Design and Rationale of a Phase 2 Study of NeurOtoxin (Botulinum Toxin Type A) for the PreVention of Post-Operative Atrial Fibrillation - The NOVA Study

Efficacy and Safety of Botulinum Toxin Type A for the Prevention of Postoperative Atrial Fibrillation

BACKGROUND

Postoperative atrial fibrillation (POAF) is associated with increased morbidity and mortality. Epicardial injection of botulinum toxin may suppress POAF.

OBJECTIVES

This study sought to assess the safety and efficacy of AGN-151607 for the prevention of POAF after cardiac surgery.

METHODS

This phase 2, randomized, placebo-controlled trial assessed the safety and efficacy of AGN-151607, 125 U and 250 U vs placebo (1:1:1), for the prevention of POAF after cardiac surgery. Randomization was stratified by age (<65, ≥65 years) and type of surgery (nonvalvular/valve surgery). The primary endpoint was the occurrence of continuous AF ≥30 seconds.

RESULTS

Among 312 modified intention-to-treat participants (placebo, n = 102; 125 U, n = 104; and 250 U, n = 106), the mean age was 66.9 ± 6.8 years; 17% were female; and 64% had coronary artery bypass graft (CABG) only, 12% had CABG + valve, and 24% had valve surgery. The primary endpoint occurred in 46.1% of the placebo group, 36.5% of the 125-U group (relative risk [RR] vs placebo: 0.80; 95% CI: 0.58-1.10; P = 0.16), and 47.2% of the 250-U group (RR vs placebo: 1.04; 95% CI: 0.79-1.37; P = 0.78). The primary endpoint was reduced in the 125-U group in those ≥65 years of age (RR: 0.64; 95% CI: 0.43-0.94; P = 0.02) with a greater reduction in CABG-only participants ≥65 years of age (RR: 0.49; 95% CI: 0.27-0.87; P = 0.01). Rehospitalization and rates of adverse events were similar across the 3 groups.

CONCLUSIONS

There were no significant differences in the rate of POAF with either dose compared with placebo; however, there was a lower rate of POAF in participants ≥65 years undergoing CABG only and receiving 125 U of AGN-151607. These hypothesis-generating findings require investigation in a larger, adequately powered randomized clinical trial. (Botulinum Toxin Type A [AGN-151607] for the Prevention of Post-operative Atrial Fibrillation in Adult Participants Undergoing Open-chest Cardiac Surgery [NOVA]; NCT03779841); A Phase 2, Multi-Center, Randomized, Double-Blind, Placebo-Controlled, Dose Ranging Study to Evaluate the Efficacy and Safety of Botulinum Toxin Type A [AGN 151607] Injections into the Epicardial Fat Pads to Prevent Post-Operative Atrial Fibrillation in Patients Undergoing Open-Chest Cardiac Surgery; 2017-004399-68).

Botulinum Toxin: A Potential Cardiovascular Agent?

Botulinum neurotoxin (BoNT) is a toxin with a wide repertoire of well-known applications in cosmetics and medicine, such as treating migraine headaches, spasticity, and achalasia, and it has generally been shown to be safe and well-tolerated. In addition to its current successes in clinical practice, studies have also demonstrated the potential of BoNT to be used as a therapeutic agent for many cardiovascular conditions. Prior investigations, as well as trials currently underway, have showcased the safety and potential efficacy of BoNT in applications such as treating ischemia-reperfusion injury, hypertension, atrial fibrillation, and heart failure. While further study in humans, as well as improved statistical power in efficacy studies, are needed before its prospective use as a treatment for the aforementioned conditions, one might consider BoNT a potential cardiovascular agent.

Recent Advances in Antiarrhythmic Drug Therapy

Cardiac arrhythmias remain a common cause of death and disability. Antiarrhythmic drugs (AADs) and antiarrhythmic agents remain a cornerstone of current cardiac arrhythmia management, despite moderate efficacy and the potential for significant adverse proarrhythmic effects. Due to conceptual, regulatory and financial considerations, the number of novel antiarrhythmic targets and agents in the development pipeline has decreased substantially during the last few decades. However, several promising candidates remain and there are exciting developments in repurposing and reformulating already existing drugs for indications related to cardiac arrhythmias. This review discusses the key conceptual considerations for the development of new antiarrhythmic agents, summarizes new compounds and formulations currently in clinical development for rhythm control of atrial fibrillation, and highlights the potential for drug repurposing. Finally, future directions in AAD development are discussed. Together with an ever-increasing understanding of the molecular mechanisms underlying cardiac arrhythmias, these components support a cautiously optimistic outlook towards improved pharmacological treatment opportunities for patients suffering from cardiac arrhythmias.

