Ionizable polymeric nanocarriers for the codelivery of bi-adjuvant and neoantigens in combination tumor immunotherapy.

Ionizable lipid nanocarriers have made historical contribution to COVID-19 mRNA vaccines. Here, we report ionizable polymeric nanoparticles that co-deliver bi-adjuvant and neoantigen peptides for cancer immunotherapy in combination with immune checkpoint blockade (ICB). Current cancer ICB benefits only a small subset of patients, largely due to a lack of pre-existing target cells and checkpoint targets for ICB, tumor antigenic heterogeneity, and tumor immunosuppression. Therapeutic vaccines hold the potential to enhance ICB therapeutic efficacy by expanding antitumor cell repertoires, upregulating immune checkpoint levels and hence sensitizing ICB, and reducing tumor immunosuppression. Chemically defined peptide vaccines are attractive, but their current therapeutic efficacy has been limited due to 1) poor vaccine delivery to immunomodulatory lymph nodes (LNs) and antigen (Ag)-presenting cells (APCs), 2) poor immunostimulant adjuvant efficacy with restricted target cell subsets in humans, 3) limited adjuvant/Ag codelivery to enhance Ag immunogenicity, and 4) limited ability to overcome tumor antigenic heterogeneity. Here, we developed nanovaccines (NVs) using pH-responsive polymeric micellular nanoparticles (NPs) for the codelivery of bi-adjuvant [Toll-like receptor (TLR) 7/8 agonist R848 and TLR9 agonist CpG] and peptide neoantigens (neoAgs) to draining LNs for efficient Ag presentation in a broad range of APC subsets. These NVs potentiated the immunogenicity of peptide Ags and elicits robust antitumor T cell responses with memory, and remodeled the tumor immune milium with reduced tumor immunosuppression. As a result, NVs significantly enhanced ICB therapeutic efficacy for murine colorectal tumors and orthotopic glioblastoma multiforme (GBM). These results suggest marked potential of bi-adjuvant/neoAg-codelivering NVs for combination cancer immunotherapy.

Circular RNA: An emerging frontier in RNA therapeutic targets, RNA therapeutics, and mRNA vaccines.

Circular RNAs (circRNA) is a class of natural (biogenic) or synthetic closed RNA without 5' or 3' ends. Meanwhile, their unique covalently-closed structures of circRNA prevent RNA degradation by exonucleases, thereby empowering them with high pharmaceutical stability and biostability relative to current standard-of-care linear mRNA. Natural circRNA can be non-coding RNAs as well as protein-coding RNA, the latter of which was recently discovered. The physiological functions of biogenic circRNAs, which largely remain elusive, include protein and gene sponges, cell activity modulators, and protein translation. The discovery that the circRNA levels can be correlated with some human diseases empowers circRNA with the potential as a novel type of disease biomarkers and a noncanonical class of therapeutic targets. Recently, synthetic circRNA have been engineered to explore their applications as a novel class of mRNA therapeutics and vaccines. In this review, we will discuss the current understanding of the biogenesis and physiological functions of natural circRNAs, the approaches to circRNA synthesis, and current research in the exploration of endogenous circRNAs as novel therapeutic targets and testing circRNAs as an emerging class of RNA therapeutics and vaccines.

Single-stranded circular DNA theranostics.

The past decade has witnessed the blossom of nucleic acid therapeutics and diagnostics (theranostics). Unlike conventional small molecule medicines or protein biologics, nucleic acid theranostics have characteristic features such as the intrinsic ability as "information drugs" to code and execute genetic and theranostic information, ready programmability for nucleic acid engineering, intrinsic stimulatory or regulatory immunomodulation, versatile functionalities, and easy conformational recovery upon thermal or chemical denaturation. Single-stranded circular DNA (circDNA) are a class of single-stranded DNAs (ssDNA) featured with their covalently-closed topology. In addition to the basic advantages of nucleic acids-based materials, such as low cost, biocompatibility, and simplicity of chemical modification, the lack of terminals in circDNA prevents exonuclease degradation, resulting in enhanced biostability relative to the corresponding linear ssDNA. circDNA has been explored for versatile theranostic applications. For instance, circDNA has been extensively studied as templates for bioanalytical signal amplification and the synthesis of nano-/micro-/macro- biomaterials via rolling circle amplification (RCA) and rolling circle transcription (RCT) technologies. circDNA has also been commonly used as the scaffolds for the self-assembly of versatile DNA origami. Finally, circDNA has been implemented as theranostic aptamers, miRNA inhibitors, as well as clustered regularly interspaced short palindromic repeats-CRISPR-associated proteins (CRISPR-Cas) gene editing donors. In this review article, we will discuss the chemistry, characteristic properties, and the theranostic applications of circDNA (excluding double-stranded circular DNA such as plasmids); we will also envision the challenges and opportunities in this research field.