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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
   DIR 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.
       --- End Quote ---
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