A technique called optogenetics has transformed neuroscience during the past 10 years by allowing researchers to turn specific neurons on and off in experimental animals. By flipping these neural switches, it has provided clues about which brain pathways are involved in diseases like depression and obsessive-compulsive disorder. "Optogenetics is not just a flash in the pan," says neuroscientist Robert Gereau of Washington University in Saint Louis. "It allows us to do experiments that were not doable before. This is a true game changer like few other techniques in science."
Since the first papers were published on optogenetics in the mid-aughts some researchers have mused about one day using optogenetics in patients, imagining the possibility of an off-switch for depression, for instance.
The technique, however, would require that a patient submit to a set of highly invasive medical procedures: genetic engineering of neurons to insert molecular switches to activate or switch off cells, along with threading of an optical fiber into the brain to flip those switches. Spurred on by a set of technical advances, optogenetics pioneer Karl Deisseroth, together with other Stanford University researchers, has formed a company to pursue optogenetics trials in patients within the next several years—one of several start-ups that are now contemplating clinical trials of the technique.
Circuit Therapeutics, founded in 2010, is moving forward with specific plans to treat neurological diseases. (It also partners with pharmaceutical companies to help them use optogenetics in animal research to develop novel drug targets for human diseases.) Circuit wants to begin clinical trials for optogenetics to treat chronic pain, a therapy that would be less invasive than applications requiring implantation deep inside the brain. Neurons affected by chronic pain are relatively accessible, because they reside in and just outside the spinal cord, an easier target than the brain. Even nerve endings in the skin might be targeted, making them much easier to reach. "In animal models it works incredibly well," says Scott Delp, a neuroscientist at Stanford, who collaborates with Deisseroth. The firm is also working to develop treatments for Parkinson's and other neurological disorders.