A preliminary assessment of the effects of ATI-2042 in subjects with paroxysmal atrial fibrillation using implanted pacemaker methodology

New methodological approaches to atrial fibrillation drug discovery

INTRODUCTION

Atrial fibrillation (AF) is the most common arrhythmia encountered in clinical practice and rhythm control using pharmacological agents is required in selected patients. Nonetheless, current medication is only modestly efficacious and associated with significant cardiovascular and systemic side effects. More efficacious and safe drugs are required to restore and maintain sinus rhythm in patients with AF.

AREAS COVERED

In this review, several potential drug targets are discussed including trans-membrane ion channels, intracellular calcium signaling, gap junction signaling, atrial inflammation and fibrosis, and the autonomic nervous system. New tools and methodologies for AF drug development are also reviewed including gene therapy, genome-guided therapy, stem cell technologies, tissue engineering, and optogenetics.

EXPERT OPINION

In recent decades, there has been an increased understanding of the underlying pathogenesis of AF. As a result, there is a gradual paradigm shift from focusing only on trans-membrane ion channel inhibition to developing therapeutic agents that target other underlying arrhythmogenic mechanisms. Gene therapy and genome-guided therapy are emerging as novel treatments for AF with some success in proof-of-concept studies. Recent advances in stem cell technology, tissue engineering, and optogenetics may allow more effective in-vitro drug screening than conventional methodologies.

How the Deuteration of Dronedarone Can Modify Its Cardiovascular Profile: In Vivo Characterization of Electropharmacological Effects of Poyendarone, a Deuterated Analogue of Dronedarone

Since deuterium replacement has a potential to modulate pharmacodynamics, pharmacokinetics and toxicity, we developed deuterated dronedarone; poyendarone, and assessed its cardiovascular effects. Poyendarone hydrochloride in doses of 0.3 and 3 mg/kg over 30 s was intravenously administered to the halothane-anesthetized dogs (n = 4), which provided peak plasma concentrations of 108 ± 10 and 1120 ± 285 ng/mL, respectively. The 0.3 mg/kg shortened the ventricular repolarization period. The 3 mg/kg transiently increased the heart rate at 5 min but decreased at 45 min, and elevated the total peripheral vascular resistance and left ventricular preload, whereas it reduced the mean blood pressure at 5 min, left ventricular contractility and cardiac output. The transient tachycardic action is considered to be induced by the hypotension-induced, reflex-mediated increase of sympathetic tone. The 3 mg/kg delayed both intra-atrial and intra-ventricular conductions, indicating Na⁺ channel inhibitory action. Moreover, the 3 mg/kg transiently shortened the ventricular repolarization period at 5 min. No significant change was detected in the late repolarization by poyendarone, indicating it might not hardly significantly alter rapidly activating delayed-rectifier K⁺ current (I_Kr). Poyendarone prolonged the atrial effective refractory period greater than the ventricular parameter. When compared with dronedarone, poyendarone showed similar pharmacokinetics of dronedarone, but reduced β-adrenoceptor blocking activity as well as the cardio-suppressive effect. Poyendarone failed to inhibit I_Kr and showed higher atrial selectivity in prolonging the effective refractory period of atrium versus ventricle. Thus, the deuteration may be an effective way to improve the cardiovascular profile of dronedarone. Poyendarone is a promising anti-atrial fibrillatory drug candidate.

Mechanisms and Drug Development in Atrial Fibrillation

Atrial fibrillation is a highly prevalent cardiac arrhythmia and the most important cause of embolic stroke. Although genetic studies have identified an increasing assembly of AF-related genes, the impact of these genetic discoveries is yet to be realized. In addition, despite more than a century of research and speculation, the molecular and cellular mechanisms underlying AF have not been established, and therapy for AF, particularly persistent AF, remains suboptimal. Current antiarrhythmic drugs are associated with a significant rate of adverse events, particularly proarrhythmia, which may explain why many highly symptomatic AF patients are not receiving any rhythm control therapy. This review focuses on recent advances in AF research, including its epidemiology, genetics, and pathophysiological mechanisms. We then discuss the status of antiarrhythmic drug therapy for AF today, reviewing molecular mechanisms, and the possible clinical use of some of the new atrial-selective antifibrillatory agents, as well as drugs that target atrial remodeling, inflammation and fibrosis, which are being tested as upstream therapies to prevent AF perpetuation. Altogether, the objective is to highlight the magnitude and endemic dimension of AF, which requires a significant effort to develop new and effective antiarrhythmic drugs, but also improve AF prevention and treatment of risk factors that are associated with AF complications.

