Kathryn M. Kitrinos

Tenofovir disoproxil fumarate (TDF), emtricitabine/TDF, and entecavir in patients with decompensated chronic hepatitis B liver disease

Data are limited on the safety and effectiveness of oral antivirals other than lamivudine and adefovir dipivoxil for treatment of chronic hepatitis B (CHB) in patients with decompensated liver disease. This Phase 2, double‐blind study randomized 112 patients with CHB and decompensated liver disease to receive either tenofovir disoproxil fumarate (TDF; n = 45), emtricitabine (FTC)/TDF (fixed‐dose combination; n = 45), or entecavir (ETV; n = 22). The primary endpoint was safety; more specifically, tolerability failure (adverse events resulting in permanent treatment discontinuation) and confirmed serum creatinine increase ≥0.5 mg/dL from baseline or confirmed serum phosphorus <2 mg/dL. Patients with insufficient viral suppression (e.g., confirmed HBV DNA ≥400 copies/mL at week 8 or 24) could begin open‐label FTC/TDF but were considered failures in this interim week 48 analysis for efficacy endpoints. Tolerability failure was infrequent across arms: 6.7% TDF, 4.4% FTC/TDF, and 9.1% ETV (P = 0.622) as were confirmed renal parameters meeting threshold 8.9%, 6.7%, and 4.5% (P = 1.000), respectively. Six patients died (none considered related to study drug) and six received liver transplants (none had HBV recurrence). The adverse event and laboratory profiles were consistent with advanced liver disease and complications, with no unexpected safety signals. At week 48, HBV DNA was <400 copies/mL (69 IU/mL) in 70.5% (TDF), 87.8% (FTC/TDF), and 72.7% (ETV) of patients. Proportions with normal alanine aminotransferase were: 57% (TDF), 76% (FTC/TDF), and 55% (ETV). Hepatitis B e antigen (HBeAg) loss/seroconversion occurred in 21%/21% (TDF), 27%/13% (FTC/TDF), and 0%/0% (ETV). Child‐Turcotte‐Pugh and Modification for End‐stage Liver Disease scores improved in all groups. Conclusion: All treatments were well tolerated in patients with decompensated liver disease due to CHB with improvement in virologic, biochemical, and clinical parameters. (HEPATOLOGY 2011.)

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)

No detectable resistance to tenofovir disoproxil fumarate after 6 years of therapy in patients with chronic hepatitis B

One major challenge in the treatment of chronic hepatitis B is to maintain long‐term viral suppression without promoting the selection of drug‐resistant mutations. We analyzed data from 347 hepatitis B e antigen‐negative and 238 hepatitis B e antigen‐positive patients receiving tenofovir disoproxil fumarate (TDF) in an open‐label, long‐term extension of two phase 3 studies. To date, resistance analyses have been completed for patients receiving up to 288 weeks (6 years) of TDF. Population sequencing of hepatitis B virus (HBV) polymerase/reverse transcriptase (pol/RT) was attempted for all patients at baseline, and any patient who remained viremic (HBV DNA ≥400 copies/mL [≥69 IU/mL]) at week 288 or at the end of treatment with TDF (n = 52) or emtricitabine (FTC)/TDF (n = 7). Phenotypic analyses were performed in HepG2 cells using recombinant HBV containing patient pol/RT sequences. Approximately half of the patients on open‐label treatment who qualified for genotyping had pol/RT sequence changes compared to baseline (23/52 [44%] on TDF, 4/7 [57%] on FTC/TDF). Most changes were at polymorphic sites and none were associated with TDF resistance. Virologic breakthrough occurred infrequently and was associated with nonadherence to study medication in the majority of cases (12/16, 75%). Per protocol, 57 patients (10%) were eligible to switch to FTC/TDF; the majority had HBV DNA <400 copies/mL at their last study visit regardless of whether they switched to FTC/TDF (n = 34) or maintained TDF monotherapy (n = 17). No patient exhibited persistent viremia (HBV DNA never <400 copies/mL) after week 240. Conclusion: TDF monotherapy maintains effective suppression of HBV DNA through 288 weeks of treatment with no evidence of TDF resistance. (Hepatology 2014;59:434–442)

Efficacy of tenofovir disoproxil fumarate at 240 weeks in patients with chronic hepatitis B with high baseline viral load

