FGFR2 / FGFR3

Class

Selective small-molecule FGFR2/FGFR3 inhibitor (second-generation, reduced FGFR1 activity)

Pathway

Inhibits FGFR2/3 receptor tyrosine kinase signaling in FGFR2/3-altered tumors while sparing FGFR1 to widen the therapeutic window

FGFR2 and FGFR3 belong to the fibroblast growth factor receptor family, receptor tyrosine kinases that convert extracellular growth-factor signals into intracellular instructions for cell growth and differentiation, largely through the RAS-MAPK and PI3K-AKT signaling pathways. In certain cancers, genetic alterations—activating point mutations, gene fusions, or amplifications—cause FGFR2 or FGFR3 to signal continuously without normal regulation, driving uncontrolled cell proliferation. This pattern appears recurrently in cancers of the bile duct, bladder, and stomach, among others. Selectively blocking the kinase activity of FGFR2 and FGFR3 aims to interrupt this aberrant signaling and curb tumor growth. A central design challenge for this drug class involves FGFR1, a closely related receptor expressed in kidney and parathyroid tissue that helps regulate phosphate balance through the hormone FGF23. Inhibitors that also block FGFR1 tend to cause hyperphosphatemia, an on-target but dose-limiting metabolic side effect. By engineering reduced potency against FGFR1 while preserving strong inhibition of FGFR2 and FGFR3, this class of agents seeks a wider therapeutic window, aiming to achieve meaningful tumor-signaling blockade while limiting the systemic phosphate disturbances that constrained earlier, less selective FGFR inhibitors.