My daughter has been on Tysabri for almost 4 1/2 years. At the end of year 2 she was put on "holiday" and after 3 months had what seemed to be a relapse but was in fact declared IRIS. She received steroids and was immediately put back on Tysabri. At the time, she was told that she could never come off Tysabri.
Fast forward 2 1/2 years. Her JC virus antibody values have tripled in the past nine months and are now at 1.3. This would suggest coming off Tysabri but what about the IRIS?
The risk of PML on Tysabri is related to duration of therapy over two years, JCV antibody index and whether or not a patient has received prior immunosupression. For my response I will assume your daughter has not been treated with an immunosuppressant in the past.
According to our current understanding of these risk factors (CLICK HERE to read my previous blog on Tysabri risk), your daughter’s current risk of PML is approximately 1 in 1,000 or 0.1%. This number is taken from the figure below showing the risk of PML after 2 years of Tysabri therapy according to various JCV index levels. We have no information at present to suggest that the manner in which JCV antibody index values vary over time affects the risk of PML. The risk stratification is based on current index value and current duration of therapy. I hope this helps with your decisions.
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