药物杂质遗传毒性评价策略与监管研究

伴随大量创新及仿制药面世而来的是对遗传毒性杂质加强监管的迫切需求。一系列与国际接轨的指南性文件的出台，弥补了我国杂质监管的空白，但难点尚存。传统评价方法具有局限性，新方法与传统方法间缺乏一致性比较，药物特定合成路线实际产生的大量含警示结构杂质缺乏毒理学评价数据支持，毒性预测软件的预测效力不足等。本文就国内外杂质遗传毒性杂质监管科学现状、遗传毒性杂质控制策略、杂质遗传毒性评价方法进行论述，并提出充分结合计算机毒理学、毒性评价方法和符合我国国情的监管限度制定三个维度开展杂质监管工作。     

药品中遗传毒性杂质的评估和控制

目的 综述药品遗传毒性杂质控制相关指南和法规,为制药企业执行国际标准和准则提供一些建议和思路。方法 通过查找数据库如Pubmed、Medline及欧洲药品管理局(European Medicines Agency,EMA)、美国食品药品监督管理局(US Food and Drug Administratio,U.S.FDA)、人用药品注册技术要求国际协调会议(ICH)等网站,比较各指南法规关于遗传毒性控制限度和控制措施的异同点,为遗传毒性杂质的控制提供一个可行性步骤。结果 通过比较发现,EMA、U.S.FDA和即将出版的ICH M7指南在关键原则的应用方面如毒理学关注阈值(threshold of toxicological concern,TTC)、风险评估步骤、杂质5分类法等基本相同,但现行EMA和U.S.FDA法规存在分歧,不利于其有效执行,而ICH M7将为遗传毒性杂质的控制提供一个可行框架。结论 目前还缺乏完善有效的遗传毒性控制指南,ICH M7将解决U.S.FDA 和EMA 指南间分歧,更好地指导制药企业遗传毒性杂质的控制。     

The application of structure-based assessment to support safety and chemistry diligence to manage genotoxic impurities in active pharmaceutical ingredients during drug development

Starting materials and intermediates used to synthesize pharmaceuticals are reactive in nature and may be present as impurities in the active pharmaceutical ingredient (API) used for preclinical safety studies and clinical trials. Furthermore, starting materials and intermediates may be known or suspected mutagens and/or carcinogens. Therefore, during drug development due diligence need be applied from two perspectives (1) to understand potential mutagenic and carcinogenic risks associated with compounds used for synthesis and (2) to understand the capability of synthetic processes to control genotoxic impurities in the API. Recently, a task force comprised of experts from pharmaceutical industry proposed guidance, with recommendations for classification, testing, qualification and assessing risk of genotoxic impurities. In our experience the proposed structure-based classification, has differentiated 75% of starting materials and intermediates as mutagenic and non-mutagenic with high concordance (92%) when compared with Ames results. Structure-based assessment has been used to identify genotoxic hazards, and prompted evaluation of fate of genotoxic impurities in API. These two assessments (safety and chemistry) culminate in identification of genotoxic impurities known or suspected to exceed acceptable levels in API, thereby triggering actions needed to assure appropriate control and measurement methods are in place. Hypothetical case studies are presented demonstrating this multi-disciplinary approach.     

亚硝胺类遗传毒性杂质的监管策略及思考

如何对药品中存在致癌风险的亚硝胺类杂质进行控制,已成为企业和监管部门关注的热点。本文对亚硝胺类杂质的常见类型、来源、致癌性作用特点进行梳理,并结合EMA、FDA、ICH及我国相关遗传毒性杂质控制指导原则,对制定符合我国国情的亚硝胺类杂质的监管限度和监管工作提出建议。尽管国外已陆续出台了一系列针对药品中亚硝胺类杂质的含量限定的指南性文件,但众多亚硝胺类杂质的毒性剂量、人体暴露量尚不明确,且药物合成工艺存在差异,我国无法完全照搬欧美等国的监管方法。当前应深入研究亚硝胺类杂质的遗传毒性和致癌性,从而制定符合我国国情的监管限度值和药品中亚硝胺杂质监管策略;此外,本文从解决实际问题的角度出发,讨论如何根据已有指导原则,确定在已知毒理学数据、毒理学数据不足和短期使用药物不同情况下亚硝胺类杂质的监管限度。本文将为药物生产和杂质评价与研究和监管领域相关人员提供借鉴。     

