Potent DGAT1 inhibitors in the benzimidazole class with a pyridyl-oxy-cyclohexanecarboxylic acid moiety

Article abstract of DOI:10.1021/ml400168h

We report the design and synthesis of a series of novel DGAT1 inhibitors in the benzimidazole class with a pyridyl-oxy-cyclohexanecarboxylic acid moiety. In particular, compound 11A is a potent DGAT1 inhibitor with excellent selectivity against ACAT1. Compound 11A significantly reduces triglyceride excursion in lipid tolerance tests (LTT) in both mice and dogs at low plasma exposure. An in vivo study in mice with des-fluoro analogue 10A indicates that this series of compounds appears to distribute in intestine preferentially over plasma. The propensity to target intestine over plasma could be advantageous in reducing potential side effects since lower circulating levels of drug are required for efficacy. However, in the preclinical species, compound 11A undergoes cis/trans epimerization in vivo, which could complicate further development due to the presence of an active metabolite.

Full text of DOI:10.1021/ml400168h

Letter
pubs.acs.org/acsmedchemlett
Potent DGAT1 Inhibitors in the Benzimidazole Class with a Pyridyl-
oxy-cyclohexanecarboxylic Acid Moiety
Shuwen He,* Qingmei Hong, Zhong Lai, Zhicai Wu, Yang Yu, David W. Kim, Pauline C. Ting,
Jeffrey T. Kuethe, Ginger X. Yang, Tianying Jian, Jian Liu, Deodial Guiadeen, Arto D. Krikorian,
Donald M. Sperbeck, Lisa M. Sonatore, Judyann Wiltsie, Christine C. Chung, Jack T. Gibson,
JeanMarie Lisnock, Beth A. Murphy, Judith N. Gorski, Jinqi Liu, Dunlu Chen, Xiaoli Chen, Michael Wolff,
Sharon X. Tong, Maria Madeira, Bindhu V. Karanam, Dong-Ming Shen, James M. Balkovec, Shirly Pinto,
Ravi P. Nargund, and Robert J. DeVita
Discovery and Preclinical Sciences, Merck Research Laboratories, 2000 Galloping Hill Road, Kenilworth, New Jersey 07033, United
States
S
* Supporting Information
ABSTRACT: We report the design and synthesis of a series of novel DGAT1 inhibitors in the benzimidazole class with a
pyridyl-oxy-cyclohexanecarboxylic acid moiety. In particular, compound 11A is a potent DGAT1 inhibitor with excellent
selectivity against ACAT1. Compound 11A significantly reduces triglyceride excursion in lipid tolerance tests (LTT) in both
mice and dogs at low plasma exposure. An in vivo study in mice with des-fluoro analogue 10A indicates that this series of
compounds appears to distribute in intestine preferentially over plasma. The propensity to target intestine over plasma could be
advantageous in reducing potential side effects since lower circulating levels of drug are required for efficacy. However, in the
preclinical species, compound 11A undergoes cis/trans epimerization in vivo, which could complicate further development due
to the presence of an active metabolite.
KEYWORDS: DGAT1, inhibitor, benzimidazole, ACAT1, cyclohexanecarboxylic acid, lipid tolerance test, epimerization, metabolite
knockout mouse phenotyping studies. DGAT1 knockout mice
were shown to be viable and resistant to diet-induced obesity.13
Furthermore, these mice appeared to have increased sensitivity
to insulin and leptin.14 This compelling data set has inspired
major efforts in identifying small molecule DGAT1 inhibitors
for potential treatment of diabetes and obesity (Figure 1).15−20
ype II diabetes mellitus (T2DM) and obesity, two
Tinterlinked disease conditions, have emerged as the
major threats to human health globally.1,2 In 2008, World
Health Organization estimated the number of overweight and
obese adults worldwide to be 1 billion and 500 million,
respectively. In 2009−2010, more than one-third of the
American population was classified as obese.3 Meanwhile, a
recent estimate indicates that there are about 371 million
people worldwide living with diabetes.4 Current drugs available
to treat diabetes and obesity have limitations in terms of long-
term efficacy and/or side effects.5−7 The unmet need prompts
significant research efforts in this area.
