What Is Rapastinel? Definition and What Research Reports

Definition

Rapastinel is a synthetic, amidated tetrapeptide that was developed and studied as a modulator of the N-methyl-D-aspartate (NMDA) subtype of glutamate receptor, and it is frequently encountered in the literature under its earlier code name GLYX-13. A 2017 development review described rapastinel as a tetrapeptide that emerged from research on the monoclonal antibody B6B21 and characterised it as an NMDA receptor modulator with rapid-acting and long-lasting antidepressant properties in preclinical and early clinical work (PMID 26997507). In short, the term refers to a specific investigational peptide molecule, not to a drug class, a receptor, or an approved medicine. It has never been approved by the U.S. Food and Drug Administration or comparable regulators for any indication, and a 2019 review discussing the evidence to date referred to it explicitly as an investigational NMDA receptor modulator for major depressive disorder (PMID 30585524).

What Class of Molecule Is It, and Where Does the Term Come From?

Rapastinel sits at the intersection of two literatures that rarely overlap: peptide chemistry and glutamatergic neuropharmacology. Structurally it is a short peptide, which is why it appears in peptide glossaries at all; pharmacologically it is discussed as an agent acting at the NMDA receptor complex rather than as a metabolic or growth-factor-related peptide. The 2017 development review traced its origin to antibody-derived research and described it as an NMDA receptor modulator distinguished from open-channel blockers (PMID 26997507). A 2020 behavioural pharmacology paper described rapastinel as an NMDA receptor positive modulator and compared its profile directly against ketamine (PMID 32461133).

Names and Terminology

How the Term Is Used in Peptide and Neuroscience Research

Three usages dominate. First, as a named investigational compound in depression research: a 2017 clinical-evidence review examined modulation of NMDA receptor activity as a treatment option for depression and focused on the therapeutic potential of rapastinel (GLYX-13) as reported at that time (PMID 28408831). Second, as a mechanistic comparator to ketamine: a 2020 review argued that rapastinel and ketamine converge on overlapping downstream mechanisms despite differing actions at the receptor (PMID 31733218), and a 2022 review placed both compounds within a broader account of glutamatergic receptors and neuroplasticity in depression (PMID 35074585). Third, as a laboratory tool for probing NMDA-dependent behaviour, memory and neuroplasticity in rodents, which is where most of the recent primary literature sits.

What the Published Literature Reports

Antidepressant-like effects in animal models

A 2019 study in a treatment-resistant animal model of depression reported that esketamine and rapastinel, but not imipramine, produced antidepressant-like effects in that model (PMID 31230597). Researchers examining signalling mechanisms in mice reported that ERK and mTOR pathway activity may underlie the antidepressant actions of rapastinel (PMID 36550125), a finding consistent with the neuroplasticity framing used in the 2022 glutamatergic review (PMID 35074585).

Memory and cognition in pharmacological models

A 2016 study reported that GLYX-13 (rapastinel) ameliorated declarative memory deficits induced by subchronic phencyclidine and ketamine in mice (PMID 26632337). A follow-up study reported that repeated administration of rapastinel produced an exceptionally prolonged rescue of memory deficits in phencyclidine-treated mice (PMID 35718230). These are pharmacological models of NMDA receptor hypofunction in rodents, not studies of memory in humans.

Withdrawal and relapse-related behaviour

A 2022 behavioural study reported that rapastinel accelerated the loss of withdrawal signs after repeated morphine and blunted relapse to conditioned place preference (PMID 36302442). This line of work illustrates how the term appears outside depression research, in studies of NMDA-dependent plasticity in dependence models.

Profile relative to ketamine

Because rapastinel is repeatedly discussed next to ketamine, several papers set out how the two differ. The study comparing the two reported that rapastinel, an NMDA receptor positive modulator, produced distinct behavioural, sleep and EEG profiles compared with ketamine (PMID 32461133), while the 2020 convergent-mechanisms review described rapastinel as a glutamatergic agent with ketamine-like antidepressant actions arising through overlapping downstream pathways (PMID 31733218).

