Thymosin Alpha-1
Also referenced as: Tα1, thymalfasin, Zadaxin
An immunomodulatory thymic peptide with real clinical trial data and approvals outside the US.
- Evidence grade
- BModerate Human Evidence
Moderate Human Evidence
- Regulatory status
- Clinical Trials
Approved as thymalfasin in a number of countries for indications including chronic hepatitis B. It is not FDA approved in the United States, where it has also appeared on compounding restriction discussions.
- Human data
- Yes
Registered clinical trials exist
- Last reviewed
- September 1, 2026
Overview
Thymosin alpha-1 is a 28-amino-acid peptide originally isolated from thymic tissue, where T-cell maturation occurs. Synthetic thymalfasin is used clinically in several countries.
It is one of the few compounds in this library with a substantial international clinical literature, though results vary considerably by indication and trial quality.
Why It's Being Studied
- Chronic hepatitis B and C as an immune adjunct.
- Sepsis and critical illness immune dysfunction.
- Vaccine response in immunocompromised populations and oncology supportive care.
Mechanism of Action
It nudges the immune system's T-cells towards maturation and a more effective response.
Thymosin alpha-1 signals via Toll-like receptors, notably TLR9 in plasmacytoid dendritic cells and TLR2/TLR9 in myeloid populations, promoting Th1 differentiation, IL-2 and interferon-gamma production and increased CD4+ and CD8+ counts, while modulating regulatory T-cell activity.
Research Areas & Routes Studied
- Viral hepatitis
- Sepsis
- Vaccine response
- Oncology support
- Subcutaneous injection
Evidence Summary
Human trials exist in hepatitis, sepsis and oncology support, and the compound is approved in several countries outside the United States. Evidence quality varies by indication.
Human clinical evidence
- Randomised trials and meta-analyses in chronic hepatitis B report virological effects, with variable magnitude.
- Sepsis trials report mixed mortality findings; some randomised studies suggest benefit in subgroups.
Clinical trials
- Ongoing registered trials in critical illness and immune reconstitution.
Animal studies
- Immune reconstitution and infection models.
Reported Adverse Events in Research
- Injection-site reactions are the most common reported effect.
- Rare reports of rash and transient laboratory changes.
- Immune stimulation is a theoretical concern in autoimmune disease.
Limitations of Current Evidence
- Trial quality and reporting vary widely between regions.
- US regulatory status differs from approvals elsewhere.
Documented Research Protocols
Thymosin alpha-1 — hepatitis B trial protocols as reported
Summarise the administration schedules reported in randomised trials and meta-analyses of chronic hepatitis B.
View documented protocol
Why It Is Used
- Immune
Immune Resilience and Inflammation
Frequent infections and chronic inflammatory conditions drive interest here — and this category has more real clinical use behind it than most.
Read the case study
Research References
- Systematic review
Thymosin alpha-1 in chronic hepatitis B: meta-analysis of randomised trials
- Regulatory document
Registered thymosin alpha-1 / thymalfasin trials