We evaluated the antiviral response of patients with chronic hepatitis B (CHB) who had baseline high viral load (HVL), defined as having hepatitis B virus (HBV) DNA ≥9 log10 copies/mL, after 240 weeks of tenofovir disoproxil fumarate (TDF) treatment. A total of 641 hepatitis B e antigen (HBeAg)‐negative and HBeAg‐positive patients (129 with HVL) received 48 weeks of TDF 300 mg (HVL n = 82) or adefovir dipivoxil (ADV) 10 mg (HVL n = 47), followed by open‐label TDF for an additional 192 weeks. Patients with confirmed HBV DNA ≥400 copies/mL on or after week 72 had the option of adding emtricitabine (FTC). By week 240, 98.3% of HVL and 99.2% of non‐HVL patients on treatment achieved HBV DNA <400 copies/mL. Both groups had similar rates of histologic regression between baseline and week 240. Patients with HVL generally took longer to achieve HBV DNA <400 copies/mL than non‐HVL patients, but by week 96, the percentages of patients with HBV DNA <400 copies/mL were similar in both groups. Among HVL patients, time to achieving HBV DNA <400 copies/mL was shorter among those initially receiving TDF, compared to ADV. No patient with baseline HVL had persistent viremia at week 240 or amino acid substitutions associated with TDF resistance. Conclusion: CHB patients with HVL can achieve HBV DNA negativity with long‐term TDF treatment, although time to HBV DNA <400 copies/mL may be longer, relative to patients with non‐HVL. (Hepatology 2013;58:505–513)

Long-term efficacy and safety of emtricitabine plus tenofovir DF vs. tenofovir DF monotherapy in adefovir-experienced chronic hepatitis B patients

BACKGROUND & AIMS Suboptimal virologic response to nucleos(t)ide analogs may represent a significant risk factor for resistance development in patients with chronic hepatitis B virus infection; treatment options have not been well studied. We evaluated long-term efficacy and safety of tenofovir alone and in combination with emtricitabine in a prospective, placebo-controlled trial in patients who remained viremic on adefovir therapy. METHODS Hepatitis B e antigen-positive and -negative patients with hepatitis B virus DNA ⩾ 1000 copies/ml despite up to 96 weeks of adefovir were randomized to double-blind tenofovir or emtricitabine/tenofovir for 168 weeks. Patients with hepatitis B virus DNA ⩾ 400 copies/ml (⩾ 69IU/ml) at or after week 24 could switch to open-label emtricitabine/tenofovir. RESULTS Overall, 90/105 (86%) patients (46/53 tenofovir and 44/52 emtricitabine/tenofovir) completed the 168-week study period, including 74/105 (70%) patients (35/53 tenofovir and 39/52 emtricitabine/tenofovir) who completed the study on their initial randomized treatment. Long-term viral suppression (hepatitis B virus DNA <400 copies/ml) was maintained at week 168 in 84% and 82% of patients receiving either emtricitabine/tenofovir combination or tenofovir monotherapy, respectively (non-completer equal to failure analysis). Baseline viral load as well as the presence of lamivudine and/or adefovir resistance-associated mutations at baseline had no impact on long-term treatment response. No resistance to tenofovir was observed through 168 weeks. Both treatments had a favorable safety profile. CONCLUSIONS Tenofovir monotherapy is as effective as emtricitabine/tenofovir combination therapy in maintaining long-term viral suppression in patients with a suboptimal response to adefovir, and is well tolerated in this population.

No Resistance to Tenofovir Disoproxil Fumarate Through 96 Weeks of Treatment in Patients With Lamivudine-Resistant Chronic Hepatitis B

