A trial of trastuzumab deruxtecan and pertuzumab for breast cancer that has spread (DESTINY-breast09)

Please note - this trial is no longer recruiting patients. We hope to add results when they are available.

Cancer type:

Breast cancer
Secondary cancers




Phase 3

This trial is looking at trastuzumab deruxtecan (T-DXd) with or without pertuzumab for breast cancer that has spread to another part of the body. 

It is for people who have not had any treatment for their secondary breast cancer Open a glossary item. Their cancer needs to have the HER2 protein Open a glossary item.

More about this trial

Doctors can treat secondary breast cancer that has the HER2 protein with chemotherapy Open a glossary item and a monoclonal antibody Open a glossary item. One standard treatment they can use is a combination of:

Docetaxel and paclitaxel are taxane chemotherapy drugs. They work by stopping cancer cells dividing into 2 new cancer cells. This stops the cancer growing. 

Trastuzumab and pertuzumab are monoclonal antibodies. Some cancers have large amounts of a protein called HER2. The cancer uses HER2 to divide and grow. Trastuzumab and pertuzumab work by attaching to the HER2 on the cancer cell. This stops the cancer cell from dividing and growing. 

Trastuzumab deruxtecan is a type of drug called an antibody drug conjugate. It is trastuzumab with a chemotherapy like drug attached to it. Deruxtecan is the chemotherapy like drug. Trastuzumab finds and attaches to the HER2 protein on the cancer cell. Deruxtecan is then released into the cancer cell causing damage. This stops the cancer from growing. 

Trastuzumab deruxtecan is already a treatment in some countries for secondary breast cancer that has the HER2 protein.

Researchers think that trastuzumab deruxtecan with pertuzumab might help people with secondary breast cancer. To find this out they will compare the following:

  • trastuzumab deruxtecan and a dummy drug (placebo Open a glossary item)
  • trastuzumab deruxtecan and pertuzumab
  • docetaxel or paclitaxel, trastuzumab and pertuzumab

The aims of this trial are to find out:

  • how well trastuzumab deruxtecan works on its own or in combination with pertuzumab 
  • what happens to the treatment in the body when people have this combination
  • about the side effects of this combination
  • how it affects quality of life Open a glossary item

Who can enter

The following bullet points are a summary of the entry conditions for this trial. Talk to your doctor or the trial team if you are unsure about any of these. They will be able to advise you. 

Who can take part

You may be able to join this trial if all of the following apply. You:

  • have breast cancer that has spread to another part of the body (secondary breast cancer) 
  • have secondary breast cancer that has HER2 Open a glossary item (HER2 positive breast cancer) 
  • had a recent tissue sample (biopsy Open a glossary item) taken that the trial team can use to test for HER2 and PIK3CA. You are willing to have a new biopsy taken if you haven’t had a recent biopsy or there isn’t enough of the other sample for the team to test. 
  • have at least 1 area of cancer that has not been treated with radiotherapy that can be measured on a scan and is a certain size. Your doctor will know what the size is. 
  • are able to look after yourself but might not be able to do heavy physical work (performance status 0 and 1)
  • have satisfactory blood test results
  • are willing to use contraception during treatment and for a time after. This is if there is any chance you or your partner could become pregnant.
  • are at least 18 years old

Who can’t take part

Cancer related 
You cannot join this trial if any of these apply. You:

  • can have treatment with the aim to cure your secondary breast cancer  
  • have had chemotherapy or HER2 treatment such as trastuzumab for your cancer spread 
  • have another cancer. This is apart from successfully treated non melanoma skin cancer Open a glossary item, any in situ cancer Open a glossary item or any other solid cancer Open a glossary item that was treated with the aim to cure and there has been no sign of it for at least the past 3 years.  
  • have ongoing side effects from previous treatment. This is apart from hair loss and mild side effects. 
  • have cancer spread to the brain or spinal cord (including spinal cord compression Open a glossary item). You might be able to join if you are no longer having treatment such as steroids and have no symptoms. If you had radiotherapy to the brain it must be more than 2 weeks ago and you have no side effects.  

