FGFR1-4

Class

pan-FGFR tyrosine kinase inhibitor (oral small molecule; erdafitinib/Balversa)

Pathway

blocks aberrant FGFR signaling that drives tumor cell proliferation

Fibroblast growth factor receptors (FGFR1 through FGFR4) are a family of receptor tyrosine kinases embedded in the cell membrane. Under normal conditions, they are activated when fibroblast growth factor ligands bind their extracellular domain, triggering receptor dimerization and intracellular signaling that regulates cell growth, tissue repair, and development. In a subset of cancers, genetic alterations such as gene fusions, activating point mutations, or gene amplification cause one or more FGFR paralogs to signal continuously, independent of normal ligand control, driving unchecked tumor cell proliferation and survival. A pan-FGFR inhibitor is a small molecule designed to block the kinase activity of all four FGFR paralogs by occupying the ATP-binding pocket they share, preventing the phosphorylation events needed to propagate downstream signals. Because different tumors carry alterations in different FGFR family members, broad coverage across FGFR1-4 allows a single agent to address multiple molecularly defined tumor subsets rather than only one specific alteration. This mechanism is broadly relevant in cancers where FGFR alterations have been identified as oncogenic drivers, including certain urothelial (bladder) cancers and cancers of the bile duct, among others, where FGFR-driven signaling represents a distinct, targetable vulnerability separate from more common oncogenic pathways.