How could they keep a marketed, patented drug from being used in another indication?
Drug/biotech companies almost never sue doctors for off-label use of a competing marketed product that technically infringes on a "use" patent. Hence, the only realistic chance to thwart such use is pushback from third-party payers.
ODE doesn't help with this problem insofar as it merely bars FDA approval of a generic version of the orphan drug.
“The efficient-market hypothesis may be the foremost piece of B.S. ever promulgated in any area of human knowledge!”