Development of small bisquaternary cholinesterase inhibitors as drugs for pre-treatment of nerve agent poisonings

Article abstract of DOI:10.2147/DDDT.S133038

Background: Intoxication by nerve agents could be prevented by using small acetylcholinesterase inhibitors (eg, pyridostigmine) for potentially exposed personnel. However, the serious side effects of currently used drugs led to research of novel potent molecules for prophylaxis of organophosphorus intoxication. Methods: The molecular design, molecular docking, chemical synthesis, in vitro methods (enzyme inhibition, cytotoxicity, and nicotinic receptors modulation), and in vivo methods (acute toxicity and prophylactic effect) were used to study bispyridinium, bisquinolinium, bisisoqui-nolinium, and pyridinium-quinolinium/isoquinolinium molecules presented in this study. Results: The studied molecules showed non-competitive inhibitory ability towards human acetylcholinesterase in vitro that was further confirmed by molecular modelling studies. Several compounds were selected for further studies. First, their cytotoxicity, nicotinic receptors modulation, and acute toxicity (lethal dose for 50% of laboratory animals [LD₅₀]; mice and rats) were tested to evaluate their safety with promising results. Furthermore, their blood levels were measured to select the appropriate time for prophylactic administration. Finally, the protective ratio of selected compounds against soman-induced toxicity was determined when selected compounds were found similarly potent or only slightly better to standard pyridostigmine. Conclusion: The presented small bisquaternary molecules did not show overall benefit in prophylaxis of soman-induced in vivo toxicity.

Full text of DOI:10.2147/DDDT.S133038

Drug Design, Development and erapy
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Open ꢄccess FullText ꢄrticle
O ꢀ ꢁ ꢂ ꢁ ꢃ ꢄ ꢅ ꢀ ꢆ ꢇ ꢆ ꢄ ꢀ ꢈ ꢉ
Development of small bisquaternary cholinesterase
inhibitors as drugs for pre-treatment of nerve
agent poisonings
This article was published in the following Dove Press journal:
Drug Design, Development andTherapy
1
,2
Kamil Kuca
Background: Intoxication by nerve agents could be prevented by using small acetylcholin-
esterase inhibitors (eg, pyridostigmine) for potentially exposed personnel. However, the serious
side effects of currently used drugs led to research of novel potent molecules for prophylaxis
of organophosphorus intoxication.
2
,3
Jana Zdarova Karasova
Ondrej ꢇoukup
2
3
Jiri Kassa
2
Methods: The molecular design, molecular docking, chemical synthesis, in vitro methods
(enzyme inhibition, cytotoxicity, and nicotinic receptors modulation), and in vivo methods (acute
toxicity and prophylactic effect) were used to study bispyridinium, bisquinolinium, bisisoqui-
nolinium, and pyridinium-quinolinium/isoquinolinium molecules presented in this study.
Results: The studied molecules showed non-competitive inhibitory ability towards human
acetylcholinesterase in vitro that was further confirmed by molecular modelling studies. Several
compounds were selected for further studies. First, their cytotoxicity, nicotinic receptors modula-
tion, and acute toxicity (lethal dose for 50% of laboratory animals [LD ]; mice and rats) were
ꢆva ꢃovotna
Vendula ꢇepsova
ꢄnna ꢉorova
Jaroslav Pejchal
2
,3
2
3
2
,3
Martina ꢉrabinova
2
ꢆva Vodakova
2
,3
Daniel Jun
5
0
1
,2
ꢆugenie ꢃepovimova
tested to evaluate their safety with promising results. Furthermore, their blood levels were
measured to select the appropriate time for prophylactic administration. Finally, the protective
ratio of selected compounds against soman-induced toxicity was determined when selected
compounds were found similarly potent or only slightly better to standard pyridostigmine.
Conclusion: The presented small bisquaternary molecules did not show overall benefit in
prophylaxis of soman-induced in vivo toxicity.
