Extrahepatic effects of nucleoside and nucleotide analogues in chronic hepatitis B treatment.

Oral nucleoside/nucleotide analogues (NAs) are the mainstay of therapy for patients with chronic hepatitis B and are generally well tolerated. Despite this, the safety profile of NAs is of paramount importance since the majority of patients will require long-term treatment. All NAs can potentially affect human DNA polymerase with decrease in mitochondrial DNA, leading to manifestations of mitochondrial toxicity. As a class effect, therefore, NAs can potentially cause extrahepatic conditions, such as myopathy, nephropathy, neuropathy, and lactic acidosis. Indeed, effects on muscles, including myopathy and creatine kinase elevations, have been described with clevudine and telbivudine use. Both adefovir and tenofovir are associated with dose-dependent nephropathy, predominantly affecting the proximal renal tubules. Neuropathy appears to be rare, and most commonly reported in patients receiving combination therapy with telbivudine and interferon. Increased risk of lactic acidosis has also been described for those with impaired liver and renal function taking entecavir. Loss of bone mineral density and hypophosphatemia have been described with the use of NAs, although the overwhelming studies have been with human immunodeficiency virus-infected patients. However, not all extrahepatic effects are detrimental. Recent evidence has suggested a potential renal beneficial effect with the use of telbivudine. The effect of NAs on pregnancy appears to be minimal for all NAs, with telbivudine and tenofovir having a more favorable category B rating. Ongoing pharmacovigilance is essential to identify new and monitor existing extrahepatic effects associated with NA use.

Oral antiviral therapy improves the diagnostic accuracy of alpha-fetoprotein levels in patients with chronic hepatitis B.

BACKGROUND AND AIMS: Analysis of alpha-fetoprotein (AFP) levels affords limited diagnostic accuracy because of the high false-positive rates, especially in those with active chronic hepatitis B (CHB). We measured AFP levels before and after commencement of oral antiviral therapy and explored the utility of these data in terms of early detection of hepatocellular carcinoma (HCC) in patients with CHB. METHODS: A total of 207 patients with CHB who were treated with an oral antiviral agent were consecutively included. Dynamic changes in AFP levels and the diagnostic utility of such changes for HCC detection during the therapy were explored. RESULTS: The proportions of patients showing elevated AFP levels (≥ 20 ng/mL) were 22.2%, 5.5%, and 1.3% at baseline; and at 6 and 12 months after commencement of antiviral therapy, respectively. All patients who did not suffer from HCC exhibited normalization of AFP levels at 12 months. The cumulative incidence of HCC was 9.5% during 36 months of follow-up. If AFP levels were over 20 ng/mL after 12 months of antiviral treatment, the probability of HCC development approached certainty. The positive predictive value for HCC development remained at 100% in patients prescribed long-term (≥ 12 months) antiviral therapy, if AFP levels persistently or abruptly elevated more than 12 ng/mL. CONCLUSIONS: In the era of oral antiviral agents, AFP might be a useful biomarker for HCC surveillance in patients with CHB.

Virologic and biochemical responses to clevudine in patients with chronic HBV infection-associated cirrhosis: data at week 48.

Clevudine shows high rates of virologic and biochemical responses in patients with chronic hepatitis B. However, the efficacy and safety of clevudine in patients with cirrhosis are unknown. The aims of this study were to evaluate the safety and to assess the virologic and the biochemical responses to clevudine in patients with cirrhosis with chronic hepatitis B virus (HBV) infection. We reviewed data from treatment-naïve patients with chronic hepatitis B with and without cirrhosis who started clevudine between April 2007 and March 2008 (n = 52, hepatitis B without cirrhosis n = 21 and chronic hepatitis B with cirrhosis n = 31) at Korea University Ansan/Guro Hospital. All of the patients were treated for more than 48 weeks. The mean age was older in the patients with cirrhosis. Baseline HBV DNA levels were 6.9 and 7.78 log copies/mL (P = 0.042), and alanine aminotransferase (ALT) levels were 104.9 and 147.4 IU/L (P = 0.204), for those with and without cirrhosis, respectively. Virologic response (HBV DNA <1000 copies/mL) (87.1%vs 71.4%, P = 0.24) and biochemical response (83.9%vs 80.9%, P = 0.99) at week 48 were not significantly different between the two groups. Early virologic response at week 12 was even higher in the patients with cirrhosis (61.3%vs 28.6%, P = 0.026). Neither ALT flare nor newly onset hepatic decompensation was found in the patients with cirrhosis, whereas ALT flare was transiently observed in 14.3% of the chronic hepatitis group. In conclusion, although clevudine may produce a transient elevation of ALT during the early treatment period, such findings were not observed in patients with cirrhosis and the virologic and biochemical responses of the groups were comparable.

