Early cytopenias and infections after standard of care idecabtagene vicleucel in relapsed or refractory multiple myeloma.

Idecabtagene vicleucel (ide-cel) was FDA approved in March 2021 for the treatment of relapsed/refractory multiple myeloma (RRMM) after 4 lines of therapy. On the KarMMa trial, grade ≥3 cytopenias and infections were common. We sought to characterize cytopenias and infections within 100 days after ide-cel in the standard of care (SOC) setting. This multi-center retrospective study included 52 patients who received SOC ide-cel; 47 reached day 90 follow-up. Data was censored at day 100. Grade ≥3 cytopenia was present among 65% of patients at day 30 and 40% of patients at day 90. Granulocyte colony stimulating factor (G-CSF) was administered to 88%, packed red blood cell (pRBC) transfusions to 63%, platelet transfusions to 42%, thrombopoietin (TPO) agonists to 21%, intravenous immunoglobulin (IVIG) to 13%, and CD34+ stem cell boosts to 8%. At day 100, 19% and 13% of patients had ongoing use of TPO agonists and G-CSF, respectively. Infections occurred in 54% of patients and were grade ≥3 in 23%. Earlier infections in the first 30 days were typically bacterial (68%) and severe (50%). Later infections between days 31 - 100 were 50% bacterial and 42% viral; only 13% were grade ≥3. On univariate analysis, high pre-CAR-T marrow myeloma burden (>/= 50%), circulating plasma cells at pre-lymphodepletion (LD), and grade ≥3 anemia at pre-LD were associated with grade ≥3 cytopenia at both days 30 and 90. Longer time from last bridging treatment to LD was the only significant risk factor for infection.