|Year : 2014 | Volume
| Issue : 1 | Page : 60-63
Antiviral efficacy of adefovir dipivoxil in the treatment of chronic hepatitis B subjects from Indian subcontinent
AM Ismail1, J Ramachandran2, R Kannangai1, P Abraham1
1 Departments of Clinical Virology, Christian Medical College, Vellore, Tamil Nadu, India
2 Gastrointestinal Sciences, Christian Medical College, Vellore, Tamil Nadu, India
|Date of Submission||21-Jan-2013|
|Date of Acceptance||04-Oct-2013|
|Date of Web Publication||4-Jan-2014|
Departments of Clinical Virology, Christian Medical College, Vellore, Tamil Nadu
Source of Support: The study was supported by Indian Council for
Medical Research (ICMR) grant (No. 5/8/7/7/2008-ECD-I),, Conflict of Interest: None
Adefovir is one of the therapeutic options for the treatment of chronic hepatitis B. A total of 30 adefovir-experienced subjects with the median treatment duration of 12 (interquartile range (IQR) 6-18) months were studied. Virological response was measured by hepatitis B virus deoxyribonucleic acid (HBV DNA) levels. HBV reverse transcriptase (rt) domains were sequenced for the identification of resistance mutations. Among the 30 subjects, two (7%) showed virological response and 19 (63%) were non-responders. The virological response for the remaining nine (30%) subjects was not determined. On sequence analysis, two subjects were identified with rtI169L and rtA181V mutation after 9 months and 18 months of adefovir treatment, respectively. Though the frequencies of adefovir resistance mutations are low, a large majority of subjects showed non-response. Therefore, adefovir in the management of HBV should be used judiciously.
Keywords: Adefovir, chronic hepatitis B, drug resistance, hepatitis B virus
|How to cite this article:|
Ismail A M, Ramachandran J, Kannangai R, Abraham P. Antiviral efficacy of adefovir dipivoxil in the treatment of chronic hepatitis B subjects from Indian subcontinent. Indian J Med Microbiol 2014;32:60-3
|How to cite this URL:|
Ismail A M, Ramachandran J, Kannangai R, Abraham P. Antiviral efficacy of adefovir dipivoxil in the treatment of chronic hepatitis B subjects from Indian subcontinent. Indian J Med Microbiol [serial online] 2014 [cited 2019 Dec 12];32:60-3. Available from: http://www.ijmm.org/text.asp?2014/32/1/60/124312
| ~ Introduction|| |
Chronic hepatitis B subjects are at increased risk for end-stage liver disease and, therefore, chronic hepatitis B infection is considered to be of public health importance.  Currently, interferon, peg-interferon, lamivudine, adefovir dipivoxil, entecavir, telbivudine and tenofovir are the approved drugs for the treatment of chronic hepatitis B.
Among 350 million chronic hepatitis B infection worldwide, approximately 75% reside in the Asia-Pacific region.  One of the practical difficulties in the management of hepatitis B in the Asia-pacific region is the cost of antiviral therapy. Treatment with standard interferon (IFN) costs approximately ₹ 140,000 and for peg-IFN therapy costs go up to approximately ₹ 660,000 for one year.  The cost of lamivudine and adefovir ranges from ₹ 3000 to 7000 per year and are more affordable antiviral drugs for hepatitis B virus (HBV) treatment. A one-year course of entecavir, telbivudine or tenofovir is estimated to be around ₹ 80,000, 65,000 and ₹ 16,000, respectively.  Since oral nucleos (t) ide analogues are to be given for over a year, cost constraints make the use of entecavir, telbivudine and tenofovir somewhat limited. Hence, treatment of HBV still depends on oral drugs particularly lamivudine and adefovir in the Indian subcontinent.
Though lamivudine is cost-efficient, the use of this antiviral drug is limited due to the increasing rate of antiviral resistance. The incidence of lamivudine resistance is reported to be 10-32% at 1 year and increases up to 69-80% after 5 years of therapy.  Therefore, the clinical use of lamivudine in the management of chronic hepatitis B is a major concern.
