Novel VEGFR-2 kinase inhibitors identified by the back-to-front approach

Article abstract of DOI:10.1016/j.bmcl.2013.03.042

We report a novel VEGFR-2 inhibitor, developed by the back-to-front approach. Docking experiments indicated that the 3-chloromethylphenylurea motif of the lead compound occupied the back pocket of VEGFR-2 kinase. An attempt was made to enhance the binding affinity of 1 by expanding the structure to access the front pocket using a triazole linker. A library of 1,4-(disubstituted)-1H-1, 2,3-triazoles were screened in silico, and one compound (VH02) was identified with an IC₅₀ against VEGFR-2 of 0.56 μM. VH02 showed antiangiogenic effects, inhibiting tube formation in HUVEC cells (EA.hy926) at 0.3 μM, 13 times lower than its cytotoxic dose. These enzymatic and cellular activities suggest that VH02 has potential as a lead for further optimization.

Full text of DOI:10.1016/j.bmcl.2013.03.042

Bioorganic & Medicinal Chemistry Letters 23 (2013) 2962–2967
Contents lists available at SciVerse ScienceDirect
Bioorganic & Medicinal Chemistry Letters
journal homepage: www.elsevier.com/locate/bmcl
Novel VEGFR-2 kinase inhibitors identified by the back-to-front
approach
Kingkan Sanphanya a, Suvara K. Wattanapitayakul b, Suwadee Phowichit b, Valery V. Fokin c,
Opa Vajragupta a,
⇑
a Excellent Center for Innovation in Drug Design and Discovery, Faculty of Pharmacy, Mahidol University, 447 Sri-Ayudya Rd, Bangkok 10400, Thailand
b Department of Pharmacology, Faculty of Medicine, Srinakharinwirot University, 114 Sukhumvit 23, Bangkok 10110, Thailand
c Department of Chemistry, The Scripps Research Institute, 10550 North Torrey Pines Rd, La Jolla, CA 92037, USA
a r t i c l e i n f o
a b s t r a c t
Article history:
We report a novel VEGFR-2 inhibitor, developed by the back-to-front approach. Docking experiments
indicated that the 3-chloromethylphenylurea motif of the lead compound occupied the back pocket of
VEGFR-2 kinase. An attempt was made to enhance the binding affinity of 1 by expanding the structure
to access the front pocket using a triazole linker. A library of 1,4-(disubstituted)-1H-1,2,3-triazoles were
Received 9 November 2012
Revised 10 February 2013
Accepted 12 March 2013
Available online 20 March 2013
screened in silico, and one compound (VH02) was identified with an IC50 against VEGFR-2 of 0.56
VH02 showed antiangiogenic effects, inhibiting tube formation in HUVEC cells (EA.hy926) at 0.3
l
l
M.
M,
Keywords:
VEGFR-2
KDR
VEGFR-2 inhibitor
Molecular modeling
Antiangiogenesis
1,4-Disubstituted 1,2,3-triazoles
CuAAC reaction
13 times lower than its cytotoxic dose. These enzymatic and cellular activities suggest that VH02 has
potential as a lead for further optimization.
Ó 2013 Elsevier Ltd. All rights reserved.
