The multiple sclerosis study published in the journal The Lancet found that alemtuzumab significantly reduced the number of attacks or relapses by people with MS.
This result was seen both in patients who had not previously received any treatment and those who have continued to show disease activity while taking an existing treatment for MS.
In one trial with patients who had recently relapsed, new episodes were reduced by 49% more than that achieved by the current standard treatment.
Over a two-year period, 65% of patients on alemtuzumab compared with 47% of patients on interferon did not relapse.
A drug which is said to "reboot" the immune system has been shown to be an effective treatment for multiple sclerosis (MS), a study has found.
The results of the trials were so encouraging in reducing the number of attacks in those affected that the MS Society is campaigning for the drug to become available on the NHS.
The research showed that alemtuzumab significantly reduced the number of attacks or relapses by people with MS compared to the current drug interferon beta-1a which is known commercially as Rebif.