Potent and orally bioavailable GPR142 agonists as novel insulin secretagogues for the treatment of type 2 diabetes

Article abstract of DOI:10.1021/ml400186z

GPR142 is a G protein-coupled receptor that is predominantly expressed in pancreatic β-cells. GPR142 agonists stimulate insulin secretion in the presence of high glucose concentration, so that they could be novel insulin secretagogues with reduced or no risk of hypoglycemia. We report here the optimization of HTS hit compound 1 toward a proof of concept compound 33, which showed potent glucose lowering effects during an oral glucose tolerance test in mice and monkeys.

Full text of DOI:10.1021/ml400186z

Letter
pubs.acs.org/acsmedchemlett
Potent and Orally Bioavailable GPR142 Agonists as Novel Insulin
Secretagogues for the Treatment of Type 2 Diabetes
Narihiro Toda,*,† Xiaolin Hao,*,‡ Yasuyuki Ogawa,† Kozo Oda,† Ming Yu,‡ Zice Fu,‡ Yi Chen,‡
Yongjae Kim,‡ Mike Lizarzaburu,‡ Sarah Lively,‡ Shauna Lawlis,‡ Michiko Murakoshi,† Futoshi Nara,†
Nobuaki Watanabe,† Jeff D. Reagan,‡ Hui Tian,‡ Angela Fu,‡ Alykhan Motani,‡ Qingxiang Liu,‡
Yi-Jyun Lin,‡ Run Zhuang,‡ Yumei Xiong,‡ Peter Fan,‡ Julio Medina,‡ Leping Li,‡ Masanori Izumi,†
Ryo Okuyama,† and Satoshi Shibuya†
†Daiichi Sankyo Co., Ltd., 1-2-58 Hiromachi, Shinagawa-ku, Tokyo 140-8710, Japan
‡Amgen Inc., 1120 Veterans Boulevard, South San Francisco, California 94080, United States
S
* Supporting Information
ABSTRACT: GPR142 is a G protein-coupled receptor that is
predominantly expressed in pancreatic β-cells. GPR142
agonists stimulate insulin secretion in the presence of high
glucose concentration, so that they could be novel insulin
secretagogues with reduced or no risk of hypoglycemia. We
report here the optimization of HTS hit compound 1 toward a
proof of concept compound 33, which showed potent glucose
lowering effects during an oral glucose tolerance test in mice
and monkeys.
KEYWORDS: GPR142, agonist, insulin secretagogue, diabetes, glucose lowering
ype 2 diabetes is characterized by high blood glucose
Tresulting from reduced insulin production from pancreatic
β-cell or insulin resistance or both of them.1 Uncontrolled
hyperglycemia increases the risk of cardiovascular complica-
tions such as coronary heart disease, stroke, nephropathy,
neuropathy, and retinopathy in patients with diabetes.2 Thus,
effective glycemic control is important to prevent chronic
diabetic complications. Currently, insulin secretagogues such as
sulfonylureas and meglitinide are widely used for patients with a
moderate degree of β-cell dysfunction.3 They trigger insulin
release independently of blood glucose level. As a result, some
of them could increase the risk of hypoglycemia.4 Therefore,
novel glucose dependent insulin secretagogues, such as DPP-IV
inhibitors,5 GLP-1 analogues,5 GPR40 agonists,6 and GPR119
agonists,7 are highly attractive alternatives for the treatment of
diabetes.
GPR142 was identified as an orphan G protein-coupled
receptor (GPCR). GPR142 is predominantly expressed in
pancreatic β-cells and coupled with the Gq signaling pathway,
and its endogenous ligands are aromatic amino acids with
tryptophan, which is the most potent ligand in inositol
phosphate accumulation assay (IP assay).8 Tryptophan
stimulates insulin secretion from isolated mice pancreatic islets
only under high glucose conditions and oral administration of
tryptophan improves glucose tolerance in mice. These findings
indicate that GPR142 agonists could be novel insulin
secretagogues with reduced or no risk of hypoglycemia.
High throughput screening (HTS) campaigns identified
several hit compounds including compound 1 (Figure 1) as
Figure 1. Structure of GPR142 agonist from HTS.
well as phenylalanine derivatives9,10 already reported. Com-
pound 1 showed modest agonistic activity against human
GPR142 (IP assay, EC50 = 1.5 μM). Compound 1 potentiated
insulin secretion in rat primary islets at high glucose conditions,
but not at low glucose conditions (see Supporting Informa-
tion). This data showed the glucose-dependent insulin
secretion of GPR142 agonist. Subcutaneous injection of
compound 1 improved glucose tolerance in mice. However,
poor pharmacokinetic (PK) profile of compound 1 was
inadequate for further proof of concept studies in vivo. High
in vivo clearance (1.3 L/h/kg) and very poor oral bioavailability
(F = 3.9%) of compound 1 in monkey are presumably due to
metabolic instability (Table 4). Moreover, compound 1
inhibited CYP3A4 (IC50 = 2.9 μM), which can cause
unfavorable drug−drug interaction.
