Derivatives of 3-Quinuclidinyl Benzilate (Bz)
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Mil. Med. Sci. Lett. (Voj. Zdrav. Listy) 2015, vol. 84(1), p. 2-41 ISSN 0372-7025 DOI: 10.31482/mmsl.2015.001 REVIEW ARTICLE DUAL USE RESEARCH OF CONCERN: DERIVATIVES OF 3-QUINUCLIDINYL BENZILATE (BZ) James C. Ball 1083 Jewell Road, Milan, MI 48160, USA Received 3 rd September 2014. Revised 10 th November 2014. Published 6 th March 2015. Summary Dual Use Research of Concern (DURC) deals with the unintended consequences of research and development and is particularly acute in the area of drug development. The United States National Science Advisory Board for Biosecurity (NSABB) has defined DURC as "research that, based on current understanding, can be reasonably anticipated to provide knowledge, products, or technologies that could be directly misapplied by others to pose a threat to public health, agriculture, plants, animals, the environment, or materiel” (1). One particular receptor antagonist and glycolate anticholinergic compound (BZ, QNB or 3 -quinuclidinyl benzilate) was stockpiled by the United States as a non-lethal chemical weapon that incapacitates and severely degrades the capability of exposed individuals (2). Given time and medical treatment, combatants and non-combatants exposed to such incapacitating agents could recover without any long-term effects. The purpose of this review is to identify potential new and more potent incapacitating agents based on the structures of BZ or atropine using peer reviewed publications of new pharmaceutical agents. A number of peer reviewed studies have reported on compounds with effects observed at lower concentrations than or comparable to BZ suggesting that these compounds could also be developed as potential chemical incapacitating chemical warfare agents and represent good examples of the principal of Dual Use Research of Concern. Key words: Dual Use Research of Concern; BZ; QNB; 3-Quinuclidinyl Benzilate; incapacitating agents; chemical warfare; muscarinic acetylcholine receptor antagonists INTRODUCTION The United States National Science Advisory Board for Biosecurity (NSABB) has defined DURC as "re - Dual Use Research of Concern (DURC) is a re - search that, based on current understanding, can be re - cent principle that is concerned with the unintended asonably anticipated to provide knowledge, products, consequences of research and development in almost or technologies that could be directly misapplied by all areas of science. The issue is particularly acute others to pose a threat to public health, agriculture, in the areas of biotechnology (e.g. bioengineering plants, animals, the environment, or materiel” (1). and gene modification) and drug development. While biotechnology research can have clear be - neficial applications there are potentially less obvious 1083 Jewell Road, Milan, MI 48160, USA military applications. Recently, the advent of sophis - [email protected] ticated biotechnology research has led to the possibi - (734) 429-1280 lity that DURC could be used to generate bioweapons Ball: Dual Use Research – BZ Derivatives based on adapting well known pathogenic organisms, • Early central nervous system (CNS) effects primarily viruses (3). Another less well known area include slurring of speech, dizziness, headache, of DURC is in the area of drug development. This nausea, ataxia (failure of muscle coordination), paper will focus on one aspect of new drug devel- and weakness in the legs. opment. Specifically, new drugs are being • During the first 4 hours an exposed individual investigated for their ability to be antagonists will feel discomfort and subjective feelings to different neurological receptor sites thereby of apprehension, restlessness with occasional blocking the normal function of these receptors sites clonic spasms. Some individuals will start for therapeutic reasons. One particular receptor to “flap” their arms in a bird-like fashion. antagonist and glycolate anticholinergic com- Individuals will show errors in speech and will pound (3-quinuclidinyl benzilate) was stockpiled be confused. by the United States as a non-lethal chemical weapon • Physiological symptoms include: dryness that incapacitates and severely degrades the capa- of mouth, tachycardia (irregular heart beat) bility of exposed individuals (2). Given time and at rest, elevated temperature, flushed face, blurred medical treatment, combatants and non-combatants vision, and dilated pupils (papillary dilation). exposed to such incapacitating agents could recover • From 4-12 hours, the exposed individual without any long-term effects. This agent is included becomes sedate, shows signs of stupor or may in the Chemical Weapons Convention (4,5) and has develop semi-comatose symptoms. The indi- been or is in the process of