The concordance between nonclinical and phase I clinical cardiovascular assessment from a cross-company data sharing initiative.

It is widely accepted that more needs to be done to bring new, safe, and efficacious drugs to the market. Cardiovascular toxicity detected both in early drug discovery as well as in the clinic, is a major contributor to the high failure rate of new molecules. The growth of translational safety offers a promising approach to improve the probability of success for new molecules. Here we describe a cross-company initiative to determine the concordance between the conscious telemetered dog and phase I outcome for 3 cardiovascular parameters. The data indicate that, in the context of the methods applied in this analysis, the ability to detect compounds that affect the corrected QT interval (QTc) was good within the 10-30x exposure range but the predictive or detective value for heart rate and diastolic blood pressure was poor. These findings may highlight opportunities to refine both the animal and the clinical study designs, as well as refocusing the assessment of value of dog cardiovascular assessments beyond phase 1. This investigation has also highlighted key considerations for cross-company data sharing and presents a unique learning opportunity to improve future translational projects.

Predicting drug-induced slowing of conduction and pro-arrhythmia: identifying the 'bad' sodium current blockers.

BACKGROUND AND PURPOSE: The regulatory guidelines (ICHS7B) for the identification of only drug-induced long QT and pro-arrhythmias have certain limitations. EXPERIMENTAL APPROACH: Conduction time (CT) was measured in isolated Purkinje fibres, left ventricular perfused wedges and perfused hearts from rabbits, and sodium current was measured in Chinese hamster ovary cells, transfected with Na(v)1.5 channels. KEY RESULTS: A total of 355 compounds were screened for their effects on CT: 32% of these compounds slowed conduction, 65% had no effect and 3% accelerated conduction. Lidocaine and flecainide, which slow conduction, were tested in more detail as reference compounds. In isolated Purkinje fibres, flecainide largely slowed conduction and markedly increased triangulation, while lidocaine slightly slowed conduction and did not produce significant triangulation. Also in isolated left ventricular wedge preparations, flecainide largely slowed conduction in a rate-dependent manner, and elicited ventricular tachycardia (VT). Lidocaine slightly slowed conduction, reduced Tp-Te and did not induce VT. Similarly in isolated hearts, flecainide markedly slowed conduction, increased Tp-Te and elicited VT or ventricular fibrillation (VF). The slowing of conduction and induction of VT/VF with flecainide was much more evident in a condition of ischaemia/reperfusion. Lidocaine abolished ischaemia/reperfusion-induced VT/VF. Flecainide blocked sodium current (I(Na)) preferentially in the activated state (i.e. open channel) with slow binding and dissociation rates in a use-dependent manner, and lidocaine weakly blocked I(Na). CONCLUSION AND IMPLICATIONS: Slowing conduction by blocking I(Na) could be potentially pro-arrhythmic. It is possible to differentiate between compounds with 'good' (lidocaine-like) and 'bad' (flecainide-like) I(Na) blocking activities in these models.

The fentanyl/etomidate-anaesthetised beagle (FEAB) dog: a versatile in vivo model in cardiovascular safety research.

The purpose of conducting cardiovascular safety pharmacology studies is to investigate the pharmacological profiles of new molecular entities (NMEs) and provide data that can be used for optimization of a possible new drug, and help make a selection of NMEs for clinical development. An anaesthetised dog preparation has been used for more than two decades by our department to measure multiple cardiovascular and respiratory parameters and to evaluate different scientific models, leading to more in-depth evaluation of drug-induced cardiovascular effects. An anaesthetic regime developed in house (induction with lofentanil, scopolamine and succinylcholine, and maintenance with fentanyl and etomidate) gives us a preparation free of pain and stress, with minimal effects on the cardiovascular system. This anaesthetic regime had minimal influences on circulating catecholamine levels, on the baroreflex sensitivity, and on all measured basal parameters compared to conscious dogs. All parameters were stable for at least 3 h, with acceptable tolerance intervals, evaluated over 99 safety studies with 3 vehicle treatments (saline, 10% and 20% hydroxypropyl-beta-cyclodextrin). This translates into a highly sensitive model for detecting possible drug-induced effects of NMEs with different mechanisms of action such as: Ca-, Na-, I(Kr)-, I(Ks)-channel blockers, K- and Ca-channel activators, alpha1- and beta-agonists, and muscarinic antagonists. Fentanyl in combination with etomidate is a successful anaesthetic regime in humans [Stockham, R.J., Stanley, T.H., Pace, N.L., King, K., Groen, F. & Gillmor, S.T. (1987). Induction of anaesthesia with fentanyl or fentanyl plus etomidate in high-risk patients. Journal of Cardiothoracic Anesthesia. 1(1), 19-23.]. In the anaesthetised dog, QT correction factors (Van de Water correction and body temperature correction) and risk factors (total, short-term and long-term instability) have been evaluated, using this regime [Van de Water, A., Verheyen, J., Xhonneux, R. & Reneman, R. (1989). An improved method to correct the QT interval of the electrocardiogram for changes in heart rate. Journal of Pharmacological Methods, 22, 207-217.; van der Linde, H.J., Van Deuren, B., Teisman, A., Towart, R. & Gallacher, D.J. (2008). The effect of changes in core body temperature on the QT interval in beagle dogs: A previously ignored phenomenon, with a method for correction. British Journal of Pharmacology, 154, 1474-1481.; van der Linde, H.J., Van de Water, A., Loots, W., Van Deuren, B., Lu, H.R., Van Ammel, K., et al. (2005) A new method to calculate the beat-to-beat instability of QT duration in drug-induced long QT in anaesthetised dogs. Journal of Pharmacological and Toxicological Methods, 52, 168-177.]. Furthermore, this anaesthetic protocol has been used to create different scientific models (long QT, short QT) with different specific end-points (ventricular fibrillation, adrenergic- or pause-dependent TdP) and also their specific precursors: e.g. aftercontractions, phase 2 EADs, phase 3 EADs, DADs, T-wave morphology changes, T-wave alternans, R-on-T, transmural and interventricular dispersion [Gallacher, D.J., Van de Water, A., van der Linde, H.J., Hermans, A.N., Lu, H.R., Towart, R., et al. (2007). In vivo mechanisms precipitating torsade de pointes in canine model of drug-induced long QT1 syndrome. Cardiovascular Research, 76-2, 247-256.]. This paper gives a brief overview of the stability, reproducibility, sensitivity and utility of a well-validated anaesthetised dog model.

