Immune Modulation Research
Investigational
Thymosin Alpha-1
Also known as: Ta1, Thymalfasin, Zadaxin, thymosin alpha 1
Naturally occurring 28-amino acid thymic peptide. Studied in T-cell and immune-signalling research.
Research overview
Thymosin alpha-1 (Tα1) is a 28-amino-acid peptide first isolated from calf thymus and sequenced in 1977 by Allan Goldstein's group (Goldstein et al., PNAS 1977). A synthetic version, thymalfasin (brand Zadaxin), is licensed in more than 35 countries, including China and several countries in Asia and Latin America, mainly for chronic hepatitis B, and in some for hepatitis C or for use alongside vaccines. It is not a licensed medicine in the UK, and the US FDA has not approved it. These research materials are not the licensed medicine. The clinical evidence is mixed. A 2026 Cochrane review of 10 randomised trials in chronic hepatitis B (1,349 people) rated the evidence low or very low certainty and could not say whether it changes deaths or liver disease. A phase 3 placebo-controlled trial in 1,106 adults with sepsis found no clear difference in 28-day deaths (Wu et al., BMJ 2025). COVID-19 studies were mostly observational, and pooled analyses disagree. Whether it changes survival in any of these conditions remains uncertain. Supplied for laboratory research use only.
Mechanism of action
In mouse and cell studies, thymosin alpha-1 signalled through Toll-like receptors (sensors that detect parts of germs) and the MyD88 pathway in dendritic cells, the cells that show germ fragments to T cells, leading to their maturation and release of interleukin-12 (Romani et al., 2004). Other lab work linked it to T-cell maturation and to more MHC class I, the molecules that display protein fragments on the cell surface. Most of this comes from cell and mouse studies, and how these effects relate to outcomes in people is not settled.