The present invention relates to compounds of Formula (Ia) and pharmaceutical compositions thereof that modulate the activity of the beta-3 adrenergic receptor. Compounds of the present invention and pharmaceutical compositions thereof are directed to methods useful in the treatment of a beta-3 adrenergic receptor-mediated disorder, such as, heart failure; cardiac performance in heart failure; mortality, reinfarction, and/or hospitalization in connection with heart failure; acute heart failure; acute decompensated heart failure; congestive heart failure; severe congestive heart failure; organ damage associated with heart failure (e.g., kidney damage or failure, heart valve problems, heart rhythm problems, and/or liver damage); heart failure due to left ventricular dysfunction; heart failure with normal ejection fraction; cardiovascular mortality following myocardial infarction; cardiovascular mortality in patients with left ventricular failure or left ventricular dysfunction; left ventricular failure; left ventricular dysfunction; class II heart failure using the New York Heart Association (NYHA) classification system; class III heart failure using the New York Heart Association (NYHA) classification system; class IV heart failure using the New York Heart Association (NYHA) classification system; LVEF<40% by radionuclide ventriculography; LVEF≤35% by echocardiography or ventricular contrast angiography; and conditions related thereto.