Maximizing the potency of siRNA lipid nanoparticles for hepatic gene silencing in vivo

Comprehensive analysis of lipid nanoparticle formulation and preparation for RNA delivery

Nucleic acid-based therapeutics are a common approach that is increasingly popular for a wide spectrum of diseases. Lipid nanoparticles (LNPs) are promising delivery carriers that provide RNA stability, with strong transfection efficiency, favorable and tailorable pharmacokinetics, limited toxicity, and established translatability. In this review article, we describe the lipid-based delivery systems, focusing on lipid nanoparticles, the need of their use, provide a comprehensive analysis of each component, and highlight the advantages and disadvantages of the existing manufacturing processes. We further summarize the ongoing and completed clinical trials utilizing LNPs, indicating important aspects/questions worth of investigation, and analyze the future perspectives of this significant and promising therapeutic approach.

Delivery of small interfering ribonucleic acid using lipid nanoparticles prepared with pH-responsive dipeptide-conjugated lipids

The development of lipid nanoparticles (LNPs) has enabled the clinical application of small interfering ribonucleic acid (siRNA)-based therapies. Accordingly, various unique ionizable lipids have been explored for efficient siRNA delivery. However, safety concerns related to the structure of ionizable lipids have been raised. Here, we developed a pH-responsive dipeptide-conjugated lipid (DPL) for efficient, high safety siRNA delivery. We synthesized a DPL library by varying the dipeptide sequence and established a strong correlation between the knockdown efficiency of the DPL-based LNPs and the dipeptide sequence. The LNPs prepared with a DPL containing arginine (R) and glutamic acid (E) (DPL-ER) exhibited the highest knockdown efficiency. In addition, the DPL-ER-based LNPs with relatively long lipid tails (DPL-ER-C22:C22) exhibited a higher knockdown efficiency than those with short ones (DPL-ER-18:C18). The zeta potential of the DPL-ER-C22:C22-based LNPs increased as the pH decreased from 7.4 (physiological condition) to 5.5 (endosomal condition). Importantly, the DPL-ER-C22:C22-based LNPs exhibited a higher knockdown efficiency than the LNPs prepared using commercially available ionizable lipids. These results suggest that the DPL-based LNPs are safe and efficient siRNA delivery carriers.

Ionizable Cationic Lipids and Helper Lipids Synergistically Contribute to RNA Packing and Protection in Lipid-Based Nanomaterials

Lipid-based nanomaterials are used as a common delivery vehicle for RNA therapeutics. They typically include a formulation containing ionizable cationic lipids, cholesterol, phospholipids, and a small molar fraction of PEGylated lipids. The ionizable cationic lipids are considered a crucial element of the formulation for the way they mediate interactions with the anionic RNA as a function of pH. Here, we show, by means of molecular dynamics simulation of lipid formulations containing two different ionizable cationic lipids (DLinDMA and DLinDAP), that the direct interactions of those lipids with RNA, taken alone, may not be sufficient to determine the level of protection and packaging of mRNA. Our simulations help and highlight how the collective behavior of the lipids in the formulation, which determines the ability to envelop the RNA, and the level of hydration of the lipid-RNA interface may also play a significant role. This allows the drawing of a hypothesis about the experimentally observed differences in the transfection efficiency of the two ionizable cationic lipids.

Amine headgroups in ionizable lipids drive immune responses to lipid nanoparticles by binding to the receptors TLR4 and CD1d

Lipid nanoparticles (LNPs) are the most clinically advanced delivery vehicle for RNA therapeutics, partly because of established lipid structure-activity relationships focused on formulation potency. Yet such knowledge has not extended to LNP immunogenicity. Here we show that the innate and adaptive immune responses elicited by LNPs are linked to their ionizable lipid chemistry. Specifically, we show that the amine headgroups in ionizable lipids drive LNP immunogenicity by binding to Toll-like receptor 4 and CD1d and by promoting lipid-raft formation. Immunogenic LNPs favour a type-1 T-helper-cell-biased immune response marked by increases in the immunoglobulins IgG2c and IgG1 and in the pro-inflammatory cytokines tumour necrosis factor, interferon γ and the interleukins IL-6 and IL-2. Notably, the inflammatory signals originating from these receptors inhibit the production of anti-poly(ethylene glycol) IgM antibodies, preventing the often-observed loss of efficacy in the LNP-mediated delivery of siRNA and mRNA. Moreover, we identified computational methods for the prediction of the structure-dependent innate and adaptive responses of LNPs. Our findings may help accelerate the discovery of well-tolerated ionizable lipids suitable for repeated dosing.

Lipid nanoparticles-based RNA therapies for breast cancer treatment

Breast cancer (BC) prevails as a major burden on global healthcare, being the most prevalent form of cancer among women. BC is a complex and heterogeneous disease, and current therapies, such as chemotherapy and radiotherapy, frequently fall short in providing effective solutions. These treatments fail to mitigate the risk of cancer recurrence and cause severe side effects that, in turn, compromise therapeutic responses in patients. Over the last decade, several strategies have been proposed to overcome these limitations. Among them, RNA-based technologies have demonstrated their potential across various clinical applications, notably in cancer therapy. However, RNA therapies are still limited by a series of critical issues like off-target effect and poor stability in circulation. Thus, novel approaches have been investigated to improve the targeting and bioavailability of RNA-based formulations to achieve an appropriate therapeutic outcome. Lipid nanoparticles (LNPs) have been largely proven to be an advantageous carrier for nucleic acids and RNA. This perspective explores the most recent advances on RNA-based technology with an emphasis on LNPs' utilization as effective nanocarriers in BC therapy and most recent progresses in their clinical applications.

Advances in the design and delivery of RNA vaccines for infectious diseases

RNA medicines represent a paradigm shift in treatment and prevention of critical diseases of global significance, e.g., infectious diseases. The highly successful messenger RNA (mRNA) vaccines against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) were developed at record speed during the coronavirus disease 2019 pandemic. A consequence of this is exceptionally shortened vaccine development times, which in combination with adaptability makes the RNA vaccine technology highly attractive against infectious diseases and for pandemic preparedness. Here, we review state of the art in the design and delivery of RNA vaccines for infectious diseases based on different RNA modalities, including linear mRNA, self-amplifying RNA, trans-amplifying RNA, and circular RNA. We provide an overview of the clinical pipeline of RNA vaccines for infectious diseases, and present analytical procedures, which are paramount for characterizing quality attributes and guaranteeing their quality, and we discuss future perspectives for using RNA vaccines to combat pathogens beyond SARS-CoV-2.

Exploring dose and downregulation dynamics in lipid nanoparticles based siRNA therapy: Systematic review and meta-analysis

Small interfering RNA (siRNA) holds promise as a therapeutic approach for various diseases, yet challenges persist in achieving efficient delivery, biodistribution, and minimizing off-target effects. Lipidic nanoformulations are being developed to address these hurdles, but the optimal dose for preclinical investigations remains unclear. This systematic review and meta-analysis aims to determine the optimal dose of nanoformulated siRNA and explore factors influencing dose and biodistribution, informing future research in this field. A comprehensive search across four electronic databases identified 25 potential studies, with 15 selected for meta-analysis after screening. Quality assessment was conducted using SYRCLE's risk of bias tool modified for animal studies based on research question. Study found an average siRNA dose of 1.513 ± 0.377 mg/kg with mean downregulation of 65.79 % achieved, with siRNA-LNPs mainly accumulating in the liver. While individual factors showed no significant correlation, a positive association between dose and downregulation was observed, alongside other influencing factors. Extrapolating intravenous doses to potential oral doses, we suggest an initial oral dose range of 1.5 to 8 mg/kg, considering siRNA-LNPs bioavailability. These findings contribute to advancing RNA interference research and encourage further exploration of siRNA-based treatments in personalized medicine.

