NT-proBNP as a biomarker for the assessment of a potential cardiovascular drug-induced liability in beagle dogs.

The amino-terminal pro-brain natriuretic peptide (NT-proBNP) is released into the plasma predominantly from ventricular cardiomyocytes, particularly in patients with chronic cardiac diseases, although small amounts are detectable in the plasma of healthy subjects. While NT-proBNP has been widely exploited in human medicine, limited literature is available related to its characterization in veterinary medicine (e.g., correlation with damage and specificity) and, particularly, in the context of preclinical drug safety assessment. This paper describes the analytical performance characteristics and the biological variability of NT-proBNP in male beagle dogs by using a commercially available enzyme-linked immunosorbent assay. Male beagle dogs were treated with Casopitant, an NK1 receptor antagonist under development for depression and anxiety, which, when administered chronically to dogs, caused cardiac toxicity. Heart weight increase, myocardial necrosis, degeneration, and inflammation associated with high serum levels of cardiac troponin I characterized the end stage pathology observed in dogs treated orally at 40 mg/kg for 39 weeks. Based on these data, ad hoc studies were designed in order to evaluate the possible relationship between NT-proBNP serum levels and both standard toxicology endpoints, such as the organ weight and histology, as well as nonstandard endpoints such as macroscopic morphometry and echocardiography. Early changes of NT-proBNP serum levels were observed following 2 weeks of treatment onward, preceding most, if not all of the anatomical and functional changes. The results obtained demonstrate that NT-proBNP acts as an early biomarker of cardiac changes, representing a sensitive and predictive marker of drug-induced cardiac liability.

Characterisation of rodent dobutamine echocardiography for preclinical safety pharmacology assessment.

INTRODUCTION: Dobutamine stress echocardiography (DSE) is performed to detect subtle ischemic regions in the myocardium in patients suffering from stenosed coronary artery disease. While in a clinical and veterinary context DSE is performed daily, in the preclinical context, a very limited application has been described in the literature. In the drug development process, the safety of new chemical entities on the cardiovascular system is a primary requirement for the development of new agents/drugs for administration in humans. There are limited tools to evaluate the impairment of myocardial performance and cardiac contractility in preclinical species and particularly in rodents. In this present paper a possible imaging application is presented. METHODS: Anesthetised male Crl:CD(SD) rats (n=14) were given single intravenous doses of vehicle (5% w/v Dextrose solution) and dobutamine hydrochloride at 10 µg/kg/min. Echocardiography was performed, starting immediately before the infusion and animals were monitored up to 5 min after the end of infusion. Standard and non-standard echocardiography parameters were evaluated to detect test article related changes compared to vehicle infused animals. RESULTS: Thickening of left ventricle walls and interventricular septum and increased velocity of circumferential stress were observed in dobutamine infused animals compared to those receiving vehicle. These changes were considered to be a direct effect on myocardial contractility, as also confirmed by increased functional parameters (i.e., Ejection Fraction, End Diastolic Volume and decrease of the ratio between pre-ejection period and ejection time of the aortic flow). In dobutamine infused rats the "Tei index" increased up to approximately 32% compared to vehicle animals, showing a clear relationship with increased contractility. DISCUSSION: As expected dobutamine infusion in the anaesthetised rat is capable of inducing a positive inotropic effect and echocardiography results are a reliable tool for the determination of changes in contractility induced by pharmacological stress testing in the rat.

A novel and integrated approach for the identification and characterization of drug-induced cardiac toxicity in the dog.

Cardiovascular toxicity represents one of the major reasons for the termination of the development of drugs, even in late development phases. This growing issue is often not restricted to specific therapeutic areas, and it is gaining critical importance, in particular for chronically administered drugs, highlighting the limitations in terms of sensitivity of the current investigational paradigms. Furthermore, drug-related changes may become evident after long-term administration for different reasons, including accumulation of the drug in the heart. This article describes how the integrated use of investigational tools represents a powerful approach for the early identification and characterization of cardiotoxicity in preclinical development. Cardiac changes were observed in the dog after long-term oral administration of casopitant, a neurokinin 1 receptor antagonist, developed for the treatment of depression and anxiety. Different approaches and sensitive biomarkers were used in a time-course study to investigate the onset, progression, and reversibility of the lesion. The integrated evaluation of cardiovascular parameters, electron microscopy, troponin I, and natriuretic peptide results highlighted any minimal early changes, allowing the full and deep characterization of the lesion. The outcome of this study was the driver for drug development decision making on casopitant and backup drugs.

An improved method of electrode placement in configuration Lead II for the reliable ECG recording by telemetry in the conscious rat.

