Gepirone hydrochloride: a novel antidepressant with 5-HT1A agonistic properties

Depression is a neuropsychiatric disorder that affects more than 350 million people all over the world. There are psychological and pharmacological treatments for depression which mainly focus on monoaminergic neurotransmission theory. The main concern regarding available antidepressants is the lag period and other side effects, such as sexual dysfunction. Gepirone is a drug of the azapirone group which is a 5-HT1A receptor agonist belonging to the buspirone family. Gepirone is under clinical development and has been shown to be more effective than selective serotonin reuptake inhibitors (SSRIs), as this drug treats the psychiatric disorders without causing sexual dysfunction, which limits the use of SSRIs. It possesses greater selectivity for the 5-HT1A receptor than SSRIs. Clinical studies have shown that gepirone has differential action at pre- and postsynaptic 5-HT1A receptors. Gepirone extended-release tablets (gepirone ER, Travivo) showed promising effects in adult outpatients for the treatment of major depressive disorder (MDD) in a double-blind, randomized, placebo-controlled clinical study. Gepirone also showed an antianxiety effect in a placebo-controlled trial in generalized anxiety disorder. Absorption of gepirone is increased when administered with food as there is no substantial change in Cmax and half-life but it significantly increases AUC and mean residence time. Gepirone undergoes first-pass metabolism and its major metabolites are 1- (2-pyrimidinyl)-piperazine (1-PP) and 3-OH-gepirone, both of which are pharmacologically active. In addition to its better efficacy, gepirone is well tolerated and the major adverse effects observed have been nausea, dizziness and lightheadedness. Evidence from preclinical and clinical studies revealed that gepirone could be a breakthrough therapeutic agent in the treatment of anxiety and MDD.