The relationship between incorporation of E-5-(2-Bromovinyl)-2'-deoxyuridine into herpes simplex virus type 1 DNA with virus infectivity and DNA integrity

E-5-(2-Bromovinyl)-2'-deoxyuridine (BrvdUrd) produced a dose-dependent shift in the density of herpes simplex virus type 1 (HSV-1) DNA at concentrations which yielded potent inhibition of virus replication in cultured Vero cells. Although the density of cellular DNA was not altered by these concentrations of BrvdUrd, incorporation of this analogue into cellular DNA of HSV-1-infected cells has been previously observed in this laboratory. The degree of inhibition correlated with the amount of BrvdUrd substituted for thymidine in HSV-1 DNA. BrvdUrd-substituted DNA was more labile as determined by a dose-dependent increase in single strand breaks when examined by centrifugation in alkaline sucrose gradients. Thus, the potent antiviral action of BrvdUrd observed in cell culture correlates not only with its incorporation into HSV-1 DNA but also with an altered stability of this DNA.     

Inhibitory effect of E-5-(2-bromovinyl)-1-beta-D-arabinofuranosyluracil on herpes simplex virus replication and DNA synthesis.

The effect of E-5-(2-bromovinyl)-1-beta-D-arabinofuranosyluracil (BVaraU) on herpes simplex virus (HSV) replication was examined and compared with that of E-5-(2-bromovinyl)-2'-deoxyuridine (BVdUrd). The 50% inhibitory dose against HSV type 1 (HSV-1) was 0.1 microgram/ml compared with 0.008 microgram/ml for BVdUrd; the antimetabolic 50% inhibitory dose of BVaraU ranged from 20 to 95 micrograms/ml. The addition of 50 micrograms of BVaraU per ml to HSV-1-infected Vero cells decreased the synthesis of viral and cellular DNA by 37 and 28%, respectively. The 5'-triphosphate (BVaraUTP) competed with dTTP in DNA synthesis by the herpes-viral and cellular DNA polymerases; the apparent Ki values of HSV-1 DNA polymerase, DNA polymerase alpha, and DNA polymerase beta were 0.14, 0.32, and 5 microM, respectively. Thus, BVaraU was a less effective antiherpesvirus agent than BVdUrd; unlike BVdUrd, it did not appear to be internally incorporated into replicating DNA in virus-infected cells.     

A comparison of the conformations adopted by some 5-bromovinyl-2''-deoxyuridines and a correlation with their antiviral properties: an X-ray study.

Crystal structures of (Z)-5-(2-bromovinyl)-2'-deoxyuridine, 3',5'-di-O-acetyl-(E)-5-(2-bromovinyl)-2'-deoxyuridine and 3',5'-di-O-p-chlorobenzoyl-5-(2-dibromovinyl)-2'-deoxyuridine are compared with each other and with that of the most potent antiviral agent (E)-5-(2-bromovinyl)-2'-deoxyuridine (E-BVDU) reported earlier. A comparison of the conformation of 3',5'-di-O-acetyl-pyrimidine nucleoside structures in which intermolecular hydrogen bond network formation is minimized, with those of their parent compounds has shown that the greatest change in rotation about the glycosyl bond and in the sugar ring pucker is exhibited by E-BVDU. Upon acylation this molecule changes from C2'-endo/C3'-exo conformation to C3'-endo/C4'-exo conformation. The relevance of these structures upon the biological activity of the nucleosides and in particular to their ability to be a substrate for thymidine kinase is discussed.     

Antiviral Activity of 1-β-D-Arabinofuranosyl-E-5-(2-Bromovinyl)Uracil against Thymidine Kinase Negative Strains of Varicella-Zoster Virus

