Trastuzumab deruxtecan (Enhertu)

At a glance

Trastuzumab deruxtecan (Enhertu) is an antibody–drug conjugate, often shortened to ADC. It combines an antibody that recognises a target on cells with a cell-killing medicine. It is given by a trained team through a drip into a vein. Although it is targeted treatment, it can affect healthy tissues and needs careful monitoring.

New cough or breathlessness needs immediate attention during Enhertu treatment because lung inflammation can become serious. Preventive anti-sickness treatment and heart-function monitoring are also important. Enhertu is different from ordinary trastuzumab and from trastuzumab emtansine, even though their names share the same first word.

Follow your own treatment calendar and the advice from your care team. Keep your medicine names and treatment dates handy to share with other clinicians.

How it works

The antibody recognises HER2, a protein involved in cell signalling. It carries a deruxtecan payload that inhibits topoisomerase I, an enzyme involved in managing DNA. After the drug enters a target-bearing cell, the payload is released and can damage cells. Some activity can also extend to nearby cells. This does not remove the need for accurate selection testing or protect all normal tissues.

The antibody, its chemical link and the attached medicine form one product. They are not separate medicines that you can take in different amounts yourself. Targeting helps deliver treatment to particular cells, but it does not mean that only cancer cells are affected. Side effects can come from the attached medicine, the antibody, your existing illness or accompanying treatment.

An ADC is different from an immune checkpoint inhibitor, even when both are given in the same treatment plan. A reaction or noticeable side effect is not proof that an ADC is working. Equally, having few side effects does not mean that treatment has failed.

Is this treatment suitable for me?

Trastuzumab deruxtecan is used for selected breast, lung, stomach or gastro-oesophageal junction cancers, and some other solid tumours, when the required HER2 finding and treatment-history criteria are met. Your oncologist will advise whether it is suitable for you, taking account of your cancer type, relevant test results, previous treatment, overall health and the applicable prescribing information and regulatory guidance in your country.

A validated test is needed to define the relevant HER2 finding. Depending on the treatment setting, the result may concern protein expression, a low or ultralow expression category, or a gene mutation. These are different findings and cannot be substituted for one another. The team reviews the actual laboratory report, previous treatment, lung history, heart function and current local prescribing guidance.

The discussion should cover the aim of treatment, the alternatives, likely appointments and how benefit will be assessed. A target found in a sample is one part of this decision; it does not guarantee a response. Tell the team what matters to you, including independence, work, caring responsibilities and the practical support available at home.

Before treatment

Bring a complete list of prescribed and non-prescribed medicines, vitamins, herbal products and allergies. Mention previous difficult reactions to infusions, infections, diabetes, liver or kidney problems and any pregnancy or breastfeeding. Explain symptoms you already have so a later change is easier to recognise.

Blood counts, liver and kidney tests and a measurement of left ventricular ejection fraction, or LVEF, are obtained before treatment. Pregnancy status is checked if pregnancy is possible. LVEF estimates how well the main pumping chamber of the heart works. Tell the team about previous lung inflammation, radiation treatment, cough, oxygen use or breathlessness. Baseline imaging and symptoms help interpret later changes. Kidney impairment or previous lung inflammation can increase the need for close lung monitoring; significant liver impairment also requires careful assessment.

A nurse or pharmacist should explain the supportive medicines and which ones start before the treatment day. Ask your team to help you plan when to take each medicine. Make sure you know how to reach your hospital's urgent oncology service outside clinic hours. You may find it helpful to save the instructions on your phone or keep a copy at home. A family member or friend can help you remember them.

Discuss fertility preservation before treatment if future parenthood matters to you. Tell the team about dental problems and planned procedures. A procedure may need to be timed around blood counts and infection risk. Do not postpone reporting an active dental infection while waiting for the next routine appointment.

