Thymosin alpha1 treatment of chronic hepatitis B: results of a phase III multicentre, randomized, double-blind and placebo-controlled study

A Reappraisal of Thymosin Alpha1 in Cancer Therapy

Thymosin alpha1 (Tα1), an endogenous peptide first isolated from the thymic tissue in the mid-sixties, has gained considerable attention for its immunostimulatory activity that led to its application to diverse pathological conditions, including cancer. Studies in animal models and human patients have shown promising results in different types of malignancies, especially when Tα1 was used in combination with other chemo- and immune therapies. For this reason, the advancements in our knowledge on the adjuvant role of Tα1 have moved in parallel with the development of novel cancer therapies in a way that Tα1 was integrated to changing paradigms and protocols, and tested for increased efficacy and safety. Cancer immunotherapy has recently experienced a tremendous boost following the development and clinical application of immune checkpoint inhibitors. By unleashing the full potential of the adaptive immune response, checkpoint inhibitors were expected to be very effective against tumors, but it soon became clear that a widespread and successful application was not straightforward and shortcomings in efficacy and safety clearly emerged. This scenario led to the development of novel concepts in immunotherapy and the design of combination protocols to overcome these limitations, thus opening up novel opportunities for Tα1 application. Herein, we summarize in a historical perspective the use of Tα1 in cancer, with particular reference to melanoma, hepatocellular carcinoma and lung cancer. We will discuss the current limitations of checkpoint inhibitors in clinical practice and the mechanisms at the basis of a potential application of Tα1 in combination protocols.

Immunotherapy for hepatitis B in the direct acting antiviral era: Reevaluating the thymosin α1 efficacy trials in the light of a combination therapy approach

Hepatitis B virus (HBV) causes both acute and chronic hepatitis and infects large numbers of individuals worldwide. Unfortunately, prediction of typical clinical outcome is problematic and there is considerable variability in the frequency, duration and severity of disease progression. The mainstay of HBV treatment is directed towards the suppression of HBV replication by nucleos(t)ide analogs (NUCs). The use of immunomodulators such as α-Interferon and thymosin α1 can, in select patients, results in elimination of both HBsAg and HBeAg. Given the observation that viral clearance is most effective in the presence of a strong immune response, this review summarizes data suggesting that the use of a combination of an immune modulator such as Tα1 with a highly effective NUC may result in a more successful therapeutic approach in patients with chronic hepatitis B (CHB). Results from small studies using combination Tα1 and NUCs are encouraging, and ongoing clinical trials combining entecavir with Tα1 are anticipated to provide important data assessing the use of a combination of Tα1 with a NUC to achieve resolution of CHB.

Future Therapy for Hepatitis B Virus: Role of Immunomodulators

Although currently available therapies for chronic hepatitis B virus infection can suppress viremia and provide long-term benefits for patients, they do not lead to a functional cure for most patients. Advances in our understanding of the virus-host interaction and the recent remarkable success of immunotherapy in cancer offer new and promising strategies for developing immune modulators that may become important components of a total therapeutic approach to hepatitis B, some of which are now in clinical development. Among the immunomodulatory agents currently being investigated to combat chronic HBV are toll-like receptor agonists, immune checkpoint inhibitors, therapeutic vaccines, and engineered T cells. The efficacy of some immune modulatory therapies is compromised by high viral antigen levels. Cutting edge strategies, including RNA interference and CRISPR/Cas9, are now being studied that may ultimately be shown to have the capacity to lower viral antigen levels sufficiently to substantially increase the efficacy of these agents. The current advances in therapies for chronic hepatitis B are leading us toward the possibility of a functional cure.

Efficacy of thymosin α-1 plus peginterferon α-2a combination therapy compared with peginterferon α-2a monotherapy in HBeAg-positive chronic hepatitis B: a prospective, multicenter, randomized, open-label study

OBJECTIVE

Thymosin α-1 plus interferon α-2a offers superior efficacy over interferon α-2a alone in patients with chronic hepatitis B. The aim was to compare the antiviral efficacy of thymosin α-1 plus peginterferon α-2a and peginterferon α-2a alone in HBeAg-positive chronic hepatitis B patients.

MATERIALS AND METHODS

HBeAg-positive CHB patients were enrolled in this prospective, randomized, open-label study. Fifty-one patients were assigned to either combination (26 patients; 180 μg of peginterferon α-2a weekly for 48 weeks and 1.6 mg of thymosin α-1 twice a week for the first 12 weeks) or monotherapy (25 patients; 180 μg of peginterferon α-2a weekly for 48 weeks) groups.

RESULTS

The rates of the combined response, defined as HBeAg seroconversion, HBV DNA suppression, and normalization of serum ALT, were 4/26 (15.4%) and 3/25 (12.0%) for the combination group and the monotherapy group at the end of treatment (p = 0.725), and 6/26 (23.1%) and 5/25 (20.0%) at the end of follow-up (p = 0.789), respectively. Based on multiple logistic regression analysis, a >2 log₁₀ IU/mL reduction of HBV DNA at week 12 was identified as an independent predictor for combined response (OR, 9.72; 95% CI, 1.33-71.06; p = 0.025) at the end of follow-up. A lower pretreatment HBV DNA level (≤ 7 log(10) IU/mL) was another predictor for combined response (OR, 9.64; 95% CI, 1.23-75.32; p = 0.031). No significant differences in adverse events were observed.

CONCLUSIONS

The short-term addition of thymosin α-1 was not superior to peginterferon α-2a alone in HBeAg-positive CHB patients on the basis of antiviral efficacy.