Inhibition of DGAT1 (diglyceride acyltransferase 1) has
emerged as a potential mechanism for the treatment of T2DM
and obesity.8,9 The DGAT family (diglyce diglyceride
acyltransferase 1 and 2) catalyzes the formation of triglyceride
(TG) from diacylglycerol and acyl-CoA, the terminal and
committed step in TG synthesis.10 DGAT1 shares only limited
sequence homology with DGAT2, the other known isoform.11
In contrast, DGAT1 has more sequence homology to acyl
CoA:cholesterol acyltransferase (ACAT1 and ACAT2). ACAT
plays an important role in cholesterol homeostasis.12 The
strong interest in DGAT1 started after the reports on DGAT1
Figure 1. Structures of selected DGAT1 inhibitors.
Received: May 8, 2013
Accepted: June 6, 2013
© XXXX American Chemical Society
A
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ACS Medicinal Chemistry Letters
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A number of drug candidates have been advanced into clinical
trials. Recently, we reported that small molecule DGAT1
inhibitors markedly alter incretin peptide release following oral
lipid challenge.21 Additionally, combination of DGAT1
inhibition with dipeptidyl-peptidase-4 (DPP-4) inhibition led
to further enhancements in active GLP-1 in mice and dogs,
suggesting potential combinability of DGAT1 inhibitors and
DPP-4 inhibitors for treatment of metabolic diseases.22
The DGAT1 inhibitor program at Merck was primarily built
upon our initial discovery of a novel benzimidazole class of
compounds bearing an acid moiety at the terminus of the
structure (Figure 2).23 Compounds 1 and 2 demonstrated
condensation of 8A with 4-(trifluoromethyl)benzene-1,2-
diamine formed a benzimidazole ring.27 Finally, the ester
group was hydrolyzed to afford acid compound 3A.
Accordingly, other compounds (3B, 4A, and 4B) were
synthesized using the corresponding cis or trans isomer and
the substituted benzene-1,2-diamine.
The profiles of compounds 3A/B and 4A/B are summarized
in Table 1. All four compounds exhibit potent inhibition on
both human and mouse DGAT1, with potencies comparable to
compounds 1 and 2. These analogues also have reduced log D
(HPLC) values relative to compounds 1 and 2. In addition to
the excellent in vitro potency on DGAT1, all four compounds
reduce triglyceride excursion in mouse LTT (lipid tolerance
test).28 In particular, compound 4A demonstrates extraordinary
efficacy in mouse LTT. It also gives the best selectivity (×1680)
against ACAT1, judging by the ratio IC50s of ACAT1 against
DGAT1 in human. Compound 4A was further evaluated for PK
in rat (Table 2). It was shown to have low plasma clearance,
reasonable half-life, and good plasma exposure after oral dosing.
Given the encouraging profiles for 3A/B and 4A/B, we
continued with a SAR study to assess the effect of the
substitution pattern on the benzimidazole ring in both the cis
and trans series in a library fashion. Scheme 2 details the
chemistry for the cis series. We decided to prepare a common
intermediate, which would be converted to the final analogues
with minimal manipulations. For this purpose, intermediate 9A
was chosen as the common intermediate instead of 8A. After
surveying a few reaction conditions, we identified a good
condition for hydrolyzing ester 8A to 9A without destroying
the aldehyde group.29 Under the standard oxidative con-
densation condition, 9A reacted with a variety of diamines to
give the required final compounds. With this protocol,
hydrolysis of the ester group was carried out once during the
preparation of common intermediate 9A rather than every time
for each compound. The compounds in the trans series were
prepared in a similar manner.
Table 3 compares the profiles for the analogues prepared
from this library approach. In general, DGAT1 potency
correlates well across human and mouse. Small substitutions
(e.g., H and F) afford the best potency (compounds 10−12).
As an exception, CN on benzimidazole maintains excellent
potency on human DGAT1 but loses potency on mouse
DGAT1 (compounds 13A and 13B). OCF3 (14A) gives good
DGAT1 potency but suffers from poor selectivity against
ACAT1.30 The sulfone, a polar group, is not tolerated for
DGAT1 potency (15A and 15B). Incorporation of an
azabenzimidazole core eliminates DGAT1 potency (16A and
16B). Introduction of the OMe group helps to regain
reasonable DGAT1 potency but with deterioration of ACAT1
selectivity (17A and 17B).
