Natalizumab January 2012 PML Update

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Another way of looking at the risk is to inverse the figures; for example 10.6/1000 = 1 person in 94, who is JCV seropositive, has received previous immunosuppression, and has had 25 to 48 infusions of natalizumab, will develop PML. 


Source: Biogen-Idec


CoI: Multiple

About the author

Prof G

Professor of Neurology, Barts & The London. MS & Preventive Neurology thinker, blogger, runner, vegetable gardener, husband, father, cook and wine & food lover.

7 comments

  • Then the big question is: ceteris paribus (i) all other factors, (ii) other options (iii) the patient's disease progression to date and prognosis ans (iv) the patient's risk tolerance – would Prof G advise patient in the higher risk bracket (1/94) to stay on the drug or not?

    COI: the above does not apply to me. Just interested how Prof G would address such difficult decision making.

  • Is there any explanation for why PML risk is low in the first year or two? What changes and makes the risk go up later?
    Could it be happenstance that there haven't been more PML cases in the first two years?

  • Re: "Then the big question is: ceteris paribus (i) all other factors, (ii) other options (iii) the patient's disease progression to date and prognosis ans (iv) the patient's risk tolerance – would Prof G advise patient in the higher risk bracket (1/94) to stay on the drug or not?"

    This is not really my call; some MS'ers with severe disease who have failed other DMTs may take this risk. What I do in this situation is providing MS'ers with other options; for example I would be prepared to write to their PCT (funders) and seek permission to put them on Fingolimod despite it not been given the green-light by NICE or I may write to offer them Rituximab off-license making the case based on the published results. I have already done the former and have used the latter option for someone who had an allergic infusion reaction to Natalizumab.

    At the end of the day our jobs are to provide the options, but access to these options often lies with the funders.

    Have I answered your question?

  • Re: "Is there any explanation for why PML risk is low in the first year or two? What changes and makes the risk go up later?"

    The process that leads to the development of PML is not understood. What we do know is that the JC virus has to undergo several changes that affects its biology. It acquires several mutations in its coat protein that allows it to infect glial cells (cells in the brain) and it also acquires duplication in the regulatory region of its genome. All these mutations and changes presumably take time to occur. This is why it takes time to develop PML and why Natalizumab is safe for 12-18 months.

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