Phenylindenone isomers as divergent modulators of p38α MAP kinase.

Two new fluorophenylindenone derivatives were designed as potential p38α MAPK modulators by preserving the key interactions of the vicinal pyridine/fluorophenyl pharmacophore with the enzyme protein. Interestingly, these two fluorophenylindenone isomers showed divergent activities, with compound 6 behaving as an inhibitor and 5 as a putative activator. These results were rationalized by docking studies and molecular dynamics simulations in terms of stabilization of DFG loop, by compound 5 in a conformation more accessible to phosphorylation.

Combining spontaneous polymerization and click reactions for the synthesis of polymer brushes: a "grafting onto" approach.

Two novel benzofulvene monomers bearing propargyl or allyl groups have been synthesized by means of readily accessible reactions, and were found to polymerize spontaneously by solvent removal, in the apparent absence of catalysts or initiators, to give the corresponding polybenzofulvene derivatives bearing clickable propargyl or allyl moieties. The clickable propargyl and allyl groups were exploited in appropriate click reactions to develop a powerful and versatile "grafting onto" synthetic methodology for obtaining tailored polymer brushes.

Non-peptide NK1 receptor ligands based on the 4-phenylpyridine moiety.

The quinoline nucleus of the previously described 4-phenylquinoline-3-carboxamides NK(1) receptor ligands 7 has been transformed into either substituted or azole-(i.e., triazole or tetrazole) fused pyridine moieties of compounds 9 and 10, respectively, in order to obtain NK(1) receptor ligands showing lower molecular weight or higher hydrophilicity. The program of molecular manipulations produced NK(1) receptor ligands showing affinity in the nanomolar range. In particular, 4-methyl-1-piperazinyl derivative 9j showed an IC(50) value of 4.8 nM and was proved to behave as a NK(1) antagonist blocking Sar(9)-SP-sulfone induced proliferation and migration of microvascular endothelial cells. Therefore, compound 9j has been labeled with [(11)C]CH(3)I (t(1/2)=20.4 min, ß(+)=99.8%) starting from the corresponding des-methyl precursor 9i using with a radiochemical yield of about 10% (not decay corrected) and a specific radioactivity>1 Ci/µmol in order to be used as a radiotracer in next PET studies.

Carborane-conjugated 2-quinolinecarboxamide ligands of the translocator protein for boron neutron capture therapy.

Potential boron neutron capture therapy (BNCT) agents have been designed on the basis of the evidence about translocator protein (TSPO) overexpression on the outer mitochondrial membrane of tumor cells. The structure of the first TSPO ligand bearing a carborane cage (compound 2d) has been modified in order to find a suitable candidate for in vivo studies. The designed compounds were synthesized and evaluated for their potential interaction with TSPO and tumor cells. In vitro biological evaluation showed in the case of fluoromethyl derivative 4b a nanomolar TSPO affinity very similar to that of 2d, a significantly lower cytotoxicity, and a slightly superior performance as boron carrier toward breast cancer cells. Moreover, compound 4b could be used as a ¹9F magnetic resonance imaging (MRI) agent as well as labeled with ¹¹C or ¹8F to obtain positron emission tomography (PET) radiotracers in order to apply the "see and treat" strategy in BNCT.

Multivalent supramolecular dendrimer-based drugs.

Supramolecular complexes consisting of a hydrophobic dendrimer host [DAB-dendr-(NHCONH-Ad)(64)] as well as solubilizing and bioactive guest molecules have been synthesized using a noncovalent approach. The guest-host supramolecular assembly is first preassembled in chloroform and transferred via the neat phase to aqueous solution. The bioactive guest molecules can bind to a natural (serotonin 5-HT(3)) receptor with nanomolar affinity as well as to the synthetic dendrimer receptor in aqueous solution, going toward a dynamic multivalent supramolecular construct capable of adapting itself to a multimeric receptor motif.

Design, synthesis, and biological evaluation of AT1 angiotensin II receptor antagonists based on the pyrazolo[3,4-b]pyridine and related heteroaromatic bicyclic systems.

