Development of a sensitive, multi-assay platform to monitor low levels of HBV DNA and pgRNA in patients with chronic hepatitis B virus infection.

HBV cure rates remain low despite prolonged nucleos(t)ide (NrtI) therapy, likely due to persistent residual viral replication and an inability to eliminate covalently closed circular DNA (cccDNA). Therapies with novel mechanisms of action against hepatitis B virus (HBV) are being explored with the goal of achieving sustained off-treatment response and a functional cure without requiring lifelong therapy. Recent studies have indicated that serum HBV DNA levels (a biomarker for viral replication) combined with serum pregenomic RNA (pgRNA) levels (a surrogate for intrahepatic cccDNA transcriptional activity), may provide a better prediction for the risk of liver-related complications. Current HBV DNA assays, such as the COBAS AmpliPrep/COBAS TaqMan HBV test v2.0, quantitate HBV DNA down to 20 IU/mL, but are not able to monitor loss of residual virus in patients on NrtI therapy. There are no commercially available assays approved to detect serum/plasma HBV pgRNA levels. We have developed a multi-assay panel of highly sensitive nucleic acid assays designed to monitor levels of HBV DNA, pgRNA and total nucleic acids (TNA, composite DNA + pgRNA) in clinical specimens and to monitor changes during treatment with new antiviral combination regimens.

Discovery of Half-life of Circulating Hepatitis B Surface Antigen in Patients With Chronic Hepatitis B Infection Using Heavy Water Labeling.

In a pilot study, heavy water labeling was used to determine hepatitis B surface antigen (HBsAg) turnover rates in chronic hepatitis B (CHB) patients. The mean (standard deviation) half-life of HBsAg in blood was 6.7 (5.5) days, which reflects recent production in the liver and supports strategies aimed at reducing HBsAg production in CHB patients.

Development of an HIV-1 integrase genotyping assay for HIV-1 subtype AE.

An human immunodeficiency virus (HIV)-1 integrase (IN) genotyping assay was developed to evaluate clinical samples from patients infected with HIV-1 subtype AE, a subtype highly prevalent in Asia. The HIV-1 IN gene was amplified from plasma-derived HIV-1 viral RNA via reverse transcription polymerase chain reaction followed by population sequencing. Assay sensitivity was also evaluated using serially diluted plasma samples. The genotyping assay successfully amplified the IN gene from patient plasma samples with HIV-1 RNA as low as 500 copies/mL. This assay is suitable for IN genotyping to identify IN drug resistance mutations in HIV-1 patients harboring subtype AE virus.

No Resistance to Tenofovir Alafenamide Detected through 96 Weeks of Treatment in Patients with Chronic Hepatitis B Infection.

Tenofovir alafenamide (TAF) has shown equivalent efficacy and improved safety profiles for patients with chronic hepatitis B (CHB) compared to tenofovir disoproxil fumarate (TDF). However, limited data are available for its resistance profiles. In two clinical trials, 1,298 hepatitis E antigen-positive and -negative patients with CHB were randomized 2:1 and treated with TAF (n = 866) or TDF (n = 432). Baseline nucleos(t)ide analog resistance substitutions in HBV polymerase/reverse transcriptase (Pol/RT) were assessed using INNO-LiPA Multi-DR v2/v3. Resistance surveillance was conducted for patients with viremia (HBV DNA ≥ 69IU/ml) by HBV Pol/RT sequencing at week 96 or at discontinuation. In vitro phenotypic analysis was performed for patients with conserved site substitutions or virologic breakthrough while adherent to the study drug. At baseline, the majority of patients harbored virus with wild-type Pol/RT (89.2%), with 10.8% harboring resistance associated mutations. A similar percentage of patients in the TAF or TDF groups qualified for sequence analysis through week 96 (TAF, 11.1%; TDF, 10.9%). Of these, a small percentage of patients experienced virologic breakthrough (TAF, 2.8%; TDF, 3.2%) that was often associated with drug nonadherence (TAF, 30%; TDF, 50%). Across treatment groups, 132 patients qualified for sequence analysis through week 96, with nearly half having no sequence changes from baseline (43.2%). Most sequence changes occurred at polymorphic positions, and no isolates showed a reduction in susceptibility in vitro After 96 weeks, the proportion of patients achieving virus suppression (HBV DNA < 69 IU/ml) was similar across treatment groups, and no substitutions associated with resistance to TAF or TDF were detected. (These studies have been registered at ClinicalTrials.gov under identifiers NCT01940471 and NCT01940341.).

