Natalizumab PML safety update Feb 2012: 207 cases of PML

IS – previous immunosuppression

As of February 1, 2012, 51 natalizumab-treated MS’ers with PML had samples tested for anti-JCV antibodies that were collected at least 6 months prior to PML diagnosis (range 6-187 months), and all 51 patients tested anti-JCV antibody positive at all time points where samples were available for testing.

This data has been kindly provided by Biogen-Idec.

“Good and bad news! Bad news is that there have been 207 cases and the risk is in certain groups of MS’ers on Natalizumab is very high; for example JCV+, IS+ and >24 month of exposure the risk of PML is 1 in 94. On the other hand if you are JCV- then the risk is less than 1 in 10,000. Is the former risk too high? That depends on the individual, how bad their MS is or was prior to going onto Natalizumab and whether or not their are suitable alternative options to switch their treatment. Some people accuse me for sitting on the fence in relation to this. However, I have to practice what I preach. If you want to empower MS’ers you need to give them the information in a form they understand and let them make their own choices. If they ask of help then you can make the choice of them. Would you agree with this approach?”

“Are these graphs and tables in a form you can digest, i.e. do you understand the risks of PML from looking at this data? If not could you let us know how you want the data presented. Thanks”

4 thoughts on “Natalizumab PML safety update Feb 2012: 207 cases of PML”

  1. Re: "I find curious the descending slope after 30 infusions. I wonder what accounts for that."It may be simply that there are too few patients in those epochs to get reliable data. The more likely explain is that the risk is decreasing due to MS'ers who have developed PML earlier are not in that group and the fact that MS'ers at high-risk are coming off Natalizumab; therefore this epochs are being enriched with MS'ers at lower risk. In my opinion, the latter is more likely to be the reason.

  2. How did you evaluate patients' serostatus? Is there a commercial kit useful to detect anti-JC antibodies in patients'serum? I'm very interested on it! Thank's!

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