Under the ODA and EU legislation, many orphan drugs have been developed, including drugs to treat glioma, multiple myeloma, cystic fibrosis, phenylketonuria, snake venom poisoning, and idiopathic thrombocytopenic purpura.
The Pharmaceutical Executive opines, that the "ODA is nearly universally acknowledged to be a success".
Before the US Congress enacted the ODA in 1983, only 38 drugs were approved in the US specifically to treat orphan diseases. In the US, from January 1983 to June 2004, 249 orphan drugs received marketing authorization and 1,129 received different orphan drug designations, compared to fewer than ten such products in the decade prior to 1983. From 1983 until May 2010, the FDA approved 353 orphan drugs and granted orphan designations to 2,116 compounds. As of 2010, 200 of the roughly 7,000 officially designated orphan diseases have become treatable.
Critics have questioned whether orphan drug legislation was the real cause of this increase, claiming that many of the new drugs were for disorders which were already being researched anyway, and would have had drugs developed regardless of the legislation, and whether the ODA has truly stimulated the production of non-profitable drugs; the act also has been criticised for allowing some pharmaceutical companies to make a large profit off drugs which have a small market but sell for a high price.
While the European Medicines Agency grants orphan drugs market access in all member states, in practice, they only reach the market when a member state decides that its national health system will reimburse for the drug. For example, in 2008, 44 orphan drugs reached the market in the Netherlands, 35 in Belgium, and 28 in Sweden, while in 2007, 35 such drugs reached the market in France and 23 in Italy.
Though not technically an orphan disease, research and development into the treatment for AIDS has been heavily linked to the Orphan Drug Act. In the beginning of the AIDS epidemic the lack of treatment for the disease was often accredited to a believed lack of commercial base for a medication linked to HIV infection. This encouraged the FDA to use the Orphan Drug Act to help bolster research in this field, and by 1995 13 of the 19 drugs approved by the FDA to treat AIDS had received orphan drug designation, with 10 receiving marketing rights. These are in addition to the 70 designated orphan drugs designed to treat other HIV related illnesses.