An Allosteric Potentiator of the Dopamine D1 Receptor Increases Locomotor Activity in Human D1 Knock-In Mice without Causing Stereotypy or Tachyphylaxis.

Allosteric potentiators amplify the sensitivity of physiologic control circuits, a mode of action that could provide therapeutic advantages. This hypothesis was tested with the dopamine D1 receptor potentiator DETQ [2-(2,6-dichlorophenyl)-1-((1S,3R)-3-(hydroxymethyl)-5-(2-hydroxypropan-2-yl)-1-methyl-3,4-dihydroisoquinolin-2(1H)-yl)ethan-1-one]. In human embryonic kidney 293 (HEK293) cells expressing the human D1 receptor, DETQ induced a 21-fold leftward shift in the cAMP response to dopamine, with a Kb of 26 nM. The maximum response to DETQ alone was ∼12% of the maximum response to dopamine, suggesting weak allosteric agonist activity. DETQ was ∼30-fold less potent at rat and mouse D1 receptors and was inactive at the human D5 receptor. To enable studies in rodents, an hD1 knock-in mouse was generated. DETQ (3-20 mg/kg orally) caused a robust (∼10-fold) increase in locomotor activity (LMA) in habituated hD1 mice but was inactive in wild-type mice. The LMA response to DETQ was blocked by the D1 antagonist SCH39166 and was dependent on endogenous dopamine. LMA reached a plateau at higher doses (30-240 mg/kg) even though free brain levels of DETQ continued to increase over the entire dose range. In contrast, the D1 agonists SKF 82958, A-77636, and dihydrexidine showed bell-shaped dose-response curves with a profound reduction in LMA at higher doses; video-tracking confirmed that the reduction in LMA caused by SKF 82958 was due to competing stereotyped behaviors. When dosed daily for 4 days, DETQ continued to elicit an increase in LMA, whereas the D1 agonist A-77636 showed complete tachyphylaxis by day 2. These results confirm that allosteric potentiators may have advantages compared with direct-acting agonists.

Synthesis of substituted diphenyl sulfones and their structure-activity relationship with the antagonism of 5-НТ6 receptors.

Substituted diphenyl sulfones (10a-n) were synthesised, and the structures were confirmed by NMR, LC-MS and X-ray crystallography. Their antagonistic activities towards 5-HT6 receptor were assessed in a cell-based functional assay. Diphenyl sulfone 10a, in spite of being the smallest and simplest known sulfonyl-containing 5-HT6R antagonist, showed a strong potency (Ki=1.6 µM). Its derivative with a methylamine substituent, 10g (N-methyl-2-(phenylsulfonyl)aniline), was ∼66-times as active as diphenyl sulfone (Ki=24.3 nM). Addition of a piperazinyl moiety in the para-position relative to the sulfonyl group in compound 10m (N-methyl-2-(phenylsulfonyl)-5-piperazin-1-ylaniline) led to a further 150-fold increase in potency (Ki=0.16 nM) to block the serotonin-induced response of HEK-293 cells that were stably transfected with the human recombinant 5-HT6 receptor.

Recombinant yeast screen for new inhibitors of human acetyl-CoA carboxylase 2 identifies potential drugs to treat obesity.

Acetyl-CoA carboxylase (ACC) is a key enzyme of fatty acid metabolism with multiple isozymes often expressed in different eukaryotic cellular compartments. ACC-made malonyl-CoA serves as a precursor for fatty acids; it also regulates fatty acid oxidation and feeding behavior in animals. ACC provides an important target for new drugs to treat human diseases. We have developed an inexpensive nonradioactive high-throughput screening system to identify new ACC inhibitors. The screen uses yeast gene-replacement strains depending for growth on cloned human ACC1 and ACC2. In "proof of concept" experiments, growth of such strains was inhibited by compounds known to target human ACCs. The screen is sensitive and robust. Medium-size chemical libraries yielded new specific inhibitors of human ACC2. The target of the best of these inhibitors was confirmed with in vitro enzymatic assays. This compound is a new drug chemotype inhibiting human ACC2 with 2.8 muM IC(50) and having no effect on human ACC1 at 100 muM.

Antagonists of 5-HT6 receptors. Substituted 3-(phenylsulfonyl)pyrazolo[1,5-a]pyrido[3,4-e]pyrimidines and 3-(phenylsulfonyl)pyrazolo[1,5-a]pyrido[4,3-d]pyrimidines-Synthesis and 'structure-activity' relationship.

