Evangelos Terpos, MD, PhD, National and Kapodistrian University of Athens, Athens, Greece presents the results from a preliminary analysis of the REBUILD study (NCT03475628) of the effect of daratumumab (dara) on bone metabolism in advanced relapsed/refractory (R/R) multiple myeloma, where osteolytic lesions are characteristic. With pre-clinical studies showing that anti-CD38 therapy inhibits osteoclast formation, the Phase II trial aims to evaluate the impact of dara monotherapy, an anti-CD38 monoclonal antibody, on bone resorption markers: C-terminal telopeptide of collagen type I (CTX) and tartrate-resistant acid phosphatase isoform 5b (TRACP-5b). Of the 29 patients with bone marker data available, the median changes in CTX and TRAXP-5b after four months were 3.9% and -2.2%, respectively. Comparing individuals who achieved a response to those who did not, changes were 3% vs 4% for CTX and -3% vs 9% for TRACP-5b. Responders also showed a greater increase in numerous bone formation markers. These initial results show dara has a positive effect on bone metabolism, likely via an osteoclast inhibitory mechanism. This interview took place during the 62nd American Society of Hematology (ASH) Annual Meeting and Exposition, 2020.