A placebo-controlled study of liposome-mediated gene transfer to the nasal epithelium of patients with cystic fibrosis

Gene therapy for atrial fibrillation

Atrial fibrillation (AF) is the most common sustained arrhythmia in adults. Current limitations of pharmacological and ablative therapies motivate the development of novel therapies as next generation treatments for AF. The arrhythmia mechanisms creating and sustaining AF are key elements in the development of this novel treatment. Gene therapy provides a useful platform that allows us to regulate the mechanisms of interest using a suitable transgene(s), vector, and delivery method. Effective gene therapy strategies in the literature have targeted maladaptive electrical or structural remodeling that increase vulnerability to AF. In this review, we will summarize key elements of gene therapy for AF, including molecular targets, gene transfer vectors, atrial gene delivery and preclinical efficacy and toxicity testing. Recent advances and challenges in the field will be also discussed.

Molecular and functional correction of a deep intronic splicing mutation in CFTR by CRISPR-Cas9 gene editing

Cystic fibrosis (CF) is an autosomal recessive disorder caused by mutations in the CFTR gene. The 10th most common mutation, c.3178-2477C>T (3849+10kb C>T), involves a cryptic, intronic splice site. This mutation was corrected in CF primary cells homozygous for this mutation by delivering pairs of guide RNAs (gRNAs) with Cas9 protein in ribonucleoprotein (RNP) complexes that introduce double-strand breaks to flanking sites to excise the 3849+10kb C>T mutation, followed by DNA repair by the non-homologous end-joining pathway, which functions in all cells of the airway epithelium. RNP complexes were delivered to CF basal epithelial cell by a non-viral, receptor-targeted nanocomplex comprising a formulation of targeting peptides and lipids. Canonical CFTR mRNA splicing was, thus, restored leading to the restoration of CFTR protein expression with concomitant restoration of electrophysiological function in airway epithelial air-liquid interface cultures. Off-target editing was not detected by Sanger sequencing of in silico-selected genomic sites with the highest sequence similarities to the gRNAs, although more sensitive unbiased whole genome sequencing methods would be required for possible translational developments. This approach could potentially be used to correct aberrant splicing signals in several other CF mutations and other genetic disorders where deep-intronic mutations are pathogenic.

A Systematic Review of the Effect of Cystic Fibrosis Treatments on the Nasal Potential Difference Test in Animals and Humans

To address unmet treatment needs in cystic fibrosis (CF), preclinical and clinical studies are warranted. Because it directly reflects the function of the Cystic Fibrosis Transmembrane conductance Regulator (CFTR), the nasal potential difference test (nPD) can not only be used as a reliable diagnostic test for CF but also to assess efficacy of experimental treatments. We performed a full comprehensive systematic review of the effect of CF treatments on the nPD compared to control conditions tested in separate groups of animal and human subjects. Our review followed a preregistered protocol. We included 34 references: 20 describing mouse studies, 12 describing human studies, and 2 describing both. We provide a comprehensive list of these studies, which assessed the effects of antibiotics, bone marrow transplant, CFTR protein, CFTR RNA, directly and indirectly CFTR-targeting drugs, non-viral and viral gene transfer, and other treatments. Our results support the nPD representing a reliable method for testing treatment effects in both animal models and human patients, as well as for diagnosing CF. However, we also observed the need for improved reporting to ensure reproducibility of the experiments and quantitative comparability of the results within and between species (e.g., with meta-analyses). Currently, data gaps warrant further primary studies.

Lipid-based nucleic acid therapeutics with in vivo efficacy

Synthetic vectors for therapeutic nucleic acid delivery are currently competing significantly with their viral counter parts due to their reduced immunogenicity, large payload capacity, and ease of manufacture under GMP-compliant norms. The approval of Onpattro, a lipid-based siRNA therapeutic, and the proven clinical success of two lipid-based COVID-19 vaccines from Pfizer-BioNTech, and Moderna heralded the specific advantages of lipid-based systems among all other synthetic nucleic acid carriers. Lipid-based systems with diverse payloads-plasmid DNA (pDNA), antisense oligonucleotide (ASO), small interfering RNA (siRNA), microRNA (miRNA), small activating RNA (saRNA), and messenger RNA (mRNA)-are now becoming a mature technology, with growing impact in the clinic. Research over four decades identified the key factors determining the therapeutic success of these multi-component systems. Here, we discuss the main nucleic acid-based technologies, presenting their mechanism of action, delivery barriers facing them, the structural properties of the payload as well as the component lipids that regulate physicochemical properties, pharmacokinetics and biodistribution, efficacy, and toxicity of the resultant nanoparticles. We further detail on the formulation parameters, evolution of the manufacturing techniques that generate reproducible and scalable outputs, and key manufacturing aspects that enable control over physicochemical properties of the resultant particles. Preclinical applications of some of these formulations that were successfully translated from in vitro studies to animal models are subsequently discussed. Finally, clinical success and failure of these systems starting from 1993 to present are highlighted, in a holistic literature review focused on lipid-based nucleic acid delivery systems. This article is categorized under: Therapeutic Approaches and Drug Discovery > Emerging Technologies Therapeutic Approaches and Drug Discovery > Nanomedicine for Oncologic Disease Toxicology and Regulatory Issues in Nanomedicine > Toxicology of Nanomaterials.

Gene Therapy: A Possible Alternative to CFTR Modulators?

Cystic fibrosis (CF) is a rare genetic disease that affects several organs, but lung disease is the major cause of morbidity and mortality. The gene responsible for CF, the CFTR (Cystic Fibrosis Transmembrane Conductance Regulator) gene, has been discovered in 1989. Since then, gene therapy i.e., defective gene replacement by a functional one, remained the ultimate goal but unfortunately, it has not yet been achieved. However, patients care and symptomatic treatments considerably increased CF patients’ life expectancy ranging from 5 years old in the 1960s to 40 today. In the last decade, research works on CFTR protein structure and activity led to the development of new drugs which, by readdressing CFTR to the plasma membrane (correctors) or by enhancing its transport activity (potentiators), allow, alone or in combination, an improvement of CF patients’ lung function and quality of life. While expected, it is not yet known whether taking these drugs from an early age and for years will improve the quality of life of CF patients in the long term and further increase their life expectancy. Besides, these molecules are not available (specific variants of CFTR) or accessible (national health policies) for all patients and there is still no curative treatment. Another alternative that could benefit from new technologies, such as gene therapy, is therefore still attractive, although it is not yet offered to patients. Faced with the development of new CFTR correctors and potentiators, the question arises as to whether there is still a place for gene therapy and this is discussed in this perspective.

