LAUSR

8042 Background: High-dose therapy (HDT) followed by autologous stem-cell transplantation (ASCT) is the standard of care in TE NDMM. In the phase 3 CASSIOPEIA study, D-VTd significantly improved stringent complete response (sCR), ≥CR, and minimal residual disease (MRD)-negative rates and reduced the risk of progression/death vs VTd in TE NDMM pts. We assessed SC yield and transplantation results among pts receiving D-VTd vs VTd induction prior to HDT/ASCT in Part 1 of CASSIOPEIA. Methods: In Part 1, TE NDMM pts ages 18-65 y were randomized 1:1 to 4 pre-transplant induction and 2 post-transplant consolidation cycles of DARA + VTd or VTd alone. After induction, pts underwent SC mobilization with cyclophosphamide 3 g/m2 (recommended dose) and GCSF. Peripheral blood SCs were harvested based on response to mobilization. Plerixafor was given if SC collection failed at first attempt and in accordance with institutional practice. Melphalan 200 mg/m2 IV was given as HDT prior to ASCT. Results: A total of 1085 pts were randomized (D-VTd, 543; VTd, 542). Among pts who completed mobilization (D-VTd, 506; VTd, 492), more pts receiving D-VTd vs VTd received plerixafor during mobilization (21.7% vs 7.9%). Pts underwent a median (range) of 2 (1-6) vs 1 (1-4) days of apheresis for D-VTd vs VTd. The median number of CD34+ cells collected was lower for D-VTd vs VTd (6.3×106/kg vs 8.9×106/kg). Nevertheless, a similar percentage of ITT pts receiving D-VTd vs VTd underwent ASCT (90.1% vs 89.3%). The median number of CD34+ cells transplanted for D-VTd vs VTd was 3.3×106/kg vs 4.3×106/kg. Hematopoietic reconstitution rates were high and similar for transplanted pts receiving D-VTd vs VTd (99.8% vs 99.6%). For D-VTd vs VTd, a median (range) of 13.0 (6-54) vs 13.0 (4-43) days was required to achieve sustained ANC > 500 cells/mm3, and a median (range) of 14.0 (2-56) vs 12.0 (1-47) days was required to achieve sustained platelets > 20,000 cells/mm3 without transfusion. Conclusions: SC mobilization and collection was feasible with D-VTd induction. Adding DARA to VTd allowed successful transplantation in pts with TE NDMM. Clinical trial information: NCT02541383.