Thymosin alpha-1

Thymosin alpha-1 is a chain of 28 amino acids. Allan Goldstein and colleagues isolated it in the 1970s from a calf thymus extract known as thymosin fraction 5. In the body it appears to be cut from a larger protein, prothymosin alpha, which is made in many tissues, not only the thymus. The thymus shrinks with age, and that drew researchers to the question of whether thymic peptides could support immune function as it declines.

The synthetic version is called thymalfasin and is sold under the brand name Zadaxin. Since the 1990s it has been approved in a number of countries outside the United States, including China, mainly for chronic hepatitis B and in some places for other uses, such as an add-on to vaccines. It is given as an injection in its approved uses. Because it has been used clinically for decades, there is more human data for it than for most peptides in this library.

Researchers think thymosin alpha-1 acts mainly on the cells that sense infection and organize the immune response. Lab studies report that it signals through Toll-like receptors on dendritic cells and other immune cells, which changes how those cells mature and which signaling molecules they release. Studies have linked it to T-cell maturation, higher output of interleukin-2 and interferon-gamma, and changes in natural killer cell activity. It is usually described as an immune modulator rather than a simple stimulant, because the effects reported depend on the state of the immune system.

In clinical trials, thymosin alpha-1 has generally been well tolerated, and serious side effects linked to it have been uncommon. The most reported problem is discomfort, redness or swelling where it is injected. Because it is designed to act on the immune system, there are open questions about its effects in some groups of people. Anyone weighing a compound like this should talk to a qualified clinician.

This page summarizes the research in plain words. To read the studies yourself: