The US Food and Drug Administration's (FDA) Oncologic Drugs Advisory Committee (ODAC) on Thursday unanimously backed the approval of biosimilar versions of two of Roche's top selling cancer drugs, Avastin (bevacizumab) and Herceptin (trastuzumab).

In the morning session, ODAC members voted 17-0 in favor of approving Amgen's Avastin biosimilar candidate, ABP 215, for six of Avastin's indications. However, the committee did not consider whether Amgen's data would support approval for two of Avastin's indications for ovarian cancer, as they are covered by orphan drug exclusivity until 2021 and 2023.

In the afternoon session, ODAC members voted 16-0 in favor of approving Mylan's Herceptin biosimilar candidate, MYL-1401O, for all of Herceptin's indications, including an indication for metastatic gastric cancer, which is protected by orphan drug exclusivity through 20 October 2017.

In both cases, ODAC and FDA reviewers found there were no clinically meaningful differences between the reference products and the biosimilars, though some panel members expressed concerns about extrapolating data from studies in a single disease to multiple indications.

But ODAC Chair Bruce Roth, a professor of medicine at the Washington University School of Medicine, reminded the panel that oncologists have to extrapolate data every day in the clinic.

"I think the magnitude of extrapolation is no greater here than we experience on a daily basis in the clinic," he said.