Functional vision restored in Leber's congenital amaurosis patients

Gene therapy has resulted in functional vision for patients withLeber's congenital amaurosis (LCA), said Albert Maguire, MD, ofthe University of Pennsylvania, Bryn Mawr. That research is theresult of a 13-year effort by Dr. Maguire and colleagues.

Their previous well-known work involved successfully delivering aviral vector into dogs with LCA. The dogs lacked the RPE65 geneneeded to process vitamin A. Successful restoration of vision indogs treated with a subretinal injection of the viral vectorcontaining RPE65 was the basis for the clinical work inhumans.

In a phase I clinical safety trial, three groups of threepatients each were treated in one eye only with a subretinalinjection of either a low-, medium-, or high-dose of the RPE65vector, Dr. Maguire said. The treated eye then was evaluated fora response and compared with the untreated fellow eye.

"All patients in the low-dose cohort had substantial visualacuity improvement," he said. Visual field testing indicated thatthe visual fields were larger in the treated eyes compared withthe control eyes. In addition, the patients' pupils alsoresponded to light despite a flat electroretinogram.

Dr. Maguire emphasized that the vision was indeed functional, andhe demonstrated patients navigating an obstacle course "quicklyand confidently," which previously had been an impossibletask.

Results of the study were published in April 2008 in the NewEngland Journal of Medicine.