Oral Abstract: MM-459 Safety and Clinical Activity of Belantamab Mafodotin with Lenalidomide Plus Dexamethasone in Patients with Relapsed/Refractory Multiple Myeloma (RRMM): DREAMM-6 Arm-A Interim Analysis

Belantamab mafodotin (belamaf; BLENREP) is a B-cell maturation antigen-targeting antibody-drug conjugate approved as monotherapy (2.5mg/kg Q3W) for patients with RRMM. Preclinical data suggest an added benefit when belamaf is combined with lenalidomide/dexamethasone.DREAMM-6 (NCT03544281) Arm A evaluates belamaf plus lenalidomide/dexamethasone in patients with RRMM.This ongoing, two-part, two-arm, open-label study included patients with RMMM treated with ≥1 line of therapy (LOT). Patients received 4 belamaf doses/schedules (Cohort (C) 1: 1.9mg/kg Q8W; C2: 1.9mg/ kg Q4W; C3: 2.5mg/kg Q4W; C4: 2.5mg/kg Q4W SPLIT dose [50% on Days 1, 8] IV) in combination with lenalidomide (20mg PO Days 1-21) and dexamethasone (20mg PO/IV Days 1, 8, 15, 22).safety graded by CTCAE, tolerability, and efficacy (overall response rate [ORR, ≥partial response]).As of this interim analysis (cut-off: 23 July 2021), 45 patients received ≥1 dose (C1: 12; C2: 4; C3: 16; C4: 13); median age was 68y (range: 36-80). Thirteen patients (29%) had high-risk cytogenetics and 6 (13%) had extramedullary disease. Median prior LOT was 3 (range: 1-11) and 26 (58%) had prior lenalidomide treatment. The median duration of follow-up (3.4-17.4 months), ORR (42-75%), and ≥very good partial response rate (17-50%) ranged across cohorts. Median duration of response was only reached in C2 (11.1 months [95% CI: 3.7-not reached]). Median progression-free survival was not reached in C1 or C3. Gr≥3 treatment-related (TR)AEs occurred in 42-85%; AEs led to dose interruption/delay in 75-92%; serious TRAEs in 0-23%. Gr≥3 keratopathy occurred in C1: 0; C2: 1 (25%); C3: 8 (50%); C4: 6 (46%).Belamaf + lenalidomide/dexamethasone had a tolerable safety profile, with no new safety signals in patients with RRMM. AEs, including keratopathy, were common but manageable with dose modifications. Encouraging clinical activity is observed with this combination in patients with RRMM. Follow-up/correlative studies are ongoing.GSK (Study 207497); drug linker technology (Seagen Inc.); mAb produced using POTELLIGENT Technology (BioWa). ©2022 American Society of Clinical Oncology, Inc. Reused with permission. This abstract was accepted and previously presented at the 2022 ASCO Annual Meeting. All rights reserved.