Latest research: CDK inhibitors

In recent issues of The Beacon and The Inside Story, we have provided you with information about a class of drugs called CDK inhibitors and the work BCNA has been doing to advocate for a subsidy for the CDK inhibitors palbociclib and ribociclib through the Pharmaceutical Benefits Scheme (PBS).

CDK inhibitors are oral treatments used to treat hormone receptor positive, HER2-negative metastatic breast cancer. The drugs work by blocking the function of enzymes involved in the pathway that helps control how cells grow and divide. The CDK4/6 pathway is commonly overactive in breast cancer cells, resulting in loss of control over cell growth.

The PALOMA-2 clinical trial tested the benefits of the CDK inhibitor palbociclib for women who had not previously received treatment for metastatic breast cancer. It showed that treatment with palbociclib in combination with the hormone therapy drug letrozole improved progression-free survival (the length of time before the cancer grows or spreads) to 24.8 months compared to 14.5 months for women treated with letrozole only. The study also found that palbociclib was generally well tolerated and women experienced low rates of the side effects common to cancer treatments, such as nausea, diarrhoea and hair loss.

After learning my breast cancer had returned after eight years and had spread to my bones, I was offered a lifeline in the form of taking part in a clinical trial for palbociclib. Since taking the drugs last July, my initial symptoms of nausea, lack of appetite and fatigue have diminished to the point where they do not figure in my consciousness and I look and feel well. Regular monthly tests have returned positive results and have also revealed that my
cancer markers continue to fall.
– Jane

Researchers are now also investigating the potential for palbociclib as a treatment option for early breast cancer in the PALLAS study, which is recruiting patients at some Australian institutions.

The MONALEESA-2 clinical trial, also for women who had received no previous treatment for metastatic breast cancer, showed that the CDK inhibitor ribociclib in combination with letrozole improved progression-free survival to 25.3 months compared to 16 months for people treated with letrozole and a placebo. Ribociclib was also found to be generally well tolerated.

At the American Society of Clinical Oncology (ASCO) Annual Meeting in June, findings from another clinical trial were presented that looked at the effectiveness of a third CDK inhibitor, abemaciclib.

The MONARCH 2 clinical trial compared abemaciclib plus fulvestrant (Faslodex) to fulvestrant plus placebo in women whose cancer had progressed on previous hormone therapy. The study found that treatment with abemaciclib in combination with fulvestrant resulted in 16.4 months of progression-free survival compared to 9.3 months for women who received fulvestrant only.

BCNA has been advocating to the Australian Government to have at least one of the CDK inhibitors added to the Pharmaceutical Benefits Scheme (PBS) so that these new treatments are available equally and affordably to all Australians who can benefit from them. We will keep you updated about developments through The Beacon and our website. You can also read our submissions to the Pharmaceutical Benefits Advisory Committee (PBAC) in support of listing palbociclib and ribociclib on the PBS on our website.

If you have metastatic breast cancer and would like to know more about accessing CDK inhibitors in Australia, read the Accessing CDK inhibitors article in The Inside Story. 

Issue 80
Spring 2017