Aminopiperidine indazoles as orally efficacious melanin concentrating hormone receptor-1 antagonists

Article abstract of DOI:10.1016/j.bmcl.2005.08.049

The synthesis and biological evaluation of novel 3-amino indazole melanin concentrating hormone receptor-1 antagonists are reported, several of which demonstrated functional activity of less than 100 nM. Compounds 19 and 28, two of the more potent compounds identified in this study, were characterized by high exposure in the brain and demonstrated robust efficacy when dosed in diet-induced obese mice.

Full text of DOI:10.1016/j.bmcl.2005.08.049

Bioorganic & Medicinal Chemistry Letters 15 (2005) 5293–5297
Aminopiperidine indazoles as orally efficacious
melanin concentrating hormone receptor-1 antagonists
Anil Vasudevan,* Andrew J. Souers, Jennifer C. Freeman, Mary K. Verzal, Ju Gao,
Mathew M. Mulhern, Derek Wodka, John K. Lynch, Kenneth M. Engstrom,
Seble H. Wagaw, Sevan Brodjian, Brian Dayton, Doug H. Falls, Eugene Bush,
Michael Brune, Robin D. Shapiro, Kennan C. Marsh, Lisa E. Hernandez,
Christine A. Collins and Philip R. Kym
Metabolic Diseases Research, Global Pharmaceutical Research and Development, Abbott Laboratories, Abbott Park, IL 60064, USA
Received 25 July 2005; revised 5 August 2005; accepted 10 August 2005
Available online 3 October 2005
Abstract—The synthesis and biological evaluation of novel 3-amino indazole melanin concentrating hormone receptor-1 antagonists
are reported, several of which demonstrated functional activity of less than 100 nM. Compounds 19 and 28, two of the more potent
compounds identified in this study, were characterized by high exposure in the brain and demonstrated robust efficacy when dosed in
diet-induced obese mice.
Ó 2005 Published by Elsevier Ltd.
R1
Melanin concentrating hormone (MCH) is an orexigenic
R1
N
neuropeptide, that is produced predominantly by neu-
rons in the lateral hypothalamus and zona incerta.1 Cen-
tral MCH administration stimulates food intake while
fasting results in an increase in MCH expression.2 Mice
lacking the MCH encoding gene are lean, hypophagic,
and maintain elevated metabolic rates,3 whereas mice
over-expressing the MCH gene are susceptible to obesity
and insulin resistance.4 The prospect of MCHr1 as an
attractive target for anti-obesity therapy has been re-
viewed extensively.5
N
HN
N
HN
O
H
O
R
N
R
X
R2
1
2
R1
HN
We have previously reported the identification of
MCHr1 antagonists based on a benzamide scaffold, 1.6
Subsequent optimization led to the identification of
ortho amino benzamides 2.7 In this Letter, we describe
our continuing efforts aimed at exploring multiple chem-
otypes for potential MCHr1 inhibition, wherein the
ortho amino benzamide scaffold is replaced by an inda-
zole moiety to afford compounds such as 3.
N
R
N
R2
3
The synthesis of the target compounds was accom-
plished as described in Scheme 1 or 2. Refluxing a solu-
tion of the suitably substituted ortho fluoro benzonitrile
4 with hydrazine hydrate in butanol afforded the 3-ami-
no indazole nucleus 5 in moderate to excellent yields,
depending on the nature of the R-group. Reductive ami-
nation with 4-oxo-piperidine-1-carboxylic acid tert-bu-
tyl ester, followed by deprotection and reductive
amination with a variety of monocyclic and bicyclic
Keywords: Melanin concentrating hormone; Obesity; Aminoindazoles;
Palladium amination.
