Agents in clinical development for the treatment of chronic hepatitis B

Adefovir dipivoxil loaded proliposomal powders with improved hepatoprotective activity: formulation, optimization, pharmacokinetic, and biodistribution studies

The present study aimed to prepare proliposomal formulae for improving the oral bioavailability of adefovir dipivoxil (AD), a nucleoside reverse transcriptase inhibitor effective against hepatitis B virus (HBV). The prepared proliposomal formulae were characterized for entrapment efficiency (E.E.%), vesicle size and in vitro drug release after reconstitution to conventional liposomes. The optimized formula (F9) with a maximum desirability value of 0.858 was selected having E.E.% of 71 ± 3.3% with an average vesicle size of 164.6 ± 5 nm. Moreover, the crystallization of AD within the optimized formula investigated via powder X-ray diffraction (XRD) and differential scanning calorimetry (DSC) confirmed the presence of the drug in an amorphous state within the lipid vesicles with enhanced stability over a storage period of 12 months. Thioacetamide-induced liver damage in rats evidenced by elevated liver enzymes was significantly improved after treatment with the optimum formula. Pharmacokinetic and biodistribution studies of formula F9 showed a higher accumulation of AD in the liver with enhanced bioavailability compared to AD suspension which highlights its potential advantage for an effective treatment of chronic HBV. Hence, proliposomal drug delivery is considered as a better choice for the oral delivery of AD.

Identification of hydrolyzable tannins (punicalagin, punicalin and geraniin) as novel inhibitors of hepatitis B virus covalently closed circular DNA

The development of new agents to target HBV cccDNA is urgently needed because of the limitations of current available drugs for treatment of hepatitis B. By using a cell-based assay in which the production of HBeAg is in a cccDNA-dependent manner, we screened a compound library derived from Chinese herbal remedies for inhibitors against HBV cccDNA. Three hydrolyzable tannins, specifically punicalagin, punicalin and geraniin, emerged as novel anti-HBV agents. These compounds significantly reduced the production of secreted HBeAg and cccDNA in a dose-dependent manner in our assay, without dramatic alteration of viral DNA replication. Furthermore, punicalagin did not affect precore/core promoter activity, pgRNA transcription, core protein expression, or HBsAg secretion. By employing the cell-based cccDNA accumulation and stability assay, we found that these tannins significantly inhibited the establishment of cccDNA and modestly facilitated the degradation of preexisting cccDNA. Collectively, our results suggest that hydrolyzable tannins inhibit HBV cccDNA production via a dual mechanism through preventing the formation of cccDNA and promoting cccDNA decay, although the latter effect is rather minor. These hydrolyzable tannins may serve as lead compounds for the development of new agents to cure HBV infection.

Recent advance of the hepatitis B virus inhibitors: a medicinal chemistry overview

Hepatitis B Virus (HBV) is one of the most prevalent viral infections of human worldwide. The therapies are limited in the clinical context because of negative side effects of interferons and the development of viral resistance to the nucleoside/nucleotide inhibitors. In this review, we summarize the recent advances in design and development of potent anti-HBV inhibitors from natural sources and synthetic compounds, targeting different steps in the life cycle of HBV. We attempt to emphasize the major structural modifications, mechanisms of action and computer-aided docking analysis of novel potent inhibitors that need to be addressed in the future to design potent anti-HBV molecules.

Ubiquitin-modified hepatitis B virus core antigen effectively facilitates antigen presentation and enhances cytotoxic T lymphocyte activity via the cytoplasmic transduction peptide in vitro

Cluster of differentiation (CD)8+ cytotoxic T lymphocytes (CTLs) have a key role in the elimination of hepatitis B virus (HBV)-infected cells. Ubiquitin (Ub) functions as a marker for protein degradation, which may promote the generation of peptides appropriate for major histocompatibility complex class I presentation, while the HBV core antigen (HBcAg) possesses marked immunogenic properties. However, it remains to be elucidated whether Ub-modified HBcAg is able to effectively elicit significant CD8+ CTL activity. In order to address this issue, a prokaryotic vector was constructed to express the Ub-HBcAg-cytoplasmic transduction peptide (CTP). The fusion protein was successfully expressed and subsequently pulsed into bone-marrow-derived dendritic cells (DCs). It was confirmed that with assistance from the cell‑penetrating properties of CTP, the fusion protein was able to directly penetrate into the cytoplasm of DCs. The results revealed that the Ub-HBcAg-CTP fusion protein not only increased the expression of surface molecules in DCs and cytokine secretion from proliferating T cells, but also induced T cells to differentiate into specific CTLs and enhanced their antiviral ability. In conclusion, the Ub-HBcAg-CTP fusion protein promoted DC maturation, enhanced the presentation of targeting antigens and efficiently induced HBcAg‑specific CTL immune responses in vitro.