Clevudine for chronic hepatitis B: antiviral response, predictors of response, and development of myopathy.

Clevudine has been approved for the treatment of chronic hepatitis B (CHB) in South Korea. However, its long-term antiviral effect and safety awaits more study. The aim of this study was to evaluate antiviral efficacy, predictors of virologic response, and development of myopathy after clevudine therapy for CHB. The study included 102 nucleoside naïve CHB patients who had received clevudine for more than 6 months with good compliance. The median duration of clevudine treatment was 53 weeks (range, 25-90 weeks). A retrospective analysis of data retrieved from medical records was performed. The cumulative rate of virologic response [hepatitis B virus (HBV) DNA level <2000 copies/mL] at 48 weeks of clevudine therapy was 81%, and cumulative rate of clevudine resistance was 11% at 60 weeks of treatment. Independent predictors of virologic response to clevudine therapy were hepatitis B e antigen (HBeAg) negativity and rapid decrease of viral load during the early phase of treatment. The clevudine-related myopathy developed in 3.9% of patients, and was reversible after discontinuation of clevudine. Clevudine showed a potent antiviral response, and its effect was higher in HBeAg-negative patients, with rapid viral load reduction after therapy. However, long-term therapy for more than 1 year resulted in the development of considerable resistance and myopathy. Therefore, we should consider alternative antiviral agents if clevudine resistance or clevudine-induced myopathy is developed in patients on clevudine for the treatment of CHB.

Treatment outcomes of clevudine versus lamivudine at week 48 in naïve patients with HBeAg positive chronic hepatitis B.

The authors assessed the efficacy and antiviral resistance of 48-week clevudine therapy versus lamivudine in treatment of naïve patients with HBeAg positive chronic hepatitis B. In this retrospective study, a total of 116 HBeAg positive patients, who received 30 mg of clevudine once daily (n=53) or 100 mg of lamivudine once daily (n=63) for 48 weeks, were included. At week 48, clevudine therapy produced a significantly greater mean reductions in serum HBV DNA levels from baseline than lamivudine therapy (-5.2 vs. -4.2 log(10)IU/mL; P=0.005). Furthermore, a significantly higher proportion of patients on clevudine achieved negative serum HBV DNA by PCR (<13 IU/mL) at week 48 (60.4% vs. 38.1%; P=0.025). The incidence of virologic breakthrough in the clevudine group was significantly lower than in the lamivudine group (9.4% vs. 25.4%; P=0.031). However, rates of alanine aminotransferase normalization and HBeAg loss or seroconversion were similar in the two groups (83.0% vs. 81.0%, 11.3% vs. 11.1%; P=0.813, 1.000, respectively). In conclusion, clevudine is more potent for viral suppression and lower for antiviral resistance at week 48 than lamivudine in treatment of naïve patients with HBeAg positive chronic hepatitis B.

[Treatment efficacy of clevudine, entecavir and lamivudine in treatment-naive patients with HBeAg-positive chronic hepatitis B].

