Synthesis, structure-affinity relationships, and modeling of AMDA analogs at 5-HT2A and H1 receptors: structural factors contributing to selectivity

Kite-Shaped Molecules Block SARS-CoV-2 Cell Entry at a Post-Attachment Step

Anti-viral small molecules are currently lacking for treating coronavirus infection. The long development timescales for such drugs are a major problem, but could be shortened by repurposing existing drugs. We therefore screened a small library of FDA-approved compounds for potential severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) antivirals using a pseudovirus system that allows a sensitive read-out of infectivity. A group of structurally-related compounds, showing moderate inhibitory activity with IC₅₀ values in the 2–5 μM range, were identified. Further studies demonstrated that these “kite-shaped” molecules were surprisingly specific for SARS-CoV-1 and SARS-CoV-2 and that they acted early in the entry steps of the viral infectious cycle, but did not affect virus attachment to the cells. Moreover, the compounds were able to prevent infection in both kidney- and lung-derived human cell lines. The structural homology of the hits allowed the production of a well-defined pharmacophore that was found to be highly accurate in predicting the anti-viral activity of the compounds in the screen. We discuss the prospects of repurposing these existing drugs for treating current and future coronavirus outbreaks.

Kite-shaped molecules block SARS-CoV-2 cell entry at a post-attachment step.. [DOI: 10.1101/2021.05.29.446272] [Citation(s) in RCA: 0] [Impact Index Per Article: 0]

Anti-viral small molecules are currently lacking for treating coronavirus infection. The long development timescales for such drugs are a major problem, but could be shortened by repurposing existing drugs. We therefore screened a small library of FDA-approved compounds for potential severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) antivirals using a pseudovirus system that allows a sensitive read-out of infectivity. A group of structurally-related compounds, showing moderate inhibitory activity with IC50values in the 1-5µM range, were identified. Further studies demonstrated that these ‘kite-shaped’ molecules were surprisingly specific for SARS-CoV and SARS-CoV-2 and that they acted early in the entry steps of the viral infectious cycle, but did not affect virus attachment to the cells. Moreover the compounds were able to prevent infection in both kidney- and lung-derived human cell lines. The structural homology of the hits allowed the production of a well-defined pharmacophore that was found to be highly accurate in predicting the anti-viral activity of the compounds in the screen. We discuss the prospects of repurposing these existing drugs for treating current and future coronavirus outbreaks.

Investigation of dielectric breakdown in silica-epoxy nanocomposites using designed interfaces

Adding nano-sized fillers to epoxy has proven to be an effective method for improving dielectric breakdown strength (DBS). Evidence suggests that dispersion state, as well as chemistry at the filler-matrix interface can play a crucial role in property enhancement. Herein we investigate the contribution of both filler dispersion and surface chemistry on the AC dielectric breakdown strength of silica-epoxy nanocomposites. Ligand engineering was used to synthesize bimodal ligands onto 15nm silica nanoparticles consisting of long epoxy compatible, poly(glycidyl methacrylate) (PGMA) chains, and short, π-conjugated, electroactive surface ligands. Surface initiated RAFT polymerization was used to synthesize multiple graft densities of PGMA chains, ultimately controlling the dispersion of the filler. Thiophene, anthracene, and terthiophene were employed as π-conjugated surface ligands that act as electron traps to mitigate avalanche breakdown. Investigation of the synthesized multifunctional nanoparticles was effective in defining the maximum particle spacing or free space length (L_f) that still leads to property enhancement, as well as giving insight into the effects of varying the electronic nature of the molecules at the interface on breakdown strength. Optimization of the investigated variables was shown to increase the AC dielectric breakdown strength of epoxy composites as much as 34% with only 2wt% silica loading.

An Unprecedented Photochemical Reaction for Anthracene-Containing Derivatives

A series of anthracene-containing derivatives have been synthesised and characterised. The photochemical behaviour of these derivatives have been investigated by ¹ H NMR spectroscopy. An unprecedented photolysis reaction for anthracene-containing derivatives was observed in the case of anthracenes directly armed with a -CH₂ O-R group upon UV irradiation. The photolysis reaction process has been demonstrated to occur in three steps. Firstly, the anthracene-containing derivatives are converted into the corresponding endoperoxide intermediate upon UV irradiation in the presence of air; then, the endoperoxide intermediate is decomposed to the corresponding starting compound and 9-anthraldehyde; finally, 9-anthraldehyde is further oxidised to anthraquinone. Additionally, the photolysis reaction of anthracene-containing derivatives is significantly promoted in the presence of a thiacalix[4]arene platform.

