Protection of pancreatic islets from oxidative cell death by a peripherally-active morphinan with increased drug safety.

OBJECTIVE: Dextromethorphan (DXM) is a commonly used antitussive medication with positive effects in people with type 2 diabetes mellitus, since it increases glucose tolerance and protects pancreatic islets from cell death. However, its use as an antidiabetic medication is limited due to its central nervous side effects and potential use as a recreational drug. Therefore, we recently modified DXM chemically to reduce its blood-brain barrier (BBB) penetration and central side effects. However, our best compound interacted with the cardiac potassium channel hERG (human ether-à-go-go-related gene product) and the µ-opioid receptor (MOR). Thus, the goal of this study was to reduce the interaction of our compound with these targets, while maintaining its beneficial properties. METHODS: Receptor and channel binding assays were conducted to evaluate the drug safety of our DXM derivative. Pancreatic islets were used to investigate the effect of the compound on insulin secretion and islet cell survival. Via liquor collection from the brain and a behavioral assay, we analyzed the BBB permeability. By performing intraperitoneal and oral glucose tolerance tests as well as pharmacokinetic analyses, the antidiabetic potential and elimination half-life were investigated, respectively. To analyze the islet cell-protective effect, we used fluorescence microscopy as well as flow cytometric analyses. RESULTS: Here, we report the design and synthesis of an optimized, orally available BBB-impermeable DXM derivative with lesser binding to hERG and MOR than previous ones. We also show that the new compound substantially enhances glucose-stimulated insulin secretion (GSIS) from mouse and human islets and glucose tolerance in mice as well as protects pancreatic islets from cell death induced by reactive oxygen species and that it amplifies the effects of tirzepatide on GSIS and islet cell viability. CONCLUSIONS: We succeeded to design and synthesize a novel morphinan derivative that is BBB-impermeable, glucose-lowering and islet cell-protective and has good drug safety despite its morphinan and imidazole structures.

Synthesis of 4-styrylpyrazoles and Evaluation of their Inhibitory Effects on Cyclin-dependent Kinases.

BACKGROUND: Cycle-regulating and transcriptional cyclin-dependent kinases (CDKs) are attractive targets in cancer drug development. Several CDK inhibitors have already been obtained or are close to regulatory approval for clinical applications. OBJECTIVE: Phenylazopyrazole CAN508 has been described as the first selective CDK9 inhibitor with an IC50 of 350 nM. Since the azo-moiety is not a suitable functionality for drugs due to pharmacological reasons, the preparation of carbo-analogues of CAN508 with similar biological activities is desirable. The present work is focused on the synthesis of carbo-analogues similar to CAN508 and their CDK inhibition activity. METHODS: Herein, the synthesis of 21 novel carbo analogues of CAN508 and their intermediates is reported. Subsequently, target compounds 8a - 8u were evaluated for protein kinase inhibition (CDK2/cyclin E, CDK4/cyclin D, CDK9/cyclin T) and antiproliferative activities in cell lines (K562, MCF-7, MV4-11). Moreover, the binding mode of derivative 8s in the active site of CDK9 was modelled. RESULTS: Compounds 8a - 8u were obtained from key intermediate 7, which was prepared by linear synthesis involving Vilsmeier-Haack, Knoevenagel, Hunsdiecker, and Suzuki-Miyaura reactions. Styrylpyrazoles 8t and 8u were the most potent CDK9 inhibitors with IC50 values of approximately 1 µM. Molecular modelling suggested binding in the active site of CDK9. The flow cytometric analysis of MV4-11 cells treated with the most active styrylpyrazoles showed a significant G1-arrest. CONCLUSION: The prepared styrylpyrazoles showed inhibition activity towards CDKs and can provide a novel chemotype of kinase inhibitors.

3H-Pyrazolo[4,3-f]quinoline-Based Kinase Inhibitors Inhibit the Proliferation of Acute Myeloid Leukemia Cells In Vivo.