Effect of Thymosin-α1 on T-helper 1 Cell and T-helper 2 Cell Cytokine Synthesis in Patients with Hepatitis B Virus e Antigen-positive Chronic Hepatitis B

Thymosin-α1 (TA1) has been shown to be effective treatment for chronic hepatitis B virus (HBV) infection. This study investigated the immune response after TA1 monotherapy in 25 HBV e antigen (HBeAg)-positive patients randomized to receive either 1.6 mg active TA1 (group A), 1.6 mg recombinant TA1 (group B) or 3.2 mg recombinant TA1 (group C) monotherapy for 52 weeks. The percentages of T-helper 1 (Th1) cytokine-producing T-cells (interleukin-2 [IL-2], interferon-γ [IFN-γ], tumour necrosis factor-α) and Th2 cytokine-producing T-cells (IL-4) were analysed using flow cytometry. In all patients treated with TA1, cytokine levels and the proportion of peripheral blood mononuclear cells producing these cytokines were significantly increased, compared with baseline and healthy controls. The proportions of each cytokine-producing cell increased gradually over time and were restored to normal levels, and proportions of IFN-γ and IL-4-producing cells reached higher levels than in normal (healthy) controls. The results showed that treatment with TA1 increased cytokine production, especially IFN-γ, and higher-dose TA1 exhibited better efficacy against HBV, compared with other treatments studied.

Thymalfasin in the treatment of hepatitis B and C

Thymalfasin exhibited an immunomodulatory and a direct antiviral mechanism of action. The low rate of sustained response of chronic hepatitis with current therapies, underscores the need for new therapeutic options. It has been suggested that thymalfasin may have efficacy in the treatment of chronic hepatitis B and C. Pilots studies in patients with chronic hepatitis B treated with thymalfasin in combination with interferon or nucleoside analogue, showed a 70% complete sustained response rate. Studies in chronic hepatitis C patients, would indicate that thymalfasin in combination with standard or pegylated interferon with ribavirin may improve response rate in hepatitis C virus (HCV) naïve and nonresponder patients. However, a large phase-III randomized study conducted in Europe in HCV patients nonresponder to Peg-interferon with ribavirin, demonstrated that thymalfasin did not improve the rate of sustained virologic responses, but, in patients who completed therapy, thymalfasin significantly diminished the relapse rate. In conclusion, thymalfasin, in combination with the standard of care, may be helpful as an adjuvant in the treatment of patients with chronic hepatitis B and C.

Vitamin E treatment for children with chronic hepatitis B: A randomized placebo controlled trial

AIM: To evaluate the safety and efficacy of vitamin E in children with chronic hepatitis B.

METHODS: We randomly assigned patients with chronic hepatitis B, positive for hepatitis B e antigen (HBeAg), to receive either vitamin E or placebo once daily for 6 mo in a 3:1 ratio and double-blind manner. The primary end point was HBeAg seroconversion, defined as the loss of HBeAg, undetectable levels of serum hepatitis B virus DNA, and the appearance of antibodies against HBeAg 12 mo after therapy.

RESULTS: At baseline visit, 49 patients had normal and 43 had increased serum aminotransferase levels. Twenty-nine patients did not respond to previous treatment with interferon-α or lamivudine. Seventy-six children completed the study; 16 were non-compliant (n = 7), lost to follow-up (n = 7), or started another antiviral treatment (n = 3). Intention-to-treat analysis showed HBeAg seroconversion in 16 children (23.2%) treated with vitamin E and two (8.7%) in the placebo group (P = 0.13). Vitamin E was well tolerated.

CONCLUSION: There is only a tendency that vitamin E may promote HBeAg seroconversion. Therefore larger studies are needed to clarify the role of antioxidants in the therapy of chronic hepatitis B.

Combination therapy of thymosin alpha-1 and lamivudine for HBeAg positive chronic hepatitis B: A prospective randomized, comparative pilot study

BACKGROUND AND AIM

Monotherapy of lamivudine, interferon-alpha (IFN-alpha), and thymosin alpha-1 (Talpha1) is unlikely to be sufficient for the eradication of a chronic hepatitis B virus (HBV) infection. The aim of our study is to elucidate whether the combination of Talpha1 and lamivudine is superior to lamivudine monotherapy in hepatitis B e antigen (HBeAg) positive naïve patients with chronic hepatitis B.

METHODS

Sixty-seven patients were assigned to two different groups in a randomized manner. The combination group (n = 34) received Talpha1 (1.6 mg subcutaneously, twice a week) and lamivudine (100 mg orally, daily) for 24 weeks, followed by continuous lamivudine therapy. The monotherapy group (n = 33) received lamivudine monotherapy continuously.

RESULTS

The incidence of HBeAg seroconversion at 24 weeks was 26.5% (9/34) in the combination group and 6.1% (2/33) in the monotherapy group (P = 0.024). However, there was no statistically significant difference between 26.5% (9/34) in the combination group and 12.1% (4/33) in the monotherapy group at 52 weeks (P = 0.138). The emergence of viral breakthrough gradually increased to 35.3% (12/34) in the combination group, and to 21.2% (7/33) in the monotherapy group at 52 weeks (P = 0.201).

CONCLUSIONS

The combination treatment of Talpha1 and lamivudine did not have an obvious benefit of virological and biochemical response as compared to the lamivudine monotherapy during the combination period. In addition, after the cessation of Talpha1 treatment, the combination therapy did not prevent the occurrence of viral and biochemical breakthroughs.

