Tandem CAR T cells targeting HER2 and IL13Rα2 mitigate tumor antigen escape (Publication with Expression of Concern. See vol. 129, pg. 3464, 2019)

In preclinical models of glioblastoma, antigen escape variants can lead to tumor recurrence after treatment with CAR T cells that are redirected to single tumor antigens. Given the heterogeneous expression of antigens on glioblastomas, we hypothesized that a bispecific CAR molecule would mitigate antigen escape and improve the antitumor activity of T cells. Here, we created a CAR that joins a HER2-binding scFv and an IL13R alpha 2-binding IL-13 mutein to make a tandem CAR exodomain (TanCAR) and a CD28 zeta. endodomain. We determined that patient TanCAR T cells showed distinct binding to HER2 or IL13R alpha 2 and had the capability to lyse autologous glioblastoma. TanCAR T cells exhibited activation dynamics that were comparable to those of single CAR T cells upon encounter of HER2 or IL13R alpha 2. We observed that TanCARs engaged HER2 and IL13R alpha 2 simultaneously by inducing HER2-IL13R alpha 2 heterodimers, which promoted superadditive T cell activation when both antigens were encountered concurrently. TanCAR T cell activity was more sustained but not more exhaustible than that of T cells that coexpressed a HER2 CAR and an IL13R alpha 2 CAR, T cells with a unispecific CAR, or a pooled product. In a murine glioblastoma model, TanCAR T cells mitigated antigen escape, displayed enhanced antitumor efficacy, and improved animal survival. Thus, TanCAR T cells show therapeutic potential to improve glioblastoma control by coengaging HER2 and IL13R alpha 2 in an augmented, bivalent immune synapse that enhances T cell functionality and reduces antigen escape.