EMA: Concept paper on the need for a single note for guidance on the chemistry of active substances

This concept paper addresses the need to update and revise the guidance available on the chemistry of the active substance (new and existing active substances). There are currently two approved guidelines on the subject; EMEA/CVMP/541/03/Final guideline on the chemistry of new active substances and 3AQ5A guideline on chemistry of the active substance. It is felt appropriate to combine the two documents into a single guideline to provide better clarity for applicants.