Tresoda

• HER2-Positive Breast Cancer:
• Early-stage breast cancer (adjuvant therapy post-surgery and chemotherapy).
• Locally advanced or metastatic breast cancer.
• HER2-Positive Gastric or Gastroesophageal Junction Adenocarcinoma:
• Advanced or metastatic disease in combination with chemotherapy.
• Other:
• Investigational use in HER2-positive bladder cancer and other HER2-expressing solid tumors.

• Route: Intravenous infusion (IV); subcutaneous form available.
• Breast Cancer:
• Loading dose: 8 mg/kg IV over 90 minutes.
• Maintenance dose: 6 mg/kg IV every 3 weeks over 30–90 minutes.
• Duration: Typically 1 year (adjuvant); until progression (metastatic).
• Gastric Cancer:
• Same dosing as breast cancer, combined with chemotherapy.
• Special Populations:
• No dose adjustment required for mild/moderate renal or hepatic impairment.
• Use caution and monitor in patients with cardiac dysfunction.
• Administration Notes:
• Infusion rate may be slowed to manage infusion reactions.

Trastuzumab is a humanized monoclonal antibody targeting the extracellular domain of the HER2 receptor, blocking receptor dimerization and downstream proliferative signaling. It also mediates antibody-dependent cellular cytotoxicity, leading to immune-mediated tumor cell death, thereby inhibiting tumor growth in HER2-overexpressing cancers.

• Absorption: Not applicable for IV; subcutaneous bioavailability ~80%.
• Distribution: Vd ~3–4 L; limited tissue penetration.
• Metabolism: Proteolytic degradation; no CYP involvement.
• Half-life: Approximately 28.5 days.
• Excretion: Catabolized to peptides and amino acids; no renal/hepatic elimination.

• Pregnancy: Category D — evidence of fetal risk; use only if benefits outweigh risks.
• Lactation: Unknown if excreted in human milk; breastfeeding not recommended during therapy and for 7 months post-treatment.

• Antineoplastic agent
• Monoclonal antibody (HER2 receptor antagonist)
• Targeted cancer immunotherapy

• Hypersensitivity to trastuzumab or excipients
• Severe infusion reactions
• Pre-existing severe cardiac dysfunction

• Cardiotoxicity risk — monitor left ventricular function before and during treatment
• Infusion reactions — may require interruption or discontinuation
• Pulmonary toxicity (rare)
• Embryo-fetal toxicity
• Potential immunogenicity

• Common: Fever, chills, nausea, diarrhea, fatigue, rash, neutropenia
• Serious: Heart failure, severe infusion reactions, pulmonary toxicity, anaphylaxis

• Increased cardiotoxicity with anthracyclines
• No significant CYP450 interactions
• Use caution with other immunosuppressants

• Endorsed in NCCN and ESMO guidelines for HER2-positive breast and gastric cancers
• FDA approved subcutaneous formulation for ease of use
• Ongoing research combining trastuzumab with immune checkpoint inhibitors
• Updated warnings emphasizing cardiac monitoring

• Refrigerate at 2°C–8°C
• Protect from light
• Do not freeze or shake vigorously
• Use diluted solutions within 24 hours if refrigerated