Context <p>Phase I study showed comparable pharmacodynamic, safety and pharmacokinetic profiles of denosumab biosimilar CMAB807 and reference product Prolia^® in healthy males. However, the efficacy and safety of CMAB807 in postmenopausal women with osteoporosis were unknown.</p> Objective <p>To compare the efficacy and safety of CMAB807 and Prolia^® in Chinese postmenopausal women with osteoporosis.</p> Method <p>This randomized, double-blind, active-controlled study enrolled Chinese postmenopausal women with osteoporosis. Participants received either CMAB807 or Prolia^® 60&#xa0;mg every 6 months for 12 months. The primary endpoint was the percentage change in BMD at lumbar spine (LS) from baseline to month 12. Secondary endpoints included BMD changes at LS at month 6, total hip (TH) and femoral neck (FN) at month 6 and 12. Additionally, bone turnover markers (BTMs) and incidence of new fragility fractures were evaluated. Safety assessments were also included.</p> Results <p>A total of 284 women were enrolled, with 276 (97.2%) completing at least one post-baseline BMD measurement. After 12 months treatments, the least square means (LSMs) differences (95% confidence interval (CI)) between groups were 0.39% (-0.56, 1.33) at LS, -0.36% (-1.08, 0.35) at TH, and − 0.44% (-1.42, 0.53) at FN, indicating no significant differences in BMD improvement. Serum C-terminal telopeptide of type I collagen (CTX1) and procollagen type I N-prepeptide (P1NP) levels decreased significantly post-treatment, with maximum inhibition at 1 month for CTX1 and 3 months for P1NP. No significant differences were observed in adverse events (AEs) or treatment-related adverse events (TRAEs).</p> Conclusion <p>The study demonstrated efficacy equivalence and comparable safety of CMAB807 to Prolia^® in Chinese postmenopausal women with osteoporosis.</p>