Thymalfasin for the treatment of chronic hepatitis B

Thymosin α1 and Its Role in Viral Infectious Diseases: The Mechanism and Clinical Application

Thymosin α1 (Tα1) is an immunostimulatory peptide that is commonly used as an immune enhancer in viral infectious diseases such as hepatitis B, hepatitis C, and acquired immune deficiency syndrome (AIDS). Tα1 can influence the functions of immune cells, such as T cells, B cells, macrophages, and natural killer cells, by interacting with various Toll-like receptors (TLRs). Generally, Tα1 can bind to TLR3/4/9 and activate downstream IRF3 and NF-κB signal pathways, thus promoting the proliferation and activation of target immune cells. Moreover, TLR2 and TLR7 are also associated with Tα1. TLR2/NF-κB, TLR2/p38MAPK, or TLR7/MyD88 signaling pathways are activated by Tα1 to promote the production of various cytokines, thereby enhancing the innate and adaptive immune responses. At present, there are many reports on the clinical application and pharmacological research of Tα1, but there is no systematic review to analyze its exact clinical efficacy in these viral infectious diseases via its modulation of immune function. This review offers an overview and discussion of the characteristics of Tα1, its immunomodulatory properties, the molecular mechanisms underlying its therapeutic effects, and its clinical applications in antiviral therapy.

Peptide-Based Antiviral Drugs

Three types of chemical entities, namely, small organic molecules (organics), peptides, and biologics, are mainly used as drug candidates for the treatment of various diseases. Even though the peptide drugs are known since 1920 in association with the clinical use of insulin, only a limited number of peptides are currently used for therapeutics due to various disadvantages associated with them such as limited serum and blood stability, oral bioavailability, and permeability. Since, through chemical modifications and structure tuning, many of these limitations can be overcome, peptide-based drugs are gaining attention in pharmaceutical research. As of today, there are more than 60 peptide-based drugs approved by FDA, and over 150 peptides are in the advanced clinical studies. In this book chapter, the peptide-based lead compounds and drugs available for treating various viral diseases and their advantages and disadvantages when compared to small molecules drugs are discussed.

Effect of recombinant adenovirus-associated virus-mediated RNA interference on HBV replication and expression

AIM: To observe the effect of recombinant adenovirus-associated virus (rAAV)-mediated RNA interference on HBV replication and expression in HepG2.2.15 cells.

METHODS: The expression box of hu6-shRNA was placed between two ITRs of AAV and then ligated to the basic core promoter (BCP) of HBV and BCP-driven Rep gene of AAV, which resulted in rAAV. The rAAV was transfected into HepG2.2.15 cells (HCC cells in which the HBV gene was inserted). The expression of HBsAg and HBeAg and replication of HBV-DNA in cultured supernatant were determined on days 1, 2, 3 and 10 after transfection, and the AAVS1 region was sequenced on day 3 after transfection.

RESULTS: The target sequence-containing vectors PLRBR322-324, PLRBR522-324, PLRBR322-2424 and PLRBR522-2424 were successfully constructed. All the four vectors had inhibitory effects on the expression of HBsAg and HBeAg and on HBV-DNA replication, with the former two (PLRBR322-324 and PLRBR522-324) having more significant inhibitory effect on HBsAg expression, the latter two on HBeAg expression and the third on HBV-DNA replication. The inhibitory effects on HBsAg and HBeAg expression and HBV-DNA replication were most obvious on day 3 after transfection, and the inhibition rate remained high on day 10. Site-directed integration of the target sequence was located in the AAVS1 region.

CONCLUSION: The rAAV constructed by several elements of AAV and HBV, together with the help of site-directed integration mediated by Rep protein, is a good exploration to solve the problem of short-term effect of RNAi against HBV.

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.

Treatment with lamivudine versus lamivudine and thymosin alpha-1 for e antigen-positive chronic hepatitis B patients: a meta-analysis

BACKGROUND

Currently, there is no evidence on the combination of lamivudine and thymosin alpha-1 on chronic hepatitis B patients. The aim of this study was to compare the effect of lamivudine monotherapy with that of lamivudine and thymosin alpha-1 combination therapy for the treatment of hepatitis B e antigen (HBeAg)-positive hepatitis B patients.

RESULTS

We searched PUBMED (from 1966 onwards), EMBASE (from 1966), CBMdisk (Chinese Biomedical Database, from 1978), CNKI (National Knowledge Infrastructure, from 1980), the Cochrane Central Register of Controlled Trials and the Cochrane Database of Systematic Reviews. Eight trials (583 patients in total) were identified. The lamivudine and thymosin alpha-1 combination treatment was significantly superior to lamivudine treatment in terms of ALT normalization rate (80.2% vs. 68.8%, P = 0.01), virological response rate (84.7% vs. 74.9%, P = 0.002), and HBeAg seroconversion rate (45.1% vs. 15.2%, P < 0.00001).

CONCLUSION

Among HBeAg-positive patients, thymosin alpha-1 and lamivudine combination therapy may be more effective than lamivudine monotherapy, providing superior rates of biochemical response, virological response, and HBeAg seroconversion.

