Anti-herpesvirus activity of (1'S,2'R)-9-[[1',2'-bis(hydroxymethyl)-cycloprop-1'-yl]methyl] x guanine (A-5021) in vitro and in vivo

The novel nucleoside analog (1S',2R')-9-[[1',2'-bis(hydroxymethyl)cycloprop-1-yl]methyl]guanine (A-5021) was previously shown to be a potent inhibitor of the replication of herpes simplex virus type 1 and 2 (HSV-1 and HSV-2) and varicella zoster virus (VZV), both in vitro and in vivo (J. Med. Chem. 41, 1284-1298; Antimicrob. Agents Chemother. 42, 1666-1670). Here we demonstrate that A-5021 is also a potent inhibitor of Epstein-Barr virus (EBV) and human herpes virus 6 (HHV-6A and HHV-6B), but that the compound lacks activity against HHV-8. A-5021, in comparison to acyclovir, was also assessed for protective activity against HSV-1-induced mortality in SCID mice. The compounds were administered at 50 mg/kg per day by subcutaneous injection for four consecutive days and treatment was initiated at either 2 h, 1 or 2 days post infection (p.i.). When administered from day 0 to 4 p.i., A-5021 conferred complete protection against the infection (as assessed at 22 days p.i.), whereas acyclovir delayed virus induced mortality by only 5 days. When treatment was begun on day 1 or 2, A-5021 still afforded marked protection against the infection, whereas acyclovir was virtually devoid of any activity under these conditions. Our data underline that A-5021 may offer great promise for the treatment of herpesvirus infections.     

The anti-herpesvirus activity of (1'S,2'R)-9-[[1',2'-bis(hydroxymethyl)-cycloprop-1'-yl]methyl]guanine is markedly potentiated by the immunosuppressive agent mycophenolate mofetil

Mycophenolic acid (MPA), the active form of the immunosuppressive agent mycophenolate mofetil (MMF), was found to markedly potentiate the anti-herpesvirus activity of the novel anti-herpesvirus agent A-5021, (1'S,2'R)-9-[[1',2'-bis(hydroxymethyl)cycloprop-1'-yl]methyl]guanine. For example, at a concentration of 1 microg/ml MPA, the activity of A-5021 against HSV-1, HSV-2 and TK(-) HSV-1 increased by a factor of 130, 14 and > or = 189, respectively. Exogenously added guanosine reversed this potentiating effect, suggesting that a depletion of the endogenous dGTP pools enhanced the inhibitory effect of the 5'-triphosphate metabolite of A-5021 on the viral DNA polymerase. The combined effect of A-5021 and MPA on the growth of uninfected Vero cells was additive rather than synergistic. The combination of topically applied MMF (5%) with 0.05% A-5021 (a subactive concentration) completely protected against HSV-1-induced cutaneous lesions in hairless mice, whereas therapy with either compound used alone had no protective effect. These findings may have implications for those transplant recipients that receive MMF as (part of) their immunosuppressive therapy and that develop intercurrent herpesvirus infections for which they need treatment.     

Evaluation of the antiviral activity of (1'S,2'R)-9-[[1',2'-bis(hydroxymethyl)cycloprop-1'-yl]methyl]guanine (A-5021) against equine herpesvirus type 1 in cell monolayers and equine nasal mucosal explants

Equine herpesvirus 1 (EHV1) is a ubiquitous equine alphaherpesvirus that causes respiratory disease, neurological symptoms and abortions. Current vaccines are not fully protective and effective therapeutics are lacking. A-5021 [(1′S,2′R)-9-[[1′,2′-bis(hydroxymethyl)cycloprop-1′-yl]methyl]guanine], previously shown to possess potent anti-herpetic activity against most human herpesviruses, was evaluated for its potential to inhibit EHV1 replication. In equine embryonic lung (EEL) cells, infected with either a non-neurovirulent (97P70) or a neurovirulent (03P37) EHV1 isolate, A-5021 proved to be about 15-fold more potent than acyclovir in inhibiting viral replication. Moreover, in equine nasal mucosal explants, A-5021 (at 8 and 32 μM) was able to completely inhibit viral plaque formation whereas acyclovir did not exert an antiviral effect at these concentrations. Our data demonstrate that A-5021 is a potent inhibitor of EHV1 replication and may have potential for the treatment and/or prophylaxis of infections with this virus.     

