E. De Clercq

Antiviral and antimetabolic activities of neplanocins

Of a series of carbocyclic analogs of adenosine, in which the ribose moiety was replaced by a cyclopentenyl ring, neplanocin A, or (-)-9-[trans-2, trans-3-dihydroxy-4-(hydroxymethyl)cyclopent-4-enyl]adenine proved particularly effective in inhibiting the multiplication of DNA viruses (i.e., vaccinia), (-)RNA viruses (i.e., parainfluenza, measles, and vesicular stomatitis), and double-stranded RNA viruses (i.e., reo) in vitro in cell culture. Depending on the cells used, the MIC of neplanocin A for these viruses ranged from 0.01 to 4 micrograms/ml, and depending on the parameter used to assess toxicity for the host cell, the specificity index of neplanocin A ranged from 50 to 4,000. As postulated before for other adenosine analogs, neplanocin A may owe its antiviral action to inhibition of S-adenosylhomocysteine hydrolase, hence perturbation of transmethylation reactions. In vivo, neplanocin A afforded only marginal protection against a lethal infection of mice with vesicular stomatitis virus.Of a series of carbocyclic analogs of adenosine, in which the ribose moiety was replaced by a cyclopentenyl ring, neplanocin A, or (-)-9-[trans-2, trans-3-dihydroxy-4-(hydroxymethyl)cyclopent-4-enyl]adenine proved particularly effective in inhibiting the multiplication of DNA viruses (i.e., vaccinia), (-)RNA viruses (i.e., parainfluenza, measles, and vesicular stomatitis), and double-stranded RNA viruses (i.e., reo) in vitro in cell culture. Depending on the cells used, the MIC of neplanocin A for these viruses ranged from 0.01 to 4 micrograms/ml, and depending on the parameter used to assess toxicity for the host cell, the specificity index of neplanocin A ranged from 50 to 4,000. As postulated before for other adenosine analogs, neplanocin A may owe its antiviral action to inhibition of S-adenosylhomocysteine hydrolase, hence perturbation of transmethylation reactions. In vivo, neplanocin A afforded only marginal protection against a lethal infection of mice with vesicular stomatitis virus.

Antiretrovirus Activity of a Novel Class of Acyclic Pyrimidine Nucleoside Phosphonates

ABSTRACT A novel class of acyclic nucleoside phosphonates has been discovered in which the base consists of a pyrimidine preferably containing an amino group at C-2 and C-4 and a 2-(phosphonomethoxy)ethoxy (PMEO) or a 2-(phosphonomethoxy)propoxy (PMPO) group at C-6. The 6-PMEO 2,4-diaminopyrimidine (compound 1) and 6-PMPO 2,4-diaminopyrimidine (compound 11) derivatives showed potent activity against human immunodeficiency virus (HIV) in the laboratory (i.e., CEM and MT-4 cells) and in primary (i.e., peripheral blood lymphocyte and monocyte/macrophage) cell cultures and pronounced activity against Moloney murine sarcoma virus in newborn NMRI mice. Their in vitro and in vivo antiretroviral activity was comparable to that of reference compounds 9-[(2-phosphonomethoxy)ethyl]adenine (adefovir) and (R)-9-[(2-phosphonomethoxy)-propyl]adenine (tenofovir), and the enantiospecificity of (R)- and (S)-PMPO pyrimidine derivatives as regards their antiretroviral activity was identical to that of the classical (R)- and (S)-9-(2-phosphonomethoxy)propyl purine derivatives. The prototype PMEO and PMPO pyrimidine analogues were relatively nontoxic in cell culture and did not markedly interfere with host cell macromolecular (i.e., DNA, RNA, or protein) synthesis. Compounds 1 and 11 should be considered attractive novel pyrimidine nucleotide phosphonate analogues to be further pursued for their potential as antiretroviral agents in the clinical setting.

