Validated HPLC-UV method for quantification of paxalisib, a pan PI3K and mTOR inhibitor in mouse plasma: Application to a pharmacokinetic study in mice.

Paxalisib is a pan-PI3K and mTOR inhibitor, currently entering into Phase II clinical trials as a potential drug to treat glioblastoma patients. We report the development and validation of a high-performance liquid chromatography (HPLC) method for the quantitation of paxalisib in mouse plasma as per the US Food and Drug Administration regulatory guidelines. From the mouse plasma, paxalisib and the internal standard (IS; filgotinib) were extracted using ethyl acetate as an extraction solvent. The chromatographic separation of paxalisib and the IS was accomplished on a Symmetry C 18 (250 × 4.6 mm, 5.0 μm) column maintained at 40°C using 10 mm ammonium formate and acetonitrile in gradient conditions at a 0.8 ml/min flow-rate. The injection volume was 20 μl. The elution was monitored using a photo-diode array detector set at λ max 280 nm. Paxalisib and the IS eluted at 6.5 and 5.9 min, respectively with a total run time of 10 min. The calibration curve was linear over the range of 111-4,989 ng/ml. Inter- and intraday precision and accuracy, stability studies, dilution integrity and incurred sample reanalysis were investigated and the results met the acceptance criteria. The validated HPLC method was extended to assess the pharmacokinetic parameters of paxalisib in mice.