasing by 50% the largest of the (QTc(max)-QTc(min)) values [(QTc(max)-QTc(min))(max)] observed in the 5 control recording sessions. The sensitivity and reliability of these criteria were tested by determining QTc intervals before and 2, 4, 6 and 24 h after placebo or quinidine (200, 400 and 800 mg p.o. per animal). The reference values of QTc(maxR) and (QTc(max)-QTc(min))(maxR) for the various dogs ranged from 246 to 270 ms and from 15 to 19.5 ms, respectively. The number of dogs responding to treatment (T: quinidine at 200, 400 and 800 mg, p.o. per animal) with a QTc(maxT) and/or a (QTc(max)-QTc(min))(maxT) equal to or greater than the respective reference values was, respectively, 1/6, 3/6 and 5/6 dogs. Additionally, the number of responders correlated well with the concentration of free quinidine in the plasma. In conclusion, this investigation succeeded in establishing reliable, reference criteria for individual dogs despite the intrinsic daily variation of QTc interval. The application of these criteria allowed identifying individual animals responding to quinidine with delayed cardiac repolarization.

An approach to minimise dog use in regulatory toxicology: production of a best practice guide to study design.

The primary non-rodent species used in toxicology is the dog. It is generally agreed that, for ethical reasons, dog use should be reduced to the minimum consistent with maintaining the scientific quality of toxicology studies and ensuring human safety. Dog use in toxicology has been discussed widely, both from a scientific and ethical viewpoint, and there appears to be real potential for achieving significant reductions in the number of dogs used in pharmaceutical safety testing. An industry animal welfare initiative commenced in 2000, with the aim of evaluating and, where possible, putting into practice, scientifically valid approaches to minimise dog use in regulatory toxicology without increasing the use of other non-rodent species, such as non-human primates or minipigs. The study's Steering Group categorised potential reduction approaches into three distinct areas, one of which is the production of a best practice guide on aspects of study design, including: group sizes, use of control animals, single sex studies and design of maximum tolerated dose (MTD) studies. Information on current practice and experience within the pharmaceutical industry is now being analysed, and additional input is invited.

Zebrafish teratogenicity test with metabolic activation (mDarT): effects of phase I activation of acetaminophen on zebrafish Danio rerio embryos.

The zebrafish Danio rerio embryo test with metabolic activation (mDarT) was developed to assess the teratogenic effects of proteratogens. In this study induced rat liver microsomes (RLM) were used as a mammalian metabolic activation system (MAS), since they contain various cytochrome P450 (CYP) isoforms at high concentrations. Acetaminophen (APAP) is considered not to be teratogenic in vivo, however, in vitro teratogenic effects were observed, e.g. in rat whole embryo culture. The CYP2E1 activation of APAP to the reactive metabolite N-acetyl-p-benzoquinone imine (NAPQI) mainly occurs, when the glucuronidation and sulfatation pathways are saturated. In vivo the soft electrophile NAPQI is usually inactivated by hepatic reduced glutathione (GSH), a soft nucleophile. In this study, we investigated the teratogenic and lethal effects of APAP after CYP activation in zebrafish embryos. In the test groups with APAP and metabolic activation 11.7+/-7.6% (2mM), 25.0+/-8.7% (4mM) and 50.0+/-21.8% (6mM) affected embryos were seen, reaching statistical significance at 4mM APAP. When embryos were exposed to 6mM APAP, MAS and 3mM GSH the percentage of affected embryos decreased to 6.7+/-5.8%. In contrast teratogenic and lethal effects of metabolically activated cyclophosphamide (CPA) could not be prevented by GSH addition, because the CPA metabolites are strong electrophiles, which preferentially bind to hard nucleophiles like DNA and RNA. The teratogenic and lethal effects of metabolically activated APAP observed in zebrafish embryos with our mDarT standard protocol could be explained by the lack of GSH as a detoxifying system. By adding GSH it was possible to mimic the situation in mammals and thus avoid teratogenic effects in zebrafish embryos.

Development of a new screening assay to identify proteratogenic substances using zebrafish danio rerio embryo combined with an exogenous mammalian metabolic activation system (mDarT).

The assessment of teratogenic effects of chemicals is generally performed using in vivo teratogenicity assays, for example, in rats or rabbits. We have developed an in vitro teratogenicity assay using the zebrafish Danio rerio embryo combined with an exogenous mammalian metabolic activation system (MAS), able to biotransform proteratogenic compounds. Cyclophosphamide (CPA) and ethanol were used as proteratogens to test the efficiency of this assay. Briefly, the zebrafish embryos were cocultured at 2 hpf (hours postfertilization) with the test material at varying concentrations, induced male rat liver microsomes and nicotinamide adenine dinucleotide phosphate (reduced) for 60 min at 32 degrees C under moderate agitation in Tris-buffer. The negative control (test material alone) and the MAS control (MAS alone) were incubated in parallel. For each test group, 20 eggs were used for statistical robustness. Afterward fish embryos were transferred individually into 24-well plates filled with fish medium for 48 h at 26 degrees C with a 12-h light cycle. Teratogenicity was scored after 24 and 48 hpf using morphological endpoints. No teratogenic effects were observed in fish embryos exposed to the proteratogens alone, that is, without metabolic activation. In contrast, CPA and ethanol induced abnormalities in fish embryos when coincubated with microsomes. The severity of malformations increased with increasing concentrations of the proteratogens. We conclude that the application of microsomes will improve and refine the D. rerio teratogenicity assay as a predictive and valuable alternative method to screen teratogenic substances.

