PRECISION-AF is designed as a single, adequate and well-controlled Phase 3 clinical trial that may be sufficient to support an New Drug Application (NDA) submission for an AF indication if the objectives of the trial are achieved. The trial is designed as a double-blind, active-controlled, multi-center, international study comparing Gencaro with Toprol-XL (metoprolol succinate) for the prevention of AF recurrence or all-cause mortality (ACM) in HF patients with mid-range ejection fraction (HFmrEF). HFmrEF is defined as HF with a left ventricular ejection fraction (LVEF) ≥ 40% and < 50%, which constituted approximately half of the enrolled population in the Phase 2 GENETIC-AF trial. PRECISION-AF will enroll approximately 400 patients who have: HFmrEF, a recent AF event, and the genotype which responds most favorably to Gencaro. The primary endpoint of the trial will be time to first event of atrial fibrillation/atrial flutter (AF/AFL) or ACM during the 26-week Follow-up Period. In the recently completed GENETIC-AF trial, Gencaro showed a 58% treatment benefit compared to Toprol-XL in reducing AF recurrence in the HFmrEF population targeted for Phase 3 (hazard ratio = 0.42; 95% CI: 0.21, 0.86; p = 0.017). With 400 patients (200 per arm) the trial will have 90% power at a p-value of 0.01 to detect a 45% treatment benefit for Gencaro compared to Toprol-XL.