The discovery of high affinity agonists of GPR109a with reduced serum shift and improved ADME properties

Article abstract of DOI:10.1016/j.bmcl.2010.11.116

Amino-anthranilic acid derivatives have been identified as a new class of low serum shifted, high affinity full agonists of the human orphan G-protein-coupled receptor GPR109a with improved ADME properties.

Full text of DOI:10.1016/j.bmcl.2010.11.116

Bioorganic & Medicinal Chemistry Letters 21 (2011) 2721–2724
Contents lists available at ScienceDirect
Bioorganic & Medicinal Chemistry Letters
journal homepage: www.elsevier.com/locate/bmcl
The discovery of high affinity agonists of GPR109a with reduced serum shift
and improved ADME properties
Jason E. Imbriglio a, , Daniel DiRocco a, Rena Bodner a, Subharekha Raghavan a, Weichun Chen a,
⇑
Daria Marley a, Craig Esser a, Tom G. Holt b, Michael S. Wolff b, Andrew K. P. Taggart c, M. Gerard Waters c,
James R. Tata a, Steven L. Colletti a
a Department of Medicinal Chemistry, Merck Research Laboratories, Merck & Co., Inc., PO Box 2000, Rahway, NJ 07065-0900, USA
b Department of Drug Metabolism, Merck Research Laboratories, Merck & Co., Inc., PO Box 2000, Rahway, NJ 07065-0900, USA
c Department of Cardiovascular Diseases, Merck Research Laboratories, Merck & Co., Inc., PO Box 2000, Rahway, NJ 07065-0900, USA
a r t i c l e i n f o
a b s t r a c t
Article history:
Amino-anthranilic acid derivatives have been identified as a new class of low serum shifted, high affinity
full agonists of the human orphan G-protein-coupled receptor GPR109a with improved ADME properties.
Ó 2010 Elsevier Ltd. All rights reserved.
Received 11 October 2010
Accepted 29 November 2010
Available online 4 December 2010
Keywords:
Niacin
Atherosclerosis
Anthranilic acid
Nicotinic acid (niacin) has been a leading treatment for dyslipi-
demia and for the prevention of atherosclerosis for over 40 years.1
Long term clinical studies have demonstrated niacin’s ability to re-
duce the incidence of mortality from coronary heart disease.2 In
spite of niacin’s clinical significance, patients treated with niacin
show low compliance of use due to an intense flushing side effect.3
In response to the maladies of niacin therapy, a number of drug
discovery programs have focused on the development of a ‘flush-
free’ niacin-like therapy. Despite considerable effort in the field,
the absence of a niacin-related target and/or mechanism of action,
has limited such investigations.
Recently, a high affinity G-protein coupled receptor, GPR109a,
has been identified for niacin.4 Mechanistic studies have suggested
that niacin may exert its therapeutic effect through the activation
of GPR109a located on adipocytes.5 Experiments have shown that
niacin activation of GPR109a results in a reduction of intracellular
cAMP. It is believed that this down regulation of cAMP in adipo-
cytes, triggers a cascade of events that results in the lipid altering
affects associated with niacin treatment (i.e., raise in HDL, lower
triglycerides and LDL).
when treated with niacin therapy, failed to show a niacin-induced
flush. As a result, it is concluded that the niacin-associated flush
and anti-lipolytic effects are both mediated through the niacin
receptor.5a
Following the identification of the high affinity niacin receptor
(GPR109a), our group initiated a drug discovery program focused
on the development of a ‘flush-free’ agonist. A high-throughput
screen of our compound collection,6 followed by a hit to lead effort,
identified anthranilic acid derivative 1 as a promising lead struc-
ture.7 Despite an excellent in vitro profile, the modest ADME prop-
erties and the high serum-potency-shift (>10,000-fold) of
compound 1 highlighted the need for further structure based
improvements.
Our initial medchem effort focused on strategies to alleviate the
large serum shift effect observed for the class. Previous work in the
group revealed a tight binding environment around the anthranilic
acid moiety and the terminal phenol group.7 With this in mind, our
strategy involved the localization of an amino moiety on the car-
bon chain connecting the head-anthranilic acid group and the
biphenyl tail region. As illustrated in Table 1, the incorporation of
an amino group into the architecture of 1 had a significant effect
on the serum shift. Analysis of 2 in our in vitro binding assay, in
the presence of 4% human serum, revealed a 20-fold reduction in
serum-potency-shift, when compared to the des-amino derivative
1. Based on this result, we were motivated to look at other mem-
bers of this lead class. In this regard, introduction of the amino
In control experiments, GPR109a receptor knockout mice, when
treated with niacin therapy, failed to show the characteristic
reduction in plasma FFA that is observed upon niacin treatment
in wild type mice. Furthermore, niacin receptor knockout mice,
⇑
Corresponding author.
E-mail address: jason_imbriglio@merck.com (J.E. Imbriglio).
group into the high affinity thiazole derivative
3 and the
0960-894X/$ - see front matter Ó 2010 Elsevier Ltd. All rights reserved.
doi:10.1016/j.bmcl.2010.11.116

