Further optimization of the K-Cl cotransporter KCC2 antagonist ML077: Development of a highly selective and more potent in vitro probe

Article abstract of DOI:10.1016/j.bmcl.2012.05.126

Further chemical optimization of the MLSCN/MLPCN probe ML077 (KCC2 IC ₅₀ = 537 nM) proved to be challenging as the effort was characterized by steep SAR. However, a multi-dimensional iterative parallel synthesis approach proved productive. Here

Full text of DOI:10.1016/j.bmcl.2012.05.126

Bioorganic & Medicinal Chemistry Letters 22 (2012) 4532–4535
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Bioorganic & Medicinal Chemistry Letters
journal homepage: www.elsevier.com/locate/bmcl
Further optimization of the K-Cl cotransporter KCC2 antagonist ML077:
Development of a highly selective and more potent in vitro probe
Eric Delpire a, Aleksandra Baranczak e, Alex G. Waterson b,e, Kwangho Kim e,f, Nathan Kett b,c,d
,
Ryan D. Morrison b,c,d, J. Scott Daniels b,c,d, C. David Weaver b,f, Craig W. Lindsley b,c,d,e,
⇑
a Department of Anesthesiology, Vanderbilt University School of Medicine, Nashville, TN 37232, USA
b Department of Pharmacology, Vanderbilt University School of Medicine, Nashville, TN 37232, USA
c Vanderbilt Center for Neuroscience Drug Discovery, Vanderbilt University School of Medicine, Nashville, TN 37232, USA
d Vanderbilt Specialized Chemistry Center for Probe Development (MLPCN), Nashville, TN 37232, USA
e Department of Chemistry, Vanderbilt University, Nashville, TN 37232, USA
f Vanderbilt Institute of Chemical Biology Synthesis Core, Vanderbilt University School of Medicine, Nashville, TN 37232, USA
a r t i c l e i n f o
a b s t r a c t
Article history:
Further chemical optimization of the MLSCN/MLPCN probe ML077 (KCC2 IC50 = 537 nM) proved to be
challenging as the effort was characterized by steep SAR. However, a multi-dimensional iterative parallel
synthesis approach proved productive. Herein we report the discovery and SAR of an improved novel
antagonist (VU0463271) of the neuronal-specific potassium-chloride cotransporter 2 (KCC2), with an
IC50 of 61 nM and >100-fold selectivity versus the closely related Na-K-2Cl cotransporter 1 (NKCC1)
and no activity in a larger panel of GPCRs, ion channels and transporters.
Received 30 April 2012
Accepted 31 May 2012
Available online 7 June 2012
Keywords:
Potassium-chloride cotransporter 2
KCC2
Ó 2012 Elsevier Ltd. All rights reserved.
NKCC1
Antagonist
Due to their key regulatory roles in CNS physiology, cation-
chloride cotransporters, and in particular, the neuronal specific
K-Cl cotransporter 2 (KCC2) has recently garnered a great deal of
attention.1–4 KCC2, identified in 1996,5 modulates inhibitory neu-
rotransmission in both the brain and spinal cord.6–11 However,
due to a complete lack of selective and potent pharmacological
tools,4 the study of KCC2 has relied on either high doses of furose-
mide or genetic models (mouse and Drosophila knockout or trans-
genic zebrafish).1–4,12–15 Based on the necessity of small molecule
probes to dissect the role of KCC2, an HTS compatible screen in
384-well plates was developed based on thallium (Tl+ flux) in
KCC2-overexpressing HEK293 cells.4,16 Under the auspice of the
MLSCN/MLPCN, 234,560 compounds were screened against KCC2,
and after obligate counter- and secondary screens, 26 hits were
identified as KCC2 antagonists.4 Of these, VU0240511 (1) emerged
as an attractive, potent hit (KCC2 IC50 = 568 nM), with >100-fold
selectivity versus Na-K-2Cl cotransporter 1 (NKCC1), a critical
anti-target as inhibition leads to ototoxic effects (Fig. 1). Upon pro-
filing in an ancillary pharmacology panel of 68 GPCRs, ion channels
O
N
O
N
S
S
S
S
N
Me
N
H
N
N
N
N
1, VU0240511
KCC2 IC50 = 568 nM
NKCC1 IC50 > 50 µM
4 significant hits in Ricerca panel
2, VU0255011 (ML077)
KCC2 IC50 = 537 nM
NKCC1 IC50 > 50
No hits in Ricerca panel
µM
Figure 1. Structures of the KCC2 antagonist HTS hit (1) and the KCC2 antagonist
MLPCN probe (2), ML077. Simple conversion to the tertiary N-Me amide eliminated
all ancillary pharmacology while maintaining KCC2 potency and selectivity.
secondary amide in 1 to a tertiary N-Me amide, VU0255011 (2).