INTRODUCTION: Telemetry represents the gold standard technique for the acquisition of animal haemodynamic signals in the pharmaceutical preclinical development of new chemical entities. In terms of electrocardiographic signal recording, the quality is well established in large animals, mainly dog, non human primates and minipig, whereas it is still lacking in terms of satisfactory results in rodents (mouse and rat in particular). In very recent times, an increasing interest in early safety prediction for the reduction of cardiovascular attrition has been raised in all the major pharmaceutical companies, focusing in particular, on in vivo models. METHODS: Crl:CD(SD) and Wistar Han rats (Crl:WI[Han], Charles River) underwent surgery for the implantation of telemetry devices (Data Science International, USA) for the acquisition of blood pressure and electrocardiogram (ECG). A group of male CD rats (N=6) was implanted using the standard procedure as described by DSI technical documentation; another male CD group (N=3) was implanted using the technique described by Sgoifo et al. (1996); a third group (total of N=46, N=26 male CD rats, and N=10 male WI and N=10 female WI) was implanted using an alternative approach developed in our laboratory. RESULTS: The new surgical procedure was analysed based on technical difficulties, time to complete the surgery, time to recover, animal care, survival time after surgery and quality of telemetry signal recordings. Although a quantitative and qualitative comparison with other techniques described in literature was beyond the scope of the present work, based on our laboratory experience, Sgoifo's methodology showed better results compared to DSI standard approach, but surgical procedure was not easy to perform and more invasive. The novel approach described in the present paper was characterised by simplicity, repeatability, high rate of survival and improved quality of ECG signals for all the implanted rats. DISCUSSION: Telemetry in small rodents became of particular interest in the early safety assessment of cardiovascular liability during the development of new chemical entities. Although several surgical procedures are well described in literature, none seem to offer high standard electrocardiography signals in order to reliably detect intervals or arrhythmias. In the Safety Pharmacology Laboratory at GlaxoSmithKline, Verona (Italy), a novel and alternative surgical placement of the electrocardiographic electrodes in Lead II configuration was developed, in the rat. The scope of the present paper is to illustrate that this alternative surgical procedure is easily reproducible, minimally invasive and gives high standard quality ECG signals.

An integrated cardiovascular and neurobehavioural functional assessment in the conscious telemetered cynomolgus monkey.

INTRODUCTION: Unwanted effects of drugs on neurobehavioural and cardiovascular functions are normally assessed in separate studies and using different animals. The purpose of this study was to validate, in the monkey, a model that incorporates the neurobehavioural assessment into the Safety Pharmacology cardiovascular study, allowing for an integrated evaluation of these two physiological systems. METHODS: Conscious male cynomolgus (Macaca fascicularis) monkeys (n=4) were given single oral doses of vehicle, D-amphetamine (0.5, 1 and 2 mg/kg) or diazepam (0.5, 1 and 2.5 mg/kg) in a dose-escalation study design. Blood pressure, heart rate, electrocardiogram (ECG), body temperature, locomotor activity and behaviour (by video) were monitored continuously for 24h post-dose. Animals underwent a standardised neurobehavioural test battery which allowed the direct examination of 31 signs, including behavioural responses and neurological examinations, conducted the day before dose, at maximal plasma concentration time (T(max)), and 24 h post-dose. The study was carried out in a first phase with telemetric cardiovascular recording only, and a second phase with telemetric cardiovascular recording and neurobehavioural observations. Results from the second phase of the study were used to evaluate the influence of the direct neurobehavioural examination on the telemetrically acquired cardiovascular parameters. RESULTS: The expected cardiovascular and neurobehavioural changes, based on the pharmacological properties of the compounds tested, were accurately detected. In the second phase of the study the direct neurobehavioural examination caused fluctuations of the telemetric cardiovascular parameters for no more than 20 min from the end of the procedure and this did not alter or jeopardize the analysis and interpretation of the cardiovascular parameters. DISCUSSION: These results confirm the validity of this combined model capable of providing in the cynomolgus monkey a reliable and reproducible neurobehavioural and cardiovascular assessment of candidate drugs during the course of safety pharmacology evaluations.

An optimised neurobehavioural observation battery integrated with the assessment of cardiovascular function in the beagle dog.

