Pyridine-2-propanoic acids: Discovery of dual PPARα/γ agonists as antidiabetic agents

Article abstract of DOI:10.1016/j.bmcl.2006.08.105

A series of novel pyridine-2-propanoic acids was synthesized. A structure-activity relationship study of these compounds led to the identification of potent dual PPARα/γ agonists with varied isoform selectivity. Based on the results of efficacy studies in

Full text of DOI:10.1016/j.bmcl.2006.08.105

Bioorganic & Medicinal Chemistry Letters 16 (2006) 6116–6119
Pyridine-2-propanoic acids: Discovery of dual PPARa/c agonists as
antidiabetic agents
Paul S. Humphries,a,* Jonathon V. Almaden,b Sandra J. Barnum,c Thomas J. Carlson,b
Quyen-Quyen T. Do,a James D. Fraser,c Mary Hess,c Young H. Kim,c
Kathleen M. Ogilviec and Shaoxian Sunb
aDepartment of Diabetes Chemistry, Pfizer Global R&D, 10770 Science Center Drive, San Diego, CA 92121, USA
bDepartment of Biochemical Pharmacology, Pfizer Global R&D, 10628 Science Center Drive, San Diego, CA 92121, USA
cDepartment of Diabetes Biology, Pfizer Global R&D, 10724 Science Center Drive, San Diego, CA 92121, USA
Received 9 May 2006; revised 23 August 2006; accepted 28 August 2006
Available online 18 September 2006
Abstract—A series of novel pyridine-2-propanoic acids was synthesized. A structure–activity relationship study of these compounds
led to the identification of potent dual PPARa/c agonists with varied isoform selectivity. Based on the results of efficacy studies in
diabetic (db/db) mice, and the desired pharmacokinetic parameters, compound (S)-13 was selected for further profiling.
Ó 2006 Elsevier Ltd. All rights reserved.
Type 2 diabetes is a chronic disease characterized by
insulin resistance in the liver and peripheral tissues
accompanied by a defect in pancreatic b-cells.1,2
Between 1997 and 1999, a new class of drugs called ‘glit-
azones’3 was approved by the FDA for the treatment of
type 2 diabetes. Glitazones correct hyperglycemia by
enhancing tissue sensitivity to insulin. Because of this
mechanism of action, glitazone treatment is not associ-
ated with dangerous hypoglycemic incidents that have
been observed with conventional sulfonylurea agents
and insulin therapy. In the mid-1990s the molecular tar-
get of the glitazones was reported to be the peroxisome
proliferator-activated receptor-c (PPARc).4–7 The
PPARs are a group of nuclear receptors that act as tran-
scriptional factors which play a major role in the regula-
tion of lipid metabolism and storage.8–10 PPARa is the
molecular target for the fibrate class of lipid-modulating
drugs.11 Designing compounds with PPARa activity in
addition to PPARc agonist activity may offer improved
alternatives toward control of hyperglycemia and hyper-
triglyceridemia in type 2 diabetics.12 Scientists at Kyorin
disclosed novel antidiabetic KRP-297, the first pub-
lished example of a dual PPARa and PPARc agonist.13
In the preceding paper, we disclosed the results of our
efforts that led to the identification of compounds of
type 1 as potent dual PPARa/c agonists.14 Based on
their efficacy in the established rodent models of type
2 diabetes, and desirable PK profile, we initiated synthe-
sis of various isomeric pyridine-2-propanoic acids 2
(Fig. 1). These additional efforts have led to the identifi-
cation of a new class of potent dual PPARa/c agonists
with excellent in vivo efficacy. Herein, we report the syn-
thesis, structure–activity relationships (SAR), and in vi-
vo activity of this new class of compounds.15
The synthetic route for the preparation of compound 8
is shown in Scheme 1. Commercially available 5-
hydroxy-2-methylpyridine 3 was converted to alcohol
5, via pyridine N-oxide 4, according to a procedure
reported by Soga and co-workers.16 Benzyl alcohol
5 was oxidized to the aldehyde, subjected to Wittig
Keywords: PPAR; Diabetes; Parallel synthesis; SAR; Pharmacokinetic
studies; In vivo efficacy.
*
Corresponding author. Tel.: +1 858 622 7956; fax: +1 858 526
4438; e-mail: paul.humphries@pfizer.com
Figure 1. Previously described lead and isomeric scaffold.
0960-894X/$ - see front matter Ó 2006 Elsevier Ltd. All rights reserved.
doi:10.1016/j.bmcl.2006.08.105

