First-in-Class Selenium-Containing Potent Serotonin Receptor 5-HT6 Agents with a Beneficial Neuroprotective Profile against Alzheimer's Disease.

Alzheimer's disease (AD) has a complex and not-fully-understood etiology. Recently, the serotonin receptor 5-HT6 emerged as a promising target for AD treatment; thus, here a new series of 5-HT6R ligands with a 1,3,5-triazine core and selenoether linkers was explored. Among them, the 2-naphthyl derivatives exhibited strong 5-HT6R affinity and selectivity over 5-HT1AR (13-15), 5-HT7R (14 and 15), and 5-HT2AR (13). Compound 15 displayed high selectivity for 5-HT6R over other central nervous system receptors and exhibited low risk of cardio-, hepato-, and nephrotoxicity and no mutagenicity, indicating its "drug-like" potential. Compound 15 also demonstrated neuroprotection against rotenone-induced neurotoxicity as well as antioxidant and glutathione peroxidase (GPx)-like activity and regulated antioxidant and pro-inflammatory genes and NRF2 nuclear translocation. In rats, 15 showed satisfying pharmacokinetics, penetrated the blood-brain barrier, reversed MK-801-induced memory impairment, and exhibited anxiolytic-like properties. 15's neuroprotective and procognitive-like effects, stronger than those of the approved drug donepezil, may pave the way for the use of selenotriazines to inhibit both causes and symptoms in AD therapy.

Superiority of the Triple-Acting 5-HT6R/5-HT3R Antagonist and MAO-B Reversible Inhibitor PZ-1922 over 5-HT6R Antagonist Intepirdine in Alleviation of Cognitive Deficits in Rats.

The multifactorial origin and neurochemistry of Alzheimer's disease (AD) call for the development of multitarget treatment strategies. We report a first-in-class triple acting compound that targets serotonin type 6 and 3 receptors (5-HT-Rs) and monoamine oxidase type B (MAO-B) as an approach for treating AD. The key structural features required for MAO-B inhibition and 5-HT6R antagonism and interaction with 5-HT3R were determined using molecular dynamic simulations and cryo-electron microscopy, respectively. Bioavailable PZ-1922 reversed scopolamine-induced cognitive deficits in the novel object recognition test. Furthermore, it displayed superior pro-cognitive properties compared to intepirdine (a 5-HT6R antagonist) in the AD model, which involved intracerebroventricular injection of an oligomeric solution of amyloid-ß peptide (oAß) in the T-maze test in rats. PZ-1922, but not intepirdine, restored levels of biomarkers characteristic of the debilitating effects of oAß. These data support the potential of a multitarget approach involving the joint modulation of 5-HT6R/5-HT3R/MAO-B in AD.

Hydrophobicity modulation via the substituents at positions 2 and 4 of 1,3,5-triazine to enhance therapeutic ability against Alzheimer's disease for potent serotonin 5-HT6R agents.

Alzheimer's disease (AD), a neurodegenerative disorder with a complex aetiology, is the most common memory dysfunction particularly affecting the elderly. Various protein targets have been classified to be involved in the AD treatment, including 5-HT6 receptor (5-HT6R). So far, the 5-HT6R ligands obtained by our research group have become a good basis for hydrophobicity modulation to give a chance for more effective action toward AD by additional influence on target enzymes, e.g. cyclin-dependent kinase 5 (CDK5). In the search for 5-HT6R agents with additional inhibitory action on the enzyme, a series of 25 new 1,3,5-triazines (7-31) as modifications of lead, 4-[1-(2,5-dichlorophenoxy)propyl]-6-(4-methylpiperazin-1-yl)-1,3,5-triazine-2-amine (6), was rationally designed. Molecular modelling, synthesis, crystallographic studies, in vitro biological assays and behavioral studies in vivo were performed. The new triazines showed high affinity (Ki < 100 nM) and selectivity for 5-HT6R. The most effective one, 4-[1-(2,5-difluorophenoxy)propyl]-6-(4-methylpiperazin-1-yl)-1,3,5-triazine-2-amine (8), exhibited the strong antagonistic action towards 5-HT6R (Ki = 5 nM, pKb = 8.16), had an impact on the memory processes in the Novel Object Recognition test and displayed anxiolytic-like activity in the Elevated Plus Maze test in rats. Moreover, it had the antiplatelet effect as well as very good permeability (PAMPA model), high metabolic stability (RLMs) and satisfactory safety in vitro. Although the CDK5 inhibitory effects in vitro for the tested compounds (8, 10, 14, 18, 26-31) missed the potency expected from in silico simulations, the novel antagonist (8) with a very satisfying pharmacological and ADMET profile can serve as a new lead structure in further searches for innovative therapy against AD with accompanying symptoms.

