Thiazole analog as stearoyl-CoA desaturase 1 inhibitor

Article abstract of DOI:10.1016/j.bmcl.2009.07.015

SCD1 inhibition may represent a novel treatment for obesity, type-2 diabetes and related metabolic disorders. A prototype thiazole amide analog 13 (MF-152) was identified as an excellent tool in the study of SCD biology in animals.

Full text of DOI:10.1016/j.bmcl.2009.07.015

Bioorganic & Medicinal Chemistry Letters 19 (2009) 5214–5217
Contents lists available at ScienceDirect
Bioorganic & Medicinal Chemistry Letters
journal homepage: www.elsevier.com/locate/bmcl
Thiazole analog as stearoyl-CoA desaturase 1 inhibitor
*
Chun Sing Li , Liette Belair, Jocelyne Guay, Renata Murgasva, Wayne Sturkenboom,
Yeeman K. Ramtohul, Lei Zhang, Zheng Huang
Merck Frosst Centre for Therapeutic Research, 16711 TransCanada Hwy, Kirkland, Quebec, Canada H9H 3L1
a r t i c l e i n f o
a b s t r a c t
Article history:
SCD1 inhibition may represent a novel treatment for obesity, type-2 diabetes and related metabolic dis-
orders. A prototype thiazole amide analog 13 (MF-152) was identified as an excellent tool in the study of
SCD biology in animals.
Received 1 June 2009
Revised 30 June 2009
Accepted 2 July 2009
Available online 9 July 2009
Ó 2009 Elsevier Ltd. All rights reserved.
Keywords:
Stearoyl-CoA desaturase 1 inhibitor
SCD1
Thiazole
MF-152
Obesity
Type-2 diabetes
Stearoyl-CoA desaturase-1 (SCD1), also known as delta-9
desaturase ( 9D), is a critical enzyme in the lipogenic pathway. It
Two additional fatty acyl-CoA specific desaturases, delta-5 and
delta-6 desaturases ( 5D and 6D), are required to catalyze the
D
D
D
converts saturated fatty acids to mono-unsaturated fatty acids with
the formation of a cis-double bond at the C-9 position.1 The
preferred substrates are the C-16 palmitoyl-CoA and the C-18 stea-
royl-CoA which are transformed into palmitoleoyl- and oleoyl-CoA,
respectively.2 The resulting mono-unsaturated acyl-CoAs are major
building blocks of lipids including phospholipid, triglyceride, cho-
lesterol ester and wax ester. Four SCD isoforms have been character-
ized in rodents and two in human. SCD1, with about 85% identity
across species, is the majorisoform found in lipogenic tissues includ-
ing liver and adipose tissues. Evidence from rodent and human
strongly supports the key roles of SCD1 in lipid and carbohydrate
metabolism. SCD1-deficient mice from natural mutation or targeted
deletion are resistant to high fat diet-induced obesity and show im-
proved insulin sensitivity as well as increased energy expenditure.3,4
This phenotype is also observed in high fat diet-induced obese (DIO)
mouse treated with anti-sense oligonucleotide (ASO)5 or small
molecule inhibitors.6,7 In human, elevated SCD activity is positively
correlated with high triglyceride in familial hypertriglyceridemia
subjects,8 increased body mass index (BMI) and high plasma
insulin levels.9 Therefore, SCD1 inhibition may represent a novel
treatment for obesity, type-2 diabetes, and related metabolic
disorders.
formation of highly unsaturated fatty acids (HUFAs) such as arachi-
donic acid from dietary essential fatty acids (polyunsaturated fatty
acids, PUFAs) in human. The primary role of HUFAs in mammals is
cell signaling. An imbalance of
D
5D and
D
6D activities will lead to
5D and 6D is
various disorders.10 Therefore, selectivity against
D
D
required for SCD1 inhibitors. In addition to the favorable metabolic
profile, global SCD1 deficiency also causes alopecia and dry eyes in
mice,3 although this effect is not observed in mice treated with
ASO.5a Thus, our initial challenge in the SCD inhibitor development
program was to identify an orally active SCD inhibitor that is suit-
able for evaluating the efficacy and potential adverse events of SCD
inhibition in animal models.11 In 2005, several SCD1 inhibitors
were disclosed12 and followed by some recent SAR studies.13–15
One of the key features of these SCD1 inhibitors is a relatively rigid
linear core template with substituents at both ends. A representa-
tive compound 1 was prepared and its SCD inhibitory activity was
confirmed (Fig. 1). However, circulating metabolites 2 and 3 de-
rived from the metabolism of the cyclopropylethyl amide were ob-
O
O
N
N
CF3
NH
N N
1
rSCD IC50: 0.3µM
* Corresponding author. Tel.: +1 514 428 3217; fax: +1 514 428 4900.
