Also included in the revision is the addition of

• Appendix 1, listing the N-nitrosamines for which AIs have been established by the Non-clinical Working Party (NcWP), including new AIs for N-nitrosamines determined using the CPCA
• Annex 2, describing the Carcinogenic Potency Categorization Approach for N-nitrosamines
• Annex 3, describing the Enhanced Ames Test Conditions for N-nitrosamines

The Carcinogenic Potency Categorization Approach (CPCA)

CPCA is considered as an approach for assigning an N-nitrosamine impurity (including nitrosamine drug substance-related impurities [NDSRIs]) based on an assessment of activating or deactivating structural features present in the molecule. In the context at hand, activating or deactivating features are defined as molecular substructures that are associated with an increase or decrease in carcinogenic potency. The underlying concept of structure-activity relationship (SAR) is described in recent scientific publications for N-nitrosamine compounds. It is based on “prediction” and as science is constantly evolving, so will the prediction of mutagenic potential and carcinogenic potency. Described in this document is a conservative approach that represents the best available science at this time. It is expected to be further adapted as new data become available.

The Enhanced Ames Test

The Ames assay, a bacterial reverse mutation test, is based on standard recommendations provided by the Organisation for Economic Co-operation and Development (OECD)’s Test Guideline No. 471 “Bacterial Reverse Mutation Test”. For N-nitrosamines, enhanced testing conditions for the Ames assay are recommended due to the reported reduced sensitivity of the assay under standard conditions for some N-nitrosamines such as N-nitroso-dimethylamine. The conditions for the enhanced Ames assay test are described in detail in Annex 3 of the document. However, if a standard Ames assay is conducted and produces a positive result, there is no need for an additional assay using enhanced testing conditions.

Source:

EMA: Questions and answers for MAHs/applicants on the CHMP Opinion for the Article 5(3) of Regulation (EC) No 726/2004 referral on nitrosamine impurities in human medicinal products