Acetylcholinesterase (AChE) is one of the few targets for which there are approved drugs for Alzheimer’s Disease (AD). It is an important drug target for other neurological diseases, such as Parkinson’s Disease dementia and Lewy Body dementia. We recently performed a high throughput screen for AChE inhibitors and discovered that the antiviral drug tilorone is a nanomolar inhibitor of eel AChE (IC50 = 14.4 nM). We then demonstrated it was similarly active against human AChE (IC50 = 64.4 nM), but not human Butyrylcholinesterase (IC50 > 50 µM). Molecular docking studies suggested tilorone likely interacts with the peripheral anionic site of AChE similar to the FDA approved AChE inhibitor donepezil. We also evaluated one micromolar tilorone against a kinase selectivity screen (SelectScreen) and a pharmacological safety profile (SafetyScreen44) and showed tilorone had no appreciable inhibition of 485 kinases and only inhibited AChE out of 44 toxicology target proteins evaluated. We then used a Bayesian machine learning model consisting of 4601 molecules for AChE to score novel tilorone analogs. Nine were synthesized and tested and the most potent predicted molecule (SRI-0031256) demonstrated an IC50 = 23 nM, which is similar to donepezil (IC50 = 8.9 nM). We have also developed a recurrent neural network (RNN) for de novo molecule design trained using molecules in ChEMBL. This software was able to generate over 10,000 virtual analogs of tilorone, which include one of the 9 molecules previously synthesized, SRI-0031250 that was found in the top 50 based on similarity to tilorone. Future work will involve using SRI-0031256 as a starting point for further rounds of molecular design. Our study has identified an approved drug in Russia and Ukraine that provides a starting point for molecular design using RNN. This study suggests there may be a potential role for repurposing tilorone or its derivatives in conditions that benefit from AChE inhibition. 

SE is founder and owner of Collaborations Pharmaceuticals, Inc. ACP, EM, PAV, TRL, DHF, KMZ, and FU and are employees of Collaborations Pharmaceuticals, Inc. PBM, JPM and DAT have no conflicts of interest.