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Barbara Cacciari

Publications and source records attributed to Barbara Cacciari.

18 recordsLinked to original sources
PubMed2007

Highlights on the development of A(2A) adenosine receptor agonists and antagonists.

Although significant progress has been made in the past few decades demonstrating that adenosine modulates a variety of physiological and pathophysiological processes through the interaction with four subtypes of a family of cell-surface G-protein-coupled receptors, clinical evaluation of some adenosine receptor ligands has been discontinued. Major problems include side effects due to the wide distribution of adenosine receptors, low brain penetration (which is important for the targeting of CNS diseases), short half-life of compounds, or a lack of effects, in some cases perhaps due to receptor desensitization or to low receptor density in the targeted tissue. Currently, three A(2A) adenosine receptor agonists have begun phase III studies. Two of them are therapeutically evaluated as pharmacologic stress agents and the third proved to be effective in the treatment of acute spinal cord injury (SCI), while avoiding the adverse effects of steroid agents. On the other hand, the great interest in the field of A(2A) adenosine receptor antagonists is related to their application in neurodegenerative disorders, in particular, Parkinson's disease, and some of them are currently in various stages of evaluation. This review presents an update of medicinal chemistry and molecular recognition of A(2A) adenosine receptor agonists and antagonists, and stresses the strong need for more selective ligands at the A(2A) human subtype.

Adenosine↗
PubMed2006

The application of a 3D-QSAR (autoMEP/PLS) approach as an efficient pharmacodynamic-driven filtering method for small-sized virtual library: application to a lead optimization of a human A3 adenosine receptor antagonist.

We have recently reported that the combination of molecular electrostatic potential (MEP) surface properties (autocorrelation vectors) with the conventional partial least squares (PLS) analysis can be used to produce a robust ligand-based 3D structure-activity relationship (autoMEP/PLS) for the prediction of the human A3 receptor antagonist activities. Here, we present the application of the 3D-QSAR (autoMEP/PLS) approach as an efficient and alternative pharmacodynamic filtering method for small-sized virtual library. For this purpose, a small-sized combinatorial library (841 compounds) was derived from the scaffold of the known human A3 antagonist pyrazolo-triazolo-pyrimidines. The most interesting analogues were further prioritized for synthesis and pharmacological characterization. Remarkably, we have found that all the newly synthetized compounds are correctly predicted as potent human A3 antagonists. In particular, two of them are correctly predicted as sub-nanomolar inhibitors of the human A3 receptor.

Adenosine A3 Receptor Antagonists↗
PubMed2006

Synthesis and biological studies of a new series of 5-heteroarylcarbamoylaminopyrazolo[4,3-e]1,2,4-triazolo[1,5-c]pyrimidines as human A3 adenosine receptor antagonists. Influence of the heteroaryl substituent on binding affinity and molecular modeling investigations.

Some pyrazolotriazolopyrimidines bearing different heteroarylcarbamoylamino moieties at the N5-position are described. We previously reported the synthesis of a water soluble compound with high potency and selectivity versus the human A3 adenosine receptor as antagonist, and herein we present an enlarged series of compounds related to the previously mentioned one. These compounds showed A3 adenosine receptor affinity in the nanomolar range and different levels of selectivity evaluated in radioligand binding assays at human A1, A2A, A2B, and A3 adenosine receptors. In particular, the effect of the heteroaryl substituents at the N5 position has been analyzed. This study allows us to recognize that the presence of a pyridinium moiety in this position not only increases water solubility but also improves or retains potency and selectivity at the human A3 adenosine receptors. In contrast, replacement of pyridine with different heterocycles produces loss of affinity and selectivity at the human A3 adenosine receptors. A molecular modeling study has been carried out with the aim to explain these various binding profiles.

Adenosine A3 Receptor Antagonists↗
PubMed2005

Autocorrelation of molecular electrostatic potential surface properties combined with partial least squares analysis as new strategy for the prediction of the activity of human A(3) adenosine receptor antagonists.

