N-Desmethylclozapine

N-Desmethylclozapine is a dengue virus inhibitor, and an agonist of δ-opioid receptor.

In Vitro:The IC50s of N-desmethylclozapine, fluoxetine hydrochloride, and salmeterol xinafoate in Huh-7 cells infected with DENV-2 are 1 μM, 0.38 μM, and 0.67 μM, respectively. The levels of NS3 are reduced in cells treated with all three inhibitors compared to DMSO treatment, suggesting that the inhibitors act at a stage prior to viral protein translation. N-Desmethylclozapine-treated cells show a >75% reduction in negative-strand RNA levels[1]. N-desmethylclozapine exhibits slight agonistic effects on the M1 mAChR, and agonistic properties at the 5-HT1A receptor in the cerebral cortex and hippocampus. This compound also behaves as an agonist at the δ-opioid receptor in the cerebral cortex and striatum[2]. N-desmethylclozapine (3 μM) greatly decreases the outward current in excitatory neurons, but not in inhibitory neurons. In excitatory neurons, N-desmethylclozapine alone is more effective than either clozapine alone or the combination of clozapine and N-desmethylclozapine. The effect of N-desmethylclozapine in excitatory neurons is significantly suppressed by 0.1 μM pirenzepine and 1 μM atropine. N-desmethylclozapine, but not clozapine, suppressed K+ channels via M1 receptors in excitatory cells[3]. N-desmethylclozapine leads to a decrease in TxB2 levels under unstimulated conditions as well as under TSST-1 stimulation. Clozapine, N-desmethylclozapine and CPZ possibly act on neurotransmitter systems via modulation of TxA2 or TxB2 production[5].

In Vivo:N-desmethylclozapine in rat and human at M2 and M4 mAChRs underlying presynaptic modulation of GABA and glutamate release, respectively. In particular, N-desmethylclozapine maybe a M2 mAChR antagonist in the rat but has no activity at this receptor in human neocortex. However, N-desmethylclozapine has an agonistic effect at M4 mAChR in the human but no such effect in the rat neocortex[4].

References:
[1]. Medigeshi GR, et al. N-Desmethylclozapine, Fluoxetine and Salmeterol inhibit post-entry stages of dengue virus life-cycle. Antimicrob Agents Chemother. 2016 Aug 29. [2]. Odagaki Y, et al. Comparative analysis of pharmacological properties of xanomeline and N-desmethylclozapine in rat brain membranes. J Psychopharmacol. 2016 Sep;30(9):896-912. [3]. Sugawara Y, et al. Electrophysiological evidence showing muscarinic agonist-antagonist activities of N-desmethylclozapine using hippocampal excitatory and inhibitory neurons. Brain Res. 2016 Jul 1;1642:255-62. [4]. Gigout S, et al. Different pharmacology of N-desmethylclozapine at human and rat M2 and M 4 mAChRs in neocortex. Naunyn Schmiedebergs Arch Pharmacol. 2015 May;388(5):487-96. [5]. Himmerich H, et al. Impact of clozapine, N-desmethylclozapine and chlorpromazine on thromboxane production in vitro. Med Chem. 2012 Nov;8(6):1032-8.

Quantification of the steady-state plasma concentrations of clozapine and N-desmethylclozapine in Japanese patients with schizophrenia using a novel HPLC method and the effects of CYPs and ABC transporters polymorphisms.[Pubmed:27932669]

Ann Clin Biochem. 2017 Nov;54(6):677-685.

Background This study developed a novel high-performance liquid chromatography (HPLC) method for the simultaneous quantification of clozapine and its active metabolite, N-Desmethylclozapine, in human plasma and investigated the effects of various factors, including genetic polymorphisms in cytochrome P450 (CYP) 2D6, CYP3A5, ABCB1 and ABCG2, on the steady-state plasma trough concentrations (C0) of clozapine and N-Desmethylclozapine in Japanese patients with schizophrenia. Methods Forty-five patients had been receiving fixed doses of clozapine for at least four weeks. The CYP2D6 ( CYP2D6*2, CYP2D6*5, CYP2D6*10), CYP3A5 ( CYP3A5*3), ABCB1 (1236C > T, 2677G > T/A, 3435C > T) and ABCG2 (421 C > A) genotypes were identified by polymerase chain reaction. Results The within- and between-day coefficients of variation (CV) were less than 11.0%, and accuracy was within 9.0% over the linear range from 10 to 2500 ng/mL for both analytes, and their LOQs were each 10 ng/mL. The median C0/dose (C0/D) ratios of clozapine were significantly higher in patients with the ABCG2 421 A allele than in those with the 421 C/C genotype ( P = 0.010). However, there were no significant differences in C0/D ratios of clozapine and N-Desmethylclozapine among ABCB1, CYP2D6 or CYP3A5 genotypes. In multiple regression analysis, including polymorphisms, age, body weight and biochemical data of patients, the ABCG2 polymorphism alone was correlated with the C0/D ratios of clozapine ( R(2 )= 0.139, P = 0.016). Conclusions Among the various CYPs and drug transporters, BCRP appeared to most strongly influence clozapine exposure. Knowledge of the patient's ABCG2 421 C > A genotype before initiating therapy may be useful when making dosing decisions aimed at achieving optimal clozapine exposure.

N-Desmethylclozapine, Fluoxetine, and Salmeterol Inhibit Postentry Stages of the Dengue Virus Life Cycle.[Pubmed:27572397]

Antimicrob Agents Chemother. 2016 Oct 21;60(11):6709-6718.

