Design of NAALADase inhibitors: a novel neuroprotective strategy

Excessive glutamatergic transmission is thought to be responsible for the injury observed in a variety of neurological disorders such as stroke. N-acetylaspartylglutamate (NAAG), a major peptidic component of the brain, has been suggested to serve as a potential storage form of glutamate. N-acetylated-a-linked acidic dipeptidase (NAALADase, EC 3.4.17.21) is responsible for the hydrolysis of NAAG into N-acetylaspartate (NAA) and glutamate. If NAAG is a storage form of glutamate, then inhibition of NAALADase should be neuroprotective in diseases in which excess glutamatergic transmission is detrimental. In addition, NAAG has been demonstrated to be an agonist at group II metabotropic glutamate receptors and functions as a mixed agonist/antagonist at N-methyl-D-aspartate receptors. Therefore, inhibition of NAALADase would also function to increase NAAG levels which, in turn, should provide neuroprotection via the interaction of NAAG with these receptors. Recently, potent and selective inhibitors of the enzyme have been designed and subsequently used to demonstrate that inhibition of NAALADase is neuroprotective in animal models of neurodegeneration. As such, NAALADase inhibition represents a novel method of regulating extracellular glutamate levels and provides a new avenue for the treatment of neurological disorders.     

7-Aminopyrazolo[1,5-a]pyrimidines as potent multitargeted receptor tyrosine kinase inhibitors

7-Aminopyrazolo[1,5- a]pyrimidine urea receptor tyrosine kinase inhibitors have been discovered. Investigation of structure-activity relationships of the pyrazolo[1,5- a]pyrimidine nucleus led to a series of 6-(4- N, N'-diphenyl)ureas that potently inhibited a panel of vascular endothelial growth factor receptor (VEGFR) and platelet-derived growth factor receptor (PDGFR) kinases. Several of these compounds, such as 34a, are potent inhibitors of kinase insert domain-containing receptor tyrosine kinase (KDR) both enzymatically (<10 nM) and cellularly (<10 nM). In addition, compound 34a possesses a favorable pharmacokinetic profile and demonstrates efficacy in the estradiol-induced murine uterine edema (UE) model (ED 50 = 1.4 mg/kg).     

Small-molecule HIV-1 gp120 inhibitors to prevent HIV-1 entry: an emerging opportunity for drug development

The HIV-1 gp120 envelope protein is an essential component in the multi-tiered viral entry process. Despite the overall genetic heterogeneity of the gp120 glycoprotein, the conserved CD4 binding site provides an attractive antiviral target. Recently, increased efforts aimed at the development of inhibitors of gp120 have been reported. This review focuses primarily on small-molecule gp120 inhibitors and discusses key characteristics of compounds that appear to fall within this class. The preclinical profiles of compounds that prevent gp120 from assuming a conformation favorable for CD4 binding are described in this review. In addition, inhibitors possessing some common structural features, including at least one compound that exhibits sub-nanomolar potency in a cell fusion assay are discussed. A series of compounds that were designed to enhance immune responses to virus via alteration of the gp120 conformation after targeting the CD4 binding pocket are also described. The efficacy of gp120 inhibitors as a microbicide to prevent sexual HIV transmission in the rhesus macaque model is discussed. Results suggest that this class of compounds may have value if included in a microbicide cocktail with inhibitors of alternate mechanisms. Importantly, preliminary results from clinical studies of orally administered BMS-488043 demonstrate that antiviral efficacy can be achieved in humans with a CD4-attachment inhibitor that targets gp120.     

Patent Evaluation Cardiovascular & Renal: Novel aminoheterocyclic derivatives as inhibitors of factor Xa

This patent from Zeneca Ltd. describes compounds which possess antithrombotic or anticoagulant activity. This activity has been attributed to their strong inhibition of the coagulation serine protease known as factor Xa. Thus, factor Xa inhibitors (i.e., anticoagulant compounds) should have application in several medical disorders, such as venous and/or arterial thrombosis, coagulation syndromes, myocardial infarction, atherosclerotic plaque formation, restenosis, stroke, cerebral and/or pulmonary embolism, ischaemia and angina.

