Alzheimer's disease is becoming a growing problem increasing at a tremendous rate. Serotonin 5-HT(6) receptors appear to be a particularly attractive target from a therapeutic perspective, due to their involvement not only in cognitive processes, but also in depression and psychosis. In this work, we present the synthesis and broad biological characterization of a new series of 18 compounds with a unique 1,3,5-triazine backbone, as potent 5-HT(6) receptor ligands. The main aim of this research is to compare the biological activity of the newly synthesized sulfur derivatives with their oxygen analogues and their N-demethylated O- and S-metabolites obtained for the first time. Most of the new triazines displayed high affinity (K(i) < 200 nM) and selectivity towards 5-HT(6)R, with respect to 5-HT(2A)R, 5-HT(7)R, and D(2)R, in the radioligand binding assays. For selected, active compounds crystallographic studies, functional bioassays, and ADME-Tox profile in vitro were performed. The exciting novelty is that the sulfur derivatives exhibit an agonistic mode of action contrary to all other compounds obtained to date in this chemical class herein and previously reported. Advanced computational studies indicated that this intriguing functional shift might be caused by presence of chalcogen bonds formed only by the sulfur atom. In addition, the N-demethylated derivatives have emerged highly potent antioxidants and, moreover, show a significant improvement in metabolic stability compared to the parent structures. The cholinesterase study present micromolar inhibitory AChE and BChE activity for both 5-HT(6) agonist 19 and potent antagonist 5. Finally, the behavioral experiments of compound 19 demonstrated its antidepressant-like properties and slight ability to improve cognitive deficits, without inducing memory impairments by itself. Described pharmacological properties of both compounds (5 and 19) allow to give a design clue for the development of multitarget compounds with 5-HT(6) (both agonist and antagonist)/AChE and/or BChE mechanism in the group of 1,3,5-triazine derivatives.
The symptomatic and disease-modifying effects of butyrylcholinesterase (BuChE) inhibitors provide an encouraging premise for researching effective treatments for Alzheimer's disease. Here, we examined a series of compounds with a new chemical scaffold based on 3-(cyclohexylmethyl)amino-2-hydroxypropyl, and we identified a highly selective hBuChE inhibitor (29). Based on extensive in vitro and in vivo evaluations of the compound and its enantiomers, (R)-29 was identified as a promising candidate for further development. Compound (R)-29 is a potent hBuChE inhibitor (IC50 = 40 nM) with selectivity over AChE and relevant off-targets, including H1, M1, alpha1A and beta1 receptors. The compound displays high metabolic stability on human liver microsomes (90% of the parent compound after 2 h of incubation), and its safety was confirmed through examining the cytotoxicity on the HepG2 cell line (LC50 = 2.85 microM) and hERG inhibition (less than 50% at 10 microM). While (rac)-29 lacked an effect in vivo and showed limited penetration to the CNS in pharmacokinetics studies, compound (R)-29 exhibited a procognitive effect at 15 mg/kg in the novel object recognition task in scopolamine-treated mice.
Butyrylcholinesterase (BuChE) and amyloid beta (Abeta) aggregation remain important biological target and mechanism in the search for effective treatment of Alzheimer's disease. Simultaneous inhibition thereof by the application of multifunctional agents may lead to improvement in terms of symptoms and causes of the disease. Here, we present the rational design, synthesis, biological evaluation and molecular modelling studies of novel series of fluorene-based BuChE and Abeta inhibitors with drug-like characteristics and advantageous Central Nervous System Multiparameter Optimization scores. Among 17 synthesized and tested compounds, we identified 22 as the most potent eqBuChE inhibitor with IC(50) of 38 nM and 37.4% of Abeta aggregation inhibition at 10 microM. Based on molecular modelling studies, including molecular dynamics, we determined the binding mode of the compounds within BuChE and explained the differences in the activity of the two enantiomers of compound 22. A novel series of fluorenyl compounds meeting the drug-likeness criteria seems to be a promising starting point for further development as anti-Alzheimer agents.
This study examines the properties of novel guanidines, designed and synthesized as histamine H(3)R antagonists/inverse agonists with additional pharmacological targets. We evaluated their potential against two targets viz., inhibition of MDA-MB-231, and MCF-7 breast cancer cells viability and inhibition of AChE/BuChE. ADS10310 showed micromolar cytotoxicity against breast cancer cells, combined with nanomolar affinity at hH(3)R, and may represent a promising target for the development of an alternative method of cancer therapy. Some of the newly synthesized compounds showed moderate inhibition of BuChE in the single-digit micromolar concentration ranges. H(3)R antagonist with additional AChE/BuChE inhibitory effect might improve cognitive functions in Alzheimer's disease. For ADS10310, several in vitro ADME-Tox parameters were evaluated and indicated that it is a metabolically stable compound with weak hepatotoxic activity and can be accepted for further studies.
