Discovery of the bifunctional modulator of angiotensin II type 1 receptor (AT1R) and PPARγ derived from the AT1R antagonist, Fimasartan

Article abstract of DOI:10.1016/j.bmcl.2018.08.036

Inspired by the well-known PPARγ partial agonism of angiotensin II type 1 receptor (AT1R) antagonists exemplified by an antihypertensive drug, Telmisartan, efforts to identify compounds with the dual activities have been pursued in order to control the two major metabolic disorders, hypertension and hyperglycemia simultaneously. Lead compound 18 derived from the AT1R antagonist, Fimasartan, has successfully presented the possibility to control the medical conditions by a single molecule.

Full text of DOI:10.1016/j.bmcl.2018.08.036

Accepted Manuscript
Discovery of the Bifunctional Modulator of Angiotensin II Type 1 Receptor
(AT1R) and PPARγ derived from the AT1R Antagonist, Fimasartan
Wonken Choung, Hui Jin Jung, Eun Hye Nam, Deokmo Yang, Byoungwook
Yoo, Hyukjoon Choi, Bo Ram Lee, Min Park, Su Min Jang, Jae SooLim, Kyung-
Hee Kim, Jungwook Chin, Kyungjin Jung, Geumwoo Lee, Seong Heon Kim
PII:
S0960-894X(18)30712-1
https://doi.org/10.1016/j.bmcl.2018.08.036
BMCL 26016
DOI:
Reference:
Bioorganic & Medicinal Chemistry Letters
To appear in:
Received Date:
Revised Date:
Accepted Date:
18 July 2018
21 August 2018
27 August 2018
Please cite this article as: Choung, W., Jung, H.J., Nam, E.H., Yang, D., Yoo, B., Choi, H., Lee, B.R., Park, M.,
Jang, S.M., Lim, J.S., Kim, K-H., Chin, J., Jung, K., Lee, G., Kim, S.H., Discovery of the Bifunctional Modulator
of Angiotensin II Type 1 Receptor (AT1R) and PPARγ derived from the AT1R Antagonist, Fimasartan, Bioorganic
& Medicinal Chemistry Letters (2018), doi: https://doi.org/10.1016/j.bmcl.2018.08.036
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Discovery of the Bifunctional Modulator of Angiotensin II Type 1 Receptor (AT1R) and PPARγ
derived from the AT1R Antagonist, Fimasartan
Wonken Chounga,*, Hui Jin Junga, Eun Hye Nama, Deokmo Yanga, Byoungwook Yooa, Hyukjoon
Choia, Bo Ram Leea, Min Parka, Su Min Janga, Jae Soo Lima, Kyung-Hee Kimb, Jungwook Chinb,
Kyungjin Jungb, Geumwoo Leeb, Seong Heon Kima,*
a
Research Center, Boryung Pharmaceuticals Co. Ltd. Republic of Korea
b
New Drug Development Center, Daegu-Gyeongbuk Medical Innovation Foundation (DGMIF),
Republic of Korea
Hypertension and Type 2 Diabetes (T2D) are known as common metabolic disorders
among the population in the developed countries 1 . According to WHO2 , prevalence of
hypertension in the developed countries is about 30% and T2D patients are consisted of nearly 10%
of population, and 70% of which also suffer from hypertension and have very high risk of the fatal
incidents such as stroke, heart failure, etc.
Particularly, among the patients with hypertension, 50% of them are known to proceed to
the hyperglycemia sooner or later. According to the literature3, the patients diagnosed with
hypertension have the risk factor for developing hyperglycemia 1.6 times higher and the increased
risk of fatal incidents mentioned above compared to those with normal blood pressure unless
controlled timely and properly.
It is well known that the high probability of having multiple metabolic conditions
simultaneously often causes difficulties in the patient’s compliance of medication prescribed.
Reducing the pill burden and inconvenience from differing dosing schedules for the individual
drugs by providing fixed dose combo pills or multifunctional agents was considered to improve
the medication compliance4 . Accordingly, we reasoned a single molecule with bifunctional
pharmacologies for the commonly accompanied metabolic conditions would have enhanced value
in market, though more challenges in development. To this end, the feasibility to identify a dual-
active molecule enabling to control blood pressure and hyperglycemia simultaneously has been
explored5.
Among the numerous ways to control hypertension6, angiotensin II type 1 receptor (AT1R)
antagonists have been known to function by blocking vasoconstricting peptide angiotensin II from
activating the receptor7. There are many antihypertensive drugs of this kind dubbed as ARBs
(angiotensin II receptor blockers) approved for the clinical use including Losartan, Candersartan
and Olmesartan among others (Figure 1). For treatment of T2D characterized by high blood
sugar, insulin resistance, and relative lack of insulin, thiazolidinediones (TZDs) represented chiefly
by Rosiglitazone and Pioglitazone have been widely used8. TZDs have insulin sensitizing effect by
binding and activating nuclear receptor PPAR to recover the proper blood glucose control.
Inspired by the well-known PPAR partial agonism of ARBs represented by Telmisartan9,