Synthesis and antiherpetic activity of (S)-, (R)-, and (+/-)-9-[(2,3-dihydroxy-1-propoxy)methyl]guanine, linear isomers of 2'-nor-2'-deoxyguanosine

Racemic 9-[(2,3-dihydroxy-1-propoxy)methyl]guanine [(+/-)-iNDG], a new analogue of acyclovir (ACV) and a structural analogue of 2'-nor-2'-deoxyguanosine (2'NDG), was synthesized and found to inhibit the replication of herpes simplex virus types 1 (HSV-1) and 2 (HSV-2). Subsequently, its optical isomers, (R)- and (S)-iNDG, were prepared from chiral intermediates. The chloromethyl ethers of 1,2-di-O-benzyl-D- and -L-glycerol were made and reacted with tris(trimethylsilyl)guanine to give the 9-alkylated guanines, which were deprotected by catalytic hydrogenolysis. Against HSV-1 and HSV-2 in cell culture, (S)-iNDG was approximately 10- to 25-fold more active than the R enantiomer and had an ED50 comparable to those for ACV and 2'NDG. The inferior activity of (R)-iNDG paralleled the poor inhibition of viral DNA polymerase by its phosphorylation products. In mice infected intraperitoneally or orofacially with HSV-1 or intravaginally with HSV-2, (S)-9-[(2,3-dihydroxy-1-propoxy)methyl]guanine [(S)-iNDG] was less efficacious than 2'NDG but comparable to or more active than ACV.     

Synthesis and antiviral activity of 9-alkoxypurines. 2. 9-(2,3-Dihydroxypropoxy)-, 9-(3,4-dihydroxybutoxy)-, and 9-(1,4-dihydroxybut-2-oxy)purines.

Reaction of alkenoxyamines (3,5) or (R,S)-, (R)-, and (S)-hydroxy-protected derivatives of hydroxyalkoxyamines (20a,b, 37a-c) with 4,6-dichloro-2,5-diformamidopyrimidine (4) and cyclization of the resultant 6-[(alkenoxy)amino]-and 6-(alkoxyamino)pyrimidines (6,7,21a,b, 38a,b,c) by heating with diethoxymethyl acetate afforded 9-alkenoxy- and 9-alkoxy-6-chloropurines (9,10,22a,b, 39a-c, 40a). These were subsequently converted to 9-(2,3-dihydroxypropoxy), 9-(3,4-dihydroxybutoxy), and 9-(1,4-dihydroxybut-2-oxy) derivatives of guanine and 2-aminopurine (13-16, 25-28, 41a-c, 42a). A 2-amino-6-methoxypurine derivative (17) was also prepared. The racemic guanine derivative 13 showed potent and selective activity against herpes simplex virus types 1 and 2 (HSV-1 and HSV-2), but was less active against varicella zoster virus (VZV). Its antiviral activity is attributable to the S isomer (28), which was found to be more active than acyclovir against HSV-1 and HSV-2 and about 4 times less active than acyclovir against VZV. The S enantiomer of 9-(1,4-dihydroxybut-2-oxy)guanine (41c) also showed noteworthy antiviral activity in cell culture. Although this acyclonucleoside (41c) is only weakly active against HSV-1 and inactive against HSV-2, it is about twice as active as acyclovir against VZV.     

Broad-spectrum antiviral activity of the acyclic guanosine phosphonate (R,S)-HPMPG

(R,S)-9-(3-hydroxy-2-phosphonomethoxypropyl)guanine [(R,S)-HPMPG] exhibits broad spectrum antiviral activity with an ED50 of less than 1 microM against herpes simplex virus (HSV) types 1 and 2, varicella zoster virus, human cytomegalovirus (HCMV) and vaccinia in plaque reduction assays. Wild type HSV-2 and its thymidine kinase deficient variant are equally sensitive to (R,S)-HPMPG. (R,S)-HPMPG is 100-fold more potent than acyclovir (ED50 = 0.45 microM vs. 44 microM, respectively) against HCMV in cell culture, and 10-fold more active than acyclovir in extending survival time in mice intraperitoneally infected with 70 LD50 HSV-1. However, (R,S)-HPMPG is toxic when administered repeatedly at 44 mg/kg/day in uninfected adult mice. The diphosphoryl derivative of HPMPG was enzymatically synthesized and is a competitive inhibitor of HSV-1 DNA polymerase relative to dGTP (K1 = 0.03 microM). HPMPG-PP is 70-fold less active at inhibiting HeLa DNA polymerase alpha than HSV-1 DNA polymerase. At concentrations between 0.3 and 1.5 microM (R,S)-HPMPG inhibited HSV-1 DNA replication greater than or equal to 50% in infected cells as measured by nucleic acid hybridization. Consistent with inhibition of viral DNA synthesis, 6 to 30 microM (R,S)-HPMPG reduces late viral polypeptide synthesis in HSV-1 infected cells. These data indicate that (R,S)-HPMPG is a thymidine kinase independent broad spectrum antiviral drug which is capable of inhibiting viral DNA polymerase.     

