Romosozumab in Skeletally Mature Adults with a Fresh Unilateral Tibial Diaphyseal Fracture A Randomized Phase-2 Study

Background: Romosozumab is an antibody that binds and inhibits sclerostin, thereby increasing bone formation and decreasing bone resorption. A double-blinded, randomized, phase-2, dose-finding trial was performed to evaluate the effect of romosozumab on the radiographic and clinical outcomes of surgical fixation of tibial diaphyseal fractures. Methods: Patients (18 to 82 years old) were randomized 3:1:1:1:1:1:1:1:1:1 to a placebo or 1 of 9 romosozumab treatment groups. Patients received subcutaneous injections of romosozumab or the placebo postoperatively on day 1 and weeks 2, 6, and 12. The primary outcome was the time to radiographic evidence of healing ("radiographic healing") analyzed after the week-24 assessments had been completed for all patients. Results: A total of 402 patients were randomized: 299 to the romosozumab group and 103 to the placebo group. The median time to radiographic healing (the primary outcome) ranged from 14.4 to 18.6 weeks in the romosozumab groups and was 16.4 weeks (95% confidence interval [CI]: 14.6 to 18.0 weeks) in the placebo group, which was not a significant difference. There was also no significant difference in the median time to clinical healing, no relationship between romosozumab dose/frequency and unplanned revision surgery, and no apparent treatment benefit in terms of physical function. The safety and tolerability profile of romosozumab was comparable with that of the placebo. Conclusions: Romosozumab did not accelerate tibial fracture-healing in this patient population. Additional studies of patients at higher risk for delayed healing are needed to explore the potential of romosozumab to accelerate tibial fracture-healing.