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   DIR Return to: TYSABRI (natalizumab)
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       #Post#: 1684--------------------------------------------------
       (AAN abst.) Tysabri therapy associated w/greater variability in 
       JC virus antibody levels
       By: agate Date: May 16, 2017, 4:13 pm
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       Presented at the annual AAN meeting in Boston, April 2017:
       [quote]Natalizumab therapy is associated with greater
       variability in JC Virus Antibody levels
       John Peters1, Eric Williamson1
       1
       Department of Neurology, University of Pennsylvania Perelman
       School of Medicine
       Objective:
       To examine the variability of serial JC Virus (JCV) index
       measurements in patients with multiple sclerosis (MS) on
       natalizumab and other disease-modifying therapies (DMTs) in
       hopes of better understanding how to use this test in assessing
       risk for progressive multifocal leukoencephalopathy (PML). We
       aimed to quantify this variability over time and explore how it
       is impacted by various factors including age, gender, DMT, and
       timing of natalizumab infusions.
       Background:
       Positive antibody titers against JC Virus are one of several
       identified risk factors for PML for patients with multiple
       sclerosis being treated with natalizumab. Positive titers are
       also hypothesized to be helpful in assessing risk with other
       DMTs. Clinicians and patients use titer values to help decide
       whether to start, continue, or stop treatments, so assessing how
       indices vary over time for patients on DMTs may allow a
       patient’s risk of PML to be better interpreted.
       Design/Methods:
       A retrospective analysis was conducted using medical records of
       MS patients with multiple JCV antibody index measurements
       exposed to therapy with natalizumab (N=171) or not (N=101).
       Variability was quantified by calculating the variance of
       multiple index values for each patient.
       Results:
       Variability of JCV antibody indices was found to be
       significantly higher for patients on natalizumab (p<0.05). For
       patients on natalizumab, infusion less than 14 days before JCV
       antibody testing was found to be associated with significantly
       higher antibody values (p<0.05).
       Conclusions:
       JCV antibody levels vary over time and therapy with natalizumab
       is associated with greater variability. One potential
       contributing factor may be the timing of natalizumab infusion
       relative to antibody testing. These results suggest that therapy
       with natalizumab may influence the test being used to assess the
       risk of treatment with it. [/quote]
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