A Study to Evaluate the Safety and Efficacy of AC01 Compared to Placebo in Participants With Chronic Heart Failure

Key Inclusion Criteria: * History of Chronic Heart Failure (CHF) diagnosed greater than or equal to (\>=6) months before screening, and in NYHA Class II to IV at screening. * Chronic advanced HFrEF defined as: * LVEF less than or equal to (\<=) 35 percentage (%) by local reading \>=6 months before screening or a record of LVEF qualitatively described as severely reduced or moderately-severely reduced \>=6 months before screening, and * LVEF \<=35% at the screening echocardiography (confirmed by core lab), and * no known LVEF greater than (\>) 35% (or qualitatively described as less than moderately-severely reduced) between the 2 readings. * Sinus rhythm or permanent, persistent, or paroxysmal atrial fibrillation flutter (AFF) (AFF at screening is capped at maximum 15% of participants enrolled) with mean resting heart rate of \>=55 and \<=90 beats per minute (bpm) at screening, and \>=50 and \<=95 bpm at randomization, regardless of rhythm. * NT-proBNP \>=400 picograms per milliliter (pg/mL) in sinus rhythm and \>=800 pg/mL in AFF at screening (confirmed by central laboratory). * Transvenous implantable cardioverter-defibrillator (ICD) for primary prevention with back-up pacing set at 40 bpm. * Treated with optimal, stable, medical therapy for HF consistent with prevailing local and international guidelines unless contraindicated or not tolerated, as judged and documented by the investigator. Key Exclusion Criteria: * Any acute or serious co-morbid condition that cou…