Phase III trial of AMG 785 (romosozumab) in osteoporosis meets primary endpoint- Amgen/UCB

Amgen and UCB announced top-line results from the STRUCTURE trial of AMG 785 (romosozumab) compared with teriparatide in postmenopausal women with osteoporosis at high risk for fracture, previously treated with bisphosphonate therapy. The study (NCT01796301) met the primary endpoint, demonstrating a statistically significant difference in favour of romosozumab in the percent change of total hip bone mineral density (measured by DXA) at month 12.

STRUCTURE was a Phase III, multi-centre, international, randomised, open-label, active comparator-controlled study that evaluated safety, tolerability and efficacy of romosozumab in women with postmenopausal osteoporosis. The overall subject incidence of adverse events was generally balanced between arms. Adverse events in patients treated with romosozumab were similar to those previously reported and no new safety signals were detected. Adverse events reported in the romosozumab arm in more than five percent of patients were nasopharyngitis, arthralgia, back pain, headache and fall. Further analysis of the Phase III STRUCTURE study results are ongoing and will be submitted to a future medical conference and for publication.

Comment: Teriparatide (Forteo/Forsteo, a recombinant parathyroid hormone analogue) increases BMD, reduces fracture risk and restores bone architecture back towards normal, but its use is hampered by the need for daily injections, high cost and safety warnings (osteosarcoma was seen in rats). Meanwhile, the older antiresorptive agents (such as alendronate) do not restore bone architecture and are associated with osteonecrosis.