NO. 026 · CYTOPROTECTION
THYMOSIN α-1
TA-1 · Zadaxin · Immune Modulator
ALIASES
Thymosin alpha-1, Tα1, Thymalfasin, Zadaxin
CLASS
Synthetic 28-residue thymic peptide · immunomodulator · approved as Zadaxin in 35+ countries
FORMULA
C₁₂₉H₂₁₅N₃₃O₅₅
SEQUENCE
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
HALF-LIFE
~2 hours plasma (subcutaneous)
ROUTES
Subcutaneous (approved Zadaxin in non-US jurisdictions)
MECHANISM OF ACTION
Twenty-eight-amino-acid peptide cleaved from prothymosin-alpha in the thymus gland. Marketed as Zadaxin in EU and Asia for chronic hepatitis B/C and immune dysfunction. FDA orphan drug status. Modulates TLR9 signaling and drives T-cell + NK-cell activity.
EVIDENCE GRADES
Multiple Phase 3 trials supporting Zadaxin approval in 35+ countries as combination therapy with IFN/pegIFN.
Wu 2013 Crit Care · 28-day mortality reduction in severe sepsis.
Multiple Chinese-population reports; not consistently meeting Western trial methodology.
SAFETY
Side effects
- Generally well-tolerated
- Mild injection-site reactions
- Rare flu-like symptoms
Drug interactions
- Immunosuppressive medications (theoretical)
Contraindications
- Active autoimmune disease (theoretical)
REGULATORY STATUS
FDA · Not FDA-approved. Research-use only in the United States.
WADA · Not currently listed on the WADA Prohibited List.
STORAGE
Lyophilized · -20 °C 24 months
Reconstituted · 2-8 °C, 28 days
PEER-REVIEWED EVIDENCE
- Goldstein AL, Goldstein AL. From lab to bedside: emerging clinical applications of thymosin alpha 1. Expert Opin Biol Ther 2009. PMID 19392576. link →
- Wu J, Zhou L, Liu J, et al.. The efficacy of thymosin alpha 1 for severe sepsis (ETASS): a multicentre, single-blind, randomized and controlled trial. Crit Care 2013. PMID 23327199. link →
- Liu Y, Pan Y, Hu Z, et al.. Thymosin Alpha 1 Reduces the Mortality of Severe Coronavirus Disease 2019. Clin Infect Dis 2020. PMID 32442287. link →
FAQ · 7 QUESTIONS
▶ What is thymosin alpha-1?
Thymosin alpha-1 (Tα1) is a 28-amino-acid synthetic peptide derived from thymosin fraction 5, originally isolated from calf thymus by Allan Goldstein in the 1970s. It is an immunomodulator approved in more than 35 countries as Zadaxin.
▶ Is thymosin alpha-1 FDA-approved?
Not in the United States. It is approved in 35+ countries including Italy, Brazil, Singapore, and across much of Asia for chronic hepatitis B and C and as an immune-system adjuvant.
▶ How does it work?
Proposed mechanisms include TLR9 agonism, dendritic-cell maturation, increased CD4+ and CD8+ T-cell function, enhanced NK cell activity, and modulation of Th1/Th2 cytokine balance toward Th1.
▶ What's the approved indication?
Chronic hepatitis B (with IFN-α or pegIFN), chronic hepatitis C (combination with antivirals), as a vaccine adjuvant, and post-chemotherapy immune support. Approved indication varies by country.
▶ Approved dose?
Standard approved dosing in non-US jurisdictions is subcutaneous 1.6 mg twice weekly for 6-12 months in hepatitis B/C. This wiki does not recommend any US off-label dose.
▶ Brand names?
Zadaxin is the principal brand, marketed by SciClone Pharmaceuticals.
▶ Is it on the WHO essential medicines list?
Thymosin alpha-1 is on the essential medicines list in some countries (e.g., China) but not the WHO Model List as of the latest revision.
SIGNATURE MOVES
Boosts T-cell + NK-cell activity. Immunomodulation.
EU/Asia approved. FDA orphan drug status.
SOURCED FROM GIGACOMPOUNDS
Reference compounds documented on this page are available as research-grade material at GigaCompounds · ≥99% purity · per-batch Certificate of Analysis. For laboratory research use only. No human dose is recommended by this wiki.
▶ LAST UPDATED · 2026-05-19