Development of a digital droplet PCR assay to measure HBV DNA in patients receiving long-term TDF treatment.

The COBAS TaqMan assay has a lower limit of quantification (LLOQ) of 169 HBV copies/mL and a lower limit of detection (LLOD) of 58 copies/mL. HBV DNA below the TaqMan LLOQ is classified as target not detected (TND) (<58 copies/mL) or target detected (TD) (between 58 and 169 copies/mL). Here we have developed a more sensitive digital droplet PCR (ddPCR) assay to evaluate the impact of long-term tenofovir disoproxil fumarate (TDF) treatment in patients that did or did not achieve HBsAg seroconversion. A ddPCR assay was developed to detect HBV DNA to 8 copies/mL. HBV DNA levels in plasma from patients with or without HBsAg seroconversion were assessed by ddPCR. For patients who did not achieve HBsAg seroconversion, the majority of TD samples (33/58, 57%) were HBV DNA positive by ddPCR while (10/37, 27%) of TND samples were positive. In contrast, for patients who achieved HBsAg seroconversion, HBV DNA was rarely detected by ddPCR after HBsAg seroconversion (1/28, 3.6%). ddPCR is a sensitive method to evaluate low-level viral replication in plasma samples. Frequent detection of HBV DNA by ddPCR among patients who did not achieve HBsAg seroconversion suggests new agents may be needed to suppress low levels of replicating HBV.

Tenofovir disoproxil fumarate (TDF) vs. emtricitabine (FTC)/TDF in lamivudine resistant hepatitis B: A 5-year randomised study.

BACKGROUND & AIMS: Long-term treatment with tenofovir disoproxil fumarate (TDF) alone, or in combination with emtricitabine (FTC) is associated with sustained viral suppression in patients with lamivudine resistant (LAM-R) chronic hepatitis B (CHB). METHODS: LAM-R CHB patients were randomised 1:1 to receive TDF 300mg or FTC 200mg and TDF 300mg once daily in a prospective, double blind, study. The proportion of patients with plasma hepatitis B virus (HBV) DNA<69IU/ml (<400copies/ml) at week 96 (primary efficacy endpoint) was reported previously. Here we present week 240 follow-up data. RESULTS: Overall, 280 patients were randomised to receive TDF (n=141) or FTC/TDF (n=139), and 85.4% completed 240weeks of treatment. At week 240, 83.0% of patients in the TDF arm, and 82.7% of patients in the FTC/TDF treatment arm had HBV DNA<69IU/ml (p=0.96). Rates of normal alanine aminotransferase (ALT) and normalised ALT were similar between groups (p=0.41 and p=0.97 respectively). Hepatitis B e antigen loss and seroconversion at week 240 were similar between groups, (p=0.41 and p=0.67 respectively). Overall, six patients achieved hepatitis B surface antigen (HBsAg) loss and one patient (FTC/TDF arm) had HBsAg seroconversion by week 240. No TDF resistance was observed up to week 240. Treatment was generally well tolerated, and renal events were mild and infrequent (∼8.6%). The mean change in bone mineral density at week 240 was -0.98% and -2.54% at the spine and hip, respectively. CONCLUSIONS: TDF monotherapy was effective and well tolerated in LAM-R CHB patients for up to 240weeks. LAY SUMMARY: The goal of oral antiviral treatment for chronic hepatitis B (CHB) is to achieve and maintain undetectable HBV DNA levels. Treatment options with enhanced potency, and low risk of resistance development for patients infected with lamivudine resistant (LAM-R) HBV are required. Tenofovir disoproxil fumarate (TDF) monotherapy was effective and well tolerated without TDF resistance development in CHB patients with LAM-R, for up to 240weeks. Clinical trial number: NCT00737568.

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.

