A novel series of heterocycle-based analogs were prepared and evaluated for their in vitro and in vivo biological activity as human β3-adrenergic receptor (AR) agonists. Several analogs demonstrated potent agonist activity at the β3-AR, functional selectivity against β1- and β2-ARs, and favorable pharmacokinetic profiles in vivo. Compound 17 increased oxygen consumption in rats, a measure of energy expenditure, with an ED20% of 2mg/kg.