The N-methyl-D-aspartate receptor (NMDAR) ketamine has produce rapid-acting and sustained antidepressant actions in treatment resistant patients with depression. Furthermore, ketamine can reduce suicidal ideation in severe patients with depression. The Johnson and Johnson in the USA developed esketamine as new antidepressant for treatment-resistant depression. In 2019, USA and Europe approved J&J esketamine nasal spray. In contrast, we reported that arketamine, another enantiomer of ketamine, could produce greater potency and longer-lasting antidepressant-like actions in rodent models of depression than esketamine. The Ph2 study of arketamine in depressed patients is underway by Perception Neuroscience (New York, USA). Otsuka Pharmaceutical company will start Ph1 study in Japan. Here, the author will discuss recent findings of novel antidepressant arketamine.