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REVIEW ARTICLE  
Year : 2010  |  Volume : 7  |  Issue : 1  |  Page : 73-85
HBV therapeutic end points


Chief of Hepatology Services, Sir Ganga Ram Hospital, New Delhi, India

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Date of Web Publication4-Aug-2015
 

   Abstract 

Chronic hepatitis B [CHB] is a major health problem especially in developing countries. Defining the end point of therapy is a key issue in management of CHB patients, since a judicious balance has to be maintained between containing the virus and its sequelae and futility of continuation of therapy beyond a point. The major goals of antiviral therapy are to prevent the complications of CHB such as the development of liver cirrhosis, liver failure, HCC and death. Major advances have been made in the treatment of chronic hepatitis B, which led to significant improvements in the management of the disease. Several virologic end points have been used to evaluate the efficacy of therapy, including HBsAg loss, HBeAg seroconversion and HBV DNA undetectability. It was shown that viral suppression induced by antiviral therapy is a major treatment end point because it is associated with an improvement in liver histology and clinical outcome, and is now achievable in the majority of patients. New end points for the treatment of chronic HBV infection are emerging in the light development of more potent drugs and availability of more sensitive assays with the quantification and kinetics of serum HBsAg, intrahepatic cccDNA and analysis of specific immunological responses. However, liver biopsy still remains the gold standard but is impractical due to invasive nature, sampling error, and the significantly delay it takes for changes to appear. There is no ideal endpoindr for evaluation of therapies for hepatitis B at the moment, and future research should be directed at development and validation of endpoints that could precisely foretell or reflect outcomes in patients with CHB.This review which discusses the various end points of treatment of CHB should be of immense benefit to the practicing clinicians.

Keywords: cccDNA; Chronic hepatitis B, HBeAg, HBsAg, HBV DNA, seroconversion

How to cite this article:
Arora A. HBV therapeutic end points. Hep B Annual 2010;7:73-85

How to cite this URL:
Arora A. HBV therapeutic end points. Hep B Annual [serial online] 2010 [cited 2019 Oct 15];7:73-85. Available from: http://www.hepatitisbannual.org/text.asp?2010/7/1/73/162150


Patients with chronic HBV infection and active inflammatory activities have progressive disease and are at high risk for the eventual development of cirrhosis and related complications such as liver failure and hepatocellular carcinoma. According to the American Association for the Study of Liver Diseases Practice Guidelines, treatment is recommended for patients with an alanine aminotransferase (ALT) level greater than two times the upper limits of normal and HBV DNA ≥ 10 5 copies/ml who are either hepatitis B e antigen (HBeAg) positive (wild-type virus) or negative (precore or core promoter mutation). In HBeAg-positive patients, durable loss of HBeAg is a widely accepted end point of treatment and is associated with improved long-term prognosis. After the failure of treatment with the purine nucleosides adenine arabinoside (vidarabine) and arabinosyladenosine monophosphate in the 1980s, interferon (IFN) alfa-2b became the first drug approved by the US Food and Drug Administration (FDA) for the treatment of chronic hepatitis B in 1992 [Figure 1]. Approximately one third of patients with HBeAg-positive chronic HBV infection had a virologic response, with loss of HBeAg and undetectable HBV DNA, after 16 to 24 weeks of IFN treatment. HBeAg seroconversion to antibody to hepatitis B e antibody (anti-HBe) and clearance of hepatitis B surface antigen (HBsAg) were found in 18% and 8%, respectively. Among patients with HBeAg-negative chronic hepatitis B, a standard course of IFN alfa-2b treatment for 16 to 24 weeks was associated with a high rate of relapse. Longer duration of IFN alfa-2b treatment for 12 to 24 months led to a higher rate of sustained response in 22% to 30% of patients based on suppression of HBV DNA and normalization of ALT levels. [1]
Figure 1: Evolving CHB Treatment Paradigm From short term to long term perspective

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A new era in drug development for the treatment of chronic hepatitis B commenced in the mid-1990s, largely fueled by efforts directed to the treatment of the HIV. Since 1998, three oral deoxynucleoside or deoxynucleotide analogues- lamivudine, adefovir dipivoxil, and most recently, entecavir- have been approved by the FDA for the treatment of chronic HBV infection. These oral agents are well tolerated and have an excellent safety profile.


   Treatment End Points in Regional Guidelines Top


Treatment cessation criteria and clinical treatment end points are difficult to define, and the best treatment end point associated with the lowest risk of relapse remains unclear.