Comparison of antiviral efficacies of 1-beta-D-arabinofuranosyl-E-5-(2-bromovinyl)uracil (brovavir) and acyclovir against herpes simplex virus type 1 infections in mice

1-beta-D-Arabinofuranosyl-E-5-(2-bromovinyl)uracil (brovavir) and acyclovir were compared for their antiviral effects against herpes simplex virus type 1 (HSV-1) model infections in mice. Both drugs were not toxic to mice when they were administered orally by the same schedule used for therapeutic experiments. Brovavir was less toxic than acyclovir when injected by the intraperitoneal (i.p.) route. Marked efficacies of brovavir by either oral or i.p. administration were demonstrated in both experimental encephalitis and i.p. infection with HSV-1 WT-51 strain. Treatment with brovavir at a dose of 15 or 25 mg/kg twice daily resulted in increasing both survival rate and mean survival time of the infected mice. On the contrary, acyclovir showed only marginal effect against the experimental encephalitis. Survival rates of mice treated with brovavir were higher than those treated with acyclovir at corresponding doses with statistical significance. The superiority of brovavir was also found in the intracerebral infection with strain VR-3, a highly virulent strain for mice. Brovavir, but not acyclovir, at a dose of 200 mg/kg reduced the mortality. Acyclovir, however, were significantly effective in reducing mortality of systemically infected mice by both oral and i.p. administrations. The effective dose of acyclovir was lower than that of brovavir against i.p. infection with strain WT-51. Differences in mortality of strain VR-3-infected mice were statistically significant between acyclovir- and brovavir-treated groups.     

Selective activity and cellular pharmacology of (1R-1 alpha,2 beta,3 alpha)-9-[2,3-bis(hydroxymethyl)cyclobutyl]guanine in herpesvirus-infected cells

The cycloburtane nucleoside analog (1R-1 alpha,2 beta,3 alpha)-9-[2,3-bis(hydroxymethyl)cyclobutyl]guanine [(R)-BHCG or SQ 34,514] was recently synthesized and shown to be the active enantiomer of (+/-)-BHCG (SQ 33,054), a potent inhibitor of several strains of herpesviruses [J. Med. Chem 34:1415-1421 (1991); Antiviral Res. 13:41-52 (1990)]. In plaque reduction assays, (R)-BHCG was about 1000 times more active than its S-enantiomer on herpes simplex virus type I (HSV-1) and over 200 times more active against a thymidine kinase-deficient mutant HSV-1 and human cytomegalovirus (HCMV). We now show that both (R)-BHCG and (S)-BHCG are efficiently phosphorylated to their mono-, di-, and triphosphates by HSV-1-infected cells, in a manner similar to that of acyclovir [Proc. Natl. Acad. Sci. USA 74:5716-5720 (1977)]. The uptake of both enantiomers was greatly increased upon infection; however, (S)-BHCG was taken up to about twice the extent of (R)-BHCG and accumulated primarily as the mono- and diphosphates. (R)-BHCG accumulated primarily as the triphosphate, and accumulation was linear with both time and added drug concentration. The triphosphate had an apparent half-life of about 10 hr. Metabolic studies using HCMV-infected cells showed only a small degree of phosphorylation of (R)-BHCG and none of (S)-BHCG. When cells were labeled with 25 microM (R)-BHCG, the amount of (R)-BHCG triphosphate formed was less than 0.5 pmol/10(6) cells. Interestingly, the ED50 value of (R)-BHCG is about 100-fold higher against HCMV than against HSV-1, and the relative levels of (R)-BHCG triphosphate formed in cells infected by the two viruses are roughly proportional to the antiviral activities.     

