A daily dose of 10 mg/kg was found to decrease serum WHV load by 400-fold after 4 wk of treatment, and a dose at 5 mg/kg per day was sufficient to maintain this antiviral effect. HBsAg loss much higher than 30% is unlikely using current modalities available. WHAT ARE THE POTENTIAL TARGETS IN THE VIRAL LIFE CYCLE? Viral Anserine life cycle Understanding the HBV life cycle is essential before attempting to discuss the mechanisms of the new targets. HBV, belonging to family, Vegfa is 42 nm in diameter comprising of approximately 3.2 kb double-stranded relaxed coiled DNA (rcDNA) formed by the reverse transcription of pregenomic RNA (pgRNA)[9]. HBV is hepatotrophic and hepatocytes are the only cells that support HBV replication in the human body[10]. Availability of the cell lines susceptible to HBV infection has led to the better understanding of the early stages of its life cycle, Anserine starting from viral attachment, entry and translocation of rcDNA into nucleus to form cccDNA, as well as the later stages viral replication, including transcription of viral RNA, reverse transcription to form daughter DNA, assembly of viral particles and secretion out of the cells[11] (Figure ?(Figure11). HBV virion enters the hepatocyte endocytosis by its N-terminal region of large (L) envelope (preS1) binding to the sodium taurocholate cotransporting polypeptides (NTCP) receptor on the plasma membrane of hepatocyte[12]. A peptide derived from this preS1 region is a possible therapeutic target to inhibit viral entry by binding to its receptors[13]. After uncoating and releasing into the cytoplasm, nucleocapsid containing rcDNA is transported to the nucleus to form cccDNA[3]. This formation is mediated by the viral polymerase that completes the incomplete plus-strand of viral rcDNA after which the polymerase is removed by cellular enzymes, leading to the formation of cccDNA by covalent ligation of both DNA strand[14]. cccDNA is also known as episomal minichromosome and is crucial for the persistence of the virus in the host hepatocytes and cause chronic infection[15]. It acts as the sole DNA template for the formation of 4 groups of viral RNA, namely precore mRNA (pre-C); pgRNA; mRNA coding for surface (S), middle (M) and large (L) envelope proteins; and mRNA coding for X protein[11]. Pre-C mRNA is processed into HBeAg that can be detected in the circulation with commercial assays, which reflects infectivity of the HBV infection. The pgRNA serves as a template for viral DNA by reverse transcription, DNA polymerase and viral capsid protein. pgRNA, together with core protein and DNA polymerase, are self-assembled and encapsidated[3]. Inside the nucleocapsid, pgRNA is reverse transcribed into rcDNA, enveloped and is either secreted out of the hepatocyte[16] or shunted back into the nucleus to replenish the HBV cccDNA pool[17]. HBV entry inhibitor PreS1 region of viral L protein is required to bind to cell surface receptor for viral entry. The functional receptor is the heparan sulphate proteoglycans, specifically NTCP on the surface of hepatocytes[13,19]. With this knowledge, Anserine the scientists discovered that a synthetic myristoylated lipopeptide derived from HBV envelop protein[13], myrcludex-B, reversibly inhibits HBV entry into the na?ve hepatocyte[19]. Six weeks of subcutaneous treatment of Myrcludex B to humanized mice infected with HBV reduced amplification of existing intrahepatic cccDNA as well as the spread of infection[20,21], without interfering with viral replication[19]. The drug has also been tested in chronic HBV infected subjects showing good tolerability and lack of serious side-effects with doses up to 5 mg intravenous and 0.8 mg subcutaneous[22]. Moreover, this entry inhibitor could be used as a treatment option for infected patient and high risk neonates. The application could potentially be extended clinically to post-liver transplantation and post-immunosuppression therapy to prevent HBV reactivation or flare[19]. In order to achieve the optimal outcome, the entry inhibitor was suggested to be used together with existing antivirals[20]. Targeting the HBV cccDNA Persistence of HBV cccDNA in patients after successful long-term viral suppression by antiviral agents suggests that the key to HBV eradication in established CHB infection lies in the elimination of the reservoir of HBV minichromosomes Anserine from the hepatocyte[23]. Efforts in this area are still in early pre-clinical phases. This can Anserine be achieved by inhibiting cccDNA synthesis and maintenance, which include inhibition of its establishment, silencing its activity by transcription inhibitors, direct deactivation of cccDNA using engineered nucleases and activation of host innate immune response. Blocking of HBV cccDNA formation: Recently, two novel compounds were reported that block conversion of relaxed circular HBV DNA into cccDNA at micromolar concentrations. Broadly known as distributed sulphonamide (DSS) compounds, they have phosphodiesterase or protease inhibitor activity, and can inhibit the conversion to cccDNA from rcDNA in human and duck hepatocytes through direct inhibition of deproteinization of rcDNA. The compounds were identified through a cell-based high throughput screen and neither the mechanism.