Generation of tumor specific immunity in canine osteosarcoma through dendritic cell hyperactivation

PROJECT SUMMARY Despite substantial improvements in therapeutic strategies, generating robust anti-tumor immune responses in human cancers with a lower somatic mutation burden remains a substantial challenge. Recent data indicate that a critical player in this process, dendritic cells (DCs), fail to effectively elicit efficient and durable T cell responses unless they have entered a unique state of hyperactivation. In this setting, DCs exhibit enhanced migration to local lymph nodes (LNs) and sustained secretion of IL-1β, a cytokine critical for memory T cell formation. In mouse tumor models, vaccination with whole tumor lysate plus an adjuvant consisting of the TLR 7/8 agonist R848 (resiquimod) in combination with a unique isolated lysophosphatidylcholine (22:0 Lyso PC) promotes DC hyperactivation, expansion of antigen specific CD8+ T cells, and robust rejection of tumors. While these findings are encouraging and suggest that identification of specific neoantigens is not necessary to prime and expand a pool of cytotoxic T cells (CTLs), validation and optimization of this approach necessitates the use of a model system that more closely recapitulates human cancers with respect to immune landscape. As such, the purpose of this proposal is to use spontaneous canine cancer, specifically osteosarcoma (OS), as a bridging animal model to validate the utility of DC hyperactivation as a foundational element for generation of robust anti-tumor immunity. The central hypothesis to be tested in this application is that combining hyperactivation of DCs with WTL derived neoantigen will expand a diverse and tumor-specific population of CTLs capable of eliminating residual microscopic metastatic OS tumor cells in dogs following primary tumor removal (amputation). We further predict, that combining DC hyperactivation/WTL with a novel tumor microenvironment (TME) conditioning regimen consisting of toceranib/losartan/ladarixin will enhance the objective response rate in dogs that develop macroscopic lung metastasis. To accomplish this, we will conduct a prospective randomized clinical trial in dogs with OS combining amputation and standard of care carboplatin chemotherapy with adjuvant alone or adjuvant+WTL. Dogs that develop lung metastasis will then be treated with the TME conditioning regimen in combination with adjuvant+WTL. A biobank of tissue samples and blood will be collected from dogs enrolled in these trials including matched primary/metastatic tumors and associated LNs, whole blood, plasma, PBMCs, cell-free DNA, and samples from the vaccine draining LNs. These will be used to perform a set of complementary assays designed to characterize the immune microenvironment and tumor genome over the course of relapse/resistance, credential a novel neoantigen prediction pipeline, and evaluate antigen specific T cell responses. An outstanding team with complementary sets of expertise across clinical trials, translational oncology, comparative genomics, and immuno-oncology has been assembled to ensure stated milestones are achieved. This is bolstered by a dynamic collaboration with our industry partner, Corner Therapeutics, which is committed to supporting this work to facilitate optimization and successful translation into human patients.