Development of a potent and selective FLT3 kinase inhibitor by systematic expansion of a non-selective fragment-screening hit

Article abstract of DOI:10.1016/j.bmcl.2016.03.006

A non-selective inhibitor (1) of FMS-like tyrosine kinase-3 (FLT3) was identified by fragment screening and systematically modified to afford a potent and selective inhibitor 26. We confirmed that 26 inhibited the growth of FLT-3-activated human acute myeloid leukemia cell line MV4-11. Our design strategy enabled rapid development of a novel type of FLT3 inhibitor from the hit fragment in the absence of target-structural information.

Full text of DOI:10.1016/j.bmcl.2016.03.006

Accepted Manuscript
Development of a potent and selective FLT3 kinase inhibitor by systematic ex-
pansion of a non-selective fragment-screening hit
Hirofumi Nakano, Tsukasa Hasegawa, Riyo Imamura, Nae Saito, Hirotatsu
Kojima, Takayoshi Okabe, Tetsuo Nagano
PII:
S0960-894X(16)30226-8
DOI:
http://dx.doi.org/10.1016/j.bmcl.2016.03.006
BMCL 23649
Reference:
Bioorganic & Medicinal Chemistry Letters
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Revised Date:
Accepted Date:
9 January 2016
27 February 2016
3 March 2016
Please cite this article as: Nakano, H., Hasegawa, T., Imamura, R., Saito, N., Kojima, H., Okabe, T., Nagano, T.,
Development of a potent and selective FLT3 kinase inhibitor by systematic expansion of a non-selective fragment-
screening hit, Bioorganic & Medicinal Chemistry Letters (2016), doi: http://dx.doi.org/10.1016/j.bmcl.2016.03.006
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Development of a potent and selective FLT3
kinase inhibitor by systematic expansion of a
non-selective fragment-screening hit
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Hirofumi Nakano, Tsukasa Hasegawa, Riyo Imamura,
Nae Saito, Hirotatsu Kojima, Takayoshi Okabe, Tetsuo Nagano

Bioorganic & Medicinal Chemistry Letters
journal homepage: www.els evier.com
Development of a potent and selective FLT3 kinase inhibitor by systematic
expansion of a non-selective fragment-screening hit
Hirofumi Nakano a, Tsukasa Hasegawa a, Riyo Imamura a, Nae Saito a, Hirotatsu Kojima a, Takayoshi
Okabe a, and Tetsuo Nagano a, ∗
aDrug Discovery Initiative, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo, Japan
ARTICLE INFO
ABSTRACT
Article history:
Received
Revised
Accepted
Available online
A non-selective inhibitor (1) of FMS-like tyrosine kinase-3 (FLT3) was identified by fragment
screening and systematically modified to afford a potent and selective inhibitor 26. We
confirmed that 26 inhibited the growth of FLT-3-activated human acute myeloid leukemia cell
line MV4-11. Our design strategy enabled rapid development of a novel type of FLT3 inhibitor
from the hit fragment in the absence of target-structural information.
2009 Elsevier Ltd. All rights reserved
.
Keywords:
FLT3
Kinase inhibitor
Kinase selectivity
Fragment based drug discovery
Acute myeloid leukemia
———
∗ Corresponding author. Tel.: +81-3-5841-1989; fax: +81-3-5841-1959; e-mail:tlong@mol.f.u-tokyo.ac.jp

FMS-like tyrosine kinase 3 (FLT3), a class-III transmembrane
receptor-type tyrosine kinase, is a validated therapeutic target for
acute myeloid leukemia (AML).1 It is expressed mainly in
hematopoietic cells, and is activated by its extracellular ligand.
FLT3 signal cascades regulate the survival and proliferation of
hematopoietic cells, and uncontrolled over-activation causes
leukemia. About 30% of AML patients possess FLT3-activating
mutations, such as point mutation at D835 or internal tandem
domain repeat (ITD) mutation in the juxtamembrane domain.
These mutations have been reported to be associated with poor
prognosis. Therefore, FLT3 kinase is an attractive therapeutic
target for treatment of AML.
Figure 1. Hypothetical binding mode of 1.