Partially Polymerized Phospholipid Vesicles for Efficient Delivery of Macromolecules

Lipid-based vesicles, namely cationic liposomal nanocarriers have been recognized early on as one of the most attractive delivery systems for RNA, protein, and oligonucleotides. Despite several advantages of conventional liposomal carriers for therapeutic macromolecules, their flexible and unsupported bilayered membranes can pose some limitations for efficient intracellular delivery of their sensitive cargos. Hence, polymerized liposomes, a concept conceived about 20 years ago, might offer structural solution to current in vivo efficiency concerns affecting traditional cationic phospholipid vectors, especially when adapted to enable superior loading and stability, typically required for effective intracellular delivery of proteins and polynucleotides.Our recent approach attempted to remodel polymerized liposomal vesicles-specifically their semi-rigid membrane structure-to create block-polymerized bilayered vesicles (generally composed of DOTAP: DOPE: Diyne PC in 0.1:1:1 molar ratio). Adopting a modified freeze-dry-rehydration technique allowed modular reassembly of such partially polymerized lipidic vesicles (PPL). Different prototype cationic partially polymerized liposomal preparations (PPLs) were successfully developed (mean particle size range 150-300 nm), demonstrating enhanced physicochemical stability and loading capacity, thus promoting improved intracellular delivery of model RNAi and protein cargos.

Lipid-Based DNA Therapeutics: Hallmarks of Non-Viral Gene Delivery

Gene therapy is a promising strategy for the treatment of monogenic disorders. Non-viral gene delivery systems including lipid-based DNA therapeutics offer the opportunity to deliver an encoding gene sequence specifically to the target tissue and thus enable the expression of therapeutic proteins in diseased cells. Currently, available gene delivery approaches based on DNA are inefficient and require improvements to achieve clinical utility. In this Review, we discuss state-of-the-art lipid-based DNA delivery systems that have been investigated in a preclinical setting. We emphasize factors influencing the delivery and subsequent gene expression in vitro, ex vivo, and in vivo. In addition, we cover aspects of nanoparticle engineering and optimization for DNA therapeutics. Finally, we highlight achievements of lipid-based DNA therapies in clinical trials.

In Vivo Calpain Knockdown Using Delivery of siRNA

Calpain is an intracellular Ca²⁺-dependent non-lysosomal cysteine protease expressed ubiquitously in mammals. In endothelial cells, dysregulation of calpain has been shown to be involved in a wide variety of pathological conditions such as angiogenesis, vascular inflammation, and diabetes. Cell- or tissue-targeted in vivo delivery of small interfering RNA (siRNA) is a powerful research tool in the analysis of protein function and has been proposed as an attractive therapeutic modality that is applicable against a large number of human diseases including cancer. In this chapter we describe a method to knockdown calpain 1 in mouse pulmonary vascular endothelium using delivery of siRNA/cationic liposome complex. This technique results in a greater than 80% reduction in calpain 1 protein levels 48 h after a single i.v. injection of calpain 1 siRNA (0.5 mg siRNA/kg)/cationic liposome complex. We also describe confocal imaging to verify the loss of calpain 1 expression in pulmonary microvessel endothelial cells and application of this technique in the mouse model of ventilator-induced lung injury.

Cystic Fibrosis Gene Therapy: Looking Back, Looking Forward

Cystic fibrosis (CF) is an autosomal recessive disease caused by mutations in the cystic fibrosis transmembrane conductance regulator (CFTR) gene that encodes a cAMP-regulated anion channel. Although CF is a multi-organ system disease, most people with CF die of progressive lung disease that begins early in childhood and is characterized by chronic bacterial infection and inflammation. Nearly 90% of people with CF have at least one copy of the ΔF508 mutation, but there are hundreds of CFTR mutations that result in a range of disease severities. A CFTR gene replacement approach would be efficacious regardless of the disease-causing mutation. After the discovery of the CFTR gene in 1989, the in vitro proof-of-concept for gene therapy for CF was quickly established in 1990. In 1993, the first of many gene therapy clinical trials attempted to rescue the CF defect in airway epithelia. Despite the initial enthusiasm, there is still no FDA-approved gene therapy for CF. Here we discuss the history of CF gene therapy, from the discovery of the CFTR gene to current state-of-the-art gene delivery vector designs. While implementation of CF gene therapy has proven more challenging than initially envisioned; thanks to continued innovation, it may yet become a reality.

The role of mucus on drug transport and its potential to affect therapeutic outcomes

A layer of mucus covers the surface of all wet epithelia throughout the human body. Mucus is a hydrogel mainly composed of water, mucins (glycoproteins), DNA, proteins, lipids, and cell debris. This complex composition yields a tenacious viscoelastic hydrogel that lubricates and protects the exposed epithelia from external threats and enzymatic degradation. The natural protective role of mucus is nowadays acknowledged as a major barrier to be overcome in non-invasive drug delivery. The heterogeneity of mucus components offers a wide range of potential chemical interaction sites for macromolecules, while the mesh-like architecture given to mucus by the intermolecular cross-linking of mucin molecules results in a dense network that physically, and in a size-dependent manner, hinders the diffusion of nanoparticles through mucus. Consequently, drug diffusion, epithelial absorption, drug bioavailability, and ultimately therapeutic outcomes of mucosal drug delivery can be attenuated.

Topical cystic fibrosis transmembrane conductance regulator gene replacement for cystic fibrosis-related lung disease

BACKGROUND

Cystic fibrosis is caused by a defective gene encoding a protein called the cystic fibrosis transmembrane conductance regulator (CFTR), and is characterised by chronic lung infection resulting in inflammation and progressive lung damage that results in a reduced life expectancy.

