摘要Objective:To evaluate the efficacy and safety of QL1206(a denosumab biosimilar to Xgeva?)in breast cancer patients with bone metastasis(BM)through subgroup analysis of a randomized,double-blind phase Ⅲ trial(No.NCT04550949).Methods:This subgroup analysis included patients with BM from breast cancer enrolled in a phase Ⅲ trial.Patients were randomized(1∶1)to receive either three cycles of QL1206 or denosumab(120 mg subcutaneously every 4 weeks).Subsequently,they received 10 cycles of QL1206(120 mg)over 40 weeks,followed by a 20-week safety follow-up.The primary endpoint was the percentage changes from baseline to week 13 in urinary N-telopeptide corrected for creatinine(uNTx/Cr).Results:The breast cancer cohort consisted of 311 patients.Vertebral involvement(66.4％)was the most prevalent BM site at enrollment,while 27.7％of patients presented with≥3 metastatic bone lesions.At week 13,QL1206 demonstrated a median uNTx/Cr reduction of-69.9％(range:-98.1％-568.0％)vs.-74.3％(range:-97.7％-386.3％)for denosumab.The analysis of covariance revealed comparable least-square means for log-transformed changes:-1.416[95％confidence interval(95％CI):-1.736 to-1.096]vs.-1.501(95％CI:-1.824 to-1.178),yielding an between-group difference of 0.085(90％CI:-0.062-0.232;P=0.343).After a 53-week treatment period,83.6％achieved bone density improvement/disease stabilization.Safety profiles were comparable between groups.Conclusions:QL1206 demonstrated similar efficacy and safety to the reference denosumab in patients with BM from breast cancer,supporting QL1206 as a new option for management of BM from breast cancer.