Discovery of cariprazine (RGH-188): A novel antipsychotic acting on dopamine D3/D2 receptors

Article abstract of DOI:10.1016/j.bmcl.2012.03.104

Medicinal chemistry optimization of an impurity isolated during the scale-up synthesis of a pyridylsulfonamide type dopamine D₃/D ₂ compound (1) led to a series of new piperazine derivatives having affinity to both dopamine D₃

Full text of DOI:10.1016/j.bmcl.2012.03.104

Bioorganic & Medicinal Chemistry Letters 22 (2012) 3437–3440
Contents lists available at SciVerse ScienceDirect
Bioorganic & Medicinal Chemistry Letters
journal homepage: www.elsevier.com/locate/bmcl
Discovery of cariprazine (RGH-188): A novel antipsychotic acting
on dopamine D /D receptors
3
2
⇑
Éva Ágai-Csongor , György Domány, Katalin Nógrádi, János Galambos, István Vágó,
György Miklós Keser u} , István Greiner, István Laszlovszky, Anikó Gere, Éva Schmidt, Béla Kiss,
Mónika Vastag, Károly Tihanyi, Katalin Sághy, Judit Laszy, István Gyertyán, Mária Zájer-Balázs,
Larisza Gémesi, Margit Kapás, Zsolt Szombathelyi
Gedeon Richter Plc, Budapest 10, PO Box 27, H-1475, Hungary
a r t i c l e i n f o
a b s t r a c t
Article history:
Medicinal chemistry optimization of an impurity isolated during the scale-up synthesis of a pyridylsulf-
Received 6 February 2012
Revised 26 March 2012
Accepted 28 March 2012
Available online 4 April 2012
onamide type dopamine D
3
/D
2
compound (1) led to a series of new piperazine derivatives having affinity
to both dopamine D and D
3
2
receptors. Several members of this group showed excellent pharmacokinetic
and pharmacodynamic properties as demonstrated by outstanding activities in different antipsychotic
tests. The most promising representative, 2m (cariprazine) had good absorption, excellent brain penetra-
tion and advantageous safety profile. Based on its successful clinical development we are looking forward
to the NDA filing of cariprazine in 2012.
Keywords:
Cariprazine
RGH-188
Ó 2012 Elsevier Ltd. All rights reserved.
3 2
Dopamine D and D ligands
Antipsychotic
Chloro-scan
The overwhelming majority of the clinically used antipsychotics
seems to exert their activity via interaction with dopamine D
CF3
2
receptors. Most of the typical and atypical antipsychotics, however,
show affinities toward several other receptor types as well. These
secondary interactions may contribute to the overall efficacy and
safety of these drugs. One of the receptors the modulation of which
could significantly influence the therapeutic value of the drug may
N
CN
N
O
O
S
be the dopamine D
a new antipsychotic was based on two hypotheses, beside the con-
viction that dopamine D affinity was indispensable. On one hand
the dopamine D antagonism/partial agonism may exert cognitive
enhancement and diminished liability for catalepsy. On the other
hand compounds should show higher affinity to the D than the
receptors because of the different expression levels of the two
receptors in the adequate brain areas.
We have recently reported on a 3-pyridylsulfonamide deriva-
tive (1) as a high-affinity dopamine D /D receptor ligand with sig-
3
receptor. Our plan aiming the development of
N
H
N
2
1
2
3
rD
3
i
-K : 0.4 nM; rD
-K : 24 nM;
i
r%F: 55; brain tmax: 1 hour, Cmax: 921 ng/ml
3
apomorphine climbing in mice ED50: 22 mg/kg (p.o.);
catalepsy in rats: MED: > 200 mg/kg (p.o.)
D
2
During the resynthesis of compound 1 (Scheme 1) a persistent
impurity was detected, and subsequently isolated and tested. It
turned out that during the deprotection (in ethyl acetate) of the
3
2
nificant antipsychotic efficacy coupled with beneficial cognitive
and extrapyramidal side effect (EPS) profile.1–3
precursor
(4-{2-[4-(3-cyano-5-trifluoromethyl-phenyl)-pipera-
zine-1-yl]-ethyl}-cyclo-hexyl)-carbamic acid tert-butyl ester and
the subsequent sulfonylation of deprotected amine with pyri-
dine-3-sulfonyl chloride, a small amount of compound 2a was
formed besides the main product 1. Interestingly, 2a showed supe-
rior properties when investigated in our early phase screening
⇑
Corresponding author. Tel.: + 36 1 431 5112; fax: +36 1 432 6002.