BACKGROUND & AIMS A recent study compared the efficacy of tenofovir disoproxil fumarate (TDF) vs the combination of emtricitabine and TDF (FTC/TDF) in patients with lamivudine-resistant chronic hepatitis B who were treated for as long as 96 weeks. We report findings from resistance analyses conducted for this study. METHODS Two hundred eighty patients with chronic hepatitis B virus (HBV) infection and lamivudine resistance (confirmed by INNO-LiPA Multi-DR) were randomly assigned (1:1) to groups treated with TDF or FTC/TDF. The HBV reverse transcriptase domain from the polymerase gene from all patients was sequenced at baseline and from 18 viremic patients at week 96 or early discontinuation. RESULTS At screening for the efficacy study, 99% of patients were found to have lamivudine resistance. Prior exposure to entecavir or entecavir resistance was observed in 12% of patients, and 22% of patients had been previously exposed to adefovir; 1.8% were resistant to adefovir. Only 18 patients (6.4%) qualified for sequence analysis, including 1 patient who experienced virologic breakthrough and 17 with persistent viremia. Six of these patients did not have any sequence changes from baseline in HBV reverse transcriptase (33%), and sequence analysis could not be performed for 5 patients (28%). In 2 patients who qualified for phenotypic analysis (1 given TDF and 1 given FTC/TDF), no resistance to TDF was observed. Neither previous treatment exposure nor resistance to entecavir or adefovir affected viral kinetics. However, the mean baseline level of HBV DNA was significantly higher in viremic patients than in patients with viral suppression by week 96 (7.28 log10 IU/mL vs 5.62 log10 IU/mL; P = .0003). CONCLUSIONS No resistance to TDF was detected through 96 weeks of treatment in patients with lamivudine-resistant chronic hepatitis B. Prior treatment or resistance to entecavir or adefovir did not affect viral kinetics through 96 weeks. No additional benefit was observed with the addition of emtricitabine vs TDF monotherapy. ClinicalTrial.gov number: NCT00737568.

Similar evolution of hepatitis B virus quasispecies in patients with incomplete adefovir response receiving tenofovir/emtricitabine combination or tenofovir monotherapy

BACKGROUND & AIMS Adefovir (ADV) resistance mutations induce low-level cross-resistance to tenofovir in vitro. Our aim was to compare viral kinetics, nucleos(t)ide analog resistance mutations, and quasispecies (QS) evolution during therapy with tenofovir disoproxil fumarate (TDF) or emtricitabine + TDF (FTC/TDF) in selected patients with incomplete ADV responses. METHODS Patients with chronic hepatitis B and incomplete response to ADV were randomized in a double-blind trial of TDF vs. FTC/TDF. Extensive analysis of QS evolution was performed in 17 patients through 48 weeks of treatment. RESULTS At week 24, 48% of patients (9/17) achieved HBV DNA undetectability (<69 IU/ml) with no difference between treatment groups. ADV and/or LAM resistance mutations were detected in all 17 patients at baseline and in 5/6 analyzable patients at week 48. A total of 1224 reverse transcriptase clones were analyzed. Clonal analysis revealed no significant difference at baseline in QS complexity or diversity between treatment groups. There was a trend in both treatment groups for an increase in QS complexity at week 12, followed by a decrease in complexity and diversity by week 48. Analysis of individual patients showed no consistent selection/accumulation of specific viral resistance patterns during treatment, but at week 48, mutations at rtA181 persisted in 4 patients. CONCLUSIONS TDF or FTC/TDF demonstrated strong viral suppression in patients with an incomplete response to ADV and no significant selective pressure on pre-existing ADV or LAM resistant strains. TDF monotherapy and FTC/TDF combination therapy had a comparable impact on QS evolution.

No detectable resistance to tenofovir disoproxil fumarate in HBeAg+ and HBeAg- patients with chronic hepatitis B after 8 years of treatment.

A major hurdle in the long‐term treatment of chronic hepatitis B (CHB) patients is to maintain viral suppression in the absence of drug resistance. To date, no evidence of resistance to tenofovir disoproxil fumarate (TDF) has been observed. A cumulative evaluation of CHB patients who qualified for resistance surveillance over 8 years of TDF treatment was conducted. Patients in studies GS‐US‐174‐0102 (HBeAg−) and GS‐US‐174‐0103 (HBeAg+) were randomized 2:1 to receive TDF or adefovir dipivoxil (ADV) for 48 weeks followed by open‐label TDF through year 8. Population sequencing of HBV pol/RT was attempted for all TDF‐treated patients at baseline and, annually if viremic, at discontinuation, or with addition of emtricitabine. Overall, 88/641 (13.7%) patients qualified for sequence analysis at one or more time points. The percentage of patients qualifying for sequence analysis declined over time, from 9 to 11% in years 1‐2 to <4% over years 3‐8. Forty‐one episodes of virologic breakthrough (VB) occurred throughout the study, with most (n=29, 70%) associated with nonadherence to study medication. Fifty‐nine per cent of VB patients with an opportunity to resuppress HBV achieved HBV DNA resuppression. A minority of patients who qualified for sequencing had polymorphic (41/165, 24.8%) or conserved (17/165, 10.3%) site changes in pol/RT, with six patients developing lamivudine and/or ADV resistance‐associated mutations. No accumulation of conserved site changes was detected. The long‐term treatment of CHB with TDF monotherapy maintains effective suppression of HBV DNA through 8 years, with no evidence of TDF resistance or accumulation of conserved site changes.