Emerging pharmacotherapies for the treatment of atrial fibrillation

INTRODUCTION

The main aim of current research on the field of atrial fibrillation (AF) treatment is to find new antiarrhythmic drugs with less side effects. Areas covered: Dronedarone and vernakalant showed promising result in term of efficacy and safety in selected patients. Ranolazine and colchicine are obtaining a role as a potential antiarrhythmic drug. Ivabradine is used in experimental studies for the rate control of AF. Moreover, new compounds (vanoxerine, moxonidine, budiodarone) are still under investigation. Monoclonal antibodies or selective antagonist of potassium channel are under investigation for long term maintenance of sinus rhythm. Clinical evidence and new pharmacological investigation on new drugs will be accurately reviewed in this article. Expert opinion: Dronedarone use is not recommended in patients with symptomatic heart failure (HF), NYHA class III-IV, depressed ventricular function and permanent AF, especially in patients assuming a concomitant therapy with digoxin. Vernakalant had superior efficacy than amiodarone, flecainide and propafenone in single studies and similar efficacy to direct current cardioversion. Several of the developing drugs examined in this paper show an interesting potential, in particular the research on selective ionic channel inhibition and on compounds which reduce the inflammation state, especially after ablation or surgery.

First clinical trial of specific IKACh blocker shows no reduction in atrial fibrillation burden in patients with paroxysmal atrial fibrillation: pacemaker assessment of BMS 914392 in patients with paroxysmal atrial fibrillation

AIMS

To assess the efficacy of BMS 914392 on atrial fibrillation (AF) burden reduction in 20 patients with pacemakers and paroxysmal atrial fibrillation (PAF). BMS 914392 is a potent, selective, oral inhibitor of the IKACh current and has been shown to suppress AF, whilst having no effect on the ventricular refractory period. This is the first efficacy study of BMS 914392 in patients with PAF.

METHODS AND RESULTS

The study was a four-way, crossover, double-blind design. A total of 20 patients with PAF and dual-chamber pacemakers were recruited. The pacemakers allowed beat-to-beat monitoring. Anti-arrhythmic drugs were withdrawn. Patients received low-dose (10 mg OD), medium-dose (10 mg TDS), and high-dose (20 mg TDS) BMS 914392 or placebo for 3 weeks before being crossed to the next phase. Patients underwent a washout period, four treatment phases and a final washout phase. Atrial fibrillation burden was downloaded from their pacemakers at the end of each study phase. BMS 914392 did not reduce AF burden when compared with placebo (10 mg OD P = 0.56, 10 mg TDS P = 0.22, 20 mg TDS P = 0.23). Heart rate and corrected QT (QTc) were not affected by BMS 914392. Adverse event (AE) rates did not differ from placebo in any of the treatment groups, with no serious AEs recorded.

CONCLUSION

BMS 914932 has not been shown to reduce AF burden in patients with PAF and pacemakers using beat-to-beat pacemaker monitoring throughout the study. BMS 914392 was well tolerated and did not affect QTc or reduce heart rate.

TRIAL REGISTRATION

Clinicaltrials.gov: NCT01356914.

The effect of C-reactive protein reduction with a highly specific antisense oligonucleotide on atrial fibrillation assessed using beat-to-beat pacemaker Holter follow-up

PURPOSE

C-reactive protein (CRP) is known to be strongly associated with atrial fibrillation (AF). However, it is not clear if CRP is a causal factor for AF. ISIS-CRPRx is a novel antisense oligonucleotide that reduces CRP production by specifically inhibiting mRNA translation. The effect of ISIS-CRPRx on AF was evaluated.

METHODS

A double-blind phase II trial of ISIS-CRPRx in patients with paroxysmal AF and DDDRP permanent pacemakers (PPMs) with advanced atrial and ventricular Holters allowing beat-to-beat arrhythmia follow-up.

RESULTS

Twenty six patients were screened and seven patients dosed with ISIS-CRPRx. After 4 weeks of baseline assessment, patients were randomly assigned to two treatment periods of either placebo then ISIS-CRPRx or ISIS-CRPRx then placebo. All patients were followed up for 8 weeks after the active treatment period. There was a 63.7 % (95 % CI 38.4 to 78.6 %, p = 0.003) relative reduction in CRP on treatment with ISIS-CRPRx versus baseline. Sensitivity analyses demonstrated a consistent treatment effect. The primary end-point was change in AF burden assessed by PPM. There was no significant difference in AF burden on treatment with ISIS-CRPRx versus baseline (OR 1.6, 95 % CI -2.42 to 5.62, p = 0.37). ISIS CRPRx was safe and well tolerated and there were no serious adverse events.

