B7-H3 CAR-T

This study demonstrates a novel high-content and high-throughput screen can identify drugs to enhance CAR T cell activity. This and other high-content technologies will pave the way to develop clinical trials implementing rational drug plus CAR T cell combinatorial therapies. Importantly, the technique could also be repurposed for an array of basic and translational research applications where drugs are needed to modulate cell surface protein expression.

Protein structure prediction suggests that linker length and compactness influence the functionality of the generated bispecific CARs. Thus, we present a bispecific CAR design strategy to prevent immune escape in AML that can be extended to other peptide-scFv combinations.

Using an immunocompetent glioma model, we evaluated a panel of seven fully murine B7-H3 CARs with variations in transmembrane, costimulatory, and activation domains...Indeed, complete brain macrophage depletion using a CSF1R inhibitor abrogated CAR T-cell anti-tumor activity. In sum, our study highlights the critical role of CAR design and its modulation of the TIME in mediating the efficacy of adoptive immunotherapy for high-grade glioma.

We have developed a simple thaw/wash procedure to prepare B7-H3-CAR T cells for their locoregional delivery to the neural axis. While we focus here on CAR T cells, the methods could be readily adapted to other cryopreserved immune effector cell products.

P1, N=32, Recruiting, St. Jude Children's Research Hospital | Trial completion date: Feb 2026 --> Mar 2027 | Trial primary completion date: Mar 2025 --> Mar 2026

P1, N=36, Recruiting, St. Jude Children's Research Hospital | Not yet recruiting --> Recruiting

P1, N=36, Not yet recruiting, St. Jude Children's Research Hospital

Patient-based determination of chemokines secreted by pediatric OS identifies robust targets for chemokine receptor modification of CAR T cells. CXCR2 and CXCR6 both enhance homing of B7-H3.CAR T cells, with improved antitumor activity and evidence of reduced non-specific expansion in vivo. Optimization of these receptors with additional CARs active in OS is warranted.

Objectives: To characterize endogenous and transgenic CXCR expression and efficacy of CXCR.B7H3.CAR-T cells +/- dasatinib. Endogenous and transgenic CXCR expression are unchanged by dasatinib resting. CXCR- modified CAR-T cells +dasatinib exhibit increased naïve-like phenotype, enhanced proliferation after OS spheroid engagement, and potentially improved antitumor activity in vivo. These findings support combining dasatinib resting with CXCR-mediated homing strategies.

Further work will utilize our novel AML models to study how both cellular interactions and secreted factors produced within the TME impact CAR T cell functionality. These findings will inform strategies to improve CAR T cell design and bypass potential challenges faced when generating effective CAR T cells for pediatric AML.

In summary, we have established an immune-competent OS model to evaluate the effector function of B7-H3-CAR T cells and have demonstrated the advantage given by 2nd genetic modifications to enhance their antitumor activity. We are currently using this model to define mechanisms of immune resistance with the goal of further enhancing OS-redirected CAR T-cell therapy.

These findings provide a strong rationale for clinically evaluating B7-H3-CAR T for pediatric patients with chemotherapy-resistant ACC. Additionally, the newly established pediatric ACC PDX models provide a valuable resource for investigating different aspects of this rare and aggressive disease.

P1, N=32, Recruiting, St. Jude Children's Research Hospital | Trial completion date: Mar 2027 --> Feb 2026 | Trial primary completion date: Mar 2026 --> Mar 2025

P1, N=32, Recruiting, St. Jude Children's Research Hospital | Not yet recruiting --> Recruiting