(Q)SAR genotoxicity evaluation and GC-MS/MS determination of three process impurities in pretomanid,an antibacterial agent
Objective To evaluate the genotoxicity of three process impurities involved in various synthetic routes of pretomanid,a new antimycobacterial drug,and to establish the quantitative method of these three impurities,namely(S)-tert-butyldimethyl(oxiran-2-ylmethoxy)silane(impurity Ⅰ),(S)-oxiran-2-ylmethyl butyrate(impurity Ⅱ),and 1-(bromomethyl)-4-(trifluoro methoxy)benzene(impurity Ⅲ).Methods Two complementary(quantitative)structure-activity relationship[(Q)SAR]evaluation models(Derek and Sarah)based on expert rules and statistics,respectively,were employed to assess and classify the genotoxicity of the three process impurities in pretomanid,and a GC-MS/MS method with the time-segmented multiple reaction monitoring(MRM)mode was subsequently developed for the simultaneous determination of the three impurities.The fragmentation patterns of the three impurities in El source were also discussed in this study.Results The Derek evaluation results were all positive for impurities Ⅰ and Ⅲ,while the Sarah results were equivocal and negative,respectively,indicating impurities Ⅰ and Ⅲ were categorized as class 3 as per ICH M7 guideline.Impurity Ⅱ was regarded as a confirmed mutagenic impurity of class 2 since Sarah showed specific positive results in Ames test.The threshold of toxicological concern(TTC)was applied to control these three impurities.The developed GC-MS/MS method was validated and showed effective resolutions between the impurities with good linearity.The LOQ values of the three impurities were all as low as 15％of the acceptable limit.The average recoveries(n=9)were 105.5％,104.4％,and 108.5％,while the repeatabilities RSD(n=6)were 2.2％,5.8％,and 2.2％,respectively.Impurity Ⅲ was detected in all batches.Conclusion The established method is easy to operate and proved selective and sensitive,which is applicable for quality control of the three potential genotoxic impurities in pretomanid.This study can also be referenced for the quality control of impurity Ⅱ in other oxazolidinone antibacterial drugs like linezolid,cadazolid,and tedizolid,as impurity Ⅱ was the common impurity.
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