Class
- Targeted therapy → Oral pan-FGFR (fibroblast growth factor receptor) tyrosine kinase inhibitor (FGFR1–4).
Indications
- Locally advanced or metastatic urothelial carcinoma (bladder cancer)
- With susceptible FGFR2 or FGFR3 genetic alterations
- In patients who have progressed during or following platinum-containing chemotherapy.
- Being studied in other FGFR-driven cancers (cholangiocarcinoma, glioma).
Dose
- 8 mg PO once daily (with or without food).
- Dose may be increased to 9 mg once daily if no significant toxicity and serum phosphate <9 mg/dL after 14–21 days.
- Treatment should be interrupted, reduced, or discontinued based on toxicities (especially ocular).
Key Toxicities
- Hyperphosphatemia (on-target effect, FGFR inhibition alters phosphate metabolism) → requires phosphate monitoring & possibly phosphate binders.
- Ocular disorders → central serous retinopathy (CSR)/retinal pigment epithelial detachment (RPED). Requires baseline and monthly ophthalmologic exams for first 4 months, then q3 months.
- Stomatitis, diarrhea, dry mouth.
- Hand-foot syndrome, nail changes.
- Fatigue.
- Rare but serious → hepatotoxicity, nail bed infections, serious ocular events.
Monitoring
- Serum phosphate: baseline, 14–21 days after start, then monthly.
- Ophthalmologic exams: baseline, monthly ×4, then q3 months.
- LFTs, renal function, electrolytes periodically.
- Monitor for signs of ocular toxicity, hyperphosphatemia symptoms.
Contraindications / Precautions
- Not recommended in patients with severe ocular disorders.
- Embryo-fetal toxicity → requires effective contraception.
- Avoid concomitant strong CYP2C9 or CYP3A4 inducers/inhibitors (erdafitinib is metabolized mainly by CYP2C9 & CYP3A4).
Key Clinical Pearl for Pharmacists:
Erdafitinib is a precision oncology drug: Only used in FGFR2/3-mutated urothelial carcinoma patients confirmed by companion diagnostic (e.g., therascreen FGFR RGQ RT-PCR Kit). The most unique monitoring point is serum phosphate and ocular toxicity, not common to most TKIs.