A sensitive LC-MS/MS method for simultaneous quantification of ulotaront and its N-desmethyl metabolite in human...

Ulotaront (SEP-363856) is a novel non-D2-receptor-binding agent under development for the treatment of patients with schizophrenia. A highly sensitive liquid chromatography-tandem mass spectrometry (LC-MS/MS) method with lower limit of quantitation of 0.0200 ng/mL (i.e. 20.0 pg/mL) was successfully developed and validated for the simultaneous quantitation of ulotaront and its N-desmethyl metabolite (M11A) in human plasma. Plasma samples were extracted by solid phase extraction with Oasis MCX 96-well plate, followed by a reversed phase LC separation coupled with MS/MS detection in positive mode (m/z 184.1 → 135.0 for ulotaront and 170.1 → 135.0 for M11A). Stable isotope-labeled compounds SEP-363856-d₃ and M11A-d₄ were used as internal standards (IS) for corresponding analytes. The validated calibration curve range was 0.0200-20.0 ng/mL for both analytes using a 0.200 mL plasma. Extraction recoveries were found to be 75.7% and 75.1% for ulotaront and IS1, and 82.7% and 83.9% for M11A and IS2, respectively. Frozen plasma samples were confirmed to be stable for up to 730 days at both -20 °C and -70 °C. The validated method has been successfully used to evaluate the pharmacokinetics (PK) of ulotaront and M11A in clinical studies. The application to the first-in-human PK study (single ascending dose) presented in this work demonstrated that ulotaront exhibited near dose proportionality for both C_max (maximum concentration) and AUC (area under the curve) over the dose range from 5 to 125 mg. M11A was found as a minor metabolite with an exposure of about 2-3% of the parent compound.