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First‐line therapies for hepatitis B in the United States: A 3‐year prospective and multicenter real‐world study after approval of tenofovir alefenamide

Abstract Real‐world data are limited on tenofovir alafenamide (TAF). We aimed to study TAF real‐world outcomes with other first‐line regimens for chronic hepatitis B (CHB). We enrolled patients with CHB from 10 centers retrospectively and followed them for 36 months prospectively. We analyzed switching patterns of antiviral therapy and treatment outcomes of TAF, tenofovir disoproxil fumarate (TDF), and entecavir therapy. For efficacy and safety, we analyzed a subset of patients with complete data at 24 months after switching to TAF or remaining on TDF or entecavir. Among 1037 enrollees, 889 patients were analyzed. The mean age was 52%, and 72% were hepatitis B e antigen–negative. After enrollment, shifts in therapies were mostly in reduced use of TDF from 63% to 30% due to switching to TAF. Clinical parameters were compared at enrollment or initiation to measures at 24 months for patients remaining on TAF (187), TDF (229), or entecavir (181). At 24 months, a significantly higher portion of patients on TAF achieved hepatitis B virus (HBV) DNA ≤ 20 IU/ml (93% vs. 86%; p = 0.012) and normalized alanine aminotransferase (ALT) (66% vs. 56%; p = 0.031) with stable estimated glomerular filtration rates (eGFRs). However, a higher percentage of the patient with eGFR < 60 ml/mi/1.7 m2 was observed in the TDF‐treated group (9% vs. 4%; p = 0.010). In patients who remained on entecavir or TDF for 24 months, ALT and HBV‐DNA results did not differ significantly from baseline. Treatment of CHB in the United States has significantly shifted from TDF to TAF. Our data suggest that switching from TDF or entecavir to TAF may result in increased frequency of ALT normalization and potential clearance of viremia at the 24‐month time point.

of patients with complete data at 24 months after switching to TAF or remaining on TDF or entecavir. Among 1037 enrollees, 889 patients were analyzed.
The mean age was 52%, and 72% were hepatitis B e antigen-negative. After enrollment, shifts in therapies were mostly in reduced use of TDF from 63% to 30% due to switching to TAF. Clinical parameters were compared at enrollment or initiation to measures at 24 months for patients remaining on TAF (187), TDF (229), or entecavir (181). At 24 months, a significantly higher portion of patients on TAF achieved hepatitis B virus (HBV) DNA ≤ 20 IU/ml (93% vs. 86%; p = 0.012) and normalized alanine aminotransferase (ALT) (66% vs. 56%; p = 0.031) with stable estimated glomerular filtration rates (eGFRs).
However, a higher percentage of the patient with eGFR < 60 ml/mi/1.7 m 2 was observed in the TDF-treated group (9% vs. 4%; p = 0.010). In patients who remained on entecavir or TDF for 24 months, ALT and HBV-DNA results did not differ significantly from baseline. Treatment of CHB in the United States has significantly shifted from TDF to TAF. Our data suggest that switching from TDF or entecavir to TAF may result in increased frequency of ALT normalization and potential clearance of viremia at the 24-month time point.

