Discovery of new quinoline ether inhibitors with high affinity and selectivity for PDGFR tyrosine kinases

Article abstract of DOI:10.1016/j.bmcl.2012.03.074

A new series of quinoline ether inhibitors, which potently and selectively inhibit PDGFR tyrosine kinases, is described in this Letter. Compounds 23 and 33 are selective, low nanomolar inhibitors of PDGFRα and β, display good pharmacokinetics in rat and dog and are active in vivo at low doses when given orally twice daily. Further evaluation of these compounds is warranted.

Full text of DOI:10.1016/j.bmcl.2012.03.074

Bioorganic & Medicinal Chemistry Letters 22 (2012) 3050–3055
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Bioorganic & Medicinal Chemistry Letters
journal homepage: www.elsevier.com/locate/bmcl
Discovery of new quinoline ether inhibitors with high affinity and selectivity
for PDGFR tyrosine kinases
Patrick A. Plé a, , Frédéric Jung a, , Sue Ashton b, Laurent Hennequin a, Romuald Laine b,
⇑
⇑
Christine Lambert-van der Brempt a, Rémy Morgentin a, Georges Pasquet a, Sian Taylor b
a AstraZeneca, Centre de Recherches, B.P. 1050, 51689 Reims Cedex 2, France
b AstraZeneca Pharmaceuticals, Alderley Park, Macclesfield, Cheshire SK10 4TG, UK
a r t i c l e i n f o
a b s t r a c t
Article history:
A new series of quinoline ether inhibitors, which potently and selectively inhibit PDGFR tyrosine kinases,
Received 1 February 2012
Revised 19 March 2012
Accepted 21 March 2012
Available online 28 March 2012
is described in this Letter. Compounds 23 and 33 are selective, low nanomolar inhibitors of PDGFRa and
b, display good pharmacokinetics in rat and dog and are active in vivo at low doses when given orally
twice daily. Further evaluation of these compounds is warranted.
Ó 2012 Elsevier Ltd. All rights reserved.
Keywords:
PDGFR inhibitors
Selective
PDGFR
Inappropriate PDGFR
a
and PDGFRb are members of the class III RTK family.
and PDGFRb signaling has been linked to a
selective PDGFR inhibitor which could be combined with Cedira-
nibÒ7 our selective and very potent VEGFR-2 inhibitor.
a
number of proliferative disorders, gastrointestinal tumors (GIST)
dermato-fibrosarcoma protuberans (DFSP), idiopathic hypereosin-
ophilic syndrome (HES), chronic myelomonocytic leukemia
(CMML) and a sub-set of high-grade glioma.1 PDGFRb is also
expressed by pericytes, a cell type involved in the maturation and
H
N
H
N
N
N
O
O
N
O
N
stabilization of newly formed blood vessels.2,3 PDGFR
a
and/or
O
O
F
O
O
N
N
PDGFRb may also be found in tumor-associated fibroblasts.
VEGFR-2 (KDR) is a key mediator in tumor-driven angiogenesis.4
Inhibition of PDGFR could have significant anti-tumor activity in
N
AZD2932
Cediranib® (AZD2171)
niche tumors dependent on PDGF signaling and
a broader
application through effects on tumor vasculature, when combined
with VEGFR-2 inhibition.5 This combination would have the added
advantage of allowing varied levels of inhibition of each target as
well as different scheduling to maximize efficacy and minimize
any potential toxicity during human clinical trials.
As reported previously, replacement of the ether by an amino
linker caused a significant drop in activity against PDGFR but
improved the selectivity versus KDR and CSF-1R (compound 2).
Despite the decrease in activity, this was positive encouragement
that achieving selectivity for PDGFR was possible. Additionally,
previous work on anilino-quinazolines as c-Src inhibitors showed
that introduction of a methoxy group in meta -position of the
central phenyl ring gave substantial selectivity for c-Src over
KDR.8 This was rationalized by the nature of the gatekeeper residue
at the entrance of the hydrophobic pocket (a Thr in c-Src and a
more lipohilic Val residue in KDR). Similar methoxy substitution
was therefore investigated in this quinazoline ether series. When
introduced in the 2-position, activity versus PDGFR was retained
(3) while it was significantly reduced when placed in the 3-posi-
tion of the phenyl ring (4). The 2-methoxy group gave good levels
Since the clinical development of a combination of two novel
drugs can be quite complicated, we first sought
a mixed
PDGFR + VEGFR-2 small molecule inhibitor. This led to the discov-
ery of the quinazoline ether 1 (AZD2932).6 It has a mixed profile
with similar nanomolar IC50 levels for the inhibition of PDGFR
and VEGFR with additional activities for Flt-3 and c-Kit (Table 1).
