Updated from 5:48 am EST with additional information.
Amgen (AMGN) announced Monday that postmenopausal women with osteoporosis reported fewer new spinal fractures following monthly injections of an experimental bone-forming drug compared to similar women treated with a placebo.
The results achieved the primary endpoint of a phase III study conducted by Amgen and its partner, Belgium-based UCB. The companies intend to seek regulatory approval for the new osteoporosis drug, romosozumab, later this year.
If approved, "romo" could generate sales of $1 billion or more split evenly between Amgen and UCB, analysts predict, although the drug faces competition from Eli Lilly's (LLY) Forteo, which is going generic soon, and an another experimental osteoporosis drug under development by Radius Health (RDUS) .
Importantly, monthly injections of romo failed to reduce the incidence of fractures outside the spine, a key secondary efficacy endpoint of the phase III study. This is a disappointing outcome because reduction in "non-vertebral fractures" was seen as a way romo could potentially differentiate itself from the osteoporosis drug competition.
Overall, results from the phase III "FRAME" study showed that women receiving a monthly injection of romo experienced a statistically significant 73% reduction in the relative risk of a spine fracture through 12 months compared to placebo.
The efficacy of romo persisted through the second year of the study after Prolia, Amgen's currently approved osteoporosis drug, was added. At two years, women treated with romo and Prolia showed a statistically significant, 75% reduction in the risk of spinal fractures compared to women treated with placebo and Prolia.