16 research outputs found
Antifibrillatory actions of K+ channel blocking drugs
No full textClass III antiarrhythmic drugs share the common mechanism of widening the cardiac action potential without affecting conduction velocity. This thesis reports on the actions of newly developed putative Class III antiarrhythmic drugs, tedisamil, KC 8851, RP 62719, UK 68798, and risotilide, as well as an ATP-sensitive K⁺ channel blocker, glibenclamide. Studies were performed to examine the actions of these drugs in acute myocardial ischaemia and possible mechanisms responsible for these actions. The hypothesis tested was that drug treatment prevented arrhythmias induced by acute myocardial ischaemia. Species dependent actions of these drugs on ECG and blood pressure were examined in rats, guinea pigs, pigs and primates.
The five putative class III drugs listed above were assessed for antiarrhythmic activity in a conscious rat model of myocardial ischaemia. It was found that only tedisamil and KC 8851, which widened the Q-T[formula omitted] interval of the ECG (by up to 65%) , were effective at suppressing fibrillation in this species. None of the drug treatments decreased the incidence of ventricular premature beats. Tedisamil, but not glibenclamide, prevented tachycardias in a rat model of myocardial ischaemia- and reperfusion-induced arrhythmias. In an anaesthetized pig model of acute myocardial ischaemia, tedisamil and UK 68,798 were shown to mildly prolong the Q-T[formula omitted] interval by less than 20%, but protection against arrhythmias was equivocal.
In further studies, tedisamil and UK 68,798 were compared to each other for effects on ventricular epicardial action potential morphology using intracellular recording in vivo, and effects on ventricular effective refractory period using electrical stimulation in vivo in both rats and guinea pigs. Tedisamil (4 mg/kg, i.v.) prolonged rat ventricular epicardial action potential duration fourfold in vivo, while UK68,798 (up to 1 mg/kg, i.v.) was ineffective in this species. Tedisamil (4 mg/kg, i.v.) widened guinea pig ventricular epicardial potentials by 80%, while UK 68,798 (25 μg/kg, i.v.) increased these by 30%. Action potential widening paralleled increases in ventricular refractoriness to electrical induction of premature beats. It was found that the species selective actions of these drugs was most likely related to differences in selectivity for K⁺ channels which contribute to repolarization in myocardium.Medicine, Faculty ofAnesthesiology, Pharmacology and Therapeutics, Department ofGraduat
Efficacy and safety of XEN1101, a novel potassium channel opener, in adults with focal epilepsy : a phase 2b randomized clinical trial
No full textEffects of Optical Enantiomers CK‐4000(S) and CK 4001(R) on Defibrillation and Enhancement of Shock‐ Induced Extension of Action Potential Duration
No full text
Efficacy and safety of vernakalant in patients with atrial flutter:a randomized, double-blind, placebo-controlled trial
No full textVernakalant is a novel, relatively atrial-selective antiarrhythmic agent for conversion of atrial fibrillation (AF) to sinus rhythm. This study examined the safety and efficacy of vernakalant in converting atrial flutter (AFL) to sinus rhythm. This was a phase 2/3, randomized, double-blind, placebo-controlled trial. Adults with AFL received either a 10 min infusion of 3.0 mg/kg vernakalant (n 39) or placebo (n 15). If AFL or AF persisted at the end of a 15 min observation period, a second 10 min infusion of 2.0 mg/kg vernakalant or placebo was administered. The primary efficacy outcome was the proportion of patients who had treatment-induced conversion of AFL to sinus rhythm for a minimum duration of 1 min within 90 min after the start of the first infusion. No patient in the placebo group met the primary outcome. Only one patient receiving vernakalant (1 of 39, 3) converted to sinus rhythm. A reduced mean absolute ventricular response rate occurred within 50 min in patients receiving vernakalant (mean change from baseline 8.2 b.p.m.) vs. patients receiving placebo (0.2 b.p.m.) (P 0.037). A post-hoc analysis revealed that vernakalant increased AFL cycle length by an average of 55 ms, whereas the AFL cycle length was unchanged in the placebo group (P 0.001). There was no occurrence of 1 : 1 atrio-ventricular conduction. Dysgeusia and sneezing were the most common treatment-related adverse events, consistent with previous reports. Vernakalant did not restore sinus rhythm in patients with AFL. Vernakalant modestly slowed AFL and ventricular response rates, and was well tolerated
Pharmacokinetics of Novel Atrial‐Selective Antiarrhythmic Agent Vernakalant Hydrochloride Injection (RSD1235): Influence of CYP2D6 Expression and Other Factors
No full textThe Impact of Disease Severity on Responder Rates in a Phase 2b Study of XEN1101, a Potent, Selective Potassium Channel Opener, in Adults with Focal Epilepsy (X-TOLE)
No full textObjective:
To report the impact of baseline disease severity on the percentage of patients achieving a ≥50% reduction in seizure frequency (RR50) in the double-blind period (DBP) of a phase 2b study (X-TOLE) of XEN1101 in adults with focal onset seizures (FOS).