Around 10,000 people die each year due to severe dengue disease, and two-thirds of the world population lives in a region where dengue disease is endemic. There has been remarkable progress in dengue virus vaccine development; however, there are no licensed antivirals for dengue disease, and none appear to be in clinical trials. We took the approach of repositioning approved drugs for anti-dengue virus activity by screening a library of pharmacologically active compounds. We identified N-Desmethylclozapine, fluoxetine hydrochloride, and salmeterol xinafoate as dengue virus inhibitors based on reductions in the numbers of infected cells and viral titers. Dengue virus RNA levels were diminished in inhibitor-treated cells, and this effect was specific to dengue virus, as other flaviviruses, such as Japanese encephalitis virus and West Nile virus, or other RNA viruses, such as respiratory syncytial virus and rotavirus, were not affected by these inhibitors. All three inhibitors specifically inhibited dengue virus replication with 50% inhibitory concentrations (IC50s) in the high-nanomolar range. Estimation of negative-strand RNA intermediates and time-of-addition experiments indicated that inhibition was occurring at a postentry stage, most probably at the initiation of viral RNA replication. Finally, we show that inhibition is most likely due to the modulation of the endolysosomal pathway and induction of autophagy.

Electrophysiological evidence showing muscarinic agonist-antagonist activities of N-desmethylclozapine using hippocampal excitatory and inhibitory neurons.[Pubmed:27048752]

Brain Res. 2016 Jul 1;1642:255-262.

The atypical antipsychotic clozapine is widely used for treatment-resistant schizophrenic patients. Clozapine and its major active metabolite, N-Desmethylclozapine (NDMC), have complex pharmacological properties, and interact with various neurotransmitter receptors. There are several biochemical studies reporting that NDMC exhibits a partial agonist profile at the human recombinant M1 muscarinic receptors. However, direct electrophysiological evidence showing the ability of NDMC to activate native M1 receptors in intact neurons is poor. Using rat hippocampal neurons, we previously demonstrated that activation of muscarinic receptors by a muscarinic agonist, oxotremorine M (oxo-M), induces a decrease in outward K(+)current at -40mV. In the present study, using this muscarinic current response we assessed agonist and antagonist activities of clozapine and NDMC at native muscarinic receptors in intact hippocampal excitatory and inhibitory neurons. Suppression of the oxo-M-induced current response by the M1 antagonist pirenzepine was evident only in excitatory neurons, while the M3 antagonist darifenacin was effective in both types of neurons. Muscarinic agonist activity of NDMC was higher than that of clozapine, higher in excitatory neurons than in inhibitory neurons, sensitive to pirenzepine, and partially masked when co-applied with clozapine. Muscarinic antagonist activity of clozapine as well as NDMC was not different between excitatory and inhibitory neurons, but clozapine was more effective than NDMC. These results demonstrate that NDMC has the ability to activate native M1 receptors expressed in hippocampal excitatory neurons, but its agonist activity might be limited in clozapine-treated patients because of the presence of excessive clozapine with muscarinic antagonist activity.

Comparative analysis of pharmacological properties of xanomeline and N-desmethylclozapine in rat brain membranes.[Pubmed:27464743]

J Psychopharmacol. 2016 Sep;30(9):896-912.

BACKGROUND: 3(3-Hexyloxy-1,2,5-thiadiazol-4-yl)-1,2,5,6-tetrahydro-1-methylpyridine (xanomeline) and N-Desmethylclozapine are of special interest as promising antipsychotics with better efficacy, especially for negative symptoms and/or cognitive/affective impairment. METHODS: The guanosine-5'-O-(3-[(35)S]thio)triphosphate ([(35)S]GTPgammaS) binding experiments were performed using (1) conventional filtration technique, (2) antibody-capture scintillation proximity assay, and (3) immunoprecipitation method, in brain membranes prepared from rat cerebral cortex, hippocampus, and striatum. RESULTS: Xanomeline had agonistic activity at the M1 muscarinic acetylcholine receptor (mAChR) in all brain regions, as well as at the 5-HT1A receptor in the cerebral cortex and hippocampus. On the other hand, N-Desmethylclozapine exhibited slight agonistic effects on the M1 mAChR, and agonistic properties at the 5-HT1A receptor in the cerebral cortex and hippocampus. This compound also behaved as an agonist at the delta-opioid receptor in the cerebral cortex and striatum. In addition, the stimulatory effects of N-Desmethylclozapine on [(35)S]GTPgammaS binding to Galphai/o were partially mediated through mAChRs (most likely M4 mAChR subtype), at least in striatum. CONCLUSIONS: The agonistic effects on the mAChRs (particularly M1 subtype, and also probably M4 subtype), the 5-HT1A receptor and the delta-opioid receptor expressed in native brain tissues, some of which are common to both compounds and others specific to either, likely shape the unique beneficial effectiveness of both compounds in the treatment for schizophrenic patients. These characteristics provide us with a clue to develop newer antipsychotics, beyond the framework of dopamine D2 receptor antagonism, that are effective not only on positive symptoms but also on negative symptoms and/or cognitive/affective impairment.

N-Desmethylclozapine is a major active metabolite of the atypical antipsychotic drug Clozapine. N-Desmethylclozapine is a potent, allosteric and partial M1 receptors agonist (EC50=115 nM) and is able to potentiate hippocampal N-methyl-d-aspartate (NMDA) receptor currents through M1 receptor activation. N-Desmethylclozapine is also a δ-opioid agonist.

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