A novel class of allosteric modulators of AMPA/Kainate receptors

Article abstract of DOI:10.1016/j.bmcl.2008.12.094

The rapid hydrolysis in vivo of IDRA21 to 2-amino-5-chlorobenzensulfonamide has been demonstrated by microdialysis experiments. The IDRA21 metabolite possess in vitro a biological activity similar to that of IDRA21 itself. Taking 2-amino-5-chlorobenzensulfonamide as lead compound, a novel class of AMPAR positive allosteric modulators has been prepared.

Full text of DOI:10.1016/j.bmcl.2008.12.094

Bioorganic & Medicinal Chemistry Letters 19 (2009) 1254–1257
Contents lists available at ScienceDirect
Bioorganic & Medicinal Chemistry Letters
journal homepage: www.elsevier.com/locate/bmcl
A novel class of allosteric modulators of AMPA/Kainate receptors
b
a
a
a
Giuseppe Cannazza a, , Krzysztof Jozwiak , Carlo Parenti , Daniela Braghiroli , Marina M. Carrozzo ,
*
Giulia Puia c, Gabriele Losi c, Mario Baraldi c, Wolfgang Lindner d, Irving W. Wainer e
a Department of Pharmaceutical Science, University of Modena e Reggio Emilia, Via Campi 183, 41100 Modena, Italy
b Laboratory of Drug-Receptor Interactions, Department of Chemistry, Medical University of Lublin, ul.K.Jaczewskiego 4, 20-950 Lublin, Poland
c Department of Biomedical Science, University of Modena e Reggio Emilia, Via Campi 183, 41100 Modena, Italy
d Department of Analytical Chemistry and Food Chemistry, University of Vienna, Währingerstrasse 38, A-1090 Vienna, Austria
e Bioanalytical and Drug Discovery Unit, Gerontology Research Center, National Institute on Aging, National Institutes of Health, 5600 Nathan Shock Drive,
Baltimore, MD 21224-6825, USA
a r t i c l e i n f o
a b s t r a c t
Article history:
The rapid hydrolysis in vivo of IDRA21 to 2-amino-5-chlorobenzensulfonamide has been demonstrated
by microdialysis experiments. The IDRA21 metabolite possess in vitro a biological activity similar to that
of IDRA21 itself. Taking 2-amino-5-chlorobenzensulfonamide as lead compound, a novel class of AMPAR
positive allosteric modulators has been prepared.
Received 16 November 2008
Revised 16 December 2008
Accepted 16 December 2008
Available online 30 December 2008
Ó 2009 Elsevier Ltd. All rights reserved.
Keywords:
IDRA21
AMPA positive modulators
2-Amino-5-chlorobenzensulfonamide
L
-Glutamate is the principal excitatory neurotransmitter in the
The observed cognition-enhancing effect of ( )IDRA21, which is
one of the most effective compound studied, suggests that the
compound may be useful in the treatment of learning, memory
and attention disorders resulting from aging, central nervous sys-
tem trauma, stroke and neurodegenerative disorders like Alzhei-
mer’s disease.18
Despite the high potency in vivo, ( )IDRA21 potency in modu-
lating AMPA receptor function in vitro is low with an EC50 close
to 100 lM. At least two hypotheses could be formulated to explain
mammalian central nervous system (CNS), which can activate
ionotropic and metabotropic specific receptors.1–3 There is evi-
dence from animal studies that an excessive excitation mediated
by glutamate receptors may lead to neuronal damages produced
by the excessive entry of Ca2+ inside the cell. However, there is also
data suggesting that a reduced function of such receptors seems to
be involved in the learning and memory deficits observed in Alz-
heimer’s disease.4–6
It has been demonstrated that a clinically used cognition-
enhancing (nootropic) drug, aniracetam, selectively inhibits the
spontaneous rapid desensitization of AMPA receptors. The poten-
tial therapeutic benefit of compounds able to activate AMPA recep-
tors has lead to the search for new AMPA receptor modulators.7
Pyrrolidinone derivatives, such as aniracetam, benzoylpiperi-
dine derivatives, such as 1-BCP [1-(1,3-benzodioxol-5-yl car-
bonyl)-piperidine], and benzothiadiazine derivatives such as
diazoxide, cyclothiadiazide and ( )IDRA21 [7-chloro-3-methyl-
the differences in ( )IDRA21 potency between in vitro and in vivo
