AB1016 ROMOSOZUMAB AS A TREATMENT FOR OSTEOPOROSIS: PREDICTORS OF EFFICACY AT 12 MONTHS

BackgroundRomosozumab (ROMO) is an antisclerostin antibody that is used in the treatment of severe osteoporosis (OP). In March 2019, ROMO was approved for use in Japan for treating severe OP in clinical practice, causing an increase in its prescription in our institute. Although efficacy data for ROMO have been presented in clinical trials, there is a lack of real-world data. In our experience, ROMO treatment results in significant bone mineral density (BMD) gain in some patients, but not all. Therefore, understanding the predictors that enhance the efficacy of ROMO treatments to achieve BMD gain is essential.ObjectivesThis study investigated the efficacy of a 12-month ROMO treatment in patients with OP and explored the efficacy predictors of increased BMD.MethodsOur study included 52 patients with OP, who were started on ROMO treatment between June 2019 and August 2020. The following information was collected: 1) baseline characteristics, 2) time-course of BMD (lumbar spine [LS] and total hip [TH]) and bone turnover markers (BTM; bone-specific alkaline phosphatase [BAP], type I procollagen-N-propeptide [P1NP], type I procollagen-N-propeptide[NTX], and tartrate-resistant acid phosphatase-5b [TRACP-5b]), 3) multiple regression analysis results following Spearman’s correlation analysis of increased BMD values (%) at 12 months and BL characteristics, including BTM change (%) at one month, to investigate the efficacy predictors of ROMO.Results1) The mean age of the participants was 72.9 years (48 female and four male). Of the 52 understudied patients, 78.8% had past insufficiency fractures, whereas 21.2% had been treated with concomitant prednisolone. Furthermore, 21 patients had primary OP, 20 had rheumatoid arthritis, nine had glucocorticoid-induced OP, and two had other conditions. Pretreatments for OP were bisphosphonate (33 patients), vitamin D (6), none (5), selective estrogen receptor modulator (4), and denosumab (3).2) Both mean LS- and TH-BMD significantly increased in the patients for whom ROMO administration was continued for 12 months. The average percentage changes of LS- and TH-BMD were 7.1% and 1.6% at six months and 11.7% and 3.0% at 12 months, respectively (Figure 1). However, BAP and P1NP increased steeply at one month, followed by a gradual decrease. As observed, the average percentage changes of BAP and P1NP were +70.1% and +166.8% at one month, +50.3% and +91.7% at six months, and +24.4% and +41.5% at 12 months, respectively. The results also showed that TRACP-5b decreased from one to 12 months, with the average percentage changes being −22.9% at one month, −13.8% at six months, and −17.7% at 12 months. Moreover, NTX, a bone-resorptive marker, was slightly increased during ROMO treatment.3) Multiple regression analysis results revealed that the baseline BAP and percentage calcium changes at 12 months were significant factors positively correlated with the percentage change of LS-BMD at 12 months. As observed, the baseline T-score of LS-BMD was a significant factor negatively correlated with the percentage change of LS-BMD at 12 months. The standardized partial regression coefficient values were +0.68, +0.26, and −0.40, respectively. Moreover, the multiple regression analysis results revealed no significant factor that was correlated with the percentage changes of TH-BMD at 12 months.Figure 1.ConclusionROMO treatments rapidly increased BMD, especially LS-BMD, and changed BTM after one month. Baseline BAP were correlated with increased LS-BMD but not with TH-BMD. The factors correlated with increased BMD may differ between LS-BMD and TH-BMD.Disclosure of InterestsNone declared