The discovery of equipotent PPARα/γ dual activators

Article abstract of DOI:10.1016/j.bmcl.2008.09.094

We report the design and synthesis of equipotent PPARα/γ dual agonists starting from selective PPAR alpha agonist 1. In vivo data for 7 in the Zucker fa/fa rat are presented.

Full text of DOI:10.1016/j.bmcl.2008.09.094

Bioorganic & Medicinal Chemistry Letters 18 (2008) 6251–6254
Contents lists available at ScienceDirect
Bioorganic & Medicinal Chemistry Letters
journal homepage: www.elsevier.com/locate/bmcl
The discovery of equipotent PPAR
a/c
dual activators
a
a
a
a
b
Paul Martres a, , Nicolas Faucher , Alain Laroze , Olivier Pineau , Marie Helene Fouchet , Florent Potvain ,
*
Didier Grillotb, Veronique Beneton c
a Department of Medicinal Chemistry, Laboratoire GlaxoSmithKline, Centre de Recherches, 25-27 avenue du Québec, 91951 Les Ulis, France
b Department of Biology, Laboratoire GlaxoSmithKline, Centre de Recherches, 25-27 avenue du Québec, 91951 Les Ulis, France
c Department of DMPK, Laboratoire GlaxoSmithKline, Centre de Recherches, 25-27 avenue du Québec, 91951 Les Ulis, France
a r t i c l e i n f o
a b s t r a c t
Article history:
We report the design and synthesis of equipotent PPARa/c dual agonists starting from selective PPAR
alpha agonist 1. In vivo data for 7 in the Zucker fa/fa rat are presented.
Received 5 September 2008
Revised 24 September 2008
Accepted 26 September 2008
Available online 1 October 2008
Ó 2008 Elsevier Ltd. All rights reserved.
Keywords:
PPAR
PPAR
Dual
a
c
Agonist
Elevated circulating levels of Low Density Lipoprotein choles-
that they produce a weak but significant improvement in glucose
homeostasis and insulin7 although in the Field study no significant
effect was observed on HbA1c.8 The pharmacological activation of
terol (LDLc) constitute a major risk-factor for coronary artery dis-
ease and there exists a wealth of clinical data supporting the use
of the LDLc-lowering statins in an increasingly wide range of
patients.1 The contribution of low circulating levels of High Density
Lipoprotein cholesterol (HDLc) to cardiovascular risk has been
clearly demonstrated. Indeed each 1 mg/dL increment in HDL-chol
is associated with a 2–3% decrease in cardiovascular risk .2
both PPARa and PPARc by a single molecule could be of great
interest for the simultaneous treatment of dyslipidemia and meta-
bolic syndrome, since they would be expected to show additive
effects on the lipid profile and a possible superior therapeutic in-
dex compared to the glitazones. Clinical studies with dual agonists
The fibrates are one of the two drug classes currently marketed
which have demonstrated the ability to increase HDL levels by up
to 20% and to decrease TG levels by up to 40%.3 The beneficial phar-
macological effects of fibrates are thought to be mediated in part
that are more potent on PPAR
c relative to PPARa have shown a
profile in which the PPAR -mediated undesired effects observed
c
in humans were still observed.9 Therefore, a more balanced profile
might be of interest and compounds displaying a similar potency
on the alpha and gamma isoforms, as determined in a transactiva-
tion assay, could potentially deliver the benefits of the synergistic
effect on lipids whilst maximizing the therapeutic window.
Thus we have targeted compounds showing equipotent activa-
by PPAR
(high micromolar concentrations are needed to activate PPAR
a
activation4 although they are not particularly potent
a).
Consequently, in humans, fibrates must be used at very high doses
(about 300–1200 mg/day) to achieve a sufficient lipid-lowering
effect.
tion of both PPARa and c isoforms whilst showing a 100-fold selec-
The glitazones (rosiglitazone, pioglitazone) are used in the clinic
tivity window towards PPARd.
to treat type II diabetes and work by activating PPAR
c
, leading to
Recently we have reported the discovery of a new potent selec-
tive PPAR
designed a new class of PPARa/c dual agonists.
insulin sensitization and decreased glucose levels.5 In addition,
pioglitazone gives a moderate decrease of TG levels (15–20%),
and both pioglitazone and rosiglitazone increase HDL levels (7–
13%).3 The glitazones induce weight gain as a major side effect
and in rare cases promote fluid retention.6
a
agonist, 1.10 Starting from the structure of 1, we have
SAR studies around 1 have demonstrated that the para substitu-
tion of the phenyl ring anchored to the thiazole moiety could mod-
ulate potency on the PPAR
analogue 1 is weakly active on PPAR
displays significant PPAR activity while being as potent as 1 on
PPAR . (Table 1)
c
isoform.10 The p-trifluoromethyl
Over the past decades, the fibrates have demonstrated an excel-
lent tolerability profile, and clinical studies have demonstrated
c whereas the p-tert-butyl 2
c
a
In addition, molecular modeling studies of the alpha and gam-
ma binding modes have been performed on the generic scaffold
* Corresponding author.
E-mail address: paul.martres@gsk.com (P. Martres).
0960-894X/$ - see front matter Ó 2008 Elsevier Ltd. All rights reserved.
doi:10.1016/j.bmcl.2008.09.094

