A single injection of an experimental drug designed to silence the gene that produces the mutant huntingtin protein in Huntington's disease can provide long-lasting relief from the condition, studies in rats and monkeys show.
The infusion not only temporarily blocks production of the mutant protein, but also allows the body to clean up some of the huntingtin that has already accumulated, leading to a "huntingtin holiday" that can persist as long as nine months, UC San Diego researchers reported this week. The team hopes to begin human trials of the treatment within 18 months.
Huntington's is a genetic disorder caused by a mutant gene on chromosome 4. The gene produces a protein called huntingtin. Normally, a section of this gene is repeated 15 to 28 times, but in the mutant form, it is repeated as many as 150 times, leading to accumulation of an abnormal form of the huntingtin protein that destroys cells in the brain. The disease produces a broad variety of symptoms, including behavioral disturbances, paranoia, psychosis, movement disorders, dementia and, eventually, death. The disease affects an estimated 30,000 Americans and there is no cure or even an effective treatment.
Researchers have tried a variety of ways to suppress the production of mutant huntingtin. But such suppressive agents have to be injected directly into the brain and they have generally been shown to exert their effects only near the site of the injection.