Researchers Identify Brain Ion Channel as New Approach to Treating Depression
Clinical trial results provide rationale for continued study of the KCNQ type of ion channel
Researchers from the Icahn School of Medicine at Mount Sinai have identified a drug that works against depression by a completely different mechanism than existing treatments.
Their study showed that ezogabine (also known as retigabine), a drug that opens KCNQ2/3 type of potassium channels in the brain, is associated with significant improvements in depressive symptoms and anhedonia in patients with depression. Anhedonia is the reduced ability to experience pleasure or lack of reactivity to pleasurable stimuli; it is a core symptom of depression and associated with worse outcomes, poor response to antidepressant medication, and increased risk of suicide.
Ezogabine was approved by the U.S. Food and Drug Administration in 2011 as an anticonvulsant for epilepsy treatment but had not been previously studied in depression. The research results, published March 3 in the American Journal of Psychiatry, provide initial evidence in humans for the KCNQ2/3 channel as a new target for novel drug discovery for depression and anhedonia.
“Our study is the first randomized, placebo-controlled trial to show that a drug affecting this type of ion channel in the brain can improve depression and anhedonia in patients. Targeting this channel represents a completely different mechanism of action than any currently available antidepressant treatment,” says James Murrough, MD, PhD, Associate Professor of Psychiatry, and Neuroscience, Director of the Depression and Anxiety Center for Discovery and Treatment at the Icahn School of Medicine at Mount Sinai, and senior author of the paper.
The new drug target, the KCNQ2/3 channel, is a member of a large family of ion channels referred to as the KCNQ (or Kv7) family that act as important controllers of brain cell excitability and function in the central nervous system. These channels affect brain cell function by controlling the flow of the electrical charge across the cell membrane in the form of potassium (K+) ions. Researchers at Mount Sinai, including study co-author Ming-Hu Han, PhD, Professor of Pharmacological Sciences, and Neuroscience, had previously conducted a series of studies in mice showing that changes in the KCNQ2/3 potassium channel play an important role in determining if the animals show depression and anhedonic-like behavior following chronic stress in an experimental model of depression. In particular, mice that appear to be resistant to developing depression in the face of stress show an increase in KCNQ2/3 channels in the brain.
“We viewed enhanced functioning of the KCNQ channel as a potential molecular mechanism of resilience to stress and depression,” said Dr. Han, who also discovered that if he gave a drug that could increase the activity of this channel, such as ezogabine, to mice that had become depressed in the stress model, the mice no longer showed the depression and anhedonic behaviors; in other words, the drug acted as an antidepressant.
The current study was a two-site, double-blind, randomized, placebo-controlled proof of concept clinical trial designed as a preliminary test of the hypothesis that increasing KCNQ2/3 channel activity in the brain is a viable new approach for the treatment of depression. Forty-five adult patients diagnosed with a depressive disorder were assigned to a five-week treatment period with daily dosing of either ezogabine or matching placebo. All participants underwent clinical evaluations and functional magnetic resonance imaging (fMRI) during a reward task at baseline and at the end of the treatment period. Compared to patients treated with placebo, those treated with ezogabine showed a significant and large reduction in several key measures of depression severity, anhedonia, and overall illness severity. For example, significant improvements following treatment with ezogabine compared to placebo was observed using the Montgomery-Asberg Depression Rating Scale (MADRS), the Quick Inventory of Depressive Symptomatology-Self Report (QIDS-SR), the Snaith-Hamilton Pleasure Scale (SHAPS), and the Temporal Experience of Pleasure Scale (TEPS)–Anticipatory Subscale. The ezogabine group showed also a trend towards an increase in response to reward anticipation in the brain compared to placebo although this effect did not reach statistical significance.
“The fundamental insight by Dr. Han’s group that a drug that essentially mimicked a mechanism of stress resilience in the brain could represent a whole new approach to the treatment of depression was very exciting to us,” said Dr. Murrough.
In collaboration with Dr. Han, Dr. Murrough carried out a series of studies in patients with depression to begin to test if the observations in mice could be translated to humans. An initial open-label (no placebo) study in patients with depression led by Dr. Murrough provided initial evidence that ezogabine could improve symptoms of depression and anhedonia in a manner that was associated with changes in brain function.
“I think it’s fair to say that most of us on the study team were quite surprised at the large size of the beneficial effect of ezogabine on clinical symptoms across multiple measures related to depression. We are greatly encouraged by these findings and the hope they offer for the prospect of developing novel, effective treatments for depression and related disorders. New treatments are urgently needed given that more than one-third of people suffering from depression are inadequately treated with currently approved therapeutics.”
This research was supported by the National Institute of Mental Health. Additional funding was provided by the Friedman Brain Institute at the Icahn School of Medicine at Mount Sinai and the Ehrenkranz Laboratory for Human Resilience, a component of the Depression and Anxiety Center for Discovery and Treatment at the Icahn School of Medicine at Mount Sinai.
Study authors James Murrough, MD, PhD and Ming-Hu-Han, PhD, are named inventors on a pending patent application for the use of ezogabine and other KCNQ channel openers to treat depression and related disorders.
About the Mount Sinai Health System
Mount Sinai Health System is one of the largest academic medical systems in the New York metro area, with more than 43,000 employees working across eight hospitals, over 400 outpatient practices, nearly 300 labs, a school of nursing, and a leading school of medicine and graduate education. Mount Sinai advances health for all people, everywhere, by taking on the most complex health care challenges of our time — discovering and applying new scientific learning and knowledge; developing safer, more effective treatments; educating the next generation of medical leaders and innovators; and supporting local communities by delivering high-quality care to all who need it.
Through the integration of its hospitals, labs, and schools, Mount Sinai offers comprehensive health care solutions from birth through geriatrics, leveraging innovative approaches such as artificial intelligence and informatics while keeping patients’ medical and emotional needs at the center of all treatment. The Health System includes approximately 7,300 primary and specialty care physicians; 13 joint-venture outpatient surgery centers throughout the five boroughs of New York City, Westchester, Long Island, and Florida; and more than 30 affiliated community health centers. We are consistently ranked by U.S. News & World Report's Best Hospitals, receiving high "Honor Roll" status, and are highly ranked: No. 1 in Geriatrics and top 20 in Cardiology/Heart Surgery, Diabetes/Endocrinology, Gastroenterology/GI Surgery, Neurology/Neurosurgery, Orthopedics, Pulmonology/Lung Surgery, Rehabilitation, and Urology. New York Eye and Ear Infirmary of Mount Sinai is ranked No. 12 in Ophthalmology. U.S. News & World Report’s “Best Children’s Hospitals” ranks Mount Sinai Kravis Children's Hospital among the country’s best in several pediatric specialties. The Icahn School of Medicine at Mount Sinai is one of three medical schools that have earned distinction by multiple indicators: It is consistently ranked in the top 20 by U.S. News & World Report's "Best Medical Schools," aligned with a U.S. News & World Report "Honor Roll" Hospital, and top 20 in the nation for National Institutes of Health funding and top 5 in the nation for numerous basic and clinical research areas. Newsweek’s “The World’s Best Smart Hospitals” ranks The Mount Sinai Hospital as No. 1 in New York and in the top five globally, and Mount Sinai Morningside in the top 20 globally.