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Updated: May 29, 2026
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A General Method for Detecting Nitrosamide Formation in the In Vitro Metabolism of Nitrosamines by Cytochrome P450s
Published on: September 25, 2017
Complex versus simple N-nitrosamines: Comprehensive genotoxicity and in silico carcinogenicity assessment toward
Xiaowen Sun1, Maik Schuler1, Shaofei Zhang1
1Pfizer Research, Development, and Medical, Groton, CT 06340, USA.
Science Advances
|May 27, 2026
Summary
Complex N-nitrosamines in pharmaceuticals are often not mutagenic, challenging current safety limits. New methods enable risk-based acceptable intakes, reducing animal testing and improving drug safety.
Area of Science:
- Pharmaceutical chemistry
- Toxicology
- Risk assessment
Background:
- N-nitrosamines are a significant concern in pharmaceuticals since 2018.
- Regulatory scrutiny necessitates understanding their mutagenic potential and developing mitigation strategies.
Purpose of the Study:
- To comprehensively evaluate the mutagenicity and acceptable intake (AI) of 25 diverse N-nitrosamines.
- To compare in vitro, in vivo, and in silico methods for N-nitrosamine assessment.
- To propose a data-driven approach for deriving risk-commensurate AIs.
Main Methods:
- In vitro assays (Ames test).
- In vivo assays (liver comet, Big Blue mutation assay, duplex sequencing).
- In silico methods (quantum mechanical modeling, CYP-binding analysis).
Main Results:
- Strong concordance observed across diverse testing methodologies.
- Complex API-derived or PRI-derived N-nitrosamines generally exhibit low mutagenic potency.
- Duplex sequencing showed high sensitivity; QM models effectively predicted potency.
- Compound-specific AIs derived from in vivo data often exceeded regulatory limits.
Conclusions:
- A weight-of-evidence approach integrating experimental and computational data is proposed for AI derivation.
- This approach reduces animal testing and supports risk-based remediation efforts for drug products.
- The findings provide a framework for more accurate N-nitrosamine risk assessment in pharmaceuticals.
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