How gene therapy works

Gene therapy aims to repair, replace or add functional genes in individuals suffering from specific genetic diseases

Gene therapy has traditionally been in the form of ‘gene addition’ which commonly utilises a ‘viral vector’ to introduce functional genes into the cells of eligible patients [1]. Other types of gene therapies developed more recently include the likes of gene editing

Genes can be delivered in vivo by introducing the viral vector directly into the body

Or ex vivo by introducing the virus to cells harvested from a patient and then reintroducing the cells after they have been genetically altered with the healthy gene

Upon successful treatment, the modified cells mature and multiply — coding for a new protein to correct a particular disease, or stopping a protein that has been causing a disease

Gene therapy is here now and being developed to help treat a wide array of severe genetic diseases

^{Sources:
1. Maeder, M. L. & Gersbach, C. A. Genome-editing Technologies for Gene and Cell Therapy. Mol. Ther. 24, 430–46 (2016)}

Advanced therapies by numbers

Gene therapies fall within the wider classification of ‘advanced therapy medicinal products’, or ATMPs, alongside cell therapies and tissue-engineered medicines. Many of these advanced therapies offer promising new opportunities for the treatment of disease

4+
So far, gene therapies have shown potential to treat disease caused by single-gene mutations in a broad variety of indications, including in: haematology, neurology, ophthalmology, and musculoskeletal conditions [3]

2nd
The UK is home to the second largest cluster of cell and gene therapy companies worldwide – beaten only by the US [4]

27%
Percentage of advanced therapy companies in Europe operating in the UK [4]

3,000
Number of jobs in the UK advanced therapy sector [4]
1 person = 100 jobs

10,000
Number of human diseases caused by mutations of single genes [1]. Many of these are ‘rare diseases’, which are estimated to affect around 3.5 million people in the UK [2]. Gene therapies have the potential to help eligible patients with many of these untreatable or hard-to-treat conditions
1 damaged helix = 1000 diseases

127
Number of advanced therapy clinical trials in the UK — up 50% since 2018 [4]. Gene therapies make up a significant proportion of the advanced therapies currently being investigated
1 helix = 10 clinical trials

9
Number of advanced therapies licensed for use in the UK [4]. ATMPs are an emerging field of medicine. This number is likely to increase significantly
1 tick = 1 licensed therapy

^{Sources:
1. https://www.who.int/genomics/public/geneticdiseases/en/index2.html;
2. https://www.raredisease.org.uk/what-is-a-rare-disease/?/;
3. https://ct.catapult.org.uk/sites/
default/fi les/publication/2020-IBI_Spring-web_compressed_FULL_pgs31-33.pdf;
4. Overview & Cell and Gene Therapy Catapult, annual review 2020}

This article first appeared in a Spectator supplement: The evolution of gene therapy. Sponsored by bluebird bio.