OBJECTIVES

To determine whether topical CFTR gene replacement therapy to the lungs in people with cystic fibrosis is associated with improvements in clinical outcomes, and to assess any adverse effects.

SEARCH METHODS

We searched the Cochrane Cystic Fibrosis and Genetic Disorders Group Trials Register comprising references identified from comprehensive electronic database searches, handsearching relevant journals and abstract books of conference proceedings.Date of most recent search: 05 May 2016.An additional search of the National Institutes for Health (NIH) Genetic Modification Clinical Research Information System (GeMCRIS) was also performed for the years 1992 to 2015.Date of most recent search: 20 April 2016.

SELECTION CRITERIA

Randomised controlled studies comparing topical CFTR gene delivery to the lung, using either viral or non-viral delivery systems, with placebo or an alternative delivery system in people with confirmed cystic fibrosis.

DATA COLLECTION AND ANALYSIS

The authors independently extracted data and assessed study quality. Authors of included studies were contacted and asked for any available additional data. Meta-analysis was limited due to differing study designs.

MAIN RESULTS

Four randomised controlled studies met the inclusion criteria for this review, involving a total of 302 participants lasting from 29 days to 13 months; 14 studies were excluded. The included studies differed in terms of CFTR gene replacement agent and study design, which limited the meta-analysis. One study only enrolled adult males, the remaining studies included both males and females aged 12 years and over.Risk of bias in the studies was moderate. Random sequence generation and allocation concealment was only described in the more recent study; the remaining three studies were judged to have an unclear risk of bias. All four studies documented double-blinding to the intervention, but there is some uncertainty with regards to participant blinding in one study. Some outcome data were missing from all four studies.There were no differences in either the number of respiratory exacerbations or the number of participants with an exacerbation between replacement therapy or placebo groups at any time point. Meta-analysis of most respiratory function tests showed no difference between treatment and placebo groups, but the smallest study (n = 16) reported forced vital capacity (litres) increased more in the placebo group at up to 24 hours. A further study reported a significant improvement in forced expiratory volume at one second (litres) at 30 days after participants had received their first dose of favouring the gene therapy agent, but this finding was not confirmed when combined with at second study in the meta-analysis. The more recent study (n = 140) demonstrated a small improvement in forced vital capacity (per cent predicted) at two and three months and again at 11 and 12 months for participants receiving CFTR gene replacement therapy compared to those receiving placebo. The same study reported a significant difference in the relative change in forced expiratory volume at one second (per cent predicted) at two months, three months and 12 months.One small study reported significant concerns with "influenza-like" symptoms in participants treated with CFTR gene replacement therapy; this was not reported on repeated use of the same agent in a larger recent study.There was no other evidence of positive impact on outcomes, in particular improved quality of life or reduced treatment burden.Two studies measured ion transport in the lower airways; one (n = 16) demonstrated significant changes toward normal values in the participants who received gene transfer agents (P < 0.0001), mean difference 6.86 (95% confidence interval 3.77 to 9.95). The second study (n = 140) also reported significant changes toward normal values (P = 0.032); however, aggregate data were not available for analysis. In the most recent study, there was also evidence of increased salt transport in cells obtained by brushing the lower airway. These outcomes, whilst important, are not of direct clinical relevance.

AUTHORS' CONCLUSIONS

One study of liposome-based CFTR gene transfer therapy demonstrated some improvements in respiratory function in people with CF, but this limited evidence of efficacy does not support this treatment as a routine therapy at present. There was no evidence of efficacy for viral-mediated gene delivery.Future studies need to investigate clinically important outcome measures.

Transgene sequences free of CG dinucleotides lead to high level, long-term expression in the lung independent of plasmid backbone design

Non-viral aerosol gene therapy offers great potential for treating chronic lung diseases of the airways such as cystic fibrosis (CF). Early clinical trials showed that transgene expression in the airways was transient whereas maximal duration of transgene expression is essential in order to minimise the frequency of aerosol treatments. Improved vector design, such as careful selection of the promoter/enhancer, can lead to more persistent levels of transgene expression, but multiple factors affect expression in vivo. Following aerosol delivery to the lungs of mice, we measured reporter gene expression from a CpG-free luciferase transgene cassette in the context of both a plasmid and minicircle vector configuration and showed that the vector backbone had no effect on expression. Transgene activity was affected by the vector backbone however, when a similar, but sub-optimal CpG-containing transgene was used, suggesting that aspects of the plasmid backbone had a negative impact on transgene expression. Similar studies were performed in Toll-like receptor-9 (TLR9) knockout mice to investigate a potential role for the TLR9 signalling pathway in detecting CpGs in the vector sequence. Even in the absence of TLR9, persistent expression could only be achieved with a CpG-free transgene. Together, these data indicate that in order to achieve high levels of persistent expression in vivo, a CpG-free transgene cassette is required.

Strategies in early clinical development for the treatment of basic defects of cystic fibrosis

INTRODUCTION

Twenty-six years after the identification of the gene responsible for cystic fibrosis (CF), controversies still surround the pathogenesis of the disease that continues to burden and shorten lives. Therefore, finding effective therapeutic strategies that target the basic defect of CF is crucially needed.

AREAS COVERED

This review offers a comprehensive survey of fundamental therapies in early stages of development for the treatment of CF. The first part describes recent strategies targeting the basic defect either at the gene or at the transcript level. The second part summarizes a panel of novel strategies targeting protein repair. The third part reports strategies targeting non-CFTR channels.

EXPERT OPINION

Recent major breakthroughs in CF therapy have been made, raising hope to find a cure for CF. Apart from Vertex corrector and potentiator molecules (lumacaftor, ivacaftor, VX-661) and from ataluren, used to correct nonsense mutations, most compounds being currently tested are in very early (I-II) phases of development and definitive clinical results are keenly expected. Among the broad list of molecules and strategies being tested, the QR-010 compound and inhibitors of phosphodiesterase type 5 (sildenafil, vardenafil) could reveal a strong potentiality as therapeutic candidates to cure CF.

