However, in cell-based assays, JNK-IN-8 shows slightly lower inhibitory activity
compared to JNK-IN-7 (IC 50 values of 486 nM and 333 nM in Hela and A375
cells, respectively) [18]. In a panel of 442 different protein kinases (also including
mutants), JNK-IN-8 only bound to two Kit mutants (V559D and V557D,T650I).
In a cellular kinase profiling versus distinct protein kinases, JNK-IN-8 exclusively
inhibited JNK1,2,3. Due to its excellent selectivity profile, the covalent pan-JNKinhibitor JNK-IN-8 was selected by the chemical probes portal as a tool compound
to further investigate the role of JNK1/2/3 inhibition (www.chemicalprobesportal.
org). However, the same portal recommends using JNK-IN-8 along with validated
JNK inhibitors as a positive control.
3.2 Pyridinylimidazole-Based Covalent Inhibitors
The concept of covalently targeting the JNK3 was also transferred to the reversible
JNK inhibitors of the 2-alkylsulfanyl-5-(pyridin-4-yl)imidazole series, which are
already optimized to interact with different regions in the ATP-binding site of
JNK3 (see Sect. 2.3) [34]. For targeting the mentioned cysteine side chain in the
JNKs, the electrophilic warhead was attached to the pyridine-C2-amino function
via a suitable linker (Fig. 16).
Fig. 14 X-ray structure of JNK-IN-7 in complex with JNK3 (PDB code: 3V6S). The protein
backbone is displayed as cartoon in gray. The compound and selected amino acids are highlighted
as sticks. Hydrogen bonds are shown as yellow dashed lines
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P. Koch
compared to JNK-IN-7 (IC 50 values of 486 nM and 333 nM in Hela and A375
cells, respectively) [18]. In a panel of 442 different protein kinases (also including
mutants), JNK-IN-8 only bound to two Kit mutants (V559D and V557D,T650I).
In a cellular kinase profiling versus distinct protein kinases, JNK-IN-8 exclusively
inhibited JNK1,2,3. Due to its excellent selectivity profile, the covalent pan-JNKinhibitor JNK-IN-8 was selected by the chemical probes portal as a tool compound
to further investigate the role of JNK1/2/3 inhibition (www.chemicalprobesportal.
org). However, the same portal recommends using JNK-IN-8 along with validated
JNK inhibitors as a positive control.
3.2 Pyridinylimidazole-Based Covalent Inhibitors
The concept of covalently targeting the JNK3 was also transferred to the reversible
JNK inhibitors of the 2-alkylsulfanyl-5-(pyridin-4-yl)imidazole series, which are
already optimized to interact with different regions in the ATP-binding site of
JNK3 (see Sect. 2.3) [34]. For targeting the mentioned cysteine side chain in the
JNKs, the electrophilic warhead was attached to the pyridine-C2-amino function
via a suitable linker (Fig. 16).
Fig. 14 X-ray structure of JNK-IN-7 in complex with JNK3 (PDB code: 3V6S). The protein
backbone is displayed as cartoon in gray. The compound and selected amino acids are highlighted
as sticks. Hydrogen bonds are shown as yellow dashed lines
218
P. Koch