Discovery and druggability evaluation of pyrrolamide-type GyrB/ParE inhibitor against drug-resistant bacterial infection.

The bacterial ATP-competitive GyrB/ParE subunits of type II topoisomerase are important anti-bacterial targets to treat super drug-resistant bacterial infections. Herein we discovered novel pyrrolamide-type GyrB/ParE inhibitors based on the structural modifications of the candidate AZD5099 that was withdrawn from the clinical trials due to safety liabilities such as mitochondrial toxicity. The hydroxyisopropyl pyridazine compound 28 had a significant inhibitory effect on Gyrase (GyrB, IC50 = 49 nmol/L) and a modest inhibitory effect on Topo IV (ParE, IC50 = 1.513 µmol/L) of Staphylococcus aureus. It also had significant antibacterial activities on susceptible and resistant Gram-positive bacteria with a minimum inhibitory concentration (MIC) of less than 0.03 µg/mL, which showed a time-dependent bactericidal effect and low frequencies of spontaneous resistance against S. aureus. Compound 28 had better protective effects than the positive control drugs such as DS-2969 (5) and AZD5099 (6) in mouse models of sepsis induced by methicillin-resistant Staphylococcus aureus (MRSA) infection. It also showed better bactericidal activities than clinically used vancomycin in the mouse thigh MRSA infection models. Moreover, compound 28 has much lower mitochondrial toxicity than AZD5099 (6) as well as excellent therapeutic indexes and pharmacokinetic properties. At present, compound 28 has been evaluated as a pre-clinical drug candidate for the treatment of drug-resistant Gram-positive bacterial infection. On the other hand, compound 28 also has good inhibitory activities against stubborn Gram-negative bacteria such as Escherichia coli (MIC = 1 µg/mL), which is comparable with the most potent pyrrolamide-type GyrB/ParE inhibitors reported recently. In addition, the structure-activity relationships of the compounds were also studied.

Assessment of the Purity of IMM-H014 and Its Related Substances for the Treatment of Metabolic-Associated Fatty Liver Disease Using Quantitative Nuclear Magnetic Resonance Spectroscopy.

An accurate, rapid, and selective quantitative nuclear magnetic resonance method was developed and validated to assess the purity of IMM-H014, a novel drug for the treatment of metabolic-associated fatty liver disease (MAFLD), and four related substances (impurities I, II, III, and IV). In this study, we obtained spectra of IMM--H014 and related substances in deuterated chloroform using dimethyl terephthalate (DMT) as the internal standard reference. Quantification was performed using the 1H resonance signals at δ 8.13 ppm for DMT and δ 6.5-7.5 ppm for IMM-H014 and its related substances. Several key experimental parameters were investigated and optimized, such as pulse angle and relaxation delay. Methodology validation was conducted based on the International Council for Harmonization guidelines and verified with satisfactory specificity, precision, linearity, accuracy, robustness, and stability. In addition, the calibration results of the samples were consistent with those obtained from the mass balance method. Thus, this research provides a reliable and practical protocol for purity analysis of IMM-H014 and its critical impurities and contributes to subsequent clinical quality control research.

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.

Determination of Methyl Methanesulfonate and Ethyl Methylsulfonate in New Drug for the Treatment of Fatty Liver Using Derivatization Followed by High-Performance Liquid Chromatography with Ultraviolet Detection.

A new derivatization high-performance liquid chromatography method with ultraviolet detection was developed and validated for the quantitative analysis of methanesulfonate genotoxic impurities in an innovative drug for the treatment of non-alcoholic fatty liver disease. In this study, sodium dibenzyldithiocarbamate was used as a derivatization reagent for the first time to enhance the sensitivity of the analysis, and NaOH aqueous solution was chosen as a pH regulator to avoid the interference of the drug matrix. Several key experimental parameters of the derivatization reaction were investigated and optimized. In addition, specificity, linearity, precision, stability, and accuracy were validated. The determined results of the samples were consistent with those obtained from the derivatization gas chromatography-mass spectrometry analysis. Thus, the proposed method is a reliable and practical protocol for the determination of trace methanesulfonate genotoxic impurities in drugs containing mesylate groups.