Analytical control of genotoxic impurities in the pazopanib hydrochloride manufacturing process

Pharmaceutical regulatory agencies are increasingly concerned with trace-level genotoxic impurities in drug substances, requiring manufacturers to deliver innovative approaches for their analysis and control. The need to control most genotoxic impurities in the low ppm level relative to the active pharmaceutical ingredient (API), combined with the often reactive and labile nature of genotoxic impurities, poses significant analytical challenges. Therefore, sophisticated analytical methodologies are often developed to test and control genotoxic impurities in drug substances. From a quality-by-design perspective, product quality (genotoxic impurity levels in this case) should be built into the manufacturing process. This necessitates a practical analysis and control strategy derived on the premise of in-depth process understanding. General guidance on how to develop strategies for the analysis and control of genotoxic impurities is currently lacking in the pharmaceutical industry. In this work, we demonstrate practical examples for the analytical control of five genotoxic impurities in the manufacturing process of pazopanib hydrochloride, an anticancer drug currently in Phase III clinical development, which may serve as a model for the other products in development. Through detailed process understanding, we implemented an analysis and control strategy that enables the control of the five genotoxic impurities upstream in the manufacturing process at the starting materials or intermediates rather than at the final API. This allows the control limits to be set at percent levels rather than ppm levels, thereby simplifying the analytical testing and the analytical toolkits to be used in quality control laboratories.     

色谱-质谱联用技术用于遗传毒性杂质检测的研究进展

遗传毒性杂质种类繁多且通常痕量存在于药物中,而色谱-质谱联用技术具有相对更高的灵敏度和选择性,极适用于分析药物中的遗传毒性杂质。主要介绍了如何根据遗传毒性杂质的极性、挥发性、热不稳定性等理化性质建立合适的色谱-质谱联用技术,并综述了气相色谱、液相色谱、超高液相色谱、亲水性相互作用色谱、超临界流体色谱、毛细管电泳色谱6种色谱技术与质谱联用在遗传毒性杂质（如亚硝胺类、磺酸酯类、卤代烷烃类等）检测中的研究进展,从而为建立科学合理的遗传毒性杂质检测方法提供参考。     

药物中基因毒性杂质检测方法研究进展

基因毒性杂质由于对DNA的破坏作用而具有一定的致癌性,危害极大。因其结构众多,患者在服药过程中有摄入该类杂质的风险。部分国家对基因毒性杂质的限度控制已成为药品上市时必须考察的指标。本文概述了基因毒性杂质的基本概念、相关法规标准、部分杂质检测方法限度等内容,以期为控制药品中基因毒性杂质的含量提供参考和依据,保证患者用药安全。     

A rationale for determining, testing, and controlling specific impurities in pharmaceuticals that possess potential for genotoxicity

The synthesis of pharmaceutical products frequently involves the use of reactive reagents and the formation of intermediates and by-products. Low levels of some of these may be present in the final drug substance and drug product as impurities. Such chemically reactive impurities may have at the same time the potential for unwanted toxicities including genotoxicity and carcinogenicity and hence can have an impact on product risk assessment. This paper outlines a procedure for testing, classification, qualification, toxicological risk assessment, and control of impurities possessing genotoxic potential in pharmaceutical products. Referencing accepted principles of cancer risk assessment, this document proposes a staged threshold of toxicological concern (TTC) approach for the intake of genotoxic impurities over various periods of exposure. This staged TTC is based on knowledge about tumorigenic potency of a wide range of genotoxic carcinogens and can be used for genotoxic compounds, for which cancer data are limited or not available. The delineated acceptable daily intake values of between approximately 1.5 microg/day for approximately lifetime intake and approximately 120 microg/day for < or = 1 month are virtually safe doses. Based on sound scientific reasoning, these virtually safe intake values do not pose an unacceptable risk to either human volunteers or patients at any stage of clinical development and marketing of a pharmaceutical product. The intake levels are estimated to give an excess cancer risk of 1 in 100,000 to 1 in a million over a lifetime, and are extremely conservative given the current lifetime cancer risk in the population of over 1 in 4 (http://seer.cancer.gov/statfacts/html.all.html). The proposals in this document apply to all clinical routes of administration and to compounds at all stages of clinical development. It is important to note that certain types of products, such as those for life-threatening indications for which there are no safer alternatives, allow for special considerations using adaptations of the principles outlined in this paper.     

