Drugs found in skin creams used for treating eczema and athlete's foot have been shown to reverse multiple sclerosis (MS), according to researchers.
Scientists hope the surprise discovery could kickstart ground-breaking new therapies for the serious auto-immune disease which affects around 100,000 people in the UK.
MS occurs when the immune system attacks myelin (a protein that surrounds every nerve fibre in the brain and spinal cord), thereby disrupting the passage of nerve signals. As the disease progresses, it produces symptoms ranging from mild numbness or tingling to full blown paralysis. Occasionally, it can prove fatal.
Scientists have found that the anti-fungal agent miconazole and the steroid clobetasol both restored movement to mice paralysed by a rodent version of MS.
In laboratory tests, they prompted inactive mouse and human stem cells to regenerate myelin, the protective insulation-like coating around nerve fibres that is destroyed by the disease.
Dr Robert Miller, from Case Western Reserve University whose findings appear in Nature journal, said: "It was a striking reversal of disease severity in the mice.
"The drugs that we identified are able to enhance the regenerative capacity of stem cells in the adult nervous system.
"This truly represents a paradigm shift in how we think about restoring function to multiple sclerosis patients."
Although both drugs are available in most chemists as creams and ointments, a way must be found to use them safely as internal human treatments before clinical trials can be considered.
The researchers are confident this problem can be solved, but have warned patients to be wary of using the drugs just yet.
Lead scientist Professor Paul Tesar, from Case Western Reserve School of Medicine, said: "We appreciate that some patients or their families feel they cannot wait for the development of specific approved medications, but off-label use of the current forms of these drugs is more likely to increase other health concerns than alleviate multiple sclerosis symptoms.
"We are working tirelessly to ready a safe and effective drug for clinical use."
Although current treatments can slow progression of MS and reduce its symptoms, the disease remains incurable.
One new approach is to focus on special stem cells called oligodendrocyte progenitor cells (OPCs) that mature into myelin-producing cells.
While other scientists have looked at ways of replacing lost stem cells using transplantation techniques, the Case Western team set out to find a way of stimulating existing, but inactive, OPCs.
After screening 727 potential drug candidates, they identified two - miconazole and clobetasol - that coaxed the OPCs to form oligodendrocytes and repair nerve fibres stripped of myelin.
"We know that there are stem cells throughout the adult nervous system that are capable of repairing the damage caused by multiple sclerosis, but until now, we had no way to direct them to act," said Tesar.
"Our approach was to find drugs that could catalyse the body's own stem cells to replace the cells lost in multiple sclerosis."
As well as testing the drugs on mice affected by MS, the scientists also observed their effect on human OPCs in the laboratory. The response was similar to that seen in mouse cells, with miconazole exerting the most potent effect.
The drugs may also hold the promise of treatments for other diseases that involve myelin loss or dysfunction, including cerebral palsy, age-related dementia, optic neuritis and schizophrenia, the scientists believe.
British immunology expert Professor Daniel Altmann, from Imperial College London, said: "This study.. offers the highly attractive possibility of re-targeting existing, safe, drugs for the purpose of promoting therapeutic remyelination.
"The data appear to suggest that the drugs can to some extent limit disability in experimental models of MS, though there is clearly much more to be optimised in this area, not least as the models tried thus far do not really look at effects on chronic demyelination.
"However, particularly for patients with progressive MS - where it can be difficult to know how to impact the ongoing deterioration, these approaches offer the great advantage that these are tried, tested and safe drugs passed for use in humans.
"Some caution is clearly warranted, however, when one considers the long haul from benefits in tissue culture models of myelination to a complex and diverse human disease such as MS."