Cystic Fibrosis Gene Therapy in the UK and Elsewhere

The cystic fibrosis transmembrane conductance regulator (CFTR) gene was identified in 1989. This opened the door for the development of cystic fibrosis (CF) gene therapy, which has been actively pursued for the last 20 years. Although 26 clinical trials involving approximately 450 patients have been carried out, the vast majority of these trials were short and included small numbers of patients; they were not designed to assess clinical benefit, but to establish safety and proof-of-concept for gene transfer using molecular end points such as the detection of recombinant mRNA or correction of the ion transport defect. The only currently published trial designed and powered to assess clinical efficacy (defined as improvement in lung function) administered AAV2-CFTR to the lungs of patients with CF. The U.K. Cystic Fibrosis Gene Therapy Consortium completed, in the autumn of 2014, the first nonviral gene therapy trial designed to answer whether repeated nonviral gene transfer (12 doses over 12 months) can lead to clinical benefit. The demonstration that the molecular defect in CFTR can be corrected with small-molecule drugs, and the success of gene therapy in other monogenic diseases, is boosting interest in CF gene therapy. Developments are discussed here.

Non-viral therapeutic approaches to ocular diseases: An overview and future directions

Currently there are no viable treatment options for patients with debilitating inherited retinal degeneration. The vast variability in disease-inducing mutations and resulting phenotypes has hampered the development of therapeutic interventions. Gene therapy is a logical approach, and recent work has focused on ways to optimize vector design and packaging to promote optimized expression and phenotypic rescue after intraocular delivery. In this review, we discuss ongoing ocular clinical trials, which currently use viral gene delivery, but focus primarily on new advancements in optimizing the efficacy of non-viral gene delivery for ocular diseases. Non-viral delivery systems are highly customizable, allowing functionalization to improve cellular and nuclear uptake, bypassing cellular degradative machinery, and improving gene expression in the nucleus. Non-viral vectors often yield transgene expression levels lower than viral counterparts, however their favorable safety/immune profiles and large DNA capacity (critical for the delivery of large ocular disease genes) make their further development a research priority. Recent work on particle coating and vector engineering presents exciting ways to overcome limitations of transient/low gene expression levels, but also highlights the fact that further refinements are needed before use in the clinic.

Gene therapy for cancer: regulatory considerations for approval

The rapidly changing field of gene therapy promises a number of innovative treatments for cancer patients. Advances in genetic modification of cancer and immune cells and the use of oncolytic viruses and bacteria have led to numerous clinical trials for cancer therapy, with several progressing to late-stage product development. At the time of this writing, no gene therapy product has been approved by the United States Food and Drug Administration (FDA). Some of the key scientific and regulatory issues include understanding of gene transfer vector biology, safety of vectors in vitro and in animal models, optimum gene transfer, long-term persistence or integration in the host, shedding of a virus and ability to maintain transgene expression in vivo for a desired period of time. Because of the biological complexity of these products, the FDA encourages a flexible, data-driven approach for preclinical safety testing programs. The clinical trial design should be based on the unique features of gene therapy products, and should ensure the safety of enrolled subjects. This article focuses on regulatory considerations for gene therapy product development and also discusses guidance documents that have been published by the FDA.

Repeated nebulisation of non-viral CFTR gene therapy in patients with cystic fibrosis: a randomised, double-blind, placebo-controlled, phase 2b trial

Background

Lung delivery of plasmid DNA encoding the CFTR gene complexed with a cationic liposome is a potential treatment option for patients with cystic fibrosis. We aimed to assess the efficacy of non-viral CFTR gene therapy in patients with cystic fibrosis.

Methods

We did this randomised, double-blind, placebo-controlled, phase 2b trial in two cystic fibrosis centres with patients recruited from 18 sites in the UK. Patients (aged ≥12 years) with a forced expiratory volume in 1 s (FEV₁) of 50–90% predicted and any combination of CFTR mutations, were randomly assigned, via a computer-based randomisation system, to receive 5 mL of either nebulised pGM169/GL67A gene–liposome complex or 0·9% saline (placebo) every 28 days (plus or minus 5 days) for 1 year. Randomisation was stratified by % predicted FEV₁ (<70 vs ≥70%), age (<18 vs ≥18 years), inclusion in the mechanistic substudy, and dosing site (London or Edinburgh). Participants and investigators were masked to treatment allocation. The primary endpoint was the relative change in % predicted FEV₁. The primary analysis was per protocol. This trial is registered with ClinicalTrials.gov, number NCT01621867.

Findings

Between June 12, 2012, and June 24, 2013, we randomly assigned 140 patients to receive placebo (n=62) or pGM169/GL67A (n=78), of whom 116 (83%) patients comprised the per-protocol population. We noted a significant, albeit modest, treatment effect in the pGM169/GL67A group versus placebo at 12 months' follow-up (3·7%, 95% CI 0·1–7·3; p=0·046). This outcome was associated with a stabilisation of lung function in the pGM169/GL67A group compared with a decline in the placebo group. We recorded no significant difference in treatment-attributable adverse events between groups.

Interpretation

Monthly application of the pGM169/GL67A gene therapy formulation was associated with a significant, albeit modest, benefit in FEV₁ compared with placebo at 1 year, indicating a stabilisation of lung function in the treatment group. Further improvements in efficacy and consistency of response to the current formulation are needed before gene therapy is suitable for clinical care; however, our findings should also encourage the rapid introduction of more potent gene transfer vectors into early phase trials.

Funding

Medical Research Council/National Institute for Health Research Efficacy and Mechanism Evaluation Programme.

Cystic fibrosis--what are the prospects for a cure?

Significant improvements in the treatment of cystic fibrosis over the last few decades have altered this lethal disease in children to a multisystem disorder with survival into adult life now common. In most developed countries the numbers of adult cystic fibrosis patients outnumber children. This is mainly due to improvements in care during early life. The principal cause of morbidity and mortality is pulmonary disease, and so the focus of new treatments has targeted the lungs. Identification of the underlying gene defect in the cystic fibrosis transmembrane conductance regulator has ushered in a new era in cystic fibrosis research, with prospects of a cure. In this article, we review the most exciting recent advances that correct defects in cellular processing, chloride channel function and gene therapy.

