Bioisosteric replacement based on 1,2,4-oxadiazoles in the discovery of 1H-indazole-bearing neuroprotective MAO B inhibitors.

Following a hybridization strategy, a series of 5-substituted-1H-indazoles were designed and evaluated in vitro as inhibitors of human monoamine oxidase (hMAO) A and B. Among structural modifications, the bioisostere-based introduction of 1,2,4-oxadiazole ring returned the most potent and selective human MAO B inhibitor (compound 20, IC50 = 52 nM, SI > 192). The most promising inhibitors were studied in cell-based neuroprotection models of SH-SY5Y and astrocytes line against H2O2. Moreover, preliminary drug-like features (aqueous solubility at pH 7.4; hydrolytic stability at acidic and neutral pH) were assessed for selected 1,2,4-oxadiazoles and compared to amide analogues through RP-HPLC methods. Molecular docking simulations highlighted the crucial role of molecular flexibility in providing a better shape complementarity for compound 20 within MAO B enzymatic cleft than rigid analogue 18. Enzymatic kinetics analysis along with thermal stability curves (Tm shift = +2.9 °C) provided clues of a tight-binding mechanism for hMAO B inhibition by 20.

Design, Synthesis, Biological Evaluation, and Computational Studies of Novel Ureidopropanamides as Formyl Peptide Receptor 2 (FPR2) Agonists to Target the Resolution of Inflammation in Central Nervous System Disorders.

Formyl peptide receptor 2 (FPR2) agonists can boost the resolution of inflammation and can offer alternative approaches for the treatment of pathologies with underlying chronic neuroinflammation, including neurodegenerative disorders. Starting from the FPR2 agonist 2 previously identified in our laboratory and through fine-tuning of FPR2 potency and metabolic stability, we have identified a new series of ureidopropanamide derivatives endowed with a balanced combination of such properties. Computational studies provided insights into the key interactions of the new compounds for FPR2 activation. In mouse microglial N9 cells and in rat primary microglial cells stimulated with lipopolysaccharide, selected compounds inhibited the production of pro-inflammatory cytokines, counterbalanced the changes in mitochondrial function, and inhibited caspase-3 activity. Among the new agonists, (S)-11l stands out also for the ability to permeate the blood-brain barrier and to accumulate in the mouse brain in vivo, thus representing a valuable pharmacological tool for studies in vivo.

Design and Synthesis of Arylpiperazine Serotonergic/Dopaminergic Ligands with Neuroprotective Properties.

Long-chain arylpiperazine scaffold is a versatile template to design central nervous system (CNS) drugs that target serotonin and dopamine receptors. Here we describe the synthesis and biological evaluation of ten new arylpiperazine derivatives designed to obtain an affinity profile at serotonin 5-HT1A, 5-HT2A, 5-HT7 receptor, and dopamine D2 receptor of prospective drugs to treat the core symptoms of autism spectrum disorder (ASD) or psychosis. Besides the structural features required for affinity at the target receptors, the new compounds incorporated structural fragments with antioxidant properties to counteract oxidative stress connected with ASD and psychosis. All the new compounds showed CNS MultiParameter Optimization score predictive of desirable ADMET properties and cross the blood-brain barrier. We identified compound 12a that combines an affinity profile compatible with antipsychotic activity (5-HT1AKi = 41.5 nM, 5-HT2AKi = 315 nM, 5-HT7Ki = 42.5 nM, D2Ki = 300 nM), and compound 9b that has an affinity profile consistent with studies in the context of ASD (5-HT1AKi = 23.9 nM, 5-HT2AKi = 39.4 nM, 5-HT7Ki = 45.0 nM). Both compounds also had antioxidant properties. All compounds showed low in vitro metabolic stability, the only exception being compound 9b, which might be suitable for studies in vivo.

The N-Formyl Peptide Receptor 2 (FPR2) Agonist MR-39 Improves Ex Vivo and In Vivo Amyloid Beta (1-42)-Induced Neuroinflammation in Mouse Models of Alzheimer's Disease.

