Nucleic acid and oligonucleotide delivery for activating innate immunity in cancer immunotherapy

Delivery of STING agonists for cancer immunotherapy

Agonists of the cyclic guanosine monophosphate-adenosine monophosphate synthase (cGAS)-Stimulator of Interferon Genes (STING) pathway, a critical mediator of innate immune response to foreign invaders with DNA, have gained significant interest in cancer immunotherapy. STING agonists are envisioned as a way of complementing the antitumor activity of the patient's immune system and immune checkpoint blockade therapy. However, their clinical development has been challenging due to the poor pharmacokinetic and physicochemical properties. This review discusses drug delivery efforts to circumvent the challenges, their accomplishment, and unmet needs based on the last five years of literature.

Emerging nanoparticle platforms for CpG oligonucleotide delivery

Unmethylated cytosine-phosphate-guanine (CpG) oligodeoxynucleotides (ODNs), which were therapeutic DNA with high immunostimulatory activity, have been applied in widespread applications from basic research to clinics as therapeutic agents for cancer immunotherapy, viral infection, allergic diseases and asthma since their discovery in 1995. The major factors to consider for clinical translation using CpG motifs are the protection of CpG ODNs from DNase degradation and the delivery of CpG ODNs to the Toll-like receptor-9 expressed human B-cells and plasmacytoid dendritic cells. Therefore, great efforts have been devoted to the advances of efficient delivery systems for CpG ODNs. In this review, we outline new horizons and recent developments in this field, providing a comprehensive summary of the nanoparticle-based CpG delivery systems developed to improve the efficacy of CpG-mediated immune responses, including DNA nanostructures, inorganic nanoparticles, polymer nanoparticles, metal-organic-frameworks, lipid-based nanosystems, proteins and peptides, as well as exosomes and cell membrane nanoparticles. Moreover, future challenges in the establishment of CpG delivery systems for immunotherapeutic applications are discussed. We expect that the continuously growing interest in the development of CpG-based immunotherapy will certainly fuel the excitement and stimulation in medicine research.

Enabling safer, more potent oligonucleotide therapeutics with bottlebrush polymer conjugates

Oligonucleotide therapeutics have the unique ability to address traditionally undruggable targets through various target engagement pathways. However, despite advances in chemically modified oligonucleotides and carrier-assisted delivery systems such as lipid nanoparticles and protein/peptide conjugates, the development of oligonucleotide drugs is still plagued with lackluster potency, narrow therapeutic window, poor delivery to non-liver target sites, and/or high potential for toxicity and unwanted immune system activation. In this perspective, we discuss an unconventional delivery solution based upon bottlebrush polymers, which overcomes many key challenges in oligonucleotide drug development. We address the molecular basis of the polymer's ability to enhance tissue bioavailability and drug potency, reduce side effects, and suppress anti-carrier immunity. Furthermore, we discuss the potential of the technology in advancing oligonucleotide-based therapies for non-liver targets.

Morphology Dictated Immune Activation with Framework Nucleic Acids

Framework nucleic acids (FNAs) of various morphologies, designed using the precise and programmable Watson-Crick base pairing, serve as carriers for biomolecule delivery in biology and biomedicine. However, the impact of their shape, size, concentration, and the spatial presentation of cytosine-phosphate-guanine oligodeoxynucleotides (CpG ODNs) on immune activation remains incompletely understood. In this study, representative FNAs with varying morphologies are synthesized to explore their immunological responses. Low concentrations (50 nM) of all FNAs elicited no immunostimulation, while high concentrations of elongated DNA nanostrings and tetrahedrons triggered strong activation due to their larger size and increased cellular uptake, indicating that the innate immune responses of FNAs depend on both dose and morphology. Notably, CpG ODNs' immune response can be programmed by FNAs through regulating the spatial distance, with optimal spacing of 7-8 nm eliciting the highest immunostimulation. These findings demonstrate FNAs' potential as a designable tool to study nucleic acid morphology's impact on biological responses and provide a strategy for future CpG-mediated immune activation carrier design.

