Discovery and in vitro Evaluation of Novel Serotonin 5-HT2A Receptor Ligands Identified Through Virtual Screening

The 5-HT2A receptor is a molecular target of high pharmacological importance. Ligands of this protein, particularly atypical antipsychotics, are useful in the treatment of numerous mental disorders, including schizophrenia and major depressive disorder. Structure-based virtual screening using a 5-HT2A receptor complex was performed to identify novel ligands for the 5-HT2A receptor, serving as potential antidepressants. From the Enamine screening library, containing over 4 million compounds, 48 molecules were selected for subsequent experimental validation. These compounds were tested against the 5-HT2A receptor in radioligand binding assays. From the tested batch, six molecules were identified as ligands of the main molecular target and were forwarded to a more detailed in vitro profiling. This included radioligand binding assays at 5-HT1A, 5-HT7, and D2 receptors and functional studies at 5-HT2A receptors. These compounds were confirmed to show a binding affinity for at least one of the targets tested in vitro. Thus, the success rate for the inactive template-based screening reached 17%, while it was 9% for the active template-based screening. Similarity and fragment analysis indicated the structural novelty of the identified compounds. Pharmacokinetics for these molecules was determined using in silico approaches.

Novel multi-target ligands of dopamine and serotonin receptors for the treatment of schizophrenia based on indazole and piperazine scaffolds-synthesis, biological activity, and structural evaluation

Schizophrenia is a chronic mental disorder that is not satisfactorily treated with available antipsychotics. The presented study focuses on the search for new antipsychotics by optimising the compound D2AAK3, a multi-target ligand of G-protein-coupled receptors (GPCRs), in particular D₂, 5-HT_1A, and 5-HT_2A receptors. Such receptor profile may be beneficial for the treatment of schizophrenia. Compounds 1-16 were designed, synthesised, and subjected to further evaluation. Their affinities for the above-mentioned receptors were assessed in radioligand binding assays and efficacy towards them in functional assays. Compounds 1 and 10, selected based on their receptor profile, were subjected to in vivo tests to evaluate their antipsychotic activity, and effect on memory and anxiety processes. Molecular modelling was performed to investigate the interactions of the studied compounds with D₂, 5-HT_1A, and 5-HT_2A receptors on the molecular level. Finally, X-ray study was conducted for compound 1, which revealed its stable conformation in the solid state.

Exploring the Potential of Sulfur Moieties in Compounds Inhibiting Steroidogenesis

This study reports on the synthesis and evaluation of novel compounds replacing the nitrogen-containing heterocyclic ring on the chemical backbone structure of cytochrome P450 17α-hydroxylase/12,20-lyase (CYP17A1) inhibitors with a phenyl bearing a sulfur-based substituent. Initial screening revealed compounds with marked inhibition of CYP17A1 activity. The selectivity of compounds was thereafter determined against cytochrome P450 21-hydroxylase, cytochrome P450 3A4, and cytochrome P450 oxidoreductase. Additionally, the compounds showed weak inhibitory activity against aldo-keto reductase 1C3 (AKR1C3). The compounds' impact on steroid hormone levels was also assessed, with some notable modulatory effects observed. This work paves the way for developing more potent dual inhibitors specifically targeting CYP17A1 and AKR1C3.

Development and Characterization of Novel Selective, Non-Basic Dopamine D2 Receptor Antagonists for the Treatment of Schizophrenia

The dopamine D₂ receptor, which belongs to the family of G protein-coupled receptors (GPCR), is an important and well-validated drug target in the field of medicinal chemistry due to its wide distribution, particularly in the central nervous system, and involvement in the pathomechanism of many disorders thereof. Schizophrenia is one of the most frequent diseases associated with disorders in dopaminergic neurotransmission, and in which the D₂ receptor is the main target for the drugs used. In this work, we aimed at discovering new selective D₂ receptor antagonists with potential antipsychotic activity. Twenty-three compounds were synthesized, based on the scaffold represented by the D2AAK2 compound, which was discovered by our group. This compound is an interesting example of a D₂ receptor ligand because of its non-classical binding to this target. Radioligand binding assays and SAR analysis indicated structural modifications of D2AAK2 that are possible to maintain its activity. These findings were further rationalized using molecular modeling. Three active derivatives were identified as D₂ receptor antagonists in cAMP signaling assays, and the selected most active compound 17 was subjected to X-ray studies to investigate its stable conformation in the solid state. Finally, effects of 17 assessed in animal models confirmed its antipsychotic activity in vivo.

Non-steroidal CYP17A1 Inhibitors: Discovery and Assessment

CYP17A1 is an enzyme that plays a major role in steroidogenesis and is critically involved in the biosynthesis of steroid hormones. Therefore, it remains an attractive target in several serious hormone-dependent cancer diseases, such as prostate cancer and breast cancer. The medicinal chemistry community has been committed to the discovery and development of CYP17A1 inhibitors for many years, particularly for the treatment of castration-resistant prostate cancer. The current Perspective reflects upon the discovery and evaluation of non-steroidal CYP17A1 inhibitors from a medicinal chemistry angle. Emphasis is placed on the structural aspects of the target, key learnings from the presented chemotypes, and design guidelines for future inhibitors.

