HTR1A and major depressive disorder: Lastly, vortioxetine (Brintellix), which acts as a SERT inhibitor, agonist at the 5-HT1A receptor, partial agonist at the 5-HT1B receptor, and antagonist at the 5-HT3, 5-HT1D, and 5-HT7 receptors, was approved by the FDA for the treatment of MDD in 2013.