Spherical nucleic acids-based nanoplatforms for tumor precision medicine and immunotherapy

Precise diagnosis and treatment of tumors currently still face considerable challenges due to the development of highly degreed heterogeneity in the dynamic evolution of tumors. With the rapid development of genomics, personalized diagnosis and treatment using specific genes may be a robust strategy to break through the bottleneck of traditional tumor treatment. Nevertheless, efficient in vivo gene delivery has been frequently hampered by the inherent defects of vectors and various biological barriers. Encouragingly, spherical nucleic acids (SNAs) with good modularity and programmability are excellent candidates capable of addressing traditional gene transfer-associated issues, which enables SNAs a precision nanoplatform with great potential for diverse biomedical applications. In this regard, there have been detailed reviews of SNA in drug delivery, gene regulation, and dermatology treatment. Still, to the best of our knowledge, there is no published systematic review summarizing the use of SNAs in oncology precision medicine and immunotherapy, which are considered new guidelines for oncology treatment. To this end, we summarized the notable advances in SNAs-based precision therapy and immunotherapy for tumors following a classification standard of different types of precise spatiotemporal control on active species by SNAs. Specifically, we focus on the structural diversity and programmability of SNAs. Finally, the challenges and possible solutions were discussed in the concluding remarks. This review will promote the rational design and development of SNAs for tumor-precise medicine and immunotherapy.

Engineered exosomes as drug and RNA co-delivery system: new hope for enhanced therapeutics?

Chemotherapy often faces some obstacles such as low targeting effects and drug resistance, which introduce the low therapeutic efficiency and strong side effects. Recent advances in nanotechnology allows the use of novel nanosystems for targeted drug delivery, although the chemically synthesized nanomaterials always show unexpected low biocompability. The emergence of exosome research has offered a better understanding of disease treatment and created novel opportunities for developing effective drug delivery systems with high biocompability. Moreover, RNA interference has emerged as a promising strategy for disease treatments by selectively knocking down or over-expressing specific genes, which allows new possibilities to directly control cell signaling events or drug resistance. Recently, more and more interests have been paid to develop optimal delivery nanosystems with high efficiency and high biocompability for drug and functional RNA co-delivery to achieve enhanced chemotherapy. In light of the challenges for developing drug and RNA co-delivery system, exosomes have been found to show very attractive prospects. This review aims to explore current technologies and challenges in the use of exosomes as drug and RNA co-delivery system with a focus on the emerging trends and issues associated with their further applications, which may contribute to the accelerated developments of exosome-based theraputics.

Influence of the Composition of Cationic Liposomes on the Performance of Cargo Immunostimulatory RNA

In this study, the impact of different delivery systems on the cytokine-inducing, antiproliferative, and antitumor activities of short immunostimulatory double-stranded RNA (isRNA) was investigated. The delivery systems, consisting of the polycationic amphiphile 1,26-bis(cholest-5-en-3-yloxycarbonylamino)-7,11,16,20 tetraazahexacosan tetrahydrochloride (2X3), and the lipid-helper dioleoylphosphatidylethanolamine (DOPE), were equipped with polyethylene glycol lipoconjugates differing in molecular weight and structure. The main findings of this work are as follows: (i) significant activation of MCP-1 and INF-α, β, and γ production in CBA mice occurs under the action of isRNA complexes with liposomes containing lipoconjugates with long PEG chains, while activation of MCP-1 and INF-γ, but not INF-α or β, was observed under the action of isRNA lipoplexes containing lipoconjugates with short PEG chains; (ii) a pronounced antiproliferative effect on B16 melanoma cells in vitro, as well as an antitumor and hepatoprotective effect in vivo, was induced by isRNA pre-complexes with non-pegylated liposomes, while complexes containing lipoconjugates with long-chain liposomes were inactive; (iii) the antitumor activity of isRNA correlated with the efficiency of its accumulation in the cells and did not explicitly depend on the activation of cytokine and interferon production. Thus, the structure of the delivery system plays a vital role in determining the response to isRNA and allows for the choice of a delivery system depending on the desired effect.