experiments.15,19
It is possible that ( )IDRA21 elicits its action on AMPA receptor
desensitization by preferential metabolism of one of the enantio-
meric forms, since it has been demonstrated that only one enantio-
mer is the active one.19 However, recently work has demonstrated
that a rapid interconversion of enantiomers of ( )IDRA21 occurred
in saline solution.21–23
The other hypothesis is that ( )IDRA21 could elicit its modifica-
tion of drug-induced cognitive deficit in vivo via a metabolite more
active than ( )IDRA21 itself.13 Although a great number of studies
on the pharmacological actions of ( )IDRA21 have been published,
no information has been performed on a possible pharmacody-
namic mechanism of the compound.24
3,4-dihydro-2H-1,2,4-benzothiadiazine
1,1-dioxide]
( )(1)
(Fig. 1), attenuate the spontaneous rapid desensitization rate of
AMPA receptors.8–19 Among the benzothiadiazine derivatives,
( )IDRA21 has attracted particular interest due to its ability to
act as cognitive enhancing agent in normal young and aged rhesus
monkeys when given orally in low (0.5–10 mg/kg) doses.20
Since ( )IDRA21 has been administered orally in the in vivo
pharmacological tests, studies on the stability of the drug in acidic
condition similar to that of stomach are clearly matter of interest.
In a recent work the rapid hydrolysis of ( )IDRA21 (1) (Scheme 1)
* Corresponding author. Tel.: +39 059 2055136; fax: +39 059 2055750.
E-mail address: giuseppe.cannazza@unimo.it (G. Cannazza).
0960-894X/$ - see front matter Ó 2009 Elsevier Ltd. All rights reserved.
doi:10.1016/j.bmcl.2008.12.094

G. Cannazza et al. / Bioorg. Med. Chem. Lett. 19 (2009) 1254–1257
1255
O
O
O
O
O
N
N
OCH3
Aniracetam
1-BCP
O
O
O
O
O
O
H2NO2S
Cl
S
Cl
S
Cl
S
NH
NH
N
NH
NH
CH3
NH
CH3
Diazoxide
Cyclothiazide
IDRA21
Figure 1. Allosteric AMPA positive modulators.
O
O
H+
Cl
S
Cl
SO2NH2
NH
+ CH3CHO
N
H
CH3
NH2
(1)
(2)
Scheme 1.
to acetaldehyde and 2-amino-5-chlorobenzenesulfonamide in sim-
ulated gastric fluid has been demonstrated.23 In the present work,
microdialysis studies have been performed in the rat in order to
determine whether oral administration of IDRA21 (1) produced 2
in hippocampus.
These results suggest that IDRA 21 could elicit its pharmacolog-
ical activity in vivo via its hydrolysis product 2 or it could under-
goes in vivo an ‘‘exchange” mechanism as part of its action and
activity, as in vivo there exist a number of carbonyl moieties which
may be used for transport or activity.
Figure 2 shows the extracellular levels of (À)IDRA21 ((À)1),
(+)IDRA21 ((+)1) and 2 in rat hippocampus after oral administra-
tion of racemic IDRA21 (100 mg/kg). The concentrations of both
enantiomers increased in the first 60 min after administration to
Using 2 as lead compound a series of 2-aminobenzensulfona-
mides (3–16) (Table 1) with different substituent at C4, C5, N1
and N2 has been prepared and studied for their activity as allosteric
modulators of KA-activated currents in primary cultures of cere-
bellar granule neurons, highlighting the molecule’s determinants
that confer the modulatory activity at AMPA receptors.
Compounds 3–5 were obtained from 5-chloro-2-nitro-
benzenesulfonyl chloride by reaction with the appropriate amine
and subsequently reduction as outlined in Scheme 2.
reach the concentration of 2
to be undetectable in the following 3 h. On the contrary levels of
2 increased in the first 4 h to reach the concentration of 12 g/
ml, 3 times the level that of single enantiomers of 1 and decreased
slowly for the next 2 h to a concentration of 8 g/ml.
lg/ml and then gradually decreased
l
l
We tested the activity of ( )IDRA21 and of 2 as allosteric mod-
ulators of KA-activated currents in primary cultures of cerebellar
The synthesis of compounds 6–9 were conducted starting from
2,5-dichlorosulfonyl chloride with alkylamine and by heating the
product in a sealed vessel with the appropriate amine (Scheme 3).
