Thymosin Alpha-1

Technical data

INN name

Thymosin Alpha-1

CAS

62304-98-7

Molecular formula

C129H215N33O55

Molecular weight

3108.32 g/mol

Identity and composition

La Thymosin Alpha-1 (also called Thymalfasin, Thymosin alpha 1, Ta1 or marketed as Zadaxin in its synthetic analog) is an immunomodulatory peptide derived from the N-terminal residues of prothymosin alpha, studied as an agent to modulate the immune response. It is a product for research use.

As for its reference chemical identity:

• Molecular formula: C129H215N33O55
• Molecular weight: 3108.3 g/mol (calculated average molecular weight)
• Sequence: N-acetylated 28-amino-acid polypeptide (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), corresponding to the N-terminal residues 1-28 of prothymosin alpha.

It is offered in presentations of 5 mg y 10 mg. The CAS number is not included because it was not confirmed in the reference source used.

Mechanism of action

Thymosin Alpha-1 is described in the literature as an immunomodulatory peptide that acts, in part, as an agonist of endogenous Toll-like receptors (TLR) (Molecules 2023; PMID 37110771).

Among the documented mechanisms are:

• Binding to Toll-like receptors: interaction with TLR2 and with TLR3/4/9 is described in myeloid and plasmacytoid dendritic cells.
• Activation of downstream signaling pathways: IRF3 and NF-kB, as well as p38 MAPK and MAPK/JNK.
• Maturation of dendritic cells and promotion of antigen presentation.
• Modulation of T lymphocytes: differentiation toward cytotoxic CD8+ T lymphocytes and maintenance of the CD4+/CD8+ ratio has been described.
• Cytokine stimulation: for example IFN-gamma and IL-2.
• Induction of indoleamine 2,3-dioxygenase (IDO) via TLR9 in dendritic cells.

This description corresponds to investigated mechanisms and does not imply an established clinical effect.

Pharmacokinetics

According to a review article, after subcutaneous injection the maximum plasma concentration (Cmax) would be reached between 1 and 2 hours, with a half-life of less than 3 hours (Molecules 2023; PMID 37110771). These parameters come from the review literature and may vary according to the experimental context.

Scientific evidence

Thymosin Alpha-1 is a compound widely studied as an immunomodulator. Its synthetic form (thymalfasin) is approved in several jurisdictions for chronic hepatitis B and chronic hepatitis C and as an immunological adjuvant, while other indications remain under research (Molecules 2023; PMID 37110771).

In the review literature, indications such as the following have been investigated:

• Hepatitis B and C
• COVID-19
• Sepsis
• HIV/AIDS
• Adjuvant use in oncology

It is important to emphasize that the level of development varies by indication: approved in some jurisdictions for hepatitis, but in the research or trial phase for sepsis, COVID-19, and oncology. These uses should be interpreted as research context and not as universally established efficacy.

Research applications

Product for research use.

Ideal for:

• In vitro studies and preclinical models of immunomodulation.
• Research on Toll-like receptor (TLR) signaling, dendritic cell maturation and T-lymphocyte response.
• Characterization work on peptides of the prothymosin alpha family.

Not applicable for:

• clinical use or administration in people or pets.
• Diagnostic or therapeutic use.
• Any application outside a controlled research environment.

Research protocols

In the review literature, a dosing regimen of 0.8 to 6.4 mg twice per week by the subcutaneous route (Molecules 2023; PMID 37110771). This range is documented as a reference from the published research and does not constitute a usage recommendation or an administration protocol. The experimental handling parameters must be defined by the responsible researcher in accordance with their study design.

Reconstitution

As a general laboratory guide, lyophilized peptides such as Thymosin Alpha-1 are usually reconstituted with bacteriostatic water (sterile water with approximately 0.9% benzyl alcohol), which helps limit microbial growth in preparations for repeated use.

Standard technique recommendations:

• Add the diluent slowly along the vial wall, letting it run down onto the powder rather than directing it straight to the peptide.
• Do not shake; gently swirl the vial until fully dissolved.
• Avoid unnecessary exposure to light and heat during handling.

The reconstitution volume depends on the desired working concentration for each presentation (5 mg or 10 mg).

Stability and storage

General laboratory handling guide:

• Lyophilized (powder): lyophilized peptides are more stable and are usually stored refrigerated for short-term use or frozen for prolonged storage, protected from moisture and light.
• Reconstituted (in solution): once reconstituted, the material is typically kept under refrigeration and used within a limited time window, since peptide solutions are less stable than the lyophilized powder.

It is recommended to minimize freeze-thaw cycles and to work with aliquots when the experimental design allows.

Safety profile

The review literature describes a generally favorable safety profile, with adverse reactions predominantly local at the injection site (Molecules 2023; PMID 37110771). It is noted caution or relative contraindication in immunocompromised individuals, due to its immunomodulatory properties. Long-term safety data depend on the indication studied.

Since this is a product for research use, it must not be administered to humans or animals and its handling is the responsibility of personnel trained in controlled settings.

Comparative context

Thymosin Alpha-1 belongs to the family of thymic peptides and is derived from prothymosin alpha. Unlike immunomodulators based on exogenous cytokines, it is described as a endogenous TLR agonist which modulates dendritic cell maturation and T-lymphocyte response, rather than directly supplying the cytokine.

In the reviewed literature, this mechanism is associated with a favorable tolerability profile. Its action through Toll-like receptors and the orientation of the immune response distinguish it within its class, although direct efficacy comparisons between agents depend on the indication and the study context.

History and development

Thymosin Alpha-1 was identified as a fragment derived from the N-terminal residues (1-28) of prothymosin alpha, within the family of thymic peptides associated with immune function. Its synthetic form, known as thymalfasin (Zadaxin brand of the synthetic analog), was developed as an immunomodulator and has achieved regulatory approval in several countries for chronic hepatitis B and chronic hepatitis C and as an immunological adjuvant, while research in other indications has continued over time.

FAQ

Certificate of analysis per batch

Thymosin Alpha-1 batches with certificate of analysis published in the COA catalog:

• Lot EXO010626159A — 5 mg, issued 2026-05-30
• Lot EXO010626159B — 10 mg, issued 2026-05-28

Scientific references (7)

Peer-reviewed literature on Thymosin Alpha-1, with its PubMed identifier where available:

• Aging and Thymosin Alpha-1 (Simonova MA et al. · International journal of molecular sciences · 2025) PMID 41373628.
• Thymosin alpha-1 treatment in chronic hepatitis B (Wu X et al. · Expert opinion on biological therapy · 2015) PMID 25640173.
• Thymosin alpha-1 (Ancell CD et al. · American journal of health-system pharmacy: AJHP: official journal of the American Society of Health-System Pharmacists · 2001) PMID 11381492.
• Thymosin alpha1: isolation and sequence analysis of an immunologically active thymic polypeptide (Goldstein, et al. · Proceedings of the National Academy of Sciences (PNAS) · 1977) PMID 265536.
• Thymosin alpha 1 treatment for patients with sepsis (Pei, et al. · Expert Opinion on Biological Therapy · 2018) PMID 30063866.
• The efficacy of thymosin alpha-1 therapy in moderate to critical COVID-19 patients: a systematic review, meta-analysis, and meta-regression (Soeroto, et al. · Inflammopharmacology · 2023) PMID 37845598.
• Thymosin alpha 1 and HIV-1: recent advances and future perspectives (Matteucci, et al. · Future Microbiology · 2017) PMID 28106477.

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