PDE5-IN-10 (compound 4b) is a potent PDE5 inhibitor with an IC50 of 20 nM. PDE5-IN-10 improves in vitro microsomal stability (t1/2 = 44.6 min) as well as excellent efficacy in restoring long-term potentiation. PDE5-IN-10 can be used for Alzheimer’s disease (AD) research[1].