Selexipag metabolite ACT-333679

Selexipag metabolite ACT-333679 is a pyridine-based derivative featuring a tetrahydropyran ring fused to a substituted benzene moiety, with a terminal hydroxyl group and a pyrrolidin-2-one side chain. It retains the core 5-ethyl-2-pyridyl scaffold of Selexipag but incorporates an additional methoxy group at the para position of the aromatic ring and a carbamoyl substitution on the cyclohexyl ring. This metabolite arises via oxidative demethylation and subsequent hydroxylation pathways. It serves as a critical HPLC reference standard for quantifying process-related impurities in Selexipag drug substance synthesis.