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PeptideFactSheets

Peptide · Fact sheet

Thymosin alpha-1

Also known as Tα1 · thymalfasin · Zadaxin

Thymosin alpha-1 is a 28-amino-acid immune-signaling peptide studied in infections, sepsis, liver disease, and cancer-support settings. It is not FDA approved to prevent or treat infection, 'boost immunity,' treat cancer, or for any other U.S. use.

Not FDA approvedModerate human evidence
Gut & immune health

What is Thymosin alpha-1?

Thymosin alpha-1 is a synthetic version of a peptide derived from prothymosin alpha and studied as an immune modulator.

It is distinct from thymosin beta-4 and from the TB-500 fragment; the shared 'thymosin' name does not make their biology or evidence interchangeable.

Benefits people look for

Trials have explored chronic hepatitis, sepsis, immune dysfunction, respiratory infections, and combinations with cancer treatment.

Broad 'immune boost' marketing flattens condition-specific and sometimes conflicting trial findings into a claim the evidence cannot support.

What the evidence supports

  • Some trials and meta-analyses report signals in selected sepsis or hepatitis outcomes.
  • Other randomized studies found no significant benefit on key clinical endpoints, so results cannot support a universal immune claim.
All research areas
  • Sepsis and critical-illness immune dysfunction
  • Chronic hepatitis B and C
  • Respiratory and other infections
  • Immune support alongside cancer treatment
  • Condition-specific immune modulation
  • Adjunctive research in infections, liver disease, and cancer care

Anecdotal reports & lived experiences

Reports describe what someone noticed. They cannot establish cause, typical results, or how often a side effect happens.

No attributable personal reports are summarized here yet. The benefits above describe research interests; the side effects below come from the cited medical sources.

We do not fill this gap with unsourced testimonials or estimated success rates.

Side effects & risks

  • FDA identifies potential immune reactions, peptide impurities, active-ingredient characterization problems, and inadequate safety information for compounded products.
  • Immune modulation can have condition-specific tradeoffs, especially in severe illness or alongside other treatments.
  • Unapproved products introduce quality, purity, sterility, strength, and labeling uncertainty.

This is a summary of the cited evidence, not a complete product label. A lack of human safety data does not establish safety.

Clinical research: how strong is it?

Moderate human evidence

Multiple human trials exist, including randomized studies in hepatitis and sepsis, but results vary by condition and design. The evidence does not support a general immune-enhancement claim or an FDA-approved U.S. use.

Selected research to read

FDA approval & research status

Thymosin alpha-1 has no FDA-approved product or indication. FDA has specifically stated that it is not approved to treat or prevent COVID-19 or any other condition and identifies compounded-product evidence and quality concerns.

No FDA-approved use is documented in the records summarized on this page.

No U.S. approval despite human research

Thymosin alpha-1 has human studies and non-U.S. product history, but FDA states it has no approved U.S. indication and identifies compounded-product concerns.

This summarizes the cited product or research record. Trial phases do not establish successful completion of earlier stages, and a stopped program is not ongoing development. Approval applies only to the labeled product, use and population.

What we still don’t know

  • Which specific conditions and patient subgroups, if any, have a reproducible clinical benefit
  • Long-term and uncommon harms
  • How it compares with current standard treatments
  • Whether findings from one formulation, country, or clinical setting transfer to another

The takeaway

Thymosin alpha-1 has more human research than many experimental peptides, but the evidence is condition-specific and mixed. It should not be described as a general immune booster or an FDA-approved U.S. therapy.

Sources & further reading

Medical evidence and regulatory sources are listed here. Personal reports are linked separately in the experiences section.

  1. 1
    fdaFDA: safety risks for selected compounded bulk substances

    FDA's current substance-specific summary of evidence gaps and potential safety risks.

  2. 2
    fdaFDA annual report: unapproved thymosin alpha-1 claims

    FDA statement that thymosin alpha-1 is not approved to treat or prevent COVID-19 or any other condition.

  3. 3
    pubmedETASS randomized sepsis trial

    Multicenter randomized study in severe sepsis with important setting and design limits.

  4. 4
    pubmedPhase 3 chronic hepatitis B trial

    Randomized placebo-controlled trial whose primary response difference was not statistically significant.

  5. 5
    pubmedRandomized study in HBV-related cirrhosis

    Large randomized study finding no significant difference in the composite clinical endpoint.

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