While 2 displayed a slight improvement in KCC2 potency (KCC2
IC50 = 537 nM) and maintained >100-fold selectivity versus NKCC1,
we were gratified to note a cleaner ancillary pharmacology profile
and transporters, 1 showed significant inhibition (>50% @ 10 lM)
(no activities >50% @ 10 l
M).4 Thus, 2 was declared an MLSCN/
of several GPCRs and key ion channels (hERG and L-Type Ca2+
channels). Based on similar issues in the past, we converted the
MLPCN probe and given the designation ML077.17 As such,
ML077 is freely available upon request,18 and we have supplied
ML077 to multiple laboratories around the world. While good data
is being generated, there is a need for a more potent KCC2 antago-
nist. In this Letter, we detail the DMPK characterization of ML077
⇑
Corresponding author.
E-mail address: craig.lindsley@vanderbilt.edu (C.W. Lindsley).
0960-894X/$ - see front matter Ó 2012 Elsevier Ltd. All rights reserved.
http://dx.doi.org/10.1016/j.bmcl.2012.05.126

E. Delpire et al. / Bioorg. Med. Chem. Lett. 22 (2012) 4532–4535
4533
Alternate heterocycles
Alternate substitution
Other azaheterocycles
O
N
S
S
N
N
Me
Substituted Aryl
Heteroaryl
N
Larger alkyl
cycloalkyl, H
Substitution
enantiospecific inhbition?
2, VU0255011 (ML077)
Figure 2. Initial chemical optimization plan for ML077 to improve KCC2 potency.
O
O
R1
O
a)
c)
Het
R1
Het
Cl
Cl
N
R
HN
R
Cl
+
R2
R2
3
4
5
R1
Y
X
SH
Y
X
S
Het
Y
Cl
N
R
b)
W
W
R2
W
Ar(Het)
Ar(Het)
Ar(Het)
X
6
7
8
W, X, Y = CH or N
W, X, Y = CH or N
W, X, Y = CH or N
Scheme 1. Reagents and conditions: (a) Et3N, CH2Cl2, 0 °C, 65–95%; (b) thiourea, 220 °C, microwave, 15 min, 70–85%; (c) Cs2CO3, CH3CN, rt, 56–80%.
and the further chemical lead optimization of ML077 en route to a
more potent in vitro KCC2 antagonist probe.
however, that despite a poor PK, ML077 was used successfully to
block KCC2 in spinal cord through intrathecal injection.11
In the pilot phase of the Molecular Libraries initiative,17 coined
the MLSCN, DMPK profiling of probes was not supported. Now in
the production phase, or MLPCN, DMPK profiling is required.18
Thus, prior to further optimization, we profiled ML077 in an effort
to assess disposition. In our tier 1 in vitro DMPK screen, compound
ML077 displayed no significant P450 inhibition in human liver
The initial chemical optimization plan for ML077, utilizing
multi-dimensional iterative parallel synthesis,19 is detailed in
Figure 2, and the synthesis of analogs of ML077 was performed
as shown in Scheme 1. Various heteroaryl amines 3 (1o and 2o)
are treated with
a-chloroacetyl chloride 4 (or
a-alkyl substituted
variants) to deliver functionalized
a-chloroamides 5. Commercially
microsomes (IC50 >30
l
M vs 3A4, 2C9, 1A2 and ꢀ24
l
M inhibition
available heteroaryl and heterobiaryl chlorides 6 are treated with
thiourea under microwave-assisted conditions to produce the
corresponding thiols 7. Finally, reaction of a-chloroamides 5 with
thiols 7 in the presence of Cs2CO3 affords a diverse array of analogs
of 2D6) and high plasma protein binding with fraction unbound
(fu) levels between 1 and 2% in rat and human plasma, respectively.
