Reference · cited facts
Thymosin Alpha-1
Thymalfasin / Zadaxin / Tα1Half-life ≈2 hoursResearch use · not FDA-approvedReviewed July 2026
Educational information and a math tool only — not medical advice, a dose recommendation, or an endorsement of peptide use. Not FDA-approved for human use. Consult a licensed healthcare provider before starting, stopping, or changing anything.
Class / mechanism
Thymosin alpha-1 (thymalfasin) is a 28-amino-acid thymic peptide that acts as an immunomodulator.
SOURCE [1]
Regulatory status
Not FDA-approved in the US (US orphan-drug designation only). Approved in 30+ other countries as Zadaxin (thymalfasin) for chronic hepatitis B and C and as an oncology adjunct; in the US it is available via 503A compounding. WADA status is not independently confirmed here — note that WADA's S2 names thymosin-beta-4 (TB-500), a DIFFERENT peptide. As of 2026-07-13 and subject to change.
FDA · July 2026
Reported half-life
≈2 hours
PUBMED
Human evidence
Limited human data
LITERATURE
What the literature reports
- Thymosin alpha-1 (thymalfasin) is a 28-amino-acid thymic peptide that acts as an immunomodulator.
- Its serum half-life is short — no more than about 2 hours (peer-reviewed review; corroborated by the Zadaxin prescribing information).
- It is not FDA-approved in the US (orphan designation only), but is approved in 30+ countries as Zadaxin for chronic hepatitis B/C and as an oncology adjunct; US supply is via compounding.
- It is distinct from thymosin beta-4 (TB-500), a different peptide with different data and status.
Honest caveats
- • Not FDA-approved in the US; foreign approvals (Zadaxin) are for specific indications and do not equal US approval.
- • Often confused with thymosin beta-4 (TB-500) — these are different peptides; don't transfer facts between them.
- • Reference facts only — no dose, protocol, or benefit is stated or implied.
Reconstitution calculator
Enter your own vial size, BAC water and target dose — get exact syringe units.
Sources