12 February, 2010
‘Eye is very suitable for gene therapy’
How is gene therapy used to tackle blindness?
In cases of inherited blindness or poor vision, it’s due to the lack of a critical gene that detects light. Our research is to replace that mutant gene with a normal working copy. We have designed a way by which the new gene can be placed in the cells. A disabled virus is taken to package the gene. The disabled virus carries it into the cells and releases it at a spot behind the retina. A micro–surgical technique is used for this.
What are the recent developments after the first human trial?
Our current research involves trials on individuals with LCA. It is caused by defects or mutation of the gene protein, RPE 65. The first result of the trials is that it pays off, there is improvement in night vision and there are no side–effects. However, it’s too early to know how long the improved vision will remain.
We have done eight trials on patients between the ages of 10 and 20 years. Three have shown considerable improvement in night vision. Again, it’s too early to know. Not all trial subjects have responded. For instance, the first subject to undergo the trial, Robert Johnson, did not respond to the treatment.
What are the shortcomings in this large–scale treatment?
Gene therapy in ophthalmology is in the clinical trial phase. There could be possible sideeffects, there could be damage to the retina, the virus that delivers the gene could lead to inflammation of the eye and there could be unpredictable effects. We need to investigate a lot more.
However, the eye is a lot more suitable for gene therapy. It is the first organ to benefit from the trials. It is because the organ is small and contained, the disabled virus is likely to remain in the tissue for some time instead of spreading across.
Is there a timeline when this therapy can be commercialised?
The changes in each trial subject take place after several months. We are monitoring them over several years. Even though we have seen encouraging results in our institute and other groups in the US have also validated it, it will take time to see what long–term impacts it will have.