Gene therapy could be cure for blindness

A clinical trial involving an incurable type of blindness has been carried out by a collaboration of researchers from Imperial College London and Oxford University. At the John Radcliffe Hospital in Oxford, Jonathan Wyatt, 63, from Bristol became the first person to receive gene therapy for blindness.

He and the other 11 patients who were involved in the clinical trial, were all sufferers of Choroideremia, a type of disease, which causes progressive loss of vision and eventually blindness. It is a rare inherited disease caused by a deficiency of the REP-1 gene on the X chromosome, making it more common in men than women. Estimates suggest 100,000 people worldwide are affected with this disease.

People who are diagnosed with Choroideremia usually suffer from loss of vision, acuity, colour and depth perception, as well as severe night blindness as the disease progresses throughout their life. The first symptom is usually night blindness noticed during childhood. As time goes by, the sufferer’s retina falls apart and eventually blindness takes over. The clinical trial could restore hope in all Choroideremia sufferers.

The gene therapy was designed to restore the missing gene on the X chromosome to stop the retina from deteriorating. The treatment comes in the form of a virus that carries the DNA with the missing gene. It is injected into the eye of the patient and is engineered to target the photoreceptor in the retina. At this site, the gene will be delivered, switched on and activated. It is thought that the gene can reside in the retinal cells indefinitely once it has been delivered, hopefully making it permanent.

Professor Miguel Seabra of the National Heart and Lung Institute at Imperial College, who was involved in the trial, expressed his gratitude towards the individuals that have had a big influence on the development of the treatment. He said that this trial only became possible when some of the affected families and private charities raised funds for the research.

Professor Seabra and Dr Tanya Tolmachova of Imperial lead much of the preclinical work. They identified the gene that caused Choroideraemia and built a mouse model to gain preclinical data necessary for the trial to be carried out.

The 12 patients involved will undergo surgery in order for the gene to be delivered through the virus. Only one eye will be involved in the gene therapy, as the other eye will be used as the control to evaluate the effectiveness of the treatments.

However, the researchers said that they would repeat the treatment with the second eye if it is shown to be effective. It is estimated that it will take up to 2 years to assess the effectiveness of the treatment. If it is proven to be successful, then this will be the first-ever treatment for the disease.