Ovarian Cancer Drug Half Way There
Amgen is half way there.
The biotech giant announced yesterday that its cancer drug trebananib combined with chemotherapy paclitaxel extended median progression-free survival in recurrent ovarian cancer patients by 1.8 months compared with paclitaxel alone. That may not seem like much, but the group that got paclitaxel alone only lasted 5.4 months before their disease progressed, so the extension of progression-free survival translates to a 34% reduction in the risk of disease progression.
But, of course, progression-free survival isn't what patients and their doctors really care about. They're more interested in overall survival than how long it takes for the disease to progress. The phase 3 clinical trial continues, but Amgen did give us a tidbit of information on how the secondary endpoint was proceeding.
"An early imbalance of deaths favoring the control arm was observed"
Amgen added that by the time the pre-planned interim analysis took place, the trend for overall survival was already in favor of trebananib.
It's possible these early deaths just happened randomly. But it's also feasible that trebananib has toxicity in some patients, but not all. Those patients die early in the study, but if there are enough patients that trebananib helps, the median overall survival trend could still be positive. Median overall survival isn't affected by the extremes -- like an arithmetic mean would be -- since the median focuses on how the middlemost patient in the study reacted to the drug and placebo.
The FDA won't ignore the early deaths, but without seeing the full data set -- which Amgen didn't release -- it's difficult to know whether they could hang up the approval. Considering that ovarian cancer is deadly already, Amgen is likely to get more leeway than a company would get for other diseases.
Amgen might be able to find a genetic marker that predicts whether the drug will help patients, like it's done with Vectibix and Bristol-Myers Squibb and Eli Lilly have done with Erbitux. Patients with mutations in a gene called KRAS don't respond to colon cancer drug Erbitux or Vectibix, so patients are routinely screened for the mutation. It cuts out some of the potential patients, but makes the drugs look better for the ones that take them.
And back to waiting
Amgen expects full overall survival data next year. The company didn't say, but I'd guess Amgen will wait for the overall survival data next year before applying to the FDA. A second phase 3 trial testing trebananib with another chemotherapy, which is expected to read out next April, should give investors -- and the FDA -- more confidence that the drug is helping ovarian cancer patients.
Dyax and its investors will also be keeping a close eye on trebananib's development. The biotech helped Amgen discover trebananib and is due milestone payments for successful development of the drug.
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