Paolo Cozzi

Reversal of multidrug resistance by new dihydropyridines with low calcium antagonist activity.

The clinical use of Ca++ antagonist agents as modulators of multidrug resistance is limited by their strong vasodilator activity. This study reports data obtained by testing a series of new 1,4 dihydropyridine derivatives (DHPs) for their in vitro resistance modulating activity and their Ca++ antagonist effect. All the tested DHPs are active to increase doxorubicin activity with dose modifying factor values ranging between 2 and 47 on P388/DX cells and 12 and 36 on LoVo/DX cells. Their resistance modulating action is exerted through an increase of DX intracellular level. The Ca++ antagonist activity of DHPs, evaluated as capacity to inhibit the KCl-induced contractions in isolated Guinea pig ileum strips, is not related to their resistance modulating activity. This finding makes it possible to select, for further in vivo evaluations, compounds IX, X and XI, which have strong ability to overcome multidrug resistance and low Ca++ antagonist effect.

Characterization of HIV-1 entry inhibitors with broad activity against R5 and X4 viral strains

BackgroundCombined antiretroviral therapy has drastically reduced mortality and morbidity of HIV-infected individuals. Nevertheless long-term toxicity and appearance of viral resistance hampers the prolonged effectiveness of combination therapy, requiring a continuous input of drugs to replace those utilized in combination regimens. We here investigated the anti-HIV activity of novel derivatives of the suradista chemical class.MethodsCompounds were tested on acute HIV-1 infection of activated peripheral blood mononuclear cells. HIV production was monitored by enzyme-linked immunosorbent assay measuring the protein p24 released in culture supernatants. Fusion assays were carried out to study the mechanism of action of these compounds. A modified version of a previously established recombinant vaccinia virus-based assay was used measuring activation of a reporter gene upon fusion of two distinct cell populations. Flow cytometry was performed in competition assays for the binding of several antibodies targeting different sites of the viral envelope glycoprotein gp120, or the receptor CD4, or the coreceptors CXCR4 and CCR5.ResultsFour compounds inhibited replication of a prototypic R5 (BaL) and X4 (IIIB) laboratory-adapted HIV-1 strain at low micromolar concentrations, in the absence of cytotoxicity. Approximately a ten fold greater activity was achieved against the X4 as compared to the R5 strain.The compounds blocked X4 and R5 HIV-1 fusion, a step of viral entry. This activity appeared specific for HIV-1, as entry of human herpesvirus 6 (HHV-6) and influenza virus was not substantially affected. Further investigation of the inhibitory mechanism revealed that these new molecules target the viral envelope, rather than the coreceptors, as previously shown for a congener of the same class characterized by a long plasmatic half-life. Indeed ND-4043, the most active compound, specifically competed with binding of monoclonal antibodies against the CD4-binding site (CD4-BS) and coreceptor-binding site (CoR-BS) of gp120. These compounds displayed broad anti-HIV activity, as they inhibited various primary R5, X4 and, importantly, dualtropic R5X4 HIV-1 isolates. Of the four derivatives tested, the dimeric compounds were consistently more potent than the monomeric ones.ConclusionsGiven their unique features, these molecules represent promising candidates for further development and exploitation as anti-HIV therapeutics.

Nucleophilic substitution on α-mesyloxy-O-alkyloximes—II. Enantiospecific synthesis of 2-(imidazol-1-yl)-1-cyclohexyl-3-phenylpropan-1-one O-alkyloximes

Abstract An enantiospecific synthesis of (S)- and (R)-(E)-5-[1-cyclohexyl-3-phenyl-2-(imidazol-1-yl)propylidene]aminooxypentanoic acids 2 using homochiral phenylalanines as starting material is described. Protected α-hydroxy-N,O-dimethylamides 4 , obtained from α-hydroxyacids 3 were coupled with 1-cyclohexenyllithium to afford α,β-enones 5 , which were in turn converted to α-hydroxyketones 6 . Configurational liability of compound 11 , prompted us to attempt imidazole introduction on the α-hydroxy-O-alkyloxymes 12 which proved to be configurationally more stable. Thus nucleophilic substitution on α-mesyloxy-O-alkyloxymes 14 led, after ester removal, to homochiral compounds 2 . The use of hydrogenolysis for 14b deblocking provided 2a with 97% ee. Considerations on the stereochemical outcome of this hitherto undescribed nucleophilic substitution on α-mesyloxy-O-alkyloxymes are reported.

Imidazolylbenzopyrane derivatives: A new class of acyl-coa: Cholesterol acyltranferase (ACAT) inhibitors

Inhibitors of the enzyme Acyl-CoA: Cholesterol Acyltransferase are regarded as potentially useful agents in the treatment of hypercholesterolemia and atherosclerosis. We report here a novel series of 2, 6-disubstituted-3-imidazolylbenzopyrane derivatives with significant in vitro ACAT inhibitory activity (IC50 range 0.05-0.5 microM). Compounds of this series such as 26 are examples of a new, structurally distinct class of potent ACAT inhibitors with high specificity for the aortic subtype of the enzyme. The structure-activity relationships of the 3-imidazolylbenzopyrane ACAT inhibitors were investigated by systematic manipulation of two regions of the parent compound 1 and the inhibitory activity resulted linked to the substituent in position 6 of the benzopyrane ring and modulated by the size of lipophilic substituents in position 2. Investigation of the mechanism of the inhibitory effect leads to the conclusion that these compounds act in a non-competitive fashion.

NEW BROAD-SPECTRUM ALKYLTHIO CEPHALOSPORINS

A series of 7-substituted alkyl-thio-acylaminocephalosporins with the following general formula were prepared and tested for in vitro antibacterial activity: (formula: see text). We tried in our research to find any relationship between antibacterial activity and pharmacokinetic properties on the one hand, and chemical structure on the other. The most interesting products were also studied for their in vivo antibacterial activity in experimental acute systemic infections in the mouse.