Stem Cell Collection with Daratumumab (DARA)-Based Regimens in Transplant-Eligible Newly Diagnosed Multiple Myeloma (NDMM) Patients (pts) in the Griffin and Master Studies

Introduction: DARA is approved across lines of therapy for multiple myeloma, including in combination with standard-of-care regimens for NDMM. The CXCR4 receptor antagonist plerixafor is used in conjunction with granulocyte colony-stimulating factor (G-CSF) to increase stem cell mobilization for autologous stem cell transplant (ASCT) and can be given by upfront decision or as a rescue strategy. The phase 2 randomized GRIFFIN study (NCT02874742) evaluates frontline DARA in combination with lenalidomide, bortezomib, and dexamethasone (D-RVd) in transplant-eligible NDMM. In the primary analysis, more pts undergoing stem cell mobilization/collection in the D-RVd group received plerixafor compared with the RVd group (69.5% [66/95] vs 56.3% [45/80]) (Voorhees PM, et al. Blood. 2020). The phase 2 MASTER study (NCT03224507) evaluates DARA plus carfilzomib, lenalidomide, and dexamethasone (D-KRd) in transplant-eligible NDMM (Costa LJ, et al. EHA Library. 2020). Here, we present a summary of stem cell mobilization, collection yields, and ASCT data following frontline DARA-based induction therapy in GRIFFIN and MASTER. Methods: Eligible pts had NDMM and were candidates for ASCT. In GRIFFIN, pts were randomized 1:1 to receive D-RVd or RVd. Pts received 4 induction cycles (21 days) of lenalidomide (R; 25 mg PO on Days 1-14), bortezomib (1.3 mg/m 2 SC on Days 1, 4, 8, and 11), and dexamethasone (d; 40 mg PO QW) ± DARA (16 mg/kg IV QW in Cycles 1-4). After Cycle 4, pts underwent stem cell mobilization with G-CSF ± plerixafor, per institutional standards; if unsuccessful, chemo mobilization was permitted. Pts then received ASCT and subsequently 2 consolidation cycles (21 days) of D-RVd or RVd followed by maintenance therapy with R ± DARA. In the single-arm MASTER study, pts received 4 D-KRd induction cycles, ASCT, and 0, 4 or 8 D-KRd consolidation cycles followed by maintenance therapy with R, based upon achievement of minimal residual disease-negativity. In each 28-day cycle, all pts received carfilzomib (20/56 mg/m 2 IV QW), R (25 mg PO on Days 1-21), d (40 mg PO or IV QW), and DARA (16 mg/kg IV QW for Cycles 1-2, Q2W for Cycles 3-6, and Q4W for Cycles 7+). Mobilization was with G-CSF ± plerixafor as per institutional standards. Results: In GRIFFIN, among 207 (D-RVd, n=104; RVd, n=103) randomized pts, 91.3% (n=95) of D-RVd pts and 77.7% (n=80) of RVd pts underwent stem cell mobilization; of those mobilized, 98.9% (n=94) and 97.5% (n=78) underwent ASCT, respectively. In