INTRODUCTION
It is estimated that 1.4 to 3 million people in the United States live with chronic hepatitis B (CHB), [1] which is associated with a higher risk of progressing to liver cirrhosis and developing hepatocellular carcinoma (HCC). [2] The goal of treatment for CHB is to improve survival by preventing disease progression to cirrhosis, liver failure, and HCC. [3,4] On treatment, virological suppression has been associated with histological improvement and regression of cirrhosis, as well as reduced risk of hepatic decompensation and HCC and can be achieved by long-term treatment with antiviral agents. [3,4] Current international guidelines recommend entecavir (ETV), tenofovir alafenamide (TAF), and tenofovir disoproxil fumarate (TDF) as the first-line oral antiviral for CHB. [3,4] Although randomized controlled trials (RCTs) have reported the aforementioned antivirals' efficacy and safety profiles, [5][6][7][8][9] real-world data are very important in terms of providing a more complete picture of clinical outcomes in highly diverse patients encountered in routine practice and capturing uncommon adverse events underreported by RCTs. [10,11] Several, but not all, real-world studies on TDF and ETV reported results in line with these clinical trials. In a study in Turkey on 355 treatment-naïve patients with CHB, Idilman et al. observed that ETV and TDF had similar efficacy and comparable safety profiles during a 4-year treatment. [12] Subsequently, larger studies in France and Germany showed that the outcomes of TDF in the real-world setting were consistent with results from pivotal trials. [13,14] In addition, several realworld studies in Asia reported similar outcomes of ETV or TDF therapy in Asian patients when compared with those in pivotal trials. [15][16][17][18][19] Another real-world study by Wong et al. in the United States suggested that the treatment outcomes of ETV and TDF were also comparable with those in pivotal trials. [20] However, in a recent report on 658 patients treated with ETV in the United States for a median duration of 4 years, Ahn et al. found that the alanine aminotransferase (ALT) normalization and hepatitis B virus (HBV) DNA suppression rates were lower than previously reported in pivotal trials. [21] While many real-world studies have examined the efficacy and safety of ETV versus TDF, few have assessed the actual treatment patterns of the regimen used in the United States, especially since the availability of TAF, which was approved by the Food and Drug Administration in November 2016. Awareness of actual treatment patterns in the United States is particularly important for improving the quality of care for these patients because a recent study showed the inconsistency of practice patterns leading to different outcomes in the United States. [22] Furthermore, given the shorter time frame of TAF availability relative to other HBV therapies, data are limited on the real-world outcomes of TAF and the alternative options. With that in mind, we established the TRIO HBV registry and conducted a retrospective and prospective national cohort study in the United States between November 2016 and January 2020. We aimed to describe the antiviral treatment landscapes for CHB in the United States. In addition, the treatment outcomes on the first-line antiviral therapies were also compared. As the U.S. Department of Health and Human Services is developing the next National Strategic Plan: A Roadmap to Elimination for the United States, 2021-2025, [23] we believe that our study could provide evidence to potentially address the gap in the care for patients with CHB and important data of antiviral outcomes in the real-world setting, which are critical steps to reduce hepatitis B burdens in the United States.

Study patient selections and data collection
This is a multicenter, observational, retrospective, and prospective study in the United States that enrolled 1037 adult patients with CHB (age above 18 years old) from November 2016, the approval date of TAF, to January 2017 with the intent of capturing clinical and treatment data at each office visit for 3 years after enrollment up to January 2020 ( Figure S1). An additional 5 months following the observation period, through June 2020, was allowed for data entry by the provider. Patients with CHB on oral antiviral agents (including those patients who were treatment-naïve and initiating therapy) were eligible to be enrolled at the index visit. The exclusion criteria were as follows: patients with documented radiological or histological HCC, serum AFP > 500 ng/ml at enrollment, unlikely to survive at least 2 years, inability to participate in the follow-up for at least 2 years, or coinfected with human immunodeficiency virus. Patients were also excluded from the current study if they had undergone solid organ transplantation, received chemotherapy, were treated with other immunosuppressive therapy, or were enrolled in other clinical trials. For the qualification of being included in the final analysis data set, patients were required to have HBV virological testing at the baseline and completed a minimum follow-up of 24 months following enrollment. For the safety and efficacy data, the subset of patients who had complete virological data at baseline and month 24 were included. The data reported here were limited to 889 patients with known hepatitis B e antigen (HBeAg) status at enrollment and completed at least 2 years of follow-up (max and mean follow-up durations were 39 and 35 months, respectively).
Data were obtained from six academic and four community-based centers across the nation, serving 17 U.S. states. As visit times varied among practices, patient assessments after the enrollment were assigned a nominal visit month every 6 ± 1 month (e.g., 6 months, 12 months) from the enrollment. Treatment details and laboratory measures were collected retrospectively at enrollment and limited to data no more than 180 days before enrollment. Prospective data were collected from the enrollment to the last visit within the observation period. Patient data were captured using an electronic case report form. Prompted data fields included patient demographics, CHB treatment at enrollment, treatment during the observation period, the reason for therapy change, adherence to therapy, and comorbidities such as anxiety, depression, hyperlipidemia, hypertension, diabetes mellitus, osteopenia, osteoporosis, hemodialysis, and chronic kidney disease. Outcome data including liver transplant or development of HCC were also recorded. Laboratory data and other test results were collected, which included the complete blood count, aspartate aminotransferase (AST), ALT, alkaline phosphatase, bilirubin, albumin, total protein, serum creatinine, alpha-fetoprotein (AFP), bone density T-scores, and HBV virological test results. The study was approved by the Western Institutional Review Board (IRB) and the IRB at each participating study site. The aforementioned central IRB was used for centers or private practices that did not have their own institutional IRB. All patients provided consent before entering the study.

