-
distribution rights.
That's to the brand Daraprim, not the drug Pyrimethamine.
Drug - Ibuprofen, brands - Advil, Motrin, and Nurofen. Anyone can make Ibuprofen, only the brand holders can sell it as Advil, Motrin, Nurofen etc.
EDIT;
I should have read your links....
The FDA grants market exclusivity to companies that are willing to take “grandfathered” compounds into compliance with their current regulatory framework,
BING
I think, and this is from 5 minutes of google fu and memory, that when they bought the company they bought the distribution rights. Which makes it difficult for other companies to get the drug to reverse engineer or something.
This guy says it better
http://blogs.sciencemag.org/pipeline/archives/2015/09/21/martin-shkreli-has-one-idea-and-its-a-bad-one#page-top
http://blogs.sciencemag.org/pipeline/archives/2014/09/12/thiola_retrophin_martin_shkrell_reddit_and_more