Compounds 10–16 were obtained by methods previously de-
scribed.25–27
granule neurons. Application of KA (100
tizing current that was mediated by both AMPA and KA receptors
activation. IDRA21 (200 M), used as reference compound, and 2
lM) evoked a nondesensi-
l
potentiated the amplitude of the KA current by 80 17% (n = 5)
and 23 2% (n = 5), respectively (Fig. 3).
As summarized in Table 2 and Figure 3, among the 2-aminoben-
zensulfonamide derivatives, tested at 200
lM, 6–9 and 12 acted as
positive modulators of KA-evoked currents.
The most active derivatives were 6, 7 and 8 that potentiate of
KA currents by 69 14% (n = 8), 91 13% (n = 8) and 80 13%
(n = 8), respectively.28
14.0
12.0
The analysis of these preliminary biological results suggests a
net of different molecular effects of these ligands, which affects ob-
served potentiation of KA-current activity. First of all, significantly
increased activity of N-alkylated derivatives 6–8, which are 3–4
times more potent comparing to compound 2, most likely is a re-
sult of inductive effect on the sulfonamide moiety produced by
the secondary amine in ortho position. High activity of compound
1, which also contains secondary amino group additionally sup-
ports this hypothesis. The trend of activities for compounds 6–8
shows that the N-alkylating moiety longer than methyl addition-
ally increase KA-current potentiation activity, however, the com-
10.0
2
8.0
(-)-1
(+)-1
6.0
4.0
2.0
0.0
0
1
2
3
4
5
6
7
time (hour)
Figure 2. Time course of 2, (À)1 and (+)1 outputs from rat hippocampus after a
single administration of ( )1 (100 mg/kg po). Values were expressed as g/ml of
mean value. SEM were always lower then 14% and omitted from the graph.
pound
9 with isopropyl substituent shows lower activity
l
comparable to that of compound 2. This suggests the second effect,

1256
G. Cannazza et al. / Bioorg. Med. Chem. Lett. 19 (2009) 1254–1257
KA
+ 7
+ 8
+ IDRA 21
+ 2
KA
A
200 pA
2 s
120
100
80
B
EC50 284 µM
EC50 134 µM
100
80
p 0.79
p 1.4
60
60
40
20
40
20
0
10
100
1000
0.1
1
10
100 1000
2 (µM)
8 (µM)
Figure 3. (A) KA-evoked currents from a cerebellar granule neuron in presence of 2-aminobenzensulfonamide derivatives and IDRA21 (all drugs are at 200
the duration of application of KA 100
with a sigmoidal function using Origin 4.1. Each data point is the mean SE of at least five cells.
lM). Bar indicates
l
M; holding potential À60 mV. (B) Dose–response curves of 2 and 8 expressed as percentage of the maximal effect. The curve was fitted
Table 1
2-Aminobenzenesulfonamides studied
the negative steric influence of the N-alkylation by the branched
substituent. It may either prevent the rotation of moieties of the li-
gand molecule and/or the receptor’s active site has some steric re-
straints that are felt by the larger volume of the isopropyl group
and not by the n-alkyl groups.
