HETEROCYCLIC CATHINONES AS POTENTIAL SCHIZOPHRENIA THERAPEUTICS
Authors: Walaska *Hana , Maryska Michal , Svobodova Lucie , Dehaen Wim , Kuchar Martin 
Published: February 2025

Abstract

Background
Schizophrenia is a serious psychiatric disease that affects more than 21 million people worldwide. There is currently no cure for this disease; however, targeting metabolites of the kynurenine pathway appears to be one of the promising treatment approaches. Kynurenic acid (KYNA) is one of the neuroactive metabolites produced in L-tryptophan catabolism via the kynurenine pathway. KYNA is an endogenous antagonist of N-methyl-D-aspartate receptor (NMDAR) and α7 nicotinic acetylcholine receptor (α 7nAChR), and is considered to have a neuroprotective effect. However, its high brain levels are associated with cognitive deficit and with the pathophysiology of schizophrenia. Key enzymes in KYNA production are kynurenine-aminotransferase (KAT) enzymes. Previous in vivo studies have shown that KAT inhibition leads to improvement in cognitive functions, so they are promising for the schizophrenia treatment. Several classes of KAT inhibitors have already been published, however none of them have reached later stages of clinical trials so far. Therefore, it is crucial to continue the process of finding suitable clinical candidates with more satisfying pharmacokinetic and pharmacodynamic properties.

Aims & Objectives
The study aimed to predict a group of new potential KAT inhibitors with a focus on the most active form KAT-II. Within the Structure Activity Relationship (SAR) study, the synthesis of the predicted candidates followed. Subsequently, the research aimed to verify the inhibitory activity of the prepared substances via in vitro study.

Method
Prediction of suitable candidates was performed by pharmacophore modelling and molecular docking methods using Molecular Operating Environment software package. The designed molecules were synthetized from commercially available starting materials and analyzed using NMR spectrometry (Agilent 400-MR DD2), HRMS (Agilent 6550 iFunnel Q-TOF) with ESI ionization and melting point measurement (PHMK 78/1742 VEB Analytik Dresden apparatus). Purity determination of all compounds was performed by HPLC/UV technique (Agilent 1290 Infinity LC). Their inhibitory activity was determined via Coupled Fluorescence In Vitro Inhibition Assay using pre-prepared enzyme hKAT-II. The inhibitory activity was calculated in %I at a given concentration and IC50 values were also determined (GraphPad Prism 8 software).

Results
In this study a group of new heterocyclic cathinone-based KAT-II inhibitors were predicted. These were successfully synthesized and fully analyzed. The inhibitory activity of the prepared pharmacophores was verified and the best compounds showed sub-micromolar inhibitory activity with one substance even showing an IC50 value of 0.097 &micro;M.

Discussion & Conclusion
In this work we designed irreversible inhibitors of KAT-II using pharmacophore modelling and molecular docking. Within the SAR study we described the synthesis of benzothiazole-, thiazole- and triazole- based cathinones. The observed inhibitory activities of prepared substances confirmed our computational model and the best compounds exhibited sub-micromolar activity. Moreover, unlike many previously proposed KAT inhibitors, cathinone-based candidates should be able to pass through the BBB. Currently, we are focusing on the in vivo evaluation of the prepared inhibitors together with pharmacokinetic experiments.

References
Maryška, M.; Svobodová, L.; Dehaen, W. et al. Heterocyclic Cathinones as Inhibitors of Kynurenine Aminotransferase II— Design, Synthesis, and Evaluation. Pharmaceuticals 2021, 14, 1291.