A Pralidoxime Nanocomplex Formulation Targeting Transferrin Receptors for Reactivation of Brain Acetylcholinesterase After Exposure of Mice to an Anticholinesterase Organophosphate

Abstract

Introduction

Organophosphates are among the deadliest of known chemicals based on their ability to inactivate acetylcholinesterase in neuromuscular junctions and synapses of the central and peripheral nervous systems. The consequent accumulation of acetylcholine can produce severe acute toxicities and death. Oxime antidotes act by reactivating acetylcholinesterase with the only such reactivator approved for use in the United States being 2-pyridine aldoxime methyl chloride (a.k.a., pralidoxime or 2-PAM). However, this compound does not cross the blood–brain barrier readily and so is limited in its ability to reactivate acetylcholinesterase in the brain.

Methods

We have developed a novel formulation of 2-PAM by encapsulating it within a nanocomplex designed to cross the blood–brain barrier via transferrin receptor-mediated transcytosis. This nanocomplex (termed scL-2PAM) has been subjected to head-to-head comparisons with unencapsulated 2-PAM in mice exposed to paraoxon, an organophosphate with anticholinesterase activity.

Results and Discussion

In mice exposed to a sublethal dose of paraoxon, scL-2PAM reduced the extent and duration of cholinergic symptoms more effectively than did unencapsulated 2-PAM. The scL-2PAM formulation was also more effective than unencapsulated 2-PAM in rescuing mice from death after exposure to otherwise-lethal levels of paraoxon. Improved survival rates in paraoxon-exposed mice were accompanied by a higher degree of reactivation of brain acetylcholinesterase.

Conclusion

Our data indicate that scL-2PAM is superior to the currently used form of 2-PAM in terms of both mitigating paraoxon toxicity in mice and reactivating acetylcholinesterase in their brains.

Keywords:

• lipid nanoparticle
• nanodelivery
• organophosphate
• paraoxon
• blood–brain barrier
• transcytosis

Acknowledgments

The authors wish to thank Chris Poki Leung and Francis Cheung for their assistance with statistical analysis of the data presented here. The research described herein was supported in part by the Defense Threat Reduction Agency of the US Department of Defense through grant HDTRA1-13-1-0049 and contract HDTRA1-20-C-0045 to SynerGene Therapeutics, Inc. The content is solely the responsibility of the authors and does not necessarily reflect the official view of the Defense Threat Reduction Agency.

Disclosure

E.H.C. and K.F.P. are two of the inventors of the described scL technology, for which several patents owned by Georgetown University have been issued. The patents have been licensed to SynerGene Therapeutics, Inc. for commercial development. K.F.P. serves as Principal Investigator for research at Georgetown University that is supported by SynerGene Therapeutics, Inc. E.H.C. owns an equity interest in SynerGene Therapeutics, Inc., and E.H.C. and A.R. serve as paid scientific consultants to SynerGene Therapeutics, Inc. S.S.K. is salaried employee of SynerGene Therapeutics, Inc. M.M. is a graduate student and M.G. an undergraduate student who were supported via a research agreement between Georgetown University and SynerGene Therapeutics, Inc. A.W. is a former paid employee of SynerGene Therapeutics, Inc. J.B.H. serves as salaried President & CEO of SynerGene Therapeutics, Inc. and owns stock in same. The authors report no other conflicts of interest in this work.