The combination of molecular electrostatic potential (MEP) surface properties (autocorrelation vectors) with the conventional partial least squares (PLS) analysis has been used for the prediction of the human A(3) receptor antagonist activities. Three-hundred-fifty-eight structurally diverse human A(3) receptor antagonists have been utilized to generate a novel ligand-based three-dimensional structure-activity relationship. Remarkably, our chemical library includes all 21 important chemical classes of human A(3) antagonists currently discovered, and it represents the largest molecular collection used to generate a general human A(3) antagonist structure-activity relationship. A robust quantitative model has been obtained as described by both cross-validated correlation coefficient (r(cv) = 0.81) and prediction capability (r(pred) = 0.82). The proposed MEP/PLS approach can be considered as an alternative hit identification tool in virtual screening applications.

Adenosine A3 Receptor Antagonists↗
PubMed2005

Combined target-based and ligand-based drug design approach as a tool to define a novel 3D-pharmacophore model of human A3 adenosine receptor antagonists: pyrazolo[4,3-e]1,2,4-triazolo[1,5-c]pyrimidine derivatives as a key study.

A combined target-based and ligand-based drug design approach has been carried out to define a novel pharmacophore model of the human A(3) receptor antagonists. High throughput molecular docking and comparative molecular field analysis (CoMFA) have been used in tandem to assemble a new target based pharmacophore model. In parallel, to provide more accurate information about the putative binding site of these A(3) inhibitors, a rhodopsin-based model of the human A(3) receptor was built and a novel Y-shape binding motif has been proposed. Docking-based structure superimposition has been used to perform a quantitative study of the structure-activity relationships for binding of these pyrazolo-triazolo-pyrimidines to adenosine A(3) receptor using CoMFA. Both steric and the electrostatic contour plots obtained from the CoMFA analysis nicely fit on the hypothetical binding site obtained by molecular docking. On the basis of the combined hypothesis, we have designed, synthesized, and tested 17 new derivatives. Consistently, the predicted K(i) values were very close to the experimental values.

Adenosine A3 Receptor Antagonists↗
PubMed2005

Synthesis, biological studies and molecular modeling investigation of 1,3-dimethyl-2,4-dioxo-6-methyl-8-(substituted) 1,2,3,4-tetrahydro [1,2,4]-triazolo [3,4-f]-purines as potential adenosine receptor antagonists.

A new series of potential adenosine receptor antagonists with a [1,2,4]-triazolo-[3,4-f]-purine structure have been synthesized, and their affinities at the four adenosine receptor subtypes (A1, A2A, A2B and A3) have been evaluated. The design was based on the demonstrated approach to novel A3 adenosine receptor antagonists of adding a third ring to the xanthine structure. Unfortunately, all the synthesized compounds were completely inactive at all four adenosine receptor subtypes independently of their substitutions. Preliminary molecular modeling investigation has demonstrated that only a low degree of steric and electrostatic complementarity has been observed for all the new synthesized triazolo-purines with respect to other structurally related A3 receptor antagonists. This analysis yielded valuable information about structure-activity relationships and further design of potential adenosine receptor antagonists.

Adenylyl Cyclases↗
PubMed2005

Carbon nanotube substrates boost neuronal electrical signaling.

We demonstrate the possibility of using carbon nanotubes (CNTs) as potential devices able to improve neural signal transfer while supporting dendrite elongation and cell adhesion. The results strongly suggest that the growth of neuronal circuits on a CNT grid is accompanied by a significant increase in network activity. The increase in the efficacy of neural signal transmission may be related to the specific properties of CNT materials, such as the high electrical conductivity.

Animals↗
PubMed2005

Non peptidic alphavbeta3 antagonists: recent developments.

The alphavbeta3 receptor, which are members of the group of the cellular adhesion molecules (CAM), are heterodimeric transmembrane glycoprotein receptors involved in processes such as cell-cell and cell-matrix adhesion, cell migration and signaling. Integrin alphavbeta3 receptor is expressed on almost all cells originating from the mesenchyme and seem to mediate several biological processes, including adhesion of osteoblasts to the bone matrix, migration of vascular smooth muscle cells, and angiogenesis. Many efforts were done in the last 10 years to individuate inhibitors for alphavbeta3 receptors, due to their involvement in important pathophysiological functions. In fact, selective alphavbeta3 antagonists offer new therapeutic opportunities for the treatment of several human pathologies like osteoporosis, restenosis and diseases involving neovascularization such as rheumatoid arthritis, tumor induced angiogenesis and metastasis. Purpose of this account is to summarize the recent developments in the field of non-peptidic alphavbetav antagonists.

Drug Design↗
PubMed2005

A2B adenosine receptor antagonists: recent developments.

