Constrained analogs of CB-1 antagonists: 1,5,6,7-Tetrahydro-4H-pyrrolo[3,2-c]pyridine-4-one derivatives

Article abstract of DOI:10.1016/j.bmcl.2006.10.095

A series of pyrrolopyridinones was designed and synthesized as constrained analogs of the pyrazole CB-1 antagonist rimonabant. Certain examples exhibited very potent hCB-1 receptor binding affinity and functional antagonism with K_i and K_b<

Full text of DOI:10.1016/j.bmcl.2006.10.095

Bioorganic & Medicinal Chemistry Letters 17 (2007) 673–678
Constrained analogs of CB-1 antagonists: 1,5,6,7-Tetrahydro-4H-
pyrrolo[3,2-c]pyridine-4-one derivatives
Roger A. Smith,a,* Zahra Fathi,b Su-Ellen Brown,b Soongyu Choi,a Jianmei Fan,a
Susan Jenkins,c Harold C. E. Kluender,a Anish Konkar,b Rico Lavoie,a Ronald Mays,c
Jennifer Natoli,b Stephen J. O’Connor,a Astrid A. Ortiz,b Brent Podlogar,a Christy Taing,b
Susan Tomlinson,a Theresa Trittob and Zhonghua Zhanga
aDepartment of Chemistry Research, Bayer HealthCare, Pharmaceuticals Division, West Haven, CT 06516, USA
bDepartment of Metabolic Disorders Research, Bayer HealthCare, Pharmaceuticals Division, West Haven, CT 06516,USA
cDepartment of Research Technologies, Bayer HealthCare, Pharmaceuticals Division, West Haven, CT 06516, USA
Received 29 September 2006; revised 27 October 2006; accepted 30 October 2006
Available online 2 November 2006
Abstract—A series of pyrrolopyridinones was designed and synthesized as constrained analogs of the pyrazole CB-1 antagonist
rimonabant. Certain examples exhibited very potent hCB-1 receptor binding affinity and functional antagonism with Ki and Kb val-
ues below 10 nM, and with high selectivity for CB-1 over CB-2 (>100-fold). A representative analog was established to cause sig-
nificant appetite suppression and reduction in body weight gain in industry-standard rat models used to develop new therapeutics
for obesity.
Ó 2006 Elsevier Ltd. All rights reserved.
The prevalence of excessive body weight and obesity has
O
N
N
dramatically increased over the last 30 years, apparently
the result of an increasingly sedentary lifestyle, as well
as the plentiful availability of energy-rich food.1 Indeed,
the World Health Organization has declared human
obesity to be one of the most significant health problems
facing mankind, with more than 250 million obese pa-
tients (body mass index (BMI) P 30) around the world,
including epidemic proportions in the US and Europe.
During the last decade, antagonism of the cannabinoid
type 1 receptor (CB-1) has emerged as a highly promising
strategy for the treatment of obesity.2 The 1,5-diarylpy-
razole rimonabant (1, SR-141716, Sanofi-Aventis) is the
most advanced CB-1 antagonist, and this compound
was recently approved in the European Union for the
treatment of obese or overweight patients with associated
risk factors, such as type 2 diabetes or dyslipidemia.3
N
H
N
Cl
Cl
Cl
1 rimonabant
(SR-141716, AcompliaTM
hCB-1 Ki = 5.6 nM4a, 25 nM5a
mCB-1 Ki = 1.8 nM5d
)
a hydrogen bond donor/acceptor functionality such as a
carboxamide group.2 1,5-Diarylpyrazoles, as exempli-
fied by rimonabant (1), represent the first series of
CB-1 antagonists to be disclosed having this pharmaco-
phore.4 Several research groups have reported com-
pounds that incorporate conformational constraints
into the antagonist structure. Such compounds have
the potential for increased binding affinity resulting
from an entropic advantage for the bioactive conforma-
tion, and improved pharmacokinetics due to altered
resistance to metabolizing enzymes. Tricyclic derivatives
A large proportion of the structure classes investigated
as CB-1 antagonists consist of a five- or six-membered
heterocyclic core, substituted by two aromatic rings and
Keywords: Cannabinoid; Antagonist; Obesity; Appetite suppressant.