Synthesis and biological evaluation of a new series of structurally unrestricted and intramolecular hydrogen bond restricted derivatives of 3-(phenylsulfonyl)pyrazolo[1,5-a]pyrido[3,4-e]pyrimidines (angular tricyclics) and 3-(phenylsulfonyl)pyrazolo[1,5-a]pyrido[4,3-d]pyrimidines (linear tricyclics) are described. Structurally restricted derivatives are highly potent and selective blockers of 5-HT(6) receptors with little difference between angular or linear shape of the tricyclic core, the angular species being only slightly more potent. The angular representative of 3-(phenylsulfonyl)pyrazolo[1,5-a]pyrido[3,4-e]pyrimidines, 5, can be considered as more favorable candidate for further development as it shows only weak 5-HT(2B) blocking activity (IC(50)=6.16 µM as compared with IC(50)=1.8 nM for 5-HT(6) receptors) and very low hERG potassium channel blocking potency (IC(50)=54.2 µM). The linear analog, 11, is less favorable as while showing no binding to the 5-HT(2B) receptor at concentrations of up to 10 µM, it exhibits quite a high potency to block the hERG channel (IC(50)=0.5 µM).

Synthesis and SAR of 3-arylsulfonyl-pyrazolo[1,5-a]pyrimidines as potent serotonin 5-HT6 receptor antagonists.

Syntheses of a series of novel 3-sulfonyl-pyrazolo[1,5-a]pyrimidines and their 5-HT(6) receptor antagonistic structure-activity relationship are disclosed. The nature and position of substituents, which affect their receptor antagonistic activity, are analyzed. Among all synthesized derivatives, {3-(3-chlorophenylsulfonyl)-5,7-dimethyl-pyrazolo[1,5-a]pyrimidin-2-yl}-methyl-amine 33 (K(i)=190 pM), (3-phenylsulfonyl-7-methyl-pyrazolo[1,5-a]pyrimidin-2-yl)-methyl-amine 44 (K(i)=240 pM), (3-phenylsulfonyl-5-metoxymethyl-7-methyl-pyrazolo[1,5-a]pyrimidin-2-yl)-methyl-amine 50 (K(i)=270 pM), and (3-phenylsulfonyl-5-methyl-7-metoxymethyl-pyrazolo[1,5-a]pyrimidin-2-yl)-methyl-amine 52 (K(i)=280 pM) are the most potent antagonists of the 5-HT(6) receptors.

Synthesis and biological activity of 5-styryl and 5-phenethyl-substituted 2,3,4,5-tetrahydro-1H-pyrido[4,3-b]indoles.

Syntheses, biological evaluation, and structure-activity relationships for a series of novel 5-styryl and 5-phenethyl analogs of dimebolin are disclosed. The novel derivatives and dimebolin share a broad spectrum of activities against therapeutically relevant targets. Among all synthesized derivatives, 2,8-dimethyl-5-[(Z)-2-phenylvinyl]-2,3,4,5-tetrahydro-1H-pyrido[4,3-b]indole and its 5-phenethyl analog are the most potent blockers of 5-HT(7), 5-HT(6), 5-HT(2C), Adrenergic alpha(2) and H(1) receptors. The general affinity rank order towards the studied receptors was Z-3(2)>4(2)4(3)>>dimebolin, all of them having highest affinities to 5-HT(7) receptors.

Synthesis of cycloalkane-annelated 3-phenylsulfonyl-pyrazolo[1,5-a]pyrimidines and their evaluation as 5-HT6 receptor antagonists.

Synthesis and biological evaluation of 1 ('angular') and 2 ('linear') cycloalkane-annelated 3-phenylsulfonyl-pyrazolo[1,5-a]pyrimidines as novel ligands of the 5-HT(6) receptors are disclosed. The new compounds 1 and 2 are highly selective antagonists of the receptor with sub-nanomolar affinities (K(i)<1 nM). In its structure, this new chemotype lacks a basic ionizable side chain, which is considered as the characteristic feature of the 5-HT(6) receptor antagonists pharmacophore model.

Synthesis and biological study of 3-(phenylsulfonyl)thieno[2,3-e][1,2,3]triazolo[1,5-a]pyrimidines as potent and selective serotonin 5-HT6 receptor antagonists.

