Background: RRMM patients (pts) triple-class exposed (to immunomodulatory drugs [IMiDs], proteasome inhibitors [PIs] and anti-CD38 monoclonal antibodies [mAbs]) have limited treatment (tx) options. The ongoing phase II KarMMa study (NCT03361748) is examining idecabtagene vicleucel (ide-cel; bb2121), a BCMA targeted CAR T cell therapy, in RRMM pts with ≥3 prior regimens (IMiD, PI and CD38 mAb inclusive) who are refractory to their last tx per IMWG criteria. This study aimed to 1) assess tx patterns and outcomes in real world (RW) RRMM pts similar to the KarMMa population and; 2) compare outcomes with SoC in a synthetic cohort vs ide-cel in KarMMa. Methods: In this global, noninterventional, retrospective study (KarMMa-RW), pt-level data from clinical sites, registries and databases were collated into a single data model. RW pts meeting KarMMa eligibility criteria (eligible cohort; EC) were compared with KarMMa (N = 128) using trimmed stabilized inverse probability of tx weighted propensity scores (IPTW PS) for pts in both studies with Poisson regression for ORR and ≥VGPR, and Cox models with study as a term for PFS. All models were adjusted for unbalanced covariates. Results: Of 1949 RW pts, 1171 were refractory to last regimen (median age, 68 y; median no. of prior regimens, 5; triple-class refractory, 41%). Further selection for subsequent tx, organ function and no comorbidities yielded 190 EC pts who had > 90 distinct tx regimens. With a median follow-up of 11.3 mo (KarMMa) and 10.2 mo (EC) at data cutoff (Oct 30, 2019), ORR, ≥VGPR and PFS were significantly improved in KarMMa vs EC (Table). Conclusions: Results from the KarMMa-RW study confirm that there is no clear SoC for heavily pretreated RW RRMM pts and responses are suboptimal with currently available therapies. Ide-cel showed deep, durable responses and significantly improved PFS in RRMM pts, representing a potential new tx option in RRMM. Clinical trial information: tbd.

HR, hazard ratio; RR, risk ratio

*Across all target doses

^†Derived for both studies using trimmed stabilized IPTW PS

^‡CR not reported due to missing biopsy data in EC to confirm CR