CART19 in tafasitamab-pretreated mice shows a better antitumor response. (A) Treatment schema. NSG mice were inoculated with luciferase⁺ JeKo-1 on day −14, and tumor burden was analyzed using BLI on day −6. Mice were randomized according to their tumor burden to receive 10 mg/kg per day tafasitamab (IP, 10 mice) or PBS vehicle control (IP, 5 mice, group 1). Tumor burden was reassessed by BLI on day −1, and tafasitamab-treated mice were randomized to tafasitamab discontinuous (5 mice, group 2) or continuous (5 mice, group 3) groups. (B-C) BLI analysis. Group 2, mice pretreated with tafasitamab before CART19 cell injection, demonstrated better tumor control than those in groups 1 or 3 (∗P < .05, 2-way ANOVA). (D) CART19 cell expansion in vivo. Peripheral blood (PB) was collected on days 11 and 23 after the CART19 infusion to analyze the expansion of CART19. Group 2 showed late-onset CART19 expansion (∗∗P < .01, 2-way ANOVA). (E) Overall survival curve. Group 2 showed superior overall survival compared with groups 1 or 3 (∗P < .05, ∗∗P < .01, log-rank test, group 2 vs group 3; HR, 0.166; 95% CI, 0.04991-0.5515, group 2 vs 1 HR, 0.294; 95% CI, 0.08938-0.9671). (F) Pharmacokinetic analysis. Serial PB sampling was performed 17, 22, 28, 32, and 47 days after the first tafasitamab administration. The serum levels of tafasitamab were measured using an electrochemiluminescence (ECLA) assay.