Pericardial Inflammatory Mediators That Can Drive Postoperative Atrial Fibrillation in Cardiac Surgery Patients

Postoperative atrial fibrillation (POAF) is a common dysrhythmia that affects a significant number of patients undergoing cardiac surgery. Many studies aim to better understand this complex postsurgical complication by analysing circulating biomarkers in patients who develop POAF. More recently, the pericardial space was shown to contain inflammatory mediators that could trigger POAF. In this review we summarise recent studies that examine the immune mediators present in the pericardial space and their potential implications for the pathophysiology of POAF in cardiac surgery patients. Ongoing research in this area should better delineate the multifactorial etiology of POAF, where specific markers may be targeted to reduce the incidence of POAF and improve outcomes for this patient population.

The pluripotential evolution and journey of Botox (onabotulinumtoxinA)

Clinical use of onabotulinumtoxinA evolved based on strategic, hypothesis-driven applications, as well as serendipitous observations by physicians and patients. The success of onabotulinumtoxinA in blepharospasm and strabismus led to its study in other head and neck dystonias, followed by limb dystonia, tremor, and spasticity. The aesthetic use of onabotulinumtoxinA followed initial reports from patients of improved facial lines after injections for facial dystonias and hemifacial spasm. Although patients with dystonias and spasticity regularly reported that their local pain improved after injections, onabotulinumtoxinA was not systematically explored for chronic migraine until patients began reporting headache improvements following aesthetic injections. Clinicians began assessing onabotulinumtoxinA for facial sweating and hyperhidrosis based on its inhibition of acetylcholine from sympathetic cholinergic nerves. Yet another line of research grew out of injections for laryngeal dystonia, whereby clinicians began to explore other sphincters in the gastrointestinal tract and eventually to treatment of pelvic sphincters; many of these sphincters are innervated by autonomic nerves. Additional investigations in other autonomically mediated conditions were conducted, including overactive bladder and neurogenic detrusor overactivity, achalasia, obesity, and postoperative atrial fibrillation. The study of onabotulinumtoxinA for depression also grew out of the cosmetic experience and the observation that relaxing facial muscle contractions associated with negative emotions may improve mood. For approved indications, the safety profile of onabotulinumtoxinA has been demonstrated in the formal development programs and post-marketing reports. Over time, evidence has accumulated suggesting clinical manifestations of systemic effects, albeit uncommon, particularly with high doses and in vulnerable populations. Although onabotulinumtoxinA is approved for approximately 26 indications across multiple local regions, there are 15 primary indication uses that have been approved in most regions, including the United States, Europe, South America, and Asia. This review describes many uses for which AbbVie has not sought and/or received regulatory approval and are mentioned for historical context only.

Botulinum neurotoxins: Future innovations

Botulinum neurotoxins (BoNTs) are multi-domain proteins whose potent and selective actions on nerve endings have led to innovations in both basic and clinical science. The various BoNT domains are responsible for binding to gangliosides and proteins associated with nerve cell membranes, internalization into the cell, and cleavage of one or more SNARE (soluble N-ethylmaleimide sensitive factor attachment protein receptor) proteins necessary for vesicle docking and fusion. Novel modifications to BoNT molecules, such as the creation of chimeras, helped identify the protein domains responsible for various aspects of BoNT action, such as localized effects. Other molecular modifications have been introduced in attempts to increase the specificity of BoNTs for autonomic or sensory neurons, with the ultimate goal of optimizing therapeutic selectivity. This research, in turn, has led to the development of BoNT-based proteins that can target non-SNARE substrates such as phosphatase and tensin homolog (PTEN). Still others are developing different BoNT serotypes, subtypes, or variants that are longer- or shorter-acting or have faster onset for various clinical purposes. New formulations of BoNTs that provide convenience for both patients and physicians are under investigation. Novel clinical uses are being evaluated for onabotulinumtoxinA, including in the prevention of post-operative atrial fibrillation. All these innovations capitalize on the unique properties of BoNTs, which continue to intrigue scientists and clinicians across numerous fields of study.