Assessments and endpoints
Our primary objective was to evaluate the practice patterns in terms of therapy selection and switching therapy during the study period. To assess the frequency of treatment change, the study population was distributed by the number of different regimens received during the entire observation period. To visualize the shifts in treatment preferences over time, the study population was classified by the treatment received at enrollment and entry into each subsequent 6-month period. To assess changes in laboratory measures or HBeAg status over time, assessments were conducted using either an index date of enrollment or an index date of the treatment start date, depending on the analysis. Index dates were compared with the first values observed in month 24 or after.
The secondary assessments were efficacy and safety of the first-line antiviral therapies on study patients. Patients were stratified into three subgroups who received ETV, TDF, or TAF for further comparison. The efficacy assessments included the percentage of patients who had HBV DNA ≤ 20 IU/ ml and normalization of ALT during the 24-month prospective follow-up period, respectively. All data evaluated were at the 24 ± 1-month time point, which was determined as the study endpoint for efficacy and safety. The safety analyses included several important parameters for disease progression and laboratory adverse events such as albumin < 3.4 g/ dl, platelet count < 150 × 9log10/L, and the estimated glomerular filtration rates (eGFR) < 60 ml/min/1.73 m 2 . We also assessed the percentage of patients who had Fibrosis-4 index (FIB-4) > 3.25, HBeAg positivity, or Reach-B ≥ 10 at the end of the study as the exploratory endpoints in the three groups.

Standard of care and laboratory testing
All study sites prospectively assessed patients' clinical progress every 3 to 6 months (window ± 1 month) as per local standard of care. All laboratory testing was performed at the respective local laboratories for each center. For HBV-DNA detection, the lower limit of quantitation was 20 IU/ml. For measures, FIB-4 scores were calculated per Sterling et al. [24] The eGFR was calculated using the CKD-EPI Creatinine Equation. [25] The risk of HCC was estimated by REACH-B scores per Yang et al. [26] In the current study, completed viral suppression was considered when the local laboratories reported the serum HBV DNA ≤ 20 IU/ml. The normalization of ALT was defined for males as ≤ 31 IU/L and females ≤ 19 IU/L, and impaired renal status was considered as eGFR < 60 ml/min/1.73 m 2 . An independent data monitor from Trio Health performed the data quality control by reviewing the submitted electronic case report forms for data completeness and accuracy.