*
Corresponding author. Tel.: +1 203 812 2154; fax: +1 203 812
6182; e-mail: roger.smith.b@bayer.com
0960-894X/$ - see front matter Ó 2006 Elsevier Ltd. All rights reserved.
doi:10.1016/j.bmcl.2006.10.095

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R. A. Smith et al. / Bioorg. Med. Chem. Lett. 17 (2007) 673–678
of 1 having a constraint between the pyrazole core and
the 5-aryl group have been reported, for example (e.g.,
2a–c).5 Compounds having a bicyclic core that effective-
ly incorporates a constraint between the pyrazole core
C-4 position and the hydrogen bond donor/acceptor
moiety have also been described (e.g., 3–5).6
consistent with the low-energy conformation that we
had determined (Fig. 1a). Furthermore, computational
studies reported for 1 docked to a model of the CB-1
receptor protein suggested that this same conformation
represented the bioactive conformation of 1, with a
key hydrogen bond from the carboxamide oxygen in 1
to a lysine residue at protein position K 3.28.8,9 Also
of interest, this model indicated that the carboxamide
nitrogen in 1 was not involved in a hydrogen bond—
thereby supporting the design of our constrained analog
6.
O
N
X
N
H
N
Cl
N
Cl
O
N
Cl
N
Cl
N
2a, X = CH2, mCB-1 Ki = 2050 nM5d
2b, X = (CH2)2, mCB-1 Ki = 14.8 nM5d
Cl
Cl
2c, X = (CH2)3, mCB-1 Ki = 0.35 nM5d
,
6
hCB-1 Ki = 126 nM5a
A novel and efficient synthesis of 1,5,6,7-tetrahydro-
4H-pyrrolo[3,2-c]pyridin-4-ones such as 6 and the
N
N
N
N
O
N
O
N
NH
related N-cyclohexyl amide
7 was developed, as
N
N
N N
depicted in Scheme 1. This protocol involved the
Michael addition of an amine or hydrazine (8) to an
acrylic ester to provide the 3-amino ester (9), followed
by N-acylation with a malonyl chloride in the presence
of base to afford a diester amide (10). This diester
amide was cyclized by a Dieckmann condensation to
give an intermediate10 that was hydrolyzed and decar-
boxylated under acidic conditions to give a ketopiper-
idinone (11). Condensation with an amino ketone
provided the key bicyclic pyrrolopyridinone intermedi-
ate 12. The introduction of a substituent on the pyr-
role core group was accomplished by bromination to
give 13, followed by a palladium-catalyzed coupling
reaction with an organoborane. This methodology
was successfully applied with some slight modifications
to produce more than fifty pyrrolopyridinone deriva-
tives.11 For a variety of constrained amide analogs
(e.g., 7) the overall synthesis yield was typically 10–
15% (6 steps), whereas for the related hydrazides
(e.g., 6) the overall yield was considerably lower
(1–3%) (Scheme 1).
N
N
Cl
Cl
Cl
Cl
Cl
Cl
3
4
5
4: hCB-1 Ki = 12 nM6b
As part of our research investigations on CB-1 antago-
nists, we conducted computational studies on 1 and con-
cluded that the preferred conformation would have a
trans-amide with the carboxamide oxygen nearly copla-
nar with the pyrazole ring and oriented in the same
direction as the pyrazole C-4 methyl group (Fig. 1a).7
Further modeling studies indicated that a constrained
analog of this conformation could be readily achieved
by linking the pyrazole N-2 position via an ethylene
bridge to the carboxamide nitrogen. An overlay of the
low-energy conformation of 1 with this type of con-
strained derivative (6), having a 1,5,6,7-tetrahydro-4H-
pyrrolo[3,2-c]pyridin-4-one scaffold, is represented in
Figure 1b.
