HTR1A and major depressive disorder: These observations have led to the development of new antidepressant drugs blocking the serotonin transporter (SERT) and having partial agonist activity at 5-HT1A receptors, in order to evoke a higher increase in extracellular 5-HT: Vilazodone, approved in 2011 by the FDA for use in the treatment of MDD, and vortioxetine (LuAA21004, in development) [147,148].