Kubota Vision Inc. has announced that the U.S. Food and Drug Administration (FDA) Office of Orphan Products Development (OOPD) has awarded an orphan products clinical trial grant to support the ongoing Phase 3 study of emixustat in Stargardt disease. The experimental trial will use a small molecule treatment, a visual cycle modulator, will be tested in a multicenter, randomized, blinded study to investigate the pharmacodynamics, safety and tolerability of emixustat in Stargardt’s patients that meet the designated inclusion criteria. Commenting on the receipt of the FDA grant, Dr. Ryo Kubota, CEO of Kubota Vision Inc., stated, “it is a great pleasure and honor to receive this grant from the FDA for our ongoing Phase 3 study of emixustat in Stargardt disease. The FDA awards this grant to approximately 15% of all applicants each year, whom the FDA recognizes as a great potential to treat rare diseases. We will continue our dedication to advancing this program and enforce our commitment to finding a treatment”.
Emixustat hydrochloride is an oral visual cycle modulator that limits the availability of 11-cis-retinal, a precursor of toxic bis-retinoids, by inhibiting RPE65. The rationale behind the mode of action of emixustat is understood to rest on the principle of reducing the impact of certain stressors in the retina, including light, oxygen tension and accumulation of toxic retinoid by-products. In particular, independent research in animal models suggests that reduction of visual chromophore biosynthesis in the visual cycle could potentially prevent retinal pathology caused by stressors such as light, retinoid by-products, and oxygen. More recent clinical studies, addressing safety, tolerability, and pharmacodynamics of emixustat, found that the treatment suppressed rod photoreceptor sensitivity in a dose-dependent and reversible manner. In a previous study in an allied retinal pathology, the majority of systemic adverse events were not considered treatment related, many of which were understood to have resolved on study or within 7 to 14 days after study drug cessation. Stargardt disease is classified as a rare genetically inherited disorder affecting the retina of young patients often leading to slow progression of vision loss. Often referred to as juvenile macular degeneration, the disorder affects approximately 1 in 10,000 individuals worldwide, in which the most common genetic lesion is in the ABCA4 gene.
To date, 23 Stargardt subjects randomized to daily emixustat treatment (7 patients to 2.5 mg, 9 patients to 5 mg and 7 patients to 10 mg), all but 1 (from the 5 mg group) have completed the most recent study. Subjects treated with 10 mg showed near-complete suppression of the rod b-wave recovery rate post-photobleaching (mean=91.9%, median=96.7%), whereas those treated with 5 mg showed moderate suppression (mean=52.2%, median=68.0%). No effect was observed for the 2.5 mg group (mean=-3.3%, median=-12.2%). No effect was seen on cone ERG in any group. Most subjects (21/23) experienced at least 1 treatment emergent adverse event (TEAE) (total of 49), the most common being delayed dark adaptation (11/23), erythropsia (5/23), blurred vision (4/23), and photophobia and visual impairment (3/23). No serious TEAEs occurred. Subjects in the 5 mg group experienced more TEAEs (21) than those in the 10 mg (16 TEAEs) or 2.5 mg (12 TEAEs) groups. Further information were identified by SeaSTAR Study, NCT03772665.