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    Treatment of Relapsed/Refractory Myeloma (excluding T-cell redirection therapy)

    (OA-56) Belantamab for the Treatment of Multiple Myeloma: Results from Part 1 of the First-in-Human Phase 1/2 DREAMM-20 Trial

    Saturday, September 20, 2025
    11:30 - 11:40 East Coast USA Time
    Location: Room 701
    Introduction: Belantamab mafodotin (belamaf) is a B-cell maturation antigen (BCMA)–targeted monoclonal antibody (mAb) conjugated with a monomethyl auristatin F (MMAF) payload. In the phase 3 DREAMM-7 and DREAMM-8 trials in patients (pts) with relapsed/refractory multiple myeloma (RRMM), belamaf combinations significantly improved progression-free survival vs standard-of-care regimens, with DREAMM-7 also showing a significant overall survival benefit. Belantamab (GSK2857914) is the unconjugated BCMA-targeted mAb without MMAF; therefore, MMAF-related ocular toxicities are not expected. DREAMM-20 is a phase 1/2 study evaluating the safety, tolerability, and clinical activity of belantamab in pts with MM. Here, we present a planned analysis of belantamab dose escalation in part 1 of DREAMM-20 (NCT05714839).

    Methods:

    Part 1 is a phase 1, open-label, multicenter, dose-escalation study in pts with RRMM with ≥3 prior lines of therapy, including an immunomodulatory agent, proteasome inhibitor, and anti-CD38 mAb. Dose escalation was conducted using a modified toxicity probability interval method. The primary endpoint was incidence of adverse events (AEs), including dose-limiting toxicities (DLTs). Secondary endpoints included overall response rate (ORR).

    Results:

    Across 3 cohorts, 18 pts received belantamab 300, 900, or 2000 mg IV Q2W (n=6 each). Data cutoff (DCO) was Feb 22, 2025. Median age was 76 y (range, 42-86 y); 17/18 pts were triple-class exposed, and 2/18 had prior BCMA-targeted therapy. Overall median duration of exposure was 63.5 d.

    No DLTs or treatment-related AEs (TRAEs) leading to discontinuation were reported. The most common TRAEs across the 3 cohorts were infusion-related reactions (4/18 [22%]), decreased neutrophil count (4/18 [22%]), and anemia (3/18 [17%]). Grade ≥3 AEs occurred in 13 pts (72%), and serious AEs occurred in 6 (33%); no fatal serious AEs were reported. Two pts (11%) had grade ≥2 corneal events per the Keratopathy and Visual Acuity scale, deemed unrelated to belantamab.

    The ORR was 28% (5/18 pts); 3 pts (2 receiving 900 mg, 1 receiving 2000 mg) had very good partial responses and 2 (1 each receiving 300 and 2000 mg) had partial responses, with responses observed across all cohorts. No pts had a minimal response, and 28% (5/18) had stable disease. Responses appeared durable, with 3 of 5 pts ongoing at DCO and only 1 pt with progressive disease discontinuing treatment after response.

    Conclusions:

    Belantamab had a favorable safety profile, with no DLTs, TRAEs leading to discontinuation, or grade ≥2 corneal events associated with belantamab. Encouraging preliminary clinical activity was observed, with durable responses occurring across dose levels in this heavily pretreated, triple class−exposed population. These findings support the potential of belantamab to provide clinical activity with an acceptable safety profile. Further evaluation is ongoing in part 2 of DREAMM-20.



    Funding: GSK.

    Monoclonal antibody produced using POTELLIGENT Technology licensed from BioWa.