Novel AT 1 receptor antagonists bearing the pyrazolo[3,4- b]pyridine bicyclic heteroaromatic system (or structurally related moieties) were designed and synthesized as the final step of a large program devoted to the development of new antihypertensive agents and to the understanding of the molecular basis of their pharmacodynamic and pharmacokinetic properties. The preliminary pharmacological characterization revealed nanomolar AT 1 receptor affinity for several compounds of the series and a potent antagonistic activity in isolated rabbit aortic strip functional assay for 7c and 8a. These results stimulated the study of the biopharmaceutical properties of some selected compounds, which were found to be characterized by a permeability from medium to high. Remarkably, the least permeable 7c showed both permeability and oral bioavailability (80%) higher than losartan, but its terminal half-life was shorter. These results suggest that the permeability is not a limiting factor in the pharmacokinetics of these AT 1 receptor antagonists.

Synthesis and biological characterization of novel 2-quinolinecarboxamide ligands of the peripheral benzodiazepine receptors bearing technetium-99m or rhenium.

Potential receptor imaging agents based on Tc-99m for the in vivo visualization of the peripheral benzodiazepine receptor (PBR) have been designed on the basis of the information provided by the previously published structure-affinity relationship studies, which suggested the existence of tolerance to voluminous substituents in the receptor area interacting with 3-position of the quinoline nucleus of 2-quinolinecarboxamides 5. In the first step of the investigation, the stereoelectronic features of the above-indicated receptor area were also probed by means of 4-phenyl-3-[(1-piperazinyl)methyl]-2-quinolinecarboxamide derivatives bearing different substituents on the terminal piperazine nitrogen atom (compounds 6a-f). The structure-affinity relationship data confirmed the existence of a tolerance to bulky lipophilic substituents and stimulated the design of bifunctional ligands based on the 4-phenyl-3-[(1-piperazinyl)methyl]-2-quinolinecarboxamide moiety (compounds 6h,j,k,m). The submicromolar PBR affinity of rhenium complexes 6j,m suggests that the presence of their metal-ligand moieties with encaged rhenium is fairly compatible with the interaction with the PBR binding site. Thus, in order to obtain information on the in vivo behavior of these bifunctional ligands, (99m)Tc-labeled compounds 6h,k were synthesized and evaluated in preliminary biodistribution and single photon emission tomography (SPET) studies. The results suggest that both tracers do not present a clear preferential distribution in tissues rich in PBR, probably because of their molecular dimensions, which may hamper both the intracellular diffusion toward PBR and the interaction with the binding site.

Design, synthesis, and structure-affinity relationship studies in NK1 receptor ligands based on azole-fused quinolinecarboxamide moieties.

The substituent in position 2 of the quinoline nucleus of NK(1) receptor ligands 5 has been constrained into different five-membered heterocyclic moieties in order to obtain information on the binding site pocket interacting with this apparently critical portion of ligands 5. This structure-affinity relationship study led to the discovery of novel tricyclic NK(1) receptor ligands 6 showing affinity in the nanomolar range to the sub-micromolar one. The systematic structure variation suggests that electronic features of the tricyclic moiety play a role in modulating the interaction of these amide derivatives with their receptor.

Synthesis and structure-activity relationship studies in peripheral benzodiazepine receptor ligands related to alpidem.

The exploration of the structure-affinity relationships concerning a new class of peripheral benzodiazepine receptor (PBR) ligands related to alpidem has been pursued in order to evaluate the consistency of the structure-affinity relationships among different classes (and subclasses) of PBR ligands. The target amide derivatives were prepared following a previously published procedure based on the condensation of pyrrolo[3,4-b]quinoline derivatives 11a,b with glyoxylic acid mono-hydrate and the subsequent amidation of the acids obtained via mixed anhydride. On the other hand, the preparation of compound 9g lacking the pharmacophoric (delta1) carbonyl group involved: (a) the double sequential attack of the dimethylmethyleneammonium salt obtained from bis(dimethylamino)methane and acetyl chloride to pyrrolo[3,4-b]quinoline derivative 11b, (b) the quaternization of the obtained allylamine derivative 13 with methyl iodide, and (c) the palladium-catalyzed allylation of N-methyl-p-anisidine by quaternary allylammonium cation 14. The structure-affinity relationship trends observed in this subclass of tricyclic alpidem-related PBR ligands find correlations in other classes (or subclasses) of PBR ligands. This result supports the initial pharmacophoric hypothesis and suggests a common mode of interaction at the PBR binding site.

