Synthesis, docking, and biological evaluation of novel 1-benzyl-4-(4-(R)-5-sulfonylidene-4,5-dihydro-1H-1,2,4-triazol-3-yl)pyrrolidin-2-ones as potential nootropic agents.

In order to search for innovative nootropic agents, new 1-benzyl-4- (4- (R)-5-sulfonylidene-4,5-dihydro-1H-1,2,4-triazol-3-yl) pyrrolidine-2-ones was synthesized by reacting benzylamine with itaconic acid to 1-benzyl-5-oxopyrrolidine-3-carboxylic acid, which was then subjected to hydrazinolysis followed by the addition of substituted isothiacyanate followed by cyclization of intermediate thiosemicarbazides. The structure and purity of the obtained substances were confirmed by elemental analysis, 1H NMR spectroscopy, 13C NMR spectroscopy and LC/MS. Docking studies were performed for the substances synthesized using Autodock 4.2 software. Approximate values of LD50 (in silico determination) are around 870-1000 mg/kg. All synthesized substances were tested for nootropic activity by the passive avoidance test on the scopolamine amnesia model in doses that are about 1/10 of the estimated LD50. Based on the results of docking and pharmacological experiment, the most promising substances 7a, as well as 7e, 7f were identified. The results of molecular docking (hit compound 7a) indicate a positive correlation between the obtained values of docking studies and experimental data.

Photoswitchable Pseudoirreversible Butyrylcholinesterase Inhibitors Allow Optical Control of Inhibition in Vitro and Enable Restoration of Cognition in an Alzheimer's Disease Mouse Model upon Irradiation.

To develop tools to investigate the biological functions of butyrylcholinesterase (BChE) and the mechanisms by which BChE affects Alzheimer's disease (AD), we synthesized several selective, nanomolar active, pseudoirreversible photoswitchable BChE inhibitors. The compounds were able to specifically influence different kinetic parameters of the inhibition process by light. For one compound, a 10-fold difference in the IC50-values (44.6 nM cis, 424 nM trans) in vitro was translated to an "all or nothing" response with complete recovery in a murine cognition-deficit AD model at dosages as low as 0.3 mg/kg.

Structure-Based Design and Optimization of FPPQ, a Dual-Acting 5-HT3 and 5-HT6 Receptor Antagonist with Antipsychotic and Procognitive Properties.

In line with recent clinical trials demonstrating that ondansetron, a 5-HT3 receptor (5-HT3R) antagonist, ameliorates cognitive deficits of schizophrenia and the known procognitive effects of 5-HT6 receptor (5-HT6R) antagonists, we applied the hybridization strategy to design dual-acting 5-HT3/5-HT6R antagonists. We identified the first-in-class compound FPPQ, which behaves as a 5-HT3R antagonist and a neutral antagonist 5-HT6R of the Gs pathway. FPPQ shows selectivity over 87 targets and decent brain penetration. Likewise, FPPQ inhibits phencyclidine (PCP)-induced hyperactivity and displays procognitive properties in the novel object recognition task. In contrast to FPPQ, neither 5-HT6R inverse agonist SB399885 nor neutral 5-HT6R antagonist CPPQ reversed (PCP)-induced hyperactivity. Thus, combination of 5-HT3R antagonism and 5-HT6R antagonism, exemplified by FPPQ, contributes to alleviating the positive-like symptoms. Present findings reveal critical structural features useful in a rational polypharmacological approach to target 5-HT3/5-HT6 receptors and encourage further studies on dual-acting 5-HT3/5-HT6R antagonists for the treatment of psychiatric disorders.

N-Skatyltryptamines-Dual 5-HT6R/D2R Ligands with Antipsychotic and Procognitive Potential.

