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.

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.

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.

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.

Novel analgesic/anti-inflammatory agents: 1,5-diarylpyrrole nitrooxyalkyl ethers and related compounds as cyclooxygenase-2 inhibiting nitric oxide donors.

A series of 3-substituted 1,5-diarylpyrroles bearing a nitrooxyalkyl side chain linked to different spacers were designed. New classes of pyrrole-derived nitrooxyalkyl inverse esters, carbonates, and ethers (7-10) as COX-2 selective inhibitors and NO donors were synthesized and are herein reported. By taking into account the metabolic conversion of nitrooxyalkyl ethers (9, 10) into corresponding alcohols, derivatives 17 and 18 were also studied. Nitrooxy derivatives showed NO-dependent vasorelaxing properties, while most of the compounds proved to be very potent and selective COX-2 inhibitors in in vitro experimental models. Further in vivo studies on compounds 9a,c and 17a highlighted good anti-inflammatory and antinociceptive activities. Compound 9c was able to inhibit glycosaminoglycan (GAG) release induced by interleukin-1ß (IL-1ß), showing cartilage protective properties. Finally, molecular modeling and (1)H- and (13)C-NMR studies performed on compounds 6c,d, 9c, and 10b allowed the right conformation of nitrooxyalkyl ester and ether side chain of these molecules within the COX-2 active site to be assessed.

Synthesis and structure-activity relationship studies in translocator protein ligands based on a pyrazolo[3,4-b]quinoline scaffold.

As a further development of our large program focused on the medicinal chemistry of translocator protein [TSPO (18 kDa)] ligands, a new class of compounds related to alpidem has been designed using SSR180575, emapunil, and previously published pyrrolo[3,4-b]quinoline derivatives 9 as templates. The designed compounds were synthesized by alkylation of the easily accessible 4-methyl-2-phenyl-1H-pyrazolo[3,4-b]quinolin-3(2H)-one derivatives 13-15 with the required bromoacetamides. Along with the expected 2-(4-methyl-3-oxo-2-phenyl-2,3-dihydro-1H-pyrazolo[3,4-b]quinolin-1-yl)acetamide derivatives 10, 2-(4-methyl-3-oxo-2-phenyl-2H-pyrazolo[3,4-b]quinolin-9(3H)-yl)acetamide isomers 11 were isolated and characterized. The high TSPO affinity shown by new pyrazolo[3,4-b]quinoline derivatives 10 and especially 11 leads the way to further expand the chemical diversity in TSPO ligands and provides new templates and structure-affinity relationship data potentially useful in the design of new anxiolytic and neuroprotective agents.

New insight into the central benzodiazepine receptor-ligand interactions: design, synthesis, biological evaluation, and molecular modeling of 3-substituted 6-phenyl-4H-imidazo[1,5-a][1,4]benzodiazepines and related compounds.

3-Substituted 6-phenyl-4H-imidazo[1,5-a][1,4]benzodiazepines and related compounds were synthesized as central benzodiazepine receptor (CBR) ligands. Most of the compounds showed high affinity for bovine and human CBR, their K(i) values spanning from the low nanomolar to the submicromolar range. In particular, imidazoester 5f was able to promote a massive flow of (36)Cl(-) in rat cerebrocortical synaptoneurosomes overlapping its efficacy profile with that of a typical full agonist. Compound 5f was then examined in mice for its pharmacological effects where it proved to be a safe anxiolytic agent devoid of the unpleasant myorelaxant and amnesic effects of the classical 1,4-benzodiazepines. Moreover, the selectivity of some selected compounds has been assessed in recombinant α(1)ß(2)γ(2)L, α(2)ß(1)γ(2)L, and α(5)ß(2)γ(2)L human GABA(A) receptors. Finally, some compounds were submitted to molecular docking calculations along with molecular dynamics simulations in the Cromer's GABA(A) homology model.

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.

Bivalent Ligands for the Serotonin 5-HT3 Receptor.

The serotonin 5-HT3 receptor is a ligand-gated ion channel, which by virtue of its pentameric architecture, can be considered to be an intriguing example of intrinsically multivalent biological receptors. This paper describes a general design approach to the study of multivalency in this multimeric ion channel. Bivalent ligands for 5-HT3 receptor have been designed by linking an arylpiperazine moiety to probes showing different functional features. Both homobivalent and heterobivalent ligands have shown 5-HT3 receptor affinity in the nanomolar range, providing evidence for the viability of our design approach. Moreover, the high affinity shown by homobivalent ligands suggests that bivalency is a promising approach in 5-HT3 receptor modulation and provides the rational basis for applying the concepts of multivalency to the study of 5-HT3 receptor function.

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.

Design, synthesis, and preliminary biological evaluation of pyrrolo[3,4-c]quinolin-1-one and oxoisoindoline derivatives as aggrecanase inhibitors.