The short-term target of antiviral therapy is currently defined in many guidelines as maintained suppression of HBV replication, with or without HBeAg seroconversion. To avoid disease progression and to minimize the risk of resistance, maintained viral suppression is important, particularly in HBeAg-negative and HBeAg-positive patients who have not yet achieved HBeAg seroconversion. For seroconverted patients, recent data have demonstrated that HBeAg seroconversion alone may not signify freedom from risk of disease progression and hepatitis relapse is common after treatment cessation. Current evidence suggests that HBsAg seroclearance would be a preferred end point. In line with recent EASL [Table 1] updates, existing guidelines need to be revised to include sustainable suppression of HBV replication, with HBsAg seroclearance as the preferred treatment end point; however, only a small proportion of patients can achieve this end point with currently available oral nucleos(t)ide analogs.
Table 1: Treatment end points in regional guidelines


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Studies have suggested that serial measurements of HBsAg concentration (titer) may be useful in determining the ideal treatment end point, and the quantitation of HBsAg may reflect the amount of covalently, closed, circular DNA inside the hepatocyte. Future studies in this area are of interest. [2]

As the timing of treatment initiation may determine the timing of HBsAg seroclearance, and ultimately affect disease progression, the adoption of a preventative approach to CHB treatment, identifying patients at risk using thorough pretreatment evaluation criteria and initiating treatment as early as possible, is strongly advocated.

Patient monitoring should continue to be mandatory upon treatment cessation. While a recent study suggested reinitiation of therapy is effective, data remain limited and re-treatment criteria should be the same as those for treatment initiation, as indicated in current APASL or American Association for the Study of Liver Diseases guidelines.

Finally, sustained HBeAg seroconversion may remain an appropriate treatment goal for some patients, for example, young HBeAg-positive patients without advanced disease. As indicated in current guidelines, 6-12 months of consolidation therapy and monitoring for relapse are crucial upon treatment cessation in these patients. [2]

As complete eradication of HBV is currently not possible with available therapy, various endpoints have been adopted as surrogate markers of successful treatment. These include HBeAg seroconversion, histology, normalisation of ALT, and HBV DNA suppression.


   Why use HBeAg and HBsAg seroconversion? Top


HBeAg seroconversion, whether spontaneous or treatment induced, is associated with clinical remission and a transition to inactive liver disease in patients with HBeAg-positive chronic hepatitis B (CHB). A reduction in liver fibrosis is noted upon liver biopsy, as is a lower incidence of cirrhosis and hepatocellular carcinoma (HCC) among patients who undergo spontaneous or treatment-induced HBeAg seroconversion. HBeAg seroconversion is also associated with a higher probability of HBsAg loss and seroconversion, which is considered to be a more permanent clinical remission of liver disease. Thus, the achievement and maintenance of HBeAg seroconversion, in association with polymerase chain reaction (PCR)-undetectable hepatitis B virus (HBV) DNA levels, is an important goal in the management of patients with HBeAg-positive CHB. Based on evidence demonstrating HBeAg seroconversion as a marker of a durable clinical remission of liver disease, major liver society treatment guidelines have adopted HBeAg seroconversion with sustained suppression of HBV DNA as an end point for treatment in patients with HBeAg-positive CHB who do not have cirrhosis or decompensated liver disease. [6]

  • HBeAg(+) associated with high levels of viral load
  • Anti-HBeAb is a measurable end point that in most cases indicates transition to inactive phase
  • HBsAg widely used to screen for HBV
    • Loss of HBsAg associated with 'clearance' of the virus
  • These markers are easily available, reliable, inexpensive.


There are limitations of HBeAg seroconversion, available data indicates that most HBeAg (+) patients cannot achieve HBeAg seroconversion with short-term treatment. Loss of HBsAg, although highly desirable, is rarely achieved with short-term antiviral therapy and, hence, is not a realistic goal for antiviral trials. [7] HBeAg seroconversion is achievable in 12-22% of patients after 1 year of oral antiviral therapy.

Studies in Asian countries showed that relapse rates are much higher than seen in Western Countries after LVD induced HBeAg seroconversion.

