Discovery and Initial SAR of Arylsulfonylpiperazine Inhibitors of 11β-Hydroxysteroid Dehydrogenase Type 1 (11β-HSD1)

Article abstract of DOI:10.1016/j.bmcl.2008.05.025

High-throughput screening of a small-molecule compound library resulted in the identification of a series of arylsulfonylpiperazines that are potent and selective inhibitors of human 11β-Hydroxysteroid Dehydrogenase Type 1 (11β-HSD1). Optimization of the initial lead resulted in the discovery of compound (R)-45 (11β-HSD1 IC₅₀ = 3 nM).

Full text of DOI:10.1016/j.bmcl.2008.05.025

Bioorganic & Medicinal Chemistry Letters 18 (2008) 3513–3516
Contents lists available at ScienceDirect
Bioorganic & Medicinal Chemistry Letters
journal homepage: www.elsevier.com/locate/bmcl
Discovery and Initial SAR of Arylsulfonylpiperazine Inhibitors
of 11b-Hydroxysteroid Dehydrogenase Type 1 (11b-HSD1)
à
*
Daqing Sun , Zhulun Wang, Yongmei Di, Juan C. Jaen , Marc Labelle , Ji Ma, Shichang Miao ,
Athena Sudom, Liang Tang, Craig S. Tomooka, Hua Tu, Stefania Ursu, Nigel Walker,
,
*
Xuelei Yan, Qiuping Ye, Jay P. Powers
Amgen Inc., 1120 Veterans Boulevard, South San Francisco, CA 94080, USA
a r t i c l e i n f o
a b s t r a c t
Article history:
Received 1 February 2008
Revised 2 May 2008
Accepted 7 May 2008
Available online 10 May 2008
High-throughput screening of a small-molecule compound library resulted in the identification of a series
of arylsulfonylpiperazines that are potent and selective inhibitors of human 11b-Hydroxysteroid Dehy-
drogenase Type 1 (11b-HSD1). Optimization of the initial lead resulted in the discovery of compound
(R)-45 (11b-HSD1 IC50 = 3 nM).
Ó 2008 Elsevier Ltd. All rights reserved.
Keywords:
11b-HSD1
11b-HSD2
Diabetes
Metabolic syndrome
Hydroxysteroid dehydrogenase
Arylsulfonylpiperazines
11b-hydroxysteroid dehydrogenase type 1 (11b-HSD1) is a key
enzyme that acts as an NADPH-dependent reductase capable of
converting the inactive 11b glucocorticoids such as cortisone into
their active form, (e.g., cortisol) in specific tissues, such as liver,
adipose, and brain tissues. Therefore, 11b-HSD1 regulates tissue-
specific glucocorticoid levels.1–4 Conversely, 11b-hydroxysteroid
dehydrogenase type 2 (11b-HSD2), a structurally related isoen-
zyme of 11b-HSD1, catalyzes the conversion of cortisol to cortisone
utilizing NAD as a cofactor. 11b-HSD2 is expressed in cells that
contain the mineralocorticoid receptor (MR) and protects the MR
by converting cortisol to the inactive form, cortisone.5
Aberrant glucocorticoid action in the liver and adipose tissue
has been linked to insulin resistance and dyslipidemia. Therefore,
selective inhibition of 11b-HSD1 over 11b-HSD2 is a promising
strategy to improve insulin sensitivity and treat type 2 diabetes,
and has attracted significant attention from the pharmaceutical re-
search community.6–12
N
N
N
CF3
S
O
O
1
Figure 1. Initial 11b-HSD1 inhibitor hit.
put screening of a small-molecule compound library utilizing a
purified recombinant human enzyme. Compound 1 did not signif-
icantly inhibit 11b-HSD2 under similar conditions (11b-HSD2
IC50 > 10 uM).
Analogs of 1 were synthesizd via the routes outlined in Schemes
1–3.13 Compounds 2–22 and 38–44 were prepared as outlined in
Scheme 1. Treatment of 2-chloro-3-trifloromethylpyridine with
excess piperazine produced pyridylpiperazine 47, which was then
coupled with benzoic acid in the presence of HBTU/HOBt to yield
amide 3. Reaction between 47 and phenyl isocyanate gave urea
4, while treatment of 47 with the appropriate benzenesulfonyl
chlorides in dichloromethane gave arylsulfonylpiperazines 2, 6–
22, and 38–44. Reductive amination of 47 with benzaldehyde
afforded the benzylpiperazine 5.
We identified arylsulfonylpiperazine 1 (Fig. 1, human 11b-HSD1
IC50 = 16 nM) as a potent inhibitor of 11b-HSD1 by high-through-
* Corresponding authors. Tel.: +1 650 244 2195 (D.S.); +1 650 210 2949 (J.P.P.).
E-mail addresses: daqings@amgen.com (D. Sun), jpowers@chemocentryx.com
(J.P. Powers).
Compounds 23–27 were prepared by treatment of 4- meth-
ylbenenesulfonyl chloride with pyridylpiperazines 48, which could
be synthesized by nucleophilic displacement of the chlorine in
substituted 2-chloropyridines with piperazine (Scheme 2).
Currently at ChemoCentryx, Inc., Mountain View, CA 94043.
Currently at Lundbeck Research USA, Inc., 215 College Road, Paramus, New Jersey
à
07652.
0960-894X/$ - see front matter Ó 2008 Elsevier Ltd. All rights reserved.
doi:10.1016/j.bmcl.2008.05.025