E-mail address: chunsing_li@merck.com (C.S. Li).
Figure 1. A representative SCD example from Xenon.
0960-894X/$ - see front matter Ó 2009 Elsevier Ltd. All rights reserved.
doi:10.1016/j.bmcl.2009.07.015

C. S. Li et al. / Bioorg. Med. Chem. Lett. 19 (2009) 5214–5217
5215
12
The potencies of representative compounds are summarized in
Table 1.
O
O
The initial thiazole analogs 10 and 11 with the amide substitu-
ent at either the 4 or 5-position of the thiazole were not potent.
However, it appeared that amide substituent at the 5-position of
11 was more favorable. When the size of the amide substituent
was reduced from cyclopropylethyl to a methyl group as shown
in 12, an 18-fold improvement in potency was observed. The best
analog in the series turned out to be the unsubstituted amide 13,
N
N
CF
NH
N
N 2
OH
IC = 2.5 µM
O
O
in vivo
N
N
CF
H N
N N
1
3
8
IC = 0.7 µM
Table 1
O
O
N
N
CF
Potency of thiazole SCD inhibitors
HO
N N
4
Compound Structure
Rat SCD
HepG2
IC50 (lm)
2
a
a
IC = >100 µM
IC50
(
lm)
O
O
S
N
Compound 1
Metabolite 2
Metabolite 3
Metabolite 4
N
N
N
N
CF3
H
N
4
10
>100
1
O
O
3
S
N
N
H
11
CF3 37
4
0
O
0
1
2
3
4
5
6
Time (h)
O
S
MeHN
12
N
N
CF3
2
4
N
Figure 2. Levels of compound 1 and its metabolites after oral dosing of 50 mg/kg in
mice over a 6 h period. Their IC50 in rat liver microsome assay are indicated below
the structures.
O
O
O
S
H2N
served at high levels following oral dosing in mice, along with low
level of the corresponding acid metabolite 4 (Fig. 2). The two amide
metabolites are also relatively active against SCD1 and thus would
complicate data interpretation from animal studies using 1. Herein,
we report our study to identify a compound with a simpler meta-
bolic profile for in vivo SCD inhibition studies.
One of our early modifications focused on diverse structures by
replacing the six-membered pyridazine in compound 1 with a five-
membered thiazole.16 Synthesis of these thiazole analogs is
described in Scheme 1. A halo-substituted thiazole was reacted
with the piperazine intermediate 6, which could be obtained from
1-Boc-piperazine 5 and the corresponding benzoyl chloride. The
13 (MF-
152)
N
N
N
N
CF3
0.1
0.3
N
O
S
N
H2N
14
2
3
7
O
S
N
N
N
CF3
15
13
68
resulting ester intermediate
7 was then converted to the
corresponding amide analogs 9 in a standard manner.
To measure the effect of modification on the intrinsic potency
against SCD enzyme, compounds were tested in a rat liver micro-
somal assay which measured the release of tritiated water in the
formation of oleoyl-CoA from 9,10-[3H]-stearoyl-CoA.17 Their cel-
lular potency on SCD1 and selectivity against the delta-5 and del-
ta-6 desaturases for selected compounds were evaluated using a
HepG2-based whole cell assay, which measures the cellular activ-
ities of SCD, delta-5 and delta-6 activities simultaneously.18
O
O
S
HO
16
N
N
CF3
N
a
IC50s are an average of at least two independent titrations.