A number of FLT3 inhibitors have been reported, but none
has yet been approved for clinical use.1 Compounds such as
lestaurtinib (CEP-701), midostaurin (PKC-412) and tandutinib
(MLN-518) are representative first-generation FLT3 inhibitors,
but they were not originally developed as FLT3 inhibitors, and
show broad kinase inhibition profiles or insufficient potency
against FLT3. Quizartinib (AC220) is a potent and selective
second-generation FLT3 inhibitor, which is in clinical trials.1,2
However, emergence of quizartinib-resistant FLT3-mutants has
already been reported.3
Compounds were synthesized as follows (Scheme 1). 1-15
were synthesized by amide coupling of aniline and carboxylic
acid precursors, both of which are commercially available. 13
was hydrolyzed to yield a carboxylic acid derivative, and then
coupled with secondary amines to furnish 16, 17, and 19-25. To
obtain 18, the resultant amide was deprotected under acidic
conditions. To obtain 26 and 27, 4-phenylpiperazine was reacted
with 4-nitrobenzyl bromide or 1-fluoro-4-nitrobenzene, and the
nitro groups were reduced. The resulting 4-substituted anilines
were coupled with indazole-3-carboxylic acid to obtain 26 and 27.
Drug candidates with different profiles can contribute to
cancer chemotherapy, since they can be used in a mutually
complementary fashion to manage inter-individual differences in
drug-metabolism and the emergence of resistance mutations. In
the case of FLT3, previously reported FLT3 inhibitors generate
non-overlapping drug-resistant mutants in vitro.4 In cancer
chemotherapy, it is a general strategy to treat patients with
several inhibitors belonging to different chemical classes. BCR-
ABL inhibitors, for example, are have different clinical spectra,
and multiple drugs have been marketed to cope with drug-
resistant mutants.5 In the case of FLT3, crenolanib (CP-868,596)
and gilteritinib (ASP2215) are in clinical trials to overcome
quizartinib resistance.6,7
Fragment screening is a strategy that provides opportunities to
search chemical space that has not been efficiently explored by
other methods. Typically, fragments are defined as small organic
molecules whose molecular weights (MWs) are in the range of
120-300 Da. It has been estimated that 107 fragments with up to
12 heavy atoms exist (average MW = 153, 87% of compounds
have MW ≤ 160).8 On the other hand, 1033 compounds can be
generated with up to 36 heavy atoms (MW ≤ 500).9 These
numbers imply that screening on a scale sufficient to provide
reasonable coverage of the chemical space is only practical for
molecules containing quite small numbers of atoms. In other
words, we may be more likely to pick up hit compounds with
novel types of structures if we focus on screening fragment
libraries.
Scheme
1.
Reagents
and
conditions:
(a)
1-ethyl-3-(3-
dimethylaminopropyl)carbodiimide hydrochloride, HOBt.H2O, DMF, 100oC,
6-83%; (b) 4 N NaOH, THF-MeOH, rt, 30%; (c) secondary amine, 1-ethyl-3-
(3-dimethylaminopropyl)carbodiimide hydrochloride, HOBt.H2O, DMF, rt,
10-99%; (d) For preparation of 18: TFA, CH2Cl2, rt, 48%; (e) 4-nitrobenzyl
bromide, Et3N, CH2Cl2, rt, 87%; (f) Fe powder, NH4Cl, EtOH-H2O, 80oC,
85%;
(g)
indazole-3-carboxylic
acid,
1-ethyl-3-(3-
dimethylaminopropyl)carbodiimide hydrochloride, HOBt.H2O, DMF, 100oC,
10%; (h) 1-fluoro-4-nitrobenzene, DMSO, rt, 85%; (i) NiCl2.6H2O, NaBH4,
MeOH, 0oC, then rt, 74%: (j) indazole-3-carboxylic acid, 1-ethyl-3-(3-
dimethylaminopropyl)carbodiimide hydrochloride, pyridine, rt, 28%.
To find fragments with FLT3-inhibitory activity, we screened
an in-house collection of 9,000 fragments. As a result, we
discovered 1 (MW = 237) as a potent FLT3 inhibitor (IC50 = 417
nM). Previously, 1 was reported as a CDK2-inhibiting fragment
(CDK2 IC50 = 3 µM).10 In a kinase selectivity study, we found
that 1 inhibited several kinases, including CDK2, in addition to
FLT3 (vide infra). Therefore, our next challenge was to improve
especially the selectivity, as well as the potency, of 1.