*
Corresponding author. Tel.: +1 847 938 6594; fax: +1 847 935 031;
e-mail: Anil.Vasudevan@abbott.com
0960-894X/$ - see front matter Ó 2005 Published by Elsevier Ltd.
doi:10.1016/j.bmcl.2005.08.049

5294
A. Vasudevan et al. / Bioorg. Med. Chem. Lett. 15 (2005) 5293–5297
Table 1. MCHr1-binding affinity (IC50) and functional activity (IC50
of indazole analogs
)
NH2
N
R
R
CN
F
a
R1
N
N
HN
H
5
4
N
R
b
N
H
R1
R1
N
N
HN
Compound
R
R1
IMR32
binding
IMR32
HN
FLIPRTM
R
c
R
N
IC50 (lM) IC50 (lM)
N
N
R2
N
H
12
13
14
15
16
17
18
19
5-Cl
5-Cl
5-Cl
5-Cl
5-Cl
5-Cl
5-Cl
5-Cl
0.85
0.20
0.15
0.10
0.24
0.04
0.07
0.02
>10
6
7
Scheme 1. Reagents and conditions: (a) NH2NH2ÆH2O, n-BuOH,
reflux, 4 h; (b) 1. 4-Oxo-piperidine-1-carboxylic acid tert-butyl ester,
NaCNBH3, AcOH, 50 °C, 12 h; 2. 4 N HCl/dioxane; 3. ArCHO,
NaCNBH3, CH3OH, AcOH (cat.); (c) R2COOH, PS-DCC, HOBt,
N,N-DMF or NaH, R2Br, N,N-DMF.
6.2
Cl
OCH3
4.5
1.38
5.2
H3CO
H3CO
a
N
N
NH2
F
OCH3
H
8
9
1.82
1.89
0.26
b
O
R1
Br
N
O
O
H3CO
HN
c
H3CO
N
N
N
O
O
N
Boc
H
11
10
20
5-Cl
0.28
>10
O
Scheme 2. Reagents and conditions: (a) 1. NaNO2, AcOH; 2. Et3N. (b)
1. KOH, NBS; 2. (Boc)2O, THF. (c) 1. Functionalized 4-amino
piperidine, Pd2dba3, Xantphos, Cs2CO3, dioxane; 2. HCl/iPrOH.
OCH3
N
21
22
23
24
25
26
27
28
29
30
5-Cl
S
0.05
0.44
4.91
N
O
aldehydes and ketones, afforded the target compounds.
An alternate synthesis shown in Scheme 2 was devised
to access target compounds, where R was an electron-
donating group, such as a methoxy moiety. Diazotiza-
tion and cyclization of 4-methoxy-2-methyl aniline affor-
ded 5-methoxy indazole 9, which was brominated using
N-bromosuccinimide. Palladium coupling of the boc-
protected intermediate 10 with a suitably functionalized
aminopiperidine using Xantphos8 as the ligand afforded
the desired target compounds.
5-H
>10
O
O
5-CF3
5-CH3
5-NO2
5-NO2
5-CN
>2
>10
O
O
0.11
0.006
0.03
0.22
0.008
0.05
0.33
1.06
O
O
0.07
0.52
3.4
O
O
All the compounds synthesized in this study were evalu-
ated for their MCHr1 inhibition in a competitive radio-
metric-binding assay using receptor obtained from
human neuronal IMR-32 cells.9 Further characteriza-
tion was performed in an assay designed to measure
functional antagonism of MCH-mediated Ca2+ release
using a fluorometric imaging plate reader (FLIPRTM).9
A cursory analysis of the binding data shown in Table
1 indicates that in general, compounds with bicyclic sub-
stituents (as R1) afforded more potent MCHr1 inhibi-
tion compared to those with monocyclic substituents.
