Nerlynx (Neratinib)

Neratinib acts on the HER2 signaling pathway and is used in HER2‑positive breast cancer management.

• Extended adjuvant treatment of HER2‑positive early‑stage breast cancer following trastuzumab therapy: reduces risk of disease recurrence.
• HER2‑positive early‑stage breast cancer after surgery: provides continued HER2 inhibition to improve disease‑free survival.
• HER2‑positive breast cancer in patients who have completed adjuvant trastuzumab: serves as maintenance therapy to sustain HER2 blockade.

• Neratinib irreversibly binds to the intracellular kinase domains of the HER family receptors (EGFR/HER1, HER2, HER4). This covalent inhibition blocks downstream signaling pathways such as PI3K/AKT and MAPK, leading to suppression of tumor cell proliferation and survival in HER2‑driven cancers.

Neratinib may cause a range of adverse reactions that vary in frequency and severity.

Common Side Effects

• Diarrhea: often mild to moderate, may require antidiarrheal therapy.
• Nausea and vomiting: can be managed with antiemetics.
• Abdominal pain: intermittent discomfort.
• Fatigue: generalized tiredness.
• Rash: skin irritation or erythema.
• Stomatitis: inflammation of the mouth lining.

Serious or Rare Side Effects

• Severe diarrhea leading to dehydration: may require hospitalization.
• Hepatotoxicity: elevated liver enzymes or liver injury.
• Interstitial lung disease: respiratory symptoms requiring immediate attention.
• Cardiac dysfunction: reduced left‑ventricular ejection fraction.
• Stevens‑Johnson syndrome or toxic epidermal necrolysis: severe skin reactions.
• Neutropenia: low white‑blood‑cell count increasing infection risk.

Patients should be monitored closely for safety concerns while receiving Neratinib.

• Liver function monitoring: assess transaminases before and during therapy.
• Cardiac assessment: evaluate baseline and periodic cardiac function.
• Diarrhea management: initiate prophylactic antidiarrheal agents and educate on hydration.
• Avoid use in severe hepatic impairment: dose adjustment may be required.
• Pregnancy and lactation: discuss risks with prescriber; drug may be contraindicated.
• Store at ambient temperature: keep in the original container, protect from moisture and direct sunlight.

Neratinib may interact with other medicines, altering its efficacy or safety.

Major Interactions (Avoid)

• Strong CYP3A4 inhibitors (e.g., ketoconazole, itraconazole): increase neratinib exposure.
• Strong CYP3A4 inducers (e.g., rifampin, carbamazepine): reduce neratinib effectiveness.
• Antacids that markedly raise gastric pH: may affect absorption.

Moderate Interactions (Monitor Closely)

• CYP3A4 substrates with narrow therapeutic index (e.g., certain immunosuppressants): monitor plasma levels.
• Anticoagulants such as warfarin: watch for changes in INR.
• Proton pump inhibitors: may modestly decrease neratinib exposure.
• Antidiarrheal agents (e.g., loperamide): adjust dose if needed.
• Oral contraceptives: assess contraceptive efficacy, consider additional methods.