In an in vitro hCB-1 (human CB-1) binding assay, the
target hydrazide analog 6 was determined to have
hCB-1 Ki = 2.2 nM (Table 1).12 This potency is very
Subsequent to our studies, an X-ray structure and con-
formational studies of 1 were reported,8 and these were
similar to that observed in our assay for
1
(Ki = 1.1 nM), validating the design of 6 as a con-
strained mimic of the bioactive conformation of 1.
The potency of 6 is also consistent with the rimona-
bant/CB-1 binding model,7,8 which indicates that the
carboxamide NH is not required for H-bonding to
the receptor. Analog 6 was also found to function
as an antagonist or inverse agonist,15 with hCB-1
Kb = 12 nM, and was also determined to be highly
selective for CB-1 over CB-2 (hCB-2 Ki = 1300 nM).
The constrained cyclohexyl amide analog 7 was also
found to be a potent hCB-1 antagonist, with hCB-1
Ki = 7.5 nM and Kb = 6.5 nM, and exhibiting high
selectivity against CB-2 (hCB-2 Ki = 8300 nM). In
Figure 1. (a) Low-energy conformation of 1. (b) Overlay of the low-
energy conformation of 1 with the 1,5,6,7-tetrahydro-4H-pyrrolo[3,2-
c]pyridin-4-one derivative 6.

R. A. Smith et al. / Bioorg. Med. Chem. Lett. 17 (2007) 673–678
675
O
O
O
O
NH
X
2
O
O
O
i) base; ii) aq. AcOH
HN
X
OMe
OMe
EtO
Cl
X
X
EtO
N
N
a
c
b
MeO C
2
O
X=N: 65-70%
X=N: 20-25%
X=N: 45-60%
X=CH: 90-95%
X=CH: 65-75%
X=CH: 65-95%
8
9
10
11
H
O
O
O
O
N
B(OH)
2
X
X
N
X
N
N
0
+
Br
; Pd cat.
Cl
; H
Cl
Cl
Cl
NBS
N
N
N
d
e
f
Cl
Cl
Cl
X=N: 60-90%
X=N or CH: 30-50%
X=N or CH: 45-55%
X=CH: 85-98%
Cl
Cl
Cl
12
6: X=N
7:X=CH
13
Scheme 1. Synthesis of 1,5,6,7-tetrahydro-4H-pyrrolo[3,2-c]pyridin-4-ones such as 6 and 7. Reagents and conditions: (a) MeOH, 0 °C, then rt, 16 h;
(b) Et3N, CH2Cl2, 0 °C, then rt, 16 h; (c) i—X = N: DMF/THF, Cs2CO3, 77 °C, 48 h; X = CH: NaH, cyHex/toluene, reflux, 3 h; ii—10% aq AcOH,
reflux, 1–2 h; (d) toluene, TsOH, H2O trap, 6–24 h; (e) N-bromosuccinimide (NBS), DMF, 0 °C, 1 h; (f) 0.1 equiv Pd(PPh3)4, DME, aq Na2CO3,
60 °C, 16–18 h.