Tenofovir alafenamide demonstrates broad cross-genotype activity against wild-type HBV clinical isolates and maintains susceptibility to drug-resistant HBV isolates in vitro.

Tenofovir alafenamide (TAF) is a novel prodrug of tenofovir (TFV). This study evaluated the antiviral activity of TAF against wild-type genotype A-H HBV clinical isolates as well as adefovir-resistant, lamivudine-resistant, and entecavir-resistant HBV isolates. Full length HBV genomes or the polymerase/reverse transcriptase (pol/RT) region from treatment-naïve patients infected with HBV genotypes A-H were amplified and cloned into an expression vector under the control of a CMV promoter. In addition, 11 drug resistant HBV constructs were created by site-directed mutagenesis of a full length genotype D construct. Activity of TAF was measured by transfection of each construct into HepG2 cells and assessment of HBV DNA levels following treatment across a range of TAF concentrations. TAF activity in vitro was similar against wild-type genotype A-H HBV clinical isolates. All lamivudine- and entecavir-resistant isolates and 4/5 adefovir-resistant isolates were found to be sensitive to inhibition by TAF in vitro as compared to the wild-type isolate. The adefovir-resistant isolate rtA181V + rtN236T exhibited low-level reduced susceptibility to TAF. TAF is similarly active in vitro against wild-type genotype A-H HBV clinical isolates. The TAF sensitivity results for all drug-resistant isolates are consistent with what has been observed with the parent drug TFV. The in vitro cell-based HBV phenotyping assay results support the use of TAF in treatment of HBV infected subjects with diverse HBV genotypes, in both treatment-naive and treatment-experienced HBV infected patients.

Modeling the functional state of the reverse transcriptase of hepatitis B virus and its application to probing drug-protein interaction.

BACKGROUND: Herein, the predicted atomic structures of five representative sequence variants of the reverse transcriptase protein (RT) of hepatitis B virus (HBV), sampled from patients with rapid or slow response to tenofovir disoproxil fumarate (TDF) treatment, have been examined to identify structural variations between them in order to assess structural and functional properties of HBV-RT variants associated with the differential responses to TDF treatment. RESULTS: We utilized a hybrid computational approach to model the atomistic structures of HBV-RT/DNA-RNA/dATP and HBV-RT/DNA-RNA/TFV-DP (tenofovir diphosphate) complexes with the native hybrid DNA-RNA substrate in place. Multi-nanosecond molecular dynamics (MD) simulations of HBV-RT/DNA-RNA/dATP complexes revealed strong coupling of the natural nucleotide substrate, dATP, to the active site of the RT, and the differential involvement of the two putative magnesium cations (Mg(2+)) at the active site, whereby one Mg(2+) directly bridges the interaction between dATP and HBV-RT and the other serves as a coordinator to maintain an optimal configuration of the active site. Solvated interaction energy (SIE) calculated in MD simulations of HBV-RT/DNA-RNA/TFV-DP complexes indicate no differential binding affinity between TFV-DP and HBV-RT variants identified in patients with slow or rapid response to TDF treatment. CONCLUSION: The predicted atomic structures accurately represent functional states of HBV-RT. The equivalent interaction between TFV-DP and each examined HBV-RT variants suggests that binding affinity of TFV-DP to HBV-RT is not associated with delayed viral clearance.

Rare emergence of drug resistance in HIV-1 treatment-naïve patients after 48 weeks of treatment with elvitegravir/cobicistat/emtricitabine/tenofovir alafenamide.