E-mail address: e.csongor@richter.hu (É. Ágai-Csongor).
0
960-894X/$ - see front matter Ó 2012 Elsevier Ltd. All rights reserved.
http://dx.doi.org/10.1016/j.bmcl.2012.03.104

3
438
É. Ágai-Csongor et al. / Bioorg. Med. Chem. Lett. 22 (2012) 3437–3440
Q2
X
Q2
X
O
C
H
N
N
Boc
i
ii
N
H
Boc
Q1
N
H
N
H
A
3 2 2 1 1 1 2 2
Scheme 1. Reagents and conditions: (i) cyclic amine/NaBH(OAc) /CH Cl ; (ii) (1) HCl/EtOAc, (2) in most cases Q Cl or Q OQ /TEA/CH Cl .
cascade. Although, it had somewhat lower affinity to the dopamine
and D receptors 2a was about 10 times more active in vivo than
low nanomolar or subnanomolar IC50 values and somewhat lower
affinities to the D receptors. The most active derivatives (in vitro
D
3
2
2
compound 1 (Table 1). This observation was rather surprising,
since it contradicts to the consensus of the relevant literature indi-
cating that an aromatic or heteroaromatic carboxamide moiety is
and in vivo) contained 2,3-dichlorophenyl-piperazine moiety. Tak-
ing into account many other features (like off-target activity, meta-
bolic stability, interactions with CYP enzymes, permeability and
an essential structural element of the dopamine D
3
receptor phar-
in vivo activity in several behavioral pharmacological models, part
4
,5
14,15
macophore. Since the formation of 2a was only observed in those
cases when the deprotection was performed with HCl-containing
ethyl acetate it is reasonable to assume that the small amount of
acetic acid, which could always be present in the raw product iso-
lated from the reaction, transformed some pyridine-3-sulfonyl
chloride to pyridine-3-sulfonyl acetate, a reactive acetylating agent
that competed with the unchanged pyridine-3-sulfonyl chloride
of which has already been published
) of the synthesized com-
pounds the most promising member of this group proved to be 2m.
N
Cl
N
Cl
O
6
for the nucleophile.
CH3
.HCl
N
N
H
In order to explore the influence of small amide-like functional-
ities at the cyclohexyl side of the molecule a series of analogues was
CH3
7,8
prepared and tested (Scheme 1). In the design of these amido-
cyclohexyl-amines (general formula A) we utilized our earlier
structure–activity relationship (SAR) experience as far as the amine
2
m (cariprazine)
rD
3 i
-K
: 0.71 nM; rD
2
-K : 9.3 nM;
i
1
hD
3
-K
i
: 0.09 nM; hD2L-K
i
: 5.7 nM; hD2S-K
i
: 0.81 nM
part was concerned. This basic moiety was either piperazine
r%F: 52; brain tmax: 0.5-1 hour, Cmax: 91 ng/ml
(
homopiperazine) or piperidine. Substituents Q
2
were selected from
apomorphine climbing in mice ED : 0.27 mg/kg p.o.);
5
0
catalepsy in rats: MED: > 85 mg/kg (p.o.)
substituted phenyl or benzyl in case of piperazines and substituted
phenyl, benzyl, and phenoxy in case of piperidines. The amide part
of A was decorated with alkylsulfonyl, substituted acyl, alkoxycar-
bonyl, carbamoyl and N-mono- or N,N-disubstituted carbamoyl
groups. A selection of the most active derivatives, their affinities
In order to determine whether the 2,3-dichlorophenyl-pipera-
zine derivative 2m was the most suitable for preclinical develop-
ment ‘chloro-scan’ was performed, and a series of analogues
having no chlorine, one chlorine or two chlorine atoms in different
positions of the phenyl ring was prepared and tested (Table 2).
3 2
to rat dopamine D and D receptors and activities in the apomor-
9
–11
phine induced climbing test in mice are shown in Table 1.