A Systematic Review of T-cell Epitopes in Hepatitis B Virus: Identification, Genotypic Variation and Relevance to Antiviral Therapeutics

Background

The immune response to hepatitis B virus (HBV) is important for both viral control and disease pathogenesis. A detailed understanding of the HBV-specific T-cell responses may potentially lead to novel therapeutic strategies for HBV.

Methods

All English language journal articles (including articles in press) up to October 2007 were retrieved using searches of MEDLINE, EMBASE and the Cochrane Controlled Trial Registry. An extensive database of HBV sequences (SeqHepB) and GenBank were used to assess the degree of sequence variation in each epitope. The new standardized nomenclature for HBV amino acid position number was applied to all previously defined epitopes.

Results

Forty-four HBV-specific human leukocyte antigen (HLA) class I restricted and 32 HBV-specific HLA class II restricted epitopes have been defined and have been identified in all HBV genes. The majority of HLA class I restricted epitopes have been defined in HLA-A2-positive individuals in the setting of acute HBV infection. There is significant sequence variation of these epitopes within and between HBV genotypes. Newer HBV immunotherapeutics appear promising but are still in early phases of development.

Conclusions

Identification of HBV-specific epitopes in non-HLA-A2-positive individuals and recognition of genotypic variation across epitopes are important for the future development of novel immunotherapeutic strategies for the management of chronic HBV infection.

Comparison of the efficacy of thymosin alpha-1 and interferon alpha in the treatment of chronic hepatitis B: a meta-analysis

Chronic hepatitis B virus (HBV) infection is a serious problem because of its worldwide distribution and possible adverse sequelae, such as cirrhosis and hepatocellular carcinoma. Thymosin alpha-1 (Talpha1) is an immune modifier that has been shown to be effective for chronic hepatitis B (CHB) in some trials. But the trials comparing Talpha1 vs. interferon alpha (IFNalpha) treatment in CHB have been small and the results have been inconsistent. So we conducted a meta-analysis to compare the efficacy of Talpha1 and IFNalpha in the treatment of CHB. Generally, four randomized controlled trials including 199 CHB patients who received Talpha1 or IFNalpha treatment were identified through MEDLINE and EMBASE online search. Virological (for hepatitis B e antigen (HBeAg) positive patients, loss of HBV DNA and HBeAg; for HBeAg negative patients, loss of HBV DNA), biochemical (normalization of transaminases) and complete responses (fulfill criteria of biochemical and virological response simultaneously) were analyzed using the intention-to-treat method. The odds ratio (OR) was used to measure the magnitude of the efficacy. The ORs (95% confidence interval) of the virological response, biochemical response and complete response of Talpha1 over IFNalpha at the end of 6 months treatment were 0.62 (0.35, 1.10), 0.60 (0.34, 1.05) and 0.54 (0.30, 0.97), respectively. The ORs (95% confidence interval) of the virological response, biochemical response and complete response of Talpha1 over IFNalpha at the end of follow-up (6 months post-treatment) were 3.71 (2.05, 6.71), 3.12 (1.74, 5.62) and 2.69 (1.47, 4.91), respectively. These data showed that compared with IFNalpha, the benefit of Talpha1 was not immediately significant at the end of therapy, but virological, biochemical and complete response had a tendency to increase or accumulate gradually after the therapy. For three of the four trials that studied HBeAg-negative patients, the results are mostly applicable to HBeAg-negative CHB.

Hepatitis B virus genotype B is associated with better response to thymosin alpha1 therapy than genotype C

Hepatitis B virus (HBV) genotype has been reported to correlate with response to interferon treatment in several studies. The relationship between HBV genotype and thymosin alpha1 (T-alpha1) treatment is unknown. We retrospectively examine HBV genotypes, precore and core promoter mutations in patients treated with Talpha1 and analyse the correlation between complete response [alanine aminotransferase (ALT) normalization plus seroclearance of HBeAg and HBV-DNA] and HBV genotype. It consisted 98 patients with chronic hepatitis B randomly allocating to three groups: (i) T6 group (n = 32) received a 26-week course of Talpha1 1.6 mg two times a week; (ii) T12 group (n = 34) received the same regimen as T6 group, but Talpha1 therapy extended for 52 weeks; (iii) T0 group (n = 32) served as a control and was followed up for 18 months without specific treatment. Stepwise logistic regression analysis showed that genotype (OR, 3.747; 95% CI, 1.066-13.170; P = 0.039), precore mutation (OR, 6.285; 95% CI, 1.874-21.086; P = 0.003) and Talpha-1 treatment (OR, 12.045; 95% CI, 2.220-65.354; P = 0.004) as independent factors associated with complete response. The complete response of Talpha-1 therapy was higher in patients with genotype B compared to patients with genotype C (52%vs 24%; P = 0.036) and in patients with precore mutation (64%vs 19%; P = 0.002). In conclusion, genotype, presence of precore mutation and Talpha-1 therapy were independent predictors to complete response. Genotype B, compared to genotype C, is associated with a higher response rate to T-alpha1 therapy.

Lipidation and glycosylation of a T cell antigen receptor (TCR) transmembrane hydrophobic peptide dramatically enhances in vitro and in vivo function

A T cell antigen receptor (TCR) transmembrane sequence derived peptide (CP) has been shown to inhibit T cell activation both in vitro and in vivo at the membrane level of the receptor signal transduction. To examine the effect of sugar or lipid conjugations on CP function, we linked CP to 1-aminoglucosesuccinate (GS), N-myristate (MYR), mono-di-tripalmitate (LP1, LP2, or LP3), and a lipoamino acid (LA) and examined the effects of these compounds on T cell activation in vitro and by using a rat model of adjuvant-induced arthritis, in vivo. In vitro, antigen presentation results demonstrated that lipid conjugation enhanced CP's ability to lower IL-2 production from 56.99%+/-15.69 S.D. observed with CP, to 12.08%+/-3.34 S.D. observed with LA. The sugar conjugate GS resulted in only a mild loss of in vitro activity compared to CP (82.95%+/-14.96 S.D.). In vivo, lipid conjugation retarded the progression of adjuvant-induced arthritis by approximately 50%, whereas the sugar conjugated CP, GS, almost completely inhibited the progression of arthritis. This study demonstrates that hydrophobic peptide activity is markedly enhanced in vitro and in vivo by conjugation to lipids or sugars. This may have practical applications in drug delivery and bioavailability of hydrophobic peptides.

