Publications

Antiviral assays carried out on the potent benzothiadiazine dioxide (BTD) human cytomegalovirus (HCMV) inhibitors have led us to find marginal but selective anti-HIV-1 activity. Specific pharmacological studies, such as time of addition experiments and assays on specific viral strains with mutations on its reverse transcriptase, have indicated that BTD compounds act as non-nucleoside reverse transcriptase inhibitors. Theoretical calculations showed a butterfly conformation for the active derivatives that are compatible with their mechanism of action. Therefore, BTD derivatives can be considered as potential lead compounds for the treatment of opportunistic HCMV infections in immunocompromised individuals such as AIDS patients.

Transgenic Mov-14 mice, which carry the provirus of Moloney murine leukemia virus (Mo-MuLV) in the germ line and begin to produce infectious virus on embryonic day 14, were used to evaluate the ability of 9-(2-phosphonylmethoxyethyl)adenine (PMEA) to cross the placenta and protect embryos from viremia. We have used the Mov-14 model previously to demonstrate the antiviral efficacy and lack of teratogenicity of transplacental therapy with 3'-azido-3'-deoxythymidine (zidovudine, ZDV). PMEA was administered to pregnant females by daily intraperitoneal injection or by osmotic pump. In contrast to ZDV, PMEA was either noneffective in preventing viremia in the offspring or embryotoxic, depending on the dose. The specific toxic effects seen were resorption of pregnancy, low birth weight, and neonatal death. Histopathological analysis of neonatal mice exposed to PMEA showed severe lymphoid depletion of the thymus. We conclude that PMEA therapy is contraindicated for use during pregnancy.

9-(2-Phosphonylmethoxyethyl)adenine (PMEA) is a potent and selective inhibitor of retrovirus (i.e., human immunodeficiency virus) replication in vitro and in vivo. Uptake of PMEA by human MT-4 cells and subsequent conversion to the mono- and diphosphorylated metabolites (PMEAp and PMEApp) are dose-dependent and occur proportionally with the initial extracellular PMEA concentrations. Adenylate kinase is unable to phosphorylate PMEA. However, 5-phosphoribosyl-1-pyrophosphate synthetase directly converts PMEA to PMEApp with a Km of 1.47 mM and a Vmax that is 150-fold lower than the Vmax for AMP. ATPase, 5'-phosphodiesterase, and nucleoside diphosphate kinase are able to dephosphorylate PMEApp to PMEAp, albeit to a much lower extent than the dephosphorylation of ATP. PMEApp has a relatively long intracellular half-life (16-18 hr) and has a much higher affinity for the human immunodeficiency virus-specified reverse transcriptase than for the cellular DNA polymerase alpha (Ki/Km: 0.01 and 0.60, respectively). PMEApp is at least as potent an inhibitor of human immunodeficiency virus reverse transcriptase as 2',3'-dideoxyadenosine 5'-triphosphate. Being an alternative substrate to dATP, PMEApp acts as a potent DNA chain terminator, and this may explain its anti-retrovirus activity.

A group of unnatural 1-(2-deoxy-beta-D-ribofuranosyl)-2,4-difluorobenzenes having a variety of C-5 substituents (H, Me, F, Cl, Br, I, CF3, CN, NO2, NH2), designed as thymidine mimics, were synthesized for evaluation as anticancer and antiviral agents. The coupling reaction of 3,5-bis-O-(p-chlorobenzoyl)-2-deoxy-alpha-D-ribofuranosyl chloride with an organocadmium reagent [(2,4-difluorophenyl)2Cd] afforded a mixture of the alpha- and beta-anomeric products (alpha:beta = 3:1 to 10:1 ratio). Treatment of the alpha-anomer with BF3.Et2O in nitroethane at 110-120 degrees C for 30 min was developed as an efficient method for epimerization of the major alpha-anomer to the desired beta-anomer. The 5-substituted (H, Me, Cl, I, NH2) beta-anomers exhibited negligible cytotoxicity in a MTT assay (CC50 = 10(-3)-10(-4) M range), relative to thymidine (CC50 = 10(-3)-10(-5) M range), against a variety of cancer cell lines. In contrast, the 5-NO2 derivative was more cytotoxic (CC50 = 10(-5)-10(-6) M range). A number of 5-substituted beta-anomers, and some related alpha-anomers, that were evaluated using a wide variety of antiviral assay systems [HSV-1, HSV-2, varicella-zoster virus (VZV), vaccinia virus, vesicular stomatitis, cytomegalovirus (CMV) and human immunodeficiency (HIV-1, HIV-2) viruses], showed that this class of unnatural C-aryl nucleoside mimics are inactive antiviral agents.

A series of novel N-substituted indophenazine derivatives were synthesised and screened for antiviral activity against a panel of human pathogenic viruses. New compounds were synthesised through modifying the N-hydrogen of indophenazine moiety with different substitution and formaldehyde by Mannich reaction. The structure of the synthetic compounds was characterised by means of infra red and nuclear magnetic resonance spectral data. The compound 10H-indolo-2-Amino pyridine [3,2-b] quinoxalines inhibits Herpes simplex virus-1 and vaccinia virus at a concentration of 12 μg/ml, and the cytotoxicy was found to be 100 μg/ml. 4-Aminobenzene sulfonamide-10H-indolo [3,2-b] quinoxalines inhibit vaccinia virus at a concentration of 12 μg/ml and cytotoxicy was found to be 100 μg/ml. The anti-HIV activities of the new compounds were also screened for in vitro antiviral activity against replication of HIV-1 (IIIB) and HIV-2 (ROD) in MT-4 cells using zidovudine (AZT) as standard. Pthalimide derivative inhibited the replication of HIV-2 (EC(50)=11.60 μg/ml and CC(50)=61.63 μg/ml) in MT-4 cells.