Development of a new class of benzoylpyrrole-based PPARα/γ activators

Article abstract of DOI:10.1016/j.bmcl.2010.11.032

Starting with a subtle blood glucose-lowering effect of a TGF-β inhibitor, we designed and synthesized a series of benzoylpyrrole-based carboxylic acids as PPARs activators. Among these compounds, 10sNa exhibited favorable blood glucose-lowering effect wi

Full text of DOI:10.1016/j.bmcl.2010.11.032

Bioorganic & Medicinal Chemistry Letters 21 (2011) 220–224
Contents lists available at ScienceDirect
Bioorganic & Medicinal Chemistry Letters
journal homepage: www.elsevier.com/locate/bmcl
Development of a new class of benzoylpyrrole-based PPARa/c activators
Kantaro Ushiroda a, Katsunori Maruta a, Makoto Kitoh a, Kiyotaka Iwai a, Jun Nagamine b, Atsushi Tsuchida b,
Mutsuo Taiji b, Ryu Nagata a,
⇑
a Dainippon Sumitomo Pharma Co., Ltd, Drug Research Division, Chemistry Research Laboratories, Osaka, Japan
b Dainippon Sumitomo Pharma Co., Ltd, Drug Research Division, Pharmacology Research Laboratories, Osaka, Japan
a r t i c l e i n f o
a b s t r a c t
Article history:
Starting with a subtle blood glucose-lowering effect of a TGF-b inhibitor, we designed and synthesized a
series of benzoylpyrrole-based carboxylic acids as PPARs activators. Among these compounds, 10sNa
exhibited favorable blood glucose-lowering effect without body weight gain. We assume that the bene-
Received 7 September 2010
Revised 2 November 2010
Accepted 4 November 2010
Available online 12 November 2010
ficial effect of 10sNa is attributed to not only its compound PPAR
a
agonistic activity but also its PPAR
c
partial agonistic activity.
Ó 2010 Elsevier Ltd. All rights reserved.
Keywords:
PPARa/c modulator
Type 2 diabetes
Type 2 diabetes is a metabolic disorder that affects approxi-
mately 150 million people worldwide with projections of 300 mil-
lion people by the year 2025.1 Current drugs used for the treatment
of type 2 diabetes are selected from biguanides, sulfonylureas,
insulin formulations, glinides,
peptidase IV inhibitors,3 Glucagon-like peptide (GLP)-1 analogs4
and peroxisome proliferator activated receptor (PPAR) agonists.
Among these classes, PPAR agonists (Fig. 1), such as rosiglitazone
a
-glucosidase inhibitors,2 dipeptidyl
c
c
Figure 1. Chemical structures of selected PPAR agonists and SMP-534 (7).
⇑
Corresponding author. Tel.: +81 6 6337 7040; fax: +81 6 6337 6010.
E-mail address: ryu-nagata@ds-pharma.co.jp (R. Nagata).
0960-894X/$ - see front matter Ó 2010 Elsevier Ltd. All rights reserved.
doi:10.1016/j.bmcl.2010.11.032

