Research has been presented at the 2014 Annual Meeting of the Association for Research in Vision and Ophthalmology (ARVO) that demonstrates healthy genes may be able to prevent blinding diseases that stem from genetic defects.
In a multi-centre clinical trial to treat the rare disease choroideremia, which causes progressive and irreversible blindness,1 scientists replaced the missing gene (that causes the disease) in the cells at the back of the eye with a virus they had developed. Six months after the virus was injected into six patients, findings showed that some patients experienced improved vision. The researchers reported that despite undergoing retinal detachment, which normally reduces vision, two patients with advanced choroideremia who had low baseline best corrected visual acuity, gained 21 letters and 11 letters (more than two and four lines of vision). Four other patients with near normal best corrected visual acuity at baseline recovered to within one to three letters.
Interpreting the findings, the researchers wrote, “the initial results of this retinal gene therapy trial are consistent with improved rod and cone function that overcome any negative effects of retinal detachment. These findings lend support to further assessment of gene therapy in the treatment of choroideremia and other diseases, such as age-related macular degeneration, for which intervention should ideally be applied before the onset of retinal thinning.”
In a separate study, researchers developed a gene therapy to stop the progression of a form of retinitis pigmentosa, which is transmitted from mothers to sons. The researchers studied the effectiveness of the treatment on dogs at an early stage in the disease and found it remained effective two years after the therapy was administered. Dogs with mid and late stages of the disease also had a positive response to the treatment.2
1. MacLaren Robert E, Groppe Markus, Barnard Alun R, Cottriall Charles L, Tolmachova Tanya, Seymour Len, Clark K Reed, During Matthew J, Cremers Frans P M, Black Graeme C M, Lotery Andrew J, Downes Susan M, Webster Andrew R, Seabra Miguel C. Improved visual function in patients with choroideremia undergoing subretinal gene therapy. www.thelancet.com published online January 16, 2014.
2. Beltran William A, Cideciyan Artur V, Lewin Alfred S, Iwabe Simone, Khanna Hemant, Sumaroka Alexander, Chiodo Vince A, Fajardo Diego S, Román Alejandro J, Deng Wen-Tao, Swider Malgorzata, Alemán Tomas S, Boye Sanford L, Genini Sem, Swaroop Anand, Hauswirth William W, Jacobson Samuel G and Aguirre Gustavo D. RPGR gene augmentation delivered at early, mid and late stage disease in a canine model of XLRP rescues photoreceptor structure and function. org/cgi/doi/10.1073/pnas.111