Mechanism of antiviral activity of 1-β-d -arabinofuranosyl-E-5-(2-bromovinyl)uracil (BV-araU) against the YSR strain of varicella-zoster virus (VZV), which is a mutant derived from the wild YS strain and is completely deficient in viral thymidine kinase (TK), was searched in comparison with antiviral activity of other thymidine analogues, guanosine analogue and thymidylate synthase (TS) inhibitor in human embryo lung fibroblast cells. Thymidine analogues, such as BV-araU, 5-iododeoxyuridine (IUDR), 1-β-d -arabinofuranosylthymine (araT), and guanosine analogue, such as 9-(2-hydroxyethoxymethyl)guanine (ACV), showed higher antiviral activity to the YS strain than to the YSR strain. Though, BV-araU also had the antiviral activity of a microgram level against the YSR strain. In contrast to these results, TS inhibitor, 5-fluorodeoxyuridine (FUDR), had higher antiviral activity to the YSR strain than to the YS strain. Highly synergistic antiviral activities of FUDR to the YS strain and the YSR strain were observed in combination with IUDR, araT, or ACV. However, weakly synergistic or additive inhibition to the YSR strain was shown in combination of BV-araU and FUDR, in spite of highly synergistic effect of this combination to the YS strain. The viral and cellular TS activity was partially inhibited by BV-araU monophosphate, but not by BV-araU. These results indicate that BV-araU is converted into BV-araU monophosphate by cellular TK, and the inhibition of TS activity by BV-araU monophosphate in the YSR strain-infected cells results in the suppression of viral replication.     

Synthesis and Biological Properties of (+) and (-)-(E)-5-(2-bronovinyl)-21 -deoxy-11 a-Carbauridine

Abstract

Carbocyclic (+)- and (-)-(E)-5- (2-bromovinyl)-2′-deoxyuridlne have been prepared from (+)- and (-)-endo-norborn-5-en-2-y1 butyrate. In cell cultures both (+)- and (-)-C-BVDU showed activity against herpes simplex virus types 1 and 2, (+)-C-BVDU being only slightly less active than BVDU itself. (-)-C-BVDU gave a smaller but still significant antiviral effect. A nomenclature for carbocyclic nucleosides is proposed.     

Combined action of nucleosides and alpha-interferon in inhibiting the reproduction of the herpes simplex type-II virus

Therapeutic effect of four combinations of antiherpetic chemical preparations--acyclovir (ACV), 9-beta-D-arabinofuranosyladenine (ARA-A) and E-5-(2-bromovinyl)-2'-desoxyuridine (BVDU)--has been studied. Mutual enhancement was observed in all the combinations studied, except for ACV and ARA-A combination, where partial antagonism was observed. ACV + BVDU was shown to be the most optimal combination, with the minimum inhibitory concentration (MIC) of BVDU decreasing 400-fold. A significant enhancement of nucleosides antiviral effect was noted when the human leucocyte interferon was used with the combinations. Along with synergistic effect during the interaction of alpha-interferon with ACV the antagonism in the combination of alpha-interferon with ARA-A was observed.     

Murine mammary FM3A carcinoma cells transformed with the herpes simplex virus type 1 thymidine kinase gene are highly sensitive to the growth-inhibitory properties of (E)-5-(2-bromovinyl)-2'-deoxyuridine and related compounds

Murine mammary carcinoma (FM3A TK-/HSV-1 TK+) cells, which are thymidine kinase (TK)-deficient but have been transformed with the herpes simplex virus type 1 (HSV-1) TK gene are inhibited in their growth by (E)-5-(2-bromovinyl)-2'-deoxyuridine (BVDU), (E)-5-(2-iodovinyl)-2'-deoxyuridine (IVDU) and (E)-5-(2-bromovinyl)-2'-deoxycytidine (BVDC) at 0.5, 0.5 and 0.8 ng/ml, respectively; i.e., a concentration 5000 to 20 000-fold lower than that required to inhibit the growth of the corresponding wild-type FM3A/0 cells. Hence, transformation of tumor cells with the HSV-1 TK gene makes them particularly sensitive to the cytostatic action of BVDU and related compounds.     

(E)-5-(2-bromovinyl)-2'-deoxyuridine-5'-triphosphate as a DNA polymerase substrate.

Time course of incorporation and the effect of 5'-triphosphate of the selective antiherpetic agent (E)-5-(2-bromovinyl)-2'-deoxyuridine (bv5dUTP) on the incorporation of dTTP and dATP into template-primers of different structure were studied in E. coli DNA polymerase I Klenow fragment enzyme-catalyzed reactions. bv5dUTP could substitute for dTTP depending on the structure of template-primer. E.g. into calf thymus DNA incorporation of bv5dUMP was around 80% of that of dTMP at 30 minutes of incubation. The analog has also inhibited dTMP incorporation, net DNA synthesis, however, was hardly affected. The substrate properties of the analog were studied with [2-14C]-labelled bv5dUTP.     

