powerwalker,
Donpezil (Aricept) is not listed in the inclusion or exclusion criteria for the Phase 2b/3 trial details at website clinical trials.gov
Therefore it does not appear that concomitent use of donepezil (Aricept) is allowed for this trial.
Since donepezil (Aricept) is a sigma-1 receptor ligand, it is thought that donepzil (Aricept) may be a competitor for binding to the sigma-1 receptor versus Blarcamesine, therefore may be a negative factor if used concomitantly with Blarcamesine.
Good luck and GOD bless,