Herzuma (Trastuzumab)

Herzuma is indicated for patients whose tumors show over‑expression of the human epidermal growth factor receptor 2 (HER2).

• HER2‑positive breast cancer in early or metastatic settings.
• HER2‑positive gastric or gastro‑esophageal junction adenocarcinoma.
• Combination with chemotherapy regimens as part of first‑line therapy.
• Use in neoadjuvant or adjuvant treatment protocols where HER2 targeting is required.

• Herzuma’s active component, trastuzumab, binds with high affinity to the extracellular domain of the HER2 receptor on tumor cells. This binding blocks ligand‑independent HER2 signaling, inhibits downstream pathways such as PI3K/AKT and MAPK, and flags the cell for immune‑mediated destruction through antibody‑dependent cellular cytotoxicity (ADCC). The combined effect reduces tumor proliferation and survival.

Adverse reactions to Herzuma vary in frequency and severity.

Common

• Infusion‑related reactions (fever, chills, nausea).
• Fatigue or asthenia.
• Diarrhea or abdominal discomfort.
• Rash or mild skin irritation.
• Transient elevations in liver enzymes.

Serious

• Cardiac dysfunction, including decreased left ventricular ejection fraction.
• Severe infusion‑related anaphylaxis.
• Pulmonary toxicity such as interstitial pneumonitis.
• Thromboembolic events.
• Severe neutropenia or thrombocytopenia.

Healthcare providers should assess patient history and monitor for specific risks before and during Herzuma therapy.

• Evaluate baseline cardiac function; repeat assessments during treatment.
• Use caution in patients with pre‑existing pulmonary disease.
• Monitor liver function tests periodically.
• Assess for signs of infection; avoid use in active uncontrolled infections.
• Consider dose adjustments in patients with severe hepatic impairment.
• Counsel patients on the possibility of infusion reactions and advise prompt reporting of symptoms.

Herzuma may interact with other agents that affect cardiac function or immune response.

Avoid

• Concurrent use of anthracyclines due to increased cardiotoxicity risk.
• Live vaccines during treatment because of immunosuppression.

Use with caution

• Other HER2‑targeted therapies (e.g., pertuzumab) may amplify cardiac effects.
• Medications that prolong QT interval.
• Systemic corticosteroids, which may mask infusion reactions.
• Drugs that cause hepatic enzyme induction or inhibition, potentially altering trastuzumab clearance.