Herzuma (Trastuzumab)

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

• HER2‑positive breast cancer, both early‑stage and metastatic, often in combination with chemotherapy.
• HER2‑positive gastric or gastro‑esophageal junction adenocarcinoma.
• Monotherapy after disease progression on prior HER2‑targeted therapy.
• Use in neoadjuvant or adjuvant settings according to clinical guidelines.
• Treatment of patients who meet validated HER2 testing criteria.

• Trastuzumab binds with high affinity to the extracellular domain IV of the HER2 receptor on tumor cells. This binding blocks ligand‑independent HER2 dimerization and downstream signaling through the PI3K/AKT and MAPK pathways, reducing cell proliferation. Additionally, the Fc region of trastuzumab recruits immune effector cells, leading to antibody‑dependent cellular cytotoxicity (ADCC) and may enhance the effectiveness of concomitant chemotherapy.

Adverse reactions reported with Herzuma cover a range of frequencies and severities, and they are monitored throughout treatment.

Common

• Fever, chills, or rigors occurring during or shortly after the infusion.
• Nausea, vomiting, or mild gastrointestinal upset.
• Fatigue, headache, or transient dizziness.
• Mild rash or skin erythema that resolves without intervention.
• Transient elevation of liver enzymes (ALT/AST) that is usually asymptomatic.
• Low‑grade thrombocytopenia, often detected on routine laboratory monitoring.

Serious

• Anaphylactic or severe hypersensitivity reactions, including bronchospasm, hypotension, or angioedema.
• Clinically significant reduction in left ventricular ejection fraction, potentially leading to symptomatic heart failure.
• Interstitial lung disease or pneumonitis presenting with cough, dyspnea, or hypoxia.

Before initiating Herzuma, clinicians should evaluate patient history and baseline assessments to mitigate potential risks.

• Assess baseline left ventricular ejection fraction (LVEF) and repeat cardiac monitoring during therapy.
• Avoid use in pregnant or nursing women; discuss potential risks and lack of safety data.
• Confirm no prior severe hypersensitivity to trastuzumab or any formulation excipients.
• Monitor complete blood counts and liver function tests regularly throughout treatment.
• Review concomitant medications for potential interactions that could increase infusion‑related toxicity.
• Evaluate pre‑existing pulmonary disease, as trastuzumab may exacerbate respiratory symptoms.

Herzuma may interact with other agents; awareness of potential pharmacodynamic and pharmacokinetic relationships helps optimize safety.

Avoid

• Concurrent use with other HER2‑targeted monoclonal antibodies (e.g., pertuzumab) when not part of an approved combination regimen.
• Live vaccines during treatment, due to immunosuppression risk.

Use with caution

• Anthracyclines such as doxorubicin or epirubicin because of additive cardiac toxicity.
• Other HER2‑targeted agents (e.g., trastuzumab‑emtansine, lapatinib) that may increase overall cardiotoxic risk.
• Concomitant chemotherapy (e.g., paclitaxel) that can heighten infusion‑related reactions.
• Medications that prolong the QT interval (e.g., certain antiarrhythmics) should be used cautiously, with ECG monitoring.
• Corticosteroids may mask early signs of infusion reactions; monitor patients closely if given concurrently.