Investors patiently waiting for the Food and Drug Administration to approve Amgen's (NASDAQ:AMGN) bone drug denosumab may finally be seeing the light at the end of the tunnel.

Yesterday Amgen released positive results from its third phase 3 trial pitting denosumab against Novartis' (NYSE:NVS) Zometa in prostate cancer patients whose tumors had spread to the bone. Compared to Zometa, denosumab was able to extend the time to the first skeletal-related event (SRE). That term sounds formidable, but it just means a fracture or requirement to treat the tumor on the bone, for instance; denosumab also had a lower rate of multiple SREs compared to Zometa.

You can add that data on top of the growing mountain of data for denosumab in treating cancer patients. Denosumab previously beat Zometa in a head-to-head trial in breast cancer patients where the cancer had spread to the bone and a second trial in advanced cancer patients showed that the two drugs performed similarly.

Patients taking denosumab saw deterioration of the jaw bone at a higher frequency than those taking Zometa, but the numbers were so small that the difference wasn't statistically significant. When the full data is released, I think we'll see that the benefit from denosumab outweighs any minor increase in side effects, even if it's real.

Amgen is awaiting a Food and Drug Administration approval of denosumab to treat osteoporosis, which will be marketed under the trade name Prolia. While an approval seems highly likely, Prolia will probably have a slow start due to the substantial competition in the osteoporosis market. Drugs already there include GlaxoSmithKline (NYSE:GSK) and Roche's Boniva, Merck's (NYSE:MRK) Fosamax, Actonel from Procter & Gamble (NYSE:PG) and sanofi-aventis (NYSE:SNY), along with Evista from Eli Lilly (NYSE:LLY), just to name a few. 

A cancer indication, which could come by the end of the year if Amgen can get the data together quickly and the FDA gives denosumab a priority six-month review, would help sales substantially.

The wait may be easier, but denosumab's biggest data set is still unknown. Amgen is also testing denosumab as a preventive treatment to keep prostate cancer from spreading to the bone in the first place. That data, which should be available in the second half of the year, would be a boon for Amgen because it would support denosumab being used in all prostate cancer patients, not just ones who have already seen their cancer spread to the bone.

Amgen is certainly for the patient investor. Fortunately the wait has been a productive one.

Editor's note: A previous version of this article identified denosumab as "Prolia" which, according to Amgen, is the trade name for the drug as a treatment for osteoporosis.

Motley Fool Rule Breakers is always on the hunt for hot drug stocks and other cutting-edge picks. Click here to see all of our latest discoveries with a free 30-day trial subscription.

Fool contributor Brian Orelli, Ph.D., doesn't own shares of any company mentioned in this article. Novartis is a Global Gains pick. Procter & Gamble is an Income Investor selection. The Fool owns shares of GlaxoSmithKline and Procter & Gamble and has a disclosure policy.