Current Status of Nonviral Vectors for Gene Therapy in China

DNA-Based Nonviral Gene Therapy─Challenging but Promising

Over the past decades, significant progress has been made in utilizing nucleic acids, including DNA and RNA molecules, for therapeutic purposes. For DNA molecules, although various DNA delivery systems have been established, viral vector systems are the go-to choice for large-scale commercial applications. However, viral systems have certain disadvantages such as immune response, limited payload capacity, insertional mutagenesis and pre-existing immunity. In contrast, nonviral systems are less immunogenic, not size limited, safer, and easier for manufacturing compared with viral systems. What's more, nonviral DNA vectors have demonstrated their capacity to mediate specific protein expression in vivo for diverse therapeutic objectives containing a wide range of diseases such as cancer, rare diseases, neurodegenerative diseases, and infectious diseases, yielding promising therapeutic outcomes. However, exogenous plasmid DNA is prone to degrade and has poor immunogenicity in vivo. Thus, various strategies have been developed: (i) designing novel plasmids with special structures, (ii) optimizing plasmid sequences for higher expression, and (iii) developing more efficient nonviral DNA delivery systems. Based on these strategies, many interesting clinical results have been reported. This Review discusses the development of DNA-based nonviral gene therapy, including novel plasmids, nonviral delivery systems, clinical advances, and prospects. These developments hold great potential for enhancing the efficacy and safety of nonviral gene therapy and expanding its applications in the treatment of various diseases.

Recent advances of engineered oncolytic viruses-based combination therapy for liver cancer

Liver cancer is a major malignant tumor, which seriously threatens human health and increases the economic burden on patients. At present, gene therapy has been comprehensively studied as an excellent therapeutic measure in liver cancer treatment. Oncolytic virus (OV) is a kind of virus that can specifically infect and kill tumor cells. After being modified by genetic engineering, the specificity of OV infection to tumor cells is increased, and its influence on normal cells is reduced. To date, OV has shown its effectiveness and safety in experimental and clinical studies on a variety of tumors. Thus, this review primarily introduces the current status of different genetically engineered OVs used in gene therapy for liver cancer, focuses on the application of OVs and different target genes for current liver cancer therapy, and identifies the problems encountered in OVs-based combination therapy and the corresponding solutions, which will provide new insights into the treatment of liver cancer.

The complexing of cationic copolymer MPC30-DEA70 with TGF-β1 antisense oligodeoxynucleotide and transfection into cardiomyocytes in vitro

Although gene therapy is an attractive option for the treatment of cardiovascular diseases, the ideal gene delivery systems are still under investigation and must meet the following criteria: safety, adequate gene transfer efficiency, and stable expression of the transgene for a duration appropriate for treating the disease. In this study, we developed a cationic phosphorylcholine-containing diblock copolymer, namely MPC₃₀-DEA₇₀, as carrier systems to deliver a chemically synthesized transforming growth factor-beta 1(TGF-β1) antisense oligonucleotide (AS-ODN) into cardiomyocytes (CMs) to observe the cell transfection efficiency of MPC₃₀-DEA₇₀ and the inhibition effect on the expression of TGF-β1. MPC₃₀-DEA₇₀/TGF-β1 AS-ODN complexes were formed through complexation between copolymer MPC₃₀-DEA₇₀ (N) and AS-ODN (P) at different N/P ratios and were characterized by DNA electrophoresis. Notably, the cytotoxicity and cell growth inhibition assay showed that the MPC₃₀-DEA₇₀ had low cytotoxicity to CMs within the effective transfection dosage range (<20 μL/mL). CLSM/TEM images displayed that most of the AS-ODN molecules engulfed by cells were located around the cell nuclei, and a few entered into the cell nuclei without harming the organelles in the cell. Transfection studies from CMs indicated a steady increase of transfection efficiency with increasing N/P ratios. The expression levels of TGF-β1 mRNA and protein in CMs were significantly inhibited at high N/P ratios. This study shows that MPC₃₀-DEA₇₀ can function as an effective transgenic vector into CMs and that TGF-β1 AS-ODN delivered by MPC₃₀-DEA₇₀ can silence the expression of the TGF-β1 gene efficiently and specifically and thereafter antagonize TGF-β1-mediated biological function in cardiomyocytes.

Appraisal for the Potential of Viral and Nonviral Vectors in Gene Therapy: A Review

Over the past few decades, gene therapy has gained immense importance in medical research as a promising treatment strategy for diseases such as cancer, AIDS, Alzheimer’s disease, and many genetic disorders. When a gene needs to be delivered to a target cell inside the human body, it has to pass a large number of barriers through the extracellular and intracellular environment. This is why the delivery of naked genes and nucleic acids is highly unfavorable, and gene delivery requires suitable vectors that can carry the gene cargo to the target site and protect it from biological degradation. To date, medical research has come up with two types of gene delivery vectors, which are viral and nonviral vectors. The ability of viruses to protect transgenes from biological degradation and their capability to efficiently cross cellular barriers have allowed gene therapy research to develop new approaches utilizing viruses and their different genomes as vectors for gene delivery. Although viral vectors are very efficient, science has also come up with numerous nonviral systems based on cationic lipids, cationic polymers, and inorganic particles that provide sustainable gene expression without triggering unwanted inflammatory and immune reactions, and that are considered nontoxic. In this review, we discuss in detail the latest data available on all viral and nonviral vectors used in gene delivery. The mechanisms of viral and nonviral vector-based gene delivery are presented, and the advantages and disadvantages of all types of vectors are also given.

