Jeff Sorbel

Tenofovir Disoproxil Fumarate versus Adefovir Dipivoxil for Chronic Hepatitis B

BACKGROUND Tenofovir disoproxil fumarate (DF) is a nucleotide analogue and a potent inhibitor of human immunodeficiency virus type 1 reverse transcriptase and hepatitis B virus (HBV) polymerase. METHODS In two double-blind, phase 3 studies, we randomly assigned patients with hepatitis B e antigen (HBeAg)-negative or HBeAg-positive chronic HBV infection to receive tenofovir DF or adefovir dipivoxil (ratio, 2:1) once daily for 48 weeks. The primary efficacy end point was a plasma HBV DNA level of less than 400 copies per milliliter (69 IU per milliliter) and histologic improvement (i.e., a reduction in the Knodell necroinflammation score of 2 or more points without worsening fibrosis) at week 48. Secondary end points included viral suppression (i.e., an HBV DNA level of <400 copies per milliliter), histologic improvement, serologic response, normalization of alanine aminotransferase levels, and development of resistance mutations. RESULTS At week 48, in both studies, a significantly higher proportion of patients receiving tenofovir DF than of those receiving adefovir dipivoxil had reached the primary end point (P<0.001). Viral suppression occurred in more HBeAg-negative patients receiving tenofovir DF than patients receiving adefovir dipivoxil (93% vs. 63%, P<0.001) and in more HBeAg-positive patients receiving tenofovir DF than patients receiving adefovir dipivoxil (76% vs. 13%, P<0.001). Significantly more HBeAg-positive patients treated with tenofovir DF than those treated with adefovir dipivoxil had normalized alanine aminotransferase levels (68% vs. 54%, P=0.03) and loss of hepatitis B surface antigen (3% vs. 0%, P=0.02). At week 48, amino acid substitutions within HBV DNA polymerase associated with phenotypic resistance to tenofovir DF or other drugs to treat HBV infection had not developed in any of the patients. Tenofovir DF produced a similar HBV DNA response in patients who had previously received lamivudine and in those who had not. The safety profile was similar for the two treatments in both studies. CONCLUSIONS Among patients with chronic HBV infection, tenofovir DF at a daily dose of 300 mg had superior antiviral efficacy with a similar safety profile as compared with adefovir dipivoxil at a daily dose of 10 mg through week 48. (ClinicalTrials.gov numbers, NCT00116805 and NCT00117676.)

Three-Year Efficacy and Safety of Tenofovir Disoproxil Fumarate Treatment for Chronic Hepatitis B

BACKGROUND & AIMS Tenofovir disoproxil fumarate (TDF), a nucleotide analogue and potent inhibitor of hepatitis B virus (HBV) polymerase, showed superior efficacy to adefovir dipivoxil in treatment of chronic hepatitis B through 48 weeks. We evaluated long-term efficacy and safety of TDF monotherapy in patients with chronic hepatitis B who were positive or negative for hepatitis B e antigen (HBeAg(+) or HBeAg(-)). METHODS After 48 weeks of double-blind comparison of TDF to adefovir dipivoxil, patients who underwent liver biopsy were eligible to continue the study on open-label TDF for 7 additional years; data presented were collected up to 3 years (week 144) from 85% of participants. Primary efficacy end points at week 144 included levels of HBV DNA and alanine aminotransferase, development of resistance mutations, and presence of HBeAg or hepatitis B surface antigen (HBsAg). RESULTS At week 144, 87% of HBeAg(-) and 72% of HBeAg(+) patients treated with TDF had levels of HBV DNA <400 copies/mL. Among patients who had previously received adefovir dipivoxil and then received TDF, 88% of the HBeAg(-) and 71% of the HBeAg(+) patients had levels of HBV DNA <400 copies/mL; overall, 81% and 74%, respectively, maintained normalized levels of alanine aminotransferase and 34% had lost HBeAg. Amino acid substitutions in HBV DNA polymerase that are associated with resistance to tenofovir were not detected in any patient. Cumulatively, 8% of HBeAg(+) patients lost HBsAg. TDF maintained a favorable safety profile for up to 3 years. CONCLUSIONS TDF was safe and effective in the long-term management of HBeAg(+) and HBeAg(-) patients with chronic hepatitis B.