INTRODUCTION: The objective of this study was to describe an optimised neurobehavioural observation battery in the beagle dog and to demonstrate that it can be used for an integrated assessment of cardiovascular and neurobehavioural functions within a single Safety Pharmacology study. METHODS: A standardised and detailed observation battery was established based on the direct examination of 44 signs, including behavioural responses and a full, systematic neurological examination, using clearly defined numerical scores. To complete the neurobehavioural assessment the remote observation of animals by video recording was also performed. Results from two studies, where cardiovascular and neurobehavioural parameters were assessed using drugs that either showed or did not show cardiovascular effects, are presented to show the influence of the direct neurobehavioural exam on the telemetrically acquired cardiovascular parameters. RESULTS: Heart rate and systolic blood pressure were affected by the handling required for the neurobehavioural procedure for a total of approximately 25 min, consisting in 20 min needed for the sequential neurobehavioural observation of four dogs (requiring approximately 5 min each) and approximately 5 min to return to baseline. Drug related cardiovascular effects were not affected by the changes associated with these neurobehavioural observations. More evident cardiovascular changes were observed with other routine procedures such as feeding. DISCUSSION: The direct neurobehavioural examination caused fluctuations of the telemetric cardiovascular parameters for no more than 5 min from the end of the procedure and this did not alter or jeopardise the analysis and interpretation of the cardiovascular parameters. These results confirmed that this optimised neurobehavioural observation battery can be used in the beagle dog for a reliable integrated assessment of neurobehavioural and cardiovascular changes during the course of Safety Pharmacology evaluations.

An optimised methodology for the neurobehavioural assessment in rodents.

INTRODUCTION: The most widely used test to identify undesired effects of drugs on the central and the peripheral nervous system is the neurobehavioural observation battery adapted from that first described by Irwin in mice. As a neurobehavioural assessment is based on observations; thus, all factors involved need to be controlled and standardised to make the data collected objective, reproducible, reliable and predictive of safety liabilities. METHODS: An observation battery comprising 58 signs with assigned full details of numerical scores was defined, and a standard design with associated recording, presenting and analysing data system was established. Validation studies were conducted with chlorpromazine, amphetamine, diazepam or clonidine given orally to rats or mice, in order to assess if this methodology could clearly differentiate the profile of effects produced by these compounds. The analysis of data from 80 control rats allowed for the assessment of the normal behaviour in order to characterise the inter-individual, daytime-related variability and the habituation of animals to the procedure. RESULTS: The reference compounds induced their typical and expected transient effects on neurobehaviour, observed both in the home cage and open-arena, and on body temperature. In particular, amphetamine induced a stimulation of the nervous system activities and marked hyperthermia. Chlorpromazine, diazepam and clonidine induced depressive, anxiolytic or sedative effects associated with hypothermia. The analysis of data collected in control animals allowed for the identification of 6 signs which scored differently from the assigned normality at the first handling occasion due to the characteristic fear reactions to the unknown, and 9 signs at 8 h post-dose due to the animal's habituation to experimental conditions and handling. DISCUSSION: The neurobehavioural changes expected by reference compounds administration were detected. These results confirm that by using this methodology the normal behaviour of the rat and the mouse, the daytime-related variability and the habituation of animals can be characterised, allowing a refined, reliable and reproducible neurobehavioural assessment of test substances in rodents.

A canine model used to simultaneously assess potential neurobehavioural and cardiovascular effects of candidate drugs.

INTRODUCTION: Unwanted effects of drugs on neurobehavioural and cardiovascular functions are normally assessed in separate studies and using different animals. A new model using dogs which allows for the integration of these assessments into a single study was established and validated, adopting the most sophisticated technologies for both monitoring behaviour by video recordings and cardiovascular parameters by telemetry. METHODS: Conscious male beagle dogs (n=4) were given single oral doses of vehicle, and D-amphetamine (0.25, 0.75, 1.5 mg/kg) or acepromazine (0.05, 0.3, 2 mg/kg) within two different studies. Blood pressure, heart rate, electrocardiogram (EKG), body temperature, motor activity and behaviour (by video) were monitored continuously for 24 h post-dose. Animals underwent a full neurobehavioural examination the day before dosing, at the time to the maximal plasma concentration (Tmax) and 24 h post-dose. RESULTS: D-Amphetamine: a dose-dependent increase in arterial blood pressure was noted at all doses and was generally associated with an increase in the QA interval, an index of cardiac contractility. Heart rate also increased but only at the 1.5 mg/kg dose. A dose-dependent general excitatory state of the nervous system was observed, characterised mainly by hyper-reactivity, and stereotyped activities. Acepromazine: a decrease in systolic blood pressure was detected at 0.3 and 2 mg/kg generally associated with a decrease in pulse pressure reflecting a negative inotropic effect. A dose-related increase in heart rate accompanied this effect. Dose-dependent general depression of the nervous system was noted; mainly characterised by half-closed eyes, subdued behaviour and impaired posture. In both studies, all dogs completely recovered at approximately 16 h after treatment. DISCUSSION: Cardiovascular and neurobehavioural changes expected from the pharmacology of test substances were accurately detected. No significant fluctuations of the telemetric parameters recorded were noted as a consequence of the handling associated with the direct neurobehavioural examination. These results confirm the validity of this combined model capable of providing a reliable neurobehavioural and cardiovascular assessment of drugs.