A series of N-skatyltryptamines was synthesized and their affinities for serotonin and dopamine receptors were determined. Compounds exhibited activity toward 5-HT1A, 5-HT2A, 5-HT6, and D2 receptors. Substitution patterns resulting in affinity/activity switches were identified and studied using homology modeling. Chosen hits were screened to determine their metabolism, permeability, hepatotoxicity, and CYP inhibition. Several D2 receptor antagonists with additional 5-HT6R antagonist and agonist properties were identified. The former combination resembled known antipsychotic agents, while the latter was particularly interesting due to the fact that it has not been studied before. Selective 5-HT6R antagonists have been shown previously to produce procognitive and promnesic effects in several rodent models. Administration of 5-HT6R agonists was more ambiguous-in naive animals, it did not alter memory or produce slight amnesic effects, while in rodent models of memory impairment, they ameliorated the condition just like antagonists. Using the identified hit compounds 15 and 18, we tried to sort out the difference between ligands exhibiting the D2R antagonist function combined with 5-HT6R agonism, and mixed D2/5-HT6R antagonists in murine models of psychosis.

Recent advances of quinones as a privileged structure in drug discovery.

Privileged structures are conductive to discover novel bioactive substances because they can bind to multiple targets with high affinity. Quinones are considered to be a privileged structure and useful template for the design of new compounds with potential pharmacological activity. This article presents the recent developments (2014-2021 update) of quinones in the fields of antitumor, antibacterial, antifungal, antiviral, anti-Alzheimer's disease (AD) and antimalarial, mainly focusing on biological activities, structural modification and mechanism of action.

Discovery of new phenyl sulfonyl-pyrimidine carboxylate derivatives as the potential multi-target drugs with effective anti-Alzheimer's action: Design, synthesis, crystal structure and in-vitro biological evaluation.

Alzheimer's disease (AD) is multifactorial, progressive neurodegeneration with impaired behavioural and cognitive functions. The multitarget-directed ligand (MTDL) strategies are promising paradigm in drug development, potentially leading to new possible therapy options for complex AD. Herein, a series of novel MTDLs phenylsulfonyl-pyrimidine carboxylate (BS-1 to BS-24) derivatives were designed and synthesized for AD treatment. All the synthesized compounds were validated by 1HNMR, 13CNMR, HRMS, and BS-19 were structurally validated by X-Ray single diffraction analysis. To evaluate the plausible binding affinity of designed compounds, molecular docking study was performed, and the result revealed their significant interaction with active sites of acetylcholinesterase (AChE) and butyrylcholinesterase (BuChE). The synthesized compounds displayed moderate to excellent in vitro enzyme inhibitory activity against AChE and BuChE at nanomolar (nM) concentration. Among 24 compounds (BS-1 to BS-24), the optimal compounds (BS-10 and BS-22) displayed potential inhibition against AChE; IC50 = 47.33 ± 0.02 nM and 51.36 ± 0.04 nM and moderate inhibition against BuChE; IC50 = 159.43 ± 0.72 nM and 153.3 ± 0.74 nM respectively. In the enzyme kinetics study, the compound BS-10 displayed non-competitive inhibition of AChE with Ki = 8 nM. Respective compounds BS-10 and BS-22 inhibited AChE-induced Aß1-42 aggregation in thioflavin T-assay at 10 µM and 20 µM, but BS-10 at 10 µM and 20 µM concentrations are found more potent than BS-22. In addition, the aggregation properties were determined by the dynamic light scattering (DLS) and was found that BS-10 and BS-22 could significantly inhibit self-induced as well as AChE-induced Aß1-42 aggregation. The effect of compounds (BS-10 and BS-22) on the viability of MC65 neuroblastoma cells and their capability to cross the blood-brain barrier (BBB) in PAMPA-BBB were further studied. Further, in silico approach was applied to analyze physicochemical and pharmacokinetics properties of the designed compounds via the SwissADME and PreADMET server. Hence, the novel phenylsulfonyl-pyrimidine carboxylate derivatives can act as promising leads in the development of AChE inhibitors and Aß disaggregator for the treatment of AD.