BACKGROUND/AIMS: clevudine is a potent antiviral agent that has demonstrated efficacy in patients with chronic hepatitis B. This study compared the efficacy of clevudine (C), entecavir (E) and lamivudine (L) in treatment-naive patient with HBeAg-positive chronic hepatitis B. METHODS: a total of 146 treatment-naive patients with HBeAg-positive chronic hepatitis B received clevudine, entecavir or lamivudine. C group (n=39) received 30 mg of clevudine, E group (n=39) received 0.5 mg of entecavir and L group (n=68) received 100 mg of lamivudine once a day for more than 48 weeks. The efficacy analysis estimated the mean changes of the HBV DNA levels as a virologic response, the normalization of the ALT levels (less than 35 IU/L) as a biochemical response and loss of HBeAg or seroconversion as a serologic response. The serum HBV DNA level was quantified by hybrid capture and real-time PCR assay. RESULTS: before the administration of clevudine, entecavir and lamivudine, the mean HBV DNA and ALT levels and the gender and age were well balanced among the three groups (p>0.05). For the virologic response at 48 weeks, the mean changes of the HBV DNA levels from baseline of the C, E and L groups were -3.8+/-2.2, -4.5+/-1.9 and -2.5+/-2.1 log copies/mL. C and E group showed superior antiviral activity compared to that of L group (p<0.0001), but no significant differences in antiviral response were noted between C and E groups. For the biochemical response at 48 weeks, the normalization of the ALT levels (less than 35 IU/L) among the C, E and L groups was 82%, 74% and 71%, respectively (p=0.46). The rates of undetectable serum HBV DNA (less than 300 copies/mL) of the C, E and L groups were 39%, 69% and 27%, respectively (p<0.0001). For the serologic response at 48 weeks, the loss of HBeAg was 13%, 31% and 24% and the seroconversion was 10%, 23% and 17%, respectively. There was no difference of efficacy among the three groups regarding ALT normalization or serologic response (p>0.05). Viral breakthrough in C group was noted at 24 weeks (5%) and 48 weeks (21%), but no biochemical breakthrough was noted. The elevation of the serum CK level was noted in only 1 patient of group C at 48 weeks (2.56%) after therapy. For the patients without or with liver cirrhosis (LC), C and E group showed superior antiviral activity compared to that of the L group, but the antiviral activity was more effective in non- LC group than LC group (p<0.0001 vs p=0.036). CONCLUSIONS: clevudine therapy compared with lamivudine for 48 weeks showed significantly potent antiviral efficacy in treatment-naive patients with HBeAg-positive chronic hepatitis B, and especially in the non-LC patients. However, the antiviral efficacy of clevudine was similar to that of entecavir even though taking into account relatively short follow up period and retrospective study.

Forty-eight weeks treatment with clevudine 30 mg qd versus lamivudine 100 mg qd for chronic hepatitis B infection: a double-blind randomized study.

BACKGROUND/AIMS: Clevudine is a pyrimidine analogue with potent activity against hepatitis B virus (HBV) replication in vitro. In a previous pivotal phase III clinical study, 24 weeks treatment with clevudine 30 mg has been shown to profoundly suppress HBV replication and normalize serum alanine aminotransferase level. METHODS: In this study, we compare the efficacy and safety of clevudine (30 mg daily) versus lamivudine (100 mg daily) for 48 weeks in treatment-naive chronic hepatitis B e antigen (HBeAg) positive patients. RESULTS: Ninety-two chronic HBeAg positive patients were randomized to receive clevudine 30 mg daily or lamivudine 100 mg daily in a 1:1 ratio. The clevudine group demonstrated greater viral suppression at week 48 when compared with the lamivudine group (median reduction: 4.27 vs. 3.17 log(10) copies/ml at week 48, p<0.0001). At week 48, serum HBV DNA level was below 300 copies/mL in 73% and 40% in the clevudine and lamivudine groups, respectively (p=0.001). HBeAg seroconversion occurred in 18% of patients in the clevudine group versus 12% in the lamivudine group at week 48. Lamivudine-resistant mutations were detected in 11 (24%) patients in the lamivudine group, who showed viral rebound during lamivudine therapy but no resistance was found in the clevudine group during 48-week treatment period. CONCLUSIONS: A 48-week dosing with clevudine 30 mg daily was superior to lamivudine 100 mg daily in suppressing HBV replication, with no emergence of viral breakthrough in patients with HBeAg positive chronic hepatits B.

Clinical and virological responses to clevudine therapy in chronic hepatitis B patients: results at 1 year of an open-labelled prospective study.