Nanotechnology for next-generation cancer immunotherapy: State of the art and future perspectives

Over the past decade, immunotherapy aiming to activate an effective antitumor immune response has ushered in a new era of cancer treatment. However, the efficacy of cancer immunotherapy is limited by low response rates and high systemic toxicity. Nanotechnology is an encouraging platform for the development of next-generation cancer immunotherapy to effectively treat advanced cancer. Nanotechnology-enabled immunotherapy has remarkable advantages, ranging from the increased bioavailability and stability of immunotherapeutic agents to the enhanced activation of immune cells and favorable safety profiles. Nanotechnology-enabled immunotherapy can target solid tumors through reprogramming or stimulating immune cells (i.e., nanovaccines); modulating the immunosuppressive tumor microenvironment; or targeting tumor cells and altering their responses to immune cells to generate effective antitumor immunity. In this Oration, I introduce the advanced strategies currently being pursued by our laboratory and other groups to improve the therapeutic efficacy of cancer immunotherapy and discuss the potential challenges and future directions.

siRNA Functionalized Lipid Nanoparticles (LNPs) in Management of Diseases

RNAi (RNA interference)-based technology is emerging as a versatile tool which has been widely utilized in the treatment of various diseases. siRNA can alter gene expression by binding to the target mRNA and thereby inhibiting its translation. This remarkable potential of siRNA makes it a useful candidate, and it has been successively used in the treatment of diseases, including cancer. However, certain properties of siRNA such as its large size and susceptibility to degradation by RNases are major drawbacks of using this technology at the broader scale. To overcome these challenges, there is a requirement for versatile tools for safe and efficient delivery of siRNA to its target site. Lipid nanoparticles (LNPs) have been extensively explored to this end, and this paper reviews different types of LNPs, namely liposomes, solid lipid NPs, nanostructured lipid carriers, and nanoemulsions, to highlight this delivery mode. The materials and methods of preparation of the LNPs have been described here, and pertinent physicochemical properties such as particle size, surface charge, surface modifications, and PEGylation in enhancing the delivery performance (stability and specificity) have been summarized. We have discussed in detail various challenges facing LNPs and various strategies to overcome biological barriers to undertake the safe delivery of siRNA to a target site. We additionally highlighted representative therapeutic applications of LNP formulations with siRNA that may offer unique therapeutic benefits in such wide areas as acute myeloid leukaemia, breast cancer, liver disease, hepatitis B and COVID-19 as recent examples.

Specificity of oligonucleotide gene therapy (OGT) agents

Oligonucleotide gene therapy (OGT) agents (e. g. antisense, deoxyribozymes, siRNA and CRISPR/Cas) are promising therapeutic tools. Despite extensive efforts, only few OGT drugs have been approved for clinical use. Besides the problem of efficient delivery to targeted cells, hybridization specificity is a potential limitation of OGT agents. To ensure tight binding, a typical OGT agent hybridizes to the stretch of 15-25 nucleotides of a unique targeted sequence. However, hybrids of such lengths tolerate one or more mismatches under physiological conditions, the problem known as the affinity/specificity dilemma. Here, we assess the scale of this problem by analyzing OGT hybridization-dependent off-target effects (HD OTE) in vitro, in animal models and clinical studies. All OGT agents except deoxyribozymes exhibit HD OTE in vitro, with most thorough evidence of poor specificity reported for siRNA and CRISPR/Cas9. Notably, siRNA suppress non-targeted genes due to (1) the partial complementarity to mRNA 3'-untranslated regions (3'-UTR), and (2) the antisense activity of the sense strand. CRISPR/Cas9 system can cause hundreds of non-intended dsDNA breaks due to low specificity of the guide RNA, which can limit therapeutic applications of CRISPR/Cas9 by ex-vivo formats. Contribution of this effects to the observed in vivo toxicity of OGT agents is unclear and requires further investigation. Locked or peptide nucleic acids improve OGT nuclease resistance but not specificity. Approaches that use RNA marker dependent (conditional) activation of OGT agents may improve specificity but require additional validation in cell culture and in vivo.