• Monitor for retinal pigment epithelial detachment with ophthalmic exam, including optic coherence tomography of the macula, prior to therapy, every 2 mo for 1st 6 mo and every 3 mo thereafter. If blurred vision or other visual changes occur, refer for urgent ophthalmic evaluation with follow-up every 3 wk until resolution. If resolving in 14 days, continue at current dose. If not resolving 14 days, hold therapy until resolving; then resume at previous or ↓ dose.
• Monitor for corneal keratitis. If dry eye occurs, treat with ocular demulcents as needed.

Lab Test Considerations:

• Monitor for hyperphosphatemia throughout therapy. For phosphate ≥5.5–7 mg/dL, initiate low-phosphate diet and phosphate-lowering therapy. Monitor serum phosphate weekly. For phosphate >7–≤10 mg/dL, initiate or adjust phosphate-lowering therapy, monitor serum phosphate weekly, and ↓ to next lower dose. If phosphate ≤7 mg/dL in 14 days after dose ↓, continue at ↓ dose. If phosphate not ≤7 mg/dL in 14 days,↓ to next lower dose. If phosphate not ≤7 mg/dL in 14 days after 2nd dose ↓, hold futibatinib until serum phosphate ≤7 mg/dL; then resume at dose prior to holding. For phosphate >10 mg/dL, initiate or adjust phosphate-lowering therapy, monitor serum phosphate weekly, and hold futibatinib until serum phosphate ≤7 mg/dL; then resume at next lower dose. If phosphate not ≤7 mg/dL in 14 days after two interruptions and dose ↓, permanently discontinue futibatinib.