WebMD reports on an experimental multiple sclerosis drug that proved to be much more effective for the treatment of early MS than a widely used treatment in a study - but the efficacy came at a price.

Patients with early relapsing-remitting MS treated with the drug alemtuzumab had far fewer relapses and evidence of MS progression than patients treated with the approved treatment, interferon beta-1a.

Some patients who got the experimental drug had less disability associated with their disease three years after starting the study than at entry, raising hopes that the treatment might stop the disease in its tracks before it progresses to its crippling stage.

But nearly one in four alemtuzumab-treated patients also developed treatment-related thyroid complications.

Even more troubling, 3% of the patients developed a potentially life-threatening autoimmune condition, which resulted in the death of one patient.

Study co-author Alasdair Coles, PhD, tells WebMD that phase III trials will soon be under way to determine if the benefits of alemtuzumab outweigh the risks in patients with early relapsing-remitting multiple sclerosis.

According to the National MS Society, relapsing-remitting MS accounts for 85% of people who are first diagnosed with MS.

The study appears in the Oct. 23 issue of TheNew England Journal of Medicine.

"The phase II results are very exciting, but this is not ready for routine use," he says. "We need to know more about the long-term effectiveness and adverse effects. That is our challenge over the next few years."

Once-a-Year Treatment

Developed by Cambridge University researchers several decades ago, alemtuzumab was the first monoclonal antibody made for use in humans, and it is approved for the treatment of chronic lymphocytic leukemia (CLL).

It works by targeting and destroying certain immune cells, which normally protect against infection but are believed to be damaged in MS and other autoimmune diseases, resulting in the destruction of healthy tissue.

Cambridge researchers first tried the drug in patients with advanced multiple sclerosis, with little success.

The newly reported phase II trial included only patients with early, relapsing-remitting multiple sclerosis who had not been treated with other MS drugs.

Between December 2002 and July 2004, 334 patients in Europe and the United States were enrolled in the study.

About a third of the patients were treated with the first-line therapy interferon beta-1a, given by injection three times a week. The remaining patients were treated with alemtuzumab, given by infusion in once-a-year cycles.

The initial cycle involved four-hour infusions given daily for five days. Twelve months later, most patients got a second, three-day course of the drug.

Response 'Unprecedented'

Three years after the trial was initiated, treatment with the experimental drug was associated with dramatic reductions in clinical relapses and a reduction in inflammatory activity (as seen on brain MRI scans) compared to the interferon treatment.

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