Lipid Nanoparticle Systems for Enabling Gene Therapies

Lipid nanoparticles for delivery of messenger RNA to the back of the eye

Retinal gene therapy has had unprecedented success in generating treatments that can halt vision loss. However, immunogenic response and long-term toxicity with the use of viral vectors remain a concern. Non-viral vectors are relatively non-immunogenic, scalable platforms that have had limited success with DNA delivery to the eye. Messenger RNA (mRNA) therapeutics has expanded the ability to achieve high gene expression while eliminating unintended genomic integration or the need to cross the restrictive nuclear barrier. Lipid-based nanoparticles (LNPs) remain at the forefront of potent delivery vectors for nucleic acids. Herein, we tested eleven different LNP variants for their ability to deliver mRNA to the back of the eye. LNPs that contained ionizable lipids with low pKa and unsaturated hydrocarbon chains showed the highest amount of reporter gene transfection in the retina. The kinetics of gene expression showed a rapid onset (within 4 h) that persisted for 96 h. The gene delivery was cell-type specific with majority of the expression in the retinal pigmented epithelium (RPE) and limited expression in the Müller glia. LNP-delivered mRNA can be used to treat monogenic retinal degenerative disorders of the RPE. The transient nature of mRNA-based therapeutics makes it desirable for applications that are directed towards retinal reprogramming or genome editing. Overall, non-viral delivery of RNA therapeutics to diverse cell types within the retina can provide transformative new approaches to prevent blindness.

PEG-OligoRNA Hybridization of mRNA for Developing Sterically Stable Lipid Nanoparticles toward In Vivo Administration

Lipid nanoparticles (LNPs) exhibit high potential as carriers of messenger RNA (mRNA). However, the arduous preparation process of mRNA-loaded LNPs remains a huge obstacle for their widespread clinical application. Herein, we tackled this issue by mRNA PEGylation through hybridization with polyethylene glycol (PEG)-conjugated RNA oligonucleotides (PEG-OligoRNAs). Importantly, mRNA translational activity was preserved even after hybridization of 20 PEG-OligoRNAs per mRNA. The straightforward mixing of the PEGylated mRNA with lipofectamine LTX, a commercial lipid-based carrier, just by pipetting in aqueous solution, allowed the successful preparation of mRNA-loaded LNPs with a diameter below 100 nm, whereas the use of non-PEGylated mRNA provided large aggregates above 100- and 1000-nm. In vivo, LNPs prepared from PEG-OligoRNA-hybridized mRNA exhibited high structural stability in biological milieu, without forming detectable aggregates in mouse blood after intravenous injection. In contrast, LNPs from non-PEGylated mRNA formed several micrometer-sized aggregates in blood, leading to rapid clearance from blood circulation and deposition of the aggregates in lung capillaries. Our strategy of mRNA PEGylation was also versatile to prevent aggregation of another type of mRNA-loaded LNP, DOTAP/Chol liposomes. Together, our approach provides a simple and robust preparation method to LNPs for in vivo application.

Oral delivery of non-viral nucleic acid-based therapeutics - do we have the guts for this?

Gene therapy with RNA and pDNA-based drugs is limited by poor enzymatic stability and poor cellular permeation. The delivery of nucleic acids, in particular by the oral route, remains a major hurdle. This review will focus on the barriers to the oral delivery of nucleic acids and the strategies, in particular formulation strategies, which have been developed to overcome these barriers. Due to their very low oral bioavailability, the most obvious and most investigated biomedical applications for their oral delivery are related to the local treatment of inflammatory bowel diseases and colorectal cancers. Preclinical data but not yet clinical studies support the potential use of the oral route for the local delivery of formulated nucleic acid-based drugs.

Huntingtin Lowering Strategies for Disease Modification in Huntington's Disease

Huntington's disease is caused by an abnormally expanded CAG repeat expansion in the HTT gene, which confers a predominant toxic gain of function in the mutant huntingtin (mHTT) protein. There are currently no disease-modifying therapies available, but approaches that target proximally in disease pathogenesis hold great promise. These include DNA-targeting techniques such as zinc-finger proteins, transcription activator-like effector nucleases, and CRISPR/Cas9; post-transcriptional huntingtin-lowering approaches such as RNAi, antisense oligonucleotides, and small-molecule splicing modulators; and novel methods to clear the mHTT protein, such as proteolysis-targeting chimeras. Improvements in the delivery and distribution of such agents as well as the development of objective biomarkers of disease and of HTT lowering pharmacodynamic outcomes have brought these potential therapies to the forefront of Huntington's disease research, with clinical trials in patients already underway.

Nanoscale platforms for messenger RNA delivery

Messenger RNA (mRNA) has become a promising class of drugs for diverse therapeutic applications in the past few years. A series of clinical trials are ongoing or will be initiated in the near future for the treatment of a variety of diseases. Currently, mRNA-based therapeutics mainly focuses on ex vivo transfection and local administration in clinical studies. Efficient and safe delivery of therapeutically relevant mRNAs remains one of the major challenges for their broad applications in humans. Thus, effective delivery systems are urgently needed to overcome this limitation. In recent years, numerous nanoscale biomaterials have been constructed for mRNA delivery in order to protect mRNA from extracellular degradation and facilitate endosomal escape after cellular uptake. Nanoscale platforms have expanded the feasibility of mRNA-based therapeutics, and enabled its potential applications to protein replacement therapy, cancer immunotherapy, therapeutic vaccines, regenerative medicine, and genome editing. This review focuses on recent advances, challenges, and future directions in nanoscale platforms designed for mRNA delivery, including lipid and lipid-derived nanoparticles, polymer-based nanoparticles, protein derivatives mRNA complexes, and other types of nanomaterials. This article is categorized under: Nanotechnology Approaches to Biology > Nanoscale Systems in Biology Biology-Inspired Nanomaterials > Lipid-Based Structures Biology-Inspired Nanomaterials > Nucleic Acid-Based Structures.