Discovery of novel arylpiperazine-based DA/5-HT modulators as potential antipsychotic agents – Design, synthesis, structural studies and pharmacological profiling

Schizophrenia is a mental disorder with a complex pathomechanism involving many neurotransmitter systems. Among the currently used antipsychotics, classical drugs acting as dopamine D₂ receptor antagonists, and drugs of a newer generation, the so-called atypical antipsychotics, can be distinguished. The latter are characterized by a multi-target profile of action, affecting, apart from the D₂ receptor, also serotonin receptors, in particular 5-HT_2A and 5-HT_1A. Such profile of action is considered superior in terms of both efficacy in treating symptoms and safety. In the search for new potential antipsychotics of such atypical receptor profile, an attempt was made to optimize the arylpiperazine based virtual hit, D2AAK3, which in previous studies displayed an affinity for D₂, 5-HT_1A and 5-HT_2A receptors, and showed antipsychotic activity in vivo. In this work, we present the design of D2AAK3 derivatives (1-17), their synthesis, and structural and pharmacological evaluation. The obtained compounds show affinities for the receptors of interest and their efficacy as antagonists/agonists towards them was confirmed in functional assays. For the selected compound 11, detailed structural studies were carried out using molecular modeling and X-ray methods. Additionally, ADMET parameters and in vivo antipsychotic activity, as well as influence on memory and anxiety processes were evaluated in mice, which indicated good therapeutic potential and safety profile of the studied compound.

Allosteric Modulators of Dopamine D2 Receptors for Fine-Tuning of Dopaminergic Neurotransmission in CNS Diseases: Overview, Pharmacology, Structural Aspects and Synthesis

Allosteric modulation of G protein-coupled receptors (GPCRs) is nowadays a hot topic in medicinal chemistry. Allosteric modulators, i.e., compounds which bind in a receptor site topologically distinct from orthosteric sites, exhibit a number of advantages. They are more selective, safer and display a ceiling effect which prevents overdosing. Allosteric modulators of dopamine D₂ receptor are potential drugs against a number of psychiatric and neurological diseases, such as schizophrenia and Parkinson's disease. In this review, an insightful summary of current research on D₂ receptor modulators is presented, ranging from their pharmacology and structural aspects of ligand-receptor interactions to their synthesis.

Multi-target derivatives of D2AAK1 as potential antipsychotics - the effect of the substitution in the indole moiety

Schizophrenia is a complex disease which is best treated with multi-target drugs, such as atypical antipsychotics. Previously, using structure-based virtual screening we found a virtual hit D2AAK1 with nanomolar affinity to dopamine and serotonin receptors important in schizophrenia pharmacotherapy. As a part of optimization campaign of D2AAK1 we obtained its 17 derivatives also displaying a multi-target profile. Selected compounds were tested against off-targets in schizophrenia, i.e. histamine H 1 receptor and muscarinic M 1 receptor and did not display considerable affinity to these receptors. Two most promising compounds were subjected to behavioral studies. These compounds decreased amphetamine-induced hyperactivity in mice which indicates their antipsychotic potential. The compounds did not interfere with the memory consolidation in mice as determined in the passive avoidance test. The favorable pharmacological profile of the compounds was rationalized using molecular modeling.

5-Methoxy-1-methyl-2-{[4-(2-hydroxyphenyl)piperazin-1-yl]methyl}-1Hindole (KAD22) with Antioxidant Activity

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Compound KAD22 (5-methoxy-1-methyl-2-[4-(2-hydroxyphenyl)piperazin-1-yl]methyl-1H-indole) was designed as a potential dopamine D2 receptor agonist with antioxidant activity for possible treatment of Parkinson’s disease. The compound was obtained from 5-methoxy-1-methyl-1H-indole-2-carbaldehyde and 2-(piperazin-1-yl)phenol. KAD22 showed no affinity to dopamine D2 receptor but it is a potent antioxidant. Experimental and computational structural studies (conformational analysis, HOMO and LUMO orbitals, electrostatic potential map, non-covalent interaction plot, spectral properties, ligand-receptor interactions) of KAD22 were performed to address its biological activity.

WaterMap guided structure-based virtual screening for acetylcholinesterase inhibitors

Structure-based virtual screening of the Enamine database of 1.7 million compounds followed by WaterMap calculations (a molecular dynamics simulation-based method) was applied to identify novel AChE inhibitors. The inhibitory potency of 29 selected compounds against electric eel (ee) AChE was determined using the Ellman's method. Three compounds were found active (success rate 10%). For the most potent compound (~40% of inhibition at 10 μM), 20 derivatives were discovered based on the Enamine similarity search. Finally, five compounds were found promising  (IC 50 ranged from 6.3 µM to 17.5 µM) inhibitors of AChE. The performed similarity and fragment analysis confirmed significant structural novelty of novel AChE inhibitors. Toxicity/safety of selected compounds was determined in zebrafish model.

