Thymosin Alpha-1
An endogenous 28-residue thymic peptide (INN thymalfasin) acting as a Toll-like receptor agonist. Studied in sepsis and chronic hepatitis B in large randomised trials. Not FDA-approved.
| Total citations | 4 |
|---|---|
| Human clinical studies | 3 |
| Animal models | 0 |
| In vitro studies | 0 |
| Reviews / meta-analyses | 1 |
Mechanism of action
Thymosin alpha-1 is cleaved from prothymosin alpha and acts principally as a Toll-like receptor agonist — notably at TLR2 and TLR9 — on dendritic cells and monocytes, promoting their maturation and Th1-polarising cytokine output.
Downstream it enhances T-cell differentiation, restores lymphocyte counts and augments NK-cell activity in immunosuppressed states, while dampening excessive T-cell activation. It has no direct antiviral activity; the effects reported in viral hepatitis are immunomodulatory.
Peer-reviewed literature
Study type is tagged on every entry so animal and in-vitro findings are never mistaken for human clinical evidence.
The efficacy of thymosin alpha 1 for severe sepsis (ETASS): a multicenter, single-blind, randomized and controlled trial
A multicentre randomised controlled trial reporting reduced 28-day mortality in severe sepsis.
The efficacy and safety of thymosin α1 for sepsis (TESTS): multicentre, double blinded, randomised, placebo controlled, phase 3 trial
A large phase 3 placebo-controlled trial — the most rigorous evidence available for this compound.
Efficacy of thymosin alpha1 in patients with chronic hepatitis B: a randomized, controlled trial
Randomised controlled trial in chronic hepatitis B reporting sustained response at follow-up.
Thymosin alpha 1: A comprehensive review of the literature
Consolidates the immunological mechanism and clinical trial evidence to date.
Limitations & open questions
Thymosin alpha-1 is not approved by the FDA — a search of Drugs@FDA returns no record under either thymalfasin or thymosin alpha-1. It is approved and marketed as Zadaxin in a number of other countries; the frequently repeated "approved in ~35 countries" figure could not be confirmed from a primary regulatory source.