Novel Strategies to Treat Diffuse Midline Glioma with CAR T Cell Therapy

PROJECT SUMMARY Although chimeric antigen receptor (CAR) T cells have been remarkably successful in the hematologic setting, identification of truly tumor specific antigens for many solid tumor indications has limited broad translation. Two targets have been considered for Diffuse Midline Glioma H3 K27M-mutant tumors (previously Diffuse Intrinsic Pontine Glioma (DIPG)), however as neither are exclusively restricted to neoplastic tissue, safety concerns exist with respect to on-target, off-tumor toxicity. Moreover, ancillary treatment meant to boost CAR T function to overcome a constellation of immune suppressive mechanisms associated with the solid tumor microenvironment also has the potential to exacerbate the problem. Our group has conducted extensive preclinical characterization of oncolytic viruses and has demonstrated them to be a highly effective immunotherapeutic agents for the treatment of cancer. We propose to leverage the tumor tropism of ∆24 oncolytic adenovirus to deliver a CAR target along with CD40L. Our preliminary data indicates that oncolytic Ad∆24-CD40L provides a significant therapeutic advantage in a GL261 glioma model as a monotherapy, and further, can potentiate CD19 CAR T therapy in a proof of concept combination setting against subcutaneous B16-CD19 tumors. The goal of this proposal is to develop a dual therapy approach which builds on direct tumor cell viral oncolysis and CAR T cytolysis, enhanced CAR T cell recruitment/activation by virus-mediated inflammation, and importantly, CD40L-mediated mobilization of endogenous antigen presenting cells, B cells and T cells. We will engineer an oncolytic vector to deliver titratable levels of CD40L using the E. coli DHFR destabilizing domain, and an intracellularly truncated signaling-dead EGFRvIII molecule to be used in conjunction with safety tested EGFRvIII CAR T cells (Aim1). The safety and efficacy of the OV-CAR T approach will be evaluated in a genetically engineered immunocompetent model of DIPG (Aim 2). This project is expected to provide novel insight into how CD40L can mobilize an endogenous B cell and T cell response and support CAR T therapy. Together, we hope to capitalize on the properties of designer oncolytic viruses to more broadly enable the use of CAR T cell therapy in solid tumors, and in particular apply existing safety tested immunotherapies to a devastating and urgent unmet clinical need.