Challenges in the discontinuation of chronic hepatitis B antiviral agents

Long-term antiviral treatment of chronic hepatitis B patients has been proven to be beneficial in reducing liver-related complications.However,lengthy periods of daily administration of medication have some inevitable drawbacks,including decreased medication adherence,increased cost of treatment,and possible longterm side effects.Currently,discontinuation of antiviral agent has become the strategy of interest to many hepatologists,as it might alleviate the aforementioned drawbacks and increase the probability of achieving functional cure.This review focuses on the current evidence of the outcomes following stopping antiviral treatment and the factors associated with subsequent hepatitis B virus relapse,hepatitis B surface antigen clearance,and unmet needs.

Changes in the Cytokine Profiles of Patients with Chronic Hepatitis B during Antiviral Therapy

Objective To investigate the changes in the cytokine profiles of chronic hepatitis B(CHB)patients undergoing antiviral treatment.Methods Hepatitis B e antigen(HBeAg)-positive patients were treated with Pegylated interferon(PEGIFN)and entecavir(ETV).Clinical biochemistry and cytokines were detected at baseline and every 3 months.Results In all,200 patients completed 48 weeks of treatment,100 in the PEG-IFN group and 100 in the ETV group.During 3–6 months of treatment,compared with baseline,the PEG-IFN group showed a significant decrease in interferon-gamma(IFN-γ),interleukin-17 A(IL-17 A),interleukin-6(IL-6),interleukin-10(IL-10),and transforming growth factor beta(TGF-β)(P<0.001)and a significant increase in interferon-alpha 2(IFN-α2)(P<0.001).In the ETV group,IL-10 and TGF-β1 decreased significantly(P<0.001).After 3 months,the levels of IFN-α2,IL-17 A,and tumor necrosis factor-alpha(TNF-α)in the PEGIFN group were significantly higher than those in the ETV group(P<0.01).The levels of IL-6 and TGF-β3 were significantly lower than those in the ETV group(P<0.01).After 6 months,the levels of IFN-α2,IFN-γ,and TNF-αin the PEG-IFN group were significantly higher than those in the ETV group(P<0.01),while the levels of IL-6 and TGF-β3 were significantly lower than those in the ETV group(P<0.01).Compared with ETV,PEG-IFN had higher HBeAg and HBsAg disappearance rates.Conclusion During antiviral therapy,a change in the cytokine profile occurred;in the aspect of immune control and functional cure,PEG-IFN was significantly better than ETV.

Investigation of immune escape-associated mutations of hepatitis B virus in patients harboring hepatitis B virus drug-resistance mutations

It is unclear whether immune escape-associated mutations in the major hydrophilic region of hepatitis B virus surface antigen(HBsAg)are associated with nucleoside/nucleotide analog resistance.AIM To evaluate the association between immune escape-associated mutations and nucleoside/nucleotide analog resistance mutations.METHODS In total,19440 patients with chronic hepatitis B virus infection,who underwent resistance testing at the Fifth Medical Center of Chinese PLA General Hospital between July 2007 and December 2017,were enrolled.As determined by sequence analysis,6982 patients harbored a virus with resistance mutations and 12458 harbored a virus lacking resistance mutations.Phenotypic analyses were performed to evaluate HBsAg production,replication capacity,and drug-induced viral inhibition of patient-derived drug-resistant mutants with or without the coexistence of sA159V.RESULTS The rate of immune escape-associated mutation was significantly higher in 9 of the 39 analyzed mutation sites in patients with resistance mutations than in patients without resistance mutations.In particular,these mutations were sQ101H/K/R,sS114A/L/T,sT118A/K/M/R/S/V,sP120A/L/Q/S/T,sT/I126A/N/P/S,sM133I/L/T,sC137W/Y,sG145A/R,and sA159G/V.Among these,sA159V was detected in 1.95%(136/6982)of patients with resistance mutations and 1.08%(134/12,458)of patients lacking resistance mutations(P<0.05).The coexistence of sA159V with lamivudine(LAM)and entecavir(ETV)-resistance mutations in the same viral genome was identified during follow-up in some patients with drug resistance.HBsAg production was significantly lower and the replication capacity was significantly higher,without a significant difference in LAM/ETV susceptibility,in sA159V-containing LAM/ETV-resistant mutants than in their sA159V-lacking counterparts.CONCLUSION In summary,we observed a close link between the increase in certain immune escape-associated mutations and the development of resistance mutations.sA159V might increase the fitness of LAM/ETV-resistant mutants under environmental pressure in some cases.

Low-level viremia in nucleoside analog-treated chronic hepatitis B patients

Low-level viremia(LLV)was defined as persistent or intermittent episodes of detectable hepatitis B virus(HBV)DNA(<2000 IU/mL,detection limit of 10 IU/mL)after 48 weeks of antiviral treatment.Effective antiviral therapies for chronic hepatitis B(CHB)patients,such as entecavir(ETV),tenofovir disoproxil fumarate(TDF),and tenofovir alafenamide(TAF),have been shown to inhibit the replication of HBV DNA and prevent liver-related complications.However,even with long-term antiviral therapy,there are still a number of patients with persistent or intermittent LLV.At present,the research on LLV to address whether adversely affect the clinical outcome is limited,and the follow-up treatment for these patients is open to question.At the same time,the mechanism of LLV is not clear.In this review,we summarize the incidence of LLV,the association between LLV and long-term outcomes,possible mechanisms,and management strategies in these patient populations.