O
O
O
R
S
N
a, b
c, d, e
HN
N
CF3
N
N
CF3
Boc
N
NH
6
5
7: R = OMe or OEt
8: R = OH
9: R = NHR1
Scheme 1. (a) 2-(Trifluoromethyl)benzoyl chloride, Et3N, CH2Cl2, room temperature, 2 h, 94%; (b) TFA, CH2Cl2, room temperature, overnight, 93%; (c) 2-halothiazole, DBU,
80 °C, 5 h to overnight, 50–90%; (d) NaOH, THF, MeOH, 60 °C, 1 h, quantitative; (e) oxalyl chloride, then RNH2, or HATU, RNH2, DIPEA, DMF, 70–90%.

5216
C. S. Li et al. / Bioorg. Med. Chem. Lett. 19 (2009) 5214–5217
6
5
4
3
2
1
0
40
38
36
34
32
30
28
HF diet control
Compound 13
13 in 0.05% HF
L-152/HF
Acid metabolite,
compound 16
AM251 in 0.014% HF
AM251/HF
**
**
**
0
1
2
3
4
5
6
Time (h)
**
**
26
24
22
Figure 3. Levels of compound 13 and its acid metabolite 16 after oral dosing of
10 mg/kg in mice over a 6 h period.
**
which showed comparable in vitro potency to compound 1. In the
0
10
20
30
40
50
whole cell assay, compound 13 displayed an IC50 of 0.3
the hSCD1 (delta-9 desaturase) and was selective against both del-
ta-5 and delta-6 desaturases with IC50’s >50 M and >10 M,
lM against
Treatment days
n=10/group
** P< 0.001
l
l
respectively. Removal of the 2-trifluoromethyl group on the ben-
zoyl moiety resulted in a 20-fold loss of potency in 14. The unsub-
stituted thiazole analog 15 was not very potent. In vitro
metabolism studies showed that compound 13 has a much cleaner
metabolic profile than 1 with amide hydrolysis being the major
metabolic pathway.19 The resulting acid metabolite 16 is a much
weaker SCD1 inhibitor and circulates in low levels after oral dosing
of 13 in mice (Fig. 3). The simpler metabolic profile rendered com-
pound 13 a more desirable compound for in vivo studies.
To measure the in vivo potency, compound 13 was dosed orally
to mice on high carbohydrate diet. The SCD activity was indexed by
following the conversion of intravenously administrated [1-14C]-
stearic acid tracer to the SCD-derived 14C-oleic acid in liver lipids.
As illustrated in Figure 4, the in vivo SCD activity index (ratio of
14C-oleic acid/14C-stearic acid in the saponified liver lipids) de-
creased dose-dependently with an increased dose of compound
13. An ED50 of ꢀ3 mg/kg was observed, demonstrating compound
13 is highly effective at suppressing the SCD activity in vivo. To
determine the consequences from chronic SCD inhibition in a
rodent model, a diet formulation containing 0.05% (w/w) of
Figure 5. Effect of compound 13 on body weight gain of C57BL6 mice. In
comparison to the control diet, 73% reduction in body weight gained was
observed when compound 13 was formulated in high fat diet (0.05%, w/w) over a
7 week study. The effect on body weight was comparable to the positive control
AM251, formulated in high fat diet (0.014%, w/w).
a
compound 13 in a high fat diet (Bio-Serv F3282) was prepared to
circumvent its short half-life of ꢀ1 h. In comparison to a group
on the control diet, C57BL6 mice on the drug-containing diet
showed a 73% reduced body weight gain throughout a 7-week
treatment duration,20 with the effect on body weight being compa-
rable to a parallel group treated with the CB1 inverse agonist AM-
25121 which was formulated at 0.014% (w/w) in the high fat diet
(Fig. 5). The resistance to HFD-induced body weight gain following
compound 13 treatment was associated with a decreased fat accu-
mulation in inguinal and epididymal adipose tissues. In addition,
an improved metabolic profile was detected as exemplified by
the reduction on plasma insulin level by 69% (p <0.01), plasma cho-
lesterol level by 41% (p <0.001), and plasma triglyceride level by
22% (p = 0.02), respectively. However, partial eye closure and pro-
gressive alopecia emerged after ꢀ14 days of drug treatment, with
features resembling those reported in the SCD1 knockout mice
and in mice treated with other SCD inhibitors,6b suggesting these
events are likely mechanism-based. However, these adverse events
reversed rapidly upon the discontinuation of drug treatment, with
new hair emerged and recovery from eye closure after ꢀ10 days.