In a study conducted by Yao-Shih Hsu et al [8] , of the 269 patients without evidence of cirrhosis at the time of HBeAg seroconversion, 21 (7.8%) patients developed new cirrhosis (15 with histologic evidence, 6 diagnosed by clinical and imaging features) during follow-up with an estimated annual incidence of 0.9%. Breakdown data showed that 14 (23%) of the 62 patients with HBeAg-negative hepatitis, 5 (55%) of the 9 patients with HBeAg reversion, 1 (7%) of the 14 patients with active hepatitis of undetermined causes, and one (0.5%) of the 184 patients with sustained remission developed cirrhosis during the follow-up period. The median time to development of cirrhosis was 204 and 127 months for the HBeAg negative hepatitis group and the HBeAg reversion group, respectively [Figure 2].The cumulative incidence of cirrhosis development was highest in the HBeAg reversion group, followed by the HBeAg-negative hepatitis group, and then the sustained remission group. The differences were statistically significant among these 3 groups (P= .0129) and between groups (all P< .01) by log rank tests. Age/sex adjusted multivariate analysis showed that patients with HBeAg-negative hepatitis were significantly associated with new cirrhosis development, whereas age at the time of HBeAg seroconversion and male sex did not correlate with the risk of new cirrhosis development. [8]
Figure 2: The cumulative incidence of cirrhosis development after spontaneous HBeAg seroconversion in patients with chronic hepatitis B. The incidence of cirrhosis development is significantly higher in patients with HBeAg reversion than in patients with HBeAg-negative hepatitis and also significantly higher in patients with HBeAg-negative hepatitis than patients with sustained remission (P = .0129)

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   Easl Clinical Practice Guidelines 2009 on End-points of Therapy Top


Therapy must reduce HBV DNA to as low a level as possible, ideally below the lower limit of detection of real-time PCR assays (10-15 IU/ml), to ensure a degree of virological suppression that will then lead to biochemical remission, histological improvement and prevention of complications. Interferon alpha or nucleoside/nucleotide analogue (NUC) therapy-induced HBV DNA reduction to low levels is associated with disease remission. Sustained HBV DNA reduction to undetectable levels is necessary to reduce the risk of resistance to NUCs. It also increases the chance of HBe seroconversion in HBeAg-positive patients and the possibility of HBsAg loss on the mid to long term in HBeAg-positive and HBeAg-negative patients. If real-time PCR is unavailable, HBV DNA should be measured by the most sensitive assay possible. [9]

  • In HBeAg-positive and HBeAg-negative patients, the ideal end-point of therapy is sustained HBsAg loss with or without seroconversion to anti-HBs. This is associated with a complete and definitive remission of the activity of chronic hepatitis B and an improved long-term outcome
  • In HBeAg-positive patients, durable HBe seroconversion is a satisfactory end-point because it has been shown to be associated with improved prognosis
  • In HBeAg-positive patients who do not achieve HBe seroconversion, and in HBeAg-negative patients, a maintained undetectable HBV DNA level on treatment with NUCs or a sustained undetectable HBV DNA level after interferon therapy is the next most desirable end-point.



   HBV DNA as an End Point Top


The third possible primary endpoint is measurement of changes in HBV DNA level before and during treatment. To date this endpoint has not been widely accepted as a primary endpoint by regulatory authorities. The major reason for this is that changes in HBV DNA levels have not been fully established as a surrogate marker for disease progression. The data supporting the suitability of HBV DNA as a surrogate marker for the clinical efficacy of a therapy are becoming available.

Serum HBV DNA levels have been shown to be important in both the development of liver cirrhosis and for development of HCC. Higher levels of HBV DNA are associated with the development of HCC independent of the HBeAg status and ALT levels. There is no current level of HBV DNA which is considered 'safe' from disease progression or from development of HCC. A cut-off level of >2000 IU/mlwas shown to be a strong risk predictor of HCC independent of HBeAg status, serum ALT and underlying cirrhosis. However, even lower HBV DNA levels have been associated with the development of HCC. Given the absence of a 'safe' lower limit for disease non-progression, the optimal treatment goal should therefore be to suppress HBV DNA to the lowest possible level, that is, non-detectability by PCR assays.

  • HBV DNA suppression is a direct marker of antiviral efficacy
  • Cohort studies indicate that HBV DNA levels directly correlate with risk of disease progression to cirrhosis and hepatocellular carcinoma.


