Thymosin Alpha-1
From PeptidePlaza, the free peptide reference · Entry #021 · Recovery · Hand-curated entry · Editorial standards
Thymosin Alpha-1 (also known as Thymalfasin, Zadaxin, TA-1) is a recovery research peptide. A 28-amino acid thymic peptide that modulates T-cell function and cytokine balance. Studied clinically for chronic hepatitis B, sepsis, and vaccine response augmentation for over 30 years.
Thymosin Alpha-1 (TA-1) is a naturally occurring 28-amino acid peptide derived from the thymus gland, produced commercially as thymalfasin. It acts as a biological response modifier: it enhances T-cell maturation and function, shifts cytokine profiles toward Th1 immunity, and improves antigen presentation. Clinical trials have evaluated TA-1 for chronic hepatitis B and C, sepsis, cancer immunotherapy adjuncts, and immune restoration in elderly or immunocompromised populations. Its mechanism is indirect — it does not kill pathogens or tumors directly but restores and coordinates host immune responses.
1 Mechanism of action
Enhances dendritic cell maturation and antigen presentation; upregulates Th1 cytokines (IL-2, IFN-γ); activates NF-κB and Toll-like receptor signaling in immune cells; promotes T-cell differentiation and natural killer (NK) cell activity.
Primary targets: TLR-9 · TLR-2 · NF-κB pathway
2 Reported effects
Effects below are those reported in the published literature cited on this page. They are not claims of clinical benefit and not medical advice.
2.1 Reported benefits
- Enhances T-cell mediated immune responses in clinical studies
- Modulates cytokine balance toward Th1 immunity
- Studied as adjunct in chronic viral infection protocols
- Potential immune restoration in aging and immunosuppression
2.2 Side effects
- Injection site reactions (pain, erythema)
- Mild transient fever or fatigue
- Rare hypersensitivity reactions
- Potential autoimmune flare in predisposed individuals
3 Chemical and physical properties
| CAS number | 62304-98-7 |
|---|---|
| Molar mass | 3108.5 g/mol |
| Purity (typical) | >99% |
| Half-life | ~2 hours (SC); immunomodulatory effects persist days |
| Storage | −20 °C, lyophilised powder, desiccated |
| Solubility | Sterile water / bacteriostatic water |
| Receptors / targets | TLR-9, TLR-2, NF-κB pathway |
3.1 Amino acid sequence
Ac-Ser-Asp-Ala-Ala-Val-Asp-Thr-Ser-Ser-Glu-Ile-Thr-Thr-Lys-Asp-Leu-Lys-Glu-Lys-Lys-Glu-Val-Val-Glu-Glu-Ala-Glu-Asn-OH
4 Research dosages
1.6 mg SC twice weekly (hepatitis protocols); 1.6 mg weekly for immune support protocols in clinical studies.
5 Research studies (5)
- Comprehensive Review of the Safety and Efficacy of Thymosin Alpha 1 in Human Clinical Trials.
Alternative therapies in health and medicine (2024) · ReviewOBJECTIVE: This study aims to assess the safety and efficacy of Thymosin Alpha 1 (Tα1) through a comprehensive narrative review of clinical studies involving over 11 000 human subjects in more than 30 trials. - Immune Modulation with Thymosin Alpha 1 Treatment.
Vitamins and hormones (2016) · ReviewThymosin alpha 1 (Ta1) is a peptide originally isolated from thymic tissue as the compound responsible for restoring immune function to thymectomized mice. - Thymosin alpha-1 treatment in chronic hepatitis B.
Expert opinion on biological therapy (2015) · ReviewINTRODUCTION: Stimulating a successful host immune response may be a promising helpful therapy to achieve elimination of hepatitis B virus (HBV) infection in chronic hepatitis B (CHB). - Thymosin alpha 1 restores the immune homeostasis in lymphocytes during Post-Acute sequelae of SARS-CoV-2 infection.
International immunopharmacology (2023) · ReviewThe complex alterations of the immune system and the immune-mediated multiorgan injury plays a key role in host response to SARS-CoV-2 infection and in the pathogenesis of COVID-19, being also associated with adverse... - Thymosin alpha 1 treatment for patients with sepsis.
Expert opinion on biological therapy (2018) · ReviewINTRODUCTION: Sepsis is a life-threatening organ dysfunction caused by host immune response to infection.
6 Safety and risk profile
6.1 Regulatory status
Thymosin Alpha-1 is currently classified as Investigational. It has no approved human indication in the United States; availability elsewhere does not imply demonstrated safety or efficacy.
Safety score: 72/100 — low concern. Derived from clinical data volume, known risks and regulatory status.
6.2 Contraindications
Conditions and populations in which use is contraindicated:
- Known hypersensitivity to thymosin products
- Active autoimmune disease (relative contraindication)
- Pregnancy or lactation
6.3 Drug interactions
| Drug or class | Interaction | Risk |
|---|---|---|
| Immunosuppressants (corticosteroids, calcineurin inhibitors) | May counteract the immunostimulatory effects of TA-1. | Moderate |
| Vaccines | May augment vaccine responses — timing should be coordinated in protocols. | Low |
6.4 Long-term risks
- Limited long-term safety data beyond 1–2 years
- Theoretical risk of immune dysregulation with chronic use
- Uncertain effects in malignancy
6.5 Research best practices
- Store lyophilized powder at −20 °C; protect from light
- Reconstitute with bacteriostatic water; use within days if refrigerated
- Monitor immune parameters in extended protocols
7 Frequently asked questions
- How is Thymosin Alpha-1 administered in research?
- TA-1 is typically given as a subcutaneous injection. Clinical hepatitis protocols used 1.6 mg twice weekly, while immune-support protocols commonly use 1.6 mg once or twice weekly.
- What is the evidence base for Thymosin Alpha-1?
- TA-1 has been studied in dozens of clinical trials, including randomized trials for chronic hepatitis B, as an adjunct in sepsis, and for improving immune responses in older adults. It is approved in over 30 countries (but not by the FDA).
- Does Thymosin Alpha-1 require refrigeration?
- Lyophilized TA-1 should be stored frozen (−20 °C) and protected from light. Reconstituted solutions should be used promptly or refrigerated short-term.
8 References
- Thymosin alpha-1. PubMed (2001). Ancell CD, et al.. View source
- Thymosin alpha-1 treatment in chronic hepatitis B. PubMed (2015). Wu X, et al.. View source
- Thymosin α-1 in cancer therapy: Immunoregulation and potential applications. PubMed (2023). Wei Y, et al.. View source
- Aging and Thymosin Alpha-1. PubMed (2025). Simonova MA, et al.. View source
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