Several protein and/or peptidic inhibitors have been previously described in the general and patent literature, but with the exception of DX-9065a there is a paucity of small molecule nonpeptidic factor Xa inhibitors. The compounds disclosed in the present patent are highly selective for factor Xa. efficacious in secondary in vivo and in vivo models and synthetically less challenging than other known factor Xa inhibitors. In addition to the previously described inhibitors of trypsin-like serine proteases such as factor Xa, the compounds described in this patent do not contain a free amidino or guanidino group. Thus, the present disclosure will provide compounds of significant interest as pharmacological tools to further evaluate the importance of factor Xa in the blood coagulation pathway, as well as compounds that may be of further clinical interest.     

NAALADase inhibition protects motor neurons against chronic glutamate toxicity

Glutamate toxicity is implicated in the pathogenesis of amyotrophic lateral sclerosis. The neuropeptide N-acetyl-aspartyl glutamate (NAAG) appears to function both as a storage form for glutamate and as a neuromodulator at glutamatergic synapses. N-acetylated-alpha-linked acidic dipeptidase (NAALADase; also termed glutamate carboxypeptidase II) yields N-acetyl aspartate (NAA) and glutamate. Prior studies have demonstrated NAALADase upregulation in motor cortex and increased NAAG, NAA and glutamate in cerebrospinal fluid from amyotrophic lateral sclerosis patients. The potent NAALADase inhibitor, 2-(phosphonomethyl)-pentanedioic acid (2-PMPA), was tested in an in vitro model of chronic glutamate-mediated motor neuron degeneration. Neuroprotection was determined (1) biochemically, by measuring choline acetyltransferase activity, (2) immunohistochemically, by counting neurofilament-H-positive motor neurons and (3) morphologically, with phase contrast microscopy. 2-PMPA (10 microM) had significant neuroprotective effects on motor neurons as evidenced by increased choline acetyltransferase activity, decreased motor neuron loss and improved gross morphology. Results suggest that NAALADase inhibitors protect against chronic glutamate-mediated motor neuron degeneration and may prove therapeutic towards amyotrophic lateral sclerosis.     

Design, synthesis, and biological evaluation of matrix metalloproteinase inhibitors derived from a modified proline scaffold

The synthesis and structure-activity relationship (SAR) studies of a series of proline-based matrix metalloproteinase inhibitors are described. The data reveal a remarkable potency enhancement in those compounds that contain an sp(2) center at the C-4 carbon of the ring relative to similar, saturated compounds. This effect was noted in compounds that contained a functionalized oxime moiety or an exomethylene at C-4, and the potencies were typically <10 nM for MMP-3 and <100 nM for MMP-1. Comparisons were then made against compounds with similar functionality where the C-4 carbon was reduced to sp(3) hybridization and the effect was typically an order of magnitude loss in potency. A comparison of compounds 14 and 34 exemplifies this observation. An X-ray structure was obtained for a stromelysin-inhibitor complex which provided insights into the SAR and selectivity trends observed within the series. In vitro intestinal permeability data for many compounds was also accumulated.     

Characterisation of a novel class of polyamine-based neuroprotective compounds

Prolonged cerebral ischaemia initiates complex intra- and inter-cellular signalling cascades ultimately resulting in neuronal death. Well-characterised mediators of ischaemic cell death are glutamate, free radicals and nitric oxide. Many drugs that block these mechanisms are neuroprotective in vitro, but have unfavourable side-effect profiles in man. We have recently demonstrated that the compound L-arginyl-3,4-spermidine (L-Arg3,4) is neuroprotective in vitro through an interaction with several of these mechanisms, and prevents ischaemic neurodegeneration in vivo with no gross side effects. In this study, we have used solid-phase combinatorial chemistry, to synthesise a number of analogues of L-Arg3,4, and investigate the structure-activity relationship using an in vitro, organotypic hippocampal slice culture model of cerebral ischaemia. A number of molecular features were identified which were essential for the neuroprotective activity including the requirement for a positive charge and an amino acid in the L-configuration. Relatively minor alterations to both the terminal arginine and polyamine moieties significantly attenuated neuroprotective efficacy. Our data implies that these compounds are neuroprotective through a currently undefined mechanism rather than non-specific ionic interactions described previously for other polyamine-containing compounds.     