P. S. Humphries et al. / Bioorg. Med. Chem. Lett. 16 (2006) 6116–6119
6117
Figure 2. Pyrazine 20 and pyrimidine 21.
activation, were measured (Table 1).19 Initially, we
decided to investigate the effects of varying the a-substit-
uents of 2 (R1 and R2). Compounds 8–9 and 12–14 high-
lighted that both binding affinity and isoform selectivity
were sensitive to the size of the a-substituent(s). We then
shifted our attention to variation of substituents on the
phenyloxazole group, whilst holding constant the 2-tet-
rahydrofuran moiety. Extension of the linker between
the pyridyl core and the phenyloxazole moiety affected
PPARc more than PPARa, resulting in a more balanced
dual agonist (compound 15).
Scheme 1. Reagents and conditions: (a) BnBr, NaOH, H2O, Me2CO,
reflux, 16 h, 96%; (b) m-CPBA, CHCl3, rt, 1 h, 97%; (c) Ac2O, 100 °C,
1 h; (d) K2CO3, MeOH, rt, 16 h, 82% (2 steps); (e) DMP, CH2Cl2,
pyridine, rt, 16 h, 50%; (f) EtO2CCH(OEt)PPh3+ClÀ, TMG, CHCl3, rt,
16 h, 100%; (g) 10% Pd/C, H2, EtOH, 50 psi, rt, 16 h, 93%; (h) PPh3,
THF, DEAD, rt, 16 h, 76%; (i) LiOH, THF, MeOH, H2O, rt, 16 h,
92%. DMP, Dess–Martin periodinane.
olefination, followed by hydrogenation to afford phenol
6.17 Mitsonobu reaction of phenol 6 with alcohol 7, fol-
lowed by ester hydrolysis, gave final products 8–9.
Compounds 16–19 demonstrated that binding affinity
and isoform selectivity were sensitive to the positioning
of substituents on the phenyl ring. 4-Cl afforded a
compound with a more balanced isoform profile,
whereas 3-OMe tended to impart isoform selectivity
favoring PPARc (e.g., compound 17 vs 18). Finally,
we briefly explored alternatives to the pyridyl core.
Compounds 20 and 21 demonstrated that addition of
another nitrogen into the central core also affects
binding to both isoforms, with pyrazine 20 displaying
selectivity for PPARc.
The synthetic route for the preparation of 12–19 is
shown in Scheme 2. Conversion of alcohol 5 into the
benzyl chloride, reaction with a variety of ester enolates,
followed by debenzylation afforded phenols 10. Mitso-
nobu reaction of phenols 10 with alcohols 11, followed
by ester hydrolysis, gave final products 12–19.
Further chemical diversity was incorporated by investi-
gating alternative heteroaromatic replacements for the
pyridyl core. Figure 2 depicts pyrazine 19 and pyrimi-
dine 20 as examples of this effort. The synthesis of these
ligands has been described previously.15
Since compound 13 appeared to possess the most
interesting biological profile and physical properties
(e.g., biased toward PPARc and satisfactory in vitro
ADME data), we separated the enantiomers by chiral
supercritical fluid chromatography (SFC). The eutomer,
predicted to have the S configuration based on literature
compounds,20 demonstrated potent dual PPARc and
PPARa binding as well as functional agonism. Com-
pound (S)-13 was then selected for rat pharmacokinetic
(PK) studies. Administration to male Sprague–Dawley
(SD) rats resulted in satisfactory PK parameters—58%
oral bioavailability, dose normalized oral AUC of
1.2 h lg/mL, iv clearance of 16.7 mL/min/kg, and oral
half-life of 1.6 h.
The newly synthesized compounds were evaluated in the
PPAR SPA binding assay to ascertain c and a binding
profiles.18 The active analogs were also tested for func-
tional activity in a PPAR-GAL4 transactivation (TA)
assay, where EC50 values, as well as percent maximal
Compound (S)-13 was evaluated in the db/db mouse
model, using rosiglitazone as the comparator.21 Com-
pound (S)-13 was shown to effectively lower glucose
by 94% at 30 mg/kg in the 8-day study. Rosiglitazone
exhibited a lowering of 74% glucose at 30 mg/kg
(Fig. 3). Interestingly, (S)-13 appeared to be a more po-
tent glucose lowering agent than rosiglitazone based on
oral dose. This could be a reflection of its improved
affinity for PPARc, superior PK parameters, and/or
suggestive of PPARa mediated insulin sensitization.22
Scheme 2. Reagents and conditions: (a) (COCl)2, DMF, CH2Cl2, rt,
2 h; (b) R1R2CHCO2Et, NaHMDS, THF, À50 °C, 3 h, 70–86% (2
steps); (c) 10% Pd/C, H2, EtOH, 45 °C, 16 h; (d) PPh3, THF, DEAD,
rt, 16 h, 54–76% (2 steps); (e) LiOH, THF, MeOH, H2O, rt, 16 h.
Compound (S)-13 was also shown to effectively lower
triglycerides by 119% at 30 mg/kg (vs 106% for rosiglit-