In vitro effect of thymosin-alpha1 and interferon-alpha on Th1 and Th2 cytokine synthesis in patients with eAg-negative chronic hepatitis B

Thymosin alpha-1 (Talpha1) has been shown to be effective in chronic hepatitis B treatment. This study investigated the effect of Talpha1 and interferon-alpha (IFNalpha) on cytokine production by peripheral blood mononuclear cells (PBMCs) of 12 patients with eAg-negative chronic hepatitis B (HBV). We evaluated the effect of incubation with Talpha1, IFNalpha or both on the synthesis of T-helper 1 (Th1) cytokines [interleukin-2 (IL-2), IFNgamma] and Th2 cytokines (IL-4, IL-10) and of antiviral protein 2',5'-oligoadenylate synthetase (2',5'-OAS) in patients and in a group of 10 healthy controls. Concerning Th1 profile, controls showed lower IL-2 synthesis than HBV patients. In HBV setting, IFNalpha/Talpha1 combination was able to increase IL-2 production significantly, when compared with baseline condition. About the Th2-cytokines, controls showed statistically lower synthesis of IL-4 and higher production of IL-10, than HBV patients. In these latter, IFNalpha increased the synthesis of IL-10 compared with baseline. Interestingly, both Talpha1 alone and the IFNalpha/Talpha1 combination reversed this effect. Finally, compared with baseline, the synthesis of 2',5'-OAS was significantly higher in the presence of Talpha1 and IFNalpha alone, and in the presence of IFNalpha/Talpha1 association, while no differences were found between controls and HBV patients. In conclusion, in PBMCs from eAg-negative HBV patients, Talpha1 alone was able to increase the antiviral protein synthesis, while in association with IFNalpha, it stimulated the IL-2 synthesis and inhibited the IFN-induced IL-10 production. These results need further investigations, but reinforce the idea of an immunotherapeutic approach for 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.

Future therapy for hepatitis B

Therapy for hepatitis B virus (HBV) infection, the most common worldwide cause of viremia and chronic liver disease, is currently limited to interferon preparations and nucleoside or nucleotide analogs. Although these treatments result in suppression of HBV replication, virologic rebounds are common when treatment is ended or when viral resistance emerges. This review considers novel approaches targeting viral or host factors involved in the HBV lifecycle, as well as immunomodulatory strategies that are likely to be used concomitantly with antiviral drugs in future research.

Effect of seasonal variation on the clinical course of chronic hepatitis B

BACKGROUND

Seasonal variation in immunity has been found in healthy individuals and in association with some diseases. It is still unknown whether seasonal variation affects the clinical course of chronic hepatitis B. Our aim in this study was to explore the effect of seasonal variation on the clinical course of chronic hepatitis B.

METHODS

The flare and remission time of chronic hepatitis B were observed in patients with hepatitis B virus (HBV) infection. All patients enrolled were followed up at least every 3 months for a mean follow-up time of 24.0 (range, 12-60) months. Seasonal decomposition was employed to analyze the relationship between seasonal variation and flares, remission, and hepatitis B e antigen (HBeAg) seroconversion in chronic hepatitis B patients during follow-up.

RESULTS

A total of 2238 patients were observed in our study. Flare and HBeAg seroconversion were seldom seen in 1076 patients (48.08%) with alanine aminotransferase (ALT) levels of less than 2.0 x upper limit of normal (ULN) during follow-up (mean, 36 months). The remaining 1162 patients (51.92%) (766, HBeAg positive; 387 anti-HBeAg positive; 9 negative for both HBeAg and anti-HBeAg) with ALT levels >or=2.0 x ULN were followed longitudinally for 12 months to judge flare, remission, and HBeAg seroconversion. Flare, remission, and HBeAg seroconversion in patients with ALT levels >or=2.0 x ULN showed clear seasonal patterns (P < 0.001), with high peaks during spring, summer, and summer, respectively. An autocorrelation correlogram showed that flares, remission, and HBeAg seroconversion occurred with distinct periodicity in winter, spring, summer, and autumn.

CONCLUSIONS

Seasonal variation might affect the clinical course of chronic hepatitis B. The role of seasonal triggering factors should be further investigated.

Novel Approaches to New Therapies for Hepatitis B Virus Infection

Hepatitis B is one of the most prevalent viral diseases in the world. It leads to chronic liver disease in 10% of infected individuals, putting them at an increased risk for liver-related morbidity and mortality from complications of cirrhosis and hepatocellular carcinoma. Despite the success of universal hepatitis B vaccination in many countries, this disease remains a major public health problem, resulting in more than 500,000 deaths per year. Although the current therapy for chronic hepatitis B (CHB) is effective, it is not optimal; novel approaches to the management of CHB are needed. An improved understanding of virus-host interactions, advances in gene therapy, the development of molecular therapies targeted at different stages of the hepatitis B virus life cycle, and new insights into various approaches of immune modulation will lead to the development of better therapeutic agents for the management of CHB. These advances herald a new era of combination therapy. In this review, we will discuss emerging therapies and potential mechanisms, and highlight the promises and pitfalls of these new treatment strategies.

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.

Entecavir for the treatment of chronic hepatitis B

Chronic infection with the hepatitis B virus remains a serious and life-threatening disease for approximately 5% of the world's population, despite the availability of effective vaccines. Although prognoses can be improved by chemotherapy, treatment options are limited and none has been consistently successful. Interferon-alpha, the longest established therapy, has limited efficacy, is slow-acting and frequently causes adverse effects. Newer drugs comprise of mainly nucleoside and nucleotide analogs. The two that are currently approved, lamivudine and adefovir dipivoxil, are well tolerated; both produce rapid and dramatic responses, but their effects may not be sustainable in the long-term due to the emergence of resistant virus. Development of resistance to lamivudine is approximately ten-times more frequent than development of resistance to adefovir dipivoxil (approximately 60 and 6%, respectively) during the first 3 years of therapy. Entecavir, a carbocyclic deoxyguanosine analog that is active against both lamivudine- and adefovir dipivoxil-resistant HBV, is in the vanguard of new antihepatitis B virus drugs that have progressed to Phase III clinical trials. It is the most potent antihepatitis B virus agent discovered to date.

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.