Comparative biochemical kinase activity analysis identifies lirafugratinib as a highly selective FGFR2 inhibitor

Background: Genomic alterations in fibroblast growth factor receptor (FGFR) occur across tumor types and pan-FGFR inhibitors are standard-of-care in FGFR fusion positive cholangiocarcinoma (CCA). Recent efforts focused on designing more selective and covalent inhibitors to improve efficacy, safety, and tolerability. Lirafugratinib, a highly selective and irreversible FGFR2 inhibitor, was designed to target oncogenic FGFR2 alterations to enhance efficacy outcomes without worsening toxicities due to inhibitions of other FGFR iso-forms (e.g., hyperphosphatemia and diarrhea related to FGFR1 and FGFR4, respectively). Methods: To understand and compare the relative selectivity of lirafugratinib kinase inhibition, we performed a head-to-head biochemical analysis against four pan-FGFR inhibitors. A KINOMEscan Profiling Service scanMAX and TREEspot™ interaction maps were used for evaluation and visualization of inhibition of kinases: a panel of 468 human target kinases and disease-relevant kinase mutant variants were tested at a concentration of 500 nM for lirafugratinib and four other pan-FGFR inhibitors (futibatinib, pemigatinib, erdafitinib, and AZD4547). The 90% and 75% inhibition thresholds were selected based on established and published research for methodologies related to kinome mapping. Results: Among the 468 kinases and disease-relevant kinase mutants, lirafugratinib at 500 nM inhibited >90% of only two kinases (FGFR2 [94.1%] and MEK5 [92.4%]). The rest of kinases, including FGFR1, FGFR3 and FGFR4, were inhibited <75% except MKNK2 (89% inhibition). In contrast, futibatinib inhibited FGFR1, FRFR2, FRFR3, and FGFR4 by more than 90%, while showing minimal (<75%) inhibition of other kinases except MKK7 (83% inhibition). Similarly, pemigatinib, erdafitinib, and AZD4547 inhibited multiple kinases (including all FGFRs) - 11, 37, and 37 kinase targets, by more than 90%. Overall, lirafugratinib demonstrated the highest selectivity to inhibit FGFR2 without substantial inhibition of FGFR1, FGFR3 and FGFR4, compared to the FGFR inhibitors tested. Conclusions: The head-to-head kinome analysis of lirafugratinib and four other FGFR inhibitors revealed that lirafugratinib inhibited FGFR2 with high selectivity, suggesting minimal off-target and off-isoform-related toxicities compared to pan-FGFR inhibitors used in clinical practice.