Further studies on imidazo[4,5-b]pyridine AT1 angiotensin II receptor antagonists. Effects of the transformation of the 4-phenylquinoline backbone into 4-phenylisoquinolinone or 1-phenylindene scaffolds.

The 4-phenylquinoline fragment of novel AT(1) receptor antagonists 4 based on imidazo[4,5-b]pyridine moiety was replaced by 4-phenylisoquinolinone (compounds 5) or 1-phenylindene (compounds 6) scaffolds to investigate the structure-activity relationships. Binding studies showed that most of the synthesized compounds display high affinity for the AT(1) receptor. Because of the in vitro high potency of carboxylic acids 5b,f, they were evaluated in permeability (in Caco-2 cells) and in pharmacokinetic studies in comparison with quinoline derivatives 4b,i,j,k. The studies showed that these compounds are characterized by rapid excretion, low membrane permeability, and low oral bioavailability. The structure optimization of the indene derivatives led to compounds 6e,f possessing interesting AT(1) receptor affinities. Optimization produced polymerizing AT(1) receptor ligand 6c, which forms a thermoreversible polymer (poly-6c) and is released from the latter by a temperature-dependent kinetics. The results suggest the possibility of developing novel polymeric prodrugs based on a new release mechanism. Finally, a set of 34 AT(1) receptor antagonists was used as a new test for the evaluation of the predictive capability of the previously published qualitative and quantitative pharmacophore models.

Physicochemical and biopharmaceutical characterization of endo-2-(8-methyl-8-azabicyclo[3.2.1]oct-3-yl)-2,3-dihydro-1H-benz[e]isoindol-1-one (CR3124) a novel potent 5-HT3 receptor antagonist.

The physicochemical and biopharmaceutical properties, such as pK(a), crystal habit, water solubility, logD, molecular structure and dynamics, and membrane permeability of CR3124 (endo-2-(8-methyl-8-azabicyclo[3.2.1]oct-3-yl)-2,3-dihydro-1H-benz[e]isoindol-1-one, a novel potent 5-HT(3) receptor antagonist) have been studied in order to obtain preformulation information. The study showed that CR3124 is a very rigid molecule in which conformational freedom due to the presence of a rotatable bond is restricted by the interaction between an activated hydrogen and the amide oxygen and the conformation of the tropane piperidine ring is regulated by the environment in such a manner as to optimize the intermolecular interactions with the solvent. This chameleon behavior appears to be capable of explaining the biopharmaceutical properties showed by CR3124, such as low wettability, relatively good solubility, and very high membrane permeability.

Design, Synthesis, and Biological Evaluation of Imidazo[1,5-a]quinoline as Highly Potent Ligands of Central Benzodiazepine Receptors.

A series of imidazo[1,5-a]quinoline derivatives was designed and synthesized as central benzodiazepine receptor (CBR) ligands. Most of the compounds showed high CBR affinity with Ki values within the submicromolar and subnanomolar ranges with interesting modulations in their structure-affinity relationships. In particular, fluoroderivative 7w (Ki = 0.44 nM) resulted in the most potent ligand among the imidazo[1,5-a]quinoline derivatives described so far. Overall, these observations confirmed the assumption concerning the presence of a large though apparently saturable lipophilic pocket in the CBR binding site region interacting with positions 4 and 5 of the imidazo[1,5-a]quinoline nucleus. The in vivo biological characterization revealed that compounds 7a,c,d,l,m,q,r,w show anxiolytic and antiamnestic activities without the unpleasant myorelaxant side effects of the classical 1,4-BDZ. Furthermore, the effect of 7l,q,r, and 8i in lowering lactate dehydrogenase (LDH) release induced by ischemia-like conditions in rat brain slices suggested neuroprotective properties for these imidazo[1,5-a]quinoline derivatives.

1,5-Diarylpyrrole-3-acetic acids and esters as novel classes of potent and highly selective cyclooxygenase-2 inhibitors.

A small set of substituted 1,5-diarylpyrrole-3-acetic and -glyoxylic acid derivatives have been synthesized, and their cyclooxygenase (COX-1 and COX-2) inhibiting properties have been evaluated. Some compounds proved to be highly selective COX-2 inhibitors, and their affinity data have been rationalized through docking simulations in terms of interactions with a crystallographic model of the COX-2 binding site.

