Nanoparticles that deliver triplex-forming peptide nucleic acid molecules correct F508del CFTR in airway epithelium

Impact of gene editing on the study of cystic fibrosis

Cystic fibrosis (CF) is a chronic and progressive autosomal recessive disorder of secretory epithelial cells, which causes obstructions in the lung airways and pancreatic ducts of 70,000 people worldwide (for recent review see Cutting Nat Rev Genet 16(1):45-56, 2015). The finding that mutations in the CFTR gene cause CF (Kerem et al. Science 245(4922):1073-1080, 1989; Riordan et al. Science 245(4922):1066-1073, 1989; Rommens et al. Science 245(4922):1059-1065, 1989), was hailed as the very happy middle of a story whose end is a cure for a fatal disease (Koshland Science 245(4922):1029, 1989). However, despite two licensed drugs (Ramsey et al. N Engl J Med 365(18):1663-1672, 2011; Wainwright et al. N Engl J Med 373(3):220-231, 2015), and a formal demonstration that repeated administration of CFTR cDNA to patients is safe and effects a modest but significant stabilisation of disease (Alton et al. Lancet Respir Med 3(9):684-691, 2015), we are still a long way from a cure, with many patients taking over 100 tablets per day, and a mean age at death of 28 years. The aim of this review is to discuss the impact on the study of CF of gene-editing techniques as they have developed over the last 30 years, up to and including the possibility of editing as a therapeutic approach.

Barriers to inhaled gene therapy of obstructive lung diseases: A review

Knowledge of genetic origins of obstructive lung diseases has made inhaled gene therapy an attractive alternative to the current standards of care that are limited to managing disease symptoms. Initial lung gene therapy clinical trials occurred in the early 1990s following the discovery of the genetic defect responsible for cystic fibrosis (CF), a monogenic disorder. However, despite over two decades of intensive effort, gene therapy has yet to help patients with CF or any other obstructive lung disease. The slow progress is due in part to poor understanding of the biological barriers to inhaled gene therapy. Encouragingly, clinical trials have shown that inhaled gene therapy with various viral vectors and non-viral gene vectors is well tolerated by patients, and continued research has provided valuable lessons and resources that may lead to future success of this therapeutic strategy. In this review, we first introduce representative obstructive lung diseases and examine limitations of currently available therapeutic options. We then review key components for successful execution of inhaled gene therapy, including gene delivery systems, primary physiological barriers and strategies to overcome them, and advances in preclinical disease models with which the most promising systems may be identified for human clinical trials.

In Vivo Delivery Systems for Therapeutic Genome Editing

Therapeutic genome editing technology has been widely used as a powerful tool for directly correcting genetic mutations in target pathological tissues and cells to cure of diseases. The modification of specific genomic sequences can be achieved by utilizing programmable nucleases, such as Meganucleases, zinc finger nucleases (ZFNs), transcription activator-like effector nucleases (TALENs), and the clustered regularly-interspaced short palindromic repeat-associated nuclease Cas9 (CRISPR/Cas9). However, given the properties, such as large size, negative charge, low membrane penetrating ability, as well as weak tolerance for serum, and low endosomal escape, of these nucleases genome editing cannot be successfully applied unless in vivo delivery of related programmable nucleases into target organisms or cells is achieved. Here, we look back at delivery strategies having been used in the in vivo delivery of three main genome editing nucleases, followed by methodologies currently undergoing testing in clinical trials, and potential delivery strategies provided by analyzing characteristics of nucleases and commonly used vectors.

Genome-editing Technologies for Gene and Cell Therapy

Gene therapy has historically been defined as the addition of new genes to human cells. However, the recent advent of genome-editing technologies has enabled a new paradigm in which the sequence of the human genome can be precisely manipulated to achieve a therapeutic effect. This includes the correction of mutations that cause disease, the addition of therapeutic genes to specific sites in the genome, and the removal of deleterious genes or genome sequences. This review presents the mechanisms of different genome-editing strategies and describes each of the common nuclease-based platforms, including zinc finger nucleases, transcription activator-like effector nucleases (TALENs), meganucleases, and the CRISPR/Cas9 system. We then summarize the progress made in applying genome editing to various areas of gene and cell therapy, including antiviral strategies, immunotherapies, and the treatment of monogenic hereditary disorders. The current challenges and future prospects for genome editing as a transformative technology for gene and cell therapy are also discussed.

