Vernakalant: A novel agent for the termination of atrial fibrillation

Drug screening platform using human induced pluripotent stem cell-derived atrial cardiomyocytes and optical mapping

Current drug development efforts for the treatment of atrial fibrillation are hampered by the fact that many preclinical models have been unsuccessful in reproducing human cardiac physiology and its response to medications. In this study, we demonstrated an approach using human induced pluripotent stem cell-derived atrial and ventricular cardiomyocytes (hiPSC-aCMs and hiPSC-vCMs, respectively) coupled with a sophisticated optical mapping system for drug screening of atrial-selective compounds in vitro. We optimized differentiation of hiPSC-aCMs by modulating the WNT and retinoid signaling pathways. Characterization of the transcriptome and proteome revealed that retinoic acid pushes the differentiation process into the atrial lineage and generated hiPSC-aCMs. Functional characterization using optical mapping showed that hiPSC-aCMs have shorter action potential durations and faster Ca²⁺ handling dynamics compared with hiPSC-vCMs. Furthermore, pharmacological investigation of hiPSC-aCMs captured atrial-selective effects by displaying greater sensitivity to atrial-selective compounds 4-aminopyridine, AVE0118, UCL1684, and vernakalant when compared with hiPSC-vCMs. These results established that a model system incorporating hiPSC-aCMs combined with optical mapping is well-suited for preclinical drug screening of novel and targeted atrial selective compounds.

Vernakalant hydrochloride for the treatment of atrial fibrillation: evaluation of its place in clinical practice

Vernakalant is an intravenous anti-arrhythmic drug available in Europe, Canada and some countries in Asia for the restoration of sinus rhythm in acute onset atrial fibrillation. Currently, it is not available in USA because the US FDA have ongoing concerns about its safety. Vernakalant has a unique pharmacological profile of multi-ion channel activity and atrial-specificity that distinguishes it from other anti-arrhythmic drugs. This is thought to enhance efficacy but there are concerns of adverse events stemming from its diverse pharmacology. This ambiguity has prompted a review of the available clinical evidence on efficacy and safety to help re-evaluate its place in clinical practice.

Vernakalant in Atrial Fibrillation: A Relatively New Weapon in the Armamentarium Against an Old Enemy

Atrial fibrillation is the most common sustained cardiac arrhythmia, and its prevalence is increasing with age; also it is associated with significant morbidity and mortality. Rhythm control is advised in recent-onset atrial fibrillation, and in highly symptomatic patients, also in young and active individuals. Moreover, rhythm control is associated with lower incidence of progression to permanent atrial fibrillation. Vernakalant is a relatively new anti-arrhythmic drug that showed efficacy and safety in recent-onset atrial fibrillation. Vernakalant is indicated in atrial fibrillation (⩽7 days) in patients with no heart disease (class I, level A) or in patients with mild or moderate structural heart disease (class IIb, level B). Moreover, Vernakalant may be considered for recent-onset atrial fibrillation (⩽3 days) post cardiac surgery (class IIb, level B). Although it is mainly indicated in patients with recent-onset atrial fibrillation and with no structural heart disease, it can be given in moderate stable cardiac disease as alternative to Amiodarone. Similarly to electrical cardioversion, pharmacological cardioversion requires a minimal evaluation and cardioversion should be included in a comprehensive management strategy for better outcome.

Inhibition of Voltage-Gated K+ Channel Kv1.5 by Antiarrhythmic Drugs

Molecular dynamics simulations are employed to determine the inhibitory mechanisms of three drugs, 5-(4-phenoxybutoxy)psoralen (PAP-1), vernakalant, and flecainide, on the voltage-gated K⁺ channel Kv1.5, a target for the treatment of cardiac arrhythmia. At neutral pH, PAP-1 is neutral, whereas the other two molecules carry one positive charge. We show that PAP-1 forms stable dimers in water, primarily through hydrophobic interactions between aromatic rings. All three molecules bind to the cavity between the Ile508 and Val512 residues from the four subunits of the channel. Once bound, the drug molecules are flexible, with the average root-mean-square fluctuation being between 2 and 3 Å, which is larger than the radius of gyration of a bulky amino acid. The presence of a monomeric PAP-1 causes the permeating K⁺ ion to dehydrate, thereby creating a significant energy barrier. In contrast, vernakalant blocks the ion permeation primarily via an electrostatic mechanism and, therefore, must be in the protonated and charged form to be effective.

Effects of new class III antiarrhythmic drug niferidil on electrical activity in murine ventricular myocardium and their ionic mechanisms

A new class III antiarrhythmic drug niferidil has been recently introduced as a highly effective therapy cure for cases of persistent atrial fibrillation, but ionic mechanisms of its action are still unknown. Effects of niferidil on action potential (AP) waveform and major ionic currents were studied in mouse ventricular myocardium. APs were recorded with glass microelectrodes in multicellular preparations of right ventricular wall. Whole-cell patch-clamp technique was used to measure K(+), Ca(2+), and Na(+) currents in isolated mouse ventricular myocytes. While 10(-7) M niferidil failed to alter the AP configuration, 10(-6) M tended to prolong APs (by 12.05 ± 1.8% at 50% of repolarization) and 10(-5) M induced significant slowing of repolarization (32.1 ± 4.9% at 50% of repolarization). Among the potassium currents responsible for AP repolarization phase, IK1 was found to be almost insensitive to niferidil. Ito demonstrated low sensitivity to niferidil with IC50 = 2.03 × 10(-4) M. IKur, which was previously hypothesized to be the main target of the drug, was more sensitive with IC50 = 6 × 10(-5) M. However, sustained delayed rectifier potassium current Iss was inhibited with even lower IC50 = 2.8 × 10(-5) M. Therefore, suppression of Iss and, second, IKur by niferidil seems to underlie the AP prolongation in mouse ventricular tissue. Niferidil also produced a modest decrease in ICaL peak amplitude (IC50≈10(-4) M), but failed to alter INa significantly. Niferidil prolongs APs in mouse ventricular myocardium mainly by inhibiting Iss and IKur K(+) currents, but not exclusively IKur, as was proposed earlier. Further investigations are required to reveal the mechanisms of niferidil action in human myocardium, where IKr is strongly expressed instead of Iss.