R5
SO2NHR1
NHR2
R4
R3
Molecular modeling studies of ligands confirm this interpreta-
tion. Compounds 1, 6–9 has higher dipole moments calculated
from the atom’s partial charges (6.75 D, 5.43 D, 5.59 D, 5.63 D,
5.66 D, respectively) than derivatives 2–5 (5.03 D, 4.89 D, 4.98 D,
4.88 D, respectively). Similarly, a significant difference was ob-
served comparing point charge distributed on nitrogen atom of
the ortho amino group among these molecules. The partial charge
of nitrogen atom in derivatives 1, 6–9 ranged from À0.33 to À0.32
whereas in derivatives 2–5 was calculated as À0.36. Results of this
simulation indicate inductive effect of N-alkyl moiety on the sul-
fonamide group which promotes activity. In case of compound 9,
this positive effect is balanced by the negative steric effect of
branched substituent. The presence of the chlorine atom in posi-
tion 5 seems to be another essential requisite for the action of 2-
aminobenzenesulfonamide type compounds as AMPA allosteric
positive modulators. The absence of chlorine atom (compound
Compound
R1
R2
R3
R4
R5
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
–H
–CH3
–CH2CH3
–CH2CH2CH3
–H
–H
–H
–H
–H
–H
–H
–H
–H
–H
–H
–H
–H
–H
–H
–H
–H
–H
–CH3
–H
-H
–H
–H
–H
–H
–H
–H
–Cl
–Cl
–Cl
–Cl
–Cl
–Cl
–Cl
–Cl
–H
–H
–Cl
–H
–NO2
–SO2NH2
–H
–H
–H
–H
–H
–H
–H
–H
–H
–H
–H
–H
–CH3
–CH2CH3
–CH2CH2CH3
–CHCH3CH3
–H
–H
–H
–H
–H
–H
–H
–H
–Cl
–Cl
–OCH3
–H
–Cl
–H

G. Cannazza et al. / Bioorg. Med. Chem. Lett. 19 (2009) 1254–1257
1257
Cl
SO2NHR
SO2Cl
SO2NHR
Cl
Cl
i
ii
NO2
NH2
NO2
Scheme 2. Reagents and conditions: (i) methylamine, ethylamine or propylamine for 3, 4, and 5, respectively; (ii) Fe, HCl.
Acknowledgements
Cl
SO2NH2
Cl
Cl
SO2NH2
NHR
i
This work was support in part by funding from the Intramural
Research Program of the National Institute on Aging/NIH.
A. Supplementary data
Scheme 3. Reagents and conditions: (i) methylamine, ethylamine, propylamine or
isopropylamine for 6, 7, 8, and 9, respectively,
D
.
Supplementary data associated with this article can be found, in
the online version, at doi:10.1016/j.bmcl.2008.12.094.
References and notes
Table 2
Variation of KA-evoked currents induced by IDRA21 (1) and by 2-aminosulfonamide
derivatives 2–16
1. Krogsgaard-Larsen, P.; Ebert, B.; Lund, T. M.; Brauner-Osborne, H.; Slk, F. A.;
Johansen, T. N.; Brehm, L.; Madsen, U. Eur. J. Med. Chem. 1996, 31, 515.
2. Excitatory Amino Acid Receptors. Design of Agonists and Antagonists; Krogsgaard-
Larsen, P., Hansen, J. J., Eds.; Ellis Horwood: Chichester, 1992.
3. The NMDA Receptor; Collingridge, G. L., Watkins, J. C., Eds.; Oxford University
Press: Oxford, 1994.
4. Bliss, T. V. P.; Collingridge, G. L. Nature 1993, 361, 31.
5. Nagarajan, N.; Quast, C.; Boxall, A. R.; Shahid, M.; Rosenmund, C.
Neuropharmacology 2001, 41, 650.
6. Vyklicky, L.; Patneau, D. K.; Mayer, M. L. Neuron 1991, 7, 971.
7. Lynch, G. Curr. Opin. Pharmacol. 2004, 4, 4.
8. Ito, I.; Tanabe, S.; Khoda, A.; Sugiyama, H. J. Physiol. 1990, 424, 533.
9. Arai, A.; Kessler, M.; Xiao, P.; Ambros-Ingerson, J.; Rogers, G.; Lynch, G. Brain
Res. 1994, 638, 343.
Compound
Variation of
Compound
Variation of
KA current, %
KA current, %
1
2
3
4
5
6
7
8
80 17
9
32
À5
8
5
5
11
23
5
2
11
10
11
12
13
14
15
16
12 11
35 11
4
5
À5
À8
À6
7
2
5
3
3
69 14
91 13
80 13
10. Yamada, K. A.; Tang, C. M. J. Neurosci. 1993, 13, 3904.
11. Pirotte, B.; Podona, T.; Diouf, O.; de Tullio, P.; Lebrun, P.; Dupont, L.; Somers, F.;
Delarge, J.; Morain, P.; Lestage, P.; Lepagnol, J.; Spedding, M. J. Med. Chem. 1998,
41, 2946.
12. Bertolino, M.; Baraldi, M.; Parenti, C.; Braghiroli, D.; DiBella, Maria; Vicini, S.;
Costa, E. Receptors Channels 1993, 1, 267.
