Early clinical trial results have ignited hope for a future class of multiple sclerosis (MS) treatments that could repair the very damage that drives disability, a groundbreaking shift from current therapies that primarily suppress the immune system.
A Cambridge-led trial suggests that a combination of a common diabetes drug, metformin, and an antihistamine, clemastine, can partially reverse the harm done to the nervous system in people with MS. While the effect was subtle and not noticeable to patients over the six-month study, specialized tests confirmed a measurable improvement in nerve function, suggesting the drugs may kickstart the repair of protective nerve coatings.
“I feel like we’re at this precipice of a new class of therapies for MS, and that’s why this is exciting,” said Dr. Nick Cunniffe, the neurologist at the University of Cambridge who led the trial, known as CCMR Two.
Understanding the Damage in MS
MS affects nearly 3 million people globally, including over 150,000 in the UK, and is the most common disabling neurological condition of young adults. The disease occurs when the immune system mistakenly attacks myelin, the fatty insulation that surrounds nerve fibres in the brain and spinal cord. This damage, called demyelination, disrupts the electrical signals travelling along the nerves, leading to a wide range of symptoms from numbness and vision problems to loss of balance and paralysis.
While many patients start with a relapsing-remitting form of the disease, where the body has some capacity to repair myelin, the repair process often fails over time. This leads to progressive MS, where nerves are permanently damaged and die, resulting in steady and irreversible disability. For decades, the central goal of MS research has been to find a way to protect nerves and, more ambitiously, to repair them—a process known as remyelination.
The Science of Repair: A Two-Drug Approach
The CCMR Two trial builds on a decade of pioneering work. Scientists previously discovered that clemastine, an over-the-counter antihistamine, showed a surprising potential to stimulate the brain’s own oligodendrocyte cells to create new myelin. However, its effect alone was modest.
Subsequent laboratory research suggested that metformin, a first-line treatment for type 2 diabetes, could enhance this process. Metformin is known to activate a cellular energy sensor called AMPK, which may help re-energize the ageing stem cells responsible for myelin repair, making them more responsive to clemastine’s prompts.
The Cambridge trial put this combination to the test in 70 people with relapsing MS. For six months, half received clemastine and metformin, while the other half received a placebo. To objectively measure remyelination, researchers used a precise test called visual evoked potentials (VEP), which times how quickly electrical signals travel from the eye to the brain’s visual cortex. In MS, damage to the optic nerve slows this signal.
Cautious Optimism from the Results
The results, presented at the European Committee for Treatment and Research in Multiple Sclerosis in Barcelona, revealed a statistically significant improvement. The electrical signals travelled 1.3 milliseconds faster in the group taking the active drugs compared to the placebo group.
“It’s smaller than we were hoping for,” admitted Dr. Cunniffe. “My conclusion is that the drugs have a biological effect to promote remyelination, but we need to be clear that people do not feel better on these drugs over six months.”
This lack of immediate clinical benefit—such as improved vision—was expected by researchers. They theorize that repairing myelin is a fundamental first step, but restoring function fully, especially in a complex system like vision, may require a longer treatment period and may be most effective when nerves are damaged but not yet dead.
Emma Gray, the director of research at the MS Society, which funded the trial, echoed this cautious optimism: “These are really positive proof-of-concept results. We would not expect them to have a clinical benefit after only six months. It will take longer for this to be seen.”
Challenges and the Road Ahead
The researchers strongly cautioned against patients self-medicating with these drugs outside of a clinical trial. The side effects in the trial were notable, including fatigue from clemastine and diarrhoea from metformin. Furthermore, remyelination drugs cannot bring back nerve cells that have already been lost.
The scientific community views these findings as a critical stepping stone. Professor Jonah Chan, a neurologist at the University of California, San Francisco, who led the earlier ReBuild trial with clemastine, emphasized the importance of the pursuit.
“I’m more convinced than ever that remyelination is the critical path to preventing permanent disability in MS,” said Prof. Chan. “We need to use everything we have learned over the last decade of hard work and struggle to pursue scientifically, experimentally validated compounds from the lab to see if they really work in people. We need to be inspired by optimism but comfortable with learning from setbacks.”
The next steps will likely involve longer and larger trials to see if a more pronounced effect on disability can be achieved over time, potentially positioning this drug combination as the vanguard of a truly restorative era in MS treatment.
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