1. The word “drug” refers to both small molecules, biologics, and macromolecules. Please see Tables 1–2 for both US and EU definition of molecules.
2. A non-rare disease or condition occurring in >200,000 persons may also be designated as an orphan drug if an orphan subset of the patient population can be justified based upon drug toxicity, mechanism of action, or previous clinical experience with the drug.
3. A sponsor may request an orphan-drug designation of an already approved drug for an unapproved use.
4. Food and Drug Administration, Orphan Drug Designation Request Form, OMB Control Number 0910–0167.
5. Food and Drug Administration, Recommended Tips for Creating an Orphan Drug Designation Application. https://www.fda.gov/media/111762/download