Many hurdles have been thrown at gene therapies in the past, but it now seems that the kinks are being worked out and many gene therapies are finally on the rise! This industry has some serious potential to cure various diseases, some of which include inherited genetic disorders, some types of cancers, and certain viral infections, as well as diseases that currently have no treatment at all [1], and so it is an important one to keep an eye on.
So, what are gene therapies anyway? Most, if not all diseases have some sort of genetic element associated with their development. Gene therapy is designed to use genes to treat and prevent disease. The goal for the future is to allow doctors to treat genetic disorders by inserting a gene into a patient’s cells rather than treatment using drugs or conducting surgery [1]. There are several approaches researchers are currently testing to bring about the desired effects. Novel genetic material can be introduced into a patient’s cells to compensate for abnormal genes, or to make a beneficial protein that combats the effects of the condition present in the patient [2]. A normal copy of the defective gene may be introduced to replace the defective copy to restore the function of the protein [2]. Lastly, novel genetic material may be incorporated to inactivate or ‘knockout’ the mutated gene that does not function properly [1].
Gene therapies are currently only being tested for diseases that have no other cures. Currently, there are very few gene therapies that have been approved worldwide, but many more clinical trials take place each year [1]. 2017 was a landmark year where 7 gene therapy products obtained approval worldwide [3]. There are currently 1,220 active worldwide clinical trials in regenerative medicine and advanced cell/gene therapies, the majority of which are in oncology, followed by indications for neurodegenerative diseases, monogenetic diseases, and infectious diseases [4]. The clinical use of gene therapies is increasing rapidly, and it is projected that by 2025, the US Food and Drug Administration (FDA) may be approving between 10-20 gene therapies every year [5].
There have been previous barriers to the approval of gene therapies in the past. One of which is the development of adverse events and issues with the technology used to deliver the genetic material. Most gene therapies intend to achieve permanent or long-lasting effects in humans, and as a result this inherently increases the risk of delayed adverse events [5]. A famous example from 1999 details the treatment of Jesse Gelsinger for ornithine transcarbamylase deficiency, a genetic disease of the liver [6]. Genes that are directly inserted into cells normally do not function; they need to be delivered. There are several methods to fulfil the role of the carrier, one such method is the use of modified viral vectors which deliver the genetic material by infecting the cells [2]. Sadly, Jesse died from the vector’s toxicity to her liver, into which it had been delivered. Another example comes from a clinical trial that aimed to treat X-linked severe combined immune deficiency or ‘bubble boy’ disease. Unfortunately, a quarter of the patients developed leukaemia directly because of the vector that was used [6]. However, the technological efficiency of the vector systems has improved since then. For instance, scientists have since identified and removed the viral sequences from the vector that activated the oncogenes which caused leukaemia in the earlier clinical trials, and a newer viral vector system has been developed from the vector used to treat Jesse [6].
Gene therapy is arguably one of the most exciting areas of biotechnology currently due to recent advancements and the pure potential of what could be in a few years’ time. Various developments that were unimaginable a decade ago will significantly speed up progress in this industry. These include the now unprecedented levels of control we have over nucleic acid delivery, modulation of the immune system, and precise manipulation of the human genome. This industry is expected to reach over $14 billion by 2025 with a projected growth rate of 30% between 2019-2025 [7]. The gene therapy industry is undoubtedly on the rise, and we can’t wait to see what the future brings.
Mia Georgiou
References:
[1] Genetics, H. and Advances, G., 2021. What is gene therapy?: MedlinePlus Genetics. [online] Medlineplus.gov. Available at: <https://medlineplus.gov/genetics/understanding/therapy/procedures/> [Accessed 14 July 2021].
[2] Genetics, H. and Advances, G., 2021. How does gene therapy work?: MedlinePlus Genetics. [online] Medlineplus.gov. Available at: <https://medlineplus.gov/genetics/understanding/therapy/procedures/> [Accessed 14 July 2021].
[3] Nature.com. 2021. The rise of gene therapies. [online] Available at: <https://www.nature.com/articles/d42473-019-00141-4> [Accessed 14 July 2021].
[4] Healio.com. 2021. After challenging year, cell and gene therapy industry poised for further growth in 2021. [online] Available at: <https://www.healio.com/news/hematology-oncology/20210203/after-challenging-year-cell-and-gene-therapy-industry-poised-for-further-growth-in-2021> [Accessed 14 July 2021].
[5] Nature Medicine, 2021. Gene therapy needs a long-term approach. 27(4), pp.563-563.
[6] HuffPost. 2021. 4 Things to Know About Gene Therapy. [online] Available at: <https://www.huffpost.com/entry/four-things-to-know-about_b_6721506> [Accessed 14 July 2021].
[7] Cellandgene.com. 2021. The Rise Of Gene & Cell Therapy And The Resulting Need For In-House Production Facilities: A Guide. [online] Available at: <https://www.cellandgene.com/doc/the-rise-of-gene-cell-therapy-and-the-resulting-need-for-in-house-production-facilities-a-guide-0001#:~:text=The%20gene%20and%20cell%20therapy,30%25%20between%202019%2D2025.> [Accessed 14 July 2021].
