Amgen has been boosted by data from a new head-to-head late-stage trial which suggests superiority of the firm’s investigational osteoporosis drug denosumab compared with Merck & Co's Fosamax.

Specifically, the one-year, 504-patient trial compared the effects of twice-yearly injections of denosumab in post-menopausal women with low bone mass who were switched from weekly Fosamax (alendronate) versus continued alendronate therapy on BMD. The study demonstrated superior results for the primary and all secondary endpoints, Amgen noted and women on denosumab achieved significantly greater BMD gains at all sites measured.

Most notably, Amgen indicated that “the relative magnitude of BMD improvement at the total hip was about 80% greater” in the denosumab versus the alendronate group. Commenting on the data, Roger Perlmutter, Amgen's executive vice president of R&D, said that this is the second Phase III head-to-head study demonstrating that administration of denosumab resulted in superior BMD gains to Fosamax.

Importantly, the incidence and types of adverse events observed in the study, including neoplasm and infection, were well-balanced between the two arms of the study, Amgen said. The most common side effects across both treatment arms were back pain, arthralgia, and nasal pharyngitis.

Denosumab is the first fully human monoclonal antibody in late-stage clinical development that specifically targets RANK Ligand, a crucial mediator of the cells that break down bone. Its success is important to the future growth plans for Amgen, which has been suffering from the regulatory and reimbursement changes that have negatively affected sales of its anaemia drugs Epogen (epoetin alfa) and Aranesp (darbepoetin alfa).