An Over-The-Counter Allergy Drug Is Reversing Damage Done by Multiple Sclerosis

Scientists have discovered that an over-the-counter antihistamine can improve function in patients with Multiple sclerosis.

UC San Francisco researchers have completed a Phase II clinical trial showing that FDA approved allergy drugs restore nervous system function in those with chronic multiple sclerosis.

MS is an autoimmune neurodegenerative disorder that affects 2.5 million people worldwide. The disease primarily affects myelin, which the immune system attacks. Myelin is comprised of layers of fatty insulating membrane that protects nerve fibers. It helps electrical neurons move faster and more efficiently.

The drug used is called clemastine fumarate and was first identified in 2013 as a useful tool in treating MS by UCSF’s Jonah R. Chan, Ph.D., Debbie and Andy Rachleff Distinguished Professor of Neurology, vice chief of the Division of Neuroinflammation and Glial Biology, and senior author of the new study. It’s believed that the compound repairs damage MS inflicts on myelin.

Clemastine is also known by brand names such as Sunmark 12 hour allergy relief, Tavist, Dayhist-1 and Leader Allerhist. Clemastine was first approved for allergies by the FDA in 1977 and has been available in generic form since 1993.

The results were published online in The Lancet and are the first to show a drug that repairs brain function damaged by a human neurological disease.

“People thought we were absolutely crazy to launch this trial because they thought that only in newly diagnosed cases could a drug like this be effective – intuitively, if myelin damage is new, the chance of repair is strong. In the patients in our trial the disease had gone on for years, but we still saw strong evidence of repair,” said study co-author UCSF’s Jonah R. Chan, Ph.D.

Current MS treatments focus primarily on preventing the immune system from attacking myelin, though none have been shown actually to repair the damaged membrane.

A five-month trial enrolled 50 patients with relapsing and long-standing MS. To test the drug, the researchers showed the volunteers flickering patterns on a screen, then placed electrodes over the brain’s visual areas at the back of the head to see how quickly the eye sent a response to the brain which would then be detected by the electrodes.

“The time from presentation of the pattern to the detection of the VEP is a measurement of how long it took for the signal to travel via nerve fibers from the retina, at the back of the eye, to the visual areas at the back of the brain,” writes UCSF news.

A crossover research design was also implemented in which the patient group was divided in two. One group was given the drug, and the other took a placebo for 90 days. They were then switched, with the later taking the drug for 60 days, while the first group took the placebo.

They were able to compare the patients to themselves which “increased the statistical power of the study by nearly an order of magnitude,” the trial’s principal investigator, Ari Green, MD told UCSF News.

It will take time before they know the full effect of these drugs on myelin because the technology just isn’t there yet. But the results they could observe were notable.

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When each group was taking the drug, the neural signal from the eye to the back of the brain was accelerated over the baseline measurement taken at the beginning of the trial.

“This is the first step in a long process,” Green said. “By no means do we want to suggest that this is a cure-all. We want to ground-truth myelination metrics – we’re designing the crucible that’s going to be used to test any future method for detecting remyelination.”