Histamine H3 Receptor Ligands-KSK-59 and KSK-73-Reduce Body Weight Gain in a Rat Model of Excessive Eating.

Noting the worldwide rapid increase in the prevalence of overweight and obesity new effective drugs are now being sought to combat these diseases. Histamine H3 receptor antagonists may represent an effective therapy as they have been shown to modulate histamine synthesis and release and affect a number of other neurotransmitters (norepinephrine, acetylcholine, γ-aminobutyric acid, serotonin, substance P) thus influencing the food intake. Based on the preliminary studies determining affinity, intrinsic activity, and selected pharmacokinetic parameters, two histamine H3 receptor ligands were selected. Female rats were fed palatable food for 28 days and simultaneously administered the tested compounds intraperitoneally (i.p.) at a dose of 10 or 1 mg/kg b.w./day. Weight was evaluated daily and calorie intake was evaluated once per week. The plasma levels of cholesterol, triglycerides, leptin, adiponectin, ghrelin, corticosterone, CRP and IL-6 were determined at the end of experiment. The glucose tolerance test was also performed. To exclude false positives, the effect of tested compounds on spontaneous activity was monitored during the treatment, as well as the amount of consumed kaolin clay was studied as a reflection of possible gastrointestinal disturbances comparable to nausea. The histamine H3 receptor antagonists KSK-59 and KSK-73 administered i.p. at a dose of 10 mg/kg b.w. prevented weight gain in a rat model of excessive eating. They reduced adipose tissue deposits and improved glucose tolerance. Both compounds showed satisfying ability to penetrate through biological membranes determined in in vitro studies. Compound KSK-73 also reduced the caloric intake of the experimental animals what indicates its anorectic effect. These results show the pharmacological properties of histamine H3 receptor antagonists, (4-pyridyl)piperazine derivatives, as the compounds causing not only slower weight gain but also ameliorating some metabolic disorders in rats having the opportunity to overeat.

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.

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.

Chlorine substituents and linker topology as factors of 5-HT6R activity for novel highly active 1,3,5-triazine derivatives with procognitive properties in vivo.

In the light of recent lines of evidence, 5-HT6R ligands are a promising tool for future treatment of memory impairment. Hence, this study has supplied highly potent 5-HT6R agents with procognitive effects, which represent an original chemical class of 1,3,5-triazines, different from widely studied sulfone and indole-like 5-HT6R ligands. The new compounds were rationally designed as modifications of lead, 4-(1-(2-chlorophenoxy)ethyl)-6-(4-methylpiperazin-1-yl)-1,3,5-triazin-2-amine (1), involving an introduction of: (i) two chlorines at benzene ring and (ii) varied linkers joining the triazine ring to aromatic ethers. Synthesis, in vitro and in vivo biological tests and computer-aided SAR analysis for 19 new compounds were carried out. Most of the new triazines displayed high affinity (Ki < 100 nM) and selectivity towards 5-HT6R, with respect to 5-HT2AR, 5-HT7R and D2R. The crystallography-supported docking studies, including quantum-polarized ligand docking (QPLD), indicated that chlorine atoms may be involved in different type of halogen bonding, however, the linker properties seem to predominately affect the 5-HT6R affinity. 4-[1-(2,5-Dichlorophenoxy)propyl]-6-(4-methylpiperazin-1-yl)-1,3,5-triazin-2-amine (9), which displayed: the highest affinity (Ki = 6 nM), very strong 5-HT6R antagonistic action (KB = 27 pM), procognitive effects in vivo in novel object recognition (NOR) test in rats, a very good permeability in PAMPA model and satisfying safety in vitro, was identified as the most potent 1,3,5-triazine agent so far, useful as a new lead for further research.

Synthesis and computer-aided SAR studies for derivatives of phenoxyalkyl-1,3,5-triazine as the new potent ligands for serotonin receptors 5-HT6.

This research has provided the most active 5-HT6R agents among 1,3,5-triazine derivatives investigated to date and has also identified the world's first selenium-containing 5-HT6R ligands. The studies are focused on design, synthesis, biological evaluation and docking-supported SAR analysis for novel 5-HT6R agents as derivatives of lead structure 4-(4-methylpiperazin-1-yl)-6-(phenoxymethyl)-1,3,5-triazin-2-amine (7). The lead modifications included an introduction of: (i) various small substituents at benzene ring, (ii) a branched ether linker or (iii) the ether oxygen replacement with other chalcogen (S, Se) or sulfonyl moiety. Hence, a series of new compounds (7-24) was synthesized and examined on their affinities for 5-HT6R and selectivity, in respect to the 5-HT1AR, 5-HT2AR, 5-HT7R and dopamine D2 receptor, in the radioligand binding assays. For representative most active compounds functional bioassays and toxicity profile in vitro and antidepressant-like activity in vivo were examined. The 2-isopropyl-5-methylphenyl derivative (10) was found as the most active triazine 5-HT6R antagonist (Ki = 11 nM). SAR analysis indicated, that an exchange of oxygen to selenium (7 vs. 22), and especially, to sulfur (7 vs. 19) was beneficial to increase both affinity and antagonistic action for 5-HT6R. Surprisingly, an introduction of SO2 caused a drastic decrease of the 5-HT6R affinity, which was explained at a molecular level based on docking studies. All in vivo tested compounds (10, 18 and 21) did not show any risk of toxicity in the safety studies in vitro.