[Durgical](https://durgical.com/en/) › [DurgiPedia](https://durgical.com/en/durgipedia/) › [Pharmacology](https://durgical.com/en/pharmacology/) › [Antibody-drug conjugates (ADCs)](https://durgical.com/en/pharmacology/classes/antibody-drug-conjugates/) › Trastuzumab deruxtecan

# 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.

Updated Nov 1, 2026

Also called: fam-trastuzumab deruxtecan, T-DXd

## Quick facts

**Group**
[Antibody-drug conjugates (ADCs)](https://durgical.com/en/pharmacology/classes/antibody-drug-conjugates/)

**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.

On this page

- The basics Mechanism of action
- Indications
- Adverse effects
- Pharmacokinetics
- Memory aid

- Clinical What the labels mean

- Safety Contraindications
- Key interactions
- What is monitored
- Administration and safety
- Pregnancy and breastfeeding
- Nursing care

- Study Test yourself

- Connections Connections

## Mechanism of action

◎**HER2 (ErbB2) receptor on tumour cells**Trastuzumab deruxtecan

ⓘ 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.

**Target in 3D:** HER2 (ErbB2) receptor on tumour cells. PDB structure 6OGE (RCSB PDB, public domain). [View the structure at RCSB PDB](https://www.rcsb.org/structure/6OGE) · Drag to rotate · pinch to zoom

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 →](https://durgical.com/en/conditions/breast-cancer/)
- HER2-positive advanced gastric or gastro-oesophageal junction cancer after a trastuzumab-based regimen. [Gastric cancer →](https://durgical.com/en/conditions/gastric-cancer/)
- Advanced non-small cell lung cancer with an activating HER2 (ERBB2) mutation after prior therapy. [Lung cancer →](https://durgical.com/en/conditions/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

### Serious (rare, important)

- Interstitial lung disease / pneumonitis, which can be fatal (boxed warning)
- Neutropenia and serious infection
- Left ventricular dysfunction (reduced heart pumping)
- Embryo-fetal toxicity (boxed warning)

## 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.

## Memory aid

«DXd = DNA + Dyspnoea»: the payload breaks DNA (topoisomerase I) and the drug's red flag is the lung (interstitial lung disease).

## 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.

[Add to my cards (4)](https://durgical.app/estudiar/?add=/en/pharmacology/trastuzumab-deruxtecan/)

[More Pharmacology questions →](https://durgical.com/en/practice/?f=pharmacology)

## What the labels mean

**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.

## Connections

## Related drugs 3

- [Trastuzumab](https://durgical.com/en/pharmacology/trastuzumab/)
- [Trastuzumab emtansine](https://durgical.com/en/pharmacology/trastuzumab-emtansine/)
- [Sacituzumab govitecan](https://durgical.com/en/pharmacology/sacituzumab-govitecan/)

## Related conditions 3

- [Breast cancer](https://durgical.com/en/conditions/breast-cancer/)
- [Gastric cancer](https://durgical.com/en/conditions/gastric-cancer/)
- [Lung cancer](https://durgical.com/en/conditions/lung-cancer/)

[← Back to the class: Antibody-drug conjugates (ADCs)](https://durgical.com/en/pharmacology/classes/antibody-drug-conjugates/)

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](https://medlineplus.gov/druginfo/meds/a620006.html) (MedlinePlus (U.S. National Library of Medicine), 2026); [Fam-Trastuzumab Deruxtecan-nxki - NCI](https://www.cancer.gov/about-cancer/treatment/drugs/famtrastuzumabderuxtecan-nxki) (National Cancer Institute, 2026); [ATCDDD - ATC/DDD Index](https://atcddd.fhi.no/atc_ddd_index/?code=L01FD04) (WHO Collaborating Centre for Drug Statistics Methodology, 2026).

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Representative model, for educational purposes only.

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Source: https://durgical.com/en/pharmacology/trastuzumab-deruxtecan/
License: CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). Cite as: DurgiPedia (durgical.com), https://durgical.com/en/pharmacology/trastuzumab-deruxtecan/