Discovery of 1-[2-(2,4-Dimethylphenylsulfanyl)phenyl]piperazine (Lu AA21004): A Novel Multimodal Compound for the Treatment of Major Depressive Disorder

The synthesis and structure-activity relationship of a novel series of compounds with combined effects on 5-HT3A and 5-HT1A receptors and on the serotonin (5-HT) transporter (SERT) are described. Compound 5m (Lu AA21004) was the lead compound, displaying high affinity for recombinant human 5-HT1A (K-i = 15 nM), 5-HT1B (K-i = 33 nM), 5-HT3A (K-i = 3.7 nM), 5-HT7 (K-i = 19 nM), and noradrenergic beta(1) (K-i = 46 nM) receptors, and SERT (K-i = 1.6 nM). Compound 5m displayed antagonistic properties at 5-HT3A and 5-HT7 receptors, partial agonist properties at 5-HT1B receptors, agonistic properties at 5-HT1A receptors, and potent inhibition of SERT. In conscious rats, 5m significantly increased extracellular 5-HT levels in the brain after acute and 3 days of treatment. Following the 3-day treatment (5 or 10 (mg/kg)/day) SERT occupancies were only 43% and 57%, respectively. These characteristics indicate that 5m is a novel multimodal serotonergic compound, and 5m is currently in clinical development for major depressive disorder.