高内涵分析在新药发现毒理学中的应用进展

在新药发现早期开展发现毒理学研究是提高新药研发效率的重要策略之一。高内涵分析(HCA)是基于高效新药筛选需求发展起来的一项新技术,其主要特点是基于活细胞、多参数、实时、高通量,能够实现化合物多种生物活性、毒性的早期、快速地检测,为发现毒理学研究提供了高效的技术手段。目前,HCA已用于多种靶器官细胞毒性、遗传毒性、神经毒性、血管毒性、生殖毒性等检测以及毒理学分子机制的研究,本文就HCA在新药发现毒理学方面的应用进展进行综述。     

新药评价中彗星试验方法学研究及发展趋势

彗星试验是一项检测单细胞损伤的试验方法,近年来在毒理学研究中发展很快。对彗星试验的原理和方法,及其在新药评价遗传毒性研究、生殖毒性研究和靶器官毒理学研究中的应用进行了分析和介绍,并提出了彗星试验技术的发展趋势。     

遗传毒性早期快速评价方法

遗传毒性评价是药物安全性评价的重要组成部分。如何早期、快速地获得药物可能的毒性反应数据,是当前遗传毒理学领域的研究热点之一。介绍几种目前应用比较广泛或有较好应用前景的早期、快速的遗传毒性评价方法,包括AmesII试验、Gadd45 Green Screen试验、高通量体外彗星试验和流式细胞术检测微核试验,主要围绕这些方法的基本原理、简要操作流程、预测毒性的可信度以及与传统方法相比的优缺点等展开。同时简要介绍计算机辅助毒性预测模型以及基因芯片技术在遗传毒性评价中的应用。     

毒理学替代方法及其在新药安全性评价中的应用

目的药物安全性是决定新药研发成功与否的关键性因素之一。近年随着实验动物使用的4Rs(减少、替代、优化和可靠)原则的倡导与实施,整体动物试验面临严重挑战。毒理学替代法使用其他方法而不用动物进行实验,其范围包括用组织学、胚胎学、细胞学或计算机等方法取代整体动物实验,以低等动物取代高等级动物等。替代方法中采用离体细胞和培养的组织,完全脱离了整体稳态和内分泌调控,在投药的准确性和结果定量上均显示出其优越性。但其方法的建立和认可过程精细繁杂,近年国际上虽然开展了大量研究,但真正成熟的替代方法并不多。本研究对目前毒理学替代方法进行概述,并应用毒理学替代方法对DCK系列化合物的早期毒性进行评价,主要包括对其一般毒性和特殊毒性的筛选与检测。方法DCK(3′,4′-di-9-o-(-)-camphanoyl-( )-cis-khellactone,DCK)系列化合物是本所研发的一类具有三环香豆素骨架结构,起源于天然植物产物suksdorfin,能有效抑制HIV-1型病毒DNA-DNA双链的合成,且与其他药物有良好的协同作用,对耐药性病毒株有较好的抑制作用,具有良好的开发前景。本次研究采用MTT法观察化合物对CHL细胞的毒性作用,并利用细胞毒性IC50值对急性毒性LD50值进行预测;上下法检测其对小鼠的急性毒性;Ames波动试验、体外微核试验及胚胎中脑和肢芽细胞微团法检测其遗传毒性和致畸性。结果DCK(554、426、2016)系列化合物对CHL细胞的半数抑制剂量(IC50)分别为0.43、0.49和0.18mg/ml。急性毒性LD50的预测值分别为2093.6、2041.2和1316.4mg/kg。对小鼠的急性毒性LD50实测值均大于2000mg/kg。提示体外细胞毒性数据对化学物质的体内急性毒性具有良好的预测性。无论有无S9的代谢活化,3种新化学物质均未显示出遗传毒性。体外致畸性研究显示,3种化合物中,仅2016化合物能严重抑制胚胎中脑和肢芽细胞的分化,存在潜在的致畸性。对DCK系列化合物的药效学及毒理学结果进行综合分析,426毒性较低且对HIV具有较高的抑制活性。结论毒理学替代法从不同的毒性终点对新化学实体进行比较和筛选,在药物早期毒性评价中具有重要的作用,细胞毒性数据对化学物质的体内急性毒性具有良好的预测性。     

