Recommended Dose: The recommended dose is 4.8 mg/kg administered by intravenous infusion once every 3 weeks (Q3W) until disease progression or unacceptable toxicity.

Time: The initial infusion should be administered over 90–120 minutes. If well tolerated, subsequent infusions may be shortened to 30–45 minutes.

Instructions for use: Reconstitute and dilute before intravenous infusion. Do not administer as an intravenous push or bolus. Patients should undergo comprehensive ophthalmologic examinations before the first four treatment cycles and regular eye examinations thereafter. Prophylactic use of preservative-free artificial tears is recommended throughout treatment. Dose interruption, reduction, or permanent discontinuation should be considered based on the severity of ocular toxicity, peripheral neuropathy, or infusion-related reactions.

Interaction: No formal clinical drug interaction studies have been conducted. Trastuzumab botidotin does not significantly inhibit or induce major CYP450 enzymes. The released payload (Duo-5) is a substrate of CYP3A and P-glycoprotein (P-gp); therefore, caution is advised when co-administered with strong CYP3A or P-gp inhibitors.

Side effects: Common adverse reactions include corneal disorders, dry eye, blurred vision, peripheral sensory neuropathy, anemia, infusion-related reactions, cataract, fatigue, and gastrointestinal adverse events. Ocular toxicity is the most characteristic adverse reaction and requires routine monitoring.