A comparison of phosphonoacetic acid and phosphonoformic acid activity in genital herpes simplex virus type 1 and type 2 infections of mice

The activity of phosphonoacetic acid (PAA) and phosphonoformic acid (PFA) against four strains of herpes simplex virus type 1 (HSV-1) and four strains of HSV-2 were compared in tissue culture and in a murine model of genital herpes. In mouse embryo fibroblast cells, both drugs were three-fold more active against the HSV-1 strains than against the HSV-2 strains. In contrast, in the animal model infections, PAA appeared to be more active against the HSV-2 strains, while PFA was equally effective against both HSV types. In mice infected intravaginally with HSV-2 and treated with intravaginal 5% PAA, none of the treated mice became infected, replication of virus in the genital tract was completely inhibited, none of the infected mice died from encephalitis, and latent infection in lumbosacral ganglia of surviving animals was completely prevented. In the HSV-1 genital infection treated with PAA, 20–60% of mice became infected, replication of virus in the genital tract was strikingly reduced, none of the infected mice died, and latent infection was completely prevented. In both HSV-2 and HSV-1 genital infections, 20–70% of animals treated with 8% PFA became infected, growth of virus in the genital tract was reduced significantly but not completely suppressed, mortality was variably altered, and there was a trend towards reduction in the frequency of latent infection. These results indicate that HSV-1 strains are more sensitive to PAA and PFA in tissue culture, but the HSV-2 strains are generally more amenable to therapy in the murine model of genital herpes. Although PAA appeared to be more active than PFA in the genital infection, both drugs significantly altered the course of the infection. Since dermal toxicity associated with PAA precludes its use in humans and since PFA is already undergoing trials in patients with recurrent herpes labialis, the current results suggest that topical PFA deserves further evaluation in the treatment of mucocutaneous HSV infections, including genital herpes.     

Antiviral activity of the marine alga Symphyocladia latiuscula against herpes simplex virus (HSV-1) in vitro and its therapeutic efficacy against HSV-1 infection in mice

The antiviral activities of extracts from 5 species of marine algae collected at Haeundae (Pusan, Korea), were examined using plaque reduction assays. Although the activity of a methanol (MeOH) extract of Sargassum ringoldianum (Sargassaceae) was the most potent against several types of viruses, it was also cytotoxic. A MeOH extract of Symphyocladia latiuscula (Rhodomelaceae) and its fractions exhibited antiviral activities against acyclovir (ACV) and phosphonoacetic acid (PAA)-resistant (AP(r)) herpes simplex type 1 (HSV-1), thymidine kinase (TK(-)) deficient HSV-1 and wild type HSV-1 in vitro without cytotoxicity. The major component, 2,3,6-tribromo-4,5-dihydroxybenzyl methyl ether (TDB) of a CH(2)Cl(2)-soluble fraction was active against wild type HSV-1, as well as AP(r) HSV-1 and TK(-) HSV-1 (IC(50) values of 5.48, 4.81 and 23.3 microg/ml, respectively). The therapeutic effectiveness of the MeOH extract and TDB from S. latiuscula was further examined in BALB/c mice that were cutaneously infected with HSV-1 strain 7401H. Three daily oral administrations of the MeOH extract and TDB significantly delayed the appearance of score 2 skin lesions (local vesicles) and limited the development of further score 6 (mild zosteriform) lesions in infected mice without toxicity compared with controls. In addition, TDB suppressed virus yields in the brain and skin. Therefore TDB should be a promising anti HSV agent.     

Synthesis, antiviral and cytotoxic activity of 2'-deoxyuridines, 2'-fluoro-2'-deoxyuridines and 2'-arabinouridines containing 5-(1-hydroxy-2-halo-2-ethoxycarbonylethyl)-, 5-(1-hydroxy-2-iodo-2- carboxyethyl)- and 5-[1-hydroxy (or methoxy)-2-iodoethyl] substituents.