A number of 3-(phenylsulfonyl)thieno[2,3-e][1,2,3]triazolo[1,5-a]pyrimidines were prepared and their 5-HT6 receptor binding affinity and ability to inhibit the functional cellular responses to serotonin were evaluated. 3-[(3-chlorophenyl)sulfonyl]-N-(tetrahydrofuran-2-ylmethyl)thieno[2,3-e][1,2,3]triazolo[1,5-a]pyrimidin-5-amine 2{5,26} appeared to be the most active in a functional assay (IC50=29.0 nM) and 3-(phenylsulfonyl)-N-(2-thienylmethyl) thieno[2,3-e][1,2,3]triazolo[1,5-a]pyrimidin-5-amine 2{1,28} demonstrated the greatest affinity in a 5-HT6 receptor radioligand binding assay (Ki=1.7 nM). A screening of 5-HT2A and 5-HT2B receptor affinity revealed that 3-(phenylsulfonyl)thieno[2,3-e][1,2,3]triazolo[1,5-a]pyrimidines are highly selective 5-HT6 receptor ligands.

Solution phase parallel synthesis of substituted 3-phenylsulfonyl-[1,2,3]triazolo[1,5-a]quinazolines: selective serotonin 5-HT(6) receptor antagonists.

Here we present the solution phase parallel synthesis of a combinatorial library consisting of 776 new substituted 3-phenylsulfonyl-[1,2,3]triazolo[1,5-a]quinazolines and a study of the relation of their structure with a 5-HT(6) receptor antagonistic activity in a functional cell (HEK 293) analysis and radioligand competitive binding. We have found highly active and selective 5-HT(6)R antagonists. The most active 5-HT(6)R antagonists have IC(50) <100 nM in a functional assay, and K(i) <10 nM in a binding assay, which is 100 times higher than the activity with respect to other serotonin receptors.

Synthesis and biological evaluation of novel gamma-carboline analogues of Dimebon as potent 5-HT6 receptor antagonists.

Synthesis, biological evaluation and structure-activity relationships for a series of novel gamma-carboline analogues of Dimebon are described. Among the studied compounds, gamma-carbolines 3{8} and 3{14} have been identified as potent small molecule antagonists of histamine H(1) (IC(50)=0.1 microM) and serotonin 5-HT(6) (IC(50)=0.37 microM) receptors, respectively.

Novel aryl and heteroaryl substituted N-[3-(4-phenylpiperazin-1-yl)propyl]-1,2,4-oxadiazole-5-carboxamides as selective GSK-3 inhibitors.

Synthesis, biological evaluation, and SAR dependencies for a series of novel aryl and heteroaryl substituted N-[3-(4-phenylpiperazin-1-yl)propyl]-1,2,4-oxadiazole-5-carboxamide inhibitors of GSK-3beta kinase are described. The inhibitory activity of the synthesized compounds is highly dependent on the character of substituents in the phenyl ring and the nature of terminal heterocyclic fragment of the core molecular scaffold. The most potent compounds from this series contain 3,4-di-methyl or 2-methoxy substituents within the phenyl ring and 3-pyridine fragment connected to the 1,2,4-oxadiazole heterocycle. These compounds selectively inhibit GSK-3beta kinase with IC(50) value of 0.35 and 0.41 microM, respectively.

AVN-492, A Novel Highly Selective 5-HT6R Antagonist: Preclinical Evaluation.

Discovery of 5-HT6 receptor subtype and its exclusive localization within the central nervous system led to extensive investigations of its role in Alzheimer's disease, schizophrenia, and obesity. In the present study, we present preclinical evaluation of a novel highly-potent and highly-selective 5-HT6R antagonist, AVN-492. The affinity of AVN-492 to bind to 5-HT6R (Ki = 91 pM) was more than three orders of magnitude higher than that to bind to the only other target, 5-HT2BR, (Ki = 170 nM). Thus, the compound displayed great 5-HT6R selectivity against all other serotonin receptor subtypes, and is extremely specific against any other receptors such as adrenergic, GABAergic, dopaminergic, histaminergic, etc. AVN-492 demonstrates good in vitro and in vivo ADME profile with high oral bioavailability and good brain permeability in rodents. In behavioral tests, AVN-492 shows anxiolytic effect in elevated plus-maze model, prevents an apomorphine-induced disruption of startle pre-pulse inhibition (the PPI model) and reverses a scopolamine- and MK-801-induced memory deficit in passive avoidance model. No anti-obesity effect of AVN-492 was found in a murine model. The data presented here strongly indicate that due to its high oral bioavailability, extremely high selectivity, and potency to block the 5-HT6 receptor, AVN-492 is a very promising tool for evaluating the role the 5-HT6 receptor might play in cognitive and neurodegenerative impairments. AVN-492 is an excellent drug candidate to be tested for treatment of such diseases, and is currently being tested in Phase I trials.

