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Multifocal leukoencephalopathy linked to natalizumab for MS.

Two new cases of progressive multifocal leukoencephalopathy have been reported in patients treated with natalizumab for multiple sclerosis, which are "notable for being the first cases occurring in the absence of concomitant or recent immunomodulatory therapy," according to an alert from the Food and Drug Administration.

The two cases, reported in Europe, also are the first cases reported in association with natalizumab since the monoclonal antibody was reintroduced in June 2006 for patients with relapsing forms of MS, after being taken off the market in February 2005. Neither was fatal. Both patients had been on natalizumab monotherapy for more than 1 year at the time that progressive multifocal leukoencephalopathy (PML) was diagnosed, although one had been treated in the past with azathioprine and [beta]-interferons, according to the FDA.

The manufacturers voluntarily withdrew natalizumab from the market after three patients in clinical trials of natalizumab developed PML; the two patients with MS also were taking interferon [beta]-1a (Avonex) and a patient with Crohn's disease had recently been treated with immunosuppressive treatments. Natalizumab was made available again in June 2006, only as monotherapy for patients with relapsing forms of MS, with a mandatory risk minimization plan in place. It was then approved by the FDA in January 2008 for patients with moderate to severely active Crohn's disease.

No new cases of PML--a rare, usually fatal demyelinating CNS infection, caused by the activation of the JC virus, a human polyomavirus--have been reported in the United States, the FDA said.

One of the two European cases described by the FDA alert was a patient with aggressive MS and high levels of relapses and MRI activity, who had been treated with natalizumab for 17 months. During treatment, this patient had developed muscle twitching, weakness of the left upper extremity, and brain MRI changes; these symptoms led to the diagnosis of PML, based on the MRI changes and detection of JC viral DNA in the cerebrospinal fluid, based on a report made to the manufacturer on July 31, 2008, the FDA alert said.

At the time that the second case was reported, the patient, who had been treated with natalizumab for 14 months, was hospitalized in stable condition, according to the FDA. This patient had a long history of treatment with azathioprine, [beta]-interferons and other disease-modifying therapies, and had developed symptoms that included hemiparesis and cognitive symptoms. This patient was diagnosed with PML after atypical lesions were identified on a brain MRI and JC viral DNA was detected in the CSE

The full alert is available at www.fda.gov /med watch/safety/2008/ safety08.htm# Tysabri2.

BY ELIZABETH MECHCATIE

Senior Writer

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Title Annotation:Clinical Rounds
Author:Mechcatie, Elizabeth
Publication:Family Practice News
Date:Sep 15, 2008
Words:439
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