Inhalable Dry Powders for Lung mRNA Delivery

Despite great promise, application of mRNA therapeutics in the lung has proven challenging. Many groups have reported success instilling liquid mRNA formulations in animal models, but direct intratracheal administration of large liquid quantities to the human lung presents significant safety and distribution concerns. To accomplish safe and effective mRNA delivery to the lung, formulations must be prepared for dosing via inhalation. An inhaled mRNA delivery system for the lung must be both robust enough to survive inhalation conditions and potent enough to deliver mRNA upon reaching the lung. In this work dry powder lipid nanoparticle formulations are developed, using spray-freeze-drying, to produce stable, biologically active, inhalable dry powders for mRNA delivery. The final powders have suitable aerosolization properties, with mean mass aerodynamic diameter (MMAD) of 3-4 microns, and fine particle fraction (FPF) ≈40%, allowing for efficient mRNA delivery to the deep lung following inhalation. Importantly, the formulations developed here are suitable for use with different ionizable lipids. Four different ionizable lipid-based formulations are evaluated as powders, and all exhibit in vivo pulmonary mRNA delivery equal to that of instilled liquid formulations. These results lay promising groundwork for the eventual development of an inhalable mRNA dry powder therapeutic.

Fast and facile synthesis of amidine-incorporated degradable lipids for versatile mRNA delivery in vivo

Lipid nanoparticles (LNPs) are widely used for mRNA delivery, with cationic lipids greatly affecting biodistribution, cellular uptake, endosomal escape and transfection efficiency. However, the laborious synthesis of cationic lipids limits the discovery of efficacious candidates and slows down scale-up manufacturing. Here we develop a one-pot, tandem multi-component reaction based on the rationally designed amine-thiol-acrylate conjugation, which enables fast (1 h) and facile room-temperature synthesis of amidine-incorporated degradable (AID) lipids. Structure-activity relationship analysis of a combinatorial library of 100 chemically diverse AID-lipids leads to the identification of a tail-like amine-ring-alkyl aniline that generally affords efficacious lipids. Experimental and theoretical studies show that the embedded bulky benzene ring can enhance endosomal escape and mRNA delivery by enabling the lipid to adopt a more conical shape. The lead AID-lipid can not only mediate local delivery of mRNA vaccines and systemic delivery of mRNA therapeutics, but can also alter the tropism of liver-tropic LNPs to selectively deliver gene editors to the lung and mRNA vaccines to the spleen.

Nanoparticle-mediated universal CAR-T therapy

In recent years, chimeric antigen receptor (CAR)-T cell therapy has been highly successful in treating hematological malignancies, leading to significant advancements in the cancer immunotherapy field. However, the typical CAR-T therapy necessitates the enrichment of patients' own leukocytes for ex vivo production of CAR-T cells, this customized pattern requires a complicated and time-consuming manufacturing procedure, making it costly and less accessible. The off-the-shelf universal CAR-T strategy could reduce manufacturing costs and realize timely drug administration, presenting as an ideal substitute for typical CAR-T therapy. Utilizing nanocarriers for targeted gene delivery is one of the approaches for the realization of universal CAR-T therapy, as biocompatible and versatile nanoparticles could deliver CAR genes to generate CAR-T cells in vivo. Nanoparticle-mediated in situ generation of CAR-T cells possesses multiple advantages, including lowered cost, simplified manufacturing procedure, and shortened administration time, this strategy is anticipated to provide a potentially cost-effective alternative to current autologous CAR-T cell manufacturing, thus facilitating the prevalence and improvement of CAR-T therapy.

Safe and effective in vivo delivery of DNA and RNA using proteolipid vehicles

Genetic medicines show promise for treating various diseases, yet clinical success has been limited by tolerability, scalability, and immunogenicity issues of current delivery platforms. To overcome these, we developed a proteolipid vehicle (PLV) by combining features from viral and non-viral approaches. PLVs incorporate fusion-associated small transmembrane (FAST) proteins isolated from fusogenic orthoreoviruses into a well-tolerated lipid formulation, using scalable microfluidic mixing. Screening a FAST protein library, we identified a chimeric FAST protein with enhanced membrane fusion activity that improved gene expression from an optimized lipid formulation. Systemically administered FAST-PLVs showed broad biodistribution and effective mRNA and DNA delivery in mouse and non-human primate models. FAST-PLVs show low immunogenicity and maintain activity upon repeat dosing. Systemic administration of follistatin DNA gene therapy with FAST-PLVs raised circulating follistatin levels and significantly increased muscle mass and grip strength. These results demonstrate the promising potential of FAST-PLVs for redosable gene therapies and genetic medicines.

Enhancing RNA-lipid nanoparticle delivery: Organ- and cell-specificity and barcoding strategies

Recent advancements in RNA therapeutics highlight the critical need for precision gene delivery systems that target specific organs and cells. Lipid nanoparticles (LNPs) have emerged as key vectors in delivering mRNA and siRNA, offering protection against enzymatic degradation, enabling targeted delivery and cellular uptake, and facilitating RNA cargo release into the cytosol. This review discusses the development and optimization of organ- and cell-specific LNPs, focusing on their design, mechanisms of action, and therapeutic applications. We explore innovations such as DNA/RNA barcoding, which facilitates high-throughput screening and precise adjustments in formulations. We address major challenges, including improving endosomal escape, minimizing off-target effects, and enhancing delivery efficiencies. Notable clinical trials and recent FDA approvals illustrate the practical applications and future potential of LNP-based RNA therapies. Our findings suggest that while considerable progress has been made, continued research is essential to resolve existing limitations and bridge the gap between preclinical and clinical evaluation of the safety and efficacy of RNA therapeutics. This review highlights the dynamic progress in LNP research. It outlines a roadmap for future advancements in RNA-based precision medicine.

Comparison of the immunogenicity of mRNA-encoded and protein HIV-1 Env-ferritin nanoparticle designs

Nucleoside-modified mRNA technology has revolutionized vaccine development with the success of mRNA COVID-19 vaccines. We used modified mRNA technology for the design of envelopes (Env) to induce HIV-1 broadly neutralizing antibodies (bnAbs). However, unlike SARS-CoV-2 neutralizing antibodies that are readily made, HIV-1 bnAb induction is disfavored by the immune system because of the rarity of bnAb B cell precursors and the cross-reactivity of bnAbs targeting certain Env epitopes with host molecules, thus requiring optimized immunogen design. The use of protein nanoparticles (NPs) has been reported to enhance B cell germinal center responses to HIV-1 Env. Here, we report our experience with the expression of Env-ferritin NPs compared with membrane-bound Env gp160 when encoded by modified mRNA. We found that well-folded Env-ferritin NPs were a minority of the protein expressed by an mRNA design and were immunogenic at 20 µg but minimally immunogenic in mice at 1 µg dose in vivo and were not expressed well in draining lymph nodes (LNs) following intramuscular immunization. In contrast, mRNA encoding gp160 was more immunogenic than mRNA encoding Env-NP at 1 µg dose and was expressed well in draining LN following intramuscular immunization. Thus, analysis of mRNA expression in vitro and immunogenicity at low doses in vivo are critical for the evaluation of mRNA designs for optimal immunogenicity of HIV-1 immunogens.IMPORTANCEAn effective HIV-1 vaccine that induces protective antibody responses remains elusive. We have used mRNA technology for designs of HIV-1 immunogens in the forms of membrane-bound full-length envelope gp160 and envelope ferritin nanoparticle. Here, we demonstrated in a mouse model that the membrane-bound form induced a better response than envelope ferritin nanoparticle because of higher in vivo protein expression. The significance of our research is in highlighting the importance of analysis of mRNA design expression and low-dose immunogenicity studies for HIV-1 immunogens before moving to vaccine clinical trials.

