Thymosin Alpha-1
Repair and Recovery
In short
- A 28-amino-acid thymic peptide and one of the best-evidenced immunomodulators in this library.
- Approved as a medicine (Zadaxin) in over 30 countries for hepatitis B and C and as a vaccine adjuvant — but NOT approved in the US.
- Has orphan drug designation in the US for hepatocellular carcinoma and DiGeorge syndrome.
- Extensively studied in sepsis, where a large Chinese trial reported reduced mortality.
- Genuinely different from most compounds here: it has real approvals, real trials, and a real safety database.
Structure
How it works
Thymosin alpha-1 is derived from prothymosin alpha and is produced by the thymus. It acts primarily on dendritic cells and T cells through Toll-like receptors, particularly TLR9 and TLR2.
The result is enhanced maturation of dendritic cells, increased T helper cell differentiation, improved natural killer cell activity, and increased IL-2 and interferon-gamma production. Its effect is best described as restoring depressed immune function rather than broadly stimulating a healthy immune system.
What the research shows
Chronic hepatitis B and C: multiple trials support benefit, and this is the basis for its approvals in over 30 countries.
Sepsis: the ETASS trial and a subsequent larger Chinese multicentre trial reported reduced 28-day mortality, though results have not been uniformly replicated.
Vaccine adjuvant use in immunocompromised and elderly populations is supported by trial data.
Cancer immunotherapy adjunct use has been explored with mixed results.
Dosing in the literature
Figures below are quoted from published studies, with the species or population they were measured in. They are records of what was studied, not recommendations.
| Studied in | Amount | Route | Source |
|---|---|---|---|
| Human — chronic hepatitis B, approved use in countries where marketed | 1.6 mg twice weekly for 6 months | subcutaneous | PubMed |
| Human — sepsis trials | 1.6 mg twice daily for 5 days, then once daily | subcutaneous | PubMed |
Commonly reported ranges
These are amounts people report using. They are not from any study, have not been evaluated for safety, and are reproduced here only because they circulate widely and are better seen alongside the evidence than instead of it.
| Reported by | Amount | Route |
|---|---|---|
| Commonly reported | 1.6 mg, one to three times weekly | subcutaneous |
Unusually for this library, the community dose coincides with an approved clinical dose, because an approved dose exists to coincide with. Note it is approved for specific infectious and immunological indications, not for general immune enhancement in healthy people.
Handling and storage
Supplied as a lyophilised powder requiring reconstitution with bacteriostatic water. The powder is comparatively stable; once reconstituted it is refrigerated and used within weeks. Track the date you reconstitute each vial — the Inventory section does this, and it is the difference between knowing a vial is three weeks old and guessing.
Subcutaneous injection, typically twice weekly in the approved hepatitis protocols. In countries where it is marketed it is supplied as a proper pharmaceutical product rather than a research chemical.
Side effects
One of the better-tolerated agents here, with a genuine post-marketing safety database from 30+ countries.
Most commonly reported: injection-site reactions and transient discomfort.
Because it enhances T cell activity, the theoretical concern is autoimmune conditions, where immune stimulation could worsen disease. Caution in autoimmunity and in transplant recipients on immunosuppression is the standard consideration.
Combinations
In its approved uses it is combined with antivirals and with vaccines, both supported by trial evidence.
Combination with immunosuppressive therapy is mechanistically opposed and clinically relevant if you are on such therapy.
Research status
Decades of research including randomised controlled trials in hepatitis, sepsis, and vaccine response. Approved in over 30 countries.
The absence of US approval is notable and reflects the trials conducted not meeting FDA requirements rather than a safety finding.
Legal status
Approved and marketed as Zadaxin in over 30 countries including much of Asia, the Middle East, and parts of Latin America. NOT FDA-approved in the United States, where it holds orphan drug designation only. US research-market supply is unapproved.
WADA status
Not specifically named on the Prohibited List. Falls under WADA class S0, which prohibits any pharmacological substance not currently approved by any governmental regulatory health authority for human therapeutic use. Treat it as prohibited in sport.
Conclusion
Thymosin alpha-1 is arguably the best-evidenced immunomodulator in this library — an approved medicine in dozens of countries with randomised trials behind it.
The honest caveat is that its evidence concerns restoring impaired immune function in sick people: hepatitis, sepsis, immunocompromise. Whether it does anything useful for a healthy adult is a different question, and one the trials were not designed to answer.
Sources
Track your own Thymosin Alpha-1 protocol
Peppers logs your doses, models your levels from this half-life, tracks your vials and tells you when you will run out. Free on iPhone.
Reference and educational information only. Not medical advice. Nothing here diagnoses, treats, or prescribes, and nothing here is a recommendation to use any compound. The compounds described are research chemicals and are not approved for human consumption. Legal and anti-doping status change — the review date above is when these claims were last checked. Talk to a qualified clinician about anything you intend to take.