Scott K. Fung

Evolution of multi-drug resistant hepatitis B virus during sequential therapy†

Multi‐drug resistant hepatitis B virus (HBV) has been reported in hepatitis B patients who received sequential antiviral therapy. In vitro studies showed that HBV constructs with mutations resistant to lamivudine and adefovir have marked reduction in sensitivity to combination of lamivudine and adefovir, whereas constructs with mutations resistant to either drug remain sensitive to the other drug. We conducted this study to determine whether mutations conferring resistance to multiple antiviral agents co‐locate on the same HBV genome in vivo and to describe the evolution of these mutations. Sera from six patients who had been found to have multi‐drug resistant HBV mutations to lamivudine + adefovir, lamivudine + hepatitis B immunoglobulin (HBIG), or lamivudine + entecavir on direct sequencing were cloned after nested polymerase chain reaction (PCR). Analysis of 215 clones from 11 samples with multi‐drug resistant mutations on direct sequencing showed that 183 (85%) clones had mutations to both therapies on the same genome; 31 clones had lamivudine‐resistant mutants only. Clonal analysis of serial samples from three patients showed progressive evolution from all clones with lamivudine‐resistant HBV mutations only to mixtures of clones that have multi‐drug resistant mutations and clones that have lamivudine‐resistant HBV mutations only, and ultimately all clones having multi‐drug resistant HBV mutations. In conclusion, mutations conferring resistance to multiple antiviral agents co‐locate on the same viral genome, suggesting that combination therapy directed against mutants resistant to each treatment may not be adequate in suppressing multi‐drug resistant HBV. De novo combination therapy may prevent the emergence of multi‐drug resistant mutants. (HEPATOLOGY 2006;44:703–712.)

Sustained response after a 2-year course of lamivudine treatment of hepatitis B e antigen-negative chronic hepatitis B.

Summary.u2002 Lamivudine has demonstrated efficacy for the treatment of hepatitis B e antigen‐negative chronic hepatitis B (e‐CHB). However, treatment withdrawal after 1u2003year has been associated with a high rate of relapse while long‐term treatment is associated with increasing risks of drug resistance. We report our treatment experience of 50 Chinese‐Canadian patients with e‐CHB. All patients received lamivudine for 2u2003years. Treatment was withdrawn at month 24 in patients who had undetectable hepatitis B virus (HBV) DNA by PCR and normal aminotransferases during the second year of therapy. All patients had HBV genotype B or C. Biochemical response at months 6, 12 and 24 was 74%, 71% and 66%, respectively. HBV DNA was undetectable at months 6, 12 and 24 by hybrid capture and PCR assays in 100%, 92% and 86%; and 94%, 88% and 74% patients, respectively. The cumulative rates of genotypic resistance (GR) after 1 and 2u2003years were 15% and 25%, respectively. Four (44%) patients with GR experienced a hepatitis flare. The probability of clinical and virological relapse 6, 12, and 18u2003months after treatment withdrawal were 12% and 30%, 18% and 50%, and 30% and 50%, respectively. Reinstitution of lamivudine resulted in prompt virological and biochemical responses. Our study demonstrates that a sustained response can be achieved after a 2‐year course of lamivudine in a subset of patients with e‐CHB.

Sensitive line probe assay that simultaneously detects mutations conveying resistance to lamivudine and adefovir

ABSTRACT The INNO-LiPA HBV DR v2 assay is designed to detect hepatitis B virus mutations conveying resistance to lamivudine and adefovir. Our study confirms that this assay can simultaneously detect the presence of lamivudine and adefovir resistance mutations in clinical samples, has a high degree of concordance with sequencing, and can detect mutants earlier.

