Natalizumab Benefits MS Patients in "Real-World" Clinical Setting

Emma Hitt, PhD

June 08, 2009

June 8, 2009 (Atlanta, Georgia) — In a "real-world" clinical setting, natalizumab (Tysabri, Biogen Idec/Élan) demonstrates a high response rate in patients with previously treated multiple sclerosis (MS), improving or stabilizing the clinical course of MS in the majority of cases, with a low incidence of antibody development, new findings suggest.

Annette Wundes, MD, assistant professor at the Multiple Sclerosis Clinic at the University of Washington, in Seattle, presented the findings here at the Consortium of Multiple Sclerosis Centers (CMSC) 23rd Annual Meeting in a poster session.

"Our clinical experience has been quite positive overall," Dr. Wundes told Medscape Neurology. "The vast majority of patients — patients who were placed on natalizumab either due to insufficient stabilization by or intolerance to previous treatments — were pleasingly stabilized, and there has been even a portion of patients who demonstrated clinical improvement," she added.

Patients also showed marked stabilization of magnetic resonance imaging (MRI) findings, and overall the tolerability has been very good, Dr. Wundes noted. "This is a very encouraging clinical experience," she concluded.

Clinical Setting

Natalizumab is being evaluated in large-scale clinical trials, but the current analysis evaluated the use of this agent in a clinical-practice setting. A total of 153 patients who received up to 34 monthly doses of natalizumab were included in the analysis.

Patients had previously been treated for MS and had a mean age of 45.3 years; 73% were female and had received a mean of 16 (range, 2 – 34) infusions of natalizumab.

Of the patients receiving natalizumab, 75% achieved disease stabilization, 21% improved, and 4% had worsening disease. With respect to MRI response, only 2 of 95 patients with ongoing treatment had a single new or enlarged lesion on repeat MRI.

The most common reason for discontinuation was disease progression (n = 8). Other reasons included hypersensitivity reaction (n =7), patient request (n = 7), and adverse effects (n = 3).

Of the 153 patients, 8 developed antibodies; 3 of these had no prior natalizumab exposure. Of the 8 patients who developed antibodies, 6 had an allergic reaction, 2 discontinued treatment, and 2 had treatment failure.

"Our data do not provide a rationale for routine antibody testing unless patients develop hypersensitivity or disease progression upon reexposure after short-term natalizumab use," the authors note.

Natalizumab caused a modest increase in circulating lymphocytes noted at 1 month that was sustained thereafter. In addition, there was a modest but statistically significant decline in the ratio of CD4/CD8 at 1 year. According to the researchers, the clinical relevance of changes in the T-cell subset remains unclear.

Well-Tolerated and Effective

"I think these findings represent what we see in general clinical practice and certainly mirror what was reported in large-scale clinical trials," said Mariko Kita, MD, a specialist in MS at the Virginia Mason Medical Center, in Seattle, Washington. "Natalizumab is exceptionally well-tolerated and is effective in the vast majority of our patients," she added. According to Dr. Kita, it is not at all surprising that no cases of progressive multifocal leukoencephalopathy (PML) were reported in this series, a complication that has been a concern with this treatment.

"The true incidence of PML cannot be accurately predicted at this point, but given the relatively small numbers of patients followed under this author's care, one would not necessarily anticipate encountering PML," she noted.

The study was funded by noncommercial sources. Dr. Wundes and Dr. Kita report no relevant financial conflicts.

The Consortium of Multiple Sclerosis Centers (CMSC) 23rd Annual Meeting and 2nd joint meeting of the American Committee for Treatment and Research in MS (ACTRIMS): Abstract S11 . Presented May 29, 2009.


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