Breaking the final barrier: Evolution of cationic and ionizable lipid structure in lipid nanoparticles to escape the endosome

In the past decade, nucleic acid therapies have seen a boon in development and clinical translation largely due to advances in nanotechnology that have enabled their safe and targeted delivery. Nanoparticles can protect nucleic acids from degradation by serum enzymes and can facilitate entry into cells. Still, achieving endosomal escape to allow nucleic acids to enter the cytoplasm has remained a significant barrier, where less than 5% of nanoparticles within the endo-lysosomal pathway are able to transfer their cargo to the cytosol. Lipid-based drug delivery vehicles, particularly lipid nanoparticles (LNPs), have been optimized to achieve potent endosomal escape, and thus have been the vector of choice in the clinic as demonstrated by their utilization in the COVID-19 mRNA vaccines. The success of LNPs is in large part due to the rational design of lipids that can specifically overcome endosomal barriers. In this review, we chart the evolution of lipid structure from cationic lipids to ionizable lipids, focusing on structure-function relationships, with a focus on how they relate to endosomal escape. Additionally, we examine recent advancements in ionizable lipid structure as well as discuss the future of lipid design.

RP-CAD for Lipid Quantification: Systematic Method Development and Intensified LNP Process Characterization

Lipid nanoparticles (LNPs) and their versatile nucleic acid payloads bear great potential as delivery systems. Despite their complex lipid composition, their quality is primarily judged by particle characteristics and nucleic acid encapsulation. In this study, we present a holistic reversed-phase (RP)-charged aerosol detection (CAD)-based method developed for commonly used LNP formulations, allowing for intensified LNP and process characterization. We used an experimental approach for power function value (PFV) optimization termed exploratory calibration, providing a single PFV (1.3) in an appropriate linearity range for all six lipids. Followed by the procedure of method calibration and validation, linearity (10-400 ng, R2 > 0.996), precision, accuracy, and robustness were effectively proven. To complement the commonly determined LNP attributes and to evaluate the process performance across LNP processing, the developed RP-CAD method was applied in a process parameter study varying the total flow rate (TFR) during microfluidic mixing. The RP-CAD method revealed a constant lipid molar ratio across processing but identified deviations in the theoretical lipid content and general lipid loss, which were both, however, entirely TFR-independent. The deviations in lipid content could be successfully traced back to the lipid stock solution preparation. In contrast, the observed lipid loss was attributable to the small-scale dialysis following microfluidic mixing. Overall, this study establishes a foundation for employing RP-CAD for lipid quantification throughout LNP processing, and it highlights the potential to extend its applicability to other LNPs, process parameter studies, or processes such as cross-flow filtration.

Lipid nanoparticle technology-mediated therapeutic gene manipulation in the eyes

Millions of people worldwide have hereditary genetic disorders, trauma, infectious diseases, or cancer of the eyes, and many of these eye diseases lead to irreversible blindness, which is a major public health burden. The eye is a relatively small and immune-privileged organ. The use of nucleic acid-based drugs to manipulate malfunctioning genes that target the root of ocular diseases is regarded as a therapeutic approach with great promise. However, there are still some challenges for utilizing nucleic acid therapeutics in vivo because of certain unfavorable characteristics, such as instability, biological carrier-dependent cellular uptake, short pharmacokinetic profiles in vivo (RNA), and on-target and off-target side effects (DNA). The development of lipid nanoparticles (LNPs) as gene vehicles is revolutionary progress that has contributed the clinical application of nucleic acid therapeutics. LNPs have the capability to entrap and transport various genetic materials such as small interfering RNA, mRNA, DNA, and gene editing complexes. This opens up avenues for addressing ocular diseases through the suppression of pathogenic genes, the expression of therapeutic proteins, or the correction of genetic defects. Here, we delve into the cutting-edge LNP technology for ocular gene therapy, encompassing formulation designs, preclinical development, and clinical translation.

Development of an Elastin-like Polypeptide-Based Nucleic Acid Delivery System Targeted to EGFR+ Bladder Cancer Cells Using a Layer-by-Layer Approach

Nucleic acid (NA)-based therapies are revolutionizing biomedical research through their ability to control cellular functions at the genetic level. This work demonstrates a versatile elastin-like polypeptide (ELP) carrier system using a layer-by-layer (LbL) formulation approach that delivers NA cargos ranging in size from siRNA to plasmids. The components of the system can be reconfigured to modulate the biochemical and biophysical characteristics of the carrier for engaging the unique features of the biological target. We show the physical characterization and biological performance of LbL ELP nucleic acid nanoparticles (LENNs) in murine and human bladder tumor cell lines. Targeting bladder tumors is difficult owing to the constant influx of urine into the bladder, leading to low contact times (typically <2 h) for therapeutic agents delivered via intravesical instillation. LENN complexes bind to bladder tumor cells within 30 min and become rapidly internalized to release their NA cargo within 60 min. Our data show that a readily adaptable NA-delivery system has been created that is flexible in its targeting ability, cargo size, and disassembly kinetics. This approach provides an alternative path to either lipid nanoparticle formulations that suffer from inefficiency and physicochemical instability or viral vectors that are plagued by manufacturing and immune rejection challenges. This agile ELP-based nanocarrier provides an alternative route for nucleic acid delivery using a biomanufacturable, biodegradable, biocompatible, and highly tunable vehicle capable of targeting cells via engagement with overexpressed cell surface receptors.

Claisen Self-Condensation of Lactones in the Synthesis of Ionizable Lipids

The Claisen self-condensation of lactones can be carried out safely and efficiently under Mukaiyama conditions, in the presence of TiCl4 and triethylamine. The primary Claisen products can be elaborated to various derivatives or converted directly into dihydroxyketones. Such compounds are valuable educts for the synthesis of ionizable lipids for the delivery of nucleic acid therapeutics and can now be accessed through a concise, economical, scalable route that avoids more technically challenging reaction sequences.

Advances in the development of lipid nanoparticles for ophthalmic therapeutics

Previously, researchers have employed Lipid nanoparticles (LNPs) to directly encapsulate medicines. In the realm of gene therapy, researchers have begun to employ lipid nanoparticles to encapsulate nucleic acids such as messenger RNA, small interfering RNA, and plasmid DNA, which are known as nucleic acid lipid nanoparticles. Recent breakthroughs in LNP-based medicine have provided significant prospects for the treatment of ocular disorders, such as corneal, choroidal, and retinal diseases. The use of LNP as a delivery mechanism for medicines and therapeutic genes can increase their effectiveness while avoiding undesired immune reactions. However, LNP-based medicines may pose ocular concerns. In this review, we discuss the general framework of LNP. Additionally, we review adjustable approaches and evaluate their possible risks. In addition, we examine newly described ocular illnesses in which LNP was utilized as a delivery mechanism. Finally, we provide perspectives for solving these potential issues.