Intrinsic clearance (CLint) determined in rat and human liver micro-
somes indicated that compound ML077 was rapidly cleared
in vitro (rat, CLint = 294 mL/min/kg; human, CLint = 228.9 mL/min/
kg). An in vitro to in vivo correlation (IVIVC) was established,
as ML077 was found to be a highly cleared compound in rat
(CL = 185 mL/min/kg) following intravenous administration
(1 mg/kg); the high volume of distribution at steady state (Vss
5.0 L/kg) and super-hepatic clearance produced a relatively short
t1/2 (26 min) in vivo. Thus, to deliver an in vivo KCC2 probe,
significant improvements in the DMPK profile are required. Note,
8 of ML077.
Analogs 8 were screened at both 20 lM and 2 lM concentra-
tions prior to full CRCs in an 86Rb uptake assay. SAR was incredibly
steep, with the majority of analogs 8 affording <20% inhibition at
20 lM. Functionalization at any position of the western 6-phenyl
moiety of ML077 with small alkyl groups, alkoxy groups or halo-
gens was not tolerated. Similarly, replacements for the pyridazine
(pyridines, pyrazines, pyrimidines and thiadiazoles) were also not
tolerated, with the exception of two weak, 2-pyridyl-based KCC2
antagonists 9 and 10 (Fig. 3). Moreover, alternative substitutions
to the eastern thiazole or alternative heterocycles (pyridines, pyr-
azine, pyrimidines, etc.) to replace the thiazole were inactive.
Thus, an unsubstituted 6-phenyl pyridazine, in combination
with the 4-methyl thiazole, was required for KCC2 inhibition.
Therefore, we focused on incorporating larger alkyl and cycloalkly
moieties to replace the tertiary N-Me amide in 2 (Fig. 2), as well as
O
N
O
N
S
S
S
S
N
N
H
N
Me
N
exploring the impact of simple alkyl substitution
a-to the amide
(Table 1).19 For the latter, we first evaluated the racemic mixture,
and then resolved, by chiral SFC, and assayed the single enantio-
mers.19 This effort was far more productive, affording KCC2 antag-
onists 11 with improved potency relative to 2, and the first
examples of enantioselective KCC2 inhibition. 11a-d employed
9
10
KCC2 IC50 = 2.9 µM
KCC2 IC50 = 6.9 µM
Figure 3. 2-Pyridyl-based weak KCC2 antagonists 9 and 10 from first generation
libraries.
either N-Me or N-Et tertiary amides with a racemic
a-Me or a-Et

4534
E. Delpire et al. / Bioorg. Med. Chem. Lett. 22 (2012) 4532–4535
Table 1
Structures and activities of analogs 11
O
N
S
S
N
N
R
R1
N
11
Compd
R
R1
% Inhib. @ 2
lM
IC50 (nM)
2
H
Me
Me
Me
Et
82
46
27
45
57
537
ND
ND
ND
ND
11a
11b
11c
11d
( )ꢁMe
( )ꢁEt
( )ꢁEt
( )ꢁMe
Et
11e
11f
11g
11h
11i
( )ꢁMe
(+)ꢁMea
(ꢁ)ꢁMea
( )ꢁEt
(+)ꢁEta
(ꢁ)ꢁEta
H
87
570
152
1,900
756
385
ND
ND
ND
84
ND
40
11j
11k
ND
61
11m
11n
H
H
ND
ND
177
1057
ND: not determined.
a
Enantiomers separted by chiral SFC and (+) or (ꢁ) rotation noted19, absolute
stereochemistry is unknown.
Figure 4. Dose-response curves for 2 (ML077) and 11k (VU0463271). (A) Full dose-
response curves for
and 11k on KCC2 function in an 86Rb uptake assay,
2
highlighting the increased potency of 11k versus the original probe ML077 (2). (B)
Full dose-response curves for 2 and 11k on NKCC1 function in an 86Rb uptake assay,
with both displaying weak partial inhibition at concentrations up to 100 lM.
moiety, and these analogs showed weak KCC2 inhibition (27–57%
@ 2
to an N-cyclopropyl moiety, KCC2 inhibitory activity was im-
proved. The racemic -Me congener 11e and the -Et derivative
lM). When the steric bulk of the tertiary amide was increased
11 k, as it was found to be unstable in rat plasma (6% remaining
after 1 h at 37 °C). Intrinsic clearance (CLint) determined in human
liver microsomes indicated that compound 11k was rapidly
cleared in vitro, and was found to be a moderate-to-high clearance
compound in rat (CL = 57 mL/min/kg) following intravenous
administration (1 mg/kg); the low volume of distribution at steady
state (Vss 0.4 L/kg), coupled with moderate-to-high clearance pro-
duced a relatively short t1/2 (9 min) in vivo. Thus, to deliver an
in vivo KCC2 probe, significant improvements in the DMPK profile
are still required. However, 11k represents a significant improve-
ment in terms of an in vitro KCC2 antagonist probe relative to
ML077.