mRNA as a Transformative Technology for Vaccine Development to Control Infectious Diseases

In the last two decades, there has been growing interest in mRNA-based technology for the development of prophylactic vaccines against infectious diseases. Technological advancements in RNA biology, chemistry, stability, and delivery systems have accelerated the development of fully synthetic mRNA vaccines. Potent, long-lasting, and safe immune responses observed in animal models, as well as encouraging data from early human clinical trials, make mRNA-based vaccination an attractive alternative to conventional vaccine approaches. Thanks to these data, together with the potential for generic, low-cost manufacturing processes and the completely synthetic nature, the prospects for mRNA vaccines are very promising. In addition, mRNA vaccines have the potential to streamline vaccine discovery and development, and facilitate a rapid response to emerging infectious diseases. In this review, we overview the unique attributes of mRNA vaccine approaches, review the data of mRNA vaccines against infectious diseases, discuss the current challenges, and highlight perspectives about the future of this promising technology.

Design concepts of polyplex micelles for in vivo therapeutic delivery of plasmid DNA and messenger RNA

Nonviral delivery of plasmid (p)DNA or messenger (m)RNA is a safe and promising therapeutic option to continuously supply therapeutic proteins into diseased tissues. In most cases of in vivo pDNA and mRNA delivery, these nucleic acids are loaded into carriers based on cationic polymers and/or lipids to prevent nuclease-mediated degradation before reaching target cells. The carriers should also evade host clearance mechanisms, including uptake by scavenger cells and filtration in the spleen. Installation of ligands onto the carriers can facilitate their rapid uptake into target cells. Meanwhile, carrier toxicity should be minimized not only for preventing undesirable adverse responses in patients, but also for preserving the function of transfected cells to exert therapeutic effects. Long-term progressive improvement of platform technologies has helped overcome most of these issues, though some still remain hindering the widespread clinical application of nonviral pDNA and mRNA delivery. This review discusses design concepts of nonviral carriers for in vivo delivery and the issues to be overcome, focusing especially on our own efforts using polyplex micelles. © 2019 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 107A: 978-990, 2019.

Systemic Alanine Glyoxylate Aminotransferase mRNA Improves Glyoxylate Metabolism in a Mouse Model of Primary Hyperoxaluria Type 1

Primary Hyperoxaluria Type 1 (PH1) is an autosomal recessive disorder of glyoxylate metabolism. Loss of alanine glyoxylate aminotransferase (AGT) function to convert intermediate metabolite glyoxylate to glycine causes the accumulation and reduction of glyoxylate to glycolate, which eventually is oxidized to oxalate. Excess oxalate in PH1 patients leads to the formation and deposition of calcium oxalate crystals in the kidney and urinary tract. Oxalate crystal deposition causes a decline in renal function, systemic oxalosis, and eventually end-stage renal disease and premature death. mRNA-based therapies are a new class of drugs that work by replacing the missing enzyme. mRNA encoding AGT has the potential to restore normal glyoxylate to glycine metabolism, thus preventing the buildup of calcium oxalate in various organs. Panels of codon-optimized AGT mRNA constructs were screened in vitro and in wild-type mice for the production of a functional AGT enzyme. Two human constructs, wild-type and engineered AGT (RHEAM), were tested in Agxt^-/- mice. Repeat dosing in Agxt^-/- mice resulted in a 40% reduction in urinary oxalate, suggesting therapeutic benefit. These studies suggest that mRNA encoding AGT led to increased expression and activity of the AGT enzyme in liver that translated into decrease in urinary oxalate levels. Taken together, our data indicate that AGT mRNA may have the potential to be developed into a therapeutic for PH1.

Sodium bicarbonate nanoparticles modulate the tumor pH and enhance the cellular uptake of doxorubicin

Acidic pH in the tumor microenvironment is associated with cancer metabolism and creates a physiological barrier that prevents from drugs to penetrate cells. Specifically, ionizable weak-base drugs, such as doxorubicin, freely permeate membranes in their uncharged form, however, in the acidic tumor microenvironment these drugs become charged and their cellular permeability is retarded. In this study, 100-nm liposomes loaded with sodium bicarbonate were used as adjuvants to elevate the tumor pH. Combined treatment of triple-negative breast cancer cells (4T1) with doxorubicin and sodium-bicarbonate enhanced drug uptake and increased its anti-cancer activity. In vivo, mice bearing orthotropic 4T1 breast cancer tumors were administered either liposomal or free bicarbonate intravenously. 3.7 ± 0.3% of the injected liposomal dose was detected in the tumor after twenty-four hours, compared to 0.17% ± 0.04% in the group injected free non-liposomal bicarbonate, a 21-fold increase. Analyzing nanoparticle biodistribution within the tumor tissue revealed that 93% of the PEGylated liposomes accumulated in the extracellular matrix, while 7% were detected intracellularly. Mice administered bicarbonate-loaded liposomes reached an intra-tumor pH value of 7.38 ± 0.04. Treating tumors with liposomal bicarbonate combined with a sub-therapeutic dose of doxorubicin achieved an improved therapeutic outcome, compared to mice treated with doxorubicin or bicarbonate alone. Interestingly, analysis of the tumor microenvironment demonstrated an increase in immune cell' population (T-cell, B-cell and macrophages) in tumors treated with liposomal bicarbonate. This study demonstrates that targeting metabolic adjuvants with nanoparticles to the tumor microenvironment can enhance anticancer drug activity and improve treatment.