Further studies on the interaction of the 5-hydroxytryptamine3 (5-HT3) receptor with arylpiperazine ligands. development of a new 5-HT3 receptor ligand showing potent acetylcholinesterase inhibitory properties.

Novel arylpiperazine derivatives bearing lipophilic probes were designed, synthesized, and evaluated for their potential ability to interact with the 5-hydroxytryptamine(3) (5-HT(3)) receptor. Most of the new compounds show subnanomolar 5-HT(3) receptor affinity. Ester 6bc showing a picomolar K(i) value is one of the most potent 5-HT(3) receptor ligands so far synthesized. The structure-affinity relationship study suggests the existence of a certain degree of conformational freedom of the amino acid residues interacting with the substituents in positions 3 and 4 of the quipazine quinoline nucleus. Thus, the tacrine-related heterobivalent ligand 6o was designed in an attempt to capitalize on the evidence of such a steric tolerance. Compound 6o shows a nanomolar potency for both the 5-HT(3) receptor and the human AChE and represents the first example of a rationally designed high-affinity 5-HT(3) receptor ligand showing nanomolar AChE inhibitory activity. Finally, the computational analysis performed on compound 6o allowed the rationalization of the structure-energy determinants for AChE versus BuChE selectivity and revealed the existence of a subsite at the boundary of the 5-HT(3) receptor extracellular domain, which could represent a "peripheral" site similar to that evidenced in the AChE gorge.

Polybenzofulvene derivatives bearing dynamic binding sites as potential anticancer drug delivery systems.

In order to obtain new advanced functional materials capable of recognizing drug molecules, the polybenzofulvene backbone of molecular brush poly-6-MOEG-9-TM-BF3k has been functionalized with a "synthetic dynamic receptor" composed of two 1-adamantylurea moieties linked together by means of a dipropyleneamino bridge as in Meijer's bis(adamantylurea) pincer (BAUP). This functional material, bearing synthetic receptors potentially capable of recognizing/loading and then delivering drug molecules, was used to prepare colloidal drug delivery systems (by means of soft interaction with BAUP) for delivering the model anti-cancer drug doxorubicin (DOXO). The resulting nanostructured drug delivery systems containing the physically loaded drug were characterized in terms of drug loading and release, dimensions and zeta potential, and in vitro cell activity and uptake on two different cell lines (i.e. the human bronchial epithelial 16HBE and the human colon cancer HCT116). On normal cells, free DOXO was found to be more cytotoxic than DOXO-loaded nanogels at the higher tested concentration and, only on cancer cells, DOXO-loaded nanogels show similar or slightly higher cytotoxicity values than free DOXO, suggesting potential advantages in the treatment of cancer. These results were supported by fluorescence microscopy studies, which suggested that DOXO-loaded nanogels provide an extracellular reservoir of the drug, which is gradually released and internalized within the cells.

The Interactions of the 5-HT(3) receptor with arylpiperazine, tropane, and quinuclidine ligands.

The serotonin 5-HT(3) receptor subtype is unique among the receptors for this neurotransmitter because it has been demonstrated to be a ligand-gated ion channel capable of mediating rapid intercellular communication. This review covers the authors work performed during more than a decade in the development of 5-HT(3) receptor ligands belonging to the classes of arylpiperazines, tropanes, and quinuclidine derivatives. The discussion is focused mainly on what the authors have learned about the interaction of these structurally different ligands with their receptor and shows the way their ideas evolved along with the progress of the project. Furthermore, a summary of the most significant structure-affinity relationships, derived from the original work, is reported to support the discussion.

Design, synthesis, structural studies, biological evaluation, and computational simulations of novel potent AT(1) angiotensin II receptor antagonists based on the 4-phenylquinoline structure.

