AWD 131-138

AWD 131-138 is a partial agonist of benzodiazepine receptor [1].

Benzodiazepine (BZD) is a psychoactive drug and acts as positive allosteric modulators of the inhibitory neurotransmitter GABA by binding to a recognition site (BZD receptor) of the GABAA receptor chloride ionophore complex [1].

AWD 131-138 is a partial benzodiazepine receptor agonist with anticonvulsant and anxiolytic activity [1]. In Xenopus oocytes expressed recombinant γ-aminobutyric acid A (GABAA) receptors of ɑ1β2γ2, ɑ1β3γ2, ɑ2β2γ2, ɑ3β2γ2 and ɑ5β2γ2, AWD 131-138 stimulated GABA currents in a dose-dependent way and acts at the binding site for benzodiazepines. AWD 131-138 (10 μM) stimulated GABA currents up to 12-21% of the maximal stimulation achieved by diazepam [2].

In a dog seizure model, AWD 131-138 increased the pentylenetetrazole (PTZ) seizure threshold. AWD 131-138 (5 or 40 mg/kg) caused relatively mild abstinence symptoms, particularly at the lower dosage. In dogs with newly diagnosed epilepsy, AWD 131-138 significantly reduced seizure frequency and severity [3].

References:
[1].  Rundfeldt C, Löscher W. The pharmacology of imepitoin: the first partial benzodiazepine receptor agonist developed for the treatment of epilepsy. CNS Drugs, 2014, 28(1): 29-43.
[2].  Sigel E, Baur R, Netzer R, et al. The antiepileptic drug AWD 131-138 stimulates different recombinant isoforms of the rat GABA(A) receptor through the benzodiazepine binding site. Neurosci Lett, 1998, 245(2): 85-88.
[3].  Löscher W, Potschka H, Rieck S, et al. Anticonvulsant efficacy of the low-affinity partial benzodiazepine receptor agonist ELB 138 in a dog seizure model and in epileptic dogs with spontaneously recurrent seizures. Epilepsia, 2004, 45(10): 1228-1239.

Evaluation of the novel antiepileptic drug, AWD 131-138, for benzodiazepine-like discriminative stimulus and reinforcing effects in squirrel monkeys.[Pubmed:12681437]

Eur J Pharmacol. 2003 Apr 4;465(3):257-65.

AWD 131-138 [1-(4-chlorophenyl)-4-morpholino-imidazolin-2-one], a new low-affinity partial benzodiazepine receptor agonist with potent anticonvulsant and anxiolytic properties in rodent models, was studied in squirrel monkeys trained to discriminate intramuscular (i.m.) injections of midazolam (0.3 mg/kg) from injections of vehicle. Diazepam produced midazolam-like responding at cumulative doses of 1.0 and 3.0 mg/kg i.m. and decreased rates of responding at 3.0 mg/kg (plasma levels of about 400 ng/ml). In contrast, AWD 131-138 did not produce midazolam-like responding or alter response rates at cumulative doses up to 18.0 mg/kg i.m. (plasma levels over 2100 ng/ml). Other monkeys were trained to intravenously (i.v.) self-administer cocaine (56.0 microg/kg/injection). When AWD 131-138 (10-100 microg/kg/injection) was studied by substitution, responding declined to vehicle substitution levels within three sessions. At the dose of 100 microg/kg i.v. AWD 131-138, sufficient drug was self-administered during the first session (about 3.5 mg/kg) to produce plasma levels above 1000 ng/ml, yet responding over the next two sessions dropped to vehicle levels. The failure of AWD 131-138 to produce benzodiazepine-like discriminative effects and the absence of drug self-administration behavior when substituted for cocaine suggest that its abuse liability is low.

[Identity and physicochemical properties of 1-(4-chlorophenyl)-4-morpholino-imidazolin-2-one, AWD 131-138].[Pubmed:11446164]

Pharmazie. 2001 Jun;56(6):458-61.

The structure of the anticonvulsant 1-(4-chlorophenyl)-4-(4-morpholinyl)-2,5-dihydro-1H-imidazolin-2-one (Code: AWD 131-138, CAS-No.: 188116-07-6) was proved by IR, UV, 1H NMR, 13C NMR and mass spectra. AWD 131-138 is practically insoluble in a neutral aqueous medium at 20 degrees C (S approximately 0.08 g/l). The solubility of the substance in 0.1 N HCl is about 2.7 g/l. In DMF, AWD 131-138 is sparingly soluble (S approximately 28.5 g/l). The pKa-value is about 2.5. The partition coefficients P = COctanol/Cwater at 37 degrees C range from 0.7 at pH approximately 1 to about 20 at pH > or = 6.

The antiepileptic drug AWD 131-138 stimulates different recombinant isoforms of the rat GABA(A) receptor through the benzodiazepine binding site.[Pubmed:9605491]

Neurosci Lett. 1998 Apr 3;245(2):85-8.

Recombinant gamma-aminobutyric acid A (GABA(A)) receptors of the subunit compositions alpha1beta2gamma2, alpha1beta3gamma2, alpha2beta2gamma2, alpha3beta2gamma2 and alpha5beta2gamma2 were expressed in Xenopus oocytes in a functionally active form. At all subunit combinations, AWD 131-138 dose-dependently stimulated GABA currents. At 10 microM AWD 131-138, this allosteric stimulation amounted in average to about 12-21% of the maximal stimulation achieved using diazepam. The threshold of stimulation was about 0.3-1.0 microM. One micrometer of the benzodiazepine antagonist flumazenil (Ro 15-1788) counteracted the current stimulation by 10 microM AWD 131-138, indicating that this drug acts at the binding site for benzodiazepines.