Anti-Inflammatory Activities of 8-Benzylaminoxanthines Showing High Adenosine A2A and Dual A1/A2A Receptor Affinity.

Chronic inflammation plays an important role in the development of neurodegenerative diseases, such as Parkinson's disease (PD). In the present study, we synthesized 25 novel xanthine derivatives with variable substituents at the N1-, N3- and C8-position as adenosine receptor antagonists with potential anti-inflammatory activity. The compounds were investigated in radioligand binding studies at all four human adenosine receptor subtypes, A1, A2A, A2B and A3. Compounds showing nanomolar A2A and dual A1/A2A affinities were obtained. Three compounds, 19, 22 and 24, were selected for further studies. Docking and molecular dynamics simulation studies indicated binding poses and interactions within the orthosteric site of adenosine A1 and A2A receptors. In vitro studies confirmed the high metabolic stability of the compounds, and the absence of toxicity at concentrations of up to 12.5 µM in various cell lines (SH-SY5Y, HepG2 and BV2). Compounds 19 and 22 showed anti-inflammatory activity in vitro. In vivo studies in mice investigating carrageenan- and formalin-induced inflammation identified compound 24 as the most potent anti-inflammatory derivative. Future studies are warranted to further optimize the compounds and to explore their therapeutic potential in neurodegenerative diseases.

Xanthine-Dopamine Hybrid Molecules as Multitarget Drugs with Potential for the Treatment of Neurodegenerative Diseases.

Multitarget drugs based on a hybrid dopamine-xanthine core were designed as potential drug candidates for the treatment of neurodegenerative diseases. Monoamine oxidase B (MAO-B) inhibitors with significant ancillary A2A adenosine receptor (A2AAR) antagonistic properties were further developed to exhibit additional phosphodiesterase-4 and -10 (PDE4/10) inhibition and/or dopamine D2 receptor (D2R) agonistic activity. While all of the designed compounds showed MAO-B inhibition in the nanomolar range mostly combined with submicromolar A2AAR affinity, significant enhancement of PDE-inhibitory and D2R-agonistic activity was additionally reached for some compounds through various structural modifications. The final multitarget drugs also showed promising antioxidant properties in vitro. In order to evaluate their potential neuroprotective effect, representative ligands were tested in a cellular model of toxin-induced neurotoxicity. As a result, protective effects against oxidative stress in neuroblastoma cells were observed, confirming the utility of the applied strategy. Further evaluation of the newly developed multitarget ligands in preclinical models of Alzheimer's and Parkinson's diseases is warranted.

Trisubstituted 1,3,5-Triazines as Histamine H4 Receptor Antagonists with Promising Activity In Vivo.

Pain is a very unpleasant experience that makes life extremely uncomfortable. The histamine H4 receptor (H4R) is a promising target for the treatment of inflammatory and immune diseases, as well as pain. H4R ligands have demonstrated analgesic effects in a variety of pain models, including inflammatory pain. Continuing the search for active H4R ligands among the alkyl derivatives of 1,3,5-triazine, we obtained 19 new compounds in two series: acyclic (I) and aliphatic (II). In vitro pharmacological evaluation showed their variable affinity for H4R. The majority of compounds showed a moderate affinity for this receptor (Ki > 100 nM), while all compounds tested in ß-arrestin and cAMP assays showed antagonistic activity. The most promising, compound 6, (4-(cyclopentylmethyl)-6-(4-methylpiperazin-1-yl)-1,3,5-triazin-2-amine; Ki = 63 nM) was selected for further in vitro evaluation: blood-brain barrier permeability (PAMPA assay; Pe = 12.26 × 10-6 cm/s) and toxicity tests (HepG2 and SH-5YSY cells; no toxicity up to 50 µM). Next, compound 6 tested in vivo in a carrageenan-induced inflammatory pain model showed anti-inflammatory and analgesic effects (strongest at 50 mg/kg i.p.). Furthermore, in a histamine- and chloroquine-induced pruritus model, compound 6 at a dose of 25 mg/kg i.p. and 50 mg/kg i.p., respectively, reduced the number of scratch bouts. Thus, compound 6 is a promising ligand for further studies.

Dual Targeting Ligands-Histamine H3 Receptor Ligands with Monoamine Oxidase B Inhibitory Activity-In Vitro and In Vivo Evaluation.

