That number for Tysabri is what Biogen tells us was the reduced "risk" for relapses/progression over placebo from their trials. Just recently, they quoted numbers from a two year study which showed a 37% reduced relapse/progression rate as compared to 7% for placebo, thus giving an approx 30% improvement. That put's it right in the CRAB category. While the cost for the drug is similar to the CRABs, the infusion charges on top of that make it by far the most expensive medication choice for MS patients.


Harry