Screening for caspase-3 inhibitors: effect of a reducing agent on identified hit chemotypes.

When studying cysteinyl proteases in general and caspases in particular, it is generally accepted that a reaction buffer must contain a reducing agent to prevent essential cysteinyl groups from spontaneous oxidation. Dithiothreitol (DTT) and beta-mercaptoethanol (beta-MCE) are 2 of the most broadly used reducing agents. While screening a library of small molecules against caspase-3, the authors have found that the nature of the reducing agent used, DTT or beta-MCE, dramatically affects screening results and leads to identification of nonoverlapping hits. Screening in DTT-containing buffer revealed few novel classes of small molecules that selectively and reversibly inhibit caspase-3 but failed to identify isatin sulfonamides recently found to be potent and selective caspase-3 inhibitors (false negatives). On the other hand, screening in the presence of beta-MCE failed to identify a series of hit compounds, 1,3-dioxo-2,3-dichloro-1H-pyrrolo[3,4-c]quinolines, discovered with DTT, whereas isatin sulphonamides in these conditions exhibited strong caspase-3 inhibition. In this work, the authors show that thiol-containing reducing agents can affect catalytic activity of caspase-3 and modify its thermostability in a redox-potential-independent manner. The authors speculate that the differential structural modifications of caspase-3 seen with different reducing agents represent structurally different caspase-3 conformations and are responsible for its differential sensitivity to small molecules of different chemotypes. Hence, selection of the reducing agent may dramatically affect the quality of high-throughput screening campaigns.

Screening for caspase-3 inhibitors: a new class of potent small-molecule inhibitors of caspase-3.

From the authors' 650,000 compound collection, they have selected approximately 15,000 potential small-molecule protease inhibitors, which were subjected to high-throughput screening against caspase-3. The screening yielded a series of hits that belong to 11 different scaffolds. Based on the structure of one of the hits, a new class of the small-molecule inhibitors with a double electrophilic warhead, 8-sulfonyl-pyrrolo[3,4-c]quinoline-1,3-diones (SPQ), was synthesized and tested in follow-up mechanistic and anti-apoptosis assays. Mechanistic analysis of a representative compound of this class, CD-001-0011, showed that the compound exhibited a high potency (IC (50)=130 nM), was reversible though noncompetitive, and had a broad selectivity profile to other caspases belonging to groups I to III. The compound was effective in preventing staurosporine induced apoptosis in a few cell lines and retinoic acid-induced apoptosis in zebrafish.

AVN-101: A Multi-Target Drug Candidate for the Treatment of CNS Disorders.

Lack of efficacy of many new highly selective and specific drug candidates in treating diseases with poorly understood or complex etiology, as are many of central nervous system (CNS) diseases, encouraged an idea of developing multi-modal (multi-targeted) drugs. In this manuscript, we describe molecular pharmacology, in vitro ADME, pharmacokinetics in animals and humans (part of the Phase I clinical studies), bio-distribution, bioavailability, in vivo efficacy, and safety profile of the multimodal drug candidate, AVN-101. We have carried out development of a next generation drug candidate with a multi-targeted mechanism of action, to treat CNS disorders. AVN-101 is a very potent 5-HT7 receptor antagonist (Ki = 153 pM), with slightly lesser potency toward 5-HT6, 5-HT2A, and 5HT-2C receptors (Ki = 1.2-2.0 nM). AVN-101 also exhibits a rather high affinity toward histamine H1 (Ki = 0.58 nM) and adrenergic α2A, α2B, and α2C (Ki = 0.41-3.6 nM) receptors. AVN-101 shows a good oral bioavailability and facilitated brain-blood barrier permeability, low toxicity, and reasonable efficacy in animal models of CNS diseases. The Phase I clinical study indicates the AVN-101 to be well tolerated when taken orally at doses of up to 20 mg daily. It does not dramatically influence plasma and urine biochemistry, nor does it prolong QT ECG interval, thus indicating low safety concerns. The primary therapeutic area for AVN-101 to be tested in clinical trials would be Alzheimer's disease. However, due to its anxiolytic and anti-depressive activities, there is a strong rational for it to also be studied in such diseases as general anxiety disorders, depression, schizophrenia, and multiple sclerosis.