In order to be able to modulate PDGFR and VEGFR-2 level of
inhibition in the clinic we then turned our attention to finding a
⇑
Corresponding authors.
E-mail address: patrick.ple@astrazeneca.com (P.A. Plé).
0960-894X/$ - see front matter Ó 2012 Elsevier Ltd. All rights reserved.
http://dx.doi.org/10.1016/j.bmcl.2012.03.074

P. A. Plé et al. / Bioorg. Med. Chem. Lett. 22 (2012) 3050–3055
3051
Table 1
In vitro SAR (IC50 lM)
2
H
N
R'
3
Ar
O
z
Y
R6
R7
X
N
#
R6; R7
X
Y
R0
Z
Ar
p-PDGFRb
p-KDR
p-CSF-1R
p-Flt3
1
2
3
4
5
6
7
8
9
MeO; MeO
MeO; MeO
MeO; MeO
MeO; MeO
MeO; MeO
H; MeO
MeO; H
H; F
N
N
N
N
C
C
C
C
C
C
C
C
C
C
C
C
C
C
C
C
N
C
C
C
C
C
C
C
C
C
C
C
C
O
NH
O
O
O
O
O
O
O
O
O
O
O
O
O
O
O
O
O
O
O
O
O
O
O
O
O
O
O
O
O
O
O
H
H
C
C
C
C
C
C
C
C
C
C
C
C
C
C
C
C
C
C
C
C
C
C
C
C
C
C
C
C
N
N
N
N
N
4-Pyrazolyl-1-iPr
4-Pyrazolyl-1-iPr
4-Pyrazolyl-1-Et
4-Pyrazolyl-1-Et
4-Pyrazolyl-1-Et
4-Pyrazolyl-1-Et
4-Pyrazolyl-1-Et
4-Pyrazolyl-1-Et
4-Pyrazolyl-1-Et
2-Thiazolyl-5-Me
3-Isoxazolyl-4,5-diMe
3-Isoxazolyl-4,5-diMe
3-Isoxazolyl-4,5-diMe
3-Isoxazolyl-4,5-diMe
3-Isoxazolyl-4,5-diMe
3-Isoxazolyl-5-Et
0.004
0.020
0.003
0.050
0.0009
0.0007
0.003
0.006
0.007
0.0003
0.0002
0.001
0.005
0.006
0.005
0.0004
0.004
0.002
0.0002
0.0005
0.050
0.006
0.004
0.010
0.009
0.005
0.005
0.005
0.002
0.020
0.003
0.004
0.003
0.008
0.485
>0.69
4.773
0.082
0.067
2.073
4.282
4.066
0.020
1.919
1.624
>10.0
>10.0
>10.0
0.020
0.515
1.277
0.003
0.004
>10.0
3.954
10.99
0.183
>10.0
2.481
>9.74
0.023
4.718
>10.0
0.245
>8.69
4.819
0.1
>1
0.5
>1
0.003
0.005
0.2
0.5
0.7
0.01
0.02
0.03
0.6
>0.9
>1
0.004
0.1
0.1
<0.0003
0.005
>1
0.05
0.2
0.3
0.5
0.1
0.1
0.009
0.02
0.08
0.3
0.6
0.2
0.007
0.02
>0.8
0.2
0.2
0.7
>1
>1
>1
>0.9
0.5
>1
>1
>1
>1
0.08
>1
2-MeO
3-MeO
2-MeO
2-MeO
2-MeO
2-MeO
2-MeO
2-MeO
2-MeO
2-MeO
2-MeO
2-MeO
2-MeO
2-MeO
2-MeO
2-MeO
2-MeO
2-MeO
2-MeO
2-MeO
2-MeO
H
F; H
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
H; MeO
MeO; MeO
H; MeO
MeO; H
H; F
F; H
H; MeO
H; MeO
H; MeO
MeO; MeO
H; MeO
MeO; MeO
MeO; MeO
H; MeO
MeO; MeO
H; MeO
H; MeO
H; MeO
H; MeO
H; MeO
H; MeO
MeO; MeO
MeO; MeO
MeO; EtO
3-Pyrazolyl-4,5-diMe
3-Pyrazolyl-4-Et
3-Pyrazolyl-5-Et
>1
0.06
0.3
>1
3-Pyrazolyl-5-Et
4-Pyrazolyl-1,3-diMe
4-Pyrazolyl-1,3-diMe
4-Pyrazolyl-1,3-diMe
4-Pyrazolyl-1,3-diMe
4-Pyrazolyl-1,5-diMe
4-Pyrazolyl-1-Me
5-Pyrazolyl-1,3-diMe
1-Phenyl-3-(CH2NMe2)-5-Me
4-Pyrazolyl-1-Et
4-Pyrazolyl-1,3-diMe
4-Pyrazolyl-1-Et
3-Pyrazolyl-4-Me 5-Et
3-Pyrazolyl-4-Me 5-Et
>1
>20
0.03
>1
>1
>1
0.3
>0.8
>1
0.04
>1
2-MeO
2-MeO
2-MeO
2-MeO
2-MeO
2-MeO
H
2-MeO
2-MeO
3
of selectivity versus all 3 kinases. Selectivity versus Flt-3 was antic-
ipated as the gatekeeper residue is a bulky and lipophilic Phe that
prevents adequate binding of the 2-methoxy phenyl group (Fig. 1).