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J. E. Imbriglio et al. / Bioorg. Med. Chem. Lett. 21 (2011) 2721–2724
Table 1
Table 2
The effect of amine substitution on serum shifta
High affinity, low serum shifted, full agonists of GPR109aa
Compound
Serum
shift
h-3H-
hGTP
EC50
c
Sc
Compound
Serum
shift
h-3H-niacinb hGTP
IC50 M) EC50
c
Sc
M)
niacinb IC50
(l
(l
(l
M)
(lM)
O
O
N
HO
N
H
40-fold hSS 0.010
7-fold hSS 0.042
0.120
0.290
N
O
O
O
>10,000-
fold hSS
N
H
O
O
O
OH
OH
OH
0.016
0.06
7
O
OH
O
NH2
O
1
HO
N
HO
HO
N
H
Speciesd
Clp
t
½
(h)
AUCN po
M.h.kg/mg)
F (%)e
e
N
8
9
(mL/min/kg)
(l
Mouse
8.7
2.4
2.0
35
N
N
H
9-fold hSS 0.041
8-fold hSS 0.108
0.89
2.96
Compound
Serum
shift
h-3H-
niacinb IC50 EC50
M) M)
hGTPc
Sc
NH2
N
(l
(l
NH2
O
N
O
HO
HO
N
H
O
O
N
N
H
O
O
OH
OH
10
500-fold hSS 0.15
300-fold hSS 0.001
30-fold hSS 0.10
500-fold hSS 0.013
70-fold hSS 0.120
3.2
NH2
O
OH
NH2
O
N
2
HO
HO
N
H
6-fold hSS 0.158
5-fold hSS 0.115
3.42
1.5
O
N
S
11
N
H
0.006
0.93
0.065
1.0
O
N
O
O
OH
OH
Cl
N
HO
N
H
3
O
N
O
NH
O
OH
Me
12
S
HO
N
H
NH2
N
O
Cl
N
N
4
5
HO
N
H
30-fold hSS 0.006
5-fold hSS 0.001
0.027
O
O
O
O
N
O
O
O
OH
OH
OH
N
N
13
14
HO
HO
N
H
N
N
O
O
O
OH
OH
N
N
HO
N
H
<0.052
NH2
O
N
O
N
H
NH2
N
N
HO
N
H
20-fold hSS 0.004
6-fold hSS 0.10
0.036
0.5
6
NH2
N
O
15
16
N
HO
HO
N
H
Me
O
40-fold hSS 0.010
0.120
0.290
O
O
N
N
O
OH
N
HO
N
H
O
NH2
7
8
N
OH
O
O
a
Values are an average of two or greater individual assays; serum shift refers to
N
N
H
the ratio of the binding affinity as determined by [3H]-Nicotinic acid competition in
the presence and absence of 4% human serum.
7-fold hSS
0.042
NH2
N
O
OH
[3H]-Nicotinic acid binding competition assay.
b
Membrane binding of compounds versus [c-
35S] GTP in active recombinant
c
a
Values are an average of two or greater individual assays; serum shift refers to
CHO-K1cells stably expressing the niacin receptor.
the ratio of the binding affinity as determined by [3H]-Nicotinic acid competition in
the presence and absence of 4% human serum.
[3H]-Nicotinic acid binding competition assay.
b
c
SAR around amino-derivative 8 revealed a number of interest-
ing trends related to the serum shift and in vitro activity (Table 2).
A comparison of derivative 8, and its epimer 9, showed that the
stereochemistry had little effect on the serum shift and the intrin-
sic affinity for the receptor.
Membrane binding of compounds versus [c-35S] GTP in active recombinant
CHO-K1cells stably expressing the niacin receptor.
d
C57BL/6-mice.
e
Dose: 1 mg/kg iv; 2 mg/kg po; t = plasma half-life (0–8 h).
½
tricyclic-pyrazole derivative 5 showed a similar 10-fold reduction
in serum shift. However, despite the amino group’s favorable effect
on serum shift, the reduced affinity for serum proteins was accom-
panied by a 10-fold loss in potency on the receptor.
In contrast, re-positioning of the amino-group adjacent to the
oxadiazole moiety, as in derivative 10, resulted in a significant loss
of activity in both our binding (h-3H-niacin) and functional assay
(h-GTPcS). Further substitution of the amine, as in methyl-amine
While this trend was consistent amongst most members of the
class, oxadiazole 7 was less affected by the change. In this case,
amino-oxadiazole 8 showed a characteristic 5-fold reduction in
serum shift, relative to the parent, and comparable in vitro activity.
12, demonstrated a modest reduction in serum shift along with a
concomitant loss of in vitro potency. The conversion of the phenol
moiety to a hydroxy-pyridine group improved the in vitro profile of
the amino-series. In this case, amino-hydroxypyridine 14