Synthesis and structure-activity relationship of 4-substituted 2-(2-acetyloxyethyl)-8-(morpholine-4-sulfonyl)pyrrolo[3,4-c]quinoline-1,3-diones as potent caspase-3 inhibitors.

Synthesis, biological evaluation, and SAR dependencies for a series of novel 1,3-dioxo-2,3-dihydro-1H-pyrrolo[3,4-c]quinoline inhibitors of caspase-3 are described. The inhibitory activity of the synthesized compounds is highly dependent on the nature of 4-substituents on the core scaffold. 4-methyl-and 4-phenyl-substituted derivatives, which were the most active compounds within this series, inhibited caspase-3 with IC50 of 23 and 27 nM, respectively.

Pyrrolo[3,4-c]quinoline-1,3-diones as potent caspase-3 inhibitors. Synthesis and SAR of 2-substituted 4-methyl-8-(morpholine-4-sulfonyl)-pyrrolo[3,4-c]quinoline-1,3-diones.

Synthesis, biological evaluation and structure-activity relationships for a series of 2-substituted 4-methyl-8-(morpholine-4-sulfonyl)-1,3-dioxo-2,3-dihydro-1H-pyrrolo[3,4-c]quinolines are described. These compounds represent a new chemotype of nonpeptide small molecule inhibitors of caspase-3. Among the studied compounds, several potent inhibitors with IC50 in the range of 3-10 nM have been identified. The most active compound within this series, 7{49} and 7{58}, inhibited caspase-3 with IC50=3 nM.

Synthesis and caspase-3 inhibitory activity of 8-sulfonyl-1,3-dioxo-2,3-dihydro-1H-pyrrolo[3,4-c]quinolines.

A convenient synthesis of novel 8-sulfonyl-1,3-dioxo-4-methyl-2,3-dihydro-1H-pyrrolo[3,4-c]quinolines is described. As key steps to assemble the target molecular scaffold, our method features (a) Pfitzinger reaction of isatin-5-sulfonate 1 with methyl 3-oxo-3-phenylpropanoate, (b) formation of 1-(1H-pyrazol-4-yl)-1H-pyrrole-2,5-dione intermediate 5, and (c) reaction of sulfinic acid 9 with acrylate or methylacrylate leading to the corresponding sulfonyl propionates. Two compounds, ester 11 and morpholide 13, have been identified as potent inhibitors of caspase-3 with IC50 = 6 nM. Our primary data suggest noncompetitive and reversible character of caspase-3 inhibition.

Serotonin antagonist profiling on 5HT2A and 5HT2C receptors by nonequilibrium intracellular calcium response using an automated flow-through fluorescence analysis system, HT-PS 100.

Characterization of the potencies of agonists and antagonists in cell-based assays can be complicated by nonequilibrium conditions of functional response. We assessed the potencies of a series of serotonin (5HT) antagonists by inhibition of intracellular calcium response in HEK 293 cells expressing 5HT(2A) or 5HT(2C) receptors. An automated system, HT-PS 100, was used to profile the antagonists in two experimental setups: coadministration of agonist and antagonist to cells and preincubation of the cells with antagonist prior to agonist administration. We showed that the antagonist potencies (pIC(50) values) determined in the preincubation configuration were close to or exceeded those measured in the coadministration configuration. Closeness of the potencies determined in the two configurations supposedly reflected a rapid antagonist-receptor equilibration, whereas a significantly higher preincubation potency implied slow antagonist dissociation from the receptor. Schild analysis of the inhibition of serotonin-induced cell response by a competitive 5HT(2A) antagonist, spiperone, showed a typical competitive inhibition pattern when both the agonist and antagonist were applied simultaneously. Contrary to this, an insurmountable diminishing of the maximal cell response to serotonin was observed when the cells were preincubated with spiperone. We conclude that a combination of the coadministration and preincubation experimental setups is necessary for appropriate mechanistic interpretation and quantitative assessment of the antagonist activity when using transient functional readouts.

Efficient optimization strategy for marginal hits active against abl tyrosine kinases.

Primary high-throughput screening of commercially available small molecules collections often results in hit compounds with unfavorable ADME/Tox properties and low IP potential. These issues are addressed empirically at follow-up lead development and optimization stages. In this work, we describe a rational approach to the optimization of hit compounds discovered during screening of a kinase focused library against abl tyrosine kinase. The optimization strategy involved application of modern chemoinformatics techniques, such as automatic bioisosteric transformation of the initial hits, efficient solution-phase combinatorial synthesis, and advanced methods of knowledge-based libraries design.