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。     

新药研发过程中的毒理学

目前在已形成体系的药物毒理学研究包括有发现毒理学、一般毒理学、安全性药理学、毒性病理学、生殖与发育毒理学、遗传毒理学、毒代动力学、临床病理学等。药物毒理学与药理学其实并没有本质的差别,都是关注药物在体内的药动学与药效动力学过程,只不过毒理学观察的范围更广泛,包括药物对各个系统的影响,大剂量药物对人体的影响等。然而在药物的发现阶段必须要建立短期高效毒性优化筛选系统,包括体内、体外毒性筛选,一般毒性筛选和特殊毒性筛选,涵盖原核和真核毒性筛选系统。通过早期毒性优化筛选,筛选出更合适研发的化合物,提高候选药物的质量,减少药物开发循环的时间;通过对(基因表达、蛋白质、代谢产物)数据系统性分析,建立更加适合于毒性预测的动物模型;选择更精确的剂量和确定安全域MOS(margin of safety),为新药研发中毒理学的检测提供可靠坚实依据。     

高通量分析药物代谢和毒性的研究进展

候选药物的不良反应往往是在新药研发的临床前或临床研究时才被发现,使得大量的候选药物在研究后期遭到淘汰,这不仅耗费大量的经费,而且大大降低了新药研发的产率。因此,目前非常需要发展能够在新药研发早期对候选药物的代谢和毒性进行有效预测的新技术,尤其是在最初的新药筛选和先导化合物优化阶段。虽然目前在新药研发的大部分阶段都已经出现高通量筛选技术,但是将这些技术转化成可以准确模拟候选药物在人体内的代谢以及预测候选药物或代谢物的毒性还是相当困难的。然而,近几年许多科学家在这方面也取得了一些令人鼓舞的最新成果,这些研究成果将有可能在新药研发中得到广泛的应用。     

Z24系列化合物遗传毒性的优化筛选

目的：对Z24系列化合物进行遗传毒性优化筛选,从中选出毒性较低的候选新药作进一步开发.方法：采用Ames波动试验,SOS显色试验和双核细胞微核试验比较5种Z24系列化合物（Z24,SU5416,L1,L3和L4）的遗传毒性.结果：Ames波动试验结果表明除Z24外,其他4种化合物均显示致突变性;SOS显色试验则表明5种化合物均无致DNA原发损伤作用;双核细胞微核试验显示SU5416,L1,L3和L4具有致染色体断裂效应.结论：Z24是该系列化合物中最具开发前景的候选新药.     

计算毒理学与中药毒性预测的研究进展

计算毒理学近几年受到美国及欧盟相关立法及研究机构的重视,被越来越多地应用于新药毒性预测及环境化合物的安全评价。化合物毒性预测方法可分为两大类:一类是以化合物本身为基础的计算方法,主要是研究结构与毒性的定量关系;另一类是以毒性靶分子结构为基础的方法,又被称为分子机理法。我国在环境化合物的毒性预测、算法及建立构效模型上取得进展,将计算毒理学应用于新药研发已经起步,但尚未见到计算毒理学用于中药及其化合物毒性的研究。而国外在天然化学成分的毒性预测、结构毒性关系的研究上取得了一些进展。由于中药化学成分与人工合成化合物在化学空间的差别,同时中药是多组分的混合物,毒性预测有较大的挑战性。随着组学技术被更多地应用于化合物毒性的研究,计算毒理学在中药毒性研究中的应用也有新的机遇。     

药物毒理学研究中体外替代试验研究现状及展望

药物的安全性和有效性是药物研发成功的决定因素,而药物毒性是终止药物研发的关键因素之一。相关监管指南和指导原则为利用动物进行毒理学研究及生物测试或其他相关试验制定了基本标准。动物体外替代试验不仅遵守了国际上提倡的“3R原则”,也符合毒理学学科发展、社会经济发展及新药研发的要求。动物体外替代试验已成为21世纪毒性测试的重要方向,毒性测试的重点将集中在敏感性终点的选择与评价、细胞-反应网络、高通量与中通量筛选方法的构建及应用、作用机制及作用模式、毒性通路以及系统生物学效应等方面,并且已获得药物研发领域广泛的支持和监管部门的认可,具有广阔的发展前景和重要的应用价值。     

Genetic toxicity assessment: employing the best science for human safety evaluation part IV: a strategy in genotoxicity testing in drug development: some examples.

