REN and heart failure: Inclusion: Receiving evidence-based therapy for HFrEF, serum potassium of ≤4.8 mEq/L, eGFR of 60 to <90 mL/min/1.73 m2 in part A or 30-60 mL/min/1.73 m2 in part B. Exclusion: Use of a renin inhibitor or an aldosterone antagonist 30 days before randomization, worsening heart failure requiring hospitalization, and IV diuretics within 30 days of screening visit (if not on an aldosterone antagonist) or 6 months before screening visit (if receiving an aldosterone antagonist immediately before the study).