Drug delivery systems for RNA therapeutics

Recent advances in therapeutic CRISPR-Cas9 genome editing: mechanisms and applications

Recently, clustered regularly interspaced palindromic repeats (CRISPR)-Cas9 derived editing tools had significantly improved our ability to make desired changes in the genome. Wild-type Cas9 protein recognizes the target genomic loci and induced local double strand breaks (DSBs) in the guidance of small RNA molecule. In mammalian cells, the DSBs are mainly repaired by endogenous non-homologous end joining (NHEJ) pathway, which is error prone and results in the formation of indels. The indels can be harnessed to interrupt gene coding sequences or regulation elements. The DSBs can also be fixed by homology directed repair (HDR) pathway to introduce desired changes, such as base substitution and fragment insertion, when proper donor templates are provided, albeit in a less efficient manner. Besides making DSBs, Cas9 protein can be mutated to serve as a DNA binding platform to recruit functional modulators to the target loci, performing local transcriptional regulation, epigenetic remolding, base editing or prime editing. These Cas9 derived editing tools, especially base editors and prime editors, can introduce precise changes into the target loci at a single-base resolution and in an efficient and irreversible manner. Such features make these editing tools very promising for therapeutic applications. This review focuses on the evolution and mechanisms of CRISPR-Cas9 derived editing tools and their applications in the field of gene therapy.

Hydrogel armed with Bmp2 mRNA-enriched exosomes enhances bone regeneration

BACKGROUND

Sustained release of bioactive BMP2 (bone morphogenetic protein-2) is important for bone regeneration, while the intrinsic short half-life of BMP2 at protein level cannot meet the clinical need. In this study, we aimed to design Bmp2 mRNA-enriched engineered exosomes, which were then loaded into specific hydrogel to achieve sustained release for more efficient and safe bone regeneration.

RESULTS

Bmp2 mRNA was enriched into exosomes by selective inhibition of translation in donor cells, in which NoBody (non-annotated P-body dissociating polypeptide, a protein that inhibits mRNA translation) and modified engineered BMP2 plasmids were co-transfected. The derived exosomes were named Exo^BMP2+NoBody. In vitro experiments confirmed that Exo^BMP2+NoBody had higher abundance of Bmp2 mRNA and thus stronger osteogenic induction capacity. When loaded into GelMA hydrogel via ally-L-glycine modified CP05 linker, the exosomes could be slowly released and thus ensure prolonged effect of BMP2 when endocytosed by the recipient cells. In the in vivo calvarial defect model, Exo^BMP2+NoBody-loaded GelMA displayed great capacity in promoting bone regeneration.

CONCLUSIONS

Together, the proposed Exo^BMP2+NoBody-loaded GelMA can provide an efficient and innovative strategy for bone regeneration.

Gene therapy for chronic pain: emerging opportunities in target-rich peripheral nociceptors

With sweeping advances in precision delivery systems and manipulation of the genomes and transcriptomes of various cell types, medical biotechnology offers unprecedented selectivity for and control of a wide variety of biological processes, forging new opportunities for therapeutic interventions. This perspective summarizes state-of-the-art gene therapies enabled by recent innovations, with an emphasis on the expanding universe of molecular targets that govern the activity and function of primary sensory neurons and which might be exploited to effectively treat chronic pain.

Nanoparticle stereochemistry-dependent endocytic processing improves in vivo mRNA delivery

Stereochemistry can alter small-molecule pharmacokinetics, safety and efficacy. However, it is unclear whether the stereochemistry of a single compound within a multicomponent colloid such as a lipid nanoparticle (LNP) can influence its activity in vivo. Here we report that LNPs containing stereopure 20α-hydroxycholesterol (20α) delivered mRNA to liver cells up to 3-fold more potently than LNPs containing a mixture of both 20α- and 20β-hydroxycholesterols (20mix). This effect was not driven by LNP physiochemical traits. Instead, in vivo single-cell RNA sequencing and imaging revealed that 20mix LNPs were sorted into phagocytic pathways more than 20α LNPs, resulting in key differences between LNP biodistribution and subsequent LNP functional delivery. These data are consistent with the fact that nanoparticle biodistribution is necessary, but not sufficient, for mRNA delivery, and that stereochemistry-dependent interactions between LNPs and target cells can improve mRNA delivery.

pfeRNAs-A Novel Class of Small Non-coding RNAs With Real Translational Potential

Small non-coding RNAs (sncRNAs) are defined by being less than 200 nucleotides (nt) in length, and consequently, have been divided into many different subclasses including mature microRNA (miRNA), small interfering RNA (siRNA), piwi-interacting RNA (piRNA), protein functional effector sncRNA (pfeRNA), precursor miRNA (pre-miRNA), small nucleolar RNA (snoRNA), 5S ribosome RNA (5SrRNA), 5.8SrRNA, and small nuclear RNA (snRNA). Except for the class of pfeRNAs, the discovery, identification, biogenesis, characterization, and function of other sncRNAs have been well documented. Herein, we provide a review, written especially for clinicians, of the least understood class of functional sncRNAs, the pfeRNAs, focusing on their initial discovery, identification, unique features, function, as well as their exciting clinical translational potential.

Programmable macromolecule-based RNA-targeting therapies to treat human neurological disorders

Disruptions in RNA processing play critical roles in the pathogenesis of neurological diseases. In this Perspective, we discuss recent progress in the development of RNA-targeting therapeutic modalities. We focus on progress, limitations, and opportunities in a new generation of therapies engineered from RNA binding proteins and other endogenous RNA regulatory macromolecules to treat human neurological disorders.

Overcoming Treatment Challenges in Posterior Segment Diseases with Biodegradable Nano-Based Drug Delivery Systems

Posterior segment eye diseases present a challenge in treatment due to the complex structures in the eye that serve as robust static and dynamic barriers, limiting the penetration, residence time, and bioavailability of topical and intraocular medications. This hinders effective treatment and requires frequent dosing, such as the regular use of eye drops or visits to the ophthalmologist for intravitreal injections, to manage the disease. Moreover, the drugs must be biodegradable to minimize toxicity and adverse reactions, as well as small enough to not affect the visual axis. The development of biodegradable nano-based drug delivery systems (DDSs) can be the solution to these challenges. First, they can stay in ocular tissues for longer periods of time, reducing the frequency of drug administration. Second, they can pass through ocular barriers, offering higher bioavailability to targeted tissues that are otherwise inaccessible. Third, they can be made up of polymers that are biodegradable and nanosized. Hence, therapeutic innovations in biodegradable nanosized DDS have been widely explored for ophthalmic drug delivery applications. In this review, we will present a concise overview of DDSs utilized in the treatment of ocular diseases. We will then examine the current therapeutic challenges faced in the management of posterior segment diseases and explore how various types of biodegradable nanocarriers can enhance our therapeutic arsenal. A literature review of the pre-clinical and clinical studies published between 2017 and 2023 was conducted. Through the advances in biodegradable materials, combined with a better understanding of ocular pharmacology, the nano-based DDSs have rapidly evolved, showing great promise to overcome challenges currently encountered by clinicians.

