Preclinical and clinical evidence suggests that tumor-associated macrophages (TAMs) are predominantly of the M2 phenotype that supports immuno-suppression, cellular invasion, angiogenesis, metastasis, and therapeutic resistance. The main objective of this project is to evaluate microRNA (miR)-125b delivery in a dual (CD44 and M2pep) targeted hyaluronic acid (HA)-based self-assembling nanoparticles to affect tumor associated macrophage (TAM) repolarization from a predominant M2 to M1 phenotype for improved therapeutic effect in in a KrasLSL-G12D/+, p53fl/fl genetically-engineered mouse (KPC-GEM) model of pancreatic ductal adenocarcinoma (PDAC). In our preliminary studies, we have shown that functionalized HA blocks form a modular self- assembling nano-platform for stable encapsulation of nucleic acid constructs, including small interfering RNA. These CD44-targeted core-shell nanoparticles have shown effective siRNA delivery and down- regulation of anti-apoptotic genes in vivo. Cieslewicz, et al. have shown that M2pep has preferential binding, rapid internalization, and accumulation in murine M2-polarized TAM's compared to other cells. In our preliminary investigation, we have observed that conjugation of M2pep sequence to the HA self- assembling nanoparticles shows preferential accumulation of these nanoparticles in vitro in M2 macrophages. The specific aims of the project are as follows: Aim-1 studies will focus on formulation and characterization of miR-125b duplex encapsulated in HA-PEI/HA-PEG/HA-m2pep nano-assemblies. Aim-2 studies will be directed towards in vitro evaluation of the nano-assemblies to re-polarize macrophages and their capacity to regulate pro-inflammatory cytokines. Aim-3 studies will address evaluation of the anti-tumor therapeutic response and inhibition of metastasis of miR-125b duplex encapsulated in HA-PEI/HA-PEG/HA- m2pep in combination with gemcitabine plus nab-Paclitaxel in a KPC-GEM model of PDAC. This study is highly significant in evaluating macrophage repolarization (from predominant M2 to M1) as a therapeutic strategy for the treatment of PDAC and using macrophage targeted HA-based nanoparticles to deliver microRNA for accomplishing repolarization. The innovative modular HA-based nano-platform is extremely versatile to afford efficient nucleic acid encapsulation, payload protection, and specific delivery to TAM in vivo for efficient repolarization.