Receptor tyrosine kinases (RTKs) are a class of protein tyrosine
kinase that regulate inter- and intracellular communications by
signal transduction. These proteins play a major role in the regula-
tion of cell growth, proliferation, differentiation, survival and
metabolism.3,4 Among RTKs, vascular endothelial growth factor
receptor-2 (VEGFR-2) is a major target in suppressing cancer
growth and metastasis because of its vital role in the regulation
of angiogenesis.5–8
Tyrosine kinase inhibitors can be classified into two main types
according to binding pose. Type I inhibitors bind specifically to the
adenine-binding or ATP site of kinases in the active form, and type
II inhibitors bind to the ATP site and an additional hydrophobic
back pocket, an allosteric site found in the inactive form of the ki-
nase. Different conformations are observed in the active and inac-
tive states of tyrosine kinases at the beginning of the activation
loop, which is composed of the highly conserved triad Asp-
Phe-Gly (DFG). In the active state the kinase adopts a ‘DFG-in’
conformation, whereas in the inactive state it adopts a ‘DFG-out’
conformation (Fig. 1). Type II kinase inhibitors are generally more
selective than type I inhibitors.9–14 Thus, the binding site normally
targeted in the structure-based drug design of small-molecule
kinase inhibitors is composed of a front ATP-binding pocket and
a hydrophobic back pocket formed by the DFG-out conformation.15
In the front pocket, the two key amino acid residues that partici-
pate in H-bond interactions with the adenine ring of ATP are
Glu917 and Cys919, which are located in the hinge area of the
binding site. The two key amino acids in the back pocket that par-
ticipate in H-bond interactions are Glu885, locating in the aC-he-
lix, and Asp1046, a part of the DFG-motif in the activation loop.
Apparently, most VEGFR-2 inhibitors form hydrogen bonds with
these key amino acid residues.16–18
The ‘back-to-front’ approach—the design of type II kinase inhib-
itors starting from the back pocket and expanding the core struc-
ture towards the front pocket—is one strategy used in drug
development targeting protein kinases. This approach was success-
ful in finding lead p38
a
kinase inhibitors,19 cFMS kinase inhibi-
tors20 and VEGFR-2 inhibitors.21
We previously reported lead compound (1), 1-((3-chloro
methyl) phenyl)-3-(2-propynyl)urea, which inhibits EGFR. This
compound did not inhibit VEGFR-2 at the screening concentration
(1 l
M).22 In this work, we have attempted to develop a novel class
of VEGFR-2 inhibitors using 1 as the core structure, because dock-
ing simulations of 1 in the active site of VEGFR-2 kinase revealed
that this compound only occupied the allosteric site (Fig. 2). Both
urea HN moieties of 1 acted as hydrogen bond donors (HBD).
⇑
Corresponding author. Tel./fax: +66 26 448 695.
E-mail address: pyovj@mahidol.ac.th (O. Vajragupta).
0960-894X/$ - see front matter Ó 2013 Elsevier Ltd. All rights reserved.
http://dx.doi.org/10.1016/j.bmcl.2013.03.042

K. Sanphanya et al. / Bioorg. Med. Chem. Lett. 23 (2013) 2962–2967
2963
(a)
Front
(b)
E885
E885
K868
K868
E917
pocket
E917
Back
F1047
C919
pocket
C919
G1048
G1048
D1046
D1046
F1047
Figure 1. The binding site in the VEGFR-2 kinase domain, with key residues participating in H-bonds highlighted (a) DFG-in conformation (PDB code: 3B8R)1 showing the
ATP-binding site (red circle) and two salt bridges from Lys868 (green dotted lines); (b) DFG-out conformation (PDB code: 3EWH),2 showing the allosteric pocket (blue circle)
behind the ATP site.
Server23) before minimizing the energy (AMBER94 force field in
N
N
N
H
N
H
H
H
N
N
N
MOE—Molecular Operating Environment—Chemical Computing
Group, Montreal, Quebec, Canada). Nonpolar hydrogens from a
new template (3EWHOK) were merged before adding Gasteiger
Huckel charges (AutoDockTools-1.5.224,25). Then, atom types were
assigned, and a grid representation of 3EWHOK was prepared
(AutoGrid425). The 3EWHOK template was validated by docking
(AutoDock 4.2, TSRI)25 six active inhibitors (K11, AAX, GIG, LIF,
887 and 900, from PDB IDs 3EWH,2 1Y6B,26 2OH4,27 1YWN,28
3B8R,1 and 3B8Q,1 respectively). All docked poses were the same
as in the corresponding crystal structures, with RMSD less than
2 Å. These results indicated that 3EWHOK was a good VEGFR-2
model for in silico experiments.