Received: May 15, 2013
Accepted: June 16, 2013
© XXXX American Chemical Society
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ACS Medicinal Chemistry Letters
Letter
We describe here the optimization of a HTS hit compound 1
to provide a potent orally bioavailable GPR142 agonist and its
pharmacological effects in mice and monkeys.
Table 2. Exploration of 4-Pyridyl Head Group
First, we investigated the structure−activity relationship
(SAR) of the pyrazole side chain (Table 1). Synthesis of
Table 1. SAR of Pyrazole Side Chains
ab
,
c
cmpd
R1
hGPR142 EC50 (μM)
MLM (% remaining)
1
MOM
Et
1.5
3
7a
7b
7c
7d
7e
7f
1.0
NT
1
nPr
0.25
0.0070
1.0
nBu
NT
NT
NT
nPent
secBu
CH2OEt
1.2
0.030
NT
a
b
Assay protocols are provided in the Supporting Information. Assay
results are the average of three replicates; standard deviation was
c
20%. % Remaining after incubation for 15 min in mouse liver
microsomes. NT = not tested.
compounds 7a−f started from Suzuki coupling between 2,4-
dichloro-5-methylpyrimidine (2) and thiopheneboronic acid to
give 3 (Scheme 1).11 Compound 3 was heated with NH2NH2
a
Scheme 1. General Synthesis of Compound
a
Reagents and conditions: (a) 2-thiopheneboronic acid, Pd(PPh3)4,
a
b
K2CO3, DME, reflux; (b) NH2NH2, pyridine; (c) 9, HOAc, EtOAc;
(d) LiOH, THF/H2O; (e) 4-(aminomethyl)pyridine, HBTU, iPr2NEt,
DMF; (f) N,N-dimethylforamide dimethyl acetal, heat.
Assay protocols are provided in the Supporting Information. Assay
results are the average of three replicates; standard deviation was
c
20%. % Remaining after incubation for 15 min in mouse liver
microsomes or human liver microsomes. NT = not tested.
in pyridine to give 4. Keto-ester 9 was conveniently prepared by
heating 8 with N,N-dimethylforamide dimethyl acetal. Con-
densation of 4 and 9 under acidic conditions resulted in methyl
ester 5, which was hydrolyzed to give acid 6. Finally, coupling
of 6 with 4-(aminomethyl)pyridine using HBTU gave
compounds 7a−f. n-Propyl (7b) and n-butyl (7c) derivatives
were found to improve agonistic activities, but their poor
metabolic stability was not improved. The size of alkyl side
chains seems to be important for GPR142 agonism.
Next, we explored the 4-pyridyl headgroup in the compound
7b or 7c to improve metabolic stability (Table 2). Compounds
10−22 were synthesized with the same method in Scheme 1.
Dimethyl substitution (10) at benzyl position was tolerated in
terms of agonistic activity but did not improve metabolic
stability. Substitution on the amide nitrogen (11) resulted in
significant loss of GPR142 potency. Replacement of pyridine
ring with 4-fluorophenyl ring (12) gave an inactive analogue. 5-
Substituted imidazole derivative (13) showed very potent
agonistic activity and modest metabolic stability. In contrast, 4-
substitued imidazole derivative (14) lost its GPR142 agonistic
activity. The orientation of a nitrogen lone pair is likely to be
crucial to GPR142 agonism. Methyl substitution at 4-position
(15) or 2-position (16) in the imidazole ring of 13 was
tolerated in agonistic activity. However, metabolic stability of
both compounds was significantly decreased. A conformation-
ally restricted analogue (17), which might resist metabolism,
resulted in the loss of agonistic activity and no improvement of
metabolic stability. Introduction of carboxylic acid in the
headgroup (18) was tolerated and improved metabolic stability;
B
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Table 3. Substitution of Thiophene Ring
a
b
c
Assay protocols are provided in the Supporting Information. Assay results are the average of three replicates; standard deviation was 20%. %
d
Remaining after incubation for 30 min in human, monkey, and rat liver microsomes. Calculated by ACD. NT = not tested.
however, its membrane permeability was too low to achieve
oral bioavailability. Pyrazole derivative (19) was a modest
agonist, which had poor metabolic stability. Isoxazole (20),
thiazole (21), and indole (22) derivatives were less potent
agonists than imidazole derivatives. By this moment, we
selected the imidazole derivative 13 for further optimization.
