One of the major deficiencies of current medical countermeasures is that current oximes cannot reactivate nerve agent-inhibited acetylcholinesterase (AChE) that has aged after exposure to organophosphorus G- and V-type chemical nerve agents. Our team has demonstrated the first, and only, compounds that have the capability to ?resurrect? in vitro the methylphosphonate-aged form of AChE to an active, native state. We posit that this resurrection accomplishes two distinct steps ? first, to realkylate the anionic aged form back to a neutral, phosphylated (inhibited) serine residue and then to reactivate the inhibited form back to the native AChE. This proposal focuses on expanding on these successful chemical frameworks in order to identify even more efficacious drug-like molecules that will enable the aged form of AChE to be resurrected in vivo. Using various quinone methide precursor (QMP) frameworks, we will use computational and experimental approaches to prepare a chemical library and then to screen these compounds for efficacy in resurrecting the aged form of AChE back to native activity. There are no approved countermeasures that can resurrect the aged form of AChE to its active form; however, resurrection of aged AChE is the holy grail against OP exposure. If realkylation of aged AChE can occur, then AChE can be fully rejuvenated as oximes (and other reactivators) exist that are potent nucleophiles for cleaving the O?P bond of the phosphylated serine, thereby reforming active AChE. Thus, the objective of this proposal is to expand on our successful chemical frameworks to react selectively with aged AChE to form stable alkylphosphonate-AChE adducts that can then be reactivated to the native state, thereby reversing the effects of aging by chemical nerve agents. The design of alkylating compounds will be guided by state-of-the-art computational methods (molecular dynamics, molecular docking, and quantum mechanical methods) that predict the ligand-receptor interactions of alkylating compounds with aged AChE. Using in silico guidance, libraries of alkylating quinone methide precursor (QMP) compounds will be synthesized, and then tested in a kinetic screening process, and complemented by mass spectrometric and proteomic studies. The best lead compounds will be evaluated for their in vitro drug-like properties and tested in vivo in a humanized mouse model for AChE.
Many organophosphorus (OP) compounds are chemical warfare agents or pesticides and are threats to human society. These chemical agents inhibit the enzyme acetylcholinesterase (AChE), and upon exposure to OP chemical nerve agents, AChE undergoes an aging process, rendering current oxime treatment to be ineffective. Our team recently reported the first compounds to demonstrate success in the in vitro resurrection of the aged form of AChE back to the native state, and this proposal will focus on developing optimized chemical frameworks for improved efficacy, activity and drug-like properties.