One of the most significant challenges facing eye and vision researchers is the development of an effective treatment for dry age-related macular degeneration (AMD). Although there are now a number of well-regarded FDA-approved drug treatments for wet AMD, the key to effective dry AMD treatment remains elusive.
Current treatments for dry AMD include a number of non-drug-related measures, including (a) nutritional supplements recommended by the Age-Related Eye Disease Study 2 (AREDS2), and (b) controlling a range of lifestyle factors, including diet, weight, blood pressure, smoking, and ultraviolet light exposure.
A Continuing Clinical Trial for Dry AMD: Emixustat Hydrochloride
Note to readers: Please read this May 27, 2016 update from the American Academy of Ophthalmology: Emixustat fails to demonstrate improvement in geographic atrophy.
Acucela Inc. is a biotechnology company that addresses unmet medical needs through the discovery and development of novel therapeutics to treat and slow the progression of sight-threatening ophthalmic diseases, including macular degeneration. One of its two lead drugs in current development is emixustat hydrochloride, an oral drug that is being studied to determine whether it slows the progression of geographic atrophy associated with dry AMD.
Here is more information about emixustat and visual cycle modulation (VCM) technology from the Acucela Inc. website:
The visual cycle is the biological conversion of light into an electrical signal in the retina, which is perceived by the brain as vision. During exposure to bright light, the visual cycle is extremely active and may produce toxic by-products that cannot be eliminated.
Over time, accumulation of these toxic by-products can compromise function of the visual cycle and damage the retina. Visual cycle modulation (VCM) is designed to slow the visual cycle and potentially reduce the accumulation of toxic by-products and … damage to the retina.
The Company’s VCM-based investigational product candidate, emixustat hydrochloride, has demonstrated … modulation of the visual cycle in pre-clinical models, is non-retinoid [i.e., not derived from vitamin A], and has a generally favorable systemic safety profile in early clinical trials.
About Dry Macular Degeneration
The dry (also called atrophic) type of AMD affects approximately 80-90% of individuals with AMD. Its cause is unknown, it tends to progress more slowly than the wet type, and there is not – as of yet – an approved treatment or cure. “Atrophy” refers to the degeneration of cells in a portion of the body; in this case, the cell degeneration occurs in the retina.
In dry age-related macular degeneration, small white or yellowish deposits, called drusen, form on the retina, in the macula – the small sensitive area in the center of the retina that provides clear central vision – causing it to deteriorate or degenerate over time.
A retina with drusen
Drusen are the hallmark of dry AMD. These small yellow deposits beneath the retina are a buildup of waste materials, composed of cholesterol, protein, and fats. Typically, when drusen first form, they do not cause vision loss. However, they are a risk factor for progressing to vision loss.
Dry Macular Degeneration and Geographic Atrophy
Geographic atrophy is the most severe and advanced form of dry AMD, involving patches of cells in the retina that have degenerated or died off. “Atrophy,” in this case, refers to the degeneration of the deepest cells of the retina, called the retinal pigment epithelium (RPE). “Geographic” refers to any condition whose shape resembles the irregular outline of a land mass, such as the atrophied portion of the retina.
The RPE helps to maintain the health of the retinal photoreceptor cells, called rods and cones. These photoreceptor cells are triggered by light to set off a series of electrical and chemical reactions that helps brain to interpret what the eye sees. The degeneration of the RPE cells also leads to the death of the rods and cones. At present, there is no medical or surgical treatment for geographic atrophy.
More about the Clinical Trial
Acucela Inc. has completed enrollment in the FDA-approved Phase 2b/3 clinical trial for emixustat hydrochloride, entitled Safety and Efficacy Assessment Treatment Trials of Emixustat Hydrochloride (SEATTLE). Here is more information from The Wall Street Journal:
Acucela Inc. has announced that it has completed enrollment in its ongoing Phase 2b/3 clinical trial investigating emixustat in subjects with geographic atrophy (GA) associated with dry age-related macular degeneration (AMD).
The Safety and Efficacy Assessment Treatment Trials of Emixustat hydrochloride (SEATTLE) study is a multicenter, randomized, double-masked, dose-ranging trial initiated in early 2013. 508 patients with GA associated with dry AMD were enrolled in the clinical trial. Emixustat is being studied to determine whether it slows the rate of progression of GA lesions in these patients.
The estimated completion date for the Phase 2b/3 clinical trial is July 2016. In addition, Acucela has been awarded Fast Track designation by the FDA for emixustat hydrochloride.
Fast Track is a process designed to facilitate the development, and expedite the review, of drugs to treat serious diseases and fill an unmet medical need. Filling an unmet medical need is defined as providing a therapy where none exists or providing a therapy which may be potentially superior to existing therapy.
About Clinical Trials
Most clinical trials are designated as Phase 1, 2, or 3, based on the questions the study is seeking to answer:
- In Phase 1 clinical trials, researchers test a new drug or treatment in a small group of people (20-80) for the first time to evaluate its safety, determine a safe and effective dosage range, and identify possible side effects.
- In Phase 2a/2b clinical trials, the study drug or treatment is given to a larger group of people (100-300) to determine if it is effective and to further evaluate its safety.
- In Phase 3 studies, the study drug or treatment is given to even larger groups of people (1,000-3,000) to confirm its effectiveness, monitor side effects, compare it to commonly used treatments, and collect information that will allow the drug or treatment to be used safely.
- In Phase 4 studies, after the Food and Drug Administration (FDA) has approved the drug, continuing studies will determine additional information, such as the drug’s risks, side effects, benefits, and optimal use.