Thymosin Alpha-1 for Hepatitis B: What Research Shows

Chronic hepatitis B affects hundreds of millions of people worldwide and remains one of the leading causes of liver-related illness and death globally. As researchers continue to explore immunomodulatory approaches to managing this persistent viral infection, a newly published Cochrane systematic review has taken a comprehensive look at one peptide-based therapy that has drawn scientific interest for decades: thymosin-α1. The review, published in The Cochrane Database of Systematic Reviews in September 2026, pooled data from 10 randomized controlled trials and 1,349 participants to evaluate whether thymosin-α1 offers measurable benefits for people living with chronic hepatitis B (Naing et al., 2026).

What This Study Found

The Cochrane review by Naing and colleagues analyzed trials conducted across six countries — Bangladesh, China, Italy, Korea, Singapore, and Taiwan — published between 1991 and 2018. Thymosin-α1 was assessed as a monotherapy or in combination with other interventions such as interferon, pegylated interferon, lamivudine, and standard antiviral therapies including entecavir and tenofovir.

Across the pooled data, the study suggests that thymosin-α1 may reduce all-cause mortality compared to control interventions (risk ratio [RR] 0.53, 95% CI 0.29 to 0.96; 3 studies, 907 participants). Researchers found a similar signal for HBV-related mortality (RR 0.53, 95% CI 0.29 to 0.96; 3 studies, 907 participants). The analysis also suggested a potential reduction in serious adverse events (RR 0.72, 95% CI 0.53 to 0.99; 5 studies, 1,056 participants) and non-serious adverse events (RR 0.47, 95% CI 0.27 to 0.83; 5 studies, 300 participants).

On outcomes such as health-related quality of life and histological liver improvement, the study suggests thymosin-α1 may have little to no meaningful effect based on current data. The effect on HBV-related morbidity remained very uncertain, with a risk ratio of 0.86 (95% CI 0.54 to 1.40; 3 studies, 854 participants).

Critically, the authors rated the certainty of evidence as very low for all outcomes except serious adverse events, which were rated as low certainty. The primary reasons for downgrading the evidence included high or unclear risk of bias across most trials, imprecision in pooled estimates due to wide confidence intervals and small sample sizes, and substantial heterogeneity in histological outcomes (I² = 74%).

Clinical Significance

The goal of treating chronic hepatitis B is to interrupt the disease's progression toward cirrhosis, hepatic decompensation, liver failure, hepatocellular carcinoma, and death. Thymosin-α1 is a naturally occurring peptide derived from thymosin fraction 5, first isolated from thymic tissue, and is known to exert immunomodulatory and antiviral effects. It has been approved or used in clinical settings in several countries, particularly in Asia, as an adjunct therapy for hepatitis B and certain other viral infections.

The biological rationale for its use in chronic hepatitis B centers on its ability to enhance T-cell function, stimulate cytokine production, and augment innate immune responses — mechanisms that are relevant given that chronic HBV infection is characterized in part by an impaired host immune response that fails to clear the virus.

However, while the mechanistic rationale is scientifically plausible, researchers found that the current clinical trial evidence is insufficient to draw firm conclusions about thymosin-α1's benefits or harms in this patient population. The authors noted that no ongoing trials were identified, and 16 additional studies remain awaiting assessment due to incomplete reporting — a gap that leaves meaningful questions unanswered.

The findings are notable in that the directional trends across mortality and adverse event outcomes were consistently favorable, but the very low certainty of evidence means these signals must be interpreted with significant caution. As the authors state, they are not sure whether thymosin-α1 reduces all-cause mortality, serious adverse events, or HBV-related mortality based on the available evidence base.

Current Access and Compliance Context

Thymosin-α1 (commercially available as Zadaxin in several countries) has been in clinical use for over two decades in parts of Asia, Europe, and Latin America, though it does not currently hold regulatory approval from the U.S. Food and Drug Administration (FDA) for any indication. In countries where it is approved, it is typically administered via subcutaneous injection, and the treatment protocols studied in clinical trials have varied considerably in terms of dose, duration, and co-intervention strategy — a variability that likely contributes to the inconsistent results seen across individual trials.

The trials included in this Cochrane review administered thymosin-α1 across a range of dosing regimens, with follow-up periods ranging from six months to five years. The authors found no statistically significant differences in outcomes between trials that used thymosin-α1 as monotherapy versus those that combined it with other agents, though the evidence base for subgroup analyses was limited.

For clinicians and patients, the heterogeneity in trial design, the age of many included studies, and the low-to-very-low certainty ratings underscore the importance of individualized decision-making grounded in current standard-of-care antiviral guidelines. Modern nucleos(t)ide analogues such as tenofovir and entecavir remain the cornerstone of chronic hepatitis B management per major international guidelines.

What Patients Should Know

If you are living with chronic hepatitis B and have encountered information about thymosin-α1, there are several important points to understand from this research:

The evidence is promising in direction but weak in certainty. The study suggests that thymosin-α1 may be associated with lower rates of mortality and adverse events in people with chronic hepatitis B, but the researchers themselves emphasize that the certainty of this evidence is very low. This means the true effect could be different from what the pooled data suggests.

Standard antiviral therapy remains the established foundation of treatment. Thymosin-α1 was studied both as a standalone therapy and alongside established antivirals. Neither approach produced high-certainty evidence of benefit in this review.

More research is needed. The Cochrane authors identified no ongoing trials and noted 16 studies awaiting full assessment. High-quality, adequately powered, prospective randomized trials with standardized outcomes are needed before thymosin-α1 can be confidently recommended or dismissed as an adjunct therapy for chronic hepatitis B.

Safety signals were relatively favorable. Across the included trials, thymosin-α1 was associated with fewer serious and non-serious adverse events compared to control groups, though again, the certainty of this evidence is low. Patients should discuss any therapy, including peptide-based treatments, with a qualified healthcare provider before initiating use.

Conclusion

This 2026 Cochrane systematic review represents the most rigorous synthesis of clinical trial data on thymosin-α1 for chronic hepatitis B to date. While the study suggests a potentially favorable directional trend in mortality and adverse event outcomes, the very low certainty of evidence across most outcomes means that definitive clinical conclusions cannot yet be drawn. The findings highlight a clear need for well-designed, adequately powered future trials to clarify whether thymosin-α1 has a meaningful role in the management of chronic hepatitis B.

If you are interested in learning more about peptide-based therapies and whether they may be appropriate for your individual health circumstances, we encourage you to consult with a qualified healthcare provider who is knowledgeable in this area. Visit peptideassociation.org/find-a-doctor to find a physician in your area who can provide personalized, evidence-informed guidance.

Medical Disclaimer: This article is intended for educational and informational purposes only and does not constitute medical advice, diagnosis, or treatment. The content presented here is based on published peer-reviewed research and is not intended to replace consultation with a qualified healthcare professional. Always seek the guidance of your physician or other licensed health provider with any questions you may have regarding a medical condition or treatment.

Citation: Naing C, Ni H, Aung HH, et al. Thymosin-α1 for people with chronic hepatitis B. Cochrane Database of Systematic Reviews. 2026;(9). doi:10.1002/14651858.CD014610.pub2. PMID: 42713852.