Figure 2. Design of benzimidazole acid class with a pyridyl−pyridyl−
ether moiety.
potent inhibition against both human and mouse isoforms of
DGAT1.24 However, both compounds had limited selectivity
against ACAT1.25 We decided to explore analogues incorporat-
ing a pyridyl−pyridyl−ether moiety. This modification was
expected to render the structure more flexible due to the ether
linkage. Furthermore, the addition of nitrogen and oxygen
atoms could help reduce log D. We began the work focusing on
the preparation of the compounds 3A, 4A, 3B, and 4B since Cl
and CF3 substitutions were shown to be favorable in the series
of 1 and 2. Cyclohexanecarboxylic acid was selected as the
terminal moiety since the corresponding starting materials were
readily available.26
The initial method for the synthesis of this series of
compounds was exemplified by the preparation of compound
3A (Scheme 1). Bromide 6A (cis) was prepared by Mitsunobu
reaction of commercially available ethyl 4-hydroxycyclohex-
anecarboxylate (a cis and trans mixture) and 5-bromo-2-
hydroxypyridine followed by SFC to separate cis and trans
isomers. Next, bromide 6A was converted into pinacol
boronate 7A, which underwent a Suzuki coupling reaction
with 6-bromonicotinaldehyde to furnish aldehyde 8A. Oxidative
a
Scheme 1. Synthesis of Compound 3A
Overall, compound 11A gave the best profile among the
analogues. As a significant advantage over 4A, compound 11A
exhibited excellent selectivity against ACAT1. Furthermore, in
the mouse LTT assay, compound 11A inhibited triglyceride
excursion by 72% after 3 mg/kg oral dosing (with plasma
trough level < 10 nM at 20 h). In a separate study, the plasma
drug level of compound 11A was determined to be also low
(<10 nM) at 4 h time point after oral dosing at 3 mg/kg in
mice. Compound 11B, the trans isomer of 11A, also showed
comparable efficacy, but compound 11A had more balanced in
vitro DGAT1 IC50 numbers across human and mouse. The
difluoro analogue, compound 12A, also gave a similar profile,
a
Reagents and conditions: (a) 1. PPh3, 5-bromo-2-hydroxypyridine,
DIAD, THF, 55 °C; 2. SFC (ChiralPak AD-H), first peak; (b)
bis(pinacolato)diboron, KOAc, PdCl2(dppf), dioxane, 80 °C; (c) 6-
bromonicotinaldehyde, Na2CO3, PdCl2(dppf), DMF−water, 80 °C;
(d) 1. potassium peroxymonosulfate, 4-(trifluoromethyl)benzene-1,2-
diamine, DMF−water; 2. LiOH, THF−water.
B
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ACS Medicinal Chemistry Letters
Letter
a
Table 1. Profiles of Compounds 3A, 3B, 4A, and 4B
human DGAT1
IC50 (nM)
mouse DGAT1
IC50 (nM)
log D
HPLC
human ACAT1
IC50 (nM)
ratio of IC50 human ACAT1
vs DGAT1
compd
mouse LTT triglyceride reduction @ 18 h
3A
3B
4A
4B
1.7
3.0
2.1
2.0
2.2
4.4
3.7
4.2
1.62
1.72
1.42
1.43
1093
1232
3528
1344
643
410
1680
672
−84%
−84%
−144%
−83%
a
Compounds were dosed in 0.5% methylcellulose at 10 mg/kg p.o. as a suspension.
a
To scale up compound 11A for additional profiling, we
modified the chemistry (Scheme 3). The modified synthesis
Table 2. Pharmacokinetic Data of 4A in Rat
PK parameters
rat
19
a
F (%)
Scheme 3. Chemistry for the Scale-up of 11A
Cl (mL min−1 kg−1
)
3.0
Vdss (L kg−1
)
0.34
3.7
t1/2 (h)
AUCn (μM·h/(mg/kg))
2.4
a
Compound dosed in Sprague−Dawley rats as a solution in EtOH/
PEG400/water (10:50:40) at 1 mg/kg, iv, and 2 mg/kg, p.o.
Scheme 2. Exploration of Substitutions on Benzimidazole
a
Ring
a
Reagents and conditions: (a) 6-bromonicotinaldehyde, potassium
peroxymonosulfate, DMF−water; (b) 1. pinacol boronate 7A,
Na2CO3, PdCl2(dppf), DMF−water, 80 °C; 2. LiOH, THF−water.
was more convergent and provided the material needed to
support further studies. In addition, compound 10A was also
scaled up according to a procedure similar to Scheme 2.