3514
D. Sun et al. / Bioorg. Med. Chem. Lett. 18 (2008) 3513–3516
Table 1
N
N
Inhibition of 11b-HSD1 by selected analogs: Sulfonamide replacements
N
a
b
N
N
N
Cl
R
N
CF3
S
HN
CF3
CF3
O
O
N
N
CF3
47
1, 2, 6-22, 38-44
X
d
Compound
X
h-HSD1 IC50 (nM) h-293 IC50 (nM) m-HSD1 IC50 (nM)
c
e
2
3
4
5
6
–SO2–
–C(O)–
–NHC(O)– >1000
–CH2– 550
–CH2SO2– 20
45
262
724
>1000
—
1930
574
122
>1000
—
>1000
47
N
N
N
N
N
N
O
N
CF3
O
N
CF3
N
CF3
NH
3
5
4
Scheme 1. Reagents and conditions: (a) piperazine, 120 °C, 74%; (b) RSO2Cl, Et3N,
CH2Cl2, 51–90%; (c) benzoic acid, HBTU, HOBT, NMM, DMF, 63%; (d) phenyl isoc-
yanate, CHCl3, 82%; (e) benzaldehyde, NaBH(OAc)3, acetic acid, dichloroethane, 90%.
moiety with amide, urea, and methylene groups (3, 4, and 5) re-
sulted in a significant loss of potency in both human and mouse
enzymatic assays, as well as in the human cell-based assay as com-
pared to 2. However, insertion of a methylene between the sulfon-
amide and the phenyl ring (6) led to a 2-fold increase in human
potency, suggesting that the sulfonamide moiety is an important
feature for binding of this class of inhibitors to 11b-HSD1.
We then turned our attention to modification of the sulfon-
amide aryl ring (Table 2). Gradually increasing the alkyl substitu-
ent size at the para-position of the sulfonamide aryl ring led to
the tert-butyl analog 10, which had fourfold increase in human bio-
chemical potency and a twofold increase of cellular potency over 1,
respectively. These data suggest that lipophilicity in the 4-substi-
tuent is beneficial to 11b-HSD1 inhibition. However, incorporation
of a chloro, trifluoromethyl, or methoxy group (12–14) did not im-
prove potency, while fluoro, nitro, or cyano groups (11, 15, and 16)
led to approximately a threefold reduction of potency. Similarly,
introduction of a phenyl group at the para-position (17) brought
a slight decrease in potency, indicating a steric limit to substituents
in this position. Interestingly, the incorporation of an additional
fused benzene ring (18, 19) resulted in potency similar to com-
pound 10. Introduction of an additional chlorine atom at the 2-po-
N
N
N
N
a
b
N
N
R
Cl
S
HN
R
O
O
R
23-27
48
Scheme 2. Reagents and conditions: (a) piperazine, 120 °C, 78–91%; (b) 4-meth-
ylbenzenesulfonyl chloride, Et3N, CH2Cl2, 75–90%.
X
F
a
X
X
c
N
NH
N
N
HN
HN
X
S
O
O
b
49
28-37, 45-46
Br
Scheme 3. Reagents and conditions: (a) piperazine, 120 °C, (X = 2-CF3, 4-NO2, 2-
NO2), 60–78%; (b) Pd(OAc)2, tritolyphosphine, NaOtBu, toluene, 110 °C, 42–63%, (X
= 2-Me, 2-Cl, 2-F, 4-Me, 4-Cl, 4-F, 4-OMe); (c) 4-t-butylbenzenesulfonyl chloride,
Et3N, CH2Cl2, 80–95%.
Table 2
Sulfonamide aryl modification
N
N
R
N
CF3
S
In a similar fashion, compounds 28–37, 45, and 46 were ob-
tained simply by reaction of tert-butylbenzesulfonyl chloride and
arylpiperazines 49, which were synthesized by either direct nucle-
ophilic displacement or palladium mediated coupling reaction be-
tween the appropriate aryl halide and piperazine (Scheme 3).
Compounds were evaluated for inhibition of human and mouse
11b-HSD1 enzymes, as well as in cell-based assays. 11b-HSD1 en-
zyme activity was determined by measuring the conversion of
[3H]-cortisone to [3H]-cortisol. Product [3H]-cortisol, captured by
an anti-cortisol monoclonal antibody conjugated to scintillation
proximity assay (SPA) beads, was quantified with a microscintilla-
tion plate reader. Biochemical enzyme assays were performed with
Baculovirus-produced recombinant full-length human or mouse
11b-HSD1 as the enzyme source and NADPH as cofactor. Cell-based
enzyme assays (h-293) utilized HEK293 cells stably expressing re-
combinant human full-length 11b-HSD1 as the enzyme source
without supplementation of NADPH. IC50 values for enzyme inhibi-
tion were calculated with a dose response curve fitting algorithm
with at least duplicate sets of samples.
O
O
Compound
R
h-HSD1 IC50
(nM)
h-293 IC50
(nM)
m-HSD1 IC50
(nM)
1
7
8
4-Me-Ph
4-Et-Ph
4-Pr-Ph
4-iPr-Ph
4-tBu-Ph
4-F-Ph
4-Cl-Ph
4-CF3-Ph
4-OMe-Ph
4-NO2-Ph
4-CN-Ph
4-Ph-Ph
2-
16
18
16
15
4
46
14
14
19
37
50
74
13
461
510
613
556
201
667
518
727
456
922
978
603
547
32
53
106
67
21
211
40
75
32
311
546
>1000
11
9
10
11
12
13
14
15
16
17
18
naphthyl
3-
19
13
329
80
naphthyl
3-Cl-Ph
3-CF3-Ph
2,4-diCl-
Ph
20
21
22
55
64
7
>1000
>1000
241
58
53
25
Initial optimization of 1 began with the replacement of the sul-
fonamide functionality (Table 1). Replacement of the sulfonamide