Lung gene therapy-How to capture illumination from the light already present in the tunnel

Gene therapy has been considered as the most ideal medical intervention for genetic diseases because it is intended to target the cause of diseases instead of disease symptoms. Availability of techniques for identification of genetic mutations and for in vitro manipulation of genes makes it practical and attractive. After the initial hype in 1990s and later disappointments in clinical trials for more than a decade, light has finally come into the tunnel in recent years, especially in the field of eye gene therapy where it has taken big strides. Clinical trials in gene therapy for retinal degenerative diseases such as Leber's congenital amaurosis (LCA) and choroideremia demonstrated clear therapeutic efficacies without apparent side effects. Although these successful examples are still rare and sporadic in the field, they provide the proof of concept for harnessing the power of gene therapy to treat genetic diseases and to modernize our medication. In addition, those success stories illuminate the path for the development of gene therapy treating other genetic diseases. Because of the differences in target organs and cells, distinct barriers to gene delivery exist in gene therapy for each genetic disease. It is not feasible for authors to review the current development in the entire field. Thus, in this article, we will focus on what we can learn from the current success in gene therapy for retinal degenerative diseases to speed up the gene therapy development for lung diseases, such as cystic fibrosis.

Gene therapy in cystic fibrosis

The principal cause of morbidity and mortality in cystic fibrosis (CF) is pulmonary disease, so the focus of new treatments in this condition is primarily targeted at the lungs. Since the cloning of the Cystic Fibrosis Transmembrane Conductance Regulator (CFTR) gene in 1989, there has been significant interest in the possibility of gene therapy as a treatment for CF. Early studies using viral vectors carrying a healthy CFTR plasmid highlighted the difficulties with overcoming the body's host defences. This article reviews the work on gene therapy in CF to date and describes the ongoing work of the UK CF Gene Therapy Consortium in investigating the potential of gene therapy as a treatment for patients with CF.

Topical cystic fibrosis transmembrane conductance regulator gene replacement for cystic fibrosis-related lung disease

BACKGROUND

Cystic fibrosis is caused by a defective gene encoding a protein called the cystic fibrosis transmembrane conductance regulator (CFTR), and is characterised by chronic lung infection resulting in inflammation and progressive lung damage that results in a reduced life expectancy.

OBJECTIVES

To determine whether topical CFTR gene replacement therapy to the lungs in people with cystic fibrosis is associated with improvements in clinical outcomes, and to assess any adverse effects.

SEARCH METHODS

We searched the Cochrane Cystic Fibrosis and Genetic Disorders Group Trials Register comprising references identified from comprehensive electronic database searches, handsearching relevant journals and abstract books of conference proceedings.Date of most recent search: 22 August 2013.An additional search of the National Institutes for Health (NIH) Genetic Modification Clinical Research Information System (GeMCRIS) was also performed for the years 1992 to 2013.Date of most recent search: 04 September 2013.

SELECTION CRITERIA

Randomised controlled trials comparing topical CFTR gene delivery to the lung, using either viral or non-viral delivery systems, with placebo or an alternative delivery system in people with confirmed cystic fibrosis.

DATA COLLECTION AND ANALYSIS

The authors independently extracted data and assessed study quality. Authors of included studies were contacted and asked for any available additional data. Meta-analysis was limited due to differing study designs.

MAIN RESULTS

Three randomised controlled trials met the inclusion criteria for this review, involving a total of 155 participants. Fourteen studies were excluded. The included studies differed in terms of CFTR gene replacement agent and study design, which limited the meta-analysis.Although the first Moss study reported a significant improvement in respiratory function (forced expiratory volume at one second) 30 days after participants had received their first dose of gene therapy agent, this finding was not confirmed in their larger second study or in our meta-analysis.In participants who received the CFTR gene transfer agents in the Alton study, "influenza-like" symptoms were found (risk ratio 7.00 (95% confidence interval 1.10 to 44.61)). There were no other significant increases in adverse events in any of the studies.Alton measured ion transport in the lower airways and demonstrated significant changes toward normal values in the participants who received gene transfer agents (P < 0.0001), mean difference 6.86 (95% confidence interval 3.77 to 9.95). In these participants there was also evidence of increased salt transport in cells obtained by brushing the lower airway. These outcomes, whilst important, are not of direct clinical relevance.

AUTHORS' CONCLUSIONS

There is currently no evidence to support the use of CFTR gene transfer agents as a treatment for lung disease in people with cystic fibrosis. Future studies need to investigate clinically important outcome measures.

Adenoviral gene transfer corrects the ion transport defect in the sinus epithelia of a porcine CF model

Cystic fibrosis (CF) pigs spontaneously develop sinus and lung disease resembling human CF. The CF pig presents a unique opportunity to use gene transfer to test hypotheses to further understand the pathogenesis of CF sinus disease. In this study, we investigated the ion transport defect in the CF sinus and found that CF porcine sinus epithelia lack cyclic AMP (cAMP)-stimulated anion transport. We asked whether we could restore CF transmembrane conductance regulator gene (CFTR) current in the porcine CF sinus epithelia by gene transfer. We quantified CFTR transduction using an adenovirus expressing CFTR and green fluorescent protein (GFP). We found that as little as 7% of transduced cells restored 6% of CFTR current with 17-28% of transduced cells increasing CFTR current to 50% of non-CF levels. We also found that we could overcorrect cAMP-mediated current in non-CF epithelia. Our findings indicate that CF porcine sinus epithelia lack anion transport, and a relatively small number of cells expressing CFTR are required to rescue the ion transport phenotype. These studies support the use of the CF pig as a preclinical model for future gene therapy trials in CF sinusitis.

