Antihistamine may stimulate myelin repair

A small, Phase II clinical trial has shown that a common over the counter antihistamine, called clemastine fumarate, has the ability to partially reverse damage to the optic nerve in people with multiple sclerosis (MS).  This release comes ahead of the researchers from the University of California, San Francisco presenting their data at the annual American Academy of Neurology Meeting being held in Vancouver, Canada, between April 15-21.

This study arose from earlier work by Dr Jonah Chan, who invented a novel system to rapidly screen thousands of current medications for their ability to promote myelin repair.  Using this system, clemastine fumarate (an oral allergy medication) was found to stimulate myelin regrowth.  To assess the impact in people with MS, this Phase II trial recruited 50 people with MS (average age = 40, average time since diagnosis = 5 years) that all suffered from chronic optic neuropathy, resulting from myelin damage to the optic nerve and causing loss of vision.

As part of the 5 month study, people received either clemastine fumarate or a placebo for the first 3 months, followed by the groups being switched for the remaining 2 months.  Vision tests were performed at the beginning and end of the study.  One of these tests, called a visual evoked potential test, measures the time taken for a signal to travel from the retina to the visual cortex.  As the speed of nerve signal transmission is altered by the myelin sheath, this test can be used as a marker for myelin repair.  Based on these results, a moderate improvement was seen in the transmission time in people that were taking the antihistamine.  A reduction in vision impairment was also observed, however, this was not statistically significant.  People taking the antihistamine treatment also reported a modest increase in fatigue levels.  This finding suggests the potential for clemastine fumarate to reverse damage and promote myelin repair in the optic nerve of people with MS.

Dr Ari Green, the lead researcher on the project, believes that “this study is exciting because it is the first to demonstrate possible repair of that protective coating in people with chronic demyelination from MS”.  Whilst he admits that the “improvement in vision appears modest”, he reinforces the importance of the study and suggests that it will hopefully provide “a framework for future MS repair studies and will hopefully herald discoveries that will enhance the brain’s innate capacity for repair”.  They are also currently working on more powerful treatments with less side-effects.

Dr Green emphasises the need for larger studies to confirm these results before doctors could recommend this treatment to people with MS.  It is known that clemastine can have potential side-effects and it should also be noted that the dose used for this study is above that recommended for over the counter use.