J. E. Imbriglio et al. / Bioorg. Med. Chem. Lett. 21 (2011) 2721–2724
2723
Table 3
Table 5
THA based agonists of GPR109aa
Amino-fluoropyridine agonists of GPR109aa
Compound
Serum
shift
h-3H-niacinb hGTP
IC50 M) EC50
M)
c
Sc
Compound
Serum
shift
h-3H-
hGTP
EC50
(lM)
c
Sc
(l
niacinb
(l
IC50
(l
M)
Me
O
N
N
N
O
HO
HO
N
H
40-fold hSS 0.003
6-fold hSS 0.005
0.024
0.039
N
N
N
100-fold hSS
0.012
0.214
0.410
F
O
O
N
H
N
O
O
OH
OH
O
N
NH2
17
O
O
OH
Me
O
21
N
N
H
O
N
NH2
18
N
F
N
H
1000-fold hSS
0.021
O
Me
N
OH
O
22
N
N
N
HO
HO
8-fold hSS 0.011
0.085
0.721
N
H
g
O
O
Cmpd
speciesd
Clp
(mL/min/kg)
t
(h)
AUCN po
(lM.h.kg/mg)
F (%)f
½
N
NH2
O
O
OH
19
21
22
Mouse
Rat
Mouse
1.7
0.7
3.3
5.6
5.5
4.7
26.2
49.3
15.2
100
81
54
O
N
N
H
e
40-fold hSS 0.020
Rat Sprague–Dawley.
a
N
NH2
OH
Values are an average of two or greater individual assays; serum shift refers to the ratio
of the binding affinity as determined by [3H]-Nicotinic acid competition in the presence and
absence of 4% human serum.
20 (mixture of diastereomers)
a
b
[3H]-Nicotinic acid binding competition assay.
Values are an average of two or greater individual assays; serum shift refers to the ratio
of the binding affinity as determined by [3H]-Nicotinic acid competition in the presence and
absence of 4% human serum.
c
Membrane binding of compounds versus
K1cells stably expressing the niacin receptor.
[c-
35S] GTP in active recombinant CHO-
d
b
[3H]-Nicotinic acid binding competition assay.
C57BL/6-mice.
Dose: 1 mg/kg iv; 2 mg/kg po.
f
c
Membrane binding of compounds versus
K1cells stably expressing the niacin receptor.
[c-
35S] GTP in active recombinant CHO-
g
t
½
= plasma half-life (0–8 h).
demonstrated excellent affinity and functional activity with a 6-
fold reduction in serum shift, when compared to the des-amino
analog 13. Additional stereochemical modifications, as in stereo-
isomer 15, showed improved in vitro potency, relative to phenol
9, but suffered from an increased affinity for serum proteins. The
introduction of a methyl group, as a means of gearing the confor-
mation of the molecule, as in derivative 16, resulted in a significant
loss in affinity for the receptor.
Previous work in the group, identified the tetrahydroanthranilic
acid (THA) moiety as an advantageous surrogate to the anthranilic
acid group.8 Replacement of the anthranilic acid piece with the
THA moiety in the amino series, as in compound 18, (Table 3).
Methyl substitution on both the cyclohexene moiety, as in 19
and 20, was also well tolerated.
With a promising in vitro profile and a reduced serum shift, we
proceeded to investigate the ADME properties of this amino-THA
series. As illustrated in Table 4, the amino-THA class had favorable
clearance and half-lives, similar to the des-amino derivative 17.
However, the generally low bioavailability prohibited further
development of this series and motivated additional structural
modifications. In this regard, we had data to suggest that the
terminal hydroxy-pyridine moiety was negatively effecting the
oral exposure of the compounds. As a result, we focused our
Table 4
Mouse and rat pharmacokinetic studies of GPR109a agonistsa,b
F (%)c
d
Compound
Species
Clp (mL/min/kg)
t
(h)
AUCN po (
lM.h.kg/mg)
½
Mouse
Rat
2.0
1.0
1.4
2.2
2.99
3.64
13
8.1
O
N
N
HO
N
H
O
O
N
OH
OH
O
O
17
18
Mouse
Rat
2.5
0.7
4.5
2.3
1.6
1.8
9
2
O
N
N
HO
N
H
NH2
N
Me
O
N
N
HO
N
H
Mouse
9.22
2.64
0.35
7.5
O
NH2
N
O
OH
19
a
b
c
C57BL/6-mice.
Rat Sprague–Dawley.
Dose: 1 mg/kg iv; 2 mg/kg po.
d
t
= plasma half-life (0–8 h).
½

