Herzuma (Trastuzumab)

Herzuma is indicated for the treatment of several HER2‑positive malignancies. It is used in both metastatic and early‑stage disease settings as part of a prescribed therapeutic regimen.

• HER2‑positive metastatic breast cancer
• HER2‑positive early breast cancer (adjuvant or neoadjuvant)
• HER2‑positive gastric adenocarcinoma
• HER2‑positive gastro‑esophageal junction adenocarcinoma
• Combination with chemotherapy in approved protocols

• Trastuzumab binds with high affinity to the extracellular domain IV of the human epidermal growth factor receptor 2 (HER2) protein expressed on the surface of certain cancer cells. This binding blocks ligand‑independent HER2 signaling, prevents receptor dimerization, and reduces downstream proliferative pathways such as PI3K/AKT and MAPK. Additionally, the Fc region of trastuzumab engages immune effector cells, triggering antibody‑dependent cellular cytotoxicity that contributes to tumor cell elimination.

Adverse reactions to Herzuma have been observed in clinical studies and post‑marketing experience. They can be grouped by frequency and severity.

Common

• Infusion‑related reactions (fever, chills, flushing)
• Nausea or vomiting
• Fatigue
• Headache

Serious

• Cardiac dysfunction or decreased left ventricular ejection fraction
• Severe hypersensitivity or anaphylaxis
• Pulmonary toxicity (interstitial pneumonitis)
• Thromboembolic events

Before initiating Herzuma, clinicians should evaluate patient history and monitor specific clinical parameters to reduce the risk of complications.

• Assess baseline cardiac function (e.g., echocardiogram) and repeat periodically.
• Review prior trastuzumab exposure or hypersensitivity reactions.
• Monitor for signs of infusion‑related reactions during and after administration.
• Use caution in patients with pre‑existing pulmonary disease.
• Avoid use in pregnant women; discuss contraception and potential fetal risk.
• Adjust treatment in patients with hepatic impairment as recommended.
• Counsel patients on the importance of reporting new cardiac symptoms promptly.

Herzuma may interact with other medicines that affect cardiac function or immune response. Relevant interactions are summarized below.

Avoid

• Concurrent use with anthracyclines (e.g., doxorubicin) due to increased cardiotoxicity risk.
• Live vaccines during treatment because of immunosuppression.

Use with caution

• Other HER2‑targeted agents (pertuzumab, lapatinib) may increase toxicity.
• Medications that prolong QT interval.
• Drugs that cause significant hepatic enzyme induction or inhibition.