In a small, phase II clinical trial, the oral antihistamine clemastine modestly improved the transmission of electrical signals in the optic nerve in participants with MS who had optic nerve damage.

The improved transmission indicates that nerve-insulating myelin was repaired along the nerve pathways.

Clemastine is an over-the-counter allergy medication. Doses in this trial exceeded the maximum recommended for over-the-counter use. Clemastine affects a range of targets in the body, and involves the risk for side effects, particularly at increased dosages.

More studies are needed before the full benefits and risks of this approach can be verified. This team is conducting an additional trial in people with optic neuritis to further determine the safety and effectiveness of clemastine, as well as studies to identify compounds that may enhance myelin repair and cause fewer side effects.

Clemastine was identified as having possible myelin-repairing properties through innovative preclinical research conducted by National MS Society-funded Jonah Chan, PhD, who went on to become first recipient of the Barancik Prize for Innovation in MS Research for this pioneering work.

for Innovation in MS Research for this pioneering work. UPDATE: The full results of the study, led by Ari Green, MD (University of California, San Francisco), have now been published in The Lancet. (Preliminary results were previously presented at the annual meeting of the American Academy of Neurology in April 2016.)

UPDATE - Study Details Now Published (Originally released 4/12/16)In MS, the immune system attacks and destroys myelin, the fatty substance that surrounds and protects the nerve fibers, and the nerve fibers can also be damaged. Current therapies are largely aimed at dampening the immune attacks. However, a therapy that repairs damage to myelin and nerve fibers is also necessary.A team at the University of California, San Francisco led by National MS Society-funded Harry Weaver Neuroscience Scholar Jonah Chan, PhD, invented a new micropillar technology to rapidly identify compounds that stimulate the regrowth of myelin. The teamusing this technology, testing a library of 1000 drugs already approved by the FDA for other conditions for their ability to promote the development of myelin-making cells and wrapping of myelin around the micropillars. Clemastine, an oral antihistamine used to treat allergy symptoms, was identified through this process. Dr. Chan was thefor Innovation in MS Research for this pioneering work.Ari Green, MD, led the team conducting the clinical trial. They administered oral clemastine or inactive placebo twice daily to 50 people with MS and optic nerve damage for 150 days. For the first three months of the study, people were given either clemastine or a placebo, and for the second two months, those initially given clemastine received the placebo and vice-versa. Tests were performed before and after treatment that measured visual evoked potentials. Visual evoked potentials measure transmission of electric signals along optic nerve pathways in response to stimulation. Delays in this transmission occur when the myelin is damaged and if these delays are reduced, it is an indication that myelin repair is occurring along the nerve pathways. (Participants had significant delays in transmission in at least one eye.)UPDATE: The full results of the study, led by Ari Green, MD (University of California, San Francisco),. (Preliminary results were previously presented at the annual meeting of the American Academy of Neurology in April 2016.)The trial met its primary endpoint, reducing delays in visual evoked potential by 1.7 milliseconds per eye, a statistically significant result. The results hinted at a reduction in vision impairment as well, but it did not reach statistical significance. Fatigue increased mildly in participants taking clemastine.Clemastine is an over-the-counter allergy medication. Doses in this trial exceeded the maximum recommended for over-the-counter use. Also, clemastine affects a range of targets in the body, and involves the risk for side effects, particularly at increased dosages.Dr. Green cautions that more research with larger numbers of people is needed before doctors can recommend clemastine as a treatment for people with MS. This team is conducting an additional trial in people with optic neuritis to further determine the safety and effectiveness of clemastine, as well as studies to identify compounds that may enhance myelin repair and cause fewer side effects.Drs. Green and Chan both received Society funding to launch their early careers as independent researchers focused on MS, including Harry Weaver Neuroscience Scholar Awards.“This is a significant step forward in one of many different approaches being taken to find a way to repair the nervous system damage caused by MS,” said Bruce Bebo, PhD, Executive Vice President, Research at the National MS Society. “Research to restore function to people with MS is a very high priority.”