A Randomized, Placebo-Controlled Trial of Thymosin-α1 and Lymphoblastoid Interferon for Hbeag-Positive Chronic Hepatitis B

Combination therapy between two immunomodulators used for treatment of chronic hepatitis B was explored based on reported therapeutic efficacy of interferon-α, and thymosin-α1 as monotherapeutic agents to determine if combination therapy was superior to interferon alone. This double-blinded, randomized, placebo-controlled trial compares the addition of thymosin-α1, 1.6 μg taken three times per week (combination therapy) or thymosin placebo (monotherapy) to lymphoblastoid interferon (Wellferon®), 5 million international units (MIU) taken three times per week, for 24 weeks. Entry criteria included positive hepatitis B e antigen (HBeAg); alanine aminotransferease (ALT) ≥1.5x upper normal limit, but ≤10xupper normal limit; positive HBV DNA; absence of cirrhosis; treatment naivety and no co-morbid factors. A total of 98 HBeAg-positive patients were recruited, of which 48 were randomized to combination therapy and 50 to monotherapy. The primary endpoint was the loss of HBeAg at 72 weeks. The secondary endpoints were HBeAg seroconversion, normalization of ALT, loss of HBV DNA and improvement in histology. The HBeAg loss was 45.8% and 28.0% for combination therapy and monotherapy, respectively (difference, 17.8%; 95% CI -1.2%-35.3%, P=0.067). There was a trend towards HBeAg loss when using combination therapy. There were also no statistically significant differences between the different therapies with respect to the secondary endpoints of HBeAg seroconversion, changes in histology, normalization of ALT or loss of HBV DNA. In conclusion, this trial showed a 17.8% improvement in HBeAg loss rates using combination therapy over interferon monotherapy. This could clinically indicate a potential important difference that would need confirmation in subsequent trials.

Immunomodulatory therapy for chronic hepatitis B virus infection

Hepatitis B virus (HBV) is one of the most prevalent viral pathogens of man with around 350 million chronically infected patients. It has been postulated that in persistently infected individuals the HBV-specific immune response is too weak to eliminate HBV from all infected hepatocytes, but sufficiently strong to continuously destroy HBV-infected hepatocytes and to induce chronic inflammatory liver disease. The primary aim in the treatment of chronic hepatitis B is to induce sustained disease remission and prevent serious complications like liver failure and/or hepatocellular carcinoma. The recent emergence of drug-resistant HBV mutants and post-treatment relapse as a consequence of nucleoside analogue monotherapy emphasizes that the principal goal should be to stimulate a successful immune response. In this paper we will focus on the immune response to HBV and we will review reported data on immunotherapeutic strategies like immunomodulatory drugs (cytokines and Thymic derivates) and vaccine therapies using currently available recombinant anti-HBV vaccines, lipopeptide-based T cell vaccine and newly developed genetic vaccines.

The efficacy and safety of thymosin alpha-1 in Japanese patients with chronic hepatitis B; results from a randomized clinical trial

Thymalfasin (thymosin alpha-1; Talpha1) is a 28-amino acid polypeptide that has shown efficacy in the treatment of chronic hepatitis B virus (HBV) infection. The objective of this study was to evaluate the long-term, dose-related efficacy and safety of Talpha1 treatment in chronic hepatitis B patients with positive HBV-DNA and abnormally high alanine aminotransferase (ALT) levels. A total of 316 patients were randomized to receive either 0.8 or 1.6 mg of Talpha1 monotherapy for 24 weeks. At the end of the 72-week observation period (12 months after cessation of therapy), 36.4% of patients in the 1.6-mg treatment group achieved normalization of ALT, 30% achieved clearance of HBV-DNA by branched DNA vs 15% by transcription-mediated amplification, and 22.8% achieved clearance of HBe-antigen. Patients in the 0.8-mg treatment group achieved similar efficacy rates, although patients with advanced fibrosis demonstrated a significantly better response rate when treated with 1.6 mg of Talpha1 monotherapy vs 0.8 mg (as determined by intragroup analysis; patients were not stratified by liver biopsy). All adverse drug reactions were mild and most involved the fluctuation of liver enzymes, which was most likely related to the positive immune effects caused by the response to Talpha1 treatment. Adverse event incidence was similar in the 1.6- and 0.8-mg treatment groups. In conclusion, Talpha1 at doses of 0.8 and 1.6 mg exhibits long-term efficacy against hepatitis B with a good safety profile.

Emerging treatments in chronic hepatitis B

Although the management of chronic hepatitis B has improved over the last decade, none of the available therapeutic agents, IFN-alpha, lamivudine and adefovir dipivoxil, can achieve sustained off-therapy responses in most cases. Therefore, several newer, mainly antiviral and immunomodulatory agents, are being evaluated. Pegylated IFN-alpha(2a) has been shown to be more effective than lamivudine or standard IFN-alpha monotherapy in achieving post-therapy biochemical and virological responses, and is expected to be licensed soon for the treatment of chronic hepatitis B. Newer antiviral agents, such as entecavir and telbivudine, appear to be quite effective initially, but their sustained off-therapy response rates remain unknown. The preliminary data of monotherapies with immunomodulatory agents, or of combination therapies, have been rather disappointing. Long-term maintenance treatment with antiviral agent(s) with good safety and tolerability profiles and low resistance rates appears to be the most realistic future therapeutic option for most chronic hepatitis B patients.

