Violetta Cecchetti

A 1,8-naphthyridone derivative targets the HIV-1 Tat-mediated transcription and potently inhibits the HIV-1 replication.

The emergence of multidrug resistant HIV-1 strains and the inability of the HAART to eradicate HIV-1 virus from infected patients demand new drugs able to interfere with an alternative step of the replicative cycle. The naphthyridone 3 (HM13N), described in the present study, is a promising anti-HIV agent due to its ability to inhibit the HIV-1 Tat-mediated transcription and the potent antiviral activity observed in acutely, chronically, and latently infected cells. The absence of any tendency to select for resistance mutations in vitro adds to the potential clinical value of this type of compounds, especially as these compounds are drug-like and obey the Lipinski rules.

Evolution from a natural flavones nucleus to obtain 2-(4-Propoxyphenyl)quinoline derivatives as potent inhibitors of the S. aureus NorA efflux pump.

Overexpression of efflux pumps is an important mechanism by which bacteria evade the effects of substrate antimicrobial agents. Inhibition of such pumps is a promising strategy to circumvent this resistance mechanism. NorA is a Staphylococcus aureus efflux pump that confers reduced susceptibility to many structurally unrelated agents, including fluoroquinolones, resulting in a multidrug resistant phenotype. In this work, a series of 2-phenyl-4(1H)-quinolone and 2-phenyl-4-hydroxyquinoline derivatives, obtained by modifying the flavone nucleus of known efflux pump inhibitors (EPIs), were synthesized in an effort to identify more potent S. aureus NorA EPIs. The 2-phenyl-4-hydroxyquinoline derivatives 28f and 29f display potent EPI activity against SA-1199B, a strain that overexpresses norA, in an ethidium bromide efflux inhibition assay. The same compounds, in combination with ciprofloxacin, were able to completely restore its antibacterial activity against both S. aureus SA-K2378 and SA-1199B, norA-overexpressing strains.

Pyrazolo[4,3-c][1,2]benzothiazines 5,5-Dioxide: A Promising New Class of Staphylococcus aureus NorA Efflux Pump Inhibitors

The increasing resistance to antibacterials commonly employed in the clinic and the growth of multidrug resistant strains suggest that the development of new therapeutic approaches should be of primary concern. In this context, EPIs may restore life to old drugs. In the present work, the EPI activity of the COX-2 inhibitor celecoxib was confirmed and a new class of pyrazolo[4,3-c][1,2]benzothiazine 5,5-dioxide analogues acting as inhibitors of the Staphylococcus aureus NorA multidrug efflux pump was identified.

New anti-human immunodeficiency virus type 1 6-aminoquinolones: Mechanism of action

ABSTRACT A 6-aminoquinolone derivative, WM5, which bears a methyl substituent at the N-1 position and a 4-(2-pyridyl)-1-piperazine moiety at position 7 of the bicyclic quinolone ring system, was previously shown to exhibit potent activity against replication of human immunodeficiency virus type 1 (HIV-1) in de novo-infected human lymphoblastoid cells (V. Cecchetti et al., J. Med. Chem. 43:3799-3802, 2000). In this report, we further investigated WM5s mechanism of antiviral activity. WM5 inhibited HIV-1 replication in acutely infected cells as well as in chronically infected cells. The 50% inhibitory concentrations were 0.60 ± 0.06 and 0.85 ± 0.05 μM, respectively. When the effects of WM5 on different steps of the virus life cycle were analyzed, the reverse transcriptase activity and the integrase and protease activities were not impaired. By using a transient trans-complementation assay to examine the activity of WM5 on the replicative potential of HIV-1 in a single round of infection, a sustained inhibition of Tat-mediated long terminal repeat (LTR)-driven transcription (>80% of controls) was obtained in the presence of 5 μM WM5. Interestingly, the aminoquinolone was found to efficiently complex TAR RNA, with a dissociation constant in the nanomolar range (19 ± 0.6 nM). These data indicate that WM5 is a promising lead compound for the development of a new class of HIV-1 transcription inhibitors characterized by recognition of viral RNA target(s).

