He says the U.S. Food and Drug Administration will use this as their justification for returning Tysabri to the market as a monotherapy with a big "black box" warning about the risk of PML on the label.

FORBES: Loving Elan's Latest Comeback

Bextra causes Stevens-Johnson Syndrome more often than Celebrex, a similar Pfizer pain drug, and Pfizer has been in discussions with the Food and Drug Administration about how to include the risk in the drug's label.

FORBES: Pfizer Says FDA Warning Likely For Bextra

The FDA initially declined to approve it, asking in March 2010 for more information about the drug's prescribing label and the companies' risk-management plan to ensure the drug's benefits outweigh its risks.

WSJ: FDA Approves Amylin's Bydureon Diabetes Drug After Delays