We hypothesized that 1 binds to the hinge region of FLT3 in
active form (Figure 1), as in the previously reported CDK2-1
analogue co-crystal structure (PDB ID: 2VTI), which contains
three hydrogen bonds in the hinge region.10 To validate this
hypothesis, we prepared derivatives of 1 that are unable to form
these hydrogen bonds by masking the proposed donor NHs with
methyl groups, or by replacing the putative acceptor N with CH
(Table 1, compounds 2-4). All three modified derivatives lost
potency, clearly confirming the importance of the three hydrogen
bonds for inhibitory potency, and supporting the idea that the
binding mode of FLT3-1 is similar to that reported for the
CDK2-1 analogue. The methylation of the amide nitrogen would
not only mask the hydrogen donor but also change the amide
conformation from trans (as shown in Figure 1) to cis. Such
conformation change would also be related to the potency loss of

2 because the phenyl ring in the cis-amide would not occupy the
hydrophobic pocket but clash with the protein.
than 50%. Improvement of selectivity was reflected in an
increase of the Gini coefficient to 0.678.
Structure-guided optimization of 1 was not feasible, because
the crystal structure of FLT3 in the active form has not been
reported, so systematic modification was the only way to evolve
1 into potent and selective lead compound.11 In order to rapidly
evaluate the potential of 1 as a starting compound, we focused on
modification of the aniline ring to obtain initial SAR, because
various aniline building blocks are commercially available, in
contrast to indazole-3-carboxylic acid derivatives.
Compound 26 showed an even better selectivity profile. We
found that converting the benzyl position from sp2 carbon (24) to
sp3 carbon (26) improved not only the potency, but also the
selectivity, presumably due to the three-dimensional character of
the sp3 carbon derivative.15 Inhibition rates of TRKA and HGK
were reduced to 81% and 63%, respectively. The IC50 value for
TRKA was 137 nM (15-fold selectivity vs FLT3), and that for
HGK was 410 nM (45-fold selectivity vs FLT3). The other 47
kinases were inhibited by less than 40%. The Gini coefficient
was improved from 0.678 to 0.757. Thus, we successfully
developed 26 as a potent and selective inhibitor of FLT3 by
simple, systematic structural evolution of fragment 1.
We first set out to identify appropriate positions in the aniline
ring to attach pendant functionalities to improve potency. By
scanning with
a
methyl group, methoxy group, and
methoxycarbonyl group, we found that the 4-position in the
aniline tolerates these modifications (Table 1, compounds 5-13).
Then, we examined 4-amide derivatives, and found that tertiary
amide 15 seemed promising for further modification.
Next, we synthesized various tertiary amide derivatives (Table
2). After comparing the potency of 15 (Table 1) and 16-19 (Table
2), we focused on piperazine amide derivatives. We attached
several moieties to the lateral NH group of the piperazine, and
found that a phenylpiperazine derivative, 24, potently inhibits
FLT3 with an IC50 value of 34 nM, which is a 10-fold
improvement over 1.
Further, we changed the linker moiety between the fragment
core and the pendant phenylpiperazine group. Transformation of
the linker from sp2 carbonyl to sp3 methylene improved the
potency (Table 2, compound 26), indicating that the flexible sp3
methylene linker allows the phenylpiperazine ring to interact
more efficiently with the protein. As expected, removal of the
linker resulted in loss of potency (27).
In addition to potency, we monitored the Ligand Efficiency
(LE) of the derivatives.12 Evolution of 1 into 26 resulted in a
change of the LE from 0.50 to 0.36, which is above the preferred
minimum score of 0.3 for lead compounds.12
Selective inhibition of the targeted kinase is a major concern
in the design of kinase inhibitors, because poor kinase selectivity
may cause unwanted side effects, such as cardiotoxicity.13 Kinase
selectivity data for 1, 24, and 26 are summarized in Fig. 2 and
Table S1 in Supporting Information. The compounds were tested
against a panel of 20 tyrosine kinases and 30 serine/threonine
kinases at a concentration 50-fold higher than the IC50 value in
FLT3 inhibition assay (carried out at Carna Biosciences, Japan).
To find suitable inhibitor concentrations for selectivity study, the
FLT3 IC50 values of 1, 24, and 26 were determined at Carna
Biosciences; they were found to be 350 nM, 23 nM, and 9 nM,
respectively. Therefore, 1, 24, and 26 were used at concentrations
of 17.5 µM, 1.15 µM, and 0.450 µM, respectively, in the kinase
selectivity study.
