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14 CLINICAL STUDIES 14.1 Overview of Clinical Trials The efficacy and safety of tenofovir disoproxil fumarate in adults and pediatric subjects were evaluated in the trials summarized in Table 19. Table 19 Trials Conducted with Tenofovir Disoproxil Fumarate in Adults and Pediatric Subjects for HIV-1 Treatment and Chronic HBV Treatment Trial Population Study Arms (N) Randomized and dosed. Timepoint (Week) Trial 903 Randomized, double-blind, active-controlled trial. ( NCT00158821 ) HIV-1 treatment-naïve adults Tenofovir disoproxil fumarate+lamivudine+efavirenz (299) stavudine+lamivudine+efavirenz (301) 144 Trial 934 Randomized, open-label active-controlled trial. ( NCT00112047 ) emtricitabine+tenofovir disoproxil fumarate+efavirenz (257) zidovudine/lamivudine+efavirenz (254) 144 Trial 907 Randomized, double-blind, placebo-controlled trial. ( NCT00002450 ) HIV-1 treatment-experienced adults Tenofovir disoproxil fumarate (368) Placebo (182) 24 Trial 0102 ( NCT00117676 ) HBeAg-negative adults with chronic HBV Tenofovir disoproxil fumarate (250) HEPSERA (125) 48 Trial 0103 ( NCT00116805 ) HBeAg-positive adults with chronic HBV Tenofovir disoproxil fumarate (176) HEPSERA (90) 48 Trial 121 ( NCT00737568 ) Adults with lamivudine-resistant chronic HBV Tenofovir disoproxil fumarate (141) 96 Trial 0108 ( NCT00298363 ) Adults with chronic HBV and decompensated liver disease Tenofovir disoproxil fumarate (45) 48 Trial 352 ( NCT00528957 ) HIV-1 treatment experienced pediatric subjects 2 years to <12 years Tenofovir disoproxil fumarate (44) stavudine or zidovudine (48) 48 Trial 321 ( NCT00352053 ) HIV-1 treatment-experienced pediatric subjects 12 years to <18 years Tenofovir disoproxil fumarate (45) Placebo (42) 48 Trial 115 ( NCT00734162 ) Pediatric subjects 12 years to <18 years with chronic HBV Tenofovir disoproxil fumarate (52) Placebo (54) 72 Trial 144 § ( NCT01651403 ) Pediatric subjects 2 years to <12 years with chronic HBV Tenofovir disoproxil fumarate (60) Placebo (29) 48 14.2 Clinical Trial Results in Adults with HIV-1 Infection Treatment-Naïve Subjects: Trial 903 Data through 144 weeks are reported for Trial 903, a double-blind, active-controlled multicenter trial comparing tenofovir disoproxil fumarate (300 mg once daily) administered in combination with lamivudine (3TC) and efavirenz (EFV) versus stavudine (d4T), 3TC, and EFV in 600 antiretroviral-naïve subjects. Subjects had a mean age of 36 years (range 18–64); 74% were male, 64% were Caucasian, and 20% were Black. The mean baseline CD4+ cell count was 279 cells/mm 3 (range 3–956) and median baseline plasma HIV-1 RNA was 77,600 copies/mL (range 417–5,130,000). Subjects were stratified by baseline HIV-1 RNA and CD4+ cell count. Forty-three percent of subjects had baseline viral loads >100,000 copies/mL and 39% had CD4+ cell counts <200 cells/mm 3 . Table 20 provides treatment outcomes through 48 and 144 weeks. Table 20 Outcomes of Randomized Treatment at Week 48 and 144 (Trial 903) At Week 48 At Week 144 Outcomes Tenofovir Disoproxil Fumarate+3TC+EFV (N=299) d4T+3TC+EFV (N=301) Tenofovir Disoproxil Fumarate+3TC+EFV (N=299) d4T+3TC+EFV (N=301) Responder Subjects achieved and maintained confirmed HIV-1 RNA <400 copies/mL through Week 48 and 144. 79% 82% 68% 62% Virologic failure Includes confirmed viral rebound and failure to achieve confirmed <400 copies/mL through Week 48 and 144. 6% 4% 10% 8% Rebound 5% 3% 8% 7% Never suppressed 0% 1% 0% 0% Added an antiretroviral agent 1% 1% 2% 1% Death <1% 1% <1% 2% Discontinued due to adverse event 6% 6% 8% 13% Discontinued for other reasons Includes lost to follow-up, subject's withdrawal, noncompliance, protocol violation and other reasons. 