In a morning interview on CNBC, Biogen CEO James Mullen said Elan and Biogen hoped a safety review would conclude Tysabri could be prescribed to certain patients, especially if they are monitored. He also reiterated that the safety review of Tysabri would be concluded by late summer and that company officials would be meeting with regulators over the coming months.
We applaud this rational, cautiously optimistic line of thinking. While we all know Tysabri is effective and relatively convenient, obviously the PML risk must be identified. Given that all dosing is currently suspended, one wonders how the companies are going to definitively quantify/classify this risk since all data is necessarily historical. In some sense, one must deliver the drug to test hypotheses.
A logical approach to this quandary might be to identify a sub-class of patients that would not be likely to develop PML-- e.g., non-immunosuppressed individuals. Combine that with vigilant monitoring-- which is going to be a very difficult task given that many MS symptoms likely mimic early PML symptoms-- and you have a tenable situation given that PML is not invariably fatal when it is caught early in individuals that are artifically immuno-suppressed.
Now after a few years of proceeding in this manner of active dosing under close supervision, it will be abundantly apparent what the risk factors for PML are and the drug can or cannot be opened up to mass adoption.
This is our speculation only. Your opinions are just as important. Share them in the forums!
