Scientists found some evidence to suggest that simvastatin may help fight MS a decade ago, but further small-scale trials did not back up the findings.
Now, a larger study says there are encouraging signs that the cholesterol-reducing drug can slow the development of MS when the disease reaches a chronic, crippling phase.
MS is a progressive disease of the brain and central nervous system in which the immune system attacks a fatty insulative sheath around nerve fibres.
The symptoms range from numbness and tingling to muscle weakness and spasms, cramps, nausea, depression and memory loss.
About 10 to 15 years after diagnosis, the disease usually becomes chronic and patients start to suffer more severe symptoms. The brain loses tissue, shrinking at a rate of about 0.6 percent of its volume per year.
The new trial gave 140 chronic MS sufferers aged 18 to 65 either a daily dose of 80 milligrams of simvastatin, or a dummy lookalike pill called a placebo, over the course of two years.
The brains of patients who took simvastatin shrank at a rate of 0.3 percent a year, 43 percent less than their "placebo" counterparts, 3-D scans showed.
There were also small but significant improvements in disabilities caused by the disease, according to reports by patients and their doctors.
Patients who took simvastatin also reported a similar number of side effects as those who were given the harmless placebo pill.
The trial was a Phase 2 test in the three-stage process to assess whether new drugs are, firstly, safe and, secondly, effective.
"Caution should be taken regarding over-interpretation of our brain imaging findings, because these might not necessarily translate into clinical benefit," said lead researcher Jeremy Chataway of Britain's National Hospital for Neurology and Neurosurgery.
"However, our promising results warrant further investigation in larger Phase 3 disability-driven trials."
Simvastatin, a type of statin anti-cholesterol treatment, is a standard, low-cost drug designed to impede the buildup of fatty deposits in the blood vessels -- a major risk for cardiovascular health.