In Vivo/In vitro metabolic profiling and evaluation of key metabolites of QO-83, a novel KCNQ channel opener with antiepileptic potential.

Abstract

KCNQ2/3 voltage-gated potassium channels constitute validated therapeutic targets for epilepsy by regulating neuronal hyperexcitability. QO-83, a novel KCNQ channel opener exhibiting potent activity and channel subtype selectivity, was undergoing preclinical studies as an antiepileptic candidate drug. This study integrated in vivo metabolism studies in rats and Beagles with in vitro models of human and rat hepatic systems using liquid chromatography-mass spectrometry (LC-MS). Key metabolites were further evaluated for channel open activity in cells and pharmacokinetics/pharmacodynamics (PK/PD) and safety in animals. The results showed that QO-83 underwent extensive phase I/II metabolism across species, primarily via ketone conjugation, hydroxylation, acetylation, and glucuronidation. Four major metabolites (M1, M2, M8, M19) were identified, with species-specific differences in M8 production. Notably, M8, as the key metabolites of compound QO-83, generated through a relatively rare acetylation phase II metabolic pathway, which may also be the reason for the species-specific differences in metabolism. M8 exhibited significant anticonvulsant activity (ED₅₀ = 9.40 ± 1.98 mg/kg) in the maximal electroshock seizure (MES) model and favorable pharmacokinetics in rats, including near-complete oral absorption (Fabs = 98.7 %). Additionally, acute toxicity assessments revealed a wide safety margin for M8. These findings elucidated the metabolic fate of QO-83 and established M8 as an active metabolite contributing to the antiepileptic efficacy while providing critical data for preclinical safety assessment.