How treatment is given

Enhertu is usually given once every three weeks. The usual starting dose is 5.4 mg/kg for breast cancer, HER2-mutant non-small cell lung cancer and other eligible solid tumours, and 6.4 mg/kg for eligible stomach or gastro-oesophageal junction cancer. These doses are not interchangeable choices based on convenience. The first infusion takes 90 minutes; subsequent infusions may take 30 minutes if the earlier dose was tolerated.

Some plans continue while treatment is helping and remains tolerable; others use a fixed number of cycles or a planned sequence with other medicines. Current US information also includes use with pertuzumab in a selected setting. Your treatment plan should identify whether Enhertu is being used alone, with a partner or before a different treatment phase.

Enhertu has a high risk of causing nausea and vomiting, including delayed symptoms. Preventive anti-sickness medicines are given according to the hospital protocol, and a take-home schedule should be supplied. Ask which tablets prevent symptoms and which are for breakthrough nausea. Do not wait for repeated vomiting before asking for a better plan.

Treatment is delivered through a cannula in a vein, a central line or an implanted port, depending on the plan and available access. Staff check the medicine, your identity, blood results and recent symptoms before starting. The appointment includes preparation and monitoring, so it will usually take longer than the infusion itself.

Tell the nurse immediately if you notice burning, pain, swelling, redness, leakage or tightness around the infusion site. These can mean medicine is leaking outside the vein. Do not wait for the drip to finish. At home, report a site that becomes more painful, blistered or discoloured, even if it looked normal when you left.

Also report flushing, itching, shivering, chest or back discomfort, wheezing, dizziness or swelling during treatment. Staff can stop or slow the infusion and assess you. Do not adjust the pump or line yourself. If a line remains in place, follow its cleaning and dressing instructions and report fever, tenderness or drainage around it.

If an appointment is missed, contact the treatment unit to arrange the next dose. Do not simply wait for the following cycle or seek an extra dose elsewhere. The correct restart date depends on why the dose was missed, the treatment schedule and recovery from side effects.

Monitoring your treatment

Blood tests usually check infection-fighting cells, red cells, platelets, kidney function and liver function. Some abnormalities cause no early symptoms. A reassuring blood test does not make a new symptom safe to ignore, and feeling well is not a reason to miss monitoring.

Blood counts are checked before each dose and when clinically indicated. Heart function is reassessed at regular intervals, with additional assessment for symptoms. The team reviews breathing symptoms and scans for possible lung inflammation. Imaging changes can precede symptoms, so attend scans even when you feel well. Response assessment and toxicity assessment are separate parts of each review.

Your team compares examinations, symptoms and relevant scans or disease tests over time. Ask when the first response assessment is planned and what the result could change. A treatment break or lower dose may protect you from accumulating harm while allowing further treatment. It is not automatically evidence that the cancer has worsened. Never try to compensate for a reduced dose with supplements or closer appointments.

Common side effects

Side effects vary between people and between treatment combinations. You may experience several, a few or none of those described. Tell the team about symptoms that interfere with eating, sleeping, walking or usual tasks; a problem does not need to be severe before support is worthwhile.

Nausea, vomiting and reduced appetite

These can persist beyond infusion day. Use the preventive schedule, eat small amounts regularly and report inadequate symptom control early. Persistent vomiting or inability to drink may need intravenous fluids and revised anti-sickness treatment. Constipation from supportive medicines may also need an agreed plan.

Hair loss and mouth soreness

Hair loss is common and may affect confidence and comfort. Ask about scalp care and support before treatment. Mouth soreness can make eating difficult; gentle oral care and early reporting of ulcers or white patches helps the team manage pain or infection.

Changes in blood counts

Low neutrophils increase infection risk, low red cells can cause fatigue and breathlessness, and low platelets can cause bruising or bleeding. Blood-test changes may require a pause or lower dose even before symptoms appear. Follow supportive-treatment appointments and the fever plan.