The 5-[1-hydroxy-2-chloro-2-(ethoxycarbonyl)ethyl]-2'-deoxyuridine (7) and 5-[1-hydroxy-2-bromo-2-(ethoxycarbonyl)ethyl]-2'- fluoro-2'-deoxyuridine/uridine nucleosides (8, 9) were synthesized by the regiospecific addition of HOX (X = Br or Cl) to the vinyl substituent of the respective (E)-5-[2-(ethoxycarbonyl)-vinyl]-2'-deoxyuridines (6a-b) and uridine (6c). A related reaction of (E)-5-(2-carboxyvinyl)-2'-deoxyuridines (10a-b) and uridine (10c) with iodine and potassium iodate afforded the 5-(1-hydroxy-2-iodo-2-carboxyethyl) derivatives (11-13). 5-(1-Hydroxy-2-iodoethyl)-arabinouridine (18) was obtained by the reaction of (17) with iodine in the presence of the oxidizing agent iodic acid. Treatment of (18) with methanolic sulfuric acid afforded 5-(1-methoxy-2-iodoethyl)-arabinouridine (19) in 65% yield. Of the newly synthesized compounds, 7, 11 and 12 showed activity in vitro against HSV-1. The most active compound (12, ID50 = 0.1 microgram/ml) was 10 times less active than acyclovir (ID50 = 0.01 microgram/ml) against HSV-1. Compounds 7 and 11 were cytotoxic to L1210 cells in culture, exhibiting an ED50 of 7.2 and 4.7 micrograms/ml respectively, relative to melphalan (ED50 = 0.15 microgram/ml), but were inactive against the KB cell line.     

Synthesis and antiviral activity of the nucleotide analogue (S)-1-[3-hydroxy-2-(phosphonylmethoxy)propyl]cytosine

The acyclic nucleotide analogue (S)-1-[3-hydroxy-2-(phosphonylmethoxy)propyl] cytosine (2, HPMPC) was prepared on a multigram scale in 18% overall yield starting from (R)-2,3-O-isopropylideneglycerol. The key step in the nine-step synthetic route is coupling of cytosine with the side-chain derivative 8 which bears a protected phosphonylmethyl ether group. In vitro data showed that HPMPC has good activity against herpes simplex virus types 1 and 2, although it was 10-fold less potent than acyclovir [AVC, 9-[(2-hydroxyethoxy)methyl]guanine]. By comparison, HPMPC exhibited greater activity than ACV against a thymidine kinase deficient strain of HSV 1 and was more potent than ganciclovir [DHPG, 9-[(1,3-dihydroxy-2-propoxy)methyl]guanine] against human cytomegalovirus. In vivo, HPMPC showed exceptional potency against HSV 1 systemic infection in mice, having an ED50 of 0.1 mg/kg per day (ip) compared with 50 mg/kg per day for ACV. HPMPC was also more efficacious than ACV in the topical treatment of HSV 1 induced cutaneous lesions in guinea pigs.     

Efficacy of ASP2151, a helicase-primase inhibitor, against thymidine kinase-deficient herpes simplex virus type 2 infection in vitro and in vivo

ASP2151 was developed as a novel inhibitor of herpes simplex virus (HSV) and varicella-zoster virus helicase-primase. The anti-HSV activity of ASP2151 toward a clinical HSV isolate with acyclovir (ACV)-resistant/thymidine kinase (TK)-deficiency was characterized in vitro and in vivo using a plaque reduction assay and the ear pinna infection in mice. The IC₅₀ ranged from 0.018 to 0.024 μg/ml, indicating the susceptibility of TK-deficient HSV-2 was similar to that of wild-type HSV-2 strains. Anti-HSV activity of ASP2151 in vivo was evaluated in mice infected with wild-type HSV-2 and TK-deficient HSV-2. ASP2151 significantly reduced the copy numbers of wild-type HSV-2 and TK-deficient HSV-2 at the inoculation ear pinna, while valacyclovir significantly reduced the copy number of wild type HSV-2 but not that of TK-deficient HSV-2 in the inoculated ear pinna. Thus, ASP 2151 showed therapeutic efficacy in mice infected with both wild-type and TK-deficient HSV-2. In conclusion, ASP2151 is a promising novel herpes helicase-primase inhibitor that indicates the feasibility of ASP2151 for clinical application for the treatment of HSV infections, including ACV-resistant/TK-deficient HSV infection.     