6118
P. S. Humphries et al. / Bioorg. Med. Chem. Lett. 16 (2006) 6116–6119
Table 1. In vitro activities of compounds 8 and 11–20
Compound
R1
R2 R3
n
hPPARc SPA hPPARa SPA
hPPARc TA EC50 (lM) hPPARa TA EC50 (lM)
Ki (lM)a
Ki (lM)a
(% max activation)b
(% max activation)b
Rosiglitazone
8
0.44
0.348
0.073
1.6
45% at 100 lM 0.158 (100%)
>10 (6%)
OMe
OEt
OMe
H
H
1
1
1
1
1
2
1
1
1
1
3.7
2.0
0.280 (98%)
0.129 (96%)
0.335 (104%)
0.041 (88%)
>10 (4%)c
3.14 (95%)
1.23 (100%)
0.882 (114%)
0.226 (90%)
>10 (5%)c
9
12
H
Me
H
H
4.8
1.6
13
14
2-Tetrahydrofuran
2-Tetrahydropyran
OEt
H
0.21
1.1
H
1.8
15
16
H
H
1.1
0.093
0.3
0.84
0.84
0.15
1.2
0.887 (87%)
0.105 (90%)
0.130 (81%)
0.005 (93%)
0.012 (93%)
0.156 (102%)
2.50 (56%)
>10 (3%)c
0.886 (76%)
0.437 (95%)
0.048 (122%)
1.57 (98%)
0.867 (93%)
1.89 (77%)
>10 (58%)c
>10 (6%)c
2-Tetrahydrofuran
2-Tetrahydrofuran
2-Tetrahydrofuran
2-Tetrahydrofuran
4-OMe
4-Cl
3-OMe
3-Me
17
18
0.02
0.043
0.16
2.3
19
20
1.1
3.49
7.3
21
(R)-13
(S)-13
2-Tetrahydrofuran
2-Tetrahydrofuran
H
H
1
1
21.0
0.043
41.0
0.34
0.026 (98%)
0.10 (97%)
a Binding affinities were measured using radioligands (darglitazone for PPARc and GW2331 for PPARa) following published procedures.19
b Agonist activities were measured in human PPAR-GAL4 chimeric HepG2 cells analogous to published procedures.20 The EC50 refers to the
concentration at which 50% of a given compounds’ intrinsic maximal response has been reached. % max activation refers to the level of maximal
activation achieved by a given compound when compared with the standard reference full agonists (darglitazone for PPARc and GW2331 for
PPARa).
c No EC50 was obtained; no plateau reached in titration; maximal activity only reported.
Table 2. Effect of Rosiglitazone (Rosi) and (S)-13 on plasma glucose,
triglycerides (TG), hematocrit (Hct), and body weight (BW)
Controls
Compound (S)-13
700
Compound Dose
Glucose TG
Hct
change change change
BW
rosiglitazone
600
500
400
(mg/kg) change
(%)a
(%)a
(%)a
(%)a
Rosi
Rosi
3
30
3
À51
À74
À74
À94
À83
À106
À105
À119
À1.2
À5.2
À4.3
À4.4
+9.5
+17.4
+15.5
+20.5
(S)-13
(S)-13
30
300
200
100
Male db/db mice (7 weeks old) and lean mice were dosed daily for 8
days by oral gavage with vehicle or the indicated doses of test com-
pound. Plasma glucose, triglycerides, hematocrit, and body weight
were measured before dosing on day À1 and 2 h post dose on day 8.
a p < 0.05 versus vehicle control.
Vehicle
1
3
10
30
Lean
Oral Dose (mg/kg)
Acknowledgments
Figure 3. Effect of (S)-13 on plasma glucose levels in db/db mice. Male
db/db mice (7 weeks old) and lean mice were dosed daily for 8 days by
oral gavage with vehicle or the indicated doses of test compound.
Plasma glucose levels were measured before dosing on day À1 and 2 h
post dose on day 8. Each data point represents the mean value ( SD)
of six individual mice.
The authors greatly acknowledge all our colleagues in
the PPAR program for their technical support in the
evaluation of the compounds presented in this manu-
script. We would also like to thank Bill Farrell and
Christie Aurigemma for chiral SFC separation of com-
pound 13 and Jie Ling for pharmacokinetic evaluation
of (S)-13.
azone at 30 mg/kg). Unfortunately, (S)-13 also caused
an increase in body weight and a reduction in hemato-
crit (suggesting the presence of hemodilution) to a simi-
lar extent as rosiglitazone (Table 2).
References and notes
1. Saltiel, A. R. Cell 2001, 104, 517.
2. Moller, D. E. Nature 2001, 414, 821.
3. Hulin, B.; McCarthy, P. A.; Gibbs, E. M. Curr. Pharm.
Des. 1996, 2, 85.
4. Kletzien, R. F.; Clark, S. D.; Ulrich, R. G. Mol.
Pharmacol. 1992, 41, 393.
5. Ibraham, A.; Teboul, L.; Gaillard, D.; Amir, E. Z.;
Ailhaud, G.; Young, P.; Cawthorne, M. A.; Grimardi, P.
A. Mol. Pharmacol. 1994, 46, 1070.
In summary, we have identified a pyridine-2-propanoic
acid class of potent dual PPARa/c agonists. Syste-
matic SAR studies generated a multitude of potent
compounds with varied isoform selectivity. Compound
(S)-13 displayed oral efficacy greater than the bench-
mark rosiglitazone in
diabetes.
a db/db mouse model of

