NYX-2925 Is a Novel NMDA Receptor-Specific Spirocyclic-β-Lactam That Modulates Synaptic Plasticity Processes Associated with Learning and Memory

Abstract

BackgroundN-methyl-D-aspartate receptors are one member of a family of ionotropic glutamate receptors that play a pivotal role in synaptic plasticity processes associated with learning and have become attractive therapeutic targets for diseases such as depression, anxiety, schizophrenia, and neuropathic pain. NYX-2925 ((2S, 3R)-3-hydroxy-2-((R)-5-isobutyryl-1-oxo-2,5-diazaspiro[3.4]octan-2-yl)butanamide) is one member of a spiro-β-lactam-based chemical platform that mimics some of the dipyrrolidine structural features of rapastinel (formerly GLYX-13: threonine-proline-proline-threonine) and is distinct from known N-methyl-D-aspartate receptor agonists or antagonists such as D-cycloserine, ketamine, MK-801, kynurenic acid, or ifenprodil.MethodsThe in vitro and in vivo pharmacological properties of NYX-2925 were examined.ResultsNYX-2925 has a low potential for “off-target” activity, as it did not exhibit any significant affinity for a large panel of neuroactive receptors, including hERG receptors. NYX-2925 increased MK-801 binding to human N-methyl-D-aspartate receptor NR2A-D subtypes expressed in HEK cells and enhanced N-methyl-D-aspartate receptor current and long-term potentiation (LTP) in rat hippocampal slices (100–500 nM). Single dose ex vivo studies showed increased metaplasticity in a hippocampal LTP paradigm and structural plasticity 24 hours after administration (1 mg/kg p.o.). Significant learning enhancement in both novel object recognition and positive emotional learning paradigms were observed (0.01–1 mg/kg p.o.), and these effects were blocked by the N-methyl-D-aspartate receptor antagonist CPP. NYX-2925 does not show any addictive or sedative/ataxic side effects and has a therapeutic index of >1000. NYX-2925 (1 mg/kg p.o.) has a cerebrospinal fluid half-life of 1.2 hours with a Cmax of 44 nM at 1 hour.ConclusionsNYX-2925, like rapastinel, activates an NMDA receptor-mediated synaptic plasticity process and may have therapeutic potential for a variety of NMDA receptor-mediated central nervous system disorders.

NYX‐2925 induces metabotropic N‐methyl‐d‐aspartate receptor (NMDAR) signaling that enhances synaptic NMDAR and α‐amino‐3‐hydroxy‐5‐methyl‐4‐isoxazolepropionic acid receptor

“…a). Dose selection was based on the previous finding that picomolar NYX‐2925 in the presence of 50 μM glutamate selectively potentiates [ 3 H]MK‐801 binding to GluN2B‐containing receptors, whereas nanomolar NYX‐2925 does so in all GluN2 subtypes, including GluN2A (Khan et al ). Following treatment, cells were washed, fixed, and immunolabeled for surface GluN2A or GluN2B and intracellular PSD‐95 to determine the effects of NYX‐2925 treatment on synaptic localization of GluN2‐containing NMDARs.…”

“…Given that nanomolar NYX‐2925 concentrations facilitate synaptic plasticity ex vivo (Khan et al ), it is intriguing that picomolar, but not nanomolar concentrations increased synaptic GluN2B. Accordingly, we sought to better understand how NYX‐2925 acts on GluN2B‐containing NMDARs.…”

“…Next, vehicle or glutamate (final concentration 50 μM) and/or NYX‐2925 (final concentration 0.1 pM–30 nM) were co‐applied for 30 or 60 min. The rationale for quantifying drug effect at these time points was based upon the findings that NYX‐2925 facilitated LTP when bath applied to rat hippocampal slices for 40 min and that the maximum concentration of NYX‐2925 in the rat cerebral spinal fluid occurs 60 min after oral dosing (Khan et al ). Cells were washed (cold PBS) and then processed for immunocytochemistry, harvested in RIPA with protease and phosphatase inhibitors (1 : 100, Sigma‐Aldrich).…”

“…NYX‐2925 is an orally bioavailable non‐peptide mimetic of GLYX‐13, which is also known as Rapastinel. In rat models, both NYX‐2925 (Khan et al ) and GLYX‐13 (Moskal et al ) are cognitive enhancers that facilitate synaptic plasticity. In brief, we found that NYX‐2925 exhibits a unique biphasic dose response.…”

“…In brief, we found that NYX‐2925 exhibits a unique biphasic dose response. Mid‐nanomolar concentrations mediate calcium transients and long‐term potentiation (LTP) (Khan et al ), whereas picomolar concentrations engage hippocampal homeostatic plasticity by augmenting synaptic levels of GluN2B via a metabotropic‐like mechanism of the NMDAR. Next, we found that NYX‐2925 pretreatment enhanced activity‐dependent synaptic insertion of α‐amino‐3‐hydroxy‐5‐methyl‐4‐isoxazolepropionic acid receptors (AMPARs).…”