8% 7% 14% 15% Achievement of plasma HIV-1 RNA concentrations of <400 copies/mL at Week 144 was similar between the two treatment groups for the population stratified at baseline on the basis of HIV-1 RNA concentration (> or ≤100,000 copies/mL) and CD4+ cell count (< or ≥200 cells/mm 3 ). Through 144 weeks of therapy, 62% and 58% of subjects in the tenofovir disoproxil fumarate and d4T arms, respectively, achieved and maintained confirmed HIV-1 RNA <50 copies/mL. The mean increase from baseline in CD4+ cell count was 263 cells/mm 3 for the tenofovir disoproxil fumarate arm and 283 cells/mm 3 for the d4T arm. Through 144 weeks, 11 subjects in the tenofovir disoproxil fumarate group and 9 subjects in the d4T group experienced a new CDC Class C event. Treatment-Naïve Subjects: Trial 934 Data through 144 weeks are reported for Trial 934, a randomized, open-label, active-controlled multicenter trial comparing emtricitabine (FTC) + tenofovir disoproxil fumarate administered in combination with efavirenz (EFV) versus zidovudine (AZT)/lamivudine (3TC) fixed-dose combination administered in combination with EFV in 511 antiretroviral-naïve subjects. From Weeks 96 to 144 of the trial, subjects received a fixed-dose combination of FTC and TDF with EFV in place of FTC + tenofovir disoproxil fumarate with EFV. Subjects had a mean age of 38 years (range 18–80); 86% were male, 59% were Caucasian, and 23% were Black. The mean baseline CD4+ cell count was 245 cells/mm 3 (range 2–1191) and median baseline plasma HIV-1 RNA was 5.01 log 10 copies/mL (range 3.56–6.54). Subjects were stratified by baseline CD4+ cell count (< or ≥200 cells/mm 3 ); 41% had CD4+ cell counts <200 cells/mm 3 and 51% of subjects had baseline viral loads >100,000 copies/mL. Table 21 provides treatment outcomes through 48 and 144 weeks for those subjects who did not have EFV resistance at baseline. Table 21 Outcomes of Randomized Treatment at Week 48 and 144 (Trial 934) Outcomes At Week 48 At Week 144 FTC+Tenofovir Disoproxil Fumarate+EFV (N=244) AZT/3TC+EFV (N=243) FTC+Tenofovir Disoproxil Fumarate+EFV (N=227) Subjects who were responders at Week 48 or Week 96 (HIV-1 RNA <400 copies/mL) but did not consent to continue the trial after Week 48 or Week 96 were excluded from analysis. AZT/3TC+EFV (N=229) Responder Subjects achieved and maintained confirmed HIV-1 RNA <400 copies/mL through Weeks 48 and 144. 84% 73% 71% 58% Virologic failure Includes confirmed viral rebound and failure to achieve confirmed <400 copies/mL through Weeks 48 and 144. 2% 4% 3% 6% Rebound 1% 3% 2% 5% Never suppressed 0% 0% 0% 0% Change in antiretroviral regimen 1% 1% 1% 1% Death <1% 1% 1% 1% Discontinued due to adverse event 4% 9% 5% 12% Discontinued for other reasons Includes lost to follow-up, subject withdrawal, noncompliance, protocol violation and other reasons. 10% 14% 20% 22% Through Week 48, 84% and 73% of subjects in the FTC + tenofovir disoproxil fumarate group and the AZT/3TC group, respectively, achieved and maintained HIV-1 RNA <400 copies/mL (71% and 58% through Week 144). The difference in the proportion of subjects who achieved and maintained HIV-1 RNA <400 copies/mL through 48 weeks largely results from the higher number of discontinuations due to adverse events and other reasons in the AZT/3TC group in this open-label trial. In addition, 80% and 70% of subjects in the FTC + tenofovir disoproxil fumarate group and the AZT/3TC group, respectively, achieved and maintained HIV-1 RNA <50 copies/mL through Week 48 (64% and 56% through Week 144). The mean increase from baseline in CD4+ cell count was 190 cells/mm 3 in the FTC + tenofovir disoproxil fumarate group and 158 cells/mm 3 in the AZT/3TC group at Week 48 (312 and 271 cells/mm 3 at Week 144). Through 48 weeks, 7 subjects in the FTC + tenofovir disoproxil fumarate group and 5 subjects in the AZT/3TC group experienced a new CDC Class C event (10 and 6 subjects through 144 weeks). Treatment-Experienced Subjects: Trial 907 Trial 907 was a 24-week, double-blind, placebo-controlled multicenter trial of tenofovir disoproxil fumarate added to a stable background regimen of antiretroviral agents in 550 treatment-experienced subjects. After 