BACKGROUND: A previous clinical study of oral clevudine monotherapy for 24 weeks demonstrated that it has potent sustained antiviral effects without inducing drug resistance. The aim of this study was to evaluate the antiviral effects and safety of clevudine monotherapy for 12 months. METHODS: In this open-labelled prospective study, 45 treatment-naive chronic hepatitis B patients treated with 30 mg clevudine once daily for 12 months were monitored at baseline and at 3-month intervals during treatment. RESULTS: At baseline, the mean age of patients was 42 years, 32 were hepatitis B e antigen (HBeAg)-positive and 15 had liver cirrhosis. After 12 months of clevudine therapy, the mean serum hepatitis B virus (HBV) DNA level in HBeAg-positive patients had decreased by 4.6 log(10) IU/ml. Serum HBV DNA was undetectable in 68.7% of patients. HBeAg loss or seroconversion was observed in five patients (15.6%) and serum alanine aminotransferase (ALT) level had normalized after 12 months of treatment in 75% of patients. In all 13 HBeAg-negative patients, serum HBV DNA level was undetectable after 12 months of therapy and ALT level was normal in 61.5% of patients. Viral breakthrough occurred in one patient after 9 months of clevudine treatment. This patient had an HBV polymerase mutation, rtM204I. There were no serious adverse events. CONCLUSIONS: One-year clevudine therapy is effective for suppressing serum HBV DNA level and for normalization of ALT level. Viral breakthrough associated with the rtM204I mutation in the HBV polymerase gene occurs during long-term clevudine treatment.

Clevudine therapy for 24 weeks further reduced serum hepatitis B virus DNA levels and increased ALT normalization rates without emergence of viral breakthrough than 12 weeks of clevudine therapy.

OBJECTIVES: The objectives of the study were to evaluate the safety and antiviral activity of 24-week treatment with clevudine 30 mg in HBeAg(+) chronic hepatitis B patients. Biochemical and serological responses were also assessed. METHOD: Twenty-one patients received clevudine 30 mg for 24 weeks and were followed up for another 24 weeks off therapy. RESULTS: Median decreases from baseline in HBV DNA were 4.65 and 1.96 log(10) copies/ml at week 24 (end of treatment) and week 48 (24 weeks off therapy), respectively. Analysis of individual data showed that HBV DNA levels were below the lower limit of detection (300 copies/ml) by Amplicor PCR assay in 19, 57, 19 and 0% at week 12, 24, 34 and 48, respectively. The proportion of patients with normal ALT were 67, 81 and 75% at week 24 (end of treatment), 34 and 48 (24 weeks off therapy), respectively. The rates of HBeAg loss were 24 and 20% at week 24 and 48, respectively. No viral breakthrough during treatment was observed. CONCLUSION: Clevudine 30 mg treatment for 24 weeks was well tolerated and exhibited more potent antiviral activity and a higher ALT normalization rate than 12-week treatment with durable efficacy at week 24 off therapy.

Imaging the pharmacokinetics of [F-18]FAU in patients with tumors: PET studies.

PURPOSE: FAU (1-(2'-deoxy-2'-fluoro-beta-D: -arabinofuranosyl) uracil) can be phosphorylated by thymidine kinase, methylated by thymidylate synthase, followed by DNA incorporation and thus functions as a DNA synthesis inhibitor. This first-in-human study of [F-18]FAU was conducted in cancer patients to determine its suitability for imaging and also to understand its pharmacokinetics as a potential antineoplastic agent. METHODS: Six patients with colorectal (n = 3) or breast cancer (n = 3) were imaged with [F-18]FAU. Serial blood and urine samples were analyzed using HPLC to determine the clearance and metabolites. RESULTS: Imaging showed that [F-18]FAU was concentrated in breast tumors and a lymph node metastasis (tumor-to-normal-breast-tissue-ratio 3.7-4.7). FAU retention in breast tumors was significantly higher than in normal breast tissues at 60 min and retained in tumor over 2.5 h post-injection. FAU was not retained above background in colorectal tumors. Increased activity was seen in the kidney and urinary bladder due to excretion. Decreased activity was seen in the bone marrow with a mean SUV 0.6. Over 95% of activity in the blood and urine was present as intact [F-18]FAU at the end of the study. CONCLUSIONS: Increased [F-18]FAU retention was shown in the breast tumors but not in colorectal tumors. The increased retention of FAU in the breast compared to bone marrow indicates that FAU may be useful as an unlabeled antineoplastic agent. The low retention in the marrow indicates that unlabeled FAU might lead to little marrow toxicity; however, the images were not of high contrast to consider FAU for diagnostic clinical imaging.