There are pharmacological evidences that A(2B) receptors are involved in inflammatory processes, such as asthma. For this reason, many efforts has been made for identifying selective A(2B) antagonists as anti-asthmatic agents. The updated material related to this field has been rationalised and arranged in order to offer an overview of the topic.

Adenosine A2 Receptor Antagonists↗
PubMed2003

Pyrazolo[4,3-e]-1,2,4-triazolo[1,5-c]pyrimidine derivatives as adenosine receptor antagonists. Influence of the N5 substituent on the affinity at the human A 3 and A 2B adenosine receptor subtypes: a molecular modeling investigation.

A new series of pyrazolo[4,3-e]-1,2,4-triazolo[1,5-c]pyrimidines bearing various substituents at both the N5-pyrimidinyl and N8-pyrazolyl positions have been synthesized, and their binding affinities at the four human adenosine receptor subtypes (hA(1), hA(2A), hA(2B), and hA(3)) have been evaluated. All the described compounds contain arylacetyl moieties at the N5 position and arylalkyl substituents at the N8 position. Surprisingly, all the compounds present their most potent affinities at the hA(2B) adenosine receptor with a range of selectivities against the other subtypes. When bulky groups are present simultaneously at the N5 and N8 positions (e.g., compound 9), the best selectivity for the hA(2B) receptor was observed (K(i)(hA(1)) = 1100 nM; K(i)(hA(2A)) = 800 nM; K(i)(hA(2B)) = 20 nM; K(i)(hA(3)) = 300 nM, K(i)(hA(1)/A(2B)) = 55, K(i)(hA(2A)/A(2B)) = 40, K(i)(hA(3)/hA(2B)) = 15). To understand the molecular significance of these results, we compared the putative TM (transmembrane) binding motif of compound 9 on both hA(2B) and hA(3) receptors. From our docking studies, compound 9 fits neatly inside the TM region of the hA(2B) receptor but not in the corresponding hA(3) region, illustrating significant differences between the two subtypes. The study herein presented permits an understanding of why the bioisosteric replacement of an -NH, present in previously reported hA(3) receptor antagonists, with a -CH(2) group at the N5 position induces such large differences in hA(2B)/hA(3) affinity. In the molecular structure of the hA(3) receptor, two residues, Ser243 (TM6) and Ser271 (TM7), create a hydrophilic region, which seems to permit a better accommodation of the phenylurea series into this putative hA(3) binding site than the phenylacetyl series.

Adenosine-5'-(N-ethylcarboxamide)↗
PubMed2003

Medicinal chemistry of A2A adenosine receptor antagonists.

Due to the clearly demonstrated receptor-receptor interaction between adenosine A(2A) and dopamine D(2) receptors in the basal ganglia, the discovery and development of potent and selective A(2A)adenosine receptor antagonists became, in the last ten years, an attractive field of research to discovery new drugs for the treatment of neurodegenerative disorders, such as Parkinsons disease. Different compounds have been deeply investigated as A(2A) adenosine receptor antagonists, which could be classified in two great families: xanthine derivatives and nitrogen poliheterocyclic systems. These studies led to the discovery of some highly potent and selective A(2A) adenosine receptor antagonists such as ZM241385, SCH58261 and some xanthine derivatives (KW6002), which have been used as pharmacological tools for studying this receptor subtype. However, those compounds showed some problems that do not permit their use in clinical studies, such as poor water solubility (SCH58261, and xanthine derivatives) or good affinity for A(2B) adenosine receptor subtype (ZM241385). In the last few years great efforts have been made to overcome these problems, trying to optimize not only the pharmacological profile but also the pharmacokinetic character of this class of compounds. The aim of this report is to briefly summarize the recent progress made in this attractive field of research.

Drug Design↗
PubMed2002

Synthesis, biological properties, and molecular modeling investigation of the first potent, selective, and water-soluble human A(3) adenosine receptor antagonist.

A new, highly potent, selective, and water-soluble antagonist of the hA(3) adenosine receptor was synthesized and tested in binding and functional assays. Compound 4 (5-[[(4-pyridyl)amino]carbonyl]amino-8-methyl-2-(2-furyl)-pyrazolo[4,3-e]1,2,4-triazolo[1,5-c]pyrimidine hydrochloride) displayed high water solubility (15 mM) and the highest affinity (K(i) = 0.01 nM) and selectivity for the hA(3) versus A(1), A(2A), and A(2B) receptors (>10000-fold) ever reported. A Schild analysis of the antagonism by 4 of agonist-induced inhibition of cAMP production in CHO cells expressing the hA(3) receptor indicated a K(B) value of 0.20 nM.

