Coffing Stephanie L, Kenyon Michelle O, Ackerman Joel I, Shutsky Thomas J, Dobo Krista L
Pfizer Worldwide Research and Development, Genetic Toxicology, Groton, Connecticut.
Environ Mol Mutagen. 2015 Apr;56(3):322-32. doi: 10.1002/em.21910. Epub 2014 Sep 17.
Understanding the mutagenic dose response could prove beneficial in the management of pharmaceutically relevant impurities. For most alkyl ester impurities, such as isopropyl methanesulfonate (IPMS), little in vivo mutagenicity data exist for dose analysis. The likelihood of a sublinear dose response for IPMS was assessed by comparing the Swain Scott constant, the SN 1/SN 2 reaction mechanism and the O(6) :N(7) guanine adduct ratio to that of more well-known alkyl esters. Based on available information, IPMS was predicted to have a mutagenic profile most like ethyl nitrosourea. To test this hypothesis, mature male Wistar Han rats were administered IPMS using acute (single administration at 3.5 to 56 mg/kg) or subchronic (28 days at 0.125 to 2 mg/kg/day) exposures. The in vivo Pig-a mutation assay was used to identify mutant phenotype reticulocyte (Ret) and red blood cell (RBC) populations. The maximum mutant response occurred approximately 15 and 28 days after the last dose administration in the mutant Ret and RBC populations respectively in the acute study and on Day 29 and 56 in the mutant Ret and RBC populations, respectively, in the subchronic study. A comparison of RBC mutant frequencies from acute and subchronic protocols suggests a sublinear response; however, this was not substantiated by statistical analysis. A No Observed Effect Level (NOEL) of 0.25 mg/kg/day resulted in a Permitted Daily Exposure equivalent to the Threshold of Toxicological Concern. An estimate of the NOEL based on the previously mentioned factors, in practice, would have pre-empted further investigation of the potent mutagen IPMS.
了解诱变剂量反应可能有助于管理与药物相关的杂质。对于大多数烷基酯杂质，如甲磺酸异丙酯（IPMS），几乎没有体内诱变数据可用于剂量分析。通过比较Swain Scott常数、SN1/SN2反应机制以及O(6):N(7)鸟嘌呤加合物比率与更知名的烷基酯，评估了IPMS亚线性剂量反应的可能性。根据现有信息，预计IPMS的诱变特征最类似于乙基亚硝基脲。为了验证这一假设，对成年雄性Wistar Han大鼠进行急性（单次给药3.5至56 mg/kg）或亚慢性（0.125至2 mg/kg/天，共28天）暴露的IPMS给药。体内Pig-a突变试验用于鉴定突变表型网织红细胞（Ret）和红细胞（RBC）群体。在急性研究中，最大突变反应分别在最后一次给药后约15天和28天出现在突变Ret和RBC群体中；在亚慢性研究中，分别在第29天和56天出现在突变Ret和RBC群体中。急性和亚慢性实验方案中RBC突变频率的比较表明存在亚线性反应；然而，这一点未得到统计分析的证实。0.25 mg/kg/天的未观察到效应水平导致的每日允许暴露量相当于毒理学关注阈值。实际上，根据上述因素对未观察到效应水平的估计本可以预先阻止对强效诱变剂IPMS的进一步研究。