we assessed the potential of our own marketed ARB, Fimasartan10 (Compound 1, Figure 1) as a
PPAR partial agonist. Telmisartan has been used as antihypertension medicine for almost 20
years and known to induce about 40% PPARγ activation compared to the full agonist,
thiazolidinedione (TZD) drug, Pioglitazone11 which has been used as an antidiabetic drug since its
FDA approval in 1999. However, unfortunately, Fimasartan was found inert of PPARγ activation
and, subsequently, this study was initiated to modify Fimasartan to have PPARγ activity while
maintaining its activity as an ARB.
Figure 1. Commercialized angiotensin II receptor blockers (ARBs) and Fimasartan
As the 8th ARB12 (Figure 1) launched in the market (approved by Korean FDA in 2010),
Fimasartan has proved its excellent clinical efficacy for the past 8 years mainly in the Korean
antihypertensive market13. Besides the clinical benefits, it has differentiated itself from other
ARBs by the unique scaffolds including pyrimidinone ring and thioamide attached as the key
characteristic structural motifs. To maintain the antihypertensive activity, based on the docking

analysis (Figure 2A) inferred from the AT1R X-ray crystallography14, we decided to keep the alkyl
chain, biphenyl attached with acidic moiety, and pyrimidinone ring which, as combined, were
deemed to have essential hydrophobic and hydrogen bonding interactions with amino acid
residues such as Arg 167, Tyr 184 and Lys 199 in the binding pocket. Accordingly, the strategy to
modify structure to induce the activity toward PPAR protein has set to include 1) the exploration
of bioisosteres for tetrazole (R1), 2) the examination of length and shape of alkyl groups on
pyrimidinone core (R2 and R4), 3) the variation of amine moiety on thioamide (R3) (Figure 2B).
Figure 2. A) Docking model of Fimasartan in the binding pocket of the AT1R X-ray structure, B)
Strategy to modify Fimasartan scaffold to activate PPARγ
A)
B)
First, the tetrazole moiety attached on biphenyl has been replaced with other acidic
bioisosteres15 such as carboxylic acid, sulfonamide and oxadiazolone. As shown in Table 1,
compound 2 containing a carboxylic acid instead of tetrazole displayed significant PPARγ agonism
while, unexpectedly, lost the ARB activity. We next tested the corresponding sulfonamide only to
find it inactive toward not only PPARγ but AT1R as well (compound 3). Then, we turned our
attention to the 5-ring heteroaromatic which share more common topology with the original
tetrazole as well as the acidic property, a reasoning also supported by the success of Azilsartan
(Figure 1). As such, oxadiazolone derivative, compound 4, was chosen to prepare and gratifyingly
we could find it indeed activating PPARγ while maintaining antihypertension activity intact.
Next we modified R2 while R1 was fixed as oxadiazolone. In the series of R2 derivatives
tested (compound 4-7), it appeared clear that the linear aliphatic chain displayed superior
activities for both of biological targets (compounds 4 and 6) compared to their cyclic or branched
analogs (compounds 5 and 7), but the chain length did not seem to affect much. Based on the
best balanced dual activity, compound 4 was selected for further optimization .
Table 1. Angiotensin II receptor antagonism and PPARγ agonism : Variations on R1 and R2