A randomized, controlled, clinical study of thymosin alpha-1 versus interferon-alpha in [corrected] patients with chronic hepatitis B lacking HBeAg in China [corrected]

BACKGROUND

This study was designed to compare the efficacy and safety of thymosin-alphal (T-alpha1) with that of interferon-alpha (IFN-alpha) in patients with chronic hepatitis B who were positive for hepatitis B virus (HBV) DNA and hepatitis B envelope antibody (anti-HBe).

METHODS

Fifty-six patients were randomly divided into groups A and B. Both groups were comparable (p > 0.05) at baseline regarding age, sex, and alanine aminotransferase (ALT) levels. Group A patients received T-alpha1 1.6 mg subcutaneously twice weekly, while group B patients received IFN-alpha 5 million IU daily for 15 days, then thrice weekly for 6 months. Results from the 2 groups were compared with data from a group of 30 patients never treated with IFN-alpha and who were followed-up for 12 months (historical control [HC] group); the 3 groups were comparable (p > 0.05).

RESULTS

After treatment, a complete response (ALT normalization and HBV DNA loss) occurred in 8 of 26 patients in group A (30.8%) and 14 of 30 in group B (46.7%; chi2 = 1.476, p = 0.224). After a follow-up period of 6 months, a complete response was observed in 11 of 26 patients in group A (42.3%) and 7 of 30 in group B (23.3%; chi2 = 2.299, p = 0.129). The rate of complete response was significantly greater in the IFN-alpha than HC group at the end of therapy (46.7% vs 3.3%; chi2 = 15.022, p = 0.0001), and in the T-alphal than HC group at the end of follow-up (42.3% vs 3.3%; chi2 = 12.566, p = 0.0001). Ten of the 12 T-alphal responders (i.e. partial responders; 83.3%) experienced sustained, non-detectable HBV DNA after 6 months' treatment; 6 of the 14 T-alphal non-responders (42.9%) showed a delayed response of non-detectable HBV DNA during the follow-up period. Corresponding values for group B patients were 50% (9/18) and 0% (0/12). The rate of delayed response was significantly higher in group A than the other 2 groups (chi2 = 6.686, p = 0.010; chi2 = 4.964, p = 0.038), whereas the rate of flare was higher in group B than in the other 2 groups (chi2 = 3.445, p = 0.063; chi2 = 7.668, p = 0.006), during the follow-up period. Unlike IFN-alpha, T-alphal was well tolerated, i.e. no adverse effects were noted in group A.

CONCLUSION

These results suggest that a 6-month course of T-alpha1 therapy is effective and safe in patients with anti-HBe-positive chronic hepatitis B; T-alpha1 can reduce HBV replication in such patients. Compared with IFN-alpha, T-alpha1 is better tolerated and seems to induce a gradual and more sustained normalization of ALT and loss of HBV DNA. Combination therapy with T-alpha1 and IFN-alpha or nucleoside analogs for hepatitis B warrants further study.

Thymalfasin for the treatment of chronic hepatitis B

Chronic hepatitis B virus infection is a serious problem because of its worldwide distribution and possible adverse chronic sequelae, such as cirrhosis and hepatocellular carcinoma. Chronic hepatitis B infection is a dynamic state of interactions between the virus, hepatocyte and host immune response. Interferon-alpha and direct antiviral agents, such as lamivudine (Epivir, GlaxoSmithKline), are effective in the therapy of chronic HBV infection but the efficacy is far from satisfactory. Thymalfasin (thymosin alpha1; Talpha1, Zadaxintrade mark, SciClone Pharmaceuticals, Inc.) is a 28-amino acid polypeptide produced synthetically but originally isolated from thymosin fraction 5, a bovine thymus extract containing a number of immunologically active peptides. In vitro studies have shown that Talpha1 can influence T-cell production and maturation, stimulate production of Th1 cytokines such as interferon-gamma and interleukin-2, and activate natural killer cell-mediated cytotoxicity. Seven randomized controlled studies on Talpha1 monotherapy in patients with chronic hepatitis B showed that 6 months treatment with Talpha1 (1.6 mg twice-weekly) resulted in a significantly higher sustained response rate than untreated controls. The benefits of Talpha1 therapy is usually not immediately apparent during therapy. There is a trend for complete virological response to increase or accumulate gradually after the end of thymosin therapy. The results of Talpha1 and interferon combination therapy in two open-label trials were also promising. In terms of the mechanisms of action, a combination of Talpha1 and nucleoside or nucleotide analogs is a logical approach in the control of chronic HBV infection and a randomized control study is ongoing.

Thymalfasin (thymosin-alpha 1) therapy in patients with chronic hepatitis B

Chronic hepatitis B virus (HBV) infection is a serious clinical problem because of its worldwide distribution and potential adverse sequelae. Globally, there are approximately 350 million people infected with chronic HBV, 75% of whom live in the Asia-Pacific region. Interferon-alfa and direct antiviral agents such as lamivudine and adefovir are effective in the therapy of chronic HBV infection but the efficacy is far from satisfactory, particularly in perinatally infected patients, patients with lower ALT levels and those with HBeAg-negative chronic hepatitis B. Thymalfasin (thymosin-alpha1) is an immunoregulatory agent able to enhance Th1 response. It has been shown to trigger maturational events in lymphocytes, to augment T-cell function, and to promote reconstitution of immune defects. Studies are underway in both monotherapy and combination therapy with thymalfasin and interferon and results are promising.

