NEW YORK (CNNMoney.com) -- The multi-billion dollar drug industry for degenerative bone disease is getting more congested, with new studies showing the benefits of the Novartis drug Aclasta, and an experimental drug from Amgen on the way.

"The market is getting crowded," said Les Funtleyder, analyst for Miller Tabak, who estimates that Aclasta annual sales could reach $1 billion.

Novartis (down $0.11 to $57.90, Charts) may have an edge on the competition. The Swiss drug giant announced this weekend that late-stage tests with Aclasta showed that the drug reduces the incidence of bone fractures in women with postmenopausal osteoporosis and would only have to be taken once a year.

"As a once-yearly infusion, this treatment has clearly been shown to be the preferred choice of patients over a once-weekly pill," said Novartis in a news release.

Competing drugs have to be taken once-weekly or once-monthly. Aclasta, if approved by the FDA for osteoporosis, could be attractive to patients because it's more convenient.

Aclasta is currently on the market for the treatment of Paget's, a bone-weakening disease. Funtleyder said that if Aclasta is approved by the Food and Drug Administration for the new indication, then it could expand the osteoporosis market, currently at about $6 billion to $7 billion in size.

Even if Aclasta grows the industry, it could also squeeze sales for Amgen's denosumab, assuming that the experimental drug gets approved by the FDA. Amgen (up $0.92 to $71.90, Charts), the biggest biotech in the world, has projected that denosumab will become a blockbuster.

These drugs would also compete with Merck's (Charts) Fosamax, the market leader, GlaxoSmithKline's (up $0.13 to $54.18, Charts) Boniva, and Actonel from Proctor & Gamble (down $0.24 to $15.23, Charts) and Sanofi-Aventis (up $0.36 to $44.27, Charts). Fosamax is taken weekly or monthly, with 2005 sales totaling $3.2 billion. GlaxoSmithKline just released Boniva in 2005 as a once-monthly pill, but the FDA approved it as a once-quarterly earlier this year. Actonel is taken once a week.

Fosamax, Merck's other drug problem