Clinical trial results
The phase III clinical trial enrolled patients aged ≥4 years of age with confirmed biallelic mutations in the RPE65 gene, visual acuity <20/60 and/or visual field <20° in any meridian, and ability to perform a standardized multi-luminance mobility test (MLMT), within the evaluated luminance range, but unable to pass at 1 lux.
It randomized 31 patients 2:1 to voretigene or observation. Observation patients became eligible for crossover to gene therapy after 1 year, and in total 29 of the 31 entered patients received intervention and were evaluated at 3 years post-entry.
Change in functional vision–as measured by performance in the MLMT at 1-year post-injection–was analyzed as the primary endpoint. Change in visual function measured by white-light, full-field sensitivity was the secondary efficacy endpoint. Changes in visual field and best-corrected visual acuity (BCV) also were evaluated.
“Spark developed the MLMT in response to the need for a relevant, reliable, and clinically meaningful measure of functional vision in low-vision subjects with nyctalopia, but this novel endpoint had to be validated first in a separate study,” said Dr. Falabella.
“One of the challenges in developing voretigene was to establish an endpoint that could show improvement in functional vision.
“Visual acuity and visual field, which are traditional endpoints in ophthalmology trials, are visual function tests measuring how the eye performs,” he added. “A functional vision test measures how patients perform with the level of vision they have.”