Marco Persico

Paclitaxel Directly Binds to Bcl-2 and Functionally Mimics Activity of Nur77

We reported previously that Bcl-2 is paradoxically down-regulated in paclitaxel-resistant cancer cells. We reveal here that paclitaxel directly targets Bcl-2 in the loop domain, thereby facilitating the initiation of apoptosis. Molecular modeling revealed an extraordinary similarity between the paclitaxel binding sites in Bcl-2 and beta-tubulin, leading us to speculate that paclitaxel could be mimetic of an endogenous peptide ligand, which binds both proteins. We tested the hypothesis that paclitaxel mimics Nur77, which, like paclitaxel, changes the function of Bcl-2. This premise was confirmed by Nur77 interacting with both paclitaxel targets (Bcl-2 and beta-tubulin) and a peptide sequence mimicking the Nur77 structural region, thus reproducing the paclitaxel-like effects of tubulin polymerization and opening the permeability transition pore channel in mitochondria. This discovery could help in the development of novel anticancer agents with nontaxane skeleton as well as in identifying the clinical subsets responsive to paclitaxel-based therapy.

Design, synthesis, and structure-activity relationship studies of 4-quinolinyl- and 9-acrydinylhydrazones as potent antimalarial agents.

Malaria is a major health problem in poverty-stricken regions where new antiparasitic drugs are urgently required at an affordable price. We report herein the design, synthesis, and biological investigation of novel antimalarial agents with low potential to develop resistance and structurally based on a highly conjugated scaffold. Starting from a new hit, the designed modifications were performed hypothesizing a specific interaction with free heme and generation of radical intermediates. This approach provided antimalarials with improved potency against chloroquine-resistant plasmodia over known drugs. A number of structure-activity relationship (SAR) trends were identified and among the analogues synthesized, the pyrrolidinylmethylarylidene and the imidazole derivatives 5r, 5t, and 8b were found as the most potent antimalarial agents of the new series. The mechanism of action of the novel compounds was investigated and their in vivo activity was assessed.

Manadoperoxides A-D from the Indonesian Sponge Plakortis cfr. simplex. Further Insights on the Structure-Activity Relationships of Simple 1,2-Dioxane Antimalarials

The new endoperoxyketal polyketides manadoperoxides A-D (2-5) have been isolated from the Indonesian sponge Plakortis cfr. simplex and their stereostructures established by means of spectroscopic data and semisynthetic transformations. Manadoperoxides were assayed in vitro against D10 and W2 strains of Plasmodium falciparum and showed moderate antimalarial activity compared to that of plakortin (1) and peroxyplakoric B(3) ester (9), the latter differing from manadoperoxide B only by minor structural details. This unexpected difference in the antimalarial activity has been rationalized on the basis of our recently published model for the interaction of 1,2-dioxanes with heme and production of C-centered radicals toxic to the parasite. For the manadoperoxides, either the endoperoxide linkage is inaccessible to the heme iron or the O1 radical cannot evolve to produce a C-centered radical.

Combining 4-aminoquinoline- and clotrimazole-based pharmacophores toward innovative and potent hybrid antimalarials.

Antimalarial agents structurally based on novel pharmacophores, synthesized by low-cost synthetic procedures and characterized by low potential for developing resistance are urgently needed. Recently, we developed an innovative class of antimalarials based on a polyaromatic pharmacophore. Hybridizing the 4-aminoquinoline or the 9-aminoacridine system of known antimalarials with the clotrimazole-like pharmacophore, characterized by a polyarylmethyl group, we describe herein the development of a unique class (4a-l and 5a-c) of antimalarials selectively interacting with free heme and interfering with Plasmodium falciparum (Pf) heme metabolism. Combination of the polyarylmethyl system, able to form and stabilize radical intermediates, with the iron-complexing and conjugation-mediated electron transfer properties of the 4(9)-aminoquinoline(acridine) system led to potent antimalarials in vitro against chloroquine sensitive and resistant Pf strains. Among the compounds synthesized, 4g was active in vivo against P. chabaudi and P. berghei after oral administration and, possessing promising pharmacokinetic properties, it is a candidate for further preclinical development.

Exploiting Protein Fluctuations at the Active-Site Gorge of Human Cholinesterases: Further Optimization of the Design Strategy to Develop Extremely Potent Inhibitors

Protein conformational fluctuations are critical for biological functions, although the relationship between protein motion and function has yet to be fully explored. By a thorough bioinformatics analysis of cholinesterases (ChEs), we identified specific hot spots, responsible for protein fluctuations and functions, and those active-site residues that play a role in modulating the cooperative network among the key substructures. This drew the optimization of our design strategy to discover potent and reversible inhibitors of human acetylcholinesterase and butyrylcholinesterase (hAChE and hBuChE) that selectively interact with specific protein substructures. Accordingly, two tricyclic moieties differently spaced by functionalized linkers were investigated as molecular yardsticks to probe the finest interactions with specific hot spots in the hChE gorge. A number of SAR trends were identified, and the multisite inhibitors 3a and 3d were found to be the most potent inhibitors of hBuChE and hAChE known to date.