Cl
Cl
R
O
O
1
E885
E917
Front
pocket
Back
pocket
C919
D1046
Virtual hits were selected by analysis of the docking results
(Fig. 3). The criteria for selecting hits were the free energy of
binding (DG), hydrogen bonding interaction with key amino acid
residues and docked conformation by visual inspection. In addi-
tion to two hydrogen bonds between core urea NH groups and
key residues in the back pocket (Asp1046 or Glu885), the virtual
hits were required to form extra hydrogen bonds with at least
one of the key residues in the ATP-binding pocket (either
Glu917 or Cys919). The docking results for eleven virtual hits
are summarized in Table 1.
Figure 2. ‘Back to front’ design strategy. Compound 1 (blue) as starting motif
buried in back pocket. Substituted group (R) on triazole to occupy the front pocket.
The hits (VH01–VH11) showed notably lower binding energy
comparing with compound 1 (Table 1). As anticipated, all com-
pounds occupied both back and front pockets in a similar manner,
with the phenylurea moiety buried in the hydrophobic back pocket
One urea HN interacted with the backbone carbonyl of Asp1046,
while the other interacted with that of Glu885. The urea carbonyl
moiety of 1 also acted as a hydrogen bond acceptor (HBA) by inter-
acting with the backbone NH-amide of Asp1046. The 3-chlorom-
ethylphenyl substructure was buried in the hydrophobic back
pocket and directed the terminal alkyne moiety to the front pocket.
Based on this data, 1 was chosen as the starting fragment in the
development of novel VEGFR-2 kinase inhibitors.
1
To design novel VEGFR-2 kinase inhibitors by the back-to-front
approach, we started by anchoring 1 in the hydrophobic back
pocket. Lead 1 possesses a terminal alkyne, a potential building
block for the preparation of 1,4-disubstituted-1H-1,2,3-triazoles,
by copper-catalyzed azide–alkyne cycloaddition (CuAAC). There-
fore a virtual library of [1-(substituted)-1H-[1,2,3]-triazol-4-yl]-
methyl-3-[30-(chloromethyl)phenyl]ureas was designed by adding
a substituent (R) to the triazole linker. The design strategy is to
extend the structure of phenylurea 1 with various substituents
(R) that fit the front pocket closely and thus increase the binding
affinity.
This library of 90 [1-(substituted)-1H-[1,2,3]-triazol-4-yl]-
methyl-3-[30-(chloromethyl)phenyl]ureas was screened virtually
by docking experiments. Details of VEGFR-2 template preparation
and validation were described previously.22 Briefly, the protein tar-
get was constructed from the crystal structure of inactive VEGFR-2
(DFG-out conformation) in complex with K11 (PDB ID: 3EWH).2
The two missing loops were reconstructed (Super Looper Web
N
N
H
N
H
N
N
R
C1
O
Virtual library
(90 compounds)
Docking with VEGFR-2 model
Rank
Filter
- ΔG < -8.0 kcal/mol
- Ligand efficiency < -0.30
- H-bond with key residues
front pocket (Glu917 and/or Cys919)
back pocket Glu885 and/or Asp1046
11 Virtual hits
Figure 3. In silico experiments to identify hits.

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K. Sanphanya et al. / Bioorg. Med. Chem. Lett. 23 (2013) 2962–2967
Table 1
Selected virtual hits for synthesisa
N
N
H
H
N
R
N
N
Cl
O
Compd
VH01
VH02
R
Free energy of binding
G, kcal/mol)
H-bonding with key residues
Glu885, Glu885, Cys919, Asp1046
Glu917, Cys919, Asp1046
(D
ꢀ9.60
ꢀ9.96
VH03
VH04
VH05
ꢀ10.13
ꢀ10.13
ꢀ10.95
Glu885, Cys919, Asp1046
Glu885, Glu885, Cys919, Asp1046
Glu885, Glu885, Cys919, Asp1046
VH06
VH07
ꢀ10.40
ꢀ10.48
Glu885, Glu885, Cys919, Asp1046
Glu885, Cys919
VH08
ꢀ10.65
Glu885, Glu885, Cys919, Asp1046
VH09
VH10
ꢀ10.42
ꢀ10.04
Glu885, Glu885, Cys919, Asp1046
Cys919, Asp1046
VH11
ꢀ10.41
Glu885, Glu885, Cys919
a
Docking result for 1: free energy of binding was ꢀ6.47 kcal/mol; H-bonding residues were Glu885, Asp1046 and Asp1046.