Comparison of the activities of compound 12 with 13–
16 indicates that the addition of hydrophobic subtitu-
ents to 12 improved MCHr1 inhibition as well as func-
tional potency. Replacement of the phenyl substituent
in 12 with a 2-naphthyl moiety (17) resulted in a 20-fold
O
O
O
O
5-OCH3
5-OCH3
4-OCH3
0.06
0.38
O
H
N
N
O
O
>10
improvement in MCHr1 inhibition. Introduction of
bicyclic heterocycles such as the 1,4-benzodioxan-6-yl
(18), piperonyl (19), and benzothiadiazolyl (21) resulted

A. Vasudevan et al. / Bioorg. Med. Chem. Lett. 15 (2005) 5293–5297
5295
in a 12-, 42-, and 17-fold improvement in MCHr1 inhi-
bition, respectively, compared to 12. Of these three het-
erocycles, incorporation of the piperonyl substituent
(19) afforded the best combination of MCHr1 inhibition
and functional potency, though substituents on the phen-
yl ring resulted (20) in a diminution of both parameters.
The substituent at the 5-position of the indazole was also
found to be a crucial determinant of activity. Removal of
the 5-chloro moiety (22) resulted in a 22-fold loss in
MCHr1-binding affinity, whereas the 5-trifluoromethyl
(23) and methyl (24) substituted analogs were inactive
and 5-fold less active than 19, respectively. The 5-nitro
substitution resulted in a very potent MCHr1 antagonist
(25) with an IC50 of 6 nM and functional activity of
70 nM. Replacement of the piperonal moiety in 25 with
a benzodioxan-6-yl substituent (26) resulted in a 5-fold
loss in MCHr1 inhibition and a 7-fold loss in functional
potency. The 5-cyano substituted compound 27 was a
moderately potent MCHr1 antagonist, though the func-
tional potency was compromised significantly.10 A meth-
oxy substituent at the 5-position (28) afforded
comparable MCHr1 inhibition and functional activity
as the 5-nitro group (8 and 60 nM, respectively). Other
bicyclic heterocycles such as the indazole moiety were also
investigated, though the MCHr1 inhibition was compro-
mised to some extent. Moving the methoxy substituent to
the 4-position resulted in a significant drop in MCHr1
inhibition and functional potency.
Prior studies on the ortho amino benzamide scaffold (2)7
had indicated that substitution off the ortho amino
group was well tolerated by the MCH1 receptor and
provided a suitable handle for modulation of pharmaco-
kinetic parameters. Alkylation and acylation of the
indazole nitrogen was performed as shown in Scheme
1, by using the requisite alkyl bromide or carboxylic
acid, respectively, and selected data are shown in Table
2. In general, a wide range of substituents and linkers on
the N-1 nitrogen were well tolerated by the MCH1
receptor, though the functional potency of these analogs
was compromised. Introduction of a methyl group
resulted in a 4-fold decrease in MCHr1 inhibition
(28 ! 31), whereas introduction of a phenyl group
resulted in a 2-fold decrease in MCHr1 inhibition
(19 ! 32). The benzyl substituted analogs 33 and 34
were comparable in potency to the parent analogs (25
and 19, respectively), whereas introduction of a pyr-
idylmethyl substituent resulted in a two to 6-fold
Table 2. MCHr1-binding affinity (IC50, lM) and functional activity (IC50, lM) of indazole analogs
R1
H
N
N
R
N
N
R2
Compound
R
R1
R2
IMR32 binding
0.03
IMR32 FLIPRTM
0.19
O
O
O
O
O
O
O
O
O
O
31
OCH3
CH3
32
33
34
35
36
37
38
39
40
41
42
Cl
NO2
Cl
Cl
Cl
Cl
Cl
Cl
Cl
Cl
Cl
0.05
0.005
0.04
0.009
0.02
0.02
0.007
0.04
0.02
0.02
0.02
>10
0.35
5.23
0.55
0.64
0.29
0.56
>10
1.14
0.93
2.54
N
N
O
O
O
O
O
O
O
O
O
O
O
O
N
N
O
O
O
N
N
O
N
O
S

5296
A. Vasudevan et al. / Bioorg. Med. Chem. Lett. 15 (2005) 5293–5297
Table 3. Plasma and brain exposure of 19, 25, 28, 37, 41, and 42 in DIO mice after 10 mg/kg oral dose
Compound
Plasma AUC
(ng h/ml)
Brain AUC
(ng h/ml)
Plasma T1/2 (h)
Brain T1/2 (h)
Plasma Cmax
(ng/ml)
Brain Cmax
(ng/ml)
Ar
Cl
N
NH
N
19
8762
14448
7626
59057
22824
28461
5342
3.1
2.9
1883
1524
1407
1692
12,140
3076
6035
758
N
H
25
28
37
3.3
3.9
4.7
4.0
4.9
6.0
Ar
O
N
N
NH
N
N
H
Ar
Cl
NH
N
11931
N
N
Ar
Cl
N
NH
N
41
164
—
2.3
—
63
—
N
O
N
Ar
Cl
N
NH
N
42
400
—
1.0
—
271
—
N
O
N
S
Ar = 3,4-methylenedioxyphenyl.