In addition to the observed mouse LTT efficacy, compound
11A performed extremely well in the dog LTT assay (Figure
3).31 One hour after oral dosing of compound 11A at 3 mg/kg
in 0.5% methyl cellulose, the dogs were challenged with lipid.
In comparison to the vehicle group, 11A was shown to abolish
lipid excursion at all time points. However, the corresponding
plasma exposure at all time-points (0 to 24 h) was low (<10
nM).
a
Reagents and conditions: (a) K2CO3, MeOH−water, 80 °C, 1.5 h;
(b) potassium peroxymonosulfate, substituted diamine, 3% HOAc in
DMF, 100 °C.
but it has slightly higher log D (1.28) than 11A (1.02).
Therefore, compound 11A was chosen for further evaluation.
Table 3. Profiles of Compounds 10−17
compd
cis/trans
X
Y
Z
human DGAT1 IC50 (nM)
mouse DGAT1 IC50 (nM)
human ACAT1 IC50 (nM)
10A
10B
11A
11B
12A
12B
13A
13B
14A
15A
15B
16A
16B
17A
17B
cis
CH
CH
CH
CH
CH
CH
CH
CH
CH
CH
CH
N
H
H
F
H
H
H
H
F
4.0
5.3
2.0
2.5
1.4
1.3
3.2
6.0
3.9
101
137
32
8.1
12
8080
trans
cis
6065
3.4
8.1
3.4
4.3
36
>10000
>10000
>10000
8440
trans
cis
F
F
trans
cis
F
F
−CN
−CN
−OCF3
−SO2Me
−SO2Me
Me
H
H
H
H
H
H
H
H
H
>10000
>10000
772
trans
cis
96
4.6
358
727
62
cis
>10000
>10000
>10000
8782
trans
cis
trans
cis
N
Me
54
161
13
N
−OMe
−OMe
11
2475
trans
N
14
16
4903
C
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ACS Medicinal Chemistry Letters
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a b c
, ,
Table 5. Pharmacokinetic Data for Compound 11A
PK parameters
rat
dog
rhesus
F (%)
2
2
3
Cl (mL min−1 kg−1
)
31.8
2.18
1.69
10
32.3
0.63
0.82
2
12.4
0.37
2.0
Vdss (L kg−1
)
t1/2 (h)
oral dose (mg/kg)
Cmax (μM)
2
0.06
2.00
0.25
2.47
0.06
0.25
0.05
0.06
0.01
8.00
0.20
0.56
Tmax (h)
AUC (μM·h) 11A
AUC (μM·h) metabolite 11B
a
Compound dosed in Sprague−Dawley rats as a solution in EtOH/
PEG400/water (10:50:40) at 1 mg/kg, iv, and 10 mg/kg, p.o., as solid
dispersion formulation. Compound dosed in beagles as a solution in
b
EtOH/PEG400/water (10:50:40) at 0.55 mg/kg, iv, and as solution in
c
0.5% methylcellulose at 2 mg/kg, p.o. Compound dosed in rhesus
monkeys as a solution in EtOH/PEG400/water (10:50:40) at 1 mg/
kg, iv, and as a solution in 0.5% methylcellulose at 2 mg/kg, p.o.
comparable or higher than parent 11A. The epimerization of
carboxylic acid is known and was previously studied in detail in
the case of ibuprofen.33,34 It has been generally accepted that
the epimerization of ibuprofen occurs enzymatically through an
acyl-CoA intermediate. A similar mechanism may also operate
for compound 11A. Although compound 11A has many
desirable attributes, the fact that the systematic exposure of
active metabolite 11B is comparable or even higher than parent
11A would likely complicate the development of 11A according
to a recent FDA guidance.35 Therefore, we decided to halt the
further progress of 11A.
Figure 3. Compound 11A demonstrates excellent efficacy in dog LTT.