Crystal structure of varicella zoster virus thymidine kinase

Herpes virus thymidine kinases are responsible for the activation of nucleoside antiviral drugs including (E)-5-(2-bromovinyl)-2'-deoxyuridine. Such viral thymidine kinases (tk), beside having a broader substrate specificity compared with host cell enzymes, also show significant variation in nucleoside phosphorylation among themselves. We have determined the crystal structure of Varicella zoster virus (VZV, human herpes virus 3) thymidine kinase complexed with (E)-5-(2-bromovinyl)-2'-deoxyuridine 5'-monophosphate and ADP. Differences in the conformation of a loop region (residues 55-61) and the position of two alpha-helices at the subunit interface of VZV-tk compared with the herpes simplex virus type 1 (human herpes virus 1) enzyme give rise to changes in the positioning of residues such as tyrosine 66 and glutamine 90, which hydrogen bond to the substrate in the active site. Such changes in combination with the substitution in VZV-tk of two phenylalanine residues (in place of a tyrosine and methionine), which sandwich the substrate pyrimidine ring, cause an alteration in the positioning of the base. The interaction of the (E)-5-(2-bromovinyl)-2'-deoxyuridine deoxyribose ring with the protein is altered by substitution of tyrosine 21 and phenylalanine 139 (analagous to herpes simplex virus type 1 histidine 58 and tyrosine 172), which may explain some of the differences in nucleoside sugar selectivity between both enzymes. The altered active site architecture may also account for the differences in the substrate activity of ganciclovir for the two thymidine kinases. These data should be of use in the design of novel antiherpes and antitumor drugs.     

Regeneration of the antiviral drug (E)-5-(2-bromovinyl)-2''-deoxyuridine in vivo

The highly potent and selective antiherpes drug BVdUrd [(E)-5-(2-bromovinyl)-2'-deoxyuridine] is cleared within 2-3 hours from the bloodstream upon intraperitoneal administration to rats. It is degraded to BVUra [(E)-5-(2-bromovinyl)uracil] and this inactive metabolite is cleared very slowly from the bloodstream so that 24 hours after the administration of BVdUrd, BVUra is still detectable in the plasma. This contrasts with several other 5-substituted uracils, i.e. 5-fluorouracil, 5-iodouracil, 5-trifluorothymine and thymine itself, which are, like their 2'-deoxyuridine counterparts FdUrd, IdUrd, F3dThd and dThd, cleared from the plasma within 2-3 hours. The injection of dThd or any of the other 5-substituted 2'-deoxyuridines at 3 hours after the injection of BVdUrd, that is at a time when BVdUrd has disappeared completely from the circulation, results in the re-apparition of BVdUrd in the plasma. Apparently, BVdUrd is regenerated from BVUra following the reaction catalyzed by pyrimidine nucleoside phosphorylases : BVUra + dThd----BVdUrd + Thy. BVdUrd can even be generated de novo if dThd (or FdUrd, IdUrd or F3dThd) are administered 3 hours after a preceding injection of BVUra. These findings represent a unique example of the (re)generation of an active drug from its inactive metabolite in vivo.     

Synthesis and antiviral activity assay of novel (E)-3',5'-diamino-5-(2-bromovinyl)-2',3',5'-trideoxyuridine

(E)-3',5'-diamino-5-(2-bromovinyl)-2',3',5'-trideoxyuridine (5), the diamino analogue of BVDU (1), was synthesized from BVDU. In contrast with BVDU, compound 5 did not show activity against herpes simplex virus or varicella-zoster virus.     

Effect of (E)-5-(2-bromovinyl)-2'-deoxyuridine on the growth and viral capsid antigen expression of Epstein-Barr virus-associated tumor (B-95-8) cells transplanted to nude mice

When persistently Epstein-Barr virus (EBV)-infected lymphoblastoid (B-95-8) cells were transplanted subcutaneously or intracerebrally to nude mice of either BALB/c or NIH background, tumors developed, and the tumor cells spontaneously expressed viral capsid antigen (VCA). This model was used to evaluate the in vivo anti-EBV activity of (E)-5-(2-bromovinyl)-2'-deoxyuridine (BVDU), a highly potent and selective antiherpes agent, which was recently shown to inhibit several parameters of EBV infection in vitro. When administered intraperitoneally at 200 mg/kg/day for 4 weeks, or 500 mg/kg/day for 2 weeks, starting immediately after B-95-8 cell inoculation, BVDU effectively reduced tumor growth and VCA expression of either subcutaneously or intracerebrally inoculated B-95-8 cells.     

