Marine natural products as lead anti-HIV agents.

Current anti-HIV drugs have extreme side effects and resistance to these drugs develops rapidly. The marine environment holds an unprecedented number of unusual chemical structural classes with activity against HIV. We review the literature on anti-HIV activity of marine natural products and discuss the efficacy of different structural classes.

Sexual transmission risk perceptions and behavioural correlates of HIV concentrations in semen.

HIV transmission risk behaviours are related to perceived infectiousness and HIV-positive men who have undetectable blood viral loads may practise less protective behaviours. The current study extends previous research by reporting the association between perceived HIV transmission risks, risk behaviours and viral load in semen. Results showed significant associations between perceived risks for transmitting HIV, unprotected intercourse and viral load in semen. Further analyses showed that men with greater concentrations of HIV in their semen were practising higher rates of transmission risk behaviours while perceiving less risk for potentially transmitting HIV. We conclude that behavioural interventions are needed for HIV-positive men to inform them that HIV infectiousness cannot be inferred from peripheral blood viral loads and to support maintenance of HIV risk reduction behaviours.

Human immunodeficiency virus in semen and plasma: investigation of sexual transmission risk behavioral correlates.

Risks for sexually transmitted HIV may be related to concentrations of virus detected in semen and previous research shows a small to moderate association between viral load in blood and semen. This study examined the association between viral load in semen and plasma in a community sample of HIV-infected men and is the first study to examine semen viral load in relation to sexual transmission risk behaviors. A sample of 44 HIV-positive men recruited from community service agencies provided semen, blood, and urine samples and completed clinical interviews assessing health and behavior. We failed to find an association between viral load in semen and plasma, Spearman rho = 0.07, p > 0.1. When restricted to participants with detectable virus in semen and plasma, the correlation remained nonsignificant, rho = -0.16, p > 0.1. Men who had higher semen viral loads relative to their plasma viral load were distinguished by having engaged in significantly higher rates of unprotected intercourse as the insertive sex partner in the previous 3 months. Semen viral load was not, however, related to recent or current sexually transmitted infections (STIs). This study is among the first to examine sexual transmission risk behaviors as marker for HIV infectiousness. Results caution against inferring sexual transmission infectiousness based on plasma viral load and suggest that HIV-positive men who practice higher rates of insertive intercourse may be more infectious even in the absence of other STIs.

Mololipids, a new series of anti-HIV bromotyramine-derived compounds from a sponge of the order verongida.

A new series of lipids called mololipids have been identified from an Hawaiian sponge of the order Verongida. The structures of these lipids was deduced from spectroscopic data of the lipid mixture combined with GC-MS analysis. The core of this novel series of lipids is a bromotyramine homoserine-derived moiety known as moloka'iamine (1) which is found in many Verongid sponge metabolites. Moloka'iamine forms bisamides with a diverse series of fatty acids and the mololipids mixture (2) was active against HIV-1 with an EC(50) of 52.2 microM without cytotoxicity in human lymphocytes (IC(50) > 100 microM).

Treatment of isografted 9L rat brain tumors with beta-5-o-carboranyl-2'-deoxyuridine neutron capture therapy.

beta-5-o-Carboranyl-2'-deoxyuridine (D-CDU) is a nontoxic pyrimidine nucleoside analogue designed for boron neutron capture therapy of brain tumors. In vitro studies indicated that D-CDU accumulates to levels 92- and 117-fold higher than the extracellular concentration in rat 9L and human U-251 glioma cells, respectively, and persists for several hours at levels 5-fold higher than the extracellular concentration. Furthermore, D-CDU was not toxic to rats injected i.p. with up to 150 mg/kg. On the basis of these studies, D-CDU was evaluated as a neutron capture therapy agent using rats bearing stereotactically implanted intracranial 9L tumors at single i.p. doses of 30 mg/kg and 150 mg/kg of D-CDU (20% 10B enriched), given 2 h before irradiation with thermal neutrons. Boron concentrations in tumors 2 h after dosing were 2.3 +/- 1.6 and 7.4 +/- 1.3 micrograms boron/g tissue (mean +/- SD), corresponding to tumor/brain ratios of 11.5 +/- 3.6 and 6.8 +/- 2.0 micrograms boron/g tissue for the low and high doses, respectively. All untreated animals died within 28 days, whereas half survived at days 32, 55, and 38 for groups receiving neutrons only, 30 mg/kg D-CDU, and 150 mg/kg D-CDU, respectively. Odds ratios of all treatment groups differed significantly from the untreated group (P < 0.002; logrank test). The median survival time for the 30 mg/kg-treated group but not for the 150 mg/kg-treated group was significantly longer than for rats treated with neutrons only (P = 0.036), which may correlate with the decreased tumor selectivity for D-CDU observed at the higher dose. Additional pharmacodynamic studies are warranted to determine optimal dosing strategies for D-CDU.

