Gene Therapy Technologies

Gene Therapy in Diseases

Gene Therapy for Oral Squamous Cell Carcinoma

The current treatment strategies for oral squamous cell carcinoma (OSCC) include a combination of surgery, radiation therapy and chemotherapy. However, surgical resection of tumors frequently causes profound defects in oral functions such as speech and swallowing as well as in cosmetic aspects. Chemotherapy is associated with well-known toxicity and has demonstrated no clear impact on the survival of patients with recurrent oral cancer. Recurrence develops in approximately one third of the patients despite definitive treatment. Two thirds of the patients dying of this disease have no evidence of symptomatic distant metastasis.

Therefore, local and regional disease control is paramount, underscoring an urgent need for more effective therapy. Several reports have indicated that the combination of radiation and gene therapies has synergistic suppressive effects on various cancer cells, including colorectal, ovarian, nasopharyngeal and head / neck cancer cells. Gene therapy can also be used as an adjuvant to surgery (at the resected tumor margins). This review highlights various gene therapy methods that are available for combating OSCC.

Gene Therapy for Cystic Fibrosis Lung Disease

Cystic fibrosis (CF) is a recessive disease associated with loss of function mutations in the CF transmembrane conductance regulator (CFTR) gene, which has a well-characterized gene product; heterozygotes, as predicted, appear to be phenotypically perfectly normal; the level of expression of CFTR in affected cells generally appears to be low; and the dysfunctional epithelial lining cells in the organ most affected by CF (the lung) are available for direct vector delivery via topical administration. However, despite an impressive amount of research in this area, there is little evidence to suggest that an effective gene-transfer approach for the treatment of CF lung disease is imminent. The inability to produce such a therapy reflects in part the learning curve with respect to vector technology and the failure to appreciate the capacity of the airway epithelial cells to defend themselves against the penetration by moieties, including gene-therapy vectors, from the outside world. This Perspective will focus on the issues that impact on moving this field forward.

Gene Therapy for Infectious Diseases

Gene therapy is being investigated as an alternative treatment for a wide range of infectious diseases that are not amenable to standard clinical management. Gene therapy for infectious diseases requires the introduction of genes designed to specifically block or inhibit the gene expression or function of gene products, such that the replication of the infectious agent is blocked or limited. In addition to this intracellular intervention, gene therapy may be used to intervene in the spread of the infectious agent at the extracellular level. This could be achieved by sustained expression in vivo of a secreted inhibitory protein or by stimulation of a specific immune response. Approaches to gene therapy for infectious diseases can be divided into three broad categories: (i) gene therapies based on nucleic acid moieties, including antisense DNA and RNA, RNA decoys and catalytic RNA moieties (ribozymes); (ii) protein approaches such as trans dominant negative proteins (TNPs) and single-chain antibodies; and (iii) immunotherapeutic approaches involving genetic vaccines or pathogen-specific lymphocytes. It is further possible that combinations of the aforementioned approaches will be used simultaneously to inhibit multiple stages of the viral life cycle.

The extent to which gene therapy will be effective against infectious agents is the direct result of several key factors: (i) selection of the appropriate target cell or tissue for gene therapy; (ii) the efficiency of the gene delivery system; (iii) appropriate expression, regulation and stability of the gene therapy product(s); and (iv) the efficiency of the inhibition of replication by the gene inhibition product.

Gene Therapy for Arthritis

Rheumatoid arthritis is an autoimmune disease with intra-articular inflammation and synovial hyperplasia that results in progressive degradation of cartilage and bone, in severe cases it causes systemic complications. Recently, biological agents that suppress the activities of proinflammatory cytokines have shown efficacy as antiarthritic drugs, but require frequent administration. Thus, gene transfer approaches are being developed as an alternative approach for targeted, more efficient and sustained delivery of inhibitors of inflammatory cytokines as well as other therapeutic agents. Recently, biological agents that modulate the proinflammatory activities of TNF- and IL1 have shown efficacy as novel antiarthritic drugs. However, arthritis therapies that employ biological agents are currently limited by possible systemic side effects such as the occurrence and re-emergence of viral and bacterial infections as well as their exorbitant expense. There are several different approaches that can be utilized for the treatment of arthritis. Genes can be delivered locally at the site of disease pathology such as the joint by intra-articular injection. Alternatively, therapeutic genes can be delivered using specific circulating cell types such as T cells or antigen-presenting cells (APCs) such as dendritic cells (DC).

Although these types of cells result in more systemic delivery of therapeutic proteins, the ability of certain immune regulatory cells to home sites of inflammation can also allow for local treatments following systemic injection. It is also possible to increase the levels of circulating therapeutic proteins by delivery of the gene to tissues such as muscle or liver.