D. Sun et al. / Bioorg. Med. Chem. Lett. 18 (2008) 3513–3516
3515
Table 3
Table 5
Pyridyl ring substitution
Piperazine modifications
N
N
N
N
N
R
CF3
N
S
S
O
O
O
O
Compound
R
h-HSD1 IC50 (nM)
h-293 IC50 (nM)
m-HSD1 IC50 (nM)
Compound Ring
h-HSD1 IC50
(nM)
h-293 IC50
(nM)
m-HSD1 IC50
(nM)
1
CF3
H
CH3
Cl
NO2
CN
16
461
32
23
24
25
26
27
>1000
152
117
291
628
>1000
>1000
>1000
>1000
>1000
>1000
240
146
—
N
10
4
3
201
315
21
N
—
N
38
84
4
N
sition (22) also led to a significant increase in potency, while sub-
stitution at the 3-position resulted in less active compounds (20
and 21) in comparison with 12 and 13. In general this set of ana-
logs showed a significant shift in potency in human biochemical
and cellular 11b-HSD1 assays.
N
N
39
9
632
N
N
40
41
42
17
>1000
6
We next turned to substituent modification and replacement of
the N-aryl ring (Tables 3 and 4). Replacing the trifluoromethyl
group in 1 by a variety of subtituents resulted in a substantial
reduction in activity (23–27). Removal of the 3-trifluoromethyl
group led to a significant reduction in potency, while substitution
at the 3-position with other groups (24–27) was more potent than
the unsubstituted analog 23, but they were less potent than parent
compound 1. Replacement of the trifluoromethylpyridyl moiety
with either meta or para-substituted phenyl groups decreased
HSD1 inhibition (28–37). In the best case, incorporation of a 4-
nitrophenyl group (33) showed a two-fold reduction in human bio-
chemical potency and a slight loss in cellular potency compared to
10. However, compound 33 displayed significant improvement in
in vitro metabolic stability as compared to 10 (90% vs. 61% remain-
ing in human liver microsomes @ 10 min). The rat in vivo PK profile
of 33 featured a moderate clearance, although oral bioavailability
was poor (CL = 1.0 L/h/Kg; %F = 7).
N
N
58
62
>1000
638
—
N
N
9
(39 and 40) showed a small loss in human potency but improved
mouse potency relative to 10. However, further substitution to give
either the 2,6- or 2,2-dimethyl analog (41 and 42) was detrimental
for activity.
Our investigation into the 11b-HSD1 inhibition pharmacophore
then moved to limited modification of the piperazine ring, includ-
ing replacement by homopiperazine and a set of substituted piper-
azines (Table 5). Replacement of the piperazine ring with
homopiperazine (38) resulted in a slight increase in human bio-
chemical potency, while both 2-methyl and 2-ethyl piperazine
The stereochemistry of substituents at the 2-position in the
piprazine ring was also examined (Table 6). In the 3-trifluoro-2-
pyridyl series, very little difference was observed between enanti-
omers (43, 44), while in the 4-nitrophenyl series, the R enantiomer
had an 11b-HSD1 IC50 = 3 nM, about 10 times more potent than the
corresponding S isomer in both the biochemical and cellular assays
(45 vs. 46).
The structure of a representative arylsulfonylpiperazine inhibi-
tor bound to human 11b-HSD1 was determined by X-ray crystal-
lography (Fig. 2) to
Table 4
N-Aryl replacements
a
resolution of 2.2 Å.14 The co-crystal
structure of compound 45 with human 11b-HSD1 reveals that
Ar
N
N
S
O
O
Table 6
Effect of stereochemistry at the 2-position of the piperazine ring
Compound Ar
h-HSD1 IC50
(nM)
h-293 IC50
(nM)
m-HSD1 IC50
(nM)
Ar
N
10
3-CF3-2-
pyridyl
2-CF3-Ph
2-Me-Ph
2-Cl-Ph
4
201
21
N
S
O
O
28
29
30
31
32
33
34
35
36
37
15
32
95
106
37
10
87
390
42
971
702
>1000
>1000
839
73
204
184
98
133
161
>1000
>1000
186
—
Compound Config Ar
h-HSD1 IC50
(nM)
h-293 IC50
(nM)
m-HSD1 IC50
(nM)
(2-F)Ph
2-NO2-Ph
4-NO2-Ph
4-Cl-Ph
4-Me-Ph
4-F-Ph
43
44
R
S
3-CF3-2-
pyridyl
3-CF3-2-
pyridyl
11
9
762
569
4
247
>1000
>1000
>1000
>1000
17
45
46
R
S
4-NO2-Ph
4-NO2-Ph
3
29
57
527
53
37
4-OMe-Ph
234

