Development and validation of the method of quantification of 5-[5-(trifluoromethyl)-1,2-oxazole-3-yl]-furan-2-sulfonamide and its metabolites in laboratory animal plasma

Introduction. The study of the systemic exposure of a new original drug is an essential part of its preclinical study. 5-[5-(trifluoromethyl)-1,2-oxazole-3-yl]-furan-2-sulfonamide is a new selective carbonic anhydrase II inhibitor for the treatment of open-angle glaucoma. Methods for the quantitative determination of this compound and its N-hydroxy- and N-acetyl metabolites in the plasma of laboratory animals have not been previously developed.Aim. Development and validation of a method of quantitative determination of 5-[5-(trifluoromethyl)-1,2-oxazole-3-yl]-furan-2-sulfonamide and its metabolites N-hydroxy-5-[5-(trifluoromethyl)-1,2-oxazole-3-yl]-furan-2-sulfonamide (M1) and N-acetyl-5-[5-(trifluoromethyl)-1,2-oxazole-3-yl]-furan-2-sulfonamide (M2) in rat and rabbit blood plasma by HPLC-MS/MS.Materials and methods. Protein precipitation by methanol was applied for sample preparation. 5-[2-(morpholine-4-carbonyl)-1,3-oxazole-5-yl]-thiophene-2-sulfonamide was used as an internal standard. A 5 % aqueous solution of ascorbic acid was added to the plasma samples at volume ratio 1 : 2 to prevent decomposition of N-hydroxy-5-[5-(trifluoromethyl)-1,2-oxazole-3-yl]-furan-2-sulfonamide. The combination of sodium fluoride and potassium oxalate was selected as an anticoagulant. Chromatographic separation was performed on Zorbax Eclipse Plus C18 column (150 × 3.0 mm, 3.5 µm) with Zorbax Eclipse Plus C18 pre-column (12.5 × 2.1 mm, 5.0 µm) using a mobile phase based on a 0.1 % aqueous solution of formic acid and methanol. Mass spectrometric detection was carried out in the MRM mode using electrospray ionization in negative polarity. The method was tested during a pharmacokinetic study of a 1 % ocular suspension of 5-[5-(trifluoromethyl)-1,2-oxazole-3-yl]-furan-2-sulfonamide on 6 Wistar rats. Blood samples were collected before administration, as well as 30 min, 1 h, 1 h 30 min, 2 h, 3 h, 4 h, 6 h, 8 h, 12 h, 24 h, 48 h, 72 h, 144 h, 216 h after administration. The non-compartment approach was used for calculation pharmacokinetic parameters.Results and discussion. The developed method has been validated in parameters of selectivity, calibration curve, accuracy and precision, matrix effect, dilution integrity, carry over, reinjection reproducibility, stability. The analytical range of determination of 5-[5-(trifluoromethyl)-1,2-oxazole-3-yl]-furan-2-sulfonamide in plasma was 10–4000 ng/ml, M1 – 1.0–400.0 ng/ml, M2 – 0.1–40.0 ng/ml. The selected combination of anticoagulant and stabilizer solution allows storage of plasma samples in freezing chamber for 28 days.Conclusion. The developed method has been fully validated and confirmed its suitability for quantitative determination of 5-[5-(trifluoromethyl)-1,2-oxazole-3-yl]-furan-2-sulfonamide and its metabolites in the blood plasma of laboratory animals. The method has been successfully used for pharmacokinetic study of 1 % ocular suspension of the drug.