Ado-trastuzumab emtansine

Ado-trastuzumab emtansine (T-DM1) is an antibody-drug conjugate (ADC) used in HER2-positive breast cancer.

Key points for oncology pharmacists:

• Composition:
  • Combines the monoclonal antibody trastuzumab (targets HER2 receptor)
  • Linked to the cytotoxic agent emtansine (DM1), a microtubule inhibitor
• Mechanism of Action:
  • Trastuzumab binds HER2-expressing cancer cells → internalization of the conjugate → release of DM1 inside the cell → inhibits microtubule assembly → cancer cell death
  • Also retains trastuzumab’s effects like HER2 signaling blockade and antibody-dependent cellular cytotoxicity (ADCC).
• Indications:
  • HER2-positive metastatic breast cancer previously treated with trastuzumab and a taxane
  • Early-stage HER2-positive breast cancer with residual invasive disease after neoadjuvant therapy
• Administration:
  • Intravenous infusion, typically every 3 weeks
• Common Toxicities:
  • Hepatotoxicity (monitor LFTs)
  • Thrombocytopenia
  • Peripheral neuropathy
  • Cardiotoxicity (less frequent than trastuzumab alone)
  • Infusion-related reactions
• Pharmacist considerations:
  • Monitor liver function and platelets regularly
  • Counsel on neuropathy symptoms
  • Ensure cardiac monitoring per HER2 therapy protocols
  • Educate patient on infusion reactions and supportive care