Ubiquitin-hepatitis B core antigen-cytoplasmic transduction peptide enhances HBV-specific humoral and CTL immune responses in vivo

Therapeutic strategies based on an enhanced hepatitis B virus (HBV)-specific cytotoxic T lymphocyte (CTL) activity may eradicate HBV. We previously verified that a fusion protein ubiquitin (Ub)-hepatitis B core antigen (HBcAg)-cytoplasmic transduction peptide (CTP) can enter the cytoplasm of dendritic cells and enhance T cell response to generate HBV-specific CTLs efficiently in vitro. Ub, a marker of protein degradation, may promote the generation of peptides appropriate for major histocompatibility complex class I presentation. In the present study, the specific immune responses of the fusion protein Ub-HBcAg-CTP in BALB/c mice were evaluated and the underlying mechanisms were investigated. Results showed that Ub-HBcAg-CTP increased the anti-HBcAg titer and produced the cytokines IFN-γ and IL-2. This fusion protein also induced higher percentages of IFN-γ(+)CD8(+) cells and specific CTL responses. Ub-HBcAg-CTP could also upregulate the expressions of Jak2, Tyk2, STAT1, and STAT4 in T lymphocytes. In conclusion, Ub-HBcAg-CTP enhanced cellular and humoral immune responses and induced robust HBV-specific CTL activities in BALB/c mice.

The modification of Tapasin enhances cytotoxic T lymphocyte activity of intracellularly delivered CTL epitopes via cytoplasmic transduction peptide

Previous studies have demonstrated that the therapeutic vaccine based on the enhancement of hepatitis B virus (HBV)-specific cytotoxic T lymphocyte (CTL) activity may lead to viral clearance in HBV-infected individuals. The endoplasmic reticulum (ER) chaperone Tapasin plays an important role in major histocompatibility complex (MHC) class I assembly and enhances specific MHC class I-restricted CTL activity by allowing more peptides to be translocated into the ER. Combining the specificity of hepatitis B core antigen (HBcAg) CTL epitope, the cell-penetrating property of cytoplasmic transduction peptide (CTP), and chaperone Tapasin may elicit robust specific HBV immune responses. In the present study, we confirmed the cytoplasmic localization preference of CTP-HBcAg(18-27)-Tapasin fusion protein in vitro and evaluated the effects on promoting bone marrow-derived dendritic cells (BMDCs) maturation and enhancing T cells response to generate specific CTLs. Our results showed that CTP-HBcAg(18-27)-Tapasin fusion protein could not only penetrate into the cytoplasm exactly and effectively to elevate Tapasin expression, but also increase the expression of surface molecules (CD80, CD83, CD86, and MHC-I) and secretion of cytokine (IL-12p70) of DCs. Moreover, DCs treated with the above fusion proteins increased significantly the cytokine secretion of proliferated T cells in vitro, the percentages of IFN-γ(+)CD8(+) T cells and specific CTL responses compared with control groups. In conclusion, the modification of Tapasin can enhance the presentation of targeting antigens via intracellular delivery to DCs and elicit specific CTL immune responses efficiently.

Synthesis, anti-HBV activity and renal cell toxicity evaluation of mixed phosphonate prodrugs of adefovir

A series of phosphonate ester prodrugs of adefovir incorporating l-amino (thio)acid and non-steroidal anti-inflammatory drug (NSAID) moieties were synthesized and their anti-HBV activity and renal cell toxicity were evaluated in HepG2 2.2.15 and HK-2 cells respectively. Bioactivity evaluation results revealed that this kind of adefovir prodrug have lower renal cell toxicity than adefovir dipivoxil. Compounds 8a and 8b, incorporating the NSAID ketoprofen and the l-amino acid (Val or Ile) structural fragments, exhibited more potent anti-HBV activity than adefovir dipivoxil with IC(50) = 0.51 and 0.73 μM, SI = 1697.64 and 881.92 respectively. In vitro stability studies showed that the synthesized prodrugs have higher chemical and plasma stability than the positive control adefovir dipivoxil.

