Ocular Disorders — BALVERSA^® can cause ocular disorders, including central serous retinopathy/retinal pigment epithelial detachment (CSR/RPED) resulting in visual field defect.

CSR/RPED was reported in 25% of patients treated with BALVERSA^®, with a median time to first onset of 50 days. Grade 3 CSR/RPED, involving central field of vision, was reported in 3% of patients. CSR/RPED resolved in 13% of patients and was ongoing in 13% of patients at the study cutoff. CSR/RPED led to dose interruptions and reductions in 9% and 14% of patients, respectively, and 3% of patients discontinued BALVERSA^®. Dry eye symptoms occurred in 28% of patients during treatment with BALVERSA^® and were Grade 3 in 6% of patients. All patients should receive dry eye prophylaxis with ocular demulcents as needed.

Perform monthly ophthalmological examinations during the first 4 months of treatment and every 3 months afterwards, and urgently at any time for visual symptoms. Ophthalmological examination should include assessment of visual acuity, slit lamp examination, fundoscopy, and optical coherence tomography. Withhold BALVERSA^® when CSR occurs and permanently discontinue if it does not resolve within 4 weeks or if Grade 4 in severity. For ocular adverse reactions, follow the dose modification guidelines [see Dosage and Administration (2.3)].

Hyperphosphatemia and Soft Tissue Mineralization — BALVERSA^® can cause hyperphosphatemia leading to soft tissue mineralization, cutaneous calcinosis, non-uremic calciphylaxis and vascular calcification. Increases in phosphate levels are a pharmacodynamic effect of BALVERSA^® [see Pharmacodynamics (12.2)]. Hyperphosphatemia was reported as adverse reaction in 76% of patients treated with BALVERSA^®. The median onset time for any grade event of hyperphosphatemia was 20 days (range: 8–116) after initiating BALVERSA^®. Thirty-two percent of patients received phosphate binders during treatment with BALVERSA^®. Cutaneous calcinosis, non-uremic calciphylaxis and vascular calcification have been observed in 0.3% of patients treated with BALVERSA^®.

Monitor for hyperphosphatemia throughout treatment. In all patients, restrict phosphate intake to 600‑800 mg daily. If serum phosphate is above 7.0 mg/dL, consider adding an oral phosphate binder until serum phosphate level returns to <5.5 mg/dL. Withhold, dose reduce, or permanently discontinue BALVERSA^® based on duration and severity of hyperphosphatemia [see Dosage and Administration (2.3), Table 2: Dose Modifications for Adverse Reactions].

Embryo-Fetal Toxicity — Based on the mechanism of action and findings in animal reproduction studies, BALVERSA^® can cause fetal harm when administered to a pregnant woman. In a rat embryo-fetal toxicity study, erdafitinib was embryotoxic and teratogenic at exposures less than the human exposures at all doses studied. Advise pregnant women of the potential risk to the fetus. Advise female patients of reproductive potential to use effective contraception during treatment with BALVERSA^® and for one month after the last dose. Advise male patients with female partners of reproductive potential to use effective contraception during treatment with BALVERSA^® and for one month after the last dose [see Use in Specific Populations (8.1, 8.3) and Clinical Pharmacology (12.1)].

Most common adverse reactions including laboratory abnormalities ≥20%:

Phosphate increased (76%), stomatitis (56%), fatigue (54%), creatinine increased (52%), diarrhea (47%), dry mouth (45%), nail disorder (45%), alanine aminotransferase increased (41%), alkaline phosphatase increased (41%), sodium decreased (40%), decreased appetite (38%), albumin decreased (37%), dysgeusia (37%), hemoglobin decreased (35%), dry skin (34%), aspartate aminotransferase increased (30%), magnesium decreased (30%), dry eye (28%), alopecia (26%), palmar-plantar erythrodysesthesia syndrome (26%), constipation (28%), phosphate decreased (24%), abdominal pain (23%), calcium increased (22%), nausea (21%), and musculoskeletal pain (20%). The most common Grade 3 or greater adverse reactions (>1%) were stomatitis (9%), nail dystrophy*, palmar-plantar erythrodysesthesia syndrome (6%), paronychia (3%), nail disorder (10%), keratitis^†, and hyperphosphatemia (1%).

• An adverse reaction with a fatal outcome in 1% of patients was acute myocardial infarction.
• Serious adverse reactions occurred in 41% of patients, including eye disorders (10%).
• Permanent discontinuation due to an adverse reaction occurred in 13% of patients. The most frequent reasons for permanent discontinuation included eye disorders (6%).
• Dosage interruptions occurred in 68% of patients. The most frequent adverse reactions requiring dosage interruption included hyperphosphatemia (24%), stomatitis (17%), eye disorders (17%), and palmar-plantar erythrodysesthesia syndrome (8%).
• Dose reductions occurred in 53% of patients. The most frequent adverse reactions for dose reductions included eye disorders (23%), stomatitis (15%), hyperphosphatemia (7%), palmar-plantar erythrodysesthesia syndrome (7%), paronychia (7%), and nail dystrophy (6%).

• Moderate CYP2C9 or strong CYP3A4 inhibitors: Consider alternative agents or monitor closely for adverse reactions. (7.1)
• Strong CYP2C9 or CYP3A4 inducers: Avoid concomitant use with BALVERSA^®. (7.1)
• Moderate CYP2C9 or CYP3A4 inducers: Increase BALVERSA^® dose up to 9 mg. (7.1)
• Serum phosphate level-altering agents: Avoid concomitant use with agents that can alter serum phosphate levels before the initial dose modification period. (2.3, 7.1)
• CYP3A4 substrates: Avoid concomitant use with sensitive CYP3A4 substrates with narrow therapeutic indices. (7.2)
• OCT2 substrates: Consider alternative agents or consider reducing the dose of OCT2 substrates based on tolerability. (7.2)
• P-gp substrates: Separate BALVERSA^® administration by at least 6 hours before or after administration of P-gp substrates with narrow therapeutic indices. (7.2)

Lactation — Because of the potential for serious adverse reactions from erdafitinib in a breastfed child, advise lactating women not to breastfeed during treatment with BALVERSA^® and for one month following the last dose.

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