Long-term entecavir therapy results in reversal of fibrosis/cirrhosis and continued histologic improvement in chronic hepatitis B patients

Long-term entecavir therapy results in reversal of fibrosis/cirrhosis and continued histologic improvement in chronic hepatitis B patients - publication pdf attached

Hepatology Epub June 2010


Ting-Tsung Chang1,*,†, Yun-Fan Liaw2, Shun-Sheng Wu3, Eugene Schiff4, Kwang-Hyub Han5, Ching-Lung Lai6, Rifaat Safadi7, Samuel S Lee8, Waldemar Halota9, Zachary Goodman10, Yun-Chan Chi11, Hui Zhang12, Robert Hindes12, Uchenna Iloeje12, Suzanne Beebe12, Bruce Kreter12. 1. National Cheng Kung University Medical College, Tainan, Taiwan 2. Liver Research Unit, Chang Gung Memorial Hospital, Chang Gung University College of Medicine, Taipei, Taiwan 3. Department of Internal Medicine, Changhua Christian Hospital, Taiwan 4. University of Miami Hospital & Clinics, Miami, FL, USA 5. Department of Internal Medicine, Yonsei University College of Medicine, Korea 6. Department of Medicine, Queen Mary's Hospital, University of Hong Kong, China 7. Division of Medicine, Hadassah Medical Center, Jerusalem, Israel 8. Liver Unit, University of Calgary, Calgary, Canada 9. Nicolaus Copernicus University, Collegium Medicum, Bydgoszcz, Poland 10. Armed Forces Institute of Pathology, Washington, USA 11. Department of Statistics, National Cheng Kung University, Tainan, Taiwan 12. Research & Development, Bristol-Myers Squibb, USA

ABSTRACT

Background and rationale: One year of treatment with entecavir 0.5 mg daily in nucleoside-naïve patients with hepatitis B e antigen (HBeAg)-positive or HBeAg- negative chronic hepatitis B resulted in significantly improved liver histology and virologic and biochemical endpoints compared to lamivudine.

Methods: Patients who received at least 3 years of cumulative entecavir therapy in phase III studies and a long- term rollover study and had a long-term liver biopsy were evaluated for improvement in histologic appearance.

Main results: Sixty-nine patients [50 HBeAg-positive; 19 HBeAg- negative] receiving entecavir therapy underwent long-term liver biopsies (median time of biopsy was 6 years; range: 3−7 yrs). Histologic improvement was analyzed for 57 patients who had an adequate baseline biopsy, a baseline Knodell necroinflammatory score ≥2, and an adequate long-term biopsy. At the time of long-term biopsy, all patients in the cohort had HBV DNA <300 copies/mL and 86% had normalized ALT. Histologic improvement (≥2-point decrease in Knodell necroinflammatory score and no worsening of Knodell fibrosis score) was observed in 96% of patients and a ≥1 point improvement in Ishak fibrosis score was found in 88% of patients, including all ten patients with advanced fibrosis or cirrhosis at phase III baseline.

Conclusion: The majority of nucleoside-naïve chronic hepatitis B patients treated with entecavir in this long-term cohort achieved substantial histologic improvement and regression of fibrosis or cirrhosis.

Chronic hepatitis B (CHB) infection affects over 350 million people worldwide.(1) The REVEAL studies demonstrated that progression to liver cirrhosis, hepatocellular carcinoma (HCC) and liver-related mortality correlates strongly with the level of circulating hepatitis B virus (HBV) DNA.(2;3) The cumulative incidence of cirrhosis increased from 4.5% in patients with HBV DNA <300 copies/mL to 36.2% in patients with HBV DNA ≥106 copies/mL (p<0.001).(3) Correspondingly, the cumulative incidence of HCC in the REVEAL study increased proportionately with serum HBV DNA, from 1.3% in patients with HBV DNA <300 copies/mL to approximately 15% when HBV DNA was >106 copies/mL.(2) Finally, all-cause and chronic liver disease mortality also increased with increasing HBV DNA levels.(4) This association between elevated serum HBV DNA and disease progression in CHB has been confirmed by several studies of similar design.(5-8)

