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02 October 2020

Remyelination is possible, but the wait goes on…

Recent news about bexarotene inspires mixed feelings.

With MS research breakthroughs, it can often feel like “one step forward, two steps back”.  We read about some new study with incredible results, but then get to the bottom of the page and see the dreaded “further larger-scale studies are now required”.  Just like that we realise that this new treatment is probably 5 years away, if it ever makes it at all.  There are no shortcuts in science, as we are all seeing all too clearly in the frantic search for a COVID-19 vaccine.

Whilst these “hurdles” and processes can be very frustrating for those of us with MS, it is of course only right and proper that any new therapy is appropriately tested before it reaches the patient, ensuring that it is primarily safe, but also actually effective.


One recent example is the skin cancer drug, bexarotene. The MS Society in the U.K. has just published some very important results from a phase 2 trial involving 50 people with relapsing remitting MS, all already taking a disease modifying treatment.  25 subjects were given bexarotene once daily for 6 months, whilst the other 25 were given a placebo.

Follow-up tests demonstrated that those pwMS taking bexarotene had evidence of increased nerve transmission rates in the visual pathways in the brain, and areas of new myelin production on MRI.  In short, remyelination had occurred in areas previously damaged by MS, and the speed of nerve signals had increased in an area of the brain commonly affected by MS. 

“Amazing news, where do I get it?!”, I hear you shout.

Well, unfortunately there is some bad news. Bexarotene is not going to be taken forward into phase 3 trials, as it was felt that the potentially serious side effects of under-active thyroid and increased levels of fats in the blood made it unsuitable as an MS treatment. This is very valid, it is already known that an unhealthy balance of fats in the blood can hasten disability progression, so it would be terrible if short-term gain with bexarotene were to be outdone by long-term loss.   

But this is not a reason to be down-hearted, far from it in fact.  This was a very well conducted study categorically demonstrating that remyelination is possible in people with MS.  Previous early studies had shown promising and similar results, but were primarily on mice. To prove the concept in humans is therefore a very important step forward, and was the primary purpose of this trial.  It gives researchers valuable insights into how myelin repair occurs, and where to target their future efforts.  If we could repair areas of damaged myelin, this could improve MS symptoms and potentially slow or stop disability progression.  Of course this is something that those of us living with MS are desperate for, but it must be done in a way that is safe. 

A perfect illustration is seen in another trial that is about to start in the U.K., this time using a combination of two drugs, both already widely prescribed and with excellent safety profiles. Metformin, an oral treatment for type II diabetes, and clemastine, an anti-histamine tablet used to treat hayfever and allergies, have both previously been shown to potentially promote remyelination.  But both studies were small, and in mice (in the case of Metformin) or not based on real-world clinical outcomes (with clemastine).  Combining the two and giving them to people with MS is therefore very exciting news.

So please take this for the good news story that it truly is.  More pieces of the remyelination puzzle have fallen into place, and we really are getting closer to the “holy grail” of MS research  all the time.