Development and Validation of a UHPLC–MS/MS Method for the Quantification of a Novel PYGB Inhibitor in Plasma: Application to Pharmacokinetic Studies

In previous studies, we reported compound 1 (5-chloro-N-(4-oxo-2,2-dipropyl-3,4-dihydro-2H-benzo[e][1,3]oxazin-6-yl)-1H-indole-2-carboxamide) as a novel PYGB inhibitor, and found that it had better anti-ischemic brain injury activity. In this study, we established and validated a novel UHPLC–MS/MS method for the quantitative determination of compound 1 in plasma, then applied the method to study the pharmacokinetic parameters and brain tissue distribution of compound 1 in SD (Sprague—Dawley) rats after intravenous administration. The experimental results showed that the method met the validation requirements set by the US FDA in terms of linearity, accuracy, precision, and stability. The validated method was then used for pharmacokinetic studies in rat plasma, and it was found that compound 1 exhibited linear pharmacokinetic characteristics when administered in the dose range of 0.8–3.2 mg/kg. Finally, we also conducted a brief preliminary investigation of the brain tissue distribution of compound 1 in rats after injection and found that the brain tissue concentrations at 0.25 h and 2 h of administration were 440 ± 19.1 ng/kg and 111 ± 23.9 ng/kg, respectively. Additionally, the C(Brain)/C(Plasma) ratio was 0.112 ± 0.0185 and 0.112 ± 0.0292, respectively. These results indicated that compound 1 was able to cross the blood–brain barrier. This study provides important support for the application of compound 1 in ischemic brain injury diseases.