Mitochondria targeting two-photon fluorescent molecules for gene transfection and biological tracking

Mitochondria targeting two-photon fluorescent organic molecules are applied in gene transfection in vitro and in vivo.

RNA Interference-Based Cancer Drugs: The Roadblocks, and the "Delivery" of the Promise

Nucleic acid-based therapeutics like synthetic small interfering RNAs have been exploited to modulate gene function, taking advantage of RNA interference (RNAi), an evolutionally conserved biological process. Recently, the world's first RNAi drug was approved for a rare genetic disorder in the liver. However, there are significant challenges that need to be resolved before RNAi can be translated in other genetic diseases like cancer. Current drug delivery platforms for therapeutic silencing RNAs are tailored to hepatic targets. RNAi therapies for nonhepatic conditions are still at early clinical phases. In this study, we discuss the critical design considerations in anticancer RNAi drug development, insights gained from initial clinical trials, and new strategies that are entering clinical development, shaping the future of RNAi in cancer.

Pancreatic Cancer Gene Therapy Delivered by Nanoparticles

Pancreatic cancer is one of the most lethal forms of cancer and has proven to be difficult to treat through conventional methods, including surgery and chemotherapy. Gene therapy serves as a potential novel treatment to interfere with genes that make this cancer so aggressive, but free nucleic acids have low cell uptake due to their negative charge and are unstable in circulation. Nanoparticles can serve as an effective carrier for a wide variety of gene therapies for pancreatic cancer as they can improve the circulation time, decrease the recognition by the immune system, and be functionalized to target specific surface proteins. In this review, we focus on therapeutic strategies using nanoparticles as carriers of small interfering RNA (siRNA), microRNA (miRNA), and gene augmentation (DNA) therapies in the context of pancreatic cancer. Lastly, we discuss the future outlook of nanoparticle-based therapies, including challenges in the clinical setting.

Co-delivery of mRNA and SPIONs through amino-ester nanomaterials

Nanoparticles have been widely explored for combined therapeutic and diagnostic applications. For example, lipid-based nanoparticles have been used to encapsulate multiple types of agents and achieve multi-functions. Herein, we enabled a co-delivery of mRNA molecules and superparamagnetic iron oxide nanoparticles (SPIONs) by using an amino-ester lipid-like nanomaterial. An orthogonal experimental design was used to identify the optimal formulation. The optimal formulation, MPA-Ab-8 LLNs, not only showed high encapsulation of both mRNA and SPIONs, but also increased the r ₂ relaxivity of SPIONs by more than 1.5-fold in vitro. MPA-Ab-8 LLNs effectively delivered mRNA and SPIONs into cells, and consequently induced high protein expression as well as strong MRI contrast. Consistent herewith, we observed both mRNA-mediated protein expression and an evident negative contrast enhancement of MRI signal in mice. In conclusion, amino-ester nanomaterials demonstrate great potential as delivery vehicles for theranostic applications.

Self-Assembled Nanomedicines for Anticancer and Antibacterial Applications

Self-assembly strategies have been widely applied in the nanomedicine field, which provide a convenient approach for building various structures for delivery carriers. When cooperating with biomolecules, self-assembly systems have significant influence on the cell activity and life process and could be used for regulating nanodrug activity. In this review, self-assembled nanomedicines are introduced, including materials, encapsulation, and releasing strategies, where self-assembly strategies are involved. Furthermore, as a promising and emerging area for nanomedicine, in situ self-assembly of anticancer drugs and supramolecular antibiotic switches is also discussed about how to regulate drug activity. Selective pericellular assembly can block mass transformation of cancer cells inducing cell apoptosis, and the intracellular assembly can either cause cell death or effectively avoid drug elimination from cytosol of cancer cells because of the assembly-induced retention (AIR) effect. Host-guest interactions of drug and competitive molecules offer reversible regulations of antibiotic activity, which can reduce drug-resistance and inhibit the generation of drug-resistant bacteria. Finally, the challenges and development trend in the field are discussed.

Biomedical applications of mRNA nanomedicine

As an attractive alternative to plasmid DNA, messenger RNA (mRNA) has recently emerged as a promising class of nucleic acid therapeutics for biomedical applications. Advances in addressing the inherent shortcomings of mRNA and in the development of nanoparticle-based delivery systems have prompted the development and clinical translation of mRNA-based medicines. In this review, we discuss the chemical modification strategies of mRNA to improve its stability, minimize immune responses, and enhance translational efficacy. We also highlight recent progress in nanoparticle-based mRNA delivery. Considerable attention is given to the increasingly widespread applications of mRNA nanomedicine in the biomedical fields of vaccination, protein-replacement therapy, gene editing, and cellular reprogramming and engineering.