Medical conditions 
You cannot join this trial if any of these apply. You:

  • had major surgery within 4 weeks before going into a trial treatment group (randomisation Open a glossary item)
  • had radiotherapy to the chest within 4 weeks of randomisation. For radiotherapy to other areas of the body to relieve symptoms it is within 2 weeks. 
  • had hormone therapy Open a glossary item within 3 weeks of randomisation
  • had chloroquine or hydroxychloroquine within 2 weeks of randomisation. These are treatments for malaria.
  • have HIV, hepatitis B, hepatitis C or any other infection that needs treatment
  • have heart problems Open a glossary item that could affect you taking part
  • have or had inflammation of the lung not caused by an infection that needed treatment with steroids 
  • have other lung problems Open a glossary item that could affect you taking part. This includes surgery to remove a lung or part of it.
  • are having another cancer treatment
  • have had a certain type of cancer treatment. Your doctor will know if you have had this treatment.
  • have had an experimental drug or used a device as part of another clinical trial within the past year
  • have been put into a group (randomised) in another trial using trastuzumab deruxtecan whether you had it or not
  • have another medical condition or mental health problem that your doctor thinks might affect you taking part

You cannot join this trial if any of these apply. You:

  • are allergic or sensitive to the treatments used in this trial or any of their ingredients
  • have a live vaccine Open a glossary item within 30 days of starting treatment. You cannot have a live vaccine during treatment and shouldn’t have one within 30 days of stopping treatment. The COVID-19 vaccines are not live vaccines. 
  • are pregnant or breastfeeding

Trial design

This is an international phase 3 trial. The team need 1,134 people to join worldwide with 25 people in the UK. 

It is a randomised trial. A computer puts you into a treatment group. Neither you nor your doctor chooses which group you go into. You have an equal chance of going into 1 of 3 groups. The groups are:

  • trastuzumab deruxtecan and a dummy drug (placebo Open a glossary item)
  • trastuzumab deruxtecan and pertuzumab
  • docetaxel or paclitaxel, trastuzumab and pertuzumab 

Whichever group you are in you have the treatment as a drip into a vein. You have the treatment every 3 weeks. Each 3 week period is a cycle of treatment Open a glossary item

You have docetaxel or paclitaxel for at least 6 cycles of treatment as long as the side effects aren’t too bad.

You continue to have trastuzumab deruxtecan, pertuzumab, trastuzumab and the dummy drug as long as they are helping and the side effects aren’t too bad.  

Quality of life
You fill in several questionnaires before starting treatment and then:

  • at regular times during treatment
  • when you finish treatment

The questions ask about:

  • your general health and wellbeing
  • what you are able to do 
  • signs and symptoms

They take about 10 to 20 minutes to complete. 

These are quality of life questionnaires

Samples for the trial
When you agree to join the trial the team ask for a piece of a previous tissue sample (biopsy). They use this to test for HER2 and PIK3CA. Sometimes there might not be enough tissue to test or the team can’t access a previous sample. In this case you must be willing to have another tissue sample taken. 

If your cancer doesn’t have HER2 you can’t continue in the trial. In this case your doctor will talk to you about the best treatment for you. 

Samples for research 
You give several blood samples during the trial. Where possible the team take these when you have blood taken as part of your treatment. 

The team ask you to give extra tissue samples during treatment and if your cancer gets worse. You don’t have to agree to have these tissue samples being taken. 

They use the blood and tissue samples to:

  • look for substances (biomarkers Open a glossary item) that might show how well treatment is working
  • find out what happens to these treatments in the body and how they affect the body

Hospital visits

You see the doctor to have tests before taking part. These tests include:

  • a physical examination Open a glossary item
  • blood tests
  • heart trace (ECG Open a glossary item)
  • heart scan (ECHO Open a glossary item or MUGA Open a glossary item)
  • breathing tests (lung function tests Open a glossary item)
  • eye tests
  • urine test
  • CT scan or MRI scan
  • bone scan

You see the doctor regularly during treatment to see how you are and for blood tests.

You have a CT scan or MRI scan:

  • every 6 weeks from start of treatment for 48 weeks  and then
  • every 9 weeks until your cancer gets worse

You see the doctor when you finish treatment and about a month later. This is for some tests and to see how you are. 

You continue seeing the doctor as part of the trial every 3 months until your cancer gets worse.

Side effects

The trial team monitor you during treatment and afterwards. Contact your advice line or tell your doctor or nurse if any side effects are bad or not getting better. 

The most common side effects of trastuzumab deruxtecan are:

We have information about the side effects of:

Your doctor will talk to you about the possible side effects of all the treatments used in the trial before you agree to take part.

Recruitment start:

Recruitment end:

How to join a clinical trial

Please note: In order to join a trial you will need to discuss it with your doctor, unless otherwise specified.

Please note - unless we state otherwise in the summary, you need to talk to your doctor about joining a trial.

If you have questions about the trial please contact our cancer information nurses

Freephone 0808 800 4040

Last review date

CRUK internal database number:


Please note - unless we state otherwise in the summary, you need to talk to your doctor about joining a trial.

Wendy took part in a new trial studying the possible side effect of hearing loss

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"I was delighted to take part in a clinical trial as it has the potential to really help others in the future.”

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