Based on the steep SAR and poor in vivo PK, we elected to revisit
our HTS hits in an effort to develop an in vivo KCC2 antagonist
probe. Very few hits from the HTS showed reasonable KCC2 potency
in conjunction with NKCC1 selectivity; however, dihydropyrimi-
dine dione 12 (IC50 = 640 nM) and [1,2,3]triazolo[4,5-d]pyrimidine
a
a
11h displayed IC50’s of 570 nM and 756 nM, respectively, compara-
ble to 2. Chiral SFC resolution of the single enantiomers of 11e
afforded 11f, the (+)-enantiomer, and 11g the (ꢁ)-enantiomer.
Here, the (+)-enantiomer 11f is
a potent KCC2 antagonist
(IC50 = 152 nM), while the (ꢁ)-enantiomer 11g is ꢀ10-fold less ac-
tive (IC50 = 1900 nM). A similar enantiopreference is observed with
the
a-ethyl congeners 11i and 11j. These data represent the first
example of enantiospecific inhibition of KCC2. Based on the impact
of the N-cyclopropyl amide, we then surveyed this modification
with an unsubstituted core, affording 11k, the most potent KCC2
antagonist reported to date (IC50 = 61 nM).19 As we further in-
creased the steric bulk of the tertiary amide to N-cyclobutyl,
11m (IC50 = 177 nM), and N-cyclopentyl, 11n (IC50 = 1057 nM),
KCC2 potency diminished (Table 1). Based on these data, efforts
focused on the further characterization of 11k (VU0463271).20
Figure 4 displays the full dose-response curves for both 2
(ML077) and 11k (VU0463271) for both KCC2 and NKCC1, our
13 (IC50 = 1.2 lM) represented acceptable starting points (Fig. 5).
Similar multi-dimensional iterative parallel synthesis approaches
for the lead optimization of 12 and 13 led to inactive compounds
once again. Recognition of the structural similarities between 12,
2 and 11k led us to generate chimeras, replacing the dihydropyrim-
idine dione of 12 with the 4-methyl thiazole moiety found in 2 and
11k and a number of other azaheterocycles. However, all the chi-
standard anti-target in 86Rb uptake assays.4,21 Here, both
2
(IC50 = 537 nM) and 11k (IC50 = 61 nM) are potent KCC2 antago-
nists, but only display weak, partial inhibition of NKCC1 function
at concentrations up to 100 lM. In the Lead Profiling screen at Ric-
erca (68 GPCRs, ion channels and transporter radioligand binding
assays),22 11k displayed no significant activities (no inhibition
meras were inactive or very weak inhibitors (IC50’s >20
KCC2.
lM) of
>50% @ 10
l
M). Thus, 11k is ꢀ9-times more potent than ML077,
and maintains an excellent ancillary pharmacology profile. In our
In summary, we have further optimized the KCC2 antagonist
probe ML077, by application of a multi-dimensional iterative paral-
lel synthesis approach, to afford 11k (VU0463271), one of the most
potent (KCC2 IC50 = 61 nM) and selective (>100-fold versus NKCC1
and inactive in an ancillary pharmacology panel of 68 GPCRs, ion
tier 1 in vitro DMPK screen, compound 11k displayed only very
P450 inhibition in human liver microsomes (IC50 >30
2C9, 2D6 and ꢀ20 M inhibition of 1A2). Plasma protein binding,
with fraction unbound (fu) levels, could not be determined for
lM vs 3A4,
l

E. Delpire et al. / Bioorg. Med. Chem. Lett. 22 (2012) 4532–4535
Substituted Ph
4535
Heteroaryl
Deletion of benzyl CH2
Substituted Ph
Heteroaryl
Deletion of benzyl CH2
Alternate
heterocycles
Alternate Ar
heteroaryl
O
N
N
NH2
N
O
O
N
S
N
N
O
N
N
N
O
Me
O
Cl
13
12
KCC2I C50 = 1.2 µM
NKCC1 40%@50 µM
KCC2 IC50 = 640 nM
NKCC1 28%@50 µM
Figure 5. Structures of the KCC2 antagonist HTS hits 12 and 13, with selectivity versus NKCC1, and the multi-dimensional iterative parallel synthesis approach for their
chemical optimization.
channels and transporters) KCC2 antagonist reported to date.23
14. Hekmat-Scafe, D. S.; Lundy, M. Y.; Ranga, R.; Tanouye, M. A. J. Neurosci. 2006,
26, 8943.
