Design, Synthesis, and Biological Evaluation of Orally Available First-Generation Dual-Target Selective Inhibitors of Acetylcholinesterase (AChE) and Phosphodiesterase 5 (PDE5) for the Treatment of Alzheimer's Disease

Through drug discovery strategies of repurposing and redeveloping existing drugs, a series of novel tadalafil derivatives were rationally designed, synthesized, and evaluated to seek dual-target AChE/PDE5 inhibitors as good candidate drugs for Alzheimer's disease (AD). Among these derivatives, 1p and 1w exhibited excellent selective dual-target AChE/PDES inhibitory activities and improved blood-brain barrier (BBB) penetrability. Importantly, 1w.Cit (citrate of 1w) could reverse the cognitive dysfunction of scopolamine-induced AD mice and exhibited an excellent effect on enhancing cAMP response element binding protein (CREB) phosphorylation in vivo, a crucial factor in memory formation and synaptic plasticity. Moreover, the molecular docking simulations of 1w with hAChE and hPDESA confirmed that our design strategy was rational. In summary, our research provides a potential selective dual-target AChE/PDE5 inhibitor as a good candidate drug for the treatment of AD, and it could also be regarded as a small molecule probe to validate the novel AD therapeutic approach in vivo.