Synthesis and anti-HIV evaluation of new 2′,3′- dideoxy-3′-thiacytidine prodrugs

Abstract

A series of anti-HIV prodrugs possessing various polyaminated side arms have been developed. The incorporation of a N-Boc protected monoamine or diamine side arm into the backbone of the 2′,3′-dideoxy-3′-thiacytidine 1 (BCH-189) provided an increase in antiviral potency, which could be several orders magnitude greater than the parent drug (1) depending on the cell culture systems used (MT-4 or MDMs). Twenty six 2′,3′-dideoxy-3′-thiacytidine prodrugs which differ from each other by the length, the nature of the 5′-O function and the 5′-O or /and N-4 position on the nucleoside moiety were synthesized. Among this new series of prodrugs, several congeners (12c and 12a) were found to inhibit HIV-1 replication in cell culture with 50% effective concentrations ECso of 10 and 50 nM respectively, in MT-4 cells. Compound 12c was found more active on infected MDMs cells with 50% effective concentration of 0.01 nM. The synthesis and the antiviral properties of these compounds are discussed.     

Are anti-HIV IgAs good guys or bad guys?

An estimated 90% of all HIV transmissions occur mucosally. Immunoglobulin A (IgA) molecules are important components of mucosal fluids. In a vaccine efficacy study, in which virosomes displaying HIV gp41 antigens protected most rhesus monkeys (RMs) against simian-human immunodeficiency virus (SHIV), protection correlated with vaginal IgA capable of blocking HIV transcytosis in vitro. Furthermore, vaginal IgG exhibiting virus neutralization and/or antibody-dependent cellular cytotoxicity (ADCC) correlated with prevention of systemic infection. In contrast, plasma IgG had neither neutralizing nor ADCC activity. More recently, a passive mucosal immunization study provided the first direct proof that dimeric IgAs (dIgAs) can prevent SHIV acquisition in RMs challenged mucosally. This study compared dimeric IgA1 (dIgA1), dIgA2, or IgG1 versions of a human neutralizing monoclonal antibody (nmAb) targeting a conserved HIV Env epitope. While the nmAb neutralization profiles were identical in vitro, dIgA1 was significantly more protective in vivo than dIgA2. Protection was linked to a new mechanism: virion capture. Protection also correlated with inhibition of transcytosis of cell-free virus in vitro. While both of these primate model studies demonstrated protective effects of mucosal IgAs, the RV144 clinical trial identified plasma IgA responses to HIV Env as risk factors for increased HIV acquisition. In a secondary analysis of RV144, plasma IgA decreased the in vitro ADCC activity of vaccine-induced, Env-specific IgG with the same epitope specificity. Here we review the current literature regarding the potential of IgA – systemic as well as mucosal – in modulating virus acquisition and address the question whether anti-HIV IgA responses could help or harm the host.     

Synthesis, QSAR and anti-HIV activity of new 5-benzylthio-1,3,4-oxadiazoles derived from α-amino acids

2-(1-[(4-Chloro/methylphenylsulfonylamino)alkyl]-5-thioxo-4,5-dihydro-1,3,4-oxadiazoles (4a-e) were synthesized, in four steps, via the sulfonyl derivatives of l-amino acids (l-alanine, l-methionine and l-phenylalanine) 1a-e, the esters 2a-e, the hydrazides 3a-e and finally the cyclization to 4a-e. Alkylation of 4a-e with 1.0 mole eq. of substituted benzyl halides furnished S-benzyl derivatives 5a-t, while 1.1 mole eq. yielded major 5a-t and minor amount of 6a-d. Alternatively, treatment of 4a-e with 2.0 mole eq. of substituted benzyl halides furnished 6a-d only. The structures of 5b and 5l were further confirmed by single crystal X-ray analysis. Compounds 5a-t and 6a-d showed no selective inhibition against HIV-1 and HIV-2 replication in MT-4 cells. However, 5f and 5j-5q exhibited some inhibitory activity against both types with EC(50) values (>11.50 - >13.00 μg/mL). These results suggest that the structural modifications of these compounds might lead to the development of new antiviral agents. The quantum structure-activity relationship of these novel structural congeners is discussed.     

5′-O-Aliphatic and amino acid ester prodrugs of (−)-β-d-(2R,4R)-dioxolane-thymine (DOT): Synthesis,anti-HIV activity,cytotoxicity and stability studies

A series of (?)-β-d-(2R,4R)-dioxolane-thymine-5′-O-aliphatic acid esters as well as amino acid esters were synthesized as prodrugs of (?)-β-d-(2R,4R)-dioxolane-thymine (DOT). The compounds were evaluated for anti-HIV activity against HIV-1_LAI in human peripheral blood mononuclear (PBM) cells as well as for their cytotoxicity in PBM, CEM and Vero cells. Improved anti-HIV potency in vitro was observed for the compound 2–4 (5′-O-aliphatic acid esters) without increase in cytotoxicity in comparison to the parent drug. Chemical and enzymatic hydrolysis of the prodrugs was also studied, in which the prodrugs exhibited good chemical stability with the half-lives from 3 h to 54 h at pH 2.0 and 7.4 phosphate buffer. However, the prodrugs were relatively labile to porcine esterase with the half-lives from 12.3 to 48.0 min.     

