You say Prolia; I say Xgeva. Tomayto, tomahto. It's all the same thing.
While the two brands contain the same active ingredient, the prospects for the two drugs are quite different. Prolia, which was approved earlier this year, treats osteoporosis. A huge market, but one with a ton of competition: Warner Chilcott
Xgeva will treat cancer patients that have tumors which have spread to the bone. Its main competition will be Novartis'
So what's the reason for the different names? The dose is different, as cancer patients get more Xgeva, but I don't know why Amgen couldn't just sell the same brand in multiple strengths. Pfizer's
My guess is Amgen didn't want the stigma of a cancer drug being used to treat osteoporosis; Prolia is going to have a hard enough time competing as it is. Xgeva really isn't treating the tumor so much as keeping the tumor from causing damage to the bone, but most osteoporosis patients aren't going to get that.
Amgen is testing denosumab in a third setting: preventing tumors from spreading to the bone, which could be worth another billion dollars or more in sales. The data from that trial is expected before the end of the year.
Let's just hope Amgen doesn't come up with a third name.
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