4
Martin Valis
1
,2
Kamil Musilek
1
Department of ꢈhemistry, Faculty
of ꢇcience, University of ꢉradec
Kralove, Biomedical ꢀesearch
ꢈenter, University ꢉospital ꢉradec
Kralove, Department of Toxicology
2
3
Keywords: AChE inhibitors, prophylaxis, pre-treatment, nerve agents, toxicity, soman
and Military Pharmacy, Faculty of
Military ꢉealth ꢇciences, University of
Defence, Department of ꢃeurology,
University ꢉospital ꢉradec Kralove,
ꢉradec Kralove, ꢈzech ꢀepublic
4
Introduction
Organophosphorus compounds (OP) are widely used (eg, in agriculture as pesticides,
in industry as softening agents). Some of them were, unfortunately, developed for
military purposes as chemical warfare agents. Sarin, soman or VX belong to the most
1
known nerve agents (NA), especially among OP. NA mechanism of action is based on
its ability to inhibit the enzyme acetylcholinesterase (AChE; EC 3.1.1.7) at peripheral
and central cholinergic synapses. Afterward, generalized cholinergic crisis occurs and
2
in severe cases may lead to death.
TopreventthedeleteriouseffectofNA, severalprophylacticapproacheswereformerly
3
developed. AChEprotectionagainsttheOPusingreversiblecholinesterase(ChE)inhibitors
istheoldestapproachforChEpre-treatment.Inthiscase,thenon-competitiveorcompetitive
reversible inhibitors of AChE are used to protect the irreversible binding of NA, and thus
protect AChE function until the most of OP is biodegraded. This effect cannot be expected
for administration of AChE reactivators (oximes) that are known to be very poor AChE
ꢈorrespondence: Kamil Kuca
Biomedical ꢀesearch ꢈenter, University
ꢉospital ꢉradec Kralove, ꢇokolska 581,
5
00 05 ꢉradec Kralove, ꢈzech ꢀepublic
Tel +420 603 289 166
ꢆmail kamil.kuca@fnhk.cz
4
5,6
inhibitors. Recently, enzymes scavenging or hydrolyzing OP are highly investigated.
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http://dx.doi.org/10.2147/DDDT.S133038

Kuca et al
Dovepress
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Figure 1 Bisquaternary compounds tested or used for organophosphorus protection or reactivation.
During last decade, some attention was turned back to 4-positioned pyridinium analogs bridged also by varying
1
5,16
the reversible ChE inhibitors including SAD-128, a bisqua- linkage (Figure 3).
ternary compound, which was considered as pre-treatment The design of presented molecules originated from known
7–10
drug candidate in eighties (Figure 1). In fact, it was the first compounds (eg, ambenonium dichloride, BW284c51 or
bisquaternary compound used for this purpose and lacking SAD-128) that were known for excellent or selective cholinest-
oxime moiety that is common for bisquaternary reactivators erase inhibition in vitro (ambenonium dichloride, BW284c51)
(eg, trimedoxime, obidoxime). The major reason for use of or in vivo (SAD-128). The heteroaromatic moieties were
charged reversible AChE inhibitor was challenge of rapidly used to cover π-cationic interactions with the aromatic amino
aging organophosphates (eg, soman), which are very difficult acid residues in the cholinesterase binding pocket (especially
to treat after intoxication, but might be prevented prior to AChE). The varying linkage was adapted to possibly connect
intoxication by combining peripherally and centrally acting the AChE cation–π binding site with the peripheral aromatic
reversible AChE inhibitor. In this case, the charged inhibitor binding site. In this case, the better reversible inhibition of
would serve as a peripherally acting one. With this hypoth- AChE was hypothesized for some of the chosen linkers (one
esis, several novel series of bisquaternary compounds were to 12 methylene units). Some heteroatoms, double bonds or
prepared and evaluated (Figures 2 and 3). In this article, we aromatic rings were also introduced to the linkage to improve
would like to summarize results, which were obtained by our the other inhibitor-enzyme interactions within the AChE bind-
group within the last seven years for bisquaternary reversible ing pocket including π-π interactions (double bonds, aromatic
AChE inhibitors with possible impact on protection against rings) of hydrogen bonding (ether fragment).
