Pre-clinical validation of combinatorial immunotherapy in somatic transgenic tumor models 3772

Abstract Description Study Objective: H3.3 K27M-mutant tumors confer a dismal prognosis and are resistant to treatment. Single-cell sequencing was employed to identify actionable combination immunotherapies in distinct immune compartments (TGFB and Lag3). Additionally, Vegfc AAVwas generated to examine how lymphatic drainage modulate these approaches. We then employed our novel modeling system, MADR, to empirically test response. Methods Custom H3.3 K27M plasmids with doxycycline (dox) inducible expression for dnTgfbr2 and solLag3-IgG were engineered. The plasmid was then electroporated into 21 neonatal mT/mG mice. Control mice were given standard food and experimental mice were given dox in their food to induce transgene expression in vivo. Results Tumors demonstrated clear induction of transgenic therapeutic mimicry elements upon dox administration and no observable leakiness was seen in controls. Kaplan-Meier survival studies demonstrated a clear survival effect in the dox-treated group--virtually doubling mean survival time (p-value: 0.03). Conclusion We have successfully modified H3.3 K27M glioma models to have inducible expression of dnTgfbr2 and solLag3-IgG to simulate local immunotherapy. Additional survival studies including AAV Vegfc are underway. Our hope is that these pre-clinical results will provide the foundation for clinical trials for these devestating maligancies. Funding Sources We acknowledge support from the Board of Governors RMI of Cedars-Sinai (to J.J.B.). J.J.B. was supported by DoD grant HT9425-23-1-0269, NIH grant R33CA236687, American Cancer Society grant RSG-16-217-01-TBG. Topic Categories Tumor Immunology: Checkpoints, Prevention, and Treatment (TIPT)