Trastuzumab emtansine
ADCs
Antibody-drug conjugates (ADCs)High alert
An error with this medicine can cause serious harm: double checks and protocols are used.Pregnancy: avoid
Avoid in pregnancy. Can harm the fetus (boxed warning); a negative pregnancy test is required and effective contraception is used during and after treatment.
Trastuzumab joined to the microtubule poison DM1; used in HER2-positive breast cancer. Watch the liver, the heart and the platelets.
Also called: ado-trastuzumab emtansine, T-DM1
Quick facts
- Group
- Antibody-drug conjugates (ADCs)
- Target
- HER2 (ErbB2) receptor on tumour cells
- Used for
- Early HER2-positive breast cancer
- Key effects
- Fatigue · Nausea · Muscle and joint pain
- Monitor
- Liver tests before each dose · Heart function
- ATC
- L01FD03
No doses: the clinician sets them by the current guideline.
Mechanism of action
The cryo-EM structure shows the HER2 extracellular domain bound by trastuzumab (the antibody part of this conjugate) and pertuzumab; the DM1 payload is not in the structure.
The antibody keeps trastuzumab's HER2 blockade and delivers DM1 (emtansine), a maytansine derivative attached to lysine residues. After binding HER2 the complex enters the cell by receptor-mediated endocytosis; proteases in the lysosome release DM1 into the cytosol, where it disrupts microtubules, arrests mitosis and triggers apoptosis.
- Binds HER2 on the breast cancer cell
- Taken in by endocytosis and digested in lysosomes
- DM1 is released and disrupts microtubules
- Mitotic arrest and apoptosis
Indications
- HER2-positive metastatic breast cancer previously treated with trastuzumab and a taxane. Breast cancer →
- Early HER2-positive breast cancer with residual invasive disease after neoadjuvant treatment (adjuvant use). Breast cancer →
Adverse effects
Common
- Fatigue, headache
- Nausea, constipation, diarrhoea
- Muscle and joint pain
- Dry or watery eyes, blurred vision
- Nosebleeds and easy bruising
Contraindications
- Allergy to the drug or to trastuzumab
- Caution in liver disease and heart disease
Key interactions
- Trastuzumab and trastuzumab deruxtecan
- Different drugs: never substituted for one another.
- Aspirin, anticoagulants and other drugs that raise bleeding risk
- Bleeding is more likely when platelets are low.
- Other liver-toxic medicines and grapefruit
- May raise the risk of liver damage; they are discussed before use.
What is monitored
- Liver tests before each dose
- Heart function (ejection fraction) before and during treatment
- Platelet count
- Signs of neuropathy
- Confirmation that the tumour is HER2-positive before starting
Administration and safety
- Intravenous infusion only, never as a push; the first infusion is watched closely for reactions.
- Check the full name: «trastuzumab» alone and the two trastuzumab conjugates are different drugs.
- Hazardous drug: prepared and handled with chemotherapy precautions.
Pregnancy and breastfeeding
Avoid in pregnancy. Can harm the fetus (boxed warning); a negative pregnancy test is required and effective contraception is used during and after treatment.
Nursing care
- Check liver tests and platelets before each dose.
- Observe the patient during and after the infusion for chills, fever or breathing difficulty.
- Ask about swelling, breathlessness or palpitations (heart failure) and tingling in the hands or feet.
- Teaching: report yellow skin, dark urine, black stools or unusual bleeding; use effective contraception.
Pharmacokinetics
- Absorption
- Intravenous infusion every few weeks.
- Elimination
- The antibody part is catabolised like other proteins.
Test yourself
Think of the answer, then tap the question to see it.
What is the payload of trastuzumab emtansine and what does it target?
DM1 (emtansine), a maytansine derivative that disrupts microtubules.
What are the three boxed warnings of trastuzumab emtansine?
Hepatotoxicity, cardiac toxicity (reduced ejection fraction) and embryo-fetal toxicity.
In which early breast cancer setting is trastuzumab emtansine used?
HER2-positive early breast cancer with residual invasive disease after neoadjuvant therapy.
Connections
← Back to the class: Antibody-drug conjugates (ADCs)
Educational content on how drugs work; not a prescribing guide and no substitute for a health professional's advice. No doses are given.
Sources: Ado-trastuzumab Emtansine Injection: MedlinePlus Drug Information (MedlinePlus (U.S. National Library of Medicine), 2026); Ado-Trastuzumab Emtansine - NCI (National Cancer Institute, 2026); ATCDDD - ATC/DDD Index (WHO Collaborating Centre for Drug Statistics Methodology, 2026).
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Representative model, for educational purposes only.