Thymosin Alpha-1
Thymosin Alpha-1 (Tα1) is a synthetic 28-amino acid peptide derived from the naturally occurring thymosin fraction 5 found in the thymus gland, specifically designed to enhance immune system function and regulation. Originally isolated from thymic extracts, Thymosin Alpha-1 represents a critical immunomodulatory peptide that plays a pivotal role in T-cell maturation, natural killer (NK) cell activation, and overall adaptive immune competence. The peptide sequence is: Ac-Ser-Asp-Ala-Ala-Val-Asp-Thr-Ser-Ser-Glu-Ile-Thr-Thr-Lys-Asp-Leu-Lys-Glu-Lys-Lys-Glu-Val-Val-Glu-Glu-Ala-Glu-Asn-OH.
This peptide has gained considerable attention in immunology and infectious disease medicine for its studied role in enhancing immune responses against viral infections, supporting cancer immunotherapy, and restoring immune function in immunocompromised populations. Thymosin Alpha-1 exhibits excellent bioavailability via subcutaneous administration and maintains therapeutic activity through its ability to modulate both innate and adaptive immunity, making it unique among immunomodulatory peptides.
Overview
Thymosin Alpha-1 demonstrates excellent water solubility and rapid absorption following subcutaneous injection. The peptide exhibits high affinity for immune cell receptors and is metabolized primarily through proteolytic degradation. Despite its relatively short plasma half-life, the peptide's biological effects persist through sustained immune cell activation for extended periods post-administration.
Chemical structure & Properties
- Molecular Formula: C129H215N33O55
- Molecular Weight: 3108.7 Da
- Sequence: Ac-SDAAVDTSSEITTKDLKEKKEVVEEAEN, 28 residues, free acid.
- International brand name: Zadaxin (thymalfasin), approved in over 30 countries.
- Half-life: Approximately 2-4 hours (plasma elimination)
- Stability: Stable in aqueous solution but requires careful storage due to proteolytic sensitivity
Mechanism of Action
Thymosin Alpha-1 exerts its therapeutic effects through multiple interconnected immunomodulatory mechanisms:
Areas Investigated in
the Research Literature
Current Clinical Evidence
Safety Profile and Considerations
Regulatory Status and Legal Considerations
Regulatory information current as of 28 August 2026. This is a summary, not legal or medical advice, and status can change.
FDA Status
- United States:Investigational status in the United States. Thymosin alpha-1 is not on the FDA's active Category 2 list. It appears in the nominated-but-withdrawn section of the FDA's bulk drug substances page, and it is not on the 503A bulk drug substances list, so no lawful compounding pathway currently exists in the United States. This does not affect its existing approvals in other countries.
- European Union: Clinical use established in several European countries for specific indications
- Asia-Pacific: Approved for clinical use in multiple countries for viral infections and cancer adjuvant therapy
- Regulatory Position: Varies by jurisdiction with established clinical use in many countries
Clinical Practice Status
- Infectious Disease: Recognized therapy for viral infections in approved jurisdictions
- Oncology: Accepted adjuvant therapy for cancer immunotherapy support
- Geriatric Medicine: Utilized for age-related immune decline management
Legal Availability
- Commercial Status: Approved as a medicine in some countries. Not FDA approved in the United States.
- Research Access: Available through clinical trials and research protocols in other jurisdictions
- Quality Control: Manufacturing standards vary by country and regulatory framework
- Clinical Use: Established clinical practice in multiple international healthcare systems
Conclusion
What the evidence supports
Thymosin alpha-1 is an immunomodulatory peptide studied for effects on T-cell and NK-cell activity, and it is approved in several countries outside the United States (as Zadaxin) for viral infections and as a cancer adjuvant. In the United States it is not FDA approved and remains in FDA Category 2; the oncology and antiviral literature describes research and non-US clinical settings, not established US therapeutic use. This page summarizes the published research and nothing further.
THYMOSIN ALPHA-1 SCIENTIFIC
DATA SUMMARY
About this library
This library is published for education. It summarizes published research on compounds studied in this field. Many have no approved medical use, and several cannot lawfully be compounded in the United States. The presence of a page here does not mean Paragon offers that compound. Nothing on these pages is an offer to treat.
This page is general education about a compound studied in this field. Nothing here is medical advice, a recommendation, or an offer to prescribe or supply. A page appearing in this library does not mean Paragon Sports Medicine offers that compound.
Disclaimer: This information is provided for educational purposes only and does not constitute medical advice. Thymosin Alpha-1 regulatory status varies by jurisdiction. Patients should consult with qualified healthcare providers familiar with local regulations before considering any immunomodulatory therapy.
Statements on this page have not been evaluated by the FDA and are not intended to diagnose, treat, cure, or prevent any disease. Many peptides described here are not FDA approved for the uses discussed, and some cannot lawfully be compounded in the United States. Nothing on this page is medical advice or a recommendation for any individual. Whether any therapy is appropriate depends on your history, your laboratory results, and a clinical evaluation. Individual results vary. This page is published for education. Use of this site does not create a physician-patient relationship.