Adefovir, a nucleotide analogue of adenosine, is an orally administered drug which is reported to be effective against both wild type and lamivudine resistant strains of HBV.  The primary adefovir-resistant mutations are rtN236T and rtA181T/V.  Recently, Li et al.,  showed a novel rtI169L mutation as a primary drug resistance mutation associated with adefovir monotherapy. The cumulative probability of mutations associated with resistance to adefovir is 0%, 3%, 11%, 18% and 29% after 1, 2, 3, 4 and 5 years, respectively.  In comparison to lamivudine, the rate of adefovir resistance is much lower and thus remains the suitable drug of choice for the long term treatment.  There is only one pilot study from Indian subcontinent that showed the antiviral response of adefovir monotherapy in 15 HBV infected subjects.  So far the antiviral resistance mutations associated with adefovir failure have not been addressed in the Indian population. Therefore, we aimed to study the virological response and antiviral resistance mutations associated with adefovir monotherapy in the Indian subcontinent subjects.
| ~ Materials and Methods|| |
The study was approved by the Institutional Review Board and written informed consent was obtained from all the subjects.
The study subjects attending the liver clinic of this institution were referred to the department of Clinical Virology for HBV deoxyribonucliec acid (DNA) testing and were recruited between March 2007 and August 2011. A total of 30 adefovir-experienced subjects were studied. Six subjects (20%) were started on adefovir in this hospital, while 24 (80%) were started on adefovir prior to their visit to this hospital. All received adefovir at a standard dosage of 10 mg/day. The inclusion criteria were chronic HBV infection and subjects who reported to adhere strictly to the treatment schedule without any interruption. Treatment compliance was checked by verbal questioning and in clinical records. The exclusion criteria were history of previous treatment with other HBV antivirals and immunomodulators, add-on or combination therapy, co-infection with hepatitis C virus (HCV), hepatitis D virus (HDV) or human immunodeficiency virus (HIV), use of immunosuppressive drugs and chemotherapy.
Serum alanine transaminase (ALT) and serum aspartate transaminase (AST) levels were obtained from the subject's hospital records. The normal range for ALT and AST levels were 8-40 U/L and 5-35 U/L, respectively.
Hepatitis B surface antigen (HBsAg) was tested in AxSYM (Abbott, Weisbaden, Germany), ARCHITECT (Abbott, Weisbaden, Germany) or Monolisa HBsAg ULTRA (Bio-Rad, Marnes-la-coquette, France). HBeAg and anti-HBe testing was performed in an enzyme immunoassay (EIA) (Diasorin S.P.A., Saluggia, Italy). HCV antibody (Ab), HDV Ab and HIV were screened in Ortho HCV 3.0 (Ortho Clinical Diagnostics, Raritan, N.J., USA), IgM anti-HD EIA (Diasorin S.P.A., Saluggia, Italy) and ARCHITECT HIV Ag/Ab combo (Abbott, Weisbaden, Germany), respectively.
HBV DNA quantification
HBV DNA was quantified using artus® HBV RG PCR (Qiagen GmbH, Hilden, Germany) in the Rotor-Gene 3000 or 6000 platform (Corbett Research, Mortlake, Australia). The lower limit of detection (LLD) in using the Qiamp DNA Blood Mini kit (Qiagen GmbH, Hilden, Germany) and the artus® HBV Rotor-Gene Polymerase Chain Reaction (RG PCR) assay was determined to be 82 IU/mL (95% detection limit) in our centre. 
HBVrt amplification and sequencing
The complete HBVrt region (1,323 bp) was amplified and sequenced as described earlier.  Obtained bidirectional sequences were analysed using BioEdit v7.0.9 and the sequences were submitted to the HBVSeq program for analysis of HBV drug resistance mutations in Stanford database.
Nucleotide sequences generated from this analysis have been deposited in GenBank database under accession numbers JQ514500 to JQ514530.
| ~ Results|| |
A total of 30 adefovir-experienced subjects were studied. Among these subjects, 28 (93%) were male and two (7%) were female; their median age was 42 (interquartile range (IQR) 30-44). The median treatment duration was 12 (IQR 6-18) months.
Among the subjects studied, 12 (40%) had normal ALT levels, 12 (40%) had ALT levels of 1-2 upper limit of normal (ULN) and 6 (20%) had > 2 ULN ALT levels at the median treatment duration of 12 (IQR 6-18) months. Likewise, 15 (50%) subjects had normal AST levels, nine (30%) subjects had 1-2 ULN and six (20%) subjects had >2 ULN AST levels. The median ALT and AST levels were 29 (IQR 43-65) U/L and 29 (IQR 42-62) U/L, respectively.
