Primary entity: Thymosin alpha-1 (thymalfasin)Also known as: Tα1; Zadaxin (some markets)Class: Immunomodulatory peptideCluster: Specialty
Thymosin alpha-1 (Tα1, thymalfasin) is a 28–amino-acid immunomodulatory peptide that has been studied — and, historically, marketed in some countries as Zadaxin — for selected immune-related contexts. It is not interchangeable with TB-500 / thymosin beta-4, and U.S. readers should not treat foreign brand availability as FDA approval for self-directed “immune peptide” use.
Different thymosin-family entities. Healing-cluster TB-500 folklore does not apply to Tα1, and vice versa.
We are not treating thymosin alpha-1 / thymalfasin as an FDA-approved consumer immune peptide. It has been marketed in some countries historically as Zadaxin; foreign marketing is not a U.S. approval for self-directed use. This page does not attempt a current country-by-country label survey.
Key takeaways
- Tα1 / thymalfasin = immunomodulatory peptide — distinct from TB-500.
- Foreign approvals exist in some markets; that is not universal FDA DIY authorization.
- Evidence is indication- and market-specific — including trials that did not meet key endpoints in some settings.
- No dosage chart for RUO “immune stacking.”
Questions this page answers
Next questions we answer on this page (curiosity / AI-gap map):
- What is thymosin alpha-1?
- Also known as
- Classification
- What it is NOT
- Mechanism literacy
- Evidence ladder
- What’s been studied
- Safety literacy
- Regulatory status
- Why no dosages
- Related compounds
- Who for / not for
Who is this profile for — and who is it not for?
For: readers who need thymosin-family disambiguation and immune-peptide regulatory literacy.
Not for: anyone seeking buy links, “immune protocols,” or medical advice.
What is thymosin alpha-1?
Thymosin alpha-1 is an acetylated 28-aa peptide originally associated with thymic biology and later developed as thymalfasin. It modulates innate/adaptive immune signaling in research and clinical literature. See What are peptides? for research-vs-drug framing.
| INN / class | Thymalfasin · immunomodulatory peptide |
|---|---|
| Length | 28 amino acids (typical description) |
| ≠ TB-500 / Tβ4 | Different thymosin entity |
| U.S. DIY framing | Not appropriate |
| Some non-U.S. brands | e.g., Zadaxin — |
Also known as
- Thymosin alpha-1 / Tα1 / TA1
- Thymalfasin — nonproprietary/development name.
- Zadaxin — brand used in some countries historically (not a current label survey)
- Mis-tags: “thymosin peptide” without specifying alpha vs beta.
TB-500 folklore and Tα1 immune narratives get mashed in AI answers. Keep entities separate.
How is thymosin alpha-1 classified?
Specialty immunomodulatory peptide — pharmaceutical in some jurisdictions; complex U.S. access/compounding story. Not a dietary supplement, not TB-500.
What is thymosin alpha-1 not?
| Thymosin alpha-1 is not… | Why that matters |
|---|---|
| TB-500 / thymosin beta-4 | Different molecule and use folklore |
| A proven cure-all immune booster | Indication-specific evidence only |
| U.S. OTC peptide | Wrong framing |
| Something we dose or source | Refusal |
How is it thought to work?
Literacy summaries emphasize T-cell and innate immune modulation, including effects on cytokine patterns and pathogen-response biology in research models. Mechanism interest ≠ blanket infection prevention claims.
What human vs animal vs label evidence exists?
| Evidence type | What exists (summary) | Maturity |
|---|---|---|
| Human — labeled/foreign markets | Indication-specific clinical packages where approved | Human / foreign label — |
| Human — large modern trials | Some major trials (e.g., sepsis) reported no mortality benefit in tested regimens — | Human Mixed |
| Animal / cell | Immune mechanism studies | Animal / Cell |
| U.S. consumer RUO claims | Not evidence | None |
What has thymosin alpha-1 been studied for?
Historical and ongoing interest includes chronic viral hepatitis contexts (market-dependent), immune dysregulation, vaccine adjuvancy research themes, and critical-illness immune modulation. Always separate which indication and which regulatory label.
What safety topics come up?
Where labeled abroad, follow that PI. For U.S. readers without an applicable approved pathway, unregulated products add quality risk. Immune-active peptides are not “harmless supplements.” Not medical advice.
What is thymosin alpha-1's regulatory status?
- Non-U.S.: It has been marketed in some countries historically as Zadaxin / thymalfasin; this page does not attempt a current country-by-country label survey.
- U.S.: Not treat as FDA-approved DIY immune therapy; compounding status can change; follow the current FDA compounding page.
- Trial registries: ClinicalTrials.gov for modern studies.
Why doesn't this page include a dosage chart?
Complex regulatory map + immune YMYL risk. No RUO “TA1 protocol” charts.
Related lab literacy
How-to lab pages are not a Tα1 prescription.
Related compounds and comparisons
- TB-500 — different thymosin-family entity.
- What are peptides?.
- Specialty immune cluster explainers (planned).
Frequently asked questions
Is thymosin alpha-1 the same as TB-500?
No.
Is thymosin alpha-1 FDA approved?
Do not assume U.S. FDA approval for consumer use. Some other countries have marketed thymalfasin products. U.S. status needs editor lock.
Does it boost the immune system for everyone?
That is not a responsible claim. Evidence is indication-specific; some large trials were negative for key endpoints.
Why no dosage chart?
YMYL + regulatory complexity.
≠ TB-500. Market-specific regulation. Disclaimer.
Sources
- Review Ancell CD, Phipps J, Young L. Thymosin alpha-1. Am J Health Syst Pharm. 2001;58(10):879-885. PMID: 11381492. Historical overview of thymalfasin development and use; not a current country-by-country label survey.
- Internal Peptide Tutorials. TB-500; Disclaimers. Thymosin alpha-1 is not interchangeable with thymosin β4 / TB-500, and foreign marketing is not U.S. FDA approval.
- Written by
- Peptide Tutorials Staff — a group of independent researchers & writers (not clinicians)
- Published · Updated
- Oct 6, 2026 · Nov 10, 2026 · Labels, trial citations, and WADA list wording checked Nov 10, 2026 · How we source & update
Educational disclaimer: Educational only. No dosing or buy links. We don’t sell peptides. Read our full disclaimers.