Pulmonary Delivery of Antiarrhythmic Drugs for Rapid Conversion of New-Onset Atrial Fibrillation

Flecainide acetate inhalation solution for cardioversion of recent-onset, symptomatic atrial fibrillation: results of the phase 3 RESTORE-1 trial

AIMS

Atrial fibrillation (AF) is the most prevalent cardiac arrhythmia. New treatments are needed to cardiovert recent-onset paroxysmal AF quickly and safely. RESTORE-1 was a multicentre, randomized, double-blind, placebo-controlled trial of a 120 mg orally inhaled solution of flecainide acetate (FlecIH-103) for cardioversion of symptomatic, recent-onset (≤48 h) paroxysmal AF. The study aim was to evaluate the efficacy and safety of FlecIH-103 administered via oral inhalation.

METHODS AND RESULTS

Patients experiencing a recent-onset paroxysmal AF episode were randomized to receive a single dose of FlecIH-103 or placebo delivered over two 3.5 min inhalation periods, while patients were monitored using 12-lead electrocardiograms and Holter. The trial was stopped prematurely after treating 55 patients, due to lower-than-expected conversion rates and plasma levels. Mean age was 59.6 years, 31.5% of patients were female, and 59.2% were having their first AF episode. Conversion rate was 30.8% (95% confidence interval: 14.7-43.8) for the active group (n = 39) and 0.0% for the placebo group (n = 12) (P = 0.04). Median time to conversion was 12.8 min (IQR: 17.2). In the active group, the mean flecainide plasma level was 198 ng/mL (SD: 156), which is ∼50% lower than in the previous studies. The most common adverse events (AEs) were dysgeusia, dyspnoea, and cough. All AEs were short-lasting and of mild or moderate intensity.

CONCLUSION

Despite early termination of the trial, FlecIH-103 was significantly more effective than placebo in cardioverting AF. Safety data did not show any serious AEs. Further studies of FlecIH-103 are needed to optimize the combination of drug formulation and inhalation delivery platform.

CLINICAL TRIAL REGISTRATION

URL: https://clinicaltrials.gov, unique identifier: NCT05039359.

Mechanisms of Chemical Atrial Defibrillation by Flecainide and Ibutilide

BACKGROUND

Effective and safe pharmacological approaches for atrial defibrillation offer several potential advantages over techniques like ablation. Pharmacological therapy is noninvasive, involving no risk associated with the procedure or resulting complications. Moreover, acute drug intervention with existing drugs is likely to be low cost and broadly accessible, thereby addressing a central tenet of health equity.

OBJECTIVES

This study aims to investigate ibutilide-mediated action potential prolongation to promote use-dependent effects of flecainide on Na+ channels by reducing the diastolic interval and, consequently, drug unbinding to reduce action potential excitability in atrial tissue and terminate re-entrant arrhythmia.

METHODS

The authors utilize a modeling and simulation approach to predict the specific combinations of sodium- and potassium-channel blocking drugs to chemically terminate atrial re-entry.

RESULTS

Computational modeling and simulation show that acute application of flecainide and ibutilide is a promising example of drug repurposing that may constitute a promising combination for chemical atrial defibrillation.

CONCLUSIONS

We predict the drug concentrations that promote efficacy of flecainide and ibutilide used in combination for atrial chemical defibrillation. We also predict the potential safety pharmacology impact of this drug combination on ventricular electrophysiology.

Orally Inhaled Flecainide for Conversion of Atrial Fibrillation to Sinus Rhythm: INSTANT Phase 2 Trial

BACKGROUND

INSTANT (INhalation of flecainide to convert recent-onset SympTomatic Atrial fibrillatioN to sinus rhyThm) was a multicenter, open-label, single-arm study of flecainide acetate oral inhalation solution (FlecIH) for acute conversion of recent-onset (≤48 hours) symptomatic atrial fibrillation (AF) to sinus rhythm.

OBJECTIVES

This study investigated the efficacy and safety in 98 patients receiving a single dose of FlecIH delivered via oral inhalation.

METHODS

Patients self-administered FlecIH over 8 minutes in a supervised medical setting using a breath-actuated nebulizer and were continuously monitored for 90 minutes using a 12-lead Holter.

RESULTS

Mean age was 60.5 years, mean body mass index was 27.0 kg/m2, and 34.7% of the patients were women. All patients had ≥1 AF-related symptoms at baseline, and 87.8% had AF symptoms for ≤24 hours. The conversion rate was 42.6% (95% CI: 33.0%-52.6%) with a median time to conversion of 14.6 minutes. The conversion rate was 46.9% (95% CI: 36.4%-57.7%) in a subpopulation that excluded predose flecainide exposure for the current AF episode. Median time to discharge among patients who converted was 2.5 hours, and only 2 patients had experienced AF recurrence by day 5. In the conversion-no group, 44 (81.5%) patients underwent electrical cardioversion by day 5. The most common adverse events were related to oral inhalation of flecainide (eg, cough, oropharyngeal irritation/pain), which were mostly of mild intensity and limited duration.