Therapeutic vaccination in chronic hepatitis B: preclinical studies in the woodchuck

Recommended treatment of chronic hepatitis B with interferon-α and/or nucleos(t)ide analogues does not lead to a satisfactory result. Induction of HBV-specific T cells by therapeutic vaccination or immunotherapies may be an innovative strategy to overcome virus persistence. Vaccination with commercially available HBV vaccines in patients did not result in effective control of HBV infection, suggesting that new formulations of therapeutic vaccines are needed. The woodchuck (Marmota monax) is a useful preclinical model for developing the new therapeutic approaches in chronic hepadnaviral infections. Several innovative approaches combining antiviral treatments with nucleos(t)ide analogues, DNA vaccines, and protein vaccines were tested in the woodchuck model. In this paper we summarize the available data concerning therapeutic immunization and gene therapy using recombinant viral vectors approaches in woodchucks, which show encouraging results. In addition, we present potential innovations in immunomodulatory strategies to be evaluated in this animal model.

Synthesis of lamivudine stearate and antiviral activity of stearic acid-g-chitosan oligosaccharide polymeric micelles delivery system

To increase lipophilicity of water-soluble antiviral drug, the prodrug of Lamivudine (LA), Lamivudine stearate (LAS) was synthesized via ester linkage between LA and stearic acid. After the esterification, the octanol-water partition coefficient (logP) of LA increased from -0.95 to 1.82. Stearic acid-g-chitosan oligosaccharide (CSO-SA) micelles have demonstrated fast internalization and accumulation ability to tumor cells. Herein, the CSO-SA with 3.79% amino substitution degree (SD) was prepared for loading LAS. The critical micelle concentration (CMC) of CSO-SA was about 0.032mg/ml. The micelles with 1mg/ml CSO-SA concentration had 460.8nm average diameters with a narrow size distribution and 29.7mV surface zeta potential. After LAS was incorporated, the micellar size decreased and the zeta potential increased. The LAS loaded CSO-SA micelles (CSO-SA/LAS) possessed high entrapment efficiency and drug loading. LA release from CSO-SA/LAS showed a pH-dependent behavior. The release rate of LA from CSO-SA/LAS increased significantly as the pH of release medium reduced from 7.4 to 6.2. CSO-SA/LAS presented a low cytotoxicity and high cellular uptake percentage of LAS against HBV transfected tumor cells (HepG2.2.15). In vitro anti-HBV activities of CSO-SA/LAS presented more conspicuous inhibitory effects on antigen expression and DNA replication compared with LA and LAS.

The woodchuck: a model for therapeutic vaccination against hepadnaviral infection

Interferon-alpha and nucleoside analogues are available for the treatment of chronic hepatitis B virus (HBV) infection but do not lead to a satisfactory result. New findings about the immunological control of HBV during acute infection suggest the pivotal role of T-cell mediated immune responses. Several preclinical and clinical trials were undertaken to explore the possibility of stimulating specific immune responses in chronically infected animals and patients by vaccination. However, vaccination with commercially available HBV vaccines in patients and immunization in woodchucks with core or surface proteins of woodchuck hepatitis virus (WHV) did not result in effective control of HBV and WHV infection, suggesting that new formulations of therapeutic vaccines are needed. Some new approaches combining antiviral treatments with nucleoside analogues, DNA vaccines and protein vaccines were tested in the woodchuck model. It could be shown that therapeutic vaccinations are able to stimulate specific B- and T-cell responses and to achieve transient suppression of viral replication. These results suggest the great potential of therapeutic vaccination in combination with antivirals to reach an effective and sustained control of HBV infection.

The delivery of HBcAg via Tat-PTD enhances specific immune response and inhibits Hepatitis B virus replication in transgenic mice

Recent studies have indicated that the therapeutic vaccine based on enhancement of HBV-specific cytotoxic T-lymphocyte (CTL) activity may lead to viral clearance in chronically infected individuals. It is demonstrated that protein transduction domains (PTD) from HIV-1-Tat protein is able to enter cells when combined with exogenous antigens and induce specific CTL responses. We have previously testified that the expressed and purified fusion protein containing Tat-PTD47-57 and HBcAg could enter cytoplasm of dendritic cells, and enhance T cells response to generate HBcAg-specific CTLs efficiently in vitro. In the present study, we evaluated HBcAg-specific immune responses of PTD-HBcAg fusion protein in BALB/c mice and antiviral immunity in HBV transgenic mice. The studies showed that PTD-HBcAg not only induced significantly higher antibody responses, but also increased production of cytokine (IFN-gamma, IL-2, IL-4 and IL-10) compared to HBcAg alone and PBS. Moreover, PTD-HBcAg fusion protein increased significantly the percentages of IFN-gamma+CD8+ T cells and HBcAg-specific (CTL) responses. Also, enhancement of immune response induced by fusion protein reduced HBV DNA and HBsAg levels and decreased the expression of HBsAg in liver tissue of HBV transgenic mice. In conclusion, PTD-HBcAg fusion protein could enhance not only cell immune response but also humoral immune response, and induce robust specific CTL activity and therapeutic effects in HBV transgenic mice.