The clinical symptoms of Parkinson's disease (PD) appear when dopamine (DA) concentrations in the striatum drops to around 20%. Simultaneous inhibitory effects on histamine H3 receptor (H3R) and MAO B can increase DA levels in the brain. A series of compounds was designed and tested in vitro for human H3R (hH3R) affinity and inhibitory activity to human MAO B (hMAO B). Results showed different activity of the compounds towards the two biological targets. Most compounds had poor affinity for hH3R (Ki > 500 nM), but very good inhibitory potency for hMAO B (IC50 < 50 nM). After further in vitro testing (modality of MAO B inhibition, permeability in PAMPA assay, cytotoxicity on human astrocyte cell lines), the most promising dual-acting ligand, 1-(3-(4-(tert-butyl)phenoxy)propyl)-2-methylpyrrolidine (13: hH3R: Ki = 25 nM; hMAO B IC50 = 4 nM) was selected for in vivo evaluation. Studies in rats of compound 13, in a dose of 3 mg/kg of body mass, confirmed its antagonistic effects for H3R (decline in food and a water consumption), decline in MAO B activity (>90%) in rat cerebral cortex (CTX), and an increase in DA content in CTX and striatum. Moreover, compound 13 caused a slight increase in noradrenaline, but a reduction in serotonin concentration in CTX. Thus, compound 13 is a promising dual-active ligand for the potential treatment of PD although further studies are needed to confirm this.

Overcoming undesirable hERG affinity by incorporating fluorine atoms: A case of MAO-B inhibitors derived from 1 H-pyrrolo-[3,2-c]quinolines.

The incorporation of the fluorine motif is a strategy widely applied in drug design for modulating the activity, physicochemical parameters, and metabolic stability of chemical compounds. In this study, we attempted to reduce the affinity for ether-à-go-go-related gene (hERG) channel by introducing fluorine atoms in a group of 1H-pyrrolo[3,2-c]quinolines that are capable of inhibiting monoamine oxidase type B (MAO-B). A series of structural modifications guided by in vitro evaluation of MAO-B inhibition and antitargeting for hERG channels were performed, which led to the identification of 1-(3-chlorobenzyl)-4-(4,4-difluoropiperidin-1-yl)-1H-pyrrolo[3,2-c]quinoline (26). Compound 26 acted as a reversible MAO-B inhibitor exhibiting selectivity over 45 targets, enzymes, transporters, and ion channels, and showed potent glioprotective properties in cultured astrocytes. In addition, the compound demonstrated good metabolic stability in rat liver microsomes assay, a favorable safety profile, and brain permeability. It also displayed procognitive effects in the novel object recognition test in rats and antidepressant-like activity in forced swim test in mice. The findings of the study suggest that reversible MAO-B inhibitors can have potential therapeutic applications in Alzheimer's disease.

2-{5-[(Z,2Z)-2-Chloro-3-(4-nitrophenyl)-2-propenylidene]-4-oxo-2-thioxothiazolidin-3-yl}-3-methylbutanoic Acid as a Potential Anti-Breast Cancer Molecule.

It was established that the synthesis of hybrid molecules containing a thiazolidinone and a (2Z)-2-chloro-3-(4-nitrophenyl)prop-2-ene structural fragments is an effective approach for the design of potential anticancer agents. Given the results of the previous SAR-analysis, the aim of the study was to synthesize a novel 4-thiazolidinone derivative Les-3331 and investigate its molecular mechanism of action in MCF-7 and MDA-MB-231 breast cancer cells. The cytotoxic properties and antiproliferative potential of Les-3331 were determined. The effect of the tested compound on apoptosis induction and mitochondrial membrane potential was checked by flow cytometry. ELISA was used to determine caspase-8 and caspase-9, LC3A, LC3B, Beclin-1, and topoisomerase II concentration. Additionally, PAMPA, in silico or in vitro prediction of metabolism, CYP3A4/2D6 inhibition, and an Ames test were performed. Les-3331 possesses high cytotoxic and antiproliferative activity in MCF-7 and MDA-MB-231 breast cancer cells. Its molecular mechanism of action is associated with apoptosis induction, decreased mitochondrial membrane potential, and increased caspase-9 and caspase-8 concentrations. Les-3331 decreased LC3A, LC3B, and Beclin-1 concentration in tested cell lines. Topoisomerase II concentration was also lowered. The most probable metabolic pathways and no DDIs risk of Les-3331 were confirmed in in vitro assays. Our studies confirmed that a novel 4-thiazolidinone derivative represents promising anti-breast cancer activity.