Gene Therapy in Diabetic Neuropathy

Gene therapy shows promise in treating diabetic polyneuropathy, a disorder that commonly affects diabetics who've had the disease for many years, a new study finds. Researchers in Boston found that intramuscular injections of vascular endothelial growth factor (VEGF) gene may help patients with diabetic polyneuropathy. The study included 39 patients who received three sets of injections of VEGF gene in one leg and 11 patients who received a placebo. Loss of sensation and pain in the legs and feet, weakness, and balance problems are among the symptoms associated with diabetic neuropathy. The loss of sensation means that ulcerations on the feet may go undetected, which can lead to amputation. Targeting Gene Delivery An important considering in gene therapy is ensuring that the pharmacophore is delivered to an area that maximize its therapeutic benefit. This can be especially complex in the living organism due to shared receptors between tissues, circulatory anomalies (such as the bloodbrain barrier) and ability of serum proteins to destabilize synthetic vector complexes. In some cases, direct application of the vector to the dysfunctional tissue may be required to maximize effect. In the case of a cationic liposome complexed to plasmid DNA encoding chloramphenicol acetyltransferase, direct injection into murine hepatic tumors resulted in higher levels of gene expression than were achieved with systemic or portal vein inoculation.

Lipoplexes complexed to the bcl-2 gene have demonstrated reduced neural apoptosis after transient cerebral ischemia in an animal model, circumventing the bloodbrain barrier by utilizing direct intra-thecal injection. Furthermore, the cystic fibrosis transmembrane regulator gene has been successfully packaged with both cationic liposomes and polymers and safely delivered intranasally to cystic fibrosis directly targeting airway mucosa. Other targeting techniques include altering the charge of the synthetic vector-DNA plasmid particle: cationic liposomes have been shown to preferentially distribute to the lung after systemic administration, an effect which is lost which decreasing positivity.

Size also plays a role as large molecules may be unable to extravasate from the circulation to reach target cells within organ parenchyma. Additionally, constitutive expression of specific ligands on targets cells can be manipulated to design advantage, for example the use of dextranspermine polycation complexing with DNA to target the liver by preferential binding to galactose receptors on hepatic parenchyma.

As gene therapy is uprising in the field of medicine, scientists believe that this will be the ultimate solution for every genetic disease. Genes may ultimately be used as medicine and given as simple intravenous injection of gene transfer vehicle that will seek our target cells for stable, site-specific chromosomal integration and subsequent gene expression. And now that a draft of the human genome map is complete, research is focusing on the function of each gene and the role of the faulty gene play in disease.

While clinical gene therapy celebrates its first successes, with several products already approved for clinical use and several hundred in the final stages of the clinical approval pipeline, there is not a single gene therapy approach that has worked for the heart. Here, we review the past experience gained in the several cardiac gene therapy clinical trials that had the goal of inducing therapeutic angiogenesis in the ischemic heart and in the attempts at modulating cardiac function in heart failure. Critical assessment of the results so far achieved indicates that the efficiency of cardiac gene delivery remains a major hurdle preventing success but also that improvements need to be sought in establishing more reliable large animal models, choosing more effective therapeutic genes, better designing clinical trials, and more deeply understanding cardiac biology. We also emphasize a few areas of cardiac gene therapy development that hold great promise for the future. In particular, the transition from gene addition studies using protein-coding cDNAs to the modulation of gene expression using small RNA therapeutics and the improvement of precise gene editing now pave the way to applications such as cardiac regeneration after myocardial infarction and gene correction for inherited cardiomyopathies that were unapproachable until a decade ago.

The heart of market access: opportunities and challenges for cell and gene therapy development for orphan and prevalent cardiovascular diseases

Heart disease is the leading cause of death globally, and there is a need for better medicines. No cell and gene therapies (CGTs) for heart disease are approved, but a new generation of companies are advancing promising science. The pipeline of CGTs is mostly focused on in vivo AAV-based therapies for prevalent cardiovascular (CVD) conditions, in contrast to broader trends favoring an initial focus on rare diseases seen in other therapeutic areas. CGTs for heart disease indications have relevant benchmarks that could be used to justify the value and price for a one-time, potentially curative gene therapy. Significant challenges stand in the way of the development, approval, pricing, and adoption of even highly effective CGTs for prevalent CVD indications. Overcoming these will require scientific breakthroughs; heavy investment in CGT manufacturing technology and capacity; commercial and financial sophistication; and a focus on the needs of patents.