In conclusion, we have identified compound 13 (designated MF-
152), a specific SCD inhibitor with an excellent in vivo potency and
no cross activity against the delta-5 and delta-6 desaturases. It is
an excellent tool in the study of SCD biology in animals. However,
further optimization is needed to develop a SCD inhibitor suitable
for therapeutic potential evaluation in human.
2.5
2.0
1.5
63% Inh.
1.0
78% Inh.
0.5
90% Inh.
0.0
Acknowledgment
We thank Drs. Renata Oballa, Cameron Black and Mr. Serge
Léger for their comments and suggestions on the Letter.
Figure 4. In vivo SCD inhibition following compound 13 treatment—compound 13
was dosed orally via 0.5% methocel vehicle in C57B6 mice. One hour later, 14C-
stearic acid in 60% aqueous PEG 200 was administrated intravenously and livers
were harvested at two hours post tracer. The SCD activity index [ratio of 14C-oleic
acid (OA)/14C-stearic acid (SA) in hydrolyzed liver lipids] decreased with increasing
doses of compound 13 with an ED50 of ꢀ3 mg/kg compared with the vehicle group.
Mean ( SE, n = 5/group, p <0.001 for all treated groups).
Reference and notes
1. Enoch, H. G.; Catala, A.; Strittmatter, P. J. Biol. Chem. 1976, 251, 5095.
2. Ntambi, J. M. Prog. Lipid Res. 1995, 34, 139.
3. Miyazaki, M.; Kim, Y.-C.; Gray-Keller, M. P.; Attie, A. D. J. Biol. Chem. 2000, 275,
30132.

C. S. Li et al. / Bioorg. Med. Chem. Lett. 19 (2009) 5214–5217
5217
4. Ntambi, J. M.; Miyazaki, M.; Stoehr, J. P.; Lan, H.; Kendziorski, C. M.; Yandell, B.
S.; Song, Y.; Cohn, P.; Friedman, J. M.; Attie, A. D. Proc. Natl. Acad. Sci. U.S.A 2002,
99, 11482.
14. Xin, Z.; Zhao, H.; Serby, M. D.; Liu, B.; Szczepankiewicz, B. G.; Nelson, L. T. J.;
Smith, H. T.; Suhar, T. S.; Janis, R. S.; Cao, N.; Camp, H. S.; Collins, C. A.; Sham, H.
L.; Surowy, T. K.; Liu, G. Bioorg. Med. Chem. Lett. 2008, 18, 4298.
5. (a) Jiang, G.; Li, Z.; Liu, F.; Ellsworth, K.; Dallas-Yang, Q.; Wu, M.; Ronan, J.; Esau,
C.; Murphy, C.; Szalkowski, D.; Bergeron, R.; Doebber, T.; Zhang, B. B. J. Clin.
Invest. 2005, 115, 1030; (b) Gutierrez-Juarez, R.; Pocai, A.; Mulas, C.; Ono, H.;
Bhanot, S.; Monia, B. P.; Rossetti, L. J. Clin. Invest. 2006, 116, 1686.
6. (a) Liu, G.; Lynch, J. K.; Freeman, J.; Liu, B.; Xin, Z.; Zhao, H.; Serby, M. D.; Kym, P.
R.; Suhar, T. S.; Smith, H. T.; Cao, N.; Yang, R.; Janis, R. S.; Krauser, J. A.; Cepa, S.
P.; Beno, D. W.; Sham, H. L.; Collins, C. A.; Surowy, T. K.; Camp, H. S. J. Med.
Chem. 2007, 50, 3086; (b) Liu, G.; Zhao, H.; Serby, M. D.; Smith, H. T.; Cao, N.;
Surowy, T. K.; Adler, A.; Mika, A.; Farb, T. B.; Keegan, C.; Landschulz, K.; Brune,
M.; Collins, C. A.; Sham, H. L.; Camp, H. S. The 233rd ACS National Meeting,
Chicago, IL, March 25–29, 2007; Abstract: MEDI 232.