Clotrimazole Scaffold as an Innovative Pharmacophore Towards Potent Antimalarial Agents : Design, Synthesis, and Biological and Structure-Activity Relationship Studies

We describe herein the design, synthesis, biological evaluation, and structure-activity relationship (SAR) studies of an innovative class of antimalarial agents based on a polyaromatic pharmacophore structurally related to clotrimazole and easy to synthesize by low-cost synthetic procedures. SAR studies delineated a number of structural features able to modulate the in vitro and in vivo antimalarial activity. A selected set of antimalarials was further biologically investigated and displayed low in vitro toxicity on a panel of human and murine cell lines. In vitro, the novel compounds proved to be selective for free heme, as demonstrated in the beta-hematin inhibitory activity assay, and did not show inhibitory activity against 14-alpha-lanosterol demethylase (a fungal P450 cytochrome). Compounds 2, 4e, and 4n exhibited in vivo activity against P. chabaudi after oral administration and thus represent promising antimalarial agents for further preclinical development.

Investigating the role of T7 and T12 residues on the biological properties of thrombin-binding aptamer: enhancement of anticoagulant activity by a single nucleobase modification.

An acyclic pyrimidine analogue, containing a five-member cycle fused on the pyrimidine ring, was synthesized and introduced at position 7 or 12 of the 15-mer oligodeoxynucleotide GGTTGGTGTGGTTGG, known as thrombin-binding aptamer (TBA). Characterization by 1H NMR and CD spectroscopies of the resulting aptamers, TBA-T7b and TBA-T12b, showed their ability to fold into the typical antiparallel chairlike G-quadruplex structure formed by TBA. The apparent CD melting temperatures indicated that the introduction of the acyclic residue, mainly at position 7, improves the thermal stability of resulting G-quadruplexes with respect to TBA. The anticoagulant activity of the new molecules was then valued in PT assay, and it resulted that TBA-T7b is more potent than TBA in prolonging clotting time. On the other hand, in purified fibrinogen assay the thrombin inhibitory activity of both modified sequences was lower than that of TBA using human enzyme, whereas the potency trend was again reversed using bovine enzyme. Obtained structure-activity relationships were investigated by structural and computational studies. Taken together, these results reveal the active role of TBA residues T7 and T12 and the relevance of some amino acids located in the anion binding exosite I of the protein in aptamer-thrombin interaction.

Discovery of Bishomo(hetero)arylpiperazines as Novel Multifunctional Ligands Targeting Dopamine D3 and Serotonin 5-HT1A and 5-HT2A Receptors

As a continuation of our efforts to develop innovative ligands for D(3), 5-HT(1A), and 5-HT(2A) receptors with low propensity to block hERG channels, we propose a series bishetero(homo)arylpiperazines 5a-m as novel and potent multifunctional ligands characterized by low occupancy at D(2) and 5-HT(2C) receptors.

Specific targeting of peripheral serotonin 5-HT3 receptors. Synthesis, biological investigation, and structure-activity relationships

The synthesis and the biological characterization of novel highly selective pyrroloquinoxaline 5-HT(3) receptor (5-HT(3)R) ligands are described. In functional and in vivo biological studies the novel quinoxalines modulated cardiac parameters by direct interaction with myocardial 5-HT(3)Rs. The potent 5-HT(3)R ligands 4h and 4n modulate chronotropy (right atrium) but not inotropy (left atrium) at the cardiac level, being antagonist and partial agonist, respectively. Preliminary pharmacokinetic studies indicate that (S)-4n and 4a, representatives of the novel 5-HT(3)R ligands, possess poor blood-brain barrier permeability, being the prototypes of peripherally acting 5-HT(3)R modulators endowed with a clear-cut pharmacological activity at the cardiac level. The unique properties of 4h and 4n, compared to their previously described centrally active N-methyl analogue 5a, are mainly due to the hydrophilic groups at the distal piperazine nitrogen. These analogues represent novel pharmacological tools for investigating the role of peripheral 5-HT(3)R in the modulation of cardiac parameters.

Identification of the first inhibitor of the GBP1:PIM1 interaction. Implications for the development of a new class of anticancer agents against paclitaxel resistant cancer cells.

Class III β-tubulin plays a prominent role in the development of drug resistance to paclitaxel by allowing the incorporation of the GBP1 GTPase into microtubules. Once in the cytoskeleton, GBP1 binds to prosurvival kinases such as PIM1 and initiates a signaling pathway that induces resistance to paclitaxel. Therefore, the inhibition of the GBP1:PIM1 interaction could potentially revert resistance to paclitaxel. A panel of 44 4-azapodophyllotoxin derivatives was screened in the NCI-60 cell panel. The result is that 31 are active and the comparative analysis demonstrated specific activity in paclitaxel-resistant cells. Using surface plasmon resonance, we were able to prove that NSC756093 is a potent in vitro inhibitor of the GBP1:PIM1 interaction and that this property is maintained in vivo in ovarian cancer cells resistant to paclitaxel. Through bioinformatics, molecular modeling, and mutagenesis studies, we identified the putative NSC756093 binding site at the interface between the helical and the LG domain of GBP1. According to our results by binding to this site, the NSC756093 compound is able to stabilize a conformation of GBP1 not suitable for binding to PIM1.