Development and validation of an LC-MS/MS method for quantifying a new G protein selective μ-opioid receptor agonist YZJ-4729 and its major metabolite M10 in human plasma to support a phase I study in healthy subjects

The use of conventional opioids that act on μ-receptors is a recognized care agent for moderate-to-severe acute treatment. However, recent attention has shifted to a new class of μ-receptor agonists which can selectively activate the G-protein pathway and thus have better efficacy and fewer side effects. Recently, YZJ-4729 was developed as a new G protein selective μ-opioid receptor agonist. And for its clinical trial investigation usage, a rapid LC-MS/MS method was established for the concurrent measurement of YZJ-4729 and its major metabolite M10 in human plasma. A step involving the precipitation of proteins was used for plasma sample preparation. The chromatography separation was done on a Poroshell 120 EC-C18 analytical column (2.1 × 50 mm, 2.7-μm, Agilent). Gradient elution was performed with 5.0 mM ammonium acetate (NH₄Ac) and 0.1 % formic acid (FA) water solution as the mobile phase A and pure acetonitrile (ACN) as the mobile phase B. Detection occurred in the mode of positive ion electrospray ionization through multiple reaction monitoring using deuterium YZJ-4729 (d6-YZJ-4729) as the internal standard. The ionic transitions used were YZJ-4729: m/z 409.3 → 244.2; d6-YZJ-4729: m/z 415.3 → 244.2; M10: m/z 425.3 → 260.2;). The method showed excellent linearity across the ranges of 0.500 to 500 ng/mL for YZJ-4729 and 0.0500 to 50.0 ng/mL for M10. The method was utilized to assess the plasma concentrations of YZJ-4729 and M10 in healthy volunteers after a 30-min intravenous infusion in the phase I clinical study, and the clinical pharmacokinetic profiles of YZJ-4729 and M10 were described.