Amgen and UCB’s experimental osteoporosis drug romosozumab has taken a step towards regulatory filing after hitting primary targets in a late-stage trial, reducing the number of new fractures in post-menopausal women compared to a placebo.

Top-line data from the Phase III, placebo-controlled FRActure study in postmenopausal woMen with ostEoporosis (FRAME) show significant reductions in vertebral fractures through months 12 and 24 of the trial.

Women receiving once-monthly subcutaneous injections of romosozumab experienced a 73 percent reduction in the relative risk of a vertebral fracture through 12 months compared to those receiving placebo, and this effect persisted after transitioning to treatment with denosumab through the second year. 

The relative risk of a clinical fracture (non-vertebral and vertebral) through 12 months was reduced by 36 percent compared to patients taking a receiving placebo.

The secondary endpoint of reducing the incidence of clinical fractures (vertebral and non-vertebral fractures) was also met at 12 months, but that of reducing the incidence of non-vertebral fractures through months 12 and 24 was not. 

On the safety side, the percentage of patients with adverse events and serious adverse events were balanced overall between the treatment groups, the firms noted, and the most commonly reported adverse events in both arms at 12 months were arthralgia, nasopharyngitis and back pain. There were two positively adjudicated events of osteonecrosis of the jaw in the romosozumab treatment group, and one of atypical femoral fracture after three months’ treatment.

Amgen and UCB say further analysis of the study data is ongoing and will be submitted to a future medical conference and for publication. The firms also intend to discuss the results with global regulators in anticipation of filing the drug this year.

Romosozumab is an investigational bone-forming monoclonal antibody designed to inhibit the protein sclerostin. It has a dual effect on bone, increasing bone formation and decreasing bone resorption.