Animals↗
PubMed2002

Synthesis, biological activity, and molecular modeling investigation of new pyrazolo[4,3-e]-1,2,4-triazolo[1,5-c]pyrimidine derivatives as human A(3) adenosine receptor antagonists.

A new series of pyrazolotriazolopyrimidines bearing different substitutions on the phenylcarbamoyl moieties at the N5 position, being highly potent and selective human A(3) adenosine receptor antagonists, is described. The compounds represent an extension and an improvement of our previous work on this class of compounds (J. Med. Chem. 1999, 42, 4473-4478; J. Med. Chem. 2000, 43, 4768-4780). All the synthesized compounds showed A(3) adenosine receptor affinity in the subnanomolar range and high levels of selectivity in radioligand binding assays at the human A(1), A(2A), A(2B), and A(3) adenosine receptors. In particular, the effect of the substitution and its position on the phenyl ring have been studied. From binding data, it is evident that the unsubstituted derivatives on the phenyl ring (e.g., compound 59, hA(3) = 0.16 nM, hA(1)/hA(3) = 3713, hA(2A)/hA(3) = 2381, hA(2B)/hA(3) = 1388) showed the best profile in terms of affinity and selectivity at the human A(3) adenosine receptors. The introduction of a sulfonic acid moiety at the para position on the phenyl ring was attempted in order to design water soluble derivatives. However, this substitution led to a dramatic decrease of affinity at all four adenosine receptor subtypes. A computer-generated model of the human A(3) receptor was built and analyzed to better interpret these results, demonstrating that steric control, in particular at the para position on the phenyl ring, plays a fundamental role in the receptor interaction. Some of the synthesized compounds proved to be full antagonists in a specific functional model, where the inhibition of cAMP-generation by IB-MECA was measured in membranes of CHO cells stably transfected with the human A(3) receptor with IC(50) values in the nanomolar range, with a statistically significative linear relationship with the binding data.

Animals↗
PubMed2002

7-Substituted 5-amino-2-(2-furyl)pyrazolo[4,3-e]-1,2,4-triazolo[1,5-c]pyrimidines as A2A adenosine receptor antagonists: a study on the importance of modifications at the side chain on the activity and solubility.

It was demonstrated in the early 1990s that adenosine exerts many physiological functions through the interaction with four different receptors, named A1, A2A, A2B, and A3. In the past few years, our group has been involved in the development of A2A antagonists, which led to the synthesis of SCH 58261 (1), the first potent and selective adenosine A2A antagonist, which has been widely used as a reference compound. In this paper, we present an extended series of pyrazolotriazolopyrimidines synthesized with the aim to investigate the influence of the substitutions on the pyrazole ring. The choice of the substituents was based on their capability to improve water solubility while retaining high affinity and selectivity at the human A2A adenosine receptor subtype. In this series, some structural characteristics that are important for activity, i.e., tricyclic structure, free amino group at 5-position, furan ring, and substituent at 7-position on the pyrazole moiety, have been maintained. We focused our attention on the nature of the phenyl ring substituent to improve water solubility. Following this strategy, we developed new compounds with good affinity and selectivity for A2A adenosine receptors, such as 8d (K(i) 0.12 nM; hA1/hA2A ratio = 1025; R(m) = 2.8), 8h (K(i) 0.22; hA1/hA2A ratio = 9818; R(m) = 3.4), 8i (K(i) 0.18 nM; hA1/hA2A ratio = 994; R(m) = 2.8), 8k (K(i) 0.13 nM; hA1/hA2A ratio = 4430; R(m) = 3.6), and 14b (K(i) 0.19 nM; hA1/hA2A ratio = 2273; R(m) = 2.7). All the new synthesized compounds have no significant interaction with either A2B or A3 receptor subtypes. This new series of compounds deeply enlightens some structural requirements to display high affinity and selectivity for the A2A adenosine receptor subtype, although our goal of identifying new compounds with increased water solubility was not completely achieved. On this basis, other strategies will be devised to improve this class of compounds with a profile that appears to be promising for treatment of neurodegenerative disorders, such as Parkinson's disease.

