Interim results from an international trial of a stem cell transplant treatment showed a much higher success rate than the control group, which received a drug treatment. MS is a disease that affects the brain, spinal cord, and immune system, leading to a number of disabilities. The stem cell treatment uses chemotherapy to wipe out a patient’s immune system and then “re-boots” it using stem cells from the patient’s blood and bone marrow that are unaffected by the disease.

Just over 100 people participated in the study in four cities: in Chicago, Sao Paolo, Sheffield (U.K.), and Uppsala in Sweden. They all had relapsing remitting MS, where periods of symptomatic “relapses” alternate with periods of remission. A year after the treatment, only one patient who received the stem cell treatment had relapsed, compared to 39 people in the control group.

In a follow-up an average of three years after treatment, the stem cells had failed in 6% (3 of 52) of recipients while the drug treatment had failed in 60% (30 of 50). The results were released at the annual meeting of the European Society for Bone and Marrow Transplantation in Lisbon.

A neurologist at Royal Hallamshire Hospital in the U.K. told the BBC this was the best result he had seen “in any trial for multiple sclerosis,” though he included the caveat that the results were only preliminary.

This study is the largest of its kind, and it bolsters results from smaller trials that have also showed stem cell transplant to be effective. The treatment has been controversial in the neurological community because it has proved more dangerous than drug treatments in the past. In an earlier trial, eight of 281 participants died.