S183: NOVEL COMBINATION IMMUNOTHERAPY FOR THE TREATMENT OF RELAPSED/REFRACTORY MULTIPLE MYELOMA: UPDATED PHASE 1B RESULTS FOR TALQUETAMAB (A GPRC5D X CD3 BISPECIFIC ANTIBODY) IN COMBINATION WITH DARATUMUMAB

Abstract

Background: Talquetamab (tal; JNJ-64407564) is a first-in-class, bispecific IgG4 antibody that binds both to G protein-coupled receptor family C group 5 member D (GPRC5D), a receptor highly expressed on malignant plasma cells but with limited expression in healthy tissue, and CD3 to mediate T-cell–activated lysis of GPRC5D+ multiple myeloma (MM) cells. Daratumumab (dara) is an anti-CD38 mAb with direct on-tumor and immunomodulatory actions. Initial clinical results from the phase 1b multicohort TRIMM-2 study identified the recommended phase 2 doses (RP2Ds) of tal as 400 μg/kg weekly or 800 μg/kg Q2W and support the combination of tal + dara for the treatment of RRMM, with manageable safety, no overlapping toxicities, and promising efficacy. Aims: Here we report updated results for both RP2Ds of tal + dara in TRIMM-2 with additional patients (pts) and longer follow-up. Methods: Eligible MM pts (aged ≥18 years) had received ≥3 prior lines of therapy (LOT; including a PI and IMiD) or were double refractory to a PI and an IMiD, and could not have received anti-CD38 therapy within 90 days. Pts received dara SC 1800 mg per approved schedule and tal (400 μg/kg weekly or 800 μg/kg Q2W) with step-up dosing. The primary objectives were to identify the RP2D(s) of tal for combination therapy and evaluate safety of the combination. AEs were graded per CTCAE v5.0; cytokine release syndrome (CRS) and immune effector cell–associated neurotoxicity syndrome (ICANS) were graded per ASTCT guidelines. Responses were assessed by IMWG criteria. Results: At data cutoff (Jan 13, 2022, N=46), median follow-up was 4.0 months (range 0.4-16.3), median age was 65 years (range 47-81), and 48% were female. Pts received a median of 5 prior LOT (range 2-16); 83% were triple-class exposed, 61% penta-drug exposed, 37% anti-BCMA non–CAR-T exposed, and 4% anti-BCMA CAR-T exposed. 96% of pts had ≥1 AE (gr 3/4: 67%). The most frequently reported AEs (≥30% across tal + dara cohorts) were CRS (65%; all gr 1/2; median time to onset: 2 days; median duration: 2 days), dysgeusia (57%), thrombocytopenia (35%; gr 3/4: 20%), anemia (39%; gr 3/4: 20%), and dry mouth (44%). Infections occurred in 50% of pts (gr 3/4: 13%). Skin disorders were reported in 72% of pts (gr 3/4: 11%): skin exfoliation in 26% (all gr 1/2) and nail disorders in 11% (all gr 1/2). Two ICANS events were reported in the 800 Q2W group (both gr 1 and resolved within 1 day). 3 pts discontinued due to AEs. Response rates were consistent across both RP2Ds supporting their equivalence (Table). Median time to first response across dosing cohorts was 0.95 months (range 0.9-9.7); median duration of response was not reached. Upregulation of CD38+/CD8+ T cells and proinflammatory cytokines was observed with tal + dara, supporting potential synergy of the combination in pts with prior anti-CD38 exposure. Updated results will be presented. Image:Summary/Conclusion: Longer follow-up with additional patients shows comparable efficacy and safety across both RP2Ds, with no new safety signals, strengthening the benefit-risk profile of tal + dara as a novel immunotherapy-based approach for heavily pretreated pts with RRMM.