Nanotechnology for delivery of peptide nucleic acids (PNAs)

Over the past three decades, peptide nucleic acids have been employed in numerous chemical and biological applications. Peptide nucleic acids possess enormous potential because of their superior biophysical properties, compared to other oligonucleotide chemistries. However, for therapeutic applications, intracellular delivery of peptide nucleic acids remains a challenge. In this review, we summarize the progress that has been made in delivering peptide nucleic acids to intracellular targets. In addition, we emphasize recent nanoparticle-based strategies for efficient delivery of conventional and chemically-modified peptides nucleic acids.

Gene-targeting pharmaceuticals for single-gene disorders

The concept of orphan drugs for treatment of orphan genetic diseases is perceived enthusiastically at present, and this is leading to research investment on the part of governments, disease-specific foundations and industry. This review attempts to survey the potential to use traditional pharmaceuticals as opposed to biopharmaceuticals to treat single-gene disorders. The available strategies include the use of antisense oligonucleotides (ASOs) to alter splicing or knock-down expression of a transcript, siRNAs to knock-down gene expression and drugs for nonsense mutation read-through. There is an approved drug for biallelic knock-down of the APOB gene as treatment for familial hypercholesterolemia. Both ASOs and siRNAs are being explored to knock-down the transthyretin gene to prevent the related form of amyloidosis. The use of ASOs to alter gene-splicing to treat spinal muscular atrophy is in phase 3 clinical trials. Work is progressing on the use of ASOs to activate the normally silent paternal copy of the imprinted UBE3A gene in neurons as a treatment for Angelman syndrome. A gene-activation or gene-specific ramp-up strategy would be generally helpful if such could be developed. There is exciting theoretical potential for converting biopharmaceutical strategies such gene correction and CRISPR-Cas9 editing to a synthetic pharmaceutical approach.

Lumacaftor and ivacaftor in the management of patients with cystic fibrosis: current evidence and future prospects

Cystic fibrosis (CF) is a genetic disorder that causes multiorgan morbidity and premature death, most commonly from pulmonary dysfunction. Mutations in the CF transmembrane conductance regulator (CFTR) gene, of which almost 2000 have been described, result in a dysfunctional CFTR protein. This protein is an adenosine triphosphate binding anion channel, present primarily at the surface of epithelial cells. Loss of function mutations in this anion channel result in decreased or absent chloride/bicarbonate transport. The subsequent abnormal salt and water transport at epithelial cell surfaces leads to thickened secretions, and infection or inflammation in affected organs. In the last 20 years, therapeutics have been developed to treat the signs and symptoms of CF. However, in 2012, the small molecule drug, ivacaftor, became the first approved therapy that addresses the basic defect in CF. Ivacaftor is a potentiator of CFTR channels defective in their chloride/bicarbonate gating/conductance, but present at the epithelial cell surface. It is only approved for 10 mutations carried by approximately 7% of the population of patients with CF. F508del is the most common CFTR mutation, present in homozygosity in approximately 50% of patients with CF. The F508del mutation results in multiple CFTR channel defects that require both correction (stabilization of misfolded CFTR and trafficking to the epithelial cell membrane) and potentiation. This article reviews the in vitro and clinical trial data for the potential use of the potentiator, ivacaftor, and the corrector, lumacaftor, in patients with CF.

Delivery and therapeutic applications of gene editing technologies ZFNs, TALENs, and CRISPR/Cas9

In recent years, several new genome editing technologies have been developed. Of these the zinc finger nucleases (ZFNs), transcription activator-like effector nucleases (TALENs), and the CRISPR/Cas9 RNA-guided endonuclease system are the most widely described. Each of these technologies utilizes restriction enzymes to introduce a DNA double stranded break at a targeted location with the guide of homologous binding proteins or RNA. Such targeting is viewed as a significant advancement compared to current gene therapy methods that lack such specificity. Proof-of-concept studies have been performed to treat multiple disorders, including in vivo experiments in mammals and even early phase human trials. Careful consideration and investigation of delivery strategies will be required so that the therapeutic potential for gene editing is achieved. In this review, the mechanisms of each of these gene editing technologies and evidence of therapeutic potential will be briefly described and a comprehensive list of past studies will be provided. The pharmaceutical approaches of each of these technologies are discussed along with the current delivery obstacles. The topics and information reviewed herein provide an outline of the groundbreaking research that is being performed, but also highlights the potential for progress yet to be made using these gene editing technologies.