While possessing a favorable in vitro DMPK profile, 11k is a highly
15. Reynolds, A.; Brustein, E.; Liao, M.; Mercado, A.; Babilonia, E.; Mount, D. B.;
cleared, short half-life compound not suitable as an in vivo probe.
Attempts to optimize additional HTS hits, including chimeras with
11k, were not productive. Overall, the SAR of all the KCC2 antago-
nist series was extremely steep. At present, the MLPCN screening
deck has more than doubled since the KCC2 screen was originally
performed, and we are actively pursuing a rescreen to identify more
tractable hits with the potential to develop an in vivo probe to com-
pliment our in vitro KCC2 probe 11k. As both ML077 and 11k were
developed for the MLPCN, they are freely available upon request.
Additional refinements and studies are in progress and will be re-
ported in due course.
Drapeau, P. J. Neurosci. 2008, 28, 1588.
16. Weaver, C. D.; Harden, D.; Dworetzky, S. I.; Robertson, B.; Knox, R. J. J. Biomol.
Screen. 2004, 9, 671.
17. For information on the MLI or MLPCN please see: http://mli.nih.gov/mli/mlpcn/.
18. To request your free sample of ML077 or 11k, please email:
craig.lindsley@vanderbilt.edu.
19. Kennedy, J. P.; Williams, L.; Bridges, T. M.; Daniels, R. N.; Weaver, C. D.;
Lindsley, C. W. J. Comb. Chem. 2008, 10, 345.
20. Experimental details and characterization data for compounds in Table 1.
Synthesis of 11k: To a solution of cyclopropyl-(4-methyl-thiazol-2-yl)-amine
(160 mg, 1 mmol) (117 mg, 1 mmol, 82.5
l
L) and chloroacetyl chloride
L) in CH2Cl2 (3.4 mL, 0.3 M) at 0 °C was added Et3N
L). After 30 min, complete consumption of starting
(117 mg, 1 mmol, 82.5
(104 mg, 1 mmol, 144
l
l
material as followed by liquid chromatography-mass spectrometry (LC–MS)
was observed. Saturated, aqueous solution of NH4Cl was added. The aqueous
layer was extracted with CH2Cl2 (ꢂ 2). The combined organic layers were dried
(MgSO4), filtered, and concentrated in vacuo. The residue was taken to the next
step without further purification. To a solution of 6-phenylpyridazine-3-thiol
(214 mg, 1.14 mmol) and 2-chloro-N-cyclopropyl-N-(4-methylthiazol-2-
yl)acetamide (ꢀ1 mmol) in CH3CN (5 mL, 0.2 M) at ambient temperature was
added Cs2CO3 (506 mg, 1.55 mmol). After 18 h the reaction mixture was
diluted with EtOAc and washed with H2O (ꢂ 2). The organic layer was dried
(MgSO4), filtered and concentrated in vacuo. The residue was purified by flash
chromatography (Hexane/EtOAc, 4:1) to provide desired product as a yellow
Acknowledgments
The authors acknowledge Emily Days and Christopher Farmer
of the Vanderbilt High Throughput Screening facility and the
legacy MLSCN Screening Center for GPCRS, ion channels and trans-
porters. This work was supported by grants from the NIH. Vander-
oil (216 mg, 56% over two steps). 1H NMR (400 MHz, CDCl3):
d 7.99 (d,
bilt is
a Specialized Chemistry Center within the Molecular
J = 1.6 Hz, 1 H), 7.97 (s, 1 H), 7.64 (d, J = 9.2 Hz, 1 H), 7.48–7.45 (m, 4 H), 6.59 (s,
1 H), 4.80 (s, 2 H), 3.31–3.28 (m, 1 H), 2.38 (s, 3 H), 1.28 (m, 2 H), 1.01 (m, 2 H);
13C NMR (100 MHz, CDCl3): d 169.4, 160.2, 159.0, 156.5, 147.5, 135.9, 129.8,
128.9, 126.6, 126.2, 123.4, 110.3, 34.8, 30.5, 17.4, 11.3; HRMS (ESI) calcd for
Libraries Probe Centers Network (U54MH84659).