NMR-based analysis of impact of siRNA mixing conditions on internal structure of siRNA-loaded LNP

This study aimed to assess the applicability of solution-state 1H NMR for molecular-level characterization of siRNA-loaded lipid nanoparticles (LNP). Dilinoleylmethyl-4-dimethylaminobutyrate (DLin-MC3-DMA, MC3) was used as an ionizable lipid, and siRNA-loaded LNPs were prepared by pre-mixing and post-mixing methods. The pre-mixing method involved mixing an acidic solution containing siRNA with an ethanolic lipid solution using a microfluidic mixer. The pre-mixed LNP was prepared by dialyzing the mixed solution into the phosphate buffered saline (PBS, pH 7.4). The post-mixed LNP was prepared by mixing the siRNA solution with empty LNP in an acidic condition with and without ethanol, resulting in post-mixed LNP (A) and (B), respectively. Both pre-mixed and post-mixed LNPs formed LNP particles with an average diameter of approximately 50 nm. Moreover, the ratio of encapsulated siRNA to lipid content in each LNP particle remained constant regardless of the preparation method. However, small-angle X-ray scattering measurements indicated structural variations in the siRNA-MC3 stacked bilayer structure formed in the LNPs, depending on the preparation method. Solution-state 1H NMR analysis suggested that the siRNA was incorporated uniformly into the LNP core for pre-mixed LNP compared to post-mixed LNPs. In contrast, the post-mixed LNPs contained siRNA-empty regions with local enrichment of siRNA in the LNP core. This heterogeneity was more pronounced in post-mixed LNP (B) than in post-mixed LNP (A), suggesting that ethanol facilitated the homogeneous mixing of siRNA with LNP lipids. The silencing effect of each siRNA-loaded LNP was reduced in the order of pre-mixed LNP, post-mixed LNP (A), and post-mixed LNP (B). This suggested that the heterogeneity of the siRNA-loaded LNP could cause a reduction in the silencing effect of the incorporated siRNA inside LNPs. The present study highlighted that NMR-based characterization of siRNA-loaded LNP can reveal the molecular-level heterogeneity of siRNA-loaded LNP, which helps to optimize the preparation conditions of siRNA-loaded LNP formulations.

Engineering CaP-Pickering emulsion for enhanced mRNA cancer vaccines via dual DC and NK activations

mRNA delivery systems, such as lipid nanoparticle (LNP), have made remarkable strides in improving mRNA expression, whereas immune system activation operates on a threshold. Maintaining a delicate balance between antigen expression and dendritic cell (DC) activation is vital for effective immune recognition. Here, a water-in-oil-in-water (w/o/w) Pickering emulsion stabilized with calcium phosphate nanoparticles (CaP-PME) is developed for mRNA delivery in cancer vaccination. CaP-PME efficiently transports mRNA into the cytoplasm, induces pro-inflammatory responses and activates DCs by disrupting intracellular calcium/potassium ions balance. Unlike LNP, CaP-PME demonstrates a preference for DCs, enhancing their activation and migration to lymph nodes. It elicits interferon-γ-mediated CD8+ T cell responses and promotes NK cell proliferation and activation, leading to evident NK cells infiltration and ameliorated tumor microenvironment. The prepared w/o/w Pickering emulsion demonstrates superior anti-tumor effects in E.G7 and B16-OVA tumor models, offering promising prospects as an enhanced mRNA delivery vehicle for cancer vaccinations.

Preformed Vesicle Approach to LNP Manufacturing Enhances Retinal mRNA Delivery

Complete encapsulation of nucleic acids by lipid-based nanoparticles (LNPs) is often thought to be one of the main prerequisites for successful nucleic acid delivery, as the lipid environment protects mRNA from degradation by external nucleases and assists in initiating delivery processes. However, delivery of mRNA via a preformed vesicle approach (PFV-LNPs) defies this precondition. Unlike traditional LNPs, PFV-LNPs are formed via a solvent-free mixing process, leading to a superficial mRNA localization. While demonstrating low encapsulation efficiency in the RiboGreen assay, PFV-LNPs improved delivery of mRNA to the retina by up to 50% compared to the LNP analogs across several benchmark formulations, suggesting the utility of this approach regardless of the lipid composition. Successful mRNA and gene editors' delivery is observed in the retinal pigment epithelium and photoreceptors and validated in mice, non-human primates, and human retinal organoids. Deploying PFV-LNPs in gene editing experiments result in a similar extent of gene editing compared to analogous LNP (up to 3% on genomic level) in the Ai9 reporter mouse model; but, remarkably, retinal tolerability is significantly improved for PFV-LNP treatment. The study findings indicate that the LNP formulation process can greatly influence mRNA transfection and gene editing outcomes, improving LNP treatment safety without sacrificing efficacy.

The 60-year evolution of lipid nanoparticles for nucleic acid delivery

Delivery of genetic information to the interior of target cells in vivo has been a major challenge facing gene therapies. This barrier is now being overcome, owing in part to dramatic advances made by lipid-based systems that have led to lipid nanoparticles (LNPs) that enable delivery of nucleic acid-based vaccines and therapeutics. Examples include the clinically approved COVID-19 LNP mRNA vaccines and Onpattro (patisiran), an LNP small interfering RNA therapeutic to treat transthyretin-induced amyloidosis (hATTR). In addition, a host of promising LNP-enabled vaccines and gene therapies are in clinical development. Here, we trace this success to two streams of research conducted over the past 60 years: the discovery of the transfection properties of lipoplexes composed of positively charged cationic lipids complexed with nucleic acid cargos and the development of lipid nanoparticles using ionizable cationic lipids. The fundamental insights gained from these two streams of research offer potential delivery solutions for most forms of gene therapies.

Modifying the Backbone Chemistry of PEG-Based Bottlebrush Block Copolymers for the Formation of Long-Circulating Nanoparticles

Nanoparticle physicochemical properties have received great attention in optimizing the performance of nanoparticles for biomedical applications. For example, surface functionalization with small molecules or linear hydrophilic polymers is commonly used to tune the interaction of nanoparticles with proteins and cells. However, it is challenging to control the location of functional groups within the shell for conventional nanoparticles. Nanoparticle surfaces composed of shape-persistent bottlebrush polymers allow hierarchical control over the nanoparticle shell but the effect of the bottlebrush backbone on biological interactions is still unknown. The synthesis is reported of novel heterobifunctional poly(ethylene glycol) (PEG)-norbornene macromonomers modified with various small molecules to form bottlebrush polymers with different backbone chemistries. It is demonstrated that micellar nanoparticles composed of poly(lactic acid) (PLA)-PEG bottlebrush block copolymer (BBCP) with neutral and cationic backbone modifications exhibit significantly reduced cellular uptake compared to conventional unmodified BBCPs. Furthermore, the nanoparticles display long blood circulation half-lives of ≈22 hours and enhanced tumor accumulation in mice. Overall, this work sheds light on the importance of the bottlebrush polymer backbone and provides a strategy to improve the performance of nanoparticles in biomedical applications.

Lipid nanoparticle-mediated hepatocyte delivery of siRNA and silibinin in metabolic dysfunction-associated steatotic liver disease

Lipid nanoparticle-mediated co-delivery of siRNA and small molecule holds a great potential to treat metabolic dysfunction-associated steatotic liver disease (MASLD). However, targeted delivery of therapeutics to hepatocytes remains challenging. Taking the advantage of rising low density lipoprotein receptor/very-low density lipoprotein receptor (LDLR/VLDR) levels in MASLD, the biological fate of dinonylamine-ethylene glycol chlorophosphate-1-nonanol (DNNA-COP-NA) based lipid nanoparticles (LNPs) was oriented to liver tissues via apolipoprotein E (ApoE)-LDLR/VLDLR pathway. We then adopted a three-round screening strategy to optimize the formulation with both high potency and selectivity to deliver siRNA-HIF-1α (siHIF1α) and silibinin (SLB) payloads to hepatocytes. The optimized SLB/siHIF1α-LNPs mediates great siRNA delivery and transfection of hepatocytes. In high fat diet (HFD)- and carbon tetrachloride (CCl4)-induced mouse models of MASLD, SLB/siHIF1α-LNPs enabled the silencing of hypoxia inducible factor-1α (HIF-1α), a therapeutic target primarily expressed by hepatocytes, leading to significantly reduced inflammation and liver fibrosis synergized with SLB. Moreover, it is demonstrated the hepatocyte-targeting delivery of SLB/siHIF1α-LNPs has the potential to restore the immune homeostasis by modulating the population of Tregs and cytotoxic T cells in spleen. This proof-of-concept study enable siRNA and small molecule co-delivery to hepatocytes through intrinsic variation of targeting receptors for MASLD therapy.

