Study to Assess the Safety, Tolerability and PK/PD After 4 Weekly SC Injections of PB1046 in Subjects With Stable HFrEF

Qualifying subjects will have a diagnosis of NYHA Class II or III heart failure with a reduced ejection fraction (HFrEF), be in stable condition, and be taking clinician-directed appropriate pharmacological therapy (e.g., angiotensin converting enzyme inhibitors, angiotensin receptor blockers or an evidence based beta blocker) for heart failure at stable doses (with the exception of diuretics) for at least 1 month prior to screening. During the period between screening and randomization (planned first dose), the study subject will remain on stable pharmacological therapy for heart failure. Also the study subject will be in stable health with no hospitalizations or clinically significant acute illnesses between screening and randomization that would put the subject at increased risk for study participation. Randomized subjects will receive a fixed weekly dose of study drug or placebo for a 4 week dosing period. Dose escalation in subsequent cohorts will continue if the safety and pharmacokinetic profile are deemed acceptable as assessed by the Study Review Committee.