Tenofovir alafenamide (TAF), a novel prodrug of the NtRTI tenofovir (TFV), delivers TFV-diphosphate (TFV-DP) to target cells more efficiently than the current prodrug, tenofovir disoproxil fumarate (TDF), with a 90% reduction in TFV plasma exposure. TAF, within the fixed dose combination of elvitegravir /cobicistat / emtricitabine (FTC)/TAF (E/C/F/TAF), has been evaluated in one Phase 2 and two Phase 3 randomized, double-blinded studies in HIV-infected treatment-naive patients, comparing E/C/F/TAF to E/C/F/TDF. In these studies, the TAF-containing group demonstrated non-inferior efficacy to the TDF-containing comparator group with 91.9% of E/C/F/TAF patients having <50 copies/mL of HIV-1 RNA at week 48. An integrated resistance analysis across these three studies was conducted, including HIV-1 genotypic analysis at screening, and genotypic/phenotypic analysis for patients with HIV-1 RNA>400 copies/mL at virologic failure. Pre-existing primary resistance-associated mutations (RAMs) were observed at screening among the 1903 randomized and treated patients: 7.5% had NRTI-RAMs, 18.2% had NNRTI-RAMs, and 3.4% had primary PI-RAMs. Pre-treatment RAMs did not influence treatment response at Week 48. In the E/C/F/TAF group, resistance development was rare; seven patients (0.7%, 7/978) developed NRTI-RAMs, five of whom (0.5%, 5/978) also developed primary INSTI-RAMs. In the E/C/F/TDF group, resistance development was also rare; seven patients (0.8%, 7/925) developed NRTI-RAMs, four of whom (0.4%, 4/925) also developed primary INSTI-RAMs. An additional analysis by deep sequencing in virologic failures revealed minimal differences compared to population sequencing. Overall, resistance development was rare in E/C/F/TAF-treated patients, and the pattern of emergent mutations was similar to E/C/F/TDF.

Tenofovir alafenamide versus tenofovir disoproxil fumarate for the treatment of HBeAg-positive chronic hepatitis B virus infection: a randomised, double-blind, phase 3, non-inferiority trial.

BACKGROUND: Tenofovir alafenamide is a novel prodrug formulated to deliver the active metabolite to target cells more efficiently than tenofovir disoproxil fumarate at a lower dose, thereby reducing systemic exposure. In patients with HIV, tenofovir alafenamide was as efficacious as tenofovir disoproxil fumarate, with reduced bone and renal toxic effects. We compared the efficacy and safety of the two drugs in patients with HBeAg-positive chronic hepatitis B virus (HBV) infection in a non-inferiority study. METHODS: We did this ongoing double-blind, non-inferiority study in 161 outpatient centres in 19 countries. Patients with chronic HBV infection who were positive for the hepatitis B e antigen (HBeAg) were randomly assigned (2:1) to receive either 25 mg tenofovir alafenamide or 300 mg tenofovir disoproxil fumarate with matching placebo. Randomisation was done by a computer-generated allocation sequence (block size six) stratified by plasma HBV DNA concentration and previous treatment experience. The primary efficacy endpoint was the proportion of patients with HBV DNA less than 29 IU/mL at week 48 in all patients who were randomly assigned and received at least one dose of study drug using a missing-equals-failed approach. The pre-specified non-inferiority margin was 10%. Key prespecified safety endpoints were bone and renal parameters at week 48. This study is registered with ClinicalTrials.gov, number NCT01940471. FINDINGS: Of the 1473 patients screened from Sept 11, 2013, to Dec 20, 2014, 875 eligible patients were randomly assigned and 873 received treatment (581 with tenofovir alafenamide and 292 with tenofovir disoproxil fumarate). 371 (64%) patients receiving tenofovir alafenamide had HBV DNA less than 29 IU/mL at week 48, which was non-inferior to the 195 (67%) of patients receiving tenofovir disoproxil fumarate who had HBV DNA less than 29 IU/mL (adjusted difference -3·6% [95% CI -9·8 to 2·6]; p=0·25). Patients given tenofovir alafenamide had a significantly smaller decrease in bone mineral density at hip (mean change -0·10% [95% CI -0·29 to 0·09] vs -1·72% [-2·02 to -1·41]; adjusted difference 1·62 [1·27 to 1·96]; p<0·0001) and at spine (mean change -0·42% [-0·66 to -0·17] vs -2·29% [-2·67 to -1·92]; adjusted difference 1·88 [1·44 to 2·31]; p<0·0001) as well as smaller mean increases in serum creatinine at week 48 (0·01 mg/dL [0·00-0·02] vs 0·03 mg/dL [0·02-0·04]; p=0·02). The most common adverse events overall were upper respiratory tract infection (51 [9%] of 581 patients receiving tenofovir alafenamide vs 22 [8%] of 292 patients receiving tenofovir disoproxil fumarate), nasopharyngitis (56 [10%] vs 16 [5%]), and headache (42 [7%] vs 22 [8%]). 22 (4%) patients receiving tenofovir alafenamide and 12 (4%) patients receiving tenofovir disoproxil fumarate experienced serious adverse events, none of which was deemed by the investigator to be related to study treatment. 187 (32%) of 581 patients in the tenofovir alafenamide group and 96 (33%) of 292 patients in the tenofovir disoproxil fumarate group had grade 3 or 4 laboratory abnormalities, the most common of which were elevations in ALT (62 [11%] of 577 patients receiving tenofovir alafenamide and 36 [13%] of 288 patients receiving tenofovir disoproxil fumarate) and AST (20 [3%] of 577 patients receiving tenofovir alafenamide and 19 [7%] of 288 patients receiving tenofovir disoproxil fumarate). INTERPRETATION: In patients with HBeAg-positive HBV infection, tenofovir alafenamide was non-inferior to tenofovir disoproxil fumarate, and had improved bone and renal effects. Longer term follow-up is needed to better understand the clinical impact of these changes. FUNDING: Gilead Sciences.