OP compounds. The whole summary is divided into several
The synthesis of presented molecules was fairly simple
sections that are presented consecutively step by step such (Figure 4). The heteroaromatic compound was dissolved in
as in the development process: synthesis, in vitro evaluation, dimethylformamide (DMF) or acetonitrile (MeCN) upon
cytotoxicity, nicotinic receptor evaluation, toxicity, pharma- addition of dihalogenated linking molecule and stirred
cokinetics and in vivo evaluation of the prophylactic effect. at about 70°C for several hours/days. The products were
obtained in good yield and purity, which was checked by
1
7
standard techniques (NMR, ESI-MS).
Design and synthesis
The bisquaternary compounds were designed as simple
molecules with two pyridinium, quinolinium, isoquinolinium
ꢁ
n vitro screening, molecular docking and
or mixed pyridinium-quinolinium/isoquinolinium moieties structure–activity relationship
1
1–14
connected by variety of linkers (Figure 2).
The latter The in vitro screening of prepared molecules was done on
compounds were derived from 4-(tert-butyl)pyridinium or human recombinant AChE and human plasmatic BChE
1
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Figure 2 Bispyridinium, bisquinolinium, bisisoquinolinium and pyridinium-quinolinium/isoquinolinium compounds designed as small cholinesterase inhibitors.
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Drug Design, Development andTherapy 2018:12
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ꢇmall bisquaternary cholinesterase inhibitors
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Figure 3 4-(tert-butyl)pyridinium or 4-positioned pyridinium analogs designed as small cholinesterase inhibitors.
(hBChE) to exclude the possible interspecies differences. The non-competitive binding. The symmetrical molecules
half maximal inhibitory concentration (IC ) was determined (K298, K344, K474, K524) presented closure of hAChE
50
for all molecules and the selected compounds were further gorge entrance via π-π or π-cationic interactions, where
tested in kinetic experiments in vivo. The IC50 data were one heteroarenium moiety was positioned into the gorge
compared to pattern bisquaternary molecules with similar and the second one was located outside the gorge close to
11–13
mechanism of action (ambenonium dichloride, BW284c51 its entrance.
Differently, the non-symmetrical compound
The selected promising compounds from K792 was found to be deep inside the gorge with pyridinium
all prepared series are presented in Figure 5 and Table 1. moiety located close to the active site (Ser203) and quino-
The in vitro results confirmed the hypothesis that the pre- linium moiety interacting with peripheral active site (Tyr124,
1
5,16
or SAD-128).
1
4
pared compounds might be potent cholinesterase inhibitors. Trp 286). Thus, the molecular modeling results confirmed
ThebestofthempresentedinhibitionofhumanAChE(hAChE) the in vitro findings of high hAChE inhibition by symmetrical
on sub-µM (K344) or nM scale (K298, K474, K524, K792). or non-symmetrical compounds plus disclosed the matter of
They were able to exceed the inhibitory ability of SAD-128 higher selectivity of K792 for hAChE.
or BW284c51 in vitro, but they were worse to ambenonium.
From the structure–activity relationship point of view, the
Concerning the selectivity issues, the selectivity of newly better inhibitory ability toward hAChE was obtained for struc-
prepared compounds was found to be worse to ambenonium turally similar compounds. Among these, two quaternary het-
or BW284c51 (selectivity standard), but better to SAD-128. eroaromatic rings connected by the linker in the length of 8–10
However, the selectivity of inhibitor molecule K524 and most methylene units were found optimal within in vitro evaluation
importantly non-symmetrical molecule K792 seemed to be with AChE inhibition from µM to nM range. In this case, the
improved with favorable hAChE inhibition. The kinetic exper- highlighted compounds (K298, K344, K474, K524, K792)
iments were performed to confirm the possible mechanism optimally connected the peripheral binding site and cation–π
of actions of newly prepared cholinesterase inhibitors. From binding site, when cation–π interactions were confirmed by
this point of view, they were found to be non-competitive molecular docking results. Less favorably, naphthyl moiety
hAChE inhibitors mostly comparable with used standards.