At this point, compound 3 was further investigated but was
later dropped for low solubility and poor rat PK reasons. While
investigating the quinazoline series, several 6,7-dimethoxyquino-
linessuch as 5, 11, 19 and 22 were also synthesized. These mole-
cules were excellent PDGFR inhibitors, among the most potent
ones made so far. This warranted further investigation even though
the selectivity level was not as good as in the quinazoline series.
Among the heterocycles introduced on the right hand side of the
quinolines, we found that the presence of a methyl group next to
the amido function on the heterocycle dramatically improved the
selectivity against KDR (compare 19 and 32). Some of these analogs
have been modeled and docked into a homology model of PDGFR
based on the structure of c-Kit–Gleevec complex. The acetanilide
side chain is deeply buried into the pocket induced by the
DFG-out shift, characteristic of the inactive conformation of the en-
zyme. Overlay of this model with the 3D structure of KDR sug-
Gatekeeper
residue
Hinge
region
H c
gested that
a single residue located on helix-C should be
Figure 1. Compound 21 (gray) docked into the ATP binding site of Flt-3 (pdb code
1rjb14). For clarity only the hinge region is shown (green). The quinazoline N1
responsible for the selectivity versus KDR. A large but flexible
Met residue in PDGFR (and Flt-3) is replaced by a more rigid Leu
in KDR which should clash with the methyl group next to the ami-
do function. In the quinoline series the presence of a central meth-
oxy was also necessary for selectivity, particularly versus Flt-3
(compare 24 and 22).
makes
a classical H-bond with the hinge region (dotted line). Selectivity of
compound 21 for Flt-3 and KDR is illustrated. The Phe gatekeeper residue (orange)
in Flt-3 is too bulky to accommodate the 2-MeO substitution on the central phenyl
ring. The Met665 residue located on Helix C (Hc) in Flt-3 has been mutated into a
Leu (yellow) as present in KDR (Leu887), to illustrate the potential steric clash
between this residue and the CH3 substituent on the pyrazole ring.

3052
P. A. Plé et al. / Bioorg. Med. Chem. Lett. 22 (2012) 3050–3055
Table 2
The increased chemical stability of the ether link in the quino-
DMPK parameters in rat and dog
line compared to the quinazoline series, allowed the removal of
one methoxy group in either the 6 or 7-position as well as their
replacement by a fluorine atom. Monomethoxy or monofluoro-
quinolines can give compounds with greater selectivity while
retaining an excellent level of activity against PDGFR (compare 5
with 6–9; 11 with 12–15; 19 with 20; 22 with 23). A fluorine atom
in either 6 or 7 on the quinoline ring (8–9 and 14–15) gave gener-
ally the best levels of selectivity albeit with a slight drop in potency
versus PDGFR. The 7-methoxyquinolines having better PK than the
6-methoxy became the series of choice. Compared to the fluoro
series the 7-methoxy had the major advantage of making the
quinoline nitrogen more basic (ꢀ6.3 vs 5.3). This allowed the syn-
thesis of stable salts of these compounds to decrease the risk of po-
tential inter-individual bioavailability variations. In order to
increase the volume of distribution as well as the t1/2 of our inhib-
itors, we also tried to introduce moderately basic side chains. This
gave little success as we either lost selectivity (e.g., 28) or bioavail-
ability for these compounds (data not shown).
