Development and Validation of an HPLC-MS/MS Method for Determining I-BET151 in Rat Plasma and Its application to Pharmacokinetic Studies.

A bromodomain and extra-terminal domain inhibitor (I-BET151) is effective in treating chronic graft-versus-host disease and has been extensively studied in recent years. However, there is limited research on the pharmacokinetics of I-BET151, especially the lack of methods for determining the concentration of I-BET151 in vivo. Therefore, the purpose of this study is to establish an HPLC-MS/MS method for determining the plasma concentration of I-BET151 and use it for pharmacokinetic study in rats. The chromatographic column is a Poroshell 120EC-C18 column (50 mm × 4.6 mm, 2.7 μm). The mobile phase consists of water containing 20 mmol ammonium acetate and 0.1% formic acid, and methanol containing 0.1% formic acid, with a flow rate of 0.6 mL/min. The extraction of I-BET151 is liquid-liquid extraction, and the extraction solvent is ether:dichloromethane=2:3. The HPLC-MS/MS method was validated based on the guidelines of quantitative methods for biological samples in the Chinese Pharmacopoeia, including specificity, standard curve, lower limit of quantification, residual effects, precision, recovery rate, matrix effects, stability, etc. The results showed that the established method met the requirements of methodological validation standards and could be used for pharmacokinetic studies of I-BET151. The pharmacokinetic results displayed that the half-life of oral and intravenous administration of I-BET151 was 4.3 h and 3.1 h, respectively. The oral bioavailability was about 60%, indicating that I-BET151 had a high oral bioavailability and appropriate half-life, demonstrating good clinical application prospects.