FDA issued the draft guidance for industry, Establishing Impurity Specifications for Antibiotics. This guidance, if finalized, will provide manufacturers with recommendations for establishing impurity limits for antibiotic drugs produced using fermentation or semi-synthetic methods. Manufacturers can use established impurity limits to develop and apply quality testing standards for these products.

The ICH guidances for industry Q3A(R) Impurities in New Drug Substances (June 2008) and Q3B(R2) Impurities in New Drug Products (August 2006) provide recommendations on thresholds for the identification, reporting, and qualification of impurities and degradation products in new drugs produced by chemical synthesis. However, these guidances lack recommendations for controlling impurities and degradation products in antibiotics manufactured by fermentation and semi-synthesis, a process that produces novel compounds through chemical modification of compounds obtained from fermentation or isolated from natural sources. Antibiotics manufactured by fermentation or semi-synthesis are typically more complex than those produced solely by chemical synthesis. The draft guidance issued today applies the principles covered in the ICH guidances to antibiotics manufactured by these more complex production methods and additionally draws upon the recommendations in the ICH guidance for industry M7(R2) Assessment and Control of DNA Reactive (Mutagenic) Impurities in Pharmaceuticals to Limit Potential Carcinogenic Risk (July 2023). Antibiotic drugs with United States Pharmacopeia (USP) monographs must meet the requirements outlined in the respective USP monographs for the drug substance and the drug product. [FDA]