Drug substance (DS)

The active ingredient before it is formulated into the final dosage form; for a biologic, the purified antibody, protein or other molecule after downstream processing. Japanese uses this one word for both a biologic drug substance and a small-molecule API. A Japanese marketing authorization holder can reference a foreign drug substance through a Master File (MF) registered in Japan, which keeps the manufacturer's confidential details out of the MAH's application. A foreign site that makes a drug substance for the Japanese market needs Accreditation of Foreign Manufacturers even if it makes nothing else for Japan.