Efficacy of Denosumab for Osteoporosis in Patients with Rheumatic Diseases

OBJECTIVE: Denosumab, an anti-RANKL monoclonal antibody, was reported to improve bone mineral density (BMD) and reduce fracture risk, offering favorable efficacy against postmenopausal osteoporosis. However, some patients have experienced a reduced BMD despite denosumab therapy. METHODS: We performed an observational study to clarify the clinical efficacy of denosumab for osteoporosis in rheumatic disease patients. Serum levels of bone turnover markers and lumber BMD in 100 rheumatic disease patients were examined at baseline and 6 and 12 months after denosumab therapy. The independent influence of changes in the BMD was examined by multiple regression analyses adjusted for patient characteristics and bone turnover markers. RESULTS: As bone resorption markers, serum levels of N-telopeptide crosslinked of type I collagen (NTx) and tartrate-resistant acid phosphatase isoform 5b were statistically decreased after 12 months. As bone formation markers, serum levels of osteocalcin, procollagen type I N-terminal peptide, and bone alkaline phosphatase were significantly decreased after 12 months. The mean BMD was significantly increased after 12 months. However, in 10 patients, the BMD decreased. A multivariate analysis of factors related to BMD changes highlighted a young age, low prednisolone dosage, and reduction in NTx. CONCLUSIONS: Denosumab increases the BMD to combat osteoporosis in rheumatic disease patients, and potential predictors of a better response to denosumab include a young age, reduction in bone turnover markers, and low-dose glucocorticoid use.