The 3H-pyrazolo[4,3-f]quinoline moiety has been recently shown to be a privileged kinase inhibitor core with potent activities against acute myeloid leukemia (AML) cell lines in vitro. Herein, various 3H-pyrazolo[4,3-f]quinoline-containing compounds were rapidly assembled via the Doebner-Povarov multicomponent reaction from the readily available 5-aminoindazole, ketones, and heteroaromatic aldehydes in good yields. The most active compounds potently inhibit the recombinant FLT3 kinase and its mutant forms with nanomolar IC50 values. Docking studies with the FLT3 kinase showed a type I binding mode, where the 3H-pyrazolo group interacts with Cys694 in the hinge region. The compounds blocked the proliferation of AML cell lines harboring oncogenic FLT3-ITD mutations with remarkable IC50 values, which were comparable to the approved FLT3 inhibitor quizartinib. The compounds also inhibited the growth of leukemia in a mouse-disseminated AML model, and hence, the novel 3H-pyrazolo[4,3-f]quinoline-containing kinase inhibitors are potential lead compounds to develop into anticancer agents, especially for kinase-driven cancers.

The synthesis and cholinesterase inhibitory activities of solasodine analogues with seven-membered F ring.

Solasodine analogues containing a seven-membered F ring with a nitrogen atom placed at position 22a were prepared from diosgenin or tigogenin in a four-step synthesis comprising of the simultaneous opening of the F-ring and introduction of cyanide in position 22α, activation of the 26-hydroxyl group as mesylate, nitrile reduction, and N-cyclization. Solasodine, six obtained 22a(N)-homo analogues, as well as four 26a-homosolasodine derivatives and their open-chain precursors (13 in total) were tested as potential inhibitors of acetyl- and butyryl-cholinesterases and showed activity at micromolar concentrations. The structure-activity relationship study revealed that activities against studied esterases are affected by the structure of E/F rings and the substitution pattern of ring A. The most potent compound 8 acted as non-competitive inhibitors and exerted IC50 = 8.51 µM and 7.05 µM for eeAChE and eqBChE, respectively. Molecular docking studies revealed the hydrogen bond interaction of 8 with S293 of AChE; further rings are stabilized via hydrophobic interaction (ring A) or interaction with Y341 and W286 (rings B and C). Biological experiments showed no neurotoxicity of differentiated SH-SY5Y cells. More importantly, results from neuroprotective assay based on glutamate-induced cytotoxicity revealed that most derivatives had the ability to increase the viability of differentiated SH-SY5Y cells in comparison to galantamine and lipoic acid assayed as standards. The newly synthesized solasodine analogues are able to inhibit and to bind cholinesterases in noncompetitive mode of inhibition and exhibited neuroprotection potential of differentiated neuroblastoma cells after Glu-induced toxicity.

Polysubstituted Pyrimidines as mPGES-1 Inhibitors: Discovery of Potent Inhibitors of PGE2 Production with Strong Anti-inflammatory Effects in Carrageenan-Induced Rat Paw Edema.

We report an extensive structure-activity relationship optimization of polysubstituted pyrimidines that led to the discovery of 5-butyl-4-(4-benzyloxyphenyl)-6-phenylpyrimidin-2-amine, and its difluorinated analogue. These compounds are sub-micromolar inhibitors of PGE2 production (IC50 as low as 12 nM). In order to identify the molecular target of anti-inflammatory pyrimidines, we performed extensive studies including enzymatic assays, homology modeling and docking. The difluorinated analogue simultaneously inhibits two key enzymes of the arachidonic acid cascade, namely mPGES-1 and COX-2, with mPGES-1 inhibition being the principal mechanism of action. Other pyrimidines studied are potent mPGES-1 inhibitors with no observed inhibition of COX-1/2 enzymes. Moreover, the two most potent compounds proved to be significantly effective in vivo in a model of acute inflammation, suppressing carrageenan-induced rat paw edema by 36 and 46 %. The promising results of this study warrant further preclinical evaluation of selected anti-inflammatory candidates.

Optimization of norbornyl-based carbocyclic nucleoside analogs as cyclin-dependent kinase 2 inhibitors.