CONCLUSIONS

The risk-benefit of orally inhaled FlecIH for acute cardioversion of recent-onset AF appears favorable. FlecIH could provide a safe, effective, and convenient first-line therapeutic option. (INhalation of Flecainide to Convert Recent Onset SympTomatic Atrial Fibrillation to siNus rhyThm [INSTANT]; NCT03539302).

Anti-arrhythmic drugs in atrial fibrillation: tailor-made treatments

During the last decades, many improvements have been made regarding the treatment of atrial fibrillation in terms of risk prevention, anti-coagulation strategies, and gain in quality of life. Among those, anti-arrhythmic drugs (AADs) have progressively fallen behind and overtaken by technological aspects as devices as procedures are now the standards of care for many patients. But is this it? Are AADs doomed to be relegated to an obscure and rarely read paragraph of the European recommendations? Or could they be still employed safely and effectively? In the present paper, we will discuss contemporary evidence in order to define where AADs still play a pivotal role, how should AADs be used, and whether a tailored approach can be the way to propose the right treatment to the right patient.

Novel Pulmonary Delivery of Drugs for the Management of Atrial Fibrillation

Atrial fibrillation (AF) is the most prevalent cardiac arrhythmia, affecting approximately 335 million patients worldwide. Comprehensive pharmacological treatment of AF includes medications for rate or rhythm control and anticoagulants to reduce the risk of thromboembolism; yet, these agents have significant limitations. Oral anti-arrhythmic agents have a slow onset of action, and rapid onset formulations require hospitalization for intravenous therapy. Orally administered drugs also require high doses to attain therapeutic levels, and thus dose-related severe adverse effects are often unavoidable. Given the therapeutic benefits of inhaled drug delivery, including rapid onset of action and very low doses to achieve therapeutic efficacy, this review will discuss the benefits of novel pulmonary delivery of drugs for the management of AF.

Open-Label, Multicenter Study of Flecainide Acetate Oral Inhalation Solution for Acute Conversion of Recent-Onset, Symptomatic Atrial Fibrillation to Sinus Rhythm

BACKGROUND

Oral and intravenous flecainide is recommended for cardioversion of atrial fibrillation. In this open-label, dose-escalation study, the feasibility of delivering flecainide via oral inhalation (flecainide acetate inhalation solution) for acute conversion was evaluated. We hypothesized that flecainide delivered by oral inhalation would quickly reach plasma concentrations sufficient to restore sinus rhythm in patients with recent-onset atrial fibrillation.

METHODS

Patients (n=101) with symptomatic atrial fibrillation (for ≤48 hours) self administered flecainide acetate inhalation solution using a nebulizer (30 mg [n=10], 60 mg [n=22], 90 mg [n=21], 120 mg [n=19], and 120 mg in a formulation containing saccharin [n=29]). Electrocardiograms and flecainide plasma concentrations were obtained, cardiac rhythm using 4-hour Holter was monitored, and adverse events were recorded.

RESULTS

Conversion rates increased with dose and with the maximum plasma concentrations of flecainide. At the highest dose, 48% of patients converted to sinus rhythm within 90 minutes from the start of inhalation. Among patients who achieved a maximum plasma concentration >200 ng/mL, the conversion rate within 90 minutes was 50%; for those who achieved a maximum plasma concentration <200 ng/mL, it was 24%. Conversion was rapid (median time to conversion of 8.1 minutes from the end of inhalation), and conversion led to symptom resolution in 86% of the responders. Adverse events were typically mild and transient and included: cough, throat pain, throat irritation; at the highest dose with the formulation containing saccharin, these adverse events were reported by 41%, 14%, and 3% of patients, respectively. Cardiac adverse events consistent with those observed with oral and intravenous flecainide were uncommon and included postconversion pauses (n=2), bradycardia (n=1), and atrial flutter with 1:1 atrioventricular conduction (n=1); none required treatment, and all resolved without sequelae.

CONCLUSIONS

Administration of flecainide via oral inhalation was shown to be safe and to yield plasma concentrations of flecainide sufficient to restore sinus rhythm in patients with recent-onset atrial fibrillation.

REGISTRATION

URL: https://www.

CLINICALTRIALS

gov; Unique identifier: NCT03539302.

Antiarrhythmic drugs for atrial fibrillation: lessons from the past and opportunities for the future

Atrial fibrillation (AF) remains a highly prevalent and troublesome cardiac arrhythmia, associated with substantial morbidity and mortality. Restoration and maintenance of sinus rhythm (rhythm-control therapy) is an important element of AF management in symptomatic patients. Despite significant advances and increasing importance of catheter ablation, antiarrhythmic drugs (AADs) remain a cornerstone of rhythm-control therapy. During the past 50 years, experimental and clinical research has greatly increased our understanding of AADs. As part of the special issue on paradigm shifts in AF, this review summarizes important milestones in AAD research that have shaped their current role in AF management, including (i) awareness of the proarrhythmic potential of AADs; (ii) increasing understanding of the pleiotropic effects of AADs; (iii) the development of dronedarone; and (iv) the search for AF-specific AADs. Finally, we discuss short- and long-term opportunities for better AF management through advances in AAD therapy, including personalization of AAD therapy based on individual AF mechanisms.