6252
P. Martres et al. / Bioorg. Med. Chem. Lett. 18 (2008) 6251–6254
Table 1
In vitro potencies of PPAR
Table 3
a
agonists.a
In vitro potencies of pyrazoles 5-17a (R1 = Me).
R3
N
O
O
Me
R2
HO2C
O
S
CF3
N
H
N
R4
H
N
N
HO2C
HO2C
O
O
1
Compound R2
R3
R4
EC50
(
lM) EC50
(
l
M) EC50
h-PPARd
(
l
M)
c
h-PPAR
a
h-PPAR
S
N
H
5
6
7
8
H
t-Bu 0.383
t-Bu 0.050
t-Bu 0.01
i-Pr 0.020
i-Pr 0.004
i-Bu 0.045
i-Bu 0.002
t-Bu 0.050
t-Bu 0.010
>25
0.270
0.03
0.006
0.05
0.008
0.05
0.008
0.030
0.015
Me
Me
Me
Et
2.165
>10
N
O
Me
Me
Me
Et
1.360
4.850
2.870
2.060
2.700
>25
2
9
10
11
12
13
Isoform
EC50 (lM)
1
2
h-PPAR
h-PPARd
a
0.004
2.83
9.71
0.004
10
0.8
14
15
t-Bu 0.045
t-Bu 0.032
1.150
>25
0.06
h-PPAR
c
0.069
a
Data generated using cell based transient transfection assays12; compounds
16
17
t-Bu 0.066
t-Bu 0.042
2.05
>25
0.303
0.478
O
behave as full agonists.
O
a
Data generated using cell based transient transfection assays12; compounds
behave as full agonists.
O
R1
R4
N
Het
H
Table 4
HO2C
O
R2
R3
In vitro potencies of pyrazoles 18-19a (R1 = Me, R4 = t-Bu).
3
R3
Me
HO2C
O
Figure 1. Generic scaffold of PPARa/c agonists.
N
N
H
N
Table 2
In vitro potencies of compound 4.a
O
R3
EC50
h-PPAR
(
l
M)
a
EC50
h-PPARd
(
l
M)
EC50 (lM)
O
Compound
h-PPAR
c
N
H
N
18
0.57
0.20
>25
>25
>25
1.7
N
O
N
HO2C
O
19
Bn
4
a
Data generated using cell based transient transfection assays12; compounds
behave as full agonists.
Isoform
EC50
0.16
10
1.0
(lM)
h-PPAR
a
h-PPARd
h-PPAR
c
aliphatic group at R4 were synthesized with variation at R1, R2
and R3. The choice of R1 was driven by our knowledge of the bind-
a
Data generated using cell based transient transfection assays12; compounds
behave as full agonists.
ing mode in the alpha and gamma subunit. Although the PPAR
and PPAR binding pockets are very similar in size and shape,
one key determinant for subtype selectivity is the size of the R1
group. Larger R1 groups generally give higher PPAR potency11
a
c
c
3 depicted in Figure 1. The model has raised the hypothesis that
aliphatic substitution at R1 and R2/R3 on 3 could lead to an increase
therefore we hypothesized that smaller groups such as methyl
and methoxy should experience diminished steric interactions
in potency on PPAR
ligand binding domain,11 two hydrophobic pockets exist on
and
subunits which could be accommodated by R1 groups for
c. According to the crystal structure of PPARs
and therefore could be more suitable for PPAR
a/c dual
a
compounds.9
c
Methyl, ethyl, allyl and methoxyethyl groups in R2 or R3 posi-
tion (compounds 6 to 17, Table 3) increased the transactivation
activity on the alpha isoform compared to the non-substituted pyr-
azole 5 and methyl, ethyl and allyl substitution at R3 delivered the
most promising overall profile. Substitution at R2 appeared to de-
crease the level of selectivity over the delta isoform (Table 3).
Larger groups introduced at the R3 position (compounds 18 and
19, Table 4) have delivered a less attractive profile on both the hu-
man alpha and gamma isoforms.
the first pocket and R3/R3 groups for the second. The pyrazole core
was selected as a versatile ring which would be synthetically ame-
nable to the rapid variation of substituents at the R2/R3 positions.
p-tert-Butyl derivative 4, the first example synthesized, maintained
potency on the gamma isoform with a significant decrease in po-
tency on the alpha isoform when compared to 2 (Table 2).
Despite the reduced PPAR
anced PPAR ratio. An SAR study was conducted retaining pyra-
zole as the central core heterocycle. Compounds bearing a bulky
a potency, 4 displayed a more bal-
a/c