P. S. Humphries et al. / Bioorg. Med. Chem. Lett. 16 (2006) 6116–6119
6119
6. Lehman, J. M.; Moorre, L. B.; Smith-Oliver, T. A.;
Wilkinson, W. O.; Willson, T. M.; Kliewer, S. A. J. Biol.
Chem. 1995, 270, 12953.
16. Takeda, Y.; Uoto, K.; Chiba, J.; Horiuchi, T.; Iwahana,
M.; Atsumi, R.; Ono, C.; Terasawa, H.; Soga, T. Bioorg.
Med. Chem. 2003, 11, 4431.
7. Martin, G.; Schoonjans, K.; Staels, B.; Aurex, J. Atheros-
crelosis 1998, 137(Suppl.), S75.
8. Desvergne, B.; Wahli, W. Endocr. Rev. 1999, 20, 649.
9. Kersten, S.; Desvergne, B.; Wahli, W. Nature 2000, 405,
421.
17. Andersson, K.; Boije, M.; Gottfries, J.; Inghardt, T.; Li,
L.; Lindstedt, A. E.-L. WO 99/62871, 1999; Chem. Abstr.
1999, 132, 22756.
18. Sun, S.; Almaden, J.; Carlson, T. J.; Barker, J.; Gehring,
M. R. Metab. Eng. 2005, 7, 38.
10. Berger, J.; Moller, D. E. Annu. Rev. Med. 2002, 53, 409.
11. Willson, T. M.; Brown, P. J.; Sternbach, D. D.; Henke, B.
R. J. Med. Chem. 2000, 43, 527.
12. Murakami, K.; Tobe, K.; Ide, T.; Mochizuki, T.; Ohashi,
M.; Akanuma, Y.; Yazaki, Y.; Kadowaki, T. Diabetes
1998, 47, 1841.
19. Berger, J.; Leibowitz, M. D.; Doebber, T. W.; Elbrecht,
A.; Zhang, B.; Zhou, G.; Biswas, C.; Cullinan, C. A.;
Hayes, N. S.; Li, Y.; Tanem, M.; Venture, J.; Wu, S. M.;
Berger, G. D.; Mosley, R.; Marquis, R.; Santini, C.;
Sahoo, S. P.; Tolman, R. L.; Smith, R. G.; Moller, D. E.
J. Biol. Chem. 1999, 274, 6718.
13. Nomura, M.; Kinoshita, S.; Satoh, H.; Maeda, T.;
Murakami, K.; Tsunoda, M.; Miyacvhi, H.; Awano, K.
Bioorg. Med. Chem. Lett. 1999, 9, 553.
14. Humphries, P. S.; Bailey, S.; Almaden, J. V.; Barnum, S.
J.; Carlson, T. J.; Christie, L. C.; Do, Q.-Q. T.; Fraser, J.
D.; Hess, M.; Kellum, J. H.; McClellan, G. A.; Skalitzky,
D. J.; Sun, S.; Zehnder, L. R. Bioorg. Med. Chem. Lett.
2006, 16, doi:10.1016/j.bmcl.2006.08.110.
20. Andersson, K. WO 99/62872, 1999; Chem. Abstr. 1999,
132, 22757.
21. All in vivo procedures were approved by the Pfizer
La Jolla Institutional Animal Care and Use Com-
mittee, and principles of laboratory animal care
(NIH publication no. 85-23, revised 1985) were
followed.
22. Guerre-Millo, M.; Gervois, P.; Raspe, E.; Madsen, L.;
Poulain, P.; Derudas, B.; Herbert, J. M.; Winegar, D. A.;
Willson, T. M.; Fruchart, J.-C.; Berge, R. K.; Staels, B.
J. Biol. Chem. 2000, 275, 16638.
15. Bailey, S.; Humphries, P. S.; Skalitzky, D. J.; Su, W.-G.;
Zehnder, L. R. WO 2004/092145, 2004; Chem. Abstr. 2004,
141, 379637.