Drug Overview

Erdafitinib is an oral, small-molecule tyrosine kinase inhibitor (TKI) and a targeted therapy. It is a first-in-class, selective inhibitor of fibroblast growth factor receptors (FGFRs) approved for the treatment of locally advanced or metastatic urothelial carcinoma with specific FGFR genetic alterations.

Generic Name: Erdafitinib
US Brand Names: Balversa®
Drug Class: Fibroblast Growth Factor Receptor (FGFR) Tyrosine Kinase Inhibitor
Route of Administration: Oral
FDA Approval Status: Approved under accelerated approval for the treatment of adult patients with locally advanced or metastatic urothelial carcinoma that has susceptible FGFR3 or FGFR2 genetic alterations and has progressed during or following at least one line of prior platinum-containing chemotherapy. Continued approval may be contingent upon verification of clinical benefit in confirmatory trials.

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What Is It and How Does It Work? (Mechanism of Action)

Erdafitinib is an oral tyrosine kinase inhibitor (TKI) and a targeted therapy that selectively inhibits fibroblast growth factor receptors (FGFRs).

Molecular Target: It binds to the ATP-binding site of FGFR1, FGFR2, FGFR3, and FGFR4, blocking their phosphorylation and activation.
Blockade of Signaling: This inhibits the downstream RAS/RAF/MEK/ERK and PI3K/AKT/mTOR pathways, which are critical for cell growth, survival, and proliferation.
Result: The blockade leads to cell cycle arrest and apoptosis (programmed cell death) in tumor cells dependent on FGFR signaling. Efficacy is exclusive to cancers with specific activating FGFR2 or FGFR3 genetic alterations.

FDA-Approved Clinical Indications

Oncological Indications:

Locally Advanced or Metastatic Urothelial Carcinoma: For adult patients with disease that has susceptible FGFR3 or FGFR2 genetic alterations and has progressed during or following at least one line of prior platinum-containing chemotherapy, including within 12 months of neoadjuvant or adjuvant platinum-containing chemotherapy.

Non-Oncological Uses:

None.

Dosage and Administration Protocols:

Erdafitinib is administered orally once daily. Dosing is guided by the patient’s serum phosphate level and the presence of toxicities.

Component	Standard Initial Dose	Schedule	Administration Time / Notes
Erdafitinib	8 mg	Once Daily (QD)	Oral tablet, taken with or without food.
Dose Escalation	9 mg QD	Day 15	May be increased to 9 mg if serum phosphate is below the individual specific threshold and no Grade or greater adverse reactions occurred.
Dose Reduction	6 mg QD	N/A	Required for management of severe adverse reactions, particularly ocular toxicity or stomatitis.

Renal and Hepatic Dose Adjustments

Renal Impairment: No dose adjustment is required for mild to moderate renal impairment. Data is limited in severe renal impairment (CrCl <30 mL/min).
Hepatic Impairment: No dose adjustment is required for mild to moderate hepatic impairment. Use in severe hepatic impairment is not well-studied.
Timing and pH: pH-altering agents (e.g., PPIs or H2 blockers) can affect absorption; avoid co-administration if possible.

Clinical Efficacy and Research Results

The accelerated approval of erdafitinib was based on the Phase 2 BLC2001 (NCT02365597) study, which demonstrated significant activity in a biomarker-selected, heavily pretreated population.

Overall Response Rate (ORR): In the pivotal trial of patients with FGFR-altered mUC after prior platinum therapy, erdafitinib achieved a confirmed objective response rate (ORR) of 40%. The complete response (CR) rate was 3%.
Duration of Response (DOR): The median duration of response was 5.6 months, indicating meaningful disease control in responders.
Confirmatory Trial (THOR): The Phase 3 THOR trial (NCT03390504) is evaluating erdafitinib in two cohorts. Results from Cohort 1 (vs. chemotherapy) were reported in 2023. Erdafitinib demonstrated a significant improvement in overall survival (OS) with a median OS of 12.1 months vs. 7.8 months for chemotherapy (Hazard Ratio [HR]=0.64). It also improved progression-free survival (PFS: 5.6 vs. 2.7 months; HR=0.58).
Biomarker-Specific Efficacy: Responses were observed across different types of FGFR alterations, including mutations and fusions, validating the importance of comprehensive genomic testing in this disease.