The minimal three-test battery of the International Conference on Harmonization guideline has been in use since 1997 for the development of new pharmaceuticals (ICH, 1997). After a 10-year experience of this core battery in regulatory genotoxicity testing, everywhere the time has come for reflection about what was learned from this experience. Different aspects of genotoxicity testing are currently being debated under different organizations (HESI, 2006; IWGT, 2007; Kirkland et al., 2007). The main concerns are to develop relevant strategies and adequate complementary tests to the minimal battery, appropriate for each specific case to assess risk for humans when in vitro positive results or findings in rodent bioassays for carcinogenicity are found. In this article, an example of an in-house decision tree is shown, with some options which can contribute to the current reflections. Additionally, tools built for early genotoxicity are presented.     

体内彗星试验在药物遗传毒性评价中的研究方法

体内彗星试验是采用单细胞凝胶电泳的方法检测体内DNA损伤的技术。具有灵敏度高、操作简便、经济快速等优点。随着遗传毒性研究的发展,体内彗星试验已经成为重要的药物遗传毒性评价方法。对动物试验阶段和彗星试验阶段各操作步骤进行了归纳总结,以期对相关方法学建立提供参考,并提出采用简化和标准化的研究方法将有利于体内彗星试验在药物遗传毒性评价的应用。     

体内Pig-a基因突变试验方法的开发

体内基因突变是遗传毒理试验中非常重要的检测终点。国际人用药物注册技术协调会议（ICH）新版遗传毒性指导原则的出台,对体内遗传毒性检测方法的发展提出了更高的要求。新的检测体细胞突变的体内实验方法即磷脂酰肌醇聚糖A（Pig-a）基因突变试验,有望成为一项新药遗传毒性评价的标准试验。本文简要综述Pig-a体内基因突变试验的特点及其在新品种开发遗传毒性检测中的应用。     

In vitro and in vivo genotoxic evaluation of Bothrops moojeni snake venom

Abstract

Context: Bothrops moojeni Hoge (Viperidae) venom is a complex mixture of compounds with therapeutic potential that has been included in the research and development of new drugs. Along with the biological activity, the pharmaceutical applicability of this venom depends on its toxicological profile.

Objective: This study evaluates the cytotoxicity and genotoxicity of the Bothrops moojeni venom (BMV).

Material and methods: The in vitro cytotoxicity and genotoxicity of a pooled sample of BMV was assessed by the MTT and Comet assay, respectively. Genotoxicity was also evaluated in vivo through the micronucleus assay.

Results: BMV displayed a 50% cytotoxic concentration (CC₅₀) on Vero cells of 4.09?µg/mL. Vero cells treated with 4?µg/mL for 90?min and 6?h presented significant (p?<?0.05, ANOVA/Newman–Keuls test) higher DNA damage than the negative control in the Comet assay. The lower DNA damage found after 6?h compared with the 90?min treatment suggests a DNA repair effect. Mice intraperitoneally treated with BMV at 10, 30, or 80?µg/animal presented significant genotoxicity (p?<?0.05, ANOVA/Newman–Keuls test) in relation to the negative control after 24?h of treatment. Contrary to the in vitro results, no DNA repair seemed to occur in vivo up to 96?h post-venom inoculation at a dose of 30?µg/animal.

Discussion and conclusion: The results show that BMV presents cyto- and genotoxicity depending on the concentration/dose used. These findings emphasize the importance of toxicological studies, including assessment of genotoxicity, in the biological activity research of BMV and/or in the development of BMV-derived products.     

