The US Food and Drug Administration (FDA) approved Phase I/II clinical trials using retinal cells derived from human embryonic stem cells (hESCs) to treat patients with Stargardt’s Macular Dystrophy (SMD).

One of the most common forms of juvenile macular degeneration, SMD affects children from 10-20 years old. Blindness results from photoreceptor loss associated with degeneration in the pigmented layer of the retina, called the retinal pigment epithelium (RPE). As with the most prevalent type of macular degeneration, “dry” age-related macular degeneration (AMD), there is currently no treatment for SMD.

Advanced Cell Technology Inc. (ACT) hopes to change that, beginning with this clinical trial. According to the company’s chief scientific officer, the stem cells can generate a virtually unlimited supply of healthy RPE cells, which are the first cells to die off in SMD and other forms of macular degeneration. Studies of RPE cells implanted in animal models of macular degeneration have shown positive results in visual performance, and they “hope to see a similar benefit in patients with various forms of macular degeneration.”

“This is good news for stem cell research – particularly for retinal diseases,” says DEF researcher Henry Klassen, an assistant professor in the Gavin Herbert Eye Institute at UC Irvine. “This is one of only two embryonic stem cell-derived trials that have been approved by the FDA so far, and the first for retinal disease.”

Klassen and his DEF-funded colleagues are currently working on a complementary approach to that of the SMD trial. “While the ACT team is working to replace the pigment epithelium of the retina, we’re using non-embryonic retinal progenitor cells to preserve existing photoreceptors and protect them from degeneration. Our cells have shown the ability to replace photoreceptors in the retina,” he says.

“If you restore the pigment epithelium, as they are testing in these trials, you’ve basically repaired half of the damage in photoreceptor degeneration,” Klassen says. “The other half is the photoreceptors themselves, which is what we are working on. Finding a potent method of preserving and restoring function to those cells is critically important, as is replacing lost photoreceptors.”

According to Klassen, if both approaches achieve success, the combination would “yield nothing short of a breakthrough in the treatment of retinal degeneration. With funding support from DEF, we expect to see therapeutic testing in AMD and other retinal diseases, as well as the availability of new treatments during the current decade.”

Posted January 2011