Survival is poor among patients with triple-class-exposed relapsed and refractory multiple myeloma. Idecabtagene vicleucel (ide-cel), a B-cell maturation antigen-directed chimeric antigen receptor (CAR) T-cell therapy, previously led to deep, durable responses in patients with heavily pretreated relapsed and refractory multiple myeloma.

In this international, open-label, phase 3 trial involving adults with relapsed and refractory multiple myeloma who had received two to four regimens previously (including immunomodulatory agents, proteasome inhibitors, and daratumumab) and who had disease refractory to the last regimen, we randomly assigned patients in a 2:1 ratio to receive either ide-cel (dose range, 150×10 to 450×10 CAR-positive T cells) or one of five standard regimens. The primary end point was progression-free survival. Key secondary end points were overall response (partial response or better) and overall survival. Safety was assessed.

A total of 386 patients underwent randomization: 254 to ide-cel and 132 to a standard regimen. A total of 66% of the patients had triple-class-refractory disease, and 95% had daratumumab-refractory disease. At a median follow-up of 18.6 months, the median progression-free survival was 13.3 months in the ide-cel group, as compared with 4.4 months in the standard-regimen group (hazard ratio for disease progression or death, 0.49; 95% confidence interval, 0.38 to 0.65; P<0.001). A response occurred in 71% of the patients in the ide-cel group and in 42% of those in the standard-regimen group (P<0.001); a complete response occurred in 39% and 5%, respectively. Data on overall survival were immature. Adverse events of grade 3 or 4 occurred in 93% of the patients in the ide-cel group and in 75% of those in the standard-regimen group. Among the 225 patients who received ide-cel, cytokine release syndrome occurred in 88%, with 5% having an event of grade 3 or higher, and investigator-identified neurotoxic effects occurred in 15%, with 3% having an event of grade 3 or higher.

Ide-cel therapy significantly prolonged progression-free survival and improved response as compared with standard regimens in patients with triple-class-exposed relapsed and refractory multiple myeloma who had received two to four regimens previously. The toxicity of ide-cel was consistent with previous reports. (Funded by 2seventy bio and Celgene, a Bristol-Myers Squibb company; KarMMa-3 ClinicalTrials.gov number, NCT03651128.).