Thymosin Alpha-1 (TA1): What the Research Shows

Thymosin alpha-1 (TA1) is a 28-amino-acid peptide first isolated from calf thymus extract in 1977. Unlike most research peptides, it has a long clinical record: a synthetic version, thymalfasin, is approved in more than 35 countries, mainly for chronic hepatitis B. That history makes it a useful case study in how promising immune research holds up in large trials.

This guide covers what TA1 is, where it came from, what the clinical research found, how it differs from TB-500, and what to check when sourcing it in Canada.

What thymosin alpha-1 is

Thymosin alpha-1, often shortened to TA1 or Tα1, is a 28-amino-acid peptide whose first residue carries an acetyl group. It is cut from a larger protein, prothymosin alpha, and was first isolated from thymus tissue, the gland where T cells mature. That origin is why most TA1 research focuses on the immune system.

Despite the shared name, thymosin alpha-1 is unrelated to thymosin beta-4, the parent protein of TB-500. “Thymosin” began as a label for a mixed thymus extract, and the peptides later isolated from it turned out to be biochemically distinct. If your research is about TB-500, our BPC-157 vs TB-500 guide is the better starting point.

From thymus extract to one peptide

In the 1960s, Allan Goldstein and Abraham White described “thymosin”, a thymus extract with immune activity. Their working preparation, thymosin fraction 5, was a mixture of many small peptides. In 1977 the group isolated and sequenced thymosin alpha-1 from that fraction, and it proved far more potent than the crude mixture in T-cell assays. A synthetic version, thymalfasin, was later developed and marketed as Zadaxin.

How TA1 is thought to work

Cell and animal studies describe TA1 as an immune modulator rather than a simple stimulant. Research links it to activation of dendritic cells through Toll-like receptor signalling, to T-cell maturation and to shifts in cytokine production. Those mechanisms come mostly from laboratory models, and they explain why TA1 has so often been tested in infection-related settings.

What clinical research found

Thymalfasin is approved in more than 35 countries, mainly for chronic hepatitis B, and has been studied as a vaccine adjuvant and alongside standard treatment in other settings. It is not approved in the United States.

Sepsis has been the clearest test of how TA1 performs in a large, modern trial. Earlier small trials had suggested lower death rates in treated patients. The TESTS trial, published in The BMJ in January 2025, randomized 1,106 adults with sepsis at 22 hospitals in China to TA1 or placebo. Twenty-eight-day mortality was 23.4% with TA1 and 24.1% with placebo, and the authors found no clear evidence of a benefit. A possible signal in people with diabetes was flagged as a question for future trials.

A meta-analysis published later in 2025 pooled randomized trials, including TESTS, and still reported an overall mortality signal, with large differences between patient subgroups. So the question isn’t fully closed. The pattern of promising small studies followed by a neutral large trial is common in immunology, and it’s the main reason TA1 remains a research compound outside its existing approvals.

Related thymic and immune peptides

Several peptides in our catalogue are often studied alongside TA1. Thymulin is a zinc-dependent nonapeptide produced by the thymus. Thymogen is a dipeptide, glutamyl-tryptophan, from the short bioregulator family covered in our bioregulator explainer. LL-37 is the human cathelicidin, an antimicrobial peptide of the innate immune system.

Thymosin alpha-1The acetylated 28-residue thymic peptide.View product and COA ThymulinZinc-dependent thymic nonapeptide.View product and COA ThymogenGlu-Trp dipeptide from the bioregulator family.View product and COA LL-37The human cathelicidin antimicrobial peptide.View product and COA

Sourcing thymosin alpha-1 in Canada

Pure Peptides Canada is a Canadian-owned supplier of laboratory research peptides, established in 2023. Before ordering TA1 from any supplier, check:

• The acetyl group is there. Mass spectrometry should match 3,108.3 g/mol. A version missing the N-terminal acetyl group would come in about 42 g/mol lighter.
• A batch-specific COA. The lot number should match your vial. See our COA guide.
• Purity and identity both. Here’s what HPLC and mass spectrometry each tell you.
• Cold, dry storage. The C-terminal asparagine can deamidate over time, so keep vials sealed, cold and dry. Our storage guide has the details.

Frequently asked questions

Prepared by Pure Peptides Canada. Sources checked October 2026. For laboratory research use only; not for human or veterinary use. This article summarizes published research for education and is not medical advice. Nothing here is intended to diagnose, treat, cure or prevent any disease.