Evaluation of the efficacy, safety and tolerability of orally administered BI 409306, a novel phosphodiesterase type 9 inhibitor, in two randomised controlled phase II studies in patients with prodromal and mild Alzheimer’s disease

Putative mode of action of phosphodiesterase type 9 inhibition by BI 409306. Ca2+, calcium; cGMP, cyclic guanosine monophosphate; GTP, guanosine triphosphate; LTP, long-term potentiation; NMDA-R, N-methyl-D-aspartate receptor; NO, nitric oxide; NOS, nitric oxide synthase; PDE9, phosphodiesterase type 9; sGC, soluble guanylate cyclase. Figure adapted from Moschetti et al. [7