As of May 15, 2024, 74 pts were enrolled and treated across 3 dose levels of ABBV-383 plus Dd. Median age was 69 years (range 39–89) and 45 (61%) pts were male. The majority of pts were White (n=65, 88%), 6 (8%) were Asian, and 3 (4%) were Black or African American. R-ISS at study entry was I in 18 (25%) pts, II in 26 (36%), and III in 15 (21%). Pts had received a median of 4 (range 3–9) prior lines of therapy; 70% were exposed to prior anti-CD38 mAb therapy. Forty-two (57%) pts were refractory to prior anti-CD38 mAb therapy, 34 (46%) were refractory to the most recent MM therapy, and 32 (43%) were triple-class refractory. After a median follow-up of 5 months (range 0–14), 48 (65%) pts remained on therapy; the majority of study drug discontinuations were due to progressive disease (n=14, 19%). Cytokine release syndrome (CRS) occurred in 20 (27%) pts. The majority of CRS events were grade 1 (n=8, 11%) or 2 (n=9, 12%); 3 (4%) pts had grade 3 events. Other most common treatment-emergent adverse events (AEs) included (any grade/grade 3–4) neutropenia (39%/38%), anemia (24%/18%), fatigue (22%/0%), and thrombocytopenia (30%/18%). Immune effector cell-associated neurotoxicity syndrome was reported in 2 (3%) pts total. Most common serious AEs were CRS (20%), COVID-19 pneumonia (7%), and pneumonia (5%). Twelve deaths occurred during the study to date; the most common cause was disease progression (n=5, 7%). At the time of data cutoff, 60 pts were evaluable for disease assessment. The aggregate overall response rate (ORR) for the total evaluable population was 70% (42/60). ORRs were 50% (7/14) in the 20-mg Q4W ABBV-383 cohort at a median follow-up of 1 month (range 0–14), 74% (26/35) in the 40-mg cohort at a median follow-up of 4.4 months (1–10), and 82% (9/11) in the 60-mg cohort at a median follow-up of 5.6 months (1–6). Median progression-free survival was not reached at time of analysis.
Conclusion: Preliminary data suggest ABBV-383 in combination with Dd is tolerable. Overall rates of CRS were low and early response rates were promising in the investigated population of heavily pretreated pts with MM.
