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Accurate and repeatable measurement of effects of test-articles on venous tone
Abstracts
e23
ECG in methoxamine-sensitized rabbits for screening proarrhythmic risk— Comparison with ECG data in dogs Philippe Guillaume, Sabrina Serpillon, Cecile Chauvin, Christophe Legrand, Stephane Herve, Sandra Picard
can be detected in the guinea-pig at clinically relevant exposures. Therefore this model is part of our integrative approach to determine the cardiovascular risk of drug candidates. Female Dunkin-Hartley guinea-pigs were anesthetized with sodium pentobarbital. Heart rate, blood pressure and the PQ, QRS, QT and QTcB intervals were measured after intravenous administration of compound or vehicle. A detailed screening of ECG morphology was performed. We recently tested compound-X in this anesthetized guinea-pig model and observed TdPs in 2 out of the 7 compound-dosed animals. An interaction with IKr and IKs channels and an increase in intracellular calcium are reported to be prerequisites for TdP induction in the guinea-pig. The observed increase in blood pressure concurs with an increase in Ca2+. However, compound-X did not notably prolong the QTc interval nor decreased heart rate, both of which are associated with IKr blockade by dofetilide in this model. Moreover, the intrinsic IKs blocking potential of the compound was low. This implies the involvement of mechanisms other than IKr and IKs blockade in the development of these TdPs. We further evaluated the electrophysiological effects of compound-X in other preclinical safety models to explore its mechanism of action. The implications for drug safety assessment are discussed.
Porsolt & Partners Pharmacology, Boulogne-Billancourt, France
doi:10.1016/j.vascn.2010.11.078
poor uptake as this only reached 0.02, 0.5, 9.1 and 108 ng/ larva, respectively, and those <10 ng were unclassified pending further investigation. Finally 5 compounds expected to cause bradycardia and 1 negative control were correctly identified. Therefore the overall predictivity for this assay excluding bioanalysis was 75%, and if those compounds failing to achieve a body burden of >10 ng/larva are removed from the data set pending further investigation, this would increase to 88%. The Zebrafish is therefore a promising model to test for cardiac dysfunction. doi:10.1016/j.vascn.2010.11.076
Poster Number: 73 Board Number: 73
Whereas QT interval prolongation assessment is mainly carried out in conscious large animals, the anesthetized methoxamine-sensitized rabbit model (Carlsson) has been proposed for evaluating torsadogenic risk. However, its sensitivity is highly dependent on the experimental conditions used. The present worked has compared rabbit and dog models for responsiveness to the effects of known torsadogenic substances. ABP and ECG were monitored in anesthetized male or female rabbits infused with methoxamine (520.2 μg/ml starting 10 min before treatment) or in conscious telemetered male dogs. Clofilium was more proarrhythmic in female than male rabbits at 100 nmol/kg/min for 45 min (40% vs 20% with ventricular tachycardia, VT). At 200 nmol/kg/ min for 20 min, it induced VT and torsades de pointes, TdeP, in 71% and 29% females, with increased QTc by +40.8 ± 6.6% (Fridericia) or +46.1 ± 7.6% (Carlsson). Sotalol induced VT or ventricular fibrillation (VF) in 75% rabbits and QTc prolongation in both species (rabbits: +9.3 ± 6.4%, Fridericia, and +11.0± 6.6%, Carlsson ; dogs: +16% max vs -1% in controls p < 0.001, Fridericia). Terfenadine induced VF in 33% rabbits with QTc prolongation (+23.2 ± 4.9%, Fridericia, and +23.7 ± 5.0%, Carlsson) but no significant effects on QTc in dogs. These findings demonstrate that, when used under appropriate experimental conditions, the rabbit TdeP model is a powerful tool for screening proarrhythmic risk and QT prolongation as it can reveal effects sometimes difficult to detect in conscious dogs after single oral dosing. doi:10.1016/j.vascn.2010.11.077
