2-(4-Aminophenyl)-1,2-dihydro-7-[(1-oxido-2-pyridinyl)methoxy]-1-oxo-4-(3,4,5-trimethoxyphenyl)-3-isoquinolinecarboxylic Acid methyl Ester Monohydrochloride, is a selective metabolite that is generated by cytochrome P450 3A5 (CYP3A5) oxidation of A622635.These compounds are also 4-Aryl-1-isoquinolinone Derivatives, which are shown to be novel, potent, and selective Phosphodiesterase 5 (PDE5) Inhibitors.