In 2005, two genetic studies of people with age-related macular degeneration (AMD)–the most common cause of blindness in people older than 65–made a surprising discovery. Research showed that defects in a gene that is an important regulator of parts of the immune system significantly increased risk of the disease. Scientists have since identified variants in several related genes that also boost risk, and which collectively account for about 50 to 60 percent of the heritability of the disorder.
At the same time that researchers identified the harmful variation linked to AMD, Gregory Hageman, now at the University of Utah, identified a protective variant found in about 20 percent of the population. “That form is so incredibly protective that people with two copies are almost guaranteed not to develop the disease,” he says. Hageman founded Optherion, a startup based in New Haven, CT, and investigated how to translate the findings into new treatments. Optherion is now producing large quantities of an engineered version of the protein and doing preclinical safety and effectiveness testing–for example, examining whether the treatment can reduce ocular deposits in mice that lack the protein, says Colin Foster, Optherion’s president. He declined to estimate when the company will begin clinical trials of the drug.
Scientists hope that these developments will prove to be an example of the benefits that can arise from a type of genetic study called genome-wide association. The genome-wide studies of macular degeneration were among the first and perhaps the biggest success for the approach, which employs specially designed chips dotted with markers to cheaply detect hundreds of thousands of the most common variations in the human genome. While these chips have allowed scientists to cheaply scan the genomes of many patients and healthy controls, the approach has come under increasing scrutiny in the last couple of years. Even huge studies of thousands of people have failed to identify the majority of the heritability of common diseases, such as type 2 diabetes or Alzheimer’s disease.
But David Altshuler, a physician and geneticist at the Broad Institute, in Cambridge, MA, and one of the primary architects of these studies, argues that this is not the best way to measure their success. Rather than using the results to design diagnostics to predict an individual risk for developing a disease, we should use genome-wide association studies to identify new drug targets, he says. And he points toward macular degeneration as an example.