The thymosins. Prothymosin alpha, parathymosin, and beta-thymosins: structure and function

The studies on thymosins were initiated in 1965, when the group of A. White searched for thymic factors responsible for the physiological functions of thymus. To restore thymic functions in thymic-deprived or immunodeprived animals, as well as in humans with primary immuno-deficiency diseases and in immunosuppressed patients, a standardized extract from bovine thymus gland called thymosin fraction 5 was prepared. Thymosin fraction 5 indeed improved immune response. It turned out that thymosin fraction 5 consists of a mixture of small polypeptides. Later on, several of these peptides (polypeptide beta 1, thymosin alpha 1, prothymosin alpha, parathymosin, and thymosin beta 4) were isolated and tested for their biological activity. The research of many groups has indicated that none of the isolated peptides is really a thymic hormone; nevertheless, they are biologically important peptides with diverse intracellular and extracellular functions. Studies on these functions are still in progress. The current status of knowledge of structure and functions of the thymosins is discussed in this review.

Nucleoside analogues and other antivirals for treatment of hepatitis B in the peritransplant period

Chronic HBV infection is a common cause of advanced liver disease that is associated with substantial mortality. Furthermore, chronic hepatitis B was historically a controversial indication for liver transplantation because of a low post-transplant survival, with graft infection being the major contributor to adverse outcomes. The initial use of hepatitis B immune globulin as prophylaxis, followed later by combined therapy with lamivudine, markedly reduced viral recurrence and improved the survival of patients transplanted for acute or chronic hepatitis B with liver failure. Lamivudine alone can also be used for long-term prophylaxis against de novo HBV infection that can be transmitted by organs from donors positive for anti-HBc or anti-HBs. When used in patients with decompensated chronic hepatitis B with cirrhosis, lamivudine has been shown to improve clinical manifestations, prolong pretransplant survival, and defer, or even obviate, the need for transplantation. Despite prophylaxis, viral mutations with breakthrough reinfection may occur and lead to liver failure. The recently approved adefovir dipivoxil, which is active against lamivudine-resistant mutation, and other nucleoside analogs that are in various phases of development, offer hope as rescue therapy for viral recurrence. Other therapeutic alternatives in the future may include gene therapy and immune interventions.

Long-term outcomes of thymosin-alpha 1 and interferon alpha-2b combination therapy in patients with hepatitis B e antigen (HBeAg) negative chronic hepatitis B

Hepatitis B e antibody (HbeAb) and hepatitis B virus (HBV) DNA positive chronic hepatitis is a clinical entity, distinct from classical hepatitis B e antigen (HbeAg) positive chronic hepatitis B. Our aim was to evaluate the long-term therapeutic efficacy of the combination of interferon alpha-2b and thymosin-alpha1 compared with lamivudine plus interferon alpha-2b and interferon alpha-2b alone. Fifty-two patients with HbeAg-negative chronic hepatitis B were assigned to three different groups in a nonrandomized manner. Group 1 (n = 27) received thymosin-alpha1 [1.6 mg subcutaneously (sc), twice a week] and interferon alpha-2b (10 MIU sc, three times per week) for 26 weeks, subsequently followed by interferon alpha-2b monotherapy at the same dosage for an additional 26 weeks. Group 2 (n = 10) received interferon alpha-2b (10 MIU sc, three times per week) for 52 weeks. Group 3 (n = 15) received interferon alpha-2b (10 MIU sc, three times per week) and lamivudine [100 mg orally (po), q.d.] for 52 weeks, followed by continuous lamivudine (100 mg po, q.d.) therapy. By the end of 78 weeks, a sustained response (SR-6 mo) was seen in 74% (20/27) of the patients within Group 1. On the contrary, Groups 2 and 3 had sustained response rates of 40 (4/10) and 53.3% (8/15), respectively (p = 0.13). At the end of 12 months post-treatment in Group 1, a virological and biochemical response rate was seen in 70.3% of patients (19/27); in contrast, Groups 2 and 3 had response rates of 20 (2/10) and 26.6% (4/15), respectively (p = 0036). At the end of the 18-month post-treatment follow-up period, 71.4% (19/27) of patients in Group 1, 10% of patients in Group 2 (1/10), and 20% of patients in Group 3(3/15) preserved their sustained response (p = 0.0003). Interferon alpha-2b and thymosin-alpha1 combination therapy results in significant virological and biochemical response rates compared with standard therapeutic regimens and is well tolerated.

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Thymosin-alpha1 and famciclovir combination therapy activates T-cell response in patients with chronic hepatitis B virus infection in immune-tolerant phase

We examined whether combination therapy with thymosin-alpha1 and famciclovir would induce hepatitis B e antigen seroconversion in patients with chronic hepatitis B infection in the immune-tolerant phase without inducing significant hepatic necro-inflammation. We studied 32 hepatitis B e antigen positive patients in the immune-tolerant phase of infection, treated with 26-weeks combination therapy of famciclovir and thymosin-alpha1 (group 1). Thirty-two patients who received 26-weeks famciclovir monotherapy (group 2) and another 32 patients who received no treatment (group 3), served as controls. Peripheral blood mononuclear cell proliferation and cytokine secretion in response to recombinant HBV core and surface antigen and serial serum HBV-DNA, were assayed. No significant difference in adverse events were observed among the three groups. By week 26, the median reduction in group 1 (0.94 log10 copies/mL) was greater than group 2 (0.70 log10 copies/mL, P < 0.001). Five (15.6%) patients in group 1 at 52 weeks (median range 13-78 weeks) and none in group 2 or 3 experienced hepatitis B e antigen seroconversion (P = 0.053). Sustained serological clearance of hepatitis B e antigen was associated with activation of CD4 positive HBV-specific T-cell reactivity and were of T-helper 1. Hence combination therapy with immunomodulatory agents and nucleoside analogues should be explored.