Investigational Anti-Atrial Fibrillation Pharmacology and Mechanisms by Which Antiarrhythmics Terminate the Arrhythmia: Where Are We in 2020?

Antiarrhythmic drugs remain the mainstay therapy for patients with atrial fibrillation (AF). A major disadvantage of the currently available anti-AF agents is the risk of induction of ventricular proarrhythmias. Aiming to reduce this risk, several atrial-specific or -selective ion channel block approaches have been introduced for AF suppression, but only the atrial-selective inhibition of the sodium channel has been demonstrated to be valid in both experimental and clinical studies. Among the other pharmacological anti-AF approaches, “upstream therapy” has been prominent but largely disappointing, and pulmonary delivery of anti-AF drugs seems to be promising. Major contradictions exist in the literature about the electrophysiological mechanisms of AF (ie, reentry or focal?) and the mechanisms by which anti-AF drugs terminate AF, making the search for novel anti-AF approaches largely empirical. Drug-induced termination of AF may or may not be associated with prolongation of the atrial effective refractory period. Anti-AF drug research has been largely based on the “suppress reentry” ideology; however, results of the AF mapping studies increasingly indicate that nonreentrant mechanism(s) plays an important role in the maintenance of AF. Also, the analysis of anti-AF drug-induced electrophysiological alterations during AF, conducted in the current study, leans toward the focal source as the prime mechanism of AF maintenance. More effort should be placed on the investigation of pharmacological suppression of the focal mechanisms.

Mechanisms of flecainide induced negative inotropy: An in silico study

It is imperative to develop better approaches to predict how antiarrhythmic drugs with multiple interactions and targets may alter the overall electrical and/or mechanical function of the heart. Safety Pharmacology studies have provided new insights into the multi-target effects of many different classes of drugs and have been aided by the addition of robust new in vitro and in silico technology. The primary focus of Safety Pharmacology studies has been to determine the risk profile of drugs and drug candidates by assessing their effects on repolarization of the cardiac action potential. However, for decades experimental and clinical studies have described substantial and potentially detrimental effects of Na⁺ channel blockers in addition to their well-known conduction slowing effects. One such side effect, associated with administration of some Na⁺ channel blocking drugs is negative inotropy. This reduces the pumping function of the heart, thereby resulting in hypotension. Flecainide is a well-known example of a Na⁺ channel blocking drug, that exhibits strong rate-dependent block of I_Na and may cause negative cardiac inotropy. While the phenomenon of Na⁺ channel suppression and resulting negative inotropy is well described, the mechanism(s) underlying this effect are not. Here, we set out to use a modeling and simulation approach to reveal plausible mechanisms that could explain the negative inotropic effect of flecainide. We utilized the Grandi-Bers model [1] of the cardiac ventricular myocyte because of its robust descriptions of ion homeostasis in order to characterize and resolve the relative effects of QRS widening, flecainide off-target effects and changes in intracellular Ca²⁺ and Na⁺ homeostasis. The results of our investigations and predictions reconcile multiple data sets and illustrate how multiple mechanisms may play a contributing role in the flecainide induced negative cardiac inotropic effect.

Flecainide-induced QRS complex widening correlates with negative inotropy

BACKGROUND

The negative inotropic effect of Class IC antiarrhythmic drugs limits their use for acute cardioversion of atrial fibrillation (AF).

OBJECTIVE

The purpose of this study was to examine, in an intact porcine model, the effects of pulmonary and intravenous (IV) administration of flecainide on left ventricular (LV) contractility and QRS complex width at doses that are effective in converting new-onset AF to sinus rhythm.

METHODS

Flecainide (1.5 mg/kg bolus) was delivered by intratracheal administration and compared to 2.0 mg/kg 10-minute IV administration (European Society of Cardiology guideline) and to 0.5 and 1.0 mg/kg 2-minute IV doses in 40 closed-chest, anesthetized Yorkshire pigs. Catheters were fluoroscopically positioned in the LV to monitor QRS complex width and contractility and at the bifurcation of the main bronchi to deliver intratracheal flecainide.

RESULTS

Peak flecainide plasma concentrations (C_max) were similar, but the 30-minute area under the curve (AUC) of plasma levels was 1.4- to 2.8-fold greater for 2.0 mg/kg 10-minute IV infusion than for the lower, more rapidly delivered intratracheal and IV doses. AUC for LV contractility (ie, negative inotropic burden) was 2.2- to 3.6-fold greater for 2.0 mg/kg 10-minute IV dose than for the lower, more rapidly delivered doses. QRS complex widening by flecainide was highly correlated with the decrease in LV contractility (r² = 0.890, P <.0001, for all IV doses; r² = 0.812, P = .01, for intratracheal flecainide).

CONCLUSION

QRS complex widening in response to flecainide is strongly correlated with decrease in LV contractility. Rapid pulmonary or IV flecainide delivery reduces the negative inotropic burden while quickly achieving C_max levels associated with conversion of AF.

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.