and the substituent (R) extended to fit the front pocket. The overlay
model of VH02 and sorafenib was illustrated in Figure 4.
cases, products were purified by column chromatography on silica
gel using 5–7% MeOH in dichloromethane as eluent (unoptimized
yields were 12–94%). All of the synthesized compounds were char-
acterized by IR, NMR and by high-resolution mass spectroscopy.
The assigned structures of all synthesized compounds were in agree-
ment with the designed structures (see Supplementary data).
All synthesized compounds were then screened for kinase inhi-
The selected virtual hits were synthesized for biological testing.
The general synthesis procedure for 11 hits was the CuAAC reaction
(Scheme 1). Briefly, 1 and one equivalent of the corresponding azide
building block were added into a 25 mL round-bottom flask and sus-
pended in t-BuOH/EtOH/H2O (2:1:1). Then 5 mol % of CuSO4 and
20 mol % of sodium ascorbate were added to the stirred reaction
mixture and heated at 60 °C for 1–2 h. The precipitates formed were
washed several times with cool diethyl ether before filtering. Pure
products were collected as off-white to yellow powders. In some
bition at 1 lM against three RTKs: VEGFR-2, EGFR and PDGFR-b
(Fig. 5). The ability of compounds to inhibit phosphorylation of a
biotinylated polypeptide substrate were measured by a previously
described protocol.22

K. Sanphanya et al. / Bioorg. Med. Chem. Lett. 23 (2013) 2962–2967
2965
Cys919, a key residue in the front pocket. The extra H-bond be-
tween VH02 and key residues observed in the front pocket of VEG-
FR-2 help to explain the activity of VH02 over other hits. In total,
VH02 formed 5 H-bonds with key amino acids in the binding site
of VEGFR-2 kinase. The indazolyl NH acted as HBD, forming one
hydrogen bond with the backbone carbonyl of Glu917, while the
N-2 indazole acted as HBA, forming a H-bond with the backbone
NH of Cys919. The aromatic part of the indazole ring interacted
with a hydrophobic region within the front pocket. This area com-
posed of the side chains of Leu840, Val848, Ala866, Lys868, Glu917
Phe918 and Gly922. The triazole linker of VH02 participated in one
H-bond, using the N-2 triazole as HBA to interact with the side
chain NH of Lys868. The urea moiety formed two hydrogen bonds
with key residues in the back pocket of VEGFR-2 kinase. Both urea
NH groups formed H-bonds with the same backbone carbonyl of
Asp1046. The substituted phenyl motif of VH02 was buried in
the hydrophobic part of the back pocket and interacted with the
side chains of Ile888, Ile892, Val898, Val899, Leu1019, His1026,
Ile1044, Cys1045 and Phe1047. The hydrophobic interactions both
in the front and allosteric pocket moderated the binding affinity
and selectivity by stabilizing the proper conformation of the com-
pound in the binding site of VEGFR-2 kinase.
The docking of VH02 and sorafenib against VEGFR2 revealed
that VH02 aligned in the binding site of VEGFR-2 in the similar
way to that of sorafenib with % members in the highest cluster
of 74% and 81% for VH02 and sorafenib, respectively. Polar sub-
structures of both VH02 and sorafenib occupied the front ATP-
binding pocket and less polar substructures of both compounds
buried in the hydrophobic back pocket (Fig. 4). It was found that
VH02 bound with VEGFR-2 with higher free binding energy
(ꢀ9.96 kcal/mol vs ꢀ14.92 kcal/mol) and formed less numbers of
H-bond interaction with key residues in both pockets (5 H-bonds
vs 3 H-bonds) which may be the main reason for less potency of
VH02 as VEGFR-2 inhibitor.
