New research suggests that palbociclib, an already approved breast cancer drug, could help to treat triple negative breast cancer.

A new use for an existing drug

Researchers funded by Breast Cancer Now have found a change in some triple negative breast cancers that makes them vulnerable to existing treatments.

The study suggests that the drug palbociclib, which is currently used to treat oestrogen receptor positive (ER+) secondary breast cancer, could also help to treat about a fifth of people with triple negative breast cancer.

This study provides a strong case for a clinical trial and could lead to a much-needed new treatment for women with triple negative breast cancer.

Much-needed treatments

Triple negative breast cancer is the name given to breast cancer that is oestrogen receptor negative (ER-), progesterone receptor negative (PR-), and HER2 negative.  

’Each year, around 8,000 UK women are diagnosed with triple negative breast cancer and we desperately need new, effective ways to treat them and stop them dying from this devastating disease,' said Dr Simon Vincent, Director of Research, Support and Influencing at Breast Cancer Now.

The research, led by Dr Rachael Natrajan at the Breast Cancer Now Toby Robins Research Centre, found a change in some triple negative breast cancers that helps the cancer grow. But looking for this change in tumour cells could also help to find people who may benefit from drugs called CDK4/6 inhibitors, such as palbociclib.

Rachael explained, ‘Our study shows what drives the growth of some triple negative breast cancers and suggests the exciting possibility that an already-approved breast cancer drug could be used to help women with triple negative breast cancer.’

A new weakness

The team looked at 200 of the most frequently altered genes in breast cancer to investigate how changes in these genes affect cancer’s ability to grow.

Researchers used an innovative technique that grows ‘mini-tumours’ in the lab. They found that triple negative breast cancer cells with low levels of a protein called CREBBP, could grow faster and more aggressively.

‘Our findings were only possible because we used an innovative model, involving the growth of 3D ‘mini tumours’ in the lab, to closely reflect how tumours develop in the body,’ said Rachael.

They also found that when CREBBP levels are low, breast cancer cells start relying on proteins called CDK4 and CDK6 to grow. These proteins can be blocked with a group of drugs called CDK4/6 inhibitors, including palbociclib, which can stop the cancer from growing.

Next steps

This study provides a strong case for a clinical trial into the use of palbociclib as a treatment for triple negative breast cancer.

Since palbociclib is an existing drug that has already been proven to be safe, it could be quickly taken into clinical trials for triple negative breast cancer.

‘We hope that if clinical trials confirm that palbociclib is beneficial for some of these women, it will be advanced through the approval process and made available for those who need it as quickly as possible,’ added Simon.


Breast Cancer Now thanks Art For Cure for their generous support of Dr Natrajan’s research. 

If you have any concerns about breast cancer, you can speak to our expert nurses on our free Helpline at 0808 800 6000 or by using our confidential Ask Our Nurses service.

The study was published in the journal Cancer Research.