Inhibition of terminal deoxynucleotidyltransferase by (E)-5-(2-bromovinyl)-2'-deoxyuridine 5'-triphosphate

(E)-5-(2-bromovinyl)-2'-deoxyuridine 5'-triphosphate (BVdUTP), known as a specific inhibitor of herpes simplex virus (type 1)-DNA polymerase, was found to be a potent inhibitor of the activity of terminal deoxynucleotidyltransferase (TdT) from calf thymus. BVdUTP was not an efficient substrate of TdT, but it inhibited the incorporation of normal deoxynucleotide substrates in competitive fashion at the nucleotide binding site of TdT molecule. The Ki value for BVdUTP (5 microM) was much less than the Km value for dGTP (83 microM), indicating stronger affinity of the inhibitor to TdT than that of the substrate. These results indicate the usefulness of BVdUTP as a potent inhibitor of TdT for elucidation of the reaction mechanism of this enzyme.     

Modified polynucleotides. VI. Properties of a synthetic DNA containing the anti-herpes agent (E)-5-(2-bromovinyl)-2''-deoxyuridine

A new modified polydeoxynucleotide, a copolymer of nucleotides of 2'-deoxyadenosine and the very efficacious anti-herpesvirus agent (E)-5-(2-bromovinyl)-2'-deoxyuridine was synthesized with E. coli DNA polymerase I enzyme. It is characterized by its physical (absorption and circular dichroism spectra, thermal transition, sedimentation analysis) and bioorganic (template activity, stability) properties. Compared to poly [d(A-T)], the modified polydeoxynucleotide had a lower thermal stability but exhibited higher stability against DNases and higher template activity for DNA synthesis. Template activity for RNA synthesis of this template was, however, poor and extent of AMP and UMP incorporation was limited as well.     

Inhibitory activity of (E)-5-(2-bromovinyl)-2'-deoxyuridine on the salmonid herpesviruses, Oncorhynchus masou virus (OMV) and Herpesvirus salmonis

The highly potent and selective anti-herpesvirus agent, (E)-5-(2-bromovinyl)-2'deoxyuridine (BVdU), was examined for its inhibitory effect on the salmonid herpesviruses Oncorhynchus masou virus (OMV) and Herpesvirus salmonis (H. salmonis). Minimum inhibitory concentrations (MIC) of BVdU for OMV and H. salmonis were 1.25 and 3.0 micrograms/ml, respectively; these values were equal to or higher than those obtained for acyclovir or cytarabine. OMV DNA polymerase activity was reduced in a dose-dependent fashion by BVdU 5'-triphosphate (BVdUTP) within the concentration range of 3 to 30 microM. However, BVdUTP could also be substituted for the natural substrate, TTP, in the OMV DNA polymerase assay. It is postulated that the inhibitory action of BVdU on the salmonid herpesviruses is more or less similar to that on other herpesviruses and resides with respect to the inhibition of the virus DNA polymerase activity as well as incorporation of BVdU into the viral DNA.     

High-performance liquid chromatographic determination of 1-β- -arabinofuranosyl-E-5-(2-bromovinyl)uracil and its metabolite (E)-5-(2-bromovinyl)uracil in serum

A high-performance liquid chromatographic method was developed to assay 1-β- -arabinofuranosyl-E-5-(2-bromovinyl)uracil and its metabolite (E)-5-(2-bromovinyl)uracil in serum. The chloro analogue of the parent drug is used as internal standard. Human serum samples were assayed to establish the pharmacokinetic parameters. Acetonitrile, used as a protein precipitant, was evaporated to dryness and the residue, containing the analytes and internal reference, was dissolved in mobile phase prior to chromatographic analysis. The minimum quantifiable level was 0.02 μg of each analyte per ml of serum.     

Antiviral activity of the 3''-amino derivative of (E)-5-(2-bromovinyl)-2''-deoxyuridine.

