Thymosin Alpha-1
Thymosin Alpha-1 (Thymalfasin)
Also known as: Zadaxin, Thymalfasin
An immune-modulating thymic peptide approved in many countries for hepatitis and used as an immune adjuvant.
Overview
Thymosin Alpha-1 is a peptide originally isolated from the thymus that modulates T-cell function and innate immunity. Marketed as Zadaxin, it is approved in 30-plus countries for chronic hepatitis B and C and as an immune adjuvant, though it holds only orphan-drug status in the US. It has been studied in infection and cancer supportive care.
Mechanism of action
Enhances T-cell maturation and function, modulates dendritic cells and cytokine signaling, and supports both adaptive and innate immune responses.
Key studies & citations
- Review2016
Immune Modulation with Thymosin Alpha 1 Treatment
Reviews the pleiotropic mechanism (Toll-like receptor signaling in myeloid and plasmacytoid dendritic cells) and summarizes preclinical and clinical studies in infection, cancer and age-related immune suppression.
Vitamins and Hormones - Human1998
Efficacy of thymosin alpha1 in patients with chronic hepatitis B: a randomized, controlled trial
98 patients: complete virological response at 18 months in 40.6% after a 26-week course and 26.5% after 52 weeks versus 9.4% of untreated controls.
Hepatology - Review2008
Comparison of the efficacy of thymosin alpha-1 and interferon alpha in the treatment of chronic hepatitis B: a meta-analysis
Meta-analysis of four RCTs (199 patients) comparing thymosin alpha-1 with interferon alpha on virological, biochemical and complete response in chronic hepatitis B.
Antiviral Research - Human2025
The efficacy and safety of thymosin alpha 1 for sepsis (TESTS): multicentre, double blinded, randomised, placebo controlled, phase 3 trial
1,106 adults with sepsis at 22 Chinese centres: 28-day mortality 23.4% with thymosin alpha-1 vs 24.1% with placebo (HR 0.99), so no clear mortality benefit.
BMJ
Frequently asked questions
Is Thymosin Alpha-1 approved in the US?
It has orphan-drug designation but is not broadly FDA-approved. It is approved in many other countries as Zadaxin.