4-Oxypiperidine Ethers as Multiple Targeting Ligands at Histamine H 3 Receptors and Cholinesterases.

This study examines the properties of a novel series of 4-oxypiperidines designed and synthesized as histamine H 3 R antagonists/inverse agonists based on the structural modification of two lead compounds, viz., ADS003 and ADS009 . The products are intended to maintain a high affinity for H 3 R while simultaneously inhibiting AChE or/and BuChE enzymes. Selected compounds were subjected to h H 3 R radioligand displacement and gp H 3 R functional assays. Some of the compounds showed nanomolar affinity. The most promising compound in the naphthalene series was ADS031 , which contained a benzyl moiety at position 1 of the piperidine ring and displayed 12.5 nM affinity at the h H 3 R and the highest inhibitory activity against AChE (IC 50 = 1.537 μM). Eight compounds showed over 60% eq BuChE inhibition and hence were qualified for the determination of the IC 50 value at eq BuChE; their values ranged from 0.559 to 2.655 μM. Therapy based on a multitarget-directed ligand combining H 3 R antagonism with additional AChE/BuChE inhibitory properties might improve cognitive functions in multifactorial Alzheimer's disease.