Nerlynx (Neratinib)

Neratinib is used in the HER2‑positive breast cancer pathway to provide adjuvant benefit after standard therapy.

• HER2‑positive early‑stage breast cancer: reduces risk of disease recurrence following trastuzumab‑based treatment.
• Post‑surgical HER2‑positive disease: extends disease‑free survival when given as extended adjuvant therapy.
• Patients who have completed trastuzumab: offers additional HER2 blockade to improve long‑term outcomes.

• Neratinib irreversibly binds to the intracellular kinase domains of HER2, HER1 (EGFR) and HER4 receptors. By blocking autophosphorylation, it prevents downstream signaling through the PI3K/AKT and MAPK pathways, which are critical for tumor cell proliferation, survival and angiogenesis.

Neratinib may cause a range of adverse reactions, from mild to severe.

Common Side Effects

• Diarrhea: often watery and may require antidiarrheal therapy.
• Nausea and vomiting: may be mitigated with antiemetics.
• Abdominal pain or cramping.
• Fatigue or reduced energy levels.
• Decreased appetite or weight loss.
• Rash or skin irritation.

Serious or Rare Side Effects

• Elevated liver enzymes (ALT, AST) indicating hepatic injury.
• Severe or persistent diarrhea leading to dehydration.
• Intestinal perforation or obstruction.
• Cardiac dysfunction, including reduced left‑ventricular ejection fraction.
• Interstitial lung disease or pneumonitis.
• Severe skin reactions such as Stevens‑Johnson syndrome.

Before initiating Neratinib, clinicians should consider several safety measures.

• Liver function monitoring: assess baseline enzymes and repeat periodically.
• Diarrhea management: start prophylactic antidiarrheal agents and educate patients.
• Cardiac assessment: evaluate baseline cardiac function and monitor during therapy.
• Pregnancy and lactation: avoid use in pregnant or breastfeeding women unless benefits outweigh risks.
• Drug‑specific counseling: inform patients about potential gastrointestinal toxicity and the need for prompt reporting.
• Store at ambient temperature: keep tablets in the original container, protect from moisture and direct sunlight.

Neratinib interacts with several drug classes that can alter its exposure or increase toxicity.

Major Interactions (Avoid)

• Strong CYP3A4 inhibitors (e.g., ketoconazole, clarithromycin): may raise neratinib plasma levels.
• Gastric pH‑raising agents (e.g., high‑dose antacids, proton‑pump inhibitors): can reduce absorption.
• Concurrent use with other irreversible HER‑family inhibitors: increases risk of overlapping toxicities.

Moderate Interactions (Monitor Closely)

• Moderate CYP3A4 inhibitors or inducers (e.g., erythromycin, rifampin): may require dose adjustment.
• Anticoagulants (e.g., warfarin): monitor coagulation parameters as neratinib may affect metabolism.