No resistance to tenofovir disoproxil fumarate detected after up to 144 weeks of therapy in patients monoinfected with chronic hepatitis B virus

Tenofovir disoproxil fumarate (TDF) is a nucleotide analogue with potent activity against human immunodeficiency virus type 1 and hepatitis B virus (HBV). To date, no reports of HBV clinical resistance to TDF have been confirmed. In two phase 3 studies (GS‐US‐174‐0102 and GS‐US‐174‐0103), 375 hepatitis B e antigen–negative (HBeAg−) patients and 266 HBeAg+ patients with chronic hepatitis B (some nucleoside‐naive and some lamivudine‐experienced) were randomized 2:1 to receive TDF (n = 426) or adefovir dipivoxil (ADV; n = 215) for 48 weeks. After week 48, eligible patients received open‐label TDF with no interruption. The studies are being continued through week 384/year 8; week 144 data are presented here. Per protocol, viremic patients (HBV DNA level ≥ 400 copies/mL or 69 IU/mL) had the option of adding emtricitabine (FTC) at or after week 72. Resistance analyses of HBV polymerase/reverse transcriptase (pol/RT) were based on population dideoxy sequencing. Phenotypic analyses were conducted in HepG2 cells with recombinant HBV derived from patient serum. Most patients maintained TDF monotherapy treatment across both studies (607/641, 95%). A resistance analysis of HBV pol/RT was performed at the baseline for all patients, for viremic patients at week 144 or at the last time when they were on TDF monotherapy (34 on TDF and 19 on ADV‐TDF), and for patients who remained viremic after the addition of FTC (7/20 on TDF and 5/14 on ADV‐TDF). No patient developed amino acid substitutions associated with resistance to TDF. Virological breakthrough on TDF monotherapy was infrequent over 144 weeks (13/426, 3%) and was attributed to documented nonadherence in most cases (11/13, 85%). Persistent viremia (≥400 copies/mL) through week 144 was rare (5/641, 0.8%) and was not associated with virological resistance to TDF by population or clonal analyses. Conclusion: No nucleoside‐naive or nucleoside‐experienced patient developed HBV pol/RT mutations associated with TDF resistance after up to 144 weeks of exposure to TDF monotherapy. (HEPATOLOGY 2010)

A phase II dose‐escalating trial of clevudine in patients with chronic hepatitis B

Current therapies available for the treatment of chronic hepatitis B are limited in their ability to result in a cure. Clevudine is a new pyrimidine analog with potent anti‐hepatitis B virus (HBV) activity in vitro. A multicenter dose‐escalation study evaluated clevudine at 10, 50, 100, and 200 mg once daily for 28 days. Eligible patients had HBV DNA levels of 3 × 106 copies/mL or more, had not undergone nucleoside treatment, and were without human immunodeficiency or hepatitis C virus coinfection. Thirty‐two patients were enrolled (5, 10, 10, and 7 patients in the 10‐, 50‐, 100‐, and 200‐mg dose groups, respectively), 81% were male, 81% Asian, and 88% were hepatitis Be antigen (HBeAg) positive at baseline. Median pretreatment serum HBV DNA levels ranged from 7.3 to 8.8 log10 copies/mL. After 28 days, the median HBV DNA log10 change from baseline was −2.5, −2.7, −3.0, and −2.6 log10. Six months after dosing, median changes from baseline were −1.2, −1.4, −2.7 and −1.7 log10 in the 10‐, 50‐, 100‐, and 200‐mg cohorts, respectively. Six of 27 patients lost HBeAg, and 3 of 27 patients seroconverted to HBe antibody. Clevudine was well tolerated, with no dose‐limiting toxicities. A transient increase in alanine aminotransferase of up to 7.8 times the upper limit of normal (increase ranged from 20 to 186 IU/L) was observed in six patients in the 100‐mg cohort, without signs of liver failure. These increases were associated with improved viral suppression. The pharmacokinetic profile of clevudine was proportional to the dose. In conclusion, these results demonstrate the tolerability and potent activity of clevudine in HBV‐infected patients and support further clinical study. (HEPATOLOGY 2004;40:140–148.)

