Identification of aminopiperidine benzamides as MCHr1 antagonists

Article abstract of DOI:10.1016/j.bmcl.2005.05.023

The identification of a novel series of benzamide-containing MCHr1 antagonists is described. Compound 22 displayed moderate efficacy in a diet induced obesity mice model.

Full text of DOI:10.1016/j.bmcl.2005.05.023

Bioorganic & Medicinal Chemistry Letters 15 (2005) 3412–3416
Identification of aminopiperidine benzamides
as MCHr1 antagonists
Anil Vasudevan,a,* Mary K. Verzal,a Derek Wodka,a Andrew J. Souers,a
Christopher Blackburn,b Jennifer Lee Che,b Sujen Lai,b Sevan Brodjian,a Doug H. Falls,a
Brian D. Dayton,a Elizabeth Govek,b Tom Daniels,b Brad Geddes,b Kennan C. Marsh,a
Lisa E. Hernandez,a Christine A. Collinsa and Philip R. Kyma
aMetabolic Diseases Research, Global Pharmaceutical Research and Development, Abbott Laboratories, Abbott Park, IL 60064, USA
bMillennium Pharmaceuticals, Inc., 40 Landsdowne St. Cambridge, MA 02139, USA
Received 11 April 2005; revised 5 May 2005; accepted 6 May 2005
Available online 9 June 2005
Abstract—The identification of a novel series of benzamide-containing MCHr1 antagonists is described. Compound 22 displayed
moderate efficacy in a diet induced obesity mice model.
Ó 2005 Published by Elsevier Ltd.
Melanin concentrating hormone (MCH) is a cyclic neu-
ropeptide that regulates feeding behavior and energy
balance in mammals.1 MCH is expressed throughout
the brain with the highest levels in the lateral hypothal-
amus and zona incerta areas.2 The hypothalamic MCH
mRNA level is up-regulated in leptin-deficient (ob/ob)
mice, and further increased by fasting.3 MCH deficient
mice are hypophagic and hypermetabolic with decreased
body weight and increased leanness,4 while over-expres-
sion of MCH peptide in mice leads to obesity and insulin
resistance.5 The evidence for MCH regulating food
intake and energy homeostasis has been reviewed
comprehensively.6
fluorometric imaging plate reader (FLIPRTM)7 showed
approximately a 20-fold decrease in potency compared
with binding IC50. The structural simplicity of this lead
allowed rapid and comprehensive investigation to delin-
eate structural features essential for potent MCHr1 inhi-
bition and functional activity.
We have previously reported on our efforts towards the
optimization of a 2-amino-8-alkoxyquinoline-contain-
ing high throughput screening hit.7 In this report, we de-
scribe our continued quest for an orally active MCHr1
antagonist as an effective treatment for obesity. The
naphthamide A-703362 was identified as a chemical lead
with weak affinity for MCHr1 in a competitive radio-
metric binding assay using receptor obtained from
human neuronal IMR-32 cells.7 Further characteriza-
tion in an assay designed to measure functional antago-
Initial SAR investigations were aimed at developing an
understanding of region A of the lead molecule. The
synthesis of these compounds was accomplished as
shown in Scheme 1.
Table 1 shows the MCHr1 binding affinity of these cinn-
amyl substituted analogs. Compounds which demon-
strated MCHr1 binding of less than 100 nM were
evaluated for functional antagonism of MCH-mediated
Ca2+ release in a FLIPRTM based assay.7 Replacement
of the 2-naphthyl moiety with a phenyl group (5)
resulted in decreased MCHr1 inhibition, as did
nism of MCH-mediated Ca2+ release using
a
Keywords: Melanin concentrating hormone; Benzamides; Obesity.
*
Corresponding author. Tel.: +1 847 938 6594; fax: +1 847 935
0310; e-mail: anil.vasudevan@abbott.com
0960-894X/$ - see front matter Ó 2005 Published by Elsevier Ltd.
doi:10.1016/j.bmcl.2005.05.023

