FINALLY, they clarified the CURRENT interpretation of numbers, publically & in writing.

In their 2008 4th Quarter presentation, filed today by way of a 8-K form, here is their breakdown:



http://www.sec.gov/Archives/edgar/da...1biexv99w1.htm

So, the new total of 10,700 (for those who have been on 18+ months now), does not include people from the trials PRE-Nov, 2004. If I remember correctly, Tysabri was brought back (fast-tracked) onto the market about that time, and in about Mar/05 was pulled because of the 3 cases of PML that were discovered. (I would presume that those 3 cases were part of the 4700 trial patients from pre-Nov/04 though . . . even though the ratio of 1:1000 was based on 3:3000 (not 4700) trial participants ...).

Either way, this would seem to indicate the current ratio for PML is 7:18,200 (10,700 + 4300 + 1800 +1400), or 1:2600 . . . bearing in mind we don't know how many are potentially being confirmed for PML at the moment. Additionally, per their 3rd quarter Q&A response, we will likely never know how many "suspected" (unable to "confirm" & just taken off ) cases there have been along the way . . .

"Operator:
Your next question from the line of Jim Birchenough with Barclays Capital.

Jim Birchenough - Barclays Capital:
Yes, hi guys. Just following up on TYSABRI trends. I'm just wondering since the two reported cases in Europe, have you've seen any uptick in trends for suspected cases, whether any patients have been plasmapherese in the U.S. and just whether plasmapheresis itself increases the risk for immune re-constitution syndrome? Thanks.

Unidentified Company Representative:
Well we're not going to comment on suspected cases. To remind you that our clinical vigilance and risk management plan requires people to be highly vigilant for TYSABRI and if they cannot exclude PML, they are meant to stop TYSABRI.

So, we expect a lot of people to be stopping TYSABRI if they can't rule out PML. And we like to see that that happens... And in terms of plasma exchange, as Cecil noted, it is in the label whether or not it increases IRIS. We've known for a long time that immune re-constitution increases IRIS. Its called the immune re-constitution inflammatory syndrome. And so, I don't think it's too surprising that plasma exchange may increase IRIS."

http://seekingalpha.com/article/1008...age=-1&qa=true

Since there are NOW only 4300 who have been on 24+ months (since the trials), but 6300 were stated to have been on 12+ months in their Dec /07 numbers (that you had linked, Chris), either they must have included the trial participants back then, OR there has been a HUGE drop-out of longer-term users since then . . .

Perhaps we'll never know . . . but at least going forward we can calculate a semi-relevant risk (and it is NOT 4:37,600, 4:48,300, OR 1:1000, for now).

Cherie