Statistical analyses
Statistical analyses were conducted using the statistical software package of IBM SPSS Statistics 24 (IBM SPSS, New York, NY, USA) or R-3.6.2 software (The R Foundation, Wien, Austria). Categorical variable comparisons were via chi-square analysis with subsequent z-tests of column proportions or by the McNemar test. Bonferroni correction was applied for repeated measures. For continuous variables, comparisons between groups were made using the Mann-Whitney U test for independent samples. The treatment pattern analyses were performed for the entire cohort and also separately for the subgroup of patients recruited at community-based centers and those recruited at university-based centers. In addition, a subgroup analysis of treatment patterns was evaluated based on the HBeAg status. For the efficacy and safety of each antiviral treatment, analyses were performed on patients with test results available at specific time intervals from each treatment group, and variables at baseline were compared among the three groups. Statistical significance was set at the 0.05 level.
When patients were stratified by HBeAg status for the comparison of baseline variables, the HBeAg positive group was younger (mean of 48 years vs. 53 years, p < 0.001), had a lower mean FIB-4 score (1.2 vs. 1.7, p < 0.001), a higher proportion of patients with detectable HBV DNA (31% vs. 11%, p < 0.001), elevated ALT (51% vs. 42%, p = 0.013), and higher REACH-B (7.8 vs. 6.1, p < 0.001). In addition, treatment regimens at enrollment were significantly different between the two groups, most notably for a significantly higher percentage of HBeAg-positive patients on TDF (69% vs. 61%; p < 0.001), whereas ETV was selected frequently in HBeAg-negative patients when compared to those with HBeAg-positive (28% vs. 18%; p < 0.001). However, HBeAg groups were not significantly different for gender, body mass index (BMI), race, region of origin, payer type, or site of care (academic vs. community).
Most patients received care in sites classified as academic (62%, n = 550 of 889). Populations by site type differed in race, the region of origin, and primary payer type but not by gender, age, BMI, or proportions with detectable levels of serum HBV DNA or elevated ALT (Table 1). When compared with community sites, the academic practices had a lower fraction of patients with platelets < 150 × 10 9 /L (20% [67 of 335] vs. 13% [69 of 546]; p = 0.005), higher prevalence of anxiety (1% vs. 4%; p = 0.014), and higher frequency of depression (1% vs. 5%; p = 0.013). In academic practices at enrollment, a significantly higher percentage of patients received ETV (28% vs. 20%; p < 0.001), and a significantly lower F I G U R E 1 Enrollment and treatment status of the study patients. ETV, entecavir; TAF, tenofovir alafenamide; TDF, tenofovir disoproxil fumarate percentage of patients were treated with TDF (58% vs. 72%; p < 0.001) compared with community practices.

Antiviral treatment patterns after TAF approval
Of 889 patients, 867 (98%) were on therapy at enrollment, and the remaining 22 (2%) initiated treatment during the observation period ( Figure 1). The proportion of patients remaining on their enrollment treatment throughout the observation window was 52% (463) and was not significantly different (p = 0.58) between HBeAg-negative (51%, 328 of 639) and HBeAg-positive (54%, 135 of 250) (Table S1). However, the proportion of patients on the same therapy throughout the study in academic sites significantly differed from that in the community practices (63% [349 of 550] vs. 34% [114 of 339]; p < 0.001). After enrollment shifts in treatments were mostly in reduced use of TDF from 63% to 30% and increased use of TAF from 2% to 38% in 24 months. The use of entecavir decreased from 25% to 22% (Figure 2A) during the same period. When the subgroup analyses were performed for TAF use at the 24-month time point, we found that the use of TAF was similar ( Figure 2B