Figure 2. Kinase selectivity profiles of 1, 24, and 26. Selectivity was
evaluated against a panel of 50 kinases at a concentration 50 times higher
than the IC50 value for FLT3 (1: 17.5 µM, 24: 1.15 µM, 26: 0.450 µM). The
y axis shows % inhibition of each kinase.
To further evaluate the potential of 26, we carried out cell-
based experiments using the FLT3-ITD-harboring human
leukemia cell line MV4-11. In growth inhibition assay, 26
potently inhibited the growth of MV4-11 (IC50 = 164 nM), but
negligibly inhibited the growth of normal human diploid lung
fibroblast cell line WI-38, which was used as a surrogate for
general toxicity (Table 3). Next, we examined the
phosphorylation-inhibitory activity of 26. In MV4-11 cells, FLT3
is reported to auto-phosphorylate Tyr-596. MV4-11 cells were
incubated with 26 for 1.5 h, then lysed, and the phosphorylation
status of FLT3 was evaluated by western blotting. As shown in
Figure 3A, 26 dose-dependently inhibited phosphorylation of
FLT3. Finally, we examined whether or not 26 induces apoptosis
of MV4-11 cells during 48 h incubation, by means of Annexin V
staining (Figure 3B). As expected, 26 induced apoptosis, as has
been reported for the representative FLT3 inhibitor quizartinib.2c,d
These results indicate that 26 is a promising lead compound.
The selectivity profile of 1 shows almost complete inhibition
of two off-target kinases, TRKA and HGK, as well as FLT3
(Figure 2). In addition, 1 potently inhibited ITK, SYK and CDK2
by more than 70%. Other kinases that were inhibited by more
than 50% were JAK3 (52%), CK1ε (51%), DYRK1B (54%), and
GSK3β (51%). Overall selectivity was evaluated in terms of the
Gini coefficient,14 and the calculated score was 0.578.
The selectivity profile of 24 is cleaner than that of 1, as shown
in Fig. 2. Although TRKA and HGK, two major off-targets of 1,
were still potently inhibited by 24 (90% and 91%), the other off-
targets were much less potently inhibited. Besides TRKA and
HGK, ITK (51%) was the only kinase that was inhibited by more
To confirm the potential of 26 for further development, the in
vitro ADME properties were examined (Table 4).16 Among five
major CYP isozymes, CYP2C19 and CYP2D6 were inhibited
about 60% by 26 at 10 µM, and the others were inhibited by less

than 50%. Metabolic stability in human liver microsomes was
moderate, and a half of the compound was recovered after 1 h
incubation. In Caco-2 permeability assay, 26 showed moderate
permeability of 4 x 10-6 cm/s, indicating that the compound has
potential for oral administration. Improvement of the poor
aqueous solubility (3 µM in PBS, pH 7.4) is a major issue to be
addressed in further development.
In this letter, we report the development of a potent, selective,
and cell-active FLT3 inhibitor 26 by means of fragment-based
screening followed by systematic modification of the non-
selective inhibitor hit 1. By careful selection of suitable
substituents, we achieved significant improvement of both on-
target potency and selectivity.
Figure 3. Cellular study of compound 26. (A) Inhibition of auto-phosphorylation of FLT3 at Tyr-596 was evaluated by immunoblotting. MV4-11 was incubated
with 26 for 1.5 h. Lane 1: DMSO control; Lane 2: 1 µM; Lane 3: 0.3 µM; Lane 4: 0.1 µM; Lane 5: 0.03 µM. (B) Induction of apoptosis was evaluated by means
of Annexin V and PI staining. MV4-11 was incubated with compounds for 48 h.
Table 1. Effects of various substituents on FLT3-inhibitory potency
Compounds
R1
H
R2
H
R3
H
X
N
FLT3 IC50 (nM)a
417
LEb
0.50
NDc
NDc
NDc
NDc
0.47
0.48
NDc
0.43
0.45
NDc
NDc
0.40
0.42
0.42
1
2
H
H
>2000
>2000
>2000
>2000
443
Me
H
N
3
H
Me
H
N
4
H
CH
H
5
2-Me
H
H
N
N
N
N
N
N
N
N
N
N
N
6
3-Me
H
H
7
4-Me
310
H
H
8
2-OMe
3-OMe
4-OMe
2-COOMe
3-COOMe
4-COOMe
4-CONHMe
4-CONMe2
>2000
786
H
H
9
H
H
10
11
12
13
14
15
352
H
H
>2000
>2000
552
H
H
H
H
H
H
281
H
H
110
H
H
a IC50 values are shown as the average of two independent experiments (n = 4). [ATP] = 30 µM. b LE = –1.4•log(IC50)/HAC; HAC = heavy atom count. c Not
determined.

