Acucela Initiates Phase 2a Study of Emixustat Hydrochloride Addressing Patients with Stargardt Disease

Acucela Inc. (“Acucela”), a clinical-stage ophthalmology company and wholly-owned subsidiary of Kubota Pharmaceutical Holdings Co., Ltd. (Tokyo 4596) committed to translating innovation into a diverse portfolio of drugs and devices to preserve and restore vision for millions of people worldwide, announced today that on January 25, 2017, the first patient has enrolled in a study to evaluate Acucela’s leading drug candidate, emixustat hydrochloride (“emixustat”) in subjects with macular atrophy secondary to Stargardt disease.

This multicenter, randomized, masked phase 2a study is designed to evaluate the pharmacodynamics, safety and tolerability of emixustat in subjects with macular atrophy secondary to Stargardt disease. Approximately 30 subjects will be enrolled at 4 to 6 clinical sites in the United States. Subjects will be randomly assigned to one of three treatment arms in a 1:1:1 ratio. Treatment arms include: emixustat 2.5 mg, emixustat 5 mg, and emixustat 10 mg. Subjects will orally take study drug once daily in the evening for one month.

“This is an important therapeutic development for patients with Stargardt Disease,” said Dr. Hendrik Scholl from the University Hospital in Basel Switzerland and Study Director of the Stargardt Disease Natural History Study (PROGSTAR) sponsored by the Foundation Fighting Blindness (FFB). “Emixustat addresses a well-understood mechanism that leads to toxic accumulation of material underneath the retina linked to visual loss in Stargardt disease and therefore is a promising compound for this debilitating disease.” Additionally, Dr. Ryo Kubota, MD, PhD, and Chairman, President and CEO of Acucela stated that “Stargardt disease represents a serious sight threatening unmet medical need, and we are pleased to start our Phase 2a study of emixustat in subjects with Stargardt disease.”

“We applaud Acucela’s evaluation of emixustat for people with Stargardt disease, a devastating form of inherited macular degeneration, which causes significant central vision loss in young people, and for which there are currently no therapies,” said Patricia Zilliox, Ph.D., chief drug development officer, FFB-CRI. “Preserving vision by slowing degeneration would be a major benefit for those affected.”

The FDA (U.S. Food and Drug Administration) granted orphan drug designation to emixustat for the treatment of Stargardt disease. (See January 5, 2017 press release titled “Acucela Receives Orphan Drug Designation from the FDA for the Treatment of Stargardt Disease”)

Stargardt Disease

Stargardt disease, or fundus flavimaculatus, is a rare, genetically inherited disease that directly affects the retina of the eye, often resulting in the slow progression of vision loss in children. It may also be referred to as Stargardt macular dystrophy or juvenile macular degeneration and affects approximately 1 in 10,000 individuals worldwide1. The most common form of the disease is caused by a genetic mutation of the ABCA4 gene leading to the accumulation of toxic vitamin A byproducts (primarily A2E) in the retina, which results in the gradual deterioration of photoreceptors and vision. Symptoms of Stargardt disease typically appear during childhood or adolescence, but in some cases difficulty with eyesight and vision loss may not be identified until later in life. Stargardt disease affects less than 40,000 patients in the U.S. where it is recognized as an orphan disease, subject to the Orphan Drug Act. Currently, there are no known therapies that exist to slow the advance of the disease, and it is recognized as a serious unmet medical need by the United States Foundation of Fighting Blindness and the National Eye Institute.

Emixustat Hydrochloride

The visual cycle is the process by which vitamin A is recycled in the eye; vitamin A is crucial to the visual process. Emixustat modulates the visual cycle by inhibiting a critical enzyme of this pathway, retinal pigment epithelium protein 65 (RPE65). Slowing the visual cycle reduces the availability of vitamin A derivatives (11-cis- and all-trans-retinal) to form precursors of A2E and related compounds. In animal models of Stargardt disease and retinal degeneration, emixustat was found to stop and reverse the accumulation of A2E and to preserve the integrity of the retina. Emixustat when delivered orally was found to be generally well tolerated in human clinical studies with delayed dark adaptation being the most common ocular adverse event.

1 Kaplan J, Gerber S, Larget-Piet D et al. A gene for Stargardt's disease (fundus flavimaculatus) maps to the short arm of chromosome 1. Nature Genetics 1993;5(3):308-311.