Drug targets in hepatitis B virus infection

Hepatitis B virus infection (HBV) is a significant global health problem. Despite the success of universal hepatitis B vaccination in many countries, more than 350 million individuals worldwide are chronically infected and 15- 40% of those will develop cirrhosis and/or hepatocellular carcinoma if left untreated. Available therapies for chronic hepatitis B (CHB) infection are effective at decreasing viremia and improving measured clinical outcomes, however, no single therapy is optimal. As such, alternative drug therapies and the investigation of their role in the management of CHB are warranted. Significant improvements in the understanding of the HBV life cycle, viral genomics, and virus-host interactions continue to lead to the development of novel viral targets and immune modulators. Currently, two major classes of agents are utilized in CHB: the interferons and the nucleos(t)ide analogues. Each agent has individual advantages and drawbacks. The development of specific antiviral therapy has led to the emergence of HBV drug-resistant strains that has limited the long-term therapeutic potential of available agents. This necessitates the development of new agents that target both wild-type and drug-resistant strains. Further understanding of the basic mechanisms and clinical nuances of drug therapy is warranted. As most novel therapies are in the earliest stages of clinical development and testing, in the near future, treatment will continue to be long-term and likely involve the use of combination therapies to prevent viral resistance. In this review, we will highlight the HBV life cycle and genome, focusing in on current and potential novel antiviral drug targets as well as the benefits and clinical challenges with these therapies.

Solid lipid nanoparticles loading adefovir dipivoxil for antiviral therapy

Herein, solid lipid nanoparticles (SLN) were proposed as a new drug delivery system for adefovir dipivoxil (ADV). The octadecylamine-fluorescein isothiocynate (ODA-FITC) was synthesized and used as a fluorescence maker to be incorporated into SLN to investigate the time-dependent cellular uptake of SLN by HepG2.2.15. The SLN of monostearin with ODA-FITC or ADV were prepared by solvent diffusion method in an aqueous system. About 15 wt% drug entrapment efficiency (EE) and 3 wt% drug loading (DL) could be reached in SLN loading ADV. Comparing with free ADV, the inhibitory effects of ADV loaded in SLN on hepatitis B surface antigen (HBsAg), hepatitis B e antigen (HBeAg) and hepatitis B virus (HBV) DNA levels in vitro were significantly enhanced.

Adenoviral-vector mediated transfer of HBV-targeted ribonuclease can inhibit HBV replication in vivo

Hepatitis B virus (HBV)-targeted ribonuclease (HBV-TR) is a fused protein of HBV core protein and a ribonuclease, human eosinophil-derived neurotoxin (hEDN). Our previous results showed that HBV-TR could effectively inhibit HBV replication in vitro. To test whether HBV-TR can inhibit HBV replication in vivo, we constructed a recombinant adenoviral vector expressing HBV-TR (Ad-TR) and used it to treat HBV-transgenic mice. Immunohistochemical staining showed that TR was expressed at varied levels in different tissues of Ad-TR-treated mice. Serum HBsAg concentration was decreased by 64.8% for the Ad-TR-treated mice compared with empty adenoviral vector-treated control mice. The amount of HBV-DNA in the livers of the Ad-TR-treated mice was 0.74 x 10(7) copies/mug of genomic DNA while the amount of HBV-DNA in the livers of the empty adenoviral vector-treated control mice was 2.86 x 10(7) copies/mug of genomic DNA. Serum HBV-DNA of Ad-TR-treated mice was also decreased by 71.4% compared with empty adenoviral vector-treated control mice. In addition, for some Ad-TR-treated mice, the expression of HBsAg in the liver cells turned negative. No discernible adverse effects were observed for Ad-TR-treated mice. Taken together, our results indicated that adenovirus mediated transfer of HBV-TR can inhibit HBV replication in vivo.

