HD Lighthouse Contributing Editor's Comment: Memantine is a glutamate receptor regulator marketed under the trade name Namenda. It was FDA approved for treatment for moderate to severe Alzheimer's after a Phase III clinical trial showed that it slowed functional and cognitive decline.

The mechanism by which memantine is thought to work in Alzheimer's and proposed to work in Huntington's Disease is by reducing excitotoxicity. The idea behind excitotoxicity is that the overstimulation of N-methyl-d-aspartate (NMDA)-type glutamate receptors causes a variety of problems including excessive calcium in the associated ion channels and eventually leads to cell death. Researchers know that this is a problem in stroke and brain injury, and have reason to believe that it also occurs in chronic neurological diseases. Memantine reduces the excessive stimulation of the NMDA glutamate receptors without blocking them altogether. See: HDL: More on Memantine

The Lighthouse previously reported on a two year pilot study which suggested that memantine might slow disease progression in Huntington's. 27 patients were followed for two years and showed no disease progression as one would expect based on past studies. See: HDL: Glutamate Blockers in the Lab and in the Clinic

As referenced below, Baylor researchers report on the results of a small, open label study with twelve patients, three of whom dropped out during the study. Patients were followed for three months, too short a time to see if the drug might slow disease progression. However, chorea improved significantly, which is a promising finding. They recommend larger clinical trials.

Johns Hopkins is conducting a clinical trial of memantine to see if it will improve memory and thinking in HD patients. More details and contact information may be found at: John Hopkins: Memantine Study

-- Marsha L. Miller, Ph.D.
Posted to the HDL: 04 Dec 2006

A Pilot Study of the Clinical Efficacy and Safety of Memantine for Huntington's Disease.

W. Ondo, N. Mejia, and C. Hunter

Excerpt from this letter to the editor: "In our small pilot trial, 20 mg daily dose of memantine significantly improved motor symptoms, powered by improved chorea, but failed to improve patient's cognitive behavioral, functional, or independence ratings. Most patients tolerated memantine without side effects. The absence of cognitive improvement may result from the small power or intrinsic differences in the dementia of Alzheimer's and HD." # # #

Source: Parkinsonism and Related Disorders 2006 Oct 12; [Epub ahead of print]

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