Integrating Dynamic Positron Emission Tomography and Conventional Pharmacokinetic Studies to Delineate Plasma and Tumor Pharmacokinetics of FAU, a Prodrug Bioactivated by Thymidylate Synthase.

FAU, a pyrimidine nucleotide analogue, is a prodrug bioactivated by intracellular thymidylate synthase to form FMAU, which is incorporated into DNA, causing cell death. This study presents a model-based approach to integrating dynamic positron emission tomography (PET) and conventional plasma pharmacokinetic studies to characterize the plasma and tissue pharmacokinetics of FAU and FMAU. Twelve cancer patients were enrolled into a phase 1 study, where conventional plasma pharmacokinetic evaluation of therapeutic FAU (50-1600 mg/m2 ) and dynamic PET assessment of 18 F-FAU were performed. A parent-metabolite population pharmacokinetic model was developed to simultaneously fit PET-derived tissue data and conventional plasma pharmacokinetic data. The developed model enabled separation of PET-derived total tissue concentrations into the parent drug and metabolite components. The model provides quantitative, mechanistic insights into the bioactivation of FAU and retention of FMAU in normal and tumor tissues and has potential utility to predict tumor responsiveness to FAU treatment.

Inhibition of dihydropyrimidine dehydrogenase by 5-propynyluracil, a metabolite of the anti-varicella zoster virus agent netivudine.

OBJECTIVE: To study the effects of the anti-herpetic drug netivudine on dihydropyrimidine dehydrogenase activity in elderly volunteers and to relate them to concentrations of netivudine and its metabolite 5-propynyluracil. METHODS: Three groups of eight elderly volunteers received 400 or 800 mg netivudine or placebo once daily for 8 days. Plasma netivudine, 5-propynyluracil, and uracil, an indirect measure of dihydropyrimidine dehydrogenase activity, were assayed before the first dose and on days 2, 3, 5, 7 and 8. Full plasma profiles of netivudine and 5-propynyluracil were determined after the last dose. RESULTS: Plasma uracil was unquantifiable in all subjects before the first dose and at all time points in the placebo group. In recipients of netivudine it reached a plateau between days 3 and 5, with mean values of 23.2 and 23.5 mumol/L on day 8 in the subjects who received 400 and 800 mg. Plasma netivudine concentrations were approximately dose proportional, but 5-propynyluracil concentrations were similar in both groups. The half-maximal rise in plasma uracil occurred after a cumulative 5-propynyluracil exposure of 120 mumol/L.hr; such exposures will be achieved even after doses as low as 50 to 100 mg daily. CONCLUSIONS: Netivudine dosing produces complete inhibition of plasma dihydropyrimidine dehydrogenase. Coadministration with the antimetabolite 5-fluorouracil will require a substantial reduction in 5-fluorouracil dose to avoid toxicity but may also improve the therapeutic index of 5-fluorouracil.

The effect of sorivudine on dihydropyrimidine dehydrogenase activity in patients with acute herpes zoster.

OBJECTIVE: Bromovinyl-uracil (BVU) is the principal metabolite of sorivudine, a potent anti-zoster nucleoside. BVU binds to, and irreversibly inhibits, the enzyme dihydropyrimidine dehydrogenase (DPD). The objective of this study was to assess the time course of recovery of DPD activity after oral administration of sorivudine in patients with herpes zoster and to correlate restoration of DPD activity and levels of uracil with the elimination of sorivudine and its metabolite BVU from the circulation. METHODS: Sorivudine was given orally as 40 mg once-daily doses for 10 consecutive days to a total of 19 patients with herpes zoster. Serum sorivudine, BVU, and circulating uracil and DPD activity in peripheral blood mononuclear cells (PBMCs) were determined before, during, and after administration of sorivudine. RESULTS: BVU was eliminated from the circulation within 7 days after the last sorivudine dose. DPD activity in PBMCs, which was completely suppressed in 18 of the 19 subjects and markedly suppressed in the remaining subject during administration of sorivudine, recovered to baseline levels within 19 days after the last dose of sorivudine in all subjects and within 14 days in all but one of the subjects. The restoration of DPD activity was temporally associated with elimination of BVU from the circulation. The elevated uracil concentrations produced by inhibition of DPD activity fell rapidly after cessation of sorivudine administration and also were temporally associated with elimination of BVU from the circulation. The time course of recovery of DPD activity in three patients with renal impairment was similar to that of the other subjects. CONCLUSIONS: This study indicates that sorivudine therapy is associated with a profound depression of DPD activity. Recovery of DPD activity occurred within 4 weeks of the completion of sorivudine therapy, which indicates that fluorinated pyrimidines may be safely administered 4 weeks after completion of sorivudine therapy.