Treatment of obesity and pulmonary arterial hypertension with inhibitors of the prostaglandin transporter: evaluation of patent WO2014/204895A1

Prostaglandins display a wide array of pharmacological effects and prostaglandin analogs are already used in the treatment of pulmonary arterial hypertension (PAH). After synthesis and release from cells, prostaglandins undergo reuptake by the prostaglandin transporter (PGT). WO2014/204895 claims the use of a series of trisubstituted triazine derivatives for the treatment of obesity and PAH. Composition of matter of these triazines has been claimed in WO2011/037610 and the compounds are described as potent inhibitors of the PGT. One compound (nr 146) was shown to improve high fat diet-induced glucose tolerance in a mouse model. In addition, this compound has been explored in the rat monocrotaline model of PAH and reduced characteristic features of the pathology. This class of compounds presents a potential new treatment paradigm in the treatment of obesity-related disorders and PAH.     

Novel 2-(substituted phenyl)benzimidazole derivatives with potent activity against IgE, cytokines, and CD23 for the treatment of allergy and asthma

The effectiveness of the injectable anti-IgE antibody omalizumab has validated IgE as an important target for allergic diseases, thus spawning the development of small-molecule IgE inhibitors. Herein, a brief SAR is described for novel phenylbenzimidazole compounds that potently suppress IgE responses. In addition to IgE, these agents inhibit other targets critical for allergic response. The profile of orally active AVP-13358, the lead compound of this series currently in clinical trials, is described.     

Discovery of 1-(2-aminomethylphenyl)-3-trifluoromethyl-N- [3-fluoro-2'-(aminosulfonyl)[1,1'-biphenyl)]-4-yl]-1H-pyrazole-5-carboxyamide (DPC602), a potent, selective, and orally bioavailable factor Xa inhibitor(1)

Factor Xa, a serine protease, is at the critical juncture between the intrinsic and extrinsic pathways of the coagulation cascade. Inhibition of factor Xa has the potential to provide effective treatment for both venous and arterial thrombosis. We recently described a series of meta-substituted phenylpyrazoles that are highly potent, selective, and orally bioavailable factor Xa inhibitors. In this paper we report our efforts to further optimize the selectivity profile of our factor Xa inhibitors with a series of ortho- and/or para-substituted phenylpyrazole derivatives. The most potent compounds display sub-nanomolar inhibition constants for factor Xa and show greater than 1000-fold selectivity against other serine proteases. These compounds are also effective in a rabbit model of arteriovenous shunt thrombosis. Optimization of this series led to the preclinical development of DPC602, a 2-(aminomethyl)phenylpyrazole analogue, as a highly potent, selective, and orally bioavailable factor Xa inhibitor.     

Hydroxamic acid inhibitors of 5-lipoxygenase

The hydroxamic acid functionality can be incorporated in a variety of simple molecules to produce potent inhibitors of 5-lipoxygenase. As an example of this, the structure-activity relationships in a series of omega-phenylalkyl and omega-naphthylalkyl hydroxamic acids are presented. Among the features described are the influence of hydrophobicity, aryl substitution, and modifications of the hydroxamate group on enzyme inhibitory potency. To assist in the selection of more potent hydroxamic acid inhibitors, a simple hypothesis about the nature of enzyme-inhibitor binding was devised. In this hypothesis, the structures of compounds were matched to a proposed geometry of arachidonic acid when bound to the enzyme. Compounds that match best without extending into disfavored regions were predicted to be the best inhibitors. Three series of hydroxamates selected according to this approach are described. Within these series are some of the most potent inhibitors of 5-lipoxygenase reported to date.     

