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FGFR1-4 Inhibitor (Pan-FGFR TKI) Pregnancy: Contraindicated — embryotoxic; effective contraception required during and for 1 month after treatment

Erdafitinib

Brand names: Balversa

Adult dose

Dose: 8 mg once daily; uptitrate to 9 mg if serum phosphate <5.5 mg/dL after 14-21 days
Route: Oral
Frequency: Once daily (with or without food)
Max: 9 mg/day
Locally advanced or metastatic urothelial carcinoma with FGFR2/3 alteration (mutation or fusion); post-platinum; FGFR mutation testing mandatory before prescribing; phosphate monitoring mandatory

Paediatric dose

Dose: Not established N/A/kg
Route: N/A
Frequency: N/A
Max: N/A
Not licensed in paediatrics

Dose adjustments

Renal

No dose adjustment for mild-moderate renal impairment; limited data in severe

Hepatic

Mild: no adjustment; moderate-severe: avoid

Paediatric weight-based calculator

Not licensed in paediatrics

Clinical pearls

  • BLC2001 trial (Loriot et al. NEJM 2019): erdafitinib achieved 40% ORR in FGFR-altered metastatic urothelial carcinoma vs 19% in a historical comparator — first precision oncology agent approved for bladder cancer; companion diagnostic (cobas FGFR mutation test) required
  • FGFR alterations in urothelial carcinoma: FGFR3 mutations (~15-20%) and FGFR2/3 fusions (~5%) define a genomic subset with activated FGFR signalling — molecular testing (NGS) required before prescribing; low tumour mutational burden in FGFR-altered tumours may explain relative PD-1 resistance
  • Hyperphosphataemia management: FGFR inhibition reduces FGF23 activity → phosphate retention; serum phosphate target <7 mg/dL — use low-phosphate diet + phosphate binders (sevelamer, lanthanum); dose uptitration only if phosphate <5.5 mg/dL, not above; monitor every 2 weeks
  • RPED (retinal pigment epithelium detachment): class effect of FGFR inhibitors — typically asymptomatic, detected on ophthalmology examination; baseline OCT/fundoscopy required; monthly monitoring during treatment; hold erdafitinib if symptomatic or severe RPED on imaging
  • THOR trial: erdafitinib vs pembrolizumab in FGFR-altered metastatic urothelial carcinoma — superiority of erdafitinib in the subset with FGFR alterations; reinforces value of molecular selection

Contraindications

  • No FGFR2/3 alteration confirmed on testing
  • Uncontrolled hyperphosphataemia
  • Known hypersensitivity

Side effects

  • Hyperphosphataemia (FGFR inhibition disrupts FGF23-phosphate axis — almost universal)
  • Stomatitis
  • Dry eye/ocular toxicity (retinal pigment epithelium detachment — RPED)
  • Skin and nail toxicity
  • Fatigue
  • Diarrhoea
  • Elevated creatinine

Interactions

  • Phosphate binders — required as prophylaxis/treatment for hyperphosphataemia
  • CYP2C9 and CYP3A4 substrates — erdafitinib inhibits CYP2C9; monitor warfarin (INR rises)
  • Strong CYP3A4 inhibitors — increase erdafitinib exposure

Monitoring

  • Serum phosphate (every 2 weeks for first 3 months, then monthly)
  • Ophthalmological assessment (OCT, monthly)
  • FBC, LFTs, creatinine (each cycle)
  • Stomatitis grading
  • FGFR mutation status (companion diagnostic before starting)

Reference: BNFc; BNF 90; BLC2001 trial (Loriot et al. NEJM 2019); THOR trial; FDA approval 2019; MHRA SPC Balversa; EAU Bladder Cancer Guidelines 2024. Verify against your local formulary and the latest BNF before prescribing.

Related

Curated clinical cross-links plus same-class fallbacks.

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