In
3
receptors, with
Besides the affinities to dopamine D
to
2
and D
3
receptors the affinities
general, these compounds had high affinity to D
a
-1 adrenoceptors were measured in order to determine the
Table 1
Selected compounds (2a–2p): affinities to rat dopamine D
2
and D
3
receptors and activities in the apomorphine-induced climbing test in mice
Q2
X
N
Q1
N
H
2
a-2p
Code
Q
1
X
Q
2
rD
3
-IC50 (nM)
rD
2
-IC50 (nM)
Apo-ED50 (mg/kg)
2
2
2
2
2
2
2
2
2
2
2
2
2
2
2
2
a
b
c
d
e
f
g
h
i
j
k
l
m
n
o
p
MeCO
N
N
N
N
CH
CH
N
N
N
N
N
N
N
N
N
N
3-CN-5-CF
3-CN-5-CF
3
-Ph
-Ph
1.9
0.9
1.9
4.8
3.3
5.3
143
135
39
66
64
85
158
25
1.54
8.2
0.7
4.34
2.2
1.8
1.34
5.37
4.32
0.17
0.91
0.21
0.27
0.38
0.71
0.87
MeSO
MeCO
2
3
3-CF
3-CF
3-CF
3-CF
3-CF
3-CF
3
3
3
3
3
3
-Ph
-Ph
-Bn
-PhO
-Bn
-Bn
MeSO
MeCO
MeCO
2
MeSO
2
11
5.1
EtOCO
CF
3
CO
2,3-Di-Cl-Ph
2,3-Di-Cl-Ph
2,3-Di-Cl-Ph
2,3-Di-Cl-Ph
2,3-Di-Cl-Ph
2,3-Di-Cl-Ph
2,3-Di-Cl-Ph
2,3-Di-Cl-Ph
0.41
0.29
0.48
0.26
1.6
0.34
0.62
0.32
5.9
MeCO
2.3
5.4
7.1
MeSO
EtCO
2
Me
EtNHCO
Et NCO
NCO
2
NCO
16
16.9
42.9
29
2
H
2

É. Ágai-Csongor et al. / Bioorg. Med. Chem. Lett. 22 (2012) 3437–3440
3439
Table 2
Close analogues of 2m (3a–3h): affinities to rat dopamine D
2
, D
3
and
a-1 receptors.
Q2
N
N
O
CH3
N
CH3
N
H
2
m, 3a-3h
a
a
a
Code
Q
2
rD
0.71
15.9
1.6
4.95
3
-K
i
(nM)
rD
2
-K
i
(nM)
D
2
/D
3
Ratio
r
a-1-K
i
(nM)
3
a-1/D Ratio
2
3
3
3
3
3
3
3
3
m
a
b
c
d
e
f
g
h
2,3-Di-Cl-Ph
Ph
2-Cl-Ph
3-Cl-Ph
4-Cl-Ph
2,4-Di-Cl-Ph
2,5-Di-Cl-Ph
3,4-Di-Cl-Ph
3,5-Di-Cl-Ph
9.3
13.1
5.9
214
204
301
12.8
28.7
14.7
8.1
28.9
52.8
8.9
94.0
19.8
53.4
392
106
8.20
110
20.2
12.3
10.8
29.9
19.6
12.4
33.3
45.9
45.9
72.9
106.4
156
34.9
29.6
667
13.1
5.40
0.66
3.3
0.44
1516
a
i
Shown are the mean K values from two to four independent experiments with at least six concentrations in duplicates.
hypotensive liability of the analogues.12 Comparing affinities mea-
sured on rat dopamine D , D receptors and -1 adrenoceptors of
m to those of compounds 3a–3h showed that most of the deriv-
atives had lower affinity to the dopamine receptors than 2m. One
of the two exceptions (3f) had higher affinity to the -1 receptors
Acknowledgment
2
3
a
2
The authors are grateful to Tony Ainsworth and Derek Buckle
for their long standing support and encouragement.
a
while the other (3h), which showed the most promising receptor
profile, had lower metabolic stability (73% in rat and 58% in human
liver microsomes) compared to that of 2m (93% in rat and 96% in
human microsomes). These results indicated that among the
close analogues 2m had the most advantageous properties at this
level. It should be noted that 2m showed practically no affinity
Supplementary data
1
3
Supplementary data associated with this article can be found, in
the online version, at http://dx.doi.org/10.1016/j.bmcl.2012.03.
