Dasatinib suppresses CAR-T cell expansion, cytokine secretion, and tumor control in vivo. (A) 1 × 10⁶ CD19⁺ Nalm6-GL, which stably express GFP and luciferase, were engrafted into 6- to 8-week-old NSG mice via IV injection (n = 5 mice/group). At 4 days postengraftment, 1 × 10⁶ mock (untransduced) or CD19.BBζ CAR-T cells were infused via IV injection. Mice were subsequently dosed with 50 mg/kg dasatinib or vehicle on the day of infusion and everyday thereafter either twice daily (shown) or daily (replicate experiment). (B) Tumor growth was monitored via bioluminescence imaging as quantified in (C) (representative plot of n = 2 independent experiments). (D) At day 8 after CAR-T infusion (day 12 postengraftment), where indicated, mice that had received vehicle were switched to 50 mg/kg dasatinib twice daily for 7 days (representative plot, n = 2 independent experiments). (E) Blood samples were collected retroorbitally on day 8 after CAR-T infusion (day 12 postengraftment), and circulating CAR-T cells were quantified via flow cytometry (n = 5 mice from n = 1 experiment). (F-G) Blood samples were collected retroorbitally on day 3 after CAR-T infusion (day 7 postengraftment), and plasma was isolated after a brief centrifugation. Circulating concentrations of cytokines, chemokines, and growth factors were measured via Luminex (mock n = 3 mice, vehicle and dasatinib n = 5 mice from n = 1 experiment). (G) Heat map values were generated by normalizing to the sum of the mean concentrations of the 3 experimental groups. Representative plots display mean ± standard error of the mean of replicate mice within 1 experiment (n = 2 independent experiments). **P < .01; ***P < .001; ****P < .0001; ns, P > .05.