Management of viral hepatitis B

Hepatitis B virus (HBV) infection is a major global health concern and is the most common cause of chronic liver disease worldwide. The natural history and clinical outcomes of chronic HBV infection are determined by the viral replication cycle and the host immune responses. Treatment of chronic hepatitis B is directed at interrupting the natural history by suppressing HBV replication before development of any significant irreversible liver cell damage. Effective antiviral therapies should be followed by sustained suppression of HBV-DNA, normalization of transaminases levels and a stable stage of HBeAg seroconversion with persistence of circulating anti-HBeAg antibodies. Two major classes of antiviral therapeutic agents that have been approved for treatment of chronic hepatitis B are immunomodulating agents (i.e. interferon) and the nucleoside analogs (i.e. lamivudine). A 4-6 month course of interferon-alpha has resulted in improvement of survival in 20%-30% of patients with chronic hepatitis B who had elevated serum ALT levels without hepatic decompensation. Interferon-alpha therapy is associated with HBeAg seroconversion; normalization of ALT levels, reduced hepatic inflammation, and possibly reduced disease progression to cirrhosis and hepatocellular carcinoma. Interferon can also be used with caution in patients with early compensated cirrhosis. A 12-month course of lamivudine has been shown to be well tolerated and effective. Lamivudine can be used in decompensated cirrhosis and immunosuppressed patients and for prevention of recurrent HBV infection after liver transplantation. The response rates after 3 years of lamivudine therapy account for 40-65%. A major problem of antiviral treatment is the emergence of drug resistance conferred by mutations in the YMDD motif of HBV reverse transcriptase. The prevalence of YMDD mutations increases with longer durations of antiviral therapies and this has been detected in 20% of immunocompetent patients receiving lamivudine per year. Contentious issues remain when to stop the treatment if HBeAg seroconversion does not occur. Many new immunomodulatory therapies and antiviral agents are in various stages of clinical development and have shown some promise. Among newer HBV antivirals, adefovir dipivoxil, entecavir, emtricitabine, DAPD and clevudine appear to be at least as potent as lamivudine in suppressing HBV replication. In vitro studies have shown that YMDD mutations confer cross-resistance between lamivudine and emtricitabine. However, adefovir, dipivoxil, lobucavir, DAPD and possibly clevudine suppress replications of both YMDD mutants and wild types of HBV. Immunomodulatory approaches for treatment of chronic hepatitis B are conceptually attractive, but newer agents used to date (thymosin-alpha, interleukin-12, therapeutic vaccines) have not demonstrated sufficient efficacy for widespread use. Combinations of an immunomodulatory agent and nucleoside analog may improve the therapeutic efficacy and reduce the emergence of drug resistance. Nevertheless, combinations of interferon and lamivudine therapies do not confer such additional benefits. The next challenge for HBV treatment is to use antivirals in combination and/or in cyclical therapy to minimize the emergence of drug resistance and increase efficacy, particularly to achieve sustainable post-treatment suppression of HBV. Randomized prospective control trials of combined antiviral therapies given simultaneously or sequentially are needed to establish safe and effective combined regimens that can be recommended for future treatment strategies.

The efficacy of thymosin in the treatment of chronic hepatitis B virus infection: a meta-analysis

BACKGROUND

Trials of thymosin treatment in chronic hepatitis B virus infection have been small and the results have been inconsistent.

AIM

To conduct a meta-analysis to evaluate the efficacy of thymosin treatment in chronic hepatitis B virus infection.

METHODS

Randomized controlled trials comparing thymosin for over 24 weeks vs. placebo (or usual care) in the treatment of chronic hepatitis B virus infection were identified through MEDLINE, EMBASE and the Cochrane Register of Clinical Trials. Biochemical (normalization of transaminases) and virological (loss of hepatitis B virus DNA and hepatitis B e antigen) responses were analysed using the intention-to-treat method. The odds ratio was used to measure the magnitude of the efficacy.

RESULTS

Five trials (353 patients) were identified. The odds ratio (95% confidence interval) of the virological response of thymosin over placebo at the end of treatment, 6 months post-treatment and 12 months post-treatment were 0.56 (0.2-1.52), 1.67 (0.83-3.37) and 2.67 (1.25-5.68), respectively. There was an increasing trend of the virological response with time since the cessation of thymosin treatment (P=0.02). There was no difference in the biochemical response between the thymosin and placebo groups at the end of treatment, 6 months post-treatment and 12 months post-treatment.

CONCLUSIONS

Thymosin is effective in suppressing viral replication in chronic hepatitis B virus infection, but the effect is delayed until 12 months after the cessation of treatment.

