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April 7, 2014
Is Palbociclib Promising? Or Not?
Here's a good test for whatever news outlets you might be using for biotech information. How are they handling Pfizer's release of palbociclib information from the AACR meeting over the weekend?
Do a news search for the drug's name, and you'll see headline after headline. Many of them include the phrase "Promising Results". And from one standpoint, those words are justified. The drug showed a near-doubling in progression-free survival (PFS) when added to the standard of care, and you'd think that that has to be good. But a first analysis of overall survival (OS) shows no statistically significant improvement.
Now, how can that be? One possibility is that the drug helps hold advanced breast cancer back, until a population of cells breaks through - and when they do, it's a very fast-moving bunch indeed. Pfizer, for its part, is certainly hoping that further collection of data will start to show a real OS effect. They're going to need to - Avastin's provisional approval for breast cancer was based on earlier PFS numbers, which did not hold up when OS data came in. And that approval was revoked, as it should have been. Now, Avastin also had side effect issues, and quality-of-life issues, so these cases aren't directly comparable. But the FDA really wants to see a survival benefit, and that's what a new cancer drug really should offer. "You'll die at the same time, but with fewer tumors, and out more money" is not an appealing sales pitch. This issue has come up several times before, with other drugs, and it will come up again.
You'd think that a PFS effect like palbociclib's should translate into a real survival benefit, and as more data are added, it may well. But it's surely not going to be as impressive as people had hoped for, or it would have been apparent in the data we have. So take a look at the stories you're reading on the drug: if they mention this issue, good. If they just talk about what a promising drug for breast cancer palbociclib is, then that reporter (and that news outlet) is not providing the full story. (Here's one that does).
Update: there is an ongoing Phase III that's more specifically looking at overall survival. Its results will be awaited with great interest. . .
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