Poster Number: 74 Board Number: 74 Compound-X-induced TdP in the anesthetized guinea-pig: Unraveling the mechanism of action Brigitte G.P. Loenders, Jan Verrelst, Hua Rong Lu, Eddy Vlaminckx, Jutta Rohrbacher, Ard Teisman, David J. Gallacher Johnson & Johnson Pharmaceutical Research & Development, Beerse, Belgium The anesthetized guinea-pig is a sensitive and relevant model that can easily be used as a first-in-line in vivo screen for the early detection of compounds that affect cardiac electrophysiology. Indeed, compounds that alter the conduction of several cardiac ion-channels
Poster Number: 75 Board Number: 75 Accurate and repeatable measurement of effects of test-articles on venous tone Robert L. Hamlina,b, C.L. del Rioa,b, A. Kijtawornrata,b, Y. Panyasinga,b, L. Sneddenb, D. Probstb, Y. Ueyamaa,b, D. Hamlina, W.W. Muira,b a
The Ohio State University, Columbus, OH, United States QTest Labs, Columbus, OH, United States
b
If affected by drugs, changes in venous capacitance (VC) and mean circulatory filing pressure (MCFP) may lead to postural hypotension (PH), an adverse drug effect. We have developed a facile, humane, minimallyinvasive, accurate, and repeatable method of measuring VC and MCFP in dogs. Under aseptic conditions, an automatic fibrillator-defibrillator (St. Jude, PROMOTETM RF) is inserted into the right ventricle and units (DSI) to telemeter arterial (AP) as well venous (vP) pressures are implanted. Following recovery, AP/vP are continuously recorded under anesthesia, while the dogs are put briefly into ventricular fibrillation (VF) for ~30 s, and then defibrillated; because duration of VF is brief and animals are unconscious, defibrillation occurs painlessly and without incident. During cardiac arrest, AP decreases and vP increases (approaching each other). The AP decay is determined by systemic vascular resistance (svr), blood viscosity (h), and elastic recoil of the aorta (e). Meanwhile, the equilibration pressure to which vP rises is determined by the ratio of blood volume (BV) to the VC; however, if neither BV nor h change, then the AP fall is determined by arterial properties (svr and e), and the pressure to which vP approaches is the MCFP (determined by tone of venous smooth muscle). For instance, in α-chloralose anesthetized normal dogs, MCFP decreased following onset of isoflurane anesthesia (from 9.6±1.0 to 6.7±0.6 mmHg), suggesting venorelaxation. Furthermore, we have shown that this methodology identifies both venorelaxation produced by sildenafil and nitroglycerine, as well as venocontraction produced by norepinepherine. This methodology can quantify the effects of test articles on these important parameters. doi:10.1016/j.vascn.2010.11.079
e23
ECG in methoxamine-sensitized rabbits for screening proarrhythmic risk— Comparison with ECG data in dogs Philippe Guillaume, Sabrina Serpillon, Cecile Chauvin, Christophe Legrand, Stephane Herve, Sandra Picard
can be detected in the guinea-pig at clinically relevant exposures. Therefore this model is part of our integrative approach to determine the cardiovascular risk of drug candidates. Female Dunkin-Hartley guinea-pigs were anesthetized with sodium pentobarbital. Heart rate, blood pressure and the PQ, QRS, QT and QTcB intervals were measured after intravenous administration of compound or vehicle. A detailed screening of ECG morphology was performed. We recently tested compound-X in this anesthetized guinea-pig model and observed TdPs in 2 out of the 7 compound-dosed animals. An interaction with IKr and IKs channels and an increase in intracellular calcium are reported to be prerequisites for TdP induction in the guinea-pig. The observed increase in blood pressure concurs with an increase in Ca2+. However, compound-X did not notably prolong the QTc interval nor decreased heart rate, both of which are associated with IKr blockade by dofetilide in this model. Moreover, the intrinsic IKs blocking potential of the compound was low. This implies the involvement of mechanisms other than IKr and IKs blockade in the development of these TdPs. We further evaluated the electrophysiological effects of compound-X in other preclinical safety models to explore its mechanism of action. The implications for drug safety assessment are discussed.