substitution
Comp.
No.
R1
R2
Angiotensin II
receptor
antagonism‡,
IC50
PPARγ
agonism#
(% activation)
1†
2
3
4
5
6
7
Tetrazole
-CO2H
n-butyl
n-butyl
4.5 nM
0%
140%
NT*
NT* (80%)**
NT (11%)
1.6 nM
-SO2NH2
n-butyl
Oxadiazolone
Oxadiazolone
Oxadiazolone
Oxadiazolone
n-butyl
120%
70%
100%
NT
Isobutyl
n-propyl
cyclopropyl
NT (0%)
4.7 nM
NT (9.5 %)
†Fimasartan, ‡the compound shown over 100% inhibition compared to Fimasartan at 20 nM was measured IC50 value from
the Calcium mobilizing assay, *NT: Not Tested, **shown % is represent for % inhibition compared to Fimasartan at 20 nM,
#% activation compared to treatment of Telmisartan at 1 μM
Table 2. Angiotensin II receptor antagonism and PPARγ agonism : Variations on R3 and R4
substitution
Comp.
No.
R3
R4
Angiotensin II
receptor
antagonism‡,
IC50
PPARγ
agonism#
(% activation)
4
8
Dimethyl amine
Diethyl amine
isobutylmethyl amine
isopropylmethyl
amine
Methyl
Methyl
Methyl
1.6 nM
120%
61%
2.0 nM
9
2.1 nM
122%
10
Methyl
Methyl
NT* (107%)
1.2 nM
106%
107%
11
12
Methyl
Methyl
1.8 nM
38 nM
100%
116%
13

14
15
Methyl
Methyl
5.6 nM
32 nM
83%
100%
16
Methyl
70 nM
121%
17
18
19
pyrrolidine
pyrrolidine
pyrrolidine
Methyl
Isopropyl
Cyclopropyl
0.7 nM
2.2 nM
105%
156%
79%
NT (63%)
‡the compound shown over 100% inhibition compared to Fimasartan at 20 nM was measured IC50 value from the Calcium
mobilizing assay, *NT: Not Tested, **shown % is represent for % inhibition compared to Fimasartan at 20 nM, #% activation
compared to treatment of Telmisartan at 1 μM
Table 2 showed the effects of variations on R3 and R4 substitutions. For R3 modifications,
dialkyl amines and pyrrolidine derivatives generally well preserved the ARB activity comparable to
the parent compound, Fimasartan, and did not show any significant variations on the PPARγ
agonism. Some bulkier groups such as six-membered ring or bicyclic-ring system observed
weaker antihypertensive activities (Compounds 13, 15, and 16) with the exception of morpholine
derivative (compound 14) which, instead, was a relatively weaker PPAR agonist. Since compound
17 containing pyrrolidine revealed well balanced decent dual activity, it was selected for further R4
modifications. Replacement of methyl by bulkier isopropyl moiety further proved beneficial to
the PPAR activation providing the best result of 156% and 66% activations compared to the
reference compound (Telmisartan) and TZD compound (Pioglitazone), respectively, while
maintaining excellent ARB activity (IC50 = 2.2 nM). On the other hand, cyclopropyl derivative,
compound 19, was found less effective toward both targets.
Further in vitro profiling revealed compound 18 had mostly acceptable hERG and CYP
inhibition profiles while the liver microsomal stabilities were overall low in most of the species
assessed (Table 3). Despite the low in vitro liver microsomal stabilities, compound 18 was
selected to proceed for further in vivo proof-of-concept (POC) study mainly due to the decent PK
exposure measured at 60 mg/kg (mpk) (p.o.) (Table 4). Compound 18 showed comparable oral
half-lives in rat and mouse, but had 4 times better exposure of 13350 ng·hr/mL AUC in rat versus
mouse (AUC = 2571 ng·hr/mL), which could be attributed partially to the better liver microsomal
stability in rat. The PK results obtained at 60 mpk were seemed reasonable to proceed the in vivo
POC studies planned to dose 30 mpk and 60 mpk in rat (angiotensin II induced hypertension
model16) and mouse (db/db mouse study17), respectively. Additionally, despite the potential
exaggerated exposures at higher doses (in this case, 60 mpk versus 10~20 mpk) due to the partial
inactivation of metabolic enzymes or efflux pumps, the PK comparison with Fimasartan18 (at 10
mpk and 20 mpk in rat and mouse, respectively, Table 4), which has proved its efficacy at as low
dose as 3 mpk (p.o.) in rat angiotensin II induced hypertension model (Figure 3A), supported our
plan to proceed compound 18 for the in vivo studies.
Table 3. In vitro profiling of compound 18