Neurodevelopmental and neuroprotection models

A 2021 paper reported that rapastinel alleviated the neurotoxic effect induced by NMDA receptor blockade in the early postnatal mouse brain (PMID 32789675), which researchers used to explore the consequences of NMDA receptor modulation versus blockade in developing tissue.

Tolerability and Safety Signals in the Literature: What Studies Report

Published discussion of rapastinel's tolerability is largely framed by comparison with NMDA channel blockers. The 2017 development review reported that rapastinel produced rapid and long-lasting antidepressant effects without the psychotomimetic side effects associated with ketamine (PMID 26997507), and the 2017 clinical-evidence review likewise examined rapastinel's therapeutic potential in the context of the tolerability limits of NMDA receptor antagonism in depression (PMID 28408831). The 2020 comparison study reported measurable differences in sleep and EEG parameters between rapastinel and ketamine (PMID 32461133). None of these reports establish a safety profile for use outside a supervised research setting, and the 2019 evidence review continued to describe the compound as investigational (PMID 30585524).

Regulatory and Research Status

Rapastinel is not an approved medicine and is not an ingredient in any approved drug product; peptide material bearing this name is encountered in research contexts and is typically labelled for research use only (RUO). The 2019 review of the evidence to date summarised the state of its clinical development programme for major depressive disorder at that point (PMID 30585524), and subsequent papers on rapastinel have been predominantly preclinical, such as the 2022 mouse signalling study (PMID 36550125).

Common Points of Confusion

• Rapastinel is not ketamine. Reviews describe rapastinel as a receptor modulator and ketamine as a channel blocker, while noting convergence in downstream mechanisms (PMID 31733218).
• Rapastinel and GLYX-13 are the same compound. The older code name still appears in titles, including the 2016 mouse memory study (PMID 26632337).
• Most primary evidence is preclinical. Memory, withdrawal and antidepressant-like findings summarised above were reported in rodents (PMID 35718230, PMID 36302442).

This page is for educational purposes only and is not medical advice; consult a licensed physician about any medical question, symptom, or treatment decision. It summarises what the cited literature reported and does not describe how any compound should be used.

References

• The Development of Rapastinel (Formerly GLYX-13); A Rapid Acting and Long Lasting Antidepressant (Current Neuropharmacology, 2017)
• Glutamatergic receptor and neuroplasticity in depression: Implications for ketamine and rapastinel as the rapid-acting antidepressants (Biochemical and Biophysical Research Communications, 2022)
• Rapastinel, a novel glutamatergic agent with ketamine-like antidepressant actions: Convergent mechanisms (Pharmacology, Biochemistry, and Behavior, 2020)
• Rapastinel - an investigational NMDA-R modulator for major depressive disorder: evidence to date (Expert Opinion on Investigational Drugs, 2019)
• Repeated administration of rapastinel produces exceptionally prolonged rescue of memory deficits in phencyclidine-treated mice (Behavioural Brain Research, 2022)
• Rapastinel accelerates loss of withdrawal signs after repeated morphine and blunts relapse to conditioned place preference (Pharmacology, Biochemistry, and Behavior, 2022)
• Modulation of the activity of N-methyl-d-aspartate receptors as a novel treatment option for depression: current clinical evidence and therapeutic potential of rapastinel (GLYX-13) (Neuropsychiatric Disease and Treatment, 2017)
• Rapastinel, an NMDAR positive modulator, produces distinct behavioral, sleep, and EEG profiles compared with ketamine (Behavioural Brain Research, 2020)
• ERK/mTOR signaling may underlying the antidepressant actions of rapastinel in mice (Translational Psychiatry, 2022)
• GLYX-13 (rapastinel) ameliorates subchronic phencyclidine- and ketamine-induced declarative memory deficits in mice (Behavioural Brain Research, 2016)
• Esketamine and rapastinel, but not imipramine, have antidepressant-like effect in a treatment-resistant animal model of depression (Acta Neuropsychiatrica, 2019)
• Rapastinel alleviates the neurotoxic effect induced by NMDA receptor blockade in the early postnatal mouse brain (European Archives of Psychiatry and Clinical Neuroscience, 2021)