Idecabtagene Vicleucel (ide-cel) Versus Standard (std) Regimens in Patients (pts) with Triple-Class-Exposed (TCE) Relapsed and Refractory Multiple Myeloma (RRMM): Analysis of Cytopenias and Infections in Pts from KarMMa-3

Abstract

Introduction In the KarMMa-3 trial (NCT03651128), ide-cel, a BCMA-directed CAR T cell therapy (Tx), significantly improved median progression-free survival (13.3 vs 4.4 mo, HR 0.49, P < 0.001) and overall response rate (71% vs 42%, P < 0.001) vs std regimens in pts with RRMM who were TCE to immunomodulatory (IMiD ®) agents, proteasome inhibitors (PIs), and daratumumab (Rodríguez-Otero NEJM 2023). Early high-grade (gr) cytopenias and severe infections have been reported post-CAR T cell infusion (Logue Blood 2022, Thibaud Blood 2022), and persistent cytopenias and infections can pose clinical challenges in pt care. In this safety analysis of KarMMa-3, we report frequency, kinetics of occurrence, and management of cytopenias and infections post-Tx with ide-cel or std regimens. Methods This international, randomized, multicenter phase 3 trial enrolled pts with RRMM who received 2-4 prior Txs (an IMiD agent, a PI, and daratumumab) and were refractory to the last Tx. Pts were randomized 2:1 to ide-cel or a std regimen (DPd, DVd, IRd, Kd, or EPd) selected by investigator based on prior anti-MM Tx. In the ide-cel arm, pts could have ≤ 1 cycle of optional bridging Tx (BTx) for disease control. Treated population (pop; ide-cel: pts who received leukapheresis [LA], BTx, lymphodepleting chemotherapy, or ide-cel; std regimens: pts who received any dose of study Tx) was used to assess adverse events (AEs), gr 3/4 AEs, and serious AEs. Safety pop (pts who received ide-cel or any dose of std regimens) was used to assess treatment-emergent AEs, AEs of special interest, investigator-identified neurotoxicity/cytokine release syndrome and others. In pts who had documented disease progression on std regimens and then underwent LA to receive ide-cel, only AEs before LA were included. In this analysis, incidence of cytopenias and infections at various time intervals and management, types of infections, and incidence of hypogammaglobulinemia (HGG) were assessed. Results At data cutoff (Oct 3, 2022), median follow-up was 24.1 (range 5.9−41.0) mo in the 386 randomized pts. In the treated pop, 248/249 (99.6%) vs 124/126 (98.4%) pts had any-gr AEs, 234 (94.0%) vs 96 (76.2%) had gr 3/4, and 36 (14.5%) vs 9 (7.1%) had gr 5 in ide-cel vs std regimens arms, respectively. Of the gr 5 AEs, 18/36 and 3/9 had verbatim terms consistent with progressive disease. In the safety pop, incidence of gr 3/4 cytopenias with ide-cel were higher early after infusion but generally resolved over time (196 [87.1%] pts at < 3 mo, 52 [24.1%] pts at 3−< 6 mo, 30 [14.7%] pts at ≥ 6 mo; Table 1) vs std regimens, which showed lower rate of resolution over time. More pts in the ide-cel (16 [7.1%]) vs std regimens arms (3 [2.4%]) had any-gr febrile neutropenia. Cytopenias were mainly managed using colony-stimulating factor in both arms (55.5% and 58.7%, respectively); RBC (48%) and platelet transfusions (32%) were more common in the ide-cel arm. Overall, incidence of gr 3/4 infections was high at < 3 mo and remained consistent over time in both arms (ide-cel: 17 [7.6%] pts at < 3 mo, 18 [8.3%] pts at 3−< 6 mo, 13 [6.4%] pts at ≥ 6 mo; Table 2). Any-gr bacterial infections were more common in the ide-cel vs std regimens arms with higher incidence at < 3 mo (10% vs 6%) but lowered at later timepoints. Incidence of gr ≥ 3 viral infections remained low and consistent with time; fungal infections were uncommon. Deaths due to infections occurred in 3 (1.3%) vs 1 (0.8%) pts at < 3 mo, 0 pts at 3−< 6 mo, and 7 (3.4%) vs 2 (2.6%) pts at ≥ 6 mo in the ide-cel vs std regimens arms, respectively. Indence of any-gr new HGG was higher in the ide-cel vs std regimens arms but decreased over time: 15 (6.7%) vs 2 (1.6%) pts at < 3 mo, 3 (1.4%) vs 1 (0.9%) at 3−< 6 mo, and 5 (2.5%) vs 0 at ≥ 6 mo, respectively; of these, 13 (5.8%) vs 1 (0.8%), 2 (0.9%) vs 1 (0.9%), and 5 (2.5%) vs 0 pts received IV immunoglobulin replacement Tx at the respective time intervals. Incidence rate (% per 100 pt-years, 95% CI) of second primary malignancies remained low and similar between arms (ide-cel, 4.0 [2.4−6.7]; std regimens, 4.4 [1.9−10.7]). Conclusion In KarMMa-3, most severe cytopenias associated with ide-cel occurred early, with a low incidence of prolonged cytopenias; all were largely manageable. Any-gr bacterial infections decreased over time while viral infections remained the same. No new safety concerns were identified for ide-cel; safety profile was consistent with previous reports. Study support 2seventy bio and Celgene, a Bristol-Myers Squibb Company.