Table 1. Binding affinities of pyrrolopyridinone compounds to the human CB-1 receptor
O
X
N
R1
N
R2
Compound
R1
R2
X
hCB-1 Ki (nM)a
6
7
4-Cl–Ph
4-Cl–Ph
4-Cl–Ph
2,4-Cl2–Ph
2,4-Cl2–Ph
4-Cl–Ph
N
2.2 0.40
7.5 0.97
>2500
CH
CH
CH
CH
CH
CH
CH
CH
CH
CH
CH
CH
CH
CH
CH
CH
CH
CH
CH
CH
CH
CH
CH
CH
CH
CH
CH
CH
CH
CH
N
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
2,4-Cl2–Ph
Ph
4-F–Ph
4-Cl–Ph
>2500
2,4-Cl2–Ph
2,4-Cl2–Ph
2,4-Cl2–Ph
2,4-Cl2–Ph
2,4-Cl2–Ph
2,4-Cl2–Ph
2,4-Cl2–Ph
2,4-Cl2–Ph
2,4-Cl2–Ph
2,4-Cl2–Ph
2,4-Cl2–Ph
2,4-Cl2–Ph
2,4-Cl2–Ph
2,4-Cl2–Ph
2,4-Cl2–Ph
2,4-Cl2–Ph
2,4-Cl2–Ph
2,4-Cl2–Ph
2,4-Cl2–Ph
2,4-Cl2–Ph
2,4-Cl2–Ph
2-Cl–Ph
16 3.5b
6.0 0.35
10 2.6
4.1 0.60
7.9 1.6b
9.8 2.8b
920 77
>2500
4-CH3–Ph
4-CF3–Ph
4-CH3O–Ph
4-CH2@CH–Ph
4-NH2–Ph
4-HOOC–Ph
4-CH3S–Ph
3-CH3–Ph
3-CH3O–Ph
3,4-(CH3O)2–Ph
3,4-(OCH2O)–Ph
3-CF3–Ph
3-NH2–Ph
3-Thienyl
2-Thienyl
2-Furyl
>2500
17 0.50b
6.8 1.6b
5.5 1.5
12 3.1b
67 13b
450 108
37 16b
19 9.6b
20 1.0b
23 16b
390 87
240 45
2.8 0.85
200 31
7.5 0.70
22 4.7b
9.3 0.60b
40 20b
3.5 1.2
20 3.7
74 1.0
2-Benzothienyl
3-Pyridinyl
H
4-Cl–Ph
4-Cl–Ph
2,6-Cl2–Ph
2-Cl–Ph
4-CH3O–Ph
4-CH3O–Ph
4-CF3–Ph
4-F–Ph
2-CH3–Ph
2-CH3–Ph
2-CH3–Ph
2-Cl–Ph
4-Cl–Ph
4-CH3O–Ph
4-CH3O–Ph
2-Cl–Ph
2-CH3–Ph
N
N
a Data are expressed as Ki SEM (nM); hCB-1 Ki = 1.1 0.04 nM was determined for 1 in our assay.
b IC50 value; incomplete displacement of receptor ligand was observed at 1–10 lM, likely due to compound solubility limitations.

676
R. A. Smith et al. / Bioorg. Med. Chem. Lett. 17 (2007) 673–678
sharp contrast to 7, when the 2-chloro substituent was
removed from the 2,4-dichlorophenyl group as in 14,
or when the 4-chlorophenyl and 2,4-dichlorophenyl
groups were interchanged as in 15, a substantial loss
in hCB-1 binding affinity was observed (Table 1).
These key structure–activity relationships (SAR) are
consistent with those reported for the 1,5-diarylpyraz-
ole series related to 1,4b as well as for related 1,2-
diarylimidazole and 4,5-diarylthiazole analogs.16 How-
ever, the effect on potency by these structural changes
is more profound for the constrained analog 7.
1,5-Diarylpyrazole hydrazides such as 1 have been dem-
onstrated to reduce food intake in rodents in a variety of
studies.2c Likewise, 44 was investigated as a representa-
tive pyrrolopyridinone hydrazide in a fasted-refed rat
model for appetite suppression,17 and was found to
cause a significant anorexigenic effect (36% cumulative
reduction in food intake at 4 h, Fig. 2). In comparison,
compound 7 caused no effect in this model (data not
shown), which is consistent with the very poor plasma
exposure determined for this compound.