E885
E917
Back
pocket
Front
pocket
D1046
C919
Figure 4. Overlay model of VH02 (blue) and sorafenib (magenta) bound to the
VEGFR-2 kinase domain (PDB code: 3EWHOK),2 showing 4 H-bonds in front and
back pockets (green dotted lines).
N
N
H
N
H
H
H
N
R
N
N
N
Cl
Cl
N3
R
O
O
a
1
VH01-VH11
(12-94% yield)
Scheme 1. Synthesis of selected virtual hits by CuAAC reaction. (a) 5 mol % CuSO4,
20 mol % sodium ascorbate, t-BuOH/EtOH/H2O (1:1:2), 60 °C, 1–2 h.
90
VEGFR2
80
EGFR
70
60
50
40
30
20
10
0
PDGFR-b
The docking between VH02 and the active site of EGFR kinase
was performed and compared with erlotinib, the prototype of EGFR
inhibitor; the docking result of VH02 against EGFR answered the
observed poor activity of this compound against EGFR. Instead of
anchoring in the hydrophobic back pocket as expected, the 1-((3-
chloromethyl)phenyl)-3-urea substructure of VH02 pointed out
to the water accessible cavity of EGFR binding site while the inda-
zole–triazole substructure aligned in the back hydrophobic cavity
(Fig. 6). No hydrogen bond interaction was observed between
VH02 and the backbone carboxylate of conserved Met769, a hinge
residue in the ATP site, while erlotinib established a hydrogen
Figure 5. Screening result at 1
l
M of hit compounds against three tyrosine kinases.
At 1
compound that noticeably inhibited phosphorylation of VEGFR-2.
The IC50 of VH02 against VEGFR-2 was 0.56 M. Modest inhibition
lM VH02, the 6-indazolyl triazole derivative was the only
l
of EGFR was observed for all synthesized compounds. Only the 5-
indazolyl triazole (VH03) exhibited activity against EGFR compara-
ble to 1, while the other extended triazoles exhibited diminished
potency against this tyrosine kinase. Inhibition of PDGFR-b was
not observed for any compound. Though its inhibition against VEG-
FR kinase was not as potent as sorafenib (IC50 = 90 nM)29,30, VH02
from in silico screening was considered as the most promising lead
VEGFR-2 inhibitor.
The kinase inhibitory activity of VH02 against VEGFR-2 can be
explained by its binding mode from molecular modeling. Though
the binding energy of VH02 was not significantly different from
other hits, the H-bonding interaction between VH02 and key resi-
dues in the front pocket of VEGFR-2 kinase was different from the
others. The 6-indazolyl substructure of VH02 formed two hydrogen
bond interactions with the key residues, Glu917 and Cys919, in the
front pocket of VEGFR-2 kinase, while the corresponding triazole
substructures (R) of other hits formed only one H-bond with
Lys721
Val702
Lys704
Leu694
Ala719
Erlotinib
Glu738
VH02
Met742
Phe832
Asp831
Pro770
Phe771
Met769
Gly772
Cys751
Thr830
Leu820
Figure 6. The overlay between docked-pose of VH02 (magenta) and erlotinib
(yellow) in the active site of EGFR (PDB code: 1M17).

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K. Sanphanya et al. / Bioorg. Med. Chem. Lett. 23 (2013) 2962–2967
Figure 7. Effect of VH02 on VEGF-stimulated tube formation at 10ꢁ magnification. (a) 0.1% DMSO; (b) control with VEGF 25 ng/mL (c) and (d) treatment with VH02 0.3 and
1.0 M, respectively.
l
bond with this key amino acid residue (see Supplementary Data).
In addition, the possibility of VH02 to conform in good binding
pose is low, % conformations in the highest cluster was signifi-
cantly lower (45% vs 100%) despite of better affinity than erlotinib
(ꢀ9.10 kcal/mol vs ꢀ7.48 kcal/mol).
