EGIS-7229, the new combined class III antiarrhythmic agent: lack of EAD inducing effect

The Reaction of Cyclopentanone with Cyanomethylene Reagents: Novel Synthesis of Pyrazole, Thiophene, and Pyridazine Derivatives

The reaction of cyclopentanone with either malononitrile or ethyl cyanoacetate gave the corresponding condensated products. The latter underwent some heterocyclic reactions to give new pyrazole, thiophene, and pyridazine derivatives. The antitumor evaluation of the newly synthesized products against the three cancer cells, namely, breast adenocarcinoma (MCF-7), nonsmall cell lung cancer (NCI-H460), and CNS cancer (SF-268) showed that some of them have high inhibitory effect towards three cell lines which is higher than the standard.

Daurisoline Suppressed Early Afterdepolarizations and Inhibited L-Type Calcium Current

Our previous studies have shown that daurisoline (DS) exerted antiarrhythmic effects on various experimental arrhythmias. In this study, the effects of DS on early afterdepolarizations (EADs) and its possible mechanisms have been investigated. Cardiac hypertrophy was induced in rabbits by coarctating the abdominal aorta. The effects of DS on action potential duration (APD) and the incidences of EADs were studied in hypertrophied papillary muscles of rabbits in the conditions of low external K + concentration ([ K +] o ) and dofetilide (dof) by using standard microelectrode technique. The whole-cell patch clamp was used to record the L-type calcium current ( ICa-L ) in isolated left ventricular cells of rabbits. The results showed that in hypertrophied papillary muscles of rabbits with low [ K +] o ([ K +]o = 2.7 mM ), 1 µM dof prolonged APD50 and APD90 markedly and the incidence of EADs was 66.7% (4/6, p < 0.01); when 15 µM DS was applied, the incidence of EADs was 0% (0/4, p < 0.01) and the prolonged APD was shortened (p < 0.01). In a single myocyte, DS could also inhibit EADs induced by dof, low [ K +] o and low external Mg 2+ concentration ([ Mg 2+] o ) ([ Mg 2+] o = 0.5 mM ). DS could decrease the triangulation. In a single myocyte, DS could make the I-V curve upward, shift the steady-state activation curves to the right and the steady-state inactivation curves to the left and prolong the τ value of recovery curve obviously. These results suggested that DS could inhibit EADs which may be associated with its blockade effects on ICa-L .

Effects of EGIS-7229 (S 21407), a novel class III antiarrhythmic drug, on myocardial refractoriness to electrical stimulation in vivo and in vitro

The I(Kr) blocker EGIS-7229 (S-21407), displays class Ib and class IV effects that may alter its pharmacologic profile compared with those of pure I(Kr) blockers. Therefore, the concentration- and frequency-dependent effects of EGIS-7229, and of the I(Kr) blockers d,l-sotalol and dofetilide, on the effective refractory period (ERP) were measured in isolated right ventricular papillary muscle of the rabbit in vitro. The effects of these drugs on right ventricular fibrillation threshold (RVFT) at increasing intravenous doses were also determined in anesthetized cats. Dofetilide and d,l-sotalol increased ERP in a concentration-dependent manner (dofetilide: 3-100 nM; d,l-sotalol: 3-100 microM) with strong reverse frequency dependence at high concentrations. EGIS-7229 concentration dependently lengthened ERP at 1-30 microM. Its effect on ERP was clearly reverse frequency dependent at 3 microM, but this feature of the drug diminished at 10 microM and was not apparent at 30 microM. The effect of EGIS-7229 (30 microM) on ERP was devoid of reverse frequency dependence as it was more effective (31%) than dofetilide (16 %) at high-pacing rate (3 Hz), whereas it was less effective (50%) than dofetilide (70%) at slow-pacing rate (1 Hz). Reverse frequency-dependent ERP effect of dofetilide (100 nM) was similarly abolished by the addition of lidocaine (30 microM). EGIS-7229 (1-8 mg/kg iv), d,l-sotalol (1-8 mg/kg iv), and dofetilide (10-80 microg/kg iv) caused a dose-dependent increase in RVFT. The minimum effective dose of d,l-sotalol and EGIS-7229 was 1 and 2 mg/kg, respectively, whereas that of dofetilide was 10 microg/kg. EGIS-7229 induced a smaller peak effect in RVFT than sotalol or dofetilide. In conclusion, EGIS-7229 markedly increased refractoriness to electrical stimulation in vitro and in vivo. Compared with pure I(Kr) blockers, the benefits of EGIS-7229 seem to be a greater lengthening of effective refractory period at rapid stimulation rates, suggesting a strong antiarrhythmic action, and a smaller effect at slow stimulation rates, suggesting low potential to induce early afterdepolarizations.

Electrophysiological characterization of BRL-32872 in canine Purkinje fiber and ventricular muscle. Effect on early after-depolarizations and repolarization dispersion

Amongst the different pharmacological approaches to the treatment of cardiac arrhythmias, compounds with multiple electrophysiological activities appear to exhibit a reduced adverse effect profile. BRL-32872 (N-(3,4-dimethoxyphenyl)-N-[3[[2-(3,4-dimethoxyphenyl) ethyl] propyl]-4-nitrobenzamide hydrochloride) is a typical example of an antiarrhythmic agent with combined K(+) and Ca(2+) blocking actions. In this study, we investigated the effects of BRL-32872 on early after-depolarizations and on dispersion of repolarization. Action potentials were recorded either in canine cardiac Purkinje fibers alone or in preparations containing both ventricular muscle and the attached Purkinje fibers. In Purkinje fibers, BRL-32872 (0. 3-10 microM) induced a bell-shaped concentration-dependent increase in action potential duration. At 90% of repolarization, the action potential was prolonged at concentrations up to 1 microM and was shortened when the concentration of BRL-32872 was further increased. In all 17 experiments, BRL-32872 did not cause early after-depolarizations in Purkinje fibers. On the contrary, BRL-32872 (3 microM) systematically suppressed early after-depolarizations induced by clofilium (4-chloro-N, N-diethyl-N-heptylbenzenebutanaminium tosylate, 1 microM), a selective inhibitor of the delayed rectifier K(+) current. A similar effect was observed once with 1 microM BRL-32872, a concentration able to prolong Purkinje fiber action potentials. Simultaneous recording of action potentials in ventricular and Purkinje preparations showed that increasing concentrations of BRL-32872 (0. 3-10 microM) induced a limited increase in the difference of repolarization time between the two tissues. The selective K(+) channel inhibitor E-4031 (N-(4-(1-[2-(6-methyl-2-pyridyl) ethyl]-4-piperidyl)-carbonyl] phenyl) methanesulfonamide dihydrochloride dihydrate) exhibited a significant concentration-dependent increase in dispersion of repolarization. We conclude from the present results that the Ca(2+) blocking activity of BRL-32872 (i) prevents the occurrence of early after-depolarizations associated with action potential prolongation and (ii) limits an excessive increase in action potential duration heterogeneity. These electrophysiological features might represent the basis for antiarrhythmic compounds with reduced proarrhythmic profile.