Pyrazolecarboxamide human neuropeptide Y5 receptor ligands with in vivo antifeedant activity

Article abstract of DOI:10.1016/S0960-894X(01)00449-8

1-Aryl-3-carboxamido-5-alkylpyrazoles were prepared based on a hit found in high-throughput screening of our corporate compound library in an assay measuring affinity for the human neuropeptide Y5 receptor. 1-(3-Trifluoromethylphenyl)-3-[N-(5-quinolinyl)carboxamido]-5-methylpyrazole (31) bound to the human neuropeptide Y5 receptor with a 80 nM IC₅₀and was shown to inhibit cumulative food consumption 43.2% 2-6 h after ip dosing in a fasting-induced feeding model in rats.

Full text of DOI:10.1016/S0960-894X(01)00449-8

Bioorganic & Medicinal Chemistry Letters 11 (2001) 2287–2290
Pyrazolecarboxamide Human Neuropeptide Y5 Receptor
Ligands with In Vivo Antifeedant Activity
Cheryl P. Kordik,a,* Chi Luo,a Brian C. Zanoni,a Timothy W. Lovenberg,b
Sandy J. Wilson,b Anil H. Vaidya,a Jeffrey J. Crooke,a Daniel I. Rosenthala
and Allen B. Reitza
aDrug Discovery Division, The R. W. Johnson Pharmaceutical Research Institute, Welsh and McKean Roads,
Spring House, PA19477, USA
bDrug Discovery Division, The R. W. Johnson Pharmaceutical Research Institute, 3210 Merryfield Row,
San Diego, CA92121, USA
Received 26 March 2001; accepted 11 June 2001
Abstract—1-Aryl-3-carboxamido-5-alkylpyrazoles were prepared based on a hit found in high-throughput screening of our corpo-
rate compound library in an assay measuring affinity for the human neuropeptide Y5 receptor. 1-(3-Trifluoromethylphenyl)-3-[N-
(5-quinolinyl)carboxamido]-5-methylpyrazole (31) bound to the human neuropeptide Y5 receptor with a 80 nM IC50 and was
shown to inhibit cumulative food consumption 43.2% 2–6 h after ip dosing in a fasting-induced feeding model in rats. # 2001
Elsevier Science Ltd. All rights reserved.
Neuropeptide Y (NPY), a 36-amino acid C-amidated
peptide, is abundantly expressed in the central nervous
system and has been shown to robustly stimulate
feeding.1À4 Afamily of six NPY receptor subtypes
belonging to the superfamily of G-protein coupled
receptors has been described in the literature.5À14 NPY
Y1 and NPY Y5 are thought to be the most likely
receptor subtypes responsible for centrally-mediated
NPY-induced feeding responses.13,15À17 In fact, antago-
nists at the NPY Y5 receptor have been shown to be
effective in reducing food intake in animal models of
feeding.18 Consequently, there has been an impetus to
discover small molecule NPY Y5 receptor antagonists
in order to provide new treatments for obesity and other
eating disorders.19
Screening our corporate chemical library in an assay
measuring affinity for the human neuropeptide Y5
receptor identified triazole carboxamide 3, obtained
through a compound aquisition program, as having low
micromolar binding affinity for the human Y5 receptor
(Fig. 2). The first modification done to 3 was to replace
the triazole core ring with a pyrazole ring, in order to
impart novelty to the system and to simplify the synth-
esis of derivatives for SAR development. The
Our labs have recently identified several series of NPY
Y5 antagonists.20À22 We have also disclosed amino-pyr-
azoles as potent NPY Y5 receptor antagonists.23 For
example, pyrazoles 1 and 2 were shown to have 15 and
10 nM IC50’s for the human NPY Y5 receptor,
respectively (Fig. 1).
*Corresponding author. Fax: +1-215-628-4985; e-mail: ckordik@
pruis.jnj.com
Figure 1. Aminopyrazole NPY5 receptor antagonists.
0960-894X/01/$ - see front matter # 2001 Elsevier Science Ltd. All rights reserved.
PII: S0960-894X(01)00449-8

