Proposed Denosumab Biosimilar SB16 vs Reference Denosumab in Postmenopausal Osteoporosis: Phase 3 Results Up to Month 12.

Context: SB16 is a proposed biosimilar to reference denosumab (DEN; brand name: Prolia).

Objective: This phase 3 randomized, double-blind, multicenter study evaluated the biosimilarity of SB16 to DEN in women with postmenopausal osteoporosis (PMO; NCT04664959).

Design: The study included 457 PMO patients who had a lumbar spine or total hip T-score between -2.5 and -4. Patients were randomized in a 1:1 ratio to receive either 60 mg of SB16 or DEN subcutaneously at Month 0 and Month 6. At Month 12, patients were re-randomized to continue with the assigned treatment or switch from DEN to SB16 up to Month 18. This report includes results up to Month 12.

Methods: The primary endpoint was the percent change from baseline in lumbar spine bone mineral density (BMD) at Month 12. Secondary endpoints including the percent change from baseline in BMD of the lumbar spine (except for Month 12), total hip and femoral neck; pharmacokinetic, pharmacodynamic (serum C-telopeptide of type I collagen [CTX] and procollagen type I N-terminal propeptide [P1NP]), safety, and immunogenicity profiles were measured up to Month 12.

Results: The least-squares mean differences in percent change from baseline in lumbar spine BMD at Month 12 were 0.33% (90% confidence interval [CI]: -0.25, 0.91) in the full analysis set and 0.39% (95% CI: -0.36, 1.13) in the per-protocol set; both within the pre-defined equivalence margin. The secondary endpoints were comparable between the two treatment groups.

Conclusion: The reported efficacy, PK, PD, safety, and immunogenicity data support the biosimilarity of SB16 to DEN.