A Genotype-Independent Real-Time PCR Assay for Quantification of Hepatitis B Virus DNA

ABSTRACT Accurate quantification of hepatitis B virus (HBV) DNA levels is important for monitoring patients with chronic HBV infection and for assessing their responses to antiviral therapy. This study aimed to develop a real-time PCR assay that is sensitive and can accurately quantify a wide range of HBV DNA levels across the known HBV genotypes. An “in-house” real-time PCR assay using primers and a TaqMan probe in a highly conserved region of the HBV surface gene was designed. The assay was standardized against a WHO standard and validated against plasmids of HBV genotypes A through H. The linear quantification range was approximately 5 × 100 to 2.0 × 109 IU/ml. Results of samples from patients infected with HBV genotypes A through H tested using our real-time “in-house” PCR assay showed an excellent correlation with those of the Cobas Amplicor HBV Monitor (R2 = 0.9435) and the Cobas TaqMan HBV (R2 = 0.9873) tests. We have established a real-time PCR assay that is genotype independent and can accurately quantify a wide range of HBV DNA levels. Further studies of additional samples are ongoing to validate the genotype independence of our assay.

Longitudinal Study of Hepatitis Activity and Viral Replication before and after HBeAg Seroconversion in Chronic Hepatitis B Patients Infected with Genotypes B and C

ABSTRACT The aims of this study were to compare chronic hepatitis B (CHB) patients with genotypes B and C for the probability of HBeAg seroconversion, hepatitis activity, and viral replication before and after HBeAg seroconversion and to compare the prevalence of core promoter and precore mutations. A total of 180 asymptomatic Chinese patients with CHB were monitored for a median of 53.8 months, and 38 patients with cirrhosis-related complications were studied. Hepatitis B virus (HBV) DNA levels were measured in 16 patients with HBeAg seroconversion at 3 months before, during, and 3 months after HBeAg seroconversion and in all patients at the last follow-up. Hepatitis B genotypes and core promoter and precore mutations were determined. Compared to patients with genotype C (n = 109), patients with subtype Ba (n = 69) had a higher rate of anti-HBe positivity on presentation (P = 0.05). HBeAg-positive patients with subtype Ba had a higher cumulative rate of HBeAg seroconversion than patients with genotype C (P = 0.02). However, there were no differences between the two groups with regard to the median HBV DNA levels before, during, and after HBeAg seroconversion; the probability of having persistently normal or elevated aminotransferase levels; and the median HBV DNA levels and liver biochemistry at the last follow-up. There was no difference in the prevalence of genotypes and core promoter and precore mutations between patients with and without cirrhosis-related complications. Though patients with subtype Ba had earlier HBeAg seroconversion, the liver biochemistry, HBV DNA levels in different phases of the disease, and the probability of development of cirrhosis-related complications were the same with genotypes Ba and C.

Treatment of chronic hepatitis B: Who to treat, what to use, and for how long?

Chronic hepatitis B infection continues to be a major public health concern worldwide. The natural history of the disease can be divided into 4 different phases: immune tolerance, immune clearance, inactive carrier, and reactivation. The goals of treatment are sustained viral suppression, normalization of ALT, and improvement in liver histology. Antiviral agents in current use include standard interferon-alpha, lamivudine, and adefovir. With an improved understanding of the natural history of the disease and a growing repertoire of antiviral drugs, the important questions are: who should receive treatment, what is the best agent to use, and what is the optimal duration of therapy? Treatment is indicated for patients in the immune clearance and reactivation phases. Patients with high pretreatment ALT level, detectable HBV DNA in the serum, and active inflammation on liver biopsy are predicted to have the highest chance of response to treatment. The choice of a particular agent must balance long-term benefits such as the likelihood of a sustained response against long-term risks such as drug resistance. Interferon treatment leads to a more durable response but is associated with unpleasant side effects. Lamivudine is effective and well tolerated but requires long-term therapy and is associated with drug resistance. Adefovir has proven efficacy and a very low rate of drug resistance but is associated with a small risk of reversible nephrotoxicity. For HBeAG-positive chronic hepatitis B and HBeAG-negative chronic hepatitis B, the duration of interferon therapy is 4-6 months and 12 months, respectively. Duration of treatment is at least 1 year with lamivudine and adefovir; longer duration of treatment is needed in most patients, but the optimal duration of treatment and the criteria for stopping treatment have not been established.

Update on viral hepatitis in 2004.

