Herwenda (Trastuzumab)

Herwenda is indicated for the treatment of cancers that overexpress the human epidermal growth factor receptor 2 (HER2).

• HER2‑positive early‑stage breast cancer as adjuvant therapy following surgery.
• HER2‑positive locally advanced or metastatic breast cancer, alone or with chemotherapy.
• HER2‑positive gastric or gastro‑esophageal junction adenocarcinoma in the metastatic setting.
• Neoadjuvant treatment of HER2‑positive breast cancer to increase surgical resectability.
• Combination therapy with taxanes or anthracyclines in HER2‑positive disease.

• Trastuzumab is a humanized IgG1 monoclonal antibody that binds with high affinity to the extracellular domain IV of the HER2 receptor. By occupying this site, it blocks ligand‑independent HER2 dimerization and downstream signaling through the PI3K/AKT and MAPK pathways. The bound antibody also recruits immune effector cells, leading to antibody‑dependent cellular cytotoxicity and tumor cell lysis. In addition, trastuzumab can inhibit HER2 shedding, reducing the formation of the active p95HER2 fragment.

Adverse reactions to Herwenda have been observed in clinical practice and may vary in frequency and severity.

Common

• Fever, chills, or flu‑like symptoms during infusion.
• Nausea, vomiting, or loss of appetite.
• Diarrhea or abdominal pain.
• Fatigue or weakness.
• Headache or dizziness.
• Rash or mild skin irritation.

Serious

• Cardiac dysfunction, including decreased left ventricular ejection fraction.
• Severe infusion‑related reactions such as anaphylaxis or bronchospasm.
• Thromboembolic events, including deep‑vein thrombosis or pulmonary embolism.
• Hepatotoxicity presenting as elevated liver enzymes.
• Severe neutropenia or leukopenia.

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

• Assess baseline cardiac function with echocardiography or MUGA scan.
• Monitor left ventricular ejection fraction periodically during treatment.
• Review prior hypersensitivity reactions to monoclonal antibodies or trastuzumab biosimilars.
• Use caution in patients with uncontrolled hypertension or active cardiac disease.
• Avoid concurrent use of anthracyclines when possible due to additive cardiotoxicity.
• Adjust dosing in patients with severe hepatic impairment as recommended.
• Counsel patients on signs of infusion reactions and when to seek medical attention.

Herwenda may interact with other agents that affect cardiac function or immune response, requiring careful management.

Avoid

• Concurrent anthracycline chemotherapy (e.g., doxorubicin) due to increased risk of cardiotoxicity.
• Live vaccines during treatment, as immunosuppression can reduce vaccine efficacy.
• High-dose corticosteroids administered immediately before infusion, which may mask early infusion reactions.

Use with caution

• Cardiotoxic drugs such as trastuzumab emtansine or other HER2‑targeted agents.
• Medications that prolong QT interval, which may exacerbate cardiac monitoring concerns.
• Immunosuppressive agents (e.g., azathioprine) that could increase infection risk.
• Radiation therapy to the chest, which may compound cardiac stress.
• Strong CYP3A4 inhibitors or inducers are not expected to affect trastuzumab but should be reviewed for overall patient safety.