Synthesis and Structure–Activity Relationships of Novel Non-Steroidal CYP17A1 Inhibitors as Potential Prostate Cancer Agents

Twenty new compounds, targeting CYP17A1, were synthesized, based on our previous work on a benzimidazole scaffold, and their biological activity evaluated. Inhibition of CYP17A1 is an important modality in the treatment of prostate cancer, which remains the most abundant cancer type in men. The biological assessment included CYP17A1 hydroxylase and lyase inhibition, CYP3A4 and P450 oxidoreductase (POR) inhibition, as well as antiproliferative activity in PC3 prostate cancer cells. The most potent compounds were selected for further analyses including in silico modeling. This combined effort resulted in a compound (comp 2, IC₅₀ 1.2 µM, in CYP17A1) with a potency comparable to abiraterone and selectivity towards the other targets tested. In addition, the data provided an understanding of the structure–activity relationship of this novel non-steroidal compound class.

Discovery of Novel Non-Steroidal Cytochrome P450 17A1 Inhibitors as Potential Prostate Cancer Agents

The current study presents the design, synthesis, and evaluation of novel cytochrome P450 17A1 (CYP17A1) ligands. CYP17A1 is a key enzyme in the steroidogenic pathway that produces androgens among other steroids, and it is implicated in prostate cancer. The obtained compounds are potent enzyme inhibitors (sub µM) with antiproliferative activity in prostate cancer cell lines. The binding mode of these compounds is also discussed.

Tuning Down the Pain - An Overview of Allosteric Modulation of Opioid Receptors: Mechanisms of Modulation, Allosteric Sites, Modulator Syntheses

Opioid signaling plays a central role in pain perception. As such, it remains the main target in the development of antinociceptive agents, despite serious side effects involved. In recent years, hopes for improved opioid painkillers are rising, together with our understanding of allosterism and biased signaling mechanisms. In this review, we focus on recently discovered allosteric modulators of opioid receptors, insights into phenomena underlying their action, as well as on how they extend our understanding of mechanisms of previously known compounds. A brief overlook of their synthesis is also presented.

Probing the Existence of a Metastable Binding Site at the β2-Adrenergic Receptor with Homobivalent Bitopic Ligands

Herein, we report the development of bitopic ligands aimed at targeting the orthosteric binding site (OBS) and a metastable binding site (MBS) within the same receptor unit. Previous molecular dynamics studies on ligand binding to the β₂-adrenergic receptor (β₂AR) suggested that ligands pause at transient, less-conserved MBSs. We envisioned that MBSs can be regarded as allosteric binding sites and targeted by homobivalent bitopic ligands linking two identical pharmacophores. Such ligands were designed based on docking of the antagonist (S)-alprenolol into the OBS and an MBS and synthesized. Pharmacological characterization revealed ligands with similar potency and affinity, slightly increased β₂/β₁AR-selectivity, and/or substantially slower β₂AR off-rates compared to (S)-alprenolol. Truncated bitopic ligands suggested the major contribution of the metastable pharmacophore to be a hydrophobic interaction with the β₂AR, while the linkers alone decreased the potency of the orthosteric fragment. Altogether, the study underlines the potential of targeting MBSs for improving the pharmacological profiles of ligands.

Synthesis, Structural Studies and Molecular Modelling of a Novel Imidazoline Derivative with Antifungal Activity

Six novel imidazoline derivatives were synthesized and tested in antifungal assays. One of the compounds, N-cyclohexyl-2-imino-3-(4-nitrophenyl)imidazolidine-1-carboxamide showed moderate activity against several clinical strains of Candida albicans. Its structure was solved by X-ray crystallography and its mode of action was deduced using molecular modelling. It was found to be similar to that of fluconazole. The potential for further optimization including SAR of the compound is briefly discussed.

Discovery of nitroaryl urea derivatives with antiproliferative properties

A series of urea derivatives bearing nitroaryl moiety has been synthesized and assayed for their potential antiproliferative activities. Some of the tested compounds displayed activity in RK33 laryngeal cancer cells and TE671 rhabdomyosarcoma cells while being generally less toxic to healthy HSF human fibroblasts cells. One compound was demonstrated to be a moderate CDK2 inhibitor with IC50 = 14.3 µM. Its structure was solved by an X-ray crystallography and molecular modelling was performed to determine structure-activity relationship. Obtained compounds constitute novel structures and generally demonstrated greater cytotoxicity in comparison to cisplatin. This study offers new structural motifs with potential for further development.