Researchers at Children’s Hospital Boston have begun a randomized, placebo-controlled trial to test a potential drug treatment for Rett syndrome, the leading known genetic cause of autism in girls. The principal researcher of the study Omar Khwaja, MD, PhD, is the director of the Rett Syndrome Program in the Department of Neurology at Children’s
Although Rett syndrome used to be seen as a degenerative, irreversible disease, recent research indicates that brain cells aren’t actually lost, and the brain is structurally normal – instead, the synapses between cells are weak, preventing brain circuits from maturing. Rett syndrome’s usual cause is mutation or deletion of a gene called MeCP2, which itself controls a group of genes that regulate synaptic changes in response to input from the environment. In 2007, working with a mouse model of Rett syndrome, researchers used genetic tricks to restore MeCP2’s function in the brain.2 The mice showed a striking recovery, suggesting that Rett syndrome, even when well established, might be a treatable disease – if only synapses could be built back up.
"This was an enormous intellectual proof-of-principle that we aren’t wasting time thinking of therapies for girls who are already symptomatic," says Khwaja. "Before, it was thought that if there ever was a treatment, it would have to be given before symptoms appeared, and that once the disease started it couldn’t be reversed."
IGF-1, the drug used in the trial, is indirectly regulated by MeCP2. It has been shown to enhance synapse maturation, and in mice missing the MeCP2 gene, treatment with IGF-1 ameliorated several features of their Rett-like disease.1
The drug, mecasermin, a synthetic form of insulin-like growth factor-1 (IGF-1), is already FDA-approved for children with short stature due to IGF-1 deficiency. The trial, now enrolling patients, marks the beginning of a trend toward drug treatments seeking to modify the underlying causes of autism spectrum disorders, rather than just behavioral symptoms such as anxiety or aggression. It follows research in animal models, published in 20091, which suggested that raising IGF-1 levels can reverse features of Rett syndrome by enhancing maturation of synapses —the points of communication between brain cells.
"We expect that therapy that stimulates synaptic maturation will serve as a model for pharmacological treatment of not only Rett syndrome, but of other autism spectrum disorders," says Khwaja.