Clinical translation of immunoliposomes for cancer therapy: recent perspectives

INTRODUCTION

Liposomes have been extensively investigated as drug delivery vehicles. Immunoliposomes (ILs) are antibody-conjugated liposomes designed to selectively target antigen-expressing cells. ILs can be used to deliver drugs to tumor cells for improving efficacy and reducing toxicity. In addition, ILs can be used in immunoassays, immunotherapy, and imaging. Although there has been extensive coverage on ILs in the literature, only a limited number of clinical trials have been reported and no IL drug has been approved by the FDA.

AREAS COVERED

Factors to consider in developing ILs are discussed, including the choice of antibody or antibody fragment, the formulation of liposomes, and the conjugation chemistry. In addition, challenges and opportunities in clinical development of ILs are discussed. The purpose of this review is to provide an overview on the state of the art of ILs and to discuss potential future developments.

EXPERT OPINION

IL research has had a lengthy history and numerous preclinical studies have yielded encouraging results. However, there are a number of obstacles to clinical translation of ILs. Given the unique capabilities of ILs, its potential for clinical application is underexplored. There is great potential for expanded role for ILs in the clinic and further efforts to this end are warranted.

ABBREVIATIONS

Ab: antibody; ADCs: antibody-drug conjugates; API: active pharmaceutical ingredient; ADCC: antibody-dependent cellular cytotoxicity; CR: complete remission; cGMP: current good manufacturing practice; DSPE: distearoyl phosphatidylethanolamine; EGF: epidermal growth factor; EGFR: epidermal growth factor receptor; EPR: enhanced permeability and retention; Fc: fragment crystalline; Tf: transferrin; HACA: human-anti-chimeric antibody; HAHA: human-anti-human antibody; HAMA: human-anti-mouse antibody; HER2: human epidermal growth factor 2; IL: immunoliposome; LNPs: lipid nanoparticles; MRI: magnetic resonance imaging; MTD: maximum tolerated dose; PEG: polyethylene glycol; PET: positron emission tomography; PR: partial response; PSMA: prostate-specific membrane antigen; scFv: single-chain variable fragment; SPECT: single photon emission computed tomography; TTR: transthyretin.

Lipid Nanoparticle-Delivered Chemically Modified mRNA Restores Chloride Secretion in Cystic Fibrosis

The promise of gene therapy for the treatment of cystic fibrosis has yet to be fully clinically realized despite years of effort toward correcting the underlying genetic defect in the cystic fibrosis transmembrane conductance regulator (CFTR). mRNA therapy via nanoparticle delivery represents a powerful technology for the transfer of genetic material to cells with large, widespread populations, such as airway epithelia. We deployed a clinically relevant lipid-based nanoparticle (LNP) for packaging and delivery of large chemically modified CFTR mRNA (cmCFTR) to patient-derived bronchial epithelial cells, resulting in an increase in membrane-localized CFTR and rescue of its primary function as a chloride channel. Furthermore, nasal application of LNP-cmCFTR restored CFTR-mediated chloride secretion to conductive airway epithelia in CFTR knockout mice for at least 14 days. On day 3 post-transfection, CFTR activity peaked, recovering up to 55% of the net chloride efflux characteristic of healthy mice. This magnitude of response is superior to liposomal CFTR DNA delivery and is comparable with outcomes observed in the currently approved drug ivacaftor. LNP-cmRNA-based systems represent a powerful platform technology for correction of cystic fibrosis and other monogenic disorders.

Nucleic acid-based vaccines targeting respiratory syncytial virus: Delivering the goods

Respiratory syncytial virus (RSV) is a massive medical burden on a global scale. Infants, children and the elderly represent the vulnerable populations. Currently there is no approved vaccine to protect against the disease. Vaccine development has been hindered by several factors including vaccine enhanced disease (VED) associated with formalin-inactivated RSV vaccines, inability of target populations to raise protective immune responses after vaccination or natural viral infection, and a lack of consensus concerning the most appropriate virus-associated target antigen. However, with recent advances in the molecular understanding of the virus, and design of highly characterized vaccines with enhanced immunogenicity there is new belief a RSV vaccine is possible. One promising approach is nucleic acid-based vaccinology. Both DNA and mRNA RSV vaccines are showing promising results in clinically relevant animal models, supporting their transition into humans. Here we will discuss this strategy to target RSV, and the ongoing studies to advance the nucleic acid vaccine platform as a viable option to protect vulnerable populations from this important disease.

Dexamethasone prodrugs as potent suppressors of the immunostimulatory effects of lipid nanoparticle formulations of nucleic acids

Lipid nanoparticles (LNPs) are playing a leading role in enabling clinical applications of gene therapies based on DNA or RNA polymers. One factor impeding clinical acceptance of LNP therapeutics is that LNP formulations of nucleic acid polymers can be immunostimulatory, necessitating co-administration of potent corticosteroid immunosuppressive agents. Here, we describe the development of hydrophobic prodrugs of a potent corticosteroid, dexamethasone, that can be readily incorporated into LNP systems. We show that the presence of the dexamethasone prodrug LD003 effectively suppresses production of cytokines such as KC-GRO, TNFα, IL-1β and IL-6 following intravenous administration of LNP loaded with immune stimulatory oligodeoxynucleotides containing cytosine-guanine dinucleotide motifs. Remarkably, LD003 dose levels corresponding to 0.5 mg/kg dexamethasone achieve a greater immunosuppressive effect than doses of 20 mg/kg of free dexamethasone. Similar immunosuppressive effects are observed for subcutaneously administered LNP-siRNA. Further, the incorporation of low levels of LD003 in LNP containing unmodified mRNA or plasmid DNA significantly reduced pro-inflammatory cytokine levels following intravenous administration. Our results suggest that incorporation of hydrophobic prodrugs such as LD003 into LNP systems could provide a convenient method for avoiding the immunostimulatory consequences of systemic administration of genetic drug formulations.