in the connecting linker was found to inhibit AChE in µM
Moreover, the interactions with hAChE and hBChE range having additional π–π interaction with aromatic resi-
active sites were further studied by molecular modeling dues within the active site, but this linker was found too short
experiments (Figure 6) to propose possible mechanism of to efficiently bind between the peripheral binding site and
11–14
action. The molecular modeling results confirmed several cation–π binding site.
The phenyl or double bond contain-
important interactions for each type of molecule and their ing linkers were found inefficient. The varying substitution
;
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1
'0)ꢄ0H&1ꢅꢃꢆꢇ°&
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Figure 4 ꢆxample of small inhibitor preparation technique.
Notes: X = ꢈl, Br; ꢄ = (ꢈꢉ2)1–12; (E/Z)-ꢈꢉ2ꢈꢉ=ꢈꢉꢈꢉ ; (ꢈꢉ )1–2O(ꢈꢉ2)1–2
.
2
2
Abbreviations: DMF, dimethylformamide; Meꢈꢃ, acetonitrile.
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Kuca et al
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Figure 5 ꢇelected promising small cholinesterase inhibitors.
Abbreviations: hꢄꢈhꢆ, human acetylcholinesterase; ꢁꢈ , half maximal inhibitory concentration.
50
on heteroaromatic moiety was another tested aspect. Firstly, favorable with nM inhibition of hAChE. Additional phenyl
the tert-butyl moiety from SAD-128 was used. Its combina- propyl scaffolds improved π–π binding and together with
tion with varying linker length (one to 12 methylene units) cation–π binding properly positioned the molecule within
proved that compound K474 is hAChE inhibitor in nM range the active site. Among other substitutions, methyl and N,N-
1
6
and is much more effective than SAD-128. The inhibi- dimethyl amino moieties were found with inhibitory ability
15
tory ability of K474 was comparable with other hete- in low µM range. In both cases and in accordance with tert-
roaromatic compounds without ring substitution (eg, K524, butyl moiety results, the electron donating substituents were
K792). Additionally, varying substitutions were used for two hypothesized to increase electron density in the heteroaromatic
15
pyridinium rings connected by double bond. In this case, ring and thus strengthen the cation–π binding, whereas com-
the phenyl propyl moiety extending the length of the mol- pounds possessing the electron withdrawing functional groups
ecule similarly to compounds K298 or K524 was found most were found with medium to low inhibitory ability.
Table 1 ꢁn vitro screening data for selected promising small cholinesterase inhibitors
Compound
hAChE IC50 ± SD (nM)*
hBChE IC50 ± SD (nM)*
SI BChE/AChE
K /K hAChE (nM)*
i1
i2
ꢄmbenonium
BW284c51
ꢇꢄD-128
K298
0.7±0.1
30±6
12000±2000
5±1
400±80
5±0.9
6800±1100
354000±58000
75000±12000
400±60
5000±800
20±3
9743
11800
6.2
5/6
10/50
ꢃot applicable
620/980
20/30
80
K344
12.5
3.2
K474
90/200
K524
1±0.2
5±1
100±20
3200±500
100
630
40/60
K792
400/400
Notes: *ꢄll experiments were done in triplicate. Ki1 and Ki2 are kinetic constants.
Abbreviations: ꢄꢈhꢆ, acetylcholinesterase; Bꢈhꢆ, butyrylcholinesterase; hꢄꢈhꢆ, human ꢄꢈhꢆ; hBꢈhꢆ, human plasmatic Bꢈhꢆ; ꢁꢈ , half maximal inhibitory concentration;
50
ꢇꢁ, selectivity index.