The Small RNA Landscape in NSCLC: Current Therapeutic Applications and Progresses

Non-small-cell lung cancer (NSCLC) is the second most diagnosed type of malignancy and the first cause of cancer death worldwide. Despite recent advances, the treatment of choice for NSCLC patients remains to be chemotherapy, often showing very limited effectiveness with the frequent occurrence of drug-resistant phenotype and the lack of selectivity for tumor cells. Therefore, new effective and targeted therapeutics are needed. In this context, short RNA-based therapeutics, including Antisense Oligonucleotides (ASOs), microRNAs (miRNAs), short interfering (siRNA) and aptamers, represent a promising class of molecules. ASOs, miRNAs and siRNAs act by targeting and inhibiting specific mRNAs, thus showing an improved specificity compared to traditional anti-cancer drugs. Nucleic acid aptamers target and inhibit specific cancer-associated proteins, such as "nucleic acid antibodies". Aptamers are also able of receptor-mediated cell internalization, and therefore, they can be used as carriers of secondary agents giving the possibility of producing very highly specific and effective therapeutics. This review provides an overview of the proposed applications of small RNAs for NSCLC treatment, highlighting their advantageous features and recent advancements in the field.

Myocarditis: causes, mechanisms, and evolving therapies

INTRODUCTION

Myocarditis is a severe lymphocyte-mediated inflammatory disorder of the heart, mostly caused by viruses and immune checkpoint inhibitors (ICIs). Recently, myocarditis as a rare adverse event of mRNA vaccines for SARS-CoV-2 has caused global attention. The clinical consequences of myocarditis can be very severe, but specific treatment options are lacking or not yet clinically proven.

AREAS COVERED

This paper offers a brief overview of the biology of viruses that frequently cause myocarditis, focusing on mechanisms important for viral entry and replication following host infection. Current and new potential therapeutic targets/strategies especially for viral myocarditis are reviewed systematically. In particular, the immune system in myocarditis is dissected with respect to infective viral and non-infective, ICI-induced myocarditis.

EXPERT OPINION

Vaccination is an excellent emerging preventative strategy for viral myocarditis, but most vaccines still require further development. Anti-viral treatments that inhibit viral replication need to be considered following viral infection in host myocardium, as lower viral load reduces inflammation severity. Understanding how the immune system continues to damage the heart even after viral clearance will define novel therapeutic targets/strategies. We propose that viral myocarditis can be best treated using a combination of antiviral agents and immunotherapies that control cytotoxic T cell activity.

Precise and systematic end group chemistry modifications on PAMAM and poly(l-lysine) dendrimers to improve cytosolic delivery of mRNA

Here, we aimed to chemically modify PAMAM dendrimers using lysine as a site-selective anchor for successfully delivering mRNA while maintaining a low toxicity profile. PAMAM dendrimers were multi-functionalised by amidation reactions in a regioselective, quantitative and stepwise manner with carefully selected property-modifying surface groups. Alternatively, novel lysine-based dendrimers were prepared in the same manner with the aim to unlock their potential in gene delivery. The modified dendrimers were then formulated with Cy5-EGFP mRNA by bulk mixing via liquid handling robotics across different nitrogen to phosphate ratios. The resulting dendriplexes were characterised by size, charge, mRNA encapsulation, and mRNA binding affinity. Finally, their in-vitro delivery activity was systematically investigated across key cellular trafficking stages to relate chemical design to cellular effect. We demonstrate our findings in different cell lines and benchmarked relative to a commercially available transfection agent, jetPEI®. We demonstrate that specific surface modifications are required to generate small, reliable and well-encapsulated positively charged dendriplex complexes. Furthermore, we show that introduction of fusogenic groups is essential for driving endosomal escape and achieving cellular delivery and translation of mRNA in these cell lines.

Engineered exosomes from different sources for cancer-targeted therapy

Exosome is a subgroup of extracellular vesicles, which has been serving as an efficient therapeutic tool for various diseases. Engineered exosomes are the sort of exosomes modified with surface decoration and internal therapeutic molecules. After appropriate modification, engineered exosomes are able to deliver antitumor drugs to tumor sites efficiently and precisely with fewer treatment-related adverse effects. However, there still exist many challenges for the clinical translation of engineered exosomes. For instance, what sources and modification strategies could endow exosomes with the most efficient antitumor activity is still poorly understood. Additionally, how to choose appropriately engineered exosomes in different antitumor therapies is another unresolved problem. In this review, we summarized the characteristics of engineered exosomes, especially the spatial and temporal properties. Additionally, we concluded the recent advances in engineered exosomes in the cancer fields, including the sources, isolation technologies, modification strategies, and labeling and imaging methods of engineered exosomes. Furthermore, the applications of engineered exosomes in different antitumor therapies were summarized, such as photodynamic therapy, gene therapy, and immunotherapy. Consequently, the above provides the cancer researchers in this community with the latest ideas on engineered exosome modification and new direction of new drug development, which is prospective to accelerate the clinical translation of engineered exosomes for cancer-targeted therapy.

Recent Advances in the Lipid Nanoparticle-Mediated Delivery of mRNA Vaccines

Lipid nanoparticles (LNPs) have recently emerged as one of the most advanced technologies for the highly efficient in vivo delivery of exogenous mRNA, particularly for COVID-19 vaccine delivery. LNPs comprise four different lipids: ionizable lipids, helper or neutral lipids, cholesterol, and lipids attached to polyethylene glycol (PEG). In this review, we present recent the advances and insights for the design of LNPs, as well as their composition and properties, with a subsequent discussion on the development of COVID-19 vaccines. In particular, as ionizable lipids are the most critical drivers for complexing the mRNA and in vivo delivery, the role of ionizable lipids in mRNA vaccines is discussed in detail. Furthermore, the use of LNPs as effective delivery vehicles for vaccination, genome editing, and protein replacement therapy is explained. Finally, expert opinion on LNPs for mRNA vaccines is discussed, which may address future challenges in developing mRNA vaccines using highly efficient LNPs based on a novel set of ionizable lipids. Developing highly efficient mRNA delivery systems for vaccines with improved safety against some severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) variants remains difficult.