Manganese-loaded lipid-micellar theranostics for simultaneous drug and gene delivery to lungs

Gadolinium (Gd) contrast agents are predominantly used for T(1) MR imaging. However, the high toxicity of Gd(3+) and potential side effects including nephrogenic systemic fibrosis have led to the search for alternative T(1) contrast agents. Since manganese (Mn) has paramagnetic properties with five unpaired electrons that permit high spin number, long electronic relaxation times, and labile water exchange, we evaluated Mn as a T(1) magnetic resonance imaging (MRI) contrast agent for lung imaging. Here we report on the design and synthesis of multifunctional lipid-micellar nanoparticles (LMNs) containing Mn oxide (M-LMNs) for MRI that can also be used for DNA and drug delivery. Oleic acid-coated MnO nanoparticles were encapsulated in micelles composed of polyethylene glycol (PEG-2000), phosphatidylethanolamine (PE), DC-cholesterol, and dioleoyl-phosphatidylethanolamine (DOPE). The particles are taken up in vitro by human embryonic kidney (HEK293), Lewis lung carcinoma (LLC1), and A549 cells and are devoid of cytotoxicity. When administered to mice intranasally, they preferentially accumulate in the lungs. In vitro phantom and ex vivo lung MRI results confirmed that M-LMNs are able to enhance T(1) MRI contrast. M-LMNs loaded with plasmid DNA and/or doxorubicin are efficiently taken up by HEK293 cells in vitro and by target cells in vivo. Taken together, these results demonstrate that M-LMNs are capable of simultaneously providing MRI contrast and DNA and/or drug delivery to target cells in the lung and therefore may prove useful as a lung theranostic, especially for lung cancers.

Topical cystic fibrosis transmembrane conductance regulator gene replacement for cystic fibrosis-related lung disease

BACKGROUND

Cystic fibrosis is caused by a defective gene encoding a protein called the cystic fibrosis transmembrane conductance regulator (CFTR), and is characterised by chronic lung infection resulting in inflammation and progressive lung damage that results in a reduced life expectancy.

OBJECTIVES

To determine whether topical CFTR gene replacement therapy to the lungs in people with cystic fibrosis is associated with improvements in clinical outcomes, and to assess any adverse effects.

SEARCH METHODS

We searched the Cochrane Cystic Fibrosis and Genetic Disorders Group Trials Register comprising references identified from comprehensive electronic database searches, handsearching relevant journals and abstract books of conference proceedings.Date of most recent search: 19 July 2012.An additional search of the National Institutes for Health (NIH) Genetic Modification Clinical Research Information System (GeMCRIS) was also performed for the years 1992 to 2012.Date of most recent search: 25 July 2012.

SELECTION CRITERIA

Randomised controlled trials comparing topical CFTR gene delivery to the lung, using either viral or non-viral delivery systems, with placebo or an alternative delivery system in people with confirmed cystic fibrosis.

DATA COLLECTION AND ANALYSIS

The authors independently extracted data and assessed study quality. Authors of included studies were contacted and asked for any available additional data. Meta-analysis was limited due to differing study designs.

MAIN RESULTS

Three randomised controlled trials met the inclusion criteria for this review, involving a total of 155 participants. Fourteen studies were excluded. The included studies differed in terms of CFTR gene replacement agent and study design, which limited the meta-analysis.Although the first Moss study reported a significant improvement in respiratory function (forced expiratory volume at one second) 30 days after participants had received their first dose of gene therapy agent, this finding was not confirmed in their larger second study or in our meta-analysis.In participants who received the CFTR gene transfer agents in the Alton study, "influenza-like" symptoms were found (risk ratio 7.00 (95% confidence interval 1.10 to 44.61)). There were no other significant increases in adverse events in any of the studies.Alton measured ion transport in the lower airways and demonstrated significant changes toward normal values in the participants who received gene transfer agents (P < 0.0001), mean difference 6.86 (95% CI of 3.77 to 9.95). In these participants there was also evidence of increased salt transport in cells obtained by brushing the lower airway. These outcomes, whilst important, are not of direct clinical relevance.

AUTHORS' CONCLUSIONS

There is currently no evidence to support the use of CFTR gene transfer reagents as a treatment for lung disease in people with cystic fibrosis. Future studies need to investigate clinically important outcome measures.

Current Status of Gene Therapy for Cystic Fibrosis Pulmonary Disease

Cystic fibrosis (CF) is a common lethal genetic disorder that affects all ethnic populations; however, it is most prevalent in Caucasians. Intensive basic research over the last 20 years has resulted in a wealth of information regarding the CF gene, its protein product and the mutational basis of disease. This increased understanding has lead to the development of gene therapy for the treatment of CF pulmonary disease. Delivery of the CF gene to the airway requires direct in vivo transfer using vectors encoding for normal CF transmembrane regulator (CFTR) protein. Several vectors are currently available for CF gene transfer and include both viral (adenoviruses, adeno-associated viruses) and non-viral (liposomal) systems. Initial clinical trials with each of these vectors have demonstrated that gene transfer to the CF airway is possible. The efficiency of transfer and duration of expression, however, have been limited. The effects of gene transfer on correction of the basic ion transport defects have also been highly variable and inconsistent, irrespective of the vector. Currently, the risk of severe immunological reactions is the primary factor limiting the clinical advancement of gene therapy. Both the adenoviral and liposomal vectors are associated with significant acute inflammatory reactions. The adenoviruses and adeno-associated viruses also elicit humoral immune responses that significantly reduce the efficiency of transgene expression and increase the risk of readministration. Several strategies are under investigation to improve the efficiency of gene transfer to the CF airway. These include overcoming local barriers in the lung, circumventing the immune response and improving vector internalization and/or uptake. Application of gene transfer in the child and possibly the fetus are also potential future clinical applications of gene therapy. However, despite considerable research with gene therapy, there is little evidence to suggest that a well tolerated and effective gene transfer method is imminent and aggressive use of conventional pharmacological therapies currently offer the greatest promise in the treatment of patients with CF.

