EMA: Reflection paper on considerations given to designation of a single stereo isomeric form (enantiomer), a complex, a derivative, or a different salt or ester as new active substance in relation to the relevant reference active substance

The scope of this paper is restricted to consideration of differences between a single enantiomer, a complex, a derivative or a different salt or ester and the corresponding reference active substance. The questions being addressed are “when should such an active substance be regarded as a new active substance (NAS) in relation to the relevant reference active substance and what level of evidence would be required to confirm the designation as a new active substance”?