Final Analysis of Overall Survival from the Phase 3 Panorama 1 Trial of Panobinostat Plus Bortezomib and Dexamethasone Versus Placebo Plus Bortezomib and Dexamethasone in Patients with Relapsed or Relapsed and Refractory Multiple Myeloma

Introduction: Panobinostat is a potent pan-deacetylase inhibitor (pan-DACi) that targets key aberrations in multiple myeloma (MM) cell biology, including epigenetics and protein metabolism. In the phase 3 clinical trial PANORAMA 1, panobinostat in combination with bortezomib and dexamethasone (PAN-BTZ-Dex) led to a statistically significant and clinically relevant increase in progression-free survival of approximately 4 months compared with that with placebo plus bortezomib and dexamethasone (Pbo-BTZ-Dex). Further analyses of patient outcomes by prior treatment demonstrated that the magnitude of PFS benefit was greatest among patients who received at least 2 prior regimens, including bortezomib and an immunomodulatory drug (IMiD; PAN-BTZ-Dex [n = 73]: 12.5 months [95% CI, 7.3-14.0 months]; Pbo-BTZ-Dex [n = 74]: 4.7 months (95% CI, 3.7-6.1 mo; HR 0.47 [95% CI, 0.32-0.72]). These data supported the regulatory approvals of PAN-BTZ-Dex for the treatment of patients with multiple myeloma who received at least 2 prior regimens, including bortezomib and an IMiD. Here we present the final analysis of overall survival (OS) for the entire patient population and among patients who received at least 2 prior regimens, including bortezomib and an IMiD.

Methods: The study design for the PANORAMA 1 trial was described previously (San-Miguel. Lancet Oncol. 2014;15:1195-206). The key secondary endpoint was OS. As of June 29, 2015, the 415 events required to conduct the final analysis of OS had been observed. Kaplan-Meier estimation was utilized for OS analyses for the entire population (N = 768), the pre-specified subgroup of patients who received prior bortezomib and IMiD (n = 193), and patients who received at least 2 prior regimens including bortezomib and an IMiD (n = 147).

Results: The median OS of patients who received PAN-BTZ-Dex in the overall population was 40.3 months (95% CI, 35.0-44.8 months) vs 35.8 months (95% CI, 29.0-40.6 months) for the Pbo-BTZ-Dex arm with HR 0.94 [95% CI, 0.78-1.14], P = .5435 (Fig 1A). The percentage of patients in each arm who received post-study therapy was 37.7% in the PAN-BTZ-Dex arm and 48.8% in the Pbo-BTZ-Dex arm. The median OS of patients who received at least 2 prior lines, including bortezomib and an IMiD, was 25.5 months (95% CI, 19.6-34.3 months) in the PAN-BTZ-Dex arm vs 19.5 months (95% CI, 14.1-32.5 months) in the Pbo-BTZ-Dex arm (Fig. 1B). The proportion of patients in this subgroup who received post-study therapy was 35.6% in the PAN-BTZ-Dex arm and 66.2% in the Pbo-BTZ-Dex arm.   

Conclusion: For the overall PANORAMA 1 study population, patients in the PAN-BTZ-Dex arm demonstrated an increase in median OS of 4.5 months vs patients in the Pbo-BTZ-Dex arm, but this result was not statistically significant (P = .5435). Median OS was also slightly longer for the PAN-BTZ-Dex arm among the more heavily pretreated subgroup of patients who received at least 2 prior regimens, including bortezomib and an IMiD. A higher percentage of patients on the Pbo-BTZ-Dex arm received post-study therapy vs the PAN-BTZ-Dex arm, which may have confounded the OS results. In summary, PAN-BTZ-Dex demonstrates statistically significant increases in PFS vs Pbo-BTZ-Dex in patients with relapsed or relapsed and refractory MM; however, this did not translate to a statistically significant increase in OS. Future trials will plan to focus on further optimization of dose and schedule of panobinostat and bortezomib to improve outcome, as well as novel combinations with other agents, including IMiDs and next-generation proteasome inhibitors.