Organ-Targeted Ionizable Lipid Nanoparticles Facilitate Sequence-Activated Fluorogenic Probe for Precise Imaging of Inflammatory Liver Disease

Activatable near-infrared (NIR) fluorogenic probes offer a potent tool for real-time, in situ detection of hepatic biomarkers, significantly advancing the precision in diagnosing inflammatory liver disease (ILD). However, the limited distribution of small molecule fluorogenic probes in the liver and their rapid clearance impair the accuracy of fluorescence imaging and in ILD diagnosis. In this study, an effective utilization of ionizable lipid nanoparticles (iLNPs) is presented as liver-targeted carriers for efficient delivery of fluorogenic probes, aiming to overcome biodistribution barriers and achieve accurate detection of hepatic biomarkers. Based on this strategy, a liver-targeted NIR fluorogenic nanoprobe hCy-H2O2@iLNP is prepared using hCy-H2O2 as a small molecule reporter for visualizing the over-produced hydrogen peroxide (H2O2) in situ of liver. Notably, iLNPs not only significantly enhance probe accumulation in the liver, but also enable sequence activation of fluorescent nanoprobes. This response is achieved through primary liposome-dissociation release and secondary hCy-H2O2 response with pathological H2O2, enabling high-precision detection of oxidative stress in hepatocytes. These distinctive features facilitate accurate early diagnosis of acetaminophen (APAP)-induced inflammatory liver injury as well as lipopolysaccharide (LPS)-induced hepatitis. Therefore, the organ-targeted nanoprobe design strategy showcasts great potential for early and accurate diagnosis of lesions in situ in different organs.

siRNA nanoparticle targeting Usp20 lowers lipid levels and ameliorates metabolic syndrome in mice

Atherosclerotic cardiovascular disease is closely correlated with elevated low density lipoprotein-cholesterol. In feeding state, glucose and insulin activate mammalian target of rapamycin 1 that phosphorylates the deubiquitylase ubiquitin-specific peptidase 20 (USP20). USP20 then stabilizes HMG-CoA reductase, thereby increasing lipid biosynthesis. In this study, we applied clinically approved lipid nanoparticles to encapsulate the siRNA targeting Usp20. We demonstrated that silencing of hepatic Usp20 by siRNA decreased body weight, improved insulin sensitivity, and increased energy expenditure through elevating UCP1. In Ldlr-/- mice, silencing Usp20 by siRNA decreased lipid levels and prevented atherosclerosis. This study suggests that the RNAi-based therapy targeting hepatic Usp20 has a translational potential to treat metabolic disease.

Nanoparticles targeting immune checkpoint protein VISTA induce potent antitumor immunity

BACKGROUND

Immune checkpoint protein V-domain immunoglobulin suppressor of T cell activation (VISTA) controls antitumor immunity and is a valuable target for cancer immunotherapy. Previous mechanistic studies have indicated that VISTA impairs the toll-like receptor (TLR)-mediated activation of myeloid antigen-presenting cells, promoting the expansion of myeloid-derived suppressor cells, and suppressing tumor-reactive cytotoxic T cell function.

METHODS

The aim of this study was to develop a dual-action lipid nanoparticle (dual-LNP) coloaded with VISTA-specific siRNA and TLR9 agonist CpG oligonucleotide. We used three murine preclinical tumor models, melanoma YUMM1.7, melanoma B16F10, and colon carcinoma MC38 to assess the functional synergy of the two cargoes of the dual LNP and therapeutic efficacy.

RESULTS

The dual-LNP synergistically augmented antitumor immune responses and rejected large established tumors whereas LNPs containing VISTA siRNA or CpG alone were ineffective. In comparison with therapies using the soluble CpG and a VISTA-specific monoclonal antibody, the dual-LNP demonstrated superior therapeutic efficacy yet with reduced systemic inflammatory cytokine production. In three murine models, the dual-LNP treatment achieved a high cure rate. Tumor rejection was associated with influx of immune cells to tumor tissues, augmented dendritic cell activation, production of proinflammatory cytokines, and improved function of cytotoxic T cells.

CONCLUSIONS

Our studies show the dual-LNP ensured codelivery of its synergistic cargoes to tumor-infiltrating myeloid cells, leading to simultaneous silencing of VISTA and stimulation of TLR9. As a result, the dual-LNP drove a highly potent antitumor immune response that rejected large aggressive tumors, thus may be a promising therapeutic platform for treating immune-cold tumors.

Time-Resolved Inspection of Ionizable Lipid-Facilitated Lipid Nanoparticle Disintegration and Cargo Release at an Early Endosomal Membrane Mimic

Advances in lipid nanoparticle (LNP) design have contributed notably to the emergence of the current clinically approved mRNA-based vaccines and are of high relevance for delivering mRNA to combat diseases where therapeutic alternatives are sparse. LNP-assisted mRNA delivery utilizes ionizable lipid-mediated cargo translocation across the endosomal membrane driven by the acidification of the endosomal environment. However, this process occurs at a low efficiency, a few percent at the best. Utilizing surface-sensitive fluorescence microscopy with a single LNP and mRNA resolution, we have investigated pH-controlled interactions between individual LNPs and a planar anionic supported lipid bilayer (SLB) formed on nanoporous silica, mimicking the electrostatic conditions of the early endosomal membrane. For LNPs with an average diameter of 140 nm, fusion with the anionic SLB preferentially occurred when the pH was reduced from 6.6 to 6.0. Furthermore, there was a delay in the onset of LNP fusion after the pH drop, and upon fusion, a significant fraction (>70%) of mRNA was released into the acidic solution representing the endosomal lumen, while a fraction of mRNA remained bound to the SLB even after reversing the pH to neutral cytosolic conditions. Finally, a comparison of the fusion efficiency of two LNP formulations with different surface concentrations of gel-forming lipids correlated with differences in the protein translation efficiency previously observed in human primary cell transfection studies. Together, these findings emphasize the relevance of biophysical investigations of ionizable lipid-containing LNP-assisted mRNA delivery mechanisms while potentially also offering means to optimize the design of LNPs with enhanced endosomal escape capabilities.

Robust genome and cell engineering via in vitro and in situ circularized RNAs

Circularization can improve RNA persistence, yet simple and scalable approaches to achieve this are lacking. Here we report two methods that facilitate the pursuit of circular RNAs (cRNAs): cRNAs developed via in vitro circularization using group II introns, and cRNAs developed via in-cell circularization by the ubiquitously expressed RtcB protein. We also report simple purification protocols that enable high cRNA yields (40-75%) while maintaining low immune responses. These methods and protocols facilitate a broad range of applications in stem cell engineering as well as robust genome and epigenome targeting via zinc finger proteins and CRISPR-Cas9. Notably, cRNAs bearing the encephalomyocarditis internal ribosome entry enabled robust expression and persistence compared with linear capped RNAs in cardiomyocytes and neurons, which highlights the utility of cRNAs in these non-dividing cells. We also describe genome targeting via deimmunized Cas9 delivered as cRNA and a long-range multiplexed protein engineering methodology for the combinatorial screening of deimmunized protein variants that enables compatibility between persistence of expression and immunogenicity in cRNA-delivered proteins. The cRNA toolset will aid research and the development of therapeutics.

