title: Regulated bioanalysis of conformers - A case study with ASP2151 in dog plasma and urine.
abstract: We developed and validated bioanalytical methods for a potent helicase-primase inhibitor ASP2151 that has two conformers. These conformers elute as unseparated broad peaks under ordinary high-performance liquid chromatographic conditions, indicating discernable differences in hydrophobicity. We observed that column temperature and mobile phase pH have no effect on these peaks and that conformers form a single symmetrical peak when tetrahydrofuran is added to the mobile phase. In addition, we needed to develop semi-automated methods where inter-conversion of the conformers is unlikely to cause sample-to-sample extraction variability. Briefly, following the addition of deuterium-labeled ASP2151 as an internal standard (IS), dog plasma samples or acetonitrile-added urine samples were filtrated. The filtrates were then injected into a column-switching liquid chromatography-tandem mass spectrometry (LC-MS/MS) system and trapped onto an extraction column. Extracts were back-flushed onto an analytical C18 column (4.6×50mm, 3μm) with a mobile phase consisting of methanol, tetrahydrofuran, and 20mmol/L ammonium acetate (45:5:50, v/v/v). The eluent was monitored in the negative atmospheric pressure chemical ionization mode. The calibration curve was linear over a range of 5-1000ng/mL for plasma and 0.5-100μg/mL for urine. Validation data met the acceptance criteria in accordance with regulatory guidance and demonstrated that these methods were selective, accurate, and reproducible. In addition, the present methods were successfully applied to a pharmacokinetic study in dogs.
authors.affiliation: Analysis & Pharmacokinetics Research Laboratories, Astellas Pharma Inc., Osaka, Japan. Electronic address: yoshiaki.ohtsu@zoho.com.
authors.forename: Yoshiaki
authors.initials: Y
authors.lastname: Ohtsu
authors.affiliation: Pharmacokinetics and Bioanalysis Center, Shin Nippon Biomedical Laboratories, Ltd., Kainan, Japan.
authors.forename: Shohei
authors.initials: S
authors.lastname: Otsuka
authors.affiliation: Pharmacokinetics and Bioanalysis Center, Shin Nippon Biomedical Laboratories, Ltd., Kainan, Japan.
authors.forename: Takeshi
authors.initials: T
authors.lastname: Nakamura
authors.affiliation: Analysis & Pharmacokinetics Research Laboratories, Astellas Pharma Inc., Osaka, Japan.
authors.forename: Kiyoshi
authors.initials: K
authors.lastname: Noguchi
mesh_terms: D000818:Animals; D002851:Chromatography, High Pressure Liquid / Q000379:methods*; D004285:Dogs; D016014:Linear Models; D010069:Oxadiazoles / Q000097:blood / Q000737:chemistry / Q000493:pharmacokinetics / Q000652:urine; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D053719:Tandem Mass Spectrometry / Q000379:methods*
chemical_list: C568714:ASP2151; D010069:Oxadiazoles
keywords: ASP2151; Column-switching; Conformer; LC–MS/MS; Plasma; Regulated bioanalysis