Safety, efficacy, and pharmacokinetics of adefovir dipivoxil in children and adolescents (age 2 to <18 years) with chronic hepatitis B.

This study investigated the efficacy, safety, and pharmacokinetics of adefovir dipivoxil (ADV) in children and adolescents with chronic hepatitis B (CHB). A total of 173 treatment‐naive and treatment‐experienced children with hepatitis B e antigen (HBeAg)+ CHB were randomized to ADV or placebo. Randomization was stratified by age (2 to <7 years; >7 to <12 years; >12 to <18 years) and prior treatment. Significantly more ADV‐treated subjects aged 12 to <18 years achieved the primary efficacy endpoint (serum hepatitis B virus [HBV] DNA <1,000 copies/mL and normal alanine aminotransferase) compared to placebo‐treated subjects (23% versus 0%; P = 0.007). In the younger groups, differences between ADV and placebo at the end of blinded treatment were not statistically significant. More ADV‐treated subjects had HBeAg seroconversion: 18 of 113 (15.9%) versus three of 57 (5.3%) (but P = 0.051), and more met the combined endpoint of HBeAg seroconversion, HBV DNA <1,000 copies/mL and normal alanine aminotransferase (12/113 versus 0/57; P = 0.009). No subject developed an ADV‐associated mutation that has been linked to HBV DNA rebound (that is, mutations rtN236T or rtA181V). ADV plasma concentrations were comparable across groups and within the target range. ADV treatment was well tolerated; no new safety issues were identified. Treatment‐related adverse events were reported for 12% of ADV‐treated and 10% of placebo‐treated subjects. After 48 weeks of ADV treatment, antiviral efficacy in subjects ages 12 to <18 years with HBeAg+ CHB was similar to that observed in a study in adult treatment‐naive subjects with HBeAg+ CHB. ADV was not different from placebo in subjects aged 2 to 11 years despite adequate plasma ADV exposure in all three age groups. Conclusion: ADV showed significant antiviral efficacy in subjects aged 12 to 17 years with HBeAg+ CHB, but was not different from placebo in subjects aged 2 to 11 years. (HEPATOLOGY 2008.)

Randomized, Double-Blind Study of Emtricitabine (FTC) plus Clevudine versus FTC Alone in Treatment of Chronic Hepatitis B

ABSTRACT Emtricitabine (FTC) is approved for the treatment of human immunodeficiency virus. FTC and clevudine (CLV) have activity against hepatitis B virus (HBV). This report summarizes the results of a double-blind, multicenter study of patients with chronic hepatitis B who had completed a phase 3 study of FTC and were randomized 1:1 to 200 mg FTC once daily (QD) plus 10 mg CLV QD or 200 mg FTC QD plus placebo for 24 weeks with 24 weeks of follow-up. One hundred sixty-three patients were treated (82 with FTC plus CLV [FTC+CLV] and 81 with FTC); 72% were men, 53% were Asian, 47% were Caucasian, and 52% were hepatitis B e antigen positive, and the median baseline HBV DNA level was 6 log10 copies/ml. After 24 weeks of treatment, 74% (FTC+CLV) versus 65% (FTC alone) had serum HBV DNA levels of <4,700 copies/ml (P = 0.114) (Digene HBV Hybrid Capture II assay). Twenty-four weeks posttreatment, the mean change in serum HBV DNA levels from baseline was −1.25 log10 copies/ml (FTC+CLV), 40% had undetectable viremia (versus 23% for FTC alone), and 63% had normal alanine aminotransferase levels (versus 42% for FTC alone) (P ≤ 0.025 for all endpoints). The safety profile was similar between arms during treatment, with less posttreatment exacerbation of hepatitis B in the combination arm. In summary, after 24 weeks of treatment, no significant difference between arms was observed, but there was a significantly greater virologic and biochemical response 24 weeks posttreatment in the FTC+CLV arm.

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.

