Thymosin α1

Description

Thymosin Alpha-1 (Tα1, Zadaxin) is a 28-amino acid peptide naturally produced by the thymus gland, first isolated and characterized by Dr. Allan Goldstein in the 1970s. It is the most extensively studied and clinically validated immunomodulatory peptide in the world, with regulatory approval in over 35 countries for the treatment of hepatitis B, hepatitis C, and various immune deficiency conditions. Tα1 is the primary active component of thymosin fraction 5, the thymic extract that was found to restore immune function in thymectomized animals. It has been studied in over 100 clinical trials covering hepatitis, cancer, sepsis, COVID-19, and vaccine adjuvancy. In the COVID-19 pandemic, Observational studies from China and Italy reported associations with lower mortality and ICU admission. These were not randomised, and the finding has not been confirmed in a controlled trial.. Its broad immunomodulatory effects — enhancing both innate and adaptive immunity while also having anti-inflammatory properties — make it uniquely valuable for conditions involving immune dysregulation.

Key Characteristics

Investigated Benefits

• Enhanced T-cell function
• Improved vaccine response
• Hepatitis B and C treatment support
• Studied in sepsis (phase 3 trial found no mortality benefit)
• COVID-19 severity reduction

* Benefits based on preclinical/animal research unless otherwise noted.

Mechanism of Action

“The most clinically validated immunomodulatory peptide, approved in 35+ countries for hepatitis, sepsis, and immune deficiency.”

Thymosin Alpha-1 acts primarily through Toll-like receptor 9 (TLR9) on dendritic cells and macrophages, triggering MyD88-dependent signaling that activates NF-κB and IRF7, leading to the production of type I interferons (IFN-α, IFN-β) and pro-inflammatory cytokines that initiate innate immune responses. In the adaptive immune system, Tα1 promotes the maturation and differentiation of naïve T-cells into Th1 effector cells (producing IFN-γ and IL-2), enhances cytotoxic T-lymphocyte (CTL) activity, and increases the expression of MHC class I and II molecules on antigen-presenting cells, improving antigen presentation. It also enhances natural killer (NK) cell cytotoxicity and promotes dendritic cell maturation. Paradoxically, Tα1 also has anti-inflammatory effects in hyperinflammatory states, reducing excessive cytokine production (the “cytokine storm”) through regulatory T-cell (Treg) induction — this dual immunomodulatory capacity explains its efficacy in both immunodeficiency and hyperinflammatory conditions.

Reconstitution Guide

Add 1 mL bacteriostatic water to 1.6 mg vial → 1.6 mg/mL

Protocols Featuring Thymosin α1

Research Highlights

1. 1Approved in 35+ countries for hepatitis B, hepatitis C, and immune deficiency
2. 2Sepsis trials have not shown a survival benefit. The ETASS trial (2013) reported 26.0% vs 35.0% mortality, p = 0.062 — not statistically significant. The larger TESTS phase 3 trial (2025, n = 1,106) reported 23.4% vs 24.1%, p = 0.82, concluding no effect.
3. 3Reduced COVID-19 severity in multiple studies
4. 4Over 100 clinical trials completed

Compatible Peptides

Peptides commonly used alongside Thymosin α1 for synergistic effects.