A. Vasudevan et al. / Bioorg. Med. Chem. Lett. 15 (2005) 3412–3416
3413
Prior to refining the SAR of region A, we explored sev-
eral changes in region C and identified the piperonyl
moiety as a suitable replacement for the cinnamyl moi-
ety. Further SAR investigations of regions A and B
were performed with this heterocycle. Table 2 outlines
further exploration of region A. The meta-methoxy and
meta-chloro substituted compounds, 12 and 13, were
comparable in potency with 7 and 9, though the
functional antagonism of 12 was approximately 4-fold
Table 2. MCHr1 binding affinity and functional activity of analogsa
Scheme 1. Reagents and conditions: (a) cinnamyl chloride, K2CO3,
DMF, 50 °C, 76%; (b) 4 N HCl/dioxane, 25 °C, 4 h, quantitative; (c)
RCOOH, PS-DCC, HOBt, DMF, 25 °C.
8
Table 1. MCHr1 binding affinity and functional activity of analogsa
Compound R1
IMR32
binding
IMR32
FLIPRTM
IC50 (lM)
IC50 (lM)
12
0.05 0.03
0.13 0.01
Compound
R
IMR32
binding
IMR32
FLIPRTM
IC50 (lM)
IC50 (lM)
13
14
0.11 0.09
0.09 0.02
—
5
6.50 0.81
5.19 0.92
0.05 0.03
0.17 0.05
0.11 0.08
>10
—
0.54 0.01
6
—
PhO
15
16
17
18
0.33 0.05
0.32 0.20
1.56 0.73
0.12 0.10
—
—
—
—
7
0.56 0.1
8
—
—
—
—
9
10
11
19
20
21
0.01 0.002
4.30 0.25
0.03 0.01
0.12 0.04
0.30 0.16
replacement with several heterocycles (only one example
is shown, 6). Introduction of a methoxy or chloro substi-
tuent at the meta position of 5 resulted in a 130- and 59-
fold increase in MCHr1 binding affinity, as demon-
strated by 7 and 9, respectively. However, the functional
potency of 7 was 10-fold lower than its binding affinity.
The benzyl analog 10 was devoid of MCHr1 affinity,
whereas introduction of a bromo moiety at the meta-
position of 10 resulted in a significant boost in binding
affinity (11). Having established that a significant
improvement in MCHr1 binding affinity could be
accomplished with a substituent at the meta position,
we sought to explore this feature in more detail.
—
0.53 0.07
22
0.003 0.001 0.09 0.002
a Values are means of three experiments.

3414
A. Vasudevan et al. / Bioorg. Med. Chem. Lett. 15 (2005) 3412–3416
Table 3. MCHr1 binding affinity and functional activity of analogsa
Compound
X
Ar
IMR32 binding IC50 (lM)a
IMR32 FLIPRTM IC50 (lM)a
23
SO2
1.95 0.72
—
24
25
C(@O)O
C(@O)O
1.61 0.29
2.99 0.95
—
—
26
27
28
29
30
31
32
33
34
35
C(@O)NH
0.32 0.08
0.23 0.11
0.49 0.01
0.51 0.02
1.04 0.25
0.06 0.03
0.09 0.01
0.02 0.01
0.05 0.02
0.09 0.02
—
C(@O)NHCH2
C(@O)NHCH2
C(@O)NHCH2
C(@O)CH2
C(@O)CH2
C(@O)CH2
C(@O)CH2
C(@O)CH2
C(@O)CH2
—
—
—
—
0.72 0.13
0.53 0.01
0.89 0.05
0.76 0.02
0.38 0.09
a Values are means of three experiments.