Deep sequencing shows that HBV basal core promoter and precore variants reduce the likelihood of HBsAg loss following tenofovir disoproxil fumarate therapy in HBeAg-positive chronic hepatitis B.

Objective Hepatitis B e antigen (HBeAg) seroconversion and hepatitis B surface antigen (HBsAg) loss are important clinical outcomes for patients with chronic hepatitis B (CHB) treated with antiviral therapy. To date, there have been few studies that have evaluated viral sequence markers predicting serological response to nucleos(t)ide analogue (NA) treatment. Design We used next-generation sequencing (NGS) and quantitative HBV serology (HBeAg and HBsAg) to identify viral sequence markers associated with serological response to long-term tenofovir disoproxil fumarate therapy among HBeAg-positive patients. In the GS-US-174-0103 study, approximately half the patients seroconverted to anti-HBe by week 192 and 11% of patients exhibited HBsAg loss, the closest outcome to functional cure. The frequency of HBV variants that have previously been associated with HBV clinical outcomes was evaluated. HBV viral diversity in baseline sequences generated by NGS was calculated using Shannon entropy. Results NGS analysis of HBV sequences from 157 patients infected with genotypes A to D showed the frequency of variants in the basal core promoter (BCP) and precore (PC) regions varied by genotype and that these mutations were associated with the absence of HBsAg loss. This was the case even when mutations were present at frequencies below the threshold of detection by population sequencing. Increased viral diversity across the HBV genome as determined by NGS was also associated with reduced likelihood of HBsAg loss. Conclusion Patients with detectable BCP and/or PC variants and higher viral diversity have a lower probability of HBsAg loss during long-term NA therapy. Strategies to achieve functional cure of HBV infection through combination therapy should consider using NGS to stratify patients according to BCP/PC sequence. Consideration should also be given to earlier initiation of therapy prior to the emergence of BCP/PC variants. Trial registration number NCT00116805; Post result.

Hepatitis B virus wild-type and rtN236T populations show similar early HBV DNA decline in adefovir refractory patients on a tenofovir-based regimen

Summary.  Hepatitis B virus (HBV) pol/RT mutations that confer clinical resistance to tenofovir disoproxil fumarate (TDF) have not been detected to date. In vitro, the rtN236T adefovir dipivoxil (ADV)‐associated resistance mutation confers low‐level cross‐resistance to tenofovir: 3‐ to 13‐fold changes in EC50 from wild type. This study evaluated the clinical response of rtN236T mutant viruses by comparing their early viral load decay kinetics to wild‐type viruses in chronic HBV monoinfected patients harbouring rtN236T prior to initiating TDF or emtricitabine (FTC)/TDF therapy. Baseline samples (n = 105) from adefovir refractory patients were tested for the presence of rtN236T using a highly sensitive allele‐specific PCR assay with an rtN236T detection cut‐off of 0.5%. The rtN236T mutation was detected at baseline in 14.3% (14/98) of analysable patient samples (0.5–93.2%, rtN236T percentage range). The median change in total HBV DNA at week 24 was comparable for patients with rtN236T detected at baseline (−3.7 log10 copies/mL, n = 14) as compared to patients with wild‐type HBV (−3.2 log10 copies/mL, n = 90). In patients with rtN236T, wild‐type and rtN236T mutant virus showed similar rates of HBV DNA decline with no statistically significant difference observed at week 4. Moreover, the proportion of rtN236T remained unchanged in patients in either arm of the study during treatment. In conclusion, the rtN236T mutant virus showed similar HBV DNA decline kinetics to wild‐type virus in adefovir refractory patients who switched to TDF or FTC/TDF. Despite low levels of cross‐resistance in vitro, TDF similarly suppresses wild‐type and rtN236T mutant viruses in vivo.