Rapastinel

N-methyl-D-aspartate (NMDA) receptors are glutamate-gated ion channels that are ubiquitously expressed throughout the central nervous system (CNS) and serve as crucial mediators of neural development and synaptic plasticity. Dysregulation of NMDA receptor activity has been implicated in a wide spectrum of neurological and psychiatric disorders. In recent years, substantial progress has been made in the clinical development of small-molecule modulators targeting NMDA receptors. In this review, we summarize recent advances in this rapidly evolving field. Among various therapeutic indications, depression has emerged as an especially active area of investigation, with mechanistically diverse compounds ranging from broad-spectrum channel blockers (ketamine, dextromethorphan, esmethadone) to glycine site modulators (rapastinel, 4-chlorokynurenine, D-cycloserine) and allosteric modulators (apimostinel, zelquistinel), progressing through clinical pipelines. Beyond depression, NMDA receptor-targeted drug discovery is also advancing in other challenging CNS disorders, including neurodegenerative diseases (salzanemdor, NYX-458), pain (NYX-2925), epilepsy (radiprodil), and stroke (nelonemdaz, NP10679). Collectively, these developments reflect the maturation of NMDA receptor pharmacology and reaffirm the broad therapeutic potential of NMDA receptor modulation, while highlighting promising directions for future drug discovery.

Treatment-resistant depression (TRD) represents a major clinical challenge. Affecting about 30 % of major depressive disorder (MDD) patients, effective treatments for TRD are urgently needed. While depression research and antidepressant (AD) development have long centred on monoaminergic targets, research over the past 35 years has increasingly explored glutamatergic mechanisms. Here we present an extended discussion on developments in glutamatergic drug discovery, focusing on mechanistic convergence between NMDA and AMPA receptor signalling. Beyond established rapid-acting antidepressants (RAADs), such as (es)ketamine and dextromethorphan/bupropion (AXS-05), we highlight novel therapeutic directions involving esmethadone (REL-1017), nitrous oxide, and positive allosteric modulators (PAMs) of NMDA receptors (e.g. rapastinel, zelquistinel, and apimostinel). Moreover, we discuss forward-looking strategies using AMPA receptor PAMs (e.g. osavampator and tulrampator) and targeting of AMPA receptor-interacting proteins. By integrating recent clinical evidence with molecular and physiological findings, we highlight a convergent mechanism across these compounds. This involves increased AMPA receptor activation, triggering BDNF release and mTOR signalling, promoting synaptic strengthening through enhanced AMPA receptor trafficking and dendritic spine formation. Together, targeting glutamatergic signalling represents a transformative path for TRD treatment with high efficacy by more directly modulating pathologically affected signalling modules. These developments place glutamatergic agents at the forefront of next-generation AD strategies.