Visual acuity advances seen with Leber's congenital amaurosis

Fort Lauderdale, FL-Five gene therapy trials are under way in Leber’s congenital amaurosis (LCA)-three in the United States, one in the United Kingdom, and one in Israel. William W. Hauswirth, PhD, reviewed the advances in gene therapy treatment of LCA.

About 40 patients are being treated in the five studies and the longest duration of treatment has been about 4 years. Thus far, investigators have found no vector-related safety issues, with two serious adverse events (i.e., one macular hole and one retinal detachment developed in association with the subretinal surgery), said Dr. Hauswirth, of the Department of Ophthalmology, University of Florida College of Medicine, Gainesville.

Importantly, the gene therapy for LCA has been efficacious in almost all patients treated. In the University of Florida-University of Pennsylvania trial, in which 15 patients participated over 3.5 years, Dr. Hauswirth and colleagues began injecting only 150 ml of vector into islands of surviving photoreceptors. Patients noted a subjective improvement in visual fields at 1 month after treatment. After about 2 weeks, patients reported brighter regions in the visual fields that corresponded to the placement of the vector in the retina.

“One patient had a 63,000-fold improvement in light sensitivity in the treated region; this did not reach the normal level, but it was close,” Dr. Hauswirth said.

He also noted an interesting slow response to treatment experienced by patients, some of whom reported improvements even as long as 1 year after injection.

“Listen to your patients who have blinding diseases,” he said. “They know what they are seeing.”

Dr. Hauswirth also noted that all patients had a significant increase in visual acuity except for those with a foveal detachment during delivery of the vector.

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