Overview

Also Known As

Tα1, Ta1, Thymalfasin, Zadaxin, Thymosin α1

Mechanism of Action

Activates TLR2/TLR9 on dendritic cells, enhances T-cell differentiation and IL-2 receptor expression, promotes Th1 responses, stimulates NK cell activity, modulates cytokine balance. Acts as immune restorer normalizing both immunosuppressed and hyperactivated states.

Product

Tα1, Ta1, Thymalfasin, Zadaxin, Thymosin α1 vial

Dosing & Administration

Typical protocols and routes

Half-Life

Approximately 2 hours

Administration Routes

subcutaneous

Dosing Protocols

Average: 0.5 mg/day (vial lasts 20 days) — reconstitute 10 mg vial with 2 mL bacteriostatic water, draw 10 units on insulin syringe (marked 0-100 units).

Research

Key findings and status

Key Research Findings

Approved in 35+ countries as Zadaxin. Multiple RCTs in hepatitis B/C showing improved viral clearance with IFN combination. Garaci et al.: improved survival in melanoma with chemotherapy. Sepsis studies: improved immune reconstitution. COVID-19: adjunctive use in lymphopenic patients.

Detailed Information

Thymosin Alpha-1 (Tα1) is a naturally occurring thymic peptide first isolated from thymosin fraction 5 by Allan Goldstein at George Washington University in 1977. It is one of the most clinically validated immune-modulating peptides, approved in over 35 countries under the brand name Zadaxin® for the treatment of hepatitis B and C, and as an immune adjuvant in cancer therapy.

Mechanism of Action

Tα1 acts as a potent immune modulator through multiple mechanisms. It activates Toll-like receptors (TLR2, TLR9) on dendritic cells, promoting maturation and antigen presentation. It enhances T-cell differentiation and function, increasing expression of IL-2 receptors and promoting Th1 immune responses while suppressing excessive Th2 activity. It stimulates natural killer (NK) cell activity and modulates the balance between pro- and anti-inflammatory cytokines.

Uniquely, Tα1 acts as an immune restorer rather than a simple immune stimulant. It helps normalize immune function in both immunosuppressed and hyperactivated states, making it useful across a broad range of immune-related conditions from infections to autoimmunity to cancer immunotherapy.

Clinical Evidence

Tα1 has an extensive clinical track record spanning four decades. In hepatitis B, multiple randomized controlled trials demonstrated sustained viral clearance rates of 25-40% when combined with interferon-alpha (vs. ~12% with IFN alone). In hepatitis C, combination therapy with IFN-alpha showed improved sustained virological response rates in non-responders to standard therapy.

In oncology, Tα1 has been studied as an adjuvant to chemotherapy and as a stand-alone immunomodulator. Garaci et al. demonstrated improved immune reconstitution and survival in melanoma patients receiving Tα1 with dacarbazine. It has also been investigated for sepsis (improving survival in severe sepsis through immune restoration) and as a vaccine adjuvant to enhance responses in immunocompromised populations.

During the COVID-19 pandemic, Tα1 was used in China and Italy as adjunctive therapy, with retrospective studies suggesting improved lymphocyte counts and outcomes in severely lymphopenic patients.

Safety & Legal

Side Effects & Warnings

Very well-tolerated. Injection site reactions (mild erythema, discomfort). No significant systemic side effects in clinical trials. No immunosuppressive rebound. Safe in immunocompromised populations. Extensive safety database from 35+ country approval.

Legal Status

Approved in 35+ countries (Zadaxin). Available from compounding pharmacies and as research peptide in the US.

Molecular Data

Chemical properties

Molecular Weight

3108.27 g/mol

Amino Acid Sequence

Ac-SDAAVDTSSEITTKDLKEKKEVVEEAEN (28 amino acids, N-terminally acetylated)