Advantages of HBV DNA as a marker

HBV DNA levels have a number of advantages as a primary endpoint. Differences in HBV DNA levels between patients receiving active therapy and those receiving placebo are easily demonstrated with a relatively small sample size and so studies using this primary endpoint can be smaller than those using seroconversion as a primary endpoint. The test is non invasive, and therefore simpler and cheaper to perform, and can be performed frequently than histology. The other advantage of HBV DNA as a primary endpoint is that it can be used to detect the development of resistance, as HBV DNA levels that have been suppressed by therapy rise when a resistance develops.

Disadvantages

Lack of standardization in

  • Measurement copies /IU
  • Cut off points.


Assay in which

Signal amplification: Poor lower limit

Target amplification: Poor higher limit

RT - PCR: Best.


   ALT: As a Marker Top


Although changes in ALT levels are seldom used as a primary study endpoint, ALT levels are useful tool for assessing both the efficacy and safety of new therapies. These can be assessed either by comparing median changes in ALT levels over time, the proportion of patients in each treatment group in whom ALT levels become normal, or time to normalization of ALT levels in each treatment group. ALT is also useful indicator of hepatotoxicity, and so patient in whom ALT levels rise on therapy should be monitored carefully.

In Asian CHB patients, it has been shown that patients with ALT levels below half the upper limit of normal (ULN) have the lowest risk of complications compared to those with 0.5 x ULN to 2 x ULN. Patients who have undergone HBeAg seroconversion with subsequent normal ALT have been traditionally regarded as "healthy carriers" with no or minimal disease progression. However, even in patients with normal ALT after HBeAg seroconversion, the cumulative probability of developing cirrhosis after 17 years was 13%. A recent study of CHB patients showed that 37% of those with persistently normal ALT had significant fibrosis or inflammation on liver histology, and the majority of cases with fibrosis occurred in those with high-normal ALT. In the light of these recent studies, the cut-off for the upper limit of normal for ALT is most likely to be lower than the values that are currently used. Even patients with ALT in the upper range of the currently accepted normal range are at risk of developing cirrhosis. Ongoing disease monitoring with consideration of antiviral therapy should be given for patients with significant degree of liver fibrosis. Furthermore, treating only those patients with ALT >2 x ULN, as indicated by most current guidelines, would exclude a significant proportion of patients (patients with ALT 0.5 - 2 x ULN) who would benefit most from antiviral therapy because of the higher risk of having or developing significant liver disease in these patients.

Advantages

  • Most simple/ accessible means of evaluating treatment response
  • Most frequently achieved 40-70% on Rx
  • Indirect measures of histological activity
  • Serial measurements - hepatitis flares or resistance
  • Very important early treatment response parameter in HBeAg -ve hepatitis.



   Histology as an End Point Top


The most commonly employed endpoint for the phase III studies that have been used to register pharmaceutical or biological products in the past is an assessment of the impact of therapy on liver histology . This is the endpoint that best evaluates the impact of therapy on the liver, the target organ of the infection, and can be used in patients with HBeAg-Positive and HBeAg -Negative chronic hepatitis B.

Pros

  • Corresponds to the ultimate goal of therapy i.e., to induce remission of liver disease
  • ≥2 HAI improvement or 1 grade improvement in fibrosis score
  • Post treatment h/p improvement associated with less long term complications.


Cons

  • Requirement for paired samples
  • Invasive procedure (not risk free)
  • Consistency of sample and interpretation.



   Treatment End Points Top


Each of the surrogate markers of treatment response can be considered endpoints of therapy, although virological suppression and loss of HBeAg and HBsAg play a more prominent role in decision-making with respect to antiviral therapy.

In HBeAg-positive disease, short-term treatment endpoints include HBeAg loss with or without anti-HBe seroconversion. Seroconversion occurs in approximately 20% of patients in the first year of antiviral therapy and increases with longer duration of therapy. It is sustained in 50% to 90% of treated patients depending on the duration of treatment after seroconversion, patient age and serum HBV DNA level at the end of treatment. Treatment-induced seroconversion is associated with suppressed HBV DNA and a reduced risk of cirrhosis.

In a small proportion of patients experiencing HBeAg loss, loss of HBsAg or anti-HBs seroconversion also occurs, often after the treatment period. In long-term follow-up of patients who received standard or pegylated interferon, HBsAg loss occurred in 11% of patients over 3-5 years. In another, smaller study of patients who experienced seroconversion during interferon therapy, HBsAg loss continued after therapy at a rate of approximately 8% per year for a cumulative rate of 86% by 9 years. Long-term complications occur at a negligible rate after the development of anti-HBs.

