The potential of genome editing

Conventional gene therapy does not correct a genetic defect. So if you take the example of haemophilia Barony there will be a mutation in the Factor 9 gene, a change in the sequence of DNA that stops the patient from producing Factor 9 protein. So conventional gene therapy technology is working by delivering working copies of that DNA into the patient’s cell, so they have their non-working copy and they also have some working copies, so their cells can make the Factor 9 protein. In other words you are not correcting that defect, you are just supplementing it with working copies. There have been attempts to refine this over the years. Certainly the refinement started a decade and a half ago.

And the refinement was that if there was a way instead to specifically correct the genetic defect itself than this would actually just restore the normal function within the cell. This has culminated in the top of the class technology at the moment which is called CRISPR-CAS genome editing. Here what you are doing is you are delivering a protein called a nucleus and you are delivering another piece of genetic material that cause the template to repair the genetic defect in the cell in which you’ve delivered those components. This is the technology which is early in development. It is not extremely efficient and it can also chop and splice bits of DNA in an unintended way.

So it is a long way from being perfect. It is a long way, I think, from being used systemically in people. However, the speed of progress in the development of this technology is breathtaking. When you are doing gene therapy on a, on a patient you must not affect their germline. In other words they must not transmit the gene therapy to their children. And there are various measures in place to, to minimize the risk of that ever happening. One of the, uh, interesting aspects of CRISPR-CAS technology of course is that it can be used to edit and change the genome of human embryos in a way that this would be transmitted on through generations.

So this then actually raises the debate over eugenics. The fact that if a family was a carrier of a severely disabling mutation, Sickle Cell Anaemia for example, they might want to use a technology that would allow them to, um, have children that were never affected by that disease. This I think is where the debate is being, is being elevated to a new level because of the implications of this technology. Which really weren’t there for, for conventional gene therapy.