Pharmacological Neuroenhancement: Current Aspects of Categorization, Epidemiology, Pharmacology, Drug Development, Ethics, and Future Perspectives.

Recent pharmacoepidemiologic studies suggest that pharmacological neuroenhancement (pNE) and mood enhancement are globally expanding phenomena with distinctly different regional characteristics. Sociocultural and regulatory aspects, as well as health policies, play a central role in addition to medical care and prescription practices. The users mainly display self-involved motivations related to cognitive enhancement, emotional stability, and adaptivity. Natural stimulants, as well as drugs, represent substance abuse groups. The latter comprise purines, methylxanthines, phenylethylamines, modafinil, nootropics, antidepressants but also benzodiazepines, ß-adrenoceptor antagonists, and cannabis. Predominant pharmacodynamic target structures of these substances are the noradrenergic/dopaminergic and cholinergic receptor/transporter systems. Further targets comprise adenosine, serotonin, and glutamate receptors. Meta-analyses of randomized-controlled studies in healthy individuals show no or very limited verifiability of positive effects of pNE on attention, vigilance, learning, and memory. Only some members of the substance abuse groups, i.e., phenylethylamines and modafinil, display positive effects on attention and vigilance that are comparable to caffeinated drinks. However, the development of new antidementia drugs will increase the availability and the potential abuse of pNE. Social education, restrictive regulatory measures, and consistent medical prescription practices are essential to restrict the phenomenon of neuroenhancement with its social, medical, and ethical implications. This review provides a comprehensive overview of the highly dynamic field of pharmacological neuroenhancement and elaborates the dramatic challenges for the medical, sociocultural, and ethical fundaments of society.

Kinetics-Driven Drug Design Strategy for Next-Generation Acetylcholinesterase Inhibitors to Clinical Candidate.

The acetylcholinesterase (AChE) inhibitors remain key therapeutic drugs for the treatment of Alzheimer's disease (AD). However, the low-safety window limits their maximum therapeutic benefits. Here, a novel kinetics-driven drug design strategy was employed to discover new-generation AChE inhibitors that possess a longer drug-target residence time and exhibit a larger safety window. After detailed investigations, compound 12 was identified as a highly potent, highly selective, orally bioavailable, and brain preferentially distributed AChE inhibitor. Moreover, it significantly ameliorated cognitive impairments in different mouse models with a lower effective dose than donepezil. The X-ray structure of the cocrystal complex provided a precise binding mode between 12 and AChE. Besides, the data from the phase I trials demonstrated that 12 had good safety, tolerance, and pharmacokinetic profiles at all preset doses in healthy volunteers, providing a solid basis for its further investigation in phase II trials for the treatment of AD.

Structure-activity relationship study of tryptophan-based butyrylcholinesterase inhibitors.

A series of tryptophan-based selective nanomolar butyrylcholinesterase (BChE) inhibitors was designed and synthesized. Compounds were optimized in terms of potency, selectivity, and synthetic accessibility. The crystal structure of the inhibitor 18 in complex with BChE revealed the molecular basis for its low nanomolar inhibition (IC50 = 2.8 nM). The favourable in vitro results enabled a first-in-animal in vivo efficacy and safety trial, which demonstrated a positive impact on fear-motivated and spatial long-term memory retrieval without any concomitant adverse motor effects. Altogether, this research culminated in a handful of new lead compounds with promising potential for symptomatic treatment of patients with Alzheimer's disease.

A dual-acting 5-HT6 receptor inverse agonist/MAO-B inhibitor displays glioprotective and pro-cognitive properties.

