Memantine Therapy in Amyotrophic Lateral Sclerosis

We have been very interested in the role of developing a more active anti-excitotoxic cocktail for patients with ALS. As part of this interest we have been investigating potential markers for disease progression. One of our candidate markers has been the presence of elevated levels of TAU in the CSF of patients with ALS. While the presence of Tau was originally described as being used for adjunctive diagnostic testing in patients with Alzheimer's disease it has become clear that many neurodegenerative diseases possess elevated levels of Tau in the CSF. Therefore Tau is truly a marker of increased neuronal death from any disease process.

While levels of Tau have not been studied in depth in ALS, there was one report in 2003 which showed that 70% of ALS patients have elevated levels of Tau in their CSF (Sussmuth et al). We have also collected a series of 24 patients with clinically definite ALS and found that 22 of them had elevated levels of Tau at the time of diagnosis.

We have been intrigued by the findings that Memantine, an NMDA receptor antagonist, can inhibit and reverse the abnormal hyperphosphorylation of Tau which leads to sequestration of the normal Tau microtubules as well as microtubule associated protein 1 (MAP-1) and MAP-2. Further, Memantine has been shown to block the disassembly of microtubules which follows the hyperphosphorylation if Tau (Li et al., 2004).

We have submitted for presentation to the International Motor Neuron Disease meeting in 2005 the data on two anecdotal cases of patients with ALS. These two patients were diagnosed with ALS on clinical and electrophysiological data and they were found to have elevated levels of Tau in their CSF at the time of diagnosis. Both patients were treated with Riluzole, as standard therapy, and with Memantine 10 mg BID for 6 months. After 6 months their disease course was clearly very slow. A repeat analysis of their CSF showed that levels of Tau had returned to normal.