Tenofovir disoproxil fumarate in Asian or Pacific Islander chronic hepatitis B patients with high viral load (≥ 9 log10 copies/ml).

BACKGROUND & AIMS: We evaluated the antiviral response of Asian or Pacific Islander (API) patients with chronic hepatitis B (CHB) who had baseline high viral load (HVL), defined as pre-treatment hepatitis B virus (HBV) DNA ≥9 log10 copies/ml, following up to 288 weeks of tenofovir disoproxil fumarate (TDF) treatment. METHODS: A total of 205 HBeAg-negative and HBeAg-positive self-described API patients received 48 weeks of TDF 300 mg (HVL n = 18) or adefovir dipivoxil 10 mg (HVL n = 15) in a blinded fashion, followed by open-label TDF for an additional 240 weeks. The proportions of HVL vs. non-HVL patients with HBV DNA <400 copies/ml were compared. Mean declines in HBV DNA were evaluated in API vs. non-API patients. RESULTS: Throughout the first 72 weeks of treatment, a smaller proportion of HVL API patients reached HBV DNA <400 copies/ml than non-HVL API patients. However, after this timepoint similar proportions of HVL and non-HVL API patients achieved HBV DNA <400 copies/ml (100% vs. 97%, respectively), which was maintained through week 288, where 92% of HVL patients and 99% of non-HVL API patients on treatment had HBV DNA <400 copies/ml. During the 288 weeks of treatment, API patients had similar mean HBV DNA declines as non-API patients, regardless of whether patients were HVL or non-HVL. No API HVL patient had persistent viremia at week 288. No resistance was detected among HVL or non-HVL patients. CONCLUSIONS: API patients with HVL CHB achieve HBV DNA <400 copies/ml with long-term TDF treatment; however, achieving viral suppression may take longer for HVL patients relative to non-HVL API patients.

Baseline interpatient hepatitis B viral diversity differentiates HBsAg outcomes in patients treated with tenofovir disoproxil fumarate.

BACKGROUND AND AIMS: HBsAg loss is a desired, but rare, treatment-induced clinical endpoint in chronic hepatitis B (CHB). Few studies have evaluated viral factors contributing to HBsAg loss. METHODS: This study evaluated baseline interpatient sequence diversity across the HBV genome in tenofovir disoproxil fumarate-treated patients who lost HBsAg and compared it to that of control patients with high HBsAg levels throughout therapy. Twenty-one HBeAg+ patients (14 genotype (GT) A and 7 GT D) who achieved HBsAg loss and 27 controls (17 GT A and 10 GT D), were analyzed. Population sequencing was performed on baseline samples and pairwise genetic distances were calculated for 17 overlapping regions across the HBV genome as a measure of interpatient viral diversity. RESULTS: Overall, viral diversity was up to 10-fold higher across GT D patients compared to GT A patients throughout the HBV genome. Within the pol/RT and HBs genes, interpatient viral diversity was significantly lower among HBsAg loss patients for both GT A and D, with the difference driven largely by a reduction in diversity in the small S gene. Conversely, interpatient viral diversity was generally higher in HBsAg loss patients across the HBx gene regulatory elements and precore region. CONCLUSION: In HBsAg loss patients, less interpatient viral diversity was observed within structural-coding regions while specific regions across the HBx and precore genes encoding nonstructural regulatory elements generally displayed higher interpatient viral diversity. These distinct patterns may reflect different responses to adaptive pressure for HBV genomic structural and nonstructural elements.