The apparent disconnect between the efficacy and plasma
exposure of 11A could be due to the preferential tissue
distribution of compound 11A in intestine, where the nutrient
absorption and reassembly of triglycerides take place. This
finding presented a good opportunity to develop a gut-targeting
DGAT1 inhibitor, which could minimize potential side effects
due to systematic plasma exposure.32
To test this hypothesis, we repeated the mouse LTT using
compound 10A, the des-fluoro surrogate, since initial mouse
LTT data showed 10A at 3 mg/kg dosing reduces lipid
excursion by 95%, similar to compound 11A. In this study, after
3 mg/kg oral dosing, the drug levels were measured in different
segments of the intestine (duodenum, jejunum, and ileum) as
well as in blood at three time points (2, 5, and 25 h) (Table 4).
As a follow-up, a pharmacokinetic study of 11B in rat
indicates that 11B is also partially converted to 11A but to a
lesser extent (Table 6). After oral dosing of 11B at 2 mg/kg,
a
Table 6. Pharmacokinetic Data for Compound 11B
PK parameters
rat
24
F (%)
Cl (mL min−1 kg−1
)
4.2
Vdss (L kg−1
)
0.46
0.86
2
t1/2 (h)
Table 4. Concentration of 10A in Segments of Intestine and
Blood after Oral Dosing at 3 mg/kg in Mouse
oral dose (mg/kg)
AUC (μM·h) 11B
AUC (μM·h) metabolite 11A
4.47
0.48
drug level (μM) of 10A
a
Compound dosed in Sprague−Dawley rats as a solution in EtOH/
time point
blood
duodenum
jejunum
ileum
PEG400/water (10:50:40) at 1 mg/kg, iv, and 2 mg/kg, p.o.
2 h
0.114
0.051
0.01
8.32
8.76
1.76
5.51
6.01
3.06
3.89
1.72
0.62
5 h
the plasma exposure of metabolite 11A is roughly 10% of the
parent 11B, approaching the 10% threshold recommended in
the FDA guidance.35 Taking together the pharmacokinetic
studies of 11A and 11B, we decided to halt this series of
compounds with the cyclohexanecarboxylic acid as the terminal
moiety.36
In summary, we have described the design and synthesis of a
novel series of DGAT1 inhibitors in the benzimidazole class
with a pyridyl-oxy-cyclohexanecarboxylic acid moiety. Com-
pound 11A shows excellent potency on DGAT1 and excellent
selectivity against ACAT1. In addition, 11A significantly
reduced triglyceride excursion in LTT tests both in mice and
dogs with low plasma exposures. The excellent in vivo efficacy
at low plasma exposure may be due to the preferential
distribution of the compound in intestine over plasma. The
ability to target the intestine over plasma could be advanta-
25 h
In agreement with our hypothesis, compound 10A showed high
concentration in the different segments of the intestine, much
higher (>30×) than the concentration in blood at all time
points.
While the profiling of 11A continued, a major issue emerged
when we carefully analyzed the plasma samples from the in vivo
studies. In the preclinical species (rat, dog, and rhesus), after
oral dosing of 11A, we detected a significant conversion of 11A
to 11B by the epimerization at carbon atom attached to the
carboxylic acid group. After oral dosing of 11A at 10 mg/kg in
rat, the plasma exposure of metabolite 11B was about ten times
the exposure of the parent 11A (Table 5). Moreover, in dog
and rhesus, the plasma exposure of metabolite 11B was also
D
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CoA:diacylglycerol acyltransferase 1. J. Clin. Invest. 2002, 109, 1049−
1055.
geous due to possibly lower risk of potential side effects.
However, this series of compounds undergo epimerization in
vivo, thereby generating active metabolites. Further efforts to
address the epimerization issue will be disclosed in the future.
(15) For recent reports of DGAT1 inhibitors, see: Serrano-Wu, M.
H.; Kwak, Y.; Coppola, G.; Foster, C.; Gilmore, T.; Gong, Y.; He, G.;
Hou, Y.; Kantor, A.; Li, J.; Mergo, W.; Nakajima, K.; Neubert, A.;
Radetich, B.; Stroup, B.; Sung, M.; Szklennik, P.; Tichkule, R.; Yang,
L.; Yoon, T.; Zhu, Y.; Wareing, J.; Hosagrahara, V.; Jain, M.; Chatelain,
R.; Commerford, R.; Dardik, B.; Meyers, D.; Hubbard, B. Discovery of
a DGAT1 inhibitor with robust suppression of postprandial
triglyceride levels in humans. Abstracts of Papers, 243rd ACS National
Meeting & Exposition, San Diego, CA, March 25−29, 2012.
