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Thymosin Alpha-1

Not FDA approved Thymosin Alpha-1 · Tα1 · Zadaxin

Not FDA approved in the U.S. Approved in more than 35 countries (China, Italy, India, etc.) under the brand Zadaxin for hepatitis B, C, and as an immunomodulator in cancer. In the U.S. only available as a compounded prescription.

What is Thymosin Alpha-1?

Thymosin Alpha-1 (Tα1) is a 28-amino-acid peptide derived from prothymosin alpha, a protein naturally produced by the thymic gland. The thymus is the organ responsible for the maturation of T lymphocytes, the central component of adaptive immunity. The thymus involutes (atrophies) with age, contributing to the immunological decline of aging.

It was first isolated in 1977 and has been extensively studied for more than 40 years, with clinical trial data in hepatitis B and C, HIV, cancer, sepsis, and COVID-19.

Immunomodulatory mechanism of action

Tα1 acts on multiple components of the immune system:

Adaptive immunity:

  • Promotes differentiation and maturation of T lymphocytes (especially T helper 1 / Th1).
  • Increases production of IL-2 and IFN-γ, cytokines that coordinate antiviral and antitumor responses.
  • Increases expression of surface receptors on T cells (CD4, CD8, MHC-II).

Innate immunity:

  • Activates NK (Natural Killer) cells to destroy infected and tumor cells.
  • Increases activity and maturation of dendritic cells, which present antigens.
  • Modulates the inflammatory response toward a more balanced profile.

“Normalizing” effect: Unlike non-specific immunostimulants, Tα1 is a modulator: it enhances the response when deficient (immunodeficiency, aging) and regulates it when in excess (autoimmunity). This dual effect is one of its most clinically valued properties.

International approvals (Zadaxin)

Zadaxin (SciClone Pharmaceuticals) is approved in 35+ countries for:

  • Chronic hepatitis B: studies show improved seroconversion vs. interferon alone.
  • Hepatitis C: enhancer of interferon response.
  • Hepatocellular carcinoma: adjuvant in chemotherapy.
  • Non-small cell lung cancer.
  • Immunodeficiency in dialysis.
  • Vaccination in immunocompromised patients (improves vaccine response).

COVID-19

During the pandemic, China used Tα1 (Zadaxin) as part of the severe COVID-19 treatment protocol, with observational data reporting reduced mortality in critically ill patients.

Reconstitution (reference)

With 5 mg + 2.0 mL bacteriostatic water: 1 unit on a U-100 syringe ≈ 25 mcg. Refrigerate at 2–8 °C once reconstituted.

Safety profile

With decades of clinical use in multiple countries, Tα1 has one of the best safety profiles among peptides. Adverse effects are minimal: mild local injection site irritation, occasional transient headache.

In the U.S., requires a compounding pharmacy prescription. In countries where Zadaxin is approved, follow the authorized protocol under medical supervision.

Reported protocol (research reference)

Vial sizes 5 mg, 10 mg
Reported dose Approved protocol in countries where authorized: 1.6 mg subcutaneous twice per week for 6–12 months for hepatitis. Varies by indication.
Half-life Approximately 2 hours.
FDA status Not FDA approved
Sources: J Hepatology — Thymosin Alpha-1 hepatitis B ·Cancer Immunology — Tα1 immune modulation
This information is for educational and research reference only. It is not medical advice. We do not sell, prescribe, or recommend any treatment. Dosages cited come from research literature and are not an indication for human use. Always consult a licensed healthcare provider.