The complex etiology of Alzheimer's disease has initiated a quest for multi-target ligands to address the multifactorial causes of this neurodegenerative disorder. In this context, we designed dual-acting 5-HT6 receptor (5-HT6R) antagonists/MAO-B inhibitors using pharmacophore hybridization strategy. Our approach involved linking priviliged scaffolds of 5-HT6R with aryloxy fragments derived from reversible and irreversible MAO-B inhibitors. The study identified compound 48 that acts as an inverse agonist of 5-HT6R at Gs signaling and an irreversible MAO-B inhibitor. Compound 48 showed moderate metabolic stability in rat microsomal assay, artificial membrane permeability, no hepatotoxicity, and it was well distributed to the brain. Additionally, 48 showed glioprotective properties in a model of cultured astrocytes using 6-OHDA as the cytotoxic agent. Finally, compound 48 (MED = 1 mg/kg, p.o.) fully reversed memory deficits in the NOR task induced by scopolamine in rats. A better understanding of effects exerted by dual-acting 5-HT6R/MAO-B modulators may impact the future development of neurodegenerative-directed treatment strategies.

Bicyclic α-Iminophosphonates as High Affinity Imidazoline I2 Receptor Ligands for Alzheimer's Disease.

Imidazoline I2 receptors (I2-IR), widely distributed in the CNS and altered in patients that suffer from neurodegenerative disorders, are orphans from a structural point of view, and new I2-IR ligands are urgently required for improving their pharmacological characterization. We report the synthesis and three-dimensional quantitative structure-activity relationship (3D-QSAR) studies of a new family of bicyclic α-iminophosphonates endowed with relevant affinities for human brain I2-IR. Acute treatment in mice with a selected compound significantly decreased Fas-associated protein with death domain (FADD) in the hippocampus, a key signaling mediator of neuroprotective actions. Additionally, in vivo studies in the familial Alzheimer's disease 5xFAD murine model revealed beneficial effects in behavior and cognition. These results are supported by changes in molecular pathways related to cognitive decline and Alzheimer's disease. Therefore, bicyclic α-iminophosphonates are tools that may open new therapeutic avenues for I2-IR, particularly for unmet neurodegenerative conditions.

LMP2 Inhibitors as a Potential Treatment for Alzheimer's Disease.

The immunoproteasome (iP), an inducible proteasome variant harboring three immunosubunits, low molecular mass polypeptide-2 (LMP2), multicatalytic endopeptidase complex subunit-1, and low molecular mass polypeptide-7 (LMP7), is involved in multiple facets of inflammatory responses. We recently reported that YU102, a dual inhibitor of the iP subunit LMP2 and the constitutive proteasome catalytic subunit ß1, ameliorates cognitive impairments in mouse models of Alzheimer's disease (AD) independently of amyloid deposits. To investigate whether inhibition of LMP2 is sufficient to improve the cognitive functions of AD mice, here we prepared 37 YU102 analogues and identified a potent LMP2 inhibitor DB-310 (28) (IC50: 80.6 nM) with improved selectivity and permeability in cells overexpressing ABCB1 transporters. We show that DB-310 induces suppression of IL-1α production in microglia cells and improves cognitive functions in the Tg2576 transgenic mouse model of AD. This study supports that inhibition of LMP2 is a promising therapeutic strategy for treatment of AD.

Discovery of Novel, Potent, Brain-Permeable, and Orally Efficacious Positive Allosteric Modulator of α7 Nicotinic Acetylcholine Receptor [4-(5-(4-Chlorophenyl)-4-methyl-2-propionylthiophen-3-yl)benzenesulfonamide]: Structure-Activity Relationship and Preclinical Characterization.

The discovery of a series of thiophenephenylsulfonamides as positive allosteric modulators (PAM) of α7 nicotinic acetylcholine receptor (α7 nAChR) is described. Optimization of this series led to identification of compound 28, a novel PAM of α7 nicotinic acetylcholine receptor (α7 nAChR). Compound 28 showed good in vitro potency, with pharmacokinetic profile across species with excellent brain penetration and residence time. Compound 28 robustly reversed the cognitive deficits in episodic/working memory in both time-delay and scopolamine-induced amnesia paradigms in the novel object and social recognition tasks, at very low dose levels. Additionally, compound 28 has shown excellent safety profile in phase 1 clinical trials and is being evaluated for efficacy and safety as monotherapy in patients with mild to moderate Alzheimer's disease.