Phenylalanine-Based AMPA Receptor Antagonist as the Anticonvulsant Agent with Neuroprotective Activity-In Vitro and In Vivo Studies.

Trying to meet the multitarget-directed ligands strategy, a series of previously described aryl-substituted phenylalanine derivatives, reported as competitive antagonists of α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptors, were screened in vitro for their free-radical scavenging and antioxidant capacity in two different assays: ferric reducing antioxidant power (FRAP) and oxygen radical absorbance capacity fluorescent (ORAC-FL) assays. The most active antioxidants 1 and 8 were further examined to evaluate their neuroprotective properties in vitro. In this study, compound 1 showed a significant neuroprotective effect against the neurotoxin 6-hydroxydopamine in neuroblastoma SH-SY5Y and IMR-32 cell lines. Both compounds also showed prevention from high levels of reactive oxygen species (ROS) in SH-SY5Y cells. Furthermore, the desired monoamine oxidase B (MAO-B) inhibition effect (IC50 = 278 ± 29 nM) for 1 was determined. No toxic effects up to 100 µM of 1 and 8 against neuroblastoma cells were observed. Furthermore, in vivo studies showed that compound 1 demonstrated significant anticonvulsant potential in 6-Hz test, but in neuropathic pain models its antiallodynic and antihyperalgesic properties were not observed. Concluding, the compound 1 seems to be of higher importance as a new phenylalanine-based lead candidate due to its confirmed promise in in vitro and in vivo anticonvulsant activity.

Benzophenone Derivatives with Histamine H3 Receptor Affinity and Cholinesterase Inhibitory Potency as Multitarget-Directed Ligands for Possible Therapy of Alzheimer's Disease.

The multitarget-directed ligands demonstrating affinity to histamine H3 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 H3R (Ki = 8 nM) and significant inhibitory activity toward BuChE (IC50 = 172 nM and 1.16 µM 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 (Pe) of 6.3 × 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 (ED50 = 20.9 mg/kg) and inflammatory (ED50 = 17.5 mg/kg) pain.

The Phenoxyalkyltriazine Antagonists for 5-HT6 Receptor with Promising Procognitive and Pharmacokinetic Properties In Vivo in Search for a Novel Therapeutic Approach to Dementia Diseases.

Among the serotonin receptors, one of the most recently discovered 5-HT6 subtype is an important protein target and its ligands may play a key role in the innovative treatment of cognitive disorders. However, none of its selective ligands have reached the pharmaceutical market yet. Recently, a new chemical class of potent 5-HT6 receptor agents, the 1,3,5-triazine-piperazine derivatives, has been synthesized. Three members, the ortho and meta dichloro- (1,2) and the unsubstituted phenyl (3) derivatives, proved to be of special interest due to their high affinities (1,2) and selectivity (3) toward 5-HT6 receptor. Thus, a broader pharmacological profile for 1-3, including comprehensive screening of the receptor selectivity and drug-like parameters in vitro as well as both, pharmacokinetic and pharmacodynamic properties in vivo, have been investigated within this study. A comprehensive analysis of the obtained results indicated significant procognitive-like activity together with beneficial drug-likeness in vitro and pharmacokinetics in vivo profiles for both, (RS)-4-[1-(2,3-dichlorophenoxy)propyl]-6-(4-methylpiperazin-1-yl)-1,3,5-triazin-2-amine (2) and (RS)-4-(4-methylpiperazin-1-yl)-6-(1-phenoxypropyl)-1,3,5-triazin-2-amine (3), but insensibly predominant for compound 2. Nevertheless, both compounds (2 and 3) seem to be good Central Nervous System drug candidates in search for novel therapeutic approach to dementia diseases, based on the 5-HT6 receptor target.

Biphenylalkoxyamine Derivatives-Histamine H3 Receptor Ligands with Butyrylcholinesterase Inhibitory Activity.