Compound 23
Compound 33
Rats
Dogs
Rats
Dogs
Dose
Cl
mg/kg po
ml/min/kg % HBF
20 (salt)
5.7
20 (salt)
2.5
3 (free base)
9
13
0.7
1.6
43
76
11.5
35
2.0
3.4
100
8
0.7
3.7
78
7
1.8
10.6
59–67
Vdss
IV t1/2
% F
L/kg
H
hERG
IC50
IC50
l
l
M
M
>100
All >10
1.8/4.3/0.9
6.3
P450a
All >8.6
3.8/5.6/3.0
6.0
% fu rat/dog/human
pKa
LogD
3.5
3.3
a
P450 tested: 1A2; 2C19; 2C9; 2D6; 3A4.
Flt3 selectivity
KDR selectivity
(CSF-1R)
The improved selectivity observed in the dimethoxyquinoline
series by introduction of steric bulk on the right hand side
heterocycle (vide supra) translated well in the 7-monomethoxy
series. A full investigation of the substitution pattern of our
best heterocycles was then carried out ( 6, 10, 12, 16–18, 20,
23 and 25–27).
O
H
N
N
N
O
O
H
Compound 23 stood out because of its overall balanced profile
both in vitro and in vivo with no P450 or hERG liabilities. It was
very stable in rat, dog and human plasma, had high permeability
(PAPP A->B: 27.10ꢁ6 cm/s) and a low potential for efflux. Having se-
lected the quinoline 23 we checked the profile of the correspond-
ing quinazoline but as can be seen from Table 1, the quinazoline
21 was 10-fold less potent versus PDGFR and gave poor oral rat
PK compared to 23.
O
N
CSF-1R selectivity
Figure 2. SAR overview of quinolines selective for PDGFR.
Using the free base, the clearance was low (2.4 ml/min/kg; 7% of
One parameter that could be improved in 23 was its modest
fraction unbound in human plasma (0.9%; Table 2). To do this we
replaced the central phenyl ring with a pyridine to increase the
hydrophilicity of the whole molecule. The first compounds made
were fairly disappointing with up to 10-fold loss in selectivity ver-
sus CSF-1R (e.g., 29 vs 23). In addition, 30, the direct pyridine analog
of 23, had a substantially reduced activity against PDGFR. As ex-
pected, removal of the methoxy group on the central pyridine
was also deleterious for the selectivity versus Flt-3 (31). Further
fine-tuning on the right hand side pyrazole substituents was there-
fore needed to identify a molecule with an adequate in vitro profile.
This investigation led to the pyrazole 32 which gave adequate levels
of selectivity. A final slight modification was done by replacement
of the 7-methoxy by an ethoxy group on the quinoline ring to give
33. An overview of the SAR summarizing the above discussion is
shown in Figure 2.
hepatic blood flow) for both sexes in dogs. This low clearance gave
a terminal iv half-life of 8.6 h with a mean steady state volume of
distribution of 1.4 L/kg.
Unlike the rat PK, exposure in dog was variable and dissolution
rate and solubility were considered to be major contributing
factors. A salt form of 23 was therefore required and the sulfate
was selected from a number of salts investigated. With it, the
bioavailability in rat was maintained around 78% (for a 3 mg/kg
dose) and varied only between 59% to 67% for the 4 dogs dosed
at 20 mg/kg (see Table 2). IV parameters were not affected. Most
importantly, the sulfate improved the consistency of the absorp-
tion and elimination phases.
For in vivo work, rat C6 glial tumors having constitutively acti-
vated PDGFR
since we had found that our series inhibited both PDGFR
PDGFRb to the same extent (23 has an IC50 of 3 nM versus PDGFR
a
were used as a surrogate for inhibition of PDGFRb
a
and
a
The synthetic routes and experimental conditions used in the
synthesis of the compounds described in this paper are described
in Schemes 1–4. Additional experimental details can be found in
Refs. 9,11–13.
Compound 33 was chosen over 32 based on superior rat PK
(lower clearance and longer t1/2. As expected, the fraction unbound
in plasma in all species was improved in this central pyridine sub-
series (Table 2) while its overall in vitro profile remained similar to
23 (Table 1).
and 4 nM vs b). In the nude rat model 23 gave >80% inhibition of
tumor growth at 3 or 12.5 mg/kg BID (Fig. 3).