The antiproliferative results indicated that VH02 exhibited higher
selectivity against EA.hy926 (representing vascular endothelial
cells), with weak cytotoxicity against other cancer cells. Thus, this
compound may be useful in the treatment of cancer, to avoid
metastasis as well as to prolong time to recurrence with low
toxicity.
In this study, molecular modeling protocol aided us in rapidly
screening for potential hit compounds from a number of virtual
compounds in the focus library. Back-to-front approach was
proved to be an efficient strategy in drug design since the amino
acid residues in the back pocket areas of each kinase were less con-
served when comparing with those in the front pocket. The flipping
of anchoring motif from the back pocket to front pocket signifi-
cantly affected both selectivity and potency of the designed com-
pound as observed in compound 1 and VH02 against EGFR and
VEGFR-2.
In conclusion, VH02 was developed as a novel lead VEGFR-2
kinase inhibitor by a back-to-front approach, starting from a 3-
(30-chloromethylphenyl)urea fragment. A triazole ring was used
as linker, due to its convenient synthesis by the CuAAC reaction.
Enzyme inhibition and cellular activity indicated that this com-
pound is an antiangiogenic agent that selectively inhibits VEG-
FR-2. Though it was not as potent as sorafenib, VH02 can be
considered a promising lead with a novel scaffold, suitable for
further optimization.
VH02 was further evaluated for antiangiogenic effects. This
compound was first screened for antiproliferative activity in
immortal HUVECs (EA.hy926), which are frequently used for
in vitro angiogenesis testing.31–33 The protocol for the antiprolifer-
ation assay was described previously.22
The IC50 for VH02 cytotoxicity against EA.hy926 was 4
which was comparable to that of sorafenib against HUVEC
(IC50 = 4–5
M)34 despite of moderate inhibition against VEGFR2
lM
l
kinase. The in vitro antiangiogenic effect of VH02 was evaluated
in a tube formation assay. The test was performed at a non-cyto-
toxic concentration to avoid false positives from the cytotoxicity.
The results from the tube formation assay are shown in Figure 7.
VH02 significantly inhibited tube formation at 0.3 lM, which
was 13 times lower than its cytotoxic IC50 against EA.hy926. Addi-
tionally, the antiproliferative activity of VH02 was investigated in
four other cancer cell lines, including cervical cancer (HELA), hu-
man breast cancer (MCF-7), large cell lung cancer (H460) and he-
patic carcinoma (HepG2). The results are summarized in Table 2.
Table 2
Acknowledgments
Antiproliferative effect of VH02 on cancer cells and
EA.hy926
This work was supported by the Royal Golden Jubilee Ph.D. Pro-
gram (RGJ Grant No. PHD/0229/2547), Thailand Research Fund
(TRF), The Office of the Higher Education Commission, Ministry
of Education, Thailand (CHE-RG 2551) and the Office of the High
Education Commission and Mahidol University under the National
Research Universities Initiative.
Type of cancer cells
IC50 (lM)
HELA
MCF-7
H460
HepG2
EA.hy 926
33
21
71
>100
4

K. Sanphanya et al. / Bioorg. Med. Chem. Lett. 23 (2013) 2962–2967
2967
18. Sammond, D. M.; Nailor, K. E.; Veal, J. M.; Nolte, R. T.; Wang, L.; Knick, V. B.;
Rudolph, S. K.; Truesdale, A. T.; Nartey, E. N.; Stafford, J. A.; Kumar, R.; Cheung,
M. Bioorg. Med. Chem. Lett. 2005, 15, 3519.
19. Regan, J.; Breitfelder, S.; Cirillo, P.; Gilmore, T.; Graham, A. G.; Hickey, E.; Klaus,
B.; Madwed, J.; Moriak, M.; Moss, N.; Pargellis, C.; Pav, S.; Proto, A.; Swinamer,
A.; Tong, L.; Torcellini, C. J. Med. Chem. 2002, 45, 2994.
