28/29 February 2024
EMA's recently updated Q&A document on nitrosamine impurities, dated 7 July 2023 (Revision 16), includes comprehensive additions. Q&A 10 ("Which limits apply for nitrosamines in medicinal products?") explains in detail how to set acceptable intakes (AI) for N-nitrosamines. Further explanations and examples are provided in the new Annex 2.
Q&A 10 describes the following two scenarios:
Calculation of TD50 value and from this derivation of lifetime exposure limit according to ICH M7(R2).
1. If other reliable data are not available, the Carcinogenic Potency Categorization Approach (CPCA) should be used to determine the AI.
2. If the extended Ames test (Appendix 3) shows a negative result, a limit of 1.5 µg/day may be established.
3. If a nitrosamine surrogate with robust data on TD 50 is available, the AI can be derived by SAR (structure activity relationship) based on this surrogate.
4. If an in vivo mutagenicity study shows a negative result, the nitrosamine can be controlled as a non-mutagenic impurity according to the limits of the ICH Q3A(R2) and Q3B(R2) guidelines. This applies even if other limits have been calculated according to options 1-3.
The new Annex 2 is exclusively dedicated to the determination of AI limits for nitrosamines for which in vivo data are not available and explains in detail the approach of SAR-based carcinogenicity categorization (CPCA). A potency score is calculated along a decision tree, which is then used to determine the potency category for the substance in question. Appendix 1 of this annex explains the calculation of the potency score in detail. Appendix 2 of the annex shows an example for each potency category.
The new Annex 1 lists the limits, including the CPCA category, of a total of 84 nitrosamines identified by the non-clinical working group (NcWP) using the CPCA method.
The revision of Q&A 10 regarding AI limits for nitrosamines without a data basis addresses a relevant gap related to the control of nitrosamine impurities in APIs and medicinal products.
Another important addition to the Q&A document (related to Option 2 of Annex 2) is Annex 3 ("Enhanced Ames Test Conditions for N-Nitrosamines"), which describes enhanced conditions for the Ames test. The reason for the modification of the Ames test is the observation that the sensitivity of the test under standard conditions is not sufficient for some nitrosamines.