Aryl Di‐Alkyl Phosphate Inhibitors of Butyrylcholinesterase as Potential Therapeutics for Alzheimer's Disease: Characteristics of Off‐Target Effects

The progression of Alzheimer's disease (AD) is characterized by an increase in brain butyrylcholinesterase (BuChE) activity and concomitant loss of acetylcholine. Aryl di‐alkyl phosphates, inhibitors of BuChE, have potential as AD therapeutics. However, their off‐target effects are unknown. In this study, nine compounds were tested for their inhibitory activity against acetylcholinesterase (AChE), trypsin, chymotrypsin, hexokinase, and protein kinase A (PKA). The compounds were also tested against rat brain BuChE. The effects of these inhibitors were observed by pre‐incubating enzyme with inhibitor for either 1 hr or 48 hr and then measuring enzyme activity. AChE and chymotrypsin were not affected after short‐term exposure to the inhibitors. However, the compounds showed varying degrees of inhibition with AChE and chymotrypsin when pre‐incubated with enzyme for 48 hrs. Rat brain BuChE was inhibited by the compounds to the same relative degree as was seen with purified BuChE. In contrast, none of the compounds affected the activity of hexokinase/glucose‐6‐phosphate dehydrogenase or trypsin after a 48 hr exposure. PKA activity was not affected after exposure to the inhibitors for 1 hr. The results suggest that the aryl di‐alkyl phosphates may be an efficient therapeutic for the treatment of AD due to their high degree of specificity.