Synthesis and biological evaluation of 2',3'-didehydro-2',3'- dideoxy-5-fluorocytidine (D4FC) analogues: discovery of carbocyclic nucleoside triphosphates with potent inhibitory activity against HIV-1 reverse transcriptase.

The discovery of a novel cytosine nucleoside, beta-D-2', 3'-didehydro-2',3'-dideoxy-5-fluorocytidine (D-D4FC), as a potent antihuman immunodeficiency virus (HIV) agent led us to synthesize a series of analogues and derivatives of beta-D-D4FC that could be more selective and also possess increased glycosidic bond stability. The synthesized D-D4FC analogues were evaluated for anti-HIV-1 activity, anticancer activity, and cytotoxicity in various cells. The biological data demonstrated that the 5-substitution of beta-D-D4FC with bromine (6c) and iodine (6d) resulted in the loss of antiviral activity, and the alpha-D anomer (7a) of D-D4FC was also devoid of activity. The 5-fluorouracil analogues (6b and 7b) of D-D4FC were less potent and more cytotoxic than the parent compound, whereas the beta-L-D4FU (11) showed both potent anti-HIV-1 activity and cytotoxicity. N4- and 5'-O-acyl derivatives (17, 15a-c) of beta-D-D4FC exhibited comparable antiviral activity to beta-D-D4FC. In contrast, the N4-isopropyl derivative (20) of beta-D-D4FC was not active against HIV-1, even at 100 microM. The carbocyclic analogues (26a,b) of D4FC demonstrated weak activity against HIV-1 and no toxicity in various cells. The triphosphates (27a,b) of the carbocyclic nucleosides demonstrated potent inhibitory activity against recombinant HIV-1 reverse transcriptase at submicromolar concentrations. Of the compounds tested as potential anticancer agents, beta-D-, alpha-D-, and beta-L-D4FU (6b, 7b, 11) showed inhibitory activity against rat glioma and modest activity against human lung carcinoma, lymphoblastoid, and skin melanoma cells.

Enantioselective synthesis and biological evaluation of 5-o-carboranyl pyrimidine nucleosides.

Base-modified carborane-containing nucleosides such as 5-o-carboranyl-2'-deoxyuridine (CDU) when combined with neutrons have potential for the treatment of certain malignancies. Lack of toxicity in various cells, high accumulation in cancer cells and intracellular phosphorylation are desirable characteristics for modified nucleosides used in boron neutron capture therapy (BNCT) for brain tumors and other malignancies. The aim of this work was to synthesize the two beta-enantiomers of several 5-o-carboranyl-containing nucleosides. These derivatives may possess favorable properties such as high lipophilicity, high transportability, the ability to be phosphorylated, and resistance to catabolism. Beta-isomers of 2',3'-dihydroxynucleosides and analogues containing a heteroatom in the sugar moiety were also synthesized. Carboranyl pyrimidine nucleosides were prepared either from the parent beta-D-nucleoside, beta-L-nucleoside, or by a coupling reaction. The dioxolane derivative 7 was prepared by a coupling reaction between protected 5-o-carboranyluracil (8, CU) and the corresponding protected heterocycle. Specific catalysts were used during the N-glycosylation process to favor the formation of the beta-isomer. Biological evaluation of these new chiral 5-o-carboranyl pyrimidine derivatives indicated that most of these compounds have low toxicity in a variety of normal and malignant cells and achieved high cellular levels in a lymphoblastoid cell line. Increasing the number of hydroxyl groups on the sugar moiety decreased the cellular accumulation and serum binding to different extents. Five compounds were identified for further biological evaluation as potential agents for BNCT.