Safety Profile and Side Effects

Black Box Warning:

Erdafitinib carries a Black Box Warning for ocular disorders, specifically Central Serous Retinopathy/Retinal Pigment Epithelial Detachment (CSR/RPED), which can cause retinal detachment and vision loss. Regular ophthalmologic examinations are required.

Common Side Effects (>10%):

Metabolic: Hyperphosphatemia (77%), due to on-target FGFR inhibition.
Ocular: Dry eye, blurred vision, corneal disorders.
Gastrointestinal: Stomatitis, diarrhea, dry mouth, decreased appetite.
General: Fatigue, nausea.
Dermatological: Nail disorders, palmar-plantar erythrodysesthesia (hand-foot syndrome).
Renal: Increased creatinine.

Serious Adverse Events:

Central Serous Retinopathy/Retinal Pigment Epithelial Detachment (CSR/RPED).
Hyperphosphatemia & Soft Tissue Mineralization.
Nail Disorders & Hand-Foot Syndrome (severe cases).
Ocular Disorders: Uveitis, iritis.
Embryo-Fetal Toxicity.

Management Strategies:

Hyperphosphatemia: Monitor serum phosphate level every 2 weeks for first month, then monthly. Initiate a low-phosphate diet and phosphate binders for levels >7.0 mg/dL. Interrupt dose and reduce for persistent hyperphosphatemia ≥7.0 mg/dL.
Ocular Toxicity: Mandatory monthly ophthalmologic exams for the first 4 months, then every 3 months. Urgently refer patients for acute visual symptoms. Dose interruption is required for asymptomatic CSR/RPED; permanent discontinuation for retinal detachment.
Stomatitis: Use alcohol-free mouthwash, topical analgesics. Dose interruption and reduction for Grade 2+.
Hand-Foot Syndrome: Moisturizers, urea-based creams, and comfortable footwear. Dose modifications for severe cases.

Research Areas

As the first approved pan-FGFR inhibitor, research focuses on expanding its use to other FGFR-altered tumors and optimizing combination strategies.

Other FGFR-Altered Cancers: Erdafitinib is being actively investigated in a wide range of solid tumors with FGFR alterations, including cholangiocarcinoma (bile duct cancer), glioblastoma, gastric cancer, and non-small cell lung cancer with FGFR fusions/mutations.
Combination Therapies: Clinical trials are exploring erdafitinib combined with immune checkpoint inhibitors (e.g., cetrelimab) or other targeted agents (e.g., cetuximab in head and neck cancer) to overcome resistance and enhance efficacy.
Biomarker Refinement: Research aims to better define which specific FGFR alterations (e.g., mutation type, fusion partner) are most predictive of response to optimize patient selection.

Patient Management and Practical Recommendations

Pre-Treatment:

Mandatory Biomarker Testing: Confirm the presence of a susceptible FGFR3 or FGFR2 genetic alteration (mutation or fusion) via an FDA-approved test.
Comprehensive Ophthalmologic Exam: Baseline exam prior to initiation.
Baseline Labs: Serum phosphate, creatinine, liver function tests.
Pregnancy Test: For women of childbearing potential.

Precautions During Treatment:

Adherence to Eye Exams: Strict adherence to scheduled monthly eye exams is critical.
Phosphate Monitoring: Regular blood tests for phosphate levels. Initiate dietary phosphate management early.
Symptom Vigilance: Report any new or worsening visual changes (blurriness, floaters, photopsia), eye pain, or redness immediately. Report severe mouth sores, skin changes on hands/feet, or nail problems.
Dietary Guidance: Consult with a dietitian for a low-phosphate diet.

Do’s and Don’ts

DO: Attend ALL scheduled eye exams without exception.
DO: Report any changes in your vision immediately, even if they seem minor.
DO: Follow dietary recommendations to manage phosphate levels.
DON’T: Start erdafitinib without confirmed FGFR alteration testing.
DON’T: Ignore eye symptoms or miss ophthalmology appointments.
DON’T: Become pregnant. Use effective contraception during and for 1 month after the final dose.

Legal Disclaimer

This guide is for informational purposes only and is intended for international patients and healthcare professionals. It does not replace professional medical advice, diagnosis, or treatment. Erdafitinib carries serious risks, including vision loss, and requires specific biomarker testing and intensive monitoring. It must be managed by a qualified oncologist. Always consult your treating physician.