Viral suppression and cirrhosis regression with tenofovir disoproxil fumarate in Asians with chronic hepatitis B.

BACKGROUND: Chronic hepatitis B (CHB) is a major public health concern, particularly in endemic areas like Asia-Pacific. Sustained virologic suppression correlates with regression of histologic fibrosis and cirrhosis. AIM: This study evaluated efficacy and safety of tenofovir disoproxil fumarate (TDF) in Asian patients through 240 weeks of treatment. METHODS: Post hoc analysis of the Asian subpopulation from two phase 3 clinical studies was performed. Following a 48-week randomized, double-blind evaluation of once-daily TDF versus once-daily adefovir dipivoxil, open-label TDF for up to 240 weeks was evaluated. Patients with both baseline and week 240 liver biopsies were evaluated for histologic changes. RESULTS: At baseline, 189/641 (29 %) patients randomized were Asian. Sixty-eight percent of Asian patients were male; 50 % were hepatitis B e antigen (HBeAg)-positive. At week 240, similar proportions of Asian (88 %) and non-Asian (87 %) patients demonstrated improvement in liver histology, and 19/22 (86 %) Asian patients with baseline cirrhosis were no longer cirrhotic. By modified intent-to-treat analysis, 74 % of Asian patients and 76 % of non-Asian patients had HBV DNA <400 copies/mL at the end of week 240 (P = 0.602). No differences were seen in HBeAg loss or seroconversion in Asian versus non-Asian patients. No Asian patient experienced hepatitis B surface antigen loss. Safety and tolerability of TDF through week 240, including changes in renal function and in hip/spine bone mineral density (from weeks 192 to 240), were comparable between Asian and non-Asian patients. CONCLUSIONS: Long-term virologic and histologic efficacy and safety of TDF are comparable in Asian and non-Asian CHB patients.

Seven-year efficacy and safety of treatment with tenofovir disoproxil fumarate for chronic hepatitis B virus infection.

BACKGROUND: Long-term tenofovir disoproxil fumarate (TDF) treatment for chronic hepatitis B (CHB) is associated with sustained viral suppression and regression of fibrosis and cirrhosis at year 5 (240 weeks) and no TDF resistance through 6 years (288 weeks). AIM: We assessed the efficacy, safety, and resistance of TDF for up to 7 years (336 weeks) in HBeAg-positive and HBeAg-negative CHB patients. METHODS: Patients who completed 1 year (48 weeks) of randomized treatment with TDF or adefovir dipivoxil were eligible to receive open-label TDF for a total duration of 8 years (384 weeks). RESULTS: Of 641 patients initially randomized, 585 (91.3 %) entered the open-label phase; 437/585 (74.7 %) remained on study at year 7. For patients on treatment at year 7, 99.3 % maintained viral suppression (HBV DNA < 69 IU/mL), 80.0 % achieved serum alanine aminotransferase normalization, and in HBeAg-positive patients, 84/154 (54.5 %) and 25/154 (11.8 %) achieved HBeAg and HBsAg loss, respectively. One/375 (0.3 %) HBeAg-negative patients achieved HBsAg loss. No resistance to TDF was detected through 7 years. During the open-label phase, grade 3/4 drug-related adverse events were uncommon (1.0 %); ten (1.7 %) patients had elevation of serum creatinine ≥ 0.5 mg/dL above baseline. No significant change in bone mineral density was observed from year 4 to year 7 (week 192 to week 336). CONCLUSIONS: Long-term TDF treatment was associated with sustained virologic, biochemical, and serologic responses, without resistance. TDF treatment was well tolerated, with a low incidence of renal and bone events. These data confirm the safety and efficacy of long-term TDF for CHB.

