Risky business

While investors and analysts are investigating the risky business of pharmaceutical investments, patients, carepartners and their neurologists are also considering the risk of PML with the use of Biogen Idec's (BIIB) Tysabri (natalizumab).

As we have said in the past, the difficulty in accurately predicting the risk of PML, is that the numerator keeps changing (is it 13, 23 or ..?), while the denominator changes much more slowly.

There has been question about a "drug holiday," the problem is that we don't have any data to suggest that this would help (on the other hand, we don't know that it won't). Perhaps a drug holiday (coming off the medicine for a certain period of time) simply helps because the immune system reconstitutes and so there is less exposure time to the medication.

There may be an independent risk for activation of the JC virus (causing progressive multifocal leukoencephalopathy) each time it is given. This would mean that there is a risk month 1, 2, 3, 4 .... and that risk is no different in month 30 from month 13, except that there is a greater chance that PML will occur because there is a monthly (continuous) risk. If this is the case, a drug holiday, in itself, only reduces the PML risk because a person is on less of the Tysabri.

The real difficulty lies in the patient, carepartner and neurologist weighing the risks of treatment vs. the risk of the MS. Supposedly (and hopefully) a patient on Tysabri is on the medication because it is absolutely necessary for that individual, not simply because of a fear of needles (IV needles are a lot bigger than the intramuscular and subcutaneous needles used with the other disease modifying agents).

So what are the European Medicines Agency (EMEA) and the Food and Drug Administration (FDA) going to do?

If someone's Multiple Sclerosis is in need of a medication like Tysabri, then the risk of being off the medication may not outweigh the risk of being on it.

That is why everyone is an individual.

- Dr. Daniel Kantor, MD BSE
Medical Director
Neurologique

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