ICH M7(R2) - Assessment and Control of DNA Reactive (Mutagenic) Impurities

What it says

Potential DNA reactive, mutagenic impurities must be assessed through structure-activity relationship analysis and, where warranted, actual mutagenicity testing, with acceptable intake limits established using a threshold of toxicological concern approach for impurities without compound-specific safety data, and control strategies implemented to keep actual patient exposure below these limits.

Paraphrased for plain-language clarity. Always verify against the current published regulation text.

What it means in practice

• This guideline provides the scientific and regulatory framework underlying the global nitrosamine impurity crisis that has significantly affected pharmaceutical manufacturing since 2018, since nitrosamines are a specific, well-known category of DNA reactive mutagenic impurity this framework directly governs.
• The threshold of toxicological concern approach allows a generic, conservative acceptable intake limit to be applied to impurities lacking compound-specific safety data, providing a practical control mechanism even without extensive individual toxicological study for every possible impurity.
• Control strategies under this framework must address not just the finished drug substance or product but the full manufacturing process and even packaging, since mutagenic impurities such as nitrosamines can form through unexpected reactions between raw materials, degradation products, and even certain excipients or packaging components under specific conditions.

What inspectors look for

• Whether a documented, current risk assessment for mutagenic impurities, including nitrosamine-specific risk assessment, exists and reflects the manufacturing process, raw materials and packaging actually in use.
• Whether root cause investigations for detected mutagenic impurities genuinely trace back to the specific formation mechanism, rather than stopping at simply confirming detection.
• Whether control strategies, once a risk is identified, actually reduce patient exposure below applicable acceptable intake limits, verified through appropriate analytical testing.

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