Trastuzumab deruxtecan
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; a pregnancy test is done first and effective contraception is used during and after treatment.
Anti-HER2 antibody carrying a topoisomerase I inhibitor; used in HER2-positive and HER2-low breast cancer and other HER2 tumours. Key risk: lung damage.
Also called: fam-trastuzumab deruxtecan, T-DXd
Quick facts
- Group
- Antibody-drug conjugates (ADCs)
- Target
- HER2 (ErbB2) receptor on tumour cells
- Used for
- HER2-positive breast cancer
- Key effects
- Nausea and vomiting · Fatigue · Hair loss
- Monitor
- New or worse cough · Pregnancy test before starting
- ATC
- L01FD04
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 deruxtecan payload is not in the structure.
The trastuzumab part binds HER2 on tumour cells. The conjugate is internalised, its linker is cut inside the cell and deruxtecan, a camptothecin-derived topoisomerase I inhibitor, is released. It traps topoisomerase I on DNA, causing DNA breaks and death of the cancer cell. It works even in tumours with low HER2 levels.
- The antibody binds HER2 on the tumour cell
- The conjugate is taken in and the linker is cut
- Deruxtecan blocks topoisomerase I: DNA breaks
- The cancer cell dies
Indications
- HER2-positive breast cancer that cannot be removed or has spread, and HER2-low or HER2-ultralow advanced breast cancer after other treatment. Breast cancer →
- HER2-positive advanced gastric or gastro-oesophageal junction cancer after a trastuzumab-based regimen. Gastric cancer →
- Advanced non-small cell lung cancer with an activating HER2 (ERBB2) mutation after prior therapy. Lung cancer →
- Other advanced HER2-positive solid tumours when no other option exists (accelerated approval).
Adverse effects
Common
- Nausea and vomiting (anti-sickness medicine is usually given)
- Fatigue
- Hair loss
- Constipation or diarrhoea, decreased appetite
- Low blood counts
Contraindications
- Allergy to the drug or its ingredients (including Chinese hamster ovary cell proteins)
Key interactions
- Trastuzumab and trastuzumab emtansine
- Different drugs with different schedules and toxicities: never substituted for one another.
- Other drugs that harm the lungs or the heart
- May add to the risk of pneumonitis or ventricular dysfunction; the full medication list is reviewed.
What is monitored
- New or worse cough, breathlessness or fever (pneumonitis)
- Complete blood count before each dose
- Left ventricular ejection fraction (echocardiogram) before and during treatment
- Pregnancy test before starting
Administration and safety
- Intravenous infusion only, never as a push or bolus; given in a clinic or hospital.
- Check the full name: trastuzumab, trastuzumab emtansine and trastuzumab deruxtecan are different products.
- The powder is reconstituted and diluted following the product instructions; it is a hazardous drug handled with chemotherapy precautions.
- Antiemetics are usually given before each dose.
Pregnancy and breastfeeding
Avoid in pregnancy. Can harm the fetus; a pregnancy test is done first and effective contraception is used during and after treatment.
Nursing care
- Ask at every visit about cough, breathlessness or fever and report them before the dose.
- Review blood counts and the latest heart function test before giving it.
- Watch for nausea and vomiting during and after treatment.
- Teaching: report breathing symptoms at once, use effective contraception, and avoid breastfeeding during treatment and for a period afterwards.
Pharmacokinetics
- Absorption
- Intravenous infusion every few weeks.
- Elimination
- The antibody part is broken down like other proteins.
Test yourself
Think of the answer, then tap the question to see it.
What kind of payload does trastuzumab deruxtecan carry?
A topoisomerase I inhibitor derived from camptothecin (deruxtecan).
What is the boxed lung toxicity of trastuzumab deruxtecan?
Interstitial lung disease or pneumonitis, which can be fatal.
Can trastuzumab deruxtecan help tumours with low HER2 levels?
Yes, it is approved in HER2-low (and HER2-ultralow) advanced breast cancer.
Why must the full drug name be checked before giving a «trastuzumab»?
Because trastuzumab, trastuzumab emtansine and trastuzumab deruxtecan are different drugs and are not interchangeable.
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: Fam-trastuzumab deruxtecan-nxki Injection: MedlinePlus Drug Information (MedlinePlus (U.S. National Library of Medicine), 2026); Fam-Trastuzumab Deruxtecan-nxki - 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.