Thymosin Alpha-1 Research for Chronic Hepatitis B

Chronic hepatitis B (CHB) affects hundreds of millions of people worldwide and remains one of the leading infectious causes of cirrhosis, liver cancer, and liver-related death. Finding effective therapies that go beyond viral suppression to genuinely improve immune control of the hepatitis B virus (HBV) has been a long-standing challenge in hepatology. A 2026 Cochrane systematic review by Naing, Ni, Aung, and colleagues examined whether thymosin alpha-1 (Tα1)—a naturally occurring thymic peptide with known immunomodulatory and antiviral properties—might offer meaningful clinical benefits for people living with chronic hepatitis B. The findings are cautiously signal-generating, but the researchers are clear: the certainty of the available evidence remains low to very low, and firm conclusions cannot yet be drawn.

What This Study Found

The Cochrane review identified 10 randomized controlled trials (RCTs) conducted across six countries—Bangladesh, China, Italy, Korea, Singapore, and Taiwan—involving a total of 1,349 participants (age range 17–75 years; 77.5% male). Trials were published between 1991 and 2018, with follow-up periods ranging from six months to five years after the end of treatment. Thymosin alpha-1 was evaluated as monotherapy or in combination with co-interventions such as interferon, pegylated interferon, lamivudine, entecavir, or tenofovir.

Across the prespecified outcomes, the study suggests the following signals:

• All-cause mortality: Thymosin alpha-1 may reduce all-cause mortality compared with control interventions (RR 0.53, 95% CI 0.29 to 0.96; 3 studies, 907 participants), though the certainty of evidence was rated very low.
• Serious adverse events: Researchers found a possible reduction in serious adverse events (RR 0.72, 95% CI 0.53 to 0.99; 5 studies, 1,056 participants). This was the only outcome rated low certainty—the highest certainty level achieved in the review.
• HBV-related mortality: The study suggests a potential reduction (RR 0.53, 95% CI 0.29 to 0.96; 3 studies, 907 participants; very low certainty).
• Non-serious adverse events: A possible reduction was observed (RR 0.47, 95% CI 0.27 to 0.83; 5 studies, 300 participants; very low certainty).
• Health-related quality of life: Based on a single trial of 161 participants, thymosin alpha-1 may have little to no effect on quality of life scores (MD 0.70, 95% CI −2.55 to 3.95; very low certainty).
• Histological improvement: Results were highly inconsistent across trials (I² = 74%), and the pooled estimate was inconclusive (RR 0.51, 95% CI 0.13 to 2.06; very low certainty).
• HBV-related morbidity: The evidence was very uncertain, with confidence intervals that crossed the line of no effect (RR 0.86, 95% CI 0.54 to 1.40; very low certainty).

Importantly, subgroup analyses found no statistically significant differences in effect based on whether thymosin alpha-1 was administered alone or alongside co-interventions (P ≥ 0.05 for all outcomes).

Clinical Significance

Thymosin alpha-1 is a 28-amino acid peptide derived from thymosin fraction 5, first isolated from thymic tissue. It is believed to enhance T-cell–mediated immune responses and has been explored across a range of viral infections and immune dysregulation conditions. Its theoretical appeal in chronic hepatitis B lies in its potential to restore the immune system's ability to suppress or clear HBV—a virus that actively evades host immunity in chronically infected individuals.

The direction of the effects observed in this Cochrane review is encouraging in the sense that most point toward potential benefit. However, the clinical significance of these findings is substantially limited by the quality of the underlying evidence. The review authors downgraded certainty ratings primarily due to:

• High or unclear risk of bias in most included trials;
• Imprecision, including wide confidence intervals and small sample sizes;
• Inconsistency, particularly the substantial heterogeneity in histological improvement data (I² = 74%).

The researchers explicitly state that they are not confident whether thymosin alpha-1 meaningfully reduces all-cause mortality, serious adverse events, HBV-related mortality, or non-serious adverse events, nor whether it affects quality of life or histological outcomes. This is a critical distinction: a signal is not a conclusion, and low-to-very-low certainty evidence should not be interpreted as established clinical effectiveness.

Notably, the review identified no ongoing trials at the time of the most recent search (June 2026), and 16 studies remain awaiting assessment due to incomplete reporting. The absence of new trial activity is itself a clinically relevant observation—it suggests that the research pipeline for thymosin alpha-1 in hepatitis B may have stalled, which has implications for whether higher-certainty evidence will become available in the near future.

Current Access and Compliance Context

Thymosin alpha-1 is available in several countries under the brand name Zadaxin and has regulatory approval in some jurisdictions for use in chronic hepatitis B and C, as well as in certain immunocompromised patients. In countries where it is approved, it is typically administered as a subcutaneous injection, often twice weekly over a defined treatment course.

In the United States, thymosin alpha-1 does not hold FDA approval and is currently considered an investigational peptide. Clinicians and patients interested in thymosin alpha-1 should be aware that its regulatory status varies significantly by country and that access through compounding pharmacies or clinical investigation protocols may be the primary avenues in jurisdictions where it lacks market authorization.

Adherence to the injection schedule in existing trials was not uniformly reported, which itself represents a limitation in interpreting outcomes. Any future trials would benefit from rigorous adherence monitoring and standardized reporting of co-interventions to reduce the heterogeneity that currently limits evidence synthesis.

What Patients Should Know

If you or someone you care for is living with chronic hepatitis B, it is natural to be interested in emerging or adjunctive therapies that might improve outcomes beyond what current first-line antivirals offer. Here is what the current evidence base supports—and what it does not:

• Thymosin alpha-1 is not an established standard-of-care treatment for chronic hepatitis B in most countries. Current evidence is insufficient to support or refute its routine clinical use.
• The signals observed are preliminary. The Cochrane review suggests possible reductions in mortality and adverse events, but the very low certainty of evidence means these findings require confirmation in well-designed, adequately powered, low-risk-of-bias clinical trials.
• Existing approved therapies remain the foundation of CHB management. Nucleos(t)ide analogues such as entecavir and tenofovir have robust evidence bases and well-characterized safety profiles. Any discussion of thymosin alpha-1 should occur within the context of—not as a replacement for—established treatment.
• Speak with a qualified healthcare provider. If you are interested in thymosin alpha-1, a physician experienced in peptide-based therapies and infectious disease can help you understand what the current evidence does and does not support, assess whether any clinical trial participation might be appropriate, and evaluate your individual risk-benefit profile.

Conclusion

The 2026 Cochrane systematic review by Naing and colleagues represents the most comprehensive synthesis to date of randomized trial evidence on thymosin alpha-1 for chronic hepatitis B. While the direction of findings tentatively suggests possible benefits in reducing mortality and adverse events, the certainty of evidence is low to very low across all outcomes. The absence of ongoing trials further underscores the need for renewed, high-quality clinical investigation before thymosin alpha-1 can be considered an evidence-based therapeutic option in this population.

At the Peptide Association, we are committed to providing accurate, evidence-based information about peptide science to both patients and clinicians. If you are interested in exploring whether peptide-based therapies may be appropriate for your health situation, we encourage you to consult with a qualified, knowledgeable physician. Visit peptideassociation.org/find-a-doctor to find a healthcare provider in our network who is experienced in peptide therapeutics.

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Medical Disclaimer: This article is intended for educational and informational purposes only and does not constitute medical advice, diagnosis, or treatment recommendations. The content reflects published research and is not a substitute for professional medical consultation. Always seek the guidance of a qualified healthcare provider regarding any medical condition or treatment, including decisions about starting, stopping, or modifying any therapy.

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AMA 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.