Do the 16 mer, 5'-GUGGUCUGAUGAGGCC-3' and the 25 mer, 5'-GGCCGAAACUCGUAAGAGUCACCAC-3', form a hammerhead ribozyme structure in physiological conditions? An NMR and UV thermodynamic study

In a wide range of salt concentrations, 10-30 mM phosphate buffer containing up to 0.5 M Li2SO4 and 300 mM NaCl, 7.5 mM Mg2+, pH 5.5-7.5, a mixture of the 16 mer and the 25 mer RNA strands does not form a hammerhead in any amount detectable by NMR at 600 MHz. The imino-, amino-, aromatic- and anomeric protons in the NMR spectra of both the 16 mer and the 25 mer RNA have been assigned separately. Both the 16 mer and the 25 mer RNA both take up very stable hairpin structures, and when mixed together there is no major change of conformation in neither oligo-RNA.     

Antiarrhythmic drugs, patients, and the pharmaceutical industry: value for patients, physicians, pharmacists or shareholders?

Antiarrhythmic drugs no longer seem to be big business. After the unexpected CAST trial results (excess mortality in the class 1C antiarrhythmic drug treatment arms in patients with coronary artery disease (CAD) and abundant ventricular extrasystoles),1 antiarrhythmic drug treatment became less popular for CAD patients. Since this category of patients represents the majority of cardiology patients with chronic disease, these results impacted on the antiarrhythmic drug market. In the years that followed, the use of class 1C drugs was even further discouraged.     

Social behavior and comparative genomics: new genes or new gene regulation?

Molecular analyses of social behavior are distinguished by the use of an unusually broad array of animal models. This is advantageous for a number of reasons, including the opportunity for comparative genomic analyses that address fundamental issues in the molecular biology of social behavior. One issue relates to the kinds of changes in genome structure and function that occur to give rise to social behavior. This paper considers one aspect of this issue, whether social evolution involves new genes, new gene regulation, or both. This is accomplished by briefly reviewing findings from studies of the fish Haplochromis burtoni , the vole Microtus ochrogaster , and the honey bee Apis mellifera , with a more detailed and prospective consideration of the honey bee.     

Neuroinfections and antimicrobials: do we need new molecules or new strategies?

Within last 15 years, analyzing patterns of etiology and resistance in organisms causing neuroinfections, emergence of resistance has been observed in Slovakia in S. haemolyticus to teicoplanin (11%), Ps. aeruginosa and A. baumannii to meropenem (20%) and Candida spp. (non-albicans Candida spp.) to fluconazol (20%). There are no new antibiotics against carbapenem resistant Ps. aeruginosa and Acinetobacter baumannii.     

Synthesis and P2Y receptor activity of nucleoside 5′-phosphonate derivatives

Ribose-based nucleoside 5′-diphosphates and triphosphates and related nucleotides were compared in their potency at the P2Y receptors with the corresponding nucleoside 5′-phosphonate derivatives. Phosphonate derivatives of UTP and ATP activated the P2Y₂ receptor but were inactive or weakly active at P2Y₄ receptor. Uridine 5′-(diphospho)phosphonate was approximately as potent at the P2Y₂ receptor as at the UDP-activated P2Y₆ receptor. These results suggest that removal of the 5′-oxygen atom from nucleotide agonist derivatives reduces but does not prevent interaction with the P2Y₂ receptor. Uridine 5′-(phospho)phosphonate as well as the 5′-methylenephosphonate equivalent of UMP were inactive at the P2Y₄ receptor and exhibited maximal effects at the P2Y₂ receptor that were ?50% of that of UTP suggesting novel action of these analogues.     

Is there sometimes T-T wobble pairing in thymidylyl-3',5'-thymidine?

A fibre-type x-ray diffraction photograph from thymidylyl-3',5'-thymidine is interpreted in terms of a seven-residues per turn, left-handed helical structure in which the first thymine of one molecule is linked to the second thymine of the next molecule by 'wobble' type hydrogen bonds. The first thymidine is in the anti conformation, with a C2'endo - C3'exo sugar and the second is in the syn conformation with a C3'endo - C4'exo sugar. The C5' - 05' bond in the inter-nucleotide linkage is in the g- conformation and that of the P-05' is g+.     

Synthesis,characterization and biological evaluation of C5′-N-cyclopropylcarboxamido-C6-amino-C2-alkynylated purine nucleoside analogues

In an effort to develop potent antibacterial and anticancer agents, a series of C5′-N-cyclopropylcarboxamido-C6-amino-C2-alkynylated purine nucleoside analogues 11a-g were synthesized through a Sonogashira cross-coupling reaction. The nine-step synthesis is easy to perform, and employs commercially available reagents. 2-Iodo-5′-N-cyclopropylcarboxamidoadenosine (9) was used as the starting intermediate for the synthesis of title derivatives 11a-g. Synthetic intermediates (2–9) and final products (11a-g) were appropriately characterized by IR, ¹H NMR, ¹³C NMR and mass spectroscopy. The synthesized purine nucleoside analogues (11a-g) were evaluated for their in vitro antibacterial activity against two gram-positive and two gram-negative bacteria. They were then tested for cytotoxicity against MDA-MB-231 and Caco-2 cancer cell lines to determine their anti-cancer activity. Among the tested compounds, compounds 11c and 11g showed most potent antibacterial activity against S.aureus and P.aeruginosa bacterial strains. Compounds 11b and 11e displayed considerable IC₅₀^s of 7.9 and 6.8 µg/mL, respectively, vs MDA-MB-231 cell lines of 7.5 and 8.3 µg/mL, respectively, against the Caco-2 cell lines.