The answer so far

In a large trial of adults hospitalised with sepsis, thymosin alpha-1 added to standard care did not show a clear overall reduction in deaths within 28 days compared with placebo. The result does not rule out every smaller effect or answer whether the peptide helps prevent infections. Sepsis is a medical emergency: seek urgent care if it is suspected.14

On this page
  1. Why investigate it for sepsis?
  2. Who was studied?
  3. What happened over 28 days?
  4. What did the safety results show?
  5. What about smaller studies and subgroups?
  6. What was corrected and who funded the study?
  7. Sources
LINKED BUILDING BLOCKSAmino acids joined into a chainSequence and structure both matter
Conceptual schematic. Simplified and not to scale; not a scan, microscopy image or validated simulation.

Why investigate it for sepsis?

Sepsis is life-threatening organ dysfunction caused by a dysregulated response to infection. Treatment needs urgent medical care, including treatment of the infection and support for affected organs. Researchers have investigated whether changing parts of the immune response might help alongside that care. That hypothesis is not evidence that a particular peptide improves survival. If sepsis is suspected, seek emergency care immediately.41

The TESTS sepsis trial at a glanceThe figures describe the corrected study analysis in critically ill adults, not a personal prediction.
  • Participants1,106 adults randomised; 1,089 received study treatment.
  • ComparisonThymosin alpha-1 or placebo, alongside standard hospital care.
  • Deaths within 28 days127 of 542 versus 132 of 547; no clear overall reduction.
  • Wider evidenceA review of 11 trials found differing results when focusing on higher-quality studies.

Who was studied?

The TESTS trial enrolled 1,106 adults with sepsis at 22 centres in China between 2016 and 2020. They were randomly assigned thymosin alpha-1 or placebo, with standard care in both groups; neither patients nor the researchers knew the assignment during the blinded phase. Seventeen people withdrew before receiving study treatment, leaving 1,089 in the main modified analysis. Many were critically ill. The trial excluded, among others, people who were pregnant or breastfeeding and people with blood cancers or previous organ or bone-marrow transplants. These results cannot simply be applied to every person or setting.1

What happened over 28 days?

Among those included in the main analysis, 127 of 542 people receiving thymosin alpha-1 died within 28 days (23.4%), compared with 132 of 547 receiving placebo (24.1%). The estimated absolute difference was −0.7 percentage points; the 95% confidence interval ranged from −5.8 to +4.4 points. In plain language, the data do not establish a clear overall reduction and are still compatible with a range of smaller benefits or harms. At 90 days there was also no statistically significant difference in mortality.12

What did the safety results show?

Within 90 days, at least one serious adverse event was recorded in 145 of 542 people in the thymosin group and 160 of 547 in the placebo group. These were critically ill people; an event recorded during a trial is not necessarily caused by the study treatment. The study did not identify a statistically significant group difference in its safety outcomes, but it cannot establish safety for every person, longer exposure or differently manufactured product.1

What about smaller studies and subgroups?

A 2025 review combined 11 randomised sepsis trials. Its pooled result across all studies favoured thymosin alpha-1, but the analysis limited to five higher-quality trials did not find a statistically significant benefit; the reviewers said the evidence remained uncertain. In TESTS, some subgroup results differed by age or diabetes status. Such comparisons can suggest questions for further research, but they do not establish who should receive treatment, especially when many comparisons are made.31

What was corrected and who funded the study?

In May 2025 the journal corrected survival analyses and some immune-cell data after outdated entries were discovered. The corrected primary conclusion remained no clear overall reduction in 28-day mortality. Funding included public research programmes and SciClone Pharmaceuticals; the authors said the funders did not direct trial conduct or interpretation. This hospital trial does not show that thymosin alpha-1 prevents infection or treats long COVID. For other questions, see the peptide profile, the flu-vaccine evidence and the immune-support guide.21

Sources, kept close.

Selected supporting sources; this is not a complete literature review.

  1. TESTS: thymosin alpha-1 for sepsisBMJ / PubMed Central · Randomised placebo-controlled phase 3 trial, corrected 2025Accessed 2026-11-06
  2. Correction to TESTS sepsis trialBMJ · Published correction, May 2025Accessed 2026-11-06
  3. Efficacy of thymosin alpha-1 for sepsis: systematic review and meta-analysisFrontiers in Cellular and Infection Microbiology / PubMed Central · Systematic review and meta-analysis of randomised trials, 2025Accessed 2026-11-06
  4. SepsisWorld Health Organization · Public-health fact sheetAccessed 2026-11-06

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