To clarify its binding mode, we carried out a docking study
with 29 in FGFR1 kinase domain. The proposed binding mode of
29 in the FGFR1 catalytic site were illustrated in Figure 3. The
pyrazolylaminoquinazoline core was in a planar conformation to
form three critical H-bonds to the hinge region: the pyrazolamine
NH and the adjacent pyrazole nitrogen of 29 formed two H-
bonds with the carbonyl and the amino group of alanine 564,
respectively; an additional H-bond occurred between the
backbone carbonyl group of glutamic acid 562 and the pyrazole
N-H. 3,5-Dimethoxylphenyl group penetrated into the back of
ATP pocket which was thought to exert selectivity,19 the phenyl
ring was in vicinity to alanine 640 (the distance between 2’-H to
the side chain of alanine 640 was approximately 4 Å ), the energy
penalty caused by a larger cysteine residue in VEGFR2 may offer
a potential rationale for the selectivity. The 5- and 6-positions of
the quinazoline were in close contact with the hinge region,
accounting for the low tolerance at these positions, while 2- and
8-positions had vectors pointing into more open space, the
piperazine moiety was protruded into the solvent region. The
binding model was consistent with the SAR described above,
which helped to rationalize the FGFR potency and selectivity.
Further structural optimization and biological evaluation of this
class of compounds are under way and will be reported in due
course.
Acknowledgments
We are grateful for financial support from the National
Natural Science Foundation of China (Grant Nos. 81273365,
81573271, 81473243, 81321092); The National Science &
Technology Major Project "Key New Drug Creation and
Manufacturing
2014ZX09304002-008-001,
Program"
of
China
(Grant
Nos.
The
2012ZX09301001-007).
Shanghai Science and Technology Commission (No.
1315431901300), SA-SIBS Scholarship Program is also
gratefully acknowledged.
References and notes
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The rapid onset of drug resistance is an important Achilles’
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of FGFR gatekeeper valine to methionine contributes to the faster
autophosphorylation rate seen in V561M FGFR1. Anderson
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Figure 4. Compound 29 (white) was docked into the asymmetric units of the
V561M FGFR1 (PDB ID: 4RWK), superimposition of 29 and AZD4547 in
different binding ways were shown respectively. AZD4547 is shown in
yellow, 29 in white.
In summary, we have identified pyrazolylaminoquinazoline
compounds as a new class of potent and selective FGFR
inhibitors. The representative compound 29 demonstrated
subnanomolar inhibition against FGFR2 in both enzymatic and
cellular assays, as well as exquisite selectivity over VEGFR2.
Compound 29 also strongly inhibited FGFR1–3 kinase activity
and suppressed FGFR signaling transduction in FGFR-addicted
cancer cells. In turn, 29 potently inhibited FGFR-driven cell
proliferation regardless of mechanistic complexity implicated in
FGFR activation, which further confirmed that 29 was a potent
pan-FGFR inhibitor. Docking study disclosed the binding mode
of 29 with the FGFR1 kinase domain, which helped to rationalize
the SAR study and selectivity. The flexibility of our structure
offered the potential to preserve good affinity for V561M FGFR1.