Nice article so the FDA is basically saying partner with Momenta or do more trials . It seems substitutability is unlikely in near term horizon.
I know it may be a bit simplistic but I know Replagal and Fabrazyme have had switches and I suspect with Genzyme's manufacturing problems a fair number of Gaucher patients switched too. So it doesn't seem unprecedented to me for the big concern mentioned in the article about being able to go back and forth from the innovator to a generic.