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ꢇmall bisquaternary cholinesterase inhibitors
Figure 6 ꢆxample of molecular modeling result at human ꢄꢈhꢆ active site for compound K524 (in blue; A) and K792 (in brown; B).
Notes: ꢁmage A reproduced from Komloova M, Musilek K, ꢉorova ꢄ, et al. Preparation, in vitro screening and molecular modelling of symmetrical bisquinolinium
1
3
cholinesterase inhibitors – implications for early Myasthenia gravis treatment. Bioorg Med Chem Lett. 2011;21:2505–2509. ꢈopyright © 2011 ꢆlsevier ꢅtd. ꢄll rights reserved.
ꢁ
mage B reproduced from Komloova M, ꢉorova ꢄ, ꢉrabinova M, et al. Preparation, in vitro evaluation and molecular modelling of pyridinium-quinolinium/isoquinolinium
14
non-symmetrical bisquaternary cholinesterase inhibitors. Bioorg Med Chem Lett. 2013;23(24):6663–6666. ꢈopyright © 2013 ꢆlsevier ꢅtd. ꢄll rights reserved.
Abbreviation: ꢄꢈhꢆ, acetylcholinesterase.
ꢈytotoxicity
ꢃicotinic receptors modulation
As a pre-step for assessing acute toxicity in vivo, cytotoxicity Both newly prepared AChE inhibitors (K298, K524) were
assay was performed in vitro. Standard MTT test was used alsocomparedwithtwostandards(BW284c51, edrophonium)
(all the cell lines were obtained from the collection of ATCC). for their modulation of nicotinic receptors. All tested com-
This method was based on the spectrophotometric assessment pounds showed a comparatively high reversible inhibition
of formazan that is produced by viable cells and has been effect (IC ). When tested compounds were pre-applied
5
0
1
8
widely used for research purposes for a long time. For the (in different concentration) for 5 s and then co-applied with
purposes of this cytotoxicity study, a comparison of com- the agonist, acetylcholine (100 µM) responses were inhibited
pounds K298 and K524 with commercially available stan- in a concentration-dependent manner. Newly synthesized
dards (pyridostigmine and BW284c51) on three different cell inhibitor K524 showed the lowest IC value 570±5 nM that
5
0
lines (HeLa – human cervical cancer cell line, BJ – fibroblasts was approximately one or two orders of magnitude lower
and ACHN – renal carcinoma cell line) was performed. compared to used standards. K298 showed approximately
Obtained results showed clear pattern of the cytotoxic 4-fold lower affinity (IC =1900±200 nM). Potentiation
5
0
19
effect on all the cell lines (Table 2) and can be considered of the muscle-type nicotinic receptors was not recorded.
as very low. Standard compound BW284c51 was found to Such potent inhibition may provide protection of nicotinic
be least toxic to all the cell lines. This fact is probably due receptors by the pre-treatment especially when combined by
to the presence of quaternary nitrogens in this structure, protection of the AChE. Furthermore, it might also be used
ensuring the low penetration across the cell membrane to as the post-exposure treatment via the antagonism of the
2
0
the cytosol. The same can be postulated for newly prepared overstimulated nicotinic receptors.
bisquaternary inhibitors; however, the cytotoxic effects
are a bit higher probably due to higher lipophilicity gained
ꢄcute toxicity
by the long carbon linker. Thus, it may be concluded that
In front of the pharmacokinetic and prophylactic evaluation
of newly prepared ChE inhibitors, acute toxicity of selected
compounds was tested in mice (K298, K344, K474) and
rats (K298, K524) by the assessment of their lethal dose
for 50% of laboratory animals (LD ) values and their 95%
newly synthesized compounds do not differ much from the
investigated standards on used cell lines. They can also be
considered as low toxic compounds and might proceed to
19
in vivo examination.
