Evaluate Efficacy, Safety and Tolerability of JTT-861 in Subjects With Heart Failure With Reduced Ejection Fraction

Inclusion Criteria:

• Has a clinical diagnosis of symptomatic heart failure (HF) ≥90 days prior to theScreening Visit;

• Is in New York Heart Association (NYHA) functional class II or III at the ScreeningVisit;

• Is on stable, guideline-directed therapy for HF, consistent with American HeartAssociation (AHA), American College of Cardiology (ACC), Heart Failure Society ofAmerica (HFSA) or European Society of Cardiology (ESC) guidelines for ≥4 weeks priorto the Screening Visit (with at least half of maximal labeled dose ofrenin-angiotensin-aldosterone system (RAAS) inhibitors and β-blockers, iftolerated);

• Has left ventricular ejection fraction (LVEF) ≤35% at the Screening Visit;

• Has a serum N-terminal pro b-type natriuretic peptide (NT-pro-BNP) level ≥600 pg/mL (or ≥900 pg/mL if the subject has atrial fibrillation or atrial flutter) at theScreening Visit.

Exclusion Criteria:

• Has a confirmed acute myocardial infarction (MI) (i.e., Type 1) or unstable anginawithin 90 days prior to the Screening Visit;

• Has a history of coronary revascularization (percutaneous coronary intervention [PCI] and/or coronary artery bypass graft [CABG]) or other cardiovascular surgerywithin 90 days prior to the Screening Visit or planned cardiovascular surgery duringthe study through the Follow-up Visit);

• Has started cardiac resynchronization therapy (CRT) within 90 days prior to theScreening Visit or has planned CRT during the study through the Follow-up Visit;

• Has clinically significant congenital heart disease, active myocarditis orconstrictive pericarditis;

• Has current acute decompensated HF requiring additional treatment with diuretics,vasodilators and/or inotropic medications at the Screening Visit;

• Has clinically significant chronic renal insufficiency (i.e., estimated glomerularfiltration rate [eGFR] <30 mL/min/1.73 m2 calculated by the Chronic Kidney DiseaseEpidemiology Collaboration [CKD-EPI] creatinine equation) at the Screening Visit.