A Longer-Lasting Treatment for Wet AMD Proves Successful in a Pre-Clinical Trial

August 23, 2013

A new treatment for the wet form of age-related macular degeneration (AMD) has the potential to last up to three times longer than current treatments, according to the results of a pre-clinical study published, online, in the journal Biomaterials.  Developed by researchers at Johns Hopkins Medical Center, the new drug and its delivery system were successfully tested in mice. While a clinical, or human, trial of the treatment is not yet planned, the Hopkins team’s work has far-ranging implications for those affected by wet AMD, the leading cause of blindness in people age 55 and older.

“Another way of inhibiting the disease, and for a longer period of time, is what makes this project so exciting,” says Brian Mansfield, Ph.D., the Foundation Fighting Blindness’ deputy chief researcher officer.

Current treatments of the disease involve monthly to bi-monthly injections of what’s known as anti-VEGF drugs, which block a protein that damages central vision by stimulating extraneous blood vessel growth in the retina. Injected directly into the eye, the FDA-approved drugs Lucentis® and Eylea™ “mop up” that area of the retina, thus reducing vision loss or, in some cases, improving vision, in patients until the next dose is needed.

Although the treatment is not painful, and presents little risk for infection, it is time-consuming and uncomfortable. “No one likes a needle in the eye,” Dr. Mansfield says. “So, now, researchers are looking for ways to reduce the number of injections.”

The Hopkins treatment is designed to do just that, by delivering the drug in a non-toxic envelope, of sorts, which keeps the drug in the eye longer by releasing it more gradually—over roughly 14 weeks, according to the study’s results.

So, how does it work? The drug is inserted into what’s called a nanoparticle, a microscopic sphere comprised of non-toxic, biodegradable materials which, as they’re gradually broken down by enzymes, release the drug slowly. To lengthen this process even more, the researchers put 100 of these nanoparticles into a larger microparticle, which was then injected into the eye, rendering the drug effective for three to four months.   

The drug itself differs from current treatments in that it’s not derived from a full-fledged protein, but from a peptide, a much smaller version of a protein with far fewer amino acids. “The smaller, the better,” Dr. Mansfield explains. “Because of their size, peptides are easier to work with and produce than proteins.”

Now that the peptide, referred to as SP6001, has proven successful in mice, the next step is to test it and other peptides the team has discovered in larger animals, to determine which is the most effective.

“We are still quite a ways from clinical trials,” says Peter Campochiaro, M.D., the George S. & Dolores Doré Eccles Professor of Ophthalmology & Neuroscience at Hopkins. “After selecting the best peptide, we have to make sure we can get good peptide levels for several months. Then it will be necessary to do toxicity studies. Then we will be ready to apply for a clinical trial.”

While the Foundation is not funding this project, specifically, it has supported Hopkins projects in the past and funded basic research which led to the discovery of anti-VEGF treatments.

“Treating wet AMD has grown by leaps and bounds over the past few years, and it’s very important because of the size of the AMD population,” says Dr. Mansfield. “But there’s always room for improvement, and reducing the number and frequency of injections is important to both the patient and their caregivers.”