P. Martres et al. / Bioorg. Med. Chem. Lett. 18 (2008) 6251–6254
6253
Table 5
Table 7
In vitro potencies of pyrazoles 20-22a (R1 = OMe).
In vitro potencies of selected pyrazoles on murine PPARs.a
R3
N
Compound
EC50
(l
M) m-PPAR
a
EC50
>25
(
lM) m-PPARd
EC50 (lM) m-PPARc
OMe
HO2C
O
7
9
13
15
26
0.64
0.28
2.26
6
0.011
0.016
0.036
0.15
N
R4
7.1
H
N
>25
>25
>25
O
1.8
0.06
a
Data generated using cell based transient transfection assays12; compounds
Compound
R3
R4
EC50
h-PPAR
(
l
M)
a
EC50
h-PPARd
(
l
M)
EC50
h-PPAR
(
l
M)
c
behave as full agonists.
20
21
22
Et
Me
Me
t-Bu
t-Bu
i-Bu
>25
>25
>25
>25
>25
>25
0.190
0.176
0.130
Table 8
Pharmacokinetic data for compound 7 in CD rat.a
a
Data generated using cell based transient transfection assays12; compounds
behave as full agonists.
F %
Cl (mL/min/kg)
17
Cmax (ng/mL)
Vdss (L/kg)
0.30
T1/2 (h)
AUCpo (ng h/mL)
1130
22
1791
0.83
a
IV dose: 2.5 mg/kg (DMSO/cyclodextrine 20% (1/99 v/v)); PO dose: 5 mg/kg
Surprisingly, moving from a methyl group to a methoxy group
for R1 appeared to be less favorable leading to a general decrease
in activity on PPAR alpha (compounds 20 to 22, Table 5).
It clearly emerged from transactivation data that the best sub-
stitution combinations were R1 = Me; R3 = Me or Et and R4 = bulky
aliphatic group. With those results in hand, the stage was set for
introduction of diversity at R4 (Table 6). Among R4 substitutions
depicted in Table 6, only the 2-tolyl 26 and the 4-pyridyl 28 deriv-
atives achieved our selectivity criteria and acceptable in vitro
potencies. N-Pyrolidine 30 displayed good in vitro potency; how-
ever its delta selectivity was insufficient.
(0.5%HPMC K100/0.1% Tween 80).
Table 9
In vivo potencies of pyrazole 7.a
Dose (mg/kg)
10 mg/kg
Total TG (p)b
Insulin (p)b
Liver weight (p)b
À57 3%
À10 18%
+9 4%
Ã
Ã
30 mg/kg
À45 4%
À35 4%
+14 3%
Ã
Ã
Ã
Several compounds achieved our goal of equipotent activation
a
Five days chronic bid Zucker Fatty rats.
* indicates values of p < 0.05, as determined by a one-way-ANOVA.
b
of h-PPARa and h-PPARc isoforms in the transactivation assay
Table 6
(see Tables 3–6). However, a 20-fold decrease in potency was gen-
erally observed in the transactivation assay when moving from hu-
In vitro potencies of pyrazoles 23–30a (R1 = R2 = Me).
man to murine PPAR
a
. We anticipated that compounds having an
Me
Me
N
EC50 higher than 4 M on m-PPAR
l
a
would not be capable of deliv-
HO2C
O
N
R4
ering a significant effect on lipid parameters in our in vivo model.
Consequently only compounds 7, 9, 13, 15 and 26, which showed
H
N
EC50 < 0.2
m-PPAR , d and
Of these, compounds 13, 15 and 26 were only weakly active
weak at the m-PPAR isoform and so were not progressed further.
l
M on h-PPAR alpha, were selected for profiling against
O
a
c
isoforms (Table 7).
Compound
R4
EC50
h-PPAR
(
l
M)
a
EC50
h-PPARd
(
l
M)
EC50 (lM)
h-PPAR
c
a
The pharmacokinetic properties of compound 7 were evaluated
in the CD rat and found to be suitable for chronic administration
(Table 8). Total plasma clearance was medium (17 mL/min/kg)
with a half-life of 0.83 h. Following a single oral dose of compound
7 at 5 mg/kg, the maximum concentration of compound in the
plasma was 1130 ng/mL and the bioavailability was 22%.
Compound 7 was evaluated in a five days chronic experiment in
the Zucker fa/fa rat (Table 9).
23
24
0.094
>25
0.028
O
O
>25
>25
0.080
0.025
25
26
0.020
0.090
1.550
As explained in the introduction, one argument in favor of an
>25
0.03
equipotent PPAR
peutic index compared to glitazones. However, in contrast to its
human PPAR profile, 7 does not profile as an equipotent PPARa/c
dual agonist in rodent therefore the in vivo experiment was per-
formed purely to assess pharmacodynamic activity.
a/c dual agonist is the potential superior thera-
27
28
29
0.004
0.730
0.085
0.008
1.63
>25
0.030
0.310
0.110
0.020
O
Triglyceride effects can be ascribed to the activation of both the
alpha and gamma isoforms. The moderate liver weight increase is a
N
common readout of PPAR
levels can be ascribed to PPAR
Starting from a selective PPAR
a
activation and the decreased insulin
activation.
agonist, we have generated
0.035
N
N
O
c
a
compounds with a balanced profile on PPAR alpha and gamma.
Pyrazole 7, a representative compound, has demonstrated in vivo
activity on Zucker fatty rat. It is noteworthy that 7 has also been
tested in a rat seven days toxicological study and no safety issues
30
1.060
a
Data generated using cell based transient transfection assays12; compounds
behave as full agonists.