How accurate is in vitro prediction of carcinogenicity?

Positive genetic toxicity data suggest carcinogenic hazard, and this can stop a candidate pharmaceutical reaching the clinic. However, during the last decade, it has become clear that many non-carcinogens produce misleading positive results in one or other of the regulatory genotoxicity assays. These doubtful conclusions cost a lot of time and money, as they trigger additional testing of apparently genotoxic candidates, both in vitro and in animals, to discover whether the suggested hazard is genuine. This in turn means that clinical trials can be put on hold. This review describes the current approaches to the 'misleading positive' problem as well as efforts to reduce the use of animals in genotoxicity assessment. The following issues are then addressed: the application of genotoxicity testing screens earlier in development; the search for new or improved in vitro genotoxicity tests; proposed changes to the International Committee on Harmonisation guidance on genotoxicity testing [S2(R1)]. Together, developments in all these areas offer good prospects of a more rapid and cost-effective way to understand genetic toxicity concerns.     

Genetic toxicity assessment: employing the best science for human safety evaluation part III: the comet assay as an alternative to in vitro clastogenicity tests for early drug candidate selection.

Early screening of drug candidates for genotoxicity typically includes an analysis for mutagenicity in bacteria and for clastogenicity in cultured mammalian cells. In addition, in recent years, an early assessment of photogenotoxicity potential has become increasingly important. Also, for screening purposes, expert computer systems can be used to identify structural alerts. In cases where structural alerts are identified, mutagenicity testing limited to bacteria can be conducted. The sequence of computer-aided analysis and limited testing using bacteria allows for screening a comparatively large number of drug candidates. In contrast, considerably more resources, in terms of supplies, technical time, and the amount of a test substance needed, are required when screening for clastogenic activity in mammalian cells. In addition, the relatively large percentage of false positive results for rodent carcinogenicity associated with clastogenicity assays is of considerable concern. As a consequence, mammalian cell-based alternatives to clastogenicity assays are needed for early screening of mammalian genotoxicity. The comet assay is a relatively fast, simple, and sensitive technique for the analysis of DNA damage in mammalian cells. This assay seems especially useful for screening purposes because false positives associated with excessive toxicity appear to occur less frequently, only relatively small amounts of a test compound are needed, and certain steps of the test procedure can be automated. Therefore, the in vitro comet assay is proposed as an alternative to cytogenetic assays in early genotoxicity/photogenotoxicity screening of drug candidates.     

Genetic toxicity assessment using liver cell models: past,present, and future

ABSTRACT

Genotoxic compounds may be detoxified to non-genotoxic metabolites while many pro-carcinogens require metabolic activation to exert their genotoxicity in vivo. Standard genotoxicity assays were developed and utilized for risk assessment for over 40 years. Most of these assays are conducted in metabolically incompetent rodent or human cell lines. Deficient in normal metabolism and relying on exogenous metabolic activation systems, the current in vitro genotoxicity assays often have yielded high false positive rates, which trigger unnecessary and costly in vivo studies. Metabolically active cells such as hepatocytes have been recognized as a promising cell model in predicting genotoxicity of carcinogens in vivo. In recent years, significant advances in tissue culture and biological technologies provided new opportunities for using hepatocytes in genetic toxicology. This review encompasses published studies (both in vitro and in vivo) using hepatocytes for genotoxicity assessment. Findings from both standard and newly developed genotoxicity assays are summarized. Various liver cell models used for genotoxicity assessment are described, including the potential application of advanced liver cell models such as 3D spheroids, organoids, and engineered hepatocytes. An integrated strategy, that includes the use of human-based cells with enhanced biological relevance and throughput, and applying the quantitative analysis of data, may provide an approach for future genotoxicity risk assessment.     

