Orphan drugs (ODs) are products developed for the diagnosis and/or treatment of rare diseases and conditions. Patients with this group of disorders have historically been denied access to medical therapy because prescription drug manufacturers could rarely make a profit from marketing such drugs. This changed in 1983, when the U.S. Congress passed the Orphan Drug Act, creating financial incentives for manufacturers. Since 2000 the EU has had a similar regulation, resulting in more than 20 ODs being granted marketing authorisation in the EU.