Targeted Genetics reported positive results from a phase I/II trial of its RPE65 gene therapy for the treatment of retinal dystrophy due to Leber’s congenital amaurosis (LCA). LCA is a rare eye disease that causes severe vision loss or blindness. The disease is genetically inherited and usually manifests itself at birth or in early infancy. There are thought to be 3,000 people in the U.S. with the disease; however, the technology has the potential to treat a variety of eye diseases such as macular degeneration which afflicts 1.25 million people in the U.S. alone.

The single-center, open label study enrolled nine young adults, between the ages of 17 and 23 years, with early-onset severe retinal dystrophy due to LCA.

The subjects were administered a single retinal injection of the Adeno-Associated Virus (AAV) vector expressing RPE65. In each subject, the eye with the worse acuity was selected as the study eye and the other was used as a control. After two weeks, data from the first three treated subjects showed that they had improved vision in the injected eye and could read several lines on an eye chart.

They also had less nystagmus (or involuntary eye movement) after six months and one subject showed a significant consistent improvement in visual function and subjective tests of visual mobility.

No adverse events or inflammation were reported. Based on the results the company planned to enroll additional subjects into the trial.

The study, called "Effect of Gene Therapy on Visual Function in Leber's Congenital Amaurosis," by Bainbridge, et al., conducted in collaboration with University College London and Moorfields Hospital, will appear in the May 22nd issue of the New England Journal of Medicine (JAMA). The full results of the trial were also presented at the Association for Research in Vision and Ophthalmology (ARVO) 2008 Annual Meeting in Fort Lauderdale, Fla.