All subjects continued to be positive for HBsAg. Hepatitis B e-antigen was positive in 15 (50%) subjects. Four (27%) of the HBeAg-positive subjects in the anti-HBe seroconversion phase and six (40%) HBeAg-negative subjects were positive for anti-HBe antibody. All the remaining subjects were negative for anti-HBe antibody. The median HBV DNA level was 3.0 (IQR 4.5-5.6) log 10 IU/mL.
Virological response and non-response was characterized by HBV DNA levels. Responders were subjects who showed ≥ 1 log 10 IU/ml of HBV DNA reduction within median treatment duration of 6 months or undetectable HBV DNA (<82 IU/mL) after median treatment duration of 12 months. Non-responders were subjects who showed < 1 log 10 IU/mL reduction of HBV DNA in median treatment duration of 6 months or subjects who continued to be positive for HBV DNA after median treatment duration of 12 months. Among the 30 subjects, two (7%) showed virological response and 19 (63%) were non-responders. The virological response for the remaining nine (30%) subjects was not categorised because these subjects continued to be positive for HBV DNA up to 6 months of adefovir and the difference in viral loads could not be measured as the subjects had only one-time point of sampling.
Among the 28 samples (non-responders, n = 19 and uncategorised, n = 9) analysed for antiviral resistance mutations, 25 samples were carried for sequence analysis. The remaining three samples with HBV DNA levels of 8, 54 and 299 IU/mL failed to amplify in HBVrt PCR. In the samples analysed, one subject was identified with rtI169L after 9 months of treatment and one subject was identified with the typical adefovir resistance rtA181V mutation after 18 months of adefovir treatment. No additional patterns of amino acid substitutions associated with adefovir non-response were identified.
| ~ Discussion|| |
Adefovir is shown to have a suboptimal virological response, characterised by slow and moderate reduction in HBV DNA levels.  The American Association for the Study of Liver diseases (AASLD) and European Association for the Study of Liver diseases (EASL) now recommend the use of more potent drugs such as entecavir or tenofovir as a first-line therapy in the management of chronic hepatitis B. , This study was conducted before the use of these drugs in the Indian subcontinent subjects and we show our experience of adefovir monotherapy in the management of chronic hepatitis B since adefovir monotherapy is still used as rescue monotherapy in chronic hepatitis B subjects with drug resistance to lamivudine.
Among the 30 adefovir-experienced subjects studied, only two (7%) showed virological response at median treatment duration of 12 months while 19 (63%) were non-responders. In a previous pilot study in India, four (26.7%) out of 15 subjects showed undetectable HBV DNA (<12 IU/mL) after 6 months of adefovir.  However, the numbers were too small for reliable comparison.
In our study, rtI169L mutation was identified in one subject. The rtI169T is well described to confer resistance to entecavir at the same HBVrt amino acid position.  The subject with rtI169L mutation had no history of entecavir treatment. Recently, Li et al.,  showed rtI169L as primary drug resistance mutation associated with adefovir treatment. This report supports our finding and illustrates rtI169L mutation to be associated with adefovir resistance. Additionally, we identified the typical adefovir resistance rtA181V mutation in one subject. Among the 30 subjects studied, two subjects showed undetectable HBV DNA (<82 IU/mL) and three samples failed to amplify in HBVrt PCR. Excluding the three samples, the cumulative proportion of adefovir-experienced subjects who developed adefovir resistance at the median treatment duration of 12 months was 7.41%. Since adefovir is sparingly used in our centre, we could study its efficacy only in 30 subjects. This is the major limitation of this study.
Though the sample size is small, the finding of this study reiterates the fact that the virological response for adefovir is suboptimal though the frequency of resistance mutations is comparatively lower than lamivudine. Therefore, we propose that future studies be directed towards extending the combination therapy approach to HBV akin to the treatment of HIV infection or the use of more potent drugs like entecavir or tenofovir.
In summary, we show that adefovir is less potent though the frequency of resistance mutations is lower. Our identification of rtI169L mutation further adds evidence to a recent finding that points to an association between rtI169L mutation and adefovir resistance.
| ~ Acknowledgment|| |
The authors acknowledge all the study participants and the administrative support of Christian Medical College, Vellore.
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