Nitrosamine Impurities: A Persistent Regulatory Challenge in Drug Development

The scrutiny around nitrosamine impurities has intensified over recent years turning them into a frequent and often complex regulatory hurdle. Nitrosamines, defined by the presence of a nitroso group (N=O) attached to an amine nitrogen are classified as probable or possible human carcinogens. Their regulatory prominence began in 2018, when unexpected nitrosamine contaminants were first detected in certain sartan products. Since then, regulators have issued guidance, expanded expectations and made nitrosamine assessments a mandatory requirement for marketing applications.

The FDA’s 2024 guidance Control of Nitrosamine Impurities in Human Drugs (Revision 2) underscores the need for manufacturers to proactively detect and prevent unacceptable nitrosamine levels in both drug substances and drug products. The guidance expands the scope of assessment and introduces updated acceptable intake (AI) limits – including those derived through carcinogenic potency categorizations and emerging scientific approaches.  EMA’s Article 5(3) assessment report and associated Q&A similarly require comprehensive, stepwise risk assessments and if needed confirmatory testing.

The requirements are:

Step 1: Risk Evaluation: Assess the potential for nitrosamine formation in both drug substance and drug product.

Step 2: Confirmatory Testing: Conduct testing if any potential risk is identified.

Step 3: Risk Mitigation: Define and justify the mitigations and control strategy if the presence of nitrosamine(s) is confirmed.

Whilst there is good alignment between EMA and FDA on the overall strategy for nitrosamines there is divergence in some of the details.  Both require nitrosamine testing in the specification if confirmatory results exceed 10% of the recommended AI limit but only the EMA currently permits skip testing when results are below 30%.

A review of European assessment reports (EPARs) from 2025 reveals a clear regulatory pattern: nitrosamine strategies remain one of the most common sources of major objections. Product such as Lynkuet (elinzanetant), Ekterly (sebetralstat) and Romvimza (vimseltinib) illustrate the same theme that EMA expects robust, complete nitrosamine risk assessments, aligned with Article 5(3) guidance and confirmatory testing to be completed when risks are identified. Incomplete risk evaluations that fail to consider all potential and actual root causes, along with missing or non‑validated nitrosamine analyses, routinely lead to major objections.

Applicants typically resolve these objections through providing validated analytical data, strengthening or clarifying the control strategy and/or providing sound scientific justification ruling out nitrosamine formation.

Conveying to the regulators that the potential nitrosamines risk is understood and controlled represents a regulatory risk but one that the team at Boyds can help you manage. At Boyds we support companies by

• reviewing nitrosamine risk assessments for completeness and regulatory alignment,
• evaluating proposed control strategies,
• and guiding early engagement with regulators to de‑risk MAAs and NDA

With the right strategy, you can minimise delays, prevent major objections, and ensure your submission aligns with current guidance. If you’re navigating nitrosamine requirements or preparing for an upcoming submission, Boyds is here to help you confidently meet regulator expectations.

References

Control of Nitrosamine Impurities in Human Drugs Guidance for Industry (September 2024, Revision 2) https://www.fda.gov/media/141720/download

Assessment report- Procedure under Article 5(3) of Regulation EC (No) 726/2004- Nitrosamine impurities in human medicinal products (EMA/369136/2020) https://www.ema.europa.eu/en/documents/opinion-any-scientific-matter/nitrosamines-emea-h-a53-1490-assessment-report_en.pdf

Questions and answers for marketing authorisation holders/applicants on the CHMP Opinion for the Article 5(3) of Regulation (EC) No 726/2004 referral on nitrosamine impurities in human medicinal products (EMA/409815/2020) https://www.ema.europa.eu/en/documents/opinion-any-scientific-matter/nitrosamines-emea-h-a53-1490-questions-answers-marketing-authorisation-holders-applicants-chmp-opinion-article-53-regulation-ec-no-726-2004-referral-nitrosamine-impurities-human-medicinal-products_en.pdf

Lynkuet EPAR https://www.ema.europa.eu/en/documents/assessment-report/lynkuet-epar-public-assessment-report_en.pdf

Ekterly EPAR https://www.ema.europa.eu/en/documents/assessment-report/ekterly-epar-public-assessment-report_en.pdf

Romvimza EPAR https://www.ema.europa.eu/en/documents/assessment-report/romvimza-epar-public-assessment-report_en.pdf