Characterization of Two Novel N-Methyl-D-aspartate Antagonists: EAA-090 (2-[8,9-Dioxo-2,6-diazabicyclo [5.2.0]non-1(7)-en2-yl]ethylphosphonic Acid) and EAB-318 (R-α-Amino-5-chloro-1-(phosphonomethyl)-1H-benzimidazole-2-propanoic Acid Hydrochloride)

Abstract

Two novel N-methyl-D-aspartate (NMDA) antagonists with unique chemical structures, .0]non-1(7)-en2-yl]ethylphosphonic acid) and EAB-318 (R-␣-amino-5-chloro-1-(phosphonomethyl)-1H-benzimidazole-2-propanoic acid hydrochloride), were compared with CGS-19755 (Selfotel) in ligand binding, electrophysiology, and neuroprotection assays. CGS-19755, EAA-090 and EAB-318 inhibited [ 3 H]3-(2-carboxypiperazin-4-yl)propyl-1-phosphonic acid binding to NMDA receptors with IC 50 values of 55, 28, and 7.9 nM, respectively. All three compounds decreased the duration of spontaneous synaptic currents and inhibited NMDA-activated currents in rat hippocampal neurons. IC 50 values for inhibition of current induced by 10 M NMDA were 795, 477, and 69 nM for CGS-19755, EAA-090, and EAB-318, respectively. The NMDA antagonists protected chick embryo retina slices and cultured rat hippocampal and cortical neurons from glutamate-and NMDA-induced neurotoxicity. In experiments in which different NMDA receptor splice variants and subtypes were expressed in Xenopus oocytes, all three antagonists preferentially blocked NMDA-elicited currents mediated by N-methyl-D-aspartate receptor (NR)1 splice variants containing the N-terminal insertion. They also favored NR2A-versus NR2B-or NR2C-containing NMDA receptors, with EAA-090 showing the greatest selectivity. EAA-090 was 10 times more potent at blocking NR2A-versus NR2B-or NR2C-containing NMDA receptors. In addition to being the most potent NMDA antagonist, EAB-318 inhibited ␣-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) and kainate receptors. The combination of NMDA and AMPA/kainate block enabled EAB-318 to protect neurons against ischemia induced cell death.Glutamate is the main excitatory neurotransmitter in the brain. It activates at least three ionotropic receptor subtypes, named for their specific agonists: ␣-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA), kainate, and N-methyl-D-aspartate (NMDA) (Nakanishi, 1992;Seeburg, 1993). Normal excitatory synaptic transmission between neurons requires the activation of AMPA/kainate receptors, which allows entry of sodium ions to depolarize the cell. Activation of NMDA receptors, which allows calcium as well as sodium ions to permeate, is necessary for learning and memory (Morris et al., 1986; Bliss, 1987, 1995). However, overstimulation of glutamate receptors can produce an un-1

Effects of the N-Methyl-d-aspartate Receptor Antagonist Perzinfotel [EAA-090; [2-(8,9-Dioxo-2,6-diazabicyclo[5.2.0]non-1(7)-en-2-yl)-ethyl]phosphonic Acid] on Chemically Induced Thermal Hypersensitivity

“…Selfotel, CGP-39653, and CPP have slightly higher (2-to 3-fold) selectivity for NR1/NR2A subunits than for other NR2 subunits (Laurie and Seeburg, 1994;Christie et al, 2000). In oocytes expressing different NR1/NR2 subunits, perzinfotel was 8-to 13-fold more selective for the NR1/NR2A than either NR1/NR2B or NR1/NR2C (Sun et al, 2004). Thus, among the compounds evaluated in the current study, only perzinfotel was selective for the NR1/NR2A subunit.…”

“…Perzinfotel is a selective, competitive NMDA receptor antagonist with high affinity (30 nM) for the glutamate site (Kinney et al, 1998). Perzinfotel lacks activity at more than 60 other receptors, ion channels, or uptake sites (Childers et al, 2002;Sun et al, 2004). In vitro, perzinfotel blocks NMDA-induced currents with an IC 50 of 0.48 M and glutamate-induced neurotoxicity with an IC 50 of 1.6 M. In contrast, perzinfotel does not have appreciable affinity (up to a concentration of 100 M) for kainate, ␣-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid, and strychnine-insensitive glycine receptors and does not block ␣-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid-or kainate-induced neurotoxicity (up to a concentration of 1 mM).…”

“…Perzinfotel is a selective, competitive small molecule antagonist that blocks the actions of glutamate at the NMDA receptor (Kinney et al, 1998;Childers et al, 2002;Sun et al, 2004). Previous studies have demonstrated its effectiveness in several animal stroke models and anticonvulsant models (Childers et al, 2002).…”

Identification and Characterization of Novel NMDA Receptor Antagonists Selective for NR2A- over NR2B-Containing Receptors

“…NR1/ NR2A-selective molecules were described in the literature, including the competitive NMDAR antagonists perzinfotel (EAA-090) or NVP-AAM077. Perzinfotel was shown to be 10 times more potent at blocking NR2A-versus NR2B-or NR2C-containing NMDARs (Sun et al, 2004). NVP-AAM077 was originally described to displace [ 3 H]CGP 39653 with nanomolar affinity, displaying greater than 100-fold preferential blockade for NR2A-compared with NR2B-containing receptors in functional assays (Auberson et al, 2002).…”

Squaryl Molecular Metaphors – Application to Rational Drug Design and Imaging Agents

“…Another interesting drug lead is the NMDA antagonists known as EAA-090 [176]. This NMDA antagonist possesses a squaramide in place of the α-amino acid functionality [131].…”