Poly(ß-aminoester) Physicochemical Properties Govern the Delivery of siRNA from Electrostatically Assembled Coatings.

Localized short interfering RNA (siRNA) therapy has the potential to drive high-specificity molecular-level treatment of a variety of disease states. Unfortunately, effective siRNA therapy suffers from several barriers to its intracellular delivery. Thus, drug delivery systems that package and control the release of therapeutic siRNAs are necessary to overcome these obstacles to clinical translation. Layer-by-layer (LbL) electrostatic assembly of thin film coatings containing siRNA and protonatable, hydrolyzable poly(ß-aminoester) (PBAE) polymers is one such drug delivery strategy. However, the impact of PBAE physicochemical properties on the transfection efficacy of siRNA released from LbL thin film coatings has not been systematically characterized. In this study, we investigate the siRNA transfection efficacy of four structurally similar PBAEs in vitro. We demonstrate that small changes in structure yield large changes in physicochemical properties, such as hydrophobicity, pKa, and amine chemical structure, driving differences in the interactions between PBAEs and siRNA in polyplexes and in LbL thin film coatings for wound dressings. In our polymer set, Poly3 forms the most stable interactions with siRNA (Keff,w/w = 0.298) to slow release kinetics and enhance transfection of reporter cells in both colloidal and thin film coating approaches. This is due to its unique physiochemical properties: high hydrophobicity (clog P = 7.86), effective pKa closest to endosomal pH (pKa = 6.21), and high cooperativity in buffering (nhill = 7.2). These properties bestow Poly3 with enhanced endosomal buffering and escape properties. Taken together, this work elucidates the connections between small changes in polymer structure, emergent properties, and polyelectrolyte theory to better understand PBAE transfection efficacy.

STING Protein-Based In Situ Vaccine Synergizes CD4+ T, CD8+ T, and NK Cells for Tumor Eradication.

Stimulator of interferon genes (STING) signaling is a promising target in cancer immunotherapy, with many ongoing clinical studies in combination with immune checkpoint blockade (ICB). Existing STING-based therapies largely focus on activating CD8+ T cell or NK cell-mediated cytotoxicity, while the role of CD4+ T cells in STING signaling has yet to be extensively studied in vivo. Here, a distinct CD4-mediated, protein-based combination therapy of STING and ICB as an in situ vaccine, is reported. The treatment eliminates subcutaneous MC38 and YUMM1.7 tumors in 70-100% of mice and protected all cured mice against rechallenge. Mechanistic studies reveal a robust TH 1 polarization and suppression of Treg of CD4+ T cells, followed by an effective collaboration of CD4+ T, CD8+ T, and NK cells to eliminate tumors. Finally, the potential to overcome host STING deficiency by significantly decreasing MC38 tumor burden in STING KO mice is demonstrated, addressing the translational challenge for the 19% of human population with loss-of-function STING variants.