(16) Dow, R. L.; Li, J.-C.; Pence, M. P.; Gibbs, E. M.; LaPerle, J. L.;
Litchfield, J.; Piotrowski, D. W.; Munchhof, M. J.; Manion, T. B.;
Zavadoski, W. J.; Walker, G. S.; McPherson, R. K.; Tapley, S.;
Sugarman, E.; Guzman-Perez, A.; Dasilva-Jardine, P. Discovery of PF-
04620110, a potent, selective, and orally bioavailable inhibitor of
DGAT-1. ACS Med. Chem. Lett. 2011, 2, 407−412.
ASSOCIATED CONTENT
* Supporting Information
■
S
Syntheses and characterization data for the new compounds.
This material is available free of charge via the Internet at
http://pubs.acs.org.
AUTHOR INFORMATION
Corresponding Author
*(S.H.) Phone: 908-740-0881. E-mail: shuwen_he@merck.
com.
■
(17) Yeh, V. S.; Beno, D. W.; Brodjian, S.; Brune, M. E.; Cullen, S.
C.; Dayton, B. D.; Dhaon, M. K.; Falls, H. D.; Gao, J.; Grihalde, N.;
Hajduk, P.; Hansen, T. M.; Judd, A. S.; King, A. J.; Klix, R. C.; Larson,
K. J.; Lau, Y. Y.; Marsh, K. C.; Mittelstadt, S. W.; Plata, D.; Rozema, M.
J.; Segreti, J. A.; Stoner, E. J.; Voorbach, M. J.; Wang, X.; Xin, X.; Zhao,
G.; Collins, C. A.; Cox, B. F.; Reilly, R. M.; Kym, P. R.; Souers, A. J.
Identification and preliminary characterization of a potent, safe, and
orally efficacious inhibitor of acyl-CoA:diacylglycerol acyltransferase 1.
J. Med. Chem. 2012, 55, 1751−1757.
(18) Barlind, J. G.; Bauer, U. A.; Birch, A. M.; Birtles, S.; Buckett, L.
K.; Butlin, R. J.; Davies, R. D. M.; Eriksson, J. W.; Hammond, C. D.;
Hovland, R.; Johannesson, P.; Johansson, M. J.; Kemmitt, P. D.;
Lindmark, B. T.; Morentin, G. P.; Noesk, T. A.; Nordin, A.;
O’Donnell, C. J.; Petersson, A. U.; Redzic, A.; Turnbull, A. V.;
Vinblad, J. Design and optimization of pyrazinecarboxamide-based
inhibitors of diacylglycerol acyltransferase 1 (DGAT1) leading to a
clinical candidate dimethylpyrazinecarboxamide phenylcyclohexyl-
acetic acid (AZD7687). J. Med. Chem. 2012, 55, 10610−10629.
(19) Waring, M. J.; Birch, A. M.; Birtles, S.; Buckett, L. K.; Butlin, R.
J.; Campbell, L.; Gutierrez, P. M.; Kemmitt, P. D.; Leach, A. G.;
MacFaul, P. A.; O’Donnell, C.; Turnbull, A. V. Optimisation of
biphenyl acetic acid inhibitors of diacylglycerol acetyl transferase 1: the
discovery of AZD2353. Med. Chem. Commun. 2013, 4, 159−164.
(20) Goldberg, F. W.; Birch, A. M.; Leach, A. G.; Groombridge, S.
D.; Snelson, W. L.; Gutierrez, P. M.; Hammond, C. D.; Birtles, S.;
Buckett, L. K. Discovery and optimization of efficacious neutral 4-
amino-6-biphenyl-7,8-dihydropyrimido[5,4-f][1,4]oxazepin-5-one di-
acylglycerol acyl transferase-1 (DGAT1) inhibitors. Med. Chem.
Commun. 2013, 4, 165−174.
Notes
The authors declare no competing financial interest.
ACKNOWLEDGMENTS
■
We thank Dr. Charles W. Ross III and Mr. Thomas J. Novak at
Merck Research Laboratories for measuring high-resolution
mass.
REFERENCES
■
(1) Scully, T. Diabetes in numbers. Nature 2012, 485, S2−S3.
