Ponatinib is a multikinase inhibitor
that is used to treat chronic
myeloid leukemia patients harboring mutated ABL1(T315I) kinase. Due
to the potent inhibition of FLT3, RET, and fibroblast growth factor
receptors (FGFRs), it is also being evaluated against acute myeloid
leukemia (AML), biliary, and lung cancers. The multikinase inhibition
profile of ponatinib may also account for its toxicity, thus analogs
with improved kinase selectivity or different kinase inhibition profiles
could be better tolerated. The introduction of nitrogen into drug
compounds can enhance efficacy and drug properties (a concept called
“necessary nitrogen”). Here, we introduce additional
nitrogen into the benzamide moiety of ponatinib to arrive at nicotinamide
analogs. A nicotinamide analogue of ponatinib, HSN748, retains activity
against FLT3, ABL1, RET, and PDGFRα/β but loses activity
against c-Src and P38α. MNK1 and 2 are key kinases that phosphorylate
eIF4E to regulate the protein translation complex. MNK also modulates
mTORC1 signaling and contributes to rapamycin resistance. Inhibitors
of MNK1 and 2 are being evaluated for anticancer therapy. Ponatinib
is not a potent inhibitor of MNK1 or 2, but the nicotinamide analogs
are potent inhibitors of MNKs. This illustrates a powerful demonstration
of the necessary nitrogen concept to alter both the potency and selectivity
of drugs.