The genetically obese Zucker fa/fa rat has been used for
evaluating compound efficacy for the reduction of body
weight, including compounds such as rimonabant (1)
that have been shown to be effective in the management
of body weight in obese humans.18 Following the deter-
mination that 44 causes a significant suppression of
appetite (Fig. 2), we also investigated its effect in this
Zucker rat model.19
The SAR for a diverse set of substituents at the 2-posi-
tion of the pyrrolopyridinone scaffold were investigated
(R1, Table 1). For a variety of substituted phenyl
groups, it was found that relatively small groups at the
4-position are preferred, such as 4-F, Cl, CH3, CH3O,
and CF3, providing compounds with Ki values in the
4–10 nM range (7 and 17–20, Table 1). Acidic or basic
groups at the 4-position result in a substantial loss in
potency (22, 23), as do certain bulky substitutions
(24). Substituents at the 3-position of phenyl groups
are reasonably well tolerated (25–29), although a basic
amino moiety once again provides a loss in potency
(30). Replacement of the 4-chlorophenyl group in 7 with
heterocycles such as thienyl, furyl, and benzothienyl re-
sults in a 3- to 5-fold decrease in hCB-1 binding affinity
(31–34), whereas replacement with a pyridyl group (35)
or a hydrogen atom (36) causes a 50- or 30-fold loss in
potency, respectively.
In the Zucker rat model, pyrrolopyridinone hydrazide
44 was dosed at 5 mg/kg qd p.o., and was observed to
cause a significant reduction in body weight gain as
compared to vehicle-treated rats (Fig. 3). The effect on
day 9 was À3.0%, which is approximately half the effect
determined for rimonabant (1) (À5.6%, 5 mg/kg po qd)
included in the study as a reference standard.20
In conclusion, a series of pyrrolopyridinones was suc-
cessfully designed and efficiently synthesized as con-
strained analogs of the pyrazole CB-1 antagonist
rimonabant. Certain examples exhibited very potent
CB-1 binding affinity and functional antagonism, with
Ki and Kb values below 10 nM. As well, these analogs
were found to be highly selective for CB-1 over CB-2
(>100-fold). Structure–activity relationships were gener-
ally consistent with SAR reported for the pyrazole series
of CB-1 antagonists. A representative analog (44) was
established to cause a significant anorexigenic effect in
the fasted-refed Wistar rat model, and a significant
reduction in body weight gain in the chronic Zucker
rat model. The efficacy established in these industry-
With respect to the N1-position of the pyrrolopyridi-
none scaffold (R2, Table 1), the ortho-chloro substitu-
ent on the 2,4-dichlorophenyl group is important for
potent activity, as described above (7 vs 14, Table
1). On the other hand, removal of the para-chloro
substituent in 7 provides analog 37, exhibiting compa-
rable or slightly increased CB-1 binding affinity. Addi-
tion of a second ortho-chloro substituent as in 38,
however, results in a substantial drop in potency.
The 2-chlorophenyl group can be replaced with a 2-
methylphenyl group without a substantial loss in bind-
ing affinity (39 vs 40).
Finally, hydrazide analogs related to 6 were investigated
(X = N, Table 1). Replacement of the 2,4-dichlorophen-
yl group in 6 with a 2-chlorophenyl group provided 43,
with similar potency against hCB-1. Compound 43 also
exhibited functional activity (hCB-1 Kb = 3.2 nM) and
high selectivity against human CB-2 (hCB-2
14
vehicle control (30% CD)
Compound 44, 10 mg/kg po
12
10
*
8
Ki = 1100 nM). Two hydrazide derivatives with
a
*
4-methoxyphenyl group at the R1 position (44, 45) were
found to be somewhat less potent than 6 or 43.
Compound 44 also exhibited hCB-1 Kb = 32 nM and
hCB-2 Ki = 850 nM.
6
*
4
*
*
2
From pharmacokinetics screening in male Wistar rats,
the constrained cyclohexyl amides were generally found
to give quite low plasma exposure after oral dosing (e.g.,
Cmax < 50 nM at 10 mg/kg for 7), whereas certain
related hydrazides provided improved exposure levels.