The liver is a rapidly regenerating organ, and persistent liver injury leads to a process of healing and scar tissue formation resulting in fibrosis, and eventually cirrhosis. Liver injury leads to fibrosis through the transformation of hepatic stellate cells from vitamin A storage cells to activated hepatic stellate cells which secrete fibrillar collagens.(9-11) Although fibrosis was previously thought to be irreversible and relentlessly progressive, recent studies have challenged these ideas. Animal models of liver fibrosis have shown that removing the underlying source of liver injury results in clearance of the activated hepatic stellate cells, allowing resorption of the extracellular matrix and consequently, reversal of fibrosis.(12-14) Treatment of the underlying cause of inflammation has been shown clinically to result in reversal of fibrosis and cirrhosis in patients with liver disease from both viral and non-viral causes.(15-20)

Short-term antiviral therapy for CHB results in the suppression of viral replication,(21;22) and has been associated with improvement of liver histology in randomized clinical trials.(23) Treatment for 3 years with the oral antiviral agent lamivudine has also been shown to slow the clinical progression of liver disease in patients with advanced fibrosis and cirrhosis.(24) However, in this landmark study, disease progression was assessed clinically and not histologically, and serum HBV DNA results were not reported. Longer-term histologic data exist from studies in nucleoside- naïve CHB patients treated with lamivudine or adefovir.(25-27) Emergence of antiviral drug resistance negatively impacted the histologic benefits that were observed with lamivudine and the impact of resistance on histologic response was not reported in the adefovir studies.

Viral replication is now recognized as the key driver of liver injury and disease progression, and thus the primary aim of treatment for chronic HBV infection is long- term suppression of HBV replication to undetectable levels.(1;28;29) Entecavir is a potent HBV antiviral which demonstrated superior virologic, histologic and biochemical outcomes after 48 weeks of therapy compared to either lamivudine or adefovir in nucleoside-naïve patients.(21;22;30) In a study of nucleoside-naïve Japanese patients, 3 years of entecavir therapy resulted in potent virologic suppression and additional improvement in necroinflammatory and fibrosis scores compared to baseline and Week 48 values.(31) Virologic suppression increased through 5 years of entecavir treatment in long-term rollover studies, with minimal emergence of resistance.(32-34) The aim of the present evaluation was to determine if long-term treatment with entecavir is associated with continued histologic improvement and reversal of fibrosis or cirrhosis.

Results

Study population

Of the 69 patients who provided a long-term biopsy, 50 were HBeAg-positive and 19 were HBeAg-negative. Fifty-seven of the 69 patients met the criteria for inclusion in the efficacy analyses. Table 1 shows the baseline characteristics for these 57 patients compared with all entecavir-treated patients from the Phase III studies. Patients with long-term liver biopsies were comparable to all-treated patients, although a slightly higher proportion of patients with long-term biopsies were Asian (67% compared to 58% in ETV-022 and 38% in ETV-027). For these 57 patients, the mean baseline HBV DNA was 9.4 log10 copies/mL, with mean baseline Knodell necroinflammatory and Ishak fibrosis scores of 8.0 and 2.4, respectively; 10 of the 57 patients (18%) had an Ishak fibrosis score ≥4, indicating advanced fibrosis or cirrhosis.

The median time on entecavir treatment for these 57 patients at the time of the long-term biopsy was 280 weeks (approximately 6 years; range of 3–7 years), with a median gap of 3.3 weeks between end of dosing in the Phase III feeder study and the first date of dosing in the rollover study. The majority of patients (51/57) received lamivudine in combination with entecavir therapy for a median of 29 weeks early in the course of ETV-901, and received entecavir monotherapy for the remainder of the study.

Histologic response

All biopsies with at least three portal areas were evaluated with the understanding that small biopsies tend to be underscored for necroinflammation and fibrosis.(37) Baseline biopsies had a mean length of 12.1 mm (60%.≥10mm), Week 48 biopsies had a mean length of 11.6 mm (65% ≥10 mm), and the long-term biopsies had a mean length of 15.2 mm (79% ≥10 mm).

After long-term treatment with entecavir, 96% (55/57) of patients demonstrated histologic improvement, which was increased from 73% (41/56) of patients after 48 weeks of therapy (Table 2). The mean change from baseline in the Knodell necroinflammatory score was a 6.37-point reduction after long-term treatment, compared to a mean reduction of 3.39 points after 48 weeks of entecavir therapy. The proportion of patients in the cohort demonstrating at least a 1-point improvement in Ishak fibrosis score also increased, from 32% (18/56) after 48 weeks to 88% (50/57) after long-term treatment. The mean change from baseline in Ishak fibrosis score was a 1.53-point reduction after long-term treatment, which was increased from a 0.20-point reduction after 48 weeks of therapy.