Acid-degradable lipid nanoparticles enhance the delivery of mRNA

Lipid nanoparticle (LNP)-mRNA complexes are transforming medicine. However, the medical applications of LNPs are limited by their low endosomal disruption rates, high toxicity and long tissue persistence times. LNPs that rapidly hydrolyse in endosomes (RD-LNPs) could solve the problems limiting LNP-based therapeutics and dramatically expand their applications but have been challenging to synthesize. Here we present an acid-degradable linker termed 'azido-acetal' that hydrolyses in endosomes within minutes and enables the production of RD-LNPs. Acid-degradable lipids composed of polyethylene glycol lipids, anionic lipids and cationic lipids were synthesized with the azido-acetal linker and used to generate RD-LNPs, which significantly improved the performance of LNP-mRNA complexes in vitro and in vivo. Collectively, RD-LNPs delivered mRNA more efficiently to the liver, lung, spleen and brains of mice and to haematopoietic stem and progenitor cells in vitro than conventional LNPs. These experiments demonstrate that engineering LNP hydrolysis rates in vivo has great potential for expanding the medical applications of LNPs.

Advances in the study of LNPs for mRNA delivery and clinical applications

Messenger ribonucleic acid (mRNA) was discovered in 1961 as an intermediary for transferring genetic information from DNA to ribosomes for protein synthesis. The COVID-19 pandemic brought worldwide attention to mRNA vaccines. The emergency use authorization of two COVID-19 mRNA vaccines, BNT162b2 and mRNA-1273, were major achievements in the history of vaccine development. Lipid nanoparticles (LNPs), one of the most superior non-viral delivery vectors available, have made many exciting advances in clinical translation as part of the COVID-19 vaccine and therefore has the potential to accelerate the clinical translation of many gene drugs. In addition, due to these small size, biocompatibility and excellent biodegradability, LNPs can efficiently deliver nucleic acids into cells, which is particularly important for current mRNA therapeutic regimens. LNPs are composed cationic or pH-dependent ionizable lipid bilayer, polyethylene glycol (PEG), phospholipids, and cholesterol, represents an advanced system for the delivery of mRNA vaccines. Furthermore, optimization of these four components constituting the LNPs have demonstrated enhanced vaccine efficacy and diminished adverse effects. The incorporation of biodegradable lipids enhance the biocompatibility of LNPs, thereby improving its potential as an efficacious therapeutic approach for a wide range of challenging and intricate diseases, encompassing infectious diseases, liver disorders, cancer, cardiovascular diseases, cerebrovascular conditions, among others. Consequently, this review aims to furnish the scientific community with the most up-to-date information regarding mRNA vaccines and LNP delivery systems.

Discovery of a Peptoid-Based Nanoparticle Platform for Therapeutic mRNA Delivery via Diverse Library Clustering and Structural Parametrization

Nanoparticle-mediated mRNA delivery has emerged as a promising therapeutic modality, but its growth is still limited by the discovery and optimization of effective and well-tolerated delivery strategies. Lipid nanoparticles containing charged or ionizable lipids are an emerging standard for in vivo mRNA delivery, so creating facile, tunable strategies to synthesize these key lipid-like molecules is essential to advance the field. Here, we generate a library of N-substituted glycine oligomers, peptoids, and undertake a multistage down-selection process to identify lead candidate peptoids as the ionizable component in our Nutshell nanoparticle platform. First, we identify a promising peptoid structural motif by clustering a library of >200 molecules based on predicted physical properties and evaluate members of each cluster for reporter gene expression in vivo. Then, the lead peptoid motif is optimized using design of experiments methodology to explore variations on the charged and lipophilic portions of the peptoid, facilitating the discovery of trends between structural elements and nanoparticle properties. We further demonstrate that peptoid-based Nutshells leads to expression of therapeutically relevant levels of an anti-respiratory syncytial virus antibody in mice with minimal tolerability concerns or induced immune responses compared to benchmark ionizable lipid, DLin-MC3-DMA. Through this work, we present peptoid-based nanoparticles as a tunable delivery platform that can be optimized toward a range of therapeutic programs.

Chemical Design Strategy of Ionizable Lipids for In Vivo mRNA Delivery

Lipid nanoparticles (LNPs) are the most clinically successful drug delivery systems that have accelerated the development of mRNA drugs and vaccines. Among various structural components of LNPs, more recent attention has been paid in ionizable lipids (ILs) that was supposed as the key component in determining the effectiveness of LNPs for in vivo mRNA delivery. ILs are typically comprised of three moieties including ionizable heads, linkers, and hydrophobic tails, which suggested that the combination of different functional groups in three moieties could produce ILs with diverse chemical structures and biological identities. In this concept article, we provide a summary of chemical design strategy for high-performing IL candidates and discuss their structure-activity relationships for shifting tissue-selective mRNA delivery. We also propose an outlook for the development of next-generation ILs, enabling the broader translation of mRNA formulated with LNPs.

Ionizable Drugs Enable Intracellular Delivery of Co-Formulated siRNA

Targeting complementary pathways in diseases such as cancer can be achieved with co-delivery of small interfering ribonucleic acid (siRNA) and small molecule drugs; however, current formulation strategies are typically limited to one, but not both. Here, ionizable small molecule drugs and siRNA are co-formulated in drug-rich nanoparticles. Ionizable analogs of the selective estrogen receptor degrader fulvestrant self-assemble into colloidal drug aggregates and cause endosomal disruption, allowing co-delivery of siRNA against a non-druggable target. siRNA is encapsulated in lipid-stabilized, drug-rich colloidal nanoparticles where the ionizable lipid used in conventional lipid nanoparticles is replaced with an ionizable fulvestrant analog. The selection of an appropriate phospholipid and formulation buffer enables endocytosis and potent reporter gene knockdown in cancer cells. Importantly, siRNA targeting cyclin E1 is effectively delivered to drug-resistant breast cancer cells, demonstrating the utility of this approach. This strategy opens the possibility of using ionizable drugs to co-deliver RNA and ultimately improve therapeutic outcomes.

Impact of in vivo fate of STING agonist-loaded lipid nanoparticles on antitumor immunity

Therapeutically manipulating the stimulator of interferon genes (STING) pathway has promising potential for enhancing antitumor immunity. Agonists of this pathway (STING agonists) are being evaluated in clinical trials. Loading the STING agonists into lipid nanoparticles (LNPs) increases their safety and efficacy. We previously developed STING agonists loaded LNPs consisting of the ionizable lipid YSK12-C4 (YSK12-LNPs), which showed significant antitumor effects. However, it is largely unclear how the in vivo fate of STING agonists loaded LNPs affects the antitumor immune responses. In this study, we compared the YSK12-LNPs with LNPs composed of DLin-MC3-DMA (MC3-LNPs) showing different in vivo fates. Biodistribution and flow cytometry analyses of mouse tissues revealed that the MC3-LNPs delivered higher amounts of STING agonists to the liver than the YSK12-LNPs. Additionally, significantly more liver leukocytes internalized the MC3-LNPs than the YSK12-LNPs. In contrast, the YSK12-LNPs delivered higher amounts of STING agonists to the liver leukocytes than the MC3-LNPs, leading to the effective induction of innate immunity and inflammation in the tumors. However, the antitumor effects in the B16-F10 lung metastasis and CT26 tumor models were comparable. Interestingly, flow cytometry analyses suggested that the YSK12-LNPs were more likely to activate natural killer cells and M1 macrophages, while the MC3-LNPs were more likely to activate CD8+ T cells. Our data suggest that different antitumor immune response mechanisms may operate depending on the characteristics and distribution of the LNPs.

