MM-219: Pivotal DREAMM-2 Study: Single-Agent Belantamab Mafodotin (Belamaf; GSK2857916) in Patients with Relapsed/Refractory Multiple Myeloma (RRMM) Refractory to Proteasome Inhibitors and Immunomodulatory Agents, and Refractory and/or Intolerant to Anti-CD38 Monoclonal Antibodies (mAbs), Including Subgroups with Renal Impairment (RI) and High-Risk (HR) Cytogenetics

Context: Belamaf showed deep and durable single-agent activity in the pivotal DREAMM-2 study primary analysis ( NCT03525678 ) (1–7) in a patient population that historically has a poor prognosis (overall survival [OS] 6–9 months). Objective: To present longer-term efficacy/safety outcomes (13-month follow-up) with single-agent belamaf in DREAMM-2 in the overall patient population and patients with HR cytogenetics and RI, subgroups with poor outcomes. Methods: DREAMM-2 is an ongoing study of belamaf 2.5 mg/kg (n=97) or 3.4 mg/kg (n=99). Primary outcome: overall response rate (ORR; ≥partial response). In post-hoc analyses, HR-cytogenetics included t(4;14), t(14;16), 17p13del, or 1q21 + . RI was based on eGFR (mild: ≥60– Results: Overall population ORRs in the 2.5 mg/kg and 3.4 mg/kg groups were 32% (97.5% CI: 21.7–43.6) and 35% (97.5% CI: 24.8–47.0); 19% and 23% of patients (58% and 66% of responders) achieved very good partial response or better. Median duration of response was 11.0 (95% CI: 4.2–not reached [NR]) and 6.2 months (95% CI: 4.8–NR). Median progression-free survival was 2.8 (95% CI: 1.6–3.6) and 3.9 months (95% CI: 2.0–5.8); median estimated OS was 13.7 (95% CI: 9.9–NR) and 13.8 months (95% CI: 10.0–NR). Most common Grade ≥3 adverse events (AEs) were keratopathy (microcyst-like epithelial changes [MECs] observed on eye examination; 2.5 mg/kg: 46%; 3.4 mg/kg: 42%), thrombocytopenia (2.5 mg/kg: 22%; 3.4 mg/kg: 32%), and anemia (2.5 mg/kg: 21%; 3.4 mg/kg: 27%). AE-related permanent discontinuation occurred in 9% and 12%; discontinuation due to MECs was rare (2.5 mg/kg: 1%; 3.4 mg/kg: 3%). HR cytogenetics and RI subgroup analyses will be presented at the conference. Conclusions: Deep and durable responses to single-agent belamaf were sustained and no new safety signals identified with longer follow-up in this heavily pretreated RRMM population. Funding: GSK (205678). Drug linker technology licensed from Seattle Genetics; mAb produced using POTELLIGENT Technology licensed from BioWa. References: [1] Lonial et al. Lancet Oncol. 2020. [2] Lonial et al. ASCO 2020. EP436. [3] Lonial et al. EHA 2020. EP970. [4] Cohen et al. ASCO 2020. EP441. [5] Trudel et al. EHA 2020. EP1037. [6] Lee et al. ASCO 2020. EP419. [7] Lee et al. EHA 2020. EP1006.