Optimal delivery strategies for nanoparticle-mediated mRNA delivery

Messenger RNA (mRNA) has emerged as a new and efficient agent for the treatment of various diseases. The success of lipid nanoparticle-mRNA against the novel coronavirus (SARS-CoV-2) pneumonia epidemic has proved the clinical potential of nanoparticle-mRNA formulations. However, the deficiency in the effective biological distribution, high transfection efficiency and good biosafety are still the major challenges in clinical translation of nanomedicine for mRNA delivery. To date, a variety of promising nanoparticles have been constructed and then gradually optimized to facilitate the effective biodistribution of carriers and efficient mRNA delivery. In this review, we describe the design of nanoparticles with an emphasis on lipid nanoparticles, and discuss the manipulation strategies for nanoparticle-biology (nano-bio) interactions for mRNA delivery to overcome the biological barriers and improve the delivery efficiency, because the specific nano-bio interaction of nanoparticles usually remoulds the biomedical and physiological properties of the nanoparticles especially the biodistribution, mechanism of cellular internalization and immune response. Finally, we give a perspective for the future applications of this promising technology. We believe that the regulation of nano-bio interactions would be a significant breakthrough to improve the mRNA delivery efficiency and cross biological barriers. This review may provide a new direction for the design of nanoparticle-mediated mRNA delivery systems.

Active Nuclear Import of Mammalian Cell-Expressible DNA Origami

DNA origami enables the creation of complex 3D shapes from genetic material. Future uses could include the delivery of genetic instructions to cells, but nuclear import remains a major barrier to gene delivery due to the impermeability of the nuclear membrane. Here we realize active nuclear import of DNA origami objects in dividing and chemically arrested mammalian cells. We developed a custom DNA origami single-strand scaffold featuring a mammalian-cell expressible reporter gene (mCherry) and multiple Simian virus 40 (SV40) derived DNA nuclear targeting sequences (DTS). Inclusion of the DTS within DNA origami rescued gene expression in arrested cells, indicating that active transport into the nucleus occurs. Our work successfully adapts mechanisms known from viruses to promote the cellular expression of genetic instructions encoded within DNA origami objects.

The Role of miRNAs in Neuropathic Pain

Neuropathic pain is a debilitating condition affecting around 8% of the adult population in the UK. The pathophysiology is complex and involves a wide range of processes, including alteration of neuronal excitability and synaptic transmission, dysregulated intracellular signalling and activation of pro-inflammatory immune and glial cells. In the past 15 years, multiple miRNAs–small non-coding RNA–have emerged as regulators of neuropathic pain development. They act by binding to target mRNAs and preventing the translation into proteins. Due to their short sequence (around 22 nucleotides in length), they can have hundreds of targets and regulate several pathways. Several studies on animal models have highlighted numerous miRNAs that play a role in neuropathic pain development at various stages of the nociceptive pathways, including neuronal excitability, synaptic transmission, intracellular signalling and communication with non-neuronal cells. Studies on animal models do not always translate in the clinic; fewer studies on miRNAs have been performed involving human subjects with neuropathic pain, with differing results depending on the specific aetiology underlying neuropathic pain. Further studies using human tissue and liquid samples (serum, plasma, saliva) will help highlight miRNAs that are relevant to neuropathic pain diagnosis or treatment, as biomarkers or potential drug targets.

Molecular Neurosurgery: Introduction to Gene Therapy and Clinical Applications

To date, more than 100 clinical trials have used sequence-based therapies to address diseases of the pediatric central nervous system. The first targeted pathologies share common features: the diseases are severe; they are due (mostly) to single variants; the variants are well characterized within the genome; and the interventions are technically feasible. Interventions range from intramuscular and intravenous injection to intrathecal and intraparenchymal infusions. Whether the therapeutic sequence consists of RNA or DNA, and whether the sequence is delivered via simple oligonucleotide, nanoparticle, or viral vector depends on the disease and the involved cell type(s) of the nervous system. While only one active trial targets an epilepsy disorder—Dravet syndrome—experiences with aromatic L-amino acid decarboxylase deficiency, spinal muscular atrophy, and others have taught us several lessons that will undoubtedly apply to the future of gene therapy for epilepsies. Epilepsies, with their diverse underlying mechanisms, will have unique aspects that may influence gene therapy strategies, such as targeting the epileptic zone or nodes in affected circuits, or alternatively finding ways to target nearly every neuron in the brain. This article focuses on the current state of gene therapy and includes its history and premise, the strategy and delivery vehicles most commonly used, and details viral vectors, current trials, and considerations for the future of pediatric intracranial gene therapy.

An RNA Paranemic Crossover Triangle as A 3D Module for Cotranscriptional Nanoassembly

RNA nanotechnology takes advantage of structural modularity to build self-assembling nano-architectures with applications in medicine and synthetic biology. The use of paranemic motifs, that form without unfolding existing secondary structure, allows for the creation of RNA nanostructures that are compatible with cotranscriptional folding in vitro and in vivo. In previous work, kissing-loop (KL) motifs have been widely used to design RNA nanostructures that fold cotranscriptionally. However, the paranemic crossover (PX) motif has not yet been explored for cotranscriptional RNA origami architectures and information about the structural geometry of the motif is unknown. Here, a six base pair-wide paranemic RNA interaction that arranges double helices in a perpendicular manner is introduced, allowing for the generation of a new and versatile building block: the paranemic-crossover triangle (PXT). The PXT is self-assembled by cotranscriptional folding and characterized by cryogenic electron microscopy, revealing for the first time an RNA PX interaction in high structural detail. The PXT is used as a building block for the construction of multimers that form filaments and rings and a duplicated PXT motif is used as a building block to self-assemble cubic structures, demonstrating the PXT as a rigid self-folding domain for the development of wireframe RNA origami architectures.

Lipid nanomaterials-based RNA therapy and cancer treatment

We summarize the most important advances in RNA delivery and nanomedicine. We describe lipid nanoparticle-based RNA therapeutics and the impacts on the development of novel drugs. The fundamental properties of the key RNA members are described. We introduced recent advances in the nanoparticles to deliver RNA to defined targets, with a focus on lipid nanoparticles (LNPs). We review recent advances in biomedical therapy based on RNA drug delivery and state-of-the-art RNA application platforms, including the treatment of different types of cancer. This review presents an overview of current LNPs based RNA therapies in cancer treatment and provides deep insight into the development of future nanomedicines sophisticatedly combining the unparalleled functions of RNA therapeutics and nanotechnology.

Noncoding RNAs in the crosstalk between multiple myeloma cells and bone marrow microenvironment

Multiple myeloma (MM) is the second most common hematological malignancy; however, it remains incurable, and the underlying pathogenesis and mechanisms of drug resistance remain unclear. It is widely recognized that the bone marrow microenvironment plays a crucial role in regulating the immune response, inducing drug resistance, and promoting tumor proliferation and invasion in MM, and thus serves as a potential therapeutic target. Among the various signaling loops between myeloma cells and components of the microenvironment, noncoding RNAs are emerging as crucial regulators of intercellular communication within the microenvironment. Noncoding RNAs, such as microRNAs, long noncoding RNAs, circular RNAs, and PIWI-interacting RNAs, have been associated with numerous biological processes involved in myeloma cell growth, survival, migration, invasion, and drug resistance. This review summarizes recent advances in the regulatory mechanisms of noncoding RNAs involved in the interaction between the MM bone marrow microenvironment and discusses the therapeutic potential of noncoding RNAs in MM.