Tiredness and reduced stamina

Plan important tasks for the part of the day when you have most energy and accept practical help. Short periods of gentle activity can be useful, with rest between them. Sudden marked weakness, breathlessness, dizziness or a racing heart needs assessment for causes such as anaemia, infection or dehydration. Do not assume every new limitation is ordinary treatment fatigue.

Nausea, appetite and bowel changes

Take prescribed anti-sickness medicines on the agreed schedule. Small regular meals, cool foods and frequent sips can be easier to manage. Tell the team if you cannot keep medicines or fluids down, are passing little urine or are losing weight. A dietitian can help when eating becomes difficult.

Record loose stools and whether there is pain, blood or fever. Severe diarrhoea, repeated vomiting or a swollen painful abdomen needs prompt advice. Constipation can be worsened by anti-sickness drugs and pain relief; use the bowel plan your team recommends. Do not repeatedly add laxatives or anti-diarrhoeal medicines without checking when there is significant pain or other new illness.

Low blood counts

A low white cell count can make infection progress quickly. Follow the urgent-help instructions below. Low red cells can cause tiredness, pallor or breathlessness; sometimes transfusions are needed. Low platelets can cause easy bruising, nosebleeds, bleeding gums or tiny red-purple spots. Report new bleeding and avoid starting aspirin or anti-inflammatory painkillers without checking. Do not stop a prescribed blood thinner yourself; the team must balance bleeding and clotting risks.

Mouth comfort and skin care

Use a soft toothbrush and the mouth-care products advised by your team. Report ulcers, white patches or soreness that limits eating, because infection or dehydration may need treatment. Avoid very hot, acidic or spicy foods if they sting. Moisturise dry skin with a simple fragrance-free product and protect it from strong sunlight. Painful skin, blisters or rapidly worsening redness need medical assessment rather than a new cosmetic product.

Important side effects

Interstitial lung disease and pneumonitis

These terms describe inflammation or injury in lung tissue. Enhertu-related lung inflammation can be fatal. Report any new or worsening cough, breathlessness, fever or reduction in exercise tolerance immediately, even if it seems mild. Do not assume it is a cold or wait for the next infusion.

The team may pause treatment, arrange chest imaging and specialist assessment and prescribe corticosteroids. Under the checked instructions, symptomatic treatment-related interstitial lung disease or pneumonitis requires permanent discontinuation of Enhertu. Confirmed treatment-related lung changes on a scan without symptoms also require Enhertu to be withheld until recovery; corticosteroids may be considered. Decisions about diagnosis and any restart belong to the specialist team.

Reduced heart pumping function

HER2-directed treatment can reduce LVEF and cause heart failure. New breathlessness, swollen ankles, rapid weight gain, difficulty lying flat or chest discomfort needs assessment. The cause may be cardiac, pulmonary or something else; do not decide at home which warning applies. Confirmed symptomatic heart failure requires permanent discontinuation.

Serious infection

Low neutrophils can allow infection to progress quickly. Fever, shaking chills or sudden illness needs immediate advice, even if the last blood test was reassuring. Severe weakness, confusion or fast breathing requires urgent in-person assessment.

Severe infection or an allergic reaction

A serious infection can occur even without a high temperature, especially if steroids or fever-reducing medicines are being taken. New confusion, marked drowsiness, rapid breathing or collapse requires emergency care. Sudden throat swelling, severe wheezing or faintness can indicate a severe allergic reaction. These symptoms should not be managed by waiting at home for the next scheduled review.

Other medicines and vaccinations

A full medicines review is needed even though the checked information does not identify a routine requirement to change the Enhertu dose with all common CYP inhibitors. Other heart-affecting treatments, prior anthracyclines and medicines used for symptoms matter to the overall plan. Never substitute trastuzumab, trastuzumab emtansine or another HER2 medicine for a scheduled Enhertu dose.