24 weeks of blinded trial treatment, all subjects continuing on trial were offered open-label tenofovir disoproxil fumarate for an additional 24 weeks. Subjects had a mean baseline CD4+ cell count of 427 cells/mm 3 (range 23–1,385), median baseline plasma HIV-1 RNA of 2,340 (range 50–75,000) copies/mL, and mean duration of prior HIV-1 treatment was 5.4 years. Mean age of the subjects was 42 years; 85% were male, 69% Caucasian, 17% Black, and 12% Hispanic. Table 22 provides the percent of subjects with HIV-1 RNA <400 copies/mL and outcomes of subjects through 48 weeks. Table 22 Outcomes of Randomized Treatment (Trial 907) Outcomes 0–24 weeks 0–48 weeks 24–48 weeks Tenofovir Disoproxil Fumarate (N=368) Placebo (N=182) Tenofovir Disoproxil Fumarate (N=368) Placebo Crossover to Tenofovir Disoproxil Fumarate (N=170) HIV-1 RNA <400 copies/mL Subjects with HIV-1 RNA <400 copies/mL and no prior study drug discontinuation at Week 24 and 48, respectively. 40% 11% 28% 30% Virologic failure Subjects with HIV-1 RNA ≥400 copies/mL efficacy failure or missing HIV-1 RNA at Week 24 and 48, respectively. 53% 84% 61% 64% Discontinued due to adverse event 3% 3% 5% 5% Discontinued for other reasons Includes lost to follow-up, subject withdrawal, noncompliance, protocol violation, and other reasons. 3% 3% 5% 1% At 24 weeks of therapy, there was a higher proportion of subjects in the tenofovir disoproxil fumarate arm compared to the placebo arm with HIV-1 RNA <50 copies/mL (19% and 1%, respectively). Mean change in absolute CD4+ cell counts by Week 24 was +11 cells/mm 3 for the tenofovir disoproxil fumarate group and −5 cells/mm 3 for the placebo group. Mean change in absolute CD4+ cell counts by Week 48 was +4 cells/mm 3 for the tenofovir disoproxil fumarate group. Through Week 24, one subject in the tenofovir disoproxil fumarate group and no subjects in the placebo group experienced a new CDC Class C event. 14.3 Clinical Trial Results in Pediatric Subjects with HIV-1 Infection In Trial 352, 92 treatment-experienced subjects 2 years to less than 12 years of age with stable, virologic suppression on a stavudine (d4T)- or zidovudine (AZT)-containing regimen were randomized to either replace d4T or AZT with tenofovir disoproxil fumarate (N=44) or continue their original regimen (N=48) for 48 weeks. Five additional subjects over the age of 12 years were enrolled and randomized (tenofovir disoproxil fumarate N=4, original regimen N=1) but are not included in the efficacy analysis. After 48 weeks, all eligible subjects were allowed to continue in the trial receiving open-label tenofovir disoproxil fumarate. At Week 48, 89% of subjects in the tenofovir disoproxil fumarate treatment group and 90% of subjects in the d4T or AZT treatment group had HIV-1 RNA concentrations <400 copies/mL. During the 48-week randomized phase of the trial, 1 subject in the tenofovir disoproxil fumarate group discontinued the trial prematurely because of virologic failure/lack of efficacy and 3 subjects (2 subjects in the tenofovir disoproxil fumarate group and 1 subject in the d4T or AZT group) discontinued for other reasons. In Trial 321, 87 treatment-experienced subjects 12 years to less than 18 years of age were treated with tenofovir disoproxil fumarate (N=45) or placebo (N=42) in combination with an optimized background regimen (OBR) for 48 weeks. The mean baseline CD4 cell count was 374 cells/mm 3 and the mean baseline plasma HIV-1 RNA was 4.6 log 10 copies/mL. At baseline, 90% of subjects harbored NRTI resistance-associated substitutions in their HIV-1 isolates. Overall, the trial failed to show a difference in virologic response between the tenofovir disoproxil fumarate and placebo groups. Subgroup analyses suggest the lack of difference in virologic response may be attributable to imbalances between treatment arms in baseline viral susceptibility to tenofovir disoproxil fumarate and OBR. Although changes in HIV-1 RNA in these highly treatment-experienced subjects were less than anticipated, the comparability of the pharmacokinetic and safety data to that observed in adults supports the use of tenofovir disoproxil fumarate in pediatric patients 12 years and older who weigh at least 35 kg and whose HIV-1 isolate is expected to be sensitive to tenofovir disoproxil fumarate [see Warnings and Precautions (5.5) , Adverse Reactions (6.1) , and Clinical Pharmacology (12.3) ]. 