Neurodegenerative diseases, e.g., Alzheimer's disease (AD), are a key health problem in the aging population. The lack of effective therapy and diagnostics does not help to improve this situation. It is thought that ligands influencing multiple but interconnected targets can contribute to a desired pharmacological effect in these complex illnesses. Histamine H3 receptors (H3Rs) play an important role in the brain, influencing the release of important neurotransmitters, such as acetylcholine. Compounds blocking their activity can increase the level of these neurotransmitters. Cholinesterases (acetyl- and butyrylcholinesterase) are responsible for the hydrolysis of acetylcholine and inactivation of the neurotransmitter. Increased activity of these enzymes, especially butyrylcholinesterase (BuChE), is observed in neurodegenerative diseases. Currently, cholinesterase inhibitors: donepezil, rivastigmine and galantamine are used in the symptomatic treatment of AD. Thus, compounds simultaneously blocking H3R and inhibiting cholinesterases could be a promising treatment for AD. Herein, we describe the BuChE inhibitory activity of H3R ligands. Most of these compounds show high affinity for human H3R (Ki < 150 nM) and submicromolar inhibition of BuChE (IC50 < 1 µM). Among all the tested compounds, 19 (E153, 1-(5-([1,1'-biphenyl]-4-yloxy)pentyl)azepane) exhibited the most promising in vitro affinity for human H3R, with a Ki value of 33.9 nM, and for equine serum BuChE, with an IC50 of 590 nM. Moreover, 19 (E153) showed inhibitory activity towards human MAO B with an IC50 of 243 nM. Furthermore, in vivo studies using the Passive Avoidance Task showed that compound 19 (E153) effectively alleviated memory deficits caused by scopolamine. Taken together, these findings suggest that compound 19 can be a lead structure for developing new anti-AD agents.

Cyanobiphenyls: Novel H3 receptor ligands with cholinesterase and MAO B inhibitory activity as multitarget compounds for potential treatment of Alzheimer's 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 Ki values) for human histamine H3 receptors (hH3R) and good nonselective inhibitory potency (micromolar range of IC50 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 hH3R/eeAChE/eqBuChE/hMAO B ligand (5: hH3R Ki = 9.2 nM; eeAChE IC50 = 2.63 µM; eqBuChE IC50 = 1.30 µM; hMAO B IC50 = 0.60 µM). 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.

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.

Rational design of new multitarget histamine H3 receptor ligands as potential candidates for treatment of Alzheimer's disease.

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 H3 receptor (H3R) antagonists/inverse agonists, and virtual docking was then performed for the enzyme acetylcholinesterase. Next, 23 compounds were synthesised and evaluated in vitro for human H3R (hH3R) affinity and inhibitory activity on cholinesterases. Most of the target compounds showed hH3R affinities in nanomolar range and exhibited cholinesterase inhibitory activity with IC50 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 hH3R (Ki = 170 nM and 100 nM respectively) and high inhibitory activity for acetylcholinesterase (IC50 = 180 nM and 136 nM respectively). Moreover, these compounds showed moderate inhibitory activity for butyrylcholinesterase (IC50 = 880 nM and 394 nM respectively) and hMAO B (IC50 = 775 nM and 897 nM respectively). Furthermore, molecular docking studies were performed for hH3R, 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.

8-Benzylaminoxanthine scaffold variations for selective ligands acting on adenosine A2A receptors. Design, synthesis and biological evaluation.

A library of 34 novel compounds based on a xanthine scaffold was explored in biological studies for interaction with adenosine receptors (ARs). Structural modifications of the xanthine core were introduced in the 8-position (benzylamino and benzyloxy substitution) as well as at N1, N3, and N7 (small alkyl residues), thereby improving affinity and selectivity for the A2A AR. The compounds were characterized by radioligand binding assays, and our study resulted in the development of the potent A2A AR ligands including 8-((6-chloro-2-fluoro-3-methoxybenzyl)amino)-1-ethyl-3,7-dimethyl-3,7-dihydro-1H-purine-2,6-dione (12d; Ki human A2AAR: 68.5 nM) and 8-((2-chlorobenzyl)amino)-1-ethyl-3,7-dimethyl-3,7-dihydro-1H-purine-2,6-dione (12h; Ki human A2AAR: 71.1 nM). Moreover, dual A1/A2AAR ligands were identified in the group of 1,3-diethyl-7-methylxanthine derivatives. Compound 14b displayed Ki values of 52.2 nM for the A1AR and 167 nM for the A2AAR. Selected A2AAR ligands were further evaluated as inactive for inhibition of monoamine oxidase A, B and isoforms of phosphodiesterase-4B1, -10A, which represent classical targets for xanthine derivatives. Therefore, the developed 8-benzylaminoxanthine scaffold seems to be highly selective for AR activity and relevant for potent and selective A2A ligands. Compound 12d with high selectivity for ARs, especially for the A2AAR subtype, evaluated in animal models of inflammation has shown anti-inflammatory activity. Investigated compounds were found to display high selectivity and may therefore be of high interest for further development as drugs for treating cancer or neurodegenerative diseases.