We report on the discovery of norbornyl moiety as a novel structural motif for cyclin-dependent kinase 2 (CDK2) inhibitors which was identified by screening a carbocyclic nucleoside analogue library. Three micromolar hits were expanded by the use of medicinal chemistry methods into a series of 16 novel compounds. They had prevailingly micromolar activities against CDK2 and the best compound of the series attained IC50 of 190 nM. The binding modes were explored in molecular details by modeling and docking. Quantum mechanics-based scoring was used to rationalize the affinities. In conclusion, the discovered 9-hydroxymethylnorbornyl moiety was shown by joint experimental-theoretical efforts to be able to serve as a novel substituent for CDK2 inhibitors. This finding opens door to the exploration of chemical space towards more effective derivatives targeting this important class of protein kinases.

Activity of 2,6,9-trisubstituted purines as potent PDGFRα kinase inhibitors with antileukaemic activity.

Receptor tyrosine kinase PDGFRα is often constitutively activated in various tumours and is regarded as a drug target. Here, we present a collection of 2,6,9-trisubstituted purines with nanomolar potency against PDGFRα and strong and selective cytotoxicity in the human eosinophilic leukaemia cell line EOL-1 that expresses the FIP1L1-PDGFRA oncogene. In treated EOL-1 cells, the example compound 14q inhibited the autophosphorylation of PDGFRα and the phosphorylation of STAT3 and ERK1/2. Interestingly, we observed pronounced and even increased effects of 14q on PDGFRα and some of its downstream signalling pathways after drug washout. In accordance with suppressed PDGFRα signalling, treated cells were arrested in the G1 phase of the cell cycle and eventually underwent apoptosis. Our results show that substituted purines can be used as specific modulators of eosinophilic leukaemia.

Tetrahydropyrazolo[1,5-a]pyridine-fused steroids and their in vitro biological evaluation in prostate cancer.

The androgen receptor (AR) is a steroid hormone receptor and its high expression and disruption of its regulation are strongly implicated in prostate cancer (PCa) development. One of the current therapies includes application of steroidal antiandrogens leading to blockade of the AR action by the abrogation of AR-mediated signaling. We introduced here novel 4,5,6,7-tetrahydropyrazolo[1,5-a]pyridine-fused steroidal compounds, described their synthesis based on [8π+2π] cycloaddition reactions of diazafulvenium methides with different steroidal scaffolds and showed their biological evaluation in different prostate cancer cell lines in vitro. Our results showed the ability of novel compounds to suppress the expression of known androgen receptor targets, Nkx3.1 and PSA in two prostate cell lines, 22Rv1 and VCaP. Candidate compound diminished the transcription of AR-regulated genes in the reporter cell line in a concentration-dependent manner. Antiproliferative activity of the most promising steroid was studied by clonogenic assay and induction of apoptosis in treated cells was documented by immunoblot detection of cleaved PARP.

Imidazo[1,2-c]pyrimidin-5(6H)-one as a novel core of cyclin-dependent kinase 2 inhibitors: Synthesis, activity measurement, docking, and quantum mechanical scoring.

We report on the synthesis, activity testing, docking, and quantum mechanical scoring of novel imidazo[1,2-c]pyrimidin-5(6H)-one scaffold for cyclin-dependent kinase 2 (CDK2) inhibition. A series of 26 compounds substituted with aromatic moieties at position 8 has been tested in in vitro enzyme assays and shown to inhibit CDK2. 2D structure-activity relationships have ascertained that small substituents at position 8 (up to the size of naphtyl or methoxyphenyl) generally lead to single-digit micromolar IC50 values, whereas bigger substituents (substituted biphenyls) decreased the compounds' activities. The binding modes of the compounds obtained using Glide docking have exhibited up to 2 hinge-region hydrogen bonds to CDK2 and differed in the orientation of the inhibitor core and the placement of the 8-substituents. Semiempirical quantum mechanics-based scoring identified probable favourable binding modes, which will serve for future structure-based design and synthetic optimization of substituents of the heterocyclic core. In summary, we have identified a novel core for CDK2 inhibition and will explore it further to increase the potencies of the compounds and also monitor selectivities against other protein kinases.

Discovery of N2-(4-Amino-cyclohexyl)-9-cyclopentyl- N6-(4-morpholin-4-ylmethyl-phenyl)- 9H-purine-2,6-diamine as a Potent FLT3 Kinase Inhibitor for Acute Myeloid Leukemia with FLT3 Mutations.