MG2+-MEDIATED BINDING OF 6-SUBSTITUTED QUINOLONES TO DNA : RELEVANCE TO BIOLOGICAL ACTIVITY

The interaction of a number of novel 6-substituted quinolone derivatives with DNA in the presence/absence of magnesium ions has been investigated by fluorometric techniques. The drug-single-stranded nucleic acid interaction is invariantly mediated by the metal ion. In all cases optimal complex formation is found at physiological Mg2+ concentration. From titrations at different [Mg2+] the binding constant for the ternary drug-DNA-Mg2+ complex (KT) has been evaluated. Interestingly, a good relationship is found between KT and gyrase poisoning activity of the test quinolones (IC50), which confirms that DNA-affinity of the quinolone, modulated by Mg2+, plays an important role in poisoning the cleavable gyrase-DNA complex and, consequently, in eliciting antibacterial activity in this family of drugs. The results obtained with different 6-substituted compounds supports the idea that position 6 of the drug, besides playing a pharmacokinetic role, is involved in recognition of the enzyme pocket. Our data do not support a mechanism of action based upon quinolone intercalation into B-DNA.

Structure-activity relationship study on anti-HIV 6-desfluoroquinolones

On the basis of our recent findings that 6-aminoquinolones inhibit the HIV Tat-mediated transactivation, we have designed a broad series of derivatives identifying novel potent agents such as the 6-desfluoroquinolones 24 (HM12) and 27 (HM13), which showed pronounced anti-HIV activity in acutely, chronically, and latently HIV-1 infected cell cultures. We demonstrate here that highly potent molecules can be obtained by optimizing the substituent in the various positions of the quinolone nucleus.

Comparative In Vitro Anti-Hepatitis C Virus Activities of a Selected Series of Polymerase, Protease, and Helicase Inhibitors

ABSTRACT We report here a comparative study of the anti-hepatitis C virus (HCV) activities of selected (i) nucleoside polymerase, (ii) nonnucleoside polymerase, (iii) α,γ-diketo acid polymerase, (iv) NS3 protease, and (v) helicase inhibitors, as well as (vi) cyclophilin binding molecules and (vii) alpha 2b interferon in four different HCV genotype 1b replicon systems.

Allosteric inhibition of the hepatitis C virus NS5B polymerase: in silico strategies for drug discovery and development

Chronic infection by hepatitis C virus (HCV) often leads to severe liver disease including cirrhosis, hepatocellular carcinoma and liver failure. Despite it being more than 20 years since the identification of HCV, the current standard of care for treating the infection is based on aspecific therapy often associated with severe side effects and low-sustained virological response. Research is ongoing to develop new and better medications, including a broad range of allosteric NS5B polymerase inhibitors. This article reviews traditional computational methodologies and more recently developed in silico strategies aimed at identifying and optimizing non-nucleoside inhibitors targeting allosteric sites of HCV NS5B polymerase. The drug-discovery approaches reviewed could provide take-home lessons for general computer-aided research projects.

In vitro phototoxic properties of new 6-desfluoro and 6-fluoro-8-methylquinolones

A representative set of potent antibacterial 6-desfluoro-8-methylquinolones, in which the C-6 fluorine atom is replaced by -NH(2) or -H, and their 6-fluoro counterparts, were investigated to evaluate their phototoxic potential and to explore the mechanism behind their phototoxicity. The capacity to photosensitize biological substrates (lipids, proteins, DNA) has been analyzed, as well as their photocytotoxicity on red blood cells and 3T3 murine fibroblasts. The results obtained show that the quinolones studied are able to photosensitize red blood cell lysis in an oxygen-dependent way and induce a high decrease in cell viability after UVA irradiation. A major correlation with phototoxicity lies in the structure of the individual antibacterials and their hydrophobicity; in particular, 6-amino derivatives are less phototoxic than corresponding unsubstituted and fluorinated compounds. Cellular phototoxicity was inhibited by the addition of free radical and hydroxyl radical scavengers (BHA, GSH and DMTU), suggesting the involvement of a radical mechanism in their cytotoxicity. A good correlation was observed between lipid peroxidation and phototoxicity, indicating that the test compounds exert their toxic effects mainly in the cellular membrane. Preliminary experiments on pBR322 DNA show that these derivatives do not photocleave DNA, differently from the two photogenotoxic fluoroquinolones, ciprofloxacin and lomefloxacin, used as reference compounds.

(1,4-Benzothiazinyloxy)alkylpiperazine derivatives as potential antihypertensive agents.

A series of compounds having a piperazine moiety variously linked to the benzothiazine nucleus were synthesized and evaluated for their in vitro alpha-adrenoceptor affinity by radioligand receptor binding assays. Some compounds bearing a oxyalkyl-(2-methoxyphenyl)piperazine side chain were good alpha1-adrenoreceptor ligands.