Which descriptor best identifies a new molecular entity in NDA coding?

• A. New salt of previously approved drug
• B. New formulation of previously approved drug
• C. New molecular entity
• D. New combo or two or more drugs

Answer: (C)

In NDA coding, the key idea is whether the active ingredient is truly new. A drug described as a new molecular entity has a chemical structure that represents a novel active moiety not previously approved by the FDA in any form. That means the substance itself is new, not just a salt, ester, or different formulation of something already approved, and not a combination of already approved drugs.

This descriptor distinguishes a truly new chemical substance from other changes. A new salt or ester of an existing drug uses the same active moiety, so it isn’t considered a new molecular entity. A new formulation involves the same active ingredient in a different dosage form or excipient, again not a new molecule. A fixed-dose combination or multi-drug product may be a new product, but it doesn’t introduce a new active moiety, so it isn’t an NME.

So the best descriptor for a genuinely novel active ingredient is the one indicating a new molecular entity. This designation has regulatory implications, such as opportunities for new-molecular-entity exclusivity in certain contexts.