IMMU-02. “Potent antitumor efficacy of anti-B7-H3 CAR T-cells in H3G34R/V mutated Diffuse Hemispheric Glioma”

Background The diffuse hemispheric glioma (DHG) with H3G34R/V mutation is a highly aggressive and fatal brain tumor affecting adolescents and young adults. Its prognosis is dismal, with no effective therapeutic options. Chimeric antigen receptor (CAR)-expressing T-cell immunotherapy has proven highly effective in treating childhood lymphoblastic leukemia and some CNS malignancies. However, it remains unexplored in DHGs. This study evaluates the anti-tumor efficacy of anti-B7-H3 CAR T cell therapy in DHG. Method We investigated B7-H3 expression across multiple DHG tumor specimens and cell lines. Developed two anti-B7-H3 CAR T-cell constructs, and their functionality was evaluated through antigen-dependent cytokine production, CAR T cell activation, exhaustion, DHG cell killing in vitro, and therapeutic efficacy in vivo using two different DHG mouse models. Results Our findings revealed robust B7-H3 expression in DHG’s tumor tissues and patient-derived cell lines, underscoring its strong potential as a therapeutic target. Co-culture of anti-B7-H3 CAR-T cells with H3G34R/V-mutated KNS42 and SJ-HGGX42 DHG cells significantly enhanced T cell activation, cytokine production, and cytotoxic markers. The anti-B7-H3 CAR-T cells demonstrated potent cytotoxic activity against B7-H3-positive KNS42 and SJ-HGGX42 cells while exhibiting no activity against B7-H3 knockout KNS42 (B7-H3-KO) cells. Furthermore, in orthotopic xenograft mouse models with KNS42 and SJ-HGGX42 cells, anti-B7-H3 CAR-T cells showed antigen-specific tumor eradication and markedly prolonged survival compared to the CD19 CAR-T cell-treated control group. Conclusion B7-H3 CAR T cells demonstrate potent and specific anti-tumor activity against H3G34R/V-mutant DHG, significantly improving survival in preclinical models, highlighting their promise as a novel therapeutic approach for this aggressive and fatal brain tumor.