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Human trialsImmune Tα1, Thymalfasin, Zadaxin

Thymosin α1

The most clinically legitimate immune peptide — approved widely, just not by the FDA.

Class
28-amino-acid thymic peptide
Molar mass
3,108 g/mol
Half-life
~2 h
Human PK
Fully characterised
Regulatory
Approved in 35+ countries; not FDA-approved. Removed from US Category 2 Sept 2024
Sport
Not listed

What it is claimed to help

These are the uses attached to Thymosin α1 in research, clinical practice, or marketing. Listing a claim is not endorsing it — tap any of them to see every other compound carrying the same claim.

What the human evidence actually is

Grade: Human trials

Randomised controlled human trials exist. Not necessarily approved, and not necessarily positive.

Substantial. Approved in over 35 countries as Zadaxin for chronic hepatitis B and C and as an immune adjuvant. Randomised trials support improved vaccine response in the elderly and there is a real sepsis literature, including a Chinese multicentre randomised trial reporting reduced 28-day mortality. FDA approval has never been obtained, and it holds US orphan designations only.

How it is supposed to work

Enhances T-cell maturation and dendritic cell function, upregulates MHC class I expression, and modulates Toll-like receptor signalling.

Safety

Well tolerated across a large clinical exposure. Injection site reactions most common.

Storage and handling

Lyophilised peptide is generally stored at 2–8 °C, or below −20 °C for long-term storage. Reconstituted in bacteriostatic water (0.9% benzyl alcohol) a solution is typically treated as usable for about 28 days refrigerated, versus roughly 24 hours for plain sterile water, which has no preservative. Add the water slowly down the vial wall and swirl — never shake, which shears peptide chains and foams the solution.

The arithmetic is the dangerous part

Whatever number a protocol or a prescriber gave you, converting it into syringe units is where a misplaced decimal becomes a tenfold error. Our calculators do that conversion and nothing else — they never invent a dose.

Open the calculators

Sources

  1. Zadaxin approval documentation, multiple national regulators
  2. Wu J et al. Thymosin α1 in sepsis, Critical Care 2013
  3. FDA 503A Category 2 removal notice, September 2024

Verified against primary sources on 27 August 2026. Regulatory status in this field changes several times a year. See How We Rate Evidence.

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