14.4 Clinical Trial Results in Adults with Chronic Hepatitis B HBeAg-Negative Chronic HBV Subjects: Trial 0102 Trial 0102 was a Phase 3, randomized, double-blind, active-controlled trial of tenofovir disoproxil fumarate 300 mg compared to HEPSERA 10 mg in 375 HBeAg- (anti-HBe+) subjects with compensated liver function, the majority of whom were nucleoside-naïve. The mean age of subjects was 44 years; 77% were male, 25% were Asian, 65% were Caucasian, 17% had previously received alpha-interferon therapy, and 18% were nucleoside-experienced (16% had prior lamivudine experience). At baseline, subjects had a mean Knodell necroinflammatory score of 7.8; mean plasma HBV DNA was 6.9 log 10 copies/mL; and mean serum ALT was 140 U/L. HBeAg-Positive Chronic HBV Subjects: Trial 0103 Trial 0103 was a Phase 3, randomized, double-blind, active-controlled trial of tenofovir disoproxil fumarate 300 mg compared to HEPSERA 10 mg in 266 HBeAg+ nucleoside-naïve subjects with compensated liver function. The mean age of subjects was 34 years; 69% were male, 36% were Asian, 52% were Caucasian, 16% had previously received alpha-interferon therapy, and <5% were nucleoside experienced. At baseline, subjects had a mean Knodell necroinflammatory score of 8.4; mean plasma HBV DNA was 8.7 log 10 copies /mL; and mean serum ALT was 147 U/L. The primary data analysis was conducted after all subjects reached 48 weeks of treatment and results are summarized below. The primary efficacy endpoint in both trials was complete response to treatment defined as HBV DNA <400 copies/mL (69 IU/mL) and Knodell necroinflammatory score improvement of at least 2 points, without worsening in Knodell fibrosis at Week 48 (see Table 23 ). Table 23 Histological, Virological, Biochemical, and Serological Response at Week 48 (Trials 0102 and 0103) 0102 (HBeAg-) 0103 (HBeAg+) Tenofovir Disoproxil Fumarate (N=250) HEPSERA (N=125) Tenofovir Disoproxil Fumarate (N=176) HEPSERA (N=90) Complete Response 71% 49% 67% 12% Histology Histological Response Knodell necroinflammatory score improvement of at least 2 points without worsening in Knodell fibrosis. 72% 69% 74% 68% HBV DNA <400 copies/mL (<69 IU/mL) 93% 63% 76% 13% ALT Normalized ALT The population used for analysis of ALT normalization included only subjects with ALT above ULN at baseline. 76% 77% 68% 54% Serology HBeAg Loss/ Seroconversion NA NA = Not Applicable NA 20%/19% 16%/16% HBsAg Loss/ Seroconversion 0/0 0/0 3%/1% 0/0 Treatment Beyond 48 Weeks: Trials 0102 and 0103 In Trials 0102 (HBeAg-negative) and 0103 (HBeAg-positive), subjects who completed double-blind treatment (389 and 196 subjects who were originally randomized to tenofovir disoproxil fumarate and HEPSERA, respectively) were eligible to roll over to open-label tenofovir disoproxil fumarate with no interruption in treatment. In Trial 0102, 266 of 347 subjects who entered the open-label period (77%) continued in the trial through Week 384. Among subjects randomized to tenofovir disoproxil fumarate followed by open-label treatment with tenofovir disoproxil fumarate, 73% had HBV DNA <400 copies/ml (69 IU/ml), and 63% had ALT normalization at Week 384. Among subjects randomized to HEPSERA followed by open-label treatment with tenofovir disoproxil fumarate, 80% had HBV DNA <400 copies/mL (69 IU/mL) and 70% had ALT normalization through Week 384. At Week 384, both HBsAg loss and seroconversion were approximately 1% in both treatment groups. In Trial 0103, 146 of 238 subjects who entered the open-label period (61%) continued in the trial through Week 384. Among subjects randomized to tenofovir disoproxil fumarate, 49% had HBV DNA <400 copies/mL (69 IU/mL), 42% had ALT normalization, and 20% had HBeAg loss (13% seroconversion to anti-HBe antibody) through Week 384. Among subjects randomized to HEPSERA followed by open-label treatment with tenofovir disoproxil fumarate, 56% had HBV DNA <400 copies/mL (69 IU/mL), 50% had ALT normalization, and 28% had HBeAg loss (19% seroconversion to anti-HBe antibody) through Week 384. At Week 384, HBsAg loss and seroconversion were 11% and 8%, respectively, in subjects initially randomized to tenofovir disoproxil fumarate and 12% and 10%, respectively, in subjects initially randomized to HEPSERA. Of the originally randomized and treated 641 subjects in the two trials, liver biopsy data from 328 subjects who received continuing open-label treatment with tenofovir disoproxil fumarate monotherapy were available for analysis at baseline, Week 48, and Week 240. There were no apparent differences between the subset of subjects who had liver biopsy data at Week 240 and those subjects remaining on open-label tenofovir disoproxil fumarate without biopsy data that would be expected to affect histological outcomes at Week 240. Among the 328 subjects evaluated, the observed histological response rates were 80% and 88% at Week 48 and Week 240, respectively. In the subjects without cirrhosis at baseline (Ishak fibrosis score 0–4), 92% (216/235) and 95% (223/235) had either improvement or no change in Ishak fibrosis score at Week 48 and Week 240, respectively. In subjects with cirrhosis at baseline (Ishak fibrosis score 5–6), 97% (90/93) and 99% (92/93) had either improvement or no change in Ishak fibrosis score at Week 48 and Week 240, respectively. Twenty-nine percent (27/93) and 72% (67/93) of subjects with cirrhosis at baseline experienced regression of cirrhosis by Week 48 and Week 240, respectively, with a reduction in Ishak fibrosis score of at least 2 points. No definitive conclusions can be established about the remaining study population who were not part of this subset analysis. Lamivudine-Resistant Chronic HBV Subjects: Trial 121 Trial 121 was a randomized, double-blind, active-controlled trial evaluating the safety and efficacy of tenofovir disoproxil fumarate compared to an unapproved antiviral regimen in subjects with chronic hepatitis B, persistent viremia (HBV DNA ≥1,000 IU/mL), and genotypic evidence of lamivudine resistance (rtM204I/V +/- rtL180M). One hundred forty-one adult subjects were randomized to the tenofovir disoproxil fumarate treatment arm. The mean age of subjects randomized to tenofovir disoproxil fumarate was 47 years (range 18–73); 74% were male, 59% were Caucasian, and 37% were Asian. At baseline, 54% of subjects were HBeAg-negative, 46% were HBeAg-positive, and 56% had abnormal ALT. Subjects had a mean HBV DNA of 6.4 log 10 copies/mL and mean serum ALT of 71 U/L at baseline. After 96 weeks of treatment, 126 of 141 subjects (89%) randomized to tenofovir disoproxil fumarate had HBV DNA <400 copies/mL (69 IU/mL), and 49 of 79 subjects (62%) with abnormal ALT at baseline had ALT normalization. Among the HBeAg-positive subjects randomized to tenofovir disoproxil fumarate, 10 of 65 subjects (15%) experienced HBeAg loss and 7 of 65 subjects (11%) experienced anti-HBe seroconversion through Week 96. The proportion of subjects with HBV DNA concentrations below 400 copies/mL (69 IU/mL) at Week 96 was similar between the tenofovir disoproxil fumarate monotherapy and the comparator arms. Across the combined chronic hepatitis B treatment trials, the number of subjects with adefovir-resistance associated substitutions at baseline was too small to establish efficacy in this subgroup. Chronic HBV and Decompensated Liver Disease Subjects: Trial 0108 Trial 0108 was a small randomized, double-blind, active-controlled trial evaluating the safety of tenofovir disoproxil