Identification and Determination of Impurities in a New Therapeutic Agent for Fatty Liver Disease

Methyl 7,7'-dimethoxy-5'-(morpholinomethyl)-[4,4'-bibenzo[d][1,3] dioxole]-5-carboxylate methanesulfonate (IMM) is an innovative drug for the treatment of nonalcoholic fatty liver disease (NAFLD) owing to its high efficacy and low toxicity. In this study, five minor impurities (I, II, III, IV, and V) were identified and analyzed using spectroscopic evidence, chemical synthetic methods, and liquid chromatography-tandem mass spectrometry (LC-MS/MS). The impurities included hydrolysates and oxidation by-products extracted from both the drug in its final formulation and during synthesis. Toxicity prediction revealed potential carcinogenicity of impurity V containing an N-oxygen fragment. A reliable and selective HPLC method for the quantitative analysis of impurities I-IV and a sensitive HPLC-MS/MS method for potential genotoxic impurity V were developed and optimized. The methods were validated based on the International Council for Harmonization guidelines. Satisfactory linearity was obtained for the analytes over the range of 0.1-2.0 μg/mL for impurities I-IV and 0.3-30.0 ng/mL for impurity V, and in all cases, the fitting correlation coefficients exceeded 0.999. The obtained limits of detection values were 0.05 ng/mL and 0.005 μg/mL for impurity V and impurities I-IV, respectively. The precision and repeatability of the methods were less than 1.08% and 8.72% for each impurity. The recovery percentages of all impurities were in the range of 91.18%-111.27%, with the relative standard deviation of less than 3.69%. The greenness assessment of the HPLC method and the HPLC-MS/MS method were evaluated by using AGREE software with a score value of 0.72 and 0.68, respectively. The recommended procedures that were accurate, specific, and ecofriendly were applied to the existing active pharmaceutical ingredients of IMM, and they generated satisfactory results.