Selank, Peptide Analogue of Tuftsin, Protects Against Ethanol-Induced Memory Impairment by Regulating of BDNF Content in the Hippocampus and Prefrontal Cortex in Rats.

The effects of a peptide anxiolytic Selank synthesized on the basis of the endogenous peptide tuftsin on memory impairment and content of brain-derived neurotrophic factor (BDNF) in brain structures were analyzed in outbred rats receiving 10% ethanol as the only source of fluid for 30 weeks. In the object recognition test, Selank (0.3 mg/kg a day, 7 days, intraperitoneally) produced a cognitive-stimulating effect in 9 months rats not exposed to ethanol (p<0.05) and prevented the formation of ethanol-induced memory and attention disturbances (p<0.01) developing during alcohol withdrawal. In ex vivo experiments, Selank prevented ethanol-induced increase in BDNF content in the hippocampus and frontal cortex (p<0.05). These results indicate positive effects of the tuftsin analogue on age-related memory disturbances associated with chronic alcohol intoxication and confirm the involvement of the neurotrophin mechanism related to BDNF production into the effect of Selank.

The chemistry toolbox of multitarget-directed ligands for Alzheimer's disease.

The discovery and development of multitarget-directed ligands (MTDLs) is a promising strategy to find new therapeutic solutions for neurodegenerative diseases (NDs), in particular for Alzheimer's disease (AD). Currently approved drugs for the clinical management of AD are based on a single-target strategy and focus on restoring neurotransmitter homeostasis. Finding disease-modifying therapies AD and other NDs remains an urgent unmet clinical need. The growing consensus that AD is a multifactorial disease, with several interconnected and deregulated pathological pathways, boosted an intensive research in the design of MTDLs. Due to this scientific boom, the knowledge behind the development of MTDLs remains diffuse and lacks balanced guidelines. To rationalize the large amount of data obtained in this field, we herein revise the progress made over the last 5 years on the development of MTDLs inspired by drugs approved for AD. Due to their putative therapeutic benefit in AD, MTDLs based on MAO-B inhibitors will also be discussed in this review.

Designing of promising medicinal scaffolds for Alzheimer's disease through enzyme inhibition, lead optimization, molecular docking and dynamic simulation approaches.

In the designed research work, a series of 2-furoyl piperazine based sulfonamide derivatives were synthesized as therapeutic agents to target the Alzheimer's disease. The structures of the newly synthesized compounds were characterized through spectral analysis and their inhibitory potential was evaluated against butyrylcholinesterase (BChE). The cytotoxicity of these sulfonamides was also ascertained through hemolysis of bovine red blood cells. Furthermore, compounds were inspected by Lipinki Rule and their binding profiles against BChE were discerned by molecular docking. The protein fluctuations in docking complexes were recognized by dynamic simulation. From our in vitro and in silico results 5c, 5j and 5k were identified as promising lead compounds for the treatment of targeted disease.

Cholinesterase inhibitors as Alzheimer's therapeutics (Review).

Alzheimer's disease (AD) is one of the most common forms of dementia. AD is a chronic syndrome of the central nervous system that causes a decline in cognitive function and language ability. Cholinergic deficiency is associated with AD, and various cholinesterase inhibitors have been developed for the treatment of AD, including naturally­derived inhibitors, synthetic analogues and hybrids. Currently, the available drugs for AD are predominantly cholinesterase inhibitors. However, the efficacy of these drugs is limited as they may cause adverse side effects and are not able to completely arrest the progression of the disease. Since AD is multifactorial disease, dual and multi­target inhibitors have been developed. The clinical applications and the limitations of the inhibitors used to treat AD are discussed in the present review. Additionally, this review presents the current status and future directions for the development of novel drugs with reduced toxicity and preserved pharmacological activity.