Sustained Hepatitis B e Antigen Seroconversion in Patients with Chronic Hepatitis B after Adefovir Dipivoxil Treatment: Analysis of Precore and Basal Core Promoter Mutants

BACKGROUND This study evaluated the persistence of hepatitis B e antigen (HBeAg) seroconversion (which is considered to be an important therapeutic end point) after adefovir dipivoxil treatment. METHODS Forty-five patients who experienced confirmed HBeAg seroconversion and had a serum hepatitis B virus DNA level < 10(5) copies/mL while receiving 10 mg of adefovir dipivoxil in a prior study were enrolled in the present study. At the time of the last dose of adefovir dipivoxil (baseline), the median age of the patients was 35 years, 64% were male, 73% were Asian, 27% were white, the median alanine aminotransferase level was 25 IU/L, and the median serum hepatitis B virus DNA level was 3.0 log copies/mL. The median follow-up time was 150 weeks (range, 13-252 weeks). RESULTS Forty-one patients maintained sustained seroconversion at the last 2 assessments, and 4 experienced seroreversion at weeks 12 (3 patients) and 16 (1 patient) of follow-up. Approximately 50% of patients had a hepatitis B virus DNA level < 1000 copies/mL at the last visit of the study period. Of 13 patients who were viremic and had available samples at the last visit, 11 had basal core promoter and/or precore mutations. Notably, 8 of these 11 patients had basal core promoter and/or precore mutations before adefovir dipivoxil therapy despite being HBeAg positive. The median duration of adefovir dipivoxil treatment was shorter before seroconversion (48 vs. 108 weeks; P = .03) and longer after seroconversion (41 vs. 22 weeks; P = .02) for patients who experienced sustained seroconversion, compared with the patients who experienced seroreversion. CONCLUSIONS Prolonged adefovir dipivoxil therapy after HBeAg seroconversion appeared to increase the likelihood of sustained HBeAg seroconversion. Most patients who experienced HBeAg seroconversion and had viremia had precore and/or basal core promoter mutants, which usually existed before initiation of adefovir dipivoxil therapy.

Posttreatment Exacerbation of Hepatitis B Virus (HBV) Infection in Long-Term HBV Trials of Emtricitabine

Posttreatment exacerbation of hepatitis B virus (HBV) infection in long-term HBV trials of emtricitabine occurred in 23% of patients. Development of antibody to hepatitis e antigen did not prevent hepatic flare. One patient with marked bridging fibrosis required liver transplantation. Patients with advanced liver disease are at risk for hepatic flare with decompensation if active treatment is withdrawn (e.g., when highly active antiretroviral treatment is modified).

Efficacy and safety of long-term adefovir dipivoxil therapy in children with chronic hepatitis B infection.

Background: The safety and efficacy of adefovir dipivoxil (ADV) for chronic hepatitis B infection in children was demonstrated in a randomized, placebo-controlled trial. Those children were followed for 4 more years, and many continued to receive ADV for all or part of this time. Objectives: To examine the therapeutic effects and safety of prolonged ADV therapy in children with chronic hepatitis B infection. Methods: After 48 weeks of double-blind treatment, all placebo-treated subjects who did not exhibit HBeAg seroconversion at week 44, and all ADV-treated subjects, were offered open-label ADV for up to 192 additional weeks. Treatment was discontinued if there was no virologic effect, except for adolescents with previous lamivudine exposure, in whom lamivudine was added to ADV. Durability of HBeAg seroconversion was assessed. Annual resistance surveillance was conducted in subjects who had detectable hepatitis B virus DNA. Results: Of the 170 subjects who completed the 48-week study, 162 participated in the open-label study. ADV was discontinued in 61 subjects due to virologic failure. In subjects who continued treatment, either as monotherapy or with lamivudine, continued viral suppression and alanine aminotransferase normalization were noted. HBeAg seroconversions were observed in 55 subjects, and hepatitis B surface antigen seroconversion in 5. Mean duration of HBeAg seroconversion at last observation was 762 ± 371.2 days in the ADV-ADV group and 643 ± 291.5 days in the PLB-ADV group. ADV was safe and well-tolerated. Resistance to ADV was observed in 1 child on ADV monotherapy. Nine treatment-experienced subjects entered the study with mutations associated with lamivudine resistance. All responded to ADV therapy. Conclusions: Prolonged ADV treatment is safe in children. If reserved only for those with virologic response within 6 months, viral resistance was minimal.