Antonia A. Nikitenko

RFI-641, a Potent Respiratory Syncytial Virus Inhibitor

ABSTRACT Human respiratory syncytial virus (RSV), a paramyxovirus, is a major cause of acute upper and lower respiratory tract infections in infants, young children, and adults. RFI-641 is a novel anti-RSV agent with potent in vitro and in vivo activity. RFI-641 is active against both RSV type A and B strains. The viral specificity and the large therapeutic window of RFI-641 (>100-fold) indicate that the antiviral activity of the compound is not due to adverse effects on normal cells. The potent in vitro activity of RFI-641 can be translated to efficacy in vivo: RFI-641 is efficacious when administered prophylactically by the intranasal route in mice, cotton rats, and African green monkeys. RFI-641 is also efficacious when administered therapeutically (24 h postinfection) in the monkey model. Mechanism of action studies indicate that RFI-641 blocks viral F protein-mediated fusion and cell syncytium formation.

RFI-641 inhibits entry of respiratory syncytial virus via interactions with fusion protein

BACKGROUND RFI-641, a small dendrimer-like compound, is a potent and selective inhibitor of respiratory syncytial virus (RSV), which is currently a clinical candidate for the treatment of upper and lower respiratory tract infections caused by RSV. RFI-641 inhibits RSV growth with an IC(50) value of 50 nM and prevents syncytia formation in tissue culture. RSV contains of three surface glycoproteins, a small hydrophobic (SH) protein of unknown function, and attachment (G) and fusion (F) proteins that enable binding and fusion of virus, respectively, with target cells. Because of their role in attachment and fusion, the G and F surface proteins are prominent targets for therapeutic intervention. RFI-641 was previously shown to bind purified preparations of RSV fusion protein. Based on this observation, in conjunction with the biological results, it was speculated that the fusion event might be the target of these inhibitors. RESULTS A fusion assay based upon the relief of self-quenching of octadecyl rhodamine R18 was used to determine effects of the inhibitors on binding and fusion of RSV. The results show that RFI-641 inhibits both RSV-cell binding and fusion events. The inhibition of RSV is mediated via binding to the fusion protein on the viral surface. A closely related analog, WAY-158830, which is much less active in the virus-infectivity assay does not inhibit binding and fusion of RSV with Vero cells. CONCLUSIONS RFI-641, an in vivo active RSV inhibitor, is shown to inhibit both binding and fusion of RSV with cells, events that are early committed steps in RSV entry and pathogenicity. The results described here demonstrate that a non-peptidic, small molecule can inhibit binding and fusion of enveloped virus specifically via interaction with the viral fusion protein.

The discovery of RFI-641 as a potent and selective inhibitor of the respiratory syncytial virus.

The design and synthesis of a new potent and selective inhibitor of the respiratory syncytial virus are described. This compound, RFI-641, emerged from analysis of the structure-activity relationship in a series of biphenyl triazine anionic compounds possessing specific anti-RSV activity. The key synthetic step involves coupling of diaminobiphenyl 11 with two equivalents of chlorotriazine 10 under microwave conditions. RFI-641 inhibited RSV in vitro and in vivo models.

Pyridone-Conjugated Monobactam Antibiotics with Gram-Negative Activity

Herein we describe the structure-aided design and synthesis of a series of pyridone-conjugated monobactam analogues with in vitro antibacterial activity against clinically relevant Gram-negative species including Pseudomonas aeruginosa , Klebsiella pneumoniae , and Escherichia coli . Rat pharmacokinetic studies with compound 17 demonstrate low clearance and low plasma protein binding. In addition, evidence is provided for a number of analogues suggesting that the siderophore receptors PiuA and PirA play a role in drug uptake in P. aeruginosa strain PAO1.

A novel reagent for regioselective cleavage of 2,3-epoxyalcohols by fluoride - a synthesis of 3-fluoro-293-dideoxy-d-erythro-pentose.

Abstract The cleavage of the oxirane ring of 3,4-anhydro-2deoxy-D-threo-pentose diethyl acetal by (isopropoxy)-titanium fluorides is discussed. The high regioselectivity found with bis(isopropoxy)titanium difluoride is the basis for an enantioselective synthesis of 3-fluoro-2,3-deoxy-D-erythreo-pentose from a non-carbohydrate precursor.

Synthesis of 3-substituted (azido, acylthio, chloro or fluoro)-2,3-dideoxy-D-erythro-pentoses and 3-methyl-3-substituted-2,3-dideoxy-D-erythro-pentoses

Abstract The enantioselective synthesis of 3-substituted and 3-methyl-3-substituted 2,3-dideoxy-D- erythro -pentoses from (3 R ,4 R )-1,1-diethoxy-3,4-epoxypentane-5-ol, (3 R ,4 R) -1,1-diethoxy-3,4-epoxy-3-methylpentane-5-ol and (2 R ,3 R )-2,3-epoxy-5-hexen-1-ol is reported. The key step is cleavage of the oxirane ring by Ti(O- i -Pr) 3 X class reagents followed by selective cyclization of the acyclic acetals to the furanosides. Fluorination with the complex of titanium (IV) iso -propoxide - titanium (IV) fluoride provides an enantioselective synthesis of 3-fluoro-2,3-dideoxy-D- erythro -pentose and 3-fluoro-3-methyl-2,3-dideoxy-D- erythro -pentose.

Total stereo- and enantio-selective synthesis of 2,3-dideoxy-3-C-methylene-D-glycero-pentose and its ethyl furanosides

Abstract A total stereo- and enantio-selective synthesis of 2,3-dideoxy-3- C -methylene- d - glycero -pentose and its ethyl furanosides is described. The key reaction of the synthesis is formation of the 3- C -methylene function by catalytic isomerisation of an epoxy alcohol, obtained by silylation of 3-methyl-2-butenal, followed by condensation of the silyl ether with triethyl orthoformate, reduction of the aldehydo group, and Sharpless asymmetric epoxidation of the allylic alcohol. The overall yield is 17% from commercially available 3-methyl-2-butenal as the starting compound.

Effect of A(1,3)-cis strain on the asymmetric epoxidation of (E)- and (Z)-6,6-diethoxy-3-hexen-2-ols and 4-methyl-6,6-diethoxy-3-hexen-2-ols

The effect of A(1,3)-cis strain on the diastereoselectivity of epoxidation of (E)-and (Z)-6,6-diethoxy-3-hexen-2-ols and 4-methyl-6,6-diethoxy-3-hexen-2-ols is analyzed, with some empiric observations provided. Increased A(1,3)-cis strain results in increased amounts of racemic threo-epoxy alcohols, while high ees are found for the erythro-epoxy alcohols.

Synthesis and crystal structure of 3′-fluoro-3′-methyl-2′,3′-dideoxythymidine. inhibitory properties of 3′-fluoro-3′-methyl-2′,3′-dideoxythymidine-5′-triphosphate in the synthesis of DNA in cell-free media

Abstract The synthesis, physicochemical properties and chain-termination properties of 3′-fluoro-3′-methyl-2′-3-dideoxythymidine is described. The synthesis was accomplished b the coupling of bis(TMS)thymine with 3-fluoro-3-methyl-2,3-dideoxy-D-erythro-pentose which is obtained from non-carbohydrate precursors.