Ana San-Félix

TSAO compounds: The comprehensive story of a unique family of HIV-1 specific inhibitors of reverse transcriptase

Emergence of drug-resistant viral strains is one of the major milestones and the main cause for the failure of antiretroviral therapy. Combination of different anti-HIV agents has become the standard clinical practice to keep the viral load at low or even undetectable levels and to prevent emergence of virus-drug resistance. Among the human immunodeficiency virus (HIV) reverse transcriptase (RT) inhibitors, the so called nonnucleoside RT inhibitors (NNRTIs) have gained a definitive place in the treatment of HIV infections in combination with nucleoside analogue RT inhibitors (NRTIs) and HIV protease inhibitors (PIs). The virus can be markedly suppressed for a relatively long period of time when exposed to multiple drug combination therapy (highly active antiretroviral therapy, HAART). TSAO derivatives are a peculiar group of highly functionalized nucleosides that belong to the so-called nonnucleoside RT inhibitors (NNRTIs). They exert their unique selectivity for HIV-1 through a specific interaction with the p51 subunit of HIV-1 RT. They are the first small molecules that seem to interfere with the dimerization process of the enzyme. This review covers the work carried out with this unique class of specific inhibitors of HIV-1 reverse transcriptase, including structure activity relationship studies (SAR), its mechanism of action, resistance studies, model of interaction with the enzyme, etc.

Synthesis of {1-[2′,5′-Bis-O-(t-butyldimethylsilyl)-β-d-xylo- and β-d-ribofuranosyl]thymine}-3′-spiro-5″-{4″-amino-1″,2″-oxathiole-2″,2″-dioxide} (TSAO). A novel type of specific anti-HIV agents

Abstract Reaction of O-mesylcyanohydrins of furanos-3′-ulosyl thymine with bases afforded β- d -xylo- and ribo-3′-substituted nucleosides. 2′-Deoxygenation of the selectively 5′-O-protected nucleoside gave the ribofuranosyl derivative of thymidine.

Targeting HIV entry through interaction with envelope glycoprotein 120 (gp120): synthesis and antiviral evaluation of 1,3,5-triazines with aromatic amino acids.

On the basis of the interesting inhibitory properties that lectins show against HIV-replication through their interaction with glycoprotein 120 (gp120), we here describe the design, synthesis, and anti-HIV evaluation of three series of 1,3,5-triazine derivatives (monomers, dimers, and trimers) functionalized with aromatic amino acids meant to mimic interactions that lectins establish with gp120. While monomers were inactive against HIV replication, dimers showed limited anti-HIV activity that is, however, considerably more significant in the trimers series, with EC(50) values in the lower μM range. These findings most likely reflect the requirement of multivalency of the 1,3,5-triazine derivatives to display anti-HIV activity, as lectins do. The pronounced anti-HIV activity (EC(50) ∼ 20 μM) is accompanied by the absence of toxicity in CEM T-cell line (CC(50) > 250 μM). Moreover, SPR experiments revealed that the prototype trimers with a central core of 2,4,6-triethylbenzene and six l-Trp or six l-Tyr residues at the periphery were efficient binders of CXCR4- and CCR5-tropic HIV-1 gp120 (estimated K(D): lower micromolar range). The collected data support the interest of this novel family of anti-HIV agents and qualify them as potential novel microbicide lead compounds.

Hiv-1 Specific Reverse Transcriptase Inhibitors: why are Tsao-Nucleosides so Unique?

1. INTRODUCTION AIDS will still be one of the most important challenges for the Scientific Community in the approaching new century. Since the identification, in 1983-84,1,2 of human immunodeficiency virus (HIV) as the etiological agent of AIDS, significant progress has been made in the treatment of HIV-infected patients. This has been in part due to the discovery and clinical use of an increasing number of anti-HIV drugs. However, while highly active antiretroviral therapy (HAART)3 approaches have reduced the morbidity and mortality, the intertwined problems of drug induced viral resistance, poor compliance with complex regimens and therapy failure continue. Therefore, there remains a pressing need for the development of new antiviral agents that can be used not only as first line therapeutic candidates, but also in the antiretroviral-experienced patient population.

Exploitation of the Low Fidelity of Human Immunodeficiency Virus Type 1 (HIV-1) Reverse Transcriptase and the Nucleotide Composition Bias in the HIV-1 Genome To Alter the Drug Resistance Development of HIV

ABSTRACT The RNA genome of the lentivirus human immunodeficiency virus type 1 (HIV-1) is significantly richer in adenine nucleotides than the statistically equal distribution of the four different nucleotides that is expected. This compositional bias may be due to the guanine-to-adenine (G→A) nucleotide hypermutation of the HIV genome, which has been explained by dCTP pool imbalances during reverse transcription. The adenine nucleotide bias together with the poor fidelity of HIV-1 reverse transcriptase markedly enhances the genetic variation of HIV and may be responsible for the rapid emergence of drug-resistant HIV-1 strains. We have now attempted to counteract the normal mutational pattern of HIV-1 in response to anti-HIV-1 drugs by altering the endogenous deoxynucleoside triphosphate pool ratios with antimetabolites in virus-infected cell cultures. We showed that administration of these antimetabolic compounds resulted in an altered drug resistance pattern due to the reversal of the predominant mutational flow of HIV (G→A) to an adenine-to-guanine (A→G) nucleotide pattern in the intact HIV-1-infected lymphocyte cultures. Forcing the virus to change its inherent nucleotide bias may lead to better control of viral drug resistance development.