Clevudine therapy with vaccine inhibits progression of chronic hepatitis and delays onset of hepatocellular carcinoma in chronic woodchuck hepatitis virus infection.

We examined a rational approach to therapy of chronic hepatitis B virus (HBV) infection that utilized the reduction of viral load combined with appropriately timed immune modulation/stimulation. In a placebo-controlled study, chronic woodchuck hepatitis virus (WHV) carrier woodchucks received clevudine (L-FMAU), previously shown to have especially potent and sustained antiviral activity in woodchucks, for 32 weeks followed by WHV surface antigen (WHsAg) alum-adjuvanted vaccine at 32, 36, 40 and 48 weeks. Clevudine induced significant reductions in viraemia, surface antigenaemia, hepatic WHV nucleic acids, and hepatic core and surface antigens. Viral replication markers remained markedly suppressed in 75% of the clevudine-treated woodchucks following drug withdrawal, but remained at high levels in the vaccine monotherapy and placebo groups. Combination drug and vaccine therapy had benefits based on sustained reduction of viraemia, antigenaemia, and hepatic WHV DNA and RNA; inhibition of progression of chronic hepatitis; reduced frequency of chronic liver injury; and delayed onset of hepatocellular carcinoma (HCC). Combination therapy contributed to prevention of HCC in up to 38% of treated carriers, although the growth rate of established HCC was not affected. This study demonstrates enhanced benefits of combination chemo-immunotherapy against viral load and disease progression in chronic hepadnaviral infection, and provides a platform for further development of such treatment regimens.

Efficacy of oral treatment with BV-araU against cutaneous infection with herpes simplex type 1 in shaved mice.

The effect of oral BV-araU was tested in cutaneous model infections of shaved Balb/c mice with herpes simplex virus type 1 (HSV-1). Progression of cutaneous symptoms associated with cutaneous infection with HSV-1 F strain was inhibited by BV-araU at doses of 20 and 50 mg/kg twice daily, beginning one day post-infection, resulting in significant increase in the survival rate. Onset of disease was suppressed in most animals receiving 100 mg of BV-araU per kg. BV-araU (20 mg/kg or more) also significantly increased the survival rate of mice infected with HSV-1 WT-51 strain. The efficacy of BV-araU was not affected by gender or age (6-9 weeks) of the mice. BV-araU was effective even when the treatment was started 2.5 days post-infection. The efficacy of BV-araU against F strain infection was comparable to that of acyclovir, but acyclovir showed therapeutic effects at lower doses compared with BV-araU against WT-51 strain infection. Against infection of cyclophosphamide-treated immunosuppressed mice with HSV-1 KOS(S) strain, BV-araU decreased the morbidity rate and severity of symptoms at doses of 200 and 100 mg/kg, respectively, and all mice given 50 mg of BV-araU or more per kg survived, suggesting oral efficacy can be achieved against HSV-1 infections in immunosuppressed individuals.

Inhibition of simian varicella virus infection of monkeys by 1-(2-deoxy-2- fluoro-1-beta-D-arabinofuranosyl)-5-ethyluracil (FEAU) and synergistic effects of combination with human recombinant interferon-beta.

1-(2-Deoxy-2-fluoro-1-beta-D-arabinofuranosyl)-5-ethyluracil (FEAU) has been shown to be a highly effective inhibitor of Simian varicella virus infection in African green monkeys. Administration of FEAU by either intravenous injection or gavage at doses as low as 1 mg/kg/day prevented the development of rash and reduced viremia. The effective dose could be further reduced to 0.2 mg/kg/day when administered in combination with a sub-effective dose of human recombinant interferon-beta. No evidence of toxicity was seen in monkeys treated for 10 days with FEAU doses of 10 mg/kg/day when they were monitored by hematology and clinical chemistry tests and by clinical observations.