15. A structurally distinct class of SCD inhibitor was published during the
preparation of this Letter. Koltun, D. O.; Parkhill, E. Q.; Vasilevich, N. I.;
Glushkov, A. I.; Zilbershshtein, T. M.; Ivanov, A. V.; Cole, A. G.; Henderson, I.;
Zautke, N. A.; Brunn, S. A.; Mollova, N.; Leung, K.; Chisholm, J. W.; Zablocki, J.
Bioorg. Med. Chem. Lett. 2009, 19, 2052.
16. There was a patent application on five-membered heterocycles during the
course of this work. However, examples disclosed are very limited in scope.
Kamboj, R.; Zhang, Z.; Fu, J.-M.; Kodumuru, V.; Liu, S.; Sun, S.; Chakka, N.
WO2006/034315.
17. Rat microsomal assay conditions: Li, C, S.; Ramtohul, Y.; Huang, Z.; Zhang, L.;
Lachance, N. WO2006/130986.
7. Winther, M. D. 2nd Annual Drug Development for Diabetes and Obesity, London,
UK, 2008, Jan 17–18.
18. Zhang, L.; Ramtohul, Y.; Gagné, S.; Styhler, A.; Wang, H.; Guay, J.; Huang, Z. J.
Biomol. Screen, accepted for publication.
8. Attie, A. D.; Krauss, R. M.; Gray-Keller, M. P.; Brownlie, A.; Miyazaki, M.;
Kastelein, J. J.; Lusis, A. J.; Stalenhoef, A. F.; Stoehr, J. P.; Hayden, M. R.; Ntambi,
J. M. J. Lipid Res. 2002, 43, 1899.
9. Hulver, M. W.; Berggren, J. R.; Carper, M. J.; Miyazaki, M.; Ntambi, J. M.;
Hoffman, E. P.; Thyfault, J. P.; Stevens, R.; Dohm, G. L.; Houmard, J. A.; Muoio, D.
M. Cell Metab. 2005, 2, 251.
10. Nakamura, M. T.; Nara, T. Y. Annu. Rev. Nutr. 2004, 24, 345.
11. The study of a small molecule of SCD inhibitor was reported recently, Ref. 6b.
12. Five applications from Xenon (WO2005/011653 to WO 2005/011657) were
published on February 10, 2005. Representative one: Abreo, M.; Chafeev, M.;
Chakka, N.; Chowdhury, S.; Fu, J.-M.; Gschwend, H. W.; Holladay, M. W.; Hou,
D.; Kamboj, R.; Kodumuru, V.; Li, W.; Liu, S.; Raina, V.; Sun, S.; Sun, S.; Sviridov,
S.; Winther, M. D.; Zhang, Z. WO2005/011655.
19. Unpublished results: Both 1 and 13 at 20
lM showed comparable parent
remaining (42–50%) after incubation at 37 °C with cryoperserved rat
hepatocytes (2 million cells/mL of Krebs–Henseleit buffer) for 2 h under 95%
O2/5% CO2 atmosphere. However, compound 1 has a total of 10 metabolites
with the hydroxylation metabolite 2 as major product whereas compound 13
has only three metabolites with the acid 16 as the major metabolite. Some of
these metabolites from both compounds were confirmed with synthetic
standard and not all metabolites were fully characterized.
20. Food consumption was not vigorously measured for this exploratory
experiment. There were ꢀ5% less food consumptions for both compound 13
and AM251, but they were not statistically significant in this study. Subsequent
studies showed that compound 13 does not appear to have effect on food
consumption (unpublished results).
13. Zhao, H.; Serby, M. D.; Smith, H. T.; Cao, N.; Suhar, T. S.; Surowy, T. K.; Camp, H.
S.; Collins, C. A.; Sham, H. L.; Liu, G. Bioorg. Med. Chem. Lett. 2007, 17, 3388.
21. Lan, R.; Liu, Q.; Fan, P.; Lin, S.; Fernando, S. R.; McCallion, D.; Pertwee, R.;
Makriyannis, A. J. Med. Chem. 1999, 42, 769.