Quantitative assessment of cumulative carcinogenic risk for multiple genotoxic impurities in a new drug substance

In pharmaceutical development, significant effort is made to minimize the carcinogenic potential of new drug substances (NDS). This involves appropriate genotoxicity and carcinogenicity testing of the NDS, and understanding the genotoxic potential of its impurities. Current available guidance recommends the use of the threshold of toxicological concern (TTC) for a single impurity where mutagenicity but no carcinogenicity information exists. Despite best efforts, the presence of more than one genotoxic impurity in an NDS may occur at trace levels. This paper repeats the analysis performed by others for a single genotoxic compound, but also uses statistical simulations to assess the impact on cancer risk for a mixture of genotoxic compounds. In summary, with the addition of multiple impurities all controlled to the TTC, an increase in cancer risk was observed. This increase is relatively small when considering the conservative assumptions of the TTC. If structurally similar compounds had an assumed strong correlation (+/-10-fold from the first randomly selected impurity) in cancer potency, the resulting cancer risk was not negatively impacted. Findings based on probabilistic analysis here can be very useful in making appropriate decisions about risk management of multiple genotoxic impurities measured in the final drug substance.     

An evaluation of the sensitivity of the Ames assay to discern low-level mutagenic impurities

Low level impurities often reside in active pharmaceutical ingredients (API). Some of these impurities are potentially genotoxic since reactive intermediates are used in the synthetic route for the production of API. Routine mutagenicity testing is conducted in support of clinical trials with the intent to identify genotoxic hazards associated with API. Depending on the amount of impurity present in the API tested, the potency of the impurities and the relative sensitivity of the Ames assay, it is possible that mutagenicity associated with the presence of genotoxic impurities could also be detected while testing API. Therefore, we evaluated published data and generated new information to understand the sensitivity of the Ames assay. Based on a literature survey of approximately 450 mutagens, it was estimated that 85% of mutagens are detected at concentrations of 250 microg/plate or less. Based on this estimate, most mutagens should be detected in an Ames assay testing API concentrations up to 5000 microg/plate if present at a 5% or greater concentration. Data from experiments where several direct and indirect-acting mutagens were spiked into representative API further support the literature-based evaluation. Some limitations of this approach, including toxicity of API and competing metabolism are discussed.     

(定量)构效关系预测利伐沙班有机杂质遗传毒性

目的 通过对利伐沙班原料中有机杂质进行遗传毒性预测，并以杂质遗传毒性进行分类，为实际生产中质量保障体系的建立提供依据。方法 分析利伐沙班的合成工艺，结合实际生产中有可能采用的生产工艺，推测有机杂质，按照国际认可的指导原则，采用基于专家规则和基于统计学规则的2个互补的（定量）构效关系评估[（quantitative） structure-activity relationships， （Q）SAR]预测软件，对18个有机杂质进行遗传毒性预测分析，并依据预测结果按照其致突变性和致癌性进行分类。结果 在18个有机杂质中，需要按遗传毒性杂质控制的杂质有5个，可以按非遗传毒性杂质控制的杂质有13个。结论 采用（Q）SAR评估有关物质的遗传毒性，可实现快速确定杂质毒性特征的目的。预测结果提示利伐沙班应针对具有遗传毒性警示结构的5个杂质建立有效的质量控制体系。     

Regulating impurities in pharmaceutical products: a tolerability of risk approach?