Synthesis and antiviral activity of novel 5-(1-cyanamido-2-haloethyl) and 5-(1-hydroxy(or methoxy)-2-azidoethyl) analogues of uracil nucleosides

A new class of 5-(1-cyanamido-2-haloethyl)-2'-deoxyuridines (4-6) and arabinouridines (7, 8) were synthesized by the regiospecific addition of halogenocyanamides (X-NHCN) to the 5-vinyl substituent of the respective 5-vinyl-2'-deoxyuridine (2) and 2'-arabinouridine (3). Reaction of 2 with sodium azide, ceric ammonium nitrate, and acetonitrile-methanol or water afforded the 5-(1-hydroxy-2-azidoethyl)-(10) and 5-(1-methoxy-2-azidoethyl)-2'-deoxyuridines (11). In vitro antiviral activities against HSV-1-TK(+) (KOS and E-377), HSV-1-TK(-), HSV-2, VZV, HCMV, and DHBV were determined. Of the newly synthesized compounds, 5-(1-cyanamido-2-iodoethyl)-2'-deoxyuridine (6) exhibited the most potent anti-HSV-1 activity, which was equipotent to acyclovir and superior to 5-ethyl-2'-deoxyuridine (EDU). In addition, it was significantly inhibitory for thymidine kinase deficient strain of HSV-1 (EC(50) = 2.3-15.3 microM). The 5-(1-cyanamido-2-haloethyl)-2'-deoxyuridines (4-6) all were approximately equipotent against HSV-2 and were approximately 1.5- and 15-fold less inhibitory for HSV-2 than EDU and acyclovir, respectively. Compounds 4-6 were all inactive against HCMV but exhibited appreciable antiviral activity against VZV. Their anti-VZV activity was similar or higher to that of EDU and approximately 5-12-fold lower than that of acyclovir. The 5-(1-cyanamido-2-haloethyl)-(7,8) analogues of arabinouridine were moderately inhibitory for VZV and HSV-1 (strain KOS), whereas compounds 10 and 11 were inactive against herpes viruses. Compounds 5 and 6 also demonstrated modest anti-hepatitis B virus activity against DHBV (EC(50) = 19.9-23.6 microM). Interestingly, the related 5-(1-azido-2-bromoethyl)-2'-deoxyuridine (1n) analogue proved to be markedly inhibitory to DHBV replication (EC(50) = 2.6-6.6 microM). All compounds investigated exhibited low host cell toxicity to several stationary and proliferating host cell lines as well as mitogen-stimulated proliferating human T lymphocytes.     

Comparative anti-herpesvirus activities of 9-(1,3-dihydroxy-2-propoxymethyl)guanine, acyclovir, and two 2'-fluoropyrimidine nucleosides

9-(1,3-Dihydroxy-2-propoxymethyl)guanine (DHPG), was evaluated in cell culture and in animals for its inhibitory effect on herpes simplex viruses. Compounds run for comparison included acyclovir, 2'-fluoro-2'-deoxy-5-iodo-arabinofuranosylcytosine (FIAC), and 2'-fluoro-2'-deoxy-5-methyl-arabinofuranosyluracil (FMAU). In plaque reduction assays DHPG, acyclovir, FIAC, and FMAU were inhibitory to six herpes types 1 and 2 virus strains at concentrations of 0.2-2.4 microM. These concentrations were much lower than those required to inhibit Vero cell proliferation. In guinea pig vaginal infections, DHPG provided significantly greater inhibition of herpetic lesions than did acyclovir. In a herpes type 2 infection model in mice, DHPG, and FMAU were active at 5 mg/kg, whereas acyclovir and FIAC showed no statistically significant effect at 80 mg/kg. In a herpes type 1 encephalitis model, DHPG and FMAU were active at doses less than 10 mg/kg, with FMAU being about 4 times more potent than DHPG in that model.     

Ganciclovir ophthalmic gel 0.15%: in acute herpetic keratitis (dendritic ulcers)

Dendritic epithelial keratitis is most commonly caused by infections of herpes simplex virus (HSV) type 1 (HSV-1), and less frequently by HSV type 2 (HSV-2). Ganciclovir, a guanosine nucleoside analogue, is a well established broad-spectrum antiviral agent that inhibits replication of viral DNA and is active against both HSV-1 and -2 and several other viruses. Ganciclovir ophthalmic gel 0.15% is a five-times-daily topical preparation that is indicated for the treatment of acute herpetic keratitis (dendritic ulcers). A randomized, open-label, phase III trial in immunocompetent patients with acute herpetic keratitis showed that ganciclovir ophthalmic gel 0.15% applied five times daily provided effective clinical resolution of dendritic ulcers following 7 days of treatment (primary endpoint). Moreover, a retrospective analysis of noninferiority showed that ganciclovir ophthalmic gel 0.15% was no less effective than aciclovir (acyclovir) ointment 3%. A pooled analysis of three randomized, single-masked, phase II multinational trials also showed high rates of dendritic ulcer healing at day 7 for eyes treated with ganciclovir ophthalmic gel 0.15% and aciclovir ointment 3%. Furthermore, in the individual phase II trials, most patients showed evidence of healed dendritic and geographic ulcers at day 14 in either treatment arm. Median healing times with either treatment ranged from 6 to 10 days. Ganciclovir ophthalmic gel 0.15% was generally well tolerated and was associated with a significantly lower incidence of visual disturbances than aciclovir ointment 3% in the phase III trial.     