Kinetics of 3-(4-methylbenzylidene)camphor in rats and humans after dermal application.

The toxicokinetics of 4-MBC after dermal administration were investigated in human subjects and in rats. Humans (3 male and 3 female subjects) were exposed to 4-MBC by topical application of a commercial sunscreen formulation containing 4% 4-MBC (w/w), covering 90% of the body surface and resulting in a mean dermal 4-MBC dose of 22 mg/kg bw. In rats, dermal 4-MBC doses of 400 and 2000 mg/kg bw were applied in a formulation using an occlusive patch for 24 h. Concentrations of 4-MBC and its metabolites were monitored over 96 h in plasma (rats and humans) and urine (humans). In human subjects, plasma levels of 4-MBC peaked at 200 pmol/ml in males and 100 pmol/ml in females 6 h after application and then decreased to reach the limit of detection after 24 h (females), respectively, 36 h (males). After dermal application of 4-MBC, peak plasma concentrations of 3-(4-carboxybenzylidene)-6-hydroxycamphor were 50-80 pmol/ml at 12 h and of 3-(4-carboxybenzylidene)camphor were 100-200 pmol/ml at 24 h. In male and female rats, peak plasma levels of 4-MBC were 200 (dose of 400 mg/kg bw) and 1 200 pmol/ml (dose of 2000 mg/kg bw). These levels remained constant for up to 24-48 h after dermal application. Peak plasma concentrations of 3-(4-carboxybenzylidene)-6-hydroxycamphor were 18,000 pmol/ml (males) and of 3-(4-carboxybenzylidene)camphor were 55,000 pmol/ml (females) between 48 and 72 h after application of the high dose of 4-MBC. In human subjects, only a small percentage of the dermally applied dose of 4-MBC was recovered in the form of metabolites in urine, partly as glucuronides. The obtained results suggest a more intensive biotransformation of 4-MBC in rats as compared to humans after dermal application and a poor absorption of 4-MBC through human skin.

Functional observational battery and motor activity in rats after single administration of two NHE 1 inhibitors.

Two tests, a functional observational battery (FOB) and measurement of motor activity, have been used to screen the two NHE inhibitors EMD 96785 and EMD 125021 for neurobehavioral effects. These two NHE inhibitors, which exhibit a marked selectivity for the NHE 1 isoform, are under development in the research laboratories of Merck KGaA. NHE inhibitors are developed for the treatment of acute myocardial infarction and chronic heart failure. In prior studies with EMD 96785 and EMD 125021, clinical symptoms, such as uncoordinated movements and weakness of the hindlimbs, were detected in rats. The aim of this study was the evaluation of clinical findings in more detail using a FOB and measurement of motor activity in 96 female rats. The time course and reversibility of the adverse effects were investigated. The animals were treated with EMD 96785 or EMD 125021 by intravenous injection at a single dose of 100 mg/kg and four different time points (2 h, 1 day, 7 days and 21 days after treatment) were chosen for the clinical examination. This neurobehavioral test battery clearly detected neurological activity and defined time-course characteristics after treatment with EMD 96785 or EMD 125021. The various clinical parameters were grouped into functional-related domains and most alterations were seen in the domains of central nervous system and neuromuscular system. The most prominent clinical findings were seen with the pharmacologically more potent NHE inhibitor EMD 125021 when compared to EMD 96785. The clinical symptoms were proven to be reversible by 7 days after the single treatment for both compounds.

Optimising the design of preliminary toxicity studies for pharmaceutical safety testing in the dog.

A working party, comprising two animal welfare organisations and some 12 pharmaceutical companies in Europe, was established to minimise the use of the dog in safety testing. As first step, the participants defined the major objectives of preliminary dose-range finding/MTD toxicity studies in non-rodents, defined the principles and requirements for this study type and agreed on a proposal for an optimised study design, based on collective experience of conducting such studies in industry, involving an evaluation of 100 individual study data sets. The suggested study design is explained and described, and reflects current best practice in the pharmaceutical industry in Europe. The implementation of such an optimised design is believed to result in a reduction in the overall numbers of animals used for this purpose, without jeopardising the scientific rationale and usefulness of the studies for informing the conduct of later regulatory studies.