Kadcyla (Trastuzumab Emtansine)

Kadcyla is an antibody‑drug conjugate indicated for HER2‑positive breast cancer across different disease stages.

• HER2‑positive metastatic breast cancer: improves progression‑free and overall survival in patients whose disease has progressed after prior HER2‑targeted therapy.
• HER2‑positive early breast cancer (adjuvant setting): reduces risk of recurrence when given after surgery and standard chemotherapy.
• HER2‑positive breast cancer with residual invasive disease after neoadjuvant therapy: provides additional disease‑free survival benefit in patients with remaining tumor after pre‑operative treatment.

• Trastuzumab emtansine binds selectively to HER2 receptors on the surface of tumor cells. After receptor‑mediated internalisation, the conjugated cytotoxic agent DM1 (emtansine) is released inside the cell, where it binds tubulin and inhibits microtubule assembly, leading to cell cycle arrest and apoptosis of HER2‑overexpressing cancer cells.

Common Side Effects

• Fatigue: persistent tiredness reported by many patients.
• Nausea: mild to moderate gastrointestinal upset.
• Thrombocytopenia: reduced platelet counts increasing bleeding risk.
• Anemia: lowered red blood cell levels causing weakness.
• Neutropenia: decreased neutrophils raising infection susceptibility.
• Elevated liver enzymes: transient increases in ALT/AST.

Serious or Rare Side Effects

• Cardiac dysfunction: reduced left ventricular ejection fraction.
• Interstitial lung disease/pneumonitis: inflammatory lung condition.
• Severe infusion‑related reactions: hypotension, bronchospasm, or anaphylaxis.
• Hepatic failure: marked liver injury.
• Hemorrhage: clinically significant bleeding events.
• Thromboembolic events: deep vein thrombosis or pulmonary embolism.

Kadcyla requires careful monitoring and patient selection.

• Cardiac monitoring: assess baseline and periodic left ventricular function.
• Hepatic assessment: evaluate liver enzymes before each cycle.
• Hematologic surveillance: monitor platelet counts, hemoglobin, and neutrophils.
• Infusion precautions: be prepared to manage severe hypersensitivity reactions.
• Pregnancy and lactation: avoid use; safety not established.
• Store at 2-8°C: keep refrigerated, protect from light, do not freeze or shake.

Kadcyla may interact with other agents that affect cardiac or hepatic function.

Major Interactions (Avoid)

• Concurrent anthracyclines: increased risk of cardiotoxicity.
• Other HER2‑targeted antibodies (e.g., pertuzumab) used together: heightened toxicity.

Moderate Interactions (Monitor Closely)

• CYP3A4 inhibitors or inducers: may alter DM1 metabolism.
• Anticoagulants: increased bleeding risk with thrombocytopenia.
• Hepatotoxic drugs: additive liver injury potential.