A 28-amino-acid immune-modulating peptide, marketed abroad as Zadaxin (thymalfasin) for hepatitis but not FDA-approved in the US, studied as an immune adjuvant.
Reviewed for accuracy · Last reviewed July 8, 2026Thymosin alpha-1 is a 28-amino-acid peptide derived from prothymosin alpha that acts as an immunomodulator rather than a simple stimulant. Reviews describe it interacting with Toll-like receptors to influence T cells, natural killer cells, and cytokine balance, which is why it has been studied as an immune adjuvant in viral infection and cancer care.
It is approved and marketed in various countries as Zadaxin (thymalfasin), for example for chronic hepatitis B and C, but it is not FDA-approved for marketing in the United States, where it holds only orphan-drug designations. Evidence quality varies by indication, so claims here are framed cautiously.
In chronic hepatitis B trials the studied regimen was 1.6 mg subcutaneous twice weekly, usually for about 26 weeks. Because it is not FDA-approved in the US, there is no US prescribing dose.
Read the full Thymosin Alpha-1 dosage guide →It is generally reported as well-tolerated, with injection-site reactions the most commonly noted effect. Longer-term and research-use safety data are limited, so this is a hedged reading.
Read the full Thymosin Alpha-1 side effects guide →Keep unmixed vials refrigerated and away from light. Once reconstituted, follow the product or research handling guidance and use within the stated window. See the full storage & safety guide for handling and disposal basics.
This page is an independent educational reference and is not medical advice, and does not indicate any approval status for any use. Talk to a doctor before starting any compound.