Merck's (NYSE:MRK) Fosamax is the 900-pound gorilla among therapy options for those who suffer from osteoporosis. Its global sales in fiscal 2006 tallied $3.1 billion, and it was among the company's top-selling drugs, accounting for about 14% of total sales. No wonder Novartis (NYSE:NVS) and Wyeth (NYSE:WYE) are looking to get a piece of this action.

On Monday, Novartis reported that results of a clinical study on patients with osteoporosis who suffered a hip fracture show that a once-yearly infusion of its Reclast reduced the risk of subsequent fractures by 35%, compared with patients treated with a placebo. The results of this phase 3 study were published in The New England Journal of Medicine. In August, Reclast was approved as the first and only once-yearly treatment for postmenopausal osteoporosis.

Not to be outdone was Wyeth, which presented phase 3 clinical data for bazedoxifene on Wednesday at the annual meeting of the American Society for Bone and Mineral Research. In a three-year study, data showed that bazedoxifene significantly reduced the risk of new vertebral fractures by about 40% when compared with a placebo.

Wyeth has already received an approvable letter about its pending New Drug Application (NDA) for bazedoxifene for preventing postmenopausal osteoporosis. In July, the drugmaker submitted a separate NDA to the Food and Drug Administration for bazedoxifene for the treatment of postmenopausal osteoporosis.

Fosamax is set to go off-patent in February, so Novartis, Wyeth, and Eli Lilly (NYSE:LLY), which also has the osteoporosis drug EVISTA, will have to compete against cheaper generic versions of Fosamax next year.

The two studies released this week by Novartis and Wyeth provide additional promising alternatives to Fosamax, but the companies have a tough road ahead in this market. 

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Fool contributor Billy Fisher does not own shares of any of the companies mentioned. Eli Lilly is a selection of the Income Investor newsletter. The Fool has a disclosure policy.