A. Vasudevan et al. / Bioorg. Med. Chem. Lett. 15 (2005) 3412–3416
Table 4. MCHr1 binding affinity and functional activity of analogsa
3415
though the potency in MCH functional assays was
not improved. Replacement of the methoxy groups of
19 with chloro groups (21) resulted in a 2-fold decrease
in MCHr1 binding affinity, whereas the dihydroxy
compound 20 demonstrated very weak MCHr1 binding
activity. Introduction of a para-methyl group to 19
afforded 22, which was a 3 nM inhibitor of MCHr1
and demonstrated functional antagonism, with an
IC50 of 90 nM.
Compound Linker
IMR32
binding
IMR32
FLIPRTM
IC50 (lM)a IC50 (lM)a
Replacement of the amide with a sulfonamide or carba-
mate resulted in at least a 40-fold decrease in MCHr1
binding affinity (Table 3), whereas a urea moiety re-
sulted in a 25-fold loss in potency. Homologation of
the urea linker to provide 27–29 resulted in comparable
MCHr1 affinity as 26.
36
>2
—
37
38
39
>2
—
—
—
—
Homologated versions of the benzamide chemotype
provided interesting results. Whereas homologation of
19 to afford 30 resulted in an 80-fold decrease in MCHr1
binding affinity, introduction of phenyl, methoxyphenyl
and cyanophenyl moieties at the para position afforded
analogs 31–35 with significantly improved MCHr1 affin-
ity. However, the functional potency of these homolo-
gated compounds was not improved compared to the
benzamide analogues described in Table 2.
>2
>2
Continued SAR investigations of region B prompted the
search for an optimal diamine linker, a few of which are
shown in Table 4. N-methylation of 22 resulted in
abolishment of MCHr1 activity as did incorporation
of a 3-aminopyrrolidine, 3-aminomethylpiperidine, and
1,3-diaminopropyl (data not shown) linkers. The (R)-
3-aminomethylpyrrolidine substituted compound 40
was the only linker amongst all the spacers investigated
which provided for sub-micromolar MCHr1 binding
affinity.
40
0.28 0.05
a Values are means of three experiments.
Table 5. Selected PK parametersa of 22 in DIO mice (10 mg/kg po)
Cmax (ng/ml or ng/g) T1/2 (h) AUC (ng h/ml or ng h/g)
Plasma 2297
Brain 5083
2.8
3.7
9801
24,926
Since the largest concentration of MCHr1 is located in
the lateral hypothalamus, it is likely that potential drug
candidates acting through this receptor will be required
to penetrate the blood–brain barrier. In order to evalu-
ate this hypothesis, compound 22, which demonstrated
the best combination of MCHr1 binding and functional
potency, was dosed orally at 10 mg/kg in diet induced
obese (DIO) mice.7 As shown in Table 5, 22 preferen-
tially partitioned into the brain suggesting that efficacy
could potentially be achieved using this compound.
a Values are means of three experiments.
better than 7. Introduction of bulky substituents such
as a phenoxy group at the meta position of the phenyl
ring (15) resulted in decreased MCHr1 binding affinity
as did replacement of the phenyl ring with a 2-napthyl
moiety (16). A dramatic decrease in MCHr1 affinity
was observed by introduction of a methoxy group at
the ortho position of 12 to give 17. A similar effect
was observed with ortho-chloro and methyl groups
(data not shown). However, introduction of a meta-
methoxy group to afford 19 resulted in a small
improvement in MCHr1 affinity compared to 12,
Compound 22 was also dosed in dogs9 to evaluate its
pharmacokinetic parameters, and details are shown in
Table 6. It was characterized by high plasma concentra-
tions, providing low plasma clearance values
(Clp = 0.18 L/h kg) and moderate volume of distribution
Table 6. Mean (n = 3) plasma concentrations of 22 in dog
IV dose (2.5 mg/kg)
t1/2 (h)
4.5
Vc (l/kg)
0.9
Vb (l/kg)
1.2
AUC0ꢀ1 (ng h/ml)
14,118
Clp (l/h kg)
0.18
a
Mean
Oral dose (2.5 mg/kg)
Meana
Cmax (ng/ml)
930
Tmax (h)
3.0
t1/2 (h)
6.0
AUC0ꢀ1 (ng h/ml)
11,885
F (%)
84.2
a Harmonic mean.

