Development and validation of an UPLC-MS/MS method for quantitative analysis of OTX015 in human plasma samples

OTX015 is a novel synthetic thienodiazepine analog, which potently inhibits bromodomains (BRD) 2, 3 and 4 of the BET (bromodomain and extraterminal) protein family. It is currently undergoing phase I evaluation in patients with hematologic malignancies using an oral formulation. We developed and validated an Ultra Performance Liquid Chromatography method with tandem Mass Spectrometry detection (UPLC-MS/MS) for quantification of OTX015 in plasma in order to investigate its pharmacokinetics in humans, using small plasma samples (50 μL), and an internal standard, Y-401. Chromatographic separation was performed on a BEH C18 UPLC column with a mobile phase gradient at a flow rate of 0.5 mL min−1 for 5 minutes. Quantification was performed using the transition 492–383 (m/z) for OTX015 and 506–383 (m/z) for Y-401. The lower limit of quantification (LLOQ) was established as 1 ng mL−1 with 10.80% precision and 94.67% accuracy. The calibration curve was linear up to 250 ng mL−1 (upper limit of quantification). Intra-assay precision ranged from 7.3% to 11.6% for the three quality control (QC) concentrations evaluated and was 16.0% for the LLOQ, and intra-assay accuracy ranged from 93.7% to 109.8% for the three QC concentrations and was 92.0% for the LLOQ. Inter-assay precision and accuracy ranged from 4.1% to 14.0% and from 92.3% to 104.8%, respectively. These data show that the UPLC-MS/MS procedure is sensitive, accurate, precise and robust, and was validated for determining OTX015 concentrations in plasma. The method was successfully applied to determine the pharmacokinetic profile of OTX015 in patients treated in an ongoing phase I clinical study.