A potent and selective β1-AR antagonist (IC50s = 7.41 and 251 nM for β1- and β2-ARs, respectively in a radioligand binding assay using rabbit lung membrane preparations); selective for β1-ARs over 5-HT1A and 5-HT2, α1- and α2-adrenergic, H1, and D2 receptors (IC50s = 27.5 and 2,239, 3,162 and >10,000, 5,623, and 10,000 nM, respectively); inhibits cAMP accumulation induced by norepinephrine in primary rat cardiac cells (IC50 = 22 nM); induces vasodilation in mouse renal arteries via a nitric oxide- and cGMP-dependent mechanism (EC50 = 11.36 μM); decreases contraction of isolated human left ventricular trabeculae induced by isoproterenol (IC50 = 7.0 μM) but does not exert ISA; inhibits proliferation of HCASMCs in the presence and absence of growth factors (IC50s = 6.1, 6.8, 6.4, and 7.7 μM for HCASMCs grown in media containing no growth factor, PDGFBB, basic FGF, and TGF-β1, respectively),