Treatment for longer than 48 weeks resulted in an increasing proportion of patients with no or minimal necroinflammation by Knodell classification (Knodell HAI score ≤3), and no or minimal fibrosis by Ishak classification (Ishak score 0 or 1) (Table 2). Among patients with a baseline Knodell HAI score ≥4, the majority (75%, 41/55) achieved a Knodell HAI ≤3 on the long-term biopsy. Among patients with a baseline Ishak fibrosis score ≥2, the majority (31/43; 72%) achieved an Ishak fibrosis score of 0 or 1 on the long-term biopsy. Figures 2(a) and 1(b) show the change in distribution of Knodell necroinflammatory and Ishak fibrosis scores at the baseline, Week 48 and long term.

One of the 57 patients had an increase in Ishak fibrosis score, rising from 1 at baseline to 2 at the long-term biopsy. This patient had undetectable HBV DNA and a normal serum ALT at the time of the long-term biopsy, as well as an improvement in the necroinflammatory score (from 3 at baseline to 1 at the long-term biopsy).

Advanced fibrosis and cirrhosis

Ten of the 57 patients had advanced fibrosis or cirrhosis (Ishak score ≥4) at baseline. With long-term entecavir therapy, all 10 patients demonstrated at least a 1-point reduction in Ishak fibrosis score, with a median reduction from baseline of 1.5 points. Four of the 10 patients had cirrhosis at baseline (Ishak fibrosis score ≥5), and all demonstrated an improvement in Ishak fibrosis score, with a median drop of 3 points (range: 1 to 4). Figure 3 shows photomicrographs of biopsies taken from a 60-year-old, HBeAg-negative Caucasian male patient. The baseline biopsy shows an Ishak fibrosis score of 6, indicating cirrhosis, which was unchanged at Week 48. Following long-term treatment with entecavir, the Week 268 biopsy shows an Ishak fibrosis score of 2, indicating minimal fibrosis.

Virologic and biochemical response

At the time of the long-term biopsy, 100% (57/57) of patients had HBV DNA <300 copies/mL (Table 2). This represents an increase from 70% (40/57) of patients with HBV DNA <300 copies/mL after 48 weeks of entecavir treatment. Similarly, the proportion of patients with ALT ≤1 x ULN increased from 67% (38/57) after 48 weeks of therapy to 86% (49/57) after long-term treatment. Genotypic testing for resistance was not performed because all the patients achieved a serum HBV DNA level <300 copies/mL.

Serologic response

According to the study design of ETV-022, patients who lost HBeAg (with or without seroconversion) during the first or second year of therapy and achieved undetectable serum HBV DNA by bDNA assay were to discontinue entecavir treatment and be followed off-treatment to determine sustained response. During the long-term rollover study, 55% (22/40) of the HBeAg-positive patients lost HBeAg and 33% (13/40) achieved HBe seroconversion. No patient in this cohort lost HBsAg.

Safety

The majority of patients (96%) experienced at least one adverse event at some time during entecavir treatment, and serious adverse events (SAE; the majority of which were grades 1 or 2) occurred in 25% of patients. However, no patient discontinued entecavir treatment due to an adverse event. Two patients experienced on-treatment ALT flares; both cases resolved with continued treatment. One patient died from myocardial ischemia during entecavir treatment; this death was not attributed to study medication.

Discussion

In the original Phase III studies, histologic improvement was observed in the majority (73%) of patients as early as Week 48, but only a minority (32%) demonstrated an improvement in fibrosis. The current analyses of the Long-Term Histology Cohort summarize the effects of continued entecavir therapy on hepatic necroinflammation and fibrosis in nucleoside-naïve HBeAg-positive and -negative CHB patients. After a median exposure to entecavir therapy of approximately 6 years, histologic improvement and improvement of fibrosis increased to 96% and 88% of patients, respectively. Most patients (75%) in the cohort who had a baseline HAI score of ≥4 achieved a score of ≤3 by the long-term biopsy. These histologic analyses extend previous observations of the clinical efficacy of entecavir at 48 weeks in patients with advanced fibrosis or cirrhosis.(38) All patients who had evidence of advanced fibrosis or liver cirrhosis at Phase III baseline demonstrated improvement in fibrosis at the long-term assessment.