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C. P. Kordik et al. / Bioorg. Med. Chem. Lett. 11 (2001) 2287–2290
Table 1. Y5 receptor binding affinity of pyrazole carboxamides with
R1 variationsa
Figure 2. Lead structures after analysis of HTS.
Compd
R1
NPY Y5 IC50
(nM)
corresponding pyrazole carboxamide 4 was equipotent
to original triazole 3. An intensive effort to elucidate
structure–activity relationships based on pyrazole-
carboxamide lead 4 was then undertaken.
8
9
Phenyl
Benzyl
759
>1000
>1000
150
>1000
218
>1000
>1000
>1000
10
11
12
13
14
15
16
2-(Trifluoromethyl)phenyl
3-(Trifluoromethyl)phenyl
4-(Trifluoromethyl)phenyl
3-Methylphenyl
3-Methoxyphenyl
2-Pyridyl
The pyrazole carboxamides were synthesized in three
steps from commercially available ethyl acetopyruvate 5
(Scheme 1). Reaction of 5 with an arylhydrazine under
refluxing conditions in acetic acid afforded a 4:1 mixture
of regioisomers 6 and 7, which were generally separable
by column chromatography on silica gel. Saponification
of the ester followed by coupling of the resultant car-
boxylic acid with an amine resulted in the formation of
the target pyrazole carboxamides in excellent yields.
2-Thienyl
aHEK 293 cells were stably transfected with the human NPY5 cDNA
and were used according to the procedure in ref 20.
of bicyclic compounds (viz. 28–31), the 5-isoquinolinyl
derivative (31) emerged as the most active (80 nM IC50).
Other N-containing heteroaryls at R2 are generally
inactive, such as for pyridine 32 and benzimidazole 33.
The pyrazole carboxamides were evaluated for binding
affinity to the human neuropeptide Y Y5 receptor. The
assay was executed using a stably transfected HEK293
cell line measuring competitive inhibition of binding of
125I-PYY (Table 1).20 Table 1 illustrates pyrazole car-
boxamides in which the substituent on the pyrazole core
(R1) was varied, and the N-(3,5-dichlorophenyl) group
on the amide was held constant. In general, R1 mod-
ifications were largely detrimental to NPY Y5 affinity
except for the original 3-(trifluoromethyl)phenyl group
(11) and also 3-methylphenyl (13). Unsubstituted
phenyl (8), benzyl (9), other 3-substituted phenyls such
as 14, and 2- and 4-substituted phenyl groups (10 and
12) resulted in loss of activity. Compounds bearing a
heteroaryl ring in R1 such as pyridine 15 and thiophene
16 were inactive at the NPY Y5 receptor in our assay.23
Several of the corresponding regioisomers derived from
7 were also prepared and evaluated in the NPY Y5
binding assay. These were completely inactive, indicat-
ing that the 1,3,5-substitution pattern on the pyrazole
core structure is critical for activity.
Table 2. Y5 receptor binding affinity of pyrazolecarboxamides with
variation of R2
In a similar manner, variations were made to R2 (Table
2). In general, 2- and 3- substituted phenyl groups were
well tolerated at the R2 position (17–25). When 4-sub-
stituted phenyl groups are incorporated at this site
activity is diminished (4 and 26). The 3,5-dichloro-
phenyl derivative 11 is one of the best compounds with
a 150 nM IC50 for the human NPY Y5 receptor. 2,6-
Difluorophenyl compound 27 is less active. From a set
Compd
R2
Y5 IC50
(nM)
17
18
19
20
21
22
23
24
25
4
26
11
27
28
29
30
31
32
33
2-Methylphenyl
2-Benzylphenyl
2-(N-Phenylamino)phenyl
2-(N-Pyrrolyl)phenyl
3-Chlorophenyl
573
292
267
763
520
359
670
622
3-Bromophenyl
3-Iodophenyl
3-Methylphenyl
3-(Trifluoromethoxy)phenyl
4-Fluorophenyl
4-Chlorophenyl
431
800
>1000
150
233
3,5-(Dichloro)phenyl
2,6-Difluorophenyl
1-Naphthyl
356
197
232
80
1-(5,6,7,8-Tetrahydronaphthyl)
5-Quinolinyl
5-Isoquinolinyl
2-Pyridyl
2-Benzimidazolyl
>1000
>1000
Scheme 1. Reagents: (a) R1NHNH2, AcOH, reflux; (b) NaOH, EtOH,
H2O; (c) HATU, DIPEA, R2NH2, CH2Cl2.

