Impact of CAR T-cell in vivo expansion kinetics on achievement of MRD-negative CR. (A) CAR T-cell counts in the blood over the first 90 days after CAR T-cell infusion for patients who achieved MRD-negative CR (blue lines) compared with patients who did not respond (red lines). Each thin line represents a single patient; bold lines represent LOESS (local polynomial regression) curve fitting data approximation with the standard error shown in gray; data were censored at the time of a subsequent CAR T-cell infusion. The dashed horizontal line indicates the limit of quantitation of the qPCR assay. Patients who achieved MRD-negative CR (blue) had a higher mean peak (P = .0002 [B]) and AUC from day 0 to day 28 (AUC28; P < .0001 [C]) of CAR T cells compared with those who did not respond (red). CAR T-cell counts in the blood were measured by qPCR for FlapEF1α transgene copies per μg of DNA in all patients (n = 53).