ZK 93423 hydrochloride

IC50: 1 nM

ZK-93423 is an anxiolytic drug from the β-Carboline family, which is a nonbenzodiazepine GABAA receptor agonist. The GABAA receptor is an ligand-gated ion channel and ionotropic receptor.

In vitro: The full agonist ZK-93423 is not subtype selective and stimulates α1, α2, α3, and α5-subunit containing GABAA receptors equally [α1β32 (Ki = 4.1 nM), α2β32 (Ki = 4.2 nM), α3β32 (Ki = 6.0 nM), α5β32 (Ki = 4.5 nM), α6β32 (Ki >1000 nM)] [1]. ZK-93423 has also been used as a base to develop new and improved beta-carboline derivatives and help map the binding site of the GABAA receptor. In rats trained to discriminate PTZ from saline, the PTZ cue was antagonized by ZK 93423, which indicated ZK 93423 may exhibit anxiolytic quality [2].

In vivo: ZK 93423 showd to have anxiolytic properties on animal models of anxiety, including social interaction, vogel, geller serfter, 4-plate test and elevated plus-maze. The anxiogenic and anxiolytic actions are mediated by the BDZ binding sites [3].

Clinical trial: So far, no clinical study has been conducted.

References:
[1] Cox ED, Diaz-Arauzo H, Huang Q, Reddy MS, Ma C, Harris B, McKernan R, Skolnick P, Cook JM.  Synthesis and evaluation of analogues of the partial agonist 6-(propyloxy)-4-(methoxymethyl)-beta-carboline-3-carboxylic acid ethyl ester (6-PBC) and the full agonist 6-(benzyloxy)-4-(methoxymethyl)-beta-carboline-3-carboxylic acid ethyl ester (Zk 93423) at wild type and recombinant GABAA receptors. J Med Chem. 1998 Jul 2;41(14):2537-52.
[2] Stephens DN, Shearman GT, Kehr W.  Discriminative stimulus properties of beta-carbolines characterized as agonists and inverse agonists at central benzodiazepine receptors. Psychopharmacology (Berl). 1984;83(3):233-9.
[3] File SE, Baldwin HA.  Effects of beta-carbolines in animal models of anxiety. Brain Res Bull. 1987 Sep;19(3):293-9.

Synthesis and evaluation of analogues of the partial agonist 6-(propyloxy)-4-(methoxymethyl)-beta-carboline-3-carboxylic acid ethyl ester (6-PBC) and the full agonist 6-(benzyloxy)-4-(methoxymethyl)-beta-carboline-3-carboxylic acid ethyl ester (Zk 93423) at wild type and recombinant GABAA receptors.[Pubmed:9651158]

J Med Chem. 1998 Jul 2;41(14):2537-52.

A pharmacophore and an alignment rule have previously been reported for BzR agonist ligands. The design and synthesis of 6-(propyloxy)-4-(methoxymethyl)-beta-carboline-3-carboxylic acid ethyl ester (6-PBC, 24, IC50 = 8.1 nM) was based on this pharmacophore. When evaluated in vivo this ligand exhibited anticonvulsant/anxiolytic activity but was devoid of the muscle relaxant/ataxic effects of "classical" 1,4-benzodiazepines (i.e., diazepam). Significantly, 6-PBC 24 also reversed diazepam-induced muscle relaxation in mice. The 3-substituted analogues 40-46 and 48 of 6-PBC 24 and Zk 93423 27(IC50 = 1 nM) were synthesized and evaluated in vitro to determine what affect these modifications would have on the binding affinity at recombinant BzR subtypes. With the exception of the 3-amino ligands 40 and 41, all the beta-carbolines were found to exhibit high binding affinity at BzR sites. The 3-propyl ether derivative 45 was also evaluated in vivo and found to be devoid of any proconvulsant or anticonvulsant activity at doses up to 40 mg/kg. The 6-(1-naphthylmethyloxy) and 6-octyloxy analogues 25, 26, 28, and 29 of 6-PBC 24 were synthesized to further evaluate the proposed alignment of agonists vs inverse agonists in the pharmacophore of the BzR. In addition, ligands 26 and 29 were designed to probe the dimensions of lipophilic pocket L3 at the agonist site. The activity of 29 was evaluated in vivo; however, this analogue elicited no pharmacological effects at doses up to 80 mg/kg. These and other related beta-carbolines were also examined in five recombinant GABAA receptor subtypes. Ligands 52-61 all exhibited moderate to high affinity at GABAA receptors containing alpha1 subunits. These ligands will be useful in further defining the pharmacophore at alpha1 beta3 gamma2 receptors.

Effects of beta-carbolines in animal models of anxiety.[Pubmed:3315125]

Brain Res Bull. 1987 Sep;19(3):293-9.

Animal models of anxiety can be classified into three main groups: those based on conflict or conditioned fear; those exploiting the anxiety produced by novelty; those in which anxiety or aversion is chemically induced. This review briefly describes the existing tests and, where available, the results obtained with beta-carbolines. Many of the beta-carbolines are anxiogenic in the tests, however ZK 91296 and ZK 93423 appear to have anxiolytic properties, and ZK 93426 has a similar profile to that of the benzodiazepine receptor antagonist RO 15-1788. By the results across the spectrum of tests, the reliability and sensitivity of the tests is assessed. The evidence that the anxiogenic and anxiolytic actions of the beta-carbolines are mediated by the BDZ binding sites is also discussed.

Discriminative stimulus properties of beta-carbolines characterized as agonists and inverse agonists at central benzodiazepine receptors.[Pubmed:6089245]

Psychopharmacology (Berl). 1984;83(3):233-9.

The discriminative stimulus properties of three beta-carboline derivatives were studied in three groups of rats trained, respectively, to discriminate diazepam (2.5 mg/kg IP), chlordiazepoxide (CDP, 5 mg/kg IP) or pentylenetetrazol (PTZ, 15 mg/kg IP) from saline in standard procedures employing two-lever operant chambers. Two beta-carbolines, ZK 91296 and ZK 93423, substituted for the benzodiazepines in both CDP- and diazepam-trained rats. The neutral benzodiazepine antagonists Ro 15-1788 blocked the diazepam discriminative stimulus and the ability of ZK 91296 to substitute for diazepam. A third beta-carboline, FG 7142, was not identified as benzodiazepine-like in generalization tests in either diazepam- or CDP-trained rats, but when administered together with CDP antagonized the benzodiazepine discriminative stimulus. In rats trained to discriminate PTZ from saline (a discrimination which is thought to depend on the anxiogenic properties of PTZ) the PTZ cue was antagonized by diazepam and ZK 93423, and partially antagonized by ZK 91296. The PTZ cue generalized to FG 7142 and this generalization was partially antagonized by Ro 15-1788. These results suggest that the three beta-carbolines provide more than one kind of discriminative stimulus, consistent with the classification of ZK 93423 as an agonist at central benzodiazepine receptors, with ZK 91296 as a partial agonist, and with FG 7142 as an inverse agonist. Pharmacologically, ZK 93423 and ZK 91296 may exhibit anxiolytic qualities, whereas FG 7142 produces anxiogenic effects.