Rapastinel, also known as GLYX-13, is a tetrapeptide compound that has shown potential in the treatment of major depressive disorder (MDD). It functions as an NMDA receptor modulator, specifically targeting the glycine site, which helps regulate glutamate signaling in the brain. This mechanism is distinct from traditional antidepressants, offering a novel approach for patients who do not respond to standard treatments. In clinical studies, Rapastinel has demonstrated rapid and sustained antidepressant effects, often within hours of administration. This makes it a promising candidate for addressing acute depressive episodes and providing relief to patients with treatment-resistant depression. Additionally, its favorable safety profile and minimal side effects further enhance its therapeutic potential. Beyond depression, research is exploring its use in other neurological conditions, such as anxiety disorders and cognitive impairments, due to its role in modulating synaptic plasticity and improving brain function. Its unique action on the NMDA receptor opens avenues for broader applications in mental health and neurodegenerative diseases.