Healthcare Resource Utilization and Economic Burden of Cytokine Release Syndrome and Neurotoxicity in Patients with Relapsed and Refractory Multiple Myeloma (RRMM) Receiving Idecabtagene Vicleucel in Earlier-Line Settings in the KarMMa-3 Clinical Trial

Introduction: Adverse events (AE), such as cytokine release syndrome (CRS) and neurological toxicity (NT), have been associated with chimeric antigen receptor (CAR) T cell therapies. Idecabtagene vicleucel (ide-cel, bb2121), a B-cell maturation antigen-directed CAR T cell therapy, demonstrated deep and durable responses in triple-class exposed (TCE) patients (pts) with RRMM in the pivotal, single-arm, open-label phase 2 KarMMa (3 prior lines of therapy [LOTs]; NCT03361748) (Munshi NC, et al. NEJM 2021;384:705–716) and superior progression-free survival with ide-cel vs standard regimens in the phase 3 KarMMa-3 trial (2–4 prior LOTS; NCT03651128) (Rodríguez-Otero P, et al. NEJM 2023;388:1002–1014). Healthcare resource utilization (HCRU) and costs associated with CRS/NT management were estimated previously for pts receiving ide-cel in the KarMMa trial (McGarvey N, et al. Value Health 2023;26:S89) and suggested low rates of severe (grade ≥ 3) CRS/NT following ide-cel infusion and higher HCRU and costs with increasing AE severity. To further assess resource and economic burden associated with care of treatment-emergent AEs, this analysis evaluated HCRU and estimated cost of CRS/NT management among pts treated with ide-cel in earlier-line settings in the KarMMa-3 study.

Methods: In this retrospective study, case report forms from the KarMMa-3 clinical trial database among pts experiencing a CRS and/or NT event that initiated within 90 days post ide-cel infusion were assessed. Pt-level HCRU data, including hospitalizations and length of hospital stay (LOS) (standard inpatient [IP], intensive care unit [ICU] days), diagnostics (eg, lab work, imaging), procedures (eg, dialysis, intubation), and medications (eg, oncology supportive care, prophylactics, other AE management) were identified from CRS/NT onset through resolution. AE management costs were estimated using a micro-costing methodology in which unit costs sourced from public databases or literature (eg, United States Centers for Medicare and Medicaid Services, Healthcare Cost and Utilization Project, IBM^® Micromedex^® RED BOOK^®) were adjusted to 2022 US dollars (USD) using the Consumer Price Index and applied to each HCRU identified.

Results: Of 225 pts treated with ide-cel in the KarMMa-3 trial, 203 (90.2%) experienced any grade CRS and/or NT event. Pts experiencing a CRS/NT event had a mean (standard deviation [SD]) age of 61.9 (8.9) years and most were male (123/203 [60.6%]), White (138/203 [68.0%]), and non-Hispanic or Latino (138/203 [68.0%]). The majority (187/203 [92.1%]) of pts experienced less severe CRS/NT events (grade ≤ 2), which resolved quicker and relatively few pts (16/203 [7.9%]) had a more severe (grade ≥ 3) event, which took longer to resolve. Among pts who received ide-cel, the estimated median cost of AE management ranged from USD 17,124 (CRS only grade 1) to USD 181,552 (nonconcurrent CRS or NT grade ≥ 3) (Figure 1). Additional median costs for a pt with a grade ≥ 3 CRS/NT event was USD 31,045 higher than a grade ≤ 2 CRS/NT event. Across AE categories, the main contributors to CRS/NT management were facility costs, namely standard IP hospitalizations and ICU stays. Almost all pts (202/203 [99.5%]) had a standard IP hospitalization; 3.9% (8/203) had an ICU stay (Table 1). The trial protocol required a stay of ≥ 15 days post infusion unless admitted to the ICU; some hospitalization days recorded during the AE overlapped with the protocol-required stay. ICU admissions were more common among pts with CRS/NT grade ≥ 3 (7/16 [43.8%]) than those with grade ≤ 2 (1/187 [0.5%]). Median (range) total LOS was 10 days longer among pts with grade ≥ 3 (14.5 [2–84] days) than those with grade ≤ 2 (4 [1–34] days) CRS/NT. Pts with grade ≥ 3 CRS/NT had higher rates of HCRU than those with grade ≤ 2 for several interventions, such as medications (eg, tocilizumab + corticosteroids: 13/16 [81.3%] vs 63/187 [33.7%]), diagnostics (eg, imaging: 14/16 [87.5%] vs 48/187 [25.7%]), and procedures (eg, dialysis:3/16 [18.8%] vs 0/187 [0%]).

Conclusions: Most pts with RRMM treated with ide-cel in the KarMMa-3 trial experienced a CRS and/or NT event, however, few were of high severity (grade ≥ 3). HCRU and costs for CRS/NT increased with AE severity and management. CAR T cell therapies associated with lower-severity AEs and planned interventions to prevent higher-grade AEs may provide an opportunity to better manage HCRU and costs.