Influence of CAR T-cell expansion and persistence in the peripheral blood on CAR T-cell therapy efficacy and adverse events in multiple myeloma

CAR T-cell expansion and persistence may be critical for treatment outcome and adverse events, such as neurotoxicity, cytokine release syndrome (CRS) and hematologic toxicity. Prior data suggest that high tumor burden, a history of grade ≥2 CRS, previous immune effector cell-associated neurotoxicity syndrome (ICANS), and pronounced CAR T-cell expansion may be associated with increased delayed neurotoxicity (DNT) risk [ 1 ], including cranial nerve palsies (CNP) and neurocognitive movement disorders (MNT), which can be severe and difficult to manage [ 2 ]. Here we analyzed the clinical outcome and the influence of BCMA-CAR T-cell expansion in peripheral blood (PB) by flow cytometry in our first 40 CAR T-treated multiple myeloma (MM) patients (cilta-cel n = 28, ide-cel n = 12) (Supplementary Table S1 ). For methods see Supplementary Material .