20. Baldwin, I.; Bamborough, P.; Haslam, C. G.; Hunjan, S. S.; Longstaff, T.; Mooney,
C. J.; Patel, S.; Quinn, J.; Somers, D. O. Bioorg. Med. Chem. Lett. 2008, 18, 5285.
21. Iwata, H.; Oki, H.; Okada, K.; Takagi, T.; Tawada, M.; Miyazaki, Y.; Imamura, S.;
Hori, A.; Lawson, J. D.; Hixon, M. S.; Kimura, H.; Miki, H. ACS Med. Chem. Lett.
2012, 3, 342.
22. Sanphanya, K.; Wattanapitayakul, S. K.; Prangsaengtong, O.; Jo, M.; Koizumi, K.;
Shibahara, N.; Priprem, A.; Fokin, V. V.; Vajragupta, O. Bioorg. Med. Chem. Lett.
2012, 22, 3001.
23. Hildebrand, P. W.; Goede, A.; Bauer, R. A.; Gruening, B.; Ismer, J.; Michalsky, E.;
Preissner, R. Nucleic Acids Res. 2009, 37, W571.
24. Forli, S.; Botta, M. J. Chem. Inf. Model. 2007, 47, 1481.
25. Morris, G. M.; Huey, R.; Lindstrom, W.; Sanner, M. F.; Belew, R. K.; Goodsell, D.
S.; Olson, A. J. J. Comput. Chem. 2009, 30, 2785.
26. Harris, P. A.; Cheung, M.; Hunter, R. N.; Brown, M. L.; Veal, J. M.; Nolte, R. T.;
Wang, L.; Liu, W.; Crosby, R. M.; Johnson, J. H.; Epperly, A. H.; Kumar, R.;
Luttrell, D. K.; Stafford, J. A. J. Med. Chem. 2005, 48, 1610.
27. Hasegawa, M.; Nishigaki, N.; Washio, Y.; Kano, K.; Harris, P. A.; Sato, H.; Mori,
I.; West, R. I.; Shibahara, M.; Toyoda, H.; Wang, L.; Nolte, R. T.; Veal, J. M.;
Cheung, M. J. Med. Chem. 2007, 50, 4453.
28. Miyazaki, Y.; Matsunaga, S.; Tang, J.; Maeda, Y.; Nakano, M.; Philippe, R. J.;
Shibahara, M.; Liu, W.; Sato, H.; Wang, L.; Nolte, R. T. Bioorg. Med. Chem. Lett.
2005, 15, 2203.
29. Wilhelm, S. M.; Carter, C.; Tang, L.; Wilkie, D.; McNabola, A.; Rong, H.; Chen, C.;
Zhang, X.; Vincent, P.; McHugh, M.; Cao, Y.; Shujath, J.; Gawlak, S.; Eveleigh, D.;
Rowley, B.; Liu, L.; Adnane, L.; Lynch, M.; Auclair, D.; Taylor, I.; Gedrich, R.;
Voznesensky, A.; Riedl, B.; Post, L. E.; Bollag, G.; Trail, P. A. Cancer Res. 2004, 64,
7099.
30. Gollob, J. A.; Wilhelm, S.; Carter, C.; Kelley, S. L. Semin. Oncol. 2006, 33, 392.
31. Wu, H.-T.; Lin, S.-h.; Chen, Y.-H. J. Agric. Food Chem. 2005, 53, 5164.
32. Cong, M.; Xue-chun, L.; Yun, L.; Jian, C.; Bo, Y.; Yan, G.; Xian-feng, L.; Li, F. Chin.
Med. J. 2012, 125, 1369.
Supplementary data
Supplementary data associated with this article can be found, in
the online version, at http://dx.doi.org/10.1016/j.bmcl.2013.03.
042.