Combination of an antiviral drug and immunomodulation against hepadnaviral infection in the woodchuck model

The essential role of multispecific immune responses for the control of hepatitis B virus (HBV) infection implies the need of multimodal therapeutic strategies for chronic HBV infection, including antiviral chemotherapy and immunomodulation. This hypothesis was tested in the woodchuck model by a combination of lamivudine pretreatment and subsequent immunizations of woodchucks chronically infected with woodchuck hepatitis virus. The immunizations were performed with DNA vaccines or antigen-antibody immune complexes (IC)/DNA vaccines. Immunizations with IC/DNA vaccines led to an anti-woodchuck hepatitis virus surface antibody response and significant reductions of viral load and antigenemia, suggesting that such a strategy may be effective against chronic HBV infection.

Therapeutic vaccination in chronic hepatitis B: preclinical studies in the woodchuck model

Interferon-alpha and nucleoside analogues are available for the treatment of chronic hepatitis B virus (HBV) infection but do not lead to a satisfactory result. New findings about the immunological control of HBV during acute infection suggest the pivotal role of T-cell mediated immune responses. Several preclinical and clinical trials were undertaken to explore the possibility of stimulating specific immune responses in chronically infected animals and patients by vaccination. However, vaccination with commercially available HBV vaccines in patients and immunization in woodchucks with core or surface proteins of woodchuck hepatitis virus (WHV) did not result in effective control of HBV and WHV infection, suggesting that new formulations of therapeutic vaccines are needed. Some new approaches combining antiviral treatments with nucleoside analogues, DNA vaccines and protein vaccines were tested in the woodchuck model. It could be shown that therapeutic vaccinations are able to stimulate specific B- and T-cell responses and to achieve transient suppression of viral replication. These results suggest the great potential of therapeutic vaccination in combination with antivirals to reach an effective and sustained control of HBV infection.

Immunomodulation as an option for the treatment of chronic hepatitis B virus infection: preclinical studies in the woodchuck model

New therapeutic approaches for chronic hepatitis B virus infection based on immunomodulation are now under investigation. The woodchuck model for hepatitis B virus infection has emerged as a useful animal model for the evaluation of such approaches, after developing necessary assays and reagents for immunologic studies in this model. Conventional and novel vaccines such as DNA vaccines were tested in woodchucks for their ability to induce protective immune responses against challenge infection with the woodchuck hepatitis virus (WHV). Furthermore, immunotherapeutic approaches for the control of chronic hepadnaviral infection were evaluated in woodchucks. Immunizations with WHV proteins and DNA vaccines led to the development of antibodies to the WHV surface antigen and to a significant decrease of viral load in chronically WHV-infected woodchucks. Viral vector-mediated gene transfer was explored for the delivery of antiviral cytokines IFN-alpha in woodchucks and resulted in the decrease of viral replication. It is now generally accepted that a combination of antiviral treatment and immunization will be necessary to achieve successful immunomodulation with a long-term control of chronic hepatitis B virus infection.

Induction of Tc1 response and enhanced cytotoxic T lymphocyte activity in mice by dendritic cells transduced with adenovirus expressing HBsAg

We evaluated the potential of dendritic cells (DCs) engineered to express antigen of hepatitis B virus (HBV) in priming Th/Tc and HBV-specific CTL responses in mice. Recombinant adenovirus expressing hepatitis B surface antigen (HBsAg) (Ad-S) was constructed, and bone marrow-derived DCs were transduced with Ad-S or pulsed with HBsAg protein. Mice were injected with either Ad-S-transduced DCs or HBsAg-pulsed DCs or plasmid DNA encoding HBsAg twice at 3-week intervals. We showed that adenovirus infection had no further effect on the phenotype, the ability to induce IFN-gamma-producing Th1/Tc1 response or the T cell stimulatory capacity of already mature DCs in vitro. We also showed that immunization with Ad-S-transduced DCs effectively induced Tc1 cells and HBsAg-specific CTLs in vivo and down-regulated the circulating HBsAg and HBV DNA in HBV transgenic mice. Furthermore, these efficacies were stronger than that of HBsAg-pulsed DCs and plasmid DNA. Thus, DCs transduced with recombinant adenovirus may be a promising candidate for an effective CTL-based therapeutic vaccine against HBV.

