Podcast episode 7 (in German)
Thymosin alpha-1 (Zadaxin): the immune peptide with real approval fact-checked
July 12, 2026
Most peptides in the scene are experimental, thymosin alpha-1 is not: under the name Zadaxin it is an approved medicine in over 30 countries. The episode shows why a messenger from the thymus is interesting for the immune system and healthy aging.
What it is about
Thymosin alpha-1 is a small peptide of 28 building blocks that the body itself produces in the thymus gland, the school of the T cells. It helps T cells mature and awakens natural killer cells, but acts as a modulator: a weak defense is strengthened, an overshooting one calmed. The episode goes through the approvals, from hepatitis B and C to accompanying cancer therapies, and a paper from the pandemic. The link to aging: the thymus regresses from puberty onward, and with it fresh T cells and messengers like this one decline. At the end stands one of the more serious peptides, which, however, is not on the market as a medicine in Germany.
Key points
- Thymosin alpha-1 consists of 28 amino acids and is produced in the thymus; it was discovered in the line of research around Allan Goldstein, from which thymosin beta-4 also originates.
- As Zadaxin it is approved in over 30 countries, classically for chronic hepatitis B and C, for immune support, alongside cancer therapy and for better vaccine responses.
- A 2020 paper by Liu and colleagues in Clinical Infectious Diseases linked treatment of severely ill COVID patients with lower mortality.
- The thymus shrinks from puberty onward and in many people over 50 has largely been replaced by fatty tissue; as a result, hardly any freshly trained T cells are produced.
- It acts mainly on the learning defense with T and B cells, but also nudges the innate defense and thus coordinates across both arms.
- In the studies it is considered very well tolerated; at most a mild reaction at the injection site occurs.
Where the data stop
The approval applies to specific diseases and not to Germany: here thymosin alpha-1 is not on the market as a medicine, as of July 2026. In the biohacking scene it therefore usually comes as a research peptide via the gray market, and none of the tested qualities of the approved product apply to these goods.
The longevity idea of supplementing a thymus signal that declines with age is coherent, but the episode does not name a study in healthy older people. For the COVID paper, too, it names neither size nor design; “linked with” is the operative phrase there. Seasonal use during infection seasons is practice from the scene, not a tested application.
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Published on July 12, 2026.
The topic in the database
- The best-studied immune peptide on this list: approved as Zadaxin in over 30 countries, it supports T-cell defense – most convincingly asThymosin Alpha-1 (TA1)
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Information only, not medical advice and not a usage or dosage recommendation. Prescription-only and unapproved substances belong in the hands of a physician. Last updated: 2026-10-09.