The major histopathological hallmarks of Alzheimer's disease (AD) include ß-amyloid (Aß) plaques, neurofibrillary tangles, and neuronal loss. Aß 1-42 (Aß1-42) has been shown to induce neurotoxicity and secretion of proinflammatory mediators that potentiate neurotoxicity. Proinflammatory and neurotoxic activities of Aß1-42 were shown to be mediated by interactions with several cell surface receptors, including the chemotactic G protein-coupled N-formyl peptide receptor 2 (FPR2). The present study investigated the impact of a new FPR2 agonist, MR-39, on the neuroinflammatory response in ex vivo and in vivo models of AD. To address this question, organotypic hippocampal cultures from wild-type (WT) and FPR2-deficient mice (knockout, KO, FPR2-/-) were treated with fibrillary Aß1-42, and the effect of the new FPR2 agonist MR-39 on the release of pro- and anti-inflammatory cytokines was assessed. Similarly, APP/PS1 double-transgenic AD mice were treated for 20 weeks with MR-39, and immunohistological staining was performed to assess neuronal loss, gliosis, and Aß load in the hippocampus and cortex. The data indicated that MR-39 was able to reduce the Aß1-42-induced release of proinflammatory cytokines and to improve the release of anti-inflammatory cytokines in mouse hippocampal organotypic cultures. The observed effect was apparently related to the inhibition of the MyD88/TRAF6/NFкB signaling pathway and a decrease in NLRP3 inflammasome activation. Administration of MR-39 to APP/PS1 mice improved neuronal survival and decreased microglial cell density and plaque load.These results suggest that FPR2 may be a promising target for alleviating the inflammatory process associated with AD and that MR-39 may be a useful therapeutic agent for AD.

Knowledge-Based Design of Long-Chain Arylpiperazine Derivatives Targeting Multiple Serotonin Receptors as Potential Candidates for Treatment of Autism Spectrum Disorder.

Autism spectrum disorder (ASD) includes a group of neurodevelopmental disorders characterized by core symptoms such as impaired social interaction and communication, repetitive and stereotyped behaviors, and restricted interests. To date, there are no effective treatments for these core symptoms. Several studies have shown that the brain serotonin (5-HT) neurotransmission system is altered in both ASD patients and animal models of the disease. Multiple pieces of evidence suggest that targeting 5-HT receptors may treat the core symptoms of ASD and associated intellectual disabilities. In fact, stimulation of the 5-HT1A receptor reduces repetitive and restricted behaviors; blockade of the 5-HT2A receptor reduces both learning deficits and repetitive behavior, and activation of the 5-HT7 receptor improves cognitive performances and reduces repetitive behavior. On such a basis, we have designed novel arylpiperazine derivatives pursuing unprecedently reported activity profiles: dual 5-HT7/5-HT1A receptor agonist properties and mixed 5-HT7 agonist/5-HT1A agonist/5-HT2A antagonist properties. Seventeen new compounds were synthesized and tested in radioligand binding assay at the target receptors. We have identified the dual 5-HT1AR/5-HT7R agonists 8c and 29 and the mixed 5-HT1AR agonist/5-HT7R agonist/5-HT2AR antagonist 20b. These compounds are metabolically stable in vitro and have suitable central nervous system druglike properties.

G-Protein Coupled Receptors Involved in the Resolution of Inflammation: Ligands and Therapeutic Perspectives.

Dysregulated inflammation is a central pathological process in diverse disease states, including neurodegenerative disorders. The recent concept of "resolution of inflammation" is offering a conceptual change for the diagnosis and the development of new therapeutic approaches for chronic inflammatory diseases. Resolution of inflammation terminates the inflammatory response promoting the return to tissue homeostasis through the action of several classes of mediators, termed specialized pro-resolving lipid mediators (SPMs), that include lipoxins, resolvins, protectins, and maresins. SPMs provide "stop signals" that reduce the number of immune cells at the site of insult and increase the clearance of apoptotic cells through phagocytosis. SPMs elicit their effects through the interaction with specific G-protein coupled receptors (GPCRs). The elucidation of the pathways downstream of the GPCRs involved in the resolution of chronic inflammation is opening novel opportunities to generate novel anti-inflammatory agents. This review focuses on the SPMs and the receptors through which their effects are mediated. The medicinal chemistry of the modulators of the GPCRs involved in the resolution of inflammation will be illustrated, by highlighting the potential for developing new antiinflammatory drugs.

Aurantiamide-related dipeptide derivatives are formyl peptide receptor 1 antagonists.

Formyl peptide receptor 1 (FPR1) is expressed on a variety of immune system cells and is a key regulator of the inflammatory environment. Therefore, the development of FPR1 antagonists may represent a novel approach for modulating innate immunity and treating inflammatory diseases. Starting from a dipeptide scaffold that is structurally related to the natural product aurantiamide, we investigated the structure-activity relationships of the dipeptide (2R,2'S)-6, which was reported as an FPR1 antagonist. We found that the absolute configuration 2R,2'S was preferred to obtain potent and selective FPR1 antagonists. The structural modifications performed on the terminal fragments of the molecule suggest that the size of the substituents can greatly influence the interaction with FPR1. These compounds behaved as antagonists in human neutrophils and were able to inhibit formyl peptide-induced chemotaxis. Since FPR1 is a key regulator of the inflammatory environment, the dipeptide derivatives described here may represent important leads for the development of new potent and selective FPR1 antagonists for the treatment of neutrophil-mediated inflammatory diseases.