ARCA biopharma, Inc. announced that the paper entitled “Bucindolol [Gencaro] Decreases AF Burden” (Jonathan Piccini, et al), which details a new analysis of the Gencaro Phase 2b data on atrial fibrillation (AF) burden and rhythm control interventions has been published in Circulation: Arrhythmia and Electrophysiology, a journal of the American Heart Association. In the Phase 2b superiority clinical trial, although the prespecified primary endpoint was not met, compared with metoprolol, Gencaro reduced AF burden, increased maintenance of sinus rhythm, and reduced the need for additional rhythm control interventions in patients with heart failure (HF) and the genotype which responds most favorably to Gencaro. In the trial, the prevalence of electrocardiograms (ECGs) in normal sinus rhythm, AF interventions for rhythm control (electrical cardioversion, catheter ablation and Class III antiarrhythmic drugs), and biomarkers were evaluated in the overall population entering efficacy follow-up (N=257). AF burden was evaluated for 24 weeks in a device substudy (N=67) in which all patients had continuous monitoring of cardiac rhythm by implanted devices. In 257 patients with HF, the mean age was 65.6 ± 10.0 years, 18% were female, mean left ventricular ejection fraction (LVEF) was 36%, and 51% had persistent AF. Cumulative 24-week AF burden was 24.4% (95% CI: 18.5, 30.2) for bucindolol and 36.7% (95% CI: 30.0, 43.5) for metoprolol (36% reduction, p =0.002). Daily AF burden at the end of follow-up was 15.1% (95% CI: 3.2, 27.0) for bucindolol and 34.7% (95% CI: 17.9, 51.2) for metoprolol (55% reduction, p < 0.001). The prevalence of ECGs in normal sinus rhythm was 4.20 and 3.03 events per patient for the bucindolol and metoprolol groups, respectively (39% increase, p < 0.001); whereas the rate of AF rhythm control interventions was 0.56 and 0.82 events per patient for the bucindolol and metoprolol groups, respectively (32% reduction, p = 0.011). Reductions in plasma norepinephrine (p = 0.038) and NT-proBNP (p = 0.009) were observed with bucindolol compared to metoprolol. An additional analysis of these new data confined to patients with ejection fractions of 40% and above showed novel evidence of a clinically significant potential treatment effect for Gencaro in preventing and treating atrial fibrillation in these patients. Patients with this classification of heart failure, known as mildly reduced (HFmrEF) blending into preserved left ventricular ejection fraction (HFpEF) HF, have few approved or effective drug therapies. This novel result provided the basis for a new patent issued to ARCA by the United States Patent and Trademark Office (USPTO) in February 2021 for use of Gencaro in treating AF in the HF population that ARCA plans to enroll in Gencaro’s planned Phase 3 development, a population that includes more than half of all HF patients in the United States and Europe. The Company believes this patent would provide effective patent coverage in the United States into 2039. ARCA has filed similar patent applications in other countries.