Patients switched to TAF versus those remaining on TDF or ETV
Among 389 patients who initiated TAF during the study period, 6% (23 of 389) initiated TAF at enrollment, 4% (14 of 389) switched from second-line therapies, 83% (321 of 389) switched from TDF, and 8% (31 of 389) switched from ETV. The reason for the switch to TAF was assessed by the principal investigators at the time of switch and is given in Table S1. Most of the switches to TAF were listed for either safety (TDF, 63%; ETV, 77%) or physician preference. To better understand the clinical profile of patients who switched to TAF from TDF or ETV compared with those who remained on these enrollment therapies during the study period, we examined the characteristics at enrollment for four subgroups ( Table 2): (A) switched to TAF from TDF (n = 321), (B) remaining on TDF (n = 229), (C) switched to TAF from ETV (n = 31), and (D) remaining on ETV (n = 181). In the subgroup assessment, among patients who switched to TAF therapy (group A, n = 321) from TDF, 58% (186/321) of them were from community practices. In contrast, 76% (175 of 229) of patients remaining on TDF were in care at academic sites (group B). Similarly, for patients switching to TAF from ETV (group C, n = 31), 55% (17 of 31) of patients who switched to TAF came from community sites, whereas 73% (133 of 181) of patients remaining on ETV (group D) were from academic sites. In the academic sites, the number of patients who remained on TDF or ETV was significantly higher than that to be treated with TAF (p < 0.001 TDF and p = 0.003 ETV).
At enrollment, a significantly lower portion of patients in group A (TDF-TAF) was HBeAg-positive (25% vs. 37%, p = 0.005) and receiving care in the academic practices (42% vs. 76%, p < 0.001) compared with group B (remaining on TDF), whereas in the comparison between group C (from ETV to TAF) and group D (remaining on ETV), a significantly lower percentage of patients in group C were treated at academic sites (45% vs. 73%, p = 0.003). To assess the independence of association with switching treatment from TDF or ETV to TAF, we examined demographic, payer, and clinical data at enrollment. Using logistic regression with backward selection (  [27] These patients had at least one of the following indications: age over 60 years (n = 63), eGFR < 60 ml/min/1.73 m 2 (n = 10), or osteoporosis (n = 6). The percentage of patients who continued on TDF with risk factors was similar between academic and community sites (30% [52 of 175] vs. 28% [15 of 54]; p = 0.870).

Real-world experience with TAF and other first-line regimens
Of the patients initiating TAF at enrollment or during the observation period (n = 389), 91% (355 of 389) were on TAF at the date of censure, and 9% (34 of 389) had discontinued. Among patients on TAF, 48% (187 of 389) received therapy for ≥ 24 months. These patients (n = 187) were included in the efficacy and safety analyses and were compared with patients who remained on TDF (n = 229) or ETV (n = 181) during the study period of 24 months (Table S1). In patients with TAF      Of the 561 patients on TDF at enrollment, 41% (229/561) did not switch therapy and completed the 24month follow-up. Comparisons of variables for efficacy and safety were made between the data obtained at enrollment and at/after 24 months (limited to patients with measures at both time points), which showed that HBV-DNA suppression to the levels of ≤ 20 IU/ml was achieved in a significantly higher percentage of patients at the end of 24 months (80% [173 of 215] vs. 87% [187 of 215]; p = 0.014). In addition, the percentage of patients with eGFR < 60 ml/min/1.73 m 2 increased significantly at/after 24 months (4% [8 of 196] vs. 9% [18 of 196]; p = 0.010). However, the percentages of patients who had albumin < 3.4 g/dl, elevated ALT levels, AST > 33 U/L, FIB-4 > 3.25, HBeAg positivity, platelets < 150 × 9log10/L, or Reach-B ≥ 10 were not significantly different between the two time points (Table 3).
Among 223 patients on ETV at enrollment, 81% (181 of 223) did not switch therapy and completed the 24-month follow-up. When compared with the baseline efficacy and safety parameters at enrollment (limited to patients with measures at both time points), we  Table 3).