(2) World Health Organization (WHO). Fact sheet No. 311. Obesity
and overweight. Updated March 2013. Available at: http://www.who.
int/mediacentre/factsheets/fs311/en/.
(3) Flegal, K. M.; Carroll, M. D.; Kit, B. K.; Ogden, C. L. Prevalence
of obesity and trends in the distribution of body mass index among US
adults, 1999−2010. J. Am. Med. Assoc. 2012, 307, 491−497.
(4) Guariguata, L. By the numbers: new estimates from the IDF
Diabetes Atlas Update for 2012. Diabetes Res. Clin. Pract. 2012, 98,
524−525.
(5) For a recent review on pharmacologic treatment for Type-2
diabetes, see: Morsink, L. M.; Smits, M. M.; Diamant, M. Advances in
pharmacologic therapies for type 2 diabetes. Curr. Atheroscler. Rep.
2013, 15, 302.
(6) Moller, D. E. Metabolic disease drug discovery: “Hitting the
target” is easier said than done. Cell Metab. 2012, 15, 19−24.
(7) Zhang, Z.-Y.; Wang, M.-W. Obesity, a health burden of a global
nature. Acta Pharmacol. Sin. 2012, 33, 145−147.
(8) King, A. J.; Judd, A. S.; Souers, A. J. Inhibitors of diacylglycerol
acyltransferase: a review of 2008 patents. Exp. Opin. Ther. Patents
2010, 20, 19−29.
(21) Liu, J. Pharmacological inhibition of diacylglycerol acyltransfer-
ase 1 reduces body weight and modulates gut peptide release: potential
insight into mechanism of action. Obesity 2013, DOI: 10.1002/
oby.20193.
(22) Lin, H. V.; Chen, D.; Shen, Z.; Zhu, L.; Ouyang, X.; Vongs, A.;
Kan, Y.; Levorse, J. M.; Kowalik, E. J.; Szeto, D. M.; Yao, X.; Xiao, J.;
Chen, S.; Liu, J.; Garcia-Calvo, M.; Shin, M. K.; Pinto, S.
Diacylglycerol acyltransferase-1 (DGAT1) inhibition perturbs post-
prandial gut hormone release. PLoS One 2013, 8, e54480
DOI: 10.1371/journal.pone.0054480.
(9) Birch, A. M.; Buckett, L. K.; Turnbull, A. V. DGAT1 inhibitors as
anti-obesity and anti-diabetic agents. Curr. Opin. Drug Discovery Dev.
2010, 13, 489−496.
(10) Cases, S.; Smith, S. J.; Zheng, Y.-W.; Myers, H. M.; Lear, S. R.;
Sande, E.; Novak, S.; Collins, C.; Welch, C. B.; Lusis, A. J.; Erickson, S.
K.; Farese, R. V., Jr. Identification of a gene encoding an acyl
CoA:diacylglycerol acyltransferase, a key enzyme in triacylglycerol
synthesis. Proc. Natl. Acad. Sci. 1998, 95, 13018−13023.
(11) Cases, S.; Stone, S. J.; Zhou, P.; Yen, E.; Tow, B.; Lardizabal, K.
D.; Voelker, T.; Farese, R. V., Jr. Cloning of DGAT2, a second
mammalian diacylglycerol acyltransferase, and related family members.
J. Biol. Chem. 2001, 276, 38870−38876.
(23) This structure class was a hybrid of the known acid series and a
HTS (high throughput screening) hit containing a benzimidazole
moiety. Liu, J. Discovery of 2-biarylbenzimidazoles as novel DGAT1
inhibitors. Poster presented at 33rd National Medicinal Chemistry
Symposium, Tucson, AZ, May 20−13, 2012
(12) Pramfalk, C.; Eriksson, M.; Parini, P. Cholesteryl esters and
ACAT. Eur. J. Lipid Sci. Technol. 2012, 114, 624−633.
(24) For a description of the protocols for enzyme inhibition assays,
see ref 21.
(13) Smith, S. J.; Cases, S.; Jensen, D. R.; Chen, H. C.; Sande, E.;
Tow, B.; Sanan, D. A.; Raber, J.; Eckel, R. H.; Farese, R. V., Jr. Obesity
resistance and multiple mechanisms of triglyceride synthesis in mice
lacking DGAT. Nat. Genet. 2000, 25, 87−90.