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.

Treatment of experimental herpes simplex virus type 1 encephalitis in mice with (E)-5-(2-bromovinyl)- and 5-vinyl-1-beta-D-arabinofuranosyluracil: comparison with bromovinyl-deoxyuridine and acyclovir.

The efficiency of (E)-5-(2-bromovinyl)- and 5-vinyl-1-beta-D-arabinofuranosyluracil (BrVaraU, VaraU) as inhibitors of three herpes simplex virus type 1 (HSV-1) strains was assessed in comparison to (E)-5-(2-bromovinyl)-2'-deoxyuridine (BrVUdR), 9-(2-hydroxyethoxymethyl)guanine (ACV), and trisodium phosphonoformate (Na3PFA) using a plaque assay in human embryonic lung fibroblast (HELF) cell cultures. The following order of decreasing activity was found: BrVaraU greater than VaraU greater than BrVU-dR greater than ACV much greater than Na3PFA. In HELF cell cultures, the selectivity indexes of VaraU and BrVaraU were 10 times higher than those of BrVUdR and ACV. Protection of mice from encephalitis and death due to intracerebral (i.c.) infection with a clinical HSV-1 isolate was nearly complete if mice were treated intraperitoneally (i.p.) with two daily doses of VaraU and BrVaraU (100 or 200 mg/kg per day) over a period of 5 or 10 days. The efficacy was similar to ACV, but, using a treatment schedule of three daily i.p. doses over 10 days, with equimolar amounts of the nucleoside analogs, VaraU and BrVaraU (140 and 180 mg/kg per day) were superior to ACV (130 mg/kg per day) (P less than 0.05).

Evaluation of 1-(2'-deoxy-2'-fluoro-beta-D-arabinofuranosyl)-5-ethyluracil in a rabbit model of herpetic keratitis.

The nucleoside analog 1-(2'-deoxy-2'-fluoro-beta-D-arabinofuranosyl)-5- ethyluracil (FEAU) was tested in a rabbit model of acute herpetic keratitis and its effectiveness compared with that of acyclovir (ACV). FEAU or ACV was applied topically 3 times daily, beginning 3 days post-HSV-1 inoculation and continued for a period of 7 days. FEAU at a concentration of 1% (w/v) or 3% ACV resulted in significant lessening of the severity of corneal lesions, conjunctivitis, iritis, and corneal clouding at 24 to 48 h after beginning chemotherapy. No toxic reaction was observed in any rabbit eyes treated with either FEAU or ACV. The duration of virus shedding into tear film and colonization of the trigeminal ganglia, however, were not reduced by either FEAU or ACV treatment begun 3 days post-inoculation. Fifty percent effective dose (ED50) of FEAU determinations performed on isolates from tear film and on the virus inoculum in secondary rabbit kidney cultures yielded a range of 4.6-7 microM, with two in vitro resistant isolates having ED50S of greater than or equal to 1500 microM of FEAU. Fifty percent cell growth inhibition for FEAU was 3000 microM at 72 h.

Mitochondrial injury. Lessons from the fialuridine trial.

Fialuridine is an antiviral agent with potent activity against hepatitis B virus replication in vitro and in vivo. In a phase II study, 7 of 15 patients experienced severe toxicity due to the drug after 9 to 13 weeks of treatment. Adverse effects included nausea, vomiting and painful paraesthesia; subsequently, hepatic failure, pancreatitis, neuropathy, myopathy and lactic acidosis developed, probably due to multisystem mitochondrial toxicity. Possible mechanisms of fialuridine toxicity include mitochondrial injury and pyruvate oxidation inhibition. While other nucleoside analogues have shown evidence of inducing mitochondrial injury (zidovudine, didanosine, zalcitabine), others to date have not (lamivudine, famciclovir). Specific recommendations for future study of existing and new nucleoside analogues include testing for toxicity after prolonged incubation, specific investigations to measure mitochondrial function, toxicological tests and well designed clinical trials with appropriate testing to monitor for any adverse effects on mitochondrial integrity and function.