Days after getting the thumbs-up in Europe, Amgen is celebrating again after regulators in the USA gave the green light to the firm’s osteoporosis drug Prolia.

The US Food and Drug Administration has approved Prolia (denosumab), an injectable treatment for postmenopausal women with osteoporosis who are at high risk for fractures. The agency noted that the safety and efficacy of the drug, a first-in-class, fully human monoclonal antibody designed to target RANK ligand, was demonstrated in a three-year trial of 7,808 postmenopausal women aged 60 to 91 which showed that Prolia reduced the incidence of vertebral, non-vertebral, and hip fractures.

The agency noted that 80% of the people in the USA with osteoporosis are women and one out of every two women over 50 will break a bone in their lifetime due to the disease. As such it is “a serious concern to public health,” said Julie Beitz, director of the FDA’s Office of Drug Evaluation III, adding that the approval of Prolia provides another treatment option.

Analysts believe Prolia will be a blockbuster but Amgen’s challenge now is to get the drug established on a market dominated by bisphosphonates such as Novartis’ Reclast/Zometa (zoledronic acid) and Merck & Co’s Fosamax (alendronate), which is now available generically. The US biotech major says that approximately 50% of patients discontinue oral bisphosphonate therapy within the first year and some cannot tolerate available osteoporosis therapy.

Competitive price
Amgen is also aware that price is a big issue and chief operating officer Robert Bradway said “we have priced Prolia responsibly while reflecting its strong therapeutic value and expect to make it commercially available in the USA within the next week”. The drug will cost $825 per 60 mg injection (taken every six months) and the price is competitive with other therapies.

As part of the approval, the company has put forward a risk evaluation and mitigation strategy that explains the risks and benefits of the drug. Specifically, the FDA noted that Prolia causes significant suppression of bone turnover which may contribute to the occurrence of osteonecrosis of the jaw.

As part of the REMS, Amgen has signed up to “comprehensive post-marketing surveillance” of more than 4,500 women with postmenopausal osteoporosis who will have exposure to Prolia for up to 10 years. In addition, Amgen will implement an international long-term safety observational study.

The US approval, which came quicker than expected, comes just after the European Commission has granted marketing authorisation for Prolia for the treatment of osteoporosis in postmenopausal women at increased risk of fractures, and for bone loss associated with hormone ablation in men with prostate cancer. Amgen recently made a second submission to the FDA for denosumab, this time for bone loss in cancer patients.