On the Formation and Morphology of Lipid Nanoparticles Containing Ionizable Cationic Lipids and siRNA

Lipid nanoparticles (LNPs) containing short interfering RNA (LNP-siRNA) and optimized ionizable cationic lipids are now clinically validated systems for silencing disease-causing genes in hepatocytes following intravenous administration. However, the mechanism of formation and certain structural features of LNP-siRNA remain obscure. These systems are formed from lipid mixtures (cationic lipid, distearoylphosphatidylcholine, cholesterol, and PEG-lipid) dissolved in ethanol that is rapidly mixed with siRNA in aqueous buffer at a pH (pH 4) where the ionizable lipid is positively charged. The resulting dispersion is then dialyzed against a normal saline buffer to remove residual ethanol and raise the pH to 7.4 (above the p K_a of the cationic lipid) to produce the finished LNP-siRNA systems. Here we provide cryogenic transmission electron microscopy (cryo-TEM) and X-ray evidence that the complexes formed between siRNA and ionizable lipid at pH 4 correspond to tightly packed bilayer structures with siRNA sandwiched between closely apposed monolayers. Further, it is shown that ionizable lipid not complexed to siRNA promotes formation of very small vesicular structures at pH 4 that coalesce to form larger LNP structures with amorphous electron dense cores at pH 7.4. A mechanism of formation of LNP-siRNA systems is proposed whereby siRNA is first sandwiched between closely apposed lipid monolayers at pH 4 and subsequently trapped in these structures as the pH is raised to 7.4, whereas ionizable lipid not interacting with siRNA moves from bilayer structure to adopt an amorphous oil phase located in the center of the LNP as the pH is raised. This model is discussed in terms of previous hypotheses and potential relevance to the design of LNP-siRNA systems.

Self-Amplifying Replicon RNA Delivery to Dendritic Cells by Cationic Lipids

Advances in RNA technology during the past two decades have led to the construction of replication-competent RNA, termed replicons, RepRNA, or self-amplifying mRNA, with high potential for vaccine applications. Cytosolic delivery is essential for their translation and self-replication, without infectious progeny generation, providing high levels of antigen expression for inducing humoral and cellular immunity. Synthetic nanoparticle-based delivery vehicles can both protect the RNA molecules and facilitate targeting of dendritic cells—critical for immune defense development. Several cationic lipids were assessed, with RepRNA generated from classical swine fever virus encoding nucleoprotein genes of influenza A virus. The non-cytopathogenic nature of the RNA allowed targeting to dendritic cells without destroying the cells—important for prolonged antigen production and presentation. Certain lipids were more effective at delivery and at promoting translation of RepRNA than others. Selection of particular lipids provided delivery to dendritic cells that resulted in translation, demonstrating that delivery efficiency could not guarantee translation. The observed translation in vitro was reproduced in vivo by inducing immune responses against the encoded influenza virus antigens. Cationic lipid-mediated delivery shows potential for promoting RepRNA vaccine delivery to dendritic cells, particularly when combined with additional delivery elements.

Reducing the Cytotoxicity of Lipid Nanoparticles Associated with a Fusogenic Cationic Lipid in a Natural Killer Cell Line by Introducing a Polycation-Based siRNA Core

Introducing siRNA into human immune cells by an artificial delivery system continues to be a challenging issue. We previously developed a multifunctional envelope-type nanodevice (MEND) containing the YSK12-C4, a fusogenic cationic lipid, (YSK12-MEND) and succeeded in the efficient delivery of siRNA into human immune cell lines. Significant cytotoxicity, however, was observed at siRNA doses needed for gene silencing in NK-92 cells. NK-92 cells, a unique natural killer (NK) cell line, would be applicable for use in clinical NK therapy. Thus, reducing the cytotoxicity of the YSK12-MEND in NK-92 cells would strengthen the efficacy of NK-92 cell-based therapy. The amount of the YSK12-C4 in the MEND needed to be reduced to reduce the cytotoxicity, because the cytotoxicity was directly associated with the YSK12-C4. In the present study, we decreased the total amount of lipid, including the YSK12-C4, by introducing a core formed by electrostatic interactions of siRNA with a polycation (protamine) (siRNA core), which led to a decrease in cytotoxicity in NK-92 cells. We prepared a YSK12-MEND containing an siRNA core (YSK12-MEND/core) at charge ratios (CR: YSK12-C4/siRNA) of 10, 5, 3, and 2.5 and compared the YSK12-MEND/core with that for a YSK12-MEND (CR16.9). Cell viability was increased by more than 2 times at a CR5 or less. On the other hand, the YSK12-MEND/core (CR5) maintained the same gene silencing efficiency (60%) as the YSK12-MEND. Interestingly, the cellular uptake efficiency and hemolytic activity of the YSK12-MEND/core (CR5) was reduced compared to that for the YSK12-MEND. In calculating the silencing activity per cellular uptake efficiency and hemolytic activity, the value for the YSK12-MEND/core (CR5) was more than 2 times as high as that of the YSK12-MEND. The fact indicates that after endosomal escape, the process can be enhanced by using a YSK12-MEND/core (CR5). Thus, introducing an siRNA core into lipid nanoparticles can be a potent strategy for decreasing cytotoxicity without an appreciable loss of gene silencing activity in NK-92 cells.