Microsomal stability
CYP
AT1R inhibition
PPARγ agonism
(% remaining @ 30min)
(%remain activity @10uM)
hERG
(IC50)
Ca
β_Arrestin
recruitment
(IC50)
Amax
mobilization
(IC50)
EC50
M
R
D
H
1A2
97
2C9
36
2C19
84
2D6
99
3A4
62
vs. pioglitazone
2.2 nM
10.5 nM
3.1 uM
66%
7 uM
11
24
62
13
Table 4. Oral rodent PK of compound 18 and Fimasartan
t1/2(hr)
Tmax(hr)
Cmax(ng/mL)
AUClast(ng·hr/mL)
Species/dose
Rat/60 mpk
4.73
3.67
3.60
NA
1.17
0.50
0.13
NA
2570
1859
518
13350
2571
1934
254
Compound 18
Mouse/60 mpk
Rat/10 mpk
Fimasartan
Mouse/20 mpk
145
*NA: Not Available
In the in vivo studies using the angiotensin II induced hypertension rat models, the
lowering effect of blood pressure by compound 18 (30 mpk, p.o.) over control has been assessed
in comparison with Fimasartan (3 mpk, p.o.). As shown in Figure 3A, compound 18 maintained
suppressive effect of blood pressure increase comparable to Fimasartan until 8 hours after dosing,
though the effect fell to about 50% of Fimasartan after 24 hours. The reduced duration of
efficacy of compound 18 (~16 h) versus Fimasartan (~22 h) at ca. 50% reduction of blood
pressure over control was inexplicable when we consider the difference in dosing amounts
(compound 18 : 30 mpk vs. Fimasartan : 3 mpk), and the comparable in vitro potencies
(compound 18 : 2.2 nM vs. Fimasartan : 4.5 nM), unless we presume the slower dissociation19 of
Fimasartan from the target protein than compound 18. For the antidiabetic effect, compound 18
was assessed in genetically induced db/db mouse diabetes models. In the 13-day QD study,
compound 18 (60 mpk, p.o.) revealed significant suppressive effect on blood glucose increase,
though it was found less effective than the reference compound, Pioglitazone (20 mpk) (Figure
3B). Particularly, compound 18 showed slight suppression in weight gain after 11 days compared
to Pioglitazone, which has been known as one of the major adverse events of drugs containing
TZDs20 (Figure 3C). Although the effects of compound 18 were found not exceed those of each
reference compounds in either of in vivo models, the in vivo study results are truly demonstrating
the prospect of compound 18 as a potential dual modulator at a reasonable dosage enabling
effective control of both conditions.
Figure 3. A) Effects on blood pressure of Compound 18 in angiotensin II induced hypertension rat
model B) Effects on blood glucose of Compound 18 in db/db mouse model C) Effects of body
weights in db/db mouse study.
A)

