FIGURE 6.

Depletion of 7 × 19 CAR‐T cells equipped with Herpes simplex virus‐thymidine kinase (HSV‐TK) by GCV treatment. (A) Anti‐GM2 7 × 19 CAR‐T cells equipped with or without HSV‐TK suicide gene were cultured for 3 days in the presence of GCV at a concentration of 0, 0.1, 1, and 10 μM. The number of residual CAR‐T cells was analyzed by flow cytometry. Data are shown as mean ± standard error (SE) of triplicate samples. (B, C) NOG‐ΔMHC mice were inoculated subcutaneously with 1 × 10⁷ Lu‐135 tumor cells on day 0, followed by intravenously injection of 1 × 10⁷ 7 × 19 CAR‐T cells expressing HSV‐TK on day 3, and then treated with i.p. administration of GCV (100 mg/kg) on days 7 and 21. (B) The proportion of CAR‐T cells in PBMC was assessed by flow cytometry. Data are shown as mean ± SE (n = 8 in the GCV‐treated mice group, n = 7 in nontreated mice group). **p < 0.01, ***p < 0.001. (C) Tumor size of Lu‐135 in the mice treated with 7 × 19 CAR‐T cells with or without GCV administration was measured twice a week by a digital caliper. Each line indicates the tumor volume of an individual mouse.