A cancer trial to test a new treatment for patients with advanced breast cancer, which is not responding to currently available treatments, has been opened.

The trial will be run by Cancer Trials Ireland, which coordinates cancer trials in this country. Since its establishment in 1996, over 15,000 people have participated in more than 350 cancer trials.

This latest trial will test, for the first time, use of the new drug copanlisib in combination with trastuzumab to treat advanced HER2-positive (HER2+) breast cancer, which has progressed or recurred in patients during or after standard treatment for this type of cancer.

HER2+ breast cancer leads to the overproduction of Human Epidermal growth factor Receptor 2 (HER2). This is a protein that stimulates the growth of cancer cells.

While current treatments to specifically target HER2, such as trastuzumab, can help to slow or even stop the growth of breast cancer cells, resistance to these treatments can develop. As a result, they can become ineffective.

However, copanlisib could help to reverse the resistance of some HER2+ cancers to trastuzumab, leading to a new therapy for this type of breast cancer.

According to Cancer Trials Ireland, it is expected that up to 34 patients will take part in this trial, which will be conducted over the next two to three years in five hospitals - Beaumont, St James's and St Vincent's University Hospital in Dublin, University Hospital Galway and Cork University Hospital.

"It is known that HER2+ breast cancer can become resistant to current HER2 therapy. We are now learning how this happens. The switching on of a pathway called the PI3K pathway in cancer cells is often responsible. One of the possible ways this happens is through mutations that occur in a gene called PIK3CA.

"Research studies that we have carried out at the laboratory level have suggested that blocking the abnormal activity of the PI3K pathway in cancer cells, may help to reverse the resistance of some HER2+ breast cancers to HER2 treatments including trastuzumab," explained Prof Bryan Hennessy, clinical lead at Cancer Trials Ireland and consultant oncologist at Beaumont Hospital, who is leading this current trial.

Copanlisib blocks the abnormal activity in the PI3K pathway and is already being tested in a number of other types of cancer.

"By combining copanlisib and trastuzumab, this trial hopes copanlisib will block the abnormal activity of the PI3K pathway and allow trastuzumab to work effectively," Prof Hennessy added.

To find out more about this trial, including whether they are suitable candidates, patients should speak to their doctor.

For more information on Cancer Trials Ireland, click here