Circularized RNA as novel therapeutics in cancer

Circular RNAs (CircRNAs) regulate gene expression by functioning as microRNA sponges, regulating protein stability, and gilding proteins for gene transcription and translation. Also, limited circRNAs harbour protein-coding ability through cap-independent pathways. These molecular mechanisms of circRNAs contribute to their importance in several cellular processes. Particularly, the dysregulation of circRNAs also plays a critical role in disease development. Targeting disease-causing circRNAs by restoring their normal expression by gain-of-function or loss-of-function approach and regulating their molecular activities could be potential direction for the development of anti-cancer therapies. Furthermore, due to unique covalently closed circular structure, the superior stability of circRNAs also grants them as novel therapeutic tools replacing the therapeutic small interfering RNAs and messenger RNAs. Here, we will review the functional and molecular mechanisms of circRNAs in pathogenesis, the current methods for targeting the dysregulated circRNAs, and the potential of using synthetic circRNAs in disease treatment and prevention.

Nanocarrier design–function relationship: The prodigious role of properties in regulating biocompatibility for drug delivery applications

The concept of drug delivery systems as a magic bullet for the delivery of bioactive compounds has emerged as a promising approach in the treatment of different diseases with significant advantages over the limitations of traditional methods. While nanocarrier-based drug delivery systems are the main advocates of drug uptake because they offer several advantages including reduced non-specific biodistribution, improved accumulation, and enhanced therapeutic efficiency; their safety and biocompatibility within cellular/tissue systems are therefore important for achieving the desired effect. The underlying power of "design-interplay chemistry" in modulating the properties and biocompatibility at the nanoscale level will direct the interaction with their immediate surrounding. Apart from improving the existing nanoparticle physicochemical properties, the balancing of the hosts' blood components interaction holds the prospect of conferring newer functions altogether. So far, this concept has been remarkable in achieving many fascinating feats in addressing many challenges in nanomedicine such as immune responses, inflammation, biospecific targeting and treatment, and so on. This review, therefore, provides a diverse account of the recent advances in the fabrication of biocompatible nano-drug delivery platforms for chemotherapeutic applications, as well as combination therapy, theragnostic, and other diseases that are of interest to scientists in the pharmaceutical industries. Thus, careful consideration of the "property of choice" would be an ideal way to realize specific functions from a set of delivery platforms. Looking ahead, there is an enormous prospect for nanoparticle properties in regulating biocompatibility.

Tailoring biomimetic dual-redox-responsive nanoplexes for enhanced RNAi-synergized photodynamic cancer immunotherapy

Despite the strong potential of RNA interference (RNAi) therapies, critical issues, such as poor permeability across biological membranes and efficacy of their delivery into the cytoplasm, remain to be addressed before their successful clinical application. The current study aimed to address these issues by constructing a biomimetic nanoplex with dual redox responsiveness, which is derived from a cationic polymer formed by the condensation of endogenous spermine monomers via diselenide bonds. The developed nanoplexes decomposed in response to the redox microenvironment in cancer cells, thereby avoiding accumulation toxicity and poor transfection efficiency owing to incomplete siRNA release. When co-delivered with siPDL1 and a photosensitizer, the reactive oxygen species generated by irradiated nanoplexes accelerated the cytoplasmic release of siPDL1, which was expected to alleviate the PDT-induced increase in immunosuppressive PD-L1 expression. In a murine model of 4T1 xenografted breast cancer, the fabricated macrophage membrane (MPM)-camouflaged nanoplexes with payloads boosted antitumor immune responses in situ through a "self-synergistic" immunogenic cell death induced by photodynamic therapy (PDT). Overall, the study reported a new strategy for harnessing photodynamic immunotherapy for treating immunologically cold tumors. STATEMENT OF SIGNIFICANCE: This study provides a biomimetic nanoplex with dual redox responsiveness, which is derived from a novel cationic polymer formed by the condensation of endogenous spermine monomers through diselenide bonds. The developed nanoplex disassembles according to the redox microenvironment in cancer cells, thereby avoiding accumulation toxicity and poor transfection efficiency due to incomplete siRNA release. When co-delivery of siPDL1 and photosensitizer in vivo, the ROS generated by irradiated nanoplexes accelerated the cytoplasmic release of siPDL1, and which is expected to alleviate PDT-induced increase in immunosuppressive PD-L1 expression, thereby boosting antitumor immune responses in situ through a "self-synergistic" immunogenic cell death induced by PDT. Our findings reveal a new strategy of harnessing photodynamic immunotherapy therapy toward immunologically cold tumors.

A Triazolium-Anchored Self-Immolative Linker Enables Self-Assembly-Driven siRNA Binding and Esterase-Induced Release

The increased importance of RNA-based therapeutics comes with a need to develop next-generation stimuli-responsive systems capable of binding, transporting and releasing RNA oligomers. In this work, we describe triazolium-based amphiphiles capable of siRNA binding and enzyme-responsive release of the nucleic acid payload. In aqueous medium, the amphiphile self-assembles into nanocarriers that can disintegrate upon the addition of esterase. Key to the molecular design is a self-immolative linker that is anchored to the triazolium moiety and acts as a positively-charged polar head group. We demonstrate that addition of esterase leads to a degradation cascade of the linker, leaving the neutral triazole compound unable to form complexes and therefore releasing the negatively-charged siRNA. The reported molecular design and overall approach may have broad utility beyond this proof-of-principle study, because the underlying CuAAC "click" chemistry allows bringing together three groups very efficiently as well as cleaving off one of the three groups under the mild action of an esterase enzyme.

Pillararene-Based Supramolecular Polymers for Cancer Therapy

Supramolecular polymers have attracted considerable interest due to their intriguing features and functions. The dynamic reversibility of noncovalent interactions endows supramolecular polymers with tunable physicochemical properties, self-healing, and externally stimulated responses. Among them, pillararene-based supramolecular polymers show great potential for biomedical applications due to their fascinating host-guest interactions and easy modification. Herein, we summarize the state of the art of pillararene-based supramolecular polymers for cancer therapy and illustrate its developmental trend and future perspective.

High-Precision Synthesis of RNA-Loaded Lipid Nanoparticles for Biomedical Applications

The recent development of RNA-based therapeutics in delivering nucleic acids for gene editing and regulating protein translation has led to the effective treatment of various diseases including cancer, inflammatory and genetic disorder, as well as infectious diseases. Among these, lipid nanoparticles (LNP) have emerged as a promising platform for RNA delivery and have shed light by resolving the inherent instability issues of naked RNA and thereby enhancing the therapeutic potency. These LNP consisting of ionizable lipid, helper lipid, cholesterol, and poly(ethylene glycol)-anchored lipid can stably enclose RNA and help them release into the cells' cytosol. Herein, the significant progress made in LNP research starting from the LNP constituents, formulation, and their diverse applications is summarized first. Moreover, the microfluidic methodologies which allow precise assembly of these newly developed constituents to achieve LNP with controllable composition and size, high encapsulation efficiency as well as scalable production are highlighted. Furthermore, a short discussion on current challenges as well as an outlook will be given on emerging approaches to resolving these issues.