improvement in MCHr1 inhibition, depending on the
pyridine regioisomer. Acylation of the N-1 nitrogen of
19 with various hydrophobic, heterocyclic, and basic
moieties resulted in retention of MCHr1 inhibition
though the functional potency was compromised.
acylated. Compound 41, and to a lesser extent 42, was
rapidly cleared from the plasma, with concentrations
declining below the limits of quantitation within four
hours after oral dosing. Further, brain concentrations
were not detected in any of the time points.
The pharmacokinetic parameters of selected analogs
were evaluated in a DIO mouse model using methods
described before,6 and the data are shown in Table 3.
Several interesting trends were observed with these com-
pounds. Compounds 19, 25, and 28 demonstrated high
exposure in the brain with peak concentrations of
12140, 3076, and 6035 ng/g, respectively. These com-
pounds preferentially partitioned into the brain, a desir-
able feature since the largest concentration of MCHr1 is
in the lateral hypothalamus. Alkylation of the N-1 nitro-
gen (37) resulted in compounds with moderate brain
exposure. However, the preferential partitioning in the
brain observed with the non-alkylated analogs was com-
promised. A drastic change in the brain exposure and
half-lives was observed when the N-1 nitrogen was
Due to their superior activity in the MCH functional as-
say and favorable pharmacokinetic profile, compounds
19 and 2811 were evaluated in an efficacy study measur-
ing food intake and body weight in DIO mice.6 Com-
pound 19 was dosed at 3, 10, and 30 mg/kg, p.o., q.d,
whereas 28 was dosed at 10 and 30 mpk, p.o. q.d. with
body weights and food intake measured at regular inter-
vals. At the 10 and 30 mg/kg dose, 19 caused significant
weight loss starting on day 4 (Fig. 1), whereas no signif-
icant weight loss was seen with the 3 mpk dose. Com-
pound 28 caused a decrease in body weight with the
10 and 30 (Fig. 2) mpk dose. Further, there was no sig-
nificant loss of lean body mass seen with any of the
treatment groups, indicating that the observed weight
loss was due to loss of fat mass.

A. Vasudevan et al. / Bioorg. Med. Chem. Lett. 15 (2005) 5293–5297
5297
Acknowledgments
19 (3 mpk)
19 (10 mpk)
19 (30 mpk)
Dex (20 mpk)
DIO Vehicle
+0.4%
2
0
The authors thank Christopher Ogiela and Dennis Fry
for preparing the IMR-32 cells and aiding with the exe-
cution of the binding and functional assays, and Paul
Richardson and J. J. Jiang for MCH production.
**
**
-6.6%
**
**
**
**
**
-10.9%
-2
-4
-6
-8
**
**
**
References and notes
**
**
1. Bittencourt, J. C.; Presse, F.; Arias, C.; Peto, C.; Vaughan,
J.; Nahon, J. L.; Vale, W.; Sawchenko, P. E. J. Comp.
