Roche and Genentech’s bid to get a breast cancer indication approved for their blockbuster Avastin may not be a straightforward affair, following doubts expressed about the drug’s effectiveness by US regulators.

Staff at the US Food and Drug Administration have reviewed Avastin (bevacizumab) ahead of an advisory committee meeting tomorrow which will make a recommendation about approval of the drug's use in combination with paclitaxel as a first-line treatment for locally recurrent or metastatic breast cancer. However their analysis falls well short of giving a wholehearted thumbs-up.

The FDA staffers say that the main issue is whether the significant improvement in progression-free survival merits approval “in the absence of an improvement in overall survival”. Also apart from not helping women with breast cancer live for a meaningfully longer time, any benefits need to be weighed against increased toxicity, and deaths, related to the administration of Avastin.

No walk in the park
The agency staff’s did not take a specific position on whether the drug should be approved but the scene is set for a review that will not be “a walk in the park,” according to a research note issued by Michael Aberman at Credit Suisse. However he noted that “at the end of the day, oncologists are very familiar with the incremental improvements required to move cancer treatment forward”.

Cowen & Co issued a note saying that it believes the panel will recommend Avastin for approval in breast cancer, due to “consultants' favourable views toward the drug in this indication, the large magnitude of the benefit in PFS, and the difficulty in demonstrating an overall survival advantage in this tumour type”. However the analysts also note that FDA panels are “notoriously unpredictable”.

Currently approved for colorectal and lung cancers, Genentech is hoping a 'yes' in breast cancer will help send sales of Avastin – already standing at $597 million in the third quarter alone – even higher. The filing is based on data presented in 2005 at the American Society of Clinical Oncology meeting that patients treated with Avastin plus paclitaxel experienced a near doubling in median PFS compared to those treated with paclitaxel alone (11 months versus six months). Furthermore, Genentech has stressed that no new safety signals emerged outside of those known to be associated with Avastin.