Thymosin Alpha-1
/ 28-amino-acid peptide derived from prothymosin alphaALIAS · Tα1 · Zadaxin · Thymalfasin
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Approved in more than 35 countries as Zadaxin for HBV, HCV (adjunct), and immune adjuvant use. Not FDA-approved in the US.
Thymosin Alpha-1 is a 28-amino-acid peptide derived from prothymosin alpha. It activates TLR9 and TLR2 signaling on plasmacytoid dendritic cells and monocytes, enhances T-cell maturation and Th1 cytokine production (IFN-γ, IL-2), and modulates regulatory T cells. It is the most pharmaceutically developed peptide in the thymic family.
Substantial compared with other peptides in the healing category. Multiple randomized controlled trials support approvals for chronic hepatitis B in >35 non-US countries. Sepsis and COVID-19 literature is mixed and largely observational.
Generally well tolerated across large clinical programs. Most common adverse events: local injection-site reactions, transient erythema. No significant systemic toxicity signal in published registrational trials.
Regulatory status
- FDA status:
- Not FDA-approved
- Compounding:
- 503A Category 2 — do-not-compound pending review
FDA non-approval in the US despite global approval is notable. Sepsis and COVID-19 meta-analyses are heterogeneous in quality. The strongest clinical evidence remains in chronic hepatitis B.