Ask the oncology pharmacist to check new prescriptions, over-the-counter remedies and herbal or traditional products. Products described as natural are not necessarily safe with cancer treatment. Do not use an unproven supplement in place of an essential supportive medicine. Keep the team informed about medicines prescribed by other specialists so that advice is coordinated.

Discuss influenza, COVID-19 and other vaccines with the team. Non-live vaccines may be suitable, although the response can be reduced during treatment. Live vaccines require specific specialist advice. Timing after treatment depends on immune recovery and the complete regimen; there is no single waiting interval that is correct for every ADC-treated patient.

Everyday life

Eating does not determine absorption of this intravenous medicine. Aim for enough food and fluids, adjusting for nausea and following any kidney, heart or diabetes restrictions. Avoid a restrictive anticancer diet that causes weight loss. Discuss alcohol with the team, particularly if liver tests are abnormal or other medicines cause sedation.

Work may remain possible with flexible hours and time for appointments. Increase activity gradually and avoid tasks that become unsafe because of fatigue, poor balance or impaired vision. Do not drive if dizzy, sleepy, visually affected or unable to use the pedals safely. Sedating premedicines can also affect driving, so arrange transport for early appointments until you know the plan.

Notice changes in what you can comfortably do, such as climbing stairs or walking a familiar distance. A new limitation can be more useful to report than waiting for severe breathlessness at rest. Balance gentle activity with rest and seek help with meals during the days when nausea is worst.

Discuss travel before booking, especially long journeys or travel far from urgent care. Carry your treatment summary and enough supportive medicines. Use careful hand hygiene and food safety; avoid close contact with people who are clearly infectious. Complete social isolation is not automatically required. Ask about additional precautions when blood counts are very low.

Sex is often possible if comfortable, with the pregnancy precautions below and any advice about infection or bleeding. Ask the team whether barrier protection is needed after a dose to reduce exposure to drug residues in body fluids; the interval depends on the treatment. Caregivers cleaning urine, stool or vomit should follow the unit's handling advice, wear gloves when instructed and wash their hands afterwards. Keep medicines away from children and pets.

Fertility, pregnancy and breastfeeding

Use effective contraception during treatment and for at least seven months after the final dose if you could become pregnant. A treated man with a partner who could become pregnant should use effective contraception during treatment and for at least four months afterwards. Do not breastfeed during treatment or for at least seven months after the final dose. Partner medicines may add further requirements. Discuss sperm storage before treatment where relevant; do not donate or freeze sperm during treatment or for at least four months afterwards.

Pregnancy should be discussed before treatment and reported promptly if it occurs or is suspected. Loss of periods does not reliably mean pregnancy is impossible. Vomiting or severe diarrhoea can interfere with oral contraception; seek advice about additional protection if this happens. Accompanying medicines may require longer precautions than the ADC itself, so obtain one clear end date for the complete regimen.

Fertility may be affected by treatment and previous therapies, and recovery cannot be guaranteed. Discuss sperm, egg or embryo preservation before starting when feasible. The interval for avoiding pregnancy is a safety precaution and does not itself establish whether fertility has recovered.

After treatment

Continue to report new breathing symptoms after the final dose and attend follow-up for any prior lung or heart effects. If corticosteroids were prescribed for lung inflammation, take the taper exactly as directed rather than stopping suddenly. Record any treatment-related pneumonitis clearly in your medical history.

Keep attending the recommended blood tests, scans and clinical reviews. Retain a treatment summary with the exact ADC name, dates, significant reactions and any ongoing medication. Tell new clinicians about past treatment when an unexplained symptom is assessed. Continue contraception, breastfeeding restrictions and prescribed supportive medicines for their own specified periods, counted from the relevant final dose.

Recovery can be gradual and may involve physical rehabilitation, dietary support or help with anxiety and sleep. A follow-up visit is also an opportunity to discuss returning to work, travel and persistent symptoms. New severe symptoms still need urgent assessment between appointments; finishing treatment does not remove the need for the urgent-care plan.

Common questions