Neurol. 1992, 319, 218.
-23.5%
0
5
10
Days on Study
** p<.01, * p<.05
by Dunnett's test
2. Qu, D.; Ludwig, D. S.; Gammeltoft, S.; Piper, M.; Pelley-
mounter, M. A.; Cullen, M. J.; Mathes, W. F.; Przypek, R.;
Kanarek, R.; Maratos-Flier, E. Nature 1996, 380, 243.
3. Shimada, M.; Tritos, N. A.; Lowell, B. B.; Flier, J. S.;
Maratos-Flier, E. Nature 1998, 396, 670.
4. Ludwig, D. S.; Tritos, N. A.; Mastaitis, J. W.; Kulkarni, R.;
Kokkotou, E.; Elmquist, J.; Lowell, B.; Flier, J. S.;
Maratos-Flier, E. J. Clin. Invest. 2001, 107, 379.
Figure 1. Effect of compound 19 (dosed at 3, 10, and 30 mg/kg, q.d.,
p.o., in 1% Tween 80 in water) on the body weight of DIO mice.
5. (a) Hervieu, G. Expert Opin. Ther. Targets 2003, 7; (b)
Browning, A. Expert Opin. Ther. Patents 2004, 14, 313; (c)
Collins, C. A.; Kym, P. R. Curr. Opin. Invest. Drugs 2003, 4,
386.
6. Vasudevan, A.; Verzal, M. K.; Wodka, D.; Souers, A. J.;
Blackburn, C.; Che, J. L.; Lai, S.; Brodjian, S.; Falls, D. H.;
Dayton, B. D.; Govek, E.; Daniels, T.; Geddes, B.; Marsh,
K. C.; Hernandez, L. E.; Collins, C. A.; Kym, P. R. Bioorg.
Med. Chem. Lett. 2005, 15, 3412.
7. Vasudevan, A.; LaMarche, M. J.; Blackburn, C.; Che, J.
L.; Luchaco-Cullis, C. A.; Lai, S.; Marsilje, T. H.; Patane,
M. A.; Souers, A. J.; Wodka, D.; Geddes, B.; Chen, S.;
Brodjian, S.; Falls, D. H.; Dayton, B. D.; Bush, E.; Brune,
M.; Shapiro, R. D.; Marsh, K. C.; Hernandez, L. E.;
Sham, H. L.; Collins, A. C.; Kym, P. R. Bioorg. Med.
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8. Yin, J.; Buchwald, S. L. J. Am. Chem. Soc. 2002, 124, 6043.
9. Souers, A. J.; Gao, J.; Brune, M.; Bush, E.; Wodka, D.;
Vasudevan, A.; Judd, A. S.; Mulhern, M.; Brodjian, S.;
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2
28 @ 10 mpk
28 @ 30 mpk
Vehicle
Dex @ 10 mpk
1
0
-1
-2
-3
-4
-5
-6
*
*
-3.6%
**
**
**
**
**
**
**
-9.6%
-9.9%
**
**
1
3
5
7
9
11 13 15
Days on Study
** p<.01, * p<.05
by Dunnett's test
Figure 2. Effect of compound 28 (dosed at 10 and 30 mg/kg, q.d., p.o.,
in 1% Tween 80 in water) on the body weight of DIO mice.
In conclusion, several indazole containing MCHr1
antagonists have been identified. The pharmacokinetic
parameters of this class of MCHr1 antagonists could
be modulated depending on substitution at the N-1
nitrogen. Compounds demonstrating the most potent
MCHr1 inhibition and functional potency demonstrated
robust efficacy in a DIO mouse model.
10. In certain cases, a significant disconnect between MCHr1-
binding affinity and activity in the functional assay was
observed. Studies are underway to determine the cause of
this phenomenon and results will be reported elsewhere.
11. Compound 25 was also evaluated for efficacy in a DIO
mouse model and was found to cause robust weight-loss
(data not shown).