of acute myeloid leukemia features two other cysteines (D1 and H2 position) which
could potentially be addressed. FF-10101 potently inhibits wild-type FLT3
(IC 50 ¼ 0.2 nM) and shows a high activity against a variety of leukemia cell lines
including those harboring quizartinib-resistance mutations. Along with several other
kinases, the compound potently hit the two related kinases KIT and FMS
(IC 50 ¼ 0.9 nM and 2.0 nM, respectively) and, to a lesser extent, the non-receptor
tyrosine kinase FGR (IC 50 ¼ 12 nM), all sharing a H3-GK + 4 cysteine. Binding to
Cys695 was demonstrated by X-ray crystallography (PDB: 5X02) and confirmed by
a set of experiments using the FLT3 C695S mutant and an unreactive analog.
FF-10101 showed promising effects in preclinical models and entered phase I/II
clinical trials as a potential treatment for patients with relapsed or refractory hematological malignancies (NCT03194685 and NCT02193958).
2.7 Development of Inhibitors Targeting Cysteines Around
the DFG Motif and in the Activation Segment
The activation segment is located between the conserved DFG and APE motifs and
contains the activation loop and the P + 1 loop. It represents a very flexible region
and is often poorly resolved in X-ray crystal structures. Thus, exhaustive analysis of
cysteine positioning and accessibility is complicated and structure-based design
approaches can be difficult to accomplish. A large set of kinases possesses cysteine
moieties in direct neighborhood to the DFG motif, either at the O2 subsite (DFG + 1/
2) or in the D1 position (DFG-1). Another set of cysteines can be found at the
a)
N
NH
N
Cl
NO 2
Cl
CF 3
N
H
O
O
N
H
N
CF 3
scaffold
morphing
N
N
H
O
O
N
H
N
CN
N
N
Me
O
H
N
OMe
66
FGF401
optimization
65
b)
N
N
H
N
Pr
HN
CN
H
N
O
N
O
NMe 2
c)
67
FF-10101
64
Fig. 24 (a) Irreversible FGFR4 inhibitor 64 engaging FGFR4-Cys552 via an S N Ar-electrophile.
(b) Covalent-reversible FGFR4 inhibitors relying on an aldehyde warhead. (c) Covalent FLT3
inhibitor FF-10101
74
M. Gehringer
could potentially be addressed. FF-10101 potently inhibits wild-type FLT3
(IC 50 ¼ 0.2 nM) and shows a high activity against a variety of leukemia cell lines
including those harboring quizartinib-resistance mutations. Along with several other
kinases, the compound potently hit the two related kinases KIT and FMS
(IC 50 ¼ 0.9 nM and 2.0 nM, respectively) and, to a lesser extent, the non-receptor
tyrosine kinase FGR (IC 50 ¼ 12 nM), all sharing a H3-GK + 4 cysteine. Binding to
Cys695 was demonstrated by X-ray crystallography (PDB: 5X02) and confirmed by
a set of experiments using the FLT3 C695S mutant and an unreactive analog.
FF-10101 showed promising effects in preclinical models and entered phase I/II
clinical trials as a potential treatment for patients with relapsed or refractory hematological malignancies (NCT03194685 and NCT02193958).
2.7 Development of Inhibitors Targeting Cysteines Around
the DFG Motif and in the Activation Segment
The activation segment is located between the conserved DFG and APE motifs and
contains the activation loop and the P + 1 loop. It represents a very flexible region
and is often poorly resolved in X-ray crystal structures. Thus, exhaustive analysis of
cysteine positioning and accessibility is complicated and structure-based design
approaches can be difficult to accomplish. A large set of kinases possesses cysteine
moieties in direct neighborhood to the DFG motif, either at the O2 subsite (DFG + 1/
2) or in the D1 position (DFG-1). Another set of cysteines can be found at the
a)
N
NH
N
Cl
NO 2
Cl
CF 3
N
H
O
O
N
H
N
CF 3
scaffold
morphing
N
N
H
O
O
N
H
N
CN
N
N
Me
O
H
N
OMe
66
FGF401
optimization
65
b)
N
N
H
N
Pr
HN
CN
H
N
O
N
O
NMe 2
c)
67
FF-10101
64
Fig. 24 (a) Irreversible FGFR4 inhibitor 64 engaging FGFR4-Cys552 via an S N Ar-electrophile.
(b) Covalent-reversible FGFR4 inhibitors relying on an aldehyde warhead. (c) Covalent FLT3
inhibitor FF-10101
74
M. Gehringer