Dihydro Donepezil (Dihydro E2020) is a metabolite of Donepezil. Donepezil is a specific and potent AChE inhibitor with IC50s of 8.12 nM and 11.6 nM for bAChE and hAChE, respectively[1].
[1]. Ogura, H., et al., Comparison of inhibitory activities of donepezil and other cholinesterase inhibitors on acetylcholinesterase and butyrylcholinesterase in vitro. Methods Find Exp Clin Pharmacol, 2000. 22(8): p. 609-13.