No doubt, the kidney cancer market is quite crowded. Pfizer (NYSE: PFE) alone has three drugs approved to treat the disease. And then there's Bayer and Onyx Pharmaceuticals' (Nasdaq: ONXX) Nexavar, Roche's Avastin, GlaxoSmithKline's (NYSE: GSK) Votrient, and Novartis' (NYSE: NVS) Afinitor, which are all approved to treat the cancer at varying stages. And AVEO Pharmaceuticals' (Nasdaq: AVEO) tivozanib is likely to gain approval after posting solid phase 3 data.

With that many competitors, combining forces would seem to be a good move to increase efficacy, potentially differentiating the combo drugs from the crowd.

It's a good idea in theory; unfortunately, it didn't work for Pfizer and Roche.

Pfizer announced on Friday that a trial combining Torisel with Avastin didn't increase progression-free survival compared to Avastin plus interferon alfa-2a, which are typically given together. Progression-free survival is a surrogate endpoint that measures how long it takes a tumor to start growing or for the patient to die.

Roche provided the drug for the trial, but this was Pfizer's baby, which makes sense because Pfizer had more to gain from the combo product working. Avastin plus interferon is approved as a first-line treatment while Torisel is only approved for a subset of patients with poor prognostic indicators.

This isn't the first fail for Torisel this year. In May, Pfizer said the drug failed to best Nexavar in kidney cancer patients who had failed another treatment. There was a trend in progression-free survival favoring Torisel, but it wasn't statistically significant.

The failures won't affect Pfizer's ability to market Torisel, but they won't help boost sales either. Currently, sales are so low that Pfizer doesn't bother to break out the sales in its quarterly earnings report; the sales just get lumped into the "all other biopharmaceutical products" category. Based on what does get broken out, it's safe to assume sales are likely under $200 million annually, nothing to get excited about.

Competition will do that.

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