This study aimed to assess the efficacy and safety of three dosing regimens of JMT103 in patients with bone metastases from solid tumors. Eligible patients were randomly assigned to receive JMT103 subcutaneously, 120 mg every 4 weeks (Cohort 1), 120 mg every 8 weeks (Cohort 2), or 180 mg every 8 weeks (Cohort 3) for up to 49 weeks. The primary endpoint was change from baseline to Week 13 in creatinine-adjusted urinary N-telopeptide (uNTx/Cr). Two hundred and ninety-five patients were randomized, and 293 received at least one dose of JMT103, of whom 96 were assigned to Cohort 1, 97 were assigned to Cohort 2, and 100 were assigned to Cohort 3. The median (interquartile range) percentage reduction in uNTx/Cr at Week 13 was 80.0% (49.9%, 93.4%) in Cohort 1, 73.0% (34.5%, 94.0%) in Cohort 2, and 75.7% (40.4%, 92.0%) in Cohort 3, respectively. On-study skeletal-related events were reported by 3.1% of patients in Cohort 1, 6.2% in Cohort 2, and 7.0% in Cohort 3. Treatment-emergent adverse events occurred in 289 patients, 162 of whom were deemed treatment-related. The most common treatment-related adverse events were hypocalcemia (23.2%), hypophosphatemia (22.9%), and increased aspartate transaminase (11.9%). JMT103 demonstrated a good safety and a strong suppression of the bone turnover markers.