1
04. These data include MOL files and InChiKeys of the most
important compounds described in this article.
1 1 5
to other dopamine receptors (for rD , hD , hD4.2 and hD
IC50 > 1000 nM) and a set of other GPCRs and ion channels while
its affinity to some serotonin receptors (5HT1A, 5HT2A, 5HT2B and
References and notes
1
4
5
HT2C was comparable to that measured for D
3 2
and D receptors.
As part of the late phase screening cascade and subsequent pre-
1
.
Ágai-Csongor, É.; Nógrádi, K.; Galambos, J.; Vágó, I.; Bielik, A.; Magdó, I.; Ignácz-
clinical development cariprazine (2m) was subjected to detailed
neurochemical and in vivo pharmacological characterization.
Cariprazine demonstrated antagonist-partial agonist properties
Szendrei, Gy.; Keser u} , G. M.; Greiner, I.; Laszlovszky, I.; Schmidt, É.; Kiss, B.;
Sághy, K.; Laszy, J.; Gyertyán, I.; Zájer-Balázs, M.; Gémesi, L.; Domány, Gy.
Bioorg. Med. Chem. Lett. 2007, 17, 5340.
Kiss, B.; Laszlovszky, I.; Horváth, A.; Némethy, Zs.; Schmidt, É.; Bugovics, Gy.;
Fazekas, K.; Gyertyán, I.; Ágai-Csongor, É.; Domány, Gy.; Szombathelyi, Zs.
Naunyn-Schmiedeberg’s Arch. Pharmacol. 2008, 378, 515.
Gyertyán, I.; Sághy, K.; Laszy, J.; Elekes, O.; Kedves, R.; Gémesi, L. I.; Pásztor, G.;
Zájer-Balázs, M.; Kapás, M.; Ágai-Csongor, É.; Domány, Gy.; Kiss, B.;
Szombathelyi, Zs. Naunyn-Schmiedeberg’s Arch. Pharmacol. 2008, 378, 529.
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2
.
.
depending on actual dopaminergic tone that suggests its unique
dopamine system stabilizer character.14 Pharmacokinetic studies
3
in rat revealed that cariprazine has good absorption and excellent
brain penetration. The apparent terminal half-life (t1/2) in rats was
h following i.v. or p.o. administration. Brain concentrations of
4
5
6
.
.
.
2
cariprazine were much higher than plasma levels, with brain to
Kumar, A.; Srivastava, N.; Mital, A. Indian J. Chem., Sect B 1991, 30, 606.
plasma AUC ratio of 7.6:1.15 Its beneficial side effect and safety
7. The IR, 1H NMR, C NMR and MS spectra of the prepared compounds were
consistent with the assigned structures. Moreover, the purity of the samples
was checked by HPLC (two eluent systems) and HRMS analysis.
13
profile compared to several known antipsychotics have also been
demonstrated in several studies.15
8.
Ágai-Csongor, É.; Galambos, J.; Nógrádi, K.; Vágó, I.; Sághy, K.; Kiss, B.;
Laszlovszky, I.; Laszy, J.; Gyertyán, I. PCT Int. Appl. WO 2005/012266, 2005;
Chem. Abstr. 2005, 142, 198107.
In conclusion, the medicinal chemistry optimization of an
impurity isolated during the synthesis of compound 1 led to a ser-
ies of new piperazine/piperidine derivatives having high affinity to
9.
D
3
binding assay was carried out on rat recombinant D
3
receptors expressed in
3
Sf9 cells using [ H]spiperone (0.85 nM) as ligand and haloperidol (10 M) for
l
3 2
both dopamine D and D receptors. The most promising represen-
determination of non-specific binding. The assay was performed according to
tative of this family of compounds, 2m (INN:cariprazine hydro-
chloride) showed good pharmacokinetic profile with excellent
brain penetration, enhanced cognitive function and did not cause
catalepsy. Based on the promising non-clinical efficacy and safety
data the compound was selected for clinical development. The
proof of concept and dose finding clinical studies revealed the effi-
cacy and safety of cariprazine in patients with acute schizophrenia
Perkin–Elmer, Life and Analytical Sciences Assay Protocol (Cat. No. 3110139).
