European healthcare regulators are reviewing the benefits of Roche’s top-selling Avastin drug in breast cancer in the light of fresh clinical data, casting more uncertainty over its prospects.

The news comes as investors await a decision from U.S. authorities on whether to revoke Avastin’s label in advanced breast cancer and follows a series of setbacks for the treatment so far this year.

The U.S. Food and Drug Administration is also considering whether to expand Avastin’s label in the United States to allow the drug to be used with other chemotherapies.

The European Medicines Agency said on Friday it had started a review of the benefits and risks of Avastin after Roche submitted a study to support its application of Avastin to treat breast cancer with anthracycline-based or capecitabine cytotoxic chemotherapy.

In comparison with results of previous studies, the agency said the latest study pointed to inconsistencies between different trials, particularly in terms of efficacy.

Roche said it was committed to working closely with EMA’s Committee for Medicinal Products for Human Use (CHMP) to make sure it had all the information it required for the review of Avastin in the first-line treatment of metastatic breast cancer.

The CHMP opinion on this label expansion is expected later this year, Roche said, adding the current use of Avastin in its licensed indications, including for the treatment of patients with metastatic breast cancer, was not affected by the review.

SETBACKS

Avastin, which brought in sales of over $6 billion for Roche last year, was once tipped to become the world’s biggest selling drug by 2014, but its prospects have faded after doubts over its benefits in breast cancer and after it failed in clinical trials for prostate and stomach cancer.

Roche, the world’s largest maker of cancer drugs, may have to grapple with a hefty dent to sales in the United States if the FDA decides to follow the advice of an advisory panel to remove the drug’s current approval for breast cancer.

About $1 billion of Avastin’s sales come from breast cancer uses, analysts estimate. The product is Roche’s top-selling drug, accounting for 13 percent of 2009 sales.

There is no set timeline for an FDA ruling on whether to revoke the breast cancer approval. If the FDA pulls it, the drug would remain on the market with clearance for colon, lung, brain and kidney cancers.

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By Katie Reid

ZURICH (Reuters)