orphan disease

https://doi.org/10.1351/goldbook.12698
Disease for which drug research, development, and marketing is economically unfavourable.
Notes:
  1. The poor commercial environment could be due to a lack of economic incentives or a lack of understanding of the diseases or a combination of both.
  2. Sometimes the term "rare disease" is used synonymously with orphan disease, although there is a slight difference. For example, a rare disease is so uncommon that there is no drug development effort.
  3. Which diseases are classified as orphan depends strongly on the country that classifies it. In the United States, for example, any disease affecting less than \(\pu{200000}\) people is considered an orphan or rare disease. Europe and countries such as Japan, Australia, and Singapore have a different definition.
Source:
PAC, 2013, 85, 1725. (Glossary of terms used in medicinal chemistry. Part II (IUPAC Recommendations 2013)) on page 1744 [Terms] [Paper]