3
1
1
0.
D
2
binding assay: binding of [ H]spiperone (0.7 nM) to rat striatal membranes
was determined according to the method described in Creese et al. Eur. J.
Pharm. 1979, 60, 55–66. The non-specific binding was determined in the
presence of (+)-butaclamole (1 lM).
1. Apomorphine-induced climbing: One hour after the oral administration of the
vehicle or doses of the test compound, male CD1 mice were placed for
habituation into cylindrical cages with walls of vertical metal bars. At the end
of the 10 min adaptation period 1.5 mg/kg apomorphine HCl was administered
subcutaneously to the animals and they were replaced into the cages. The
measurement of climbing behaviour started 10 min after the apomorphine
treatment and lasted for 16 min. Every minute the climbing behaviour was
1
6,17
and mania.
The recently available top line results from pivotal
clinical trials demonstrated the safety and efficacy of cariprazine in
1
8
19
bipolar mania and schizophrenia indications. These positive
results validate the NDA filing of cariprazine as a new atypical
antipsychotic drug.
scored from 0 (four paws on the floor) to 2 (four paws grasping the bars).
3
12.
a
-1 binding assay: binding of [ H]-prazosin (0.5 nM) to rat cerebral cortical
membranes was determined according to the method described in Greengrass,

3
440
É. Ágai-Csongor et al. / Bioorg. Med. Chem. Lett. 22 (2012) 3437–3440
P.; Bremner, R. Eur. J. Pharmacol. 1979, 55, 32. The nonspecific binding was
determined in the presence of phentolamine (10 M).
3. Metabolic stability was assessed in vitro using human and rat liver
microsomes. Test compounds at 2.5 final initial concentration were
14. Kiss, B.; Horváth, A.; Némethy, Zs.; Schmidt, É.; Laszlovszky, I.; Bugovics, Gy.;
l
Fazekas, K.; Hornok, K.; Szabolcs, O.; Gyertyán, I.; Ágai-Csongor, É.; Domány,
Gy.; Tihanyi, K.; Adham, N.; Szombathelyi, Zs. J. Pharmacol. Exp. Ther. 2010, 333,
328.
1
l
M
incubated up to 20 min with human (XenoTech, USA) or rat (Richter,
Hungary) liver microsomes. Kinetic analysis of test substance consumption
was undertaken using linear regression (Graphpad Prism, 4.0). The plot of
substrate consumption against time was linear. In vitro intrinsic clearance
15. Gyertyán, I.; Kiss, B.; Sághy, K.; Laszy, J.; Szabó, Gy.; Szabados, T.; Gémesi, L. I.;
Pásztor, G.; Zájer-Balázs, M.; Kapás, M.; Ágai-Csongor, É.; Domány, Gy.;
Tihanyi, K.; Szombathelyi, Zs. Neurochem. Int. 2011, 59, 925.
16. Knesevich, M.; Papadakis, K.; Bose, A.; Wang, Q.; Korotzer, A.; Laszlovszky, I.
Bipolar Disord. 2009, 11, 54.
(
CLint) and metabolic bioavailability (FM) were calculated using the basic
concept of clearance prediction (1) according to the following equations:
FM = (1ÀEH) Â 100; EH = CLint/(CLint + HBF); CLint = Vmax/KM or if [S] << KM
CLint = V/S; EH = hepatic extraction ratio; HBF = hepatic blood flow;
17. Bose, A.; Li, D.; Migliore, R.; Papadakis, K.; Werner, P.; Németh, G.; Laszlovszky,
I. Int. J. Neuropsychopharmacol. 2010, 13, 88.
18. Company communication on February 8, 2012 http://www.richter.hu/EN/
Pages/220120208.aspx.
Vmax = maximal rate of enzyme reaction; KM = affinity constant of a
substrate; [S] = substrate concentration; V = actual rate of enzyme reaction
under first order conditions (Rane, A. et.al. J. Pharmacol. Exp. Ther., 1977, 200,
19. Company communication on February 28, 2012 http://www.richter.hu/EN/
Pages/pr120228e.aspx.
4
20–424).