Table 2. Effects of 4-substituents on the aniline moiety upon FLT3-inhibitory potency.
Compound
R
FLT3 IC50
(nM)a
LEb
Compound
R
FLT3 IC50
(nM)a
LEb
16
107
0.39
22
46
0.33
O
17
18
19
113
61
0.37
0.39
0.38
23
24
25
42
34
56
0.29
0.33
0.26
N
O
N
O
95
20
21
90
43
0.37
0.33
26
27
10
0.36
NDc
>2000
a IC50 values are shown as the average of two independent experiments (n = 4). [ATP] = 30 µM. b LE = –1.4•log(IC50)/HAC; HAC = heavy atom count. c Not
determined.
Table 3. Cell growth-inhibitory potency of 1 and 26. a
FLT3-ITD-positive leukemia cell line
MV4-11 IC50 (nM)
Diploid lung fibroblast cell line
WI-38 IC50 (nM)
1
26
1
26
7,700
a Incubated for 48 h.
164
>10,000
>10,000
Table 4. In vitro ADME properties of 26.a
CYP (%)b
Human liver microsomes (%)c
50
Caco-2 (cm/s)d
4 x 10-6
Aqueous solubility (µM)e
1A2
36
2C9
36
2C19
2D6
62
3A4
48
57
3
a Carried out at Cerep. b Compound concentration was 10 µM. c % Remaining after incubation of 1 µM compound at 37oC for 1 h. d A-B permeability at 10 µM.
e Aqueous solubility in PBS, pH 7.4.
Carter, T. A.; Velasco, A. M.; Gunawardane, R. N.; Cramer, M.
D.; Gardner, M. F.; James, J.; Zarrinkar, P. P.; Patel, H. K.;
Acknowledgments
Bhagwat, S. S. J. Med. Chem. 2009, 52, 7808. (c) Gunawardane, R.
N.; Nepomuceno, R. R.; Rooks, A. M.; Hunt, J. P.; Ricono, J. M.;
Belli, B.; Armstrong, R. C. Mol. Cancer Ther. 2013, 12, 438. (d)
Kampa-Schittenhelm, K. M.; Heinrich, M. C.; Akmut, F.; Döhner,
H.; Döhner, K.; Schittenhelm, M. M. Molecular Cancer 2013, 12,
19.
This work was supported by the Platform for Drug Discovery,
Informatics and Structural Life Science from the Ministry of
Education, Culture, Sports, Science and Technology of Japan.
References and notes
3. Smith, C. C.; Wang, Q.; Chin, C.-S.; Salerno, S.; Damon, L. E.;
Levis, M. J.; Perl, A. E.; Travers, K. J.; Wang, S.; Hunt, J. P.;
Zarrinkar, P. P.; Schadt, E. E.; Kasarskis, A.; Kuriyan, J.; Shah, N.
P. Nature, 2012, 485, 260.
4. (a) von Bubnoff, N.; Engh, R. A.; Åberg, E.; Sänger, J.; Peschel,
C.; Duyster. J. Cancer Res. 2009, 69, 3032. (b) Williams, A. B.;
Nguyen, B.; Li, L.; Brown, P.; Levis, M.; Leahy, D.; Small, D.
Leukemia, 2013, 27, 48. (c) Smith, C. C.; Lasater, E. A.; Zhu, X.;
Lin, K. C.; Stewart, W. K.; Damon, L. E.; Salerno, S.; Shah, N. P.
Blood, 2013, 121, 3165.
1. (a) Prescott, H.; Kantarjian, H.; Cortes, J.; Ravandi, F. Expert
Opin. Emerging Drugs 2011, 16, 407. (b) Pemmaraju, N.;
Kantarjian, H.; Ravandi, F.; Cortes, J. Cancer, 2011, 117, 3293.
(c) Wander, S. A.; Levis, M. J.; Fathi, A. T. Ther. Adv. Hematol.
2014, 5, 65.
