# FGFR3 alteration (mutation or fusion)

Source: https://onco.cc/biomarkers/fgfr3-alteration/  
OnCo record `fgfr3-alteration` (Biomarker). Data CC BY-NC 4.0, attribute "Data from OnCo (onco.cc)"; commercial use needs a licence.

## TL;DR

FGFR3 point mutations and TACC3 fusions drive about 15 to 20 percent of advanced bladder cancers. Erdafitinib is approved for tumours with these 'susceptible' alterations after one prior treatment.

## Summary

The erdafitinib (Balversa) label covers locally advanced or metastatic urothelial carcinoma with susceptible FGFR3 genetic alterations after at least one line of systemic therapy (THOR); the original 2019 approval also covered FGFR2 fusions, dropped in 2024. The therascreen FGFR RGQ RT-PCR Kit is the companion diagnostic and detects the point mutations R248C, S249C, G370C and Y373C and the FGFR3::TACC3 v1 and v3 fusions from RNA. Sequencing panels report a wider set; the label's word 'susceptible' refers to alterations shown to respond in the trials.

## Fields

- Kind: Biomarker
- Last checked: 2026-09-23
- Also known as: FGFR3 mutation; FGFR3 fusion; FGFR3-TACC3; FGFR3::TACC3; FGFR3 S249C; FGFR3 R248C; FGFR3 Y373C; susceptible FGFR3 genetic alterations; FGFR alteration bladder
- Tags: biomarker; fgfr

## Sources

- BALVERSA prescribing information (DailyMed): https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=2a8aa5c0-6c92-4566-8c45-e8f4d1fc20ee

## Connected records

- biomarkers: [FGFR2 fusion or rearrangement](https://onco.cc/biomarkers/fgfr2-fusion-rearrangement/), [Nectin-4 expression](https://onco.cc/biomarkers/nectin-4-expression/)
- cancers: [Bladder & urothelial cancer](https://onco.cc/cancers/urothelial/)
- drugs: [Erdafitinib](https://onco.cc/drugs/erdafitinib/), [therascreen companion diagnostic kits (KRAS, EGFR, PIK3CA, FGFR, BRAF)](https://onco.cc/drugs/therascreen-cdx/)
- terms: [FGFR3 alterations (bladder cancer)](https://onco.cc/terms/fgfr3/), [Gene fusion](https://onco.cc/terms/gene-fusion/)
- targets: [FGFR3](https://onco.cc/targets/fgfr3-receptor/)

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JSON: https://onco.cc/api/v1/entities/fgfr3-alteration.json