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Clemastine (otherwise known as clemastine fumarate) is an over the counter antihistamine. It could reduce immune activity, and may help to promote myelin repair.

Current phase of trial:
Phase 2
Type of MS:
Relapsing MS

Find out more about clemastine

How does clemastine work?

Clemastine is an active ingredient in antihistamines. It's also used to relieve itching associated with chickenpox or eczema. Clemastine enters the brain and causes drowsiness, so it is known as a sedating antihistamine.

The treatment has been shown to suppress the immune system both in mice and healthy volunteers, which could be useful in MS. It's also been shown to promote myelin repair in mice with a condition similar to MS.

How is clemastine taken?

As a tablet or liquid that is taken orally.

Latest research

Metformin and clemastine trial

In September 2020 we announced our new clinical trial, which will be testing clemastine in a Phase 2a clinical trial in combination with metformin, a drug which is already used to treat type 2 diabetes.

This trial will recruit 50 participants with relapsing MS. Half will take a placebo (dummy drug) and the other half will take both metformin and clemastine. Researchers want to know if the combination of metformin and clemastine could repair myelin damage in relapsing MS.

Although both metformin and clemastine have been trialled in people with MS before, the effects of metformin on myelin repair in people has not been tested. And evidence from animal studies has shown that metformin enhances the effect of clemastine on myelin repair, but the two drugs have never been tested in combination.

Earlier research

The ReBUILD trial

Results of this small phase 2 trial were published in October 2017. Researchers found that clemastine improved the speed at which messages travelled from the eye to the brain - an early indication that clemastine can boost remyelination.

The treatment was associated with increased fatigue, but no severe adverse events were reported.

The trial involved 50 people with relapsing MS, and ran for five months. Researchers tested if 4 mg clemastine twice daily taken alongside a licensed disease modifying therapy (DMT) was better than taking the DMT alone. After three months, everyone involved in the trial took clemastine.

Phase 1 research

A small phase 1 trial completed in 2010 suggested that clemastine could suppress the immune response. The researchers found that the immune cells in 10 healthy volunteers injected with 2mg clemastine were less active than in volunteers given a placebo.

What are the side effects of clemastine?

Clemastine has not been widely tested in people with MS so its side effects specifically for people with MS are not yet known. However, when used to treat allergy symptoms, side effects include drowsiness and fatigue, dizziness, and sometimes headaches, dry mouth, and nausea.

How does clemastine compare with current therapies?

Clemastine has not been widely tested in people with MS so it isn’t yet known how it compares to existing MS treatments.

When is clemastine likely to become available?

Clemastine is already licensed for other conditions but will need to undergo larger phase 2 and phase 3 trials to definitively test its effectiveness in MS. This process will take several years.