NEWS & ANALYSIS FRESH FROM THE PIPELINE Vernakalant Dobromir Dobrev, Bashar Hamad and Peter Kirkpatrick In September 2010, vernakalant Basis of discovery of patients receiving vernakalant compared (Brinavess; Cardiome/Merck) was Many drugs used for the treatment of with 3 out of 84 (3.6%) of patients receiving granted marketing authorization AF affect ion channels in both atrial and placebo in the ACT III study6. Conversion by the European Commission for the ventricular tissue, and this lack of selectivity of AF to sinus rhythm occurred rapidly (the rapid conversion of recent-onset means that they are associated with a risk of median time to conversion in responders atrial fibrillation to sinus rhythm. ventricular pro-arrhythmias1. Vernakalant was 10 minutes from the start of the first was discovered through a search for infusion) and sinus rhythm was maintained Atrial fibrillation (AF) is the most common atrial-selective agents in a canine model over 24 hours (97%)6. Vernakalant provided cardiac arrhythmia, affecting millions of AF1,3. relief of the symptoms of AF consistent with of people worldwide, and its prevalence conversion to sinus rhythm6. is expected to increase owing to factors Drug properties No significant differences in safety such as the growing aged population1. Vernakalant (FIG. 1) is an anti-arrhythmic or effectiveness were observed based on Its effects range from symptoms such as agent that affects cardiac Na+ and K+ currents, age, gender, use of rate-control drugs, breathlessness and chest pain to potentially including the atrial-selective currents IKur use of anti-arrhythmic drugs, use of the 1,2 (REFS 4–6) fatal complications such as stroke . and IK,ACh . In animal models of AF anticoagulant warfarin, history of ischaemic To reduce the risk of stroke, and in initial clinical studies, vernakalant heart disease or renal impairment6. patients with AF are often treated with significantly prolonged the atrial refractory Assessment of the conversion of AF in anticoagulants and with drugs that period without significantly affecting patients with longer-duration AF in a total control heart rate, such as β-adrenoceptor ventricular refractoriness4–6. of 185 patients did not show statistically antagonists1,2. Restoration and maintenance significant differences between vernakalant of sinus rhythm is also a major approach Clinical data and placebo6. for the management of AF1,2. However, The efficacy and safety of vernakalant for The ACT II trial investigated the effect of established drugs for achieving this goal the treatment of patients with AF has been vernakalant in 150 patients with sustained are limited by either modest efficacy and/ assessed in three randomized, double-blind, AF (3–72 hours duration) that occurred or side effects, such as life-threatening placebo-controlled studies (known as between 24 hours and 7 days after coronary ventricular pro-arrhythmias or severe ACT I, ACT II and ACT III) and in an artery bypass graft and/or valvular surgery6,8. extracardiac toxicities1,2. For example, active comparator trial versus intravenous The primary end point was the conversion amiodarone, which is generally amiodarone (known as AVRO)6–8. In all of to sinus rhythm within 90 minutes of dosing, considered to be the most effective drug these studies, vernakalant was administered which was achieved in 47 out of 100 (47%) for the treatment of AF and has low by a 10 minute intravenous infusion at a patients who received vernakalant compared pro-arrhythmic potential, is associated dose of 3 mg per kg followed by a second with 7 out of 50 (14%) patients who received with serious systemic side effects1. In 10 minute infusion at a dose of 2 mg per placebo6,8. The median time to conversion 2009, a derivative of amiodarone that was kg 15 minutes later if AF had not been was 12 minutes from the start of treatment developed with the aim of overcoming terminated6–8. infusion6. these limitations, dronedarone (Multaq; The ACT I and ACT III trials investigated In the AVRO trial, vernakalant was Sanofi–Aventis), was approved for AF, vernakalant in the treatment of patients with compared with intravenous amiodarone although it might not be as effective as sustained AF (duration >3 hours, but not (administered over 2 hours) in 116 patients amiodarone in maintaining sinus rhythm1,2. more than 45 days)6,7. The primary end point with recent-onset AF (3–48 hours)6. The in both trials was the proportion of patients primary end point was the proportion with short-duration AF (3 hours to 7 days) of patients who achieved sinus rhythm who had treatment-induced conversion of at 90 minutes after initiating treatment6. OH AF to sinus rhythm (cardioversion) for at Treatment with vernakalant converted 51.7% least 1 minute within 90 minutes of treatment of patients to sinus rhythm at 90 minutes N infusion6,7. A secondary efficacy end point compared with 5.2% of patients treated with O O was conversion of AF in patients with amiodarone6. longer-duration AF (>7 days and ≤45 days)6,7. O Treatment with vernakalant effectively