DISCUSSION
In this U.S. patient registry of predominantly Asian, over-50-year-old patients with HBeAg-negative CHB, we observed treatment shifting significantly from TDF as a dominant regimen (63% of all therapies) in 2017 to TAF (38%) at the start of 2020. Adoption of TAF was similar between HBeAg-positive and HBeAgnegative subgroups, although considerably greater in populations treated in the community (62% of patients at 24 months) compared with academic (25% of patients at 24 months) practices. TAF adoption for treatment of HBeAg-negative disease was anticipated, given the renal safety profile of TAF and long-term therapy required to achieve a functional cure in this population. [3,4,28] The rapid uptakes of TAF observed in HBeAg-positive patients and community settings were expected, because HBeAg-positive cases had a higher frequency of viremia and elevation of ALT on other regimens, and patients in the community often had comorbidity and compensated disease (TAF was off-label for decompensated disease during the study period). [7,8,29,30] The most common reason given for switching to TAF was patient safety, but interestingly, a significant number of patients (n = 63) who met the criteria for a switch with renal disease, older age, or diabetes were not switched over the study duration. Although a few real-world studies on TAF (primarily in Asia) have been published, data are limited to the TAF effects on ETV-treated patients with a relatively small sample size (ranging from 100-300 patients). [30][31][32][33] To our knowledge, the current study is by far the largest one to assess real-world outcomes of all first-line regimens. We found that patients who switched from TDF or ETV to TAF had a significantly higher frequency of clearing their viremia and/or normalizing ALT at 24 months, whereas patients who continued ETV did not achieve those outcomes, and patients who continued on TDF only improved viremia but not the frequency of ALT normalization at 24 months. In the initial registration studies comparing TAF to TDF, a higher frequency of ALT normalization was also seen on TAF. [7,8] Many studies have shown that low-level viremia or persistent abnormal ALT while on antivirals increases the risk of disease progression and HCC. [34][35][36][37] Our data suggested that switching ETV or TDF therapy to TAF may be a more favorable option for patients with persistent viremia and/or abnormal ALT, which further enhances our understanding of the efficacy of TAF treatment (pivotal RCTs only showed that TAF was superior to TDF on ALT normalization). [7,8,29] In terms of safety, significantly more patients on TDF therapy had worsening eGFR from baseline after 24 months of therapy. In contrast, there were no safety concerns for patients with TAF or ETV. These outcomes were consistent with the findings in pivotal trials. [6][7][8]29] The reasons for more patients with FIB-4 > 3.25 at/after 24 months of ETV therapy compared with baseline were not fully understood, due to the limitation of the study design and the small number of patients. We believe that failure to achieve outcomes on both viremic control and ALT normalization may contribute to the worsening of FIB-4 scores in this group. [34] There are several study limitations primarily associated with the non-randomized design and loss to follow-up, although this is a small proportion of patients in a real-world setting. The efficacy data are interesting but should be interpreted with the caveats that they do not represent the entire patient population, even though the subset analyzed was well matched at baseline. When comparing baseline profiles between the TAF and ETV groups, the TAF group had a significantly higher portion of patients with elevation of ALT, which could potentially underestimate the TAF effects on ALT. In addition, patients treated with ETV were older and often associated with HBeAg negativity, high BMI, or hyperlipidemia. These factors, including metabolic syndrome, may reduce the generality of these findings, particularly on ALT normalization. Finally, our findings may not be fully applicable to the non-Asian populations, as they are underrepresented in our study.
In conclusion, we found a significant shift in the treatment paradigm from TDF to TAF in this U.S. registry cohort and identified gaps in managing patients with CHB, including deviations from the standard of care. In comparison, of the first-line antiviral therapies, our data suggest that TAF is a good first option for patients with CHB in the United States, and within the limitations of this real-world study may also be considered for populations with abnormal ALT or viremia on other therapies.

A C K N O W L E D G M E N T
The authors thank Kimmi Cox, Nicole Wick, Karen Daidone, and Yoori Lee for their contributions to the Trio HBV Registry. They also thank Gilead Sciences, Inc for the research grant support.

C O N F L I C T O F I N T E R E S T
Dr. Pan is a speaker for Gilead, AbbVie, and Intercept. His institution has received research support from Gilead, Assembly Bio, and Trio Health. Dr. Afdhal is a paid consultant/advisory board member for Gilead,