Elotuzumab in Combination with Lenalidomide, Bortezomib, Dexamethasone and Autologous Transplantation for Newly-Diagnosed Multiple Myeloma: Results from the Randomized Phase III GMMG-HD6 Trial

Background: Treatment regimens including a proteasome inhibitor, immunomodulating agent and a monoclonal antibody (moAb) play an emerging role in the treatment of newly-diagnosed multiple myeloma (NDMM). This multicenter phase III trial of the German-speaking Myeloma Multicenter Group (GMMG HD6) investigated the addition of the anti-SLAMF7 moAb elotuzumab to lenalidomide / bortezomib / dexamethasone (RVd) in induction and consolidation therapy as well as to lenalidomide maintenance treatment in transplant-eligible NDMM. Patients and Methods: Patients were equally randomized into four treatment arms, stratified by International Staging System (ISS). Treatment consisted of four 21-day cycles of RVd (arms A1/A2) or elotuzumab-RVd (arms B1/B2) induction therapy, respectively. High-dose melphalan (HDM) and autologous blood stem cell transplantation (ASCT) were followed by two 21-day cycles of RVd or elotuzumab-RVd consolidation and lenalidomide or elotuzumab-lenalidomide maintenance for two years (arms A1/B1 vs. A2/B2). Primary objective of the trial was determination of the best of four treatment strategies regarding progression-free survival (PFS) from randomization. Secondary endpoints included overall survival (OS), response rates and safety. Results: Between 06/2015 and 09/2017, 564 patients were included in the trial. The evaluable intention-to-treat (ITT) and safety population comprised 559 and 555 patients (A1: n=139/137; A2: n=141/138; B1: n=137/138; B2: n=142/142). Median age at randomization was 59 (range 27-70) years. Baseline characteristics were well balanced between the four treatment arms. Four cycles of induction therapy were completed by 517 patients (92.5% of ITT). At least one HDM/ASCT was applied in 495 (88.6%), of which 116 patients (20.8%) received tandem HDM/ASCT. Consolidation and maintenance therapy were initiated in 469 (83.9%) and 454 (81.2%) patients, respectively. Rates of very good partial response or better (≥VGPR) prior to start of consolidation therapy were 78.9%, 78.2%, 81.5% and 80.7% in arms A1, A2, B1 and B2, respectively (p=0.95). With a median follow-up time of 49.8 months, PFS was not significantly different between the four treatment arms (adjusted log-rank p value stratified by ISS, p=0.86; primary endpoint). OS was similar in all treatment arms (stratified log-rank p=0.43). 3-year PFS/OS rates are 68.8%/89.4%, 68.5%/89.1%, 66.2%/92.5% and 67.2%/89.7% in arm A1, A2, B1 and B2, respectively. Multivariate analyses includ