Gene Therapy

• Genetic Therapy


  Treatment of genetic diseases using genetic approaches
• Aetiology


  Cause of a disease
• Pathogenesis


  Development of a disease
• Factors influencing diseases


  • Genetics
  • Epigenetics
  • Environmental drivers
  • Other host factors
• Approaches to treating diseases

  • Treatment of genetic diseases
  • Genetic treatment of diseases
• Treatment of genetic diseases


  Relies on knowledge about natural history and pathophysiology of a disease and uses traditional strategies for therapy
• Genetic treatment of diseases


  Uses genetic technologies, such as screening for chemical or biological drugs, or therapeutic genetic modifications for treatment
• Role of molecular biology in disease treatment


  • Small molecule drugs screening & novel development
  • Production of recombinant therapeutic proteins
  • Production of genetically engineered antibodies
  • Genotyping of patients in pharmacogenetics
  • Production of reagents for gene therapies
  • Genetic modification or donor cells in gene & cell therapy
• Clinical trials


  Precede applications for regulatory approval of novel drugs, with defined phases that have to be passed
• Clinical trials can be very expensive and time consuming. Commercialisation is only realistic for drugs developed by pharmaceutical industry or tested in a collaboration with pharmaceutical industry
• Drug targets in biological drugs


  Carbohydrates, fatty acids, enzymes that chop the molecule step by step
• Gaucher disease


  A rare autosomal recessive lipid storage disorder characterised by the deposition of glucocerebroside (glucosylceramide) in cells of the macro-phage-monocyte system
• Biological drug approaches for Gaucher disease


  • Protein substitution
  • Substrate reduction therapy
• Effective biological drugs for genetic diseases can be developed based on knowledge about pathway & drug target
• Drug development relies on disease models
• Improved drugs reflect advances in genetic and clinical understanding
• CFTR


  The cystic fibrosis transmembrane conductance regulator that is mutated in cystic fibrosis
• Knowledge about the molecular pathophysiology, i.e. different classes of mutations in CFTR, has strongly contributed to the development of causative therapies using small molecules
• Based on the pathologies of different mutations in CFTR, 5 major classes of mutations can be differentiated
• p.G551D


  A class III mutation in CFTR, where the protein is synthesised and incorporated into the membrane, but the ion channel is inactive
• Ivacaftor (VX770)


  A drug that helps open the CFTR channel, but is efficacious only for patients with at least one class III mutant allele
• Therapeutic antibodies


  Use complementary determining regions (hypervariable regions) for production of human monoclonal antibodies in rodents
• Personalised treatment


  A goal of pharmacogenomics studies, which identify drug targets and predict drug responses depending on genotypes
• Gene therapy


  Strategies for direct genetic modification of cells, including germline cell gene therapy (banned in most countries) and somatic gene therapy (by modifying or killing target cells)
• Gene delivery


  A major challenge to gene therapy, achieved through in vivo or ex vivo approaches, using transfection (non-viral) or transduction (virus-mediated) methods that may lead to integration or non-integration of the DNA
• Non-viral gene delivery methods


  • Naked DNA
  • DNA nanoparticles
  • Liposomes (for DNA or RNA)
  • Liposomes (for RNAi)
• Characteristics of non-viral gene delivery methods

  • Genome type
  • Capacity
  • Interaction
  • Target cells
  • Expression
• Non-viral gene delivery can be inefficient and provide only medium-term or short-term expression
• Viral vector types


  • Group 1 - Group 7
• Retroviral structure


  Gag, pol, env genes replaced by target gene
• Retroviral life cycle


  Involves integration of viral genome into host cell genome
• Viral vectors used in gene therapy

  • AAV
  • Lentivirus
  • Adenovirus
• Viral gene delivery can provide more efficient and longer-term gene expression compared to non-viral methods
• Sickle cell disease symptoms typically appear after childhood
• Gene therapy for sickle cell disease aims to switch from fetal to adult globin gene expression
• The Victoria Gray & CTX001 clinical trial is an example of gene therapy for sickle cell disease
• Casgevy is another gene therapy approach for sickle cell disease