(25) Inhibition of ACAT has been shown to cause adverse changes in
preclinical species, see: Floettmann, J. E.; Buckett, L. K.; Turnbull, A.
V.; Smith, T.; Hallberg, C.; Birch, A.; Lees, D.; Jones, H. B. ACAT-
selective and nonselective DGAT1 inhibition: Adrenocortical effects−a
cross-species comparison. Toxicol. Pathol. 2013, DOI: 10.1177/
0192623313477753.
(14) Chen, H. C.; Smith, S. J.; Ladha, Z.; Jensen, D. R.; Ferreira, L.
D.; Pulawa, L. K.; McGuire, J. G.; Pitas, R. E.; Eckel, R. H.; Farese, R.
V., Jr. Increased insulin and leptin sensitivity in mice lacking acyl
E
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ACS Medicinal Chemistry Letters
Letter
(26) After our work in the series was completed, an interesting report
appeared recently in the literature describing DGAT1 inhibitors in the
oxadiazole amide series containing this pyridyl-oxy-cyclohexanecarbox-
ylic acid side chain: Plowright, A. T.; Barton, P.; Stuart, B.; Alan, M.;
Birtles, S.; Buckett, L. K.; Butlin, R. J.; Davies, R. D. M.; Ertan, A.;
Gutierrez, P. M.; Kemmitt, P. D.; Leach, A. G.; Svensson, P. H.;
Turnbull, A. V.; Waring, M. J. Design and synthesis of a novel series of
cyclohexyloxy-pyridyl derivatives as inhibitors of diacylglycerol acyl
transferase 1. Med. Chem. Commun. 2013, 4, 151−158.
(27) For the reaction condition forming benzimidazole: Beaulieu, P.
́
L.; Hache, B.; von Moos, E. A practical Oxone®-mediated, high-
throughput, solution-phase synthesis of benzimidazoles from 1,2-
phenylenediamines and aldehydes and its application to preparative
scale synthesis. Synthesis 2003, 11, 1683−1692.
(28) For a description of the mouse LTT protocol, see ref 21.
(29) Jones, D. A.; Nongrum, F. M. Intramolecular Diels−Alder
additions to 2-benzopyran-3-ones; endo-selective additions and some
reactions of the adducts. J. Chem. Soc., Perkin Trans. 1 1996, 705−713.
(30) The corresponding trans isomer was not prepared due to the
predicted poor selectivity against ACAT1 based on the data for 14A.
(31) For a description of the dog LTT protocol, see ref 20.
(32) Intestine targeted DGAT1 inhibitors were recently reported:
Serrano-Wu, M. H.; Coppola, G. M.; Gong, Y.; Neubert, A. D.;
Chatelain, R.; Clairmont, K. B.; Commerford, R.; Cosker, T.; Daniels,
T.; Hou, Y.; Jain, M.; Juedes, M.; Li, L.; Mullarkey, T.; Rocheford, E.;
Sung, M. J.; Tyler, A.; Yang, Q.; Yoon, T.; Hubbard, B. K. Intestinally
targeted diacylglycerol acyltransferase 1 (DGAT1) inhibitors robustly
suppress postprandial triglycerides. ACS Med. Chem. Lett. 2012, 3,
411−415.
(33) Sanins, S. M.; Adams, W. J.; Kaiser, D. G.; Halstead, G. W.;
Hosley, J.; Barnes, H.; Baillie, T. A. Mechanistic studies on the
metabolic chiral inversion of R-ibuprofen in the rat. Drug Metab.
Dispos. 1991, 19, 405−10.
(34) Knihinicki, R. D.; Williams, K. M.; Day, R. O. Chiral inversion of
2-arylpropionic acid nonsteroidal anti-inflammatory drugs. 1. In vitro
studies of ibuprofen and flurbiprofen. Biochem. Pharmacol. 1989, 38,
4389−95.
(35) Center for Drug Evaluation and Research, U.S. FDA. Guidance
for Industry: Safety Testing of Drug Metabolites, February 2008.
h t t p : / / w w w . f d a . g o v / d o w n l o a d s / D r u g s /
GuidanceComplianceRegulatoryInformation/Guidances/ucm079266.
pdf (downloaded April 2013).
(36) The drug levels reported in Table 2 for 4A and Table 4 for 10A
are likely to be the total concentrations of the cis and trans isomers
combined.
F
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