Scientists in Britain say a drug which was developed to treat leukaemia may also be a powerful new weapon against multiple sclerosis (MS).
They say the drug Alemtuzumab appears to stop the progression of the disease in patients with early stage active relapsing-remitting MS - the most common form of the condition.
The scientists from Cambridge University say though their work is still in the early stages, the drug may also repair previous damage, but they warn that Alemtuzumab can have potentially serious side-effects.
During the trial, 20% of patients treated with alemtuzumab developed either an under-active or over-active thyroid gland and a small number developed a low platelet count, making them vulnerable to bleeding - one case actually died - the researchers say this complication can be easily treated if it is recognised early.
Alemtuzumab is a drug known as a monoclonal antibody and was created at Cambridge in the late 1970s, and has long been used to treat leukaemia by killing off the cancerous white cells of the immune system.
The Cambridge researchers conducted the clinical study over a three year period involving 334 patients with relapsing-remitting MS which had not as yet been treated.
The researchers found that the drug reduced the number of attacks of the disease by 74% which is more than the reduction achieved by conventional interferon-beta therapy and Alemtuzumab also reduced the risk of sustained accumulation of disability by 71% compared to beta-interferon.
It was also found that some who received the drug also recovered some functions that had been thought of as permanently lost, and as a result were less disabled after three years than at the beginning of the study, whereas people given interferon-beta showed signs of their disability becoming progressively worse.
These effects were confirmed by brain scans in which Alemtuzumab patients showed signs that their brains had actually increased in size, while the beta-interferon patients' brains shrank over time.
The researchers suggest that Alemtuzumab may allow damaged brain tissue to repair itself but they say more work is needed to confirm the effects before the drug can be considered for widespread use.
Lead researcher Professor of Neurology Alastair Compston says Alemtuzumab is the most promising experimental drug for the treatment of multiple sclerosis, and it is hoped that phase 3 trials will confirm that it can both stabilise and allow some recovery of what had previously been assumed to be irreversible disabilities.