Alzheimer's disease (AD) is a global health problem in the medical sector that will increase over time. The limited treatment of AD leads to the search for a new clinical candidate. Considering the multifactorial nature of AD, a strategy targeting number of regulatory proteins involved in the development of the disease is an effective approach. Here, we present a discovery of new multi-target-directed ligands (MTDLs), purposely designed as GABA transporter (GAT) inhibitors, that successfully provide the inhibitory activity against butyrylcholinesterase (BuChE), beta-secretase (BACE1), amyloid beta aggregation and calcium channel blockade activity. The selected GAT inhibitors, 19c and 22a - N-benzylamide derivatives of 4-aminobutyric acid, displayed the most prominent multifunctional profile. Compound 19c (mGAT1 IC(50) = 10 microM, mGAT4 IC(50) = 12 microM and BuChE IC(50) = 559 nM) possessed the highest hBACE1 and Abeta(40) aggregation inhibitory activity (IC(50) = 1.57 microM and 99 % at 10 microM, respectively). Additionally, it showed a decrease in both the elongation and nucleation constants of the amyloid aggregation process. In contrast compound 22a represented the highest activity and a mixed-type of eqBuChE inhibition (IC(50) = 173 nM) with hBACE1 (IC(50) = 9.42 microM), Abeta aggregation (79 % at 10 microM) and mGATs (mGAT1 IC(50) = 30 microM, mGAT4 IC(50) = 25 microM) inhibitory activity. Performed molecular docking studies described the mode of interactions with GATs and enzymatic targets. In ADMET in vitro studies both compounds showed acceptable metabolic stability and low neurotoxicity. Successfully, compounds 19c and 22a at the dose of 30 mg/kg possessed statistically significant antiamnesic properties in a mouse model of amnesia caused by scopolamine and assessed in the novel object recognition (NOR) task or the passive avoidance (PA) task.
The multitarget-directed ligands demonstrating affinity to histamine H(3) receptor and additional cholinesterase inhibitory potency represent a promising strategy for research into the effective treatment of Alzheimer's disease. In this study, a novel series of benzophenone derivatives was designed and synthesized. Among these derivatives, we identified compound 6 with a high affinity for H(3)R (K(i) = 8 nM) and significant inhibitory activity toward BuChE (IC(50) = 172 nM and 1.16 microM for eqBuChE and hBuChE, respectively). Further in vitro studies revealed that compound 6 (4-fluorophenyl) (4-((5-(piperidin-1-yl)pentyl)oxy)phenyl)methanone) displays moderate metabolic stability in mouse liver microsomes, good permeability with a permeability coefficient value (P(e)) of 6.3 x 10(-6) cm/s, and its safety was confirmed in terms of hepatotoxicity in the HepG2 cell line. Therefore, we investigated the in vivo activity of compound 6 in the Passive Avoidance Test and the Formalin Test. While compound 6 did not show a statistically significant influence on memory and learning, it showed analgesic properties in both acute (ED(50) = 20.9 mg/kg) and inflammatory (ED(50) = 17.5 mg/kg) pain.
Neurodegeneration leading to Alzheimer's disease results from a complex interplay of a variety of processes including misfolding and aggregation of amyloid beta and tau proteins, neuroinflammation or oxidative stress. Therefore, to address more than one of these, drug discovery programmes focus on the development of multifunctional ligands, preferably with disease-modifying and symptoms-reducing potential. Following this idea, herein we present the design and synthesis of multifunctional ligands and biological evaluation of their 5-HT(6) receptor affinity (radioligand binding assay), cholinesterase inhibitory activity (spectroscopic Ellman's assay), antioxidant activity (ABTS assay) and metal-chelating properties, as well as a preliminary ADMET properties evaluation. Based on the results we selected compound 14 as a well-balanced and potent 5-HT(6) receptor ligand (K(i) = 22 nM) and human BuChE inhibitor (IC(50) = 16 nM) with antioxidant potential expressed as a reduction of ABTS radicals by 35% (150 microM). The study also revealed additional metal-chelating properties of compounds 15 and 18. The presented compounds modulating Alzheimer's disease-related processes might be further developed as multifunctional ligands against the disease.