Current Status of Messenger RNA Delivery Systems

Messenger RNA is emerging as a highly versatile biological construct for creation of impactful medicines. mRNA vaccines directed toward infectious disease and cancer are in clinical development with encouraging early reads on tolerability and efficacy. The use of mRNA to direct intense but transient expression of paracrine factors is finding utility in reprogramming progenitor cells for wound healing and cardiac regeneration and for stimulation of antitumor immune responses, at least preclinically as we await clinical results. The use of mRNA for prolonged and repeated expression of proteins and enzymes to treat rare, typically monogenic disease is nearing clinical entry. These uses of mRNA require delivery solutions, and the application of and improvement to existing nanoparticle nucleic acid delivery systems have jump started the pace of development and reenergized the field of particle based nucleic acid delivery. The current status of mRNA delivery is reviewed in this article with an eye toward clinical tractability.

Polymeric Nanocapsules for Vaccine Delivery: Influence of the Polymeric Shell on the Interaction With the Immune System

The use of biomaterials and nanosystems in antigen delivery has played a major role in the development of novel vaccine formulations in the last few decades. In an effort to gain a deeper understanding of the interactions between these systems and immunocompetent cells, we describe here a systematic in vitro and in vivo study on three types of polymeric nanocapsules (NCs). These carriers, which contained protamine (PR), polyarginine (PARG), or chitosan (CS) in the external shell, and their corresponding nanoemulsion were prepared, and their main physicochemical properties were characterized. The particles had a mean particle size in the range 250–450 nm and a positive zeta potential (~30–40 mV). The interaction of the nanosystems with different components of the immune system were investigated by measuring cellular uptake, reactive oxygen species production, activation of the complement cascade, cytokine secretion profile, and MAP kinases/nuclear factor κB activation. The results of these in vitro cell experiments showed that the NC formulations that included the arginine-rich polymers (PR and PARG) showed a superior ability to trigger different immune processes. Considering this finding, protamine and polyarginine nanocapsules (PR and PARG NCs) were selected to assess the association of the recombinant hepatitis B surface antigen (rHBsAg) as a model antigen to evaluate their ability to produce a protective immune response in mice. In this case, the results showed that PR NCs elicited higher IgG levels than PARG NCs and that this IgG response was a combination of anti-rHBsAg IgG1/IgG2a. This work highlights the potential of PR NCs for antigen delivery as an alternative to other positively charged nanocarriers.

Gene therapy clinical trials worldwide to 2017: An update

To date, almost 2600 gene therapy clinical trials have been completed, are ongoing or have been approved worldwide. Our database brings together global information on gene therapy clinical activity from trial databases, official agency sources, published literature, conference presentations and posters kindly provided to us by individual investigators or trial sponsors. This review presents our analysis of clinical trials that, to the best of our knowledge, have been or are being performed worldwide. As of our November 2017 update, we have entries on 2597 trials undertaken in 38 countries. We have analysed the geographical distribution of trials, the disease indications (or other reasons) for trials, the proportions to which different vector types are used, and the genes that have been transferred. Details of the analyses presented, and our searchable database are available via The Journal of Gene Medicine Gene Therapy Clinical Trials Worldwide website at: http://www.wiley.co.uk/genmed/clinical. We also provide an overview of the progress being made in gene therapy clinical trials around the world, and discuss key trends since the previous review, namely the use of chimeric antigen receptor T cells for the treatment of cancer and advancements in genome editing technologies, which have the potential to transform the field moving forward.

RNA-Targeted Therapeutics

RNA-targeted therapies represent a platform for drug discovery involving chemically modified oligonucleotides, a wide range of cellular RNAs, and a novel target-binding motif, Watson-Crick base pairing. Numerous hurdles considered by many to be impassable have been overcome. Today, four RNA-targeted therapies are approved for commercial use for indications as diverse as Spinal Muscular Atrophy (SMA) and reduction of low-density lipoprotein cholesterol (LDL-C) and by routes of administration including subcutaneous, intravitreal, and intrathecal delivery. The technology is efficient and supports approaching "undruggable" targets. Three additional agents are progressing through registration, and more are in clinical development, representing several chemical and structural classes. Moreover, progress in understanding the molecular mechanisms by which these drugs work has led to steadily better clinical performance and a wide range of mechanisms that may be exploited for therapeutic purposes. Here we summarize the progress, future challenges, and opportunities for this drug discovery platform.

