Despite it’s well known genetic underpinnings, there are currently no drugs to treat the underlying cause of Huntington’s disease (HD). However, a new study reports promising results for a new HD drug that has been found to be safe and lowers the levels of the abnormal huntingtin protein, giving hope for future use in the clinic.
“This is a tremendously exciting and promising result for patients and families affected by this devastating genetic brain disorder,” said Blair Leavitt, MD, professor in the department of medical genetics & medicine, division of neurology at the University of British Columbia. “For the first time, we have evidence that a treatment can not only decrease levels of the toxic disease-causing protein in patients, but that it is also safe and very well tolerated.”
The work is published in the New England Journal of Medicine, in a paper titled, “Targeting Huntingtin Expression in Patients with Huntington’s Disease.”
The experimental drug developed by Ionis Pharmaceuticals and Roche was tested in a randomized, double-blind, multiple-ascending-dose, Phase I–IIa trial involving adults with early Huntington’s disease. The trial enrolled 46 patients with early Huntington’s disease at nine study centers in Canada, the United Kingdom, and Germany. Of the 46 patients, 34 were randomized to receive the drug and 12 were randomized to receive placebo. Each participant received four doses of the drug and all study participants completed the study and have continued to receive the active drug in an on-going open-label study. The drug was administered monthly to patients via an injection directly into the cerebrospinal fluid.
The trial has demonstrated for the first time that the drug, successfully lowered levels of the mutant huntingtin protein—the toxic protein that causes Huntington’s disease—in the central nervous system of patients. While such reductions aren’t guaranteed to yield clinical benefits, the study is the first time that a targeted huntingtin-lowering agent has been shown to lower mutant protein levels.
The researchers, led by Sarah Tabrizi, MB, ChB, PhD, director of the Huntington Disease Centre at University College London, found that the drug produced significant decreases in the levels of mutant huntingtin protein in the patients’ cerebrospinal fluid. None of the patients experienced any serious adverse reactions, suggesting that the treatment is safe and well tolerated by patients.
Huntington’s disease is a fatal genetic neurological disease. It usually develops in adulthood and causes abnormal involuntary movements, psychiatric symptoms, and dementia. To date, no effective treatments have been proven to slow down progression of this disorder. Huntington’s disease is caused by a single known genetic mutation, and each child of a carrier of the mutation has a 50% chance of inheriting the disease.
The drug is currently being evaluated in a large Phase III multi-center clinical trial being performed at the Centre for Huntington Disease at UBC and other centers around the world. This study is designed to determine whether the treatment slows or halts the progression of disease symptoms.