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Genentech Aims to Set Precedent With FDA OK in Early Breast Cancer

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save companies months, or even years, in development, and millions and millions of dollars.

FDA staff released their own briefing document for the Oncologic Drugs Advisory Committee online yesterday, and it was a pretty straightforward and positive summary of Genentech’s dataset. The drug in question, pertuzumab (Perjeta), was first approved in June 2012 for women with breast cancer that overexpresses the HER2 protein, and which has spread through the body. It’s approved in combination with Genentech’s other HER2-directed antibody, trastuzumab (Herceptin) and chemotherapy. The drug generated about 108 million Swiss francs in sales during the first half of 2013, which translates to about $115 million at today’s currency conversion rates.

Last year when the drug was approved by the FDA, it was primarily on the basis of a study called Cleopatra. That study, of 808 women, showed that when pertuzumab was added to the other antibody and chemotherapy, it was able to keep tumors from spreading for an additional six months, without adding significant side effects.

That study was good enough to get pertuzumab on the market, but it wasn’t the only trial where the product showed promise. The drug, which looked like a loser back in 2005, was revived five years later by the results of a study known as Neosphere. That trial looked at 417 women with HER2-overexpressing tumors, who were still in the early, preoperative stage of disease, with “neoadjuvant” status. Researchers found that 39.3 percent of women randomly assigned to get pertuzumab, trastuzumab and chemo achieved a pathological complete response, compared with 21.5 percent who did that well on the original trastuzumab and chemo alone. The difference was statistically significant, meaning it was unlikely due to chance.

The FDA has tried to do its own analysis of a variety of clinical trials that enrolled a total of 12,000 patients with neoadjuvant status, to see whether pathological complete response truly indicates a patient is on track for a better long-term outcome. As it notes in this week’s briefing document, the analysis was discussed at some length in a workshop with industry representatives in March, and described in an industry guidance document.

So on one level, Thursday’s FDA advisory panel will be about whether Genentech’s dataset looks solid enough to support an expanded approval for one breast cancer drug. But the vote, and the tenor of the debate among the FDA panel, could also have a more far-reaching influence on what the FDA considers acceptable medical evidence for cancer drug developers.

Those readers who make a living on knowing which way the wind blows at the FDA may want to tune in for the webcast of the panel meeting. The discussion is scheduled to start here at 8 am Eastern/5 am Pacific tomorrow.

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