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Thymosin Alpha-1

In clinical trials

Thymic immunomodulatory peptide

Also known as: Tα1, Thymalfasin, Zadaxin

Immune

Thymosin Alpha-1 is a naturally occurring thymic peptide and immunomodulator, approved in many countries (as thymalfasin) for hepatitis and as a vaccine adjuvant, studied for its effects on T-cell function.

Molecular & research data

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 (28 aa, N-acetylated)
CAS number
62304-98-7
Molecular formula
C129H215N33O55
Molecular weight
3108.3 g/mol
Half-life
≈2 hours
Primary targets
Toll-like receptors, T-cell maturation
Routes (research)
Subcutaneous
Storage
Lyophilised: −20 °C. Reconstituted: 2–8 °C, use within weeks.

Overview

Thymosin Alpha-1 (Tα1) is a naturally occurring thymic peptide — a 28-amino-acid immunomodulator originally isolated from thymus tissue, the organ where T-cells mature. Unlike most research peptides, it has a substantial clinical footprint: as thymalfasin (brand name Zadaxin) it is approved in many countries for chronic viral hepatitis and as an immune adjuvant, though not in the United States.

Mechanism of action

Thymosin Alpha-1 acts as a modulator rather than a blunt stimulator of immunity. Its described effects include:

  • Promoting the maturation and differentiation of T-cells
  • Influencing Toll-like receptor (TLR) signalling on immune cells
  • Helping restore balance in immune responses — enhancing antiviral and antitumour defences while tempering excessive inflammation

This balancing action is why it has been investigated across such varied settings, from chronic infection to sepsis.

Common research uses

  • Chronic hepatitis B and C (approved in many countries)
  • Vaccine adjuvant and immune-response enhancement
  • Sepsis and immune-dysregulation research
  • Adjunctive cancer immunotherapy studies

Thymosin Alpha-1 FAQ

Is Thymosin Alpha-1 approved anywhere?+

Yes. As thymalfasin (Zadaxin) it is approved in many countries for chronic hepatitis B and C and as an immune adjuvant, though it is not FDA-approved in the United States.

How does Thymosin Alpha-1 work?+

It modulates the immune system, promoting the maturation and function of T-cells and influencing Toll-like receptor signalling, helping to balance immune responses.

What is it studied for?+

Beyond its approved antiviral uses, research has examined roles in immune support, sepsis, vaccine response, and adjunctive cancer immunotherapy.

References

  1. [1]Thymalfasin (Thymosin alpha-1) — PubChemPubChem
  2. [2]Thymosin alpha 1 immunomodulation literaturePubMed

Related peptides

LL-37

Preclinical

Human cathelicidin antimicrobial peptide

LL-37 is the only human cathelicidin antimicrobial peptide, a key part of innate immunity studied for its direct antimicrobial action, wound healing, and immune-signalling roles.

Immune

Last reviewed: 2026-06-26. Information is provided for research and educational reference only — see our disclaimer.