K. Ushiroda et al. / Bioorg. Med. Chem. Lett. 21 (2011) 220–224
221
in glucose and lipid homeostasis.8 Up to date, three PPAR subtypes,
PPAR , PPAR and PPARd have been identified. Activation of PPAR
a
c
a
by fibrates, such as fenofibrate (3), is known to be useful in the
treatment of dyslipidemia. On the other hand, compounds that
act on both PPAR
(5) and tesaglitazar (6) have been identified as very attractive can-
didates in the treatment of dyslipidemic type
diabetes.8a
a and c including ragaglitazar (4), muraglitazar
2
Although such dual agonists have shown promising efficacy both
in rodent models and in human clinical trials, almost all have failed
the late stages of clinical trial with no PPARa/c agonist being mar-
keted so far. For example, the clinical development of tesaglitazar
(6) was discontinued in phase III studies due to potential kidney
toxicity. Thus, development of novel, efficacious, and yet safe
PPARa/c agonists is considered of great therapeutic value.
We have recently reported the pharmacological profile of SMP-
534 (7), a TGF-b signaling pathway inhibitor and potential candi-
date for the treatment of diabetic nephropathy.9 During our phar-
macological evaluation of 7 and its related compounds, we have
found that repetitive administration of one of 7 derivatives slightly
lowered blood glucose level in a rodent model of diabetic nephrop-
athy. Since SMP-534 itself did not affect the blood glucose levels,
we assumed that inhibition of the TGF-b signaling pathway9a
would be independent of hypoglycemic action.9b It then occurred
to us that chemical modification of this derivative could provide
us with a new class of antidiabetic drugs possessing affinity for
PPARs, since the chemical structure of 7 resembles a typical phar-
macophore chemotype of PPARs agonists as depicted in Figure 2. In
this Letter, we report the synthesis, structure–activity relation-
Figure 2. (a) Simplified topology of typical synthetic PPAR agonists (b) Schematic
representation of SMP-534 (7).
(1) and pioglitazone (2), which belong to the thiazolidinediones
(TZDs) class of anti-diabetics, have achieved profitable sales
amounting to 2.4 and 3.6 billion dollars, respectively, in 2007.5
However, these drugs are reported to have side effects, including
body weight gain and fluid retention, that limit their wider use.6
Indeed, TZDs cannot be used to treat type 2 diabetes patients with
risk for congestive heart failure.7
PPARs, which belong to a nuclear hormone receptor superfam-
ily, act as transcription factors in the regulation of genes involved
Scheme 1. Reagents and conditions: (a) KOtert-Bu, allyl bromide, THF, 40 °C, 85–96%; (b) iodophenyl acetic acid or ethyl iodophenoxy acetate, Pd(OAc)2, Cy2NMe, Et3NBnCI,
DMF, 70 °C, 69–83%, (c) NaOH aq, THF, MeOH, rt, quant.; (d) NaOH aq, EtOH, rt, 86%.