Development of the "hidden" multifunctional agents for Alzheimer's disease.

Alzheimer's disease (AD) is a chronic, fatal and complex neurodegenerative disorder, which is characterized by cholinergic system dysregulation, metal dyshomeostasis, amyloid-ß (Aß) aggregation, etc. Therefore in most cases, single-target or single-functional agents are insufficient to achieve the desirable effect against AD. Multi-Target-Directed Ligand (MTDL), which is rationally designed to simultaneously hit multiple targets to improve the pharmacological profiles, has been developed as a promising approach for drug discovery against AD. To identify the multifunctional agents for AD, we developed an innovative method to successfully conceal the metal chelator into acetylcholinesterase (AChE) inhibitor. Briefly, the "hidden" agents first cross the Blood Brain Barrier (BBB) to inhibit the function of AChE, and the metal chelator will then be released via the enzymatic hydrolysis by AChE. Therefore, the AChE inhibitor, in this case, is not only a single-target agent against AD, but also a carrier of the metal chelator. In this study a total of 14 quinoline derivatives were synthesized and biologically evaluated. Both in vitro and in vivo results demonstrated that compound 9b could cross the BBB efficiently, then release 8a, the metabolite of 9b, into brain. In vitro, 9b had a potent AChE inhibitory activity, while 8a displayed a significant metal ion chelating function, therefore in combination, both 9b and 8a exhibited a considerable inhibition of Aß aggregation, one of the observations that plays important roles in the pathogenesis of AD. The efficacy of 9b against AD was further investigated in both a zebrafish model and two different mice models.

Novel Deoxyvasicinone-Donepezil Hybrids as Potential Multitarget Drug Candidates for Alzheimer's Disease.

In this study, we designed and synthesized a series of deoxyvasicinone-donepezil hybrids and determined whether they could be used as novel multitarget inhibitors for Alzheimer's disease. In vitro studies showed that most of the hybrids demonstrated moderate to potent inhibition of hAChE, BACE1, and Aß1-42 aggregation. In particular, the hybrids 10a, 10d, 11a, and 11j exhibited excellent inhibitory activities against hAChE (IC50 = 56.14, 5.91, 3.29, and 8.65 nM, respectively), BACE1 (IC50 = 0.834, 0.167, 0.129, and 0.085 µM, respectively), and Aß1-42 aggregation (IC50 = 13.26, 19.43, 9.26, and 5.41 µM, respectively). In addition, 10a and 11a exhibited very low cytotoxicity and showed remarkable neuroprotective activity against Aß1-42-induced damage in SH-SY5Y cells.

Biphenyl-3-oxo-1,2,4-triazine linked piperazine derivatives as potential cholinesterase inhibitors with anti-oxidant property to improve the learning and memory.

A series of novel piperazine tethered biphenyl-3-oxo-1,2,4-triazine derivatives were designed, and synthesized. Amongst the synthesized analogs, compound 6g showed significant non-competitive inhibitory potential against acetylcholinesterase (AChE, IC50; 0.2 ±â€¯0.01 µM) compared to standard donepezil (AChE, IC50: 0.1 ±â€¯0.002 µM). Compound 6g also exhibited significant displacement of propidium iodide from the peripheral anionic site (PAS) of AChE (22.22 ±â€¯1.11%) and showed good CNS permeability in PAMPA-BBB assay (Pe(exp), 6.93 ±â€¯0.46). The in vivo behavioral studies of compound 6g indicated significant improvement in cognitive dysfunctions against scopolamine-induced amnesia mouse models. Further, ex vivo studies showed a significant AChE inhibition and reversal of the scopolamine-induced oxidative stress by compound 6g. Moreover, molecular docking and dynamics simulations of compound 6g showed a consensual binding affinity and active site interactions with the PAS and active catalytic site (CAS) residues of AChE.