2. (a) Zarrinkar, P. P.; Gunawardane, R. N.; Cramer, M. D.; Gardner,
M. F.; Brigham, D.; Belli, B.; Karaman, M. W.; Pratz, K. W.;
Pallares, G.; Chao, Q.; Sprankle, K. G.; Patel, H. K.; Levis, M.;
Armstrong, R. C.; James, J.; Bhagwat, S. S. Blood 2009, 114,
2984. (b) Chao, Q.; Sprankle, K. G.; Grotzfeld, R. M.; Lai, A. G.;
5. (a) Desogus, A.; Schenone, S.; Brullo, C.; Tintori, C.; Musumeci,
F. Expert Opin. Ther. Patents 2015, 25, 397. (b) Zhang, J.; Adrián,
F. J.; Jahnke, W.; Cowan-Jacob, S. W.; Li, A. G.; Iacob, R. E.;

Sim, T.; Powers, J.; Dierks, C.; Sun, F.; Guo, G.-R.; Ding, Q.;
Okram, B.; Choi, Y.; Wojciechowski, A.; Deng, X.; Liu, G.;
Fendrich, G.; Strauss, A.; Vajpai, N.; Grzesiek, S.; Tuntland, T.;
Liu, Y.; Bursulaya, B.; Azam, M.; Manley, P. W.; Engen, J. R.;
Daley, G. Q.; Warmuth, M.; Gray, N. S. Nature, 2010, 463, 501.
F.; Lippke, J.; Saxena, K. Molecular Cell 2004, 13, 169. (b) Zorn,
J. A.; Wang, Q.; Fujimura, E.; Barros, T.; Kuriyan, J. PLoS ONE,
2015, 10, e0121177.
12. (a) Hopkins, A. L.; Groom, C. R.; Alex, A. Drug Discov. Today
2004, 9, 430. (b) Schultes, S.; de Graaf, C.; Haaksma, E. E. J.; de
Esch, I. J. P.; Leurs, R.; Krämer, O. Drug Discov. Today Technol.
2010, 7, e157.
13. (a) Hasinoff, B. B. Toxicol. Appl. Pharmacol. 2010, 244, 190. (b)
Hasinoff, B. B.; Patel, D. Toxicol. Appl. Pharmacol. 2010, 249,
132.
14. Graczyk, P. P. J. Med. Chem. 2007, 50, 5773.
15. Lovering, F. Med. Chem. Commun. 2013, 4, 515.
16. In vitro ADME assay was carried out at Cerep.
6. (a) Zimmerman, E. I.; Turner, D. C.; Buaboonnam, J.; Hu, S.;
Orwick, S.; Roberts, M. S.; Janke, L. J.; Ramachandran, A.;
Stewart, C. F.; Inaba, H.; Baker, S. D. Blood, 2013. 122, 3607. (b)
Galanis, A.; Ma, H.; Rajkhowa, T.; Ramachandran, A.; Small, D.;
Cortes, J.; Levis, M. Blood, 2014, 123, 94. (c) Smith, C. C.;
Lasater, E. A.; Lin, K. C.; Wang, Q.; McCreery, M. Q.; Stewart,
W. K.; Damon, L. E.; Perl, A. E.; Jeschke, G. R.; Sugita, M.;
Carroll, M.; Kogan, S. C.; Kuriyan, J.; Shah, N. P. Proc. Natl.
Acad. Sci. USA 2014, 111, 5319.
7. Myers, S. H.; Brunton, V. G.; Unciti-Broceta, A. J. Med. Chem. in
press.
8. Fink T.; Bruggesser H.; Reymond J.-L. Angew. Chem. Int. Ed.
Supplementary Material
2005, 44, 1504.
Details of chemistry, protocols of biological assay and raw
data of the kinase selectivity studies (compounds 1, 24 and 26).
9. Polishchuk, P. G.; Madzhidov, T. I.; Varnek, A. J. Comput. Aided
Mol. Des. 2013, 27, 675.
10. Wyatt, P. G.; Woodhead, A. J.; Berdini, V.; Boulstridge, J. A.;
Carr, M. G.; Cross, D. M.; Davis, D. J.; Devine, L. A.; Early, T.
R.; Feltell, R. E.; Lewis E. J.; McMenamin, R. L.; Navarro, E. F.;
O’Brien, M. A.; O’Reilly, M.; Reule, M.; Saxty, G.; Seavers, L. C.
A.; Smith, D.-M.; Squires, M. S.; Trewartha, G.; Walker, M. T.;
Woodford, A. J.-A. J. Med. Chem. 2008, 51, 4986.
11. Crystal structure of FLT3 in inactive form has been reported. (a)
Griffith, J.; Black, J.; Faerman, C.; Swenson, L.; Wynn, M.; Lu,