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New Data on Natalizumab (Tysabri) in Multiple Sclerosis

Relapses less likely than with IFN and glatiramer acetate (Mar. 18)

Results have been announced from several studies of natalizumab (Tysabri, Biogen Idec/Elan Corporation) in patients with multiple sclerosis (MS). The new data will be presented at the 65th Annual Meeting of the American Academy of Neurology (AAN) in San Diego, California.

In a statistical analysis, natalizumab demonstrated a significantly lower rate of first relapse compared with interferon-beta (IFN-beta) and glatiramer acetate (GA). This analysis was conducted using data from two MS patient registries. The results indicated that relapses were more likely to occur, and to occur more quickly, in patients taking IFN-beta or GA compared with those taking natalizumab (hazard ratio: 2.73; P < 0.001).

To help physicians better identify the most appropriate patients for treatment with natalizumab, a risk-stratification approach (developed by the drug’s manufacturers) assesses each patient’s personal benefit-risk profile based on several factors, including anti-John Cunningham virus (JCV) antibody status, which was added to the U.S. label for natalizumab in 2012.

An analysis of data from the STRATIFY-1 trial — a longitudinal, observational U.S. study of natalizumab-treated patients — showed that anti-JCV antibody status remained consistent in 90% of the study population when tested every 6 months over an 18-month period. Approximately 38% of patients tested consistently negative, and 52% tested consistently positive.

Results from ongoing research into progressive multifocal leukoencephalopathy (PML), an infrequent but serious brain infection, suggest that natalizumab-treated patients who develop PML and are asymptomatic at the time of diagnosis may have improved survival and less functional disability compared with patients who are diagnosed when symptomatic.

This analysis included preliminary data from 4 years of case reports and evaluated outcomes in 319 natalizumab-treated patients who developed PML. Twenty-one of these patients (6.5%) had no clinical symptoms of PML but were diagnosed based on magnetic resonance imaging (MRI) findings that were consistent with PML and on spinal fluid that was positive for the presence of JCV.

The results showed that the survival rate following PML was 100% in the patients without symptoms at diagnosis compared with 77% in patients with symptoms at diagnosis. Functional outcomes and disability were also better in the asymptomatic group 1 year after the diagnosis of PML. The average score on the Karnofsky Performance Scale, which measures functional outcomes, was 70 for asymptomatic patients (meaning that the person could care for him/herself) compared with 47 for those with symptoms at diagnosis (meaning that the person may have been disabled and required considerable assistance and frequent medical care; P = 0.021). In addition, scores on the Expanded Disability Status Scale were numerically better for asymptomatic patients (3.7 vs. 6.5, respectively; P = 0.066).

Tysabri (natalizumab) is approved in the U.S. as monotherapy for relapsing forms of MS, generally for patients who have had an inadequate response to, or are unable to tolerate, an alternative MS therapy.

Source: Biogen Idec; March 18, 2013.

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