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.

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.

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.

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 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.

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 Outcomes of Clevudine versus Lamivudine at Week 48 in Naive 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 naive 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 naive patients with HBeAg positive chronic hepatitis B.

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

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.

Treatment Efficacy of Clevudine, Entecavir and Lamivudine in Treatment-naive Patients with HBeAg-Positive Chronic Hepatitis B / 대한소화기학회지

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 (p0.05). 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.

Bacterial thymidine kinase as a non-invasive imaging reporter for Mycobacterium tuberculosis in live animals.

BACKGROUND: Bacteria can be selectively imaged in experimentally-infected animals using exogenously administered 1-(2'deoxy-2'-fluoro-beta-D-arabinofuranosyl)-5-[(125)I]-iodouracil ([(125)I]-FIAU), a nucleoside analog substrate for bacterial thymidine kinase (TK). Our goal was to use this reporter and develop non-invasive methods to detect and localize Mycobacterium tuberculosis. METHODOLOGY/PRINCIPAL FINDINGS: We engineered a M. tuberculosis strain with chromosomally integrated bacterial TK under the control of hsp60 -- a strong constitutive mycobacterial promoter. [(125)I]FIAU uptake, antimicrobial susceptibilities and in vivo growth characteristics were evaluated for this strain. Using single photon emission computed tomography (SPECT), M. tuberculosis P(hsp60) TK strain was evaluated in experimentally-infected BALB/c and C3HeB/FeJ mice using the thigh inoculation or low-dose aerosol infection models. M. tuberculosis P(hsp60) TK strain actively accumulated [(125)I]FIAU in vitro. Growth characteristics of the TK strain and susceptibility to common anti-tuberculous drugs were similar to the wild-type parent strain. M. tuberculosis P(hsp60) TK strain was stable in vivo and SPECT imaging could detect and localize this strain in both animal models tested. CONCLUSION: We have developed a novel tool for non-invasive assessment of M. tuberculosis in live experimentally-infected animals. This tool will allow real-time pathogenesis studies in animal models of TB and has the potential to simplify preclinical studies and accelerate TB research.

Clevudine for hepatitis B.

Clevudine is distinguished from other oral agents by its sustained suppression of HBV DNA for several months after cessation of therapy, according to a comprehensive review of hepatitis B in the 2 October 2008 issue of the New England Journal of Medicine. Clevudine is differentiated by i) an unusual activation pathway to the biochemically active triphosphate; ii) a mechanism of action of clevudine triphosphate that inhibits multiple steps of the hepatitis B virus (HBV) intracellular life cycle; iii) a long half-life and iv) significant reduction of covalently closed circular DNA (cccDNA) in animal models. Clevudine was approved and is marketed in South Korea based on two 24-week phase III trials vs. placebo. In these studies with treatment-naïve patients, 59% of 248 HBeAg-positive patients had undetectable HBV DNA after 24 weeks of treatment compared with 92% of 89 HBeAg-negative patients, while the percentage of patients with normal liver enzymes was 68% in the HBeAg-positive patients and 75% in the HBeAg-negative patients (all statistically significant versus placebo). Follow-up studies include trials vs. lamivudine as well as a phase IV study of long-term clevudine. Larger and longer phase III trials in the United States, European Union, Asia and South America of clevudine vs. adefovir are ongoing. An ANRS-sponsored trial of clevudine vs. tenofovir vs. the combination of the two agents is poised to begin. Literature published through November 2008 and presentations from the 59th annual meeting of the American Association for the Study of Liver Diseases held 31 October to 4 November 2008 are included.

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.

Clinical trial: a phase II, randomized study evaluating the safety, pharmacokinetics and anti-viral activity of clevudine for 12 weeks in patients with chronic hepatitis B.

