A novel compound that has not previously been approved for use in humans.

NCE (or new drug substance in the EU) is a formal definition used by regulatory authorities, designed to give protection to the developers of new drugs during clinical evaluation phases of drug development.

More informally, NCE is used to describe a newly developed drug compound, as opposed to the re-use of an existing drug for a different disease, re-formulation of an existing drug, or a novel combination of existing drugs.

Development of new antibiotic treatments depends both on the discovery and development of NCEs.