Significant Inhibition of Porcine Epidemic Diarrhea Virus In Vitro by Remdesivir,Its Parent Nucleoside and β-D-N^(4)-hydroxycytidine

Porcine epidemic diarrhea(PED)caused by porcine epidemic diarrhea virus(PEDV)is widespread in the world.In recent years,the increased virulence of the virus due to viral variations,has caused great economic losses to the pig industry in many countries.It is always worthy to find effective therapeutic methods for PED.As an important class of antivirals,nucleoside drugs which target viral polymerases have been applied in treating human viral infections for half a century.Herein,we evaluated the anti-PEDV potential of three broad-spectrum antiviral nucleoside analogs,remdesivir(RDV),its parent nucleoside(RDV-N)andβ-D-N^(4)-hydroxycytidine(NHC).Among them,RDV-N was the most active agent in Vero E6 cells with EC_(50) of 0.31μmol/L,and more potent than RDV(EC_(50)=0.74μmol/L)and NHC(EC_(50)=1.17μmol/L).The activity of RDV-N was further confirmed using an indirect immuno-fluorescence assay.Moreover,RDV-N exhibited a good safety profile in cells and in mice.The high sequence similarity of the polymerase functional domains of PEDV with other five porcine coronaviruses indicated a broader antiviral spectrum for the three compounds.Generally,RDV-N is a promising broad-spectrum antiviral nucleoside,and it would be worthy to make some structural modifications to increse its oral bioavailability.

Targeting Tyrosyl-DNA phosphodiesterase I to enhance toxicity of phosphodiester linked DNA-adducts

Our genomic DNA is under constant assault from endogenous and exogenous sources,which needs to be resolved to maintain cellular homeostasis.The eukaryotic DNA repair enzyme Tyrosyl-DNA phosphodiesterase I(Tdp1)catalyzes the hydrolysis of phosphodiester bonds that covalently link adducts to DNA-ends.Tdp1 utilizes two catalytic histidines to resolve a growing list of DNA-adducts.These DNA-adducts can be divided into two groups:small adducts,including oxidized nucleotides,RNA,and non-canonical nucleoside analogs,and large adducts,such as(drug-stabilized)topoisomerase-DNA covalent complexes or failed Schiff base reactions as occur between PARP1 and DNA.Many Tdp1 substrates are generated by chemotherapeutics linking Tdp1 to cancer drug resistance,making a compelling argument to develop small molecules that target Tdp1 as potential novel therapeutic agents.Tdp1’s unique catalytic cycle,which is centered on the formation of Tdp1-DNA covalent reaction intermediate,allows for two principally different targeting strategies:(1)catalytic inhibition of Tdp1 catalysis to prevent Tdp1-mediated repair of DNA-adducts that enhances the effectivity of chemotherapeutics;and(2)poisoning of Tdp1 by stabilization of the Tdp1-DNA covalent reaction intermediate,which would increase the half-life of a potentially toxic DNA-adduct by preventing its resolution,analogous to topoisomerase targeted poisons such as topotecan or etoposide.The catalytic Tdp1 mutant that forms the molecular basis of the autosomal recessive neurodegenerative disease spinocerebellar ataxia with axonal neuropathy best illustrates this concept;however,no small molecules have been reported for this strategy.Herein,we concisely discuss the development of Tdp1 catalytic inhibitors and their results.

What Should Be Done to Re-evaluate Cessation of Nucleos(t)ide Analog Therapy for Chronic Hepatitis B Infection?

Anti-viral therapy with nucleos(t)ide analogs(NUCs)for chronic hepatitis B(CHB)is generally considered to be a long-term treatment.Relevant guidelines issued by Asian Pacific Association for the Study of the Liver,European Association for the Study of the Liver,and American Association for the Study of Liver Diseases have recently proposed requirements and standards for cessation of NUCs,but it remains unclear which proportion of CHB patients on long-term or prolonged treatment of NUCs will relapse after NUCs cessation.Recently,paradoxical increase in loss of hepatitis B surface antigen(HBsAg)with or without the development of anti-hepatitis B surface antibody has been observed in NUCs’treated CHB patients with cessation of therapy.Hence,it is of great clinical relevance to identify CHB who might have been over-treated with NUCs and might even benefit HBsAg loss or seroconversion with cessation of therapy.To address these issues,our review comprehensively analyzed the data from recent clinical trials in which the antiviral efficacy in the long-term or prolonged treatment of NUCs and/or interferon-a for CHB patients were evaluated.Furthermore,the relevant problems and deficiencies existing in the study design of previous clinical studies were also described.To solve the unmet issues in the field,a prospective study with a large-enough sample size would be required to understand the related virologic and immunological markers that can accurately predict the outcome and prognosis of the CHB patients who stop the NUCs treatment.With the rapid advancement of antiviral drug development for CHB patients,the future ideal regimens should include multiple targets for antiviral drug therapy combined with efficient immune-modulatory therapy,which will help more CHB patients to obtain functional cure with NUCs cessation.