For patients with HBeAg-positive chronic hepatitis B in whom seroconversion does not occur but HBV DNA is fully suppressed on therapy, continued normalization of the ALT and sustained HBV DNA suppression are the only markers of successful treatment and the absence of antiviral resistance, as observed in HBeAg-negative hepatitis.

In HBeAg-negative disease, loss of HBsAg is the only clear indication for stopping therapy.

It tends to occur after long-term HBV DNA suppression. Among patients receiving adefovir therapy, 5% had HBsAg loss over a five-year period. Short of this endpoint, treatment goals in HBeAg-negative chronic hepatitis B include HBV DNA suppression and normalization of ALT levels.

For both HBeAg-negative and HBeAg-positive disease, sustained virological suppression is a critical on-treatment endpoint. Indeed, a recent phase III trial comparing telbivudine and lamivudine for the treatment of chronic hepatitis B used reduction in serum HBV DNA as a primary treatment outcome. [10]


   Conclusion Top


The major goals of antiviral therapy are to stop the natural history of chronic hepatitis B to prevent the complications such as the development of liver cirrhosis, liver failure, HCC and death. Major advances have been made in the treatment of chronic hepatitis B, which led to significant improvements in the management of the disease. Several virologic end points have been used to evaluate the efficacy of therapy, including HBsAg loss, HBeAg seroconversion and HBV DNA undetectability. It was shown that viral suppression induced by antiviral therapy is a major treatment end point because it is associated with an improvement in liver histology and clinical outcome, and is now achievable in the majority of patients. The efficacy of antiviral treatment on the main clinical end points, such as survival and complications of the disease, has been demonstrated in patients with severe disease at baseline (cirrhosis with or without decompensation), but not yet in patients with minimal-to-moderate chronic hepatitis. Long-term studies will be required in the latter population of patients.

New end points for the treatment of chronic HBV infection should be considered in light of the development of more potent drugs and more sensitive assays with the quantification and kinetics of serum HBsAg, intrahepatic cccDNA and analysis of specific immunological responses.

Financial support and sponsorship

Nil.

Conflict of interest

There are no conflicts of interest.

 
   References Top

1.
Francis Y. Yao. Newer Antiviral Agents and Therapeutic Approaches for Chronic Hepatitis B. Current Hepatitis Reports 2006, 5:14-22.  Back to cited text no. 1
    
2.
Sang Hoon Ahn et al. Chronic hepatitis B: whom to treat and for how long? Propositions, challenges, and future directions. Hepatol Int. 2010 March; 4(1): 386-395.  Back to cited text no. 2
    
3.
Lok AS and McMahon BJ. Chronic hepatitis B. Hepatology 2007;45:507-539.  Back to cited text no. 3
    
4.
Liaw YF, et al. Asian-Pacific consensus statement on the management of chronic hepatitis B: a 2008 update. Hepatol Int 2008;2:263-283.  Back to cited text no. 4
    
5.
EASL Clinical Practice Guidelines: management of chronic hepatitis B. J Hepatol 2009;50:227-242.  Back to cited text no. 5
    
6.
Lau GK. Current treatments for patients with HBeAg-positive chronic hepatitis B virus infection: a comparison focusing on HBeAg seroconversion. Liver Int. 2010 Apr;30(4):512-20.  Back to cited text no. 6
    
7.
Keeffe EB, et al. A Treatment Algorithm for the Management of Chronic Hepatitis B Virus Infection in the United States: 2008 Update. Clin Gastroenterol Hepatol 2008;6:1315-1341.  Back to cited text no. 7
    
8.
Yao-Shih Hsu et al. Long-Term Outcome After Spontaneous HBeAg Seroconversion in Patients With Chronic Hepatitis B. HEPATOLOGY 2002;35:1522-1527.  Back to cited text no. 8
    
9.
EASL Clinical Practice Guidelines: Management of chronic hepatitis B. European Association for the Study of the Liver / Journal of Hepatology 50 (2009) 227-242.  Back to cited text no. 9
    
10.
Karin L. Andersson, and Raymond T. Chung. Monitoring During and After Antiviral Therapy for Hepatitis B. Hepatology. 2009 May ; 49(5 Suppl): S166-S173.  Back to cited text no. 10
    

Top
Correspondence Address:
Anil Arora
Chief of Hepatology Services, Sir Ganga Ram Hospital, New Delhi - 110060
India
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/0972-9747.162150

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