Maybe we need a charity that builds a research war chest to threaten companies like this with redevelopment. It costs a lot to replicate a pill and go through the FDA hoops, and once a private company does, the price just gets competed down to the point where it doesn't cover sunk the redevelopment costs--so in some scenarios no one bothers.
Instead, a charity doesn't have to take profit into consideration and can just threaten: drop your price or we'll persue independent redevelopment. With only the credible threat of spending on independent redevelopment, they could devalue a lot of these orphan drugs, and then buy up the rights/trade secrets to them for open release.
Competing businesses can't do this, because they can't pose a credible threat, because following through wouldn't make business sense. A charity can have non-business aims.