Results from the Phase III HALT breast cancer 135 study showed that denosumab, a fully human monoclonal antibody under investigation as a twice yearly subcutaneous injection, increased bone density worsened by aromatase inhibitor (AI) therapy, including in highly cortical areas of the skeleton. In addition to increasing bone mineral density (BMD) of the trabecular bone (spongy bone matrix), denosumab showed increases in cortical bone, the dense outer shell of the skeleton which is responsible for the supportive and protective function of the skeleton.
The Phase III data showed that lumbar spine BMD increased significantly at all time points with the denosumab group (n=127) as early as one month. At month 12 (primary endpoint) a 5.5% (p<0.0001) difference from placebo (n=125) was observed. Additionally, a consistent effect of denosumab was demonstrated on the total hip BMD (3.7% difference from placebo) and femoral neck BMD (2.5% difference from placebo) at 12 months (secondary endpoints). In the study, denosumab was generally well tolerated, with overall rates of adverse events similar to placebo. The most common adverse events were consistent with those usually associated with AI therapy, and included, arthralgia, pain in extremity, fatigue, back pain, constipation, cough and insomnia.