FLT3 tyrosine kinase is a potential drug target in acute myeloid leukemia (AML) because patients with FLT3-ITD mutations respond poorly to standard cytotoxic agents and there is a clear link between the disease and the oncogenic properties of FLT3. We present novel 2,6,9-trisubstituted purine derivatives with potent FLT3 inhibitory activity. The lead compound 7d displays nanomolar activity in biochemical assays and selectively blocks proliferation of AML cell lines harboring FLT3-ITD mutations, whereas other transformed and normal human cells are several orders of magnitude less sensitive. The MV4-11 cells treated with 7d suppressed the phosphorylation of FLT3 and its downstream signaling pathways, with subsequent G1 cell cycle arrest and apoptosis. Additionally, a single dose of 7d in mice with subcutaneous MV4-11 xenografts caused sustained inhibition of FLT3 and STAT5 phosphorylation over 48 h, in contrast to the shorter effect observed after administration of the reference FLT3 inhibitor quizartinib.

Unraveling the Structure-Affinity Relationship between Cucurbit[n]urils (n = 7, 8) and Cationic Diamondoids.

We report the measurement of the binding constants (Ka) for cucurbit[n]uril (n = 7, 8) toward four series of guests based on 2,6-disubstituted adamantanes, 4,9-disubstituted diamantanes, 1,6-disubstituted diamantanes, and 1-substituted adamantane ammonium ions by direct and competitive 1H NMR spectroscopy. Compared to the affinity of CB[7]·Diam(NMe3)2, the adamantane diammonium ion complexes (e.g., CB[7]·2,6-Ad(NH3)2 and CB[7]·2,6-Ad(NMe3)2) are less effective at realizing the potential 1000-fold enhancement in affinity due to ion-dipole interactions at the second ureidyl C═O portal. Comparative crystallographic investigation of CB[7]·Diam(NMe3)2, CB[7]·DiamNMe3, and CB[7]·1-AdNMe3 revealed that the preferred geometry positions the +NMe3 groups ≈0.32 Å above the C═O portal; the observed 0.80 Å spacing observed for CB[7]·Diam(NMe3)2 reflects the simultaneous geometrical constraints of CH2···O═C close contacts at both portals. Remarkably, the CB[8]·IsoDiam(NHMe2)2 complex displays femtomolar binding affinity, placing it firmly alongside the CB[7]·Diam(NMe3)2 complex. Primary or quaternary ammonium ion looping strategies lead to larger increases in binding affinity for CB[8] than for CB[7], which we attribute to the larger size of the carbonyl portals of CB[8]; this suggests routes to develop CB[8] as the tightest binding host in the CB[n] family. We report that alkyl group fluorination (e.g., CB[7]·1-AdNH2Et versus CB[7]·1-AdNH2CH2CF3) does not result in the expected increase in Ka value. Finally, we discuss the role of solvation in nonempirical quantum mechanical computational methodology, which is used to estimate the relative changes in Gibbs binding free energies.

Explicit treatment of active-site waters enhances quantum mechanical/implicit solvent scoring: Inhibition of CDK2 by new pyrazolo[1,5-a]pyrimidines.

We present comprehensive testing of solvent representation in quantum mechanics (QM)-based scoring of protein-ligand affinities. To this aim, we prepared 21 new inhibitors of cyclin-dependent kinase 2 (CDK2) with the pyrazolo[1,5-a]pyrimidine core, whose activities spanned three orders of magnitude. The crystal structure of a potent inhibitor bound to the active CDK2/cyclin A complex revealed that the biphenyl substituent at position 5 of the pyrazolo[1,5-a]pyrimidine scaffold was located in a previously unexplored pocket and that six water molecules resided in the active site. Using molecular dynamics, protein-ligand interactions and active-site water H-bond networks as well as thermodynamics were probed. Thereafter, all the inhibitors were scored by the QM approach utilizing the COSMO implicit solvent model. Such a standard treatment failed to produce a correlation with the experiment (R2 = 0.49). However, the addition of the active-site waters resulted in significant improvement (R2 = 0.68). The activities of the compounds could thus be interpreted by taking into account their specific noncovalent interactions with CDK2 and the active-site waters. In summary, using a combination of several experimental and theoretical approaches we demonstrate that the inclusion of explicit solvent effects enhance QM/COSMO scoring to produce a reliable structure-activity relationship with physical insights. More generally, this approach is envisioned to contribute to increased accuracy of the computational design of novel inhibitors.

