Gene Therapy Research for AMD
I’m writing this in October 2019 when 3 scientific articles were just published about how gene therapy research is giving hope to many people who have age-related macular degeneration (AMD). I've gotten a lot of questions about this. I hope to answer some of them. If you have more, let me know.
Understanding genes and gene mutations
I like to use analogies for complex topics when possible. When I searched for ‘analogy dna gene,’ I got several different ones. I found one that is frequently used:
- All the instructions needed for the functioning of the cells of our body are in a cookbook which is called your genome.
- In your genome/cookbook, there are chapters for types of recipes. Those are the chromosomes.
- In each chromosome/chapter, there are individual recipes which are genes.
- In each gene/recipe, individual letters make up sentences. These letters in sentences are DNA.
- We want to be making healthy, good tasting cookies which are the proteins that are needed for our cells to be functioning properly. When everything is working right, there will be different types of proteins/healthy, good tasting cookies. These are gene variants/variations.
- Sometimes, however, we get unhealthy, bad tasting cookies/proteins or ones that are produced at the wrong rate. These are gene mutations.
A combination of genes involved
Age-related macular degeneration (AMD) is not caused by just one gene as some diseases are. Unfortunately, we have yet to determine which exact genes are at fault. It is likely to be a combination of genes, some of which are from heredity, some of which are not. Researchers have decided that the risk of AMD can be substantially increased if there are flaws in our ‘recipes’ in an area of our genetic code that directs the functioning of the immune system in our eyes (that is the subject for another page!). That’s not the only system that researchers looking at. In fact, researchers are now looking at something like 30 genes that they suspect are involved.1
What if we knew where the flaws were? What if we knew exactly what needed to be fixed? Could we go in there and fix things? This is actually what is being done. Genetic therapy is working on a cure by providing ‘fixes’ for faulty genes.
What is gene therapy?
I’ll bet by now you don’t need the cookbook analogy, right? Gene therapy is the process of altering genes in cells related to the macula.
One thing to keep in mind: gene therapy can’t fix any damage to the macula that may have been done. Gene therapy is done to protect from further damage by stopping progression of the disease. Stem cell research is working on reversing damage.
I know it sounds scary, but researchers use certain viruses to get genetic material to the cells that they are to help. These are special viruses that have had the ‘nasty stuff’ that makes them spread taken out in the lab. How that’s done is called genetic engineering and is way beyond my understanding!
These special viruses are called vectors where the word 'vector' means a carrier of something. It’s like putting a recipe in an envelope to mail to someone - the envelope is the vector to deliver the recipe. In the case of gene therapy, a virus is the vector that carries genetic material to cells. It’s more complicated than that, but it’s enough for our purpose.
Gene therapy for wet AMD
Some of you know, all too well, that the treatment for wet AMD is an injection into the eye. This means repeated visits to the retina specialist and repeated anxiety (for some) about the injections.
What do the injections actually do? There is a protein called VEGF (Vascular Endothelial Growth Factor). Too much VEGF in the eye causes the blood vessels to grow where they aren't supposed to be. The injections are of one of 4 medications called anti-VEGF because they reduce the amount of VEGF. The big problem is that they don't do that for long. That's why you have to keep going back.
Anti-VEGF gene therapy
There are 4 clinical trials where the researchers are trying to rid the eye of VEGF by getting cells to produce the equivalent of anti-VEGF medications. That would mean a one-time injection of a gene therapy product - the virus vector and the genetic material - to create cell anti-VEGF ‘factories.’ Are you thinking that it would mean the end of those repeated, regular eye injections? That’s the plan.
Two clinical trials
If you want to know more, here is the information for 2 clinical trials where preliminary results were recently reported. If you are interested, you can enter the NCT number or gene therapy product name in the site clinicaltrials.gov:
- Clinical Trial Number NCT03748784 using ADVM-022 Gene Therapy Product2
- Clinical Trial Number NCT03066258 using RGX-314 Gene Therapy Product3
Gene therapy for dry AMD
The goal of gene therapy for dry AMD is to identify and target faulty genes that contribute to the progression of the disease. Again, gene therapy won’t be able to repair any damage. Stem cell therapy will hopefully be able to do that.
There are genes involved in our immune system. The immune system regulates inflammation. These genes are part of the complement system. One of those genes being targeted is the CFI gene.4 The purpose of CFI is to make a protein that helps to properly regulate the complement system. A rare variant (variation) of this CFI gene causes the complement system to be overactive. This variant occurs in about 5% of people who have dry AMD.
Clinical trial study
This study uses the gene therapy product GT005 to produce a protein that deactivates the complement system in the back of the eye of people with this variant. So far one woman in the UK was treated with GT005. At the time I’m writing this, it’s too early to tell if it has worked to stop progression. The plan is to treat a total of 10 people:
- Clinical Trial Number NCT03846193 Using Gene Therapy Product4
When will gene therapy be available?
Now we come to the important question. In an interview, Dr. Szilard Kiss, M.D. with the ADVM-022 clinical trial said, “Now, these are 6 patients in the first cohort [group] of the OPTIC trial. More definitely needs to be done, but with a safety profile that we are seeing, which is favorable, and with the efficacy profile that we're seeing, I think within the next 3 to 5 years we can expect gene therapy with anti-VEGF in the office treating our patients who now require frequent injections.”2
That's a big question. We know that gene therapy for other diseases is not affordable because of the expensive and time-consuming process of approving them. There are people who are working on correcting that. Cross your fingers, eyes, toes! 😊
I've written before about the hope for a cure for AMD in our lifetime. That depends, of course, on how long our lifetime is.
If not for us, though, it is hope for the generations who come after us.
Are you aware of assistive technology for AMD?