Ionizable nanoemulsions for RNA delivery into the central nervous system - importance of diffusivity

Lipid nanoparticles (LNPs) currently dominate the RNA delivery landscape; however their limited diffusivity hampers targeted tissue dissemination, and, hence, their capacity for intracellular drug delivery. This is especially relevant for tissues such as the central nervous system (CNS), where overcoming proactive brain barriers is crucial for the efficacy of genetic therapeutics. This research aimed to create ionizable nanoemulsions (iNEs), a new generation of RNA delivery systems with enhanced diffusivity. The developed iNEs (consisting of the combination of C12-200, DOPE, Vitamin E, and DMG-PEG) with a size below 100 nm, neutral surface charge, and high RNA loading capacity, showed excellent cell viability and transfection efficiency in various cellular models, including neurons, astrocytes, and microglia. Subsequently, iNEs containing mRNA GFP were tested for CNS transfection, highlighting their exceptional diffusivity and selective transfection of neurons following intra-parenchymal administration.

Lipid nanoparticle (LNP) mediated mRNA delivery in cardiovascular diseases: Advances in genome editing and CAR T cell therapy

Cardiovascular diseases (CVDs) are the leading cause of global mortality among non-communicable diseases. Current cardiac regeneration treatments have limitations and may lead to adverse reactions. Hence, innovative technologies are needed to address these shortcomings. Messenger RNA (mRNA) emerges as a promising therapeutic agent due to its versatility in encoding therapeutic proteins and targeting "undruggable" conditions. It offers low toxicity, high transfection efficiency, and controlled protein production without genome insertion or mutagenesis risk. However, mRNA faces challenges such as immunogenicity, instability, and difficulty in cellular entry and endosomal escape, hindering its clinical application. To overcome these hurdles, lipid nanoparticles (LNPs), notably used in COVID-19 vaccines, have a great potential to deliver mRNA therapeutics for CVDs. This review highlights recent progress in mRNA-LNP therapies for CVDs, including Myocardial Infarction (MI), Heart Failure (HF), and hypercholesterolemia. In addition, LNP-mediated mRNA delivery for CAR T-cell therapy and CRISPR/Cas genome editing in CVDs and the related clinical trials are explored. To enhance the efficiency, safety, and clinical translation of mRNA-LNPs, advanced technologies like artificial intelligence (AGILE platform) in RNA structure design, and optimization of LNP formulation could be integrated. We conclude that the strategies to facilitate the extra-hepatic delivery and targeted organ tropism of mRNA-LNPs (SORT, ASSET, SMRT, and barcoded LNPs) hold great prospects to accelerate the development and translation of mRNA-LNPs in CVD treatment.

Expanding RNAi to Kidneys, Lungs, and Spleen via Selective ORgan Targeting (SORT) siRNA Lipid Nanoparticles

Inhibition of disease-causing mutations using RNA interference (RNAi) has resulted in clinically approved medicines with additional candidates in late stage trials. However, targetable tissues currently in preclinical development are limited to liver following systemic intravenous (IV) administration because predictable delivery of siRNA to non-liver tissues remains an unsolved challenge. Here, evidence of durable extrahepatic gene silencing enabled by siRNA Selective ORgan Targeting lipid nanoparticles (siRNA SORT LNPs) to the kidneys, lungs, and spleen is provided. LNPs excel at dose-dependent silencing of tissue-enriched endogenous targets resulting in 60%-80% maximal knockdown after a single IV injection and up to 88% downregulation of protein expression in mouse lungs after two doses. To examine knockdown potency and unbiased organ targeting, B6.129TdTom/EGFP mice that constitutively express the TdTomato transgene across all cell types are utilized to demonstrate 58%, 45%, and 15% reduction in TdTomato fluorescence in lungs, spleen, and kidneys, respectively. Finally, physiological relevance of siRNA SORT LNP-mediated gene silencing is established via acute suppression of endogenous Tie2 which induces lung-specific phenotypic alteration of vascular endothelial barrier. Due to plethora of extrahepatic diseases that may benefit from RNAi interventions, it is anticipated that the findings will expand preclinical landscape of therapeutic targets beyond the liver.

Rational design of lipid nanoparticles: overcoming physiological barriers for selective intracellular mRNA delivery

This review introduces the typical delivery process of messenger RNA (mRNA) nanomedicines and concludes that the delivery involves a at least four-step SCER cascade and that high efficiency at every step is critical to guarantee high overall therapeutic outcomes. This SCER cascade process includes selective organ-targeting delivery, cellular uptake, endosomal escape, and cytosolic mRNA release. Lipid nanoparticles (LNPs) have emerged as a state-of-the-art vehicle for in vivo mRNA delivery. The review emphasizes the importance of LNPs in achieving selective, efficient, and safe mRNA delivery. The discussion then extends to the technical and clinical considerations of LNPs, detailing the roles of individual components in the SCER cascade process, especially ionizable lipids and helper phospholipids. The review aims to provide an updated overview of LNP-based mRNA delivery, outlining recent innovations and addressing challenges while exploring future developments for clinical translation over the next decade.

The mRNA vaccine platform for veterinary species

Vaccination has proven to be an effective means of controlling pathogens in animals. Since the introduction of veterinary vaccines in the 19th century, several generations of vaccines have been introduced. These vaccines have had a positive impact on global animal health and production. Despite, the success of veterinary vaccines, there are still some pathogens for which there are no effective vaccines available, such as African swine fever. Further, animal health is under the constant threat of emerging and re-emerging pathogens, some of which are zoonotic and can pose a threat to human health. The severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) pandemic has highlighted the need for new vaccine platforms that are safe and efficacious, but also importantly, are adaptable and can be modified rapidly to match the circulating pathogens. mRNA vaccines have been shown to be an effective vaccine platform against various viral and bacterial pathogens. This review will cover some of the recent advances in the field of mRNA vaccines for veterinary species. Moreover, various mRNA vaccines and their delivery methods, as well as their reported efficacy, will be discussed. Current limitations and future prospects of this vaccine platform in veterinary medicine will also be discussed.

Computationally designed mRNA-launched protein nanoparticle vaccines

Both protein nanoparticle and mRNA vaccines were clinically de-risked during the COVID-19 pandemic1-6. These vaccine modalities have complementary strengths: antigen display on protein nanoparticles can enhance the magnitude, quality, and durability of antibody responses7-10, while mRNA vaccines can be rapidly manufactured11 and elicit antigen-specific CD4 and CD8 T cells12,13. Here we leverage a computationally designed icosahedral protein nanoparticle that was redesigned for optimal secretion from eukaryotic cells14 to develop an mRNA-launched nanoparticle vaccine for SARS-CoV-2. The nanoparticle, which displays 60 copies of a stabilized variant of the Wuhan-Hu-1 Spike receptor binding domain (RBD)15, formed monodisperse, antigenically intact assemblies upon secretion from transfected cells. An mRNA vaccine encoding the secreted RBD nanoparticle elicited 5- to 28-fold higher levels of neutralizing antibodies than an mRNA vaccine encoding membrane-anchored Spike, induced higher levels of CD8 T cells than the same immunogen when delivered as an adjuvanted protein nanoparticle, and protected mice from vaccine-matched and -mismatched SARS-CoV-2 challenge. Our data establish that delivering protein nanoparticle immunogens via mRNA vaccines can combine the benefits of each modality and, more broadly, highlight the utility of computational protein design in genetic immunization strategies.

