Thymosin α-1

From Retapedia, the free peptide encyclopedia
"Thymalfasin" redirects here. For other uses, see Thymosin α-1 (disambiguation).
Medical disclaimer. This article is for informational purposes only and does not constitute medical advice. Consult a qualified clinician before considering any compound discussed below. See Retapedia : Medical disclaimer.

Thymosin α-1 (also known as Thymalfasin or Tα1) is a therapeutically researched peptide studied for its effects on anti-inflammatory, anti-aging, injectable. Thymosin α-1 (thymalfasin) is a 28-amino-acid immune-modulating peptide, approved abroad as Zadaxin for hepatitis B. Permitted under WADA rules.

Thymosin α-1 (international nonproprietary name thymalfasin) is a 28-amino-acid immune-modulating peptide cleaved from prothymosin alpha, the precursor protein encoded by the human PTMA gene. It acts on dendritic cells and T-cell maturation through Toll-like receptor signalling, sharpening the adaptive immune response rather than driving tissue growth. Marketed as Zadaxin, it is an approved prescription medicine in roughly 30 countries, including China and Italy, for chronic hepatitis B and as a vaccine adjuvant in immunocompromised patients; it has never been approved by the FDA in the United States, where it holds only orphan-drug designation.

Natty status
Thymosin α-1 is generally regarded as compatible with natural bodybuilding, though competitive federations may differ. See § Natty status.
Contents [hide]
  1. 1 Overview
  2. 2 Mechanism of action
  3. 3 Reported effects
  4. 4 Dosage and administration
  5. 5 Natty status
  6. 6 Research
  7. 7 Related compounds
  8. 8 References
  9. 9 External links

Overview

It is one of the few compounds in this encyclopedia with genuine late-stage clinical evidence rather than rodent data alone.

Thymosin α-1 is permitted under World Anti-Doping Agency (WADA) rules.

That sets it apart from thymosin β-4 (TB-500), a tissue growth factor that WADA restricts under class S2.

Mechanism of action

Sharpens adaptive immunity by driving T-cell maturation and dendritic cell activity. Approved abroad as Zadaxin for chronic hepatitis B and as a vaccine adjuvant. Subcutaneous injection.

Reported effects

Effects reported in the literature and from preclinical models include:

  • Stimulates T-cell differentiation and enhances thymic output, helping restore immune function lost to age-related thymic involution. [2] Preclinical
  • Shows immunomodulatory, anti-inflammatory, and antioxidant activity, and modulates dendritic cell and macrophage activity. [2] Preclinical
  • Reported to improve vaccine response and mitigate immunosenescence in elderly people. [2] Anecdotal
  • Acts on immune signaling and inflammatory regulation pathways relevant to autoimmune thyroid disease such as Hashimoto's thyroiditis, with evidence limited to preclinical, mechanistic, and early exploratory reports. [1] Preclinical
  • Subcutaneous injection every 12 hours for seven days did not reduce 28-day all-cause mortality against placebo in 1089 adults with sepsis. [3] Phase III
  • No secondary or safety outcome differed significantly from placebo in a 1106-participant sepsis trial. [3] Phase III

Evidence grades: FDA approvedApproved (non-US)Phase IIIPhase IIPhase IPreclinicalAnecdotal

Dosage and administration

⚠
Dosage information is included for encyclopedic purposes only. Retapedia does not provide medical advice. See Retapedia : Medical disclaimer.

Subcutaneous

  • Chronic hepatitis B (approved regimen outside the US): 1.6mg twice weekly

Natty status

See also: Peptide § Natty status

Thymosin α-1 is generally regarded as compatible with the natty designation, particularly when used for therapeutic healing purposes. Opinions vary across natural bodybuilding federations, and athletes who compete should consult the rulebook of their respective sanctioning body.[4]

Research

14 active clinical trials on record — highest phase: Phase 3
View on ClinicalTrials.gov · fetched Aug 4, 2026

The peptide has been the subject of 4 studies and reference works collected on this site. Additional bibliography is in § External links below.

Other peptides in this catalogue with overlapping mechanisms or status:

Glutathione Natty
The body's master intracellular antioxidant. Scavenges free radicals and supports liver phase-II detoxification. Regenerates vitamins C and E. Used for liver health, skin brightening, and anti-aging.
Epithalon Not natty
Marketed as an anti-aging peptide. In preclinical studies it boosts telomerase activity, supports the body's own melatonin production, and shows antioxidant effects. Human evidence is minimal.
Selank Not natty
Synthetic tuftsin analogue used as an anxiolytic nootropic. Reported to act on GABA and monoamine signalling without sedation or dependence. Registered in Russia; no FDA or EMA approval.
Sermorelin Not natty
Stimulates the pituitary to release growth hormone and IGF-1 under normal feedback control. FDA-approved for GH deficiency; used off-label for anti-aging via nightly injection.

References

  1. ^ Peptide Therapies in Thyroid Health: Emerging Applications in Endocrine and Immune Modulation. Recent review
  2. a b c Aging and Thymosin Alpha-1. Recent review
  3. a b The efficacy and safety of thymosin α1 for sepsis (TESTS): multicentre, double blinded, randomised, placebo controlled, phase 3 trial. Unfiltered
  4. a b World Anti-Doping Agency. (2026). Prohibited List 2026.

External links

Categories: Peptides | Therapeutic peptides | Anti-inflammatory | Anti-aging | Injectable | Subcutaneous

This page was last updated on August 4, 2026, at 00:44 (UTC).

Research last reviewed on August 4, 2026.

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