Superior Performance of the SQM/COSMO Scoring Functions in Native Pose Recognition of Diverse Protein-Ligand Complexes in Cognate Docking.

General and reliable description of structures and energetics in protein-ligand (PL) binding using the docking/scoring methodology has until now been elusive. We address this urgent deficiency of scoring functions (SFs) by the systematic development of corrected semiempirical quantum mechanical (SQM) methods, which correctly describe all types of noncovalent interactions and are fast enough to treat systems of thousands of atoms. Two most accurate SQM methods, PM6-D3H4X and SCC-DFTB3-D3H4X, are coupled with the conductor-like screening model (COSMO) implicit solvation model in so-called "SQM/COSMO" SFs and have shown unique recognition of native ligand poses in cognate docking in four challenging PL systems, including metalloprotein. Here, we apply the two SQM/COSMO SFs to 17 diverse PL complexes and compare their performance with four widely used classical SFs (Glide XP, AutoDock4, AutoDock Vina, and UCSF Dock). We observe superior performance of the SQM/COSMO SFs and identify challenging systems. This method, due to its generality, comparability across the chemical space, and lack of need for any system-specific parameters, gives promise of becoming, after comprehensive large-scale testing in the near future, a useful computational tool in structure-based drug design and serving as a reference method for the development of other SFs.

A Nexus between Theory and Experiment: Non-Empirical Quantum Mechanical Computational Methodology Applied to Cucurbit[n]uril⋠Guest Binding Interactions.

A training set of eleven X-ray structures determined for biomimetic complexes between cucurbit[n]uril (CB[7 or 8]) hosts and adamantane-/diamantane ammonium/aminium guests were studied with DFT-D3 quantum mechanical computational methods to afford ΔGcalcd binding energies. A novel feature of this work is that the fidelity of the BLYP-D3/def2-TZVPP choice of DFT functional was proven by comparison with more accurate methods. For the first time, the CB[n]⋅guest complex binding energy subcomponents [for example, ΔEdispersion , ΔEelectrostatic , ΔGsolvation , binding entropy (-TΔS), and induced fit Edeformation(host) , Edeformation(guest) ] were calculated. Only a few weeks of computation time per complex were required by using this protocol. The deformation (stiffness) and solvation properties (with emphasis on cavity desolvation) of cucurbit[n]uril (n=5, 6, 7, 8) isolated host molecules were also explored by means of the DFT-D3 method. A high ρ2 =0.84 correlation coefficient between ΔGexptl and ΔGcalcd was achieved without any scaling of the calculated terms (at 298 K). This linear dependence was utilized for ΔGcalcd predictions of new complexes. The nature of binding, including the role of high energy water molecules, was also studied. The utility of introduction of tethered [-(CH2 )n NH3 ]+ amino loops attached to N,N-dimethyl-adamantane-1-amine and N,N,N',N'-tetramethyl diamantane-4,9-diamine skeletons (both from an experimental and a theoretical perspective) is presented here as a promising tool for the achievement of new ultra-high binding guests to CB[7] hosts. Predictions of not yet measured equilibrium constants are presented herein.

IDD388 Polyhalogenated Derivatives as Probes for an Improved Structure-Based Selectivity of AKR1B10 Inhibitors.

