Some MS doctors are starting to stop advising patients to start Tysabri that test positive for the JC virus. And some doctors are advising patients that have been on the drug more than two years to stop. If Biogen is in trouble with Tysabri again, then this stock will fall below all time lows real quick
That's true, and that has been true. Nothing new here. The only thing that's different is that some patients who were JC+ were rolling the dice and taking Tysabri despite the risks, because it's just so effective. Now, they have an alternative (Tecfidera) that is slightly less effective, but has a superior safety profile. Anyone going off of Tysabri are likely going to Tecfidera, so it's a wash. For those who test negative for the JC virus, Tysabri is still an option, and new patients are still trickling in.
I am sorry to disagree with you, but 50% of patients on tysabri have tested positive for the JC virus. A new label came out in 2012, that states your risks of getting PML increases if you have been on Tysabri more that 2 years and there is no data available for patients that have been on the drug longer than 2 years.
That is the whole point of the JC antibody test, to find out who has it and to move them to a different treatment. What you are describing isn't trouble with Tysabri, it's the success of the testing program.