Drug discovery and development of antiviral agents for the treatment of chronic hepatitis B virus infection

A safe and effective vaccine for hepatitis B virus (HBV) has been available for nearly twenty years and currently campaigns to provide universal vaccination in developing countries are underway. Nevertheless, chronic HBV infection remains a leading cause of chronic hepatitis worldwide and there is a strong need for safe and effective antiviral therapies. Attempts to identify and develop antiviral agents to treat chronic HBV infection remains focused on nucleoside analogs such as 3TC (lamivudine), adefovir dipivoxil, (bis-POMPMEA), and others. However, advances in our understanding of the molecular biology of HBV and the development of new assays for HBV polymerase activity, such as the reconstitution of active HBV polymerase in vitro, should facilitate large screening efforts for non-nucleoside reverse transcriptase inhibitors. Recent advances have furthered our understanding of clinical resistance to lamivudine, have provided new approaches to treatment, and have offered new perspectives on the major challenges to the identification and development of antiviral agents for chronic HBV infection. Here, in an update to our previous review article that appeared in this series [59a], we focus on recent advances that have occurred in the areas of virus structure and replication, in vitro viral polymerase assays, cell culture systems, and animal models.

Vitamin E as treatment for chronic hepatitis B: results of a randomized controlled pilot trial

BACKGROUND AND AIMS

Interferon-alpha treatment has been the treatment of choice for chronic hepatitis with unpredictable results. Recently, Lamivudine has been licensed for use against HBV infection with good results. Unfortunately, recurrence of viremia after lamivudine withdrawal is common and prolonged treatment can induce the emergence of resistant mutant strains. It has been shown that vitamin E can increase the host immune response, and this may provide protection against infectious diseases.

METHODS

We evaluated vitamin E supplementation as therapy for chronic hepatitis B in a pilot study including 32 patients. Patients were randomly allocated to receive vitamin E at the dose of 300 mg twice daily for 3 months (15 patients) or no treatment (17 patients). They were seen monthly during the first 3 months and thereafter quarterly for additional 12 months.

RESULTS

The two groups were comparable at enrollment. At the end of the study period, alanine aminotransferase (ALT) normalization was observed in 7 (47%) patients in vitamin E group and only in 1 (6%) of the controls (P=0.011); HBV-DNA negativization was observed in 8 (53%) patients in the vitamin E group as compared to 3 (18%) in the control group, respectively (P=0.039). A complete response (normal ALT and negative HBV-DNA) was obtained in 7 (47%) patients taking vitamin E and in none of the controls (P=0.0019).

CONCLUSION

Vitamin E supplementation might be effective in the treatment of chronic hepatitis B.

Combination chemotherapy for hepatitis B virus: the path forward?

Hepatitis B virus (HBV) was identified as a cause of viral hepatitis more than 30 years ago and hepatitis B vaccines have been available for almost 20 years, but HBV infection continues to be a global health problem, responsible for about 1.2 million deaths annually. By the end of this year, almost 400 million people--about 5% of the world's population and more than ten times the number infected with human immunodeficiency virus (HIV)--will be infected with HBV. Chemotherapy remains the only treatment option for controlling chronic HBV infection once acquired, but none of the many different chemotherapeutic strategies used in the past has proven consistently successful. Prospects for successful treatment of HBV have improved dramatically during the past decade due to the development of new, well tolerated and efficacious anti-HBV drugs, and to advances in our understanding of HBV replication and pathogenesis. The newer anti-HBV drugs are capable of reducing viral loads very rapidly, but the initial response is invariably followed by very much slower elimination of residual virus. As more effective anti-HBV drugs become available, the emergence of drug resistance during the slower phase of HBV elimination will probably become the most significant obstacle in the way of eventual control of HBV infection. Experience with HIV indicates that combination chemotherapy may suppress or eliminate drug resistance and methods for pre-clinical and clinical assessment of anti-HBV drug combinations are being developed. Basic research into mechanisms of drug action and interaction should assist in the design and optimisation of combination chemotherapy for HBV infection, for which additional new anti-HBV drugs will undoubtedly be required in future.

Use of immunomodulatory therapy (other than interferon) for the treatment of chronic hepatitis B virus infection

Chronic hepatitis B virus (HBV) infection is a major health threat in Asia. In order to design a better therapeutic regimen, the underlying mechanism of HBV viral persistence must be understood. Immunological studies have found that impaired HBV virus-specific T cell reactivity is the major cause of chronic infection, whereas strong and multispecific T cell responses to HBV are associated with long-term control, but not elimination of the virus. Furthermore, in the serological clearance of hepatitis B surface antigen (HBsAg) in allogeneic haematopoietic cell transplantation, HBsAg seroconversion is associated with activation of the donor's hepatitis B core antigen-specific CD4+ T lymphocytes. This suggests that the donor's hepatitis B core antigen-specific CD4+ T cells provide 'intermolecular T cell help' for the HBsAg seroconversion. These findings are relevant to the future development of therapeutic vaccines or DNA vaccine as immunotherapy for chronic hepatitis B. Apart from interferon-alpha, thymosin alpha1 (Talpha1) has been investigated for treatment of chronic hepatitis B. Meta-analysis of 4 randomized controlled studies investigating the safety and efficacy of Talpha1 monotherapy for the treatment of chronic hepatitis B showed that 6 months treatment with Talpha1 (1.6 mg twice weekly) almost doubles the sustained response rate (36%) compared with controls (19%; P=0.04). However, more specific immunological approaches are being developed; notably, hepatitis B core antigen-based therapeutic vaccine was found to induce T cell proliferative responses in chronically infected hepatitis B patients to the T helper epitope included in the construct. However, the cytokine profile observed suggested the induction of a T helper 0/T helper 2 CD4+ T cell response rather than T helper 1 response. Thus, its combination with interferon-gamma or interleukin-12, which might reverse the CD4+T cell response, should be considered. In the future, it is likely that different types of combination therapy may have to be tailor-made for chronic HBV infection with different virological and immunological profiles and different degrees of liver damage.