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attention on finding a suitable replacement of the hydroxy-pyri-
dine moiety and ultimately discovered fluoropyridine 21. As illus-
trated in Table 5, this simple functional group exchange
significantly improved the ADME properties for the series. The
clearance and half-lives, in both mouse and rat species, for 21 were
quite favorable, however, it was the bioavailability that showed the
most notable improvement. In mice, the bioavailability showed a
10-fold improvement when compared to hydroxypyridine 18.
The rat pharmacokinetic parameters showed a similar trend, with
a bioavailability of 81%, good oral exposure, clearance less than
1 mL/min/kg, and a half-life of 5 h. Finally, the comparison of ami-
no-fluoropyridine 21 to the des-amino derivative 22 illustrates
clearly the positive effect the amino group has on the serum shift,
GPR109a activity, and the pharmacokinetic profile.
References and notes
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6. Identification of leads was based on the ability of compounds to decrease cAMP
levels in cells stably transfected with the niacin receptor (GPR109a).
7. Shen, C. H.; Ding, F. Z.; Raghavan; Luell, S.; Forrest, M. J.; Carballo-Jane, E.; Wu, K.
K.; Wu, T. J.; Cheng, K.; Wilsie, L. C.; Krsmanovic, M. L.; Taggart, A. K.; Ren, N.;
Cai, T. Q.; Deng, Q.; Chen, Q.; Wang, J.; Wolff, M. S.; Tong, X.; Holt, T. G.; Waters,
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C.; Krsmanovic, M. L.; Holt, T. G.; Wolff, M. S.; Waters, M. G.; Hammond, M. L.;
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In summary, we have disclosed
a new class of amino-
anthranilic acid agonists of GPR109a9 that are potent agonists,
have reduced serum shift and excellent ADME properties.
Supplementary data
9. For details on the synthesis of the disclosed agonists refer to WO2007075749A2.
Supplementary data associated with this article can be found, in
the online version, at doi:10.1016/j.bmcl.2010.11.116.