3516
D. Sun et al. / Bioorg. Med. Chem. Lett. 18 (2008) 3513–3516
ADME and potency parameters. Replacement of the N-aryl moiety
by various substituted phenyl groups demonstrated that some
changes were allowed in this region. This finding encouraged us
to explore the replacement of the N-aryl moiety with non-aromatic
groups to improve water solubility and metabolic stability, as well
as cellular activity. These results will be reported in subsequent
publications.
References and notes
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Wang, M.; Zhang, X.; Fotsch, C. J. Med. Chem. 2007, 50, 429–432.
13. All compounds gave satisfactory 1H NMR, HPLC, and MS data in full agreement
with their proposed structures, and purity (>95%) was determined by HPLC
analysis.
Figure 2. Co-crystal structure of compound 45 in human 11b-HSD1. The protein is
shown in both stick and molecular surface representations which are color coded
(red for oxygen atoms, blue for nitrogen, orange for sulfur, and slate for carbon). The
inhibitor and the cofactor NADP+ are shown in sticks and color coded grey for
carbon atoms in NADP+ and green for the inhibitor. The hydrogen bond is shown in
magenta dashed line.
the inhibitor binds to the substrate site in a V-shape with its tert-
butyl phenyl group pointing toward the cofactor NADP+ side. The
central sulfonyl group makes a hydrogen bond from one of its oxy-
gen atom to the backbone amide of Ala172, as well as VDW con-
tacts with Ser170 in the catalytic site.
In conclusion, we have identified a series of novel and selective
arylsulfonylpiperazine inhibitors of 11b-HSD1 through screening
of a small-molecule library. SAR studies resulted in a significant
improvement of human biochemical and cellular potencies, and
established features of the pharmacophore for 11b-HSD1 inhibi-
tion in the series. The sulfonamide functionality was found to be
important for 11b-HSD1 inhibition, while modification of the sul-
fonamide aryl ring via substituent replacement resulted in a four-
fold increase of human biochemical potency and a twofold increase
of cellular potency. Most of potent arylsulfonylpiperazine inhibi-
tors of 11b-HSD1 showed little activity toward 11b-HSD2. Stereo-
chemical studies at the 2-position of the methylpiperazine showed
that R and S enantiomers can have a significant difference in prop-
erties, which may be important for future studies to optimize both
14. The atomic coordinate has been deposited in the Protein Data Bank under an
accession code 3CZR.