Binding, Competitive↗
PubMed2002

Pyrazolo-triazolo-pyrimidine derivatives as adenosine receptor antagonists: a possible template for adenosine receptor subtypes?

Adenosine, a widely distributed modulator, regulates many physiological functions through specific cell membrane G-protein-coupled receptors classified as A(1), A(2A), A(2B) and A(3). An intense medicinal chemistry effort made over the last 20 years has led to a variety of selective adenosine receptor agonists and antagonists. In particular, the pyrazolo-triazolo-pyrimidine nucleus has been strongly investigated in the last years by our group. All the modifications performed and a tentative of structure-activity-relationship is reported. In fact, the combination of different substitutions at the N(7), N(8) and N(5) positions afford compounds which showed good affinity and selectivity for the different adenosine receptor subtypes. The data herein summarized, permit to speculate on the use of this nucleus as possible template for the adenosine receptor subtypes.

Animals↗
PubMed1996

Synthesis and Properties of Substituted CBI Analogs of CC-1065 and the Duocarmycins Incorporating the 7-Methoxy-1,2,9,9a-tetrahydrocyclopropa[c]benz[e]indol-4-one (MCBI) Alkylation Subunit: Magnitude of Electronic Effects on the Functional Reactivity.

The synthesis of 7-methoxy-1,2,9,9a-tetrahydrocyclopropa[c]benz[e]indol-4-one (MCBI), a substituted CBI derivative bearing a C7 methoxy group para to the C4 carbonyl, is described in efforts that establish the magnitude of potential electronic effects on the chemical and functional reactivity of the agents. The core structure of the MCBI alkylation subunit was prepared by a modified Stobbe condensation/Friedel-Crafts acylation for generation of the appropriately functionalized naphthalene precursors (15 and 20) followed by 5-exo-trig aryl radical-alkene cyclization (24 --> 25, 32 --> 33) for completion of the synthesis of the 1,2-dihydro-3H-benz[e]indole skeleton and final Ar-3' alkylation of 28 for introduction of the activated cyclopropane. Two approaches to the implementation of the key 5-exo-trig free radical cyclization are detailed with the former proceeding with closure of 24 to provide 25 in which the required product functionalization was introduced prior to cyclization and the latter with Tempo trap of the cyclization product of the unfunctionalized alkene substrate 32 to provide 33. The latter concise approach provided the MCBI subunit and its immediate precursor in 12-13 steps in superb overall conversions (27-30%). Resolution of an immediate MCBI precursor and its incorporation into both enantiomers of 39-46, analogs of CC-1065 and the duocarmycins, are detailed. A study of the solvolysis reactivity and regioselectivity of N-BOC-MCBI (29) revealed that introduction of the C7 methoxy group accelerates the rate of solvolysis by only 1.2-1.06x. This remarkably modest effect is inconsistent with C4 carbonyl protonation as the slow and rate-determining step of solvolysis or acid-catalyzed nucleophilic addition but is consistent with a mechanism in which protonation is rapid and reversible followed by slow and rate-determining nucleophilic addition to the cyclopropane requiring both the presence and assistance of a nucleophile (S(N)2 mechanism). No doubt this contributes to the DNA alkylation selectivity of this class of agents and suggests that the positioning of an accessible nucleophile (adenine N3) and not C4 carbonyl protonation is the rate-determining step controlling the sequence selectivity of the DNA alkylation reaction. This small electronic effect on the solvolysis rate had no impact on the solvolysis regioselectivity, and stereoelectronically-controlled nucleophilic addition to the least substituted carbon of the activated cyclopropane was observed exclusively. For the natural enantiomers, this unusually small electronic effect on functional reactivity had little or no perceptible effect on their DNA alkylation selectivity, efficiency, and relative rates or on their biological properties. Perceptible effects of the C7 methoxy substituent on the unnatural enantiomers were observed and they proved to be 4-40x more effective than the corresponding CBI-based unnatural enantiomers and comparable in cytotoxic potency with the MCBI natural enantiomers. This effect is most consistently rationalized not by a C7 methoxy substituent effect on functional reactivity but rather through introduction of additional stabilizing noncovalent interactions which increase the unnatural enantiomer DNA alkylation efficiency and further stabilize its inherently reversible DNA alkylation reaction.

Journal Article↗