7-Desmethyl-agomelatine is a primary metabolite of agomelatine formed via CYP450-mediated demethylation. This compound, monitored at a mass transition of m/z 230.1→171.1, acts as a melatonin receptor agonist with lower affinity than the parent molecule. Quantified in human plasma across a linear range of 0.1372–300 ng/mL, it is frequently employed in LC-MS/MS method development to study metabolic clearance and validate bioanalytical procedures for simultaneous metabolite profiling.