The family of Fibroblast Growth Factor Receptors (FGFRs) is an important class of validated targets for cancer therapeutics as they play a crucial role in tumor proliferation, angiogenesis, migration, and survival. Mutations and overexpression of FGFRs and their ligands have been reported in cancers from several tissues, such as breast, lung, bladder, and liver. Amplification and activating mutations of FGFR4, for instance, have been described in 8% of rhabdomyosarcoma patients. Furthermore, it is estimated that 30% of patients with hepatocellular carcinoma, which accounts for most liver cancers, carry tumors with abnormally activated FGFR4 signaling. Although small-molecule inhibitors of FGFRs have been developed and evaluated in clinical trials for treating cancer, most of them are pan-FGFR inhibitors with promiscuous kinome activity. Sequence analysis reveals FGFR4 contains a rare cysteine residue within its ATP-binding site. This residue is unique to FGFR4 and is not found among the other members of the FGFR subfamily, despite their high homology. In order to develop new potent and selective drugs against FGFR4, we designed and synthesized electrophilic derivatives to covalently target this rare cysteine residue on FGFR4 (C552). Cp 1 showed highly potent inhibitory activity against recombinant wild-type FGFR4 kinase, with a half maximal inhibitory concentration (IC50) of 0.2 nM. Amongst 250 human kinases, Cp 1 (100 nM) caused 98% inhibition of FGFR4 and no significant inhibition (&lt; 40%) of other kinases, demonstrating great specificity for FGFR4. Cocrystal structure of Cp 1 in complex with FGFR4 kinase confirmed the covalent interaction between the warhead of Cp 1 with the targeted cysteine residue. Modification of Cp 1 with a terminal alkyne group generated Probe 1, which labeled recombinant wild-type FGFR4 kinase at concentration as low as 1 nM. The same probe failed to label a mutant form of FGFR4 in which the cysteine was substituted with alanine (C552A). Probe 1 also showed selective labeling of overexpressed FGFR4 in HEK293 cells at concentration as low as 10 nM. In future work, we aim to fully characterize the potency, selectivity, target engagement, toxicity, and pharmacokinetics of Probe 1 in vitro and in vivo in order to elucidate valuable information about this poorly understood FGFR isoform.

Development of potent and specific inhibitors for oncogenic kinase FGFR4

2019 Spring National Meeting

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.