Virtual Screening Approaches to Identify Promising Multitarget-Directed Ligands for the Treatment of Autism Spectrum Disorder

Abstract

Autism spectrum disorder is a complex neurodevelopmental disorder. The available medical treatment options for autism spectrum disorder are very limited. While the etiology and pathophysiology of autism spectrum disorder are still not fully understood, recent studies have suggested that wide alterations in the GABAergic, glutamatergic, cholinergic, and serotonergic systems play a key role in its development and progression. Histamine neurotransmission is known to have complex interactions with other neurotransmitters that fit perfectly into the complex etiology of this disease. Multitarget-directed compounds with an affinity for the histamine H₃ receptor indicate an interesting profile of activity against autism spectrum disorder in animal models. Here, we present the results of our research on the properties of (4-piperazin-1-ylbutyl)guanidine derivatives acting on histamine H₃ receptors as potential multitarget ligands. Through the virtual screening approach, we identified promising ligands among 32 non-imidazole histamine H₃ receptor antagonists/inverse agonists with potential additional activity against the dopamine D₂ receptor and/or cholinesterases. The virtual screening protocol integrated predictions from SwissTargetPrediction, SEA, and PPB2 tools, along with molecular docking simulations conducted using GOLD 5.3 and Glide 7.5 software. Among the selected ligands, compounds 25 and 30 blocked radioligand binding to the D₂ receptor at over 50% at a screening concentration of 1 µM. Further experiments allowed us to determine the pK_i value at the D₂ receptor of 6.22 and 6.12 for compounds 25 and 30, respectively. Our findings suggest that some of the tested compounds could be promising multitarget-directed ligands for the further research and development of more effective treatments for autism spectrum disorder.

Keywords: autism spectrum disorder; cholinesterases; dopamine receptors; histamine H3 receptor; multitarget-directed ligands; virtual screening.

Figure 1

Structures of ST-2223, acting as histamine H₃, D₂/D₃ receptor antagonists, and E100, H₃R antagonist with acetylcholinesterase inhibitory activity.

Figure 2

The common structural pattern in the majority of the compounds that underwent testing. X and Y are either CH or N atoms; n ranges from 2 to 6 carbon atoms.

Figure 3

Structure (A) and predicted conformations of compound 25, which was highly rated by target predictors and molecular docking, within binding sites of H₃R (B) and D₂R (C).

Figure 4

Structure of the strongest BChE inhibitor, compound 16 (A), and its binding mode to H₃R (B), AChE (C), and BChE (D).

Figure 5

Structures of novel multitarget-directed ligands 25 and 30, combining activity against H₃R and D₂R.