Human enzyme aldo-keto reductase family member 1B10 (AKR1B10) has evolved as a tumor marker and promising antineoplastic target. It shares high structural similarity with the diabetes target enzyme aldose reductase (AR). Starting from the potent AR inhibitor IDD388, we have synthesized a series of derivatives bearing the same halophenoxyacetic acid moiety with an increasing number of bromine (Br) atoms on its aryl moiety. Next, by means of IC50 measurements, X-ray crystallography, WaterMap analysis, and advanced binding free energy calculations with a quantum-mechanical (QM) approach, we have studied their structure-activity relationship (SAR) against both enzymes. The introduction of Br substituents decreases AR inhibition potency but improves it in the case of AKR1B10. Indeed, the Br atoms in ortho position may impede these drugs to fit into the AR prototypical specificity pocket. For AKR1B10, the smaller aryl moieties of MK181 and IDD388 can bind into the external loop A subpocket. Instead, the bulkier MK184, MK319, and MK204 open an inner specificity pocket in AKR1B10 characterized by a π-π stacking interaction of their aryl moieties and Trp112 side chain in the native conformation (not possible in AR). Among the three compounds, only MK204 can make a strong halogen bond with the protein (-4.4 kcal/mol, using QM calculations), while presenting the lowest desolvation cost among all the series, translated into the most selective and inhibitory potency AKR1B10 (IC50 = 80 nM). Overall, SAR of these IDD388 polyhalogenated derivatives have unveiled several distinctive AKR1B10 features (shape, flexibility, hydration) that can be exploited to design novel types of AKR1B10 selective drugs.

Synthesis, structural characterization, docking, lipophilicity and cytotoxicity of 1-[(1R)-1-(6-fluoro-1,3-benzothiazol-2-yl)ethyl]-3-alkyl carbamates, novel acetylcholinesterase and butyrylcholinesterase pseudo-irreversible inhibitors.

In the current study, sixteen novel derivatives of (R)-1-(6-fluorobenzo[d]thiazol-2-yl)ethanamine were synthesized as acetylcholinesterase (AChE) and butyrylcholinesterase (BChE) inhibitors. Chemical structures together with purity of the synthesized compounds were substantiated by IR, (1)H, (13)C, (19)F NMR, high resolution mass spectrometry and elemental analysis. The optical activities were confirmed by optical rotation measurements. The synthesized compounds were evaluated for their AChE and BChE inhibitory activities. In addition, the cytotoxicity of the most active compounds was investigated against human cell lines employing XTT tetrazolium salt reduction assay and xCELLigence system allowing a label-free assessment of the cells proliferation. Our results demonstrated that the inhibitory mechanism was confirmed to be pseudo-irreversible, in line with previous studies on carbamates. Compounds indicated as 3b, 3d, 3l and 3n showed the best AChE inhibitory activity of all the evaluated compounds and were up to tenfold more potent than standard drug rivastigmine. The binding mode was determined using state-of-the-art covalent docking and scoring methodology. The obtained data clearly demonstrated that 3b, 3d, 3l and 3n benzothiazole carbamates possess high inhibitory activity against AChE and BChE and concurrently negligible cytotoxicity. In conclusion, our results indicate, that these derivatives could be promising in an effective therapeutic intervention for Alzheimer's disease.

Effect of introducing aib in a designed helical inhibitor of hdm2-p53 interaction: A molecular dynamics study.

Although p53 is an intrinsically disordered protein, upon binding to Hdm2, a short stretch (residues 19-25) comprising the binding epitope assumes a helical backbone. Because the allowed conformational space of α-aminoisobutyric acid (Aib) is restricted to only the helical basin, Aib-containing helical mimics of p53 (binding epitope) are expected to inhibit interaction between p53 and Hdm2 with a much stronger affinity than the wild type p53 peptide (binding epitope), due to the entropic advantage associated with Aib. However, the IC50 values for the disruption of p53-Hdm2 interaction by Aib-p53 peptides and wild type p53 peptide were found to be comparable (J. Peptide Res. 2002, 60:88-94). To understand why incorporation of Aib didn't substantially increase Hdm2 affinity of Aib-p53 peptides, a series of molecular dynamics simulations were performed. It was found that despite stabilizing a helical backbone in the unbound state, the Aib residues in Aib-p53 peptide arrested two functionally important side-chains (F19 and W23) in non-productive conformations, resulting in relative side-chain orientations of the binding triad F19-W23-L26 incompatible with the bound conformation. Therefore, although a Aib-induced pre-formed helical peptide backbone in the unbound state is expected to favor binding, the locked side-chain orientations of the binding triad in non-productive modes would disfavor binding. This study shows that when using Aib to design functionally important helical peptides, care must be taken to consider potential interactions between side-chains of neighboring residues and Aib in the unbound state.