Dual Target Ligands with 4-tert-Butylphenoxy Scaffold as Histamine H3 Receptor Antagonists and Monoamine Oxidase B Inhibitors.

Dual target ligands are a promising concept for the treatment of Parkinson's disease (PD). A combination of monoamine oxidase B (MAO B) inhibition with histamine H3 receptor (H3R) antagonism could have positive effects on dopamine regulation. Thus, a series of twenty-seven 4-tert-butylphenoxyalkoxyamines were designed as potential dual-target ligands for PD based on the structure of 1-(3-(4-tert-butylphenoxy)propyl)piperidine (DL76). Probed modifications included the introduction of different cyclic amines and elongation of the alkyl chain. Synthesized compounds were investigated for human H3R (hH3R) affinity and human MAO B (hMAO B) inhibitory activity. Most compounds showed good hH3R affinities with Ki values below 400 nM, and some of them showed potent inhibitory activity for hMAO B with IC50 values below 50 nM. However, the most balanced activity against both biological targets showed DL76 (hH3R: Ki = 38 nM and hMAO B: IC50 = 48 nM). Thus, DL76 was chosen for further studies, revealing the nontoxic nature of DL76 in HEK293 and neuroblastoma SH-SY5Ycells. However, no neuroprotective effect was observed for DL76 in hydrogen peroxide-treated neuroblastoma SH-SY5Y cells. Furthermore, in vivo studies showed antiparkinsonian activity of DL76 in haloperidol-induced catalepsy (Cross Leg Position Test) at a dose of 50 mg/kg body weight.

Novel, Dual Target-Directed Annelated Xanthine Derivatives Acting on Adenosine Receptors and Monoamine Oxidase B.

Annelated purinedione derivatives have been shown to act as possible multiple-target ligands, addressing adenosine receptors and monoaminooxidases. In this study, based on our previous results, novel annelated pyrimido- and diazepino[2,1-f]purinedione derivatives were designed as dual-target-directed ligands combining A2A adenosine receptor (AR) antagonistic activity with blocking monoamine oxidase B. A library of 19 novel compounds was synthesized and biologically evaluated in radioligand binding studies at AR subtypes and for their ability to inhibit MAO-B. This allowed 9-(2-chloro-6-fluorobenzyl)-3-ethyl-1-methyl-6,7,8,9-tetrahydropyrimido[2,1-f]purine-2,4(1H,3H)-dione (13 e; Ki human A2A AR: 264 nM and IC50 human MAO-B: 243 nM) to be identified as the most potent dual-acting ligand from this series. ADMET parameters were estimated in vitro, and analysis of the structure-activity relationships was complemented by molecular-docking studies based on previously published X-ray structures of the protein targets. Such dual-acting ligands, by selectively blocking A2A AR, accompanied by the inhibition of dopamine metabolizing enzyme MAO-B, might provide symptomatic and neuroprotective effects in, among others, the treatment of Parkinson disease.

KSK19 - Novel histamine H3 receptor ligand reduces body weight in diet induced obese mice.

AIMS: Histamine H3 receptors ligands act anorectic by blocking the H3 autoreceptors in the CNS, that results in increased synthesis and disinhibition of histamine release. Histamine further influencing H1 receptors participates in the leptin-dependent inhibition of food intake. It also affects the peripheral metabolism by increasing white adipose tissue lipolysis. Thus, ligands such as KSK19 with significant antagonistic properties at the H3 receptor might serve as an useful treatment for obesity. MATERIALS AND METHODS: To induce obesity, female CD-1 mice were fed a high-fat diet for 14 weeks. The test compound at the doses of 10 or 15 mg/kg, i.p. was administrated for 21 days. Glucose and insulin tolerance tests was performed at the beginning of week 15. At the end of study, amount of intraperitoneal fat pads, AlAT, IL-6 and TNF-α plasma levels were determined. RESULTS: Animals fed with high-fat diet and treated with test compound at the dose of 15 mg/kg showed significantly less weight gain, than mice from the control group. The use of KSK19 for 21 days in obese mice also significantly improved glucose tolerance and insulin resistance. In the tested doses KSK19 did not affect locomotor activity neither in lean nor in obese mice after single i.p. administration, but spontaneous activity increased during three hour after twentieth administrations. CONCLUSION: KSK19 is a strong, selective histamine H3 receptor antagonist with a favorable influence on body weight after multiple administration at the dose of 15 mg/kg. Moreover it significantly improves glucose tolerance.