13. Impagnatiello, F.; Oberto, A.; Longone, P.; Costa, E.; Guidotti, A. Proc. Natl. Acad.
Sci. U.S.A. 1997, 94, 7053.
14. Thompson, D. M.; Guidotti, A.; Di Bella, M.; Costa, E. Proc. Natl. Acad. Sci. U.S.A.
1995, 92, 7667.
15. Zivkovic, I.; Thomson, D. M.; Bertolino, M.; Uzunov, D.; Di Bella, M.; Costa, E.;
Guidotti, A. J. Pharmacol. Exp. Ther. 1994, 272, 300.
16. Arai, A.; Guidotti, A.; Costa, E.; Lynch, G. Neuroreport 1996, 7, 2211.
17. Puia, G.; Losi, G.; Razzini, G.; Braghiroli, D.; Di Bella, M.; Baraldi, M. Prog.
Neuropsychopharmacol. Biol. Psychiatry 2000, 24, 1007.
18. Yamada, K. A. Neurobiol. Dis. 1998, 5, 67.
19. Braghiroli, D.; Puia, G.; Cannazza, G.; Tait, A.; Parenti, C.; Losi, G.; Baraldi, M. J.
Med. Chem. 2002, 45, 2355.
20. Buccafusco, J. J.; Weiser, T.; Winter, K.; Klinder, K.; Terry, A. V.
Neuropharmacology 2004, 46, 10.
21. Cannazza, G.; Braghiroli, D.; Baraldi, M.; Parenti, C. J. Pharm. Biomed. Anal. 2000,
23, 117.
22. Cannazza, G.; Braghiroli, D.; Tait, A.; Baraldi, M.; Parenti, C.; Lindner, W.
Chirality 2001, 13, 94.
23. Cannazza, G.; Carrozzo, M. M.; Braghiroli, D.; Parenti, C. J. Chromatogr. A 2008,
in press. doi:10.1016/j.chroma.2008.09.087.
24. Uzunov, D. P.; Zivkovich, I.; Pirkle, W. H.; Costa, E.; Guidotti, A. J. Pharm. Sci.
1995, 84, 937.
25. Tait, A.; Parenti, C.; Zanoli, P.; Veneri, C.; Truzzi, C.; Brandoli, C.; Baraldi, M.; Di
Bella, M. Farmaco 1993, 48, 1463.
26. Parenti, C.; Costantino, L.; Di Bella, M.; Raffa, L.; Baggio, G. G.; Zanoli, P. Arch.
Pharm. 1985, 318, 903.
27. Girard, Y.; Atkinson, J. G.; Rokach, J. J. Chem. Soc., Perkin Trans. 1: Org. Bioorg.
Chem. 1979, 1043.
28. Cannazza, G.; Parenti, C.; Lindner, W.; Puia, G.; Baraldi, M.; Braghiroli, D.; Tait,
A. WO02/089734, 2002.
10) or its substitution at C5 with a nitro or sulfamoyl group (com-
pounds 14 and 15) resulted in a loss of activity. A chlorine or meth-
oxy group in position
4 (compounds 11 and 13) leads to
compounds without positive modulator activity on AMPA receptor.
Chlorine atom at the meta position should not produce significant
inductive effect on the sulfamoyl group (compound 11 is less ac-
tive than 2 and compound 12 is as active as 2). On the other hand,
the chlorine groups can form hydrogen bond, have some hydro-
phobic characteristics and are bulky, thus, one should assume that
this substituent at C5 helps to position the compounds within the
active site of the molecule. The lack of activity of compounds 13–
16 supports this assumption.
The results of this study suggest that in vivo IDRA21 (1) is rap-
idly hydrolyzed to 2-amino-5-chlobenzensulfonamide (2), which
display in vitro biological activity similar to that of IDRA21. Taking
2-amino-5-chlobenzensulfonamide (2) as the lead compound, a
novel class of AMPA positive allosteric modulators has been pre-
pared, in which compounds 7 and 8 had the highest biological
activity. The analysis of the relationship between the structures
of the synthesized compounds and their biological activity has
indicated structural features that may be manipulated to increase
biological activity. This possibility is currently being investigated
and will be expanded and confirmed. The objective will be the
development of new lead drug candidates for the treatment of cog-
nitive deficits.