In addition to the constitutively activated PDGFRa, phosphory-
lation of PDGFRb can also be induced in C6 rat glioma tissue by iv
administration of PDGFBB ligand just prior to cull. In tumor lysates
obtained at the end of a C6 tumor growth inhibition study (6 h post
last dose of 23), inhibition of PDGFRb phosphorylation followed the
same profile as inhibition of PDGFRa phosphorylation as shown in
Figure 4. This proves that 23 inhibits PDGFRa and b to the same
The rat clearance for the free base of 23 was approximately 8%
of the hepatic blood flow, the steady state volume of distribution
was 0.7 L/kg with a 3.7 h terminal iv half-life. Linear increase in
exposure was observed with doses up to 20 mg/kg.
level in vivo and fits with the in vitro data.
Finally, xenograft experiments using 23 (12.5 mg/kg BID) in a
combination dosing with a VEGFR-2 inhibitor (AZD2171 at 3 mg/
kg QD) gave even greater inhibition (Fig. 5), thus opening the
way for varied schedules and dose regimens of each inhibitor in
the clinic.
For compound 33 the clearance was approximately 13% of the
hepatic blood flow and the steady state volume of distribution in
In the quinazoline series both methoxy groups are needed to stabilize this ether
link.

P. A. Plé et al. / Bioorg. Med. Chem. Lett. 22 (2012) 3050–3055
3053
R'
R'
COOH
COOH
N
Y
Cl
O
N
R6
R7
R6
R6
R7
X
X
xii-xv
i-xi
N
R7
N
II
III
I
II
R’
Y
Cond.
I
R6
R7
X
Ref.
III
R’
Cond.
a
b
a
c
d
g
g
g
g
H
O
O
O
O
O
O
O
O
i
a
b
c
d
e
f
OMe
F
OMe
H
C
C
C
C
C
C
N
9,10
10
a
a
c
f
H
xii,vii
2-OMe
2-OMe
2-OMe
2-OMe
H
ii,iii
iv,v
vi,vii
vi,iii
viii
ix,vii
x
OMe
OMe
OMe
xiii,xiv
xiii,xiv
xiii,xv
H
OMe
F
10
H
10
OMe
OMe
OMe
H
OEt
OMe
10
11
3-OMe
2-OMe
H
g
10,12
NH
xi
Scheme 1. Reagents and conditions: (i) 4-hydroxyphenylacetic acid, Cs2CO3, DMF, 170 °C, 9 h, 69%, (ii) tert-butyl 2-(4-hydroxy-2-methoxyphenyl)acetate, Cs2CO3, DMF,
120 °C, 2 h, 86%, (iii) dioxane HCl, CH2Cl2, rt, 12 h, 94%, (iv) methyl 2-(4-hydroxy-2-methoxyphenyl)acetate, DMAP, chlorobenzene, 130 °C, 6 h, 58%, (v) NaOH, MeOH, H2O,
rt,1.5 h, 81%, (vi) tert-butyl 2-(4-hydroxy-2-methoxyphenyl)acetate, DMAP, chlorobenzene, 130 °C, 16 h, (65%, IIc) (54% IId) (vii) TFA, CH2Cl2, H2O, rt, 8 h, (89% IIc) (77% IIg)
(65% IIIa), (viii) 4-hydroxyphenylacetic acid, K2CO3, DMF, 9O °C, 5 h, 81%, (ix) tert-butyl 2-(4-hydroxy-3-methoxyphenyl)acetate, K2CO3, DMA, 9O °C, 2 h, 91%, (x) 4-hydroxy-
2-methoxyphenylacetic acid 5, K2CO3, DMA, 7O °C, 14 h, 87%, (xi) 4-aminophenylacetic acid, dioxane HCl, DMA, 110 °C, 4H, 45%, (xii) tert-butyl 2-(5-hydroxypyridin-2-
yl)acetate, DMAP, chlorobenzene, 130 °C, 8 h, 82%, (xiii) methyl 2-(5-hydroxy-3-methoxypyridin-2-yl)acetate, DMAP, chlorobenzene, 130 °C, 14 h, (89% IIIa) (77% IIIc) (78%
IIIf), (xiv) LiOH, THF/H2O, rt, 6 h, (74% IIIa) (100% IIIc), (xv) NaOH, THF/H2O, rt, 14 h, 92%. (See above-mentioned reference for further information.)