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K. Ushiroda et al. / Bioorg. Med. Chem. Lett. 21 (2011) 220–224
Table 1
PPAR transactivation activity of benzoylpyrrole-based derivatives
Compound
X
Y
hPPAR transactivation
(10 EC50
M)a
a
l
a
(
l
M) (% effect)b
c
(10
l
M)a
c
EC50
(l
M) (% effect)b
a:c ratio
Pioglitazone (2)
Fenofibric acid
SMP-534 (7)
10a
10b
10c
101
10m
10n
10o
n.d.
5.6
0.9
1.0
1.6
0.8
0.8
5.8
3.5
0.9
1.4
1.1
1.9
5.2
n.d.
7.8
n.d.
1.5
2.8
3.6
1.5
1.2
2.2
1.9
1.1
1.3
1.2
1.2
2.0
0.39 (100%)c
n.d.
12 (19%)
n.d.
2.0 (37%)
n.d.
n.d.
1.9 (16%)
n.d.
n.d.
n.d.
n.d.
n.d.
n.d.
>7.5
n.d.
11
n.d.
n.d.
1.9
n.d.
n.d.
n.d.
n.d.
n.d.
1.5
12 (100%)d
>90
4-OMe
4-OMe
4-OMe
4-OMe
4-OMe
4-OMe
4-OMe
2-OMe
3-OMe
2-Me
2-CONHSO2Me
2-CH2CO2H
3-CH2CO2H
n.d.e
21 (43%)
n.d.
n.d.
3.7 (42%)
n.d.
n.d.
n.d.
n.d.
n.d.
4-CH2CO2H
2-OCH2CO2H
3-OCH2CO2H
4-OCH2CO2H
3-OCH2CO2H
3-OCH2CO2H
3-OCH2CO2H
3-OCH2CO2H
3-OCH2CO2H
10p
10q
10r
3-Me
4-Me
n.d.
1.2 (17%)
10sf
1.8 (37%)
a
b
c
d
e
f
Activities are presented as fold induction of PPAR
EC50 value is the molar concentration of the test compound that affords 50% of the maximal reporter activity.
a and c activation.
The maximum efficacy of PPAR
The maximum efficacy of PPAR
n.d. = not done.
c
a
activation of pioglitazone was defined as 100%.
activation of fenofibric acid was defined as 100%.
Compound 10s was also tested in mouse PPARa assay. EC50 = 4.9 lM (25%).
had been used extensively in PPAR drug discovery research
(Fig. 2). We also examined the effects of changing the substituted
positions on the right-hand benzene ring. According to these strat-
egies, we prepared compounds 10a–c and 10l–s. As shown in Ta-
ble 1, introduction of a carboxylic acid moiety at the meta-
Table 2
Pharmakokinetic properties of 10sNa in rats
po
iv
Dose (mg/kg)
AUC ( g h/mL)
Cmax g/mL)
Tmax (h)
T1/2 (h)
CL (mL/min/kg)
Vdss (L/kg)
BA (%)
10
59
4.3
4.0
1
14
l
position on the right-hand benzene ring increased PPAR
ity compared to the ortho- or para-position (10b vs 10a and 10c,
10m vs 10l and 10n) in terms of fold induction at 10 M of the test
a/c activ-
(
l
3.2
1.2
0.3
l
compounds, whereas the antifibrotic activity was totally abolished
(data not shown). Among compounds 10a–c and 10l–n listed in Ta-
ble 1, the meta-phenoxy acetic acid 10m displayed potent and bal-
42
anced dual PPAR
PPAR was next examined. Compounds 10b and 10m, which acti-
vated PPAR with a maximal efficacy of 37% and 16%, respectively,
as compared to that of pioglitazone (defined as 100%), were consid-
ered as PPAR partial agonists.
Based on the results of this initial SAR survey, we systematically
examined the effects of the substituent on the left-hand benzene
ring of 10m. According to this plan, we prepared compounds
10o–s. Moving the para-substituent to the ortho- or meta-position
a/c activity. Efficacy of compounds to activate
c
ships (SARs) and pharmacological profile of a new class of benzoyl-
pyrrole-based PPAR activators.
c
a/c
The compounds were synthesized as shown in Scheme 1.10 Ally-
lation of 2-benzoylpyrrole derivatives 811 with allyl bromide in the
presence of KOtert-Bu gave allyl pyrroles 9. Heck coupling of 9 with
iodophenyl acetic acid or ethyl iodophenoxy acetate in the pres-
ence of a catalytic amount of Pd(OAc)2 gave carboxylic acids
10a–c or esters 10d–k. Standard hydrolysis of esters 10d–k affor-
ded carboxylic acids 10l–s. Compound 10s was converted to its so-
dium salt 10sNa to increase its solubility in water for in vivo study.
The compounds synthesized in this study were evaluated in a
c
on the left-hand benzene ring resulted in a decrease in PPARa/c
activity (10m vs 10o and 10p, 10s vs 10q and 10r). Importantly,
converting the para-methoxy group to the para-methyl group gave
a modest increase in the activity for both receptor subtypes (10m vs
10s) in terms of the fold induction. The representative compound
transactivation assay using GAL4-hPPAR
selected compound was also evaluated using GAL4-mPPAR
results of these assays are given in Table 1, where activity is re-
ported as fold induction of PPAR activation as well as EC50 val-
ues. SMP-534 (7) showed slight activity at PPAR but was inactive
at PPAR (EC50 >90 M).
c
and GAL4-hPPARa 12
. The
.
A
a
10s showed well-balanced PPAR
of 1.8 and 1.2 M, respectively. Moreover, compound 10s showed
partial agonistic activity for PPAR , as indicated by 17% of the max-
imal activation obtained with pioglitazone (2). Furthermore, com-
pound 10s exhibited species-dependent PPAR activity with EC50
values of 1.8 and 4.9 M for human and mouse PPAR , respectively.
a and c activity with EC50 values
l
a/c
c
c
a
l
a
First of all, we planned to introduce a carboxylic acid as a bio-
isostere of acyl sulfonamide of SMP-534 (7), because most PPARs
agonists possess a carboxylic acid as an acidic head group.13 Addi-
tionally, we examined the effects of inserting a linker between the
carboxylic group and the right-hand benzene ring, because appro-
priate linkers between a carboxylic group and an aromatic center
l
a
Since the next step in this investigation was to perform studies
in a diabetic rodent model, the pharmacokinetic properties of the
sodium salt of 10s (10sNa) were first evaluated in rats to deter-
mine whether this compound would be suitable for oral adminis-
tration. Bioavailability, distribution volume, plasma clearance and

