The largest trial of thymosin alpha-1 in sepsis found no survival benefit
In 1,106 adults with sepsis, 23.4% on thymosin alpha-1 and 24.1% on placebo had died after 28 days.
The study at a glance
- Who took part
- 1,106 adults with sepsis at 22 hospitals in China, 2016–2020
- How it was tested
- Thymosin alpha-1 or placebo injections every 12 hours for seven days; double-blind
- Main result
- Deaths at 28 days: 23.4% vs 24.1%, no significant difference
- Safety
- No safety outcome differed significantly between groups
- Published in
- BMJ, January 2025
The research, explained
Thymosin alpha-1 is an immune-signaling peptide from the thymus gland. As Zadaxin, it is approved in a number of countries, mainly for hepatitis B. Because sepsis can leave the immune system exhausted, it has also been tried as an add-on treatment.
The TESTS trial was designed to give a clear answer. At 22 hospitals in China, 1,106 adults with sepsis were randomly assigned to thymosin alpha-1 or placebo injections every 12 hours for seven days. Neither patients nor doctors knew who got which.
Of the 1,089 people analysed, 23.4% on thymosin alpha-1 and 24.1% on placebo had died 28 days later. The difference was far too small to be meaningful (a hazard ratio of 0.99). No secondary outcome or safety measure differed significantly between the groups.
Pre-planned subgroup analyses hinted that the effect might differ by age and by whether people had diabetes. Findings like these are clues for future trials, not proof.
The authors concluded there was no clear evidence that thymosin alpha-1 lowers deaths from any cause in adults with sepsis. Large trials like this one matter because smaller studies can point in a different direction.
Thymosin alpha-1 research material, where listed, is in the research shop for laboratory use.
What does this mean?
In the most rigorous sepsis test so far, thymosin alpha-1 did not change survival. Its approved uses in other countries are for different conditions.
What don’t we know yet?
Whether some groups, such as people with diabetes, could benefit would need a trial designed to test that question.
Watch and learn
Videos discussing the compounds in this article, plus background on the biology or the research methods. Each card explains its connection; recordings may predate the findings described here.
U.S. Food and Drug Administration
FDA compounding meeting: CJC-1295, AOD-9604 and thymosin alpha-1
The original discussion of these substances and proposed uses. Committee advice is separate from a final regulatory decision.
Official FDA recording · December 4, 2024
Official regulatory recording
Historical FDA discussion of CJC-1295, AOD-9604 and thymosin alpha-1. An advisory meeting is not approval or evidence of clinical benefit.
Khan Academy
Phagocytes and innate immunity
How part of the immune system responds to threats and contributes to inflammation.
Immune-system biology education
Related biology
Background on immune cells and inflammation for understanding Thymosin alpha-1. It does not demonstrate benefits of this compound or formulation.
National Institute of Mental Health
Different types of clinical research
An introduction to the different questions and designs used in studies involving people.
NIMH · US National Institutes of Health
Research skills
Helps you judge the study design or uncertainty in Thymosin alpha-1 research; it is not a trial of the compound.
Sources and references
- The efficacy and safety of thymosin α1 for sepsis (TESTS): multicentre, double blinded, randomised, placebo controlled, phase 3 trialWu et al. · BMJ · 2025
- Thymosin alpha 1: a comprehensive review of the literatureDominari et al. · World Journal of Virology · 2020
VETUD Learn explains published research in plain language. It is general information, not medical advice. Talk to a doctor before starting, stopping or changing any treatment.
In the research shop
Check the catalog for related laboratory research materials. These products are separate from the approved medicines and clinical trial formulations discussed here.
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