Indications Vernakalant (RSD1235) converted AF to sinus rhythm compared Vernakalant is approved by the European with placebo6,7. The primary end point was Commission for the rapid conversion of (3R)-1-{(1R,2R)-2-[2-(3,4-dimethoxy- phenyl)ethoxy]cyclohexyl}pyrrolidin-3-ol; met in 74 out of 145 (51.0%) of patients recent-onset AF (≤7 days duration for C20H31NO4; Mr = 349.5 receiving vernakalant compared with 3 out of non-surgery patients, and ≤3 days duration 75 (4.0%) of patients receiving placebo in the for post-cardiac surgery patients) to sinus Figure 1 | Structure of vernakalant. ACT I study6,7, and in 44 out of 86 (51.2%) rhythm in adults6. ▶ Nature Reviews | Drug Discovery NATURE REVIEWS | DRUG DISCOVERY VOLUME 9 | DECEMBER 2010 | 915 © 2010 Macmillan Publishers Limited. All rights reserved NEWS & ANALYSIS ANALYSIS | ATRIAL FIBRILLATION ▶ Analysing clinical issues in the treatment of Vernakalant is the first atrial-selective has a substantially lower AF conversion rate AF is Dobromir Dobrev, M.D., Professor and drug to reach the market. Atrial-selectivity in congestive heart failure (26.9%) than in 6–8 Chair, Division of Experimental Cardiology, of vernakalant is achieved by inhibiting IK,ACh haemodynamically stable patients (54.1%) , Medical Faculty Mannheim, University of and IKur and by exploiting state-selective suggesting that vernakalant is safe but less Heidelberg, Germany. rapidly unbinding Na+ channel-inhibitory effective in patients with structural heart properties that produce stronger effects disease. Vernakalant was also not found to Current pharmacotherapy for AF has major on atrial than ventricular action potentials, be effective in converting typical primary limitations, including moderate efficacy especially during rapid rhythms like AF. atrial flutter to sinus rhythm6, and so cannot and unpredictable risks of life-threatening Consequently, vernakalant is associated with replace established drugs used for the acute pro-arrhythmia with anti-arrhythmic a low pro-arrhythmic risk for ventricular termination of atrial flutter, such as ibutilide drugs, and bleeding complications with tachyarrhythmias. Owing to its very short and dofetilide. Finally, the clinical value of anticoagulants1. Non-pharmacological half-life, vernakalant has primarily been used vernakalant for prevention of AF recurrence (ablation) approaches have improved, but still intravenously for termination of recent-onset requires further large-scale trials with suitable have safety and efficacy limitations, and are AF, but a longer-acting slow-release oral AF patient populations. not applicable for a substantial proportion formulation is in clinical trials. Overall, given the atrial selectivity and of the AF patient population. The efficacy of vernakalant for acute AF different safety profile of vernakalant, These considerations and the growing termination seems comparable with other it provides an important addition to the importance of AF as a clinical problem have available compounds9, although comparative options for anti-arrhythmic pharmacotherapy, fostered efforts to develop anti-arrhythmic studies have not been conducted. Although with the potential to change the algorithm drugs with improved efficacy and safety the AVRO trial compared intravenous for acute AF cardioversion. profiles, focusing on favourable multichannel- vernakalant with amiodarone in recent-onset Dobromir Dobrev is at the Division of Experimental 6 blocking profiles, atrial-specific currents AF , amiodarone is less suitable for acute AF Cardiology, University of Heidelberg, 10 Theodor-Kutzer-Ufer 1–3, 68167 Mannheim, Germany. such as IK,ACh and IKur, and atrial-selective cardioversion because of its slow (up to Na+-channel blockade. Molecular modification 24 hour) onset of action, and thus is not the Bashar Hamad is at IMS Health, 7 Harewood Avenue, of the highly effective multichannel-blocker most appropriate comparator when assessing London NW1 6JB, UK. amiodarone to improve safety and tolerability the short-term (90 minutes) success rate of Peter Kirkpatrick is at Nature Reviews Drug Discovery. led to dronedarone, which is the first anti- pharmacological cardioversion. Head-to- e-mails: [email protected]; arrhythmic drug that reduces cardiovascular head trials with intravenous flecainide [email protected]; [email protected] mortality and hospitalization of patients with (not available in North America) are needed doi:10.1038/nrd3323 2 AF . However, dronedarone was approved for to validate the superiority of vernakalant 1. Dobrev, D. & Nattel, S. New antiarrhythmic drugs for treatment of atrial fibrillation. Lancet 375, 1212–1223 the suppression of AF, but not for the reduction for acute AF cardioversion in the different (2010). of cardiovascular mortality in patients with AF. patient populations. Of note, vernakalant 2. Page, R. L. et al. Dronedarone. Nature Rev. Drug Discov. 8, 769–770 (2009). 3. Nattel, S. et al. RSD1235: a novel antiarrhythmic agent with a unique electrophysiological profile that terminates AF in dogs. Eur. Heart. J. 22, S448 (2001).