Roche's pertuzumab potential major advance in breast cancer

Adding Roche's pertuzumab to a regimen of Herceptin and docetaxel in patients with HER2-positive breast cancer has significantly improved progression-free survival in a phase III trial.

Updated results from the CLEOPATRA study were presented yesterday at the San Antonio Breast Cancer Symposium yesterday, and shortly after being published online in the New England Journal of Medicine.

The data revealed that the combination of pertuzumab, Herceptin (trastuzumab) and docetaxel was associated with progression-free survival of 18.4 months, compared to 12.4 months from Herceptin and docetaxel alone, a 38 per cent improvement.

The objective response rate in the trial was 80.2 per cent for patients receiving the triple combination and 69.3 per cent in the Herceptin and docetaxel group. Meanwhile, pertuzumab also seemed to be well-tolerated, with no increase in cardiovascular side effects compared to the comparator therapy.

While Herceptin was a major advance in HER2-positive breast cancer - and a spectacular success for Roche with sales of $6.8bn last year - most cases of advanced disease eventually progress despite treatment with the drug.

For that reason there has been considerable excitement over the potential of pertuzumab because it targets HER2 in a different and complementary way to Herceptin.

There are preliminary signs in CLEOPATRA that this optimism may be well-founded. Specifically, there was a trend towards improved overall survival with pertuzumab which, if confirmed in additional follow-up, could represent a significant advance over current therapy. Those data are due in 2013.

"These results show we may soon improve on the current standard of care, Herceptin plus chemotherapy, to further help people with this advanced form of the disease," said Hal Barron, Roche's chief medical officer and head of global product development.

Analysts have suggested that if pertuzumab can fulfil its potential in HER2-positive breast cancer it could achieve sales of around $2bn, helping to support Roche's oncology franchise when Herceptin starts to lose patent protection in 2015.