For example, 44 provided Cmax = 0.62 lM and
AUC(0–2h) = 0.58 lMÆh at 10 mg/kg p.o.
0
30
60
90
240
180
* p ≤ 0.05
time (min)
Figure 2. Effect of the pyrrolopridinone hydrazide 44 on food intake in
overnight-fasted Wistar rats, after dosing at 10 mg/kg p.o. as a
suspension in 30% cyclodextrin.

R. A. Smith et al. / Bioorg. Med. Chem. Lett. 17 (2007) 673–678
677
`
1109; (b) Mussinu, J. M.; Ruiu, S.; Mule, A. C.; Pau, A.;
Carai, M. A.; Loriga, G.; Murineddu, G.; Pinna, G. A.
Bioorg. Med. Chem. 2003, 11, 251; (c) Murineddu, G.;
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Vehicle (MSA/PEG)
44, 5 mg/kg qd po
1, 5 mg/kg qd po
4
3
2
1
0
-1
-2
-3
-4
-5
6. (a) Carpino, P. A.; Dow, R. L. U.S. Pat. Appl.
US2004214855, 2004; (b) Carpino, P. A.; Griffith, D. A.;
Sakya, S.; Dow, R. L.; Black, S. C.; Hadcock, J. R.;
Iredale, P. A.; Scott, D. O.; Fichtner, M. W.; Rose, C. R.;
Day, R.; Dibrino, J.; Butler, M.; DeBartolo, D. B.;
Dutcher, D.; Gautreau, D.; Lizano, J. S.; O’Connor, R.
E.; Sands, M. A.; Kelly-Sullivan, D.; Ward, K. M. Bioorg.
Med. Chem. Lett. 2006, 16, 731; (c) Carpino, P. A.;
Griffith, D. A. U.S. Pat. Appl. US2004214838, 2004; (d)
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7. Conformational analysis was carried out by molecular
mechanics computations, using SybylÒ 6.6 software and
the Tripos force field (Tripos, Inc., St. Louis, MO).
8. Hurst, D. P.; Lynch, D. L.; Barnett-Norris, J.; Hyatt, S.
M.; Seltzman, H. H.; Zhong, M.; Song, Z. H.; Nie, J.;
Lewis, D.; Reggio, P. H. Mol. Pharmacol. 2002, 62,
1274.
all points
p ≤ 0.05
0
1
2
3
4
5
6
7
8
9
Days of Treatment
Figure 3. Effect of the pyrrolopridinone hydrazide 44 on body weight
in genetically obese Zucker fa/fa rats, upon dosing at 5 mg/kg po qd as
a suspension in PEG/20 mM methanesulfonic acid (80:20).
standard models validates this series of analogs as prom-
ising leads for the potential treatment of obesity.
9. McAllister, S. D.; Rizvi, G.; Anavi-Goffer, S.; Hurst, D.
P.; Barnett-Norris, J.; Lynch, D. L.; Reggio, P. H.;
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Acknowledgments
10. Micovic, I. V.; Roglic, G. M.; Ivanovic, M. D.; Dosen-
Micovic, L.; Kiricojevic, V. D.; Popovic, J. B. J. Chem.
Soc., Perkin Trans. 1 1996, 16, 2041.
11. Smith, R. A.; O’Connor, S. J.; Wong, W. W.; Choi, S.;
Kluender, H. C. E.; Fan, J.; Zhang, Z.; Lavoie, R.;
Podlogar, B. U.S. Pat. 7,071,207, 2006.
We thank Romulo Romero for assistance with chroma-
tographic separations and the Analytical Chemistry
Group for NMR and LC-MS analyses. We are grateful
to J. Evenski, S. Hudgins, D. Kelly-Sullivan, L. Milar-
do, and C. Ralphalides for assistance with in vivo phar-
macology studies. We also thank W. Wong, R.