Alzheimer's disease (AD) is a complex and incurable illness that requires the urgent approval of new effective drugs. However, since 2003, no new molecules have shown successful results in clinical trials, thereby making the common "one compound - one target" paradigm questionable. Recently, the multitarget-directed ligand (MTDL) approach has gained popularity, as compounds targeting at least two biological targets may be potentially more effective in treating AD. On the basis of these findings, we designed, synthesized, and evaluated through biological assays a series of derivatives of alicyclic amines linked by an alkoxy bridge to an aromatic lipophilic moiety of [1,1'-biphenyl]-4-carbonitrile. The research results revealed promising biological activity of the obtained compounds toward the chosen targets involved in AD pathophysiology; the compounds showed high affinity (mostly low nanomolar range of K(i) values) for human histamine H(3) receptors (hH(3)R) and good nonselective inhibitory potency (micromolar range of IC(50) values) against acetylcholinesterase from electric eel (eeAChE) and equine serum butyrylcholinesterase (eqBuChE). Moreover, micromolar/submicromolar potency against human monoamine oxidase B (hMAO B) was detected for some compounds. The study identified compound 5 as a multiple hH(3)R/eeAChE/eqBuChE/hMAO B ligand (5: hH(3)R K(i) = 9.2 nM; eeAChE IC(50) = 2.63 microM; eqBuChE IC(50) = 1.30 microM; hMAO B IC(50) = 0.60 microM). Further in vitro studies revealed that compound 5 exhibits a mixed type of eeAChE and eqBuChE inhibition, good metabolic stability, and moderate hepatotoxicity effect on HepG2 cells. Finally, compound 5 showed a beneficial effect on scopolamine-induced memory impairments, as assessed by the passive avoidance test, thus revealing the potential of this compound as a promising agent for further optimization for AD treatment.
Looking for an effective anti-Alzheimer's agent is very challenging; however, a multifunctional ligand strategy may be a promising solution for the treatment of this complex disease. We herein present the design, synthesis and biological evaluation of novel hydroxyethylamine derivatives displaying unique, multiple properties that have not been previously reported. The original mechanism of action combines inhibitory activity against disease-modifying targets: beta-secretase enzyme (BACE1) and amyloid beta (Abeta) aggregation, along with an effect on targets associated with symptom relief - inhibition of butyrylcholinesterase (BuChE) and gamma-aminobutyric acid transporters (GATs). Among the obtained molecules, compound 36 exhibited the most balanced and broad activity profile (eeAChE IC50 = 2.86 microM; eqBuChE IC50 = 60 nM; hBuChE IC50 = 20 nM; hBACE1 IC50 = 5.9 microM; inhibition of Abeta aggregation = 57.9% at 10 microM; mGAT1 IC50 = 10.96 microM; and mGAT2 IC50 = 19.05 microM). Moreover, we also identified 31 as the most potent mGAT4 and hGAT3 inhibitor (IC50 = 5.01 microM and IC50 = 2.95 microM, respectively), with high selectivity over other subtypes. Compounds 36 and 31 represent new anti-Alzheimer agents that can ameliorate cognitive decline and modify the progress of disease.
Multifunctional ligands as an essential variant of polypharmacology are promising candidates for the treatment of multi-factorial diseases like Alzheimer's disease. Based on clinical evidence and following the paradigm of multifunctional ligands we have rationally designed and synthesized a series of compounds targeting processes involved in the development of the disease. The biological evaluation led to the discovery of two compounds with favorable pharmacological characteristics and ADMET profile. Compounds 17 and 35 are 5-HT(6)R antagonists (K(i) = 13 nM and K(i) = 15 nM respectively) and cholinesterase inhibitors with distinct mechanisms of enzyme inhibition. Compound 17, a tacrine derivative is a reversible inhibitor of acetyl- and butyrylcholinesterase (IC(50) = 8 nM and IC(50) = 24 nM respectively), while compound 35 with rivastigmine-derived phenyl N-ethyl-N-methylcarbamate fragment is a selective, pseudo-irreversible inhibitor of butyrylcholinesterase (IC(50) = 455 nM). Both compounds inhibit aggregation of amyloid beta in vitro (75% for compound 17 and 68% for 35 at 10 microM) moreover, compound 35 is a potent tau aggregation inhibitor in cellulo (79%). In ADMET in vitro studies both compounds showed acceptable metabolic stability on mouse liver microsomes (28% and 60% for compound 17 and 35 respectively), no or little effect on CYP3A4 and 2D6 up to a concentration of 10 microM and lack of toxicity on HepG2 cell line (IC(50) values of 80 and 21 microM, for 17 and 35 respectively). Based on the pharmacological characteristics and favorable pharmacokinetic properties, we propose compounds 17 and 35 as an excellent starting point for further optimization and in-depth biological studies.