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.

Evaluation of HBV DNA decay kinetics in patients containing both rtM204V/I mutant and wild-type HBV subpopulations during tenofovir DF (TDF) monotherapy or combination therapy with emtricitabine (FTC)/TDF.

Tenofovir disoproxil fumarate (TDF) is recommended as treatment for chronic hepatitis B patients harboring lamivudine-associated resistance mutations (LAM-R, rtM204V/I ± rtL180M). This study evaluated the clinical response of rtM204V and rtM204I subpopulations to TDF by comparing their early viral load decay kinetics to wild-type (WT) subpopulations in chronic hepatitis B patients harboring rtM204V/I prior to initiating TDF or emtricitabine (FTC)/TDF therapy. Allele-specific PCR assays capable of detecting rtM204V or rtM204I subpopulations as low as 0.5% were developed and used to assess patient samples from a Phase 3b study evaluating TDF and FTC/TDF treatment in LAM-R patients. Baseline samples (n = 280) were quantified for rtM204V/I subpopulations and rtM204V or rtM204I subpopulations were detected in 269/273 (98.5%) baseline samples with a range of 0.7% to >95%. On-treatment analyses were conducted for seventeen patients (TDF, n = 8; FTC/TDF, n = 9) that harbored baseline WT and either rtM204V or rtM204I (no rtM204V/I mixtures) and HBV DNA ≥1,000 copies/ml at/after week 4. The median change in HBV DNA through week 12 for WT and rtM204V/I subpopulations was similar, -2.64 and -3.30 log10 copies/ml, respectively, with no significant difference between TDF and FTC/TDF treatment. In conclusion, rtM204V/I subpopulations demonstrate similar early HBV DNA decline kinetics to WT subpopulations during treatment with either TDF or FTC/TDF. These results demonstrate that TDF is similarly active against both WT and rtM204V/I subpopulations in vivo.

HBV clinical isolates expressing adefovir resistance mutations show similar tenofovir susceptibilities across genotypes B, C and D.

BACKGROUND & AIMS: Hepatitis B virus (HBV) genotypes can influence clinical outcomes as well as response to antiviral therapy. This study evaluated the tenofovir (TFV) susceptibility of HBV genotype B, C and D clinical isolates with adefovir resistance-associated mutations (ADV-R). METHODS: Full-length HBV isolates from patients infected with genotype B, C and D virus had rtA181T, rtA181V, rtN236T, rtA181T+rtN236T and rtA181V+rtN236T mutations introduced by site-directed mutagenesis. Phenotypic analyses were performed in HepG2 cells and susceptibility to TFV and ADV were assessed. RESULTS: Clinical HBV isolates containing rtA181T, rtA181V or rtN236T as single mutants remained sensitive to TFV across genotypes B, C and D. Clinical isolates containing the rtA181T+rtN236T double mutant remained sensitive to TFV in genotype D but exhibited reduced susceptibility to TFV in genotypes B and C. Viruses containing the double mutant rtA181V+rtN236T in genotypes B and D exhibited reduced susceptibility to TFV with EC50 fold changes (FC) of 3.8 and 2.5, respectively, while genotype C viruses containing rtA181V+rtN236T either remained sensitive (FC=1.3) or exhibited reduced susceptibility to TFV (FC=2.9) depending on the isolate. All rtA181V+rtN236T isolates conferred reduced susceptibility to ADV (FC values 2.3-4.2). CONCLUSIONS: Genotype B, C and D isolates with single ADV resistance mutations remained fully sensitive to TFV, while the double mutants rtA181T+rtN236T and rtA181V+rtN236T exhibited either no change or low-level reduced susceptibility to TFV across genotypes. These results are consistent with the clinical efficacy observed with tenofovir disoproxil fumarate (TDF) treatment across all genotypes in vivo and the limited impact of ADV-R mutations on TDF therapy.

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 detectable resistance to tenofovir disoproxil fumarate after 6 years of therapy in patients with chronic hepatitis B.

UNLABELLED: 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, longterm 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 (n552) or emtricitabine(FTC)/TDF (n57). 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 (n534) or maintained TDF monotherapy (n517). 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.