orphan drug
n.— «Some of the most successful blockbuster drugs in the world treat diseases that most people have never heard of. They’re called orphan drugs, and the government doles out big tax breaks to companies that deliver them. Even without the tax incentives, plenty of biotechs have found ways to profit big off drugs for rare diseases.» —“Cashing in on ‘orphans’” by Aaron Smith CNN Mar. 13, 2007. (source: Double-Tongued Dictionary)