R'
R'
CONHAr
COOH
z
z
Y
N
Y
R6
R7
R6
i-xxxi
X
X
R7
N
R6
R7
X
Y
Z
R’
Cond.
Product
OMe OMe
OMe OMe
OMe OMe
OMe OMe
OMe OMe
N
N
N
N
C
C
C
C
N
C
C
C
C
C
O
NH
O
O
O
O
O
O
O
O
O
O
O
O
C
C
C
C
C
C
C
C
C
C
N
N
N
N
H
i
1
2
3
4
H
ii
2-OMe
3-OMe
2-OMe
2-OMe
2-OMe
2-OMe
2-OMe
H
2-OMe
H
2-OMe
2-OMe
iii
iv
v or ix, xvi, xix
5 or 11, 19, 22
H
H
F
OMe
F
vi or viii, x, xiii-xv, xvii, xx, xxii-xxv
6 or 10, 12, 16-18,20,23,25-28
vii or xi
8 or 14
15
H
xii
OMe OMe
OMe OMe
xviii
21
24
xxi
H
OMe
xxvi or xxvii, xxviii
29-30
31
OMe OMe
OMe OMe
OMe OEt
xxix
xxx
xxxi
32
33
Scheme 2. Reagents and conditions: (i) 1-propan-2-ylpyrazol-4-amine, 2-hydroxypyridine N-oxide, EDCI, DIEA, DMF, 50 °C, 2 h, 72%, (ii) 1-propan-2-ylpyrazol-4-amine,
HATU, DIEA, DMF, rt, 1 h, 70%, (iii) 1-ethylpyrazol-4-amine, 2-hydroxypyridine N-oxide, EDCI, DIEA, DMF, 60 °C, 14 h, 38%, (iv) As in (iii), 50 °C, 2 h, 59%, (v) 1-ethylpyrazol-4-
amine, HATU, DIEA, DMF, rt, 4 h, 74%, (vi) As in (v) 12 h, 16%, (vii) As in (v) 55%, (viii) 5-methyl-1,3-thiazol-2-amine, HATU, DIEA, DMF, rt, 9 h, 68%, (ix) 4,5-dimethyl-1,2-
oxazol-3-amine, HATU, DIEA, DMF, rt, 4 h, 12%, (x) As in (ix) 12 h, 42%, (xi) As in (ix) 70 °C, 14 h, 43%, (xii) As in (ix) 55 °C, 5 h, 45%, (xiii) 5-ethyl-1,2-oxazol-3-amine HATU,
DIEA, DMF, rt, 12 h, 56%, (xiv) 4,5-dimethyl-1H-pyrazol-3-amine, 2-hydroxypyridine N-oxide, EDCI, DIEA, DMF, 70 °C, 5 h, 31%, (xv) 4-ethyl-1H-pyrazol-3-amine, 2-
hydroxypyridine N-oxide, EDCI, DIEA, NMP, 85 °C, 16 h, 41%, (xvi) 5-ethyl-1H-pyrazol-3-amine, HATU, DIEA, DMF, 55 °C, 14 h, 32%, (xvii) As in (xvi) 60 °C, 24 h, 22%, (xviii)
1,3-dimethylpyrazol-4-amine, HATU, DIEA, DMF, rt, 14 h, 46%, (xix) As in (xviii), 1 h, 37%, (xx) As in (xviii), 65%, (xxi) As in (xviii), 3 h, 21%, (xxii) 1,5-dimethylpyrazol-4-
amine, HATU, DIEA, DMF, rt, 14 h, 77%, (xxiii) 1-methylpyrazol-4-amine, HATU, DIEA, DMF, rt, 14 h, 72%, (xxiv) 2,5-dimethylpyrazol-3-amine, HATU, DIEA, DMF, rt, 48 h, 62%,
(xxv) 3-(dimethylaminomethyl)-5-methylaniline, HATU, DIEA, DMF, rt, 24 h, 66%, (xxvi) As in (xvi) 11%, (xxvii) As in (v) 1 h, 62%, (xxviii) As in (xviii), 65%, (xxix) As in (v)
70 °C, 14 h, 24% (xxx) 2-tert-butyl-5-ethyl-4-methylpyrazol-3-amine, HATU, DIEA, DMA, rt, 16 h, 93% followed by TFA, anisole, 95 °C, 16 h, 50%, (xxxi) As in (xxx) 56% in last
step.