Structure-Activity Relationships in Nucleic-Acid-Templated Vectors Based on Peptidic Dynamic Covalent Polymers

The use of nucleic acids as templates, which can trigger the self-assembly of their own vectors represent an emerging, simple and versatile, approach toward the self-fabrication of tailored nucleic acids delivery vectors. However, the structure-activity relationships governing this complex templated self-assembly process that accompanies the complexation of nucleic acids remains poorly understood. Herein, the class of arginine-rich dynamic covalent polymers (DCPs) composed of different monomers varying the number and position of arginines were studied. The combinations that lead to nucleic acid complexation, in saline buffer, using different templates, from short siRNA to long DNA, are described. Finally, a successful peptidic DCP featuring six-arginine repeating unit that promote the safe and effective delivery of siRNA in live cancer cells was identified.

Efficient in vivo genome editing prevents hypertrophic cardiomyopathy in mice

Dominant missense pathogenic variants in cardiac myosin heavy chain cause hypertrophic cardiomyopathy (HCM), a currently incurable disorder that increases risk for stroke, heart failure and sudden cardiac death. In this study, we assessed two different genetic therapies-an adenine base editor (ABE8e) and a potent Cas9 nuclease delivered by AAV9-to prevent disease in mice carrying the heterozygous HCM pathogenic variant myosin R403Q. One dose of dual-AAV9 vectors, each carrying one half of RNA-guided ABE8e, corrected the pathogenic variant in ≥70% of ventricular cardiomyocytes and maintained durable, normal cardiac structure and function. An additional dose provided more editing in the atria but also increased bystander editing. AAV9 delivery of RNA-guided Cas9 nuclease effectively inactivated the pathogenic allele, albeit with dose-dependent toxicities, necessitating a narrow therapeutic window to maintain health. These preclinical studies demonstrate considerable potential for single-dose genetic therapies to correct or silence pathogenic variants and prevent the development of HCM.

Iterative Design of Ionizable Lipids for Intramuscular mRNA Delivery

Lipid nanoparticles (LNPs) are the most clinically advanced delivery vehicles for RNA and have enabled the development of RNA-based drugs such as the mRNA COVID-19 vaccines. Functional delivery of mRNA by an LNP greatly depends on the inclusion of an ionizable lipid, and small changes to these lipid structures can significantly improve delivery. However, the structure-function relationships between ionizable lipids and mRNA delivery are poorly understood, especially for LNPs administered intramuscularly. Here, we show that the iterative design of a novel series of ionizable lipids generates key structure-activity relationships and enables the optimization of chemically distinct lipids with efficacy that is on-par with the current state of the art. We find that the combination of ionizable lipids comprising an ethanolamine core and LNPs with an apparent pK_a between 6.6 and 6.9 maximizes intramuscular mRNA delivery. Furthermore, we report a nonlinear relationship between the lipid-to-mRNA mass ratio and protein expression, suggesting that a critical mass ratio exists for LNPs and may depend on ionizable lipid structure. Our findings add to the mechanistic understanding of ionizable lipids and demonstrate that hydrogen bonding, ionization behavior, and lipid-to-mRNA mass ratio are key design parameters affecting intramuscular mRNA delivery. We validate these insights by applying them to the rational design of new ionizable lipids. Overall, our iterative design strategy efficiently generates potent ionizable lipids. This hypothesis-driven method reveals structure-activity relationships that lay the foundation for the optimization of ionizable lipids in future LNP-RNA drugs. We foresee that this design strategy can be extended to other optimization parameters beyond intramuscular expression.

Novel long noncoding RNA LINC02820 augments TNF signaling pathway to remodel cytoskeleton and potentiate metastasis in esophageal squamous cell carcinoma

Esophageal squamous cell carcinoma (ESCC) is one of the most common malignant tumors in China. However, there are no targets to treat ESCC because the molecular mechanism behind the cancer is still unclear. Here, we found a novel long noncoding RNA LINC02820 was upregulated in ESCC and associated with the ESCC clinicopathological stage. Through a series of functional experiments, we observed that LINC02820 only promoted the migration and invasion capabilities of ESCC cell lines. Mechanically, we found that LINC02820 may affect the cytoskeletal remodeling, interact with splice factor 3B subunit 3 (SF3B3), and cooperate with TNFα to amplify the NF-κB signaling pathway, which can lead to ESCC metastasis. Overall, our findings revealed that LINC02820 is a potential biomarker and therapeutic target for the diagnosis and treatment of ESCC.

Development of mRNA Vaccines/Therapeutics and Their Delivery System

The rapid development of mRNA vaccines has contributed to the management of the current coronavirus disease 2019 (COVID-19) pandemic, suggesting that this technology may be used to manage future outbreaks of infectious diseases. Because the antigens targeted by mRNA vaccines can be easily altered by simply changing the sequence present in the coding region of mRNA structures, it is more appropriate to develop vaccines, especially during rapidly developing outbreaks of infectious diseases. In addition to allowing rapid development, mRNA vaccines have great potential in inducing successful antigen-specific immunity by expressing target antigens in cells and simultaneously triggering immune responses. Indeed, the two COVID-19 mRNA vaccines approved by the U.S. Food and Drug Administration have shown significant efficacy in preventing infections. The ability of mRNAs to produce target proteins that are defective in specific diseases has enabled the development of options to treat intractable diseases. Clinical applications of mRNA vaccines/therapeutics require strategies to safely deliver the RNA molecules into targeted cells. The present review summarizes current knowledge about mRNA vaccines/ therapeutics, their clinical applications, and their delivery strategies.

Delivering mRNAs to mouse tissues using the SEND system

mRNAs produced in a cell are almost always translated within the same cell. Some mRNAs are transported to other cells of the organism through processes involving membrane nanotubes or extracellular vesicles. A recent report describes a surprising new phenomenon of encapsulating mRNAs inside virus-like particles (VLPs) to deliver them to other cells in a process that was named SEND (Selective Endogenous eNcapsidation for cellular Delivery). Although the seminal work demonstrates the SEND process in cultured cells, it is unknown whether this phenomenon occurs in vivo . Here, we demonstrate the SEND process in living organisms using specially designed genetically engineered mouse models. Our proof of principle study lays a foundation for the SEND-VLP system to potentially be used as a gene therapy tool to deliver therapeutically important mRNAs to tissues.

