Thymosin Alpha-1
28 amino acid peptide studied extensively as an immune modulator.
Also known as: TA-1, Tα1, Zadaxin
Thymosin alpha-1 is a naturally occurring peptide originally isolated from thymus extracts. It has been studied as an immune modulator for decades and is approved in several countries as Zadaxin for specific indications including chronic hepatitis B. It is not FDA approved in the United States.
Key facts
- Class
- Thymic peptide / immune modulator
- Structure
- 28 amino acid peptide with acetylated N-terminus
- Origin
- Cleavage product of prothymosin alpha, originally isolated from thymus tissue
- Regulatory status
- Approved as Zadaxin in over 30 countries; not FDA approved in the United States
- Approved indications abroad
- Chronic hepatitis B, chronic hepatitis C (as adjunct), some cancer contexts
What is thymosin alpha-1?
Thymosin alpha-1 was originally purified from bovine thymus extracts in the 1970s by Allan Goldstein and colleagues. It is a small acidic peptide derived as a cleavage product from a larger precursor protein called prothymosin alpha. Synthetic thymosin alpha-1 is manufactured using solid-phase peptide synthesis.
The compound is marketed as Zadaxin by SciClone Pharmaceuticals and is approved in more than 30 countries, including China, Italy, and several others. It is not approved by the FDA in the United States, though it has been used in clinical research and in some compassionate use settings.
Mechanism of action
Thymosin alpha-1 is considered an immune modulator rather than a direct antimicrobial or antiviral agent. Published research describes effects on T cell maturation, dendritic cell function, and toll-like receptor signaling, though the precise receptors and pathways involved are still being characterized.
- •Reported effects on maturation of T cells in the thymic environment
- •Influences dendritic cell function and antigen presentation
- •Interacts with toll-like receptor signaling pathways in preclinical research
- •Does not directly target pathogens; effects are mediated through the host immune system
Clinical trial history
Thymosin alpha-1 has been evaluated in clinical trials for chronic hepatitis B, chronic hepatitis C (often as an adjunct to interferon), certain cancers, and sepsis. A meta-analysis of thymosin alpha-1 trials for sepsis was published in 2015, and additional studies during the COVID-19 pandemic in 2020 and 2021 examined its use as an adjunct therapy in specific clinical contexts.
Clinical evidence is mixed across indications. The approved uses abroad reflect positive results in specific regulatory submissions, but major US and European regulatory bodies have not approved it, in part reflecting the heterogeneity of the clinical trial data across populations and endpoints.
Safety and regulatory context
Published safety data for thymosin alpha-1 generally describe a low incidence of serious adverse events. Injection site reactions are the most commonly reported local effects. Because it is an immune modulator, effects on autoimmune conditions are a theoretical concern that clinicians discuss in case-by-case evaluations.
In the United States, thymosin alpha-1 is not FDA approved and is not available as a prescription drug. Material sold as a research peptide is intended strictly for laboratory use and is not cleared for human administration.
Research sourcing
Thymosin Alpha-1 is listed by our research partner, GLP1 Research Lab, which supplies lyophilized peptides for laboratory use. Listings include product identifiers relevant to research documentation.
View Thymosin Alpha-1 listing at GLP1 Research LabAffiliate partnership. Metabolic Playbook may earn a commission on purchases made through this link at no additional cost to the researcher.