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Episomal vectors as gene delivery systems for therapeutic application

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Towards safer gene therapy vectors

Gene therapy can provide therapeutic benefit to many chronic diseases by replacing the mutated gene. An EU-funded project proposed the development of novel DNA vectors for safe extra-chromosomal gene expression.


Clinical trials of gene replacement therapy have been met with limited success due to the side-effects caused by chromosomal integration of delivery vectors. To overcome the limitation of gene expression duration, the majority of gene therapy groups have utilised viral-based delivery systems that integrate into the host genetic material. However, they cause disruption of gene expression and cancer. Although we know the genetic elements that regulate chromatin function, it has proved an immense challenge to understand how these genetic elements might be configured to provide regulated, efficient and sustained gene expression from extra-chromosomal DNA. The key objective of the ‘Episomal vectors as gene delivery systems for therapeutic application’ (EPI-Vector) project was to develop novel vectors that did not integrate into host chromosomes but rather mimicked their behaviour. By incorporating existing knowledge of genetic and epigenetic factors that regulate chromatin function in mammalian cells, project partners designed DNA vectors specifically for ectopic gene expression. These episomal vectors contained components of human origin, avoiding the potential complications of viral-based systems. They were tested for human gene therapy applications in various model systems to ensure safe, efficient and sustained gene expression. Project partners are hopeful that these EPI-Vector vectors are superior to currently used viral systems as they combine efficiency and safety, and will be the vectors of choice in future gene therapy clinical trials.

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Scientific advances

9 September 2019