Progression-Free Survival Analysis of Denosumab Vs Zoledronic Acid in Intent to Transplant Multiple Myeloma Patients Based on Treatment Regimen and Baseline Characteristics

Introduction: Denosumab is a monoclonal antibody targeting Receptor Activator of Nuclear Factor-Kappa B Ligand (RANKL) that has been shown to reduce skeletal related events associated with bone lesions in patients with multiple myeloma and solid tumors. Results from the full primary analysis of 1718 patients with newly diagnosed multiple myeloma in an international double blind, randomized, controlled phase 3 (20090482) study that assessed the efficacy of denosumab (Dmab) vs zoledronic acid (ZA) for preventing SREs met its primary end point of non-inferiority regarding time to first SRE. The analysis of the PFS exploratory endpoint showed a clinically meaningful 10.7 months median PFS benefit (HR, 0.82; 95% CI, 0.68-0.99; descriptive P= 0.036) of Dmab vs ZA. This benefit was most pronounced in patients who were stratified into the "intent to undergo Autologous Stem Cell Transplant (ASCT)" group at randomization. Thus, we present an in-depth analysis of relevant baseline characteristics, treatment regimens and PFS outcome in patients with intent to undergo transplant receiving Dmab and ZA.

Methods: Adult patients with newly diagnosed multiple myeloma (NDMM) and stratified as "intent to undergo ASCT" at randomization were included in this analysis. Patients received subcutaneous denosumab (120 mg) plus intravenous placebo or intravenous zoledronic acid (4 mg) plus subcutaneous placebo in 4-week cycles. In this subgroup, the PFS outcome was examined. Baseline characteristics and treatment regimens were compared between treatment arms.

Results: 54.1% of the 1718 enrolled patients were stratified into "intent to undergo ASCT" as part of their front-line therapy, and 61.8% of "intent to undergo ASCT" did receive an ASCT. In the "intent to undergo ASCT" group, 19.6% patients had disease progression in the Dmab arm compared to 28.0% in the ZA arm (HR 0.65 (0.49-0.85)) (Figure 1). No imbalance in terms of triplet therapy use between the two study arms (TABLE 1). 55.1% in Dmab vs 52.6% in ZA arm received Triplet Therapies which included Bortezomib, Cyclophosphamide, Dexamethasone (VCD), Bortezomib, Thalidomide, Dexamethasone (VTD), Cyclophosphamide, Thalidomide, Dexamethasone (CTD), or Bortezomib, Lenalidomide, Dexamethasone (VRD). The percentage of triplet therapies used in the "intent to undergo ASCT"patients was higher than in patients with no intent to undergo ASCT.

Percentage of patients with ECOG performance status 2 was 19.4% in the Dmab group vs 18.6% in the ZA group. 26.2% of patients in the Dmab arm and 25% in the ZA arm had Multiple Myeloma ISS stage III upon diagnosis.

Among intent to transplant patients there was no imbalance in terms of age, performance status, ISS stage, risk status, weight, bone marrow plasma cell % between the ZA and the Dmab arm

Conclusion: Results from this post-hoc subgroup analysis suggest a more profound PFS benefit in the "intent to undergo ASCT" patient subgroup. Multiple myeloma treatment received in the intent to undergo transplant subjects was similar between the denosumab and zoledronic acid arms. No significant imbalance in demographics or baseline disease characteristics was observed between the two treatment arms.

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