Infections Within 100 Days of Idecabtagene Vicleucel and Impact on Survival for Relapsed/Refractory Multiple Myeloma: A CIBMTR Analysis

Infections are common after chimeric antigen receptor (CAR) T-cell therapy and contribute to morbidity and mortality. While well characterized with CD19 CAR T-cells, data related to infections with B-cell maturation antigen (BCMA) CAR T-cell therapy are limited. This study aims to characterize the burden, patterns, risk factors, and clinical impact of infections on outcomes in patients with relapsed/refractory multiple myeloma (RRMM) treated with idecabtagene vicleucel (ide-cel). In this real-world analysis, we evaluated 807 patients with RRMM who received ide-cel after ≥4 prior lines of therapy between March 2021 and December 2023, using the Center for International Blood and Marrow Transplant Registry database. The infection density within 100 d post-ide-cel was 0.49 for any infection, and 0.23, 0.22, and 0.012 for bacterial, viral, and fungal infections, respectively. Bacterial infections predominated during the first 30 d post-infusion, whereas viral infections were more prevalent between day +30 and d +100. After a median follow-up among survivors of 11.6 months, 364 patients relapsed and 222 died, translating into a 1-yr progression-free survival of 46.5% and overall survival (OS) of 67.3%. Disease progression was the leading cause of death, followed by infections. Infection-related mortality was 1.1% at d +100. On multivariable Cox regression, baseline infection history prior to ide-cel, poor performance status (KPS<80), grade≥2 cytokine release syndrome, and grade≥3 neurotoxicity were independent predictors of infection. Recurrent infections (≥2 events) within 100 d and relapse within 100 d after ide-cel were associated with inferior OS. Infections are common and can result in inferior outcomes after ide-cel, underscoring the importance of risk stratification, surveillance, and stringent infection prevention strategies to optimize outcomes.