Background:
In the DBP, XEN1101 showed a significant, dose-dependent, and rapid-onset reduction in FOS frequency in adults with a median of 13.5 seizures/month and 6 tried and stopped antiseizure medications (ASMs) at baseline. 50.5% were taking 3 concomitant ASMs. A post hoc analysis suggested that the efficacy of XEN1101, measured by the median percentage change (MPC) in monthly FOS frequency, may be most pronounced in patients with less-severe disease. We report the potential impact of baseline disease severity on the RR50, another widely used endpoint for evaluating ASMs.
Design/Methods:
Patients (n=325) received 25, 20, or 10 mg XEN1101 or placebo in a 2:1:1:2 ratio, QD with food, with no titration required. Post hoc analyses assessed the influence of baseline disease severity (seizure frequency, number of concomitant ASMs, and number of previously tried ASMs) on the RR50 in FOS frequency through the 8-week DBP.
Results:
RR50 was achieved by 14.9% of placebo (n=114) and 54.5% of XEN1101 25-mg (n=112) patients. With XEN1101 25-mg treatment, RR50 was achieved by 65.5% of patients with ≤8.5 seizures/month (n=29) and 50.6% with >8.5 seizures/month (n=83) at baseline, 64.2% of patients with ≤6 prior ASMs (n=67) and 40.0% with >6 ASMs (n=45), and 56.9% of patients with 1–2 concomitant ASMs (n=58) and 51.9% with 3 concomitant ASMs (n=54).
Conclusions:
Consistent with the significant MPC seizure reduction, 54.5% of patients in the 25-mg XEN1101 group achieved RR50. XEN1101 was relatively more effective in patients with indicators of less-severe disease. XEN1101 may be appropriate for patients with focal epilepsy across the spectrum of disease severity
A randomized, placebo-controlled study of vernakalant (oral) for the prevention of atrial fibrillation recurrence after cardioversion
No full textVernakalant, a relatively atrial-selective antiarrhythmic drug, has previously demonstrated efficacy for the acute conversion of atrial fibrillation (AF) to sinus rhythm. This study was designed to determine the most appropriate oral dose of vernakalant for the prevention of AF recurrence postcardioversion
TMS as a pharmacodynamic indicator of cortical activity of a novel anti‐epileptic drug, XEN1101
No full textOBJECTIVE:Transcranial magnetic stimulation (TMS) produces characteristic deflections in the EEG signal named TMS-evoked EEG potentials (TEPs), which can be used to assess drug effects on cortical excitability. TMS can also be used to determine the resting motor threshold (RMT) for eliciting a minimal muscle response, as a biomarker of corticospinal excitability. XEN1101 is a novel potassium channel opener undergoing clinical development for treatment of epilepsy. We used TEPs and RMT to measure the effects of XEN1101 in the human brain, to provide evidence that XEN1101 alters cortical excitability at doses that might be used in future clinical trials.METHODS:TMS measurements were incorporated in this Phase I clinical trial to evaluate the extent to which XEN1101 modulates TMS parameters of cortical and corticospinal excitability. TEPs and RMT were collected before and at 2-, 4-, and 6-hours post drug intake in a double-blind, placebo-controlled, randomized, two-period crossover study of 20 healthy male volunteers.RESULTS:Consistent with previous TMS investigations of antiepileptic drugs (AEDs) targeting ion channels, the amplitude of TEPs occurring at early (15-55 msec after TMS) and at late (150-250 msec after TMS) latencies were significantly suppressed from baseline by 20 mg of XEN1101. Furthermore, the RMT showed a significant time-dependent increase that correlated with the XEN1101 plasma concentration.INTERPRETATION:Changes from baseline in TMS measures provided evidence that 20 mg of XEN1101 suppressed cortical and corticospinal excitability, consistent with the effects of other AEDs. These results support the implementation of TMS as a tool to inform early-stage clinical trials
