Uplyso getting 15% market share in US once approved is about reasonable estimate. The bigger opportunity will be overseas especially in developing countries like Brazil where PFE is trying very hard there. There are also patients whose onset symptoms are very mild, don't need to be on ERT yet. Cheaper drugs certainly can help getting them on ERT.
In my opinion, PFE's goal here isn't just revenue alone. PFE wanted to get experience in this ultra orphan indication. It is entirely different from what PFE was used to. Patients don't switch drug that easily because they have developed personal relationship with GENZ through the years, and have been on Cerezyme for a long time. Even though they have been frustrated with rationing during GENZ manufacture crisis, surprise to outsiders, most patients had expressed strong support for GENZ during the crisis. People who think GENZ is going to lose huge number of patients are wrong. Cerezyme annual run rate in 4Q2010 was almost $900m, not far from all time peak even though Shire's drug has been on the market for almost one year now.
For PLX, the largest opportunity will be from Israel where PLX kept the right to itself. Israel is the second largest Gaucher market in the world.