5
0
confidence limits using probit-logarithmical analysis of
death occurring within 24 hours after intramuscular (im)
administration of each inhibitor. According to the obtained
results, tested quaternary ChE inhibitors were about one
order of magnitude more toxic than commonly used AChE
Table 2 ꢈytotoxicity of tested compounds expressed as ꢁꢈ50
Cell line IC50 (µM)
HeLA
ACHN
BJ
pyridostigmine
BW284c51
K298
380
3000
970
1120
3000
1050
1470
3000
1009
−
1
reactivators (LD for asoxime in mice 671 mg⋅kg , in rats
50
−1
21,22
K524
2720
1710
1230
781 mg⋅kg ) (Tables 3 and 4).
Ethics Committee of the
Abbreviation: ꢁꢈ , half maximal inhibitory concentration.
Faculty of Military Health Sciences in Hradec Kralove (Czech
50
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Kuca et al
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Table 3 ꢄcute toxicity of reversible inhibitors of ꢄꢈhꢆ in mice
Table 5 Pharmacokinetics of reversible inhibitors in rat after
after intramuscular administration
intramuscular administration
Reversible inhibitor
of AChE
LD50 (mg/kg) ±95% IS*
References
Reversible inhibitor Tmax ± SD Half-life ± SD References
of AChE
(min)
(min)
2
2
2
2
2
8
1
8
8
8
24
pyridostigmine
asoxime (ꢉꢁ-6)
K298
K344
K474
3.08 (2.44–4.53)
671.3 (627.4–718.3)
97.2 (74.6–141.3)
63.9 (51.3–92.5)
33.4 (22.7–49.2)
Kassa et al
Kassa et al
Kassa et al
Kassa et al
Kassa et al
pyridostigmine
K298
2.41±0.51
30.00±3.30 50.5±8.8
39.00±9.00 54.7±6.2
24.8±4.2
Meyer et al
23
23
Karasova et al
Karasova et al
K524
Abbreviations: ꢄꢈhꢆ, acetylcholinesterase; Tmax, time that a drug is present at the
maximum concentration.
Note: *95% confidence limit using probit-logarithmic analysis.
Abbreviations: ꢄꢈhꢆ, acetylcholinesterase; ꢅD , lethal dose for 50% of laboratory
animals.
50
of their LD50 values. Soman-induced toxicity was found
via evaluation of its LD50 value and its 95% confidence
limit using probit-logarithmical analysis of death that was
Republic) approved the animal experiments. The Guide for
the Care and Use of Laboratory Animals was followed.
2
8
observed within 24 h after its administration. The effect
of selected prophylactic compounds was calculated as
protective ratio (LD value of soman in pretreated mice/LD
50
Pharmacokinetics
50
Time-dependent concentration changes of selected AChE value of soman in non-pretreated mice).
inhibitors (K298, K524) were measured in rat plasma to select
Further, the inhibitors pyridostigmine, K298, K344 and
appropriate time for administration as prophylactics. For this K474 were evaluated for the therapeutic effect when antidotal
purpose, equitoxic doses (5% LD ) were applied intramus- treatment was tested. All selected inhibitors were adminis-
50
cularly. HPLC-MS instrumentation was selected as the most tered 30 min prior to soman injection, while the antidotal
appropriate for determination of low inhibitor concentrations. treatment (5% LD50 asoxime dichloride in combination
The maximal plasma concentrations were achieved with atropine 21 mg/kg) was carried out by i.m. injection
in 30 min (K298) and 39 min (K524) and corresponded 1 min after the soman challenge. Again, soman-induced
2
3
to 100 nM concentration (Table 5). The pyridostigmine toxicity was found via evaluation of its LD50 value and its
maximal levels after i.m. administration in rats were formerly 95% confidence limit using probit-logarithmical analysis of
2
8
found in about 3 min with elimination half-life in about death that was observed within 24 h after its administration.