K. Ushiroda et al. / Bioorg. Med. Chem. Lett. 21 (2011) 220–224
223
*
**
Figure 3. Evaluation of 10sNa in db/db mice for 14 days. P <0.05, P <0.01 compared to vehicle control (Dunnett’s test). #P <0.05, ##P <0.01 compared to vehicle control
(Student’s test). Values are the means of 6 animals/group.
the measured half-life values of 10sNa were all acceptable for
in vivo study (Table 2).
examining in detail the pharmacological mechanism of PPARc par-
tial agonists or modulators using 10sNa and its derivatives.
Compound 10sNa was evaluated in db/db mouse model show-
ing both hyperglycemia and obesity.14 Two-week-old male db/db
mice were randomly assigned to four groups that received control
rodent chow, compound 10sNa (15 or 141 mg/kg/day) in chow, or
pioglitazone (2) (41 mg/kg/day) in chow. The results of this in vivo
study are described in Figure 3. Although compound 10sNa at
15 mg/kg/day demonstrated a weaker blood glucose-lowering ef-
fect than pioglitazone (2) at 41 mg/kg/day, this effect was statisti-
cally-significant compared to that of the vehicle control.
Compound 10sNa at 141 mg/kg/day demonstrated favorable blood
glucose-lowering effect similar to that observed with pioglitazone
(2) at 41 mg/kg/day. Surprisingly, treatment with pioglitazone (2)
caused a significant increase in body weight compared to the vehi-
cle control, whereas treatment with 10sNa did not cause body
weight gain. No difference in mice food intake was observed be-
tween test drugs treated groups and the vehicle control group.
Acknowledgments
We gratefully thank Takahiro Nagasaki for his chemistry techni-
cal assistance. We also appreciate the help of Masako Sumitomo
and Satomi Nakai in obtaining data of PPARa/c activity. Kei-ichi
Fujimoto is acknowledged for obtaining all pharmacokinetic data.
References and notes
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While body weight gain is a well-known side effect of PPAR
agonist,15 body weight reduction in rodents has been reported
with PPAR
agonists, such as fenofibrate 316 and other drugs.17 It
has also been reported that PPAR partial agonists or modulators
cause little change in body weight.18 Compound 10sNa showed
4-fold weaker activity for mouse PPAR than for human PPAR
and displayed partial agonistic activity for PPAR . We therefore as-
c full
a
c
a
c,
c
sume that such beneficial profile of the blood glucose-lowering ef-
fect without body weight gain observed with 10sNa is attributed to
not only its PPARa agonistic activity but also its PPARc partial ago-
nistic activity.
In summary, starting with a subtle glucose-lowering effect of a
TGF-b inhibitor, a new class of benzoylpyrrole-based carboxylic
acids was found to show PPAR
pounds were then examined, and meta-phenoxy acetic acid ana-
logs were identified as potent PPAR agonists. The selected
a/c activity. The SARs of these com-
a/c
compound 10sNa showed an acceptable pharmacokinetic profile
for in vivo study and a favorable blood glucose-lowering effect
without body weight gain. Compound 10sNa differs from other
PPARa/c agonists in that it is a PPARc partial agonist. It is therefore
believed that the analogs described in this study are attractive can-
didates for the treatment of type 2 diabetes. We are currently

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K. Ushiroda et al. / Bioorg. Med. Chem. Lett. 21 (2011) 220–224
10. All new compounds gave consistent 1H NMR spectra and satisfactory LC/MS
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