fumarate compared to other antiviral drugs in subjects with chronic hepatitis B and decompensated liver disease through 48 weeks. Forty-five adult subjects (37 males and 8 females) were randomized to the tenofovir disoproxil fumarate treatment arm. At baseline, 69% of subjects were HBeAg-negative and 31% were HBeAg-positive. Subjects had a mean Child-Pugh score of 7, a mean MELD score of 12, mean HBV DNA of 5.8 log 10 copies/mL, and mean serum ALT of 61 U/L at baseline. Trial endpoints were discontinuation due to an adverse event and confirmed increase in serum creatinine ≥0.5 mg/dL or confirmed serum phosphorus of <2 mg/dL [see Adverse Reactions (6.1) ] . At 48 weeks, 31/44 (70%) and 12/26 (46%) tenofovir disoproxil fumarate-treated subjects achieved an HBV DNA <400 copies/mL (69 IU/mL), and normalized ALT, respectively. The trial was not designed to evaluate treatment impact on clinical endpoints such as progression of liver disease, need for liver transplantation, or death. 14.5 Clinical Trial Results in Pediatric Subjects with Chronic Hepatitis B Pediatric Subjects 12 Years to less than 18 Years of Age with Chronic HBV In Trial 115, 106 HBeAg negative (9%) and positive (91%) subjects aged 12 to less than 18 years with chronic HBV infection were randomized to receive blinded treatment with tenofovir disoproxil fumarate 300 mg (N=52) or placebo (N=54) for 72 weeks. At trial entry, the mean HBV DNA was 8.1 log 10 copies/mL and mean ALT was 101 U/L. Of 52 subjects treated with tenofovir disoproxil fumarate, 20 subjects were nucleos(t)ide-naïve and 32 subjects were nucleos(t)ide-experienced. Thirty-one of the 32 nucleos(t)ide-experienced subjects had prior lamivudine experience. At Week 72, 88% (46/52) of subjects in the tenofovir disoproxil fumarate group and 0% (0/54) of subjects in the placebo group had HBV DNA <400 copies/mL (69 IU/mL). Among subjects with abnormal ALT at baseline, 74% (26/35) of subjects receiving tenofovir disoproxil fumarate had normalized ALT at Week 72 compared to 31% (13/42) in the placebo group. One tenofovir disoproxil fumarate-treated subject experienced sustained HBsAg-loss and seroconversion to anti-HBs during the first 72 weeks of trial participation. Pediatric Subjects 2 Years to less than 12 Years of Age with Chronic HBV In Trial 144, 89 HBeAg positive (96%) and negative (4%) subjects 2 years to less than 12 years of age with chronic HBV infection were treated with tenofovir disoproxil fumarate 8 mg/kg up to a maximum dose of 300 mg (N=60) or placebo (N=29) once daily for 48 weeks. At trial entry, the mean HBV DNA was 8.1 log 10 IU/mL and mean ALT was 123 U/L. There was an overall higher proportion in the tenofovir disoproxil fumarate group with HBV DNA <400 copies/mL (69 IU/mL) and ALT normalization rate at Week 48 compared to the placebo group (Table 24). There was no difference between treatment groups in those who achieved HBeAg loss or HBeAg seroconversion. Table 24 Outcomes of Randomized Treatment (Trial 144) in Children 2 Years to <12 Years of Age Endpoint at Week 48 Tenofovir Disoproxil Fumarate N=60 Placebo N=29 HBV DNA <400 copies/mL (69 IU/ml) 46/60 (77%) 2/29 (7%) ALT Normalization Normal ALT was defined as ≤34 U/L for females 2-15 years or males 1-9 years old, and ≤43 U/L for males 10-15 years. The ALT Normalization analysis excluded 4 treated subjects who had normal ALT at baseline. 38/58 (66%) 4/27 (15%) HBeAg loss The analysis excluded 4 subjects who were HBeAg negative and HBeAb positive at baseline. 17/56 (30%) 8/29 (28%) HBeAg seroconversion 14/56 (25%) 7/29 (24%) In Trials 115 and 144, sequencing data from paired baseline and on treatment HBV isolates from subjects who received tenofovir disoproxil fumarate were available for 14 of 15 subjects who had plasma HBV DNA≥400 copies/mL. No amino acid substitutions associated with resistance to tenofovir disoproxil fumarate were identified in these isolates by Week 72 (Trial 115) or Week 48 (Trial 144).