male rats was 0.7 L/kg with a 1.6 h terminal iv half-life. Linear in-
crease in exposure was seen with doses up to 40 mg/kg. For both
sexes the clearance in dogs for 33 was higher than for 23 (11.5
vs 2.5 ml/min/kg) and equated to 35% of hepatic blood flow. The
mean steady state volume of distribution was similar to 23
(2.0 L/kg). The combination of low volume of distribution and
moderate clearance gave rise to a shorter terminal iv half-life of
3.4 h, most likely still adequate for BID dosing in human. Bioavail-
ability was excellent at low doses (3 mg/kg) and further dog PK at
higher doses is ongoing. Evaluation of various salt forms is also

3054
P. A. Plé et al. / Bioorg. Med. Chem. Lett. 22 (2012) 3050–3055
2.5
O
O
O
Vehicle control
i
ii
Br
Cl
Br
Br
AZD2171 3mg/kg/day PO
23 at 12.5mg/kg BID PO
N
N
CN
N
COOMe
2.0
1.5
1.0
0.5
0.0
iii
23 at 12.5mg/kg BID + AZD2171
3mg/kg/day PO
O
O
iv
O
O
HO
B
N
COOMe
N
COOMe
Scheme 3. Reagents and conditions: (i) LiHMDS, CH3CN, THF, rt, 59%,9 (ii) TMSCl,
MeOH, 65 °C, 4 h, 85%, (iii) bis(pinacolato)diboron, PdCl2dppf, KOAc, 1,4-dioxane,
85 °C, 6 h, used without purification in next step, (iv) H2O2, CH2Cl2, rt, 1.5 h, 60%.
OMe
O
H
O
Cl
0
5
10
15
R6
R7
CONH-Ar
CONH-Ar
7, 9, 13
days after start of dosing
O
N
i, ii
R6
R7
N
Figure 5. EGFR (AZD2171) + PDGFR (23) inhibitors combination studies in C6 rat
glial xenograft in athymic (nude) mice.
R6
R7
F
H
H
being considered for this compound. Regarding in vivo activity,
OMe
compound 33 showed good potency in mouse C6 glial model with
70% inhibition of both PDGFRa and b at 6 h at 2 mg/kg po.
Scheme 4. Reagents and conditions: (i) Cs2CO3, DMF, 120 °C, 2.5 h, 82%, (for 9) (ii)
DMAP, chlorobenzene, 140 °C, 14 h, 68% and 60%, (for 7,13).
In conclusion, extensive exploration of C-4 quinoline ethers al-
lowed us to find potent and selective PDGFR inhibitors. These
agents inhibited the phosphorylation of PDGFRa and b in xenograft
tissue in a dose dependent manner and both 23 and 33 demon-
strated good PK parameters in rats and dogs. These data indicate
that 23 and 33 have the potential to become clinically useful
anti-angiogenic agents. Further in vivo and toxicology evaluations
of 23 and 33 are ongoing.
7.0
HPMC/Tween Control PO
6.0
5.0
4.0
3.0
2.0
1.0
0.0
23 at 12.5mg/kg/BID PO
23 at 3mg/kg/BID PO
Acknowledgments
We would like to acknowledge the excellent technical expertise
of the following scientists: -In vitro and in vivo biology: Claire
Barnes, Nicola Broadbent, Hannah Burn, Lee Cooper, Jack Dawson,
Karen Malbon, John Stawpert, Cliff Thurrell, Zena Wilson, Linda
Yarwood; -Chemistry: Alain Bertrandie, Myriam Didelot, Maryan-
nick Lamorlette, Mickael Maudet, Marie-Jeanne Pasquet; -NMR:
Christian Delvare; -Pharmacokinetics: Mike Hutton, Pamela Smith;
-Physical chemistry: Delphine Dorison-Duval; -Robotic synthesis:
Patrice Koza, Jacques Pelleter; -Large scale lab: Harj Bansal,
Dominique Boucherot, Stephen Brook, Ben McKeever, Walter
Grundy and Fabrice Renaud.
0
5
10
Days dosed
15
20
Figure 3. Tumor growth inhibition in the C6 rat glial xenograft in athymic (nude)
rats.
References and notes
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pPDGFR alpha
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pPDGFR beta
60
40
20
0
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2 x 25
2 x 12.5
dose (mg/kg)
2 x 6
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doses of 23.
a
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