Neratinib

 Class:

• Oral irreversible tyrosine kinase inhibitor (TKI) targeting HER2, HER1 (EGFR), and HER4 receptors

Mechanism of Action:

• Blocks the intracellular tyrosine kinase domains of HER receptors, inhibiting downstream signaling pathways responsible for tumor cell proliferation and survival.

Indications:

• Extended adjuvant treatment of early-stage HER2-positive breast cancer following trastuzumab-based therapy to reduce the risk of recurrence.
• Under investigation/used in some metastatic HER2-positive breast cancers.

Dosing:

• Oral, typically 240 mg once daily for 12 months.
• Dose reductions required for toxicity.

Common Adverse Effects:

• Diarrhea (very common and potentially severe; prophylaxis with antidiarrheals recommended)
• Nausea and vomiting
• Fatigue
• Hepatotoxicity (monitor liver function)
• Rash

Pharmacist Considerations:

• Educate patients on proactive diarrhea management and importance of antidiarrheal prophylaxis (e.g., loperamide).
• Monitor liver function tests regularly.
• Counsel on adherence to daily oral therapy and managing GI side effects.
• Assess for drug interactions (CYP3A4 substrate).