The lack of an effective treatment makes Alzheimer's disease a serious healthcare problem and a challenge for medicinal chemists. Herein we report interdisciplinary research on novel multifunctional ligands targeting proteins and processes involved in the development of the disease: BuChE, 5-HT6 receptors and beta-amyloid aggregation. Structure-activity relationship analyses supported by crystallography and docking studies led to the identification of a fused-type multifunctional ligand 50, with remarkable and balanced potencies against BuChE (IC50 = 90 nM) and 5-HT6R (Ki = 4.8 nM), and inhibitory activity against Abeta aggregation (53% at 10 microM). In in vitro ADME-Tox and in vivo pharmacokinetic studies compound 50 showed good stability in the mouse liver microsomes, favourable safety profile and brain permeability with the brain to plasma ratio of 6.79 after p.o. administration in mice, thus being a promising candidate for in vivo pharmacology studies and a solid foundation for further research on effective anti-AD therapies.
Design and development of multitarget-directed ligands (MTDLs) has become a very important approach in the search of new therapies for Alzheimer's disease (AD). In our present research, a number of xanthone derivatives were first designed using a pharmacophore model for histamine H(3) receptor (H(3)R) antagonists/inverse agonists, and virtual docking was then performed for the enzyme acetylcholinesterase. Next, 23 compounds were synthesised and evaluated in vitro for human H(3)R (hH(3)R) affinity and inhibitory activity on cholinesterases. Most of the target compounds showed hH(3)R affinities in nanomolar range and exhibited cholinesterase inhibitory activity with IC(50) values in submicromolar range. Furthermore, the inhibitory effects of monoamine oxidases (MAO) A and B were investigated. The results showed low micromolar and selective human MAO B (hMAO B) inhibition. Two azepane derivatives, namely 23 (2-(5-(azepan-1-yl)pentyloxy)-9H-xanthen-9-one) and 25 (2-(5-(azepan-1-yl)pentyloxy)-7-chloro-9H-xanthen-9-one), were especially very promising and showed high affinity for hH(3)R (K(i) = 170 nM and 100 nM respectively) and high inhibitory activity for acetylcholinesterase (IC(50) = 180 nM and 136 nM respectively). Moreover, these compounds showed moderate inhibitory activity for butyrylcholinesterase (IC(50) = 880 nM and 394 nM respectively) and hMAO B (IC(50) = 775 nM and 897 nM respectively). Furthermore, molecular docking studies were performed for hH(3)R, human cholinesterases and hMAO B to describe the mode of interactions with these biological targets. Next, the two most promising compounds 23 and 25 were selected for in vivo studies. The results showed significant memory-enhancing effect of compound 23 in dizocilpine-induced amnesia in rats in two tests: step-through inhibitory avoidance paradigm (SIAP) and transfer latency paradigm time (TLPT). In addition, favourable analgesic effects of compound 23 were observed in neuropathic pain models. Therefore, compound 23 is a particularly promising structure for further design of new MTDLs for AD.
Alzheimer's disease (AD) is a major public health problem, which is due to its increasing prevalence and lack of effective therapy or diagnostics. The complexity of the AD pathomechanism requires complex treatment, e.g. multifunctional ligands targeting both the causes and symptoms of the disease. Here, we present new multitarget-directed ligands combining pharmacophore fragments that provide a blockade of serotonin 5-HT6 receptors, acetyl/butyrylcholinesterase inhibition, and amyloid beta antiaggregation activity. Compound 12 has displayed balanced activity as an antagonist of 5-HT6 receptors ( Ki = 18 nM) and noncompetitive inhibitor of cholinesterases (IC50 hAChE = 14 nM, IC50 eqBuChE = 22 nM). In further in vitro studies, compound 12 has shown amyloid beta antiaggregation activity (IC50 = 1.27 muM) and ability to permeate through the blood-brain barrier. The presented findings may provide an excellent starting point for further studies and facilitate efforts to develop new effective anti-AD therapy.