B)
C)
All the compounds listed in Table 1 and 2 were prepared according to the routes
summarized in Scheme 1. The key intermediate pyrimidin-4(3H)-one 23 was prepared in four
steps from a nitrile 20. Conversion of nitrile 20 into amidine hydrochloride was achieved by the
treatment of methanol saturated with HCl followed by addition of gaseous NH3 at 0 °C.
Condensation of 21 with diethyl acylsuccinate derivatives prepared from acylation of -ketoester
22 with chloroacetate in the presence of sodium ethoxide provided pyrimidin-4(3H)-one 2321.
Coupling of 23 with commercially available 4'-(bromomethyl)biphenyl-2-carbonitrile 24 in the
presence of lithium hydride led to the formation of N-alkylated nitrile 25. Compound 25 was
treated with aqueous hydroxylamine in dimethylsulfoxide (DMSO) at 90 °C, followed by treatment
with dimethyl carbonate and NaOMe in DMSO to afford the desired oxadiazolone derivative 2622.
Hydrolysis of ester 26 with 10% sodium hydroxide gave the corresponding carboxylic acid which
was subjected to the amide coupling condition with various amines to afford the amide
23
derivatives.
Treatment of the amides with Lawesson’s reagent
afforded the desired
oxadiazolone-thioamides (compounds 4-6 and 8-19). For the synthesis of compound 2, the ester
23 was hydrolysed and coupled with dimethylamine to provide the amide 27. Alkylation of
pyrimidinone 27 with the bromide 28 gave the ester 29 which was hydrolysed under basic
condition followed by treatment with Lawesson’s reagnt to afford the desired compound 2.
Synthesis of compound 3 began with the Suzuki coupling24 of sulfonyl amide 31 derived from the

sulfonyl chloride 30, with boronic acid 32 under Pd-catalysed condition to provide the biphenyl
intermediate 33. After bromination of compound 33, the resulting bromide 34 was coupled with
pyrimidinone 27 in the presence of lithium hydride to afford amide 35, which was converted to
the corresponding thioamide 3 by Lawesson’s reagent.
In summary, we successfully identified a lead, compound 18, with dual activity as a
PPARγ partial agonist and an angiotensin II type 1 receptor antagonist (ARB). Starting from the
molecular backbone of ARB, Fimasartan, which was inactive to the PPAR activation, structure-
activity-relationship (SAR) study on multiple sites including oxadiazolone installation, isopropyl
substitution on pyrimidione ring, and pyrrolidine thioamide as the key modifications has been
effectively carried out. The POC study of compound 18 in disease models such as angiotensin II
induced hypertension rat model and db/db mouse diabetes model verified the compound 18 as a
lead candidate for the development of potential dual modulator for the simultaneous control of
hypertension and hyperglycemia. Further optimization and safety assessment are currently
underway and the results will be published in due courses.
Acknowledgments
This research was supported by the Bio & Medical Technology Development Program of the
National Research Foundation (NRF) funded by the Ministry of Science & ICT
(2014M3A9D9033717 & 2014M3A9D9070788).

Scheme 1. General Synthetic Scheme, a) HCl, EtOH, reflux, b) ammonia, EtOH, c) ethyl
chloroacetate, NaOEt, THF, d) EtOH, reflux, e) LiH, DMF/EtOAc f) aq. NH2OH, DMSO, 90 °C, g)
dimethyl carbonate, NaOMe, DMSO, h) NaOH, H2O/MeOH, i) amine, EDCI, HOBT, Et3N, THF, J)
Lawesson’s reagent, toluene, reflux. k). LiOH, EtOH/H2O, l). NH4OH, CH2Cl2, m) K2CO3, Pd(PPh3)4,
toluene, EtOH, H2O, n) NBS, AIBN, CCl4

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Highlights



A lead compound with dual activity for PPAR and AT1R has been identified.
Extensive SAR on antihypertensive Fimasartan led to the lead, Compound 18.
Lead has proved its POC in animal models of type 2 diabetes and hypertension,
respectively.