Rapid identification of novel functional promoters for gene therapy

Transcriptional control of transgene expression is crucial to successful gene therapy, yet few promoter/enhancer combinations have been tested in clinical trials. We created a simple, desktop computer database and populated it with promoter sequences from publicly available sources. From this database, we rapidly identified novel CpG-free promoter sequences suitable for use in non-inflammatory, non-viral in vivo gene transfer. In a simple model of lung gene transfer, five of the six promoter elements selected, chosen without prior knowledge of their transcriptional activities, directed significant transgene expression. Each of the five novel promoters directed transgene expression for at least 14 days post-delivery, greatly exceeding the duration achieved with the commonly used CpG-rich viral enhancer/promoters. Novel promoter activity was also evaluated in a more clinically relevant model of aerosol-mediated lung gene transfer and in the liver following delivery via high-pressure tail vein injection. In each case, the novel CpG-free promoters exhibited higher and/or more sustained transgene expression than commonly used CpG-rich enhancer/promoter sequences. This study demonstrates that novel CpG-free promoters can be readily identified and that they can direct significant levels of transgene expression. Furthermore, the database search criteria can be quickly adjusted to identify other novel promoter elements for a variety of transgene expression applications.

CpG-free plasmid expression cassettes for cystic fibrosis gene therapy

Clinical studies are underway for the aerosol delivery of plasmid DNA complexed with Genzyme Lipid GL67A to the lungs of patients with cystic fibrosis (CF). Plasmid vectors contain several functional elements all of which play a role in determining the efficacy of the final clinical product. To optimise the final plasmid, variations of CpG-free 5' enhancer elements and 3'UTR regions were inserted into a common CpG-free, plasmid backbone containing Luciferase or CFTR transgenes. Plasmids were compared in immortalised cell culture, human airway liquid interface primary cell cultures, and mouse lung models to determine which design directed optimal transgene expression. Following aerosol delivery to mouse lung, plasmids containing the murine CMV enhancer showed higher peak Luciferase activity than the human CMV enhancer, but the human version resulted in persistent expression. In cell culture, the SV40 3'UTR and a novel BGH2 3'UTR exhibited up to 20-fold higher Luciferase activity than the commonly used BGH 3'UTR, but in mouse lung aerosol studies the activity and duration was greater for BGH 3'UTR. Systematic evaluation of each functional component of the plasmid has resulted in an improved design, exhibiting superior levels and duration of lung gene expression.

Gene therapy for the treatment of cystic fibrosis

Gene therapy is being developed as a novel treatment for cystic fibrosis (CF), a condition that has hitherto been widely-researched yet for which no treatment exists that halts the progression of lung disease. Gene therapy involves the transfer of correct copies of cystic fibrosis transmembrane conductance regulator (CFTR) DNA to the epithelial cells in the airways. The cloning of the CFTR gene in 1989 led to proof-of-principle studies of CFTR gene transfer in vitro and in animal models. The earliest clinical trials in CF patients were conducted in 1993 and used viral and non-viral gene transfer agents in both the nasal and bronchial airway epithelium. To date, studies have focused largely on molecular or bioelectric (chloride secretion) outcome measures, many demonstrating evidence of CFTR expression, but few have attempted to achieve clinical efficacy. As CF is a lifelong disease, turnover of the airway epithelium necessitates repeat administration. To date, this has been difficult to achieve with viral gene transfer agents due to host recognition leading to loss of expression. The UK Cystic Fibrosis Gene Therapy Consortium (Imperial College London, University of Edinburgh and University of Oxford) is currently working on a large and ambitious program to establish the clinical benefits of CF gene therapy. Wave 1, which has reached the clinic, uses a non-viral vector. A single-dose safety trial is nearing completion and a multi-dose clinical trial is shortly due to start; this will be powered for clinically-relevant changes. Wave 2, more futuristically, will look at the potential of lentiviruses, which have long-lasting expression. This review will summarize the current status of translational research in CF gene therapy.

Advances in cell and gene-based therapies for cystic fibrosis lung disease

Cystic fibrosis (CF) is a disease characterized by airway infection, inflammation, remodeling, and obstruction that gradually destroy the lungs. Direct delivery of the cystic fibrosis transmembrane conductance regulator (CFTR) gene to airway epithelia may offer advantages, as the tissue is accessible for topical delivery of vectors. Yet, physical and host immune barriers in the lung present challenges for successful gene transfer to the respiratory tract. Advances in gene transfer approaches, tissue engineering, and novel animal models are generating excitement within the CF research field. This review discusses current challenges and advancements in viral and nonviral vectors, cell-based therapies, and CF animal models.

Gene therapy for ALI/ARDS

Acute lung injury (ALI) and acute respiratory distress syndrome (ARDS) are characterized by acute respiratory failure and are associated with diverse disorders. Gene therapy is a potentially powerful approach to treat diseases related to ALI/ARDS, and numerous viral and nonviral methods for gene delivery to the lung have been developed. Discussed are recent advances in the development of more efficient viral and nonviral gene transfer systems, and the current status of gene therapy applied to ALI/ARDS-associated pulmonary diseases is reviewed. With the development of more efficient gene therapy vectors, gene therapy is a promising strategy for clinical application.

Design of gene therapy trials in CF patients

The report of the first CF patients to receive CFTR gene therapy appeared in 1993; since then, there have been over 20 clinical trials of both viral and non-viral gene transfer agents. These have largely been single dose to either nose or lower airway and have been designed around molecular or bioelectrical outcome measures. Both transgene mRNA and partial correction of chloride secretion have been reported, although sodium hyperabsorption has not been improved. The UK CF Gene Therapy Consortium is focussed on a clinical programme to establish whether these proof-of-principle measures translate into clinical benefit. Here, we discuss the considerations in designing such a programme, focusing in particular on our choice of the optimal, currently available delivery method and established and novel outcome measures. We highlight the logistic and regulatory complexities of such a clinical programme and finally, we look to the future and consider possible alternative strategies.

Efficient, specific and targeted delivery of genes to the lung

Many inherited and acquired pulmonary disorders without satisfactory therapies may be amenable to gene therapy. Despite numerous advances, efficient delivery and expression of the therapeutic transgene at physiological levels for phenotypic correction of disease has proved elusive. This article focuses on various strategies aimed at achieving targeted delivery to the lungs. Both physical methods and biological targeting have been successfully applied in various gene delivery systems. Targeting of different cell types has been achieved by pseudotyping of viral vectors with capsids from different serotypes and modification of nonviral vectors with targeting ligands. Both classes of vectors are discussed with respect to their gene delivery and expression efficiencies, longevity of expression and immunogenicity. Moreover, gene therapy clinical trials for different lung diseases are discussed.

