BACKGROUND: Idecabtagene vicleucel (ide-cel, also called bb2121), a B-cell 
maturation antigen-directed chimeric antigen receptor (CAR) T-cell therapy, has 
shown clinical activity with expected CAR T-cell toxic effects in patients with 
relapsed and refractory multiple myeloma.
METHODS: In this phase 2 study, we sought to confirm the efficacy and safety of 
ide-cel in patients with relapsed and refractory myeloma. Patients with disease 
after at least three previous regimens including a proteasome inhibitor, an 
immunomodulatory agent, and an anti-CD38 antibody were enrolled. Patients 
received ide-cel target doses of 150 × 106 to 450 × 106 CAR-positive (CAR+) T 
cells. The primary end point was an overall response (partial response or 
better); a key secondary end point was a complete response or better (comprising 
complete and stringent complete responses).
RESULTS: Of 140 patients enrolled, 128 received ide-cel. At a median follow-up 
of 13.3 months, 94 of 128 patients (73%) had a response, and 42 of 128 (33%) had 
a complete response or better. Minimal residual disease (MRD)-negative status 
(<10-5 nucleated cells) was confirmed in 33 patients, representing 26% of all 
128 patients who were treated and 79% of the 42 patients who had a complete 
response or better. The median progression-free survival was 8.8 months (95% 
confidence interval, 5.6 to 11.6). Common toxic effects among the 128 treated 
patients included neutropenia in 117 patients (91%), anemia in 89 (70%), and 
thrombocytopenia in 81 (63%). Cytokine release syndrome was reported in 107 
patients (84%), including 7 (5%) who had events of grade 3 or higher. Neurotoxic 
effects developed in 23 patients (18%) and were of grade 3 in 4 patients (3%); 
no neurotoxic effects higher than grade 3 occurred. Cellular kinetic analysis 
confirmed CAR+ T cells in 29 of 49 patients (59%) at 6 months and 4 of 11 
patients (36%) at 12 months after infusion.
CONCLUSIONS: Ide-cel induced responses in a majority of heavily pretreated 
patients with refractory and relapsed myeloma; MRD-negative status was achieved 
in 26% of treated patients. Almost all patients had grade 3 or 4 toxic effects, 
most commonly hematologic toxic effects and cytokine release syndrome. (Funded 
by bluebird bio and Celgene, a Bristol-Myers Squibb company; KarMMa 
ClinicalTrials.gov number, NCT03361748.).