Purpose of review This article highlights recent advances in viral hepatitis published from December 2003 to November 2004. Studies reporting novel and clinically relevant findings were selected after a PubMed search. The aim is to provide an up-to-date summary of important developments in viral hepatitis. Recent findings Lamivudine was shown to reduce the rate of long-term complications of hepatitis B virus-induced cirrhosis. Adefovir was effective in suppressing lamivudine-resistant hepatitis B virus. Pegylated interferon alone was as effective as pegylated interferon plus lamivudine in the management of HBeAg-negative chronic hepatitis B. A 24-week course of pegylated interferon plus low-dose ribavirin was optimal in patients with hepatitis C virus infected with genotype 2 or 3, but a 48-week course and standard dose of ribavirin were needed in patients with genotype 1. Pegylated interferon plus ribavirin was fairly well tolerated in HIV-hepatitis C virus coinfected patients with stable HIV infection and resulted in response rates that were only slightly lower than that in patients with hepatitis C virus infection only. A dramatic reduction in hepatitis C virus RNA level was observed after 2 days of treatment with an hepatitis C virus protease inhibitor. Summary The optimal management of chronic viral hepatitis is evolving rapidly. Newer treatment options for hepatitis B, including pegylated interferon, tenofovir, and combination regimens were shown to be effective in treatment-naïve and treatment-experienced patients. In addition, impressive gains were made in the treatment of hepatitis C virus infection in difficult-to-treat patients, including African Americans and those with HIV-hepatitis C virus coinfection.

Drug insight: Nucleoside and nucleotide analog inhibitors for hepatitis B

In the past decade, substantial advances have been made in the treatment of chronic hepatitis B. Approved treatments include interferon-α, the nucleoside analog inhibitor lamivudine, and the nucleotide analog inhibitor adefovir dipivoxil. This review provides insights into the benefits and limitations of lamivudine and adefovir dipivoxil for the treatment of chronic hepatitis B. Lamivudine and adefovir dipivoxil have similar antiviral efficacies. Lamivudine has negligible side effects but a high rate of drug resistance, whereas adefovir dipivoxil has a low rate of drug resistance but long-term use is associated with a small risk of nephrotoxicity. Several other nucleoside and nucleotide analogs are being evaluated in phase II/III clinical trials for hepatitis B.

Hepatitis B virus genotypes, precore and core promoter variants among predominantly Asian patients with chronic HBV infection in a Canadian center

Abstract: Background and Aims: The epidemiology of hepatitis B virus (HBV) infection in North America may be changing as a result of immigration from endemic countries. The purpose of this study was to determine the prevalence of HBV genotypes, precore (PC) and core promoter (CP) variants, and the proportion of patients meeting treatment criteria for HBV.

Viral hepatitis in 2003

Purpose of review This article discusses over 40 studies in the field of viral hepatitis that were published in 2003. Studies that reported novel findings of clinical relevance were selected after a MEDLINE search. This article focuses on hepatitis B and hepatitis C. Recent findings In the United States, all genotypes of hepatitis B virus were reported, and precore and core promoter mutations were found in approximately a third of patients. The response to lamivudine was less durable than that induced by interferon. Adefovir dipivoxil was safe and effective for treatment-naïve patients as well as for lamivudine-resistant patients. In acute hepatitis C infection, close monitoring of hepatitis C virus RNA and treatment of patients with persistent viremia is a reasonable alternative to immediate treatment of all patients. Noninvasive indices to predict liver fibrosis are currently being tested. Failure to achieve an early virologic response to pegylated interferon plus ribavirin can identify more than 95% patients who will not have a sustained response. Summary The clinical significance of hepatitis B virus genotypes and viral variants continues to be elucidated worldwide. Long-term lamivudine treatment is safe, despite a rising rate of resistance. Adefovir appears to be safe and effective as initial therapy for chronic hepatitis B virus infection or for the management of lamivudine-resistant hepatitis B infection. Noninvasive indices for liver fibrosis require validation but may reduce the need for liver biopsy in the future. Newer agents for the treatment of hepatitis C virus infection show promise.