TSAO Derivatives, Inhibitors of HIV-1 Reverse Transcriptase Dimerization: Recent Progress

There is an urgent need for the development of new and safer drugs for the treatment of HIV (human immunodeficiency virus) infection, active against the currently resistant viral strains or directed to novel targets in the viral replicative cycle that may be useful for multiple drug combination. TSAO derivatives are a peculiar group of highly functionalized nucleosides that belong to the so-called nonnucleoside RT inhibitors (NNRTIs). HIV-1 reverse transcriptase (RT) is a key enzyme that plays an essential and multifunctional role in the life cycle of the virus and thus represents a key target for antiviral chemotherapeutic intervention. The dimeric form of the enzyme is absolutely required for all enzymatic activities. Thus, the process of dimerization and subsequent maturation into the p66/p51 heterodimer is essential for a fully functional RT and constitutes a target for therapeutic intervention, however to date such agents have not been developed. TSAO molecules are a peculiar group of non-nucleoside RT inhibitors that exert a unique selectivity for HIV-1 through a specific interaction with the p51 subunit of HIV-1 RT. They interact at the p66/p51 heterodimer interface of the enzyme. They were the first small non peptidic molecules shown to interfere with the dimerization process of the enzyme. This review covers the recent work within this family of compounds aimed at enhancing their interaction with the dimer interface of HIV-1 RT.

Tryptophan dendrimers that inhibit HIV replication, prevent virus entry and bind to the HIV envelope glycoproteins gp120 and gp41

Dendrimers containing from 9 to 18 tryptophan residues at the peryphery have been efficiently synthesized and tested against HIV replication. These compounds inhibit an early step of the replicative cycle of HIV, presumably virus entry into its target cell. Our data suggest that HIV inhibition can be achieved by the preferred interaction of the compounds herein described with glycoproteins gp120 and gp41 of the HIV envelope preventing interaction between HIV and the (co)receptors present on the host cells. The results obtained so far indicate that 9 tryptophan residues on the periphery are sufficient for efficient gp120/gp41 binding and anti-HIV activity.

Improving the selectivity of acyclic nucleoside analogues as inhibitors of human mitochondrial thymidine kinase: replacement of a triphenylmethoxy moiety with substituted amines and carboxamides.

Two series of analogues of the novel human mitochondrial thymidine kinase inhibitor 1-[(Z)-4-(triphenylmethoxy)-2-butenyl]thymine were synthesized by replacing the triphenylmethoxy moiety by a variety of substituted amines and carboxamides. In all the cases, the selectivity against the mitochondrial enzyme was either maintained or improved, and several derivatives were almost as potent as the parent compound. A molecular model was built that can account for the observed selectivities.

Metabolism and pharmacokinetics of the anti-HIV-1-specific inhibitor [1-[2′,5′-Bis-O-(tert-butyldimethylsilyl)-β-d-ribofuranosyl]-3-N-methyl-thymine]-3′-spiro-5″-(4″-amino-1″,2″-oxathiole-

[1-[2′,5′-Bis-O-(tert-butyldimethylsilyl)-β-D-ribofuranosyl]-3-N-methyl-thymine]-3′-spiro-5″-(4″-amino-1″,2″-oxathiole-2″ (TSAO-m3T) is a potent, selective and specific inhibitor of human immunodeficiency virus type 1 replication in vitro. Uptake of TSAO-m3T by human CEM cells is drug concentration-dependent and increased proportionally with increasing initial extracellular TSAO-m3T concentrations up to 20 μg/mL. Within 6 hr of incubation, the cells were almost completely saturated with the test compound; further incubation up to 72 hr did not markedly increase the intracellular concentration of the compound. No intracellular metabolic conversion of TSAO-m3T was observed in CEM, MT-4 or MOLT-4 cells. Upon intravenous bolus administration of TSAO-m3T to mice at 0.75 mg/kg, TSAO-m3T was rapidly cleared from the plasma in a mono-exponential manner (half-life: 22 min; distribution volume: 9.5 L/kg; total body clearance: 17.8 L/hr/kg). TSAO-m3T mainly accumulated in the lungs, followed by the heart, kidney and liver. Significant amounts of different metabolites of TSAO-m3T were detected in most tissues, the liver, kidney and spleen being the organs that showed the most extensive metabolism. The principal metabolites identified were TSAO-m3T derivatives in which the t-butyldimethylsilyl moiety at C-2′ and/or C-5′ had been split off. The free base N3-methylthymine was not detected.

Novel N-3 substituted TSAO-T derivatives: synthesis and anti-HIV-evaluation.

Novel derivatives of the anti-HIV-1 agent, TSAO-T, bearing at the N-3 position alkylating groups or photoaffinity labels were prepared and evaluated for their anti-HIV activity. All of these compounds demonstrated pronounced anti-HIV-1 activity and inhibited HIV-1 RT; however, we were unable to detect stable covalent linkages between inhibitor and enzyme. In addition, compounds with an alcohol functional group connected to the N-3 position through a cis or trans double bond have been prepared. These compounds have been useful to study how the conformational restriction of the linker affects in the interaction between the N-3 substituent and the HIV-1 RT enzyme.