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A decade after UC San Francisco scientists identified an over-the-counter antihistamine as a treatment for multiple sclerosis, researchers have developed an approach to measure the drug’s effectiveness in repairing the brain, making it possible to also assess future therapies for the devastating disorder.

The researchers, led by physician-scientist Ari Green, MD, who together with neuroscientist Jonah Chan, PhD, first identified clemastine as a potential MS therapy, used MRI scans to study the drug’s impact on the brains of 50 participants in a clinical study.

In the brain, water trapped between the thin layers of myelin that wrap nerve fibers cannot move as freely as water floating between brain cells. This unique property of myelin allowed imaging experts to develop a technique to compare the difference in myelin levels before and after the drug was administered, by measuring the so-called myelin water fraction, or the ratio of myelin water to the total water content in brain tissue.

In their study, published May 8, 2023, in PNAS, the researchers found that patients with MS who were treated with clemastine experienced modest increases in myelin water, indicating myelin repair. They also proved that the myelin water fraction technique, when focused on the right parts of the brain, could be used to track myelin recovery.

This is the first example of brain repair being documented on MRI for a chronic neurological condition. The study provides the first direct, biologically validated, imaging-based evidence of myelin repair induced by clemastine. This will set the standard for future research into remyelinating therapies.
Ari Green, medical director of the UCSF Multiple Sclerosis and Neuroinflammation Center and a member of the Weill Institute for Neurosciences.


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