Incorporation of mRNA in Lamellar Lipid Matrices for Parenteral Administration

Insertion of high molecular weight messenger RNA (mRNA) into lyotropic lipid phases as model systems for controlled release formulations for the mRNA was investigated. Low fractions of 1,2-dioleoyl-3-trimethylammonium-propane (DOTAP) were used as an anchor to load the mRNA into a lamellar lipid matrix. Dispersions of zwitterionic lipid in the aqueous phase in the presence of increasing fractions of mRNA and cationic lipid were prepared, and the molecular organization was investigated as a function of mRNA and cationic lipid fraction. Insertion of both cationic lipid and mRNA was clearly proven from the physicochemical characteristics. The d-spacing of the lipid bilayers, as determined by small-angle X-ray scattering (SAXS) measurements, responded sensitively to the amount of inserted DOTAP and mRNA. A concise model of the insertion of the mRNA in the lipid matrices was derived, indicating that the mRNA was accommodated in the aqueous slab between lipid bilayers. Depending on the DOTAP and mRNA fraction, a different excess of water was present in this slab. Results from further physicochemical characterization, including determination of free and bound mRNA, zeta potential, and calorimetry data, were in line with this assumption. The structure of these concentrated lipid/mRNA preparations was maintained upon dilution. The functionality of the inserted mRNA was proven by cell culture experiments using C2C12 murine myoblast cells with the luciferase-encoding mRNA. The described lipid phases as carriers for the mRNA may be applicable for different routes of local administration, where control of the release kinetics and the form of the released mRNA (bound or free) is required.

Microfluidic Production and Application of Lipid Nanoparticles for Nucleic Acid Transfection

Lipid nanoparticles (LNPs) are established in the biopharmaceutical industry for efficient encapsulation and cytosolic delivery of nucleic acids for potential therapeutics, with several formulations in clinical trials. The advantages of LNPs can also be applied in basic research and discovery with a microfluidic method of preparation now commercially available that allows preparations to be scaled down to quantities appropriate for cell culture. These preparations conserve expensive nucleic acids while maintaining the particle characteristics that have made LNPs successful in later stages of genetic medicine development. Additionally, this method and the resulting LNPs are seamlessly scalable to quantities appropriate for in vivo models and development of nucleic acid therapeutics.The present work describes the methodology for preparing LNPs loaded with siRNA, mRNA or plasmids using a commercially available microfluidic instrument and an accompanying transfection kit. Guidelines for application to cultured cells in a well-plate format are also provided.

Co-delivery of hypoxia inducible factor-1α small interfering RNA and 5-fluorouracil to overcome drug resistance in gastric cancer SGC-7901 cells

BACKGROUND

Drug resistance cancer cells have become a major problem in chemotherapy. To solve this problem, the co-delivery of small interefering RNA (siRNA) and 5-fluorouracil chitosan nanoparticles was employed, aiming to reverse the multidrug resistance of gastric cancer SGC-7901 cells in vitro.

METHODS

Chitosan nanoparticles were prepared using an ionic gel method. siRNA nanoparticles were characterized by gel retardation assays. Particle size and zeta potential were measured to confirm nanoparticle formation. The transfection efficiency of siRNA was determined by flow cytometry and high-content screening. Western blotting and a quantitative real-time-polymerase chain reaction were used to assess the silencing efficiency of siRNA. Accumulation and efflux experiments for rhodamine-123, cell migration experiments, cell sensitivity analyses and cell apoptosis assays were used to determine whether siRNA could reverse multidrug resistance. A systemic toxicity assay was used to evaluate the safety of nanoparticles.

RESULTS

Compared to naked siRNA, the co-delivery system demonstrated a higher transfection efficiency and gene silencing efficiency by inhibiting the efflux of P-glycoprotein and cell migration. Moreover, the combination treatment with siRNA and 5-fluorouracil co-delivered by chitosan nanoparticles can increase the sensitivity of drug resistance cells and cell apoptosis. Finally, the safety of nanoparticles was evaluated in vivo and the results obtained suggested that nanoparticles did not have any obvious toxicity.

CONCLUSIONS

Co-delivery of siRNA and 5-fluorouracil chitosan nanoparticles is an attractive strategy for overcoming multidrug resistance.

Nanoparticle Delivery of miR-34a Eradicates Long-term-cultured Breast Cancer Stem Cells via Targeting C22ORF28 Directly

Rationale: Cancer stem cells (CSCs) have been implicated as the seeds of therapeutic resistance and metastasis, due to their unique abilities of self-renew, wide differentiation potentials and resistance to most conventional therapies. It is a proactive strategy for cancer therapy to eradicate CSCs. Methods: Tumor tissue-derived breast CSCs (BCSC), including XM322 and XM607, were isolated by fluorescence-activated cell sorting (FACS); while cell line-derived BCSC, including MDA-MB-231.SC and MCF-7.SC, were purified by magnetic-activated cell sorting (MACS). Analyses of microRNA and mRNA expression array profiles were performed in multiple breast cell lines. The mentioned nanoparticles were constructed following the standard molecular cloning protocol. Tissue microarray analysis has been used to study 217 cases of clinical breast cancer specimens. Results: Here, we have successfully established four long-term maintenance BCSC that retain their tumor-initiating biological properties. Our analyses of microarray and qRT-PCR explored that miR-34a is the most pronounced microRNA for investigation of BCSC. We establish hTERT promoter-driven VISA delivery of miR-34a (TV-miR-34a) plasmid that can induce high throughput of miR-34a expression in BCSC. TV-miR-34a significantly inhibited the tumor-initiating properties of long-term-cultured BCSC in vitro and reduced the proliferation of BCSC in vivo by an efficient and safe way. TV-miR-34a synergizes with docetaxel, a standard therapy for invasive breast cancer, to act as a BCSC inhibitor. Further mechanistic investigation indicates that TV-miR-34a directly prevents C22ORF28 accumulation, which abrogates clonogenicity and tumor growth and correlates with low miR-34 and high C22ORF28 levels in breast cancer patients. Conclusion: Taken together, we generated four long-term maintenance BCSC derived from either clinical specimens or cell lines, which would be greatly beneficial to the research progress in breast cancer patients. We further developed the non-viral TV-miR-34a plasmid, which has a great potential to be applied as a clinical application for breast cancer therapy.

