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发表于 2015-10-10 09:31:06
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The toxicological assessment of genotoxic impurities and the determination of acceptable limits for such impurities in active substances is a difficult issue and not addressed in sufficient detail in the existing ICH Q3X guidances. The data set usually available for genotoxic impurities is quite variable and is the main factor that dictates the process used for the assessment of acceptable limits. In the absence of data usually needed for the application of one of the established risk assessment methods, i.e. data from carcinogenicity long-term studies or data providing evidence for a threshold mechanism of genotoxicity, implementation of a generally applicable approach as defined by the Threshold of Toxicological Concern (TTC) is proposed. A TTC value of 1.5 μg/day intake of a genotoxic impurity is considered to be associated with an acceptable risk (excess cancer risk of <1 in 100,000 over a lifetime) for most pharmaceuticals. From this threshold value, a permitted level in the active substance can be calculated based on the expected daily dose. Higher limits may be justified under certain conditions such as short-term exposure periods.
基因毒性杂质的毒理学评估和这些杂质在活性药物中的可接受标准的测定是一件困难的事情,并且在现有的ICH Q3X指南中也没有详细的规定。现有的关于基因毒性杂质的相关数据是容易变化的,也是对杂质可接受标准如何进行评价的主要影响因素。如果缺少风险评估方法所需要的数据,比如,致癌作用的长期研究数据,或为基因毒性的阀值提供证据的数据,一般建议使用一般通用的被定义为 Threshold of Toxicological Concern (TTC)的方法。一个“1.5ug/day”的TTC值,即相当于每天摄入1.5ug的基因毒性杂质,被认为对于大多数药品来说是可以接受的风险(一生中致癌的风险小于100000分之1)。按照这个阀值,可以根据这个预期的每日摄入量计算出活性药物中可接受的杂质水平。较高的临界值可以在特定的条件下,如短期暴露周期等,进行推算。 |
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