CONCLUSIONS

Treatment with ISIS-CRPRx did not reduce AF burden in patients with paroxysmal AF and PPMs, despite a large relative reduction in CRP. In this population, highly specific CRP reduction had no clinically discernable effect upon paroxysmal AF. However, average levels of CRP at baseline were relatively low, so it remains possible that AF patients with higher levels of CRP may benefit from CRP-directed therapy.

AF burden is important - fact or fiction?

Asymptomatic atrial fibrillation (AF) is common and in view of its prognostic impact (the same as of clinically overt AF) knowledge of the overall AF burden (defined as the amount of time spent in AF) appears to be important, both for scientific and clinical reasons. Data collected on more than 12,000 patients indicate that cardiac implantable electrical devices (CIEDs) are validated tools for measuring AF burden and that AF burden is associated with an increased risk of stroke. A maximum daily AF burden of ≥ 1 h carries important negative prognostic implications and may be a clinically relevant parameter for improving risk stratification for stroke. Decision-making should primarily consider the context in which asymptomatic, subclinical arrhythmias are detected (i.e. primary or secondary prevention of stroke and systemic embolism) and the risk profile of every individual patient with regard to thromboembolic and haemorrhagic risk, as well as patient preferences and values. Continuous monitoring using CIEDs with extensive data storage capabilities allow in-depth study of the temporal relationship between AF and ischaemic stroke. The relationships between AF and stroke are complex. AF is certainly a risk factor for cardioembolic stroke, with a cause-effect relationship between the arrhythmia and a thromboembolic event, the latter being related to atrial thrombi. However, AF can also be a simple 'marker of risk', with a non-causal association between the arrhythmia and stroke, the latter being possibly related to atheroemboli from the aorta, the carotid arteries or from other sources.

Antiarrhythmic drugs 2013: state of the art

Antiarrhythmic drugs are widely used, but are of modest efficacy and have important side effects. However, even with the advance of catheter ablation for atrial fibrillation and ventricular tachycardia, antiarrhythmic drugs remain an important tool for treating arrhythmias. Antiarrhythmic drug development has remained slow despite much effort given our limited understanding of what role various ionic currents play in arrhythmogenesis and how they are modified by arrhythmias. This review will focus on promising new antiarrhythmic drugs undergoing clinical investigation or currently approved for clinical use, including amiodarone analogues, agents with novel ionic targets, and new drug combinations.

Management strategies in atrial fibrillation in patients with heart failure

Atrial fibrillation (AF) and heart failure (HF) frequently occur together, and their coexistence is associated with a poor prognosis. AF and HF share risk factors, but their relationship involves complex hemodynamic, neurohormonal, inflammatory, ultrastructural, and electrophysiologic processes that extend beyond epidemiological associations. The shared mechanisms underlying AF and HF have important implications for the treatment of AF in patients with HF. This article focuses on reviewing contemporary data as it pertains to AF management in patients with HF and provides insight into investigational therapies currently under development.

Cardiac ion channels and mechanisms for protection against atrial fibrillation

Atrial fibrillation (AF) is recognised as the most common sustained cardiac arrhythmia in clinical practice. Ongoing drug development is aiming at obtaining atrial specific effects in order to prevent pro-arrhythmic, devastating ventricular effects. In principle, this is possible due to a different ion channel composition in the atria and ventricles. The present text will review the aetiology of arrhythmias with focus on AF and include a description of cardiac ion channels. Channels that constitute potentially atria-selective targets will be described in details. Specific focus is addressed to the recent discovery that Ca(2+)-activated small conductance K(+) channels (SK channels) are important for the repolarisation of atrial action potentials. Finally, an overview of current pharmacological treatment of AF is included.

[Basic mechanisms of the new antiarrhythmic drugs in atrial fibrillation]

Atrial fibrillation (AF) is the most common sustained arrhythmia seen in clinical practice. Despite of new technological breakthroughs and the understanding of the mechanisms underlying AF, based on animal models and ablation procedures in patients, the antiarrhythmic drugs remain the main therapeutic strategy to restore and maintain the sinus rhythm. New antiarrhythmic drugs are already available in the clinical practice and many others are under development. The new antiarrhythmic drugs have the capability to block atrial-specific ionic currents, which are involved in the maintenance of the arrhythmia. Parallel, increasing evidence supports the use of compounds to regulate the arrhythmogenic atrial substrate involved in the long-term maintenance of the arrhythmia (upstream therapies). This article reviews the new antiarrhythmic drugs and upstream therapies, based on the current knowledge of the mechanisms involved in the maintenance of AF.