BACKGROUND: Clevudine is a polymerase inhibitor that has the unusual feature of delayed viral rebound after therapy in some patients which may be related to its pharmacokinetics. AIM: To characterize pharmacokinetic and pharmacodynamic profile of clevudine, a potent hepatitis B polymerase inhibitor. METHODS: A multicenter, randomized study comparing 10, 30 and 50 mg clevudine once daily for 12 weeks with 24 weeks off-treatment follow-up. Patients had chronic HBV infection, were nucleoside-naïve without co-infection. HBV viral load (VL) was assayed using Digene Hybrid Capture II with a lower limit of detection of 4700 copies/mL (940 IU/mL). Clevudine levels were measured using a liquid chromatography/mass spectrometery method. RESULTS: A total of 31 patients were enrolled into the 10 mg (n = 10), 30 mg (n = 11) and 50 mg (n = 10) groups, respectively. At week 12, the median VL change was -3.2, -3.7 and -4.2 log(10) copies/mL (-0.64, -0.74 and -0.84 log(10) IU/mL) in the 10, 30 and 50 mg groups, respectively (P = 0.012). At week 12, one of 10, five of 11 and two of 10 patients had VL below the assay lower limit of detection. Clevudine was well tolerated with no severe/serious adverse events. The mean plasma half-life of clevudine was 70 h and consequently is not the cause of the delayed viral rebound seen in some patients. Through modelling, 97% of the maximal treatment effect was reached with a 30 mg daily dose. Six patients had genomic changes without viral rebound. CONCLUSION: Clevudine appears to be a potent and tolerable (over 12 weeks) anti-viral and the optimal dosage appears to be 30 mg once daily.

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.

Clevudine: a potent inhibitor of hepatitis B virus in vitro and in vivo.

Clevudine (CLV) is a nucleoside analog of the unnatural L-configuration that has potent anti-hepatitis B virus (HBV) activity in vitro and in vivo with a favorable toxicity profile in all species tested. In cell culture, CLV is readily phosphorylated to the corresponding 5'-triphosphate form of the compound. The mechanism of action of CLV involves the inhibition of the HBV polymerase by CLV 5'-triphosphate. In vivo efficacy studies performed in the duck and woodchuck models showed marked, rapid inhibition of virus replication and no significant toxicity. In the woodchuck model, there was a dose-dependent delay in viral recrudescence and a reduction or loss of covalently closed circular DNA. In Phase II clinical studies, CLV was well tolerated and exhibited potent antiviral activity at all doses investigated. In Phase III studies in both hepatitis B e antigen (HBeAg)-positive and -negative patients, CLV 30 mg administered once daily demonstrated potent antiviral efficacy and significant biochemical improvement after only 24 weeks of therapy. These effects were sustained in a significant portion of the patients when therapy was stopped after 6 months with no viral rebound occurring in approximately 3 and 16% in HBeAg-positive and -negative patients, respectively. There have been no significant safety or tolerance issues associated with the drug in these studies. Future studies will investigate the safety and tolerance of CLV 30 mg given once daily over 48 weeks and longer.

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.

Adenovirus-based gene therapy during clevudine treatment of woodchucks chronically infected with woodchuck hepatitis virus.

Interferon-alpha (IFN-alpha) is a potent suppressor of hepatitis B virus (HBV) replication in the HBV-transgenic mouse, depleting virus replication intermediates from infected hepatocytes via pathways mediated by interferon-gamma (IFN-gamma) and tumor necrosis factor alpha (TNF-alpha). It has also been hypothesized that cytokines induce curing of infected hepatocytes via non-cytolytic pathways during resolution of transient hepadnavirus infections. We have therefore evaluated therapy of chronic woodchuck hepatitis virus (WHV) infections using treatment with the nucleoside analog clevudine [L-FMAU; 1-(2-fluoro-5-methyl-b-L-arabinofuranosyl) uracil] and therapy with adenovirus vectors expressing INF-gamma, TNF-alpha, and beta-galactosidase. Before their use in vivo, expression of IFN-gamma and TNF-alpha from the adenovirus vectors was evaluated in vitro. Conditioned media from adenovirus-infected WC-3 cells was shown to inhibit WHV replication in baculovirus-transduced cells. Adenovirus super-infection of the liver in woodchucks led to declines in the percentage of hepatocytes with detectable core antigen and nucleic acids, and in levels of covalently closed circular DNA (cccDNA) and total WHV DNA, but a major long-term benefit of adenovirus super-infection during clevudine treatment was not demonstrated. Moreover, the effect took at least 2 weeks to develop suggesting that the declines in the percentage of WHV-infected cells, ccc, and total WHV DNA resulted from induction of the adaptive immune response by the adenovirus super-infection, and only indirectly from the expression of cytokines by the vectors.