Porsolt & Partners Pharmacology, Boulogne-Billancourt, France
doi:10.1016/j.vascn.2010.11.078
poor uptake as this only reached 0.02, 0.5, 9.1 and 108 ng/ larva, respectively, and those <10 ng were unclassified pending further investigation. Finally 5 compounds expected to cause bradycardia and 1 negative control were correctly identified. Therefore the overall predictivity for this assay excluding bioanalysis was 75%, and if those compounds failing to achieve a body burden of >10 ng/larva are removed from the data set pending further investigation, this would increase to 88%. The Zebrafish is therefore a promising model to test for cardiac dysfunction. doi:10.1016/j.vascn.2010.11.076
Poster Number: 73 Board Number: 73
Whereas QT interval prolongation assessment is mainly carried out in conscious large animals, the anesthetized methoxamine-sensitized rabbit model (Carlsson) has been proposed for evaluating torsadogenic risk. However, its sensitivity is highly dependent on the experimental conditions used. The present worked has compared rabbit and dog models for responsiveness to the effects of known torsadogenic substances. ABP and ECG were monitored in anesthetized male or female rabbits infused with methoxamine (520.2 μg/ml starting 10 min before treatment) or in conscious telemetered male dogs. Clofilium was more proarrhythmic in female than male rabbits at 100 nmol/kg/min for 45 min (40% vs 20% with ventricular tachycardia, VT). At 200 nmol/kg/ min for 20 min, it induced VT and torsades de pointes, TdeP, in 71% and 29% females, with increased QTc by +40.8 ± 6.6% (Fridericia) or +46.1 ± 7.6% (Carlsson). Sotalol induced VT or ventricular fibrillation (VF) in 75% rabbits and QTc prolongation in both species (rabbits: +9.3 ± 6.4%, Fridericia, and +11.0± 6.6%, Carlsson ; dogs: +16% max vs -1% in controls p < 0.001, Fridericia). Terfenadine induced VF in 33% rabbits with QTc prolongation (+23.2 ± 4.9%, Fridericia, and +23.7 ± 5.0%, Carlsson) but no significant effects on QTc in dogs. These findings demonstrate that, when used under appropriate experimental conditions, the rabbit TdeP model is a powerful tool for screening proarrhythmic risk and QT prolongation as it can reveal effects sometimes difficult to detect in conscious dogs after single oral dosing. doi:10.1016/j.vascn.2010.11.077
Poster Number: 74 Board Number: 74 Compound-X-induced TdP in the anesthetized guinea-pig: Unraveling the mechanism of action Brigitte G.P. Loenders, Jan Verrelst, Hua Rong Lu, Eddy Vlaminckx, Jutta Rohrbacher, Ard Teisman, David J. Gallacher Johnson & Johnson Pharmaceutical Research & Development, Beerse, Belgium The anesthetized guinea-pig is a sensitive and relevant model that can easily be used as a first-in-line in vivo screen for the early detection of compounds that affect cardiac electrophysiology. Indeed, compounds that alter the conduction of several cardiac ion-channels
Poster Number: 75 Board Number: 75 Accurate and repeatable measurement of effects of test-articles on venous tone Robert L. Hamlina,b, C.L. del Rioa,b, A. Kijtawornrata,b, Y. Panyasinga,b, L. Sneddenb, D. Probstb, Y. Ueyamaa,b, D. Hamlina, W.W. Muira,b a
The Ohio State University, Columbus, OH, United States QTest Labs, Columbus, OH, United States
b
If affected by drugs, changes in venous capacitance (VC) and mean circulatory filing pressure (MCFP) may lead to postural hypotension (PH), an adverse drug effect. We have developed a facile, humane, minimallyinvasive, accurate, and repeatable method of measuring VC and MCFP in dogs. Under aseptic conditions, an automatic fibrillator-defibrillator (St. Jude, PROMOTETM RF) is inserted into the right ventricle and units (DSI) to telemeter arterial (AP) as well venous (vP) pressures are implanted. Following recovery, AP/vP are continuously recorded under anesthesia, while the dogs are put briefly into ventricular fibrillation (VF) for ~30 s, and then defibrillated; because duration of VF is brief and animals are unconscious, defibrillation occurs painlessly and without incident. During cardiac arrest, AP decreases and vP increases (approaching each other). The AP decay is determined by systemic vascular resistance (svr), blood viscosity (h), and elastic recoil of the aorta (e). Meanwhile, the equilibration pressure to which vP rises is determined by the ratio of blood volume (BV) to the VC; however, if neither BV nor h change, then the AP fall is determined by arterial properties (svr and e), and the pressure to which vP approaches is the MCFP (determined by tone of venous smooth muscle). For instance, in α-chloralose anesthetized normal dogs, MCFP decreased following onset of isoflurane anesthesia (from 9.6±1.0 to 6.7±0.6 mmHg), suggesting venorelaxation. Furthermore, we have shown that this methodology identifies both venorelaxation produced by sildenafil and nitroglycerine, as well as venocontraction produced by norepinepherine. This methodology can quantify the effects of test articles on these important parameters. doi:10.1016/j.vascn.2010.11.079