Testing the use of embryonic stem cells in humans is easier said then done. While researchers have made significant advancements into the use of stem cells to treat diseases in animal models, transplanting them into humans poses several risks. Stem cells can develop into any tissue type - even cancerous tumors. And as in organ transplants, patients are at risk for rejecting newly implanted stem cells, requiring them to take powerful drugs for the rest of the lives that suppress their immune systems. That's why earliest stem cell therapies have focused on immune-privileged sites - in the eye and nervous system - that do not elicit the rejection response.

And now, the Worcester, MA-based company, Advanced Cell Technology (ACT), is using embryonic stems cells to re-create retinal pigment epithelium (RPE), cells that support the photoreceptors required for vision. RPE cells are usually the first to die off in a variety of eye diseases, including age-related macular degeneration, a disease that affects more than 30 million people worldwide and is the leading cause of blindness in people over 60 years of age in the United States.

Mouse models have shown that embryonic stem cells are a source for RPE, with recent studies showing that they restore vision in mouse models of macular degeneration. Studies conducted by ACT researchers and investigators from the Casey Eye Institute at Oregon Health and Science University have now shown a long-term benefit in animal models with Stargardt's disease, a rare but untreatable illness that causes blindness early on in life. In fact, after three months, the retinas of treated rats not only had many more photoreceptors than the untreated control group, but they performed better in vision tests, although the researchers reported that test performance diminished over time. On the flip side, however, the safety of the cells was also tested in a second study, with no evidence demonstrating the development of tumors.

The company is hoping to receive approval sometime over the next few months to begin early human trials. If approved, it will be only the second embryonic stem cell-based treatment to move onto human trials. The hope is that it could provide a test case for other applications of stem cells.

"We have worked with Dr. Lund and his team from the Casey Eye Institute for over three years investigating the safety and efficacy of our RPE cell therapy," states William M. Caldwell IV, Chairman and CEO of ACT. "We are now completing the finishing touches to seek FDA approval to conduct human clinical trials with a cell therapy that may be able to address many of the 200-plus known retinal diseases." And says Robert Lanza, Chief Scientific Officer at ACT, and co-senior author of the study, "We're delighted with these results. Everything looks great so far. Based on these and other studies, we're on schedule to file an IND with the FDA to begin human clinical trials sometime in the next 3 or 4 months."

News Release: A stem-cell therapy for blindness www.beta.technologyreview.com   June 17, 2009

News Release: Assessment of safety and efficacy of human embryonic stem cell therapy  www.eurekalert.org      June 11, 2009