A structural chemogenomics analysis of aminergic GPCRs: lessons for histamine receptor ligand design

BACKGROUND AND PURPOSE

Chemogenomics focuses on the discovery of new connections between chemical and biological space leading to the discovery of new protein targets and biologically active molecules. G-protein coupled receptors (GPCRs) are a particularly interesting protein family for chemogenomics studies because there is an overwhelming amount of ligand binding affinity data available. The increasing number of aminergic GPCR crystal structures now for the first time allows the integration of chemogenomics studies with high-resolution structural analyses of GPCR-ligand complexes.

EXPERIMENTAL APPROACH

In this study, we have combined ligand affinity data, receptor mutagenesis studies, and amino acid sequence analyses to high-resolution structural analyses of (hist)aminergic GPCR-ligand interactions. This integrated structural chemogenomics analysis is used to more accurately describe the molecular and structural determinants of ligand affinity and selectivity in different key binding regions of the crystallized aminergic GPCRs, and histamine receptors in particular.

KEY RESULTS

Our investigations highlight interesting correlations and differences between ligand similarity and ligand binding site similarity of different aminergic receptors. Apparent discrepancies can be explained by combining detailed analysis of crystallized or predicted protein-ligand binding modes, receptor mutation studies, and ligand structure-selectivity relationships that identify local differences in essential pharmacophore features in the ligand binding sites of different receptors.

CONCLUSIONS AND IMPLICATIONS

We have performed structural chemogenomics studies that identify links between (hist)aminergic receptor ligands and their binding sites and binding modes. This knowledge can be used to identify structure-selectivity relationships that increase our understanding of ligand binding to (hist)aminergic receptors and hence can be used in future GPCR ligand discovery and design.

Affinity of aporphines for the human 5-HT2A receptor: insights from homology modeling and molecular docking studies

Analogs of nantenine were docked into a modeled structure of the human 5-HT(2A) receptor using ICM Pro, GLIDE, and GOLD docking methods. The resultant docking scores were used to correlate with observed in vitro apparent affinity (K(e)) data. The GOLD docking algorithm when used with a homology model of 5-HT(2A), based on a bovine rhodopsin template and built by the program MODELLER, gives results which are most in agreement with the in vitro results. Further analysis of the docking poses among members of a C1 alkyl series of nantenine analogs, indicate that they bind to the receptor in a similar orientation, but differently than nantenine. Besides an important interaction between the protonated nitrogen of the C1 alkyl analogs and residue Asp155, we identified Ser242, Phe234, and Gly238 as key residues responsible for the affinity of these compounds for the 5-HT(2A) receptor. Specifically, the ability of some of these analogs to establish a H-bond with Ser242 and hydrophobic interactions with Phe234 and Gly238 appears to explain their enhanced affinity as compared to nantenine.

9-Aminomethyl-9,10-dihydroanthracene (AMDA) analogs as structural probes for steric tolerance in 5-HT2A and H1 receptor binding sites

Synthesis, radioligand binding and molecular modeling studies of several 9-aminomethyl-9,10-dihydroanthracene (AMDA) analogs were carried out to determine the extent of the steric tolerance associated with expansion of the tricyclic ring system and amine substitution at 5-HT(2A) and H(1) receptors. A mixture of (7,12-dihydrotetraphene-12-yl)methanamine and (6,11-dihydrotetracene-11-yl)methanamine in a 75-25% ratio was found to have an apparent K(i) of 10nM at the 5-HT(2A) receptor. A substantial binding affinity for (7,12-dihydrotetraphene-3-methoxy-12-yl)methanamine at the 5-HT(2A) receptor (K(i)=21 nM) was also observed. Interestingly, this compound was found to have 100-fold selectivity for 5-HT(2A) over the H(1) receptor (K(i)=2500 nM). N-Phenylalkyl-AMDA derivatives, in which the length of the alkyl chain varied from methylene to n-butylene, were found to have only weak affinity for both 5-HT(2A) and H(1) receptors (K(i)=223 to 964 nM). Our results show that large rigid annulated AMDA analogs can be sterically accommodated within the proposed 5-HT(2A) binding site.