References and notes
C
19H19N4OS2 [M+H+] 383.1000 found 383.1000. Characterization of 11e–g: 1
H
1. Woo, N.-S.; Lu, J.; England, R.; McClellan, R.; Dufour, S.; Moint, D. B.; Deutch, A.
Y.; Lovinger, D. M.; Delpire, E. Hippocampus 2002, 12, 258.
2. Zhu, L.; Polley, N.; Mathews, G. C.; Delpire, E. Epilepsy Res. 2008, 79, 201.
3. Morgado, C.; Pinto-Ribeiro, F.; Tavares, I. Neurosci. Lett. 2008, 438, 102.
4. Delpire, E.; Days, E.; Lewis, L. M.; Mi, D.; Kim, K.; Lindsley, C. W.; Weaver, C. D.
Proc. Natl. Acad. Sci. U.S.A. 2009, 106, 5383.
5. Payne, J. A.; Stevenson, T. J.; Donaldson, L. F. J. Biol. Chem. 1996, 271, 16245.
6. Nomura, H.; Sakai, A.; Umino, M.; Suzuki, H. Neurosci. Res. 2006, 56, 435.
7. Jolivalt, C. G.; Lee, C. A.; Ramos, K. M.; Calcutt, N. A. Pain 2008, 140, 48.
8. Miletic, G.; Miletic, V. Pain 2008, 137, 532.
9. Zhang, W.; Liu, L.-Y.; Xu, T. L. Neuroscience 2008, 152, 502.
10. Cramer, S. W.; Baggott, C.; Cain, J.; Tilghman, J.; Allcock, B.; Miranpuri, G.;
Rajpal, S.; Sun, D.; Resnicj, D. Mol. Pain 2008, 4, 36.
NMR (400 MHz, CDCl3): d 8.01 (d, J = 2.0 Hz, 1 H), 7.99 (d, J = 1.6 Hz, 1 H), 7.65
(d, J = 9.2 Hz, 1 H), 7.51–7.48 (m, 3 H), 7.37 (d, J = 9.2 Hz, 1 H), 6.60 (s, 1 H), 6.05
(bs, 1 H), 3.33 (bs, 1 H), 2.36 (s, 3 H), 1.77 (d, J = 6.8 Hz, 3 H), 1.24–1.18 (m, 2 H),
1.10–1.05 (m, 1 H), 0.90–0.86 (m, 1 H); 13C NMR (100 MHz, CDCl3): d 173.7,
160.3, 159.1, 156.6, 147.6, 135.8, 129.9, 129.0, 128.9, 127.7, 126.6, 126.2, 123.5,
110.5, 40.86, 30.68, 18.59, 17.44; HRMS (ESI) calcd for C20H21N4OS2 [M+H+]
397.1154 found 397.1157. Peak A ½a D20
ꢃ +290.3° (c = 0.033, CHCl3) SFC preffered
column: chiralpak ia RT = 2.23 min; Peak A ½a D20
ꢃ ꢁ296.0° (c = 0.036, CHCl3) SFC
preferred column: chiralpak ia RT = 2.79 min.
21. Experimental details for the KCC2-overexpressing HEK293 cells and for 86Rb
uptake experiments can be found in Ref. 4
22. For full information on the targets in the Lead Profiling Screen at Ricerca, please
see: www.ricerca.com.
11. Austin, T. M.; Delpire, E. Anesth. Analg. 2011, 113, 1509.
12. Hubner, C. A.; Stein, V.; Hermans-Borgmeyer, I.; Meyer, T.; Ballanyl, K.; Jentsch,
T. J. Neuron 2001, 30, 515.
23. Pégurier, C.; Bosman, N.; Collart, P.; Delporte, M.-L.; Leclercq, K.; Lengelé, S.;
Kanduluru, A. K.; Meunier, S.; Pacico, N.; Vadail, L. R.; Wangner, A.; Wolff, C.;
Provins, L. Bioorg. Med. Chem. Lett. 2010, 20, 2542.
13. Zhu, L.; Lovinger, D.; Delpire, E. J. Neurophysiol. 2005, 93, 1557.