Cancer-cell-membrane-camouflaged supramolecular self-assembly of antisense oligonucleotide and chemodrug for targeted combination therapy

The anti-apoptotic B-cell lymphoma-2 (Bcl-2) family of proteins are critical regulators of cell death that are overexpressed in many cancer cells, especially in multi-drug resistant cancer cells. Combinatorial gene- and chemotherapies using antisense oligonucleotides (ASOs) to suppress the expression of Bcl-2-family mRNA and restore the sensitivity of the cell to chemodrugs provide a promising pathway for anticancer treatment. However, intrinsic differences between macromolecular ASOs and small molecular chemodrugs make their co-delivery challenging. Moreover, extraneous carriers may induce immunogenicity and inflammation problems. Herein, we develop a targeted nanodrug delivery system using the cationic amphiphilic chemodrug mitoxantrone (Mito), which interacts with Bcl-2 ASO through electrostatic interaction and self-assembles into nanoparticles (NP_[Bcl-2/Mito]), whose size can be controlled by regulating the ratio of ASO and Mito. NP_[Bcl-2/Mito] can protect the ASO from degradation during delivery and combine gene- and chemotherapies to improve the anticancer effect. Furthermore, cancer cell membranes (CCMs) derived from homologous tumors were used to camouflage NP_[Bcl-2/Mito] (NP_[Bcl-2/Mito]@CCM) to achieve immune escape and tumor targeting. Both in vitro and in vivo assessments demonstrate the excellent performance of NP_[Bcl-2/Mito]@CCM for drug-resistant breast tumor therapy. This CCM-camouflaged ASO/chemodrug nanoplatform provides a promising pathway for the targeted delivery of ASOs and chemodrugs for tumor combination therapy.

microRNA-181a silencing by antisense oligonucleotides delivered by virus-like particles

Cowpea chlorotic mottle virus (CCMV) is a positive-sense RNA virus that can be repurposed for gene delivery applications. Understanding the self-assembly process of the virus enabled to remove its genome and replace it with desired nucleic acids, and we and others have previously reported using CCMV virus-like particle (VLP) to encapsulate siRNA, mRNA, as well as CpG oligodeoxynucleotides. In this study, the CCMV VLP was applied to encapsulate two different formats of anti-miR-181a oligonucleotides: naked RNA and chemically stabilized RNA to knockdown highly regulated miR-181a in ovarian cancer cells. miR-181a expression in ovarian tumors is associated with high aggressiveness, invasiveness, resistance to chemotherapy, and overall poor prognosis. Therefore, miR-181a is an important target for ovarian cancer therapy. qPCR data and cancer cell migration assays demonstrated higher knockdown efficacy when anti-miR-181a oligonucleotides were encapsulated and delivered using the VLPs resulting in reduced cancer cell invasiveness. Importantly, delivery of anti-miR-181a oligonucleotide into cells could be achieved without the aid of a transfection agent or surface modification. These results highlight the opportunity of plant-derived VLPs as nucleic acid carriers.

Small Molecule-Activated O-GlcNAcase for Spatiotemporal Removal of O-GlcNAc in Live Cells

The nutrient sensor O-linked N-acetylglucosamine (O-GlcNAc) is a post-translational modification found on thousands of nucleocytoplasmic proteins. O-GlcNAc levels in cells dynamically respond to environmental cues in a temporal and spatial manner, leading to altered signal transduction and functional effects. The spatiotemporal regulation of O-GlcNAc levels would accelerate functional interrogation of O-GlcNAc and manipulation of cell behaviors for desired outcomes. Here, we report a strategy for spatiotemporal reduction of O-GlcNAc in live cells by designing an O-GlcNAcase (OGA) fused to an intein triggered by 4-hydroxytamoxifen (4-HT). After rational protein engineering and optimization, we identified an OGA-intein variant whose deglycosidase activity can be triggered in the desired subcellular compartments by 4-HT in a time- and dose-dependent manner. Finally, we demonstrated that 4-HT activation of the OGA-intein fusion can likewise potentiate inhibitory effects in breast cancer cells by virtue of the reduction of O-GlcNAc. The spatiotemporal control of O-GlcNAc through the chemically activatable OGA-intein fusion will facilitate the manipulation and functional understanding of O-GlcNAc in live cells.

Towards a Cure for HARS Disease

Histidyl-tRNA synthetase (HARS) ligates histidine to its cognate transfer RNA (tRNA^His). Mutations in HARS cause the human genetic disorders Usher syndrome type 3B (USH3B) and Charcot-Marie-Tooth syndrome type 2W (CMT2W). Treatment for these diseases remains symptomatic, and no disease specific treatments are currently available. Mutations in HARS can lead to destabilization of the enzyme, reduced aminoacylation, and decreased histidine incorporation into the proteome. Other mutations lead to a toxic gain-of-function and mistranslation of non-cognate amino acids in response to histidine codons, which can be rescued by histidine supplementation in vitro. We discuss recent advances in characterizing HARS mutations and potential applications of amino acid and tRNA therapy for future gene and allele specific therapy.

Evolution of nanobodies specific for BCL11A

Transcription factors (TFs) control numerous genes that are directly relevant to many human disorders. However, developing specific reagents targeting TFs within intact cells is challenging due to the presence of highly disordered regions within these proteins. Intracellular antibodies offer opportunities to probe protein function and validate therapeutic targets. Here, we describe the optimization of nanobodies specific for BCL11A, a validated target for the treatment of hemoglobin disorders. We obtained first-generation nanobodies directed to a region of BCL11A comprising zinc fingers 4 to 6 (ZF456) from a synthetic yeast surface display library, and employed error-prone mutagenesis, structural determination, and molecular modeling to enhance binding affinity. Engineered nanobodies recognized ZF6 and mediated targeted protein degradation (TPD) of BCL11A protein in erythroid cells, leading to the anticipated reactivation of fetal hemoglobin (HbF) expression. Evolved nanobodies distinguished BCL11A from its close paralog BCL11B, which shares an identical DNA-binding specificity. Given the ease of manipulation of nanobodies and their exquisite specificity, nanobody-mediated TPD of TFs should be suitable for dissecting regulatory relationships of TFs and gene targets and validating therapeutic potential of proteins of interest.

Suppression of Lung Cancer Malignancy by Micellized siRNA through Cell Cycle Arrest

UBA6-specific E2 conjugation enzyme 1 (USE1) is frequently overexpressed in lung cancer patients. Moreover, the critical role of USE1 in the progression of human lung cancer is also indicated. As the next step, the authors aim to develop USE1-targeted therapeutic agents based on RNA interference (RNAi). In this study, a lipid-modified DNA carrier, namely U4T, which consists of four consecutive dodec-1-ynyluracil (U) nucleobases to increase the cell permeability of siRNA targeting of USE1 is introduced. The U4Ts aggregate to form micelles, and the USE1-silencing siRNA-incorporated soft spherical nucleic acid aggregate (siSNA) can be created simply through base-pairing with siRNA. Treatment with siSNA is effective in suppressing tumor growth in vivo as well as cell proliferation, migration, and invasion of lung cancer cells. Furthermore, siSNA inhibited tumor cell growth by inducing cell cycle arrest in the G1 phase and apoptosis. Thus, the anti-tumor efficacy of siSNA in lung cancer cell lines and that siSNA possesses effective cell-penetrating ability without using cationic transfection moieties are confirmed. Collectively, these results suggest that siSNA can be applied to the clinical application of RNAi-based therapeutics for lung cancer treatment.

