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Resources for Dose Extension on Tysabri

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    Resources for Dose Extension on Tysabri

    Hello Sara,

    First, a study about increased JCV conversion on Tysabri which is self-explanatory.

    IMO, it is logical to believe that those who are JCV- and go from 4 week dosing to extended dosing would convert to positive less frequently. Remember, the JC virus alone causes PML so if you donít have it you canít get PML unless you convert to positive. I would think any neuro would respond to a patientís concern about conversion and agree to dose extension.

    No, it is true, we donít have class 1 evidence that dose extension prevents conversion from negative to positive but I bet time and data will reflect that someday. I draw that inference from the first study listed. If more tysabri leads to more conversions, why wouldn't less Tysabri lead to less conversions?

    All of the remaining links are the same basic Ryerson study in different forms with clarifying comments. You may have to sign in to the ECTRIMS library but it is totally safe.

    Therapy with natalizumab is associated with high JCV seroconversion and rising JCV index values

    Here is Ryerson making her presentation and some links & comments you may find helpful regarding dose extension:


    This is a print article dated Oct. 7, 2015 which helps explain Ryersonís research:
    New Data Show Longer Natalizumab Dosing Interval in MS Is Feasible

    Sara, keep in mind that sufficient patient years to achieve statistical significance had not been achieved when the article was written in 2015 but have been since.

    You will find the following site and this post of March 9, 2018 helpful, Iím sure:
    Guest Post: Extending natalizumab dosing interval may reduce the risk of PML

    Same study presented with additional comments:
    Extending the Dose interval of natalizumab
    Last edited by KoKo; 08-10-2018, 10:32 AM. Reason: Myoak request

    Dear Moderators,

    Could you please edit the title of this thread to reflect correct spelling?

    Resources not resouces.

    Also, since all posts are read by moderators before they are posted, would you be so kind as to consider a policy of correcting glaring spelling errors? Especially in title posts. Everyone would appreciate it. It would save time and would be a courtesy much appreciated.

    Thank You!


      Hi Myoak - we have a policy to not spell check everyone's post. It would be too time consuming for all of us who moderate. If someone has a glaring spelling error and wants it changed, an email to would be most useful and we would be happy to help!
      1st sx '89 Dx '99 w/RRMS - SP since 2010
      Administrator Message Boards/Moderator


        Thanks Myoak - lots of interesting things to read here. I'll add to the thread if I find any more resources!


          I actually feel this information is important enough to become a "sticky".