Introduction of the ethoxymethyl side chain instead of the
butyl side chain gave compound 23, which showed comparable
GPR142 agonistic activity and metabolic stability to 13;
moreover, its hydrophobicity (LogD = 2.2) was in an optimal
range (Table 3).12 Thiophene is known to give reactive
metabolite in vivo and have potential of idiosyncratic toxicity,13
in that we investigated substitution of thiophene ring
particularly with a nonaromatic saturated group. To facilitate
the exploration of replacements for the thiophene, an efficient
synthesis was developed to allow the introduction of this
moiety at the last step, as shown in Scheme 2. Compound 24
was obtained by treatment of 2 with the sodium salt of 2-
Scheme 2. Synthesis of 4-Substituted Analogues to Replace
Thiophene
a
a
Reagents and conditions: (a) 2-(trimethylsilyl)ethanol, NaH, THF;
(b) NH2NH2, pyridine; (c) 9, HOAc, EtOAc; (d) 1. TBAF, THF,
MeCN; 2. LiOH, THF/H2O; (e) POCl3, 110 °C, quench with H2O;
(f) 1-methyl-5-(aminomethyl)-1H-imidazole, HBTU, iPr2NEt, DMF;
(g) alkoxide or amine, DMF.
(trimethylsilyl)ethanol in THF according to Lluis et al.14
A
two-step sequence to install the pyrazole (as described in
Scheme 1) gave compound 25, which was treated with TBAF
in MeCN to liberate the hydroxypyrimidine. The methyl ester
was then hydrolyzed to the acid 26. The acid 26 was heated at
reflux with POCl3 to provide 4-chloro pyrimidine acid chloride,
which was isolated as an acid 27 after workup in ice water.
Coupling with the methyl imidazole amine gave 28, a key
precursor for the preparation of 29−33. Ether and amine
derivatives were made by direct nucleophilic aromatic displace-
ment with the appropriate sodium alkoxide or with an excess of
the amine in DMF. Compound 29 having ethoxy moiety was
found to be a modest GPR142 agonist. A series of alkyl amine
analogues (30−33) showed good GPR142 agonistic activity as
well as good metabolic stability. Cyclobutylamine (30) and
azetidine (31) derivatives had poor membrane permeability.
Pyrrolidine (32) and piperidine (33) derivatives had good
membrane permeability with increasing hydrophobicity. Un-
fortunately, CYP inhibition of a series of compounds described
here was still not appropriate for further development
(CYP3A4 IC50 = 1.0 μM for 33). We assessed PK profiles of
33 in monkeys. Compound 33 demonstrated good oral
bioavailability (F = 26%), which was consistent with its good
metabolic stability (Table 4).
Therefore, we selected 33 as a proof of concept compound
for in vivo studies in mice (Figure 2) and monkeys (Figure 3).
C57BL/6J mice were dosed orally with compound 33. After
that, mice were challenged with an oral glucose, and blood
samples were collected for the assay of blood glucose levels.
Compound 33 (1−30 mg/kg) decreased blood glucose
concentration in C57BL/6J mice in a dose dependent manner.
The maximum glucose lowering effect of 33 is similar to that of
C
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ACS Medicinal Chemistry Letters
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tolerance test. Furthermore, at a dose of 10 mg/kg, compound
33 tended to show greater efficacy than sitagliptin.15
In conclusion, we described the optimization leading from
HTS hit compound 1 to the orally bioavailable compound 33, a
structurally novel potent GPR142 agonist. The antidiabetic
effect that compound 33 demonstrated in mice and monkeys
strongly suggests that GPR142 agonists have great potential for
the treatment of type II diabetes. Detailed pharmacological
evaluation and further optimization of this series will be
reported elsewhere.
Table 4. Monkey PK Parameters of 33
a
a
b
b
cmpd
Cl (L/h/kg)
Vdss (L/kg)
t1/2 (h)
F (%)
c
1
1.3
1.0
1.0
NA
3.9
26
33
0.77
1.2
a
b
Compounds were dosed iv at 0.5 mg/kg. Compounds were dosed
c
po at 1 mg/kg. Not applicable.
ASSOCIATED CONTENT
* Supporting Information
Experimental procedures and analytical data. This material is
available free of charge via the Internet at http://pubs.acs.org.
■
S
AUTHOR INFORMATION
Corresponding Author
*E-mail: toda.narihiro.jw@daiichisankyo.co.jp (N.T.); xhao@
amgen.com (X.H.).
■
Notes
The authors declare no competing financial interest.
ABBREVIATIONS
■
HTS, high throughput screening; CYP, cytochrome P450;
HBTU, o-benzotriazole-N,N,N′,N′-tetramethyl-uronium-hexa-
fluoro-phosphate; MLM, mouse liver microsome; HLM,
human liver microsome; MkLM, monkey liver microsome;
RLM, rat liver microsome
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