Non-viral vectors in cystic fibrosis gene therapy: recent developments and future prospects

Gene therapy has been proposed for a wide range of human diseases but few have received the level of attention over such a prolonged period as cystic fibrosis (CF) with over 20 clinical studies undertaken. Following a 10-year interval, clinical trials of an aerosolisable non-viral gene transfer agent have recently been initiated by researchers in the United Kingdom. Here we review the rationale and requirements for effective gene therapy for CF lung disease. The previous non-viral gene therapy trials are discussed and the prospects for the current leading non-viral formulations for CF gene therapy are considered. Factors affecting the selection and design of the plasmid DNA molecule, likely to be of central importance to clinical efficacy, are reviewed and we describe the potential merits of the formulation that has been selected for the forthcoming UK trials.

Lipidic systems for in vivo siRNA delivery

The ability of small-interfering RNA (siRNA) to silence specific target genes not only offers a tool to study gene function but also represents a novel approach for the treatment of various human diseases. Its clinical use, however, has been severely hampered by the lack of delivery of these molecules to target cell populations in vivo due to their instability, inefficient cell entry, and poor pharmacokinetic profile. Various delivery vectors including liposomes, polymers, and nanoparticles have thus been developed in order to circumvent these problems. This review presents a comprehensive overview of the barriers and recent progress for both local and systemic delivery of therapeutic siRNA using lipidic vectors. Different strategies for formulating these siRNA-loaded lipid particles as well as the general concern about their safe use in vivo will also be discussed. Finally, current advances in the targeted delivery of siRNA and their impacts on the field of RNA interference (RNAi)-based therapy will be presented.

Women and heart disease--physiologic regulation of gene delivery and expression: bioreducible polymers and ischemia-inducible gene therapies for the treatment of ischemic heart disease

Ischemic heart disease (IHD) is the leading cause of death in the United States today. This year over 750,000 women will have a new or recurrent myocardial infarction. Currently, the mainstay of therapy for IHD is revascularization. Increasing evidence, however, suggests that revascularization alone is insufficient for the longer-term management of many patients with IHD. To address these issues, innovative therapies that extend beyond revascularization to protection of the myocyte and preservation of ventricular function are required. The emergence of gene therapy and proteomics offers the potential for innovative prophylactic and treatment strategies for IHD. The goal of our research is to develop therapeutic gene constructs for the treatment of myocardial ischemia that are clinically safe and effective. Toward this end, we describe the development of physiologic regulation of gene delivery and expression using bioreducible polymers and ischemia-inducible gene therapies for the potential treatment of ischemic heart disease in women.

[Characterization of expression of alpha1-acid glycoprotein gene in Beijing fatty chicken (Gallus gallus)]

The specific expression of alpha1-AGP gene in eight different tissues of Beijing fatty chicken was investigated by RT-PCR. The full-length cDNA of alpha1-AGP was inserted into pEGFP-C1 multi-cloning sites to construct recombinant eukaryotic expression vector pEGFP-alpha1-AGP. The lipofectin method was used to transfect the pEGFP-alpha1-AGP into Beijing fatty chicken fibroblast cells. The open reading frame of Beijing fatty chicken alpha1-AGP gene was 612 base pairs in length, which was expressed higher in liver and lung than in muscle. This gene did not express in heart and kidney. The expression efficiency ranged from 31.3% to 47.6% in 24, 48, and 72 h after transformation. The green fluorescence mainly concentrated in the nucleus. With the increase of the expression of green fluorescence, granula was observed in the nucleus. RT-PCR and Western blotting analyses showed that pEGFP-alpha1-AGP had been integrated into the genome of Beijing chicken fibroblast cell with normal expression level. In optimized condition, there was no significant effect (P>0.05) on apoptosis ratio, positive cell shape, growth and reduplication state comparing with the control group. This research established the foundation for further function research of alpha1-AGP gene and application in transgenic animal cloning.

Gene transfer to the lung: lessons learned from more than 2 decades of CF gene therapy

Gene therapy is currently being developed for a wide range of acute and chronic lung diseases. The target cells, and to a degree the extra and intra-cellular barriers, are disease-specific and over the past decade the gene therapy community has recognized that no one vector is good for all applications, but that the gene transfer agent (GTA) has to be carefully matched to the specific disease target. Gene therapy is particularly attractive for diseases that currently do not have satisfactory treatment options and probably easier for monogenic disorders than for complex diseases. Cystic fibrosis (CF) fulfils these criteria and is, therefore, a good candidate for gene therapy-based treatment. This review will focus on CF as an example for lung gene therapy, but lessons learned may be applicable to other target diseases.

The effect of nocodazole on the transfection efficiency of lipid-bilayer coated gold nanoparticles

Nonviral vectors are safer than viral systems for gene therapy applications. However, the limited efficacy always prevents their being widely used in clinical practice. Aside from searching new gene nonviral vectors, many researchers focus on finding out new substances to improve the transfection efficiency of existent vectors. In this work, we found a transfection enhancer, nocodazole (NCZ), for dimethyldioctadecylammonium (DODAB, a cationic lipid) bilayer coated gold nanoparticles (AuNPs) mediated gene delivery. It was found that NCZ produces 3-fold transfection enhancement to HEK 293T cells assessed by flow cytometry (FCM). The result was further confirmed by luciferase assay, in which NCZ induced more than 5 times improvement in transfection efficiency after 48 h of transfection. The results from the inductively coupled plasma mass spectrometry (ICP-MS) and FCM showed that NCZ did not affect the internalization of DODAB-AuNPs/DNA complexes. The trafficking of the complexes by transmission electron microscopy (TEM) indicated that the interrupted transportation of the complexes to the lysosomes contributed greatly to the transfection enhancement. Therefore, NCZ can be used as a transfection enhancer in DODAB-AuNPs mediated transfection system. This work also gave an insight to improving the efficiency of lipid-mediated transfection: modifying lipid on gold nanoparticles and pre-treating cells by NCZ before the transfection.