Effectiveness of romosozumab following prior raloxifene treatment in primary osteoporosis: An observational study

Romosozumab is an anti-sclerostin antibody that increases bone formation and decreases bone resorption. It has been available for patients at high risk of osteoporotic fractures in Japan since 2019. The aim of this study was to clarify the clinical effectiveness and safety of romosozumab following previous treatment with raloxifene. The study had an observational pre-post design and included 62 women with primary osteoporosis. Romosozumab 210 mg was administered subcutaneously every 4 weeks for 12 months in patients who had been previously treated with raloxifene (raloxifene group, n = 12) and in those who were treatment-naïve (treatment-naïve group, n = 50). The incidence of new fractures, safety, and changes in bone mineral density (BMD) and bone turnover markers (BTMs) were recorded. No new fractures occurred in either group. Ten patients (16.1%) in the treatment-naïve group discontinued romosozumab for the following reasons: non-serious adverse events (n = 2, 3.2%), a change to another hospital (n = 1, 1.6%), self-discontinuation (n = 5, 8.1%), and financial constraints (n = 2, 3.2%). The percent changes in spine BMD and total hip BMD at 12 months were respectively +13.5% and + 4.9% in the treatment-naïve group and + 16.0% and + 3.4%, respectively, in the raloxifene group. We did not detect significant differences in the changes in BTMs according to whether there was previous treatment with raloxifene. Prior raloxifene treatment may be well tolerated and may not affect increases in BMD, changes in BTMs, and fracture prevention in romosozumab therapy.