Substance P containing peptide gene delivery vectors for specifically transfecting glioma cells mediated by a neurokinin-1 receptor

Gene therapy provides a promising treatment for glioblastoma multiforme, which mainly depends on two key aspects, crossing the blood brain barrier (BBB) effectively and transfecting target cells selectively. In this work, we reported a series of peptide-based vectors for transfecting glioma cells specifically consisting of several functional segments including a cell-penetrating peptide, targeting segment substance P (SP), an endosomal escape segment, a PEG linker and a stearyl moiety. The conformations and DNA-loading capacities of peptide vectors and the self-assembly behaviors of peptide/pGL3 complexes were characterized. The in vitro gene transfection was evaluated in U87, 293T-NK1R, and normal 293T cell lines. The transfection efficiency ratio of P-02 (SP-PEG₄-K(C₁₈)-(LLHH)₃-R₉) to Lipo2000 in the U87 cell line was about 36% higher than that in the 293T cell line. The neurokinin-1 receptor (NK1R) in U87 cells mediated the transfection process via interactions with the ligand SP in peptide vectors. The mechanism of NK1R mediated transfection was demonstrated by the use of gene-modified 293T cells expressing NK1R, as well as the gene transfection in the presence of free SP. Besides, P-02 could promote the pGL3 plasmids to cross the BBB model in vitro and achieved the EGFP gene transfection in the brain of zebrafish successfully. The designed peptide vectors, owing to their specific transfection capacity in glioma cells, provide a potential approach for glioblastoma multiforme gene therapy.

Haploinsufficiency, Dominant Negative, and Gain-of-Function Mechanisms in Epilepsy: Matching Therapeutic Approach to the Pathophysiology

This review summarizes the pathogenic mechanisms that underpin the monogenic epilepsies and discusses the potential of novel precision therapeutics to treat these disorders. Pathogenic mechanisms of epilepsy include recessive (null alleles), haploinsufficiency, imprinting, gain-of-function, and dominant negative effects. Understanding which pathogenic mechanism(s) that underlie each genetic epilepsy is pivotal to design precision therapies that are most likely to be beneficial for the patient. Novel therapeutics discussed include gene therapy, gene editing, antisense oligonucleotides, and protein replacement. Discussions are illustrated and reinforced with examples from the literature.

A fluorinated low-molecular-weight PEI/HIF-1α shRNA polyplex system for hemangioma therapy

RNAi technology targeting HIF-1α could benefit hemangioma therapy effectively and FPEI polyplexes which could inhibit the expression of HIF-1α at the translational level can provide a practicable strategy for clinical hemangioma treatment in the future.

Clinical Evaluations of Toxicity and Efficacy of Nanoparticle-Mediated Gene Therapy

Considerable efforts have been devoted to develop safe and efficient gene therapies for life-threatening or inherited diseases. The choice of gene delivery vehicle plays key roles in enhancing the therapeutic effect of nucleic acid cargo. To date, gene therapy approaches involving both viral vectors and nonviral vectors have been evaluated in clinical trials. With improvements in material science and nanotechnologies, positively charged nanoparticles have emerged as potential gene delivery vehicles. In this review, we highlight clinical trials that examined cationic nanocarrier-mediated gene therapy as well as discuss both the toxicity and efficacy of nanocarrier-based therapeutics.

Delivery approaches for CRISPR/Cas9 therapeutics in vivo: advances and challenges

INTRODUCTION

Therapeutic gene editing is becoming a viable biomedical tool with the emergence of the CRISPR/Cas9 system. CRISPR-based technologies have promise as a therapeutic platform for many human genetic diseases previously considered untreatable, providing a flexible approach to high-fidelity gene editing. For many diseases, such as sickle-cell disease and beta thalassemia, curative therapy may already be on the horizon, with CRISPR-based clinical trials slated for the next few years. Translation of CRISPR-based therapy to in vivo application however, is no small feat, and major hurdles remain for efficacious use of the CRISPR/Cas9 system in clinical contexts.

AREAS COVERED

In this topical review, we highlight recent advances to in vivo delivery of the CRISPR/Cas9 system using various packaging formats, including viral, mRNA, plasmid, and protein-based approaches. We also discuss some of the barriers which have yet to be overcome for successful translation of this technology.

EXPERT OPINION

This review focuses on the challenges to efficacy for various delivery formats, with specific emphasis on overcoming these challenges through the development of carrier vehicles for transient approaches to CRISPR/Cas9 delivery in vivo.