In vivo measurement of QT prolongation, dispersion and arrhythmogenesis: application to the preclinical cardiovascular safety pharmacology of a new chemical entity.

In addition to in silico and in vitro measurements, cardiac electrophysiology in experimental animals plays a decisive role in the selection of a potential 'cardio-safe' new chemical entity (NCE). The present synopsis critically reviews such in vivo techniques in experimental animals. In anaesthetized guinea-pigs, surface ECG recordings readily identify the typical effects of Class I to IV anti-arrhythmic compounds and of If blockers such as zatebradine on ECG intervals and morphology, but also of non-cardiovascular NCEs affecting cardiac electrical activity via ion channels or neurogenic mechanisms. QT/RR plots indicate that bradycardia is a dominant effect of IKr blockers (dual modulation by IKr of sinus node activity and ventricular repolarization). Nevertheless, correction of QT with Bazett's formula usually distinguishes between drug-induced heart rate reduction and real prolongation of ventricular repolarization (QTc). The anaesthetized guinea-pig model thus is a useful tool for first line in vivo testing of an NCE for effects on cardiac electrophysiology, in particular when combined with measurements of drug levels in plasma and heart tissues. In anaesthetized dogs, advanced ECG analyses identify drug-induced effects on atrial and ventricular intervals, on temporal and transmural dispersion of ventricular repolarization and on incidences of early after-depolarizations. This can be combined with complete haemodynamic, pulmonary and pharmacokinetic analyses in one preparation. However, compound doses/plasma levels needed for effects on ventricular repolarization in this model are substantially higher than those identified in guinea-pigs, at least for IKr blocking compounds. Therefore, we use this 'information-rich' canine model as a second line approach. In awake, trained and appropriately instrumented dogs, readings of surface ECG in combination with cardio-haemodynamic and behavioural assessments can be performed after the administration of an NCE via the expected therapeutic route, including oral medication. However, at higher doses the compound under scrutiny may induce overall behavioural side-effects, related to its primary pharmacological action, such as gastrokinetic repercussions or CNS-mediated sedation or excitation. Such primary pharmacological effects are bound to compromise the evaluation of real drug-induced changes on cardiac electrophysiology, readily identified by resource-friendly setups in smaller animals. Therefore, we use such paradigms as an imperative, final cardiovascular check-up, before a 'First in Man' administration of the NCE. In anaesthetized, methoxamine-challenged rabbits, arrhythmogenic effects of IKr blockers (torsades de pointes) and of dual channel INa/IKr blockers (conduction disturbances) are readily identified. Drug-induced QT dispersion rather than a 'simple' QTc prolongation determines the ventricular arrhythmogenic effect of IKr blockers. The latter effect also depends on the rate of drug delivery (plasma levels vs. heart level, equilibrium throughout the myocardium). Therefore, we use models sensitized for arrhythmogenesis to document further the profile of a comparatively 'cardio-safe' NCE. We conclude that the interpretation of an integrated profile of activity of an NCE on in vitro and in vivo cardiovascular parameters, in comparison with the characteristics of its primary pharmacology and target disease, determines its eventual selection via a scientific, rather than a 'checklist' or 'menu' approach to cardiovascular safety pharmacology. Appropriate tests in experimental animals play a key role in this process.