ABSTRACT Although the past decade was marked by the tremendous success of immunotherapeutics in oncology, few have provided significant benefit to patients with pancreatic cancer. The long-term goal of this project is to develop therapeutically useful immunotherapies for the clinical treatment of pancreatic cancer. The overall objectives in this application are to (i) characterize the role for MARCO in the TME, (ii) to evaluate the therapeutic efficacy of antibodies blocking this receptor, and (iii) improve antigen presentation within the pancreatic TME with a combination of Fc-enhanced antibodies targeting MARCO and CD40. Our central hypothesis is that pancreatic cancer repolarizes tumor associated macrophages to an M2 phenotype an this can be reversed through engagement of MARCO with antibodies, therefore promoting anti-tumor responses. The rationale for this project is that a determination of the immunosuppressive role of TAMs expressing MARCO in pancreatic cancer will likely offer a strong scientific framework whereby new immunotherapies can be developed. The central hypothesis will be tested by pursuing three specific aims: 1) Develop anti-human TAM antibodies for cancer immunotherapy and set up novel assays for large-scale evaluation of anti-TAM antibodies, 2) Define the role for MARCO in the polarization of TAMs in pancreatic cancer, and 3) Augment TAM repolarization in the pancreatic cancer TME using the Fc-enhanced CD40 agonist antibody 2141-V11, alone or in combination with anti- hMARCO antibodies.. Under the first aim, novel antibodies will be generated against human MARCO and optimized for Fc-receptor binding. In the second Aim, mice genetically engineered to express human MARCO will be studied for their role in the TME of pancreatic cancer. Following characterization immune cells expressing MARCO that can be targeted by antibody therapy, a panel of antibody variants will be tested to determine the Fc-requirements for optimal in vivo activity. MARCO expression and characterization of the immune microenvironment will also be evaluated in human pancreatic cancer specimens. Finally, in the third aim, we will use knowledge gained in Aims 1 and 2 to test novel combinations targeting the myeloid axis in pancreatic tumors. Here, the anti-tumor activity of the Fc-enhanced anti-CD40 antibody will be tested alone or in combination with anti-MARCO antibodies in pancreatic cancer models. The research proposed in this application is innovative, in the investigator’s opinion, because it focuses on defining novel pathways on myeloid cells contributing to the immune suppressive TME of pancreatic cancer, while identifying lead therapeutic candidates through Fc- engineering. The proposed research is significant because it is expected to provide strong scientific justification for the development of macrophage targeting immunotherapies. Ultimately, such knowledge has the potential of offering new opportunities for the translation of innovative therapies...