Role of surface charge and oxidative stress in cytotoxicity and genotoxicity of graphene oxide towards human lung fibroblast cells

Recently, attempts have been made to apply graphene oxide (GO) in the field of biology and medicine, such as DNA sensing and drug delivery with some necessary modifications. Therefore, the toxicity of GO must be evaluated before it is applied further in biomedicine. In this paper, the cytotoxicity and genotoxicity of GO to human lung fibroblast (HLF) cells have been assessed with methyl thiazolyl tetrazolium (MTT), sub‐G1 measurement and comet assays, and the mechanism of its toxicity has been explored. Various modifications of GO have been made to help us determine the factors which could affect the toxicity of GO. The results indicated that cytotoxicity and genotoxicity of GO to HLF cells were concentration dependent, and the genotoxicity induced by GO was more severe than the cytotoxicity to HLF cells. Oxidative stress mediated by GO might explain the reason of its toxic effect. Furthermore, the electronic charge on the surface of GO would play a very important role in the toxicity of GO to HLF cells. Copyright © 2013 John Wiley & Sons, Ltd.     

Genetic toxicity assessment: employing the best science for human safety evaluation. Part II: Performances of the in vitro micronucleus test compared to the mouse lymphoma assay and the in vitro chromosome aberration assay.

The in vitro micronucleus test is commonly used in the early stages of pharmaceutical development as a predictive tool for the regulatory mouse lymphoma assay or in vitro chromosome aberration test. The accumulated data from this assay leads to the suggestion that it could be used as an alternative to the chromosome aberration test or the mouse lymphoma assay in the regulatory genotoxicity battery. In this paper, we present the results of the in vitro micronucleus test on L5178Y mouse lymphoma cells with 25 compounds from Servier research and have compared these results to those obtained in the genotoxicity regulatory battery. All the negative compounds were also negative in the in vitro micronucleus assay. Among the 14 positive compounds, two of them, positive in the mouse lymphoma assay, were found negative in the in vitro micronucleus test. However, this apparent discordance was likely to be due to cytotoxicity- or high concentration-related false positive responses in the mouse lymphoma assay. In addition, we confirmed that the in vitro micronucleus assay is useful for detecting aneugens, especially, when cells in metaphasis and multinucleated cells are also scored and when cells are allowed to recover after the long treatment. On this series of compounds, the in vitro micronucleus assay showed high sensitivity and possibly a better specificity than the mouse lymphoma assay. Thus, the in vitro micronucleus assay was shown to be at least as adequate as the mouse lymphoma assay or the in vitro chromosome aberration test to be used in the standard genotoxicity battery.     

Curcumin attenuates quinocetone-induced oxidative stress and genotoxicity in human hepatocyte L02 cells

Abstract

Quinocetone (QCT), a new quinoxaline 1,4-dioxides, has been used as antimicrobial feed additive in China. Potential genotoxicity of QCT was concerned as a public health problem. This study aimed to investigate the protective effect of curcumin on QCT-induced oxidative stress and genotoxicity in human hepatocyte L02 cells. Cell viability and intracellular reactive oxygen species (ROS), biomarkers of oxidative stress including superoxide dismutase (SOD) activity and glutathione (GSH) level were measured. Meanwhile, comet assay and micronucleus assay were carried out to evaluate genotoxicity. The results showed that, compared to the control group, QCT at the concentration ranges of 2–16?μg/mL significantly decreased L02 cell viability, which was significantly attenuated with curcumin pretreatment (2.5 and 5?μM). In addition, QCT significantly increased cell oxidative stress, characterized by increases of intracellular ROS level, while decreased endogenous antioxidant biomarkers GSH level and SOD activity (all p?<?0.05 or 0.01). Curcumin pretreatment significantly attenuated ROS formation, inhibited the decreases of SOD activity and GSH level. Furthermore, curcumin significantly reduced QCT-induced DNA fragments and micronuclei formation. These data suggest that curcumin could attenuate QCT-induced cytotoxicity and genotoxicity in L02 cells, which may be attributed to ROS scavenging and anti-oxidative ability of curcumin. Importantly, consumption of curcumin may be a plausible way to prevent quinoxaline 1,4-dioxides-mediated oxidative stress and genotoxicity in human or animals.