FDA focuses on mixed data of Genentech's Avastin in patients with advanced breast cancer

The Food and Drug Administration will ask outside experts Wednesday whether Genentech's Avastin should be approved to treat breast cancer, despite mixed results in company studies.

After reviewing the San Francisco-based company's data, FDA said Monday patients on Avastin and chemotherapy had slower cancer progression, but did not survive longer overall than patients using chemotherapy alone.

Shares of Genentech Inc. fell $2.75, or 3.6 percent, Monday to close at $73.50.

Genentech has asked FDA to approve Avastin alongside the chemotherapy drug paclitaxel for patients with advanced breast cancer who have not already taken other cancer drugs. Avastin is currently approved for patients with certain types of colon and lung cancer. It was the company's second best-selling product last year with revenue of $1.7 billion.

FDA will ask a panel of cancer experts Wednesday if Genentech's data warrant approval for the drug in the U.S, despite the fact patients did not have longer survival times overall. The agency is not required to follow the guidance of its panels, though it often does.

FDA noted in documents posted online that a second Genentech study of Avastin in patients who had already taken two chemotherapy drugs showed no major benefits in overall survival or in slowing cancer progression. The panel Wednesday is expected to weigh in on the importance of these results as well as side effects seen with Avastin, including heart attack, hypertension and blood clots.

Stanford Group Co. analyst Gregory Frykman lowered his odds Monday for a positive panel vote to 40 percent from 65 percent "based on conservative posturing by the agency." Frykman said the outcome of Wednesday's meeting will likely depend on whether safety concerns raised by FDA scientists overshadow the effectiveness of Genentech's data.