C. P. Kordik et al. / Bioorg. Med. Chem. Lett. 11 (2001) 2287–2290
Table 3. Data from rat feeding modela
2289
Experimental groups compared to
control group
Drug
(IP)
Dose
(mg/kg)
2 h
(g)
4 h
(g)
6 h
(g)
2–6 h
(g)
Scheme 2. Reagents: (a) NaOEt, diethyl oxalate, Et2O, 0 ꢀC; (b)
R1NHNH2, H2SO4, H2O, CHCl3; (c) NaOH, EtOH, H2O; (d) HATU,
DIPEA, R2NH2, CH2Cl2.
PEG-200
(N=24)
Fluoxetine
0
AVG=
SE=
AVG=
SE=
8.63
12.3
18.8
10.2
0.398
4.38*
0.294
0.53
7.25*
0.479
0.756
12.6*
0.648
0.59
8.25*
0.512
10
(N=24)
11
%CH= À49.2
À41.06 À32.98 À19.12
Since the aminopyrazoles such as 1 and 2 were very
active,24 we also prepared hybrid structures of that ser-
ies and the one reported in this paper. These derivatives
were obtained as illustrated in Scheme 2, involving the
reaction of the anion of acetonitrile with diethyl oxalate,
followed by formation of the pyrazole from the resul-
tant intermediate by treatment with an aryl hydrazine.
The pyrazole ester was then saponified with aqueous
sodium hydroxide, and the acid that formed coupled to
appropriate amines using standard peptide coupling
procedures.
p=
AVG=
SE=
<0.01
5.31*
0.538
<0.01
9.44*
0.652
<0.01
13.9*
0.856
<0.05
8.56
0.612
30
(N=16)
%CH= À38.47 À23.25 À26.06 À16.08
p=
<0.01
<0.01
<0.01
>0.05
PEG-200
(N=8)
Fluoxetine
0
AVG=
SE=
AVG=
SE=
10.4
16
23.4
13
0.905
4.50*
0.824
0.845
8.25*
1.06
0.778
13.4*
1.82
0.681
8.88*
1.17
10
(N=8)
31
%CH= À56.73 À48.4
À42.74 À31.69
p=
AVG=
SE=
<0.01
6.88*
0.718
<0.01
9.13*
0.934
<0.01
14.6*
1.37
<0.05
7.38*
1.22
30
(N=8)
%CH= À33.85 À42.94 À37.61 À43.23
The best R1 and R2 groups from the pyrazole carbox-
amide series were incorporated into an aminopyrazole
scaffold to provide 34 and 35 (Fig. 3). Both of these
compounds had substantially decreased affinity for Y5
(>1000 and 400 nM IC50’s, respectively).
p= <0.05 <0.01 <0.01 <0.01
%CH, % change; * signifies statistical significance.
aMale Long–Evans rats were fasted for 18 h prior to testing. At the
end of the fasting period, animals were administered either the test
compound or vehicle 30 min intraperitoneally prior to the experiment.
The test compounds were administered as a solution or suspension in
PEG 200. Food consumption was determined at 2, 4, and 6 h after
administration by weighing the special jar containing the food before
the experiment and at each specified time.
Compounds 11 and 31 were tested in a fasting-induced
feeding model in rats.20,25 Both compounds were admi-
nistered ip and compared to vehicle (PEG-200) and
reference compound (fluoxetine). They caused statisti-
cally significant decreases in food consumption relative
to fluoxetine as control (Table 3), and both were well
tolerated. Since NPY was not added initially to enhance
feeding, it is not possible to know whether this reduc-
tion of feeding is entirely mediated by an interaction
with the NPY Y5 receptor. Neither compound was
active upon oral administration.
be seen for NPY Y5 receptor antagonists, even when
exogenous NPY is not added to amplify NPY-induced
feeding.
Acknowledgements
We describe here another related class of compounds,
pyrazole carboxamides, which modulate the human
NPY5 receptor. The compound resulting from the
combination of the best R1 (3-trifluoromethyl) and R2
substituents (5-isoquinolinyl) was 31. This compound
and an additional member of this series (11) decreased
fasting-induced feeding in a rodent model upon ip
administration, indicating that they may be useful for
the treatment of human feeding disorders and obesity,
especially if suitable compounds can be found that are
orally bioavailable. The antifeedant activity seen for 11
and 31 are additional examples in which this effect can
We thank our colleagues for their helpful advice and
encouragement, specifically Scott Dax, Carlos Plata-
Salaman, Richard Shank, Jim McNally, Mark Young-
man, Barry Dubinsky, and Coralie Hochman.
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