Aveo believes overall survival of tivozanib was snake bit by a study design that allowed kidney cancer patients treated initially with Nexavar to receive effective, subsequent therapy, including tivozanib.

This chart explains Aveo's case:

Of the 257 kidney caner patients who started the study on Nexavar, 65% went on to receive additional therapy. The vast majority of these patients received tivozanib.

Of the 260 patients treated with tivozanib initially, only 26% went on to receive additional treatment, mostly other VEGF therapies like Pfizer's ( PFE) Sutent or GlaxoSmithKline's ( GSK) Votrient. Tivozanib is also a VEGF therapy.

Aveo argues that survival trended against tivozanib because the control patients (those who started on Nexavar) benefited from receiving more "add-on" therapy.

Point taken, and it could be enough to persuade the FDA panel to vote in the drug's favor next week. But what if we look at a more equitable comparison of tivozanib and Nexavar survival by examining only patients who received secondary therapy.

Here's that chart:

The top "A" graph depicts an overall survival analysis of "2 vs 2" line of therapy, meaning it compares overall survival of Tivozanib patients who went on to receive another therapy (two) versus Nexavar patients who also went on to receive another therapy (Two, with the vast majority receiving tivozanib.)

Uh oh, once again, overall survival trends in favor of the Nexavar control arm and against tivozanib. Two-year survival is 50% for the tivozanib arm compared to 64% for the Nexavar arm.

If tivozanib is a truly effective kidney cancer drug, why can't it demonstrate a survival benefit, even when patients are treated with another drug following tumor progression? If anything, the data from the study suggest tivozanib, if approved, should only be used after a patient is treated with Nexavar.

Take a look at the "B" graph now. This further drills down to analyze patients who only received subsequent treatment with another VEGF drug -- the most effective kidney cancer therapies. Yet again, the patients who began the study on Nexavar outlive the patients starting on tivozanib. (Two-year survival 63% vs. 55%.)

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