being destroyed by those vidual may appear to sleep and can be aroused countries that have stockpiled the agent and signed with only strong stimulation. The subject may the treaty. mutter incoherently, grope or crawl and some- times the individual will attempt to move through Quinuclidinyl benzilate obstacles known as “obstinate progression.” • After 12 hours, exposed individuals begin to hal- Quinuclidinyl benzilate (Figure 1), abbreviated as BZ lucinate to the point that real objects and persons (used in this paper) by the chemical weapons are ignored. Individuals are sensitive to touch community or QNB by the drug-development com- and continuously grope and explore clothes, munity, is a compound originally developed to be walls, beds and in general, their local envi- an antispasmodic agent or to treat gastrointestinal ronment. spasms (6). BZ was further developed into a non- • Symptoms generally subside over time and lethal incapacitating agent designed to be used the individual begins to accept food, water, and against opposing forces in a modern-day battle. BZ will follow simple instructions. The individual is can be absorbed from inhaling an aerosol of the com- generally quite tractable at this stage but may pound or can be ingested. If the compound is show aggressive behavior if annoyed. dissolved in a suitable solvent, there is also the pos- • During the recovery phase, the exposed sibility that BZ could be absorbed through the skin. individual will begin to appear rational and The onset of symptoms from BZ exposure is dose coherent and may deny that he is impaired in any dependent and typically take hours for the full effects fashion. The subject may feel paranoid. Finally, to be manifested. A typical exposure of ~ 7 µg/kg if the symptoms last more than a day, the subject (~0.56 mg for an 80 kg male) to BZ leads to the fol- may have a period of deep sleep. Subjects fully lowing effects (7-9): recover from the exposure to BZ. N * O OH O Figure 1. 3-Quinuclidinyl Benzilate (BZ or QNB) (1-azabicyclo[2.2.2]oct-3-yl 2-hydroxy-2,2-diphenylacetate; * = chiral carbon) 3 Ball: Dual Use Research – BZ Derivatives BZ was first synthesized and described by was estimated by comparison to the dose of atropine chemists from the laboratories of Hoffman-La Roche (Figure 2) which caused a relaxation response. in 1952 (10-12). The pharmacologic activities of sev- The racemic mixture (the 3 rd carbon on the quin- eral compounds were measured using isolated rabbit uclidinol moiety is a chiral carbon, noted by a star intestine by measuring the relaxation produced in Figure 1) of the benzilic acid ester of 3-quin- by the compound in question from a spasm induced uclidinol (BZ) was twice as potent as atropine by a known concentration of acetylcholine. Potency in relaxing the spasm induced by acetylcholine (11). N O O * OH Figure 2. Atropine (RS)-(8-methyl-8-azabicyclo[3.2.1]oct-3-yl) 3-hydroxy-2-phenylpropanoate; * = chiral carbon) BZ and similar compounds were investigated for according to location and receptor subtype (14). their potential as incapacitating agents for deploy- Muscarinic receptors are located primarily ment as chemical weapons. The United States in the parasympathetic autonomically innervated vis- stockpiled thousands of tons of BZ for chemical ceral organs, piloerector muscles, parasympathetic warfare usage, but most if not all of the stockpile has nervous system and post and pre-synaptically been destroyed (2,13). It is not clear from the open in the CNS (15). Specifically, muscarinic receptors literature if BZ or other similar incapacitating agents associated with the parasympathetic nervous system, were ever developed for use as chemical weapons by a subsystem of the peripheral nervous system, other governments. After further research with US innervates the following organs systems: the eye, Army volunteers, BZ was not considered a viable heart, respiratory system, skin, gastrointestinal tract, incapacitating agent due to a wide variability and bladder. In the CNS, muscarinic receptors are in effects, a long onset time and an inefficient method involved in motor control, temperature and car- of delivering the chemical (2,7,13). However, other diovascular regulation, and memory. muscarinic antagonists were deemed more suitable as incapacitating agents, but required further research Five different muscarinic receptor subtypes and development (7,13). There are no publically (M1 –M5) are well known. However, the precise available reports suggesting that BZ has ever been location and function of these receptor subtypes is used by the United States nor has the military incomplete and not yet completely characterized. of United States been exposed to this or similar The following organ systems have been studied agents . for the presence and distribution of