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P. Martres et al. / Bioorg. Med. Chem. Lett. 18 (2008) 6251–6254
H
O
O
O
O
O
a)
OEt
O
O
+
O
I
b)
N
N
N
N
N
N
c)
OH
OEt
+
OEt
O
O
O
IV
d)
III : 22%
II : 47%
O
O
N
OEt
H2N
V
O
O
O
O
OEt
OH
N
N
N
e)
H
H
N
N
O
O
VI
7
Scheme 1. Synthetic pathway. Reagents and conditions: (a) EtOH, Na 0 °C, rt 16 h, then 80 °C 16 h, 99%; (b) methyl-hydrazine, EtOH 90 °C, 16 h; silica gel column first eluted
II; (c) NaOH 1 M, 4 h, 98%; (d) thionyl chloride, toluene, 80 °C, 3 h 30 min then V Et3N, CH2Cl2, rt, 1 h (for preparation of V see Ref. 13), 96%; (e) NaOH, 80 °C, 4 h, 80%.
6. (a) Goldberg, R. B.; Kendall, D. M.; Deeg, M. A.; Buse, J. B.; Zagar, A. J.; Pinaire, J.
were raised that could preclude further development (results not
shown) (Scheme 1).
A.; Tan, M. H.; Khan, M. A.; Perez, A. T.; Jacober, S. J. Diabetes Care 2005, 28,
1547; (b) Elte, J. W. F.; Blicklé, J. F. Eur. J. Int. Med. 2007, 18, 18.
7. Chinetti-Gbaguidi, G.; Fruchart, J. C.; Staels, B. Curr. Atheroscler. Rep. 2005, 7,
396.
Acknowledgments
8. Keech, A.; Simes, R. J.; Barter, P.; Best, J.; Scott, R.; Taskinen, M. R.; Forder, P.;
Pillai, A.; Davis, T.; Glasziou, P.; Drury, P.; Kesaniemi, Y. A.; Sullivan, D.; Hunt,
D.; Colman, P.; d’Emden, M.; Whiting, M.; Ehnholm, C.; Laakso, M. Lancet 2005,
366, 1849.
9. Henke, B. R. J. Med. Chem. 2004, 47, 4118.
We thank Dr. Andrew Brewster (GlaxoSmithKline) for proof-
reading of the manuscript.
10. Sierra, M. L.; Beneton, V.; Boullay, A.-B.; Boyer, T.; Brewster, A. G.; Donche, F.;
Forest, M.-C.; Fouchet, M.-H.; Gellibert, F. J.; Grillot, D. A.; Lambert, M. H.;
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G.; Ruault, C.; Saunders, M.; Toum, J.; Xu, H. E.; Xu, R. X.; Pianetti, P. M. J. Med.
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Supplementary data
Supplementary data associated with this article can be found, in
the online version, at doi:10.1016/j.bmcl.2008.09.094.
11. Xu, H. E.; Lambert, M. H.; Montana, V. G.; Plunket, K. D.; Moore, L. B.; Collins, J.
L.; Oplinger, J. A.; Kliewer, S. A.; Gampe, R. T., Jr.; McKee, D. D.; Moore, J. T.;
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L., ; Harrington, W. W., Jr.; Hashim, M. A.; Hull-Ryde, E. A.; Kaldor, I.; Kliewer, S.
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L. A.; Miller, J. F.; Mook, R. A.; Noble, S. A.; Oliver, W.; Parks, D. J.; Plunket, K. D.;
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