This paper explores the implications of the EMEA guideline EMEA/CHMP/QWP/251344/2006 for pharmaceutical risk decisions. The guidelines propose to consider the intake of 1.5 µg/day of a genotoxic impurity as a ‘threshold of toxicological concern’, and to treat this level as an acceptable risk (excess cancer risk of <10^-5 over a lifetime). The guidance document also introduces a specific decision-tree to assess the acceptability of genotoxic impurities. According to this decision-tree, when the presence of genotoxic impurities is unavoidable, their levels should be reduced ‘as low as reasonably practicable’ (ALARP). In the UK, the Health and Safety Executive has developed a ‘tolerability of risk’ (ToR) model to support ALARP requirements. The paper compares the EMEA risk-reduction requirements and the ToR model. EMEA/CHMP/QWP/251344/2006 introduces a risk-avoidance principle based on a controversial interpretation of ‘pollution control’. The paper supports the view that this model is not optimal from a risk-management point of view. Using a ToR model could bring improvements to pharmaceutical risk decisions and would support a more practical and consensual approach to meeting the ALARP requirements.     

An impact analysis of the application of the threshold of toxicological concern concept to pharmaceuticals

The recent application of the threshold of toxicological concern (TTC) concept to the regulation of pharmaceuticals in the European Union is analyzed. The derivation of TTC and the threshold of regulation that followed it were originally intended to provide makers of food contact materials greater flexibility with their products, while allowing the CFSAN branch of FDA to conserve its resources for more important issues. A reanalysis of the scientific data employed by EMEA regulators to rationalize its 1.5 mcg default genotoxic impurity limit is presented to demonstrate (a) that direct translation of conclusions relevant to food consumption are unduly influenced by many classes of potent carcinogens of historic concern which would be impossible to generate unknowingly as pharmaceutical impurities, and (b) that the majority of reactive chemicals that would be useful to synthetic chemists are among the least potent carcinogens in the underpinning supportive analyses. Evidence is further presented to show that implementation and acceptance of a 1.5 mcg TTC-based total limit on such impurities can be expected to impede pharmaceutical research and development efficiency while providing an insignificant cancer risk-avoidance benefit to patients who require pharmaceutical treatments. The conclusion drawn is that a significantly higher default limit can readily be defended that would be both in keeping with TTC principles and the best interest of patients.     

原料药中基因毒性杂质控制的研究进展

目的介绍原料药(active pharmaceutical ingredient,API)中基因毒性杂质控制的法规要求、评估方法和控制方法。方法通过学习欧美法规发展历史,理解国际高端市场对基因毒性杂质控制的监管期望,提出原料药中基因毒性杂质风险评估方法。结果与结论企业基于半定量评估,结合清除研究数据,建立科学的控制策略,使实际工艺中所有可能涉及的基因毒性杂质风险得到明确鉴别和控制,是达到监管期望的有效途径。     

药物中痕量磺酸酯类物质的检测技术研究进展

烷基磺酸酯和芳基磺酸酯类化合物作为潜在性基因毒性杂质,严重威胁人类健康,因此需要控制食品及药品中磺酸酯的限度。主要介绍了磺酸酯类物质的痕量分析检测技术手段,如GC-MS、HPLC-MS、NMR等,同时阐述了各种检测技术的优缺点。另外,还论述了这些杂质产生的条件,从而提出了避免生成该类杂质的具体措施。因此,主要从避免杂质的产生和痕量检测两方面进行了综述,讨论了有效控制药品中基因毒杂质限度的方法,以保证用药安全。     

Guidelines and pharmacopoeial standards for pharmaceutical impurities: Overview and critical assessment

