PDE1-IN-9 (Compound 7a) is a selective inhibitor for phosphodiesterase 1 ( PDE1 ), that inhibits PDE1C with an IC 50 of 11 nM. PDE1-IN-9 reduces mRNA expression of IL-1β, IL-6 , TNF-α and iNOS , inhibits the production of nitric oxide ( NO ) and reactive oxygen species ( ROS ). PDE1-IN-9 exhibits good metabolic stability in rat liver microsomes.