Novel AT(1) receptor antagonists bearing substituted 4-phenylquinoline moieties instead of the classical biphenyl fragment were designed and synthesized as the first step of an investigation devoted to the development of new antihypertensive agents and to the understanding of the molecular basis of their pharmacodynamic and pharmacokinetic properties. The newly synthesized compounds were tested for their potential ability to displace [(125)I]Sar(1),Ile(8)-Ang II specifically bound to AT(1) receptor in rat hepatic membranes. These AT(1) receptor binding studies revealed nanomolar affinity in several of the compounds under study. The most potent ligands 4b,t were found to be equipotent with losartan and possessed either a 3-tetrazolylquinoline or a 2-amino-3-quinolinecarboxylic moiety, respectively. Moreover, some selected compounds were evaluated for antagonism of Ang II-induced contraction in rabbit aortic strips, and the most potent compounds in the binding test 4b,t were slightly more potent than losartan in inhibiting Ang II-induced contraction. Finally, the most relevant structure-affinity relationship data were rationalized by means of computational studies performed on the isolated ligands as well as by computational simulations on the ligands complexed with a theoretical AT(1) receptor model.

Synthesis, biological evaluation, and receptor docking simulations of 2-[(acylamino)ethyl]-1,4-benzodiazepines as kappa-opioid receptor agonists endowed with antinociceptive and antiamnesic activity.

The synthesis and biological evaluation of a series of new derivatives of 2-substituted 5-phenyl-1,4-benzodiazepines, structurally related to tifluadom (5), are reported. Chemical and pharmacological studies on compounds 6 have been pursued with the aim of expanding the SAR data and validating the previously proposed model of interaction of this class of compounds with the kappa-opioid receptor. The synthesis of the previously described compounds 6 has been reinvestigated in order to obtain a more direct synthetic procedure. To study the relationship between the stereochemistry and the receptor binding affinity, compounds 6e and 6k were selected on the basis of their evident structural resemblance to tifluadom. Since a different specificity of action could be expected for the enantiomers of 6e and 6k, owing to the results shown by (S)- and (R)-tifluadom, their racemic mixtures have been resolved by means of liquid chromatography with chiral stationary phases (CSP), and the absolute configuration of the enantiomers has been studied by circular dichroism (CD) and (1)H NMR techniques. Moreover, some new 2-[(acylamino)ethyl]-1,4-benzodiazepine derivatives, 6a-d,f,g,j, have been synthesized, while the whole series (6a-o) has been tested for its potential affinity toward human cloned kappa-opioid receptor. The most impressive result obtained from the binding studies lies in the fact that this series of 2-[2-(acylamino)ethyl]-1,4-benzodiazepine derivatives binds the human cloned kappa-opioid receptor subtype very tightly. Indeed, almost all the ligands within this class show subnanomolar K(i) values, and the least potent compound 6o shows, in any case, an affinity in the nanomolar range. A comparison of the affinities obtained in human cloned kappa-receptor with the correspondent one obtained in native guinea pig kappa-receptor suggests that the human cloned kappa-receptor is less effective in discriminating the substitution pattern than the native guinea pig kappa-receptor. Furthermore, the results obtained are discussed with respect to the interaction with the homology model of the human kappa-opioid receptor, built on the recently solved crystal structure of rhodopsin. Finally, the potential antinociceptive and antiamnesic properties of compounds 6e and 6i have been investigated by means of the hot-plate and passive avoidance test in mice, respectively.

A non-peptide NK1 receptor agonist showing subpicomolar affinity.

3-Quinolinecarboxamides have been synthesized and evaluated for their binding to the human NK(1) receptor. Several secondary amide derivatives show NK(1) receptor affinity in the picomolar range. The most active compound, hydroxymethylcarboxamide 3h showing an IC(50) value in the subpicomolar range, behaved as an agonist of NK(1) receptor in endothelial cell proliferation, inositol phosphate turnover, and NO-mediated cyclic GMP accumulation, thus proving it to be the first non-peptide NK(1) receptor agonist showing very high potency.

Structure-activity relationships in carboxamide derivatives based on the targeted delivery of radionuclides and boron atoms by means of peripheral benzodiazepine receptor ligands.

The structure-activity relationship studies on 2-quinolinecarboxamide peripheral benzodiazepine receptor (PBR) ligands have been refined with the aim of using these ligands as carriers of radionuclides and boron atoms. Some new ligands show enhanced affinity and steroidogenic activity with respect to reference compound 1 and are interesting candidates for radiolabeling and PET studies. Moreover, carborane derivative 3q, representing the first example of PBR ligand bearing a carborane cage, can be useful to explore an alternative mechanism in BNCT.