Atrial Fibrillation Occurring During Acute Hospitalization: A Scientific Statement From the American Heart Association

Acute atrial fibrillation is defined as atrial fibrillation detected in the setting of acute care or acute illness; atrial fibrillation may be detected or managed for the first time during acute hospitalization for another condition. Atrial fibrillation after cardiothoracic surgery is a distinct type of acute atrial fibrillation. Acute atrial fibrillation is associated with high risk of long-term atrial fibrillation recurrence, warranting clinical attention during acute hospitalization and over long-term follow-up. A framework of substrates and triggers can be useful for evaluating and managing acute atrial fibrillation. Acute management requires a multipronged approach with interdisciplinary care collaboration, tailoring treatments to the patient's underlying substrate and acute condition. Key components of acute management include identification and treatment of triggers, selection and implementation of rate/rhythm control, and management of anticoagulation. Acute rate or rhythm control strategy should be individualized with consideration of the patient's capacity to tolerate rapid rates or atrioventricular dyssynchrony, and the patient's ability to tolerate the risk of the therapeutic strategy. Given the high risks of atrial fibrillation recurrence in patients with acute atrial fibrillation, clinical follow-up and heart rhythm monitoring are warranted. Long-term management is guided by patient substrate, with implications for intensity of heart rhythm monitoring, anticoagulation, and considerations for rhythm management strategies. Overall management of acute atrial fibrillation addresses substrates and triggers. The 3As of acute management are acute triggers, atrial fibrillation rate/rhythm management, and anticoagulation. The 2As and 2Ms of long-term management include monitoring of heart rhythm and modification of lifestyle and risk factors, in addition to considerations for atrial fibrillation rate/rhythm management and anticoagulation. Several gaps in knowledge related to acute atrial fibrillation exist and warrant future research.

Cellular electrophysiological effects of botulinum toxin A on neonatal rat cardiomyocytes and on cardiomyocytes derived from human-induced pluripotent stem cells

Botulinum toxin A is a well-known neurotransmitter inhibitor with a wide range of applications in modern medicine. Recently, botulinum toxin A preparations have been used in clinical trials to suppress cardiac arrhythmias, especially in the postoperative period. Its antiarrhythmic action is associated with inhibition of the nervous system of the heart, but its direct effect on heart tissue remains unclear. Accordingly, we investigate the effect of botulinum toxin A on isolated cardiac cells and on layers of cardiac cells capable of conducting excitation. Cardiomyocytes of neonatal rat pups and human cardiomyocytes obtained through cell reprogramming were used. A patch-clamp study showed that botulinum toxin A inhibited fast sodium currents and L-type calcium currents in a dose-dependent manner, with no apparent effect on potassium currents. Optical mapping showed that in the presence of botulinum toxin A, the propagation of the excitation wave in the layer of cardiac cells slows down sharply, conduction at high concentrations becomes chaotic, but reentry waves do not form. The combination of botulinum toxin A with a preparation of chitosan showed a stronger inhibitory effect by an order of magnitude. Further, the inhibitory effect of botulinum toxin A is not permanent and disappears after 12 days of cell culture in a botulinum toxin A-free medium. The main conclusion of the work is that the antiarrhythmic effect of botulinum toxin A found in clinical studies is associated not only with depression of the nervous system but also with a direct effect on heart tissue. Moreover, the combination of botulinum toxin A and chitosan reduces the effective dose of botulinum toxin A.

Post-operative atrial fibrillation after cardiac surgery: Challenges throughout the patient journey

Atrial fibrillation (AF) is the most common complication of cardiac surgery, occurring in up to half of patients. Post-operative AF (POAF) refers to new-onset AF in a patient without a history of AF that occurs within the first 4 weeks after cardiac surgery. POAF is associated with short-term mortality and morbidity, but its long-term significance is unclear. This article reviews existing evidence and research challenges for the management of POAF in patients who have had cardiac surgery. Specific challenges are discussed in four phases of care. Pre-operatively, clinicians need to be able to identify high-risk patients, and initiate prophylaxis to prevent POAF. In hospital, when POAF is detected, clinicians need to manage symptoms, stabilize hemodynamics and prevent increases in length of stay. In the month after discharge, the focus is on minimizing symptoms and preventing readmission. Some patients require short term oral anticoagulation for stroke prevention. Over the long term (2-3  months after surgery and beyond), clinicians need to identify which patients with POAF have paroxysmal or persistent AF and can benefit from evidence-based therapies for AF, including long-term oral anticoagulation.

Neuromodulation therapy for atrial fibrillation

Atrial fibrillation has a multifactorial pathophysiology influenced by cardiac autonomic innervation. Both sympathetic and parasympathetic influences are profibrillatory. Innovative therapies targeting the neurocardiac axis include catheter ablation or pharmacologic suppression of ganglionated plexi, renal sympathetic denervation, low-level vagal stimulation, and stellate ganglion blockade. To date, these therapies have variable efficacy. As our understanding of atrial fibrillation and the cardiac nervous system expands, our approach to therapeutic neuromodulation will continue evolving for the benefit of those with AF.