Amgen Inc. (NASDAQ: AMGN) is having a really good day today. Its shares closed up 12.17% to $60.48 (on a day markets were down in the neighborhood of 2%) after it said late Friday a study on denosumab, a bone-strengthening drug, met its desired results and showed statistically significant improvements over a placebo.

Amgen shares rocketed 17% at some point as denosumab has the potential to become a blockbuster drug, especially with women with postmenopausal osteoporosis, a market that could represent $8 billion and $10 billion by 2010. The strong study results also improve the drug's chances with FDA approval. Analysts just loved the results of the study (although the details won't be out until September), upgrading the shares and their target prices.

To top it off, Amgen reported second-quarter financial results after the close, beating analyst estimates. The biotechnology giant recorded net income of $941 million, or 87 cents a share, lower than last year's period, but excluding acquisition-related and stock-compensation costs, earnings rose to $1.14 a share from $1.13. Revenue rose 1% to $3.76 billion. Analysts forecast profit of $1.02 per share on revenue of $3.58 billion, according to a survey by Thomson Financial. Looking ahead, Amgen raised both its earnings and revenue guidance higher than what Wall Street expected. Analysts, in general, liked these results too.

Not all has been rosy with Amgen lately, as the sales of Aranesp, its anemia treatment and what is considered Amgen's most important product, show. Aranesp sales declined 13% on safety concerns. Sales of Epogen, the older treatment, also declined somewhat. Still the sales of both beat estimates.

Amgen's stock has already been punished for the Aranesp concerns throughout 2007, and has been recovering since, today hitting a 52-week high. Amgen showed better-than-expected sales across all products, even its under-scrutiny anemia drugs; it showed it's not resting and that it can and will recover. Combine that with the strong clinical trial results for denosumab, and the potential is great.

Amgen shares are up about 2.8% in after-hours trading to $62.15.