Fine-Tuned Polymer Nanoassembly for Codelivery of Chemotherapeutic Drug and siRNA

Successful clinical application of siRNA to liver-associated diseases reinvigorates the RNAi therapeutics and delivery vectors, especially for anticancer combination therapy. Fine tuning of copolymer-based assembly configuration is highly important for a desirable synergistic cancer cell-killing effect via the codelivery of chemotherapeutic drug and siRNA. Herein, an amphiphilic triblock copolymer methoxyl poly(ethylene glycol)-block-poly(L-lysine)-block-poly(2-(diisopropyl amino)ethyl methacrylate) (abbreviated as mPEG-PLys-PDPA or PLD) consisting of a hydrophilic diblock mPEG-PLys and a hydrophobic block PDPA is synthesized. Three distinct assemblies (i.e., nanosized micelle, nanosized polymersome, and microparticle) are acquired, along with the increase in PDPA block length. Furthermore, the as-obtained polymersome can efficiently codeliver doxorubicin hydrochloride (DOX) as a hydrophilic chemotherapeutic model and siRNA against ADP-ribosylation factor 6 (siArf6) as an siRNA model into cancer cell via lysosomal pH-triggered payload release. PC-3 prostate cell is synergistically killed by the DOX- and siArf6-coloading polymersome (namely PLD@DOX/siArf6). PLD@DOX/siArf6 may serve as a robust nanomedicine for anticancer therapy.

Race with virus evolution: The development and application of mRNA vaccines against SARS-CoV-2

Since the COVID-19 pandemic was declared, vaccines against SARS-CoV-2 have been urgently developed around the world. On the basis of the mRNA vaccine technology developed previously, COVID-19 mRNA vaccines were promptly tested in animals, advanced to clinical trials, and then authorized for emergency use in humans. The administration of COVID-19 mRNA vaccines has successfully reduced the hospitalization and mortality caused by the viral infection, although the virus continuously evolves with its transmission. Therefore, the development of mRNA vaccine technology, including RNA modification and delivery systems, is well recognized for its contribution to moderating the harms caused by the COVID-19 pandemic. The scientists who developed these technologies, Katalin Karikó, Drew Weissman, and Pieter Cullis, were awarded the 2022 Tang Prize in Biopharmaceutical Science. In this review, we summarize the principles, safety and efficacy of as well as the immune response to COVID-19 mRNA vaccines. Since mRNA vaccine approaches could be practical for the prevention of infectious diseases, we also briefly describe mRNA vaccines against other human viral pathogens in clinical trials.

Intradermally delivered mRNA-encapsulating extracellular vesicles for collagen-replacement therapy

The success of messenger RNA therapeutics largely depends on the availability of delivery systems that enable the safe, effective and stable translation of genetic material into functional proteins. Here we show that extracellular vesicles (EVs) produced via cellular nanoporation from human dermal fibroblasts, and encapsulating mRNA encoding for extracellular-matrix α1 type-I collagen (COL1A1) induced the formation of collagen-protein grafts and reduced wrinkle formation in the collagen-depleted dermal tissue of mice with photoaged skin. We also show that the intradermal delivery of the mRNA-loaded EVs via a microneedle array led to the prolonged and more uniform synthesis and replacement of collagen in the dermis of the animals. The intradermal delivery of EV-based COL1A1 mRNA may make for an effective protein-replacement therapy for the treatment of photoaged skin.

Nucleic acid-based artificial nanocarriers for gene therapy

Nucleic acid nanotechnology is a powerful tool in the fields of biosensing and nanomedicine owing to their high editability and easy synthesis and modification. Artificial nucleic acid nanostructures have become an emerging research hotspot as gene carriers with low cytotoxicity and immunogenicity for therapeutic approaches. In this review, recent progress in the design and functional mechanisms of nucleic acid-based artificial nano-vectors especially for exogenous siRNA and antisense oligonucleotide delivery is summarized. Different types of DNA nanocarriers, including DNA junctions, tetrahedrons, origami, hydrogels and scaffolds, are introduced. The enhanced targeting strategies to improve the delivery efficacy are demonstrated. Furthermore, RNA based gene nanocarrier systems by self-assembly of short strands, rolling circle transcription, chemical crosslinking and using RNA motifs and DNA-RNA hybrids are demonstrated. Finally, the outlook and potential challenges are highlighted. The nucleic acid-based artificial nanocarriers offer a promising and precise tool for gene delivery and therapy.

Regulation by noncoding RNAs of local translation, injury responses, and pain in the peripheral nervous system

Neuropathic pain is a chronic condition arising from damage to somatosensory pathways that results in pathological hypersensitivity. Persistent pain can be viewed as a consequence of maladaptive plasticity which, like most enduring forms of cellular plasticity, requires altered expression of specific gene programs. Control of gene expression at the level of protein synthesis is broadly utilized to directly modulate changes in activity and responsiveness in nociceptive pathways and provides an effective mechanism for compartmentalized regulation of the proteome in peripheral nerves through local translation. Levels of noncoding RNAs (ncRNAs) are commonly impacted by peripheral nerve injury leading to persistent pain. NcRNAs exert spatiotemporal regulation of local proteomes and affect signaling cascades supporting altered sensory responses that contribute to hyperalgesia. This review discusses ncRNAs found in the peripheral nervous system (PNS) that are dysregulated following nerve injury and the current understanding of their roles in pathophysiological pain-related responses including neuroimmune interactions, neuronal survival and axon regeneration, Schwann cell dedifferentiation and proliferation, intercellular communication, and the generation of ectopic action potentials in primary afferents. We review progress in the field beyond cataloging, with a focus on the relevant target transcripts and mechanisms underlying pain modulation by ncRNAs.

CNS Delivery of Nucleic Acid Therapeutics: Beyond the Blood-Brain Barrier and Towards Specific Cellular Targeting

Nucleic acid-based therapeutic molecules including small interfering RNA (siRNA), microRNA(miRNA), antisense oligonucleotides (ASOs), messenger RNA (mRNA), and DNA-based gene therapy have tremendous potential for treating diseases in the central nervous system (CNS). However, achieving clinically meaningful delivery to the brain and particularly to target cells and sub-cellular compartments is typically very challenging. Mediating cell-specific delivery in the CNS would be a crucial advance that mitigates off-target effects and toxicities. In this review, we describe these challenges and provide contemporary evidence of advances in cellular and sub-cellular delivery using a variety of delivery mechanisms and alternative routes of administration, including the nose-to-brain approach. Strategies to achieve subcellular localization, endosomal escape, cytosolic bioavailability, and nuclear transfer are also discussed. Ultimately, there are still many challenges to translating these experimental strategies into effective and clinically viable approaches for treating patients.