A small set of aggrecanase inhibitors based on the pyrrolo[3,4-c]quinolin-1-one or oxoisoindoline frameworks bearing a 4-(benzyloxy)phenyl substituent and different zinc binding groups were rationally designed and evaluated in silico by docking studies using the crystal structure of the ADAMTS-5 catalytic domain (PDB code: 3B8Z). The designed compounds were synthesized via straightforward routes and tested for their potential inhibitory activity against ADAMTS-5 and ADAMTS-4. Among the compounds containing the pyrrolo[3,4-c]quinolinone tricyclic system, hydroxamate derivative 2 b inhibited both ADAMTS-5 and ADAMTS-4, with IC(50) values in the submicromolar range and an inhibitory profile very similar to that of reference carboxylate derivative 11. Conversely, the corresponding carboxylate derivative 2 a was significantly less active and unable to discriminate between ADAMTS-5 and -4. The structure-activity relationship analysis of pyrroloquinolinone derivatives 2 a-i suggests that the carboxylate or hydroxamate groups of compounds 2 a,b play a key role in the interaction of these compounds with ADAMTS-5 and -4. On the other hand, the oxoisoindoline derivatives 3 a,b lack significant ADAMTS-4 inhibitory activity and inhibit ADAMTS-5 showing IC(25) values in the micromolar range.

The interactions of the 5-HT3 receptor with quipazine-like arylpiperazine ligands: the journey track at the end of the first decade of the third millennium.

The 5-HT(3) receptor (5-HT(3)R) occupies a special place among the serotonin receptor subtypes because it has been shown to be a ligand-gated ion channel, which is involved in a number of physiological functions and important pathologies. 5-HT(3)R antagonists have shown an outstanding efficacy in the control of the emesis induced by anticancer chemotherapy and few adverse side-effects, so as to revolutionize the treatment of nausea in cancer patients. This review covers the authors' work performed during the past decade in the development of 5-HT(3)R ligands belonging to the class of arylpiperazine derivatives related to quipazine (quipazine-like arylpiperazines, QLAs) and represents the extension of the review previously published in Current Topics in Medicinal Chemistry in 2002. The discussion is focused mainly on the most significant structure-affinity relationships emerged in the progress of the work and shows how the original ideas have evolved in the recent years.

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.

Synthesis and biological evaluation of amidine, guanidine, and thiourea derivatives of 2-amino(6-trifluoromethoxy)benzothiazole as neuroprotective agents potentially useful in brain diseases.

A series of amidine, thiourea, and guanidine derivatives of 2-amino-6-(trifluoromethoxy)benzothiazole termed 2, 3, and 4, respectively, and structurally related to riluzole, a neuroprotective drug in many animal models of brain disease, have been synthesized. The biological activity of compounds 2a-e, 3a-f, and 4a,b was preliminarily tested by means of an in vitro protocol of ischemia/reperfusion injury. The results demonstrated that 2c and 3a-d significantly attenuated neuronal injury. Selected for testing of their antioxidant properties, compounds 3a-d were shown to be endowed with a direct ROS scavenging activity. Compounds 3b and 3d were also evaluated for their activity on voltage-dependent Na(+) and Ca(2+) currents in neurons from rat piriform cortex. At 50 microM, compound 3b inhibited the transient Na(+) current to a much smaller extent than riluzole, whereas 3d was almost completely ineffective.

Synthesis, biological evaluation, and enzyme docking simulations of 1,5-diarylpyrrole-3-alkoxyethyl ethers as selective cyclooxygenase-2 inhibitors endowed with anti-inflammatory and antinociceptive activity.

A series of substituted 1,5-diarylpyrrole-3-alkoxyethyl ethers (6, 7, and 8) has been synthesized with the aim to assess if in the previously reported 1,5-diarylpyrrole derivatives (5) the replacement of the acetic ester moiety with an alkoxyethyl group still led to new, highly selective and potent COX-2 inhibitors. In the in vitro cell culture assay, all the compounds proved to be potent and selective COX-2 inhibitors. In the human whole blood (HWB) assay, compound 8a had a comparable COX-2 selectivity to valdecoxib, while it was more selective than celecoxib but less selective than rofecoxib. The potential anti-inflammatory and antinociceptive activities of compounds 7a, 8a, and 8d were evaluated in vivo, where they showed a very good activity against both carrageenan-induced hyperalgesia and edema in the rat paw test. In the abdominal constriction test compound 7a, 8a, and 8d were able to reduce the number of writhes in a statistically significant manner. Furthermore, the affinity data of these compounds have been rationalized through enzyme docking simulations in terms of interactions with a crystallographic model of the COX-2 binding site by means of the software package Autodock 3.0.5, GRID 21, and MacroModel 8.5 using the complex between COX-2 and SC-558 (1b), refined at a 3 A resolution (Brookhaven Protein Data Bank entry: 6cox ).

Ethyl 8-fluoro-6-(3-nitrophenyl)-4H-imidazo[1,5-a][1,4]benzodiazepine-3-carboxylate as novel, highly potent, and safe antianxiety agent.

Ethyl 8-fluoro-6-(4-nitrophenyl)- and ethyl 8-fluoro-6-(3-nitrophenyl)-4 H-imidazo[1,5-a][1,4]benzodiazepine 3-carboxylate 6 and 7 were synthesized as central benzodiazepine receptor (CBR) ligands and tested for their ability to displace [(3)H]flumazenil from bovine and human cortical brain membranes. Both compounds showed high affinity for bovine and human CBR. In particular, compound 7 emerged as the most interesting compound, having a partial agonist profile in vitro while possessing useful activity in various animal models of anxiety. In accordance with its partial agonist profile, compound 7 was devoid of typical benzodiazepine side effects. The homology model of the GABA A receptor developed by Cromer et al. was used to assess the binding modes of ligands 6 and 7. From our docking results, the partial agonist activity elicited by compound 7 is likely to be due to the 3'-nitro substituent, which is in the appropriate position to interact with Thr193 of the gamma 2-subunit by means of a hydrogen bond.

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 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 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 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.