Antisense oligonucleotides targeted against asialoglycoprotein receptor 1 block human hepatitis B virus replication

Chronic hepatitis B virus (HBV) infection is a major worldwide public health problem. Better therapeutics and treatment strategies are urgently needed because of ineffective clinical treatment. Our previous study showed that asialoglycoprotein receptor 1 (ASGPR1) was upregulated by HBV but downregulated by lamivudine in HepG2.2.15 cells. It has also been reported that ASGPR is a candidate receptor for HBV attachment to hepatocytes. Therefore, as a major subunit of ASGPR, ASGPR1, might be a potential target for anti-HBV drugs. To validate this hypothesis, antisense oligonucleiotides (ASODNs) were used to downregulate ASGPR1 level in HepG2.2.15 cells. By using the MFOLD web server and BLAST searches, five ASODNs theoretically targeting ASGPR1 were selected. After 72 h post-transfection, HBV-DNA level in cell medium were examined by real-time polymerase chain reaction (PCR). Hepatitis B surface antigen (HBsAg) and Hepatitis B e antigen (HBeAg) were detected using enzyme-linked immunosorbent assay (ELISA). ASGPR1 mRNA and protein level were measured by semi-quantitative reverse transcriptase (RT)-PCR and Western blot analysis respectively. The results showed that ASODN2 significantly downregulated ASGPR1 level. It also reduced HBV-DNA, HBsAg and HBeAg level in cell medium as observed with lamivudine. In contrast, the sense sequence and scrambled sequence of ASODN2 had no effect on ASGPR1 and HBV markers in HepG2.2.15 cells. This indicated that ASODN2 could specifically reduce HBV replication in vitro. Additionally, cell proliferation and apoptosis assay suggested that downregulation of ASGPR1 did not affect cell viability. We, therefore, proposed that ASODNs targeted against ASGPR1 could block HBV replication without the influence of other changes, and ASGPR1 could be targeted for anti-HBV drug development.

Treatments for hepatitis B

New optimism surrounds treatments for chronic hepatitis B (CHB). Interferon- alpha , lamivudine, and adefovir dipivoxil are currently approved by the United States Food and Drug Administration for the treatment of CHB. All 3 treatments possess unique characteristics with respect to their side effect profiles, potencies, and treatment niches within the spectrum of CHB. New agents, which are in various stages of clinical development, represent potential improvements within existing, as well as novel, classes of antiviral therapy, and they offer significant promise of a cure for the many patients with chronic and progressive hepatitis B. However, there remain many challenges in understanding the implications of drug resistance, the role of combination therapy, and how to define the response to therapy within subsets of patients with hepatitis B.

Patterns of circulating hepatitis B virus serum nucleic acids during lamivudine therapy

Lamivudine treatment of individuals with chronic HBV infection leads to a rapid decline of hepatitis B virus (HBV) serum DNA. Because HBV replication quickly reaches pretreatment values following cessation of the drug, we addressed the question of whether changes during therapy in composition and amount of discernible circulating viral DNA and RNA might provide an explanation for this phenomenon. Nucleic acids were extracted from serial serum samples of two chronically infected patients. The first patient was treated with lamivudine for 14 weeks, whereas the second one, who displayed an HBV virus with a core gene mutation, received lamivudine for 10 weeks. Three sequence segments of the HBV genome synthesized successively during replication, namely, X, C, and X-preC, were analyzed via competitive polymerase chain reaction (PCR) and reverse transcriptase (RT)/PCR. HBV transcripts were also analyzed for differential polyadenylation. At the start of treatment, identical DNA copy numbers (10(9)/mL) were found for all three segments in the first patient. C segment DNA displayed the expected rapid decline. X-preC, a target contiguous only on plus-strand DNA, behaved similarly. In contrast, the X segment DNA copy numbers showed a less pronounced decrease, remaining at higher values (10(7)/mL) than the C and X-preC segments (both about 2 x 10(5)/mL) at the end of therapy. X segment RNA displayed a persisting copy number of about 10(7)/mL, whereas C and X-preC RNA decreased to about 10(5) copies/mL. Polyadenylated HBV RNA, both full-length and truncated, initially persisted at 10(5) but decreased to 10(4) to 10(3) copies/mL at the end of treatment. As expected, C segment DNA and RNA were not detected in the second patient, whereas X and X-preC segments showed essentially the same pattern as the first patient, although at a slightly lower level. We conclude that: (1) actual numbers of HBV genome equivalents during lamivudine therapy can be assessed only via X segment DNA, because it is reverse transcribed first; (2) lamivudine induces coexistence of DNA and RNA for the C and X segments at similar levels, indicating drug-arrested intermediates of reverse-transcribed HBV DNA minus-strand; and (3) packaged HBV RNA lacks a poly(A) tail, whereas polyadenylated RNA is likely not packaged.