Scientists in Canada described as “very exciting” the results from a trial of 24 patients who have a highly active, relapsing form of the autoimmune disease.
However, they warned that the procedure was risky, and only likely to benefit a proportion of patients in early stages of the illness.
MS occurs when the immune system strips nerve fibres in the brain and spinal cord of myelin, a fatty, insulating material without which nerve signals cannot be transmitted properly.
Symptoms range from blurred vision or tingling sensations to paralysis. Usually, the disease becomes more aggressive over time, but some patients’ health deteriorates rapidly.
Doctors testing the therapy, known as IAHSCT (immunoablation and autologous hematopoietic stem cell transplantation), took stem cells from patients’ bone marrow and froze them before injecting powerful chemotherapy drugs to destroy the immune system.
The stem cells were then transplanted back into the body to generate a new immune system with no ‘memory’ of attacking the brain.
Results over a period of up to 13 years were dramatic, with not one patient relapsing and 70% experiencing a complete halt in disease progression.
In 40% of cases, patients saw lasting reversal of symptoms, such as vision loss, muscle weakness and balance problems, the scientists reported in The Lancet medical journal.
Some participants were able to return to work or school, drive again, or get married and have children.
Harold Atkins, from the University of Ottawa, in Canada, said: “Our trial is the first to show the complete, long-term suppression of all inflammatory activity in people with MS.
“This is very exciting. However, it is important to note that this therapy can have serious side-effects and risks, and would only be appropriate for a small proportion of people with very active MS.
“People with MS who have had significant disability for a long time would likely not benefit.”
A similar procedure has been used for decades to treat patients with life-threatening leukaemia.
They face similar risks from the severe side-effects of the drugs, and the threat of infection, while unprotected by an immune system.
One participant in the study died of liver failure, due to the treatment, and another required intensive care for liver complications. All the patients developed fevers that were frequently associated with infections.
Trial volunteer Jennifer Molson, who was diagnosed with MS in 1996, at the age of 21, and who received the treatment in 2002, said: “Before my transplant, I was unable to talk or work and was living in assisted care.
“Now, I am able to walk independently, live in my own home and work full-time. I was also able to get married, walk down the aisle with my dad, and dance with my husband. I’ve even gone downhill skiing.
“Thanks to this research, I have been given a second chance at life.”
The trial, which cost €4.5m, was funded by the MS Society of Canada, whose chief executive, Yves Savoie, said: “What started as a bold idea has translated into a treatment option for people living with highly active, relapsing MS.”