I understand tivozanib met the study's primary endpoint by demonstrating a statistically significant progression-free survival (PFS) benefit. And I also know FDA has approved other kidney cancer drugs based on PFS. But overall survival is the gold standard measurement of efficacy for cancer drug trials and tivozanib has significant issues based on these data. It's not like kidney cancer patients are lacking effective treatments today -- Sutent, Votrient, Avastin and Nexavar are all approved and in wide use.
A few more controversies in the tivozanib data to point out:
Here's another overall survival chart, this one breaking out only the patients from North America and Western Europe:
Tivozanib performs best here, demonstrating a 50% reduction in the risk of death compared to Nexavar and a strong two-year survival trend -- not statistically significant. Still, I expect Aveo likes this survival chart the best, particularly since it's seeking approval in the U.S. and Europe.
But take a look at the number of patients in this analysis. Yes, there were only 40 patients out of 517 enrolled in North America and Western Europe. [Aveo has not disclosed how many of the 40 patients were from the U.S.] These 40 Western Europe/North American patients are driving a lot of the tivozanib benefit, but will FDA be concerned that this group makes up just 8% of the total enrollment?
Let's return to the next-line therapies chart for a related point and question. As I said above, only 26% of the tivozanib patients went on to receive additional therapy compared to 65% of Nexavar patients. Why?
Take a look at that chart again:
Aveo obviously enrolled most of its patients from Russia and Eastern Europe where access to modern kidney cancer drugs is limited. The company was also willing to supply tivozanib gratis to patients in the study, which explains why the drug was used so heavily as the "cross over" drug in the control arm. But depriving tivozanib patients of other follow-on therapies shouldn't sit right with anyone and raises questions about the conduct of the study.
I've focused entirely on survival but let me make one niggling point about the PFS data in the study and where FDA may have a problem.
Recall, median PFS was 11.9 months in the tivozanib arm compared to 9.1 months in the Nexavar arm -- a statistically significant benefit. Likewise, in the 70% of kidney cancer patients who were treatment naive prior to enrollment, median PFS was 12.7 months versus 9.1 months, again benefiting tivozanib over Nexavar.
Great news for Aveo, right? Perhaps, but what the 30% of kidney cancer patients receiving one prior systemic therapy before entering the study? It's not possible to be precise but it sure looks like these "previously treated" patients performed worse on tivozanib. Did they even underperform Nexavar? It's not clear from the data we have available but perhaps the answer will come Tuesday when the FDA releases its briefing documents.
Big week for Aveo coming up. Stay tuned.
-- Reported by Adam Feuerstein in Boston.