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A General Method for Detecting Nitrosamide Formation in the In Vitro Metabolism of Nitrosamines by Cytochrome P450s
07:38

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
PubMed

Insights

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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