Synthesis and anti-HIV activity of 4-[(1,2-dihydro-2-oxo-3H-indol-3-ylidene) amino]-N(4,6-dimethyl-2-pyrimidinyl)-benzene sulfonamide and its derivatives.

4-[(1,2-Dihydro-2-oxo-3H-indol-3-ylidene) amino]-N(4,6-dimethyl-2-pyrimidinyl)-benzene sulphonamide and its derivatives were synthesized by reaction of isatin and its derivatives with sulphadimidine. Their chemical structures have been confirmed by IR, (1)H NMR data and elemental analysis. Investigation of anti-HIV activity of compounds were tested against replication of HIV-1 (IIIB) and HIV-2 (ROD) strains in acutely infected MT-4 cells and the activity compared with standard azidothymidine. Among the compounds tested, 4-[(1,2-dihydro-2 oxo-3H-indol-3-ylidene)amino]-N(4,6-dimethyl-2-pyrimidinyl)-benzene sulphonamide and its N-acetyl derivative were the most active compounds.

Differential antiviral activity of derivatized dextrans

The antiviral activity of water-soluble dextrans derivatized with varying percentages of carboxymethyl, benzylamide, and sulfonate groups was evaluated. Several of the polymers exhibited potent antiviral activity against a variety of enveloped viruses, but not against non-enveloped viruses, and only when present during virus adsorption. The mechanism of activity against retroviruses [i.e. human immunodeficiency virus (HIV)] and herpes viruses (i.e. human cytomegalovirus) could be ascribed to inhibition of virus binding to the cells. An absolute requirement for anti-HSV activity appeared to be a sufficiently high percentage of benzylamide and benzylamide sulfonate groups. This did not, however, apply for human cytomegalovirus, respiratory syncytial virus, and HIV. The sensitivity of the latter viruses appeared to be influenced by factors other than the global chemical composition, which leads us to assume that physical factors such as the distribution and sequence of the substituents on the sugar backbone play an important role in the antiviral activity of the derivatized dextrans.

Anti-HIV Activity of Thiosemicarbazone and Semicarbazone Derivatives of (±)-3-Menthone

A series of thiosemicarbazones and semicarbazone derivatives of (±)‐3‐menthone have been synthesized and their anti‐HIV activity evaluated against HIV‐1(IIIB)and HIV‐2 (ROD). The studies revealed that maximum protection is offered by chloro‐substituted derivatives 2 and 7 against HIV‐1 (IIIB) and HIV‐2 (ROD).

ENHANCED INHIBITION OF HIV-1 REPLICATION IN MACROPHAGES BY ANTISENSE OLIGONUCLEOTIDES, RIBOZYMES AND ACYCLIC NUCLEOSIDE PHOSPHONATE ANALOGS DELIVERED IN pH-SENSITIVE LIPOSOMES

An antisense oligodeoxynucleotide against the human immunodeficiency virus type 1 (HIV-1) Rev response element, a ribozyme complementary to the HIV-1 5′-LTR, and the reverse transcriptase inhibitors 9-(2-phosphonylmethoxyethyl) adenine (PMEA) and(R)-9-(2-phosphonylmethoxypropyl)-adenine (PMPA) inhibited virus replication in monocyte-derived macrophages more effectively when delivered in pH-sensitive liposomes compared to the free drugs.

Synthests and Biological Evaluation of a Series of Substituted-2-Pyridine-C-Nucleosides. Part II

Abstract A cyclistation reaction of the D-allo- and D-altro isomers of 2-(2, 4:3, 5′-di-O-benzylidenepentitol-1-yl)pyridine derivatives to afford the corresponding substituted 2-(D-ribofuranosyl) pyridine-C-nucleosides, was investigated. The latter compounds were obtained in good yield (90%) if the reaction was performed in 1 N HCI. The structures were confirmed by 13C-NMR studies and an HPLC method with was developed specifically for a determination of their purity. All compounds were evaluated for biological activity in a variety of antiviral and antitumor cell systems in vitro.

