A drug which was originally developed to treat leukaemia and other cancers of the immune system offers substantial improvements over existing treatments in reducing relapse rates for people with multiple sclerosis (MS), even when they have not responded well to first-line treatment, according to the results of two phase 3 trials published in The Lancet.

MS is thought to affect around 100 000 people in the UK, and around 400 000 people in the USA.  The causes of MS are not clear, but the disease occurs when the body’s immune system starts to attack the coating of nerve fibres, causing a range of symptoms affecting vision, movement, balance, sensation, bladder control and, eventually, memory and thinking. 

Around 85% of people diagnosed with MS start with a form known as "relapsing remitting" MS, where symptoms appear sporadically (a relapse), and then fade away, either partially or completely (remitting). 

Since there is currently no known cure for MS, existing drugs aim to reduce symptoms of the disease due to intermittent disease activity in the relapsing remitting phase, with effectiveness often measured by a reduction in the frequency of relapses.

Two teams of researchers, each led Professor Alastair Compston from the University of Cambridge, assessed the effectiveness of a monoclonal antibody called alemtuzumab, originally developed to treat leukaemia and other cancers of the immune system, which works by altering the number, proportions and functions of certain types of lymphocytes (white blood cells which play an essential role in the functioning of the immune system). 

In one trial (CARE MS I), researchers compared alemtuzumab to a drug called interferon beta 1a – the most common drug currently used to treat MS – in a group of 563 patients who had not yet undergone any treatment for MS.  Patients who received alemtuzumab were nearly half as likely to relapse within two years than those who received interferon, with 22% of patients who received alemtuzumab relapsing within two years, compared to 40% of the group who received interferon beta 1a.

In the other trial (CARE MS II, of 840 patients, of whom 628 were used for the principal analysis), researchers compared alemtuzumab to interferon beta 1a in patients who had already been treated with either interferon beta 1a or glatiramer (another drug currently used to control the symptoms of MS), but had gone on to experience at least one relapse since undergoing initial treatment.  They found that, even in this refractory group of patients, relapse rates were significantly lower in the alemtuzumab group, with 35% of patients who received alemtuzumab relapsing, compared to 51% of patients who received interferon beta 1a. 

In the CARE MS II trial, alemtuzumab also appeared to improve the outlook for patients in terms of MS-related disability (such as loss of coordination or the ability to walk), with 13% of patients in the alemtuzumab group judged, according to standardised tests, to have a sustained accumulation of disability, compared to 20% of patients in the interferon beta 1a group.  However, in the CARE MS I trial, there was no significant difference over the two years of the study between groups in terms of sustained accumulation of disability.

In both trials, researchers noted that alemtuzumab appears to increase the risk of certain autoimmune disorders, particularly those affecting the thyroid.  While these side-effects could potentially be serious, the authors note that they can be effectively treated, provided appropriate monitoring takes place. 

According to Professor Compston, principal investigator on both studies and Chair of the Steering Committee which oversaw these and earlier clinical trials, “Throughout its development as a potential therapy for MS, alemtuzumab has consistently shown superior efficacy against an active comparator.  These phase 3 results confirm the promise that alemtuzumab has shown in earlier studies carried out over the last 20 years, and offers the prospect of substantial improvement in quality of life and a better future for thousands of people with MS. As a clinical neurologist, it is helpful to have available a treatment that can potentially transform the future for young people with a potentially disabling disease.”

Dr Alasdair Coles, a clinician from the University of Cambridge and lead author of the CARE MS II paper, adds, “Currently, it is not clear how best to treat people with multiple sclerosis whose disease is still active on a first-line treatment.  Such patients are at increased risk of accumulating permanent disability, even in the short term.  This trial shows that, with appropriate monitoring to reduce the risk of potentially serious but nonetheless treatable adverse effects, alemtuzumab offers the prospect for effective therapy in patients whose MS is not controlled on first-line treatment.  Alemtuzumab is the only drug for multiple sclerosis that has been shown to prevent worsening of disability more effectively than interferon beta 1a in a phase 3 trial.”

A Lancet Editorial published to accompany the Articles states that the results of these trials are “encouraging”, adding that, “Alemtuzumab is licensed to treat leukaemia, and has been used off-label in patients with multiple sclerosis for many years. These trials have been keenly awaited by clinicians and patients wishing to establish evidence for this practice…However, there is concern that with a licence for multiple sclerosis, the cost of alemtuzumab could rise and might become too expensive for many patients (and health systems).”

The Editorial concludes that, “Multiple sclerosis runs a chronic and progressive course, eventually disabling many patients. More effective, affordable, evidence-based treatments with long-term benefits are desperately needed. Finding promising treatments such as alemtuzumab is important. But so is keeping alemtuzumab accessible and affordable if its early success in these trials proves to be of enduring value.”

Source: The Lancet