The use of chemical antidotes is likely the first treatment for civilian and military-installation nerve agent (NA) casualties. These treatments would include the current standard of care (SOC) therapies (United States) of acetylcholine receptor blocker atropine, acetylcholinesterase (AChE) reactivator pralidoxime (2-[(hydroxyimino)methyl]-1-methylpyridinium, 2-PAM), and symptom modulator diazepam. From a single intramuscular (IM) dose these compounds do provide some immediate protection, but for persistent NAs (VX, VR) and pesticides (parathion- active derivative paraoxon, PX) and chlorpyrifos (Cpf)) the therapeutic regimen of continuous infusion of 2-PAM for up to 7 d may be required. 2-PAM however has other limitations as it does not cross the blood brain barrier (BBB) and therefore not available to reactivate poisoned brain AChE. The BBB is comprised of an endothelial cell layer that is nearly impenetrable to proteins and polar molecules. The Tokyo sarin attack in 1995 with 5500 casualties and immense impact on the emergency health services demonstrates the need for reactivators with improved pharmacokinetics, reduced toxicity, and the potential to cross the BBB for reducing treatment requirements in mass casualty situations. To this last point, glucose transporters (GLUTs) are present at high concentrations in the brain capillary epithelial cells and it has been demonstrated that glucose-drug conjugates can be transferred across the BBB by these transporters. We propose to exploit this by coupling broad spectrum reactivators (oximes) to glucose sites predicted by in silico modeling to not interfere with transport by the GLUT facilitative transporter.
Organophosphate nerve agents (OPs) inactivate acetylcholinesterase (AChE) causing a buildup of the neurotransmitter acetylcholine. This build up can result in convulsions, and seizures, and if at a high enough dose, death. The current US Army standard of care (SOC) reactivators can revive poisoned AChE; however, there are limitations for their use in mass casualty situations by the toxicity, poor penetration of the bloo brain barrier (BBB), rapid clearance pharmacokinetics, and treatment regimen especially against depot forming nerve agents (i.e. V- agents). We propose therefore to evaluate novel sugar linked reactivators of AChE with broader specificity, improved pharmacokinetics, and potential to cross the blood brain barrier. Compounds will be screened in silico for reactivation and transport potential. Compounds will be synthesized in analytical quantities for in vitro reactivation potential and BBB testing in cell culture model. The information will be used to refine the computer models. Lead compounds will be selected for large scale synthesis. Acute toxicity experiments will be done to determine the LD50 and efficacy testing will then be done using an LD12.5 to determine brain AChE reactivation in mouse models. Based on these results the compounds will be evaluated for transition to the USAMRICD CORE program for GLP efficacy studies in larger rodent species.
