Bispecific CAR T cells prevent antigen loss in a CD19 escape xenograft model. (A) Representative flow plot of BM tumor cells from mice treated CD19 CAR T cells in the CD19 escape model. (B) Bioluminescent imaging of mice engrafted with 99% JeKo-1^wt + 1% JeKo-1^CD19KO cells and then treated with 0.6 × 10⁶ of the indicated CAR T cells or mock-transduced T cells (CD4:CD8 at 1:1 ratio). ∗∗∗P ≤ .001 with a q ≤ 0.01 on day 41 was calculated using multiple Mann-Whitney t test. (C) Survival of mice in each treatment group shown in panel B. (D) Quantification of CD79b or CD19 expression measured by flow cytometry on BM tumor cells from mice in each treatment group. For panel B, ∗∗∗P ≤ .001 was calculated with log-rank (Mantel-Cox) test. Data shown were pooled from 2 independent experiments with a total of 5 (mock) or 7 mice per group.