Background: Belantamab mafodotin, a B-cell maturation antigen targeting immunoconjugate, demonstrated clinically meaningful, single-agent activity in patients with heavily pre-treated RRMM refractory to an immunomodulatory agent, a proteasome inhibitor, and refractory and/or intolerant to an anti-CD38 monoclonal antibody (DREAMM-2, NCT03525678, Lancet Oncol.2020). The multimodal mechanism of action and manageable safety profile make belantamab mafodotin a promising candidate for use in different RRMM combination regimens. Methods: DREAMM-6 (NCT03544281) is an ongoing, two-part, two-arm, study evaluating the safety, tolerability, and clinical activity of belantamab mafodotin in combination with bortezomib/dexamethasone (BorDex) and lenalidomide/dexamethasone in patients previously treated with ≥1 prior therapy line. Here, we present data for belantamab mafodotin in combination with BorDex. Part 1 (dose escalation) and Part 2 (dose expansion) evaluated belantamab mafodotin (2.5 and 3.4 mg/kg) administered as SINGLE (Day 1) or SPLIT dose (divided equally on Days 1 and 8) in combination with BorDex. Results: As of February 6, 2020, 52 patients were enrolled: 6 patients were enrolled at 2.5 mg/kg single dose and 7 at 3.4 mg/kg single dosing in Part 1, and 45 patients in Part 2. No dose-limiting toxicities were observed. Corneal events (including keratopathy, blurred vision, and dry eye) and thrombocytopenia were the most frequently reported AEs and were clinically manageable. Conclusions: In DREAMM-6, preliminary data demonstrate that the combination of belantamab mafodotin and BorDex has an acceptable safety profile, with no new safety signals identified. Funding: GlaxoSmithKline (207497). Drug linker technology licensed from Seattle Genetics; monoclonal antibody produced using POTELLIGENT Technology licensed from BioWa. Clinical trial information: NCT03544281.