How to use implantable loop recorders in clinical trials and hybrid therapy

Epidemiological studies show that atrial fibrillation (AF) is associated with a doubling of mortality, even after adjustment for confounders. AF can be asymptomatic, but this does not decrease the thromboembolic risk of the patient. Office ECGs, occasional 24-h Holter recordings and long-term ECG event recording might not be sensitive and accurate enough in patients with AF, especially in those with paroxysmal episodes. In one study, 7 days of continuous monitoring with event recorders detected paroxysmal AF in 20 of 65 patients with a previous negative 24-h Holter recording. Over the last decade, enormous improvements have been made in the technology of implantable devices, which can now store significant information regarding heart rhythm. The first subcutaneous implantable monitor (Reveal XT, Medtronic) was validated for continuous AF monitoring by the XPECT study. The dedicated AF detection algorithm uses irregularity and incoherence of R–R intervals to identify and classify patterns in ventricular conduction. Its sensitivity in identifying patients with AF is >96%. Numerous clinical data from continuous monitoring of AF have recently been published. The first applications of this technology have been in the field of surgical and catheter AF ablation. With regard to cryptogenic stroke, an international randomized trial is ongoing to compare standard care with standard care plus the implantable cardiac monitor for AF detection in patients discharged with the diagnosis of cryptogenic stroke: the Crystal AF trial. Continuous AF monitoring provides an optimal picture of daily AF burden, both symptomatic and asymptomatic. Implantable cardiac monitors have high sensitivity, enable better assessment of therapy success and may guide further AF therapy.

The pharmaceutical pipeline for atrial fibrillation

Atrial fibrillation (AF) is associated with a significant burden of morbidity and increased risk of mortality. Beyond outstanding advances in catheter ablation procedures, antiarrhythmic drug therapy remains a corner-stone to restore and maintain sinus rhythm. However, potentially life-threatening hazards (proarrhythmia) and significant non-cardiac organ toxicity have made new drug development of prominent relevance. Multichannel blocking, atrial selectivity, and the reduction of the risk of adverse events have all constituted the main theme of modern antifibrillatory drug development. Dronedarone, an analog of amiodarone, has the unique characteristic of being the first antiarrhythmic drug demonstrated to reduce hospitalizations in AF. Dronedarone is associated with less systemic toxicity than amiodarone, although being less effective for sinus rhythm maintenance. Atrial selective agents have been developed to target ion channels expressed selectively in the atria. Among the most promising drugs of this class is vernakalant, which has been shown effective for the acute conversion of AF with small risk of proarrhythmia. Finally, increasing evidences support antiarrhythmic effectiveness of traditional non-antiarrhythmic drugs, such as renin-angiotensin system blockers, statins, and omega-3 fatty acids. In this article, we will focus on recent advances in antiarrhythmic therapy for AF, reviewing the possible clinical utility of novel antifibrillatory agents.

New pharmacological targets and treatments for atrial fibrillation

Atrial fibrillation (AF) is an arrhythmia of growing clinical concern that is increasing in prevalence and is associated with significant morbidity and mortality. Pharmacological agents remain the first-line therapy for the AF patient, and the potential advantages of sinus rhythm maintenance motivate continued efforts to identify novel pharmacological means to restore and maintain sinus rhythm. Traditional antiarrhythmic agents only moderately suppress AF and present problematic concerns of proarrhythmia and extracardiac toxicity. Current investigational or recently approved strategies for improving efficacy and safety of anti-AF agents include (i) specific or predominant blockade of atrial ion channels; (ii) "upstream therapies" affecting non-ion channel targets that influence electrical and structural remodeling, inflammation and oxidative stress; (iii) amiodarone derivatives with an improved safety profile; (iv) intracellular calcium handling; and (v) therapies aiming at alleviating conduction disturbances (gap junction coupling enhancers). This review provides a succinct overview of some of these strategies.

Drug therapy in atrial fibrillation management: where do we stand in 2010?

Atrial fibrillation (AF) is a commonly encountered arrhythmia in our daily practice. Every year a huge bulk of data is published about different management strategies, new antiarrhythmic drugs, anticoagulation protocols and ablation procedures in these patients. In this review article, we discuss different management strategies and new antiarrhythmic drugs as well as those commonly used. We will also have a brief look at anticoagulation in AF.We try to introduce the most recent publications in this field and we think that this review article may not only give information about the current state of antiarrhythmic therapy of AF, it may also show some progresses that we may anticipate in the near future. New drugs are promising in the management of AF because of better safety profile and also acceptable efficacy. A comparison between the catheter ablation procedure and antiarrhythmic therapy is beyond the scope of this article.