Properties of a 9-(2-phosphonylmethoxyethyl)adenine (PMEA)-resistant herpes simplex virus type 1 virus mutant

After repeated passages of herpes simplex type 1 (HSV-1) KOS virus in the presence of 9-(2-phosphonylmethoxyethyl)adenine (PMEA) a mutant denoted PMEAr HSV-1 was isolated which grew well in the presence of 50-100 micrograms.ml-1 of the drug. PMEAr HSV-1 was still sensitive to the related phosphonate analogue (S)-9-(3-hydroxy-2-phosphonylmethoxypropyl)adenine (HPMPA). In fact, it was more susceptible to the action of HPMPA than the original virus. PMEAr HSV-1 also retained sensitivity to 5-bromo-2'-deoxyuridine and other, viral thymidine kinase-dependent substances such as (E)-5-(2-bromovinyl)-2'-deoxyuridine. However, PMEAr HSV-1 was much less sensitive to acyclovir, 1-(beta-D-arabinofuranosyl)cytosine and 1-(beta-D-arabinofuranosyl)thymine than the parental KOS virus.     

(E)-5-(2-bromovinyl)-2'-desoxyuridine--a new nucleoside analog with selective inhibitory action against herpesviruses. Studies in cell culture and animal experiments

(E)-5-(2-Bromovinyl)-2'-deoxyuridine (1; BrVUdR) inhibits the replication of herpes simplex virus type 1 (HSV-1) and of varicella-zoster virus (VZV) in vitro at concentrations of 0.01 to 0.23 mumol/l, whereas herpes simplex virus type 2 (HSV-2) is influenced only at 5.5 to 27 mumol/l. In comparison to some classical and newly developed antiherpetics, i. e. 5-iodo-2'-desoxyuridine (2; idoxuridine, IDU), 9-beta-D-arabinofuranosyladenine (4; vidarabine Ara-A), 9-(2-hydroxyethoxymethyl) guanine (5; acyclovir, ACV) and 2'-fluoro-5-iodo-1-beta-D-aracytosine (6;FIAC) the following order of decreasing activity was found:1 greater than 6 greater than 5 greater than 2 greater than 4 (against HSV-1) and 6 greater than 2 greater than 5 greater than 1 greater than 4 (against HSV-2). The high selectivity of the antiviral effect of BrVUdR towards HSV-1 and TZV is based on the fact, that proliferation of different mammalian cell lines is inhibited by 50% only at concentrations as high as 90 to 170 mumol/l, resulting in a therapeutical index of 1000 to 10,000. Successful treatment of an HSV-1 encephalitis in mice as well as an HSV-1 keratitis of rabbits confirmed the efficiency of 1 in experimental animal infections. No toxic side effects in both local and systemic applications were observed. Promising data from cell culture and animal experiments recommend 1 as a potential candidate for the local and systemic treatment of HSV-1 and VZV infections in man.     

Acyclovir treatment of disseminated herpes simplex virus type 2 infection in weanling mice: alteration of mortality and pathogenesis

Intranasal inoculation of weanling mice with herpes simplex virus type 2 (HSV-2) provides an experimental infection that closely resembles disseminated and central nervous system HSV infections of human neonates. Intraperitoneal treatment with acyclovir (ACV) successfully reduced mortality even when therapy was begun as late as 2 days and oral therapy as late as 4 days after viral challenge. Treatment with ACV beginning on day 1 completely inhibited HSV-2 replication in lung, spleen, kidney, olfactory lobe, and cerebrum and decreased viral titers in the pons by 2-3 logs. Comparison of these data with our previous experiments using adenine arabinoside and adenine arabinoside 5' monophosphate indicates that ACV is more effective in the murine model of neonatal disease and suggests that ACV may also be more effective in treating the disease in humans.