3416
A. Vasudevan et al. / Bioorg. Med. Chem. Lett. 15 (2005) 3412–3416
2. 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.
3. Kokkotou, E. G.; Tritos, N. A.; Mastaitis, J. W.; Slieker,
L.; Maratos-Flier, E. Endocrinology 2001, 142, 680.
4. (a) Shimada, M.; Tritos, N. A.; Lowell, B. B.; Flier, J. S.;
Maratos-Flier, E. Nature 1998, 396, 670; (b) Chen, Y.; Hu,
C.; Hsu, C. K.; Zhang, O.; Bi, C.; Asnicar, M.; Hsiung, H.
M.; Fox, N.; Slieker, L. J.; Yang, D. D.; Heiman, M. L.;
Shi, Y. Endocrinology 2002, 143, 2469.
5. 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.
6. Hervieu, G. Expert Opin. Ther. Targets 2003, 7, 495.
7. Souers, A. J.; Wodka, D.; Gao, J.; Lewis, J. C.; Vasu-
devan, A.; Gentles, R.; Brodjian, S.; Dayton, B.; Ogiela,
C. A.; Fry, D.; Hernandez, L. E.; Marsh, K. C.; Collins,
C. A.; Kym, P. R. Bioorg. Med. Chem. Lett. 2004, 14,
4873; Vasudevan, A.; Wodka, D.; Verzal, M. K.; Souers,
A. J.; Gao, J.; Brodjian, S.; Fry, D.; Dayton, B.; Marsh,
K. C.; Hernandez, L. E.; Ogiela, C. A.; Collins, C. A.;
Kym, P. R. Bioorg. Med. Chem. Lett. 2004, 14, 4879;
Souers, A. J.; Wodka, D.; Gao, J.; Lewis, J. C.;
Vasudevan, A.; Brodjian, S.; Dayton, B.; Ogiela, C. A.;
Fry, D.; Hernandez, L. E.; Marsh, K. C.; Collins, C. A.;
Kym, P. R. Bioorg. Med. Chem. Lett. 2004, 14, 4883.
8. PS-DCC was purchased from Argonaut Technologies
(www.argotech.com).
Figure 1. Effect of compound 22 (dosed at 10 and 30 mpk, q.d., po,
dosed in 1% Tween 80 in water) on the body weight of DIO mice.
(Vss = 1.2 L/kg) with an apparent elimination half-life of
4.5 h. Peak plasma concentration after oral dosing aver-
aged 930 ng/ml, with 84% bioavailability.
Encouraged by these results, we explored the effects of
administration of 22 in a study measuring food intake
and body weight in DIO mice10 (see Fig. 1). For a
two-week period, DIO mice fed a high-fat diet ad libitum
were dosed orally with 22 (10 or 30 mpk, q.d.), sibutr-
amine (10 mpk, q.d.), or vehicle. Food intake and body
weight were measured at days 1, 4, 7, 11, and 14 for each
group. DIO mice receiving a 30 mpk dose of 22 steadily
decreased body weight commencing from day 1, though
the loss in body weight had stabilized by the end of the
study (ꢁ 6% body weight loss). Mice receiving 10 and
30 mpk of 22 continued to eat comparable amounts of
food compared with DIO vehicle-treated controls. In
the Irwin behavioral study (data not shown), there was
no evidence of hypothermia or gross abnormalities.
These results suggest that the weight loss observed upon
treatment with MCHr1 antagonist 22 could be the result
of an alteration in energy expenditure.
9. Souers, A. J.; Gao, J.; Brune, M.; Bush, E.; Wodka, D.;
Vasudevan, A.; Judd, A. S.; Mulhern, M.; Brodjian, S.;
Dayton, B.; Shapiro, R.; Hernandez, L. E.; Marsh, K. C.;
Sham, H. L.; Collins, C. A.; Kym, P. R. J. Med. Chem.
2005, 48, 1318.
10. Efficacy studies were performed according to the follow-
ing protocol: C57BL/6J mice were group housed in
groups of five under conditions of 12 h lights on, 12 h
lights off, with food and water available ad libitum. At
the beginning of the study, mice were administered a
purified low fat diet (D12450Bi, 10 kcal% fat, 3.8 kcal/g)
or a high fat content diet (D12492i, 60 kcal% fat,
5.2 kcal/g) for approximately 16 weeks. Mice were
weighed, individually housed, and food consumption
monitoring initiated three weeks prior to commencement
of drug administration. Pharmacological treatments were
administered twice a day at 08:00 h and 15:00 h. Mice
were conditioned to oral gavage and daily vehicle
administration for one week prior to drug administra-
tion. The vehicle used for conditioning and study was
1% Tween 80. All doses were given in 4 ml/kg body
weight volume of vehicle. All compound doses are
expressed as base equivalent weights per unit body
weight. Food intake and body weight were determined
on the first day and periodically thereafter for 28 days.
Compound 22 was administered po by gavage, at doses
of 10 and 30 mg/kg q.d., and sibutramine at a dose of
10 mg/kg po, q.d. At the end of the study (day 28),
statistical analyses of body weight, food intake, plasma
analyte, DEXA, dual-energy X-ray absorptiometry and
tissue weight data were performed by analysis of
variance, followed by DunnettÕs post hoc test. All
comparisons were made at a 0.05 level of significance.
Data are presented as means SEM.
In summary, a series of potent benzamide containing
MCHr1 antagonists have been identified. The com-
pound with the best combination of MCHr1 binding
affinity and functional activity had good oral bioavail-
ability in dog and was evaluated in a DIO mouse model
for efficacy. Compound 22 demonstrated sustained
moderate efficacy when dosed at 30 mpk q.d. in this
chronic model of weight loss.11
Acknowledgments
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, Paul Rich-
ardson and J. J. Jiang for MCH peptide synthesis and
Michael Brune with interpretation of the efficacy data.
11. During the course of this work, a poster describing
benzamide MCH antagonists was reported. Ma, V. V.;
Balan, C.; Tempest, P. A.; Hulme, C.; Bannon, T.
Abstract of Papers, 224th National Meeting of the
American Chemical Society, Boston, MA; American
Chemical Society: Washington, DC, 2002; Abstract
MEDI-343.
References and notes
1. Saito, Y.; Nothacker, H. P.; Civelli, O. Trends Endocrinol.
Metab. 2000, 11, 299.