Methylfluorophosphonylcholine

Methylfluorophosphonylcholine (MFPCh) is an extremely toxic chemical compound related to the G-series nerve agents. It is an extremely potent acetylcholinesterase inhibitor which is around 100 times more potent than sarin at inhibiting acetylcholinesterase "in vitro", and around 10 times more potent "in vivo", depending on route of administration and animal species tested. MFPCh is resistant to oxime reactivators, meaning the acetylcholinesterase inhibited by MFPCh can't be reactivated by oxime reactivators. MFPCh also acts directly on the acetylcholine receptors. However, despite its high toxicity, methylfluorophosphonylcholine is a relatively unstable compound and degrades rapidly in storage, so it was not deemed suitable to be weaponised for military use.