Characteristics of a σ-Hole and the Nature of a Halogen Bond.

The nature of halogen bonding in 128 complexes was investigated using advanced quantum mechanical calculations. First, isolated halogen donors were studied and their σ-holes were described in terms of size and magnitude. Later, both partners in the complex were considered and their interaction was described in terms of DFT-SAPT decomposition. The whole set of complexes under study was split into two categories on the basis of their stabilisation energy. The first subset with 38 complexes possesses stabilisation energies in the range 7-32 kcal/mol, while the second subset with 90 complexes has stabilisation energies smaller than 7 kcal/mol. The first subset is characterised by small intermolecular distances (less than 2.5 Å) and a significant contraction of van der Waals (vdW) distance (sum of vdW radii). Here the polarisation/electrostatic energy is dominant, mostly followed by induction and dispersion energies. The importance of induction energy reflects the charge-transfer character of the respective halogen bonds. Intermolecular distances in the second subset are large and the respective contraction of vdW distance upon the formation of a halogen bond is much smaller. Here the dispersion energy is mostly dominant, followed by polarisation and induction energies. Considering the whole set of complexes, we conclude that the characteristic features of their halogen bonds arise from the concerted action of polarisation and dispersion energies and neither of these energies can be considered as dominant. Finally, the magnitude of the σ-hole and DFT-SAPT stabilisation energy correlates only weakly within the whole set of complexes.

Malonate-based inhibitors of mammalian serine racemase: kinetic characterization and structure-based computational study.

Overactivation of NMDA receptors has been implicated in various neuropathological conditions, including brain ischaemia, neurodegenerative disorders and epilepsy. Production of d-serine, an NMDA receptor co-agonist, from l-serine is catalyzed in vivo by the pyridoxal-5'-phosphate (PLP)-dependent enzyme serine racemase. Specific inhibition of this enzyme has been proposed as a promising strategy for treatment of neurological conditions caused by NMDA receptor dysfunction. Here we present the synthesis and activity analysis of a series of malonate-based inhibitors of mouse serine racemase (mSR). The compounds possessed IC50 values ranging from 40 ± 11 mM for 2,2-bis(hydroxymethyl)malonate down to 57 ± 1 µM for 2,2-dichloromalonate, the most effective competitive mSR inhibitor known to date. The structure-activity relationship of the whole series in the human orthologue (hSR) was interpreted using Glide docking, WaterMap analysis of hydration and quantum mechanical calculations based on the X-ray structure of the hSR/malonate complex. Docking into the hSR active site with three thermodynamically favourable water molecules was able to discern qualitatively between good and weak inhibitors. Further improvement in ranking was obtained using advanced PM6-D3H4X/COSMO semiempirical quantum mechanics-based scoring which distinguished between the compounds with IC50 better/worse than 2 mM. We have thus not only found a new potent hSR inhibitor but also worked out a computer-assisted protocol to rationalize the binding affinity which will thus aid in search for more effective SR inhibitors. Novel, potent hSR inhibitors may represent interesting research tools as well as drug candidates for treatment of diseases associated with NMDA receptor overactivation.

Synthesis and structure-activity relationship of potent, selective and orally active anthranilamide-based factor Xa inhibitors: application of weakly basic sulfoximine group as novel S4 binding element.

A novel series of potent and efficacious factor Xa inhibitors which possesses sulfoximine moiety as novel S4 binding element in anthranilamide chemotype has been identified. Lead optimization at this novel P4 group led to many potent factor Xa inhibitors with excellent anticoagulant activity in human plasma. Selected compounds were dosed orally in rats and checked for their ex vivo prothrombin time prolonging activity, which resulted in identification of compound 5-chloro-N-(5-chloropyridin-2-yl)-2-(4-(N-(2-(diethylamino)acetyl)-S-methylsulfonimidoyl)benzamido)benzamide (18f). The detailed pharmacokinetic evaluation and subsequent metabolism study of 18f suggested the presence of an active metabolite. The compound 18f and its active metabolite 18b demonstrated excellent in vivo efficacy in both arterial and venous thrombosis model in rats and were found to be highly selective against related serine proteases. Based on this promising profile, compound 18f was selected for further evaluation.