Zhang Shaofei, Cheung Jennifer, Kostal Jakub, Voutchkova-Kostal Adelina, Schuler Maik
Pfizer Research, Development, and Medical, Groton, Connecticut, USA.
DOT Consulting LLC, Alexandria, Virginia, USA.
Environ Mol Mutagen. 2025 Mar;66(3):80-98. doi: 10.1002/em.70007. Epub 2025 Mar 22.
Establishing regulatory limits for Drug Substance-Related Impurities (NDSRIs) is challenging due to the limited genotoxicity and carcinogenicity data available for many of these impurities, often leading to conservative approaches. In this study, we evaluated the genotoxic potential of two structurally related nitrosamines: N-nitrosomorpholine (NMOR) and N-nitroso reboxetine. Compared to the well-studied NMOR, there is little toxicological information available for N-nitroso reboxetine. Currently, both compounds have an acceptable intake value of 127 ng/day, based on a read-across using the available carcinogenicity data of NMOR. While both compounds tested positive in a series of in vitro and in vivo assays, we found that the mutagenic potential of N-nitroso reboxetine was significantly lower than that of NMOR. The benchmark dose (BMD) analysis of in vivo mutagenicity data supports an acceptable intake of 24,000 ng/day for N-nitroso reboxetine. Computational studies, carried out using the quantum-mechanical CADRE program, were consistent with in vitro and in vivo outcomes, suggesting an acceptable intake at or above 1500 ng/day for N-nitroso reboxetine. In comparison to NMOR, this prediction is supported by lower computed reactivity in the hydroxylation step, greater steric hindrance of the alpha carbons, and more facile proton transfer in the heterolysis toward the aldehyde metabolite. The data presented in this work can be used to refine and improve the Carcinogenic Potency Categorization Approach (CPCA). It also underscores the importance of collaboration between regulatory authorities, the pharmaceutical industry, and scientific researchers to address potential risks while avoiding overestimation of the acceptable intake limits for certain NDSRIs.
由于许多药物物质相关杂质（NDSRIs）的遗传毒性和致癌性数据有限，为其设定监管限度具有挑战性，这通常导致采用保守方法。在本研究中，我们评估了两种结构相关的亚硝胺的遗传毒性潜力：N-亚硝基吗啉（NMOR）和N-亚硝基瑞波西汀。与研究充分的NMOR相比，关于N-亚硝基瑞波西汀的毒理学信息很少。目前，基于对NMOR现有致癌性数据的类推，这两种化合物的可接受摄入量均为127纳克/天。虽然这两种化合物在一系列体外和体内试验中均呈阳性，但我们发现N-亚硝基瑞波西汀的诱变潜力明显低于NMOR。体内诱变性数据的基准剂量（BMD）分析支持N-亚硝基瑞波西汀的可接受摄入量为24,000纳克/天。使用量子力学CADRE程序进行的计算研究与体外和体内结果一致，表明N-亚硝基瑞波西汀的可接受摄入量为1500纳克/天或更高。与NMOR相比，这一预测得到了以下支持：羟基化步骤中计算出的反应性较低、α-碳的空间位阻较大以及向醛代谢物的异裂过程中质子转移更容易。本研究中提供的数据可用于完善和改进致癌潜能分类方法（CPCA）。它还强调了监管机构、制药行业和科研人员之间合作的重要性，以应对潜在风险，同时避免高估某些NDSRIs的可接受摄入限度。