3'-NH2-BV-dUrd, the 3'-amino derivative of (E)-5-(2-bromovinyl)-2'-deoxyuridine, was found to be a potent and selective inhibitor of herpes simplex virus type 1 (HSV-1) and varicella-zoster virus (VZV) replication. 3'-NH2-BV-dUrd was about 4-12 times less potent but equally selective in its anti-herpes activity as BV-dUrd. Akin to BV-dUrd, 3'-NH2-BV-dUrd was much less inhibitory to herpes simplex virus type 2 than type 1. It was totally inactive against a thymidine kinase-deficient mutant of HSV-1. The 5'-triphosphate of 3'-NH2-BV-dUrd (3'-NH2-BV-dUTP) was evaluated for its inhibitory effects on purified herpes viral and cellular DNA polymerases. Among the DNA polymerases tested, HSV-1 DNA polymerase and DNA polymerase alpha were the most sensitive to inhibition by 3'-NH2-BV-dUTP (Ki values 0.13 and 0.10 microM, respectively). The Km/Ki ratio for DNA polymerase alpha was 47, as compared with 4.6 for HSV-1 DNA polymerase. Thus, the selectivity of 3'-NH2-BV-dUrd as an anti-herpes agent cannot be ascribed to a discriminative effect of its 5'-triphosphate at the DNA polymerase level. This selectivity most probably resides at the thymidine kinase level. 3'-NH2-BV-dUrd would be phosphorylated preferentially by the HSV-1-induced thymidine kinase (Ki 1.9 microM, as compared with greater than 200 microM for the cellular thymidine kinase), and this preferential phosphorylation would confine the further action of the compound to the virus-infected cell.     

Potent inhibitory effects of the 5'-triphosphates of (E)-5-(2-bromovinyl)-2'-deoxyuridine and (E)-5-(2-bromovinyl)-1-beta-D-arabinofuranosyluracil on DNA polymerase gamma

(E)-5-(2-Bromovinyl)-2'-deoxyuridine 5'-triphosphate (BrVdUTP) and (E)-5-(2-bromovinyl)-1-beta-D-arabinofuranosyluracil 5'-triphosphate (BrVarafUTP), which are known as specific inhibitors of herpes simplex viral (type 1 and 2) DNA polymerase, were found to be strong inhibitors of DNA polymerase gamma from human KB and murine myeloma cells. In fact BrVdUTP and BrVarafUTP were found to be stronger inhibitors of DNA polymerase gamma than of other DNA polymerases having viral (herpes simplex virus or retrovirus) origin or cellular (eukaryotic alpha and beta, or prokaryotic) origin. The mode of inhibition of DNA polymerase gamma by BrVdUTP and BrVarafUTP was competitive with respect to dTTP, the normal substrate. Whereas BrVdUTP was an efficient substrate for DNA polymerase gamma and other DNA polymerases that were examined, BrVarafUTP failed to serve as a substrate for DNA synthesis. Ki values for BrVdUTP (40 nM) and BrVarafUTP (7 nM) with DNA polymerase gamma, as determined with (rA)n.(dT) as the template.primer, were much smaller than the Km values for dTTP (0.16 microM and 0.71 microM for murine and human DNA polymerase gamma, respectively). Thus, the affinity of BrVdUTP or BrVarafUTP for DNA polymerase gamma was much stronger than that of dTTP.     

Selective inhibition of the proliferation of herpes simplex virus type 1 thymidine kinase gene-transformed murine mammary FM3A carcinoma cells by (E)-5-(2-bromovinyl)-2'-deoxyuridine and related compounds

Mouse mammary carcinoma FM3A cells deficient in thymidine kinase were transformed by a cloned gene for herpes simplex virus type 1 thymidine kinase. Among several anti-herpetic nucleoside analogues, (E)-5-(2-bromovinyl)-2'-deoxyuridine, (E)-5-(2-iodovinyl)-2'-deoxyuridine and (E)-5-(2-bromovinyl)-2'-deoxycytidine inhibited the growth of the transformed cells at concentrations 5000- to 20000-fold lower than those required to inhibit the growth of the corresponding wild-type cells. The selective inhibitory action of these compounds was due to a specific phosphorylation by the viral thymidine kinase. From the transformed cells, thymidine-auxotrophic mutants that are deficient in thymidylate synthase were isolated. These mutant cell lines should prove useful in elucidating the mechanism of action of the antiherpetic nucleoside analogues.     

Differential effect of nucleoside analog triphosphates on ribonucleotide reductases from uninfected and herpes simplex virus-infected HeLa cells.

Effects of the triphosphates of eight pyrimidine nucleoside analogs (5-substituted, 2'-fluoroara-, and acyclonucleosides) and acycloguanosine were examined on the ribonucleotide reductases prepared from uninfected and herpes simplex virus (types 1 and 2)-infected HeLa cells. Of the analogs tested, E-5-propenyl- and E-5-(2-bromovinyl)-dUTP were more potent inhibitors than dTTP of the enzymes from virus-infected cells, whereas only the former compound showed this effect on the uninfected HeLa enzyme.