This list of pharmaceutical compound number prefixes provides codes used by individual pharmaceutical companies when naming their pharmaceutical drug candidates. Pharmaceutical companies generally produce large numbers of compounds in the research phase for which it is impractical to use often long and cumbersome systematic chemical names, and for which the effort to generate nonproprietary names may not be warranted, see article on drug nomenclature. Instead, these compounds are usually given a number for internal reference at the company. To distinguish the numbered compounds from different companies (or academic laboratories), each compound number is prefixed with a letter code indicating the company that developed the compound, that claims intellectual property on that compound etc. Th