Summary:​ Our 6-month study showed the usefulness of romosozumab for preventing fractures and its safety. It was effective in patients with low baseline spine BMD, high TRACP-5b, and high iP1NP. Percent change from baseline of TRACP-5b and iP1NP after 1 month correlated with that from baseline of BMD after four to 6-month treatment.

Introduction:​ Romosozumab appeared as a new osteoporosis medication in Japan in 2019. It is an anti-sclerostin antibody which increases bone formation and suppresses bone resorption. In this study, we analyzed the actual clinical effects, adverse effects, and the optimal way to evaluate the treatment.

Methods:​ Romosozumab was administered as subcutaneous injection of 210 mg once every 4 weeks. We conducted pre-post study in 185 patients treated for 6 months. We focused on the incidence of new vertebral fractures, safety, bone mineral density (BMD) at the spine and total hip, and bone metabolism markers. We evaluated BMD before romosozumab treatment and after 4 to 6 months and performed the serum analysis before romosozumab treatment, after 1, 3, and 6 months.

Results:​ There was no new fracture during treatment, and there was no fatal adverse event including cardiovascular disease. Since percent changes from baseline of the spine and total hip BMD were 6.34% and 1.53% after 4- to 6-month treatment, the treatment was effective for spine osteoporosis. Tartrate-resistant acid phosphatase 5b (TRACP-5b) and intact type I procollagen N-terminal propeptide (iP1NP) had significant changes during romosozumab treatment (p < 0.05). Percent change from baseline of TRACP-5b and iP1NP after 1 month correlated with percent change from baseline of BMD after 4 to 6 months of treatment.

Conclusion:​ Romosozumab is effective in preventing fractures and useful for increasing the spine BMD.

Also, romosozumab is relatively safe to use. It is especially effective in patients with low baseline spine BMD, high TRACP-5b, and high iP1NP.