Optimization of Pharmacokinetics through Manipulation of Physicochemical Properties in a Series of HCV Inhibitors

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Anti-parkinsonian efficacy of target-specific GSK3β inhibitors demonstrated in Caenorhabditis elegans

Parkinson's disease (PD) is the second most common form of neurodegeneration among elderly individuals. PD is clinically characterized by tremors, rigidity, slowness of movement, and postural imbalance. Glycogen synthase kinase (GSK)-3β, a multifunctional protein has been implicated in the pathological characteristics of PD, including the heightened levels of α-synuclein, aberrant phosphorylated tau, and neurodegeneration. Hence, Gsk3β has been nominated as prime target for the development of new anti-parkinsonian agents. We have previously reported several series of target-specific inhibitors with the strong affinity toward GSK3β. In the present study, anti-parkinsonian efficacy of these inhibitors was evaluated in Caenorhabditis elegans model of PD. The inhibitors displayed low micromolar rescue potency when administered post-symptomatically, indicating both prevention and reversal of the dopaminergic deficit. The results indicate that GSK3β inhibitors rescued the behavioral deficit characteristic of dopaminergic impairment in transgenic C. elegans expressing human α-synuclein. In addition, GSK3β inhibition led to long-lasting prevention and rescue of neurodegeneration. Our findings indicate that the GSK3β activity is critical for neurodegeneration caused by α-synuclein accumulation, suggesting that kinase inhibition of GSK3β may represent a promising therapeutic strategy for PD.     

Design, synthesis, and biological evaluation of 3,4-dihydroquinolin-2(1H)-one and 1,2,3,4-tetrahydroquinoline-based selective human neuronal nitric oxide synthase (nNOS) inhibitors

Neuronal nitric oxide synthase (nNOS) inhibitors are effective in preclinical models of many neurological disorders. In this study, two related series of compounds, 3,4-dihydroquinolin-2(1H)-one and 1,2,3,4-tetrahydroquinoline, containing a 6-substituted thiophene amidine group were synthesized and evaluated as inhibitors of human nitric oxide synthase (NOS). A structure-activity relationship (SAR) study led to the identification of a number of potent and selective nNOS inhibitors. Furthermore, a few representative compounds were shown to possess druglike properties, features that are often difficult to achieve when designing nNOS inhibitors. Compound (S)-35, with excellent potency and selectivity for nNOS, was shown to fully reverse thermal hyperalgesia when given to rats at a dose of 30 mg/kg intraperitonieally (ip) in the L5/L6 spinal nerve ligation model of neuropathic pain (Chung model). In addition, this compound reduced tactile hyperesthesia (allodynia) after oral administration (30 mg/kg) in a rat model of dural inflammation relevant to migraine pain.     

Synthesis, protein kinase inhibitory potencies, and in vitro antiproliferative activities of meridianin derivatives

The synthesis of new meridianin derivatives is described. The indolic ring system was substituted at the C-4 to C-7 positions either by a bromine atom or by nitro or amino groups. Additionally, an iodine atom or various aryl groups were introduced at the C-5 position of the 2-aminopyrimidine ring. These compounds as well as some of their synthetic intermediates were tested for their kinase inhibitory potencies and for their in vitro antiproliferative activities. We found that this series of compounds is particularly interesting in the development of new inhibitors of DYRK1A and CLK1 kinases. The most effective compounds toward these two kinase families are the 6- and 7-bromo derivatives 30, 33, and 34 that showed more than 45-fold selectivity toward DYRK1A/CLK1 kinases over the other kinases tested. Meridianin derivatives could thus be developed toward potent and selective inhibitors of key RNA splicing regulators and potential therapeutic agents.     