Schoenleber, D. Campbell, C. Mahle, and S. Gardell
for helpful discussions.
12. The data in Table 1 are the average of two or more
triplicate determinations for purified and characterized
(1H NMR, LC-MS) samples. Hydrazide derivatives 6 and
43–45 were isolated as the HCl salts. Cannabinoid
receptor binding assays were performed with cell mem-
branes from human CB-1 or human CB-2 receptor
expressing HEK 293 cells using [3H]CP 55940 as radioli-
gand.10 Membrane pellets were suspended in ice-cold
binding buffer (50 mM Tris, pH 7.4, 2.5 mM EDTA,
5 mM MgCl2, and 0.1% fatty acid free BSA) and
immediately used for determining protein content (Bio-
Rad Assay) and binding assays. Competition binding
assays were performed in triplicate by incubating cell
membranes (corresponding to 3.3 lg protein) with 0.3 nM
[3H]CP 559440 and varying concentrations of competing
compounds. Reactions were carried out in a final volume
of 200 lL binding buffer in polypropylene plates with
constant shaking at 30 °C for 90 min. Non-specific binding
was determined in the presence of unlabeled 10 lM WIN
55212-2. The binding reaction was terminated by filtration
through pretreated (50 mM Tris, pH 7.4) Millipore GF/C
filter plates using a vacuum manifold. Filters were washed
seven times with ice-cold 50 mM Tris (pH 7.4). Microscint
O (25 lL) was added to each well and radioactivity bound
to the filters was measured using a Wallac 1450 MicroBeta
Trilux liquid scintillation counter. All competition binding
and concentration-response curves were analyzed using
nonlinear regression with Prism software (GraphPad
Software, San Diego, CA). Ki values were calculated from
IC50 values according to the Cheng and Prusoff formula.13
Antagonist potencies were determined mathematically by
evaluation of pKb values (pKb = Àlog [antagonist
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(M)] + log (DR À 1)) where DR is the agonist concentra-
taking food spillage into account. Data shown in Fig. 2
represent means SEM for 10 rats per treatment group.
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19. Genetically obese male Zucker fa/fa rats (average 550 g
body weight at start of study) were kept in standard
animal rooms under controlled temperature and humidity
and a reversed 12-h/12-h light/dark cycle. Water and food
were continuously available. Rats were single-housed in
large rat shoeboxes containing grid floor. Animals were
adapted to the grid floors and sham dosed with vehicle
(PEG/25 mM methanesulfonic acid (80:20)) for at least 5
days before the recording of two-days baseline measure-
ment of body weight and 24 h food and water consump-
tion. Using the baseline body weight data, rats were
weight-matched and assigned to the different treatment
groups. Rats received a daily oral dose of vehicle or test
compound in a volume of 2 mL/kg, before their feeding
phase (nocturnal cycle). Body weights were recorded daily
during the treatment period. Data shown in Figure 3
represent means SEM for 9–10 rats per treatment group.
20. The superior in vivo potency exhibited by rimonabant in
this study is presumably due, at least in part, to its greater
CB-1 binding affinity (hCB-1 Ki = 1.1 nM in our assay).
However, interpretation of the in vivo efficacy SAR for
these agents is complicated by factors such as oral
absorption, metabolic half-life, and brain penetration of
the compounds administered.
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17. Male Wistar rats were individually housed in suspended
cages with a mesh floor and were kept in standard animal
rooms under controlled temperature and humidity and a
12-h/12-h light/dark cycle for a minimum of week before
the start of the experiment. Rats were fasted overnight
(18 h) and then dosed orally with vehicle or test compound
at 10 mg/kg in a volume of 2 mL/kg, 1 h before re-feeding.
Cumulative food intake was recorded 30, 60, 90, 180, and
240 min after the return of the pre-weighed food jar,