Synthesis of Lipidated Ligands and Formulation of Glia-Specific LNPs for RNAi-Mediated BBB Protection

Pro-inflammatory polarization of microglia and astrocytes results in neuroinflammation and blood-brain barrier (BBB) disruption after a primary traumatic brain injury (TBI). Herein, we demonstrate that the dual-ligand functionalized lipid nanoparticles (AM31 LNPs) were actively and specifically internalized by microglia and astrocytes via mannose receptor (MR)- and adenosine receptor (AR)-mediated endocytosis, respectively, in a mouse model of TBI. Systemic administration of AM31 LNPs carrying siRNA against p65 resulted in internalization by the glial cells in the peri-infarct region and a robust knockdown of p65 at both mRNA and protein levels in these cells, leading to significant down-regulation of key pro-inflammatory cytokines and up-regulation of key anti-inflammatory cytokines. AM31 LNP-mediated silencing of p65 ameliorated TBI-induced BBB disruption. Our data proved that AM 31 LNP is a promising vehicle for RNA therapeutics for targeting microglia and astrocytes in neural disorder.

Lipid-nanoparticle-enabled nucleic acid therapeutics for liver disorders

Inherited genetic disorders of the liver pose a significant public health burden. Liver transplantation is often limited by the availability of donor livers and the exorbitant costs of immunosuppressive therapy. To overcome these limitations, nucleic acid therapy provides a hopeful alternative that enables gene repair, gene supplementation, and gene silencing with suitable vectors. Though viral vectors are the most efficient and preferred for gene therapy, pre-existing immunity debilitating immune responses limit their use. As a potential alternative, lipid nanoparticle-mediated vectors are being explored to deliver multiple nucleic acid forms, including pDNA, mRNA, siRNA, and proteins. Herein, we discuss the broader applications of lipid nanoparticles, from protein replacement therapy to restoring the disease mechanism through nucleic acid delivery and gene editing, as well as multiple preclinical and clinical studies as a potential alternative to liver transplantation.

An overview of lipid constituents in lipid nanoparticle mRNA delivery systems

mRNA therapeutics have shown great potential for a broad spectrum of disease treatment. However, the challenges of mRNA's inherent instability and difficulty in cellular entry have hindered its progress in the biomedical field. To address the cellular barriers and deliver mRNA to cells of interest, various delivery systems are designed. Among these, lipid nanoparticles (LNPs) stand out as the most extensively used mRNA delivery systems, particularly following the clinical approvals of corona virus disease 2019 (COVID-19) mRNA vaccines. LNPs are comprised of ionizable cationic lipids, phospholipids, cholesterol, and polyethylene glycol derived lipids (PEG-lipids). In this review, we primarily summarize the recent advancements of the LNP mRNA delivery technology, focusing on the structures of four lipid constituents and their biomedical applications. We delve into structure-activity relationships of the lipids, while also exploring the future prospects and challenges in developing more efficacious mRNA delivery systems. This article is categorized under: Therapeutic Approaches and Drug Discovery > Emerging Technologies Biology-Inspired Nanomaterials > Lipid-Based Structures Nanotechnology Approaches to Biology > Nanoscale Systems in Biology.

High-Throughput In Vivo Screening Identifies Differential Influences on mRNA Lipid Nanoparticle Immune Cell Delivery by Administration Route

Immune modulation through the intracellular delivery of nucleoside-modified mRNA to immune cells is an attractive approach for in vivo immunoengineering, with applications in infectious disease, cancer immunotherapy, and beyond. Lipid nanoparticles (LNPs) have come to the fore as a promising nucleic acid delivery platform, but LNP design criteria remain poorly defined, making the rate-limiting step for LNP discovery the screening process. In this study, we employed high-throughput in vivo LNP screening based on molecular barcoding to investigate the influence of LNP composition on immune tropism with applications in vaccines and systemic immunotherapies. Screening a large LNP library under both intramuscular (i.m.) and intravenous (i.v.) injection, we observed differential influences on LNP uptake by immune populations across the two administration routes, gleaning insight into LNP design criteria for in vivo immunoengineering. In validation studies, the lead LNP formulation for i.m. administration demonstrated substantial mRNA translation in the spleen and draining lymph nodes with a more favorable biodistribution profile than LNPs formulated with the clinical standard ionizable lipid DLin-MC3-DMA (MC3). The lead LNP formulations for i.v. administration displayed potent immune transfection in the spleen and peripheral blood, with one lead LNP demonstrating substantial transfection of splenic dendritic cells and another inducing substantial transfection of circulating monocytes. Altogether, the immunotropic LNPs identified by high-throughput in vivo screening demonstrated significant promise for both locally- and systemically-delivered mRNA and confirmed the value of the LNP design criteria gleaned from our screening process, which could potentially inform future endeavors in mRNA vaccine and immunotherapy applications.

Optimized lipid nanoparticles (LNPs) for organ-selective nucleic acids delivery in vivo

Nucleic acid therapeutics offer tremendous promise for addressing a wide range of common public health conditions. However, the in vivo nucleic acids delivery faces significant biological challenges. Lipid nanoparticles (LNPs) possess several advantages, such as simple preparation, high stability, efficient cellular uptake, endosome escape capabilities, etc., making them suitable for delivery vectors. However, the extensive hepatic accumulation of LNPs poses a challenge for successful development of LNPs-based nucleic acid therapeutics for extrahepatic diseases. To overcome this hurdle, researchers have been focusing on modifying the surface properties of LNPs to achieve precise delivery. The review aims to provide current insights into strategies for LNPs-based organ-selective nucleic acid delivery. In addition, it delves into the general design principles, targeting mechanisms, and clinical development of organ-selective LNPs. In conclusion, this review provides a comprehensive overview to provide guidance and valuable insights for further research and development of organ-selective nucleic acid delivery systems.

Delivery of mRNA Encoding Interleukin-12 and a Stimulator of Interferon Genes Agonist Potentiates Antitumor Efficacy through Reversing T Cell Exhaustion

T cell exhaustion has emerged as a major hurdle that impedes the clinical translation of stimulator of interferon genes (STING) agonists. It is crucial to explore innovative strategies to rejuvenate exhausted T cells and potentiate the antitumor efficacy. Here, we propose an approach utilizing MSA-2 as a STING agonist, along with nanoparticle-mediated delivery of mRNA encoding interleukin-12 (IL-12) to restore the function of T cells. We developed a lipid nanoparticle (DMT7-IL12 LNP) that encapsulated IL12 mRNA. Our findings convincingly demonstrated that the combination of MSA-2 and DMT7-IL12 LNP can effectively reverse the exhausted T cell phenotype, as evidenced by the enhanced secretion of cytokines, such as tumor necrosis factor alpha, interferon gamma, and Granzyme B, coupled with reduced levels of inhibitory molecules such as T cell immunoglobulin and mucin domain-3 and programmed cell death protein-1 on CD8+ T cells. Furthermore, this approach led to improved survival and tumor regression without causing any systemic toxicity in melanoma and lung metastasis models. These findings suggest that mRNA encoding IL-12 in conjunction with STING agonists has the potential to confer superior clinical outcomes, representing a promising advancement in cancer immunotherapy.

Transient growth factor expression via mRNA in lipid nanoparticles promotes hepatocyte cell therapy in mice

Primary human hepatocyte (PHH) transplantation is a promising alternative to liver transplantation, whereby liver function could be restored by partial repopulation of the diseased organ with healthy cells. However, currently PHH engraftment efficiency is low and benefits are not maintained long-term. Here we refine two male mouse models of human chronic and acute liver diseases to recapitulate compromised hepatocyte proliferation observed in nearly all human liver diseases by overexpression of p21 in hepatocytes. In these clinically relevant contexts, we demonstrate that transient, yet robust expression of human hepatocyte growth factor and epidermal growth factor in the liver via nucleoside-modified mRNA in lipid nanoparticles, whose safety was validated with mRNA-based COVID-19 vaccines, drastically improves PHH engraftment, reduces disease burden, and improves overall liver function. This strategy may overcome the critical barriers to clinical translation of cell therapies with primary or stem cell-derived hepatocytes for the treatment of liver diseases.