Repurposing of USFDA-approved drugs to identify leads for inhibition of acetylcholinesterase enzyme: a plausible utility as an anti-Alzheimer agent.

In the quest to identify new anti-Alzheimer agents, we employed drug repositioning or drug repositioning techniques on approved USFDA small molecules. Herein, we report the structure-based virtual screening (SBVS) of 1880 USFDA-approved drugs. The in silico-based identification was followed by calculating Prime MMGB-SA binding energy and molecular dynamics simulation studies. The cumulative analysis led to identifying domperidone as an identified hit. Domperidone was further corroborated in vitro using anticholinesterase-based assessment, keeping donepezil as a positive control. The analysis revealed that the identified lead (domperidone) could induce an inhibitory effect on AChE in a dose-dependent manner with an IC₅₀ of 3.67 μM as compared to donepezil, which exhibited an IC₅₀ of 1.37 μM. However, as domperidone is known to have poor BBB permeability, we rationally proposed new analogues utilizing the principles of bioisosterism. The bioisostere-clubbed analogues were found to have better BBB permeability, affinity, and stability within the catalytic domain of AChE via molecular docking and dynamics studies. The proposed bioisosteres may be synthesized in the future. They may plausibly be explored for their implication in the developmental progress of new anti-Alzheimer agent achieved via repurposing techniques in future.