Amgen (NASDAQ:AMGN) already had a ball flying high above the outfield in its osteoporosis treatment, denosumab, but yesterday's clinical trial results were the wind that could push it out of the park. Shares are soaring as well, up 15% so far today.

In a phase 3 head-to-head trial, denosumab worked better than Novartis' (NYSE:NVS) Zometa in treating the bones of breast cancer patients whose cancer had spread to the bone (which can weaken and destroy the bone around the tumor). The extra indication beyond osteoporosis could result in a landslide of additional sales. After all, Novartis sold $1.4 billion worth of Zometa last year treating the same indication.

Amgen held back most of the data so that it can present it at a scientific meeting, but the company did say that the drug produced a few cases of osteonecrosis of the jaw (ONJ). The side effect, which causes the jaw to deteriorate, has been seen in patients taking Zometa. The best-case scenario was that denosumab wouldn't have the side effect, but, given the better efficacy, an apparently equivalent side-effect profile is an acceptable outcome.

We'll get a better idea of what the FDA thinks of denosumab for osteoporosis in August when the agency holds an advisory panel meeting, but the chances for approval seem pretty good considering the data.

The prospects for marketing success for denosumab as an osteoporosis treatment, on the other hand, are a little less clear. There are a lot of drugs available to treat osteoporosis -- including Roche and GlaxoSmithKline's (NYSE:GSK) Boniva, Novartis' Reclast, Eli Lilly's (NYSE:LLY) Evista and Forteo, and generic versions of Merck's (NYSE:MRK) Fosamax -- and it's not clear that denosumab's efficacy is enough to get doctors to switch en masse.

But yesterday's cancer data should easily push denosumab into blockbuster status, assuming the other trials Amgen is running in cancer patients turn out similar results.

With slumping sales of its anemia drugs, Amgen really needs denosumab to hit a home run. It's not there yet, but yesterday's news helped it get a little closer to going over the fence.

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Fool contributor Brian Orelli, Ph.D., likes to print out The Fool's disclosure policy, wad it up, and use it as an office baseball. He doesn't own shares of any company mentioned in this article. Novartis is a Motley Fool Global Gains selection.