References and notes
1. Weiss, M. M.; Harmange, J.-C.; Polverino, A. J.; Bauer, D.; Berry, L.; Berry, V.;
Borg, G.; Bready, J.; Chen, D.; Choquette, D.; Coxon, A.; DeMelfi, T.; Doerr, N.;
Estrada, J.; Flynn, J.; Graceffa, R. F.; Harriman, S. P.; Kaufman, S.; La, D. S.; Long,
A.; Neervannan, S.; Patel, V. F.; Potashman, M.; Regal, K.; Roveto, P. M.; Schrag,
M. L.; Starnes, C.; Tasker, A.; Teffera, Y.; Whittington, D. A.; Zanon, R. J. Med.
Chem. 2008, 51, 1668.
2. Cee, V. J.; Cheng, A. C.; Romero, K.; Bellon, S.; Mohr, C.; Whittington, D. A.; Bak,
A.; Bready, J.; Caenepeel, S.; Coxon, A.; Deak, H. L.; Fretland, J.; Gu, Y.; Hodous,
B. L.; Huang, X.; Kim, J. L.; Lin, J.; Long, A. M.; Nguyen, H.; Olivieri, P. R.; Patel, V.
F.; Wang, L.; Zhou, Y.; Hughes, P.; Geuns-Meyer, S. Bioorg. Med. Chem. Lett.
2009, 19, 424.
3. Zwick, E.; Bange, J.; Ullrich, A. Trends Mol. Med. 2002, 8, 17.
4. Culhane, J.; Li, E. US Pharm. 2008, 33, 3.
5. Folkman, J. Semin. Oncol. 2002, 29, 15.
6. Hoeben, A.; Landuyt, B.; Highley, M. S.; Wildiers, H.; Van Oosterom, A. T.; De
Bruijn, E. A. Pharmacol. Rev. 2004, 56, 549.
7. Schenone, S.; Bondavalli, F.; Botta, M. Curr. Med. Chem. 2007, 14, 2495.
8. Holmes, K.; Roberts, O. L.; Thomas, A. M.; Cross, M. J. Cell. Signal. 2003, 2007, 19.
9. Liu, Y.; Gray, N. S. Nat. Chem. Biol. 2006, 2, 358.
10. Zhang, J.; Yang, P. L.; Gray, N. S. Nat. Rev. Cancer 2009, 9, 28.
11. Okram, B.; Nagel, A.; Adrian, F. J.; Lee, C.; Ren, P.; Wang, X.; Sim, T.; Xie, Y.;
Wang, X.; Xia, G.; Spraggon, G.; Warmuth, M.; Leu, Y.; Gray, N. S. J. Chem. Biol.
2006, 13, 779.
12. Zuccotto, F.; Ardini, E.; Casale, E.; Angiolini, M. J. Med. Chem. 2010, 53, 2681.
13. Kufareva, I.; Abagyan, R. J. Med. Chem. 2008, 51, 7921.
14. Xie, Q.-Q.; Xie, H.-Z.; Ren, J.-X.; Li, L.-L.; Yang, S.-Y. J. Mol. Graph. Model. 2009,
27, 751.
15. Schwartz, P. A.; Murray, B. W. Bioorg. Chem. 2011, 39, 192.
16. Bauer, D.; Whittington, D. A.; Coxon, A.; Bready, J.; Harriman, S. P.; Patel, V. F.;
Polverino, A.; Harmange, J.-C. Bioorg. Med. Chem. Lett. 2008, 18, 4844.
17. Honda, T.; Nagahara, H.; Mogi, H.; Ban, M.; Aono, H. Bioorg. Med. Chem. Lett.
2011, 21, 1782.
33. Jones, M. K.; Sarfeh, I. J.; Tarnawski, A. S. Biochem. Biophys. Res. Commun. 1998,
249, 118.
34. Plastaras, J. P.; Kim, S.-H.; Liu, Y. Y.; Dicker, D. T.; Dorsey, J. F.; McDonough, J.;
Cerniglia, G.; Rajendran, R. R.; Gupta, A.; Rustgi, A. K.; Diehl, J. A.; Smith, C. D.;
Flaherty, K. T.; El-Deiry, W. S. Cancer Res. 2007, 67, 9443.