ICH/regional guidances and agency scrutiny provide the regulatory framework for safety assessment and control of impurities in small-molecule drug substances and drug products. We provide a critical assessment of the principal impurity guidances and, in particular, focus on deficiencies in the derivation of the threshold of toxicological concern (TTC) as applied to genotoxic impurities and the many toxicological anomalies generated by following the current guidelines on impurities. In terms of pharmacopoeial standards, we aim to highlight the fact that strictly controlling numerous impurities, especially those that are minor structural variants of the active substance, is likely to produce minimal improvements in drug safety. It is believed that, wherever possible, there is a need to simplify and rebalance the current impurity paradigm, moving away from standards derived largely from batch analytical data towards structure-based qualification thresholds and risk assessments using readily available safety data. Such changes should also lead to a minimization of in vivo testing for toxicological qualification purposes. Recent improvements in analytical techniques and performance have enabled the detection of ever smaller amounts of impurities with increased confidence. The temptation to translate this information directly to the regulatory sphere without any kind of safety evaluation should be resisted.     

药物中肼类基因毒性杂质分析研究进展

基因毒性杂质具有在极低暴露水平下即能导致严重毒性的特点,对用药的安全性造成严重的威胁。作为一类重要的基因毒性杂质,肼是一种常见的中间体,而且是常见药物的降解产物。对基因毒性杂质进行了概述,并较为详尽地介绍了肼类基因毒性杂质的分析方法,为需要测定此类基因毒性杂质的分析人员提供参考。     

N-亚硝胺类基因毒性杂质的研究进展

自“缬沙坦事件”之后，N-亚硝胺类基因毒性杂质引起了业界的广泛关注。本文概述了药物中N-亚硝胺类基因毒性杂质和相关检测方法的研究进展，以及近20年来国内外有关药物中基因毒性杂质监管指南的完善历程。N-亚硝胺类基因毒性杂质作为一类高反应活性的基因毒性杂质，主要来源于药物合成过程中发生的副反应，以及药物在储存或者运输过程中发生的氧化或还原等反应。所有的动物实验表明，N-亚硝胺类具有很强的致癌性。在理论上，所有药物都存在N-亚硝胺类杂质或被N-亚硝胺类杂质污染的风险，由于该类化合物在药物中常以痕量形式存在，在分析检测过程中药物基质干扰大，因此建立便捷、高效的分析方法是非常有必要的。     

Eliminating pharmaceutical impurities: Recent advances in detection techniques

The elimination of organic impurities to produce highly pure drug substances is an important goal of process chemistry. For the detection of general impurities, hyphenated techniques (eg, liquid chromatography-mass spectrometry [LC-MS]) play a critical role in rapid structural identification (qualitative detection) and in understanding the mechanisms of formation of the impurities, enabling informed decisions to control and eliminate the impurities resulting from the chemical process where possible. Concern regarding genotoxic impurities (GTIs), which must typically be controlled at low parts-per-million limits, continues to increase, and significant advances have been achieved in recent years for the selective and sensitive quantitation (quantitative detection) of such impurities. Conventional detection techniques, such as ultraviolet (UV) detection, are often inadequate for the detection of potentially minute quantities of GTIs; therefore, various advanced MS-based detection strategies, either stand-alone or in conjunction with chemical approaches, are playing an increasing role in this field. The primary aim of this review is to highlight recent advances in qualitative and quantitative detection of impurities at trace levels, with a particular focus on GTIs.     

药物杂质的毒理学评价要求及进展

 药物原料或制剂中的杂质可能引起临床不良反应。杂质毒理学评价是药物研究的重要内容。ICH关于药物及制剂杂质方面指导原则规定了杂质的报告、鉴定和质控限度,含量超过质控限度的杂质应进行毒理学评价。但指导原则对于研发阶段的药物杂质和遗传毒性杂质的限度未作明确要求。EMEA对于遗传毒性杂质制定了专门的指导原则,引入了毒理学担忧阈值（TTC）的概念对遗传毒性杂质限度进行控制,遗传毒性杂质每日接触量应小于1.5 μg。FDA也推荐采用TTC原则控制遗传毒性和致癌性杂质。本文结合ICH,EMEA及美国FDA等指导原则,对药物杂质毒理学评价的要求及其进展进行了综述。