2
2
4
5 min. The fast absorption and also fast elimination from The influence of tested prophylactic compounds on the
blood stream were characteristic for tested compounds, when antidotal treatment within soman poisoning was calculated
their elimination was partially slower with half-life of about as protective ratio A (LD50 value of soman in pretreated
23
5
0–55 min. Obtained plasma curves were similar to typical mice with antidotal treatment/LD value of soman in non-
50
plasma absorption curves obtained for AChE reactivators pretreated mice without antidotal treatment) and protective
25–27
(
HI-6, obidoxime, K027 and K203).
ratio B (LD value of soman in pretreated mice with antidotal
50
treatment/LD value of soman in non-pretreated mice with
5
0
ꢁ
n vivo prophylactic effect
antidotal treatment). The differences between LD50 values
2
9
The prophylactic effect of selected AChE reversible inhibi- were considered to be significant when p0.05.
tors pyridostigmine, K298, K344 and K474 was evaluated
The results of the study showed that none of the tested
in vivo. They were administered by i.m. injection 30 minutes ChE inhibitors was able to decrease acute soman-induced
2
8
prior to i.m. soman challenge in dose corresponding to 2% toxicity in mice (Table 6). The standard in the field
Table 6 Prophylactic effect of reversible ꢄꢈhꢆ inhibitors with
Table 4 ꢄcute toxicity of reversible inhibitors of ꢄꢈhꢆ in rat
one ꢅD50 of soman in mice
after intramuscular administration
Reversible inhibitor
of AChE
LD50 (µg⁄kg) ±95% IS
Protective
ratio
Reversible inhibitor
of AChE
LD50 (mg/kg) ±95%*
References
ꢇoman only
pyridostigmine
K298
K344
K474
81.8 (70.8–94.4)
73.5 (59.3–85.1)
70.9 (52.5–98.0)
74.0 (62.2–84.2)
80.2 (48.2–115.2)
ꢃone
0.90
0.87
0.91
0.98
pyridostigmine
asoxime (ꢉꢁ-6)
K298
ꢃot available
ꢃot available
Kassa et al
Karasova et al
Karasova et al
2
1
781.3 (738.4–826.6)
56.2 (37.59–86.75)
45.3 (30.11–60.81)
2
2
3
3
K524
Note: *95% confidence limit using probit-logarithmic analysis.
Abbreviations: ꢄꢈhꢆ, acetylcholinesterase; ꢅD , lethal dose for 50% of laboratory
Abbreviations: ꢄꢈhꢆ, acetylcholinesterase; ꢅD , lethal dose for 50% of laboratory
50
50
animals.
animals.
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Dovepress
ꢇmall bisquaternary cholinesterase inhibitors
(
pyridostigmine) was found to be poorly effective. This
Results obtained in this work could be utilized also in a
finding was most probably caused by its i.m. administration different way. Many structurally different compounds were
3
2
0 min prior to intoxication, when its half-life was about prepared and tested (differing in length and shape of the
5 min. Thus, its plasma level in time of intoxication was linker, heteroarenium moiety). These compounds form a
apparently low and it cannot increase the protection of rats relatively large dataset, which could be used in future for a
against the soman challenge. The prophylactic administration structure-activity study enabling prediction of more promis-
of reversible AChE inhibitors K298 and K344 was found not ing compounds using different computational methods.
to influence the therapeutic effect of used antidotal treatment
in soman-poisoned mice, when their pharmacokinetics was Acknowledgments
properly adjusted in this case. Only inhibitor K474 slightly This work was supported by the Ministry of Defence of the
increased the effect of the antidotal treatment (asoxime in Czech Republic (Long Term Development Plan-1011), the
combination with atropine) in soman-poisoned mice and was University Hospital in Hradec Kralove (number 00179906)
slightly better than pyridostigmine, although the differences and the University of Hradec Kralove (number 2201-2017).
between treated soman-poisoned mice with or without pre-
2
8
treatment for K474 were found not significant.
Disclosure
The authors report no conflicts of interest in this work.
Discussion
In this summary, whole pipeline for development of novel References
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opment of novel small quaternary inhibitors of ChE were
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