In vitro Activity of a Novel Series of Polyoxosilicotungstates against Human Myxo-, Herpes- and Retroviruses

A series of silicon-containing polyoxotungstates belonging to the ‘Keggin-type’ (‘Keggin’, ‘Keggin sandwich’) were evaluated for their antiviral activity against enveloped viruses (myxo-, herpes- and retroviruses). The compounds exhibited antiviral activity against influenza virus type A, respiratory syncytial virus (RSV), herpes simplex virus type-1 (HSV-1), type-2 (HSV-2), thymidine kinase-deficient (TIC) HSV-1, human cytomegalovirus (HCMV), human immunodeficiency virus type-1 (HIV-1) and type-2 (HIV-2) at concentrations that were well below their cytotoxic threshold. The ‘Keggin’ compound JM2815 (K5[Si-(TiCp)W11O39].12H2O) and the ‘Keggin sandwich’ compound JM1590 (K13[Ce(SiW11O39)2].26H2O) resulted in the highest selectivity indices against HIV-1 and HIV-2, and compound JM2820 ([Me3NH]8.[Si2Nb6W18O77]) was the most potent inhibitor of HSV and HCMV replication. These compounds proved active against HCMV and HSV when present during virus adsorption, and against influenza virus A and RSV when present after virus adsorption. Polyoxosilicotungstates inhibited the binding of radiolabeled HCMV particles to the cells at concentrations that were antivirally active, and the compounds were able to displace HCMV particles that were bound to a heparin-Sepharose matrix. Presumably, the polyoxosilicotungstates interact with positively charged domains on the viral envelope site(s) involved in the attachment of the (HCMV) virions to the cell surface receptor heparan sulphate.

Inhibition of African swine fever virus DNA synthesis by (S)-9-(3-hydroxy-2-phosphonylmethoxypropyl)adenine

The acyclic nucleotide analogue (S)-9-(3-hydroxy-2-phosphonylmethoxypropyl)adenine [(S)-HPMPA] is a potent and selective inhibitor of African swine fever virus (ASFV) replication. Using the DNA-DNA hybridization technique with plasmid pRPEL-2 as probe, we have shown that (S)-HPMPA exerts a specific, dose-dependent, inhibitory effect on viral DNA synthesis. Also, (S)-HPMPA inhibits the production of late viral proteins, especially IP-73, in ASFV-infected MS and Vero cells. When evaluated under the same experimental conditions, phosphonoacetic acid (PAA) also caused an inhibition of viral DNA and late viral protein synthesis but only so at a concentration which was 10- to 20-fold higher than that required for (S)-HPMPA.

Metabolism of EICAR (5-ethynyl-1-beta-D-ribofuranosylimidazole-4-carboxamide), a potent inhibitor of inosinate dehydrogenase

The cytostatic agent 5-ethynyl-l-β-D-ribofuranosylimidazole-4-carboxamide (EICAR) causes a rapid and marked inhibition of inosinate (IMP) dehydrogenase activity in intact tumor cells. [3H]EICAR is metabolised in L1210 cells to its 5′-mono-, 5′-di- and 5′-triphos-phate in a concentration-dependent manner. The metabolites accumulate proportionally with the initial extracellular EICAR concentrations (ranging from 0.25 to 200 μM). The nicoti-namide adenine dinucleotide (NAD) analogue of EICAR, designated EAD, also accumulates within the cells and becomes the major metabolite after 48 hr incubation with 5 μM [3H]EI-CAR. EAD has a markedly longer intracellular half-life than EICAR 5′-mono-, 5′-di- and 5′-triphosphate. An additional EICAR metabolite elutes on an anion exchange Partisphere SAXHPLC chromatogram between EICAR 5′-di- and 5′-triphosphate. Its intracellular levels are~10-fold lower than those of EAD and the nature of this metabolite has still to be identified. The differential role of EAD and EICAR 5′-monophosphate in the inhibition of IMP dehydrogenase is currently under investigation.