Discovery of 2-(6-{[(6-fluoroquinolin-2-yl)methyl]amino}bicyclo[3.1.0]hex-3-yl)-N-hydroxypyrimidine-5-carboxamide (CHR-3996), a class I selective orally active histone deacetylase inhibitor

A novel series of HDAC inhibitors demonstrating class I subtype selectivity and good oral bioavailability is described. The compounds are potent enzyme inhibitors (IC?? values less than 100 nM), and improved activity in cell proliferation assays was achieved by modulation of polar surface area (PSA) through the introduction of novel linking groups. Employing oral pharmacokinetic studies in mice, comparing drug levels in spleen to plasma, we selected compounds that were tested for efficacy in human tumor xenograft studies based on their potential to distribute into tumor. One compound, 21r (CHR-3996), showed good oral activity in these models, including dose-related activity in a LoVo xenograft. In addition 21r showed good activity in combination with other anticancer agents in in vitro studies. On the basis of these results, 21r was nominated for clinical development.     

Estrogen synthetase inhibitors. 2. Comparison of the in vitro aromatase inhibitory activity for a variety of nitrogen heterocycles substituted with diarylmethane or diarylmethanol groups

The preparation and in vitro aromatase inhibitory activity of a wide variety of heterocyclic (4,4'-dichlorodiphenyl)methanes and -methanols are described. The choice of the two diaryl-bearing moieties as a vehicle for the evaluation of the heterocycles was made by the comparison of series of imidazole and pyridine-derived compounds with similar pyrimidine compounds reported previously. A structural model for the most active compounds is also presented. The activity of a related series of the compounds which contain two heterocyclic moieties was found to be consistent with the model. Many of the compounds evaluated, including representatives of the pyridine, imidazole, pyrimidine, pyrazole, triazole, thiazole, and isothiazole classes, exhibit EC50 potencies for aromatase inhibition at low nanomolar levels. These compounds are at least as potent as other nonsteroidal aromatase inhibitors reported previously.     

Redefining the Histone Deacetylase Inhibitor Pharmacophore: High Potency with No Zinc Cofactor Interaction

A novel series of histone deacetylase (HDAC) inhibitors lacking a zinc-binding moiety has been developed and described herein. HDAC isozyme profiling and kinetic studies indicate that these inhibitors display a selectivity preference for HDACs 1, 2, 3, 10, and 11 via a rapid equilibrium mechanism, and crystal structures with HDAC2 confirm that these inhibitors do not interact with the catalytic zinc. The compounds are nonmutagenic and devoid of electrophilic and mutagenic structural elements and exhibit off-target profiles that are promising for further optimization. The efficacy of this new class in biochemical and cell-based assays is comparable to the marketed HDAC inhibitors belinostat and vorinostat. These results demonstrate that the long-standing pharmacophore model of HDAC inhibitors requiring a metal binding motif should be revised and offers a distinct class of HDAC inhibitors.     

Development of tetrahydroisoquinoline-based hydroxamic acid derivatives: potent histone deacetylase inhibitors with marked in vitro and in vivo antitumor activities

Inhibition of histone deacetylase (HDAC) results in growth arrest, differentiation, and apoptosis in nearly all tumor cell lines, promoting HDACs as promising targets for antitumor therapy. In our previous study we developed a novel series of 1,2,3,4-tetrahydroisoquinoline-3-carboxylic acid derivatives as HDAC inhibitors (HDACi), among which compound 7d exhibited promising HDAC8 inhibitory and antiproliferative activities. Herein, we report the design and development of a new class of tetrahydroisoquinoline-bearing hydroxamic acid analogues as potential HDACi and anticancer agents. In vitro biological evaluation of these compounds showed improved HDAC8 inhibition (compounds 31a and 31b exhibited mid-nM IC(50) values against HDAC8) and potent growth inhibition in multiple tumor cell lines. Most importantly, compounds 25e, 34a, and 34b exhibited excellent in vivo anticancer activities in a human breast carcinoma (MDA-MB-231) xenograft model compared with suberoylanilide hydroxamic acid (SAHA), an approved HDACi. Collectively, our results indicate that tetrahydroisoquinoline bearing a hydroxamic acid is an excellent template to develop novel HDACi as potential anticancer agents.