Abstract B47: Engineering immunomodulatory nanoparticles for 'cold'-to-'hot' tumor microenvironment remodeling for treatment of high-risk neuroblastoma

This study seeks to develop a systemic immunomodulatory nanoparticle (immuno-NP) therapy that harnesses proinflammatory innate immune cells to remodel tumor microenvironment (TME) immunity in humanized mouse models of high-risk neuroblastoma (NB). Currently, survival for high-risk metastatic NB remains ~50% at 5 years, even with chemotherapy given at maximal tolerated dosing, which itself imparts debilitating long-term sequelae in >90% of survivors. The success of immunotherapies for leukemias and lymphomas has not translated to pediatric solid tumors, which typically present as immunosuppressed “cold” tumors with microenvironments that limit antigen presentation and sustained activation of cytotoxic CD8+ T cells. To date, immune checkpoint inhibitor and chimeric antigen receptor (CAR) T approaches have primarily focused on augmenting CD8+ T cells that are suppressed by the “cold” TME of high-risk solid tumors. However, it has now been demonstrated that proinflammatory cytokines secreted by innate antigen-presenting cells (APCs), such as dendritic cells (DCs) and macrophages, can restimulate anti-tumor T cell responses by remodeling the TME from “cold” to “hot”. Here, we use a novel engineering approach to design and systemically deliver lipid-based immuno-NPs coencapsulating synergistic innate immune agonists of the stimulator of interferon genes (STNG) and Toll-like receptor 4 (TLR4) pathways to target APCs that are enriched in the TME perivascular region. APCs taking up NPs synergistically produce Type I interferons, priming and recruiting CD8+ T cells for clearance. We hypothesized that treatment of humanized mice bearing human NB xenografts with immuno-NPs will drive APC-mediated “cold”-to-“hot” TME remodeling, leading to sustained recruitment and activation of CD8+ T cells. Humanized NOD scid gamma (NSG) mice bearing orthotopic CMYC-expressing metastatic SH-SY5Y cell xenografts were treated with immuno-NPs and tumor burden assessed via bioluminescent imaging just 3 days afterwards indicated a significant 47% reduction in primary tumor mass and 53% reduction in liver metastasis. Confocal imaging of both the primary tumor and metastatic sites indicated clear immuno-NP deposition surrounding the CD31+ vascular tumor endothelium. Flow cytometry analysis of primary tumors indicated a significant 7.8-fold increase in infiltrating CD8+ T cells in mice that received immuno-NPs compared to control mice that received empty NPs. Subsequent survival experiments demonstrated that immuno-NPs significantly increased survival by driving proinflammatory cytokine production in the TME and also combined effectively with PD1 blockade for enhanced CD8+ T cell activation and function. In conclusion, these findings demonstrated the feasibility of our engineering strategy as a safer, more effective therapy for high-risk NB by confirming that immuno-NPs deposit avidly in NB primary tumors and even sites of metastasis upon systemic delivery, bolster TME APC function and CD8+ T cell-mediated clearance, and drive protective long-term anti-tumor immunity. Citation Format: Prabhani Atukorale, Jason Shohet, Christina Lusi, Kim Wigglesworth, Griffin Kane, Esteban Rozen. Engineering immunomodulatory nanoparticles for "cold"-to-"hot" tumor microenvironment remodeling for treatment of high-risk neuroblastoma [abstract]. In: Proceedings of the AACR Special Conference: Tumor Immunology and Immunotherapy; 2022 Oct 21-24; Boston, MA. Philadelphia (PA): AACR; Cancer Immunol Res 2022;10(12 Suppl):Abstract nr B47.