Discovery of a Novel and Potent Kir4.1 Inhibitor as a Safe and Rapid‐Onset Antidepressant Agent in Mice

Abstract Major depressive disorder is a serious psychiatric disorder for which novel and fast‐acting antidepressants are required. Targeted inhibition of the astrocytic inwardly rectifying potassium channel 4.1 (Kir4.1) in the lateral habenula could rapidly alleviate depression‐like behaviors. A previous study identified Kir4.1 as a promising target for achieving rapid‐onset antidepressant effects. The aim of this study is to identify novel Kir4.1 inhibitors with good druggability through structural modification of the lead compound EHop‐016, resulting in fifty derivatives. Among these, JX3212 exhibits the most potent in vitro inhibitory activity against Kir4.1, with acceptable selectivity and excellent brain exposure. Notably, a single administration of JX3212 results in rapid‐onset antidepressant effects within 1 h in multiple rodent models of depression, with comparable efficacy to ( S )‐ketamine; this inhibitor‐like effect is abolished in mice with tamoxifen‐induced conditional Kir4.1 knockout in astrocytes. Additionally, JX3212 demonstrates superior safety margins compared to both ( S )‐ketamine and the conventional antidepressant imipramine in murine behavioral assays. In summary, JX3212 functions as a selective Kir4.1 inhibitor with favorable druggability and stable antidepressant efficacy in preclinical models. This pharmacological profile supports the further development of JX3212 as a promising therapeutic candidate for major depressive disorder.