Agomelatine (S-20098) L(+)-Tartaric acid is a specific agonist of MT1 and MT2 receptors (Kis: 0.1, 0.06, 0.12, and 0.27 nM for CHO-hMT1, HEK-hMT1, CHO-hMT2, and HEK-hMT2). It also is a selective 5-HT2C receptor antagonist (pKis: 6.4 and 6.2 at native (porcine) and cloned (human) 5-HT2C receptors).