RNAi-Based Therapeutics and Novel RNA Bioengineering Technologies

RNA interference (RNAi) provides researchers with a versatile means to modulate target gene expression. The major forms of RNAi molecules, genome-derived microRNAs (miRNAs) and exogenous small interfering RNAs (siRNAs), converge into RNA-induced silencing complexes to achieve posttranscriptional gene regulation. RNAi has proven to be an adaptable and powerful therapeutic strategy where advancements in chemistry and pharmaceutics continue to bring RNAi-based drugs into the clinic. With four siRNA medications already approved by the US Food and Drug Administration (FDA), several RNAi-based therapeutics continue to advance to clinical trials with functions that closely resemble their endogenous counterparts. Although intended to enhance stability and improve efficacy, chemical modifications may increase risk of off-target effects by altering RNA structure, folding, and biologic activity away from their natural equivalents. Novel technologies in development today seek to use intact cells to yield true biologic RNAi agents that better represent the structures, stabilities, activities, and safety profiles of natural RNA molecules. In this review, we provide an examination of the mechanisms of action of endogenous miRNAs and exogenous siRNAs, the physiologic and pharmacokinetic barriers to therapeutic RNA delivery, and a summary of the chemical modifications and delivery platforms in use. We overview the pharmacology of the four FDA-approved siRNA medications (patisiran, givosiran, lumasiran, and inclisiran) as well as five siRNAs and several miRNA-based therapeutics currently in clinical trials. Furthermore, we discuss the direct expression and stable carrier-based, in vivo production of novel biologic RNAi agents for research and development. SIGNIFICANCE STATEMENT: In our review, we summarize the major concepts of RNA interference (RNAi), molecular mechanisms, and current state and challenges of RNAi drug development. We focus our discussion on the pharmacology of US Food and Drug Administration-approved RNAi medications and those siRNAs and miRNA-based therapeutics that entered the clinical investigations. Novel approaches to producing new true biological RNAi molecules for research and development are highlighted.

Substituting racemic ionizable lipids with stereopure ionizable lipids can increase mRNA delivery

Lipid nanoparticles (LNPs) have delivered siRNA and mRNA drugs in humans, underscoring the potential impact of improving the therapeutic window of next-generation LNPs. To increase the LNP therapeutic window, we applied lessons from small-molecule chemistry to ionizable lipid design. Specifically, given that stereochemistry often influences small-molecule safety and pharmacokinetics, we hypothesized that the stereochemistry of lipids within an LNP would influence mRNA delivery. We tested this hypothesis in vivo using 128 novel LNPs that included stereopure derivatives of C12-200, an ionizable lipid that when formulated into LNPs delivers RNA in mice and non-human primates but is not used clinically due to its poor tolerability. We found that a novel C12-200-S LNP delivered up to 2.8-fold and 6.1-fold more mRNA in vivo than its racemic and C12-200-R controls, respectively. To identify the potential causes leading to increased delivery, we quantified LNP biophysical traits and concluded that these did not change with stereochemistry. Instead, we found that stereopure LNPs were better tolerated than racemic LNPs in vivo. These data suggest that LNP-mediated mRNA delivery can be improved by designing LNPs to include stereopure ionizable lipids.

A hybrid nanoassembly for ultrasound-inducible cytosolic siRNA delivery and cancer sono-gene therapy

Cancer gene therapy by small-interfering RNAs (siRNAs) holds great promise but is impeded by a low cytoplasmic delivery efficiency. The past two decades have witnessed many efforts that are dedicated to discover biomaterials in order to increase cellular uptake efficiency of siRNAs. However, less attention has been paid to the lysosomal trapping dilemma that greatly restricts gene silencing outcomes. Herein, to address this challenge, we developed a sono-controllable strategy for ultrasound-promoted cytosolic siRNA delivery. A hybrid nanoassembly (HNA) was prepared via electrostatic self-assembly of a siRNA and a nona-arginine modified with protoporphyrin IX that is a sonosensitizer. After cellular uptake and exposure to sono-irradiation, HNA generated singlet oxygen to facilitate the lysosomal escape of siRNA to knock down anti-apoptotic Bcl-2 in the cytoplasm. We showed that the colocalization ratios between siRNA and the lysosome decreased from 91 % to 33 % post sono-irradiation; meanwhile, the gene silencing efficacy increased from 46 % to 68 % at 300 nM of HNA. Furthermore, sonodynamic therapy was achieved by the sonosensitizer under ultrasound irradiation, which combined gene therapy to eradicate cancer cells, resulting in a cell death rate of 82 %. This study thus presents a novel ultrasonic approach for effective cytoplasmic delivery of siRNAs and combinational sono-gene therapy of cancer.

Clinical Pharmacokinetics of Approved RNA Therapeutics

RNA-mediated drugs are a rapidly growing class of therapeutics. Over the last five years, the list of FDA-approved RNA therapeutics has expanded owing to their unique targets and prolonged pharmacological effects. Their absorption, distribution, metabolism, and excretion (ADME) have important clinical im-plications, but their pharmacokinetic properties have not been fully understood. Most RNA therapeutics have structural modifications to prevent rapid elimination from the plasma and are administered intravenously or subcutaneously, with some exceptions, for effective distribution to target organs. Distribution of drugs into tissues depends on the addition of a moiety that can be transported to the target and RNA therapeutics show a low volume of distribution because of their molecular size and negatively-charged backbone. Nucleases metabolize RNA therapeutics to a shortened chain, but their metabolic ratio is relatively low. Therefore, most RNA therapeutics are excreted in their intact form. This review covers not only ADME features but also clinical pharmacology data of the RNA therapeutics such as drug-drug interaction or population pharmacokinetic analyses. As the market of RNA therapeutics is expected to rapidly expand, comprehensive knowledge will contribute to interpreting and evaluating the pharmacological properties.

Lipid Nanoparticles for Nucleic Acid Delivery to Endothelial Cells

Endothelial cells play critical roles in circulatory homeostasis and are also the gateway to the major organs of the body. Dysfunction, injury, and gene expression profiles of these cells can cause, or are caused by, prevalent chronic diseases such as diabetes, cardiovascular disease, and cancer. Modulation of gene expression within endothelial cells could therefore be therapeutically strategic in treating longstanding disease challenges. Lipid nanoparticles (LNP) have emerged as potent, scalable, and tunable carrier systems for delivering nucleic acids, making them attractive vehicles for gene delivery to endothelial cells. Here, we discuss the functions of endothelial cells and highlight some receptors that are upregulated during health and disease. Examples and applications of DNA, mRNA, circRNA, saRNA, siRNA, shRNA, miRNA, and ASO delivery to endothelial cells and their targets are reviewed, as well as LNP composition and morphology, formulation strategies, target proteins, and biomechanical factors that modulate endothelial cell targeting. Finally, we discuss FDA-approved LNPs as well as LNPs that have been tested in clinical trials and their challenges, and provide some perspectives as to how to surmount those challenges.