In Vivo Transgene Expression in the Pancreas by the Intraductal Injection of Naked Plasmid DNA

Patients with type I diabetes, which is caused by the destruction of pancreatic islets, now require regular therapeutic injections of insulin. The use of transgene therapy represents an alternate and potent strategy for the treatment of type I diabetes. However, only a limited number of studies regarding in vivo gene delivery targeting the pancreas and islets have been reported. Here, we report on the possibility of in vivo transgene expression in the pancreas by the intraductal injection of naked plasmid DNA (pDNA). Gene expression activities were detected in the pancreas of mice after the injection of naked pDNA encoding luciferase into the common bile duct. We then investigated the effects of injection dose, volume, and speed on gene delivery and determined the optimal conditions for the delivery of pDNA to the pancreas. Exogenous luciferase mRNA was detected in the pancreatic islets by reverse transcription PCR analysis. Moreover, no injury was detected in the liver, the common bile duct, or the pancreas over time after the injection. These findings indicate that the intraductal injection of naked pDNA promises to be a useful technique for in vivo gene delivery targeted to pancreatic tissue and islets.

Boosting Intracellular Delivery of Lipid Nanoparticle-Encapsulated mRNA

Intracellular delivery of mRNA holds great potential for vaccine1-3 and therapeutic4 discovery and development. Despite increasing recognition of the utility of lipid-based nanoparticles (LNPs) for intracellular delivery of mRNA, particle engineering is hindered by insufficient understanding of endosomal escape, which is believed to be a main limiter of cytosolic availability and activity of the nucleic acid inside the cell. Using a series of CRISPR-based genetic perturbations of the lysosomal pathway, we have identified that late endosome/lysosome (LE/Ly) formation is essential for functional delivery of exogenously presented mRNA. Lysosomes provide a spatiotemporal hub to orchestrate mTOR signaling and are known to control cell proliferation, nutrient sensing, ribosomal biogenesis, and mRNA translation. Through modulation of the mTOR pathway we were able to enhance or inhibit LNP-mediated mRNA delivery. To further boost intracellular delivery of mRNA, we screened 212 bioactive lipid-like molecules that are either enriched in vesicular compartments or modulate cell signaling. Surprisingly, we have discovered that leukotriene-antagonists, clinically approved for treatment of asthma and other lung diseases, enhance intracellular mRNA delivery in vitro (over 3-fold, p < 0.005) and in vivo (over 2-fold, p < 0.005). Understanding LNP-mediated intracellular delivery will inspire the next generation of RNA therapeutics that have high potency and limited toxicity.

Challenges and opportunities in bioanalytical support for gene therapy medicinal product development

Gene and nucleic acid therapies have demonstrated patient benefits to address unmet medical needs. Beside considerations regarding the biological nature of the gene therapy, the quality of bioanalytical methods plays an important role in ensuring the success of these novel therapies. Inconsistent approaches among bioanalytical labs during preclinical and clinical phases have been observed. There are many underlying reasons for this inconsistency. Various platforms and reagents used in quantitative methods, lacking of detailed regulatory guidance on method validation and uncertainty of immunogenicity strategy in supporting gene therapy may all be influential. This review summarizes recent practices and considerations in bioanalytical support of pharmacokinetics/pharmacodynamics and immunogenicity evaluations in gene therapy development with insight into method design, development and validations.

Advances in the Understanding and Treatment of Mitochondrial Fatty Acid Oxidation Disorders

Purpose of review

This review focuses on advances made in the past three years with regards to understanding the mitochondrial fatty acid oxidation (FAO) pathway, the pathophysiological ramifications of genetic lesions in FAO enzymes, and emerging therapies for FAO disorders.

Recent findings

FAO has now been recognized to play a key energetic role in pulmonary surfactant synthesis, T-cell differentiation and memory, and the response of the proximal tubule to kidney injury. Patients with FAO disorders may face defects in these cellular systems as they age. Aspirin, statins, and nutritional supplements modulate the rate of FAO under normal conditions and could be risk factors for triggering symptoms in patients with FAO disorders. Patients have been identified with mutations in the ACAD9 and ECHS1 genes, which may represent new FAO disorders. New interventions for long-chain FAODs are in clinical trials. Finally, post-translational modifications that regulate fatty acid oxidation protein activities have been characterized that represent important new therapeutic targets.

Summary

Recent research has led to a deeper understanding of FAO. New therapeutic avenues are being pursued that may ultimately cause a paradigm shift for patient care.

Splice-Switching Therapy for Spinal Muscular Atrophy

Spinal muscular atrophy (SMA) is a genetic disorder with severity ranging from premature death in infants to restricted motor function in adult life. Despite the genetic cause of this disease being known for over twenty years, only recently has a therapy been approved to treat the most severe form of this disease. Here we discuss the genetic basis of SMA and the subsequent studies that led to the utilization of splice switching oligonucleotides to enhance production of SMN protein, which is absent in patients, through a mechanism of exon inclusion into the mature mRNA. Whilst approval of oligonucleotide-based therapies for SMA should be celebrated, we also discuss some of the limitations of this approach and alternate genetic strategies that are currently underway in clinical trials.