Suppression of viral replication to below the level of PCR assay detection (serum HBV DNA <300 copies/mL) occurred in all patients, and most patients (86%) also had a normal serum ALT level at the time of the long-term biopsy. Because of the sustained suppression of HBV DNA to <300 copies/mL, these patients were at minimal risk for antiviral drug resistance, and no evidence of virologic rebound or genotypic resistance to entecavir was observed in this study. A majority (55%) of patients lost HBeAg, and 33% experienced HBe seroconversion at the time of the long-term biopsy. Patients who did not demonstrate HBe seroconversion during long-term treatment also experienced improvements in liver histology and reversal of fibrosis, suggesting that these outcomes are more closely associated with HBV DNA suppression than with immunologic response to therapy.

The baseline demographics of the patients in the Long-Term Histology Cohort and the Phase III studies suggest that the two populations are comparable; however, the current data set has some limitations. For all patients who entered the rollover study, the dose of entecavir increased from 0.5 mg in the Phase III studies to 1.0 mg daily in the rollover study, and 51/57 patients (89%) in this cohort received a median of 29 weeks of concurrent lamivudine before continuing on entecavir monotherapy for the remainder of the observation period. Because amendments were made to the long-term rollover study as new data emerged, it is not possible to evaluate any potential contribution of the increased dose of entecavir or the brief period of concurrent lamivudine to the results.
Although all 57 patients eventually went on to achieve HBV DNA <300 copies/mL by the time of their long-term biopsy, the additional increase in virologic suppression is likely related to the longer duration of entecavir therapy and absence of resistance, rather than the brief period of concurrent lamivudine therapy or the increased dose of entecavir. The histologic benefits observed in the Long-Term Histology Cohort are therefore more likely driven by the durable antiviral suppression and avoidance of antiviral drug resistance observed with entecavir therapy in these nucleoside-naïve patients. This assessment is supported by a separate long-term histology cohort of 19 Japanese patients who received continuous therapy with entecavir 0.5 mg once daily for 3 years, in whom histologic improvement and improvement in fibrosis was observed in 100% and 63% of patients respectively.(31)

Clinical data on the degree of fibrosis or cirrhosis were not collected as part of the entecavir Phase III studies or the rollover study. Thus, is it not clear from this data set whether the macroscopic architectural abnormalities typically observed in patients with advanced fibrosis or cirrhosis remain among patients who have experienced histologic regression. However, the reductions in portal pressure observed among cirrhotic patients receiving treatment with entecavir or lamivudine would suggest that architectural remodeling does occur to some degree.(39;40)

The possibility that successful treatment of CHB could result in reversal of cirrhosis was first suggested in a case series of three patients who were treated with either interferon or lamivudine.(41) Three subsequent publications have reported the effects of nucleos(t)ide analogs on histologic outcome beyond 48 weeks.

A cohort of previously nucleoside-naïve HBeAg-positive CHB patients were treated with lamivudine and followed for 3 years.(25) In this report, 35/65 patients (56%) experienced histologic improvement. Forty-one (63%) of these patients developed YMDD resistance, and the histologic improvement was lost in many of those patients. Two smaller cohorts of nucleoside-naïve HBeAg-negative CHB patients treated with adefovir were followed for 4 years (N=22) or 5 years (N=24).(26) In this report, 12/22 (55%) patients treated for 4 years and 17/24 (71%) patients treated for 5 years demonstrated improvements in Ishak fibrosis score. In a recently published cohort of 65 nucleoside-naïve HBeAg-positive CHB patients treated with adefovir for 5 years, 39% achieved a serum HBV DNA <1000 copies/mL, and resistance emerged to adefovir in 20% of patients. A subset of 15 patients had paired baseline and long-term biopsies, and improvement in necroinflammation and fibrosis was shown in 9/15 (60%) patients using the Knodell scoring system.(27)

These data support the conclusion that in most nucleoside-naïve patients, long-term entecavir therapy leads to potent suppression of HBV DNA, normalization of ALT and improvement in liver histology with accompanying regression of fibrosis, including those with advanced fibrosis or cirrhosis at baseline. Substantially more patients demonstrated histologic improvement at the time of the long-term biopsy compared to Week 48, confirming the value of long-term treatment for CHB. The safety profile, potent suppression of HBV replication, and low potential for antiviral drug resistance in nucleoside-naïve patients make long-term treatment of CHB with entecavir monotherapy possible.