Thymosin Alpha-1
$Immune-modulating peptide; Evidence is indication-specific
Thymosin alpha-1 is an immune-modulating peptide used in some countries as thymalfasin. It is discussed for antiviral, sepsis, vaccine-response, and immune-support contexts.
Evidence is strongest in specific disease settings such as chronic hepatitis B and some sepsis research. It should not be simplified into a universal immune booster. Distinguish immune modulation from immune stimulation. Match claims to indication, trial population, immune status, and endpoint.
Classification details
- A 28-amino-acid acetylated peptide (about 3,108 Da) cleaved from the N-terminus of prothymosin alpha by the enzyme legumain.
- First isolated from calf thymus by Allan Goldstein in 1972 and fully synthesized by 1977.
- The synthetic form, thymalfasin, is sold as Zadaxin by SciClone and is approved in 35+ countries (including China, Italy, and much of Asia) for chronic hepatitis B, chronic hepatitis C, and as an immune adjuvant.
- Not FDA-approved in the United States, though it has held Orphan Drug Designation for hepatocellular carcinoma, chronic hepatitis B, and DiGeorge syndrome.
- Thymosin alpha-1 is an immune-modulating 28-amino-acid peptide used in some countries as thymalfasin/Zadaxin. It is not U.S. FDA-approved.
A bidirectional immune modulator: it amplifies deficient responses and dampens overactive ones, rather than simply boosting immunity.
- Toll-like receptor agonism: binds TLR2, 3, 4, 7, and 9 on dendritic cells (TLR9 is the signature action), activating MyD88, IRF3, and NF-κB signaling.
- Dendritic-cell maturation: primes a Th1-biased response, shifting adaptive immunity toward the cell-mediated arm that handles intracellular viruses and tumors.
- T-cell reconstitution: drives maturation of CD4+ helper and CD8+ cytotoxic T-cells and opposes cortisol-induced thymocyte apoptosis, the basis for its use in lymphopenic states.
- NK-cell activation and cytokine rebalancing: raises IL-2, IFN-γ, and IL-12 while suppressing excess IL-6, TNF-α, and IL-1β during cytokine storms.
- Zinc dependency: it needs zinc to fold into its active shape, so subclinical zinc deficiency blunts the response.
- Mechanisms include T-cell, dendritic-cell, NK-cell, Toll-like receptor, and antiviral immune modulation. It is immune-regulatory, not simply immune-boosting.